JP4990195B2 - Carbon fiber precursor acrylic fiber bundle and method for producing the same - Google Patents

Description

  The present invention is a flameproofing process in which a carbon fiber precursor acrylic fiber bundle (hereinafter also simply referred to as a precursor fiber bundle) is converted into a flameproof fiber bundle in the process of producing a carbon fiber bundle, and is fused between single fibers. TECHNICAL FIELD The present invention relates to a method for producing a carbon fiber precursor acrylic fiber bundle having a step of uniformly imparting an oil agent for carbon fiber precursor acrylic fibers (hereinafter also simply referred to as an oil agent) used for the purpose of preventing the occurrence of water to the fiber surface. . In addition, the present invention relates to a carbon fiber precursor acrylic fiber bundle in which an oil agent is uniformly applied to the fiber surface by the production method of the present invention, and a high-quality homogeneous carbon fiber bundle can be obtained when it is fired.

  Conventionally, as a method for producing a carbon fiber bundle, the acrylic fiber bundle is converted into a flame-resistant fiber bundle by heat treatment in an atmosphere containing 200 to 400 ° C. and subsequently carbonized in an inert atmosphere of 1000 ° C. or more. Thus, a method for obtaining a carbon fiber bundle is known. Carbon fiber bundles obtained by this method are widely used industrially as reinforcing fibers for composite materials because of their excellent mechanical properties.

  However, in the method for producing a carbon fiber bundle, in the flameproofing step of converting the precursor fiber bundle into a flameproofed fiber bundle, fusion occurs between single fibers, and the flameproofing step and the subsequent carbonization step (hereinafter referred to as flameproofing) In the synthesis process and the carbonization process, which is also referred to as a firing process), process failures such as fluff and bundle breakage may occur. In order to avoid this fusion, it is known that selection of the oil agent to be attached to the acrylic fiber bundle is important, and many oil agent compositions have been studied.

  Among them, silicone-based oils containing silicone that have a good effect of preventing fusion in the flameproofing step are most commonly used. However, the silicone-based oil agent is heated to undergo a cross-linking reaction to increase the viscosity, and the adhesive is deposited on the surface of the precursor fiber bundle manufacturing process or the flame-proofing process, such as a fiber transport roller or a guide, It may cause a decrease in operability such as a bundle being wound or caught to break the yarn. In addition, the oil composition containing silicone produces silicon compounds such as silicon oxide, silicon carbide, and silicon nitride in the firing process, and these scales have the problem of reducing process stability and product quality. ing.

  For this reason, several oil agent technologies for reducing the silicone content of the oil agent to be imparted to the precursor fiber bundle and, consequently, the silicon content have been proposed. For example, an oil agent composition (see Patent Document 1) in which an emulsifier composed of a polycyclic aromatic compound is contained in an amount of 40 to 100 wt% to reduce the silicone content has been proposed. However, the convergence property of the precursor fiber bundle to which the oil composition with a reduced silicone content is applied is poor, and is not suitable for production with high production efficiency, and a carbon fiber bundle with excellent mechanical properties cannot be obtained. There was a problem.

  For the purpose of uniform adhesion, several apparatuses for applying an oil agent to a fiber bundle have been proposed. For example, an oil agent application nozzle (see Patent Document 2), an oil agent application guide (see Patent Document 3), an oil agent application roller (see Patent Document 4), and the like have been proposed. However, these devices are based on the idea of spreading the oil treatment liquid in the fiber bundle, and the oil agent component cannot be applied to the surface of the single fiber in the fiber bundle without any unevenness. It was not possible to limit to the limit, and it was not possible to solve the decrease in operability in the firing step described above.

Furthermore, a method has been proposed in which a part of the applied oil agent is removed by passing the precursor fiber bundle after applying and drying the oil agent through a cleaning liquid containing a surfactant (see Patent Document 5). However, with this method, it is not possible to remove only the excess oil component that has been dry-fixed, and it is not possible to obtain a precursor fiber bundle in a uniform oil agent application state only by reducing the amount of oil agent applied as a whole. It was.
JP 2005-264384 A JP-A-10-280224 JP 2004-300582 A JP 2001-98410 A JP 2007-113141 A

  As described above, the oil composition with reduced silicone content according to the prior art, or the production method of the apparatus and the precursor fiber bundle cannot provide a uniform oil agent from a single fiber viewpoint, and the process stability, the carbon fiber bundle In the expression of mechanical properties, it is not possible to obtain a material satisfying both of them.

  In other words, in order to solve the problem of reduced operability due to the generation of silicon compounds in the firing process starting from the oil composition containing silicone as a main component without reducing the mechanical properties of the obtained carbon fiber, A technique for uniformly applying the minimum necessary amount to the precursor fiber bundle is indispensable.

  The object of the present invention is to provide a carbon fiber precursor that can suppress fusion between single fibers in the flameproofing process, and can suppress the deposition of scale in the spinning process and firing process derived from silicone and improve process passability. It aims at providing the manufacturing method of a body acrylic fiber bundle. Another object of the present invention is to provide a precursor fiber bundle for high-quality, high-quality carbon fibers produced by the production method and having an oil agent uniformly attached thereto.

  In the present invention, as a means for solving the above-mentioned problems, the oil agent component is uniformly applied to the precursor fiber bundle by the following method, and the excess oil agent component is reduced, whereby the spinning step and the firing step. Process for producing a carbon fiber precursor acrylic fiber bundle capable of improving the process passability and obtaining high-quality carbon fibers with low spots, and high-productivity, high-quality carbon fiber production obtained by the production method The precursor fiber bundle for use is provided.

The method for producing a carbon fiber precursor acrylic fiber bundle of the present invention includes a step of bringing an acrylic fiber bundle into contact with an oil treatment liquid in which an oil component is dispersed in water;
Thereafter, a method of producing a carbon fiber precursor acrylic fiber bundle having a step of drying and densifying the acrylic fiber bundle,
It is a manufacturing method of the carbon fiber precursor acrylic fiber bundle whose time from making the said oil agent treatment liquid contact an acrylic fiber bundle and touching a drying roll is 5 to 60 second.

  In the oil treatment liquid, it is preferable that micelles having an average particle diameter of 0.01 μm or more and 0.5 μm or less are formed.

  The carbon fiber precursor acrylic fiber bundle of the present invention is a precursor fiber bundle manufactured by the above-described manufacturing method.

  According to the present invention, since the silicone-based oil agent can be uniformly applied to the precursor fiber bundle, fusion between single fibers in the flameproofing process can be suppressed, and high-quality and high-performance carbon fibers can be produced.

  As a result of earnest search for a precursor fiber bundle for producing high-quality carbon fibers excellent in productivity, and a method for producing the same, the present inventor has obtained a necessary and sufficient amount by utilizing the interaction between the oil component and the fibers. It has been found that the silicone-based oil agent can be uniformly applied to the precursor fiber bundle. That is, the method for producing a carbon fiber precursor acrylic fiber bundle of the present invention makes it possible to simultaneously improve the operability of the firing process and the quality of the obtained carbon fiber.

  In the present invention, first, the acrylic fiber bundle is brought into contact with an oil agent treatment liquid in which an oil agent component is dispersed in water. As the acrylic fiber bundle, an acrylic fiber bundle spun by a known technique can be used. A water-swelled acrylic fiber bundle is preferred.

  A more preferable example of the acrylic fiber bundle is an acrylic fiber bundle obtained by spinning an acrylonitrile polymer.

  The acrylonitrile-based polymer is a polymer obtained by polymerizing acrylonitrile as a main monomer. The acrylonitrile-based polymer is not limited to a homopolymer obtained only from acrylonitrile, but may be an acrylonitrile-based copolymer obtained by using other monomers in addition to the main component acrylonitrile.

  The content of the acrylonitrile unit in the acrylonitrile-based copolymer is 96.0 to 98.5 wt%, preventing heat fusion of the fiber in the firing step, heat resistance of the copolymer, stability of the spinning dope and It is more preferable from the viewpoint of quality when the carbon fiber is used. When the acrylonitrile unit is 96 wt% or more, it is preferable because the excellent quality and performance of the carbon fiber can be maintained without inducing the thermal fusion of the fiber in the firing step when converting to the carbon fiber. In addition, the heat resistance of the copolymer itself is not lowered, and adhesion between single fibers can be avoided in spinning the precursor fiber or in a process such as fiber drying or drawing with a heating roller or pressurized steam. On the other hand, when the acrylonitrile unit is 98.5 wt% or less, the solubility in the solvent does not decrease, the stability of the spinning stock solution can be maintained, and the precipitation and solidification properties of the copolymer are not increased. This is preferable because stable production of fibers is possible.

  The monomer other than acrylonitrile used for obtaining the copolymer can be appropriately selected from vinyl monomers copolymerizable with acrylonitrile, and has acrylic acid, methacrylic acid having an action of promoting flameproofing reaction. An acid, itaconic acid, or an alkali metal salt or ammonium salt thereof, or a monomer such as acrylamide is preferable because flame resistance can be promoted. As the vinyl monomer copolymerizable with acrylonitrile, carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid and itaconic acid are more preferable. The content of other monomer units in the acrylonitrile copolymer is preferably 0.5 to 2.0 wt%. One kind or two or more kinds of other monomers may be used.

  When spinning the acrylonitrile polymer, the acrylonitrile polymer is dissolved in a solvent to form a spinning dope. The solvent used at this time can be appropriately selected from known solvents such as organic solvents such as dimethylacetamide, dimethylsulfoxide, dimethylformamide, and aqueous inorganic compounds such as zinc chloride and sodium thiocyanate. From the viewpoint of improving productivity, dimethylacetamide, dimethylsulfoxide or dimethylformamide having a high coagulation rate is preferable, and dimethylacetamide is more preferable.

  At this time, in order to obtain a dense coagulated yarn, it is preferable to prepare the spinning dope so that the polymer concentration of the spinning dope becomes a certain level or more. Specifically, the concentration of the acrylonitrile polymer in the spinning dope is preferably 17 wt% or more, more preferably 19 wt% or more. Furthermore, the spinning dope requires an appropriate viscosity and fluidity, and the concentration of the acrylonitrile polymer is preferably within a range not exceeding 25 wt%.

  Spinning methods are known, such as a wet spinning method in which the above-mentioned spinning solution is directly spun into a coagulation bath, a dry spinning method in which the solution is coagulated in air, and a dry and wet spinning method in which the solution is once coagulated in the air and then coagulated in the bath. A spinning method can be appropriately employed, but a wet spinning method or a dry-wet spinning method is preferable for obtaining a carbon fiber bundle having higher performance.

  The spinning shaping by the wet spinning method or the dry-wet spinning method can be performed by spinning the above spinning solution into a coagulation bath from a nozzle having a circular cross-sectional hole. As the coagulation bath, it is preferable to use an aqueous solution containing a solvent used in the above-mentioned spinning dope from the viewpoint of easy solvent recovery.

  When using an aqueous solution containing a solvent as the coagulation bath, the concentration of the solvent in the aqueous solution is such that a dense structure without voids can be obtained, a high-performance carbon fiber bundle can be obtained, stretchability can be ensured, and productivity is excellent. For the reason, 50 to 85 wt%, and the temperature of the coagulation bath is preferably 10 to 60 ° C.

  After the polymer or copolymer is dissolved in a solvent and discharged into a coagulation bath as a spinning solution to be fiberized, stretching in a bath in which the coagulated yarn is stretched in a coagulation bath or in a stretching bath can be performed. Alternatively, it may be partially stretched in the air and then stretched in a bath. The acrylic fiber bundle in a water-swollen state can be obtained by washing with water before or after stretching or simultaneously with stretching. Stretching in the bath is usually carried out in a water bath at 50 to 98 ° C. by dividing it into multiple stages of one or more times, and stretching so that the total ratio of in-air stretching and stretching in the bath is 2 to 10 times. Is preferable from the viewpoint of the performance of the obtained carbon fiber bundle.

  In the present invention, as a method for imparting the oil component to the acrylic fiber bundle, the above-mentioned acrylic fiber bundle is brought into contact with an oil treatment liquid (hereinafter also referred to as an emulsion) in which the oil component is dispersed in water. it can. When washing is performed after stretching in the bath, the acrylic fiber bundle that has been stretched and washed in the bath can be brought into contact with the emulsion of the oil component. The emulsion is used after being diluted to a predetermined concentration by adding ion exchange water.

  As a method of bringing the oil treatment liquid into contact with the acrylic fiber bundle, the roller lowering method in which the lower part of the roller is immersed in the oil treatment liquid and the acrylic fiber bundle is brought into contact with the upper part of the roller, a certain amount of oil treatment liquid is guided by the pump. A guide adhesion method in which the acrylic fiber bundle is discharged from the guide surface and the acrylic fiber bundle is brought into contact with the guide surface, a spray adhesion method in which a predetermined amount of the oil treatment liquid is sprayed from the nozzle onto the acrylic fiber bundle, and a dip in which the acrylic fiber bundle is immersed in the oil treatment liquid A known method such as an adhesion method can be used.

  From the viewpoint of uniform adhesion, this is a dip adhesion method suitable for sufficiently spreading the oil treatment liquid into the acrylic fiber bundle. More preferably, it is a dip-jet attachment method in which the oil treatment liquid is applied to the acrylic fiber bundle from the nozzle in the oil treatment liquid tank, and the oil treatment liquid is put into the acrylic fiber bundle.

In order to uniformly apply the oil agent component to the surface of the single fiber, a mechanism for fixing the acrylic fiber bundle by the oil agent component interaction in a state where the oil agent treatment solution and the acrylic fiber bundle are in contact with each other is preferable. It is preferable that the time from the contact of the oil treatment liquid with the bundle to the contact with the drying roll is 5 to 60 seconds, and more preferably 20 to 60 seconds. If it is 5 seconds or more, the oil component is dried before fixing on the surface of the single fiber, the oil agent component is deposited in a state of being unevenly distributed on the surface of the single fiber, and there may be a part where the adhesion is partially insufficient. Hard to occur. If it is 60 seconds or less, the layer of the oil component that precipitates by breaking the micelles on the oil component fixed by the interaction on the surface of the single fiber becomes thick, and the oil component also precipitates in the gap between the single fibers. , No adhesion spots occur. Moreover, since the oil agent component is provided more than the necessary amount, the silicone oil agent has a large amount of Si scattering in the firing step and does not deteriorate the operability.

  During this time, even if the acrylic fiber bundle is immersed in the oil treatment liquid, it may be a step of transporting in the air using a roll at room temperature.

  In the step of fixing the oil component to the acrylic fiber bundle by interaction, the emulsion is stabilized when the temperature is low, while the adsorptivity of the micelle to the acrylic fiber bundle is high. Further, when the temperature is high, the stability of the emulsion is lowered, but when the interaction between the oil component and the acrylic fiber bundle is a chemical reaction, the fixability may be improved. Therefore, the temperature at which this step is performed is preferably 0 to 50 ° C, more preferably 10 to 40 ° C.

  If it is 0 ° C. or lower, the diffusion of the oil component may be restricted, and if it exceeds 50 ° C., emulsification may become unstable. In a general process, it is not necessary to adjust the temperature in particular, and a room temperature processing solution and apparatus may be used.

  In the present invention, the oil agent treatment liquid preferably contains an amino-modified silicone. Amino-modified silicone has an amino group and thus has good affinity with acrylic fibers, and is preferable in a method of uniformly applying an oil agent component to an acrylic fiber bundle using interaction fixing. More preferably, it is a side chain primary amino-modified silicone.

  In the present invention, the oil treatment liquid preferably contains a nonionic emulsifier, and preferably contains a copolymerized polyether composed of propylene oxide (PO) units and ethylene oxide (EO) units. More preferred. In the case of an emulsion using this emulsifier, the fixability of the oil component to the fibers is improved and more uniform application can be achieved.

  In the present invention, the adhesion amount of the oil component is preferably 0.1 to 2.0 wt% with respect to the dry fiber mass in the precursor fiber bundle after being dried and densified, which will be described later. More preferably, it is 1-1.0 wt%. When the adhesion amount of the oil component is lower than 0.1 wt%, it becomes difficult to sufficiently express the original function of the oil component. On the other hand, when the adhesion amount of the oil agent component is higher than 2.0 wt%, the excess oil agent component is polymerized in the firing process to cause adhesion between single fibers, and is deposited on the conveyance roll. The operability may be reduced.

  Moreover, it is preferable that the micelle with an average particle diameter of 0.01 micrometer or more and 0.5 micrometer or less is formed in the oil agent processing liquid. By carrying out like this, it becomes possible to disperse | distribute a micelle uniformly in an acrylic fiber elementary bundle. In addition, the average particle diameter of the micelle which exists in said aqueous emulsion can be measured using a laser diffraction / scattering type particle size distribution measuring apparatus (trade name: LA-910, manufactured by Horiba, Ltd.).

  In the present invention, the acrylic fiber bundle to which the oil agent component is adhered by the oil agent application method is dried and densified in the subsequent drying step. The temperature for drying and densification needs to be performed at a temperature exceeding the glass transition temperature of the fiber, but the temperature may vary depending on the drying state from the water-containing state, and the temperature is a method using a heating roller of about 100 to 200 ° C. Is preferred. At this time, the number of heating rollers may be one or more.

  It is preferable to perform pressurized steam stretching after drying, since the denseness and the degree of orientation of the resulting carbon fiber bundle can be further increased. Pressurized steam stretching is a method of stretching in a pressurized steam atmosphere, and since it can be stretched at a high magnification, it is possible to perform stable spinning at a higher speed, and at the same time, the denseness of the obtained carbon fiber bundle and It also contributes to improving the degree of orientation.

  In the present invention, in this pressurized steam stretching, it is preferable to control the temperature of the heating roller immediately before the pressurized steam stretching apparatus to 120 to 190 ° C., and the variation rate of the steam pressure in the pressurized steam stretching to 0.5% or less. By doing in this way, the fluctuation | variation of the draw ratio made | formed to a precursor fiber bundle and the fluctuation | variation of the tow | fineness degree to be generated by it can be suppressed. When the temperature of the heating roller is less than 120 ° C., the temperature of the precursor fiber bundle is not sufficiently increased and the drawability is lowered.

  The pressure of water vapor in the pressurized steam stretching is preferably 200 kPa · g (gauge pressure, the same shall apply hereinafter) or more so that the stretching by the heating roller and the characteristics of the pressurized steam stretching method appear clearly. The water vapor pressure is preferably adjusted as appropriate in consideration of the treatment time, but if the pressure is high, leakage of water vapor may increase. Therefore, it is preferably about 600 kPa · g or less industrially.

  The precursor fiber bundle obtained through drying and densification is passed through a roll at room temperature, cooled to a normal temperature state, and then wound around a bobbin with a winder. Alternatively, it is transferred to a can and stored, and transferred to a firing step. And a carbon fiber bundle can be obtained by baking a precursor fiber bundle.

  The precursor fiber bundle produced by the method for producing the carbon fiber precursor acrylic fiber bundle of the present invention described above can suppress the fusion in the spinning process and the firing process, and has a uniform and excellent physical property. Is useful for manufacturing. Moreover, the amount of silicone adhering to the precursor fiber bundle can be suppressed by removing the excess oil agent component accompanying the acrylic fiber bundle with water in the oil agent application step. As a result, it is possible to suppress the scattering of the silicone degradation product and the amount of silicon compound produced in the firing process, and the operability and processability are remarkably improved. A carbon fiber bundle obtained by such a carbon fiber precursor acrylic fiber bundle is suitable as a reinforcing fiber used for a fiber reinforced resin composite material used for various structural materials.

  The present invention will be described more specifically with reference to the following examples. However, the method for producing a precursor fiber bundle of the present invention and the precursor fiber bundle obtained thereby are not limited to the examples. In addition, the amount of oil agent adhesion of the precursor fiber bundle, the evaluation of the oil agent adhesion state, the number of single-fiber fusions of the carbon fiber bundle obtained by firing the precursor fiber bundle, the strand strength, and the silicon-derived silicon compound in the firing step The scattering evaluation was carried out by the following method.

[Oil agent adhesion amount]
The precursor fiber bundle was dried at 105 ° C. for 1 hour and then immersed in methyl ethyl ketone at 90 ° C. for 8 hours to extract the oil agent component adhering thereto. The oil agent adhesion amount was obtained from this difference by precisely weighing the mass of the precursor fiber bundle before and after this extraction.

[Evaluation of oil adhesion]
The oil agent component adhering to the surface of the single fiber of the precursor fiber bundle was vapor-deposited and dyed with ruthenic acid, and then the surface was observed with an optical microscope and evaluated according to the following criteria.
○: The oil component is uniformly adhered to the surface, which is good.
Δ: There are some adhesion spots such as a part adhering in large quantities.
X: There are a lot of sites with insufficient adhesion and adhesion spots, which are defective

[Number of fusions between single fibers (number of fusions)]
The carbonized carbon fiber bundle is cut into 3 mm lengths, dispersed in acetone, and after stirring for 10 minutes, the total number of single fibers and the number of fusions are counted, and the number of fusions per 100 single fibers is calculated. evaluated. The evaluation criteria are as follows.
○: Number of fusions (pieces / 100 pieces) ≦ 1
×: Number of fusions (pieces / 100 pieces)> 1

[Strand strength (CF strength)]
It measured according to the epoxy resin impregnation strand method prescribed | regulated to JIS-R-7608. The number of measurements was 30 times, and the average value was used for evaluation. The coefficient of variation of 30 measurements was used as an index of homogeneity.

[Silicon-derived silicon compound scattering evaluation]
The amount of silicon-derived silicon compound scattered in the flameproofing process is determined by measuring the Si element content of the precursor fiber bundle and the flameproofed fiber bundle obtained by flameproofing it with a fluorescent X-ray analyzer. The amount of Si scattered in the process was calculated and used as an evaluation index.
(Si scattering amount) =
(Si content of precursor fiber bundle)-(Si content of flameproof fiber bundle) [mg / kg]
For the X-ray fluorescence analyzer, ZSX100e (trade name) manufactured by Rigaku Denki Kogyo Co., Ltd. was used. The measurement sample was set in the apparatus by uniformly winding a fiber bundle on an acrylic resin plate having a length of 20 mm, a width of 40 mm, and a width of 5 mm so that there was no gap. At this time, it is important that the winding length of the fiber bundle attached to the measurement is the same. Thereafter, the fluorescent X-ray intensity of Si was measured by a normal fluorescent X-ray analysis method. The Si content of each fiber bundle was determined from the X-ray fluorescence X-ray intensity of the obtained precursor fiber bundle and flame-resistant fiber bundle using a calibration curve. The number of measurements was n = 10, and the average value was used for evaluation.

<Example 1>
An emulsion of the oil composition was prepared by the following method. Amino-modified silicone (product name: KF-864, manufactured by Shin-Etsu Chemical Co., Ltd.) having a kinematic viscosity of 1700 mm ² / s (25 ° C.) and an amino equivalent of 3800 g / mol, propylene oxide (PO) and ethylene oxide (EO) 90: 9: 1 (amino-modified silicone) comprising block copolymer polyether (trade name: F-68, manufactured by Adeka Co., Ltd.) and an antioxidant (trade name: IRGANOX 1010, manufactured by Ciba Japan Co., Ltd.). : Block copolymerized polyether: antioxidant) was mixed at a mass ratio, and ion-exchanged water was added so that the concentration of the oil composition was 30 wt%, and the mixture was emulsified with a homomixer. In this state, since the average micelle particle diameter is about 2 μm, it was further dispersed to a particle diameter of 0.2 μm or less by a high-pressure homogenizer. This emulsion was used as an oil agent stock solution in the following steps.

  The acrylic fiber bundle to which the oil agent composition was adhered was prepared by the following method. Acrylonitrile copolymer (composition ratio: acrylonitrile / acrylamide / methacrylic acid = 96/3/1 (mass ratio)) is dissolved in dimethylacetamide, a spinning stock solution is prepared, and the pore size is set in a coagulation bath filled with a dimethylacetamide aqueous solution. (Diameter) 75 μm, discharged from a spinning nozzle having a hole number of 6000 to obtain a coagulated yarn. The coagulated yarn was desolvated in a water washing tank and stretched 5 times to obtain an acrylic fiber bundle in a water swollen state.

  The acrylic fiber bundle in the water swelling state is guided to an oil agent treatment tank containing a treatment liquid obtained by diluting the oil agent stock solution with ion exchange water, and after the oil agent composition is adhered, a roll having a surface temperature of 180 ° C. Dried. In order to remove the excess oil agent treatment liquid accompanying the fiber bundle, the sheet was nipped with a guide bar immediately before the drying roll. In the oil treatment tank, the conveyance speed and the distance between the oil treatment tank and the drying roll so that the time from the contact of the acrylic fiber bundle in the water swelling state with the oil treatment liquid to the touch of the drying roll is 5 seconds. Adjusted.

  Subsequently, the film was stretched three times in water vapor at a pressure of 0.2 MPa, and then wound around a bobbin to collect a carbon fiber precursor acrylic fiber bundle.

  Table 1 shows the results of observation of the adhesion state of the oil agent to the surface of the single fiber of the precursor fiber bundle by the method described above. In the oil agent application process, the excess oil agent treatment liquid accompanying the precursor fiber bundle cannot be completely removed at the nip before the drying roll, so a portion with a slightly high amount of the oil agent composition was seen, but it was almost uniform It was attached to.

  This carbon fiber precursor acrylic fiber bundle is passed through a flameproofing furnace having a temperature gradient of 220 to 260 ° C., and further baked in a carbonization furnace having a temperature gradient of 400 to 1300 ° C. in a nitrogen atmosphere. did.

  The number of fusion of carbon fiber bundles obtained here, the carbon fiber bundle strand strength (hereinafter also referred to as CF strength), and the silicone-derived silicon compound scattering evaluation results in the flameproofing process are shown in Table 1. It was good without fusing, high CF strength and small variation.

<Examples 2 to 4>
Examples 2 to 4 were the same as Example 1 except that the time from the contact of the acrylic fiber bundle and the oil treatment liquid to the contact with the drying roll in the oil treatment tank was set to 15, 30, and 60, respectively. The precursor fiber bundle was collected. These oil agent application conditions are summarized in Table 1.

  The evaluation results of the oil agent adhesion state of the collected precursor fiber bundle are also shown in Table 1. In any case, the adhesion state of the oil component to the surface of the single fiber was uniform and good.

The obtained precursor fiber bundle was fired in the same manner as in Example 1 to obtain a carbon fiber bundle. Table 1 shows the number of fusions and CF strength of the obtained carbon fiber bundle, and the evaluation results of the silicone-derived silicon compound scattering in the flameproofing process. In any case, there was no fusion, the CF strength was high, the variation was good, and it was good .

The reason why a more uniform carbon fiber bundle with small variation in CF strength was obtained was the time from the contact of the swelled acrylic fiber bundle with the oil treatment liquid to the contact with the drying roll in the oil treatment tank. Was Example 3 adjusted to 30 seconds.

<Comparative Examples 1 and 2>
Comparison is made in the same manner as in Example 1 except that the time from the contact between the acrylic fiber bundle and the oil treatment liquid in the oil treatment tank to the contact of the acrylic fiber bundle with the drying roll is 3 and 90 seconds, respectively. Examples 1 and 2 were performed and precursor fiber bundles were collected. These oil agent application conditions are summarized in Table 1.

  In Comparative Examples 1 and 2, the coefficient of variation in CF strength tended to increase.

Claims (3)

Contacting the acrylic fiber bundle with an oil treatment liquid in which the oil component is dispersed in water;
Thereafter, a method of producing a carbon fiber precursor acrylic fiber bundle having a step of drying and densifying the acrylic fiber bundle,
The manufacturing method of the carbon fiber precursor acrylic fiber bundle whose time from making the said oil agent process liquid contact an acrylic fiber bundle and touching a drying roll is 5 to 60 second.
  The method for producing a carbon fiber precursor acrylic fiber bundle according to claim 1, wherein micelles having an average particle diameter of 0.01 µm or more and 0.5 µm or less are formed in the oil treatment liquid.   A carbon fiber precursor acrylic fiber bundle produced by the production method according to claim 1 or 2.