WO2018047692A1

WO2018047692A1 - Coagulated yarn and manufacturing method thereof, carbon fiber precursor fiber, and method for manufacturing carbon fiber

Info

Publication number: WO2018047692A1
Application number: PCT/JP2017/031124
Authority: WO
Inventors: 梶原健太郎; 堀之内綾信; 奥田治己; 野口知久; 渡邉史宜
Original assignee: 東レ株式会社
Priority date: 2016-09-12
Filing date: 2017-08-30
Publication date: 2018-03-15
Also published as: CN109689950A; JPWO2018047692A1; KR20190044588A; EP3511450A4; EP3511450A1; US20190194829A1; TW201819699A

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

Coagulated yarn and method for producing the same, carbon fiber precursor fiber, and method for producing carbon fiber

The present invention relates to carbon fibers that are suitably used for sports applications such as golf shafts, fishing rods, and other general industrial applications, including aircraft members, automobile members, and ship members.

Carbon fiber has been widely used in sports applications, aerospace applications, etc. as a reinforcing fiber for composite materials because of its low specific gravity and high specific strength and specific elastic modulus. In recent years, the application range of automobiles, civil engineering / architecture applications, pressure vessels, windmill blades, and the like has been expanded, and accordingly, further performance improvement has been demanded.

It is known that the performance of carbon fibers is greatly influenced by the performance of carbon fiber precursor fibers. In particular, if the surface layer of the carbon fiber precursor fiber has irregularities, it is considered to cause a decrease in the strength of the carbon fiber, a dry and wet spinning method that is easy to form a smooth surface has been proposed, Further, techniques for improving the strength are widely studied.

For example, Patent Document 1 proposes a technique for controlling the conditions of a wet and wet spinning process using a water-based coagulation bath and a bath stretching process and densifying the oil agent by densifying the surface layer.

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

As a technique characteristic of the coagulation process, Patent Document 3 discloses that a low-concentration polymer solution is gelled in a low-temperature coagulation bath made of alcohol, and the process speed is increased by stretching at a high magnification to improve productivity. Technology has also been proposed.

International Publication No. 2010/143680 Japanese Patent Laid-Open No. 2-74607 Japanese Patent Application Laid-Open No. 2010-100100

When the solidified yarn with a dense surface layer described in Patent Document 1 or the solidified yarn with less voids described in Patent Document 2 is used, the effect of improving the strength of the carbon fiber can be obtained. It was not enough.

Patent Document 1 describes that it is preferable to stretch a coagulated yarn having a degree of swelling of 160% or less under specific conditions, and Examples show examples having a degree of swelling of 100 to 155%. However, according to the study by the present inventors, it has been found that a swelling degree of 100% or more is not sufficient for greatly improving the strength. Patent Document 2 discloses a technique for further reducing the degree of swelling. However, according to the study by the present inventors, if the ratio of paraffinic hydrocarbons is increased in order to reduce the degree of swelling, the solidification rate is increased. It was found that the effect of improving the strength is limited although the carbon fiber has low uniformity, the surface layer has a larger pore size, and the degree of swelling is reduced. Although the technique of Patent Document 3 has an effect of improving productivity, it does not necessarily have an effect of improving strength. This is probably because the polymer concentration of the polymer solution is low, and it is difficult to obtain the denseness necessary to achieve high strength in the coagulation process.

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

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

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

3 is a diagram showing a TEM image of a surface layer of a solidified yarn of Example 1. FIG. 3 is a diagram showing a TEM image of a solidified yarn inner layer of Example 1. FIG. 4 is a diagram showing a TEM image of a surface layer of a coagulated yarn of Comparative Example 1. 5 is a diagram showing a TEM image of a solidified yarn inner layer of Comparative Example 1. FIG.

The present invention provides a carbon fiber with high strength by controlling the pore diameter of the surface layer of the coagulated yarn to be small and controlling the degree of swelling to be extremely small. Further, as another aspect, a high strength carbon fiber is obtained by controlling the pore diameter of the surface layer of the coagulated yarn to be small and also controlling the pore diameter of the inner layer to be small.

In addition, the carbon fiber precursor fiber referred to in the present invention is a precursor fiber that can be converted into carbon fiber, for example, a fiber obtained by stretching a coagulated yarn.

[Coagulated yarn]
(Pore diameter of the surface layer of coagulated yarn)
The coagulated yarn of the present invention has a surface layer pore diameter of 30 nm or less. Since the strength tends to increase as the size decreases, the surface layer pore diameter is preferably 20 nm or less, and more preferably 10 nm or less. If the surface layer pore diameter is 1 nm or less, the solvent is removed in the water washing step, so the lower limit is about 1 nm. The surface layer pore diameter is more preferably 1 nm to 10 nm because the balance between carbon fiber strength and processability can be achieved.

The surface layer referred to in the present invention is a range within 500 nm from the outer periphery toward the inner side in the cross section in the fiber radial direction. The pore diameter 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)
In one aspect of the present invention, the degree of swelling of the coagulated yarn is less than 100%. When the surface layer pore diameter is in the above range, the degree of swelling tends to increase as the degree of swelling decreases, so it is preferably less than 90% and more preferably less than 85%. When the degree of swelling is 3% or less, the solvent is removed in the washing step with time, so the lower limit is about 3%. The degree of swelling is more preferably 3% to 85%, because the carbon fiber strength and processability can be balanced.

(Hole diameter of inner layer of coagulated yarn)
In another aspect of the present invention, the inner layer pore diameter of the coagulated yarn is 30 nm or less. When the surface layer pore diameter is in the above-described range, the smaller the inner layer pore diameter, the higher the strength. Therefore, the inner layer pore diameter is preferably 20 nm or less, and more preferably 10 nm or less. When the inner layer pore diameter is 1 nm or less, the solvent is removed in the water washing step, so that the lower limit is about 1 nm. The inner layer pore diameter is more preferably 1 nm to 10 nm, since the balance between carbon fiber strength and processability can be achieved.

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

[Method for producing coagulated yarn]
The coagulated yarn of the present invention includes, 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 a solvent of the polymer solution used for forming the coagulated yarn. Using a coagulation bath mixed at a ratio of solvent: solvent = 1: 9 to 9: 1, the polymer can be produced by a process including a process of coagulating the polymer.

In the present invention, after the polymer solution is discharged from the die in the spinning process and introduced into the coagulation bath in the coagulation process to precipitate the polymer to form a coagulated thread, the water washing process, the in-bath drawing process, the oil agent application process And 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 diameter and the degree of swelling can be controlled by the condition for solidifying the polymer solution in the coagulation bath, that is, the condition for precipitating the polymer in the polymer solution from the solvent.

(Spinning process)
The spinning method may be either a wet spinning method or a dry and wet spinning method. However, as will be described later, in the present invention, the temperature of the coagulation bath is preferably set low. On the other hand, from the viewpoint of spinnability, the polymer solution needs to have a temperature at which a certain fluidity can be obtained. In many cases, the temperature of the polymer solution is different. For this reason, the dry-wet spinning method is preferred because it 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 converted into carbon fiber, and examples thereof include polyacrylonitrile, a copolymer based on polyacrylonitrile, and a mixture based on polyacrylonitrile. In the description of the present invention, a copolymer having polyacrylonitrile as a main component is called a polymer unless otherwise specified.

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

The polymer concentration 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 polymer concentration. If the polymer is dissolved in the solvent, the upper limit is not particularly limited, but is generally 30% by mass or less. In addition, a high polymer concentration is often preferable for reducing the pore diameter.

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 easily precipitates in the coagulation bath, the size growth is difficult to proceed during the liquid-liquid phase separation process, and the pore diameter tends to be small. Therefore, the polymer solution temperature is preferably 15 to 95 ° C.

(Coagulation process)
The coagulated yarn of the present invention includes, 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 a solvent of the polymer solution used for forming the coagulated yarn. It can be produced by a process including a process of coagulating the polymer using a coagulation bath mixed at 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 larger the difference between the solubility parameter of the non-solvent and the solubility parameter of the polymer, the more difficult it is to dissolve. The present invention has been found that the degree of swelling and the pore size of the inner layer can be reduced by selecting a non-solvent that is close 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 with respect to the solubility parameter of the polymer. When polyacrylonitrile is used as the polymer, the solubility parameter of polyacrylonitrile is 27.4, and the solubility parameter of the preferred non-solvent 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 used herein means a polymer that precipitates when added to a polymer solution in an environment of normal pressure and room temperature. As the solubility parameter, for example, a value of a handbook (see Hansen Solubility Parameters A User's Handbook Second Edition, CRC Press (2007)) or a value calculated by a method described therein is used. When the polymer is a mixture, the difference between the solubility parameter (δ) of the non-solvent and the solubility parameter of each polymer is compared, and the non-solvent parameter having a solubility parameter of -11 to +20 with respect to the solubility parameter of at least one polymer is compared. A solvent is used. When the non-solvent is a mixture, the three parameters of dispersion force (δ _d ), dipole interaction (δ _p ), and hydrogen bond (δ _h ) are added together according to the volume fraction of the mixture. Then, the square root of the sum of the values obtained by squaring the three obtained parameters is taken as the solubility parameter of the non-solvent.
For example, when the non-solvent is a binary mixture 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. Based on the calculated mixed non-solvent δ _d , δ _p , δ _h , the solubility parameter (δ) of the mixed non-solvent is

And can be calculated.

Further, the present inventors have found that the pore diameters of the surface layer and the inner layer can be controlled by mixing a polymer solvent in the coagulation bath. Further, when a non-solvent in the above-described range was used, the roundness tended to decrease. However, by increasing the polymer solvent, an effect of increasing the roundness with a small degree of swelling was found. On the other hand, it was also found that the pore size of the surface layer and the inner layer can be reduced by reducing 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. ~ 6: 4 is more preferred. Further, other substances may be contained within a range not impairing the effects of the present invention. In addition, the ratio said here is a ratio of mass.

The diffusion coefficient D of the non-solvent in the coagulation bath in the present invention is preferably 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 surface layer and inner layer pore sizes. Here, the non-solvent diffusion coefficient D is obtained by a pulse 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 normal NMR measurement, it is possible to extract information on the diffusion transfer distance of a substance, that is, the position of a nuclear spin.

Specifically, it is a method of tracking the attenuation of the target peak intensity based on the PFG intensity change and obtaining the diffusion coefficient from the slope of the attenuation change by exponential function analysis. For the measurement of the non-solvent diffusion coefficient D using actual PFG-NMR, an NMR apparatus (AVANCE III HD 400 manufactured by Bruker Biospin) equipped with a Diff60 probe was used, and the Stejskal-Tanner equation was used.
ln (I / I ₀ ) =-Dγ ² G ² α ² (Δ-α / 3)
Was used to evaluate. Here, G is the magnetic field gradient strength, α is the magnetic field gradient pulse width, Δ is the magnetic field gradient pulse interval (diffusion time), and γ is the nuclear magnetic rotation ratio of the observation nucleus. Ln (I / I ₀ ), which is the signal intensity I normalized by the signal intensity I ₀ when G is the minimum, is plotted against G ² γ ² α ² (Δ-α / 3), and the non-solvent is determined from the slope. The diffusion coefficient D was determined. When two or more kinds of non-solvent species are included, D of the non-solvent having the largest diffusion coefficient D (non-solvent having the fastest diffusion) is defined as D of the coagulating liquid.

The viscosity of the coagulation bath in the present invention is preferably 2 to 1000 mPa · s. When the viscosity of the coagulation bath is high, the degree of swelling tends to be low, and when the viscosity of the coagulation bath is low, the polymer tends to precipitate and the pore diameter tends to be small. The viscosity of the coagulation bath is more preferably 5 to 500 mPa · s, further preferably 10 to 200 mPa.

The coagulation bath in the present invention preferably has a temperature of 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 to precipitate the polymer. On the other hand, when the temperature of the coagulation bath is increased, the yarn forming property is improved, and it is easy to obtain fibers with less fuzz and less interfiber adhesion. The temperature of the coagulation bath is more preferably 20 to 80 ° C lower than that of the polymer solution, and more preferably 30 to 60 ° C.
[Method for producing carbon fiber precursor fiber]
Next, the manufacturing method of the carbon fiber precursor fiber of this invention is demonstrated.

In the present invention, the carbon fiber precursor fiber manufacturing method preferably includes a step of drawing after forming a coagulated yarn by the above-described method. Moreover, after forming a coagulated yarn, it is more preferable to obtain a carbon fiber precursor fiber through a washing process, a drawing process in bath, an oil agent application process, and a drying process. Moreover, it is also a preferable aspect to add a dry heat extending process and a vapor extending process to the above-mentioned process. The solidified yarn may be directly stretched in the bath without the water washing step, or may be stretched in the bath after removing the solvent by the water 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 agent. Moreover, it is preferable to extend | stretch in a heating-heat medium after a drying process as an improvement of productivity or improvement of a crystal orientation degree. As the heating heat medium, for example, pressurized steam or superheated steam is preferably used in terms of operational stability and cost.

When the draw ratio is increased, the molecules are easily aligned in the fiber axis direction, so that the tensile strength when converted to carbon fiber is easily improved. On the other hand, it becomes easy to improve the uniformity in the length direction of the fiber by reducing the draw ratio. For this reason, the total draw ratio is preferably 1 or more and less than 20 times.

[Method for producing carbon fiber]
Next, the manufacturing method of the carbon fiber of this invention is demonstrated.

In the present invention, the carbon fiber production method preferably includes a step of heat treating the carbon fiber precursor fiber after obtaining the carbon fiber precursor fiber. The step of heat treatment here is not particularly limited as long as the carbon fiber precursor fiber is heated when the carbon fiber precursor fiber is converted to carbon fiber. 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 the air at a temperature of 200 to 300 ° C, and the fiber obtained in the flameproofing process is 300 to 800 ° C. Carbon fiber through a preliminary carbonization step of pre-carbonizing in an inert atmosphere at a temperature of 5 and a carbonization step of carbonizing the fiber obtained in the preliminary carbonization step in an inert atmosphere at a temperature of 1,000 to 3,000 ° C. It is preferable to obtain

If a carbon fiber having a higher elastic modulus is desired, graphitization can be performed following the carbonization step. The temperature of the graphitization step is preferably 2,000 to 2,800 ° C. The maximum temperature is appropriately selected and used according to the required characteristics of the desired carbon fiber. The drawing ratio in the graphitization step is preferably selected as appropriate within a range where no deterioration in quality such as generation of fluff occurs according to the required characteristics of the desired carbon fiber.

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

After the electrolytic treatment, a sizing treatment can be applied to give the carbon fiber a converging property. 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.

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

1. Pore diameter of coagulated yarn (1) Sample preparation The liquid contained in the coagulated yarn was replaced with water. Next, the coagulated yarn obtained by freeze-drying the water-substituted coagulated yarn was embedded in a resin, and a 100 nm section was prepared 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 times.

(3) Pore diameter measurement Image processing software JTrim ver. Using 1.53c (Jay Trim), noise removal was performed with an application strength of 50.
B. Using JTrim, A. Histogram normalization was performed on the image obtained in (1).
C. Using JTrim, B. The image obtained in (2) was converted into two gradations with a boundary threshold value of 145.
D. Using image processing software ImageJ 1.50i (Image Jay), C.I. An area was selected with the area selection tool from the image obtained in (1) (surface layer: a range of 500 nm inward from the outer periphery, inner layer: a range of a circle with a diameter of 500 nm centered on the center of gravity of the cross section).
E. Using image processing software ImageJ 1.50i (Image Jay), The area of the portion corresponding to the pores was measured using the particle analysis command with respect to the image obtained in the above, and the particle size was obtained by converting the area into a circle.
F. E. Among the particle diameters obtained in step 1, the average value from the second largest particle to the 31st largest particle size was defined as the particle size. When 31 were not detected, the value of the detected range was used.

2. Swelling degree of coagulated yarn First, about 10 g of coagulated yarn is sampled and washed with water for 12 hours or more. Next, the fiber mass after dehydration is determined by dewatering at 3000 rpm for 3 minutes with a centrifugal dehydrator (for example, H-110A manufactured by Kokusan Co., Ltd.). Thereafter, the dehydrated sample is dried for 2.5 hours with a drier temperature-controlled at 105 ° C., the fiber mass after drying is determined, and the fiber swelling degree is calculated by the following formula.
Formula: Fiber swelling degree (%) = ((fiber mass after dehydration−fiber mass after drying) / fiber mass after drying)) × 100.

3. Tensile strength and elastic modulus of carbon fiber bundles
It was determined in accordance with JIS R7608 (2007) “Testing method for tensile properties using carbon fiber-resin impregnated yarn sample”. The carbon fiber resin-impregnated strand to be measured was 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate (100 parts by mass) / 3 boron trifluoride monoethylamine (3 parts by mass) / acetone (4 parts by mass). Part) was impregnated with carbon fiber or graphitized fiber and cured at a temperature of 130 ° C. for 30 minutes. The number of carbon fiber strands measured was 6, 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 Co., Ltd. was used as 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate.

4). Measurement of non-solvent diffusion coefficient (D) Based on the PFG-NMR method, the 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. did. The measurement temperature was 5 ° C.

(Example 1)
A copolymer of acrylonitrile and itaconic acid was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent and a polymerization initiator to produce a polyacrylonitrile-based copolymer, which was used as a spinning solution.

The obtained spinning solution was controlled at 50 ° C. and once discharged into the air, and dimethyl sulfoxide as a polymer solvent controlled at 5 ° C. was mixed at a ratio of 48% by mass, and non-solvent ethylene glycol was mixed at a ratio of 52% by mass. The coagulated yarn was introduced into a coagulation bath and formed into a coagulated yarn by a dry and wet spinning method with a spinning draft of 2.5. The coagulated yarn 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 stretching in the water bath, dry densification treatment is performed using a heating roller, and stretching is performed in pressurized steam, thereby fully stretching the yarn. The polyacrylonitrile-based carbon fiber precursor fiber having a single fiber fineness of 0.8 dtex was obtained at a magnification of 10. Next, the obtained polyacrylonitrile-based carbon fiber precursor fiber was subjected to a flame resistance treatment in air having a temperature gradient of 220 to 270 ° C. to obtain a flame resistant fiber bundle. The obtained flame-resistant fiber bundle was subjected to a preliminary carbonization treatment in a nitrogen atmosphere at a temperature of 300 to 800 ° C. to obtain a preliminary 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 surface treatment was performed using an aqueous sulfuric acid solution as an electrolytic solution, washing with water and drying, and then a sizing agent was applied to obtain a carbon fiber.

(Example 2)
Carbon fibers were obtained in the same manner as in Example 1 except that methanol was used as a non-solvent 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 at 45 ° C.

Example 4
Carbon fibers were 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)
Carbon fibers were obtained in the same manner as in Example 1 except that glycerin and ethanol were used as non-solvents for the coagulation bath.

(Example 6)
Carbon fibers were obtained in the same manner as in Example 1 except that dimethylformamide was used as the polymer solvent.

(Example 7)
Carbon fibers were 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 of the polymer solvent was changed.

(Example 8)
Carbon fibers were 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 of the polymer solvent was changed.

Example 9
Carbon fibers were obtained in the same manner as in Example 1 except that water and glycerin 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 2.7 × 10 ⁻¹⁰ m ² · S ⁻¹ .

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

(Example 11)
Carbon fibers were obtained in the same manner as in Example 10 except that the coagulation bath temperature was controlled at 25 ° C.

(Example 12)
Carbon fibers were obtained in the same manner as in Example 10 except that the coagulation bath temperature was controlled at −15 ° C.

(Example 13)
Carbon fibers were 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 of the polymer solvent was changed. D evaluated based on PFG-NMR was 3.3 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 14)
Carbon fibers were 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 fibers were obtained in the same manner as in Example 1 except that water and ethanol 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 3.4 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Example 16)
Carbon fibers were 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 of the polymer solvent was changed. D evaluated based on PFG-NMR was 5.3 × 10 ⁻¹⁰ m ² · S ⁻¹ .

(Comparative Example 1)
Carbon fibers were 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 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 no polymer solvent was used in the coagulation bath.

(Comparative Example 3)
Carbon fibers were obtained in the same manner as in Example 1 except that liquid paraffin and decanol were used as non-solvents for the coagulation bath and no polymer solvent was used. The non-solvent species used and their combinations are the same as in the example described in Patent Document 2. The surface layer pore diameter of the obtained coagulated yarn was 42 nm, which was outside the scope of claims 1 to 3.

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

(Comparative Example 5)
Carbon fibers were 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

A coagulated yarn used for the production of 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, wherein the surface layer pore diameter is 30 nm or less and the inner layer pore diameter is 30 nm or less.
The coagulated yarn according to claim 1, wherein the surface layer 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, wherein a non-solvent having a solubility parameter of -11 to +20 with respect to the solubility parameter of the polymer forming the coagulated yarn; A method for producing a coagulated yarn, comprising a step of coagulating the polymer using a coagulation bath in which a solvent of a polymer solution used for formation is mixed at a ratio of non-solvent: solvent = 1: 9 to 9: 1.
The method for producing a coagulated yarn according to claim 4, wherein a coagulation bath having a non-solvent diffusion coefficient of 3.4 × 10 -10 m 2 · S -1 or less is used.
The method for producing a coagulated yarn according to claim 4 or 5, wherein the coagulation bath has a viscosity of 2 to 1000 mPa · s.
The method for producing a coagulated yarn according to any one of claims 4 to 6, wherein the temperature of the coagulation bath is 10 to 100 ° C lower than that of the polymer solution.
The method for producing a coagulated yarn according to any one of claims 4 to 7, comprising a step of spinning with a spinning draft of 1 to 20.
A method for producing a carbon fiber precursor fiber, comprising a step of drawing the coagulated yarn according to any one of claims 1 to 3.
A method for producing a carbon fiber precursor fiber comprising a step of drawing a coagulated yarn by the method for producing a coagulated yarn according to any one of claims 4 to 8, and then drawing the coagulated yarn.
The carbon fiber precursor fiber manufacturing method including the process of heat-treating this carbon fiber precursor fiber, after obtaining the carbon fiber precursor fiber by the manufacturing method of the carbon fiber precursor fiber of Claim 9 or 10.