JP2015001039A - Carbon fiber precursor fiber and carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carbon fiber precursor fiber and carbon fiber, capable of improving the productivity of a flame resistant step and enhancing a carbonization yield.SOLUTION: Carbon fiber precursor fibers are formed of a mixture containing an aromatic polymer including a structural unit represented by the following general formula (1) and a polyacrylonitrile based polymer. Carbon fibers are obtained by flame-proofing and carbonizing the carbon fiber precursor fiber. R-Rand R-Rare independently selected from a group consisting of -H, -OH, -COOH, -SOH, metal salt of -SOH and -NH(where, except the case that all of R-Rare -H). A is -C≡C- or an aromatic group represented by the above-mentioned general formula (2), and m is 0 or 1.

Description

  The present invention relates to a carbon fiber precursor fiber and a carbon fiber.

  Carbon fiber has excellent mechanical properties and is widely used as a reinforcing material for composite materials. The carbon fiber is manufactured by subjecting the precursor fiber to be a carbon fiber to flame resistance treatment (flame resistance step) to make the flame resistant fiber, and then carbonizing the flame resistant fiber (carbonization step). So far, studies have been made on producing carbon fibers using various raw materials.

In particular, polyacrylonitrile-based carbon fibers (hereinafter abbreviated as “PAN-based carbon fibers”) are used for sports and space applications, civil engineering / architecture, pressure vessels, windmill blades, etc. due to their light weight and excellent mechanical properties. It has been adopted for general industrial use. In recent years, development for aircraft and automobile applications has attracted a great deal of attention.
In order to further expand the market application of PAN-based carbon fibers, it is indispensable to reduce manufacturing costs. In recent years, efforts have been made to improve the productivity of the flameproofing treatment and the carbonization yield.

  However, the PAN-based carbon fiber precursor fiber has the following problems. That is, if the amount of precursor fiber introduced into the flameproofing furnace is increased for the purpose of improving the productivity of the flameproofing process, or if the ambient temperature in the flameproofing furnace is increased, the heat generated by the flameproofing reaction is rapidly increased. Therefore, it becomes easy to store heat excessively in the fiber bundle. As a result, a runaway reaction such that the fiber bundle is burnt / damaged is likely to occur.

In order to solve this problem, a method has been proposed in which the flameproofing treatment is performed at the lowest possible atmospheric temperature to suppress the heat generation associated with the flameproofing reaction.
However, this method has problems such as spending a long time for the flameproofing treatment, difficult to improve the flameproofing speed, and requiring a large amount of heat energy. In addition, PAN-based polymers used as precursor fibers for PAN-based carbon fibers tend to be partially thermally decomposed when the ambient temperature is raised and carbonized, and the carbonization yield is theoretically predicted. It was difficult to improve.

Various techniques have been reported so far to solve the above problems. For example, Patent Document 1 discloses a technique for accelerating a flame resistance reaction of a nitrile group of a PAN polymer by copolymerizing an acrylonitrile monomer and a monomer having a functional group such as a carboxy group. ing.
In Patent Document 2, by adding 0.01 to 10% by mass of boron or a boron compound to a precursor fiber of a PAN-based carbon fiber, a uniform flameproof yarn structure is formed in the fiber cross-sectional direction, Techniques for obtaining carbon fibers having high strength and elastic modulus by carbonization have been proposed.

JP 2002-145939 A Japanese Patent Laid-Open No. 3-174019

The technique described in Patent Document 1 has a certain effect in improving the productivity and carbonization yield of the flameproofing process, but in order to maintain the physical properties and quality of the carbon fiber, it is copolymerized with an acrylonitrile monomer. There was a limit to the amount of monomer.
The technique described in Patent Document 2 has a certain effect on improving the physical properties of the carbon fiber, but Patent Document 2 particularly describes the suppression of heat generation during the flameproofing treatment and the final carbonization yield of the carbon fiber. It has not been.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the carbon fiber precursor fiber and carbon fiber with improved productivity of a flame-proofing process, and a high carbonization yield.

The present invention has the following aspects.
[1] A carbon fiber precursor fiber comprising a mixture containing an aromatic polymer containing a structural unit represented by the following general formula (1) and a polyacrylonitrile polymer.

In formula (1), R ¹ , R ² , R ³ and R ⁴ are independently selected from the group consisting of a hydrogen atom, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. . However, the case where all of R ¹ , R ² , R ³ , and R ⁴ are hydrogen atoms is excluded. A is —C≡C— or an aromatic group represented by the following general formula (2), and m is 0 or 1.

In formula (2), R ⁵ , R ⁶ , R ⁷ and R ⁸ are independently selected from the group consisting of a hydrogen atom, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. .

[2] The carbon fiber precursor fiber according to [1], wherein the mixture contains the aromatic polymer in an amount of 30 parts by mass to 100 parts by mass with respect to 100 parts by mass of the polyacrylonitrile polymer.
[3] A carbon fiber obtained by flameproofing and carbonizing the carbon fiber precursor fiber according to [1] or [2].

  ADVANTAGE OF THE INVENTION According to this invention, the productivity of a flameproofing process improves and the carbon fiber precursor fiber and carbon fiber with a high carbonization yield can be provided.

Hereinafter, the present invention will be described in detail.
[Carbon fiber precursor fiber]
The carbon fiber precursor fiber of the present invention comprises a mixture containing an aromatic polymer described below and a polyacrylonitrile polymer (hereinafter also referred to as “PAN polymer”).

<Aromatic polymer>
The aromatic polymer includes a structural unit represented by the following general formula (1).

In formula (1), R ¹ , R ² , R ³ and R ⁴ are independently selected from the group consisting of a hydrogen atom, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. . However, the case where all of R ¹ , R ² , R ³ , and R ⁴ are hydrogen atoms is excluded. A is —C≡C— or an aromatic group represented by the following general formula (2), and m is 0 or 1.

In formula (2), R ⁵ , R ⁶ , R ⁷ and R ⁸ are independently selected from the group consisting of a hydrogen atom, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. .

That is, the structural unit represented by the general formula (1) has at least one benzene ring in the main chain structure, and one or two hydrogen atoms of the benzene ring are an acetylene group (—C≡C -), And at least one of the remaining hydrogen atoms is substituted with a polar functional group selected from the group consisting of a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group.
By introducing one or more of the above polar functional groups into a benzene ring having an acetylene group, it becomes soluble in a polar solvent that dissolves the PAN-based polymer, and the compatibility between the aromatic polymer and the PAN-based polymer. Will improve.
The number of substitution of the polar functional group per benzene ring is not particularly limited, but if it is 1 substitution or 2 substitution per benzene ring, the compatibility with the PAN polymer can be maintained well.

  The structural unit represented by the general formula (1) is any of the structural units represented by the following general formulas (3), (4), and (5). These structural units may be used individually by 1 type, and may use 2 or more types together. When two or more types are used in combination, a structural unit represented by the following general formula (4) in which the acetylene group (—C≡C—) is bonded to the position of A at the meta position, and the acetylene group is A The greater the proportion of the structural unit represented by the following general formula (5) bonded in the ortho position with respect to the position, the higher the solubility of the aromatic polymer in the polar solvent becomes. This is preferable because the compatibility of the PAN-based polymer is improved and the carbonization yield is increased.

R ¹ , R ² , R ³ , R ⁴ , A and m in the formulas (3), (4) and (5) are respectively R ¹ , R ² , R ³ and R in the general formula (1). ^4. Same as A, m.

  The aromatic group represented by the general formula (2) is any of the aromatic groups represented by the following general formulas (6), (7), and (8). These aromatic groups may be used individually by 1 type, and may use 2 or more types together. When two or more kinds are used in combination, the aromatic group represented by the following general formula (7) in which two bonds are in a meta position and the following general formula (8 in which two bonds are in an ortho position) ), The higher the aromatic group ratio, the higher the solubility of the aromatic polymer in the polar solvent, the better the compatibility of the aromatic polymer and the PAN polymer, and the higher the carbonization yield. Since it becomes high, it is preferable.

Equation (6), (7), R 5, R 6, R 7, R 8 in (8), respectively the same as ^{R 5, R 6, R 7} , R 8 in the general formula (2) is there.

  Specific examples of the structural unit represented by the general formula (1) include structural units represented by the following general formulas (9), (10), and (11). By using an aromatic polymer containing these structural units, it is possible to improve the problem of productivity of the flameproofing process and the carbonization yield, which are problems of the precursor fiber of the conventional PAN-based carbon fiber.

R ¹ , R ² , R ³ , R ⁴ , A and m in the formulas (9), (10) and (11) are respectively R ¹ , R ² , R ³ and R in the general formula (1). ^4, a, is the same as ^{m, R 5, R 6,} R 7, R 8 in the formula (9), and ^{R 5, R 6, R 7} , R 8 in each of the above general formula (2) The same.

As a method for obtaining an aromatic polymer containing any of the structural units represented by the general formulas (9), (10), and (11), the following known methods can be used. The method is not particularly limited.
For example, the aromatic polymer containing the structural unit represented by the formula (9) is prepared by combining a compound of any combination shown in the following (a) to (c) with palladium in the presence of a basic compound such as triethylamine. A Heck reaction method (J. Organomet. Chem., J. Org. 93, 259 (1975)).
The aromatic polymer containing the structural unit represented by the formula (10) is obtained by the above Heck reaction method using a combination of compounds shown in the following (b).
(A): Combination of a diethynylbenzene substitute and a dihalogenated benzene (b): A combination of a diethynylbenzene substitute and a dihalogenated benzene substitute (c): A diethynylbenzene and a dihalogenated benzene substitute Combination with

  The aromatic polymer containing the structural unit represented by the formula (11) uses a diethynylbenzene substitution product as a catalyst with a copper complex having a bidentate ligand (such as copper-TMEDA (tetramethylethylenediamine)). And a Hay coupling method (J. Polym. Sci., Part A, 7, 1652, (1969)) in which oxidative polycondensation is performed in an oxygen atmosphere.

Examples of the diethynylbenzene include 1,4-diethynylbenzene, 1,3-diethynylbenzene, and 1,2-diethynylbenzene.
Examples of the substituted diethynylbenzene include 1,4-diethynylbenzene, 1,3-diethynylbenzene, and at least one hydrogen atom on the benzene ring of 1,2-diethynylbenzene, which is a hydroxy group or a carboxy group. , Sulfonic acid groups, metal salts of sulfonic acid groups, and compounds substituted with at least one substituent (polar functional group) selected from the group consisting of amino groups. Specifically, 1,4-diethynyl-2-hydroxybenzene, 1,4-diethynyl-2-carboxybenzene, 1,4-diethynyl-2-benzenesulfonic acid, 1,4-diethynyl-2-aminobenzene, 1,3-diethynyl-5-hydroxybenzene, 1,3-diethynyl-5-carboxybenzene, 1,3-diethynyl-5-benzenesulfonic acid, sodium 1,3-diethynyl-5-benzenesulfonate, 1,3 Examples include, but are not limited to, -diethynyl-5-aminobenzene.

  Examples of the dihalogenated benzene include 1,4-dibromobenzene, 1,3-dibromobenzene, 1,2-dibromobenzene, 1,4-dichlorobenzene, 1,3-dichlorobenzene, 1,2-dichlorobenzene, 1 , 4-diiodobenzene, 1,3-diiodobenzene, 1,2-diiodobenzene, 1-bromo-4-chlorobenzene, 1-bromo-3-chlorobenzene, and the like. is not.

  The substituted dihalogenated benzene is selected from the group consisting of at least one hydrogen atom on the benzene ring of the dihalogenated benzene, consisting of a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. And a compound substituted with at least one substituent (polar functional group). Specifically, 1,4-dibromo-2-hydroxybenzene, 1,4-dibromo-2-carboxybenzene (2,5-dibromobenzoic acid), 1,4-dibromo-2-benzenesulfonic acid, 1, 4-dibromo-2-aminobenzene, 1,3-dibromo-5-hydroxybenzene, 1,3-dibromo-5-carboxybenzene, 1,3-dibromo-5-benzenesulfonic acid, 1,3-dibromo-5 -Sodium benzenesulfonate, 1,3-dibromo-5-aminobenzene, 1,4-dichloro-2-hydroxybenzene, 1,4-dichloro-2,5-dihydroxybenzene (2,5-dichloro-1,4 -Benzenediol), 1,4-dichloro-2-carboxybenzene (2,5-dichlorobenzoic acid), 1,4-dichloro-2-benzenesulfonic acid 2,5-dichlorobenzenesulfonic acid), 1,4-dichloro-2-aminobenzene, 1,4-dichloro-2,5-diaminobenzene (2,5-dichloro-1,4-phenylenediamine), 1, 3-dichloro-5-hydroxybenzene, 1,3-dichloro-5-carboxybenzene, 1,3-dichloro-5-benzenesulfonic acid, sodium 1,3-dichloro-5-benzenesulfonate, 1,3-dichloro Although -5-aminobenzene etc. are mentioned, it is not limited to these.

Of the total units (100 mol%) constituting the aromatic polymer, the proportion of the structural unit represented by the general formula (1) is preferably 80 mol% or more, more preferably 90 mol% or more, Especially preferably, it is 100 mol%.
When the aromatic polymer is composed of only the structural unit represented by the general formula (1), the number of repeating units (n) is not particularly limited as long as it is 1 or more, preferably 2 or more. More preferably, it is 10 or more, and particularly preferably 30 or more. In addition, the upper limit of the number of repetitions (n) in this case is not particularly limited, but is preferably 1000 or less from the viewpoint that good compatibility between the aromatic polymer and the PAN polymer can be maintained.

The aromatic polymer may contain other structural units other than the structural unit represented by the general formula (1).
As the monomer from which the other structural unit is derived, for example, the above-described diethynylbenzene and a substituted product thereof, a dihalogenated benzene and a monomer copolymerizable with the substituted product are preferable.

<Polyacrylonitrile polymer>
As the PAN-based polymer, a homopolymer of acrylonitrile (polyacrylonitrile) or a copolymer of acrylonitrile and another monomer can be used. These homopolymers and copolymers may be used in combination.
When a copolymer is used, all the units (100 mol%) constituting the copolymer are reduced from the viewpoint of reducing defects caused by the copolymer component when the carbon fiber is formed and improving the quality and performance of the carbon fiber. Of these, the proportion of acrylonitrile units is preferably 80 mol% or more.

  Other monomers are not particularly limited as long as they are copolymerizable with acrylonitrile. For example, acrylic esters such as methyl acrylate and ethyl acrylate; methacrylic esters such as methyl methacrylate and ethyl methacrylate; Examples thereof include unsaturated monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, styrene, and vinyl toluene; methallylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, and alkali metals thereof. These other monomers may be used alone or in combination of two or more. In terms of maintaining melt spinnability, the proportion of other monomer units is preferably 5 mol% or more.

The PAN-based polymer can be obtained, for example, by radical polymerization of acrylonitrile and other monomers as necessary. Radical polymerization is preferred because it is easy to operate.
When performing radical polymerization, any polymerization method such as solution polymerization, suspension polymerization, and emulsion polymerization may be employed. In particular, suspension polymerization and emulsion polymerization are preferable because a polymer having a high degree of polymerization can be obtained relatively easily.

  The polymerization initiator and catalyst used for radical polymerization are not particularly limited, and examples thereof include azo compounds, organic peroxides, or redox catalysts such as persulfuric acid / sulfurous acid, chloric acid / sulfurous acid, or ammonium salts thereof.

In the case of radical emulsion polymerization, at least one of an emulsifier and a dispersant is required. The emulsifier and dispersant in this case are not particularly limited, and various anionic types, nonionic types, and cationic types can be used.
In particular, as an emulsifier, an anionic surfactant (for example, aliphatic soap, alkyl sulfate, dialkyl sulfosuccinate, sulfonated ester, sulfonated amide, etc.) and a nonionic surfactant (for example, fatty acid such as polyethylene glycol, polypropylene glycol) Radical emulsion polymerization using propyl mercaptan, isopropyl mercaptan, butyl mercaptan, benzyl mercaptan, octyl mercaptan, lauryl mercaptan, etc. as molecular weight regulators is suitable. .

<Other ingredients>
The mixture contains at least the above-mentioned aromatic polymer and PAN-based polymer, but if it is within the range not impairing the effects of the present invention, the aromatic polymer and the PAN-based polymer may be used as necessary. You may contain other components other than coalescence.

<Composition of the mixture>
The mixture preferably contains 30 to 100 parts by mass of an aromatic polymer, more preferably 40 to 80 parts by mass, particularly preferably 100 parts by mass of the PAN polymer. Is 50 parts by mass or more and 60 parts by mass or less. If content of an aromatic polymer is 30 mass parts or more, the exothermic reaction at the time of a flame-proofing process will fully be suppressed, and a carbonization yield will improve more. On the other hand, when the content of the aromatic polymer is 100 parts by mass or less, the strength of the obtained carbon fiber precursor fiber can be made sufficient while maintaining spinnability.
In addition, when a mixture contains another component, the content is preferable 20 mass parts or less with respect to 100 mass parts of PAN polymers, More preferably, it is 10 mass parts or less.

<Method for producing carbon fiber precursor fiber>
The carbon fiber precursor fiber includes, for example, a preparation step in which a polymer solution is prepared by dissolving a mixture containing an aromatic polymer and a PAN polymer in a solvent, and a wet spinning method or a wet and dry method from the polymer solution. It is obtained through a spinning step of obtaining precursor fibers by a type spinning method. That is, the spinning dope used in the present invention is a polymer solution containing at least an aromatic polymer, a PAN polymer, and a solvent.

As the solvent used in the preparation step, an aprotic polar solvent can be used. Examples of the aprotic polar solvent include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, tetrahydrofuran, N-methylpyrrolidone, sulfolane and the like. These aprotic polar solvents may be used alone or in combination of two or more.
The aprotic polar solvent mentioned above is excellent in the solubility of an aromatic polymer and a PAN polymer. Among them, N-methylpyrrolidone is particularly preferable in that the spinning stock solution has high coagulability.

In order to perform stable spinning using this polymer solution and obtain a dense and homogeneous coagulated yarn, it is important that the polymer concentration of the spinning dope is in an appropriate range.
The total concentration of the aromatic polymer and the PAN polymer in the spinning dope is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less, and particularly preferably. Is 10 mass% or more and 20 mass% or less. If the polymer concentration is 1% by mass or more, the spinning dope has sufficient spinnability, so that spinning can be performed stably. On the other hand, if the polymer concentration is 40% by mass or less, the aromatic polymer and the PAN polymer can be uniformly dissolved in the solvent, and the viscosity increases rapidly even if the spinning solution is left for a long time. It's hard to get up.

  The present inventor is examining the fiberization of the mixture containing the aromatic polymer and the PAN polymer described above, and that these polymers are dissolved in an aprotic polar solvent (good solvent). Focused on. The inventors have found that when the polymer solution is used as a spinning stock solution and discharged into a specific solvent (poor solvent), a fibrous material is formed by a coagulation action.

That is, according to the present invention, the precursor fiber can be obtained from the polymer solution using a wet spinning method or a dry wet spinning method.
Here, the “wet spinning method” is a method of obtaining a coagulated yarn (precursor fiber) by discharging a spinning solution from a die having a predetermined pore diameter to a coagulation bath solution. On the other hand, the “dry and wet spinning method” is a method in which a spinning stock solution is once discharged into the air from a die having a predetermined pore diameter and then introduced into a coagulating bath solution to obtain a coagulated yarn.
The coagulation bath solution used in the present invention is preferably water (tap water, pure water, ion exchange water, etc.).

If necessary, the coagulation bath solution may contain the aprotic polar solvent used in the polymer solution.
The concentration of the aprotic polar solvent in 100% by mass of the coagulation bath solution is preferably 5% by mass to 40% by mass, more preferably 10% by mass to 30% by mass, and particularly preferably 15% by mass to 20% by mass. % Or less. If the concentration of the aprotic polar solvent is 5% by mass or more, it is easy to prevent the coagulation rate from increasing, and it is easy to prevent the coagulated yarn from shrinking rapidly or the yarn compactness from decreasing. Can do. On the other hand, if the concentration of the aprotic polar solvent is 40% by mass or less, it is possible to easily prevent the coagulation rate from being lowered, and to suppress adhesion between single yarns of the obtained precursor fiber.

  The temperature of the coagulation bath solution is preferably 20 ° C. or higher and 45 ° C. or lower, and more preferably 25 ° C. or higher and 40 ° C. or lower. If the temperature of the coagulation bath solution is 20 ° C. or more, it is possible to easily prevent the coagulation tension from increasing and to suppress the occurrence of single yarn breakage in the coagulation bath solution. On the other hand, if the temperature of the coagulation bath solution is 45 ° C. or lower, it is possible to prevent the strand strength of the carbon fibers obtained by firing the precursor fibers from being lowered.

<Effect>
The carbon fiber precursor fiber of the present invention described above is obtained by spinning a mixture containing an aromatic polymer and a PAN polymer. The aromatic polymer is a polymer containing the structural unit represented by the above general formula (1), and has a feature that the calorific value upon heat treatment is extremely small and the carbonization yield is excellent. Yes. At least one polar function selected from the group consisting of at least one hydrogen atom on the benzene ring of the aromatic polymer, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. Substitution with a group has an effect of improving the compatibility between the aromatic polymer and the PAN-based polymerization.

In addition, the carbon fiber precursor fiber of the present invention has flame resistance compared to a carbon fiber precursor fiber made of a PAN polymer alone, due to the effect that an aromatic polymer is blended with a PAN polymer. The reaction exotherm and exotherm rate are suppressed. Thereby, the operation of the flame resistance treatment, which was difficult to control with the precursor fiber of the conventional PAN-based carbon fiber, becomes easy, and the productivity is improved.
In addition, the carbon fiber precursor fiber of the present invention also has a marked improvement in carbonization yield after carbonization compared to a carbon fiber precursor fiber made of a PAN polymer alone.
These characteristics are that the PAN polymer and the aromatic polymer are uniformly compatible, and the flameproofing reaction and the carbonization reaction are synergistic and synergistic between the PAN polymer and the aromatic polymer. It is thought that it progresses to.

  Moreover, since the aromatic polymer containing the structural unit represented by the general formula (1) is soluble in a polar solvent that dissolves the PAN polymer, the aromatic polymer, the PAN polymer, Can be mixed and dissolved in the above-mentioned aprotic polar solvent to obtain a spinning dope. From this spinning dope, carbon fiber precursor fibers can be stably obtained by a wet spinning method or a dry and wet spinning method. Moreover, the obtained carbon fiber precursor fiber also has sufficient mechanical strength.

  Therefore, if the carbon fiber precursor fiber of the present invention is used, flame-resistant fibers can be stably produced at a low temperature and with a small amount of heat supply, and carbon fibers having a high carbonization yield can be produced at low cost.

[Carbon fiber]
Next, the carbon fiber of the present invention will be described.
The carbon fiber of the present invention is obtained by flameproofing and carbonizing the above-described carbon fiber precursor fiber of the present invention. Specifically, first, a carbon fiber precursor fiber is subjected to a flameproofing treatment (flameproofing step) to obtain a flameproofed fiber, and then the flameproofing fiber is carbonized (carbonization step) to produce a carbon fiber. To do.

The flameproofing treatment can be performed by a known method. The temperature of the flameproofing treatment is preferably 150 ° C. or higher and 400 ° C. or lower. When the temperature of the flameproofing treatment is less than 150 ° C., the progress rate of the flameproofing reaction is slowed down, and it becomes difficult to perform the flameproofing treatment in a short time, so that it is difficult to reduce the manufacturing cost. On the other hand, if the temperature of the flameproofing treatment exceeds 400 ° C., the aromatic polymer or PAN polymer constituting the carbon fiber precursor fiber is likely to be thermally decomposed.
The time for the flameproofing treatment is preferably 5 hours or less, more preferably 3 hours or less from the viewpoint of productivity.

As the atmosphere for performing the flameproofing treatment, either an inert atmosphere or an oxidizing atmosphere can be used, but an inert atmosphere is preferable from the viewpoint of the thermal stability of the aromatic polymer.
Here, the “inert atmosphere” is an atmosphere containing a known inert substance such as nitrogen, argon, or helium. Among these, a nitrogen atmosphere is preferable from the viewpoint of economy. The nitrogen purity may be 99% or more. On the other hand, the “oxidizing atmosphere” is an atmosphere containing a known oxidizing substance such as air, oxygen, or nitrogen dioxide.

The carbonization treatment can be performed by a known method. The carbonization treatment temperature is preferably 500 ° C. or more and 2000 ° C. or less.
The atmosphere for performing the carbonization treatment is preferably an inert atmosphere.

  The carbonized fiber obtained in the carbonization step can be used as carbon fiber as it is. Moreover, you may use what carbonized fiber was graphitized by the well-known method as needed (graphite fiber) as carbon fiber. For example, graphitized carbon fiber is obtained by heating the carbonized fiber under an inert atmosphere at a maximum temperature exceeding 2000 ° C. and not exceeding 3500 ° C.

<Effect>
As described above, since the carbon fiber of the present invention uses the carbon fiber precursor fiber of the present invention, the productivity and carbonization yield in the flameproofing process are greatly improved. And according to this invention, carbon fiber can be manufactured at low cost.

<Application>
The carbon fiber of the present invention is suitable for a flameproof material, a heat insulating material and the like. It is also useful for electrode materials for applications such as water purification, air purification, gas adsorption, water treatment, decolorization, tobacco filters, clean room filters, secondary batteries, electrolytic capacitors, and electric double layer capacitors.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.
Each measurement / evaluation method in this example is as follows.

[Measurement / Evaluation]
<Measurement of maximum heat generation rate, maximum heat generation temperature, and heat generation>
Using a differential scanning calorimeter (“DSC220” manufactured by SII Nano Technology Co., Ltd.), DSC measurement was performed according to the following procedure.
2 mg ± 0.5 mg of carbon fiber precursor fiber was put in a sample container and kept at 30 ° C. for 30 minutes in a nitrogen atmosphere. Next, the temperature was increased from 30 ° C. to 400 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen atmosphere. In DSC measurement, heat generation starts after a slight induction period, and the heat generation amount attenuates after the heat generation amount reaches a peak. The temperature at which the exothermic peak showed the maximum value was taken as the maximum exothermic temperature. The maximum value of the exothermic peak was defined as the maximum exothermic rate, and the area of the exothermic peak was defined as the calorific value.

<Measurement of carbonization yield>
The mass of the carbon fiber precursor fiber and the mass of the carbon fiber obtained from the carbon fiber precursor fiber were measured, and the carbonization yield was determined from the following formula (I).
Carbonization yield (%) = (mass of carbon fiber / mass of carbon fiber precursor fiber) × 100 (I)

<Evaluation of spinnability>
The spinning solution was prepared by dissolving the polymer in a predetermined solvent to a concentration of 6% by mass. The obtained spinning dope was temperature adjusted to 30 ° C., and discharged into a coagulation bath solution adjusted to 30 ° C. from a die having a pore diameter of 0.1 mm at a speed of 1.0 m / min. The solidified yarn thus shaped was wound on a drive roller at a speed of 1.5 m / min for 30 minutes. During this time, the number of yarn breaks in the coagulation bath solution was counted, and the spinnability was evaluated according to the following evaluation criteria.
A: The number of thread breaks is 5 or less.
○: The thread breakage number is 6 times or more and 10 times or less.
Δ: The yarn breakage number was 11 or more, but the coagulated yarn could be wound up.
X: It is difficult to wind up the coagulated yarn.

[Production Example 1: Synthesis of Compound A]
In a reaction vessel, 3.3 g (26 mmol) of 1,4-diethynylbenzene, 5.1 g (26 mmol) of 2,5-dichlorobenzoic acid, 0.1 mol equivalent of palladium chloride, 0.1 mol equivalent of copper acetate, , 0.31 mol equivalent of triphenylphosphine and 300 mL of triethylamine were reacted in a nitrogen atmosphere at 70 ° C. for 16 hours, whereby compound A represented by the following general formula (12) (poly [(2-carboxyl 4.3 g of -p-phenyleneethynylene)-(p-phenyleneethynylene)]) was obtained (yield 61%).
The obtained compound A was dissolved in tetrahydrofuran (THF) and filtered through a membrane filter to prepare a sample solution. It was 6300 when the mass mean molecular weight (Mw) of the compound A in this sample solution was measured by gel filtration chromatography (GPC), and converted into polystyrene.

[Production Example 2: Synthesis of Compound B]
In the same manner as in Production Example 1 except that 5.0 g (28 mmol) of 2,5-dichloro-1,4-benzenediol was used in place of 2,5-dichlorobenzoic acid, it was represented by the following general formula (13). 4.9 g of the compound B (poly [(2,5-dihydroxy-p-phenyleneethynylene)-(p-phenyleneethynylene)]) was obtained (76% yield).
About the obtained compound B, it was 7500 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion was carried out.

[Production Example 3: Synthesis of Compound C]
Compound C represented by the following general formula (14) in the same manner as in Production Example 1 except that 6.0 g (26 mmol) of 2,5-dichlorobenzenesulfonic acid was used instead of 2,5-dichlorobenzoic acid. 5.7 g of poly [(2-sulfonic acid-p-phenyleneethynylene)-(p-phenyleneethynylene)]) was obtained (yield 70%).
About the obtained compound C, it was 7200 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion was carried out.

[Production Example 4: Synthesis of Compound D]
In the same manner as in Production Example 1, except that 5.0 g (28 mmol) of 2,5-dichloro-1,4-phenylenediamine was used in place of 2,5-dichlorobenzoic acid, it was represented by the following general formula (15). 4.9 g of the compound D (poly [(2,5-diamino-p-phenyleneethynylene)-(p-phenyleneethynylene)]) obtained was obtained (76% yield).
About the obtained compound D, it was 6500 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion was carried out.

[Production Example 5: Synthesis of Compound E]
In a reaction vessel, 2.5 g (15 mmol) of 1,4-diethynyl-2-carboxybenzene, 0.26 mol equivalent of copper chloride, 0.25 mol equivalent of N, N, N ′, N′-tetramethylethylenediamine and Then, 400 mL of THF was charged and reacted at 25 ° C. for 16 hours in an oxygen atmosphere, whereby compound E (poly (2-carboxy-p-phenylenebutadienylene)) represented by the following general formula (16) was added. 0 g was obtained (yield 80%).
About the obtained compound E, it was 8100 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion.

[Production Example 6: Synthesis of Compound F]
In a reaction vessel, 4.9 g (24 mmol) of 1,4-diethynyl-2-carboxybenzene, 6.7 g (24 mmol) of 2,5-dibromobenzoic acid, 0.03 mol equivalent of copper iodide, 0.01 mol equivalent Of tetrakis (triphenylphosphine) palladium, THF (60 mL), and triethylamine (25 mL) were reacted in a nitrogen atmosphere at 25 ° C. for 16 hours, whereby compound F represented by the following general formula (17) (poly (2- 6.2 g of carboxy-p-phenyleneethynylene)) was obtained (yield 93%).
About the obtained compound F, it was 7600 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion was carried out.

[Production Example 7: Synthesis of Compound G]
It is represented by the following general formula (18) in the same manner as in Production Example 5 except that 1.9 g (15 mmol) of 1,4-diethynylbenzene is used instead of 1,4-diethynyl-2-carboxybenzene. 1.5 g of compound G (poly (p-phenylenebutadienylene)) was obtained (yield 82%).
About the obtained compound G, it was 8800 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion.

[Production Example 8: Synthesis of Compound H]
In place of 1,4-diethynyl-2-carboxybenzene, 3.0 g (24 mmol) of 1,4-diethynylbenzene was used, and in place of 2,5-dibromobenzoic acid, 5.7 g of 1,4-dibromobenzene was used. Except for using (24 mmol), 8.1 g of compound H (poly (p-phenyleneethynylene)) represented by the following general formula (19) was obtained in the same manner as in Production Example 6 (yield: 93%). .
About the obtained compound H, it was 8600 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion.

[Production Example 9: Synthesis of Compound I]
Acrylonitrile was homopolymerized by an aqueous suspension polymerization method to obtain Compound I (polyacrylonitrile).
About the obtained compound I, it was 82000 when the mass mean molecular weight (Mw) was measured like the compound A, and polystyrene conversion.

[Example 1]
<Manufacture of carbon fiber precursor fiber>
The compound I synthesized in Production Example 9 as a PAN-based polymer was dissolved in N-methylpyrrolidone to a concentration of 6% by mass to prepare a polymer solution (i). The obtained polymer solution (i) was used as a spinning solution, pure water was used as a coagulation bath solution, and a coagulated yarn was obtained according to the spinning property evaluation method described above. The obtained coagulated yarn was collected, repeatedly washed with water and washed with methanol, and then dried to obtain a carbon fiber precursor fiber.
The carbon fiber precursor fiber measured using a differential scanning calorimeter had a maximum heat generation rate of 10 mW / mg, a heat generation amount of 720 mJ / mg, and a maximum heat generation temperature of 310 ° C.
Table 1 shows the evaluation results of the spinnability and the measurement results of the maximum heat generation rate, the heat generation amount and the maximum heat generation temperature.

<Manufacture of carbon fiber>
The obtained carbon fiber precursor fiber was heated at 250 ° C. for 60 minutes in a nitrogen atmosphere to flameproof. Then, after heating up to 1400 degreeC with the temperature increase rate of 10 degree-C / min and carbonizing, it cooled to room temperature and obtained carbon fiber.
The carbonization yield was measured and found to be 30%. The results are shown in Table 1.
Example 1 is a comparative example.

[Example 2]
The compound I synthesized in Production Example 9 as a PAN-based polymer was dissolved in N-methylpyrrolidone to a concentration of 6% by mass to prepare a polymer solution (i).
Separately, Compound A synthesized in Production Example 1 as an aromatic polymer was dissolved in N-methylpyrrolidone so as to have a concentration of 6% by mass to prepare a polymer solution (ii).
The mass ratio of the PAN polymer (compound I) to the aromatic polymer (compound A) (PAN polymer (compound I) / aromatic polymer (compound A)) is 100/33. The polymer solution (i) and the polymer solution (ii) were mixed and then dissolved by stirring for 3 hours to prepare a spinning solution.
A carbon fiber precursor fiber and a carbon fiber were produced in the same manner as in Example 1 except that the obtained spinning solution was used.
Various measurements and evaluations were performed on the obtained carbon fiber precursor fibers and carbon fibers. The results are shown in Table 1.
Example 2 is an example.

[Examples 3 and 4]
The polymer solution (i) and the polymer solution (ii) are prepared so that the mass ratio of the PAN polymer (Compound I) and the aromatic polymer (Compound A) is 100/50 or 100/100. A spinning solution was prepared in the same manner as in Example 2 except for mixing.
A carbon fiber precursor fiber and a carbon fiber were produced in the same manner as in Example 1 except that the obtained spinning solution was used.
Various measurements and evaluations were performed on the obtained carbon fiber precursor fibers and carbon fibers. The results are shown in Table 1.
Examples 3 and 4 are examples.

[Example 5]
The polymer A synthesized in Production Example 1 as an aromatic polymer was dissolved in N-methylpyrrolidone so as to have a concentration of 6% by mass to prepare a polymer solution (ii).
Except for using the obtained polymer solution (ii) as a spinning solution, an attempt was made to produce a carbon fiber precursor fiber in the same manner as in Example 1. As a result, the aromatic polymer (compound A) was found in the coagulation bath solution. It was difficult to obtain coagulated yarn. Therefore, the maximum heat generation rate, the heat generation amount, and the maximum heat generation temperature were measured using a solid powder of an aromatic polymer (Compound A). However, with the aromatic polymer (compound A) alone, no exothermic peak was observed, and the maximum exothermic rate, maximum exothermic temperature, and exothermic amount could not be measured. The results are shown in Table 1 as “ND”.
The carbonization yield was measured by subjecting a solid powder of the aromatic polymer (compound A) to flameproofing treatment and carbonization treatment. The results are shown in Table 1.
Example 5 is a comparative example.

[Examples 6 to 8]
As the aromatic polymer, the compound B synthesized in Production Example 2 was used instead of the compound A, and the mass ratio of the PAN polymer (Compound I) to the aromatic polymer (Compound B) was 100/33, 100. A spinning solution was prepared in the same manner as in Example 2 except that the polymer solution (i) and the polymer solution (ii) were mixed so as to be / 50 or 100/100.
A carbon fiber precursor fiber and a carbon fiber were produced in the same manner as in Example 1 except that the obtained spinning solution was used.
Various measurements and evaluations were performed on the obtained carbon fiber precursor fibers and carbon fibers. The results are shown in Table 1.
Examples 6-8 are examples.

[Example 9]
A polymer solution (ii) was prepared by dissolving the compound B synthesized in Production Example 2 as an aromatic polymer in N-methylpyrrolidone so as to have a concentration of 6% by mass.
Except for using the obtained polymer solution (ii) as a spinning solution, an attempt was made to produce a carbon fiber precursor fiber in the same manner as in Example 1. As a result, the aromatic polymer (compound B) was found in the coagulation bath solution. It was difficult to obtain coagulated yarn. Therefore, the maximum heat generation rate, the heat generation amount, and the maximum heat generation temperature were measured using a solid powder of an aromatic polymer (Compound B). However, with the aromatic polymer (compound B) alone, no exothermic peak was observed, and the maximum exothermic rate, maximum exothermic temperature, and exothermic amount could not be measured. The results are shown in Table 1 as “ND”.
Further, the carbonization yield was measured by subjecting the solid powder of the aromatic polymer (compound B) to flame resistance treatment and carbonization treatment. The results are shown in Table 1.
Example 9 is a comparative example.

[Examples 10 to 12]
As the aromatic polymer, the compound C synthesized in Production Example 3 was used instead of the compound A, and the mass ratio of the PAN polymer (Compound I) to the aromatic polymer (Compound C) was 100/33, 100. A spinning solution was prepared in the same manner as in Example 2 except that the polymer solution (i) and the polymer solution (ii) were mixed so as to be / 50 or 100/100.
A carbon fiber precursor fiber and a carbon fiber were produced in the same manner as in Example 1 except that the obtained spinning solution was used.
Various measurements and evaluations were performed on the obtained carbon fiber precursor fibers and carbon fibers. The results are shown in Table 1.
Examples 10-12 are examples.

[Example 13]
Compound C synthesized in Production Example 3 as an aromatic polymer was dissolved in N-methylpyrrolidone so as to have a concentration of 6% by mass to prepare a polymer solution (ii).
Except that the obtained polymer solution (ii) was used as a spinning solution, an attempt was made to produce a carbon fiber precursor fiber in the same manner as in Example 1. As a result, the aromatic polymer (compound C) was found in the coagulation bath solution. It was difficult to obtain coagulated yarn. Therefore, the maximum heat generation rate, the heat generation amount, and the maximum heat generation temperature were measured using a solid powder of an aromatic polymer (Compound C). However, with the aromatic polymer (compound C) alone, no exothermic peak was observed, and the maximum exothermic rate, maximum exothermic temperature, and exothermic amount could not be measured. The results are shown in Table 1 as “ND”.
The carbonization yield was measured by subjecting a solid powder of the aromatic polymer (compound C) to flameproofing treatment and carbonization treatment. The results are shown in Table 1.
Example 13 is a comparative example.

[Examples 14 and 15]
As the aromatic polymer, the compound D synthesized in Production Example 4 was used instead of the compound A, and the mass ratio of the PAN polymer (Compound I) to the aromatic polymer (Compound D) was 100/33, or A spinning solution was prepared in the same manner as in Example 2 except that the polymer solution (i) and the polymer solution (ii) were mixed so as to be 100/50.
A carbon fiber precursor fiber and a carbon fiber were produced in the same manner as in Example 1 except that the obtained spinning solution was used.
Various measurements and evaluations were performed on the obtained carbon fiber precursor fibers and carbon fibers. The results are shown in Table 1.
Examples 14 and 15 are examples.

[Example 16]
A compound D synthesized in Production Example 4 as an aromatic polymer was dissolved in N-methylpyrrolidone so as to have a concentration of 6% by mass to prepare a polymer solution (ii).
Except for using the obtained polymer solution (ii) as a spinning solution, an attempt was made to produce a carbon fiber precursor fiber in the same manner as in Example 1. As a result, the aromatic polymer (compound D) was found in the coagulation bath solution. It was difficult to obtain coagulated yarn. Therefore, the maximum heat generation rate, the heat generation amount, and the maximum heat generation temperature were measured using a solid powder of an aromatic polymer (Compound D). However, with the aromatic polymer (compound D) alone, no exothermic peak was observed, and the maximum exothermic rate, maximum exothermic temperature, and exothermic amount could not be measured. The results are shown in Table 1 as “ND”.
The carbonization yield was measured by subjecting the solid powder of the aromatic polymer (compound D) to flameproofing treatment and carbonization treatment. The results are shown in Table 1.
Example 16 is a comparative example.

[Examples 17 and 18]
A spinning solution was prepared in the same manner as in Example 2 except that Compound E synthesized in Production Example 5 or Compound F synthesized in Production Example 6 was used instead of Compound A as the aromatic polymer.
A carbon fiber precursor fiber and a carbon fiber were produced in the same manner as in Example 1 except that the obtained spinning solution was used.
Various measurements and evaluations were performed on the obtained carbon fiber precursor fibers and carbon fibers. The results are shown in Table 1.
Examples 17 and 18 are examples.

[Examples 19 and 20]
An attempt was made to prepare a spinning solution in the same manner as in Example 2 except that Compound G synthesized in Production Example 7 or Compound H synthesized in Production Example 8 was used instead of Compound A as the aromatic polymer. Since the aromatic polymer (compounds H and G) was not dissolved in N-methylpyrrolidone, a spinning dope could not be obtained.
Examples 19 and 20 are comparative examples.

As shown in the results of Examples 2 to 4, 6 to 8, 10 to 12, 14, 15, 17, and 18, carbon composed of a PAN polymer and an aromatic polymer by using a wet spinning method. The fiber precursor fiber could be stably produced. The carbon fiber precursor fibers obtained from these examples show a decrease in maximum heat generation rate and calorific value compared to the carbon fiber precursor fibers made of the PAN-based polymer of Example 1, and production in the flameproofing process. Improved. Moreover, the carbonization yield was high.
On the other hand, as shown in the results of Examples 5, 9, 13, and 16, it was difficult to obtain the carbon fiber precursor fiber with the aromatic polymer alone.

  The present invention relates to a mixture containing an aromatic polymer and a PAN polymer, which has a maximum exotherm rate and a calorific value lower than those of conventional PAN-based carbon fibers and can suppress a rapid exothermic reaction. By using it as a raw material for spinning precursor fibers, it is possible to improve the productivity of the flameproofing process, and it is possible to produce high-quality carbon fibers in the subsequent carbonization process, which is useful.

Claims (3)

A carbon fiber precursor fiber composed of a mixture containing an aromatic polymer containing a structural unit represented by the following general formula (1) and a polyacrylonitrile polymer.

In formula (1), R ¹ , R ² , R ³ and R ⁴ are independently selected from the group consisting of a hydrogen atom, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. . However, the case where all of R ¹ , R ² , R ³ , and R ⁴ are hydrogen atoms is excluded. A is —C≡C— or an aromatic group represented by the following general formula (2), and m is 0 or 1.

In formula (2), R ⁵ , R ⁶ , R ⁷ and R ⁸ are independently selected from the group consisting of a hydrogen atom, a hydroxy group, a carboxy group, a sulfonic acid group, a metal salt of a sulfonic acid group, and an amino group. .   The carbon fiber precursor fiber according to claim 1, wherein the mixture contains 30 to 100 parts by mass of the aromatic polymer with respect to 100 parts by mass of the polyacrylonitrile polymer.   Carbon fiber obtained by making the carbon fiber precursor fiber according to claim 1 or 2 flameproof and carbonized.