JP2010077578A - Precursor fiber for carbon fiber production and method of production therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precursor fiber for carbon fiber production, scarcely requiring prevention of adhesion of single fiber to each other, single fiber breakage prevention and the like and excellent in process stability, in the carbon fiber production step especially in the flameproofing treatment step. <P>SOLUTION: An acrylic precursor fiber for carbon fiber production is provided by supplying a silicone oil solution, wherein the oil solution adhesion in the precursor fiber is 0.01-0.25 mass%; the maximum shrinkage stress generated in increasing the temperature of the precursor fiber from 25°C to 100°C at 20°C/min is 5.0 mN/30 dtex or less; and the number of single fiber breakages is less than 1.5/m. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a precursor fiber for producing carbon fibers having a small shrinkage stress when heated to 50 to 100 ° C. and a small number of single yarn breakage, and a method for producing the same.

  Conventionally, a precursor fiber for producing carbon fiber is used as a raw material, and flameproofing treatment is performed on this to obtain a flameproofing fiber. Further, carbonization treatment is applied to this flameproofing fiber to obtain a high-performance carbon fiber. Widely known. This method is also practiced industrially.

  Generally, precursor fibers for carbon fiber production are produced by spinning a polyacrylonitrile (PAN) copolymer to obtain a PAN-based raw fiber, washing the PAN-based raw fiber with water, drying, and then steam drawing. The This precursor fiber is subjected to a flameproofing treatment while being stretched or contracted in an oxidizing atmosphere of 200 to 300 ° C., and then carbonized in an inert gas atmosphere of 300 ° C. or higher, usually 1000 ° C. or higher to form carbon fibers. Manufactured.

  Among the precursor fibers, an aqueous solution of zinc chloride is used as a solvent in the spinning process when producing the PAN-based raw fiber, and solution polymerization is performed in the zinc chloride-based solvent, and the polymer is dissolved in the zinc chloride-based solvent. What is obtained by wet spinning is widely used because it has advantages such as a sharp molecular weight distribution and a common use of a polymerization solvent and a spinning solvent. The carbon fiber thus obtained has good physical properties such as high strength and elastic modulus.

  In the production of the PAN-based carbon fiber, the PAN-based copolymer is spun, washed, dried, steam-stretched to produce a carbon fiber precursor fiber, and the carbon fiber precursor fiber is fired (flame-resistant treatment, The rate at which carbon fiber is produced by carbonization treatment is significantly different. Therefore, when manufacturing carbon fiber, it is generally divided into two steps (pre-process and post-process), and the intermediate fiber obtained in the pre-process is temporarily stored as a precursor fiber for carbon fiber. It is.

  However, during this storage, the precursor fiber for carbon fiber is likely to relax the orientation of molecules inside the fiber. For this reason, a heat setting step (heat setting step) is provided at the end of the previous step, and the subsequent steps may be stabilized so that molecular orientation in the fiber does not relax (for example, Patent Document 1). reference).

  The object of the invention described in Patent Document 1 is to provide a high-strength carbon fiber so that molecular orientation does not relax. In order to achieve this object, a PAN-based copolymer is spun and steam-stretched, and then subjected to a drying treatment while giving a relaxation of 3 to 10% with a hot roll having a surface temperature of 150 to 220 ° C. There has been proposed a method for producing carbon fiber by obtaining a precursor fiber for use and carbonizing the obtained precursor fiber.

  In order to increase the efficiency of carbon fiber production, it is necessary to stabilize the process such as prevention of adhesion between single yarns and prevention of single yarn breakage in the flameproofing treatment process. In order to stabilize this process, it has been proposed to apply an oil agent, particularly a silicone-based oil agent, to the fiber after spinning, washing, drying or steam drawing in a process from spinning to flameproofing treatment (for example, , See Patent Document 2).

  As described in Patent Document 2, when an excessive amount of silicone-based oil is applied, not only does the oil cost increase, but the oil that drops off from the PAN-based material fiber and adheres to the hot roll in the drying process is heated. Gelling (gum up) on the roll causes the raw fiber to be wound around the hot roll and process stability is also reduced. Further, in a furnace used in the carbon fiber manufacturing process, particularly in a flameproofing furnace, silica powder generated by thermal decomposition of a silicone-based oil agent is generated and contaminates the furnace.

  Furthermore, when an excessive amount of oil is applied to the strand-shaped PAN-based raw material fibers in a swollen state after spinning and washing with water, the oil component remains excessively between the fibers of the strands or inside the fibers, resulting in poor quality of the carbon fiber. Causes below. For this reason, it is necessary to reduce the amount of oil agent attached in terms of process stabilization, carbon fiber quality and oil agent cost.

  However, even if the amount of oil agent is reduced, fiber damage such as single yarn breakage occurs due to friction during contact heating in the heat setting process and flame resistance process after steam stretching, and the quality deteriorates. It lacks process stability, such as increased winding. For example, since the precursor fiber described in Patent Document 1 is obtained by performing a heat setting process using a heat roller, if the amount of the oil agent is reduced, the fiber quality deteriorates and the process stability described above in the heat setting process and the flame resistance process. Problems such as lack occur.

  In addition, as a specific method for reducing the amount of the oil agent adhering to the fiber, for example, as described in Patent Document 3, the oil agent component adhering to the precursor fiber after washing with water, applying the oil agent and drying is used as a surfactant. There is a method of removing the excess oil agent by passing through the washing step. However, a process for treating the washed and recovered oil is added, which is not preferable because of high cost and complicated processes. Further, in the method described in Patent Document 3, even if the amount of the oil agent adhering to the fiber is reduced, problems such as deterioration in fiber quality and lack of process stability in the heat setting process and flameproofing process occur.

  On the other hand, as described in Patent Document 4, when the heat setting process using a heat roller such as a dry heat roller is not performed, the fiber contracts due to the stress remaining in the precursor fiber, and thus stable for a long time. The quality of the precursor fiber cannot be maintained.

Furthermore, when a precursor fiber that has been steam-stretched without being subjected to a heat setting process is wound on a bobbin, and the precursor fiber is put into the flameproofing furnace from this bobbin, it is oriented over time to the molecules inside the precursor fiber. Relaxation occurs and the fibers contract and damage the bobbin.
JP 63-159526 A (Claims) JP 2005-89884 A (Claims, paragraph number [0005]) JP 2007-113141 A (Claims) JP 2004-60126 A (Claims)

  As a result of repeated studies to solve the above problems, the present inventor has come to think as follows. That is, a steam treatment obtained by applying a silicone-based oil to a crude acrylic fiber obtained by wet spinning a copolymer obtained by polymerizing a monomer containing acrylonitrile in a predetermined amount or more, followed by drying and steam stretching treatment. The fiber still has shrinkage stress.

  As shown in FIG. 1, the shrinkage stress increases rapidly from around 60 ° C. and reaches a peak at 70 to 80 ° C.

  From this, when heating the steam-treated fiber in the heat setting process with a heat roller, when the fiber temperature reaches 60 to 80 ° C., the fiber is subjected to a rapid tension, and the contact pressure between the heat roller and the fiber increases, As a result, a large frictional force is generated between the heat roller and the fiber.

  Since the frictional force also leads to fiber damage, when the fiber temperature reaches 60 to 80 ° C., by starting the relaxation process at an appropriate relaxation rate, the contraction stress generated when the temperature of the fiber to be relaxed is raised. Has been found to be reduced. Therefore, this relaxation treatment reduces the friction between the roller and the fiber in the heat setting process and flameproofing process after the steam stretching process, even when the amount of oil applied to the steam treated fiber is small, and the single yarn breaks. This reduces the occurrence of fiber damage such as, improves the quality of the resulting precursor fiber and flame-resistant fiber, and further improves the stability of the process after steam stretching, such as less wrapping around the roller. The headline and the present invention have been completed.

  Accordingly, an object of the present invention is to provide a precursor fiber and a method for producing the same that solve the above-described problems.

  The present invention for achieving the above object is described below.

  [1] An acrylic precursor fiber for carbon fiber production to which a silicone-based oil agent is applied, and the amount of oil agent adhesion in the precursor fiber is 0.01 to 0.25% by mass, and the precursor fiber The maximum shrinkage stress generated between 25 ° C. and 20 ° C./min to 100 ° C. is 5.0 mN / 30 dtex or less, and the number of single yarn breakage is less than 1.5 / m A precursor fiber for carbon fiber production.

[2] The precursor fiber for producing a carbon fiber according to [1], wherein a water vapor adsorption amount at a humidity of 90% measured by a gas adsorption amount measuring device using water vapor is 15 cm ³ / g or less.

  [3] The carbon fiber precursor fiber according to [1] or [2], which is made of a copolymer containing 90% by weight or more of acrylonitrile and has wrinkles on the fiber surface.

  [4] After applying a silicone-based oil to a crude acrylic fiber obtained by wet spinning a copolymer obtained by polymerizing a monomer containing 90% by mass or more of acrylonitrile, drying, steam stretching treatment, The steam-treated fiber is brought into contact with a heat roller whose temperature is set to 50 to 240 ° C. to heat the steam-treated fiber, and when the temperature of the steam-treated fiber reaches 60 to 80 ° C., the relaxation treatment is started. The method for producing a precursor fiber for producing carbon fibers according to any one of [1] to [3], wherein a relaxation treatment is performed until the temperature reaches 120 to 150 ° C.

  The precursor fiber for carbon fiber production of the present invention is a precursor fiber for carbon fiber production comprising an acrylic fiber and provided with a silicone-based oil agent, and the shrinkage stress generated when the temperature of the fiber is increased is within a predetermined low range. Therefore, the friction between the roller and the fiber in the flameproofing process and the carbonization process is reduced, and the occurrence of fiber damage such as single yarn breakage occurs despite the small amount of oil agent adhesion in the fiber. The quality of the obtained flame resistant fiber and carbon fiber is improved, and the stability of the flame resistant process and the carbonization process is improved, for example, the winding around the roller is reduced.

  According to the production method of the present invention, a silicone oil is applied to a crude acrylic fiber obtained by wet-spinning a copolymer obtained by polymerizing a monomer containing acrylonitrile in a predetermined amount or more, followed by drying and steam drawing. Then, the steam treated fiber is heated by setting the contact length between the steam treated fiber and the heat roller obtained and the temperature of the heat roller to a predetermined range, and when the steam treated fiber reaches the predetermined temperature, the relaxation treatment is performed. Since it has started, the precursor fiber suitable for manufacturing the flame-resistant fiber and the carbon fiber can be easily and stably manufactured.

  Hereinafter, the present invention will be described in detail.

  The precursor fiber for producing a carbon fiber of the present invention is a precursor fiber made of an acrylic fiber and provided with a silicone oil. Moreover, the precursor fiber for carbon fiber production of the present invention has an oil agent adhesion amount in the fiber of 0.01 to 0.25% by mass, preferably 0.03 to 0.10% by mass.

  Despite the small amount of oil agent adhering to the fiber, the shrinkage stress generated between 25 ° C. and 20 ° C./min to 100 ° C. is as low as 5.0 mN / 30 dtex or less. The number of single yarn breaks is less than 1.5 / m, preferably less than 1.0 / m.

  Therefore, in spite of the small amount of oil agent in the fiber, the friction between the roller and the fiber is reduced in the flameproofing process and carbonization process for treating this precursor fiber, and fiber damage such as single yarn breakage As a result, the quality of the obtained flame-resistant fiber and carbon fiber is improved, and the stability of the flame-proofing process and the carbonization process is improved, for example, the winding around the roller is reduced.

The precursor fiber for producing carbon fiber of the present invention preferably has a water vapor adsorption amount at a humidity of 90% as measured by a gas adsorption amount measuring apparatus using water vapor of 15 cm ³ / g or less, more preferably 11 to 13.5 cm. ³ / g.

  Although the manufacturing method of the precursor fiber for carbon fiber manufacture of this invention, and also the manufacturing method of a flame-resistant fiber and the manufacturing method of carbon fiber are not specifically limited, For example, it can manufacture with the following method. .

<Spinning stock solution>
As the spinning raw solution of the crude acrylic fiber as a starting material used in the method for producing the precursor fiber for carbon fiber production of this example, any conventionally known spinning solution can be used without any limitation as long as it is a spinning raw solution for producing acrylic carbon fiber. Specifically, a stock solution for spinning composed of a copolymer obtained by polymerizing a monomer containing 90% by mass or more, preferably 94% by mass or more of acrylonitrile is exemplified. Examples of the monomer copolymerized with acrylonitrile include known monomers such as itaconic acid, methyl acrylate, ethyl acrylate, and acrylic acid.

  As a method for polymerizing the monomer, solution polymerization, suspension polymerization, emulsion polymerization and the like can be used. However, solution spinning is preferable because it can be spun as it is, and it is most preferable to use a zinc chloride solvent as a polymerization solvent.

  The spinning solution (spinning stock solution) is preferably a spinning solution using a polymer solution obtained by polymerizing the above monomers using an aqueous zinc chloride solution as a solvent.

  Since the concentration of the spinning dope affects the specific gravity of the carbon fiber precursor fiber, it is preferably 10 to 40% by mass, and more preferably 20 to 30% by mass when a zinc chloride aqueous solution is used as the solvent. When the concentration of the spinning dope is too low, the specific gravity of the obtained carbon fiber precursor fiber is low, and carbon fibers having a low specific gravity cannot be obtained. On the other hand, if the concentration is too high, there is a limit to the solubility of the polymer in the solvent, which is not preferable because the spinning dope becomes a non-uniform solution.

<Spinning>
A spinning stock solution is spun from a spinneret having preferably 1,000 to 30000 spinning holes in one spinneret and solidified to obtain a raw acrylic fiber for carbon fiber production. In this spinning, a method of spinning in a coagulation bath containing a coagulating liquid cooled to a low temperature (a solvent-water mixture at the time of spinning), a wet spinning method, a dry-wet spinning method, or the like can be used. A wet spinning method of spinning directly into a coagulation liquid is preferred. The dry-wet spinning method is a method in which after first discharging into the air, it has a space of about 3 to 5 mm and is put into a coagulation bath and coagulated. Since the finally obtained carbon fiber forms wrinkles on the surface and adhesion with the resin can be expected, the wet spinning method is more preferable.

<Spinning process oil agent application treatment>
The crude acrylic fiber obtained by solidification is subjected to a washing / spinning process oiling / drying / steam stretching process to obtain a crude acrylic fiber for carbon fiber production after the stretching process.

  The crude acrylic raw fiber after washing with water is then subjected to a spinning process oil agent application treatment. The application of the spinning process oil is performed for the purpose of preventing sticking and improving the fiber opening property in the drying, steam stretching, and flame resistance processes. The adhesion amount of the spinning process oil is 0.01 to 0.25% by mass, preferably 0.03 to 0.10% by mass with respect to the fiber mass after the spinning process oil is applied.

  It is preferable to use a silicone-based oil as the spinning process oil, and to use this silicone-based oil in combination with a permeable oil having a hydrophilic group.

  The osmotic oil agent preferably has sulfinic acid, sulfonic acid, phosphoric acid, carboxylic acid, its alkali metal salt, ammonium salt or its derivative as a functional group. Among these penetrating oils, it is particularly preferable to use ammonium phosphate or a derivative thereof that easily penetrates.

  The silicone oil may be either unmodified or modified, but modified silicone is more preferable. Among the modified silicones, epoxy-modified silicone, ethylene oxide-modified silicone, polysiloxane, and amino-modified silicone are preferable, and amino-modified silicone is particularly preferable.

<Drying process>
In a drying process, it is preferable to dry with a hot air dryer. About drying temperature, it is preferable to adjust suitably to 70-150 degreeC, and it is still more preferable to adjust suitably to 80-140 degreeC. The drying time is preferably 1 to 10 minutes.

<Steam stretching treatment>
In the steam stretching conditions, the temperature is preferably 100 to 150 ° C., and the saturated steam pressure is preferably 0.1 to 5.0 MPa (absolute pressure). The stretching ratio is preferably 10 to 15 times as the total stretching ratio through washing, drying and steam stretching.

<Relaxation treatment>
The fiber after the above steam stretching treatment is heated by bringing the fiber into contact with a heat roller set at a temperature of 50 to 240 ° C., preferably 100 to 200 ° C., and relaxed when the temperature of the fiber reaches 60 to 80 ° C. The treatment is started and relaxation treatment is performed until the temperature of the fiber reaches 120 to 150 ° C. to obtain a precursor fiber for producing carbon fiber made of acrylic fiber.

  This relaxation treatment is a relaxation treatment apparatus having, for example, a heat treatment chamber and a heat roller having 5 to 25 stages in the heat treatment chamber, and the set temperature of the heat roller is processed from the upstream where the steam treatment fiber is supplied. The temperature of the hot roller on the most downstream side is set to 130 to 250 ° C, preferably 150 to 180 ° C. And it carries out by carrying out the relaxation | loosening process on the relaxation conditions which make the roller speed from the heat roller when the temperature of the fiber reaches 60 to 80 ° C. to the heat roller when the temperature of the fiber reaches 120 to 150 ° C. low. be able to.

  More specifically, the time required for the crude acrylic fiber to pass through all the 10-stage heat rollers in which the temperature of the most upstream heat roller is 100 ° C., and the temperature of the most downstream heat roller is set to 180 ° C. Is 5 seconds, it takes 0.2 to 3 seconds for the temperature of the crude acrylic fiber to reach 60 to 80 ° C.

Incidentally, relaxation rate of the fibers in the relaxed _{[R r} (%)], when the draw ratio and R _d following formula _{R r = (1 - R d} ) × 100
Is calculated by The relaxation treatment means that the relaxation rate exceeds 0%, and more preferably 0.5 to 5%.

<Flame resistance process oil agent application treatment>
The precursor fiber for carbon fiber production composed of the acrylic fiber after the relaxation treatment is subjected to a flameproofing process oil agent application treatment as necessary in order to stabilize the process in the flameproofing process. The application of the flameproofing process oil is effective for increasing the strength and elongation of the carbon fiber for the purpose of preventing sticking in the flameproofing process and improving the spreadability. The adhesion amount of the flameproofing process oil is 0.01 to 0.20 mass% with respect to the mass of the precursor fiber.

  As the flameproofing process oil, the same silicone oil as the above spinning process oil is used. It is preferable to use this silicone oil agent in combination with a penetrating oil agent having a hydrophilic group. The penetrating oil is the same as described above.

<Flame resistance treatment>
The precursor fiber is subsequently flameproofed in heated air at 230-260 ° C. for 30-100 minutes. By this flameproofing treatment, a cyclization reaction of the acrylic fiber is caused in the precursor fiber made of the acrylic fiber, and the oxygen bond amount is increased and infusible to obtain a flameproof fiber.

In general, the flameproofing treatment is preferably performed in a range of a draw ratio of 1.00 to 1.20. By this flameproofing treatment, a flameproof fiber having a fiber density of 1.33 to 1.36 g / cm ³ is obtained. The tension at the time of flame resistance is not particularly limited as long as it does not exceed the range of the draw ratio.

<First carbonization treatment>
The flame-resistant fiber can be carbonized by employing a conventionally known method. For example, a temperature gradient is gradually applied in a firing furnace (first carbonization furnace) at 300 to 800 ° C. in a nitrogen atmosphere, and the tension of the flame-resistant fiber is controlled so that the first carbonization (first carbonization) is performed under tension. )do.

<Second carbonization treatment>
To further promote carbonization and graphitization (high crystallization of carbon), raise the temperature in an inert gas atmosphere such as nitrogen, gradually apply a temperature gradient in the firing furnace (second carbonization furnace), The first carbonized fiber is fired under relaxed conditions by controlling the tension.

  About a calcination temperature, a temperature gradient is applied in a 2nd carbonization furnace, Preferably it is 800 to 2500 degreeC in a maximum temperature range, More preferably, 1200 to 2100 degreeC is good.

  If the residence time in the high-temperature part in the furnace becomes long, graphitization proceeds too much, and brittle carbon fibers are obtained, which is not preferable.

<Surface oxidation treatment>
The second carbonized fiber is subsequently subjected to surface oxidation treatment. A gas phase or liquid phase treatment can also be used for the surface oxidation treatment, but the liquid phase treatment is preferable from the viewpoint of easy process control and productivity. Among the liquid phase treatments, electrolytic treatment using an electrolytic solution is preferable from the viewpoint of liquid safety and stability. Examples of the electrolytic solution used for the electrolytic oxidation treatment include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, inorganic hydroxides such as sodium hydroxide and potassium hydroxide, and inorganic salts such as ammonium sulfate, sodium carbonate, and sodium bicarbonate. Can be mentioned.

<Sizing process>
The fiber after the surface oxidation treatment is subsequently subjected to sizing treatment as necessary. The sizing method can be carried out by a conventionally known method, and the sizing agent is preferably used after changing its composition as appropriate according to the application, and after uniformly adhering.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Moreover, the processing conditions in each Example and a comparative example, and the evaluation method about the physical property of the rough acrylic fiber after a steam extending process, a precursor fiber, a flame-resistant fiber, and carbon fiber were implemented with the following method.

[Adhesion amount of silicone oil]
By the method prescribed | regulated to JISL1013, the silicone system oil agent adhesion amount of the fiber after oil agent provision was measured.

[Water vapor adsorption]
The water vapor adsorption amount of the crude acrylic fiber after the steam stretching treatment was obtained by cutting the crude acrylic fiber into a length of about 100 cm (about 0.3 g), and a fully automatic gas adsorption amount device “AUTOSORB-1” manufactured by Quantachrome. Under the following conditions Adsorption gas: H ₂ O
Dead volume: He
Adsorption temperature: 293K
Measuring range: relative pressure (P / Po) = 0-1.0
P: Measurement pressure and Po: H ₂ O saturated vapor pressure. The value of the water vapor adsorption amount at a humidity of 90% is a value obtained at a location where the relative pressure (P / Po) is 0.9.

[Shrinkage stress]
Using a thermomechanical analyzer TMA 4000S manufactured by Bruker AXS, the following 1. Precursor fibers are collected, 30 filaments are bundled, and fixed to a fiber measurement jig with an effective measurement length of 1.0 cm.
2. The constant length mode is set, and the load during this period is measured at a temperature rising rate of 20 ° C./min between 50 and 100 ° C.
3. Measured maximum load at 50 to 100 ° C., the following formula shrinkage stress = 50 to 100 ° C. measured load (mN) / fineness of precursor fiber sample (30 dtex)
Therefore, the maximum shrinkage stress is converted to 50 to 100 ° C.
It measured by the method of.

[Evaluation of relaxation process stability]
Evaluation of relaxation treatment process stability is as follows: ◎… Number of windings (times / day) ≦ 0.5
○… 0.5 <Number of windings (times / day) ≦ 1
△ ... 1 <Number of windings (times / day) ≤ 5
×… Number of windings (times / day)> 5
It was evaluated in four stages.

[Evaluation of single yarn breakage]
Since the carbon fiber precursor fiber has an oil agent attached, it is difficult to confirm the appearance even if there is a single yarn breakage. Therefore, the measurement of single yarn breakage is as follows. The oil agent adhering to the precursor fiber is washed with acetone.
2. The precursor fibers are air dried for 2 hours.
3. 1 m of the precursor fiber is cut out and spread, and the number of single yarn breakage is counted visually.
The single fiber breakage occurrence state of the precursor fiber is as follows: ◎… Less than 1 piece / m ○… 1 to 1.5 pieces / m
Δ: 1.5-2 pcs / m
X: Evaluation was made in four stages of 2 months / m or more.

[Example 1]
A copolymer spinning stock consisting of 95% by mass of acrylonitrile / 4% by mass of methyl acrylate / 1% by mass of itaconic acid was passed through a spinneret having 3000 holes in one spinneret, and in a 25% by mass zinc chloride aqueous solution at 6 ° C. Were discharged and solidified to obtain raw acrylic fibers.

  The crude acrylic fiber was washed with water and then introduced into a spinning process oil treatment bath, and an amino-modified silicone oil was added as the spinning process oil in the amount shown in Table 1 to obtain a spinning process oil-applied crude acrylic fiber.

  This spinning process oil-applied crude acrylic fiber was dried at 140 ° C. Thereafter, steam drawing was performed at a temperature of 120 ° C. so that the draw ratio was 6 times, and steam-treated fibers having 3000 filaments were obtained.

  The steam-treated fiber is heated at a temperature of 100 ° C. at the most upstream temperature, and the temperature is increased in order, the temperature of the third heat roller is set at 105 ° C., and the temperature of the most downstream heat roller is set at 180 ° C. A relaxation treatment was performed by passing through a heat treatment chamber having a roller in 4 seconds to obtain a precursor fiber for carbon fiber production. The fiber temperature reaches 50 ° C with the uppermost heat roller, reaches 65 ° C with the third heat roller from the uppermost heat roller, reaches 140 ° C with the eighth heat roller from the uppermost heat roller, and reaches the highest temperature. The temperature reached 170 ° C. with the downstream heat roller. By operating at a low speed between the third heat roller to the eighth heat roller, the condition between the third heat roller and the eighth heat roller was set to be relaxed. The fiber relaxation rate after passing through the heat treatment chamber was 2.0%. The time taken for the fiber to pass from the most upstream heat roller to the third heat roller (fiber preheating time) was 0.5 seconds.

The obtained precursor fiber has an oil agent adhesion amount of 0.05% by mass, a water vapor adsorption amount of 13.1 cm ³ / g at a humidity of 90% measured by a gas adsorption amount measuring apparatus using water vapor, a single yarn breakage Is rated as ◯, the stability of relaxation treatment process is evaluated as ◯, the maximum shrinkage stress generated between the temperature of 25 ° C. and 20 ° C./min after placing the fiber on a thermomechanical measuring device is 4 It was as good as 1 mN / 30 dtex.

[Examples 2 to 4]
The steam-treated fiber obtained in Example 1 was treated in the same manner as in Example 1 except that it was subjected to a relaxation treatment under the conditions of the relaxation rate in the heat treatment chamber shown in Table 1. Carbon fiber having physical properties shown in Table 1 A precursor fiber for production was obtained.

[Comparative Example 1]
The steam-treated fiber obtained in Example 1 was treated in the same manner as in Example 3 except that a relaxation treatment was performed between the most upstream heat roller to the eighth heat roller from the most upstream heat roller. The precursor fibers for producing carbon fibers having the physical properties shown in Table 1 were obtained.

[Example 5]
The steam-treated fiber obtained in Example 1 is set to the highest temperature of the hot roller at 100 ° C., and the temperature is sequentially increased, the temperature of the eighth heat roller is set to 120 ° C., and the temperature of the most downstream heat roller is set to 180 ° C. The heat treatment chamber having a 17-stage heat roller was passed in 6.8 seconds for relaxation treatment to obtain a precursor fiber for carbon fiber production. The fiber temperature reaches 50 ° C with the most upstream heat roller, reaches 80 ° C with the 8th heat roller from the most upstream heat roller, reaches 140 ° C with the 14th heat roller from the most upstream heat roller, and reaches the maximum temperature. The temperature reached 170 ° C. with the downstream heat roller. By operating between the 8th heat roller to the 14th heat roller at a low speed, the space from the 8th heat roller to the 14th heat roller was in a relaxed condition. Except these conditions, it processed similarly to Example 3, and obtained the precursor fiber for carbon fiber manufacture of the physical property shown in Table 1.

[Comparative Example 2]
The steam-treated fiber obtained in Example 1 was heated to the highest temperature of the hot roller at 100 ° C., and the temperature was increased in order to set the temperature of the 10th hot roller to 130 ° C. Then, a relaxation treatment was performed by passing through a heat treatment chamber having a 20-stage heat roller in 8 seconds to obtain a precursor fiber for carbon fiber production. The fiber temperature reaches 50 ° C with the most upstream heat roller, reaches 95 ° C with the 10th heat roller from the most upstream heat roller, reaches 140 ° C with the 16th heat roller from the most upstream heat roller, and reaches the highest temperature. The temperature reached 170 ° C. with the downstream heat roller. By operating between the 10th heat roller to the 16th heat roller at a low speed, the space between the 10th heat roller and the 16th heat roller was set to be relaxed. Except these conditions, it processed similarly to Example 3, and obtained the precursor fiber for carbon fiber manufacture of the physical property shown in Table 1.

[Comparative Example 3]
The steam-treated fiber obtained in Example 1 is set to the highest temperature of the hot roller at 100 ° C., and the temperature is sequentially increased, the temperature of the eighth heat roller is set to 170 ° C., and the temperature of the most downstream heat roller is set to 180 ° C. The heat treatment chamber having a 17-stage heat roller was passed in 6.8 seconds for relaxation treatment to obtain a precursor fiber for carbon fiber production. The fiber temperature reaches 50 ° C with the most upstream heat roller, 150 ° C with the 8th heat roller from the most upstream heat roller, and 165 ° C with the 14th heat roller from the most upstream heat roller. The temperature reached 170 ° C. with the downstream heat roller. By operating between the 8th heat roller to the 14th heat roller at a low speed, the space from the 8th heat roller to the 14th heat roller was in a relaxed condition. Except these conditions, it processed similarly to Example 3, and obtained the precursor fiber for carbon fiber manufacture of the physical property shown in Table 1.

[Comparative Example 4]
The steam-treated fiber obtained in Example 1 was set to the highest temperature of the hot roller at 100 ° C., and the temperature was sequentially increased, the third heat roller temperature was set to 105 ° C., and the temperature of the most downstream heat roller was set to 150 ° C. The heat treatment chamber having a 10-stage heat roller was passed in 4 seconds for relaxation treatment to obtain carbon fiber precursor fibers. The fiber temperature reaches 50 ° C. with the most upstream heat roller, reaches 65 ° C. with the third heat roller from the most upstream heat roller, and reaches 110 ° C. with the eighth heat roller from the most upstream heat roller. The temperature reached 140 ° C. with the downstream heat roller. By operating at a low speed between the third heat roller to the eighth heat roller, the condition between the third heat roller and the eighth heat roller was set to be relaxed. Except these conditions, it processed similarly to Example 3, and obtained the precursor fiber for carbon fiber manufacture of the physical property shown in Table 1.

[Example 6]
The steam-treated fiber obtained in Example 1 is set to the highest temperature of the hot roller at 100 ° C., and the temperature is sequentially increased, the temperature of the third heat roller is set to 105 ° C., and the temperature of the most downstream heat roller is set to 170 ° C. The heat treatment chamber having a 10-stage heat roller was passed in 4 seconds for relaxation treatment to obtain carbon fiber precursor fibers. The fiber temperature reaches 50 ° C with the uppermost heat roller, reaches 65 ° C with the third heat roller from the uppermost heat roller, reaches 130 ° C with the eighth heat roller from the uppermost heat roller, and reaches the highest temperature. The temperature reached 160 ° C. with a downstream heat roller. By operating at a low speed between the third heat roller to the eighth heat roller, the condition between the third heat roller and the eighth heat roller was set to be relaxed. Except these conditions, it processed similarly to Example 3, and obtained the precursor fiber for carbon fiber manufacture of the physical property shown in Table 1.

[Comparative Example 5]
The steam-treated fiber obtained in Example 1 was set to the highest temperature of the hot roller at 100 ° C., and the temperature was sequentially increased. The temperature of the third heat roller was set to 105 ° C., and the temperature of the most downstream heat roller was set to 200 ° C. The heat treatment chamber having a 10-stage heat roller was passed in 4 seconds for relaxation treatment to obtain carbon fiber precursor fibers. The fiber temperature reaches 50 ° C with the most upstream heat roller, reaches 65 ° C with the third heat roller from the most upstream heat roller, reaches 160 ° C with the eighth heat roller from the most upstream heat roller, and reaches the highest temperature. The temperature reached 190 ° C. with the downstream heat roller. By operating at a low speed between the third heat roller to the eighth heat roller, the condition between the third heat roller and the eighth heat roller was set to be relaxed. Except these conditions, it processed similarly to Example 3, and obtained the precursor fiber for carbon fiber manufacture of the physical property shown in Table 1.

[Comparative Example 6]
The steam-treated fiber obtained in Example 1 was used as a precursor fiber for carbon fiber production without being subjected to relaxation treatment, and the physical properties are shown in Table 1.

[Comparative Example 7]
The raw material fiber obtained in Example 1 was treated in the same manner as in Example 2 except that a steam-treated fiber was obtained without applying an oil agent to the raw acrylic fiber, and the steam-treated fiber was subjected to a relaxation treatment. . However, yarn breakage occurred during the process, and the target fiber could not be obtained.

[Examples 7 to 10, Comparative Example 8]
Except that the raw acrylic fiber obtained in Example 1 was subjected to an amino-modified silicone oil with an oil agent adhesion amount shown in Table 1 to obtain a steam-treated fiber, and this steam-treated fiber was subjected to a relaxation treatment. The same treatment as in Example 2 was performed to obtain carbon fiber precursor fibers having physical properties shown in Table 1.

[Comparative Examples 9 to 10]
The crude acrylic fiber of the raw material fiber obtained in Example 1 was given an amino-modified silicone oil with an oil agent adhesion amount shown in Table 1 to obtain a steam-treated fiber, and this steam-treated fiber was not subjected to relaxation treatment ( Except for the heat setting treatment (with a fiber relaxation rate of 0%), treatment was carried out in the same manner as in Example 2 or 9 to obtain precursor fibers for producing carbon fibers having the physical properties shown in Table 1.

[Comparative Example 11]
A relaxation treatment was performed in the same manner as in Comparative Example 9, except that the crude acrylic fiber of the raw material fiber obtained in Example 1 was given an amino-modified silicone oil at an oil agent adhesion amount shown in Table 1 to obtain a steam-treated fiber. Without being applied (with a fiber relaxation rate of 0%), heat setting treatment was performed to obtain carbon fiber precursor fibers having physical properties shown in Table 1.

It is a graph which shows the raise of the shrinkage stress with respect to the temperature rise in a steam processing fiber.

Claims (4)

An acrylic precursor fiber for carbon fiber production provided with a silicone-based oil agent, the oil agent adhesion amount in the precursor fiber is 0.01 to 0.25% by mass, and the precursor fiber is 25 ° C. Carbon fiber having a maximum shrinkage stress of 5.0 mN / 30 dtex or less and a single yarn breakage number of less than 1.5 / m Precursor fiber for production. 2. The precursor fiber for producing carbon fiber according to claim 1, wherein the moisture adsorption amount at a humidity of 90% measured by a gas adsorption amount measuring apparatus using water vapor is 15 cm ³ / g or less. The carbon fiber precursor fiber according to claim 1 or 2, comprising a copolymer containing 90% by weight or more of acrylonitrile and having wrinkles on the fiber surface. After applying a silicone oil to a crude acrylic fiber obtained by wet spinning a copolymer obtained by polymerizing a monomer containing 90% by mass or more of acrylonitrile, drying, steam stretching treatment, and then the steam treatment The fiber is brought into contact with a heat roller set at a temperature of 50 to 240 ° C. to heat the steam-treated fiber, and when the temperature of the steam-treated fiber reaches 60 to 80 ° C., the relaxation treatment is started. The method for producing a precursor fiber for producing carbon fibers according to any one of claims 1 to 3, wherein a relaxation treatment is performed until the temperature reaches 120 to 150 ° C.

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