TW201819699A - Coagulated yarn and manufacturing method thereof, carbon fiber precursor fiber, and method for manufacturing carbon fiber - Google Patents

Abstract

Provided are a coagulated yarn for obtaining carbon fiber having high strength, a carbon fiber precursor fiber using same, and carbon fiber using same. The coagulated yarn, which is used for manufacturing carbon fiber, is a coagulated yarn the surface hole diameter of which is 30 nm or less and the degree of swelling is less than 100% or a coagulated yarn the surface hole diameter of which is 30 nm or less and the inner hole diameter is 30 nm or less. The carbon fiber precursor fiber and the carbon fiber are obtained using such a coagulated yarn.

Description

   Coagulation yarn and its manufacturing method, and carbon fiber precursor fiber and carbon fiber manufacturing method   

The present invention relates to a carbon fiber, which is applicable to aircraft parts, automobile parts, and ship parts, and is applicable to sports applications such as golf clubs, fishing rods, and other general industrial applications.

Carbon fiber is widely used in sports and aerospace applications as a reinforcing fiber for composite materials because of its low specific gravity and high specific strength and modulus of elasticity. In recent years, the range of applications for automobiles and civil / construction applications, pressure vessels and windmill blades has expanded, and with this, the performance has also been required to be further improved.

It is known that the properties of carbon fiber precursor fibers greatly affect the properties of carbon fibers. In particular, if the surface layer of the carbon fiber precursor fiber has irregularities, it is considered to be the main cause of the decrease in the strength of the carbon fiber. Although some wet and dry spinning methods that easily form a smooth surface have been proposed, currently there are extensive discussions on improving the strength technology.

For example, Patent Document 1 proposes a technique for controlling the conditions of the step of dry-wet spinning using a water-based coagulation bath and the step of stretching in the bath, and by densifying the surface layer portion, the penetration of the oil agent is suppressed.

Further, Patent Document 2 proposes a technique for reducing the voids of the coagulated yarn by performing wet-dry spinning using a coagulation bath containing a paraffin-based hydrocarbon.

Patent Document 3 also proposes a technique as a characteristic technique in the coagulation step, which gels a low-concentration polymer solution in a low-temperature coagulation bath containing alcohols, and improves the step by stretching at a high magnification. Speed to increase productivity.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] International Publication No. 2010/143680

[Patent Document 2] Japanese Unexamined Patent Publication No. 2-74607

[Patent Document 3] Japanese Patent Laid-Open No. 2010-100970

When the coagulated filaments for densifying the surface layer described in Patent Document 1 and the pores with fewer holes described in Patent Document 2 are used, the effect of improving the strength of carbon fibers is obtained, but the effect is not sufficient.

Patent Document 1 discloses that it is preferable to extend the coagulated silk having a degree of swelling of 160% or less under specific conditions, and an example in which the degree of swelling is 100 to 155% is disclosed in the Examples. However, according to the study by the inventor of the present case, it is found that in order to greatly increase the strength, the swelling degree of 100% or more is not sufficient. In addition, although Patent Document 2 discloses a technique for making the degree of swelling smaller, according to research by the inventors of the present application, it is known that if the proportion of paraffin-based hydrocarbons is increased in order to reduce the degree of swelling, the carbon fiber may be caused by a slow solidification rate. The uniformity is reduced, and the pore diameter of the surface layer is increased. Even if the swelling degree is reduced, the effect of increasing the strength is limited. The technology of Patent Document 3 has an effect of improving productivity, but it does not necessarily have an effect of increasing strength. The reason is considered to be because the polymer concentration of the polymer solution is low, and it is difficult to obtain the density required to achieve high strength in the coagulation step.

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 the same.

In order to solve the above-mentioned problems, the coagulated silk 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.

In the coagulated filament of the present invention, the surface pore diameter is below 30 nm and the swelling degree is less than 100%; or the surface pore diameter is below 30 nm and the inner layer pore diameter is below 30 nm, thereby obtaining a carbon fiber precursor fiber capable of obtaining high-strength carbon fibers. , And high-strength carbon fiber.

FIG. 1 is a view showing a TEM image of the surface layer of the coagulated silk of Example 1. FIG.

FIG. 2 is a view showing a TEM image of an inner layer of a coagulated filament of Example 1. FIG.

FIG. 3 is a view showing a TEM image of a surface layer of a coagulated silk of Comparative Example 1. FIG.

4 is a view showing a TEM image of an inner layer of a coagulated filament of Comparative Example 1. FIG.

    [Form of Implementing Invention]    

The present invention can obtain high-strength carbon fibers by reducing the pore diameter of the surface layer of the solidified silk and controlling the degree of swelling to be extremely low. Furthermore, as another aspect, by controlling the reduction of the pore diameter of the surface layer of the solidified silk and also the pore diameter of the inner layer, a high-strength carbon fiber can be obtained.

In addition, the carbon fiber precursor fiber referred to in the present invention is a precursor fiber that can be carbonized, for example, a fiber that extends a coagulated filament.

    [Coagulated silk]    

(Hole diameter of solidified silk surface layer)

The coagulated filament of the present invention has a surface layer with a 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. If the surface pore diameter is below 1 nm, there is time to remove the solvent in the water washing step, so the lower limit is about 1 nm. In order to achieve a balance between carbon fiber strength and processability, the surface pore diameter is preferably 1 nm to 10 nm.

The surface layer referred to in the present invention is within a range of 500 nm from the outer circumference to the inner side in the radial cross section of the fiber. The pore size refers to the size of the pores formed by the fibril structure of the coagulated filament and the pores contained therein.

(Swelling degree of coagulated silk)

In one aspect of the present invention, the swelling degree of the coagulated silk is less than 100%. When the surface pore diameter is in the above range, the smaller the degree of swelling, the higher the strength. Therefore, it is preferably less than 90%, and more preferably less than 85%. If the swelling degree is below 3%, there is time to remove the solvent in the water washing step, so the lower limit is about 3%. In order to achieve a balance between carbon fiber strength and processability, the swelling degree is even better at 3% to 85%.

(Hole diameter of the inner layer of coagulated silk)

In another aspect of the present invention, the inner pore diameter of the coagulated filament is 30 nm or less. When the surface layer pore diameter is in the above range, the smaller the inner layer pore diameter, the higher the strength tends to be. Therefore, the inner layer pore diameter is preferably 20 nm or less, and more preferably 10 nm or less. If the inner pore diameter is less than 1 nm, there is time to remove the solvent in the water washing step, so the lower limit is about 1 nm. In order to achieve a balance between carbon fiber strength and processability, the inner layer pore diameter is preferably 1 nm to 10 nm.

The inner layer referred to in the present invention refers to a range of a circle with a diameter within 500 nm, centered on the center of gravity of the cross section in the radial section of the fiber. The pore size refers to the size of the pores formed by the fibril structure of the coagulated filament and the pores contained therein.

    [Manufacturing method of coagulated silk]    

The coagulated silk of the present invention may use, 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 silk and a solvent for forming a polymer solution of the coagulated silk. A coagulation bath mixed at a ratio of non-solvent: solvent = 1: 9 to 9: 1 is produced by a step including a step of coagulating the polymer.

In addition, in the present invention, the polymer solution is preferably discharged from a nozzle in the spinning step, and is introduced into the coagulation bath in the coagulation step to precipitate the polymer to form coagulated yarn, and then the water washing step and the bath extension step Steps of applying an oil agent and drying to obtain carbon fiber precursor fibers. The polymer solution may be subjected to wet spinning or dry-wet spinning to produce the coagulated yarn of the present invention. At this time, the pore diameter and the degree of swelling can be controlled by the conditions under which the polymer solution is coagulated in the coagulation bath, and even the conditions under which the polymer in the polymer solution is precipitated from the solvent.

(Spinning step)

The spinning method may be any of the wet spinning method and the dry-wet spinning method. However, as described below, in the present invention, the temperature of the coagulation bath is preferably set to be low. On the other hand, from the viewpoint of spinnability, the polymer solution must be at a temperature at which a certain flowability can be obtained, and There are many cases where a temperature difference is set between the temperature of the coagulation bath and the temperature of the polymer solution. Therefore, a dry-wet spinning method in which a temperature difference is easily set between the coagulation bath temperature and the polymer temperature (the temperature at which the polymer is discharged from the nozzle) is preferred.

The polymer used in the present invention is not particularly limited as long as it is carbon fiber-soluble, and may be, for example, polyacrylonitrile or a copolymer mainly containing polyacrylonitrile, 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 of the polymer is not particularly limited as long as it dissolves the polymer, and may be, for example, dimethylarsine, dimethylformamide, or dimethylacetamide.

The polymer concentration in the polymer solution is not particularly limited, but it is preferably 10% by mass or more from the viewpoint that a high polymer concentration tends to decrease the degree of swelling. The upper limit is not particularly limited as long as the polymer is dissolved in a solvent, but it is generally 30% by mass or less. In addition, if the polymer concentration is high, there are many cases where it is preferable to reduce the pore diameter.

The higher the temperature of the polymer solution discharged from the nozzle, the easier it is to obtain fluidity. On the other hand, the lower the temperature of the polymer solution, the easier it is to precipitate in the coagulation bath. If the polymer is easily precipitated in the coagulation bath, it becomes difficult to grow in size during the liquid-liquid phase separation process, and therefore it is easy to reduce the pore diameter. Therefore, the temperature of the polymer solution is preferably 15 to 95 ° C.

(Coagulation step)

The coagulated silk of the present invention can be produced, for example, by a step including the steps of using a non-solvent having a solubility parameter of -11 to +20 with respect to the solubility parameter of the polymer forming the coagulated silk, and A step of coagulating the polymer in a coagulation bath in which a solvent of the polymer solution forming the coagulated filament is mixed at a ratio of non-solvent: solvent = 1: 9 to 9: 1. The solubility parameter referred to in the present invention is the Hansen solubility parameter (MPa ^0.5 ).

The difference between the solubility parameter of the non-solvent and the solubility parameter of the polymer has the meaning that the larger the difference, the more difficult it is to dissolve. In the present invention, it has been found that by selecting a non-solvent close to the solubility parameter of the polymer, the swelling degree and the pore diameter of the inner layer can be reduced. Relative to the solubility parameter of the polymer, the solubility parameter of the non-solvent is preferably -9 to +15, and more preferably -7 to +10. When polyacrylonitrile is used as the polymer, the solubility parameter of polyacrylonitrile is 27.4, and the preferred non-solvent solubility parameter is 16.4 to 47.4. Examples of such a non-solvent include methanol or ethanol, propanol, butanol, glycerol or ethylene glycol, propylene glycol, butanediol, acetic acid, ethyl acetate, acetone, benzene, toluene, xylene, cyclohexane, Methyl ethyl ketone, chloroform. The non-solvent referred to here is one which is added to a polymer solution under a normal pressure and normal temperature environment to precipitate a polymer. The solubility parameter is a value calculated using, for example, a value in a manual (refer to Hansen Solubility Parameters A User's Handbook Second Edition, CRC Press (2007)) or a method described. When the polymer is a mixture, the following non-solvent is used: The difference between the solubility parameter (δ) of the non-solvent and the solubility parameter of each polymer is compared with the solubility parameter of at least one polymer by -11 ~ +20 solubility parameter for non-solvent. When the non-solvent is a mixture, three parameters, such as dispersion force (δ _d ), dipole interaction (δ _p ), and hydrogen bond (δ _h ), are added to correspond to the volume fraction of the mixture. Calculate and open the sum of the squared values of the three parameters obtained as the non-solvent solubility parameter.

For example, when the non-solvent includes a two-component mixture of non-solvents A and B, the δ _d , δ _p , and δ _h of the mixed non-solvent are:

Here, and Is the volume fraction of the mixture, . Based on the calculated δ _d , δ _p , and δ _{h of the} mixed non-solvent, the solubility parameter (δ) of the mixed non-solvent can be calculated as .

The inventors of the present invention have found that by mixing the solvent of the polymer with the coagulation bath, the pore diameters of the surface layer and the inner layer can be controlled. In addition, it has been found that when a non-solvent in the above range is used, the roundness tends to decrease, but by increasing the polymer solvent, there is an effect of improving the roundness in a state where the degree of swelling is small. On the other hand, it was also found that if the polymer solvent is reduced, the pore diameters of the surface layer and the inner layer can be reduced. In the aspect of the present invention, the ratio of non-solvent: solvent = 2: 8 ~ 8: 2 is better, the ratio of non-solvent: solvent = 3: 7 ~ 7: 3 is even better, and non-solvent: solvent = 4: 6 ~ 6: 4 is even better. Further, other substances may be included as long as the effects of the present invention are not impaired. In addition, the ratio mentioned here is a ratio of mass.

In the present invention, the diffusion coefficient D of the non-solvent in the coagulation bath is preferably 3.4 × 10 ^-10 m ² / S ^-1 or less. The smaller the diffusion coefficient D, the smaller the swelling degree of the obtained coagulated yarn and the smaller the pore diameters of the surface layer and the inner layer. Here, the non-solvent diffusion coefficient D is obtained by a pulsed magnetic field gradient nuclear magnetic resonance method (PFG-NMR method). In PFG-NMR, by applying a pulsed magnetic field gradient (PFG) in the direction of a static magnetic field in a normal NMR measurement, it is possible to obtain the diffusion distance of a substance, that is, information related to the position of a nuclear spin.

Specifically, it is a method of tracking the attenuation of the peak intensity of an object according to the PFG intensity change, and then obtaining the diffusion coefficient from the slope obtained by analyzing the exponential function of the attenuation change. For the measurement of the non-solvent diffusion coefficient D using actual PFG-NMR, an NMR device (AVANCE III HD 400 manufactured by Bruker Biospin) equipped with a Diff60 probe was used, and the evaluation was performed using the formula of Stejskal-Tanner: ln (I / I ₀ ) =-Dγ ² G ² α ² (Δ-α / 3).

Here, G is the magnetic field gradient intensity, α is the magnetic field gradient pulse width, Δ is the interval (diffusion time) of the magnetic field gradient pulse, and γ is the nuclear magnetic force rotation ratio of the observation core. Plot "In (I / I ₀ ) whose signal intensity I is normalized with signal intensity I ₀ when G is minimum" against G ² γ ² α ² (△ -α / 3), and determine the non-solvent from the slope The diffusion coefficient D. When two or more kinds of non-solvent are included, D of the non-solvent (the fastest-diffusing non-solvent) having the largest diffusion coefficient D 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. Because the viscosity of the coagulation bath is high, it is easy to reduce the swelling degree; because of the low viscosity of the coagulation bath, the polymer is easily precipitated, and the pore diameter is easily reduced. The viscosity of the coagulation bath is more preferably 5 to 500 mPa / s, and even more preferably 10 to 200 mPa.

The temperature of the coagulation bath in the present invention is preferably 10 to 100 ° C lower than the polymer discharged from the nozzle. The lower the temperature of the coagulation bath, the easier it is to precipitate the polymer, and therefore it is easy to reduce the pore diameter. On the other hand, when the temperature of the coagulation bath is increased, the silk-making property is improved, and fibers with less hairiness or adhesion between the fibers are easily obtained. The temperature of the coagulation bath is preferably 20 to 80 ° C lower than the polymer solution, and more preferably 30 to 60 ° C lower.

    [Manufacturing method of carbon fiber precursor fiber]    

Next, the manufacturing method of the carbon fiber precursor fiber of this invention is demonstrated.

In the present invention, the method for producing a carbon fiber precursor fiber preferably includes a step of stretching after forming the coagulated yarn by the above method. Furthermore, it is more preferable to obtain a carbon fiber precursor fiber through the water washing step, the bath stretching step, the oil application step, and the drying step after forming the coagulated yarn. In addition, it is also preferable to add a dry heat extension step or a steam extension step to the above steps. After the coagulated silk thread, the water washing step can be omitted, and the yarn can be directly stretched in the bath, or the solvent can be stretched in the bath after removing the solvent in the water washing step.

After the elongation step in the bath, for the purpose of preventing the single fibers from adhering to each other, it is preferable to provide a silicone oil to the extended fiber threads.

It is preferable to dry after giving an oil agent. In addition, in order to improve productivity and increase the degree of crystal orientation, it is preferable to perform stretching in a heating heat medium after the drying step. As the heating heat medium, for example, pressurized water vapor or superheated water vapor is suitably used from the viewpoint of operation stability and cost.

If the stretching ratio is increased, since the molecules are easily aligned in the fiber axis direction, it is easy to increase the tensile strength during carbon fiber formation. On the other hand, reducing the draw ratio can easily improve the uniformity of the fiber in the length direction. Therefore, the total stretching ratio is preferably more than 1 time and less than 20 times.

    [Manufacturing method of carbon fiber]    

Next, the manufacturing method of the carbon fiber of this invention is demonstrated.

In the present invention, the method for producing a carbon fiber preferably includes a step of heat-treating the carbon fiber precursor fiber after obtaining the carbon fiber precursor fiber. The heat treatment step referred to here is not particularly limited as long as the carbon fiber precursor fiber is heated when the carbon fiber precursor fiber is carbonized, for example, the flameproofing step, the precarbonizing step, the carbonizing step, and the graphitizing step described later. .

In the present invention, it is preferred that the carbon fiber precursor fiber obtained in the above manner is flame-retarded by sequentially performing a flame-retardation step in air at a temperature of 200-300 ° C in an inactive environment at a temperature of 300-800 ° C. The fiber obtained in the flameproofing step is subjected to a pre-carbonization pre-carbonization step, and the fiber obtained in the pre-carbonization step is carbonized in a non-reactive environment at a temperature of 1,000 to 3,000 ° C to obtain a carbon fiber.

In the case where a carbon fiber having a higher elastic modulus is desired, the carbonization step may be followed by graphitization. The temperature of the graphitization step may be 2,000 to 2,800 ° C. The maximum temperature can be appropriately selected and used in accordance with the characteristics required of the expected carbon fiber. The elongation ratio in the graphitization step can be appropriately selected within a range in which no degradation of quality such as hairiness occurs in accordance with the desired characteristics of the carbon fiber.

(Surface modification step)

The obtained carbon fiber can be subjected to electrolytic treatment because its surface is modified. This is because the adhesion to the carbon fiber matrix in the obtained fiber-reinforced composite material can be optimized by electrolytic treatment. It can solve the problems such as brittle failure of the composite material caused by excessive bonding, reduction in tensile strength in the fiber direction, and the high tensile strength in the fiber direction but poor adhesion to the resin, which does not appear in the non-fiber direction. Problems such as strength characteristics occur. As a result, the obtained fiber-reinforced composite material exhibited balanced strength characteristics in both the fiber direction and the non-fiber direction.

After the electrolytic treatment, a sizing treatment may be performed in order to impart binding properties to the carbon fibers. As the sizing agent, a sizing agent having good compatibility with the matrix resin can be appropriately selected according to the type of resin used.

    [Example]    

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

Empty pore diameter

(1) Sample production

The liquid contained in the coagulated silk was replaced with water. Next, the coagulated silk obtained by freezing and drying the coagulated silk replaced with water was embedded with a resin, and then a 100-nm slice was prepared with an ultra-thin microtome.

(2) Observation

After removing the resin from the prepared sections, the observation was performed at an acceleration voltage of 100 kV using a transmission electron microscope. At this time, the cross section of the fiber radial direction was observed at a magnification of 10,000 times.

(3) Measurement of void diameter

A. Use image processing software JTrim ver.1.53c (JTrim) to make the intensity of the application be 50 to remove noise.

B. Use JTrim to normalize the histogram of the image obtained in A.

C. Using JTrim, for the image obtained in B., the threshold of the boundary is 145, and binarization is performed.

D. Use the image processing software ImageJ 1.50i (ImageJ). For the image obtained in C., use the area selection tool to select the area (surface layer: 500nm from the outer circumference to the inside, inner layer: the diameter centered on the center of gravity of the section) 500nm circle range).

E. Use the image processing software ImageJ 1.50i (ImageJ). For the image obtained in D., use the particle analysis command to measure the area of the part corresponding to the pores, and circle convert the area to obtain the particle size.

F. Among the particle diameters obtained in E., an average value from the second largest particle diameter to the 31st largest particle diameter is taken as the particle diameter. When 31 are not detected, the value of the detected range is used.

2. Swelling degree of coagulated silk

First, about 10 g of coagulated silk was sampled and washed with water for more than 12 hours. Next, in a centrifugal dehydrator (for example, H-110A manufactured by Kokusan Co., Ltd.), dehydration is performed at 3000 rpm for 3 minutes, and the fiber quality after dehydration is obtained. Then, the dehydrated sample was dried for 2.5 hr in a dryer adjusted to 105 ° C. to obtain the dried fiber mass, and the fiber swelling degree was calculated by the following formula.

Formula: fiber swelling (%) = ((dehydrated fiber mass-dried fiber mass) / dried fiber mass)) x 100.

3. Tensile strength and elastic modulus of carbon fiber bundles

It was determined in accordance with JIS R7608 (2007) "Test method for tensile characteristics using carbon fiber-resin impregnated yarn samples". 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylic acid ester (100 parts by mass) / 3 boron fluoride monoethylamine (3 parts by mass) / acetone (4 The quality part) is impregnated with carbon fiber or graphitized fiber, and is cured at 130 ° C. for 30 minutes to prepare a resin-impregnated strand of the carbon fiber to be measured. The number of carbon fiber strands measured was six, and the average value of each measurement result was taken as the tensile strength. In this example, "Bakelite" (registered trademark) ERL4221 manufactured by Union Carbide was used as the 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate.

4.Determination of non-solvent diffusion coefficient (D)

According to the PFG-NMR method, a non-solvent diffusion coefficient (D) of each coagulation bath was measured using an NMR apparatus (AVANCE III HD 400 manufactured by Bruker Biospin) equipped with a Diff60 probe. The measurement temperature was 5 ° C.

(Example 1)

A copolymer containing acrylonitrile and itaconic acid was polymerized by a solution polymerization method using dimethylarsinide as a solvent and a polymerization initiator to prepare a polyacrylonitrile copolymer as a spinning solution.

The obtained spinning solution was controlled at 50 ° C, firstly spit out into the air, and then introduced into 48% by mass of dimethylarsin in a polymer solvent controlled at 5 ° C and 52% by mass of non-solvent ethylene glycol. The coagulation bath mixed at this ratio was used as a coagulated yarn by a dry-wet spinning method in which the spinning head was drawn at a speed of 2.5 to draw. The coagulated filaments were washed in a water bath, and then stretched in a water bath. Next, an amine-modified polysiloxane-based polysiloxane oil agent is applied to the fiber bundles after the water bath stretching, and a drying and densification treatment is performed using a heating roller, and the total draw ratio of the yarn is extended by stretching in pressurized steam. 10 times, and a polyacrylonitrile-based carbon fiber precursor fiber having a single fiber fineness of 0.8 dtex was obtained. Next, the obtained polyacrylonitrile-based carbon fiber precursor fiber is subjected to a flame prevention treatment in air having a temperature gradient of 220 to 270 ° C to obtain a flame prevention fiber bundle. In a nitrogen environment at a temperature of 300 to 800 ° C., the obtained flame-retardant fiber bundle is pre-carbonized to obtain a pre-carbonized fiber bundle. The obtained pre-carbonized fiber bundle was subjected to carbonization treatment in a nitrogen environment at a maximum temperature of 1400 ° C. Next, an electrolytic surface treatment was performed using an aqueous sulfuric acid solution as an electrolytic solution, and a sizing agent was added after washing with water and drying to obtain carbon fibers.

(Example 2)

A carbon fiber was obtained in the same manner as in Example 1 except that methanol was used as the non-solvent of the coagulation bath.

(Example 3)

A carbon fiber was 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 the non-solvent of the coagulation bath and the ratio to the polymer solvent was changed.

(Example 5)

Carbon fiber was obtained in the same manner as in Example 1 except that glycerin and ethanol were used as the non-solvent of 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 of 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 of 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 the non-solvent of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated by 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 the non-solvent of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated by 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 of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated by 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 of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated by 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 the non-solvent of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated by 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 of the coagulation bath, and the ratio to the polymer solvent was changed. D evaluated by PFG-NMR was 5.3 × 10 ^-10 m ² ‧S ^-1 .

(Comparative example 1)

A carbon fiber was obtained in the same manner as in Example 1 except that water was used as the non-solvent of the coagulation bath and the ratio to the polymer solvent was changed. D evaluated by PFG-NMR was 3.5 × 10 ^-10 m ² ‧S ^-1 .

(Comparative example 2)

A carbon fiber was obtained in the same manner as in Example 1 except that a 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 fluid paraffin and decanol were used as the non-solvent of the coagulation bath, and no polymer solvent was used. The types of non-solvents used and their combinations are the same as the examples described in Patent Document 2. The surface pore diameter of the obtained coagulated filament was 42 nm, which was outside the range of claims 1 to 3 in the present application.

(Comparative Example 4)

Carbon fiber was obtained in the same manner as in Example 1 except that water was used as the non-solvent of the coagulation bath, dimethylformamide was used as the polymer solvent, and the ratio to the polymer solvent was changed. The type of the non-solvent, the type of the solvent, and the mixing ratio are the same as the examples described in Patent Document 1. The surface pore diameter of the obtained coagulated filament was 35 nm and the degree of swelling was 108%, which was outside the range of claims 1 to 3 of the present application. D evaluated by PFG-NMR was 5.5 × 10 ^-10 m ² ‧S ^-1 .

(Comparative example 5)

A carbon fiber was obtained in the same manner as in Example 1 except that water was used as the non-solvent of the coagulation bath and the ratio to the polymer solvent was changed. D evaluated by PFG-NMR was 5.8 × 10 ^-10 m ² ‧S ^-1 .

Claims (11)

    A coagulated yarn, which is a coagulated yarn used for manufacturing carbon fiber precursor fibers, is characterized in that the surface pore diameter is below 30 nm and the degree of swelling is less than 100%.         A coagulated filament is a coagulated filament used for manufacturing carbon fiber precursor fibers, and is characterized in that the surface layer pore diameter is below 30 nm and the inner layer pore diameter is below 30 nm.         For example, the coagulated silk of claim 1 has a surface pore diameter below 30 nm and an inner layer pore diameter below 30 nm.         A method for producing a coagulated silk, which is the method for producing a coagulated silk according to any one of claims 1 to 3, comprising the step of coagulating the polymer using a coagulation bath described below; Relative to the solubility parameter of the polymer forming the coagulated filament, the non-solvent having a solubility parameter of -11 to +20 and the solvent used to form the polymer solution of the coagulated filament are non-solvent: solvent = 1: 9 ~ 9: 1 ratio mixing coagulation bath.     For example, the method for producing a coagulated yarn according to claim 4 uses a coagulation bath having a non-solvent diffusion coefficient of 3.4 × 10 ^-10 m ² / S ^-1 or less.     For example, the method for manufacturing a coagulated silk according to claim 4 or 5, wherein the viscosity of the coagulation bath is 2 to 1000 mPa‧s.         The method for manufacturing a coagulated silk according to any one of claims 4 to 6, wherein the temperature of the coagulation bath is 10 to 100 ° C lower than the polymer solution.         The method for producing a coagulated yarn according to any one of claims 4 to 7, further comprising a step of spinning a spinning draft of 1 to 20 to perform spinning.         A method for producing a carbon fiber precursor fiber, comprising: a step of extending the coagulated yarn according to any one of claims 1 to 3.         A method for producing a carbon fiber precursor fiber, comprising the steps of: obtaining a coagulated filament by the method for producing a coagulated filament according to any one of claims 4 to 8, and extending the coagulated filament.         A method for producing a carbon fiber, comprising the steps of: after obtaining the carbon fiber precursor fiber by the method for producing a carbon fiber precursor fiber according to claim 9 or 10, and heat-treating the carbon fiber precursor fiber.