Diene polymer composition, carbon fiber precursor fiber, method for producing flame-resistant fiber, and method for producing carbon fiber

Abstract

To provide: a diene polymer composition that suppresses thread breakage during melt spinning; a carbon fiber precursor fiber composed of the diene polymer composition, which suppresses thread breakage and fiber fusion during flame-resistant treatment; a method for producing a flame-resistant fiber using the carbon fiber precursor fiber as a precursor; and a method for producing a carbon fiber with excellent tensile strength.SOLUTION: A diene polymer composition comprises: a) a diene polymer containing a structural unit represented by the following formula (1), where R represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and n represents an integer of 1 or greater; and b) a polymer other than the diene polymer. A blending ratio (mass ratio) between the diene polymer and the polymer other than the diene polymer is 99.5:0.5 to 10:90, and at least a part of the polymer other than the diene polymer forms a dispersed phase, or the diene polymer and the polymer other than the diene polymer are compatible.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a diene-based polymer composition, a carbon fiber precursor fiber, a method for producing a flame-resistant fiber, and a method for producing a carbon fiber. [Background technology]

[0002] Because carbon fibers are lightweight and have excellent mechanical properties, carbon fiber composite materials are being developed for a variety of applications, including aerospace applications, automotive applications, building materials, etc. Known methods for producing carbon fibers include spinning polyacrylonitrile or pitch to obtain fiber bundles, making the bundles flame-resistant, and then carbonizing the resulting fiber bundles (e.g., Patent Documents 1, 2, and 3).

[0003] However, polyacrylonitrile-based carbon fibers made from fibers obtained by spinning polyacrylonitrile are the most widely used because they have high mechanical properties. However, because they are spun by wet spinning or dry-wet spinning using organic solvents such as dimethyl sulfoxide or dimethylformamide, energy is required to recycle the organic solvent, which increases production costs. In addition, there are problems with the generation of toxic gases such as hydrogen cyanide during flame retardation and carbonization.

[0004] On the other hand, when pitch is used as a raw material, melt spinning can be performed without using an organic solvent, and hydrogen cyanide is not generated during flame-proofing and carbonization, but melt spinning of pitch-based fibers generally requires high temperatures of 250°C or higher.In addition, the fibers themselves are relatively brittle, and are prone to fusion between fibers and breakage of some fibers during flame-proofing, making them difficult to handle (for example, Patent Document 3).

[0005] Fibers using 1,2-polybutadiene as a precursor that can be melt-spun and does not generate hydrogen cyanide have also been disclosed (for example, Patent Documents 4, 5 and 6). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-183159 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-202208 [Patent Document 3] Japanese Patent Application Publication No. 6-10215 [Patent Document 4] Japanese Patent Application Publication No. 48-82199 [Patent Document 5] Japanese Patent Application Publication No. 48-92699 [Patent Document 6] Japanese Unexamined Patent Publication No. 49-106490 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Documents 4, 5, and 6, single fibers are obtained by melt spinning 1,2-polybutadiene, while in Patent Documents 5 and 6, the single fibers are obtained and then bundled to form a fiber bundle. To reduce costs by improving productivity during melt spinning, it is necessary to obtain a fiber bundle (multifilament) using a multi-hole nozzle rather than a single fiber by melt spinning. However, 1,2-polybutadiene is prone to breakage, so it was necessary to improve its spinnability. Furthermore, it was necessary to suppress breakage due to fusion between fibers and thermal decomposition when flame-resistant fiber bundles are made. There is also a need to improve the tensile strength of carbon fibers in order to expand their use in applications requiring strength, such as aerospace and automotive applications.

[0008] An object of one embodiment of the present disclosure is to provide a diene polymer composition that suppresses yarn breakage during melt spinning (particularly during high-speed spinning), a carbon fiber precursor fiber that is formed using the diene polymer composition and suppresses yarn breakage and fiber fusion during flame retardation, a method for producing a flame retardant fiber that uses the carbon fiber precursor fiber as a precursor, and a method for producing a carbon fiber that has excellent tensile strength. [Means for solving the problem]

[0009] The means for solving the above problems include the following aspects. <1> The present invention comprises a diene-based polymer containing a structural unit represented by the following formula (1) (wherein R represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and n represents an integer of 1 or more), and a polymer other than the diene-based polymer, A diene polymer composition, wherein the blending ratio (mass ratio) of the diene polymer to the polymer other than the diene polymer is 99.5:0.5 to 10:90, and at least a part of the polymer other than the diene polymer forms a dispersed phase, or the diene polymer and the polymer other than the diene polymer are compatible with each other.

[0010] [ka]

[0011] <2> The polymer other than the diene-based polymer includes at least one selected from the group consisting of an olefin-based polymer, a petroleum resin, and an aromatic vinyl-based polymer. <1> The diene-based polymer composition according to claim 1. <3> The average particle size of the dispersed phase is 1 μm or less. <1> or <2> The diene-based polymer composition according to claim 1. <4> <1> ~ <3> A carbon fiber precursor fiber comprising the diene-based polymer composition according to any one of the above. <5> <1> ~ <3> and a gel fraction of 30% or more. <4> The carbon fiber precursor fiber according to claim 1. <6> <5> 2. A method for producing a flame-resistant fiber, comprising the step of heating the carbon fiber precursor fiber according to claim 1 in an oxidizing atmosphere. <7> <6> and carbonizing the flame-resistant fiber.

[0012] According to one embodiment of the present disclosure, there are provided a diene-based polymer composition that suppresses yarn breakage during melt spinning (particularly during high-speed spinning), a carbon fiber precursor fiber that is formed using the diene-based polymer composition and suppresses yarn breakage and fiber fusion during flame-resistant treatment, a method for producing a flame-resistant fiber that uses the carbon fiber precursor fiber as a precursor, and a method for producing a carbon fiber that has excellent tensile strength. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described. The description is for illustrating the embodiments and is not intended to limit the scope of the present disclosure.

[0014] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values before and after "to" as the minimum and maximum values, respectively. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0015] In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0016] In this specification, each component may contain a plurality of corresponding substances. When referring to the amount of each component in a composition in this specification, if a plurality of substances corresponding to each component are present in the composition, the amount refers to the total amount of the plurality of substances present in the composition, unless otherwise specified.

[0017] In this specification, the term "(meth)acrylic" means either "acrylic" or "methacrylic".

[0018] The weight average molecular weight is a value measured by gel permeation chromatography (GPC). The measurement device may be an HLC-8220GPC manufactured by Tosoh Corporation or a device equivalent thereto. In the present disclosure, when measuring the weight-average molecular weight of a diene polymer, the diene polymer is dissolved in the following eluent, and then filtered using a membrane filter with a pore size of 0.45 μm, and the resulting solution is used as the measurement solution. (Measurement conditions) Column: TSKgel GMH HR -H x 2 Eluent: Chloroform ·Eluent flow rate: 1.0ml / min Column temperature: 40℃ Molecular weight standard: Standard polystyrene Detector: Differential refractive index detector

[0019] <Diene-based polymer composition> The diene polymer composition of the present disclosure comprises a diene polymer containing a structural unit represented by the following formula (1) (wherein R represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and n represents an integer of 1 or more), and a polymer other than the diene polymer, wherein the blending ratio (mass ratio) of the diene polymer to the polymer other than the diene polymer is 99.5:0.5 to 10:90, and at least a portion of the polymer other than the diene polymer forms a dispersed phase, or the diene polymer and the polymer other than the diene polymer are compatible with each other.

[0020] [ka]

[0021] The diene polymer composition having the above-described structure suppresses thread breakage during melt spinning (particularly during high-speed spinning) (particularly suppresses thread breakage at the nozzle when the nozzle has multiple holes), and can also suppress thread breakage even when stretched during flame retardation. Furthermore, a carbon fiber precursor fiber that suppresses fiber fusion can be obtained. Furthermore, the carbon fiber obtained by carbonizing the carbon fiber precursor fiber after flame retardation has excellent tensile strength.

[0022] -Diene polymer- The diene polymer contains a structural unit represented by the following formula (I) (hereinafter also referred to as "structural unit (I)"). The inclusion of the structural unit (I) suppresses thread breakage during melt spinning (particularly during high-speed spinning), and also allows an intramolecular cyclization reaction and / or an intermolecular crosslinking reaction to proceed in response to an external stimulus. This suppresses thread breakage and fiber fusion during the flame-proofing process, and further improves the tensile strength of the resulting carbon fiber. Examples of external stimuli include radiation treatment, electron beam treatment, ultraviolet treatment, heat treatment, acid treatment, addition of a crosslinking agent, and addition of a radical initiator.

[0023] The diene polymer may contain only one type of structural unit represented by formula (I), or may contain two or more types.

[0024] [ka]

[0025] In formula (I), R represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and n represents an integer of 1 or more.

[0026] The number of carbon atoms in the "organic group" represented by R is preferably 1 to 10, more preferably 1 to 6, and even more preferably 1 to 3, from the viewpoint of improving the yield of the obtained carbon fiber.

[0027] Examples of the "organic group" represented by R include hydrocarbon groups. At least a portion of the carbon atoms constituting the hydrocarbon group may be substituted with a group substituted with a halogen atom (e.g., a chlorine atom, a bromine atom, or a fluorine atom), an oxygen atom, a nitrogen atom, or a sulfur atom. The hydrocarbon group may be linear or branched, or may contain a ring structure.

[0028] The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. Among these, the hydrocarbon group is preferably an aliphatic hydrocarbon group, more preferably an alkyl group, and even more preferably a linear alkyl group. Specifically, the hydrocarbon group is preferably a hydrocarbon group having 1 to 10 carbon atoms (preferably 1 to 6), such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a sec-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a hexyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, a heptyl group, a 2-methylhexyl group, a 3-methylhexyl group, a 2,2-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3-ethylpentyl group, a 2,2,3-trimethylbutyl group, an o-methyl ...2,4-dimethylpentyl group Examples of the alkyl group include octyl, methylheptyl, dimethylhexyl, 2-ethylhexyl, 3-ethylhexyl, trimethylpentyl, 3-ethyl-2-methylpentyl, 2-ethyl-3-methylpentyl, 2,2,3,3-tetramethylbutyl, nonyl, methyloctyl, 3,7-dimethyloctyl, dimethylheptyl, 3-ethylheptyl, 4-ethylheptyl, trimethylhexyl, 3,3-diethylpentyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl groups. From the viewpoint of suppressing thread breakage and fusion of fibers during the flame-proofing step, R is preferably a hydrogen atom or a methyl group.

[0029] Examples of raw materials for producing diene polymers containing the structural unit (I) include 1,3-butadiene, isoprene, 2-ethyl-1,3-butadiene, 2-propyl-1,3-butadiene, 2-butyl-1,3-butadiene, 2-pentyl-1,3-butadiene, 2-hexyl-1,3-butadiene, 2-heptyl-1,3-butadiene, 2-octyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 2-methoxy-1,3-butadiene, 2-ethoxy-1,3-butadiene, 2-propoxy-1,3-butadiene, 2-isopropoxy-1,3-butadiene, 2-hexyloxy-1,3-butadiene, and myrcene. The raw materials for producing the diene polymer containing the structural unit (I) may be used alone or in combination of two or more.

[0030] An example of a raw material for producing a diene polymer containing a structural unit (I) in which "R" in formula (I) is a hydrogen atom is 1,3-butadiene. An example of a raw material for producing a diene polymer containing a structural unit (I) in which "R" in formula (I) is a methyl group is isoprene. The raw material for producing a diene polymer containing the structural unit (I) is preferably at least one selected from the group consisting of 1,3-butadiene and isoprene.

[0031] The content of the structural unit (I) is not particularly limited. The content of the structural unit (I) is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, even more preferably 30 mol% or more, particularly preferably 40 mol% or more, even particularly preferably 50 mol% or more, particularly preferably 60 mol% or more, and most preferably 70 mol% or more, relative to the total amount of the diene polymer. The upper limit of the content of the structural unit (I) is not particularly limited. The content of the structural unit (I) may be 100 mol%.

[0032] The diene polymer may contain, in addition to the structural unit (I), structural units derived from other conjugated diene monomers, such as 1,2-butadiene, 1-pentyl-1,3-butadiene, 1-hexyl-1,3-butadiene, 1-heptyl-1,3-butadiene, 1-octyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1-hexyloxy-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, and 3-butyl-1,3-octadiene.

[0033] The diene polymer may also contain structural units derived from other polymerizable monomers, such as aromatic vinyl monomers such as styrene, α-methylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene, 2,4-dibromostyrene, vinylnaphthalene, and indene; linear olefin monomers such as ethylene, propylene, and 1-butene; cyclic olefin monomers such as cyclopentene and 2-norbornene; non-conjugated diene monomers such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene; methyl Examples of the other polymerizable monomers include α,β-unsaturated carboxylic acid esters such as (meth)acrylate, ethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, monomethyl maleate, monomethyl itaconate, dimethyl itaconate, ethyl itaconate, and diethyl itaconate; vinyl cyanide monomers such as (meth)acrylonitrile; nitrogen-containing vinyl monomers such as (meth)acrylamide and dimethylaminoethyl (meth)acrylamide; α,β-unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid; α,β-unsaturated carboxylic anhydrides such as maleic anhydride and itaconic anhydride; sulfo-containing vinyl monomers such as vinyl sulfonic acid; halogenated vinyl monomers such as vinyl chloride; vinyl carboxylates such as vinyl acetate, vinyl butyrate, and vinyl pivalate; and vinyl alcohol. The other polymerizable monomers may be used alone or in combination of two or more.

[0034] In the diene polymer, when "R" in formula (I) is a hydrogen atom, the 1,2-bond content is not particularly limited, and the diene polymer may contain a cis-1,4-bond or a trans-1,4-bond. In the diene polymer, when "R" in formula (I) is a hydrogen atom, the 1,2-bond content is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, even more preferably 30 mol% or more, particularly preferably 50 mol% or more, particularly preferably 80 mol% or more, and most preferably 90 mol% or more, from the viewpoint of reducing the fusion rate and improving the carbonization yield in the flame-proofing step in which an intramolecular cyclization reaction occurs due to an external stimulus. The 1,2-bond content of the diene polymer may be 100 mol%, but is preferably 99.5 mol% or less, more preferably 99 mol% or less, from the viewpoint of reducing the production (polymerization) cost for increasing the 1,2-bond content of the diene polymer. The "1,2-bond content" refers to the proportion of 1,2-bonds when the total of the cis-1,4-bonds, trans-1,4-bonds, and 1,2-bonds that constitute the diene polymer is taken as 100 mol %. The 1,2-bond content is 1 H-nuclear magnetic resonance (NMR) 13 This can be confirmed by C-NMR.

[0035] In a diene polymer, when "R" in formula (I) is a methyl group, the content of 3,4-bonds corresponding to the structural unit (I) is not particularly limited, and may contain cis-1,4-bonds, trans-1,4-bonds, and 1,2-bonds. In a diene polymer, when "R" in formula (I) is a methyl group, the content of 3,4-bonds is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, even more preferably 30 mol% or more, particularly preferably 50 mol% or more, particularly preferably 80 mol% or more, and most preferably 90 mol% or more, from the viewpoint of reducing the fusion rate and improving the carbonization yield in the flame-proofing step in which an intramolecular cyclization reaction occurs due to an external stimulus. When "R" in formula (I) is a methyl group, the 3,4-bond content of the diene polymer may be 100 mol %, but from the viewpoint of reducing the production (polymerization) cost for increasing the 3,4-bond content of the diene polymer, it is preferably 99.5 mol % or less, and more preferably 99 mol % or less. The "3,4-bond content" refers to the proportion of 3,4-bonds when the total of 3,4-bonds, cis-1,4-bonds, trans-1,4-bonds, and 1,2-bonds constituting the diene polymer when "R" in formula (I) is a methyl group is taken as 100 mol %. The 3,4-bond content is 1 H-nuclear magnetic resonance (NMR) 13 This can be confirmed by C-NMR. In the present disclosure, the stereoregularity of the diene polymer is not particularly limited, and may be any of isotactic, syndiotactic, and atactic. The ratio of these is not particularly limited.

[0036] The weight average molecular weight of the diene polymer is usually 10,000 or more, but from the viewpoint of the strength of the carbon fiber precursor fiber and the carbon fiber, it is preferably 15,000 or more, more preferably 20,000 or more, and particularly preferably 25,000 or more.

[0037] The melting point of the diene polymer is not particularly limited. When the diene polymer component contains one or more diene polymers, the melting point of at least one diene polymer is preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, and particularly preferably 60°C or higher, from the viewpoint of preventing bleed-out to the surface during flame retardation. The melting point of the diene polymer is preferably 220°C or lower, more preferably 200°C or lower, even more preferably 180°C or lower, particularly preferably 160°C or lower, and most preferably 150°C or lower, from the viewpoint of improving spinnability at multiple fibers and reducing energy costs by realizing melt spinning at a relatively low temperature. The melting point of a diene polymer is measured by differential scanning calorimetry (DSC). Specifically, the melting point of a diene polymer indicates the peak temperature (°C) of the main melting peak. The presence of a diene polymer in a carbon fiber precursor can be determined by the following: 1 H-nuclear magnetic resonance spectroscopy (NMR) and 13 This can be confirmed by C-NMR analysis, infrared spectroscopy analysis, etc.

[0038] -Polymers other than diene polymers- Examples of polymers other than diene polymers include olefin polymers, petroleum resins, aromatic vinyl polymers, acrylic polymers (poly(meth)acrylic acid esters (polymethyl acrylate, polymethyl methacrylate, etc.), poly(meth)acrylic acid, (meth)acrylic acid ester / (meth)acrylic acid copolymers, etc.), polyesters (polyethylene terephthalate, polybutylene terephthalate, polylactic acid, etc.), polyamides, polyvinylidene chloride, polyphenylene sulfide, polyimides, polycarbonates, and polyacrylonitriles whose main component is a vinyl cyanide monomer unit, such as acrylonitrile. Preferred are nitrile-based polymers (polyacrylonitrile, acrylonitrile / itaconic acid copolymer, acrylonitrile / methyl acrylate copolymer, etc.), acrylamide-based polymers (polyacrylamide, acrylamide / acrylonitrile copolymer, etc.) containing acrylamide monomer units such as acrylamide as the main component, vinyl alcohol-based polymers (polyvinyl alcohol, vinyl alcohol / vinyl acetate copolymer, etc.) containing vinyl alcohol monomers as the main component, and phenol-based polymers (novolac-type phenolic resin, lignin, etc.), and one or more of these can be used. From the viewpoints of improving the spinnability of the diene-based polymer composition, suppressing yarn breakage and fiber fusion in the flame-proofing step, and improving the tensile strength of the resulting carbon fiber, it is more preferred that the diene-based polymer composition contains at least one selected from the group consisting of olefin-based polymers, petroleum resins, and aromatic vinyl-based polymers. When a diene polymer is mixed with a polymer other than the diene polymer, which polymer includes at least one selected from the group consisting of an olefin polymer, a petroleum resin, and an aromatic vinyl polymer, yarn breakage during melt spinning (particularly at high speed) is likely to be suppressed, yarn breakage and fiber fusion during the flame-resistant treatment step are likely to be suppressed, and the tensile strength of the resulting carbon fiber is likely to be improved.

[0039] Furthermore, when a diene polymer composition containing a polymer other than the diene polymer is irradiated with active energy rays such as electron beams and ultraviolet rays, crosslinking reactions may occur between diene polymers, between olefin polymers, between petroleum resins, between aromatic vinyl polymers, between diene polymers and olefin polymers, between diene polymers and petroleum resins, and between diene polymers and aromatic vinyl polymers. These crosslinking reactions tend to suppress thread breakage and fiber fusion during the flame-proofing step, and also tend to improve the tensile strength of the resulting carbon fiber.

[0040] The olefin-based polymer and aromatic vinyl-based polymer may be either linear or branched. The olefin-based polymer and aromatic vinyl-based polymer may be hydrogenated olefin-based polymers and hydrogenated aromatic vinyl-based polymers.

[0041] The olefin-based polymer is not particularly limited, and examples thereof include homopolymers and copolymers of olefin-based monomers. Examples of olefin-based monomers include ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene, 2,3-dimethyl-2-butene, 1-butene, 1-hexene, 1-octene, 1-nonene, 1-decene, cyclopentene, and 2-norbornene. One type of olefin-based monomer may be used alone, or two or more types may be used in combination.

[0042] The weight average molecular weight of the olefin polymer is not particularly limited, but from the viewpoint of improving spinnability, it is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 20,000 or less, particularly preferably 10,000 or less, and most preferably 9,000 or less.

[0043] Examples of petroleum resins include copolymerized petroleum resins of each fraction, such as C5 petroleum resins, C9 petroleum resins, and C5 / C9 petroleum resins; alicyclic (dicyclopentadiene) petroleum resins; and hydrogenated petroleum resins (partially hydrogenated petroleum resins, fully hydrogenated petroleum resins) obtained by hydrogenating these petroleum resins. Here, C5 petroleum resins are petroleum resins made from the C5 fraction of naphtha, C9 petroleum resins are petroleum resins made from the C9 fraction of naphtha, and C5 / C9 petroleum resins are petroleum resins made from both the C5 and C9 fractions of naphtha. Here, the C5 fraction and C9 fraction also include their analogs. Examples of C5 fractions include 1,3-pentadiene, 2-methyl-2-butene, cyclopentadiene, methylcyclopentadiene, dimethylcyclopentadiene, isoprene, and pentane. Examples of C9 fractions include styrene, methylstyrene, vinyltoluene, ethylstyrene, dimethylstyrene, indene, and methylindene. C5 petroleum resins and C5 / C9 petroleum resins preferably contain a dicyclopentadiene (DCPD) skeleton derived from cyclopentadiene, a type of C5 fraction.

[0044] The aromatic vinyl polymer is not particularly limited, and examples thereof include homopolymers and copolymers of aromatic vinyl monomers. Examples of aromatic vinyl monomers include styrene, α-methylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene, 2,4-dibromostyrene, vinylnaphthalene, and indene. Only one type of aromatic vinyl monomer may be used, or two or more types may be used in combination. Preferred examples of aromatic vinyl polymers include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), acrylonitrile-butadiene-styrene (ABS) resins, methyl (meth)acrylate-acrylonitrile-butadiene-styrene (MABS) resins, methyl (meth)acrylate-butadiene-styrene (MBS), acrylonitrile-ethylene propylene rubber-styrene (AES) resins, and acrylonitrile-acrylic rubber-styrene (AAS) resins.

[0045] In the diene polymer composition of the present disclosure, the blending ratio (mass ratio) of the diene polymer to the polymer other than the diene polymer is 99.5:0.5 to 10:90, preferably 99.0:1.0 to 25:75, more preferably 98.0:2.0 to 50:50, and even more preferably 98.0:2.0 to 77:23. When the blending ratio (mass ratio) of the diene polymer to the polymer other than the diene polymer is 99.5:0.5 to 10:90, at least a portion of the polymer other than the diene polymer is likely to form a dispersed phase, or the diene polymer and the polymer other than the diene polymer are likely to be compatible with each other.

[0046] In the diene polymer composition of the present disclosure, at least a portion of the polymer other than the diene polymer forms a dispersed phase, or the diene polymer and the polymer other than the diene polymer are compatible with each other. As a result, although the reason is not clear, a diene polymer composition that suppresses yarn breakage during melt spinning (particularly during high-speed spinning) and a carbon fiber precursor fiber that is composed of the diene polymer composition and suppresses yarn breakage and fiber fusion during flame retardation can be obtained.

[0047] When at least a portion of the polymer other than the diene polymer forms a dispersed phase, the shape of the dispersed phase is not particularly limited and may be a shape other than spherical (oblate spheroid, striated, or other irregular shape). The average particle size of the dispersed phase is not particularly limited, but is preferably 1 μm or less, more preferably 900 nm or less, even more preferably 500 nm or less, particularly preferably 200 nm or less, and most preferably 100 nm or less. The average particle size of the dispersed phase is preferably 1 nm or more, more preferably 3 nm or more, even more preferably 5 nm or more, and particularly preferably 7 nm or more.

[0048] The average particle size of the dispersed phase can be obtained, for example, by preparing an ultrathin section of a cross section perpendicular to the fiber axis direction of a carbon fiber precursor fiber made of a diene-based polymer composition, and observing the phase structure using a transmission electron microscope (e.g., H-7650 manufactured by Hitachi High-Technologies Corporation); when a dispersed phase containing a polymer other than a diene-based polymer is dispersed in a diene-based polymer, randomly selecting 20 dispersed phases, measuring the primary particle sizes of the dispersed phases, and calculating the average value.

[0049] -Additives- The diene polymer composition of the present disclosure may contain an additive. The additive preferably contains a photopolymerization initiator. When the diene polymer composition contains a photopolymerization initiator, an intramolecular cyclization reaction and / or an intermolecular crosslinking reaction can proceed by ultraviolet treatment, which makes it easier to suppress thread breakage and fiber fusion during the flame-proofing step and also makes it easier to improve the tensile strength of the resulting carbon fiber.

[0050] Examples of photopolymerization initiators that can be used include hydrogen abstraction initiators such as benzophenone, methyl 2-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, isopropylthioxanthone, diethylthioxanthone, and ethyl 4-(diethylamino)benzoate. Examples of intramolecular cleavage initiators among photopolymerization initiators include benzoin ether and benzyl dimethyl ketal. Examples of α-aminoalkylphenone initiators include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1 and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1. Examples of α-hydroxyalkylphenone initiators include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, alkylphenyl glyoxylate, and diethoxyacetophenone.

[0051] As the photopolymerization initiator, at least one of these may be used, or two or more of them may be used. The content of the photopolymerization initiator is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass, relative to 100 parts by mass of the diene polymer composition. When the content of the photopolymerization initiator is 0.1 part by mass or more, high resistance to flame retardant treatment is likely to be obtained, and when it is 20 parts by mass or less, unreacted substances and by-products after crosslinking do not become too large, and good strength can be maintained.

[0052] The diene polymer composition of the present disclosure may contain additives other than the photopolymerization initiator, as long as the effects of the present disclosure are not impaired. Examples of other additives include radical polymerization initiators, antioxidants, release agents, lubricants, plasticizers, colorants, crosslinking aids (e.g., ultraviolet crosslinking aids), crosslinking catalysts (e.g., acid catalysts, base catalysts), crosslinking retarders, reinforcing materials (fillers such as graphite, carbon nanotubes, graphene, cellulose, cellulose nanofibers, carbon black, boron nitride, boron nitride nanotubes, boron nitride nanosheets, glass fibers, and metal fibers), ultraviolet absorbers, light shielding agents, light stabilizers, antistatic agents, and compatibilizers.

[0053] When the diene polymer composition of the present disclosure contains a release agent, a conventionally known release agent is preferably used as appropriate, such as carnauba wax. The content of the release agent is not particularly limited, and is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the diene polymer composition. From the viewpoint of improving spinnability, the content of the release agent is more preferably 0.3 parts by mass or more, and particularly preferably 0.5 parts by mass or more, per 100 parts by mass of the diene polymer composition.

[0054] Furthermore, when the diene polymer composition of the present disclosure contains a plasticizer, the content of the plasticizer is not particularly limited, and is preferably 0.1 parts by mass to 100 parts by mass relative to 100 parts by mass of the diene polymer composition. From the viewpoint of improving the spinnability and drawability of the carbon fiber precursor and suppressing fusion during flame retardation, the content of the plasticizer is preferably 0.5 parts by mass to 70 parts by mass relative to 100 parts by mass of the diene polymer composition, more preferably 1 part by mass to 60 parts by mass, even more preferably 2 parts by mass to 50 parts by mass, even more preferably 3 parts by mass to 40 parts by mass, particularly preferably 4 parts by mass to 30 parts by mass, and most preferably 4 parts by mass to 20 parts by mass.

[0055] <Carbon fiber precursor fiber> The carbon fiber precursor fiber of the present disclosure is a fiber obtained by fiberizing the diene polymer composition. The carbon fiber precursor fiber may be a single fiber or a fiber bundle (hereinafter, the fiber bundle of the carbon fiber precursor fiber may be referred to as the carbon fiber precursor fiber bundle). However, carbon fibers used for structural components for aerospace applications, automotive applications, building materials, and the like are preferably carbon fiber precursor fiber bundles from the viewpoint of exhibiting high mechanical properties. When the carbon fiber precursor fiber of the present disclosure is a carbon fiber precursor fiber bundle, the number of filaments per bundle is not particularly limited. However, from the viewpoints of productivity and mechanical properties of the flame-resistant fiber and carbon fiber, it is preferably 10 to 360,000, more preferably 20 to 180,000, even more preferably 30 to 72,000, and particularly preferably 50 to 36,000. Furthermore, by limiting the number of filaments per bundle to 360,000 or less, the occurrence of uneven sintering during the flame-resistant treatment or carbonization treatment can be suppressed. To increase the number of filaments, it is preferable to bundle multiple bundles of multiple filaments, but from the viewpoint of reducing production costs, it is more preferable to have a large number of filaments after spinning. In the case of melt spinning, the number of holes in the nozzle may be 1 hole, but is preferably 10 holes or more, more preferably 20 holes or more, even more preferably 30 holes or more, and particularly preferably 36 holes or more.

[0056] The carbon fiber precursor fiber of the present disclosure can be obtained by spinning the diene polymer composition. Spinning methods include melt spinning, dry spinning, wet spinning, dry-wet spinning, gel spinning, and electrospinning. From the viewpoint of producing a carbon fiber precursor fiber at low cost and under environmentally friendly conditions, melt spinning is preferred.

[0057] The fineness of the carbon fiber precursor fiber is not particularly limited, but is preferably 1 × 10 -8 tex / line to 100tex / line is preferable, and 1×10 -6The fineness of the carbon fiber precursor fiber is more preferably 1×10 tex to 60 tex, even more preferably 0.001 tex to 40 tex, even more preferably 0.01 tex to 10 tex, particularly preferably 0.02 tex to 2 tex, and most preferably 0.03 tex to 0.4 tex. -8 When the fineness of the carbon fiber precursor fiber is 100 tex / fiber or more, yarn breakage is unlikely to occur, and stable winding and flame-retardation can be easily performed. When the fineness of the carbon fiber precursor fiber is 100 tex / fiber or less, the structural difference between the surface layer and the center of the flame-retardant fiber does not become too large, and the tensile modulus of the obtained carbon fiber can be well maintained.

[0058] The average fiber diameter of the carbon fiber precursor fiber is not particularly limited, but is preferably 3 nm to 300 μm, more preferably 30 nm to 250 μm, even more preferably 500 nm to 200 μm, even more preferably 1 μm to 100 μm, particularly preferably 2 μm to 60 μm, and most preferably 3 μm to 40 μm. When the average fiber diameter of the single fibers of the carbon fiber precursor fiber is 3 nm or more, thread breakage is less likely to occur, and stable winding and flame-resistant treatment can be easily performed. When the average fiber diameter is 300 μm or less, the structural difference between the surface layer and the center of the flame-resistant fiber is not too large, and the tensile modulus of the resulting carbon fiber can be maintained at a good level.

[0059] From the viewpoint of suppressing fiber breakage and fiber fusion during the flame-proofing step and from the viewpoint of improving the tensile strength of the resulting carbon fiber, the carbon fiber precursor fiber of the present disclosure preferably contains a crosslinked product of the diene polymer composition and has a gel fraction of 30% or more.

[0060] The crosslinked product of the diene polymer composition has a structure formed by intramolecular crosslinking (including intramolecular cyclization reactions between adjacent vinyl groups) and / or intermolecular crosslinking reactions. An example of a structure formed by intramolecular cyclization reactions between adjacent vinyl groups (a polymerization reaction of vinyl groups when the structural unit represented by the formula (1) above is introduced consecutively (as a chain) as repeating units) is the chemical structure represented by the following formula (2). Furthermore, when a repeating structural unit having a 1,4-trans bond unit or a 1,4-cis bond unit is included, a preferred structure formed by intramolecular cyclization reactions is, for example, the chemical structure represented by formula (3).

[0061] [ka]

[0062] In formula (2), R 14 ~R 17 are each independently a hydrogen atom or an organic group having 1 to 20 carbon atoms, and a is an integer of 0 or more. n is an integer of 1 or more.

[0063] [ka]

[0064] In formula (3), R 12 , R 13 are each independently a hydrogen atom or an organic group having 1 to 20 carbon atoms, and n is an integer of 1 or more.

[0065] In the carbon fiber precursor fiber, the content of the crosslinked product of the diene polymer composition is not particularly limited, but is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, particularly preferably 70% by mass or more, especially preferably 80% by mass or more, and most preferably 90% by mass or more, relative to the total mass of the carbon fiber precursor fiber. The upper limit of the content of the crosslinked product of the diene polymer composition is not particularly limited. The content of the crosslinked product of the diene polymer composition may be 100% by mass. The fact that the carbon fiber precursor fiber contains the crosslinked product of the diene polymer composition means that: 1 H-nuclear magnetic resonance spectroscopy (NMR) and 13 This can be confirmed by C-NMR analysis, infrared spectroscopy analysis, etc.

[0066] Furthermore, from the viewpoint of suppressing thread breakage and fiber fusion during the flame-proofing step and from the viewpoint of suppressing fiber breakage during the carbonization step, the carbon fiber precursor fiber preferably has a gel fraction of 30% or more, more preferably 40% or more, even more preferably 50% or more, even more preferably 60% or more, particularly preferably 80% or more, and most preferably 90% or more. There is no particular upper limit to the gel fraction, and it is preferably 100% or less, but from the viewpoint of reducing the cost of the crosslinking process, it is more preferably 99.9% or less.

[0067] The crosslinked body can be obtained by subjecting the precursor fiber of carbon fiber made of the diene polymer to at least one crosslinking treatment of active energy ray irradiation and heat treatment.

[0068] Examples of active energy rays include X-rays, gamma rays, alpha rays, beta rays, electron beams, neutron beams, proton beams, and heavy particle beams. Among these, electron beams or ultraviolet rays are preferred from the viewpoint of having a specific gel fraction in the present disclosure and suppressing thread breakage and fusion of fibers in the flame-resistant treatment step, and electron beams are more preferred from the viewpoint of improving the tensile strength of the resulting carbon fiber.

[0069] When irradiating with electron beams, the dose of the electron beams to be irradiated is preferably 20 kGy or more, more preferably 30 kGy or more, even more preferably 60 kGy or more, even more preferably 80 kGy or more, particularly preferably 150 kGy or more, and most preferably 400 kGy or more, from the viewpoint of increasing the gel fraction. There is no particular upper limit to the dose, but from the viewpoint of reducing energy costs and damage to the fibers, it is preferably 50 MGy or less, more preferably 10 MGy or less, even more preferably 5 MGy or less, particularly preferably 2000 kGy or less, and most preferably 1000 kGy or less.

[0070] When irradiating with ultraviolet light, the illuminance of the ultraviolet light is preferably 5 mW / cm 2 ~1000mW / cm 2 , more preferably 10 mW / cm 2 ~900mW / cm 2 , and more preferably 50 mW / cm 2 ~800mW / cm 2 The ultraviolet irradiation time is not particularly limited, but from the viewpoint of reducing production energy, it is preferably 6 hours or less, more preferably 4 hours or less, even more preferably 2 hours or less, particularly preferably 1 hour or less, and most preferably 20 minutes or less. The lower limit of the irradiation time, although it depends on the output of the device, is preferably 1 second or more, more preferably 5 seconds or more, even more preferably 10 seconds or more, and particularly preferably 30 seconds or more. By including a polymer other than the diene polymer, the diene polymer composition of the present disclosure can preferably exhibit the effects of the present disclosure even with a short ultraviolet irradiation time.

[0071] When irradiating the carbon fiber precursor fiber with electron beams and / or ultraviolet rays, tension may be applied, for example, tension of 0.03 mN / dtex or more, 0.05 mN / dtex or more, 0.1 mN / dtex or more, 0.3 mN / dtex or more, or 0.5 mN / dtex or more.

[0072] Furthermore, the carbon fiber precursor fiber of the present disclosure may be coated with a conventionally known oil such as a silicone-based oil from the viewpoints of improving fiber bundling and handling, and preventing adhesion of fibers to each other.

[0073] <Method of manufacturing flame-resistant fiber> The method for producing an oxidized fiber of the present disclosure includes a step of heating the carbon fiber precursor fiber in an oxidizing atmosphere (hereinafter also referred to as a "oxidization step"). By heating the carbon fiber precursor fiber in an oxidizing atmosphere, an oxidized fiber can be obtained.

[0074] Examples of the oxidizing atmosphere in the flame-proofing step include oxygen, ozone, air, nitrogen oxides, halogens, sulfur dioxide gas, mixed gases of these, and mixed gases of these with inert gases, etc. Among these, air, mixed gases of oxygen and air, mixed gases of oxygen and inert gas, and mixed gases of air and inert gas are preferred, and air is particularly preferred from the viewpoint of cost reduction.

[0075] The flame-proofing step is preferably carried out in an oxidizing atmosphere at a temperature of 120°C to 500°C, more preferably at a temperature of 150°C to 480°C, even more preferably at a temperature of 170°C to 470°C, particularly preferably at a temperature of 180°C to 460°C, and most preferably at a temperature of 200°C to 450°C. There are no particular restrictions on the maximum temperature in the flame-proofing step, but from the viewpoints of improving the tensile strength of the carbon fiber obtained later and reducing production costs by shortening the production time, it is preferably 290°C or higher, more preferably 300°C or higher, and particularly preferably 330°C or higher.

[0076] The flame-proofing time (heating time at the maximum temperature) is not particularly limited, and although heating for a long time (for example, more than 4 hours) is possible, 1 minute to 4 hours is preferred, 2 minutes to 2 hours is more preferred, 3 minutes to 100 minutes is even more preferred, 4 minutes to 90 minutes is particularly preferred, and 4 minutes to 60 minutes is most preferred. By setting the heating time in the flame-proofing step to be equal to or greater than the lower limit, the carbonization yield can be improved, while by setting it to be equal to or less than the upper limit, costs can be reduced.

[0077] Furthermore, in the method for producing an oxidation-resistant fiber according to the present disclosure, tension may or may not be applied to the carbon fiber precursor fiber during the temperature rise process up to the oxidation temperature, etc., but from the viewpoint of sufficiently obtaining the effect of applying tension, it is preferable that tension be applied also during the temperature rise process, etc. Furthermore, tension may be applied from the initial stage of the temperature rise process, etc., or from an intermediate stage.

[0078] <Carbon manufacturing method> The method for producing a carbon fiber according to the present disclosure includes a step of producing a flame-resistant fiber by the method for producing a flame-resistant fiber, and a step of carbonizing the flame-resistant fiber (hereinafter also referred to as a "carbonization step").

[0079] The process for producing a flame-resistant fiber by the method for producing a flame-resistant fiber may be the same as the flame-resistant process. In the carbonization step, the flame-resistant fiber is preferably heated in an inert atmosphere (in an inert gas such as nitrogen, argon, or helium) at a temperature higher than that in the flame-resistant step, thereby carbonizing the flame-resistant fiber and obtaining the desired carbon fiber.

[0080] The heating temperature in the carbonization step is preferably 500° C. or higher, more preferably 1000° C. or higher, even more preferably 1100° C. or higher, particularly preferably 1200° C. or higher, and most preferably 1300° C. or higher. The upper limit of the heating temperature in the carbonization step is preferably 3000° C. or lower, more preferably 2500° C. or lower.

[0081] The heating time in the carbonization step is not particularly limited, but is preferably 30 seconds to 120 minutes, more preferably 30 seconds to 60 minutes, and more preferably 1 to 30 minutes. From the viewpoint of reducing production costs, the upper limit of the heating time is more preferably 20 minutes or less, and particularly preferably 10 minutes or less.

[0082] The carbonization step may include a "graphitization step" which is generally performed by heating at 2000 to 3000°C in an inert gas atmosphere. The carbonization step may, for example, involve first heating at a temperature below 1000°C (hereinafter also referred to as a "pre-carbonization step") and then heating at a temperature of 1000°C or higher, or may involve heating at a temperature below 1000°C, then heating at a temperature of 1000°C or higher, and then further heating at a temperature of 2000°C or higher. In the carbonization step of the present disclosure, heating may be performed multiple times.

[0083] The average fiber diameter of the single carbon fibers thus obtained is not particularly limited, but is preferably 3 nm to 300 μm, more preferably 30 nm to 150 μm, even more preferably 100 nm to 60 μm, even more preferably 1 μm to 40 μm, particularly preferably 2 μm to 30 μm, and most preferably 2.5 μm to 25 μm. If the average fiber diameter of the single carbon fibers is less than the lower limit, when a composite material is produced using a resin or the like as a matrix, if the viscosity of the matrix is high, impregnation of the resin or the like into the carbon fibers may be insufficient, resulting in a decrease in the tensile strength of the composite material. On the other hand, if the average fiber diameter exceeds the upper limit, the tensile strength of the single carbon fibers tends to decrease.

[0084] <Applications of diene polymer compositions> The diene polymer composition of the present disclosure can be processed into various shapes such as fibers, films, sheets, blocks, and powders for use. The diene polymer composition of the present disclosure has high processability and excellent crosslinkability, making it suitable for use in a variety of applications. The applications of the diene polymer composition of the present disclosure are not particularly limited, and it can be preferably used, for example, as a carbon fiber precursor, as well as in footwear, industrial parts, melt bags, films (such as household wrap films and stretch films for food packaging), sheets, hoses, tubes, sponge products, and resin restraining materials.

[0085] Hereinafter, the embodiments of the present disclosure will be described in more detail using examples, but the embodiments of the present disclosure are not limited to the following examples. [Example]

[0086] The following was prepared: <Diene polymer> Diene polymer (a-1): Syndiotactic 1,2-polybutadiene ("RB840" manufactured by ENEOS Materials Corporation, 1,2-bond content: 94 mol%, melting point: 126°C, melt flow rate (MFR, based on ASTM D1238, temperature: 150°C, load: 21.2 N): 9 g / 10 min, density: 0.914 g / cm 3 ) <Polymers other than diene polymers> Polymers other than diene polymers (b-1): Polyethylene wax (Clariant "Polyethylene Wax PE520", weight average molecular weight 5500, viscosity at 140°C: approximately 0.65 Pa s, melting point 117-123°C, density 0.93 g / cm 3 ) Polymers other than diene polymers (b-2): Low-density polyethylene (Japan Polyethylene Co., Ltd. "Low-density polyethylene UJ480", melting point 121°C, density 0.92 g / cm 3 ) Polymers other than diene polymers (b-3): Oxidized polyethylene (Clariant "Oxidized polyethylene PED191", weight-average molecular weight 9100, viscosity at 140°C: approximately 1.8 Pa s, melting point 120-125°C, acid value 15-19 mg KOH / g, density 0.98 g / cm 3 Polymers other than diene polymers (b-4): Hydrogenated dicyclopentadiene / C9 type petroleum resin (T-REZ HB103 manufactured by ENEOS Materials Corporation, aromatic content (measured in accordance with TSTM 4030): 8-11%, weight-average molecular weight: 720, softening point: 103°C, density: approximately 1.06 g / cm 3 ) Polymers other than diene polymers (b-5): C5 / C9 type petroleum resin ("T-REZ PR802" manufactured by ENEOS Materials Co., Ltd.), weight average molecular weight 1370, softening point: 88℃, density approximately 1.06g / cm 3 ) Polymers other than diene polymers (b-6): Acid-modified hydrocarbon resin C5 type ("T-REZ RE100" manufactured by ENEOS Material Corporation, weight average molecular weight 2900, softening point 98°C, acid value: 0.50-0.90 mgKOH / g, density approximately 1.06 g / cm 3 ) <Additives> Photopolymerization initiator (c-1): Methyl 2-benzoylbenzoate (Fujifilm Wako Pure Chemical Industries, Ltd.) Photopolymerization initiator (c-2): 4,4'-bis(dimethylamino)benzophenone (Tokyo Chemical Industry Co., Ltd.)

[0087] <Examples 1 to 4> The diene polymer (a-1) and the polymer other than the diene polymer (b-1) were charged into the chamber of a Labo Plastomill ("10C100" manufactured by Toyo Seiki Seisaku-sho, Ltd., chamber: R100H, blade shape: roller type) in the mixing ratios shown in Table 1, and melt-kneaded for 5 minutes at a screw rotation speed of 100 rpm and a temperature of 150°C to obtain diene polymer compositions (d-1) to (d-4). The obtained diene-based polymer composition was fed into the hopper of a single-screw extruder of a melt spinning apparatus equipped with a single-screw extruder (screw diameter: 20 mm) and a nozzle (nozzle hole diameter: 200 μm, number of holes: 36 holes), and melt spun at 150°C to obtain a fiber bundle of carbon fiber precursor fiber (average fiber diameter: 15 μm). The carbon fiber precursor fiber bundle was stretched 1.7 times at room temperature to obtain a fiber bundle with a fiber diameter of 12 μm, and then 10 bundles were aligned to obtain a fiber bundle of 360 fibers per bundle. Next, using an electron beam irradiation device ("EBC800-35" manufactured by NHV Corporation), the carbon fiber precursor fiber bundle was transported at a speed of 20 m / min, and the acceleration voltage was set to 800 kV and the electron beam dose to 550 kGy. Electron beam irradiation was performed in an air atmosphere to obtain an electron beam-irradiated carbon fiber precursor fiber bundle (average fiber diameter: approximately 12 μm). Here, the tension during electron beam irradiation was 3 mN / dtex. Two electron beam irradiated carbon fiber precursor fiber bundles (360 fibers / bundle) were bundled to form a fiber bundle of 720 fibers / bundle. This fiber bundle was then unwound under a tension of 50 cN and fed into a heat treatment device with a temperature gradient of 200°C to 350°C under an air stream. The fiber was passed through the heat treatment device for 60 minutes for heat treatment (flame retardation treatment). During this passage, the fiber draw ratio was set to 1.1. Further, a tension of 50 cN was applied, and the fiber draw ratio was maintained at 1.0, followed by flame retardation treatment at 350°C for 30 minutes to obtain flame retardant fiber (average fiber diameter: approximately 9 μm). While the flame-retardant fiber was applied with a tension of 30 cN, it was transported under a nitrogen stream into a heat treatment device whose temperature was adjusted to 800°C and subjected to a preliminary carbonization treatment (3 minutes) to produce a pre-carbonized fiber. Next, while the pre-carbonized fiber was applied with a tension of 30 cN, it was transported under a nitrogen stream into a heat treatment device whose temperature was adjusted to 1400°C and subjected to a carbonization treatment for 3 minutes to obtain a carbon fiber.

[0088] <Examples 5 to 14> Diene polymer (a-1) and polymers other than the diene polymer (b-1) to (b-5) were mixed in the ratios shown in Table 1 and fed into a single-screw extruder (manufactured by Toyo Seiki Seisaku-sho, Ltd., "D2020", screw shape: full-flight, screw length / screw diameter (L / D): 20) attached to a Laboplastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd., "10C100"), and melt-kneaded at a screw rotation speed of 90 rpm and a temperature of 145°C (melt-kneading with a higher shear force than in Examples 1 to 4), to obtain diene polymer compositions (d-5) to (d-14). The obtained diene polymer composition was charged into the hopper of a single-screw extruder of a melt spinning apparatus equipped with a single-screw extruder (screw diameter: 20 mm) and a nozzle (nozzle hole diameter: 200 μm, number of holes: 36 holes), and melt spun at 150 ° C to obtain a carbon fiber precursor fiber bundle (average fiber diameter: 15 μm). Next, the fiber bundle was stretched 1.7 times at room temperature to obtain a fiber bundle with a fiber diameter of 12 μm, and 10 bundles were aligned to obtain a fiber bundle of 360 fibers per bundle (average fiber diameter: 12 μm). Next, using an electron beam irradiation device (manufactured by NHV Corporation, "EBC800-35"), the carbon fiber precursor fiber bundle was transported at a speed of 20 m / min, and electron beam irradiation was performed in an air atmosphere with an acceleration voltage set to 800 kV and an electron beam dose set to 550 kGy, to obtain an electron beam-irradiated carbon fiber precursor fiber bundle (average fiber diameter: approximately 12 μm). Thereafter, in the same manner as in Examples 1 to 4, flame-resistant fibers (average fiber diameter: about 9 μm) and carbon fibers were obtained.

[0089] <Examples 15 to 18> The diene polymer (a-1), the polymer (b-1) other than the diene polymer, and the photopolymerization initiator (c-1) or the photopolymerization initiator (c-2) were charged into the chamber of a Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd., "10C100", chamber: R100H, blade shape: roller type) in the mixing ratios shown in Table 2, and melt-kneaded for 5 minutes at a screw rotation speed of 100 rpm and a temperature of 150°C to obtain diene polymer compositions (d-15) to (d-18). Next, the diene polymer composition was charged into the hopper of a single-screw extruder of a melt spinning device equipped with a single-screw extruder (screw diameter: 20 mm) and a nozzle (nozzle hole diameter: 200 μm, number of holes: 36 holes), and melt spun at a temperature of 150°C to obtain a carbon fiber precursor fiber bundle (average fiber diameter: 15 μm). The carbon fiber precursor fiber bundle was stretched 1.7 times at room temperature, and then 10 bundles were aligned to form a fiber bundle of 360 fibers per bundle (average fiber diameter: 12 μm). Next, these fiber bundles were irradiated with a UV-LED irradiator ("HLDL-350×270" manufactured by CCS) at an irradiance of 200 mW / cm under a tension of 0.07 mN / dtex. 2 In Example 16, ultraviolet irradiation was performed in the same manner as in Example 15, except that the irradiation time was set to 10 minutes, to obtain an ultraviolet-irradiated carbon fiber precursor fiber bundle (average fiber diameter: about 12 μm). Next, the ultraviolet-irradiated carbon fiber precursor fiber bundle was subjected to the same treatment as in Examples 1 to 4 to obtain flame-resistant fiber (average fiber diameter: about 9 μm) and carbon fiber.

[0090] <Comparative Example 1> A flame-retardant fiber (average fiber diameter: about 10 μm) and a carbon fiber were obtained in the same manner as in Example 1, except that the diene polymer (a-1) was fed into a hopper of a single-screw extruder of a melt spinning apparatus equipped with a single-screw extruder (screw diameter: 20 mm) and a nozzle (nozzle hole diameter: 200 μm, number of holes: 36 holes), melt-spun at a temperature of 150°C, and the fiber was discharged from the nozzle and wound up to obtain a carbon fiber precursor fiber bundle (average fiber diameter: 15 μm).

[0091] <Comparative Example 2> A mixture was obtained by adding 2 parts by mass of photopolymerization initiator (c-1) to 100 parts by mass of diene polymer (a-1), and mixing using a Labo Plastomill in the same manner as in Example 15. Next, the mixture was poured into the hopper of a single-screw extruder of a melt spinning apparatus equipped with a single-screw extruder (screw diameter: 20 mm) and a nozzle (nozzle hole diameter: 200 μm, number of holes: 36 holes), melt-spun at a temperature of 150°C, and fibers were discharged from the nozzle and wound up to obtain a carbon precursor fiber bundle (average fiber diameter: 15 μm). Except for this, flame-resistant fibers (average fiber diameter: about 10 μm) and carbon fibers were obtained in the same manner as in Example 15.

[0092] <Comparative Example 3> To 100 parts by mass of diene polymer (a-1), 2 parts by mass of (c-2) was added as a photopolymerization initiator, and the mixture was mixed in a Labo Plastomill in the same manner as in Example 15. Next, the mixture was charged into the hopper of a single-screw extruder of a melt spinning apparatus equipped with a single-screw extruder (screw diameter: 20 mm) and a nozzle (nozzle hole diameter: 200 μm, number of holes: 36 holes), and melt spun at a temperature of 150 ° C. to discharge fibers from the nozzle, which were then wound up to obtain a carbon fiber precursor fiber bundle (average fiber diameter: 15 μm). Except for this, flame-resistant fibers (average fiber diameter: about 10 μm) and carbon fibers were obtained in the same manner as in Example 15.

[0093] <Various evaluations> -Spinnability of diene polymer compositions (fiber breakage prevention)- Spinnability was evaluated by melt spinning (nozzle diameter of melt spinning device: 200 μm, number of holes in the nozzle: 36 holes). Melt spinning was performed and wound at high speed (spinning speed 100 m / min) to obtain a fiber bundle of carbon precursor fiber with a fiber diameter of 15 μm. Spinnability was evaluated according to the following criteria based on the number of broken fibers that occurred at the nozzle one minute after the start of winding. The results are shown in Table 1. A: The number of broken fibers at the nozzle was 0 out of 36. B: The number of broken threads is 1 out of 36. C: The number of broken yarns is 2 or more out of 36.

[0094] -Fineness of carbon fiber precursor fiber- The mass of the fiber bundle of the carbon fiber precursor fiber was measured, and the mass per 10,000 m was calculated as the fineness [dtex] of the fiber bundle of the carbon fiber precursor fiber.

[0095] -Degree of crosslinking (gel fraction) after electron beam or ultraviolet irradiation- A 0.2 g sample was cut from the irradiated carbon fiber precursor fiber after electron beam irradiation or ultraviolet irradiation. After drying at 80°C for 4 hours, the mass was precisely weighed using a precision electronic balance and used as the initial mass (g). The sample was then immersed in 30 ml of toluene and allowed to stand in a hot air circulating oven at 60°C for 8 hours. After standing, the sample was subjected to suction filtration using a membrane filter with a pore size of 1.0 μm (Omnipore™ Membrane Filter JAWP04700, manufactured by Merck) to separate the gel fraction. The separated gel fraction, together with the membrane filter, was air-dried in the atmosphere in a fume hood for 12 hours or more and then allowed to stand in a hot air circulating oven at 90°C for 12 hours to remove the toluene. The masses of the gel fraction and membrane filter after standing were precisely weighed using a precision electronic balance, and the gel fraction was calculated using the following formula. Gel fraction (%) = {(mass of gel and membrane filter (g) - mass of membrane filter (g)) / initial mass of sample (g)} × 100 Using the calculated gel fraction, the degree of crosslinking of the irradiated carbon fiber precursor fiber was evaluated according to the following criteria. The results are shown in Table 1. A: The gel fraction was 90% or more. B: The gel fraction was 80% or more and less than 90%. C: The gel fraction was less than 80%.

[0096] - Flame-resistant treatment resistance of carbon fiber precursor fiber bundles (fiber breakage prevention) - To evaluate the resistance to flame retardation treatment when the fiber was maintained at a draw ratio of 1.1 and flame retarded, a fiber bundle (3 cm long) for evaluation was cut from the flame retarded fiber bundle obtained by flame retardation to check for fiber breakage during the flame retardation treatment. The fiber bundle for evaluation was observed for breakage using a microscope (Keyence Corporation, "Digital Microscope VHX-7000") and evaluated according to the following criteria. The results are shown in Table 1. A: No fiber breakage occurred. B: 1 to 10 single fibers were broken. C: 11 or more single fibers were broken.

[0097] -Fusion rate of carbon fiber precursor fiber bundles- A 3 cm long fiber bundle for evaluation was cut out from a fiber bundle of flame-retardant fiber. The cross section of this fiber bundle for evaluation was observed using a microscope (Keyence Corporation, "Digital Microscope VHX-7000"), and the number of fibers was counted. At this time, the number of fused fibers and the number of all fibers constituting the fiber bundle for evaluation were counted. The number of fused fibers was counted as two, for example, when two fibers were fused to each other. The number of all fibers was counted by separating the fused fibers into their pre-fusion state. The fusion rate was calculated based on the following formula. The results are shown in Table 1. Fusion rate (%) = (number of fused fibers / total number of fibers) x 100

[0098] - Carbonization yield of flame-retardant fiber - A piece of flame-retardant fiber with a mass of approximately 2 mg was cut out from the flame-retardant fiber obtained by the flame retardation treatment, and heated from room temperature to 1000°C at a heating rate of 10°C / min in a nitrogen gas flow of 1000 ml / min using a high-temperature differential thermobalance (Rigaku Corporation, Thermo plus EV02 TG-DTA / H), and the carbonization yield was calculated using the following formula (1). Equation (1): Carbonization yield (%) = (mass of carbon fiber at 1000°C / mass of flame-retardant fiber at room temperature) × 100 The carbonization yield was evaluated according to the following criteria, and the results are shown in Table 1. A: 60% or more B: 50% or more but less than 60% C: Less than 50%

[0099] - Carbonization resistance of flame-retardant fibers - The side surfaces of the carbon fibers obtained after carbonization were observed visually and using a microscope (Keyence Corporation, "Digital Microscope VHX-7000") and evaluated according to the following criteria. The results are shown in Table 1. A: No fluffing occurred. B: Fluff occurred due to the breakage of 1 to 10 single fibers. C: Fluffing occurred due to breakage of 11 or more single fibers.

[0100] -Tensile modulus and tensile strength of carbon fiber- Five single fibers were taken out from the obtained carbon fiber bundle, and a tensile test (gauge length: 25 mm, tensile speed: 1 mm / min) was performed on each single fiber at room temperature in accordance with JIS R7606 using a micro strength evaluation tester ("Micro Autograph MST-I" manufactured by Shimadzu Corporation), and the tensile modulus and tensile strength were measured and averaged. The results are shown in Table 1.

[0101] - Observation of the cross-sectional phase structure of carbon fiber precursor fibers before and after cross-linking - Ultrathin sections of each fiber were prepared from a cross section perpendicular to the fiber axis, and the phase structure was observed using a transmission electron microscope (Hitachi High-Tech, H-7650). When a dispersed phase containing a polymer other than a diene-based polymer was dispersed in a diene-based polymer, 20 dispersed phases were randomly selected, the particle sizes of these dispersed phases were measured, and the average value was taken as the average particle size of the dispersed phase. In the particle size measurement of the dispersed phase, if the shape observed was other than circular (e.g., elliptical, streaky, or other irregular shape), the lengths of the long side (longest part) and short side (shortest part) of the dispersed phase were measured, and the sum of the lengths of the long side and the short side was divided by 2 (the average value) to determine the particle size.

[0102] -Average fiber diameter of each fiber- The side surfaces of each fiber bundle of carbon fiber precursor fiber, electron beam irradiated carbon fiber precursor fiber, ultraviolet irradiated carbon fiber precursor fiber, flame-resistant fiber, and carbon fiber were observed using a microscope (Keyence Corporation, "Digital Microscope VHX-7000"). At this time, the diameters of 12 randomly selected single fibers in each fiber bundle were measured, and the average value was calculated to obtain the average fiber diameter of each fiber.

[0103] [Table 1]

[0104] As shown in Table 1, the diene polymer compositions of Examples 1 to 14, which contain polymers other than diene polymers, are superior in spinnability (resistance to yarn breakage) during melt spinning compared to the diene polymer composition of Comparative Example 1, and the carbon fiber precursor fiber bundles containing crosslinked products (electron beam crosslinked) of the diene polymer compositions are superior in flame retardant treatment resistance (resistance to yarn breakage during stretching after flame retardant treatment). As a result, the flame retardant fibers are superior in carbonization treatment resistance, and the carbon fibers are superior in tensile strength.

[0105] [Table 2]

[0106] Furthermore, as shown in Table 2, the diene polymer compositions of Examples 15 to 18, which contain polymers other than diene polymers, are superior in spinnability (resistance to yarn breakage) during melt spinning compared to Comparative Examples 2 and 3. Furthermore, carbon fiber precursor fiber bundles containing crosslinked (ultraviolet crosslinked) diene polymer compositions have high flame retardant treatment resistance (resistance to yarn breakage during stretching after flame retardant treatment) and suppressed fusion. As a result, the flame retardant fibers have excellent carbonization treatment resistance, and the carbon fibers have excellent tensile strength. Furthermore, the carbon fiber precursor fiber of Example 16 exhibited the same effect as Example 15, which was irradiated for 60 minutes, even when irradiated for 10 minutes, demonstrating that the inclusion of a polymer other than a diene-based polymer leads to energy-saving production with a short ultraviolet irradiation time of 10 minutes. The polymer other than a diene-based polymer exhibits a plasticizing effect that improves the spinnability of the diene-based polymer composition during melt spinning, and a crosslinking-promoting effect.

Claims

1. a diene-based polymer containing a structural unit represented by the following formula (1) (wherein R represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and n represents an integer of 1 or more); a polymer other than the diene-based polymer; Including, a blending ratio (mass ratio) of the diene polymer to the polymer other than the diene polymer is 99.5:0.5 to 10:90; At least a part of the polymer other than the diene-based polymer forms a dispersed phase, or the diene-based polymer and the polymer other than the diene-based polymer are compatible with each other. Diene-based polymer compositions. 【Chemical 1】

2. 2. The diene-based polymer composition according to claim 1, wherein the polymer other than a diene-based polymer comprises at least one member selected from the group consisting of an olefin-based polymer, a petroleum resin, and an aromatic vinyl-based polymer.

3. 2. The diene-based polymer composition of claim 1, wherein the average particle size of the dispersed phase is 1 μm or less.

4. A carbon fiber precursor fiber, which is a fiber made from the diene polymer composition according to any one of claims 1 to 3.

5. 5. The carbon fiber precursor fiber according to claim 4, which comprises a crosslinked product of the diene polymer composition according to any one of claims 1 to 3 and has a gel fraction of 30% or more.

6. The carbon fiber precursor fiber according to claim 5 is heated in an oxidizing atmosphere. Method for producing flame-resistant fibers.

7. a step of producing a flame-resistant fiber by the method for producing a flame-resistant fiber according to claim 6; carbonizing the flame-resistant fiber; A method for producing carbon fiber, comprising:

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