JP2010236139A - Method for producing acrylic fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide dry and wet spinning high in hole density of more than 2,000 holes and using a gas phase part between the spinneret and the coagulation bath solution and of less than 20 mm, wherein a carbon fiber precursor bundle, as the whole, much improved in productivity and excellent in quality is provided by suppressing causation of dew formation on the spinneret and improving coiling around the roller in the post-processing, nap in the drawing step and quality degradation caused by thread breakage. <P>SOLUTION: A method for producing an acrylic fiber includes once ejecting an acrylic polymer solution from a spinneret set above a coagulation bath solution into an inert gas atmosphere so as to be introduced into the coagulation bath solution, wherein the moisture of a gas phase formed between the discharge surface of the spinneret in a coagulation bath and the coagulation bath solution is controlled to be 10-40%rh. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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-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, once discharged into an inert atmosphere, and immediately introduced into a coagulation bath liquid to be coagulated. However, since the draft is relaxed in an inert atmosphere with less bath resistance compared to the wet spinning method, spinning at a high speed or high draft is possible, which is useful for the production of clothing and industrial fibers. It's being used. Moreover, since the fiber can be densified by the dry-wet spinning method, it has recently been utilized for the production of acrylic precursor fibers for producing high-strength and high-modulus carbon fibers. In particular, in the process for producing acrylic precursor fibers for producing carbon fibers, high-speed spinning and multi-hole spinning are performed by dry-wet spinning to increase productivity.

  In such a dry-wet spinning method, an acrylic polymer solution, which is a spinning stock solution, is extruded from a spinneret installed at the top of a coagulation bath solution, so that a gas phase portion exists between the die surface and the coagulation bath solution. When so-called multi-hole formation is performed to increase the number of holes in one spinneret, the vapor amount of the solvent constituting the spinning dope increases in the gas phase portion, and this vapor tends to stay in the gas phase portion. Furthermore, since the coagulation bath does not discharge the gas evaporated from the spinning dope out of the machine, it is often considered environmentally by enclosing it with a screen and supplying exhaust air. In general, outside air is often used as the gas to be supplied, and the temperature and humidity vary greatly between seasons. The gas evaporated from the spinning dope condenses in the spinneret discharge surface hole in a low temperature and high humidity atmosphere, and the condensed condensation droplets prevent contact with or hole in the spinneret discharge stock solution, adhesion of fibers, fineness spots, and single yarn breakage. Furthermore, when the liquid droplet comes into contact with the coagulation liquid surface, it becomes immersed in the die, causing roller wrapping in the post-process, fluffing in the stretching process, and thread breakage, and the operability and quality are significantly reduced. Such a problem is particularly noticeable by increasing the number of holes in the spinneret in order to increase productivity.

  For the purpose of improving these problems, a method for preventing condensation by circulating gas from one direction on the spinneret surface in dry and wet spinning and the gas phase part of the coagulation bath has been proposed (see Patent Document 1). . However, when the number of holes used in the spinneret is as small as about 300 holes, the technique proposed in Patent Document 1 can also effectively suppress dew condensation, but with a hole number exceeding 2000 holes, the hole density can be reduced. In the condition where the vapor of the solvent is likely to stay in the gas phase part where the distance between the spinneret and the coagulation bath liquid is less than 20 mm in dry and wet spinning, the technique proposed in Patent Document 1 is applied as it is. However, there was a problem that condensation could not be eliminated.

In addition, when a hollow fiber membrane is produced by dry and wet spinning of a film-forming resin solution, dew condensation occurring on the spinneret surface has been studied (see Patent Documents 2 and 3). In this study, the air between the spinneret and the coagulation bath liquid is separated by 4 to 6 cm and humidity-controlled air is introduced into the gas phase and divided into a low-humidity low-temperature atmosphere region, a low-humidity high-temperature atmosphere region, and a high-humidity high-temperature atmosphere region In addition, it has been proposed that the product of the absolute humidity and the gas phase idling time be 0.04 kg / m ³ · S or more. However, in order to increase productivity, the distance between the spinneret and the coagulation bath solution is shortened, and in order to prevent adhesion between fibers, for example, less than 20 mm, it is necessary to increase the number of holes and increase the speed. Therefore, the gas phase atmosphere between the coagulation bath liquid and the spinneret installed on the upper part of the coagulation bath liquid is controlled. It is substantially difficult to apply these techniques because of the increase in equipment and the equipment cost. Is real.

  Further, a method for preventing the stagnation of the solvent vapor by alternately sucking the expectation of the gas phase portion formed between the discharge surface of the spinneret and the coagulation bath from two directions sandwiching the discharge surface has been studied. (Patent Document 4). However, this method has a problem that when the hole density is high due to the increase in the number of holes, the gas phase is not sufficiently sucked and the solvent vapor is aggregated.

JP-A-5-044104 JP 2004-025066 A JP 2004-025067 A JP 2007-239170 A

  The object of the present invention is to suppress the occurrence of condensation in the spinneret even under the condition that the hole density is higher than 2000 holes, for example, and the distance between the spinneret and the coagulation bath liquid in dry and wet spinning is less than 20 mm. An object of the present invention is to provide a method for producing a fiber, which can improve the productivity and quality as a whole by improving roller wrapping in a subsequent process, fuzz in a stretching process, and quality deterioration due to yarn breakage.

  In order to solve the above problems, the present invention has the following configuration. That is, a method for producing acrylic fibers by dry-wet spinning, in which an acrylic polymer solution is once discharged into an inert atmosphere from a spinneret provided on the top of a coagulation bath liquid and then introduced into the coagulation bath liquid. The method for producing an acrylic fiber is characterized in that the humidity of the gas phase portion formed between the discharge surface of the spinneret in the coagulation bath and the coagulation bath liquid is controlled to 10 to 40% rh.

  In the method for producing acrylic fiber of the present invention, the temperature of the acrylic polymer solution discharged from the spinneret and the atmospheric temperature of the gas phase portion formed between the discharge surface of the spinneret and the coagulation bath liquid are set. It is preferable to control the difference ΔT within a range of ± 10 ° C.

  Moreover, it can apply preferably to the spinneret whose hole number is 2000-24000.

  According to the present invention, in dry and wet spinning, even when the distance between the spinneret and the coagulation bath liquid is less than 20 mm, the condensation is prevented from occurring in the spinneret, the roller winding in the subsequent process, and the fluff in the stretching process. Further, quality deterioration due to yarn breakage can be improved, and for example, productivity and quality can be significantly improved as a whole even under conditions where the hole density is high, for example, exceeding 2000 holes.

It is the schematic of the spinning area | region in which the apparatus which controls the temperature and humidity of the gas supplied to a coagulation bathroom in this invention was installed.

  The acrylic fiber production method of the present invention is based on dry-wet spinning in which an acrylic polymer solution is once discharged into an inert atmosphere from a spinneret provided on the top of the coagulation bath liquid and then introduced into the coagulation bath liquid. A method for producing an acrylic fiber, characterized in that the humidity of the gas phase portion formed between the discharge surface of the spinneret in the coagulation bath and the coagulation bath liquid is controlled to 10 to 40% rh.

  In the present invention, a spinning stock solution in which an acrylic fiber polymer is dissolved in a solvent (hereinafter sometimes simply referred to as “spinning stock solution”) is used. The acrylic polymer refers to a polymer composed of 90% by weight or more of acrylonitrile and a vinyl monomer copolymerizable therewith. As the polymerization method for obtaining the acrylic 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.

  Solvents for dissolving the acrylic polymer include dimethyl sulfoxide (hereinafter referred to as DMSO), dimethylformamide (hereinafter referred to as DMF), dimethylacetamide (DMAc), a zinc chloride aqueous solution (hereinafter ZnCl2aq), a sodium thiosulfate aqueous solution (NaSCNaq). In the dry and wet spinning method, DMSO, DMF or DMAc having a fast solidification rate of the acrylic polymer is preferable, and DMSO having a particularly fast solidification rate is particularly preferable.

  Such an acrylic polymer solution (spinning stock solution) is once discharged into an inert atmosphere from a discharge surface of a spinneret placed on the coagulation bath solution via a gas phase portion, and then introduced into the coagulation bath solution. To form fibers.

In the present invention, it is necessary to control the humidity of the gas in the gas phase formed between the discharge surface of the spinneret in the coagulation bath and the coagulation bath liquid to 10 to 40% rh. This is because when the humidity exceeds 40% rh, the vapor of the solvent tends to condense and condense. As for the lower limit, the lower the better, but the lower limit is 10 in order to adjust the humidity of the coagulation bath in which a large amount of coagulation bath liquid exists, because a large amount of air supply / exhaust equipment is required and the equipment becomes huge. % Rh is good.
Further, in the present invention, the temperature [A ° C.] of the acrylic polymer solution discharged from the spinneret and the atmospheric temperature [B ° C.] of the gas phase portion formed between the discharge surface of the spinneret and the coagulation bath liquid. By controlling the difference ΔT (ΔT = A−B) in the range of ± 10 ° C., it is preferable because the vapor of the solvent becomes difficult to condense. When ΔT is higher than 10 ° C., the vapor in the solvent tends to condense and condensation tends to occur. On the other hand, when ΔT is lower than −10 ° C., it is difficult to control the temperature of the acrylic polymer solution discharged from the spinneret, and the spinning performance may be lowered.

  In the present invention, as a method for controlling the humidity (and temperature), for example, a coagulation bath liquid surface and a spinneret discharge surface are supplied by supplying a gas whose temperature and humidity are indirectly controlled in a partitioned coagulation bathroom. A method for controlling the temperature and humidity of the gas in the gas phase portion between the two. As a specific example, a temperature controller and a humidity controller are provided on the entrance side of the outside air supply fan supplied to the coagulation bathroom, and the temperature is adjusted with the temperature controller, and then the humidity is adjusted to 40% rh or less with the humidity controller. An example of supplying gas into the coagulation bathroom can be given. In this example, in order to control the temperature and humidity of the gas phase part between the coagulation bath liquid and the discharge surface of the spinneret, outside air via the temperature controller and the humidity controller is supplied into the coagulation bathroom, Although the airflow from the upper layer portion to the lower layer portion is made to flow, there is no problem even if the direction of the airflow is reversed depending on the gas supply position. What is required here is to create a certain air flow in the coagulation bath by flowing the gas. By creating this air flow, the temperature and humidity between the coagulation bath liquid and the gas phase part of the discharge surface of the spinneret Is to control.

This will be described in more detail with reference to FIG.
Although FIG. 1 is a specific example, the present invention is not limited to this. The outside air is supplied to the coagulation bathroom 9 by the air supply fan 3 in the figure, but the temperature controller 1 and the humidity controller 2 are installed on the suction side of the air supply fan 3, and the outside air supplied into the coagulation bath is controlled by the temperature controller. It supplies to the inside of the solidification bathroom 9 through a humidity controller. Further, a temperature measuring element 6 for measuring the temperature of the acrylic polymer solution is provided inside the spinneret 5, and a thermometer 7 and humidity are provided at the gas phase portion of the coagulating bath liquid 4 in the coagulation bath and the discharge surface of the spinneret. A total 8 is installed, and based on the temperature and humidity detected here, the temperature controller 1 and the humidity controller 2 can be controlled to arbitrarily change the temperature and humidity in the coagulation bath. Moreover, in order to generate an air flow in the coagulation bath, forced exhaust is performed from the lower part of the coagulation bath 9.

  The polymerization solution discharged from the spinneret 5 generates mist when passing through the gas phase portion between the discharge surface of the spinneret 5 and the liquid surface of the coagulation bath liquid 4. When the dew point of the mist staying in the gas phase part and the gas in the gas phase part is lower than the ambient temperature, no condensation occurs, but when the dew point is high, condensation occurs on the discharge nozzle surface. Also, the minute condensation once adhered absorbs the mist generated constantly from the spinneret and grows further, forming a liquid droplet and coming into contact with the spun yarn, or the discharge surface of the spinneret 5 and the coagulation bath liquid surface. In some cases, the gas phase portion between them is blocked. Such a phenomenon appears more conspicuously as the number of holes of the spinneret 5 exceeds 2000 holes and mist fog from the discharge solution increases. Therefore, it is important to set the atmospheric dew point in the coagulation bath below the dew point of the gas in the gas phase and the generated mist. In addition, since the outside air to be supplied varies depending on the season, the outside air temperature is high in summer, so only the humidity controller is used.In winter, the humidity is low, so only the temperature controller is used. May be obtained. In the present invention, the shape of the spinneret is not particularly limited.

  As the temperature of the acrylic polymer solution (spinning stock solution), a lower temperature is preferable because the amount of evaporation of the solvent is small, and it may be higher than the freezing point of the solvent used in the acrylic polymer solution (spinning stock solution), If the temperature is too low, the viscosity of the acrylic polymer solution (spinning stock solution) increases and the spinnability deteriorates and the operability is lowered. Therefore, the freezing point is higher than the freezing point + 20 ° C or lower, more preferably the freezing point + 5 ° C or higher. It is preferably + 15 ° C. or lower. As the coagulation bath liquid, an aqueous solution of the same solvent as that used for the acrylic polymer solution (spinning stock solution) is usually used. However, since condensation easily occurs particularly in an organic solvent system, an aqueous solution of DMSO, DMF, or DMAc. In particular, the effect of the present invention appears remarkably when using as a coagulation bath liquid. In addition, since condensation is likely to occur due to the vapor of the bath liquid when the temperature of the coagulation bath liquid is high, the temperature of the coagulation bath liquid is preferably 20 ° C. or less, more preferably 10 ° C. or less from the viewpoint of suppressing the occurrence of condensation as much as possible. More preferably, the temperature is set to 7 ° C. or lower. However, if the temperature is too low, the spinnability is deteriorated and the operability is lowered, so that the temperature is 0 ° C. or higher, preferably 1 ° C. or higher.

As the spinneret, in consideration of productivity, a spinneret having a hole number of 2000 holes or more and 24000 holes or less was used, and the occupied area of the die per hole (spinneret area / number of holes) was 5 mm ² or more and 10 mm ² or less. The effect of the present invention is most easily manifested when a product is used. When the number of holes is small or the area occupied by the die per hole is large, the productivity is remarkably reduced, and a sufficient gap is secured in the gas phase part between the spinneret and the coagulation bath liquid during dry / wet spinning. In particular, condensation often does not occur.

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

  A solution having an acrylic polymer content of 18 to 22% by weight is used as the acrylic polymer solution (spinning stock solution) for dry and wet spinning. If the amount of acrylonitrile used in the acrylic polymer is too small, the strength of the carbon fiber obtained by firing the resulting acrylic fiber is low, making it difficult to produce carbon fiber having excellent mechanical properties. There is. In addition, when the content of the polymer in the acrylic polymer solution (spinning stock solution) is small, the content of the solvent is large, and the solvent is present in the gas phase portion between the spinneret and the coagulation bath liquid in dry and wet spinning. A large amount of steam is a factor that causes condensation. Conversely, when the polymer content is too high, the solvent vapor amount is small, but when the acrylic polymer is polymerized, the viscosity increases and the gelation accelerates, so dry and wet spinning is performed. In this case, the discharge hole of the spinneret is prevented, causing fiber adhesion, fineness unevenness, and single fiber breakage, causing roller wrapping in the subsequent process, fluffing in the stretching process, and thread breakage, operability and quality. It becomes a factor to reduce.

  The present invention can be suitably used when the number of filaments per fiber bundle is usually in the range of 2000 to 24000, and the single fiber fineness is usually in the range of 0.5 to 3.3 dtex. The fiber bundle fiberized in the coagulation bath may be stretched directly in the stretching bath, or may be stretched in the bath after the solvent is washed away with water. The stretching in the bath is preferably stretched about 1.5 to 6 times in a bath at 40 to 98 ° C.

  Furthermore, it is preferable to apply a silicone oil after stretching in the bath. As the method for applying the oil agent, specifically, means such as a dipping method, a kiss roller method, a guide oiling method and the like are employed. The amount of silicone oil to be applied is preferably 0.01 to 8% by weight, more preferably 0.02 to 5% by weight, and still more preferably 0.1 to 3% by weight. If the amount of such adhesion is small, the quality of the carbon fibers that can cause fusion between single fibers may be reduced. If the amount is too large, the operability deteriorates due to an increase in the amount of oil dropout in the spinning and firing processes. Degradation due to oil adhesion spots in the process may occur.

  The yarn provided with the oil agent can be dried and densified in the fiber bundle by drying with at least one hot drum or the like. A higher drying temperature is preferable because the crosslinking reaction of the silicone oil agent is promoted. Specifically, the drying temperature is preferably 150 ° C or higher, and more preferably 180 ° C or higher.

  Furthermore, the fiber bundle after drying and densification can also be heat-treated while further drawing in a high-temperature environment such as in pressurized steam, if necessary. By such heat treatment, the oil agent spreads uniformly and the effect of preventing the occurrence of surface defects due to adhesion between single fibers is increased, and a fiber bundle having more preferable fineness and crystal orientation can be obtained. The steam pressure, temperature, draw ratio, etc. at the time of drawing may be appropriately selected and used within a range not causing yarn breakage and fluff generation.

  The fiber bundle obtained in this manner can produce carbon fibers having excellent economic efficiency by appropriately selecting and firing the firing conditions according to the application and physical properties.

  Hereinafter, the present invention will be described more specifically with reference to examples. The degree of condensation on the base surface used in this example was determined as follows. That is, the size 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 (Examples 1 to 7)
A 20 wt% DMSO solution of an acrylic polymer having an intrinsic viscosity [η] of 1.8 consisting of 99 wt% acrylonitrile and 1 wt% itaconic acid was prepared by solution polymerization.

  The obtained acrylic polymer solution (spinning stock solution) was discharged into the air from the discharge surface of the spinneret using a base having a total number of 4000 stock solution discharge holes, and allowed to pass through a gas phase portion having a distance of about 5 mm. Thereafter, the solution was discharged into a coagulation bath liquid consisting of 35% by weight of DMSO / 65% by weight of water to obtain coagulated fibers.

Here, in Examples 1 to 6, the outside air supplied into the coagulation bathroom was heated to the temperature shown in Table 1 with a temperature controller, and the outside air whose humidity was controlled to the humidity shown in Table 1 with a humidity controller was 500 Nm ³ / Supplied in hr. Moreover, 500 Nm < ³ > / hr forced exhaustion was carried out with the exhaust fan from the lower part in the solidification bathroom. The temperature of the acrylic polymer solution (spinning solution) was controlled to 30 ° C., which is 11.6 ° C. higher than the freezing point of DMSO, and the temperature of the coagulation bath solution was controlled to 5 ° C. Further, in the examples, a base having a total number of stock solution discharge holes of 4000 is used, and a stock solution is discharged so that the discharge amount of the acrylic polymer solution (spinning stock solution) becomes a single fiber fineness of 1.1 dtex. Table 1 shows the degree of condensation.

The obtained coagulated fiber was subsequently washed with water, then stretched 3 times in warm water at 70 ° C., and further passed through an oil agent bath to give a silicone oil. The silicone oil component was a water emulsion system containing amino-modified silicone, epoxy-modified silicone and alkylene oxide-modified silicone. The concentration in the oil bath was adjusted by diluting with water so that the pure content was 2.0% by weight. Furthermore, the drying process for 40 second of contact time was performed using the 180 degreeC heating roller. The obtained dried yarn was stretched about 5 times in a pressurized steam of 0.4 MPa-G to obtain a total yarn drawing ratio of about 13 times to obtain an acrylic precursor fiber.
(Comparative Examples 1-2)
Acrylic system was used in the same manner as in the examples except that the supplied outside air was heated to the temperature shown in Table 1 with a temperature controller and further controlled to supply the humidity (forced deterioration condition) shown in Table 1 with a humidity controller. Precursor fibers were obtained. The degree of condensation on the discharge surface of the spinneret is shown in Table 1.

  As shown in Table 1, it can be seen that the present invention can suppress condensation on the discharge surface of the spinneret.

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

DESCRIPTION OF SYMBOLS 1 Temperature controller 2 Humidifier 3 Supply fan 4 Coagulation bath liquid 5 Spinneret 6 Temperature sensor 7 Thermometer 8 Hygrometer 9 Coagulation bathroom 10 Acrylic fiber

Claims (3)

  A method for producing acrylic fibers by dry-wet spinning in which an acrylic polymer solution is discharged from a spinneret provided at the top of a coagulation bath liquid into an inert atmosphere and then introduced into the coagulation bath liquid. A method for producing an acrylic fiber, characterized in that the humidity of a gas phase portion formed between a discharge surface of a spinneret in a bath and a coagulation bath liquid is controlled to 10 to 40% rh.   The difference ΔT between the temperature of the acrylic polymer solution discharged from the spinneret and the atmospheric temperature of the gas phase formed between the discharge surface of the spinneret and the coagulation bath liquid is controlled within a range of ± 10 ° C. 2. A method for producing an acrylic fiber according to 1.   The method for producing an acrylic fiber according to claim 1 or 2, wherein the spinneret has 2000 to 24000 holes.

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