JPWO2018047692A1 - Solidified yarn, method for producing the same, carbon fiber precursor fiber, method for producing carbon fiber - Google Patents

Abstract

Provided are a coagulated yarn for obtaining high strength carbon fiber, a carbon fiber precursor fiber using the same, and a carbon fiber using the same. A coagulated yarn used in the production of carbon fibers, wherein the surface pore diameter is 30 nm or less and the degree of swelling is less than 100%, or the surface yarn pore diameter is 30 nm or less, and the inner layer pore diameter is 30 nm or less , And coagulated yarn. Such coagulated yarn is used to obtain carbon fiber precursor fibers and carbon fibers.

Description

  The present invention relates to a carbon fiber suitably used for sports applications such as golf shafts and fishing rods, as well as for general industrial applications, including aircraft parts, automobile parts and marine parts.

  Carbon fibers have been widely used in sports and aerospace applications as reinforcing fibers for composite materials because of their low specific gravity and high specific strength and specific elastic modulus. In recent years, the application range has been expanded for automobiles, civil engineering / building applications, pressure vessels and wind turbine blades, and accordingly, further performance improvement is required.

  It is known that the performance of carbon fibers is largely dependent on the performance of carbon fiber precursor fibers. In particular, if the surface layer of the carbon fiber precursor fiber is uneven, it is considered to be a cause of the decrease in the strength of the carbon fiber, and a dry-wet spinning method that easily forms a smooth surface is proposed. Techniques for further improving the strength are widely studied.

  For example, Patent Document 1 proposes a technique for controlling the conditions of the step of performing dry / wet spinning using a water-based coagulation bath and the step of performing bath drawing, and densifying the surface layer to suppress oil agent intrusion.

  Further, Patent Document 2 proposes a technique for reducing the voids of coagulated yarn by dry and wet spinning using a coagulation bath made of paraffinic hydrocarbon.

  As a technology characterized by the coagulation process, Patent Document 3 gelates a low concentration polymer solution in a low temperature coagulation bath made of alcohol, and improves productivity by increasing the process speed by stretching at a high magnification. Technology has also been proposed.

International Publication No. 2010/143680 JP-A-2-74607 Unexamined-Japanese-Patent No. 2010-100970

  When the coagulated yarn obtained by densifying the surface layer described in Patent Document 1 or the solidified yarn with few voids described in Patent Document 2 is used, although the effect of improving the strength of the carbon fiber is obtained, the effect is obtained. It was not enough.

  Patent Document 1 describes that it is preferable to draw a coagulated yarn having a degree of swelling of 160% or less under a specific condition, and examples show an example of a degree of swelling of 100 to 155%. However, according to the study of the present inventors, it was found that a swelling degree of 100% or more is not sufficient to greatly improve the strength. Further, Patent Document 2 discloses a technique for further reducing the degree of swelling, but according to the study of the present inventors, when the proportion of paraffinic hydrocarbon is increased to reduce the degree of swelling, the solidification rate is increased. It was found that the effect of improving the strength is limited despite the fact that the uniformity of the carbon fiber is low, the pore diameter of the surface layer is large, and the degree of swelling is reduced. Although the technology of Patent Document 3 has the effect of improving the productivity, it has not necessarily the effect of improving the strength. The reason for this is believed to be that it is difficult to obtain the necessary compactness to achieve high strength in the coagulation process because the polymer concentration of the polymer solution is low.

  An object of the present invention is to provide a coagulated yarn and a carbon fiber precursor fiber for obtaining high strength carbon fiber, and a carbon fiber using them.

  In order to solve the above problems, the coagulated yarn of the present invention has a surface pore diameter of 30 nm or less and a swelling degree of less than 100%, or a surface pore diameter of 30 nm or less and an inner layer pore diameter of 30 nm or less. It is

  The coagulated yarn of the present invention is a carbon having high strength because the surface pore diameter is 30 nm or less and the degree of swelling is less than 100%, or the surface pore diameter is 30 nm or less and the inner layer pore diameter is 30 nm or less. Carbon fiber precursor fibers from which fibers are obtained, as well as high strength carbon fibers are obtained.

5 is a view showing a TEM image of the coagulated yarn surface layer of Example 1. FIG. 5 is a view showing a TEM image of the solidified thread inner layer of Example 1. FIG. It is a figure which shows the TEM image of the coagulation | solidification thread surface layer of the comparative example 1. FIG. It is a figure which shows the TEM image of the coagulation | solidification thread | yarn inner layer of the comparative example 1. FIG.

  The present invention is to obtain a carbon fiber with high strength by controlling the pore diameter of the surface layer of the coagulated yarn to a small value and controlling the degree of swelling to an extremely small value. In another embodiment, a carbon fiber having high strength is obtained by controlling the pore diameter of the surface layer of the coagulated yarn to a small value and controlling the pore diameter of the inner layer to a small value.

  In addition, the carbon fiber precursor fiber said by this invention is a precursor fiber which can be carbon-fiber-ized, for example, is the fiber which extended | stretched coagulation | solidification yarn.

[Coagulation yarn]
(Pore diameter of the surface of coagulated yarn)
The coagulated yarn of the present invention has a surface pore diameter of 30 nm or less. The smaller the size, the higher the strength. Therefore, the surface pore diameter is preferably 20 nm or less, and more preferably 10 nm or less. When the surface layer pore diameter is 1 nm or less, the lower limit is about 1 nm because desolvation in the water-washing step has time. The surface pore diameter is more preferably 1 nm to 10 nm because the carbon fiber strength and processability can be balanced.

  The surface layer referred to in the present invention is a range of 500 nm or less inward from the outer periphery in a cross section in the fiber diameter direction. Further, the pore size refers to the size of the pores formed by the fibril structure of the coagulated yarn and the contained voids.

(Swelling degree of coagulated yarn)
One aspect of the present invention is that the degree of swelling of the coagulated yarn is less than 100%. When the surface layer pore diameter is in the above-mentioned range, the degree of swelling tends to be higher as the degree is smaller, so less than 90% is preferable and less than 85% is more preferable. When the degree of swelling is 3% or less, the lower limit is about 3% because it has time for desolvation in the water washing step. It is further preferable that the degree of swelling be 3% to 85% because the carbon fiber strength and processability are well balanced.

(Pore size of inner layer of coagulated thread)
Another aspect of the present invention is that the inner diameter of the coagulated yarn is 30 nm or less. When the surface layer pore size is in the above-mentioned range, the strength tends to increase as the inner layer pore size decreases, so the inner layer pore size is preferably 20 nm or less, more preferably 10 nm or less. When the inner layer pore diameter is 1 nm or less, the lower limit is about 1 nm because there is time for desolvation in the water washing step. The inner layer pore diameter is more preferably 1 nm to 10 nm because the carbon fiber strength and processability are well balanced.

  The inner layer referred to in the present invention is a range of a circle having a diameter of 500 nm or less centering on the center of gravity of the cross section in the cross section in the fiber radial direction. Further, the pore size refers to the size of the pores formed by the fibril structure of the coagulated yarn and the contained voids.

[Method of producing coagulated yarn]
The coagulated yarn of the present invention comprises, as an example, a non-solvent having a solubility parameter of -11 to +20 with respect to the solubility parameter of the polymer forming the coagulated yarn, and the solvent of the polymer solution used for forming the coagulated yarn. It can be manufactured by a process including the process of coagulating the polymer using a coagulation bath mixed in a ratio of solvent: solvent = 1: 9 to 9: 1.

  In the present invention, after a polymer solution is discharged from a die in a spinning step and introduced into a coagulation bath in a coagulation step to precipitate a polymer to form a coagulated yarn, a water washing step, a bath stretching step, an oil agent application step It is preferable to obtain a carbon fiber precursor fiber through a drying process. The coagulated yarn of the present invention can be produced by wet spinning or dry / wet spinning of a polymer solution. At this time, the pore size and the degree of swelling can be controlled by the conditions under which the polymer solution is solidified in the coagulation bath, that is, the conditions under which the polymer in the polymer solution is precipitated from the solvent.

(Spinning process)
The spinning method may be either a wet spinning method or a dry / wet spinning method. However, as described later, in the present invention, it is preferable to set the temperature of the coagulation bath low. On the other hand, from the viewpoint of spinnability, the polymer solution needs to be at a temperature at which constant fluidity can be obtained. In many cases, the temperature of the polymer solution is different. For this reason, a dry-wet spinning method is preferred which easily makes a difference between the coagulation bath temperature and the polymer temperature (polymer discharge nozzle temperature).

  The polymer used in the present invention is not particularly limited as long as it can be carbon fiber, and is, for example, polyacrylonitrile, a copolymer containing polyacrylonitrile as a main component, and a mixture containing polyacrylonitrile as a main component. In the description of the present invention, unless otherwise specified, a copolymer containing polyacrylonitrile as a main component is referred to as a polymer.

  The solvent for the polymer is not particularly limited as long as it dissolves the polymer, and examples thereof include dimethylsulfoxide, dimethylformamide and dimethylacetamide.

  The concentration of the polymer in the polymer solution is not particularly limited, but is preferably 10% by mass or more because the degree of swelling tends to be small due to the high concentration of the polymer. The upper limit is not particularly limited as long as the polymer is dissolved in the solvent, but generally 30% by mass or less. Also, a high polymer concentration is often preferred for reducing the pore size.

  The higher the temperature of the polymer solution discharged from the die, the easier it is to obtain fluidity. On the other hand, the lower the temperature of the polymer solution, the easier the precipitation in the coagulation bath. If the polymer is easily deposited in the coagulation bath, the growth of size is difficult to progress in the liquid-liquid phase separation process, and the pore diameter tends to be small. For this reason, the polymer solution temperature is preferably 15 to 95 ° C.

(Coagulation process)
The coagulated yarn of the present invention comprises, as an example, a non-solvent having a solubility parameter of -11 to +20 with respect to the solubility parameter of the polymer forming the coagulated yarn, and the solvent of the polymer solution used for forming the coagulated yarn. It can be manufactured by a process comprising coagulating the polymer using a coagulation bath mixed in a ratio of solvent: solvent = 1: 9 to 9: 1. The solubility parameter referred to in the present invention is a Hansen solubility parameter (MPa ^0.5 ).

The difference between the nonsolvent's solubility parameter and the polymer's solubility parameter means that the larger the difference, the less soluble it is. The present invention has found that the degree of swelling and the pore size of the inner layer can be reduced by selecting a non-solvent close to the solubility parameter of the polymer. With respect to the solubility parameter of the polymer, the solubility parameter of the nonsolvent is preferably -9 to +15, and more preferably -7 to +10. When polyacrylonitrile is used as a polymer, the solubility parameter of polyacrylonitrile is 27.4, and the preferable nonsolvent solubility parameter is 16.4 to 47.4. Examples of such non-solvents include methanol, ethanol, propanol, butanol, glycerin, ethylene glycol, propylene glycol, butanediol, acetic acid, ethyl acetate, acetone, benzene, toluene, xylene, cyclohexane, methyl ethyl ketone and chloroform. it can. The non-solvent as referred to herein is one which is added to the polymer solution in the environment of normal pressure and normal temperature to precipitate the polymer. As the solubility parameter, for example, the value of a handbook (see Hansen Solubility Parameters A User's Handbook Second Edition, see CRC Press (2007)) or a value calculated according to the described method is used. When the polymer is a mixture, the nonsolvent's solubility parameter (δ) is compared with the difference in the solubility parameter of each polymer, and the nonsolvent has a solubility parameter of -11 to +20 with respect to the solubility parameter of at least one polymer. It uses a solvent. Also, when the non-solvent is a mixture, three parameters of dispersion force (δ _d ), dipolar interaction (δ _p ) and hydrogen bond (δ _h ) are calculated according to the volume fraction of the mixture. Then, for the sum of the values obtained by squaring the three obtained parameters, the square root is taken as the nonsolvent solubility parameter.
For example, in the case of a binary mixture in which the non-solvent is composed of non-solvents A and B, the mixed non-solvents δ _d , δ _p and δ _h are

It is. Here, φ _A and φ _B are volume fractions of the mixture, and φ _A + φ _B = 1. The solubility parameter (δ) of the mixed nonsolvent is calculated from the calculated δ _d , δ _p and δ _h of the mixed nonsolvent

It can be calculated as

  The present inventors also found that the pore diameter of the surface layer and the inner layer can be controlled by mixing the solvent of the polymer into the coagulation bath. Moreover, although the tendency for roundness to fall was seen when the nonsolvent of the above-mentioned range was used, the effect which makes high circularity while swelling degree was small was found by increasing a polymer solvent. On the other hand, it was also found that the pore diameter of the surface layer and the inner layer can be reduced by decreasing the amount of the polymer solvent. In the embodiment of the present invention, the ratio of non-solvent: solvent = 2: 8 to 8: 2 is more preferable, the ratio of non-solvent: solvent = 3: 7 to 7: 3 is more preferable, and non-solvent: solvent = 4: 6 To 6: 4 is more preferable. In addition, other substances may be contained as long as the effects of the present invention are not impaired. In addition, the ratio said here is a ratio of mass.

It is preferable that the nonsolvent's diffusion coefficient D in the coagulation bath in the present invention is 3.4 × 10 ⁻¹⁰ m ² · S ⁻¹ or less. The smaller the diffusion coefficient D, the smaller the degree of swelling of the obtained coagulated yarn and the pore diameter of the surface layer and the inner layer. Here, the nonsolvent's diffusion coefficient D is obtained by pulsed magnetic field gradient nuclear magnetic resonance (PFG-NMR). In PFG-NMR, by applying a pulsed magnetic field gradient (PFG) in the direction of the static magnetic field in normal NMR measurement, it is possible to extract information on the diffusion migration distance of a substance, that is, the position of nuclear spins.

Specifically, it is a method of tracking the attenuation of the target peak intensity based on the PFG intensity change, and determining the diffusion coefficient from the slope by the exponential function analysis of the attenuation change. For measurement of non-solvent diffusion coefficient D using actual PFG-NMR, using the NMR apparatus (AVANCE III HD 400 manufactured by Bruker Biospin) equipped with a Diff 60 probe, the Stejskal-Tanner equation
ln (I / I ₀ ) =-Dγ ² G ² α ² (Δ-α / 3)
It evaluated using. Here, G is the magnetic field gradient strength, α is the magnetic field gradient pulse width, Δ is the interval of the magnetic field gradient pulse (diffusion time), and γ is the nuclear magnetic rotation ratio of the observed nucleus. Plot ln (I / I ₀ ), where signal intensity I is normalized by signal intensity I ₀ when G is minimum, against G ² γ ² α ² (Δ-α / 3), and from the slope, nonsolvent The diffusion coefficient D of was determined. When two or more non-solvent species are contained, D of the non-solvent having the largest diffusion coefficient D (the non-solvent having the fastest diffusion) is defined as D of the coagulation liquid.

  The coagulation bath in the present invention preferably has a viscosity of 2 to 1000 mPa · s. The high viscosity of the coagulation bath tends to lower the degree of swelling, and the low viscosity of the coagulation bath makes it easy for the polymer to precipitate and the pore diameter to be reduced. The viscosity of the coagulation bath is more preferably 5 to 500 mPa · s, further preferably 10 to 200 mPa.

In addition, the coagulation bath in the present invention preferably has a temperature 10 to 100 ° C. lower than that of the polymer discharged from the die. The lower the temperature of the coagulation bath, the easier it is for the polymer to precipitate, and therefore the smaller the pore diameter. On the other hand, when the temperature of the coagulation bath is raised, the spinning property is improved, and it is easy to obtain a fiber with little fluff and adhesion between fibers. The temperature of the coagulation bath is more preferably 20 to 80 ° C. lower than that of the polymer solution, and still more preferably 30 to 60 ° C. lower.
[Method of producing carbon fiber precursor fiber]
Next, the method for producing the carbon fiber precursor fiber of the present invention will be described.

  In the present invention, it is preferable that the method for producing a carbon fiber precursor fiber includes a step of forming a coagulated yarn by the above-mentioned method and then stretching it. In addition, it is more preferable to obtain a carbon fiber precursor fiber after forming a coagulated yarn and then passing through a water washing step, a bath stretching step, an oil agent application step and a drying step. Moreover, it is also a preferable aspect to add a dry heat drawing process and a steam drawing process to the above-mentioned process. The yarn after coagulation may be directly drawn in a bath by omitting a washing step, or may be drawn in a bath after the solvent is removed by a washing step.

  After the in-bath drawing step, it is preferable to apply a silicone-based oil to the drawn fiber yarn for the purpose of preventing adhesion between single fibers.

  It is preferable to dry after applying the oil solution. Moreover, it is preferable to extend | stretch in a heating heat medium after a drying process as a productivity improvement and the improvement of the degree of crystal orientation. As the heating heat medium, for example, pressurized steam or superheated steam is suitably used in terms of operation stability and cost.

  When the draw ratio is increased, the molecules are easily aligned in the fiber axis direction, and thus the tensile strength at the time of carbon fiber formation is easily improved. On the other hand, it becomes easy to improve the uniformity of the longitudinal direction of a fiber by making a draw ratio small. Therefore, the total stretch ratio is preferably 1 or more and less than 20.

[Method of producing carbon fiber]
Next, the method for producing a carbon fiber of the present invention will be described.

  In the present invention, it is preferable that the method for producing carbon fibers includes the step of heat treating the carbon fiber precursor fibers after obtaining the carbon fiber precursor fibers. The heat treatment step is not particularly limited as long as the carbon fiber precursor fiber is heated when carbon fiber precursor fiber is carbonized. A carbonization process, a carbonization process, and a graphitization process.

  In the present invention, the carbon fiber precursor fiber obtained as described above is flameproofed in air at a temperature of 200 to 300 ° C., and the fiber obtained in the flameproof step is 300 to 800 ° C. Carbon fiber through a pre-carbonization step of pre-carbonizing in an inert atmosphere at a temperature of 1, and a carbonization step of carbonizing the fibers obtained in the pre-carbonization step in an inert atmosphere at a temperature of 1,000 to 3,000 ° C. It is preferable to obtain

  If carbon fibers having a higher modulus of elasticity are desired, graphitization can also be performed following the carbonization step. The temperature of the graphitization step may be 2,000 to 2,800 ° C. Moreover, the maximum temperature is suitably selected and used according to the request | requirement characteristic of the desired carbon fiber. The draw ratio in the graphitization step may be appropriately selected within a range that does not cause deterioration in quality such as fuzz generation, according to the required characteristics of the carbon fiber desired.

(Surface modification process)
The obtained carbon fiber can be subjected to an electrolytic treatment for surface modification. It is because the adhesiveness with a carbon fiber matrix can be optimized in the fiber reinforced composite material obtained by electrolytic treatment. It has the problem of brittle fracture of the composite material due to too strong adhesion, the problem that the tensile strength in the fiber direction is reduced, the tensile strength in the fiber direction is high but the adhesion to resin is inferior, and the strength characteristics in the non-fiber direction The problem of not expressing is resolved. As a result, in the fiber-reinforced composite material obtained, balanced strength characteristics are developed in both the fiber direction and the non-fiber direction.

  After the electrolytic treatment, the carbon fiber may be subjected to a sizing treatment in order to impart focusing. As the sizing agent, a sizing agent compatible with the matrix resin can be appropriately selected according to the type of resin used.

  The data in the examples and comparative examples were measured by the following methods.

1. Pore diameter of coagulated yarn (1) Preparation of sample The liquid contained in the coagulated yarn was replaced with water. Next, the coagulated yarn obtained by lyophilizing the water-replaced coagulated yarn was embedded in a resin, and a 100 nm section was produced with an ultramicrotome.

(2) Observation After removing the resin in the prepared section, it was observed at an acceleration voltage of 100 kV using a transmission electron microscope. At this time, the cross section in the fiber diameter direction was observed at a magnification of 10,000.

(3) Pore diameter measurement A. Image processing software JTrim ver. A noise removal was performed with an application strength of 50 using 1.53c (Je Trim).
B. Using JTrim, A. Histogram normalization was performed on the image obtained in.
C. B. using JTrim; Two-tone processing was performed on the image obtained in the above with the threshold of the boundary being 145.
D. C. using the image processing software ImageJ 1.50i (image J); A region was selected with the region selection tool with respect to the image obtained in (Surface: range of 500 nm from the outer periphery toward the inside, inner layer: range of a circle with a diameter of 500 nm centered on the center of gravity of the cross section).
E. Using the image processing software ImageJ 1.50i (image J), D.I. The area of the portion corresponding to the void was measured using the particle analysis command with respect to the image obtained in 4., and the area was converted into a circle to determine the particle size.
F. E. Among the particle sizes obtained in the above, the average value of the second largest particle to the 31st largest particle diameter was taken as the particle diameter. When 31 were not detected, the value of the detected range was used.

2. First, about 10 g of coagulated yarn is sampled and washed with water for 12 hours or more. Next, it spin-dry | dehydrates for 3 minutes at 3000 rpm with a centrifugal dehydrator (for example, H-110A by Koksan Co., Ltd.), and calculates the fiber mass after dewatering. Thereafter, the dehydrated sample is dried for 2.5 hours with a dryer adjusted to a temperature of 105 ° C., the fiber mass after drying is determined, and the degree of fiber swelling is calculated by the following equation.
Formula: degree of swelling of fiber (%) = ((weight of fiber after dehydration−weight of fiber after drying) / weight of fiber after drying) × 100.

3. Tensile strength and elastic modulus of carbon fiber bundle
It was determined in accordance with JIS R 7608 (2007) “Test method for tensile characteristics using carbon fiber-resin-impregnated yarn sample”. The resin impregnated strand of the carbon fiber to be measured is 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate (100 parts by mass) / 3 boron monofluoride monoethylamine (3 parts by mass) / acetone (4 parts by mass) Part) were prepared by impregnating carbon fiber or graphitized fiber and curing at a temperature of 130 ° C. for 30 minutes. Further, the number of carbon fiber strands measured was six, and the average value of the respective measurement results was taken as the tensile strength. In this example, "Bakelite" (registered trademark) ERL4221 manufactured by Union Carbide Co., Ltd. was used as 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate.

4. Measurement of the nonsolvent's diffusion coefficient (D) Based on PFG-NMR method, the nonsolvent's diffusion coefficient (D) of each coagulation bath was measured using NMR equipment (AVANCE III HD 400 manufactured by Bruker Biospin) equipped with a Diff 60 probe. did. The measurement temperature was 5 ° C.

Example 1
A copolymer composed of acrylonitrile and itaconic acid is polymerized by solution polymerization using dimethylsulfoxide as a solvent and a polymerization initiator to prepare a polyacrylonitrile-based copolymer, which is used as a spinning solution.

  The obtained spinning solution was controlled at 50 ° C. and discharged once into the air, and a polymer solvent controlled at 5 ° C. was mixed with 48% by mass of dimethylsulfoxide as a polymer solvent and 52% by mass of ethylene glycol as a nonsolvent. It was introduced into a coagulating bath and was coagulated by a dry-wet spinning method which was pulled at a speed of a spinning draft of 2.5. The coagulated filament was washed in a water bath and then stretched in a water bath. Subsequently, an amino-modified silicone-based silicone oil agent is applied to the fiber bundle after the water-bath drawing, and a drying roller is used to perform a drying and densification treatment, and drawing in pressurized steam is performed. The magnification was made 10 times to obtain a polyacrylonitrile-based carbon fiber precursor fiber having a single fiber fineness of 0.8 dtex. Next, the obtained polyacrylonitrile-based carbon fiber precursor fiber was subjected to a flameproofing treatment in air having a temperature gradient of 220 to 270 ° C. to obtain a flameproofed fiber bundle. The obtained flame-resistant fiber bundle was subjected to pre-carbonization treatment in a nitrogen atmosphere at a temperature of 300 to 800 ° C. to obtain a pre-carbonized fiber bundle. The obtained pre-carbonized fiber bundle was carbonized at a maximum temperature of 1400 ° C. in a nitrogen atmosphere. Subsequently, an electrolytic solution was subjected to electrolytic surface treatment using a sulfuric acid aqueous solution as an electrolytic solution, washed with water and dried, and then a sizing agent was applied to obtain a carbon fiber.

(Example 2)
A carbon fiber was obtained in the same manner as in Example 1 except that methanol was used as a nonsolvent for the coagulation bath.

(Example 3)
Carbon fibers were obtained in the same manner as in Example 1 except that the coagulation bath temperature was controlled to 45 ° C.

(Example 4)
Carbon fiber was obtained in the same manner as in Example 1 except that n-butanol was used as a non-solvent for the coagulation bath and the ratio to the polymer solvent was changed.

(Example 5)
A carbon fiber was obtained in the same manner as in Example 1 except that glycerin and ethanol were used as the non-solvent for the coagulation bath.

(Example 6)
A carbon fiber was obtained in the same manner as in Example 1 except that dimethylformamide was used as the polymer solvent.

(Example 7)
Carbon fiber was obtained in the same manner as in Example 1 except that ethylene glycol and ethanol were used as the non-solvent for the coagulation bath, and the ratio to the polymer solvent was changed.

(Example 8)
Carbon fiber was obtained in the same manner as in Example 1 except that propylene glycol and ethanol were used as the non-solvent for the coagulation bath, and the ratio to the polymer solvent was changed.

(Example 9)
Carbon fiber was obtained in the same manner as in Example 1 except that water and glycerin were used as non-solvents of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 2.7 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 10)
Carbon fiber was obtained in the same manner as in Example 1 except that water and ethylene glycol were used as non-solvents for the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 2.7 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 11)
A carbon fiber was obtained in the same manner as in Example 10 except that the coagulation bath temperature was controlled to 25 ° C.

(Example 12)
A carbon fiber was obtained in the same manner as in Example 10 except that the coagulation bath temperature was controlled to -15 ° C.

(Example 13)
Carbon fiber was obtained in the same manner as in Example 1 except that water and propylene glycol were used as the non-solvent for the coagulation bath and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 3.3 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 14)
Carbon fiber was obtained in the same manner as in Example 1 except that water and methanol were used as the non-solvent for the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 4.4 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 15)
Carbon fiber was obtained in the same manner as in Example 1 except that water and ethanol were used as non-solvents for the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 3.4 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 16)
Carbon fiber was obtained in the same manner as in Example 1 except that water and 1-propanol were used as the non-solvent for the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 5.3 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Comparative example 1)
Carbon fiber was obtained in the same manner as in Example 1 except that water was used as a nonsolvent for the coagulation bath and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 3.5 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Comparative example 2)
Carbon fibers were obtained in the same manner as in Example 1 except that the polymer solvent was not used in the coagulation bath.

(Comparative example 3)
A carbon fiber was obtained in the same manner as in Example 1 except that liquid paraffin and decanol were used as the non-solvent for the coagulation bath and no polymer solvent was used. The non-solvent species used and the combination thereof are the same as the example described in Patent Document 2. The surface pore diameter of the obtained coagulated yarn was 42 nm, which was outside the range of claims 1 to 3.

(Comparative example 4)
Carbon fiber was obtained in the same manner as in Example 1 except that water was used as a nonsolvent for the coagulation bath, dimethylformamide was used as a polymer solvent, and the ratio to the polymer solvent was changed. The non-solvent species, solvent species and mixing ratio used are the same as in the example described in Patent Document 1. The surface layer pore diameter of the obtained coagulated yarn was 35 nm, the degree of swelling was 108%, and it was out of the range of claims 1 to 3. D evaluated based on PFG-NMR was 5.5 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Comparative example 5)
Carbon fiber was obtained in the same manner as in Example 1 except that water was used as a non-solvent for the coagulation bath and the ratio to the polymer solvent was changed. D evaluated based on PFG-NMR was 5.8 × 10 ⁻¹⁰ m ² · S ⁻¹ .

Claims (11)

A coagulated yarn used for producing a carbon fiber precursor fiber, wherein the surface layer pore diameter is 30 nm or less and the degree of swelling is less than 100%. A coagulated yarn used for producing a carbon fiber precursor fiber, the coagulated yarn having a surface pore diameter of 30 nm or less and an inner layer pore diameter of 30 nm or less. The coagulated yarn according to claim 1, wherein the surface pore diameter is 30 nm or less and the inner layer pore diameter is 30 nm or less. The method for producing a coagulated yarn according to any one of claims 1 to 3, comprising: a non-solvent having a solubility parameter of -11 to +20 with respect to a solubility parameter of a polymer forming the coagulated yarn; A method for producing a coagulated yarn, comprising coagulating the polymer using a coagulation bath in which a solvent of a polymer solution used for formation is mixed in a ratio of non-solvent: solvent = 1: 9 to 9: 1. The manufacturing method of the coagulation | solidification thread | yarn of Claim 4 using the coagulation | solidification bath whose diffusion coefficient of a nonsolvent is 3.4 * 10 <^-10> m < ^{2 >} S <^-1> or less. The manufacturing method of the coagulation | solidification thread | yarn of Claim 4 or 5 whose viscosity of the said coagulation bath is 2-1000 mPa * s. The manufacturing method of the coagulation | solidification yarn in any one of Claims 4-6 whose temperature of the said coagulation bath is 10-100 degreeC lower than the said polymer solution. The manufacturing method of the coagulation | solidification yarn in any one of Claims 4-7 including the process of spinning as a spinning draft 1-20. The manufacturing method of a carbon fiber precursor fiber including the process of extending | stretching the coagulation | solidification thread | yarn in any one of Claims 1-3. The manufacturing method of carbon fiber precursor fiber including the process of extending | stretching this coagulation | solidification yarn, after obtaining coagulation | solidification yarn by the manufacturing method of coagulation | solidification yarn in any one of Claims 4-8. A method for producing carbon fiber, comprising the step of heat treating the carbon fiber precursor fiber after obtaining the carbon fiber precursor fiber by the method for producing a carbon fiber precursor fiber according to claim 9 or 10.