JP2008075205A - Method and apparatus for stretching fiber by using pressurized steam, and method for producing acrylic precursor fiber bundle for carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stretching a fiber, which is capable of suppressing the formation of fluffs even if performing high magnitude stretching, obtaining a fiber of a thin-fineness, and obtaining a fiber bundle having a large total fineness, etc., and especially suitable for actually producing an acrylic precursor fiber bundle for carbon fibers, and a stretching apparatus using pressurized steam. <P>SOLUTION: The method for controlling the temperature of the fiber bundle introduced into a stretching bath, and the water content, pressure, and temperature of the pressurized steam so as to condense the pressurized steam supplied into the stretching bath of the stretching apparatus using pressurized steam on the surface of the fiber bundle introduced into the stretching bath and stretch the fibers by the plastisizing effect of the condensed water formed on the surface of the fiber bundle, and the stretching apparatus using pressurized steam, which is capable of controlling them are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fiber drawing method and a drawing device, and more particularly to a drawing method and a pressure steam drawing device for drawing a fiber bundle using pressurized steam. Moreover, this invention relates to the manufacturing method of the acrylic precursor fiber bundle for carbon fibers which has a pressurization steam extending process.

  As a drawing method performed at the fiber production stage, a drawing method using pressurized steam is conventionally known. This is because a temperature higher than that of hot water under atmospheric pressure can be obtained, and the presence of moisture produces a plasticizing effect of the fiber polymer and enables stretching at a high magnification. In particular, acrylic fiber bundles used as carbon fiber precursors, unlike other thermoplastic fibers, have no melting point and cannot be stretched by the effect of heat alone. Is often applied to the stretching of acrylic fibers.

  However, in the case of subjecting the fiber to steam stretching, problems such as generation of fuzz may occur in the case of stretching at a high magnification, in the case of obtaining a fine fiber, in the case of obtaining a fiber bundle having a large total fineness, etc. there were.

Patent Document 1 proposes to use steam having a dryness of 0.7 to 1.0. Patent Documents 2 and 3 propose that the wetness of steam, in other words, the dryness, is adjusted so that the moisture content of the fiber bundle after being stretched is within a certain range. In Patent Document 4, the temperature T ₁ (° C.) and the saturation temperature T ₂ (° C.) of the pressurized steam used are controlled to satisfy T ₂ <T ₁ <T ₂ +3, in other words, this condition is satisfied. It has been proposed to adjust the dryness of the pressurized steam.
JP 2000-345429 A JP-A-8-158162 JP 58-214521 A Japanese Patent Laid-Open No. 10-292240

  However, fluffing may still occur even if the dryness of steam is adjusted as in the methods of Patent Documents 1 to 4.

  The object of the present invention is to suppress the occurrence of fluff even when drawing at a high magnification, obtaining a fine fiber, obtaining a fiber bundle having a large total fineness, etc., and producing high-quality fibers, particularly carbon fibers. Another object of the present invention is to provide a fiber drawing method suitable for actual production of an acrylic precursor fiber bundle for use.

  Another object of the present invention is to suppress the occurrence of fluff even when stretching at a high magnification, when obtaining a fine fiber, when obtaining a fiber bundle having a large total fineness, etc., and for fibers, particularly carbon fibers. An object of the present invention is to provide a pressurized steam drawing apparatus capable of maintaining the quality of an acrylic precursor fiber bundle high and stably.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the generation of fluff, stretching, and loops are caused by minute water droplets in the steam colliding with the fibers and damaging the fibers. I thought because. Then, by condensing the pressurized steam supplied to the pressurized steam stretching apparatus on the surface of the fiber introduced into the pressurized steam stretching apparatus, it is avoided that minute water droplets in the pressurized steam collide with the fibers. And it has been found that it is extremely effective to stretch due to the plasticizing effect of the heated water generated on the surface of the fiber, leading to the present invention.

  The present invention relates to a method for stretching an acrylic fiber bundle for carbon fibers by stretching the acrylic fiber bundle for carbon fibers with pressurized steam, and the stretching of the pressurized steam supplied into a stretching tank of a pressurized steam stretching apparatus is performed. Condensed on the surface of the acrylic fiber bundle for carbon fibers introduced into the tank, and stretched by the plasticizing effect of the condensed water generated on the surface of the acrylic fiber bundle for carbon fibers A method for drawing an acrylic fiber bundle is provided.

More specifically, the following methods for stretching an acrylic fiber bundle for carbon fibers are provided.
(1) Dry saturated steam or superheated steam is used as the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus, and the temperature of the acrylic fiber bundle for carbon fiber introduced into the drawing tank is T ₁ ( C.), and the temperature of the pressurized steam is T ₂ (° C.), and the temperature is controlled so as to satisfy 80 ≦ T ₁ <T ₂ .
(2) Acrylic fiber for carbon fiber introduced into the drawing tank using wet steam having a dryness of 0.9 or more and less than 1.0 as the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus. The acrylic precursor fiber bundle for carbon fibers is temperature-controlled so as to satisfy 80 ≦ T ₁ <T ₃ when the bundle temperature is T ₁ (° C.) and the pressure steam temperature is T ₃ (° C.). Stretching method.

The present invention is a pressurized steam stretching apparatus for stretching a plurality of acrylic fiber bundles for carbon fibers arranged in parallel by pressurized steam,
A drawing tank capable of maintaining the inside in a pressurized state by a labyrinth seal portion provided at the inlet and outlet of the acrylic fiber bundle for carbon fiber;
Stretching rollers arranged on the upstream side and downstream side of the stretching tank;
Means for controlling the surface temperature of the stretching roller disposed on the upstream side of the stretching tank;
A detector for detecting the temperature of the acrylic fiber bundle for carbon fibers introduced into the drawing tank from the inlet portion;
A pressurized steam supply means for supplying pressurized steam into the stretching tank;
There is provided a pressurized steam stretching apparatus characterized by comprising:

  This invention provides the manufacturing method of the acrylic precursor fiber bundle for carbon fibers characterized by using the pressurized steam drawing apparatus of this invention.

  According to the present invention, when high-stretching is performed, when obtaining fine fibers, when obtaining a fiber bundle having a large total fineness, generation of fluff can be suppressed, and high-quality fibers, particularly carbon fiber acrylics. A fiber drawing method suitable for actual production of a system precursor fiber bundle is provided. At the same time, it is possible to suppress process troubles such as stretching and looping.

  According to the present invention, when high-stretching is performed, when a fine fiber is obtained, or when a fiber bundle having a large total fineness is obtained, generation of fluff can be suppressed, and an acrylic precursor for fibers, particularly carbon fibers. There is provided a pressurized steam drawing apparatus capable of maintaining the quality of a fiber bundle high and stably. At the same time, it is possible to suppress process troubles such as stretching and looping.

  Furthermore, by producing the acrylic precursor fiber bundle for carbon fiber using the present invention, and further producing the carbon fiber, it can be obtained by suppressing generation of fluff in the flameproofing process and the carbonization process. The quality of carbon fiber can be improved.

  Hereinafter, the present invention will be described in detail.

  The stretching of fibers by pressurized steam is said to be possible at a higher temperature than hot water under atmospheric pressure, and the presence of water produces the plasticizing effect of the fiber polymer, enabling stretching at a high magnification. Conventionally, wet steam, in which liquid water (simply referred to as “water”) and gaseous water (referred to as “steam”), which are microscopic water droplets, coexist, is used for fiber stretching by pressurized steam. Yes. Stretching is performed by the plasticizing effect using the water in the wet steam, that is, the high-temperature water at 100 ° C. or higher because it is in a pressurized state. However, in some cases, fine water droplets in the pressurized steam collide with the fiber and damage the fiber.

  Here, in addition to the wet steam, in the pressurized steam, the dry steam corresponding to the state in which the wet steam is heated to become completely steam and does not contain water, and the dry saturated steam is heated to a high temperature state. There is superheated steam corresponding to. And hot water is produced | generated also by condensing wet steam, dry saturated steam, and superheated steam.

  FIG. 5 is a graph showing the relationship between supplied heat energy and temperature. In the region on the left side of the figure where the temperature rises as the supply heat energy increases, the form of water is liquid.

  And in the area | region where temperature is constant even if supply heat energy is increased, except for the start point and the end point, the form of water is a gas of wet steam having a dryness greater than 0 and less than 1.0. This constant temperature is called the saturation temperature. The saturation temperature increases with increasing pressure. The dryness at the start point is 0, and the dryness at the end point is 1.0. When all the water is changed to steam, that is, steam with a dryness of 1.0 is called dry saturated steam.

  Further, in the region on the right side of the end point of the region where the temperature is constant, the temperature rises as the supplied heat energy increases. In this region, the form of water is superheated steam (gas).

  In the present invention, this condensation is caused on the surface of the fiber, so that water necessary for plasticization can be given to the acrylic fiber bundle. It is also possible to avoid the minute water droplets in the pressurized steam from colliding with the fibers. Furthermore, since heat transfer by condensed water is more efficient than heat transfer by contact of water in wet steam, the heat transfer effect and the plasticizing effect of hot water can be efficiently extended. As a result, it is possible to prevent the occurrence of fluff, process troubles such as drawing breaks, and the occurrence of loops, and the fiber quality can be maintained high and stably.

  Suitable conditions for performing such stretching will be described below.

  First, in the present invention, it is important to use wet steam having a dryness of 0.9 or more and less than 1.0, or dry saturated steam or superheated steam. That is, the water contained in the pressurized steam is highly likely to cause a so-called drain attack that damages the fiber, and further inhibits the heat transfer of the condensed water of the pressurized steam, There is a high possibility that the spot where water adheres becomes a heating spot. If the wet steam has a dryness of 0.9 or more and less than 1.0, or if it is dry saturated steam or superheated steam, the amount of water contained in the pressurized steam is small or substantially no water exists. It becomes difficult to occur. In the case of wet steam, the dryness is preferably 0.9 or more, more preferably 0.95 or more.

  In the present invention, temperature control is also important.

  For example, the stretching of an acrylic fiber bundle by pressure steam is conventionally introduced into a pressure steam stretching apparatus immediately after being dried and densified by a heating roller or the like. Therefore, the temperature of the acrylic fiber bundle is determined by the temperature at the time of drying and densification and the thermal history until it is introduced into the pressurized steam drawing apparatus. If the temperature of the acrylic fiber bundle introduced into the pressurized steam drawing apparatus is higher than or equal to the temperature of the pressurized steam, the water will undergo phase transformation when the pressurized steam contacts the acrylic fiber bundle. It is difficult to break, that is, it is considered that efficient condensation does not occur, and it is considered that water necessary for plasticization is hardly given to the acrylic fiber bundle. On the other hand, when the temperature of the acrylic fiber bundle introduced into the pressurized steam drawing apparatus is lower than the temperature of the pressurized steam, the steam condenses upon contact with the acrylic fiber bundle, that is, accompanied by a phase transformation of water. Condensation is considered to occur easily, and water necessary for plasticization is considered to be easily given to the acrylic fiber bundle.

  By making the temperature of the fiber bundle lower than the pressure steam temperature in this way, it is possible to stretch by efficiently applying heat by plasticization with water generated by condensation and heat transfer performed efficiently during condensation. It becomes. By stretching in this way, the water and energy in the pressurized steam can be utilized to the maximum, and the influence of the drain attack of the water contained in the pressurized steam and the inhibition of heat transfer due to the presence of water can be suppressed. . As a result, when stretching at a high magnification, when obtaining fine fibers, even when obtaining a fiber bundle with a large total fineness, it is possible to prevent occurrence of fuzz, process troubles such as stretch breaks, and occurrence of loops, The fiber quality can be kept high and stable.

Specifically, when dry saturated steam or superheated steam is used as the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus, the temperature of the fiber bundle introduced into the drawing tank is T ₁ ( C), and the temperature of the pressurized steam is preferably T ₂ (° C.), the temperature is preferably controlled so as to satisfy 80 ≦ T ₁ <T ₂ . T ₁ (° C.) of 80 ° C. or higher is preferable because sufficient energy can be obtained for plasticizing with hot water. T ₁ (° C.) is more preferably higher than 80 ° C., and more preferably 90 ° C. or higher. Further, if T ₁ <T ₂ , the pressurized steam can be condensed on the surface of the fiber, which is preferable. The larger the temperature difference between T ₁ and T ₂ , the more efficiently and uniformly the pressurized steam can be condensed on the surface of the fiber bundle. Therefore, T ₁ ≦ T ₂ −3 is more preferable, and T ₁ <T ₂ -3 is more preferable, T ₁ ≦ T ₂ -10 is particularly preferable, and T ₁ ≦ T ₂ -20 is most preferable. T ₂ (° C.) is selected from, for example, 100 to 180 ° C.

Further, wet steam having a dryness of 0.9 or more and less than 1.0 is used as the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus, and the temperature of the fiber bundle introduced into the drawing tank is T _1. When the temperature of the pressurized steam is T ₃ (° C.), it is preferable to control the temperature so that 80 ≦ T ₁ <T ₃ is satisfied. T ₁ (° C.) of 80 ° C. or higher is preferable because sufficient energy can be obtained for plasticizing with hot water. T ₁ (° C.) is more preferably higher than 80 ° C., and more preferably 90 ° C. or higher. Further, if T ₁ <T ₃ , it is preferable because the pressurized steam can be condensed on the surface of the fiber bundle. The larger the temperature difference between T ₁ and T ₃ , the more efficiently and uniformly condensing the pressurized steam on the surface of the fiber bundle, T ₁ ≦ T ₃ −3 is more preferable, and T ₁ <T ₃ −3 is more preferable, T ₁ ≦ T ₃ −10 is particularly preferable, and T ₁ ≦ T ₃ −20 is most preferable. T ₃ (° C.) is selected from 100 to 180 ° C., for example.

  By adopting the preferred embodiment as described above, the relationship between the temperature of the fiber bundle introduced into the drawing tank of the pressurized steam drawing apparatus and the amount of water given to the acrylic fiber bundle by condensation of the pressurized steam is shown in FIG. As shown.

  The pressure of the pressurized steam can be appropriately set to a pressurized state, that is, a pressure higher than the atmospheric pressure, and is not particularly limited as long as it meets the purpose. That is, it is appropriately adjusted depending on the type of fiber to be drawn, the treatment state in the pre-steam drawing process, or the desired fiber characteristics. For example, it can be adjusted to 20 to 1,000 kPa (gauge pressure).

  The range in which the fiber stretching method of the present invention can be applied is not particularly limited depending on the process or the like, but in the production of an acrylic precursor fiber bundle for carbon fibers, a plurality of parallel acrylic fiber bundles are stretched by pressurized steam. It is effective in the case. Moreover, when extending | stretching by high magnification (for example, 10-20 times), when obtaining the fiber of fineness (for example, 0.01-1.5 dtex), a fiber bundle (for example, 30,000- This is effective in obtaining 300,000 dtex).

  When introducing the acrylic precursor fiber bundle for carbon fiber into the steam drawing machine, it is preferable to spread it into a tape shape. This width is preferably the width shown by the following calculation formula because damage to the acrylic precursor fiber bundle for carbon fibers can be suppressed.

  Here, Y is the width (mm) of the acrylic precursor fiber bundle for carbon fibers introduced into the steam drawing machine, and d is the total fineness (dtex) of the acrylic precursor fiber bundle for carbon fibers after steam drawing. . Table 1 below shows a specific calculation example.

  A well-known process in the field of fiber manufacture can be appropriately performed before and after the fiber stretching by the pressure steam.

  For example, when producing an acrylic precursor fiber bundle for carbon fiber, a solution obtained by dissolving a homopolymer of acrylonitrile as a raw polymer or an acrylonitrile copolymer containing a comonomer in a known organic or inorganic solvent is spun. Then, when stretching, the stretching method of the present invention can be performed. The spinning method may be any of so-called wet, dry wet, and dry processes, and solvent removal, stretching in a bath, oil agent adhesion treatment, drying, and the like can be performed in subsequent steps. The steam drawing of the acrylic fiber bundle may be carried out at any stage. However, in the case of solution spinning, it is preferable to remove the solvent in the acrylic fiber bundle to some extent, that is, after washing or drawing in a bath, or after drying. From the viewpoint of obtaining highly oriented acrylic fiber bundles, after drying is more preferable. In the steam drawing of an acrylic fiber bundle, a plurality of acrylic fiber bundles arranged in parallel are usually drawn by pressurized steam. By doing so, it becomes possible to produce a high-quality acrylic precursor fiber bundle for carbon fibers free from fluff, yarn breakage, and loops.

  Furthermore, by firing the obtained acrylic precursor fiber bundle for carbon fibers by a known technique (flame resistance or carbonization), it becomes possible to produce high-quality carbon fibers free from fluff, yarn breakage, and loops.

In the present invention, it is important to control the temperature of the acrylic acrylic fiber bundle for carbon fibers introduced into the pressurized steam drawing apparatus and the properties and temperature of the steam supplied to the pressurized steam drawing apparatus. Therefore, as a pressure steam stretching apparatus suitable for stretching the acrylic fiber bundle for carbon fibers according to the present invention,
A drawing tank capable of maintaining the inside in a pressurized state by a labyrinth seal portion provided at the inlet and outlet of the acrylic fiber bundle for carbon fiber;
Stretching rollers arranged on the upstream side and downstream side of the stretching tank;
Means for controlling the surface temperature of the stretching roller disposed on the upstream side of the stretching tank;
A detector for detecting the temperature of the acrylic fiber bundle for carbon fibers introduced into the drawing tank from the inlet portion;
A pressurized steam supply means for supplying pressurized steam into the stretching tank;
The apparatus which has is mentioned.

  As a drawing tank of the pressurized steam drawing apparatus, a tube-like or box-like container having a fiber bundle inlet and outlet provided with a steam sealing mechanism can be used. A box-shaped container is preferable from the viewpoint of easily processing a plurality of parallel fiber bundles at the same time, and the steam sealing mechanism is an inlet portion of the fiber bundle from the viewpoint of easily suppressing the amount of pressurized steam leakage. Further, it is preferable to use a labyrinth seal portion provided at the outlet portion and capable of maintaining the inside in a pressurized state.

  Control of the temperature of the acrylic fiber bundle immediately before being introduced into the pressure steam drawing apparatus is controlled by the temperature of the drawing roller of the pressure steam drawing apparatus, control by spraying water, air or steam onto the acrylic fiber bundle. It is possible to perform control by, for example, providing a hot water bath immediately before the pressure steam drawing apparatus and guiding an acrylic fiber bundle to the hot water bath. Especially, it is preferable to carry out by controlling the surface temperature of the extending | stretching roller of a pressurizing steam extending | stretching apparatus to the preset range. As a method of controlling the surface temperature of the stretching roller within a preset range, a method of controlling the temperature of steam, hot water, and oil supplied to the stretching roller as a jacket roller is preferable. Further, a method of controlling the current value to be supplied by using the stretching roller as an electric heating roller is also preferable. From the viewpoint of effective use of heat, it is particularly preferable to use a stretching roller as a jacket roller and control the pressure of steam supplied thereto.

  If water or steam is sprayed on the acrylic fiber bundle, or if the acrylic fiber bundle is guided to the hot water bath, water is given to the acrylic fiber bundle, and the water impedes heat conduction by the pressurized steam. There is a case. When air is sprayed onto the acrylic fiber bundle, the width of the acrylic fiber bundle increases in the steam drawing apparatus, and as a result, the number of acrylic fiber bundles that can be introduced into the steam drawing apparatus may be limited. The method of controlling the surface temperature of the drawing roller of the pressure steam drawing apparatus to a preset range is preferable in that the acrylic fiber bundle can be put into the steam drawing apparatus without hindering heat conduction by the pressure steam with water. It is also preferable in that each of the plurality of acrylic fiber bundles arranged in parallel can be set to a uniform temperature. Further, a heat insulating cover or the like may be installed between the drawing roller and the pressure steam drawing device to prevent heat radiation of the acrylic fiber bundle.

  Examples of means for detecting the temperature of the acrylic fiber bundle immediately before being introduced into the pressure steam drawing apparatus include a contact-type surface thermometer, a non-contact type radiation thermometer, and a non-contact type infrared thermal imager. It is done. However, the contact-type thermometer is preferably a non-contact-type thermometer because damage to the acrylic fiber bundle due to contact may cause yarn breakage and fluff. For example, when the temperature of an acrylic fiber bundle is detected using a non-contact type radiation thermometer, one acrylic fiber among a plurality of parallel acrylic fiber bundles introduced into a pressurized steam drawing apparatus The temperature detected for the bundle may be used as the representative value, or may be the average value of the temperatures detected for the plurality of acrylic fiber bundles. In the case of a non-contact type infrared thermal imaging apparatus, the temperature detected for one acrylic fiber bundle from the obtained image may be used as a representative value, or the average value of the temperatures detected for a plurality of acrylic fiber bundles. Also good.

  As the pressurized steam supply means for supplying the pressurized steam into the stretching tank, one capable of supplying pressurized steam having a desired water content, pressure and temperature is appropriately selected. For example, having a plurality of pressure reducing valves, heat exchangers, drain traps, or drain traps, pressure reducing valves, having a plurality of heat exchangers, steam pressure control valves, water amount control valves, drains A device having a trap and an atomizer can be used as a pressurized steam supply device. From the viewpoint of stabilizing the dryness of steam and the temperature of supplied steam, those having a steam pressure control valve, a water amount control valve, a drain trap, and an atomizer are preferable. Supply of pressurized steam to the pressurized steam drawing chamber in the drawing tank was installed in the pressurized steam drawing chamber in the drawing tank, or the structure that prevents the fiber bundle from directly hitting the fiber bundle through the perforated plate. It can be set as the structure connected to the steam ejection header by steam piping. A configuration in which steam is uniformly applied to each of a plurality of fiber bundles introduced into the pressurized steam drawing chamber, and is connected to a steam ejection header installed in the pressurized steam drawing chamber in the drawing tank by a steam pipe. Is preferable. In addition, a dryness meter can be installed at a position where the dryness of the pressurized steam to be supplied can be measured.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(Evaluation of fuzz generation frequency in acrylic precursor fiber bundle for carbon fiber)
The acrylic precursor fiber bundle for carbon fibers is measured by measuring the number of fluffs generated per hour in a plurality of running acrylic precursor fiber bundles for carbon fibers drawn out from the pressurized steam drawing apparatus. The average number of occurrences per bottle was calculated. Table 2 shows the evaluation criteria. The average number of fluff occurrences was determined by the following formula.

    (Average number of fluff occurrences) = (total number of fluffs generated per hour in a plurality of running acrylic precursor fiber bundles for carbon fibers drawn out from a pressurized steam drawing apparatus) / (additional) Number of acrylic precursor fiber bundles for carbon fibers charged into the pressure steam drawing apparatus)

(Amount of water given to the acrylic precursor fiber bundle for carbon fiber from pressurized steam)
The fiber bundle immediately after being drawn out from the pressure steam drawing apparatus is sampled for 1 meter, dried in a hot air circulating dryer at 105 ° C. for 1 hour, and the moisture content of the fiber bundle is measured. The amount of water given to the acrylic precursor fiber bundle for fibers was used.

Moisture content (mass%) = (weight of fiber bundle before drying−weight of fiber bundle after drying) ÷ (weight of fiber bundle after drying) × 100
(Evaluation of fluff frequency in carbon fiber bundles)
In one running carbon fiber bundle coming out of the carbonization furnace, the fluff generated visually is observed every 1 to 3 minutes, and the occurrence of the fluff is “none”, “somewhat”, “somewhat” , Classified into four stages of “many”, and scored 3, 2, 1, 0 points for each. Observation was performed at n = 25 per carbon fiber bundle, and the average value was calculated. Table 3 shows the evaluation criteria. In addition, it has shown that the favorable carbon fiber bundle with few fuzz is obtained, so that an average value is high.

(Pressurized steam stretcher)
FIG. 2 is a schematic diagram showing the pressurized steam stretching apparatus used in the examples, and FIG. 4 is a schematic sectional view showing an example of the inside of the stretching tank of the pressurized steam stretching apparatus.

  This pressurizing steam drawing apparatus has a box-type drawing tank 1 that can be divided in a plane including a traveling path of fiber bundles. Inside the drawing tank 1, there are a fiber bundle inlet part and a fiber bundle outlet part. The labyrinth seal portion 11 is provided, and a box-type stretching chamber 13 that can be maintained in a pressurized state is formed. In this apparatus, the cross section of the running path of the fiber bundle in the labyrinth seal portion 11 is a slit shape, and the labyrinth seal portion 11 has a labyrinth nozzle made of a plate piece perpendicular to the running direction of the fiber bundle from the inner wall surface of the labyrinth seal portion 11. And is arranged in multiple stages in the running direction of the fiber bundle. The ratio (L / P) of the length L extending from the inner wall surface of the labyrinth nozzle to the pitch P between the front and rear nozzles is 0.5, and the number of stages of the labyrinth nozzles is the front and rear labyrinth seal portion. Both have 80 stages. The slit shape of the cross section of the fiber bundle traveling path has a ratio (H / W) of the horizontal width W to the height H of the traveling path cross section of 1/200.

  In the drawing chamber 13 in the drawing tank 1, a pair of ladder-like steam jetting headers 9 as shown in FIG. 3 are arranged on the entire surface at positions where steam is jetted toward the fiber bundle. The ladder-like steam ejection header 9 is provided with a large number of steam ejection holes 12 equally on the fiber bundle traveling surface side, and has two steam supply pipes 14 on the opposite side of the fiber bundle traveling surface. The diameter of the steam ejection hole 12 here is 3 mm, and steam can be ejected in a direction perpendicular to the fiber bundle.

  A pressurized steam supply device 3 is connected to the steam supply pipe 14. The pressurized steam supply device 3 includes a steam pressure adjusting valve 3a, a water amount adjusting valve 3b, a drain trap 3c, and an atomizer 3d, and a pressurized steam having a desired water content, pressure, and temperature is prepared. The dryness of the pressurized steam is measured by a dryness meter 3e. As a dryness meter 3e, Ogawa Sampling Co., Ltd. O.D. S. K129 type (product name) is installed. Thus, the steam supply device 3, the steam supply pipe 14, and the steam ejection header 9 constitute a pressurized steam supply means.

  On the other hand, a jacket roller 2 as a stretching roller is disposed on the upstream side and the downstream side of the stretching tank 1. A heat medium supply pipe 4 is connected to the jacket roller 2 and can be heated by supplying steam, hot water, oil or the like. In the vicinity of the fiber bundle inlet of the drawing tank 1, a heat insulating cover 8 and a thermometer 6 for detecting the temperature of the fiber bundle 7 immediately before being introduced from the fiber bundle inlet are arranged. As the thermometer 6, a non-contact type radiation thermometer (manufactured by Konica Minolta, trade name: HT-10D) is installed.

  The fiber bundle 7 is introduced from the fiber bundle inlet portion formed in the front wall portion of the drawing tank 1 by the rotation of the jacket roller 2, and the running path extending over the entire length of the drawing tank 1 is arranged in parallel in a sheet shape in the horizontal direction. Run. The pressurized steam 10 is uniformly supplied into the drawing chamber 13 of the drawing tank 1, and the fiber bundle 7 is drawn at a predetermined draw ratio in the drawing chamber 13 maintained at a predetermined pressure. Thereafter, the fiber bundle 7 drawn from the fiber bundle outlet formed on the rear wall of the drawing tank 1 is led out.

  The pressurized steam supplied into the stretching chamber 13 of the stretching tank 1 is set to a predetermined pressure by the steam pressure control valve 3a, excess water is removed by the drain trap 3c, and the water amount control valve 3b and the atomizer 3d are further removed. The water can be supplied from and adjusted to the desired water content, pressure and temperature.

  The surface temperature of the jacket roller can be set to a predetermined temperature by adjusting the pressure of the supplied steam. Further, with respect to the jacket roller 2 disposed immediately before the upstream side of the stretching tank 1, the steam pressure can be set separately from the other jacket rollers by the pressure reducing valve 5, and the surface temperature can be set to a predetermined temperature. .

(Example 1)
An acrylic copolymer obtained by copolymerizing 96% by mass of acrylonitrile, 1% by mass of methacrylic acid, and 3% by mass of acrylamide was dissolved in dimethylacetamide to prepare a spinning dope (polymer concentration 21% by mass, temperature 60 ° C.). This spinning dope was wet-spun into a dimethylacetamide aqueous solution having a temperature of 35 ° C. and a concentration of 66% by mass from six nozzles having a diameter of 0.065 mm and a pore number of 12,000 to obtain a coagulated yarn. The cross-sectional shape of the coagulated yarn was almost a perfect circle. The coagulated yarn was subjected to cold drawing and hot water drawing, and then immersed in a 1% by weight aqueous solution of an aminosilicone oil and dried and densified with a roller having a surface temperature of 180 ° C. The wet heat draw ratio so far is 3.5 times.

  Subsequently, pressurized steam stretching was performed by a pressurized steam stretching apparatus having the configuration shown in FIG. The surface temperature of the jacket roller immediately before the stretching tank was adjusted to 162 ° C. by changing the steam pressure supplied to the jacket roller with a pressure reducing valve. Subsequently, the temperature of the fiber bundle entering the drawing tank was set to 95 ° C. by passing through a space covered with a heat insulating cover installed between the drawing roller and the pressure steam drawing apparatus to control the heat radiation of the fiber bundle. Regarding the temperature, one of the six fiber bundles was measured with a radiation thermometer. Further, by adjusting the amount of water supplied from the atomizer, the steam supplied into the stretching tank was adjusted to 133 ° C. dry saturated steam (gauge pressure: 212 kPa). Under such conditions, the pressure steam stretching was performed so that the stretching ratio was 10.0 times in total, and the surface temperature of the stretching roller disposed on the downstream side of the pressure steam stretching apparatus was set to 185 ° C. and heat setting was performed. At the same time, the moisture content of the fiber bundle was reduced to substantially 0% by mass and then gradually cooled to obtain an acrylic precursor fiber bundle for carbon fibers. At this time, the fiber bundle immediately after being drawn out from the pressure steam drawing apparatus was collected and the moisture content was measured. The moisture content was 25% by mass. The generation of fluff was very small, and the steam could be stretched stably.

The obtained acrylic precursor fiber bundle for carbon fiber was fired to obtain a carbon fiber bundle. Specifically, the acrylic precursor fiber bundle for carbon fiber is heated to tension in air at 230 to 260 ° C. to be converted into a flame-resistant fiber bundle having a density of 1.36 g / cm ³ , and further, 700 ° C. Pre-carbonization treatment was performed by tensioning in nitrogen to obtain a pre-carbonized fiber bundle. The heating rate at 300 to 500 ° C. in the pre-carbonization treatment was 200 ° C./min. The obtained pre-carbonized fiber bundle was carbonized at 1,450 ° C. in a carbonization furnace, and a sizing agent was applied after the surface treatment to obtain a carbon fiber bundle. In addition, the temperature increase rate in 1,000-1200 degreeC was 400 degreeC / min. The generation of fluff was very small, and a carbon fiber bundle could be produced stably.

  Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Example 2)
The same procedure as in Example 1 was performed except that the amount of water supplied from the atomizer was adjusted so that the supplied steam was adjusted to 140 ° C. superheated steam (gauge pressure: 212 kPa). The temperature of the fiber bundle entering the drawing tank was 95 ° C. The production of the acrylic precursor fiber bundles for carbon fibers and the carbon fiber bundles produced very little fluff and was able to be stably stretched with steam. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Example 3)
Except for adjusting the amount of water supplied from the atomizer, the steam supplied to the pressurized steam stretching apparatus was adjusted to 133 ° C. wet steam (gauge pressure: 212 kPa) with a dryness meter of 0.95. 1 was carried out. The temperature of the fiber bundle entering the drawing tank was 95 ° C. There was little generation of fluff at the production stage of the acrylic precursor fiber bundle for carbon fiber and the carbon fiber bundle, and the steam could be stably stretched. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Comparative Example 1)
It was carried out in the same manner as in Example 1 except that the steam roller supplied to the jacket roller was changed by a pressure reducing valve so that the surface temperature of the jacket roller immediately before the drawing tank was adjusted to 185 ° C. The temperature of the fiber bundle entering the drawing tank was 143 ° C. Since efficient condensation did not occur as compared with Example 1, water required for plasticization was not given, so the moisture content of the fiber bundle immediately after being drawn out from the pressurized steam drawing apparatus was As compared with 1, a large amount of fluff was generated in the acrylic precursor fiber bundle for carbon fiber, and a lot of fluff was also generated in the carbon fiber bundle obtained by firing the fiber. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Comparative Example 2)
This was carried out in the same manner as in Example 2 except that the steam roller supplied to the jacket roller was changed by a pressure reducing valve so that the surface temperature of the jacket roller immediately before the drawing tank was adjusted to 185 ° C. The temperature of the fiber bundle entering the drawing tank was 143 ° C. Since efficient condensation did not occur as compared with Example 2, the water necessary for plasticization was not given, so the moisture content of the fiber bundle immediately after being drawn out from the pressurized steam drawing apparatus was Compared with 2, a large amount of fluff was generated in the acrylic precursor fiber bundle for carbon fiber, and a lot of fluff was also generated in the carbon fiber bundle obtained by firing it. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Comparative Example 3)
It was carried out in the same manner as in Example 3 except that the surface temperature of the jacket roller immediately before the stretching tank was adjusted to 185 ° C. by changing the steam pressure supplied to the jacket roller with a pressure reducing valve. The temperature of the fiber bundle entering the drawing tank was 143 ° C. Since efficient condensation did not occur as compared with Example 3, the water necessary for plasticization was not given, so the moisture content of the fiber bundle immediately after being drawn out from the pressurized steam drawing apparatus was Compared with 3, a large amount of fluff was generated in the acrylic precursor fiber bundle for carbon fiber, and a lot of fluff was also generated in the carbon fiber bundle obtained by firing the fiber. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Comparative Example 4)
Example 1 except that the steam supplied to the pressurized steam stretching apparatus was adjusted to 133 ° C. wet steam (gauge pressure: 212 kPa) with a dryness of 0.6 by adjusting the amount of water supplied from the atomizer. It carried out like. The temperature of the fiber bundle entering the drawing tank was 95 ° C. Compared with Example 1, since the ratio of minute water droplets in the pressurized steam colliding with the fibers is large, the acrylic precursor fiber bundle for carbon fibers has a very large amount of fluff, and the carbon fiber bundle obtained by firing the fluff There were very many fluffs. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

(Comparative Example 5)
The same procedure as in Comparative Example 4 was performed except that the surface temperature of the jacket roller immediately before the stretching tank was adjusted to 185 ° C. by changing the steam pressure supplied to the jacket roller with a pressure reducing valve. The temperature of the fiber bundle entering the drawing tank was 143 ° C. Compared with Example 1, since the ratio of minute water droplets in the pressurized steam colliding with the fibers is large, the acrylic precursor fiber bundle for carbon fibers has a very large amount of fluff, and the carbon fiber bundle obtained by firing the fluff There were very many fluffs. Table 4 shows the moisture content of the fiber bundle immediately after coming out from the pressurized steam drawing apparatus and the results of the fluff evaluation.

It is a graph which shows the relationship between the temperature of the fiber bundle introduce | transduced in the drawing tank of the pressurized steam drawing apparatus of this invention, and the quantity of the water given to an acrylic fiber bundle by condensation of pressurized steam. It is a schematic diagram which shows an example of the pressurized steam extending | stretching apparatus of this invention. It is a schematic diagram which shows an example of the steam ejection header of the pressurized steam extending | stretching apparatus of this invention. It is a cross-sectional schematic diagram which shows an example inside the extending tank of the pressurized steam extending | stretching apparatus of this invention. It is a graph which shows the relationship between supply heat energy and steam temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stretching tank 2 Jacket roller 3 Pressurized steam supply device 3a Steam pressure control valve 3b Water quantity control valve 3c Drain trap 3d Atomizer 3e Dryness meter 4 Heat medium supply pipe 5 Pressure reducing valve 6 Thermometer 7 Fiber bundle 8 Heat insulation cover 9 Steam ejection Header 10 Pressurized steam 11 Labyrinth seal 12 Steam outlet 13 Pressurized steam drawing chamber 14 Steam supply pipe

Claims (5)

In the method for stretching an acrylic fiber bundle for carbon fiber, the acrylic fiber bundle for carbon fiber is stretched by pressurized steam.
The surface of the acrylic fiber bundle for carbon fiber is condensed by condensing the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus on the surface of the acrylic fiber bundle for carbon fiber introduced into the drawing tank. A method for stretching an acrylic precursor fiber bundle for carbon fibers, characterized by stretching due to the plasticizing effect of the condensed water produced in the step. In the method for stretching an acrylic fiber bundle for carbon fiber, the acrylic fiber bundle for carbon fiber is stretched by pressurized steam.
Using dry saturated steam or superheated steam as the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus, the temperature of the acrylic fiber bundle for carbon fibers introduced into the drawing tank is T ₁ (° C.), A method for stretching an acrylic precursor fiber bundle for carbon fibers, wherein the temperature is controlled to satisfy 80 ≦ T ₁ <T ₂ when the temperature of the pressurized steam is T ₂ (° C.). In the method for stretching an acrylic fiber bundle for carbon fiber, the acrylic fiber bundle for carbon fiber is stretched by pressurized steam.
The temperature of the acrylic fiber bundle for carbon fiber introduced into the drawing tank using wet steam having a dryness of 0.9 or more and less than 1.0 as the pressurized steam supplied into the drawing tank of the pressurized steam drawing apparatus Is T ₁ (° C.), and the temperature of the pressurized steam is T ₃ (° C.), the temperature is controlled so as to satisfy 80 ≦ T ₁ <T _3. Acrylic precursor fiber for carbon fiber, Bundle stretching method. In a pressurized steam stretching apparatus for stretching a plurality of acrylic fiber bundles for carbon fibers arranged in parallel by pressurized steam,
A drawing tank capable of maintaining the inside in a pressurized state by a labyrinth seal portion provided at the inlet and outlet of the acrylic fiber bundle for carbon fiber;
Stretching rollers arranged on the upstream side and downstream side of the stretching tank;
Means for controlling the surface temperature of the stretching roller disposed on the upstream side of the stretching tank;
A detector for detecting the temperature of the acrylic fiber bundle for carbon fibers introduced into the drawing tank from the inlet portion;
A pressurized steam supply means for supplying pressurized steam into the stretching tank;
A pressurizing steam stretching apparatus comprising:   A method for producing an acrylic precursor fiber bundle for carbon fibers, wherein the pressurized steam drawing apparatus according to claim 4 is used.

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