Oil agent and carbon material precursor

Abstract

To provide an oil agent and the like which can suppress fusion between carbon material precursors during flame-resistant treatment and can also decrease residues after carbonization treatment.SOLUTION: An oil agent comprises a multifunctional (meth)acrylate not containing any siloxane structure, and is used for surface treatment of carbon material precursors. Also provided are applications thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an oil agent and a carbon material precursor. [Background technology]

[0002] Carbon fiber is attracting attention as a substitute for metal because it is lightweight and has excellent mechanical properties. A known method for producing carbon fiber is to spin a polymer such as polyacrylonitrile into a fiber bundle, which is then flame-retarded and then carbonized. However, when heat treatment such as flame retardant treatment is performed, the polymer may soften due to heat and fuse. To prevent this, it is known to use an oil agent.

[0003] For example, Patent Document 1 describes a silicone oil agent for carbon fiber precursor fibers, which is composed of an amino-modified silicone, an alicyclic epoxy-modified silicone, and an alkylene oxide-modified silicone, in which the silicone compounds contained in the oil agent components have an average silicone kinematic viscosity at 25°C of 750 to 1500 cSt, and the difference in pendulum oscillation period measured by the rigid pendulum free damped oscillation method is 0.03 to 0.4, and the ratio of alkylene oxide-modified silicone to 100 parts by weight of amino-modified silicone is 15 to 900 parts by weight, and the ratio of alicyclic epoxy-modified silicone to 100 parts by weight of all silicone compounds is 3 to 20 parts by weight. Patent Document 2 describes a method for producing a precursor fiber for carbon fiber, in which a silicone-based oil solution is applied to a fiber whose constituent component is a flame-resistant polymer having a polyacrylonitrile skeleton, so that the amount of oil solution component attached per dry weight of the fiber is 0.1 to 5 wt % to obtain a precursor fiber for carbon fiber. Patent Document 3 describes a carbon fiber precursor fiber bundle to which an oil solution containing at least a nonionic surfactant and an amino-modified silicone having a kinematic viscosity at 25°C of 3500 to 20000 mm2 / s is applied, and the ratio of the amino-modified silicone in the oil solution is 25 to 50 mass%. Patent Document 4 describes a carbon fiber precursor fiber that includes an acrylamide polymer fiber and a self-crosslinked product of a self-crosslinking silicone oil that is present on the surface of the acrylamide polymer fiber. Patent Document 5 describes a carbon fiber precursor comprising an acrylamide-based polymer fiber and an oil agent composition layer on the surface of the acrylamide-based polymer fiber, the oil agent composition layer containing a crosslinked product of a silicone-based oil agent, wherein the degree of crosslinking of the oil agent composition layer is 3% or more, where X is the mass of the oil agent composition layer and Y is the mass of the oil agent composition layer that dissolves upon immersion in hexane at 23°C for 48 hours. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4543922 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-202208 [Patent Document 3] Patent Publication No. 2021-50428 [Patent Document 4] Japanese Patent Application Publication No. 2023-64697 [Patent Document 5] Japanese Patent Application Publication No. 2023-174468 Summary of the Invention [Problem to be solved by the invention]

[0005] When a carbon material precursor coated with a silicone-based oil is subjected to carbonization, the silicone-based oil changes to silicon oxide, silicon carbide, silicon nitride, etc. at the carbonization temperature (800 to 2000°C), and these remain on the carbon material. If residue remains on the carbon material, it can cause a deterioration in the appearance quality of the resulting carbon material, a decrease in the efficiency of the sizing treatment and contamination of the treatment liquid, and a decrease in adhesion and strength when producing carbon fiber reinforced plastic. Therefore, it is required to suppress fusion between carbon material precursors during the flame-resistant treatment and to reduce residues after the carbonization treatment.

[0006] An object of one embodiment of the present disclosure is to provide an oil agent that can suppress fusion between carbon material precursors during flame-resistant treatment and reduce residues after carbonization treatment. Another problem to be solved by another embodiment of the present disclosure is to provide a carbon material precursor that suppresses fusion during flame-proofing treatment and reduces residues after carbonization treatment. [Means for solving the problem]

[0007] Specific means for achieving the above object are as follows: <1> An oil containing a polyfunctional (meth)acrylate that does not contain a siloxane structure and is used for surface treatment of polymers for carbon material precursors. <2> Further containing a monofunctional (meth)acrylate that does not contain a siloxane structure, <1> The oil agent described in <3> The content of the monofunctional (meth)acrylate not containing a siloxane structure is 10 parts by mass to 2000 parts by mass relative to 100 parts by mass of the polyfunctional (meth)acrylate not containing a siloxane structure. <2> The oil agent described in <4> The polyfunctional (meth)acrylate not containing a siloxane structure includes at least one selected from the group consisting of polybutadiene (meth)acrylate, polyester (meth)acrylate, polyfunctional (meth)acrylate whose main chain is a saturated hydrocarbon group, and poly(meth)acryl (meth)acrylate. <1> ~ <3> One of the following oil solutions. <5> The carbon material precursor polymer includes an acrylamide polymer. <1> ~ <4> One of the following oil solutions. <6> When the oil agent is crosslinked, the gel fraction is 50% or more, and the weight residual rate at 300°C is 50% or more. <1> ~ <5> 1. The oil agent according to any one of the preceding items. <7> On the surface of the carbon material precursor polymer, <1> ~ <6> 10. A carbon material precursor comprising the oil agent according to any one of the above items. <8> The oil agent is a crosslinked material. <7> The carbon material precursor according to claim 1. <9> The carbon material precursor polymer includes an acrylamide polymer. <8> The carbon material precursor according to claim 1. <10> A method for producing a carbon material, comprising the steps of subjecting a polymer for use as a precursor of a carbon material, which has been surface-treated with an oil containing a polyfunctional (meth)acrylate that does not contain a siloxane structure, to a flame-retardant treatment and a carbonization treatment. <11> The oil agent further contains a monofunctional (meth)acrylate that does not contain a siloxane structure. <10> A method for producing the carbon material described in [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, there is provided an oil agent that can suppress fusion between carbon material precursors during flame-resistant treatment and reduce residues on the carbon material after carbonization treatment. According to another embodiment of the present disclosure, there is provided a carbon material precursor that suppresses fusion during flame-proofing treatment, reduces residues on the carbon material after carbonization treatment, and has a high carbonization yield. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0010] In the present disclosure, each component may contain multiple types of corresponding substances. When multiple types of substances corresponding to each component are present in the polymer for carbon material precursor and the carbon material precursor, the content or amount of each component means the total content or amount of the multiple types of substances present in the polymer for carbon material precursor and the carbon material precursor, unless otherwise specified.

[0011] In this disclosure, "(meth)acryloyl group" means an acryloyl group or a methacryloyl group. "(meth)acrylate" means an acrylate or a methacrylate. "(meth)acrylic" means an acrylic or a methacrylic.

[0012] In the present disclosure, the term "carbon material precursor polymer" refers to a material that can be subjected to a carbonization treatment, or a flame-proofing treatment and a carbonization treatment, to obtain a carbon material. In the present disclosure, the term "carbon material" refers to a material that has been carbonized. The form of the carbon material is not particularly limited, and may be, for example, fiber, plate, film, powder, granules, or the like.

[0013] <Oil> The oil agent of the present disclosure contains a polyfunctional (meth)acrylate that does not contain a siloxane structure, and is used for surface treatment of a polymer for use as a carbon material precursor.

[0014] The oil agent of the present disclosure can suppress fusion between carbon material precursors during flame-resistant treatment and reduce residues on the carbon material after carbonization treatment.

[0015] The oil agent of the present disclosure contains a polyfunctional (meth)acrylate that does not contain a siloxane structure and is unlikely to vaporize at the temperature of the flame-resistant treatment (for example, 400°C or lower), which can suppress fusion between carbon material precursors. Furthermore, the oil agent of the present disclosure contains a polyfunctional (meth)acrylate that does not contain a siloxane structure and is likely to vaporize at the temperature of the carbonization treatment (for example, 800°C to 2000°C), which can reduce residues after the carbonization treatment.

[0016] (polyfunctional (meth)acrylate not containing a siloxane structure) The oil agent of the present disclosure contains a polyfunctional (meth)acrylate that does not contain a siloxane structure (hereinafter also referred to as a "specific polyfunctional (meth)acrylate").

[0017] The specific polyfunctional (meth)acrylate is a compound that does not contain a siloxane structure and has two or more (meth)acryloyl groups in one molecule.

[0018] The number of (meth)acryloyl groups in the specific polyfunctional (meth)acrylate is 2 or more, preferably 2 to 10, and more preferably 2 to 8. In addition, the (meth)acryloyl groups are preferably acryloyl groups.

[0019] The term "siloxane structure" refers to a structure represented by -Si-O-Si-. The absence of a siloxane structure in a compound can be determined by measurement using a nuclear magnetic resonance method, gas chromatography mass spectrometry, or the like.

[0020] Examples of the specific polyfunctional (meth)acrylate include: bifunctional (meth)acrylates whose main chain is a saturated hydrocarbon group, such as 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-nonanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-hydroxy-1,3-di(meth)acryloyloxypropane, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, glycerin di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate; Tri- or higher functional (meth)acrylates whose main chain contains a saturated hydrocarbon group, such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and glycerin tri(meth)acrylate; Dipentaerythritol, ditrimethylolpropane polyfunctional (meth)acrylate; alkylene oxide-modified polyfunctional (meth)acrylates such as trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, glycerin, bisphenol A, and bisphenol F; Caprolactone-modified isocyanurate multifunctional (meth)acrylate; Alkylene oxide modified polyfunctional (meth)acrylate of isocyanuric acid; Examples of the polyfunctional (meth)acrylate oligomer and polyfunctional (meth)acrylate polymer include urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, polyether (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, polytetramethylene glycol acrylate, polypentaerythritol polyacrylate, polybutadiene (meth)acrylate, and poly(meth)acrylic (meth)acrylate.

[0021] From the viewpoints of suppressing fusion between carbon material precursors during flame retardation treatment and reducing residues on the carbon material after carbonization treatment, the specific polyfunctional (meth)acrylate preferably contains at least one selected from the group consisting of polybutadiene (meth)acrylate, polyester (meth)acrylate, polyfunctional (meth)acrylate whose main chain is a saturated hydrocarbon group, and poly(meth)acrylic (meth)acrylate.

[0022] Polybutadiene (meth)acrylate is a compound in which a (meth)acryloyl group is linked to the terminal, side chain, or terminal and side chain of polybutadiene. The polybutadiene and the (meth)acryloyl group may be linked directly or via a linking group (e.g., an ether bond, an ester bond, a urethane bond, etc.).

[0023] Polyester (meth)acrylate is a compound in which a (meth)acryloyl group is linked to the end, side chain, or both the end and side chain of a polyester. Polyester (meth)acrylate is synthesized, for example, by reacting polyester polyol or polyether polyol with acrylic acid or acrylic anhydride.

[0024] A polyfunctional (meth)acrylate whose main chain is a saturated hydrocarbon group is a compound in which a (meth)acryloyl group is linked to the end of the saturated hydrocarbon group. The saturated hydrocarbon group is preferably an alkylene group. The saturated hydrocarbon group preferably has 4 to 12 carbon atoms.

[0025] Poly(meth)acrylic(meth)acrylate is a compound in which a (meth)acryloyl group is linked to the end, side chain, or both the end and side chain of a (meth)acrylic resin.

[0026] (Monofunctional (meth)acrylate not containing a siloxane structure) From the viewpoints of application properties and low viscosity, the oil agent of the present disclosure preferably contains, in addition to the specific polyfunctional (meth)acrylate, a monofunctional (meth)acrylate that does not contain a siloxane structure (hereinafter also referred to as "specific monofunctional (meth)acrylate").

[0027] The specific monofunctional (meth)acrylate is a compound that does not contain a siloxane structure and has one (meth)acryloyl group in one molecule. The (meth)acryloyl group is preferably an acryloyl group.

[0028] Examples of the specific monofunctional (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tert-octyl (meth)acrylate, isoamyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and cyclohexyl (meth)acrylate. acrylate, 4-n-butylcyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl diglycol (meth)acrylate, butoxyethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 4-bromobutyl (meth)acrylate, cyanoethyl (meth)acrylate, benzyl (meth)acrylate, butoxymethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-(2-methylpropyl)-2-methylpropyl (2-ethoxyethoxy)ethyl (meth)acrylate, 2-(2-butoxyethoxy)ethyl (meth)acrylate, 2,2,2-tetrafluoroethyl (meth)acrylate, 1H,1H,2H,2H-perfluorodecyl (meth)acrylate, 4-butylphenyl (meth)acrylate, phenyl (meth)acrylate, 2,4,5-tetramethylphenyl (meth)acrylate, 4-chlorophenyl (meth)acrylate, 2-phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, glycidyl (meth)acrylate , glycidyloxybutyl (meth)acrylate, glycidyloxyethyl (meth)acrylate, glycidyloxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate,Phenyl glycidyl ether (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, trimethoxysilylpropyl (meth)acrylate, trimethylsilylpropyl (meth)acrylate, polyethylene oxide monomethyl ether (meth)acrylate, polyethylene oxide (meth)acrylate, polyethylene oxide monoalkyl ether (meth)acrylate, dipropylene glycol (meth)acrylate, polypropylene oxide monoalkyl ether (meth)acrylate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyhexahydrophthalate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, ethoxydiethylene glycol (meth)acrylate, butoxydi Examples of the acrylates include ethylene glycol (meth)acrylate, trifluoroethyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, ethylene oxide (EO)-modified phenol (meth)acrylate, EO-modified cresol (meth)acrylate, EO-modified nonylphenol (meth)acrylate, propylene oxide (PO)-modified nonylphenol (meth)acrylate, EO-modified 2-ethylhexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (3-ethyl-3-oxetanylmethyl) (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-carboxyethyl (meth)acrylate, and 2-(meth)acryloyloxyethyl succinate.

[0029] From the viewpoints of suppressing fusion between carbon material precursors during flame retardation treatment and reducing residues on the carbon material after carbonization treatment, the content of the specific monofunctional (meth)acrylate is preferably 10 parts by mass to 2000 parts by mass, and more preferably 25 parts by mass to 1000 parts by mass, per 100 parts by mass of the specific polyfunctional (meth)acrylate.

[0030] The oil agent of the present disclosure may contain components other than the specific polyfunctional (meth)acrylate and the specific monofunctional (meth)acrylate. Examples of other components include antioxidants, fillers, thixotropic agents, thermal crosslinking agents, ultraviolet crosslinking agents, antistatic agents, smoothing agents, surfactants, and plasticizers.

[0031] From the viewpoints of suppressing fusion between carbon material precursors during flame-resistant treatment and reducing residues on the carbon material after carbonization, the proportion of the specific polyfunctional (meth)acrylate and the specific monofunctional (meth)acrylate in the oil agent of the present disclosure is preferably 80% by mass or more, and more preferably 90% by mass or more. The proportion may be 100% by mass. In other words, the oil agent of the present disclosure may be composed of the specific polyfunctional (meth)acrylate and the specific monofunctional (meth)acrylate.

[0032] When the oil agent of the present disclosure is crosslinked, the gel fraction of the oil agent is preferably 20% or more, and more preferably 50% or more. Furthermore, when the oil agent of the present disclosure is crosslinked, the gel fraction of the oil agent is more preferably 50% or more, and the weight residual rate at 300°C is more preferably 50% or more. Note that, in the present disclosure, a crosslinked form means that the molecular structure of the oil agent contains a crosslinked structure. When the oil agent contains a crosslinked structure, for example, it is preferable that the liquid oil agent has become solid and the gel fraction is 20% or more.

[0033] The method for crosslinking the oil agent is not particularly limited, and examples thereof include a heating method and a method of irradiating with ultraviolet rays, X-rays, gamma rays, alpha rays, beta rays, electron beams, neutron beams, proton beams, heavy particle beams, etc. Among these, the method for crosslinking the oil agent is preferably a heating method, a method of irradiating with ultraviolet rays, or a method of irradiating with an electron beam, and more preferably a method of irradiating with an electron beam. When the oil agent is crosslinked by heating, it is preferable to add a thermal crosslinking agent. When the oil agent is crosslinked by ultraviolet irradiation, it is preferable to add an ultraviolet crosslinking agent. When the oil agent is crosslinked by electron beam irradiation, a crosslinking agent is not necessary.

[0034] The gel fraction of an oil agent having a crosslinked structure and the weight remaining rate at 300°C are measured by the following method.

[0035] First, the oil is subjected to a crosslinking treatment to obtain an oil having a crosslinked structure (a crosslinked oil). An example of the crosslinking method is described below. Using an electron beam irradiation device (product name "EPS-750kV machine", manufactured by NHV Corporation), the oil is irradiated with an electron beam under a nitrogen atmosphere at an acceleration voltage of 750kV and a dose of 100kGy. Approximately 0.1 mg of the cross-linked oil is collected and immersed in a solvent (such as acetone) at room temperature (25°C) for 24 hours. After that, the cross-linked oil is removed and dried at room temperature (25°C) for 24 hours. The mass before immersion in the solvent (pre-test mass) and the mass after immersion in the solvent and drying (post-test mass) are measured. The gel fraction is calculated using the following formula: Gel fraction (%) = (mass after test / mass before test) x 100 Approximately 1 to 2 mg of the crosslinked oil solution was sampled, placed on a platinum pan, and set in a thermal analyzer (product name "ThermoPlusEV02", manufactured by Rigaku Corporation). The temperature was raised to 350°C at a rate of 10°C / min in air, and the residual weight rate was measured when the temperature reached 300°C.

[0036] From the viewpoint of suppressing fusion between carbon material precursors during flame-resistant treatment, the gel fraction when the oil agent is crosslinked is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The upper limit of the gel fraction is not particularly limited, but is, for example, 100%.

[0037] From the viewpoint of suppressing fusion between carbon material precursors during flame retardation treatment, when the oil agent is crosslinked, the weight residual ratio at 300° C. is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The upper limit of the weight residual ratio at 300° C. is not particularly limited, but is, for example, 100%.

[0038] <Carbon material precursor polymer> Carbon materials can be obtained by subjecting a carbon material precursor polymer to a carbonization treatment, or a flame-retardant treatment followed by a carbonization treatment. Examples of carbon material precursor polymers include acrylamide-based polymers (homopolymers, copolymers, and mixtures of homopolymers and copolymers), acrylonitrile-based polymers (homopolymers, copolymers, and mixtures of homopolymers and copolymers), vinyl alcohol-based polymers (homopolymers, copolymers, and mixtures of homopolymers and copolymers), olefin-based polymers (homopolymers, copolymers, and mixtures of homopolymers and copolymers), diene-based polymers (homopolymers, copolymers, and mixtures of homopolymers and copolymers, such as polybutadiene and polyisoprene), pitch (coal tar pitch, mesophase pitch, etc.), and phenol-based polymers (novolac-type phenolic polymers, lignin, etc.). Only one type of carbon material precursor polymer may be used, or two or more types may be used. Among these, the carbon material precursor polymer preferably contains an acrylamide-based polymer or an acrylonitrile-based polymer, and more preferably contains an acrylamide-based polymer. The polymer for the carbon material precursor may be crosslinked intramolecularly or intermolecularly.

[0039] The content of the acrylamide polymer in the polymer for carbon material precursor is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more. The upper limit of the acrylamide polymer content is not particularly limited, and may be 100% by mass.

[0040] The form of the polymer for a carbon material precursor of the present disclosure is not particularly limited, and may be, for example, a fiber, a plate, a film, a powder, or a particle.

[0041] The method for molding the polymer for a carbon material precursor of the present disclosure is not particularly limited, and may be, for example, a method in which the polymer is dissolved in a solvent and then formed into a fiber by a spinning method such as dry spinning, dry / wet spinning, wet spinning, melt spinning, or solution spinning; a method in which the polymer is dissolved in a solvent and then formed into a film, sheet, or the like using a mold or roller, and then dried; melt spinning, injection molding, extrusion molding, or the like.

[0042] -Acrylamide polymer- An acrylamide polymer is a polymer containing structural units derived from acrylamide monomers (hereinafter also referred to as "acrylamide monomer units").

[0043] The content of acrylamide-based monomer units in the acrylamide-based polymer is preferably 50 mol % or more, more preferably 55 mol % or more, and even more preferably 60 mol % or more.

[0044] When the content of the acrylamide-based monomer unit is 50 mol % or more, the solubility of the acrylamide-based polymer in water can be improved.

[0045] The upper limit of the content of the acrylamide-based monomer unit is not particularly limited, but from the viewpoint of the shape stability of the carbon material precursor, it is preferably 99.9 mol% or less, more preferably 99 mol% or less, even more preferably 95 mol% or less, particularly preferably 90 mol% or less, and most preferably 80 mol% or less. The content of the acrylamide-based monomer unit is preferably 50 mol% to 99.9 mol%.

[0046] Examples of acrylamide monomers include acrylamide, ethacrylamide, crotonamide, itaconic acid diamide, cinnamic acid amide, maleic acid diamide, N-alkylacrylamides such as N-methylacrylamide, N-ethylacrylamide, Nn-propylacrylamide, N-isopropylacrylamide, Nn-butylacrylamide, and N-tert-butylacrylamide, N-cycloalkylacrylamides such as N-cyclohexylacrylamide, dialkylacrylamides such as N,N'-dimethylacrylamide, dialkylaminoalkylacrylamides such as dimethylaminoethylacrylamide and dimethylaminopropylacrylamide, hydroxyalkylacrylamides such as N-(hydroxymethyl)acrylamide and N-(hydroxyethyl)acrylamide, N-arylacrylamides such as N-phenylacrylamide, diacetoneacrylamide, and N,N'-methylenebisacrylamide. dialkylaminoalkyl methacrylamides such as dimethylaminoethyl methacrylamide and dimethylaminopropyl methacrylamide; hydroxyalkyl methacrylamides such as N-(hydroxymethyl)methacrylamide and N-(hydroxyethyl)methacrylamide; N-aryl methacrylamides such as N-phenyl methacrylamide; diacetone methacrylamide; and N,N'-alkylene bismethacrylamides such as N,N'-methylene bismethacrylamide.

[0047] Furthermore, from the viewpoint of the solubility of the acrylamide-based polymer in water, among the above-mentioned acrylamide-based monomers, acrylamide, N-alkylacrylamide, dialkylacrylamide, methacrylamide, N-alkylmethacrylamide, or dialkylmethacrylamide is preferred, and acrylamide is more preferred.

[0048] The acrylamide-based polymer may contain only one type of acrylamide-based monomer unit, or two or more types.

[0049] The acrylamide polymer may be composed of only acrylamide monomer units, but preferably contains structural units derived from other polymerizable monomers in addition to the acrylamide monomer units.

[0050] From the viewpoint of suppressing fusion, etc., the content of other polymerizable monomer units is preferably 0.1 mol % or more, more preferably 1 mol % or more, even more preferably 5 mol % or more, particularly preferably 10 mol % or more, and most preferably 20 mol % or more, relative to the total amount of constituent units of the acrylamide-based polymer. From the viewpoint of improving the solubility of the acrylamide polymer in aqueous solvents or aqueous mixed solvents, the content of other polymerizable monomer units is preferably 50 mol % or less, more preferably 45 mol % or less, and even more preferably 40 mol % or less, relative to the total amount of constituent units of the acrylamide polymer. The content of the other polymerizable monomer units is preferably 0.1 mol % to 50 mol %.

[0051] Examples of other polymerizable monomers include vinyl cyanide monomers, unsaturated carboxylic acids and their salts, unsaturated carboxylic anhydrides, unsaturated carboxylic acid esters, sulfonic acid vinyl monomers and their salts, phosphoric acid vinyl monomers and their salts, nitric acid vinyl monomers and their salts, phenolic vinyl monomers and their salts, vinyl monomers, and olefinic monomers.

[0052] Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, 2-hydroxyethyl acrylonitrile, chloroacrylonitrile, chloromethyl acrylonitrile, ethoxyacrylonitrile, and vinylidene cyanide.

[0053] Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, crotonic acid, and isocrotonic acid. Examples of the salts of unsaturated carboxylic acids include metal salts (for example, sodium salts, potassium salts, etc.), ammonium salts, and amine salts of unsaturated carboxylic acids.

[0054] Examples of the unsaturated carboxylic acid anhydride include maleic anhydride and itaconic anhydride.

[0055] Examples of unsaturated carboxylic acid esters include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, lauryl acrylate, lauryl methacrylate, dodecyl acrylate, dodecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, stearyl acrylate, stearyl methacrylate, octadecyl acrylate, octadecyl methacrylate, phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzyl methacrylate, allyl acrylate, methacrylate, Examples of the acrylate include allyl acrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, chloromethyl acrylate, chloromethyl methacrylate, 2-chloroethyl acrylate, 2-chloroethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2,3,4,5,6-pentahydroxyhexyl acrylate, 2,3,4,5,6-pentahydroxyhexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 2,3,4,5-tetrahydroxypentyl acrylate, 2,3,4,5-tetrahydroxypentyl methacrylate, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, and cyclohexylaminoethyl methacrylate.

[0056] Examples of vinyl monomers include aromatic vinyl monomers such as styrene and α-methylstyrene; vinyl carboxylates such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl pivalate; vinyl chloride; and vinyl alcohol.

[0057] Examples of the olefin monomer include ethylene, propylene, isopropylene, and butadiene.

[0058] Among these, from the viewpoint of the spinnability and fusion suppression of the acrylamide polymer, the other polymerizable monomer is preferably a vinyl cyanide monomer, and more preferably acrylonitrile. Furthermore, from the viewpoint of the fusion suppression property, the promotion of flame retardation, the solubility, etc. of the acrylamide-based polymer, the other polymerizable monomer is preferably an unsaturated carboxylic acid or a salt thereof, or an unsaturated carboxylic acid anhydride, more preferably acrylic acid, maleic acid, fumaric acid, itaconic acid, or maleic acid anhydride, and even more preferably acrylic acid.

[0059] The acrylamide polymer may contain only one type of structural unit derived from other polymerizable monomers, or may contain two or more types.

[0060] From the viewpoints of solubility in water, spinnability, fusion suppression, flame retardancy promotion, carbonization yield, and shape stability, the acrylamide-based polymer is particularly preferably a copolymer of an acrylamide-based monomer, a vinyl cyanide-based monomer, and an unsaturated carboxylic acid, and most preferably a copolymer of acrylamide, acrylonitrile, and acrylic acid.

[0061] The content of vinyl cyanide monomer units in the acrylamide polymer may be 0 mol %, but is preferably 0.1 mol % to 50 mol %, more preferably 5 mol % to 45 mol %, and even more preferably 10 mol % to 40 mol %.

[0062] The content of unsaturated carboxylic acid units in the acrylamide polymer may be 0 mol%, but is preferably 0.1 mol% to 30 mol%, more preferably 1 mol% to 20 mol%, even more preferably 2 mol% to 15 mol%, and particularly preferably 3 mol% to 10 mol%.

[0063] The weight average molecular weight of the acrylamide polymer is not particularly limited and is usually 5 million or less. From the viewpoint of the molding processability of the carbon fiber precursor, however, it is preferably 2 million or less, more preferably 1 million or less, even more preferably 500,000 or less, particularly preferably 200,000 or less, even more particularly preferably 130,000 or less, and most preferably 100,000 or less.

[0064] The lower limit of the weight-average molecular weight of the acrylamide polymer is not particularly limited, but is usually 10,000 or more. From the viewpoint of the strength of the carbon fiber precursor and the carbon fiber, the lower limit is preferably 20,000 or more, more preferably 30,000 or more, and particularly preferably 40,000 or more.

[0065] The acrylamide polymer may be a homopolymer of an acrylamide monomer, a copolymer of an acrylamide monomer and another polymerizable monomer, or a mixture of a homopolymer and a copolymer. From the viewpoints of solubility in water, spinnability, suppression of fusion, promotion of flame retardancy, carbonization yield, and shape stability, the acrylamide polymer is preferably a copolymer or a mixture of a homopolymer and a copolymer, and more preferably a copolymer.

[0066] In the present disclosure, the weight average molecular weight is measured by gel permeation chromatography under the following conditions. The measuring device may be an HLC-8220GPC manufactured by Tosoh Corporation or a device equivalent thereto. -Measurement conditions- Column: TSKgel GMPWXL x 2 + TSKgel G2500PWXL x 1 Eluent: 100 mM sodium nitrate aqueous solution / acetonitrile (= 80 / 20 (volume ratio)) ·Eluent flow rate: 1.0ml / min Column temperature: 40℃ Molecular weight standards: Standard polyethylene oxide / standard polyethylene glycol Detector: Differential refractive index detector

[0067] The carbon material precursor polymer may contain a flame retardant accelerator from the viewpoint of promoting flame retardant and suppressing fusion.

[0068] Examples of the flame retardant accelerator include inorganic acids such as phosphoric acid, polyphosphoric acid, boric acid, sulfuric acid, nitric acid, and carbonic acid, organic acids such as oxalic acid, citric acid, and sulfonic acid, and salts of these acids. Examples of the salts of the above acids include metal salts (sodium salts, potassium salts, etc.), ammonium salts, amine salts, guanidine salts, urea salts, melamine salts, and imidazole salts, with ammonium salts and amine salts being preferred, and ammonium salts being more preferred. Among these, from the viewpoints of promoting flame retardancy, suppressing fusion, carbonization yield, and shape stability, the other component is preferably phosphoric acid, polyphosphoric acid, boric acid, sulfuric acid, or an ammonium salt thereof, more preferably phosphoric acid, polyphosphoric acid, boric acid, or an ammonium salt thereof, still more preferably phosphoric acid, polyphosphoric acid, an ammonium salt of phosphoric acid, or an ammonium salt of polyphosphoric acid, and particularly preferably phosphoric acid or an ammonium salt of phosphoric acid.

[0069] From the viewpoint of suppressing fusion, the content of the flame retardant accelerator in the polymer for carbon material precursor is preferably 0.1% by mass to 100% by mass, more preferably 0.2% by mass to 50% by mass, even more preferably 0.5% by mass to 30% by mass, and particularly preferably 1% by mass to 20% by mass.

[0070] The polymer for carbon material precursor of the present disclosure may contain other additives as needed, such as organic solvents, surfactants, thermal crosslinking agents, ultraviolet crosslinking agents, cationic metals, various fillers such as biomass fibers (cellulose nanofibers, cellulose microfibers, etc.), glass fibers, carbon black, carbon nanotubes, and graphene, dispersants, smoothing agents, moisture absorbents, viscosity modifiers, plasticizers, release agents, spreading agents, antioxidants, antibacterial agents, preservatives, rust inhibitors, and pH adjusters.

[0071] <Carbon material precursor> The carbon material precursor of the present disclosure comprises a polymer for carbon material precursors and the oil agent of the present disclosure, and is characterized in that the oil agent is present on the surface of the polymer for carbon material precursors. In addition, the oil agent preferably has a crosslinked structure.

[0072] The form of the carbon material precursor of the present disclosure is not particularly limited, and may be, for example, fiber, plate, film, powder, granule, or the like.

[0073] Details of the oil agent and the carbon material precursor are as described above. A polymer for a carbon material precursor having the oil agent of the present disclosure on its surface can be obtained by a method such as surface-treating a carbon material precursor with an oil agent. Examples of the surface treatment method include a method of immersing a polymer for a carbon material precursor in an oil agent, a method of spraying an oil agent onto a polymer for a carbon material precursor, and a method of applying an oil agent using a touch roller, a guide oiling device, or the like. After the polymer for a carbon material precursor is surface-treated with the oil agent, it may be dried.

[0074] The amount of oil applied to the carbon material precursor is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, even more preferably 1 to 10 parts by mass, and particularly preferably 2 to 8 parts by mass, relative to 100 parts by mass of the polymer for the carbon material precursor.

[0075] Furthermore, a carbon material precursor having a crosslinked product of the oil agent of the present disclosure on its surface can be obtained by surface-treating a polymer for a carbon material precursor with an oil agent and then performing a crosslinking treatment. Examples of crosslinking methods include heating and irradiating with ultraviolet rays, X-rays, gamma rays, alpha rays, beta rays, electron beams, neutron beams, proton beams, and heavy particle beams. Among these, heating, ultraviolet irradiation, and electron beam irradiation are preferred, with electron beam irradiation being more preferred. The crosslinking treatment may be performed on both the oil agent and the carbon material precursor.

[0076] From the viewpoint of suppressing fusion, etc., the dose of the electron beam is preferably 10 kGy or more, more preferably 30 kGy or more, even more preferably 50 kGy or more, particularly preferably 100 kGy or more, most preferably 200 kGy or more, and extremely preferably 500 kGy or more. From the viewpoint of the stretchability of the carbon material precursor polymer, production costs, etc., the dose of the electron beam is preferably 10,000 kGy or less, more preferably 5,000 kGy or less, and even more preferably 1,000 kGy or less. From the viewpoint of suppressing fusion, production costs, etc., the dose of the electron beam is preferably 10 kGy to 10,000 kGy.

[0077] When electron beams are used, the dose is measured using a film dosimeter, etc. As a film dosimeter, the FTR-125 manufactured by Fujifilm, the FWT-60 manufactured by Toyo Medic, or a device of similar quality can be used.

[0078] From the viewpoints of suppressing fusion, production costs, etc., the acceleration voltage of the electron beam is preferably 10 MV or less, more preferably 3 MV or less, and even more preferably 1 MV or less. The acceleration voltage of the electron beam is preferably 50 kV or more, more preferably 100 kV or more, and even more preferably 200 kV or more.

[0079] The atmospheric gas used for electron beam irradiation is not particularly limited, and may be an inert gas such as nitrogen, argon, or helium, or may be the air. From the viewpoint of improving crosslinking efficiency, the atmospheric gas used for electron beam irradiation is preferably an inert gas such as nitrogen, argon, or helium. From the viewpoint of reducing production costs, the atmospheric gas used for electron beam irradiation is preferably the air.

[0080] A carbon material precursor having a cross-linked product of the oil agent of the present disclosure on its surface can be subjected to a heat treatment in an oxidizing atmosphere to obtain a flame-resistant material. Hereinafter, the heat treatment in an oxidizing atmosphere is also referred to as "flameproofing treatment."

[0081] By carrying out the flame retardant treatment, a heat-resistant cyclic structure is formed in the carbon material precursor polymer, and thermal decomposition during the carbonization treatment can be suppressed.

[0082] The temperature for the flame retardant treatment is not particularly limited, but is preferably in the range of 120°C to 500°C, more preferably in the range of 130°C to 490°C, even more preferably in the range of 140°C to 480°C, even more preferably in the range of 150°C to 470°C, particularly preferably in the range of 160°C to 460°C, and most preferably in the range of 170°C to 450°C. The above temperature includes not only the maximum temperature in the flame-proofing treatment described below, but also the temperature during the temperature rise process up to the flame-proofing treatment temperature.

[0083] From the viewpoints of improving carbonization resistance and reducing production costs by shortening the processing time, the maximum temperature in the flame-resistant treatment is preferably 290°C or higher, more preferably 300°C or higher, even more preferably 310°C or higher, even more preferably 320°C or higher, particularly preferably 330°C or higher, and most preferably 340°C or higher. The upper limit of the flame-resistant treatment temperature is not particularly limited, and the flame-resistant treatment temperature is, for example, preferably 500°C or lower, more preferably 450°C or lower, and even more preferably 400°C or lower.

[0084] The heating time at the flame-resistant treatment temperature is not particularly limited and may be 4 hours or more, but is preferably 1 minute to 4 hours, more preferably 2 minutes to 2 hours, even more preferably 3 minutes to 90 minutes, particularly preferably 4 minutes to 75 minutes, and most preferably 5 minutes to 60 minutes. By setting the heating time at the flame-resistant treatment temperature to 1 minute or more, the carbonization yield can be improved. By setting the heating time at the flame-resistant treatment temperature to 4 hours or less, the production cost can be reduced.

[0085] Examples of the oxidizing atmosphere include oxygen, ozone, air, nitrogen oxides, halogens, sulfur dioxide gas, mixed gases thereof, and mixed gases of oxygen, ozone, air, nitrogen oxides, halogens, or sulfur dioxide gas with an inert gas. Among these, the oxidizing atmosphere is preferably air, a mixed gas of oxygen and air, a mixed gas of oxygen and an inert gas, or a mixed gas of air and an inert gas, and particularly preferably air from the viewpoint of reducing production costs.

[0086] The flame-resistant material can be further subjected to a carbonization treatment to obtain a carbon material.

[0087] The carbonization treatment may be carried out, for example, by heat treatment at a temperature equal to or higher than that used in the flame-proofing treatment in an inert gas atmosphere, such as nitrogen, argon, or helium.

[0088] By subjecting the flame-resistant material to carbonization treatment, the flame-resistant material is carbonized to obtain a carbon material.

[0089] The carbonization temperature 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. There are no particular limitations on the upper limit of the carbonization temperature. From the viewpoint of reducing production costs by reducing the energy required for production, the carbonization temperature is preferably 3000°C or lower, more preferably 2500°C or lower.

[0090] In the present disclosure, "carbonization" may also include "graphitization," which is generally carried out by heating at a temperature of 2000°C to 3000°C in an inert gas atmosphere.

[0091] The carbonization treatment may include multiple heat treatments. For example, a heat treatment can be first performed at a temperature below 1000°C (hereinafter also referred to as "pre-carbonization treatment"), followed by a heat treatment (carbonization treatment) at a temperature of 1000°C or higher, and then a heat treatment (graphitization treatment) at a temperature of 2000°C or higher.

[0092] The carbonization time is not particularly limited, but is preferably 30 seconds to 120 minutes, more preferably 30 seconds to 60 minutes, and even more preferably 1 minute to 30 minutes. From the viewpoint of reducing production costs, the carbonization time is particularly preferably 20 minutes or less, and most preferably 10 minutes or less. [Example]

[0093] The above embodiment will be specifically described below using examples, but the above embodiment is not limited to these examples.

[0094] <Preparation of acrylamide polymer> An acrylamide-based polymer, acrylamide (AM) / acrylonitrile (AN) / acrylic acid (AA) terpolymer (AM / AN / AA = 60 mol% / 35 mol% / 5 mol%), was prepared according to the following procedure. 100 parts by weight of a monomer consisting of 60 mol% AM, 35 mol% AN, and 5 mol% AA, and 5 parts by weight of tetramethylethylenediamine were dissolved in 400 parts by weight of ion-exchanged water. Ammonium persulfate was added to the resulting aqueous solution while stirring under a nitrogen atmosphere, and the mixture was then heated at 80°C for 150 minutes to polymerize. The resulting aqueous solution was added dropwise to methanol to precipitate the copolymer, which was then recovered and vacuum-dried at 80°C for 12 hours to obtain a water-soluble AM / AN / AA (60 mol% / 35 mol% / 5 mol%) copolymer. 100 parts by mass of the obtained acrylamide polymer and 3 parts by mass of phosphoric acid were dissolved in ion-exchanged water to obtain an aqueous solution of the acrylamide polymer, which was then dried to prepare an acrylamide polymer film having a thickness of approximately 0.1 mm.

[0095] Example 1 The following ingredients were mixed to prepare oil solution 1. - Polyfunctional (meth)acrylate containing no siloxane structure - Polybutadiene (meth)acrylate (product name "BAC-45", number of functional groups: 2, manufactured by Osaka Organic Chemical Industry Co., Ltd.) ... 69 parts by mass 1,9-nonanediol diacrylate (polyfunctional (meth)acrylate with saturated hydrocarbon main chain, number of functional groups: 2) ... 31 parts by mass -Monofunctional (meth)acrylate containing no siloxane structure- Lauryl acrylate...38 parts by mass

[0096] <Example 2> The following ingredients were mixed to prepare oil solution 2. - Polyfunctional (meth)acrylate containing no siloxane structure - Polyester (meth)acrylate (product name "M-6500", functional group number: 2, manufactured by Toagosei Co., Ltd.) ... 100 parts by mass -Monofunctional (meth)acrylate containing no siloxane structure- Lauryl acrylate...400 parts by mass

[0097] Example 3 The following ingredients were mixed to prepare oil solution 3. - Polyfunctional (meth)acrylate containing no siloxane structure - 1,9-nonanediol diacrylate (polyfunctional (meth)acrylate with saturated hydrocarbon main chain, number of functional groups: 2) ... 100 parts by mass -Monofunctional (meth)acrylate containing no siloxane structure- Lauryl acrylate...1000 parts by mass

[0098] Example 4 The following ingredients were mixed to prepare oil solution 4. - Polyfunctional (meth)acrylate containing no siloxane structure - Poly(meth)acrylic(meth)acrylate (40% by mass of product name "MAP-2801", functional group number: approximately 6.7, manufactured by Negami Chemical Industrial Co., Ltd.) ... 100 parts by mass -Monofunctional (meth)acrylate containing no siloxane structure- Mixture of 4-hydroxybutyl acrylate and cyclic trimethylolpropane formal acrylate (60% by mass of product name "MAP-2801", manufactured by Negami Chemical Industrial Co., Ltd.) ... 150 parts by mass Cyclic trimethylolpropane formal acrylate...125 parts by mass

[0099] <Example 5> The following ingredients were mixed to prepare oil solution 5. - Polyfunctional (meth)acrylate containing no siloxane structure - Poly(meth)acrylic(meth)acrylate (40% by mass of product name "MAP-2801", functional group number: approximately 6.7, manufactured by Negami Chemical Industrial Co., Ltd.) ... 100 parts by mass -Monofunctional (meth)acrylate containing no siloxane structure- Mixture of 4-hydroxybutyl acrylate and cyclic trimethylolpropane formal acrylate (60% by mass of product name "MAP-2801", manufactured by Negami Chemical Industrial Co., Ltd.) ... 150 parts by mass 4-Hydroxybutyl acrylate...750 parts by mass

[0100] <Comparative Example 1> As the oil agent 1A, a methacryloyl group-modified silicone (product name "X-22-164A", manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

[0101] <Comparative Example 2> As the oil agent 2A, an acryloyl group-modified silicone (product name "KP-420", manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

[0102] <Comparative Example 3> As the oil agent 3A, unmodified silicone (product name "KF-96-100cs", manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

[0103] <Comparative Example 4> Lauryl acrylate was used as oil 4A.

[0104] Oil solutions 1 to 5 and 1A to 4A were irradiated with electron beams using an electron beam irradiation device (product name "EPS-750kV machine", manufactured by NHV Corporation) under nitrogen atmosphere at an acceleration voltage of 750kV and a dose of 100kGy to obtain crosslinked oil solutions (oil solutions with a crosslinked structure).

[0105] Using the crosslinked product of the above oil agent, the gel fraction, the weight residual ratio when the temperature reached 300°C, the weight residual ratio after flame retardation treatment, and the weight residual ratio after carbonization treatment were measured, and the final weight residual ratio was calculated.

[0106] Oil solutions 1 to 5 and 1A to 4A were each applied to the surface of an acrylamide-based polymer film in an amount of 5 parts by mass per 100 parts by mass of the acrylamide-based polymer, and then the film was irradiated with electron beams in the atmosphere using an electron beam irradiation device (product name "EPS-750kV machine", manufactured by NHV Corporation) at an acceleration voltage of 750kV and a dose of 600kGy, thereby obtaining a carbon material precursor film having a crosslinked body of the oil solution (oil solution containing a crosslinked structure) on the surface. Here, the dose used to obtain the carbon material precursor film was set higher than that used in a nitrogen atmosphere because the electron beam irradiation was performed in the atmosphere, and the crosslinking efficiency tends to be lower than that used in a nitrogen atmosphere due to the influence of oxygen inhibition.

[0107] The carbon material precursor film was used to evaluate fusion bonding.

[0108] (gel fraction) Approximately 0.1 g of the crosslinked oil agent was collected and used as a sample. The sample was immersed in the solvent at room temperature (25°C) for 24 hours. In order to dissolve the uncrosslinked components in the crosslinked oil agent, hexane was used as the solvent in Comparative Examples 1 to 4, and acetone was used as the solvent in Examples 1 to 5. After 24 hours, the samples were removed from the solvent and allowed to dry at room temperature (25°C) for 24 hours. The mass of the sample before immersion in the solvent (mass before test) and the mass after immersion in the solvent and drying (mass after test) were measured. The gel fraction was calculated using the following formula: Gel fraction (%) = (mass after test / mass before test) x 100

[0109] (Weight retention rate when reaching 300℃) Approximately 1-2 mg of the crosslinked oil was sampled, placed on a platinum pan, and set in a thermal analyzer (product name "ThermoPlusEV02", manufactured by Rigaku Corporation). The temperature was raised to 350°C at a rate of 10°C / min in air, and flame-resistant treatment was carried out at 350°C for 10 minutes. The weight remaining ratio when the temperature reached 300°C was measured. At this time, the weight remaining rate after the flameproofing treatment (that is, the weight remaining rate after 10 minutes at 350° C.) was also measured.

[0110] (weight remaining rate after carbonization) The sample after the flame retardant treatment was placed in a Pt pan and heated to 1200°C at a heating rate of 20°C / min in a nitrogen atmosphere, where it was carbonized. The weight remaining rate after carbonization was measured.

[0111] (Final weight remaining rate) The final weight residual rate was calculated using the following formula. Final weight residual rate (%) = {(weight residual rate after flame retardant treatment) × (weight residual rate after carbonization treatment)} / 100

[0112] (Evaluation of fusion) Two carbon material precursor films each having a crosslinked oil on their surface were prepared, and placed on a hot plate with the surfaces with the crosslinked oil facing each other. The film was heated from room temperature (25°C) to 300°C, and at 300°C, it was checked with tweezers whether the films peeled off from each other on the hot plate. If the films peeled off, the film was evaluated as A, and if the films could no longer be peeled off, the film was evaluated as B.

[0113] [Table 1]

[0114] In Examples 1 to 5, the oil agent contained a polyfunctional (meth)acrylate that did not contain a siloxane structure, and it was found that this could suppress fusion between carbon material precursors during the flame-resistant treatment and reduce residues after the carbonization treatment.

[0115] On the other hand, in Comparative Examples 1 and 2, fusion between the carbon material precursors during the flame-resistant treatment was suppressed, but much residue remained after the carbonization treatment. In Comparative Example 3, the oil agent did not crosslink, and fusion between the carbon material precursors during the flame-resistant treatment could not be suppressed. In Comparative Example 4, although crosslinking of the oil agent progressed, the crosslink density was low and the product was in a semi-solid state. Therefore, it was difficult to measure the gel fraction, the weight residual ratio at 300°C, the weight residual ratio after the flame-resistant treatment, and the weight residual ratio after the carbonization treatment. In addition, fusion between the carbon material precursors during the flame-resistant treatment could not be suppressed.

[0116] Next, the carbon material precursor film was used to evaluate the flame retardant yield and the carbonization yield.

[0117] <Example 102> A carbon material precursor film having a crosslinked body of oil agent 2 on the surface was used. <Example 105> A carbon material precursor film having a crosslinked body of oil agent 5 on the surface was used.

[0118] <Comparative Example 101> An acrylamide polymer film with no oil coating was used. <Comparative Example 102> An acrylamide-based polymer that had not been coated with oil was irradiated with electron beams in the atmosphere using an electron beam irradiation device (product name "EPS-750kV" manufactured by NHV Corporation) at an acceleration voltage of 750kV and a dose of 600kGy to produce a carbon material precursor film.

[0119] (Evaluation of flame retardation yield and carbonization yield) Approximately 1 to 2 mg of the carbon material precursor film was sampled, placed on a platinum pan, and set in a thermal analyzer (product name "ThermoPlusEV02", manufactured by Rigaku Corporation). The temperature was raised to 350°C at a rate of 10°C / min in air, and a flame-resistant treatment was performed at 350°C for 10 minutes. The film after the flame retardant treatment was placed in a Pt pan and heated to 1200°C at a heating rate of 20°C / min in a nitrogen atmosphere, where it was carbonized. The flame retardation yield and carbonization yield were calculated using the following formulas. Flame retardant yield (%) = (mass after flame retardant treatment / mass at 150°C during temperature rise during flame retardant treatment) × 100 Carbonization yield (%) = (mass after carbonization treatment / mass after flame retardant treatment) × 100 Since acrylamide polymers easily absorb water, the flame retardant yield was calculated based on the mass at 150°C, at which point it is assumed that all the water contained in the acrylamide polymer has evaporated. Since the acrylamide polymer after the flame-resistant treatment becomes less likely to absorb water, the carbonization yield was calculated based on the mass after the flame-resistant treatment.

[0120] [Table 2]

[0121] In Examples 102 and 105, carbon materials could be obtained by using the carbon material precursor of the present disclosure. Furthermore, in Examples 102 and 105, the carbonization yield tended to be higher than in Comparative Examples 101 and 102. It is believed that the use of the oil agent of the present disclosure can increase the carbonization yield of the carbon material precursor.

[0122] The reason for the increased carbonization yield is unclear, but is presumed to be as follows. During flame retardation treatment, thermal and oxidative degradation usually occurs in parallel with the formation of a heat-resistant cyclic structure, and part of the cyclic structure may be cleaved. It is believed that cleavage of part of the cyclic structure makes thermal decomposition more likely to occur during carbonization. On the other hand, when a crosslinked oil agent is present on the surface of an acrylamide-based polymer, the oil agent functions as a protective layer, suppressing thermal and oxidative degradation during flame retardation treatment. As a result, it is believed that thermal decomposition that occurs during carbonization treatment is suppressed, resulting in a higher carbonization yield.

Claims

1. An oil agent containing a polyfunctional (meth)acrylate that does not contain a siloxane structure and is used for surface treatment of polymers for carbon material precursors.

2. The oil according to claim 1 , further comprising a monofunctional (meth)acrylate that does not contain a siloxane structure.

3. 3. The oil agent according to claim 2, wherein the content of the monofunctional (meth)acrylate not containing a siloxane structure is 10 parts by mass to 2000 parts by mass per 100 parts by mass of the polyfunctional (meth)acrylate not containing a siloxane structure.

4. 4. The oil according to claim 3, wherein the polyfunctional (meth)acrylate not containing a siloxane structure comprises at least one selected from the group consisting of polybutadiene (meth)acrylate, polyester (meth)acrylate, polyfunctional (meth)acrylate having a saturated hydrocarbon group as a main chain, and poly(meth)acrylic (meth)acrylate.

5. The oil agent according to claim 4 , wherein the polymer for a carbon material precursor includes an acrylamide-based polymer.

6. 2. The oil agent according to claim 1, wherein when the oil agent is crosslinked, the gel fraction is 50% or more and the weight residual ratio at 300°C is 50% or more.

7. A carbon material precursor comprising a polymer for a carbon material precursor, the polymer having the oil agent according to any one of claims 1 to 6 on the surface thereof.

8. The carbon material precursor according to claim 7 , wherein the oil agent is a crosslinked material.

9. The carbon material precursor according to claim 8 , wherein the polymer for the carbon material precursor includes an acrylamide-based polymer.

10. A method for producing a carbon material, comprising the steps of subjecting a polymer for use as a precursor of a carbon material, which has been surface-treated with an oil containing a polyfunctional (meth)acrylate that does not contain a siloxane structure, to a flame-retardant treatment and a carbonization treatment.

11. The method for producing a carbon material according to claim 10 , wherein the oil agent further contains a monofunctional (meth)acrylate that does not contain a siloxane structure.

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