JP7168909B2 - Precursor material for producing carbon material and method for producing carbon material using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a precursor material for producing a carbon material and a method for producing a carbon material using the same, and more particularly, a precursor material for producing a carbon material comprising an acrylamide-based copolymer and producing a carbon material using the precursor material. Regarding the method.

As a method for producing carbon fiber, which is one type of carbon material, a method of applying a flameproofing treatment to a carbon fiber precursor obtained by spinning polyacrylonitrile and then carbonizing the precursor has been mainly adopted. (For example, JP-B-37-4405 (Patent Document 1), JP-A-2015-74844 (Patent Document 2), JP-A-2016-40419 (Patent Document 3), JP-A-2016-113726 ( Patent document 4)). Since the polyacrylonitrile used in this method is difficult to dissolve in inexpensive general-purpose solvents, it is necessary to use expensive solvents such as dimethylsulfoxide and N,N-dimethylacetamide during polymerization and spinning. There was a problem of high cost.

Further, Japanese Patent Application Laid-Open No. 2013-103992 (Patent Document 5) describes 96 to 97.5 parts by mass of acrylonitrile units, 2.5 to 4 parts by mass of acrylamide units, and 0.01 to 0.01 parts by mass of a carboxylic acid-containing vinyl monomer. A carbon material precursor fiber made of a polyacrylonitrile-based copolymer of 5 parts by mass is described. Although this polyacrylonitrile-based copolymer contains acrylamide units and carboxylic acid-containing vinyl monomer units that contribute to the water solubility of the polymer, since these contents are small, it is insoluble in water. In some cases, it is necessary to use an expensive solvent such as N,N-dimethylacetamide, which raises the problem of high production costs for carbon fibers.

Furthermore, when polyacrylonitrile and its copolymer are subjected to heat treatment, rapid heat generation occurs, accelerating the thermal decomposition of polyacrylonitrile and its copolymer, which reduces the yield of carbon materials (carbon fibers). There was a problem. For this reason, when producing a carbon material (carbon fiber) using polyacrylonitrile or its copolymer, a long period of time must be taken during the temperature rising process of the flameproofing treatment or carbonization treatment so as not to generate sudden heat generation. It was necessary to gradually raise the temperature over time.

On the other hand, acrylamide-based polymers containing a large amount of acrylamide units are water-soluble polymers, and water, which is inexpensive and has a low environmental impact, can be used as a solvent during polymerization and molding processes (filming, sheeting, spinning, etc.). Therefore, it is expected that the manufacturing cost of carbon materials will be reduced. Japanese Patent Application Laid-Open No. 2018-90791 (Patent Document 6) describes a carbon material precursor containing an acrylamide-based polymer and at least one additive component selected from the group consisting of acids and salts thereof. . This carbon material precursor contains at least one additive component selected from the group consisting of acids and salts thereof in order to improve the carbonization yield. When a carbon material precursor containing such an additive component such as an acid is subjected to a flameproofing treatment and a carbonization treatment, a trace amount of the additive component may remain in the resulting carbon material. Therefore, development of a method for efficiently obtaining a carbon material that does not contain additive components such as acid is expected.

Japanese Patent Publication No. 37-4405 JP 2015-74844 A JP 2016-40419 A JP 2016-113726 A JP 2013-103992 A JP 2018-90791 A

The present invention has been made in view of the above-mentioned problems of the prior art. It is an object of the present invention to provide a precursor material for producing a carbon material comprising an acrylamide-based copolymer and a method for producing a carbon material using the same.

The present inventors have made intensive studies to achieve the above object, and found that acrylamide/cyanide containing acrylamide-based monomer units, vinyl cyanide-based monomer units, and unsaturated carboxylic acid-based monomer units in a specific ratio. By using a vinyl/unsaturated carboxylic acid-based copolymer, a carbon having a high flame resistance yield, a high carbonization yield, and a high flame resistance and carbonization total yield without blending an additive component such as an acid. The inventors have found that a material precursor can be obtained, and have completed the present invention.

That is, the precursor material for carbon material production of the present invention (hereinafter also referred to as "carbon material precursor") contains 40 to 99.8 mol % of acrylamide-based monomer units and 0.1 to 35 mol of vinyl cyanide-based monomer units. % and 0.1 to 25 mol % of unsaturated carboxylic acid monomer units.

In such a precursor material for carbon material production, the molar ratio of the unsaturated carboxylic acid-based monomer unit to the vinyl cyanide-based monomer unit (unsaturated carboxylic acid-based monomer unit/vinyl cyanide-based monomer unit) is 0. It is preferably between 0.01/1 and 1/1.

Further, the method for producing a carbon material of the present invention is a method characterized by subjecting the precursor material for producing a carbon material of the present invention to a flameproofing treatment and then to a carbonizing treatment.

The reason why the carbon material precursor of the present invention exhibits a high flameproofing yield, a high carbonization yield, and a high flameproofing/carbonization total yield is not necessarily clear even without adding an additive component such as an acid. However, the present inventors conjecture as follows. That is, in the carbon material precursor of the present invention, due to the presence of unsaturated carboxylic acid-based monomer units, during the flameproofing treatment, An intramolecular cyclization reaction occurs between unsaturated carboxylic acid-based monomer units, introducing a cyclic structure into the polymer chain to improve heat resistance. In addition, the intermolecular cross-linking reaction proceeds during the flameproofing treatment and carbonization treatment, which facilitates the formation of a carbon material. It is presumed that the yield and the total yield of flameproofing and carbonization are improved. In addition, since the unsaturated carboxylic acid-based monomer unit acts as a catalyst for the cyclization reaction, the flameproofing yield, the carbonization yield, and the total yield of flameproofing and carbonization can be improved without adding an additive component such as an acid. expected to improve.

According to the present invention, a carbon material comprising an acrylamide-based copolymer that exhibits a high flameproofing yield, a high carbonization yield, and a high flameproofing/carbonization total yield without blending an additive component such as an acid. It becomes possible to obtain a precursor. Moreover, by using such a carbon material precursor of the present invention, it is possible to efficiently produce a carbon material.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to its preferred embodiments.

[Carbon material precursor]
First, the carbon material precursor of the present invention will be described. The carbon material precursor of the present invention contains 40 to 99.8 mol % of acrylamide-based monomer units, 0.1 to 35 mol % of vinyl cyanide-based monomer units, and 0.1 to 25 mol % of unsaturated carboxylic acid-based monomer units. It consists of an acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer containing and is a precursor material used in the production of carbon materials.

(acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer)
The acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer used in the present invention contains 40 to 99.8 mol % of acrylamide monomer units with respect to 100 mol % of all monomer units. be. When the content of the acrylamide-based monomer units is less than the above lower limit, the acrylamide/vinyl cyanide/unsaturated carboxylic acid-based copolymer becomes difficult to dissolve in the aqueous solvent or aqueous mixed solvent described below. On the other hand, if the acrylamide-based monomer unit content exceeds the above upper limit, a carbon material precursor having a high flameproofing yield, a high carbonization yield, and a high flameproofing/carbonization total yield cannot be obtained. From the viewpoint of solubility of the copolymer in an aqueous solvent or an aqueous mixed solvent, the lower limit of the content of acrylamide-based monomer units is preferably 50 mol% or more, more preferably 60 mol% or more, and 70 mol% or more. is particularly preferred. Furthermore, from the viewpoint of improving the flameproofing yield, the carbonization yield, and the total flameproofing/carbonization yield of the carbon material precursor, the upper limit of the content of acrylamide-based monomer units is preferably 99 mol% or less. 97 mol % or less is more preferable, 95 mol % or less is still more preferable, and 90 mol % or less is particularly preferable.

The acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer contains vinyl cyanide monomer units at a ratio of 0.1 to 35 mol% with respect to 100 mol% of all monomer units. be. If the content of the vinyl cyanide-based monomer unit is less than the above lower limit, the moldability of the carbon material precursor deteriorates. On the other hand, if the vinyl cyanide monomer unit content exceeds the above upper limit, the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer becomes difficult to dissolve in the aqueous solvent or aqueous mixed solvent described below. In addition, from the viewpoint of improving the moldability of the carbon material precursor, the lower limit of the content of the vinyl cyanide-based monomer unit is preferably 1 mol% or more, more preferably 5 mol% or more, and 10 mol% or more. is more preferred, and 15 mol % or more is particularly preferred. Furthermore, from the viewpoint of the solubility of the copolymer in an aqueous solvent or an aqueous mixed solvent, the upper limit of the vinyl cyanide-based monomer unit content is preferably 30 mol % or less, more preferably 25 mol % or less.

Further, the acrylamide/vinyl cyanide/unsaturated carboxylic acid-based copolymer contains unsaturated carboxylic acid-based monomer units at a ratio of 0.1 to 25 mol% with respect to 100 mol% of all monomer units. is. If the content of unsaturated carboxylic acid-based monomer units is less than the above lower limit, a carbon material precursor having a high flameproofing yield, a high carbonization yield, and a high flameproofing/carbonization total yield cannot be obtained. On the other hand, if the content of the unsaturated carboxylic acid-based monomer unit exceeds the above upper limit, the moldability of the carbon material precursor is lowered. In addition, from the viewpoint of improving the flameproofing yield, the carbonization yield, and the total yield of flameproofing and carbonization of the carbon material precursor, the lower limit of the content of the unsaturated carboxylic acid-based monomer unit is 0.2 mol. % or more is preferable, 1 mol % or more is more preferable, and 2 mol % or more is particularly preferable. Furthermore, from the viewpoint of excellent moldability of the carbon material precursor, the upper limit of the content of the unsaturated carboxylic acid-based monomer unit is preferably 20 mol% or less, more preferably 10 mol% or less, and 5 mol% or less. is particularly preferred.

In the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer, the molar ratio of unsaturated carboxylic acid monomer units to vinyl cyanide monomer units (unsaturated carboxylic acid monomer units/vinyl cyanide monomer unit) is preferably 0.01/1 to 1/1, more preferably 0.02/1 to 0.6/1, and 0.05/1 to 0.5/1 is particularly preferred. If the ratio of unsaturated carboxylic acid-based monomer unit/vinyl cyanide-based monomer unit is less than the above lower limit, the total yield of flameproofing and carbonization tends to decrease. Machinability tends to decrease.

Examples of the acrylamide-based monomers include acrylamide; N- alkylacrylamide; N-cycloalkylacrylamide such as N-cyclohexylacrylamide; dialkylacrylamide such as N,N-dimethylacrylamide; dialkylaminoalkylacrylamide such as dimethylaminoethylacrylamide and dimethylaminopropylacrylamide; N-(hydroxymethyl)acrylamide, Hydroxyalkylacrylamides such as N-(hydroxyethyl)acrylamide; N-arylacrylamides such as N-phenylacrylamide; diacetone acrylamide; N,N'-alkylenebisacrylamides such as N,N'-methylenebisacrylamide; methacrylamide; N-alkylmethacrylamides such as N-methylmethacrylamide, N-ethylmethacrylamide, Nn-propylmethacrylamide, N-isopropylmethacrylamide, Nn-butylmethacrylamide, N-tert-butylmethacrylamide; N - N-cycloalkyl methacrylamides such as cyclohexyl methacrylamide; dialkyl methacrylamides such as N,N-dimethyl methacrylamide; dialkylaminoalkyl methacrylamides such as dimethylaminoethyl methacrylamide and dimethylaminopropyl methacrylamide; N-(hydroxymethyl ) hydroxyalkyl methacrylamides such as methacrylamide and N-(hydroxyethyl) methacrylamide; N-aryl methacrylamides such as N-phenylmethacrylamide; diacetone methacrylamide; N, such as N,N'-methylenebismethacrylamide; N'-alkylene bis methacrylamides can be mentioned. These acrylamide-based monomers may be used alone or in combination of two or more. Among these acrylamide-based monomers, acrylamide, N-alkylacrylamide, dialkylacrylamide, methacrylamide, N-alkylmethacrylamide, and dialkylmethacrylamide are preferable from the viewpoint of high solubility in aqueous solvents or aqueous mixed solvents. , acrylamide is particularly preferred.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, 2-hydroxyethyl acrylonitrile, chloroacrylonitrile, chloromethacrylonitrile, methoxyacrylonitrile, and methoxymethacrylonitrile. These vinyl cyanide monomers may be used alone or in combination of two or more. Among these vinyl cyanide-based monomers, acrylonitrile is preferable from the viewpoint of improving the flameproofing yield, the carbonization yield, and the total yield of flameproofing and carbonization of the carbon material precursor.

Examples of the unsaturated carboxylic acid-based monomers include unsaturated carboxylic acids and salts thereof such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, crotonic acid, and isocrotonic acid; Unsaturated carboxylic acid anhydrides such as anhydrides and itaconic anhydrides are included. These unsaturated carboxylic acid-based monomers may be used alone or in combination of two or more. Among these unsaturated carboxylic acid-based monomers, acrylic acid, maleic acid, fumaric acid, and maleic anhydride are preferable from the viewpoint of improving the total yield of flame resistance and carbonization.

In the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer used in the present invention, acrylamide-based monomer units, vinyl cyanide-based monomer units and unsaturated carboxylic acid are added to the extent that the effects of the present invention are not impaired. Polymerizable monomer units other than the system monomer units may be included. The content of such other polymerizable monomer units is preferably 20 mol% or less, more preferably 10 mol%, based on 100 mol% of the total monomer units of the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer. The following is more preferable, 5 mol % or less is even more preferable, 2 mol % or less is particularly preferable, and 1 mol % or less is most preferable. Examples of other polymerizable monomers include unsaturated carboxylic acid esters such as methyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate; aromatics such as styrene and α-methylstyrene; vinyl-based monomers; vinyl-based monomers other than vinyl cyanide-based monomers such as vinyl chloride and vinyl alcohol; and olefin-based monomers such as ethylene and propylene.

The upper limit of the weight-average molecular weight of the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer used in the present invention is not particularly limited, but is usually 5 million or less. from the viewpoint of the nature, preferably 2,000,000 or less, more preferably 1,000,000 or less, more preferably 500,000 or less, still more preferably 300,000 or less, particularly preferably 200,000 or less, particularly preferably 130,000 or less, 100,000 Most preferred are: The lower limit of the weight-average molecular weight of the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer is not particularly limited, but is usually 10,000 or more, and from the viewpoint of the strength of the carbon material precursor, 20,000. More than 30,000 is preferable, 30,000 or more are more preferable, and 40,000 or more are especially preferable. The weight average molecular weight of the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer is measured by gel permeation chromatography.

Furthermore, the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer used in the present invention can be used in aqueous solvents (water, alcohol, etc., and mixed solvents thereof) and aqueous mixed solvents (the aqueous solvent and the organic solvent (tetrahydrofuran) etc.) and a mixed solvent). As a result, when molding the carbon material precursor, dry molding (dry spinning), dry-wet molding (dry-wet spinning), wet molding (wet spinning), or electroforming using the aqueous solvent or the aqueous mixed solvent can be performed. Spinning becomes possible, and it becomes possible to manufacture a carbon material safely at low cost. Further, when producing the carbon material precursor composition described later, wet mixing using the aqueous solvent or the aqueous mixed solvent becomes possible, and the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer, which will be described later, can be obtained. It becomes possible to mix the additive components uniformly and safely at a low cost. Furthermore, when molding the obtained carbon material precursor composition, dry molding (dry spinning), dry-wet molding (dry-wet spinning), wet molding (wet spinning) using the aqueous solvent or the aqueous mixed solvent. ), or electrospinning becomes possible, and it becomes possible to manufacture carbon materials safely at low cost. The content of the organic solvent in the aqueous mixed solvent is the amount that the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer, which is insoluble or sparingly soluble in the aqueous solvent, dissolves when mixed with the organic solvent. There are no particular restrictions. In addition, among such acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymers, it is possible to form a carbon material precursor or to produce a carbon material precursor composition or a carbon material at a lower cost and safety. From the viewpoint of making it possible to achieve A saturated carboxylic acid-based copolymer is more preferred.

As a method for producing the carbon material precursor of the present invention comprising such an acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer, known polymerization such as radical polymerization, cationic polymerization, anionic polymerization and living radical polymerization can be used. A method of carrying out the reaction by a polymerization method such as solution polymerization, suspension polymerization, precipitation polymerization, dispersion polymerization, emulsion polymerization (for example, inverse emulsion polymerization) can be employed. Among the above polymerization reactions, radical polymerization is preferred from the viewpoint that the carbon material precursor can be produced at low cost. When solution polymerization is employed, it is preferable to use a solvent that dissolves the raw material monomers and the obtained acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer, so that the production can be carried out safely at a low cost. From the viewpoint of being able to It is particularly preferred to use said aqueous solvents, most preferably water.

In the radical polymerization, conventionally known radical polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, 4,4'-azobis(4-cyanovaleric acid), ammonium persulfate, and potassium persulfate are used as polymerization initiators. agent can be used, and when the aqueous solvent or the aqueous mixed solvent is used as the solvent, 4,4′-azobis(4-cyanovaleric acid), ammonium persulfate, potassium persulfate A radical polymerization initiator soluble in a solvent or the aqueous mixed solvent (preferably the aqueous solvent, more preferably water) is preferred. In addition, from the viewpoint of improving the molding processability of the carbon material precursor and improving the solubility of the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer in the aqueous solvent or the aqueous mixed solvent, the polymerization initiator Instead of or in addition to, it is preferable to use a conventionally known polymerization accelerator such as tetramethylethylenediamine or a molecular weight modifier such as an alkyl mercaptan such as n-dodecyl mercaptan, and the polymerization initiator and the polymerization accelerator are combined. The combined use is preferred, and the combined use of ammonium persulfate and tetramethylethylenediamine is particularly preferred.

Although the temperature at which the polymerization initiator is added is not particularly limited, it is preferably 35° C. or higher, more preferably 40° C. or higher, and even more preferably 45° C. or higher, from the viewpoint of improving the moldability of the carbon material precursor. , 50° C. or higher is particularly preferred, and 55° C. or higher is most preferred. The temperature of the polymerization reaction is not particularly limited, but from the viewpoint of improving the solubility of the copolymer in the aqueous solvent or the aqueous mixed solvent, it is preferably 50° C. or higher, more preferably 60° C. or higher. 70° C. or higher is most preferred.

[Carbon material precursor composition]
The carbon material precursor of the present invention exhibits a high yield of flameproofing, a high yield of carbonization, and a high total yield of flameproofing and carbonization. However, from the viewpoint of further improving the yield of flameproofing, the yield of carbonization, and the total yield of flameproofing and carbonization, the group consisting of acids and salts thereof is added to the carbon material precursor of the present invention. A carbon material precursor composition may be prepared by blending at least one additional component selected from the following, and this carbon material precursor composition may be used in the production of the carbon material.

In such a carbon material precursor composition, from the viewpoint of further improving the flameproofing yield, the carbonization yield, and the total yield of flameproofing and carbonization, the content of the additive component is It is preferably 0.1 to 100 parts by mass, more preferably 0.2 to 50 parts by mass, even more preferably 0.5 to 30 parts by mass, and particularly preferably 1 to 20 parts by mass based on 100 parts by mass.

Examples of the acid include inorganic acids such as phosphoric acid, polyphosphoric acid, boric acid, polyboric acid, sulfuric acid, nitric acid, carbonic acid and hydrochloric acid, and organic acids such as oxalic acid, citric acid, sulfonic acid and acetic acid. Examples of such acid salts include metal salts (eg, sodium salts, potassium salts), ammonium salts, amine salts and the like, with ammonium salts and amine salts being preferred, and ammonium salts being more preferred. In particular, among these additive components, phosphoric acid, polyphosphoric acid, boric acid, Polyboric acid, sulfuric acid and their ammonium salts are preferred, and phosphoric acid, polyphosphoric acid and their ammonium salts are particularly preferred.

The additive component is preferably soluble in at least one of the aqueous solvent and the aqueous mixed solvent (more preferably the aqueous solvent, particularly preferably water). As a result, when the carbon material precursor composition is produced, wet mixing using the aqueous solvent or the aqueous mixed solvent becomes possible, and the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer and the added components can be mixed uniformly and safely at low cost. Further, when molding the obtained carbon material precursor composition, dry molding (dry spinning), dry-wet molding (dry-wet spinning), wet molding (wet spinning) using the aqueous solvent or the aqueous mixed solvent. ), or electrospinning becomes possible, and it becomes possible to manufacture carbon materials safely at low cost.

Methods for producing such a carbon material precursor composition include a method of directly mixing the additive component with the carbon material precursor in a molten state (melt mixing), and a method of mixing the carbon material precursor and the additive component by drying. A method of blending (dry mixing), an aqueous solution or aqueous mixed solution containing the additive component, or a solution in which the carbon material precursor is not completely dissolved but the additive component is dissolved in a desired shape (for example, It is also possible to adopt a method of immersing or passing the carbon material precursor formed into a film, sheet, or fiber), but the carbon material precursor and the additive component to be used can be used. When the carbon material precursor and the additive component are soluble in the aqueous solvent or the aqueous mixed solvent, the carbon material precursor and the additive component can be uniformly mixed. A method of mixing in an aqueous solvent or the aqueous mixed solvent (wet mixing) is preferred. Further, as wet mixing, when the above-described polymerization is carried out in the above-mentioned aqueous solvent or the above-mentioned aqueous mixed solvent in the production of the above-mentioned carbon material precursor, a method of mixing the above-mentioned additive components after the polymerization is also adopted. be able to. Further, by removing the solvent from the obtained solution, the carbon material precursor composition can be recovered and used for the production of the carbon material described later. It can also be used as it is for the production of a carbon material to be described later. In the wet mixing, the aqueous solvent is preferably used as the solvent, and water is more preferably used, from the viewpoint that the carbon material precursor composition can be produced safely at a lower cost. Furthermore, the method for removing the solvent is not particularly limited, and at least one of known methods such as distillation under reduced pressure, reprecipitation, hot air drying, vacuum drying, and freeze drying can be employed.

[Method for producing carbon material]
Next, the method for producing the carbon material of the present invention will be described. As the method for producing the carbon material of the present invention, the carbon material precursor or the carbon material precursor composition can be directly carbonized. It is preferable to apply a flameproof treatment and then a carbonization treatment.

In a preferred method for producing the carbon material of the present invention, first, the carbon material precursor or the carbon material precursor composition is subjected to heat treatment in an oxidizing atmosphere (for example, in air) (flameproof treatment). The carbon material precursor of the present invention is composed of an acrylamide/vinyl cyanide/unsaturated carboxylic acid-based copolymer, is resistant to thermal decomposition by flame-resistant treatment, and has acrylamide/vinyl cyanide/unsaturated carboxylic acid Since the structure of the system copolymer is converted to a highly heat-resistant structure by the flameproofing treatment, it exhibits a high flameproofing yield. Furthermore, the flame-resistant carbon material precursor (flame-resistant material) has a highly heat-resistant structure, and therefore exhibits a high carbonization yield. In particular, in the carbon material precursor composition, the deammonification reaction and dehydration reaction of the acrylamide/vinyl cyanide/unsaturated carboxylic acid-based copolymer are promoted by the catalytic action of the acid or its salt as an additive component. Therefore, a cyclic structure (imide ring structure) is easily formed in the molecule, and the structure of the acrylamide/vinyl cyanide/unsaturated carboxylic acid copolymer is easily converted into a highly heat-resistant structure. The flameproofing yield, the carbonization yield of the flameproof material, and the total yield of flameproofing and carbonization are further increased.

The heating temperature in such flameproofing treatment is preferably 150 to 500°C, more preferably 200 to 450°C. 280 to 420°C is more preferable, 300 to 410°C is even more preferable, 310 to 400°C is particularly preferable, and 320 to 390°C is most preferable. When the heating temperature in the flameproofing treatment exceeds the above upper limit, the resulting flameproof material tends to be thermally decomposed. Ammonia reaction and dehydration reaction are not promoted, and a cyclic structure (imide ring structure) is difficult to form in the molecule. Yield and total yield of flameproofing and carbonization tend to decrease. Moreover, the heating time in the flameproofing treatment is not particularly limited, and heating for a long time (for example, more than 1 hour) is possible, but from the viewpoint of cost reduction, 1 to 60 minutes is preferable.

Next, the carbon material precursor (flame-resistant material) that has been subjected to the flame-retardant treatment in this way or the composition containing it is subjected to the above-described Heat treatment is performed at a temperature higher than the heating temperature in the flameproofing treatment (carbonization treatment). As a result, the flameproof substance is carbonized, and the desired carbon material is obtained. The heating temperature in such carbonization treatment is preferably 500° C. or higher, more preferably 1000° C. or higher. Moreover, the upper limit of the heating temperature is preferably 3000° C. or less, more preferably 2500° C. or less. Furthermore, the heating time in the carbonization treatment is not particularly limited, but is preferably 1 to 60 minutes, more preferably 1 to 30 minutes. Further, in the carbonization treatment, the heat treatment can be performed multiple times, for example, the heat treatment is first performed at a temperature of less than 1000° C. and then the heat treatment is performed at a temperature of 1000° C. or higher. In the method for producing a carbon material of the present invention, it is also possible to directly apply such a carbonization treatment to the carbon material precursor or the carbon material precursor composition of the present invention without applying the flameproofing treatment. However, from the viewpoint of increasing the total yield of the carbon material, it is preferable to perform the carbonization treatment after performing the flameproofing treatment. Further, the "carbonization treatment" according to the present invention may generally include "graphitization" performed by heating at 2000 to 3000° C. in an inert gas atmosphere.

Further, in the method for producing a carbon material of the present invention, before the flameproofing treatment (before the carbonization treatment when the flameproofing treatment is not performed), the carbon material precursor or the carbon material precursor composition to be used is is preferably molded into a desired shape (for example, film, sheet, fiber) in advance. At this time, the carbon material precursor or the carbon material precursor composition is pressure-molded as it is, or the carbon material precursor or the carbon material precursor composition in a molten state is melt-molded (for example, melt cast molding, melt extrusion). molding, injection molding, melt spinning, spunbonding, meltblown, centrifugal spinning), but when the carbon material precursor or the carbon material precursor composition is soluble in the aqueous solvent or the aqueous mixed solvent From the viewpoint of improving moldability, the carbon material precursor or the carbon material precursor composition is dissolved in the aqueous solvent or the aqueous mixed solvent, and the resulting aqueous solution or aqueous mixed solution is used for molding. Alternatively, the solution of the carbon material precursor after polymerization or the solution of the carbon material precursor composition obtained by the wet mixing described above is preferably molded as it is or after adjustment to a desired concentration. As such a molding method, solution cast molding, wet molding, dry spinning, wet spinning, dry-wet spinning, gel spinning, flash spinning, or electrospinning is preferably performed. Thereby, a carbon material precursor or a carbon material precursor composition having a desired shape can be produced safely at low cost. Moreover, from the viewpoint that the carbon material can be produced safely at a lower cost, it is more preferable to use the aqueous solvent as the solvent, and it is particularly preferable to use water. By using a carbon material precursor or a carbon material precursor composition that has been molded into a desired shape in advance, a carbon material (for example, a carbon film, a carbon sheet, or a carbon fiber) having a desired shape can be produced. can.

EXAMPLES The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)
Acrylamide (AAm) 16.82 g (237 mmol), acrylonitrile (AN) 4.30 g (81.1 mmol), acrylic acid (AAc) 0.468 g (6.50 mmol) and tetramethylethylenediamine 0.940 g (8.09 mmol) It was dissolved in ion-exchanged water (116.4 ml) and stirred at 200 rpm using a mechanical stirrer. An aqueous solution of 0.740 g (3.24 mmol) of ammonium persulfate dissolved in ion-exchanged water (5.76 ml) was added dropwise to the resulting aqueous solution while heating to 35° C. and stirring at 200 rpm under a nitrogen atmosphere. A polymerization reaction was carried out at 70° C. for 150 minutes. After that, the solution temperature was raised to 90° C. over 30 minutes, and the polymerization reaction was continued at this solution temperature for 60 minutes. After cooling the resulting aqueous solution to room temperature, it is poured into methanol to precipitate a copolymer, which is recovered, vacuum dried at 100° C. for 12 hours, and further vacuum dried at 120° C. for 3 hours. , a carbon material precursor consisting of a water-soluble acrylamide/acrylonitrile/acrylic acid copolymer (AAm/AN/AAc copolymer) was obtained.

(Example 2)
Acrylamide (AAm) 26.88 g (378 mmol), acrylonitrile (AN) 7.17 g (135 mmol), acrylic acid (AAc) 1.95 g (27.0 mmol) and tetramethylethylenediamine 1.57 g (13.5 mmol) were ion-exchanged. It was dissolved in water (194 ml) and stirred at 200 rpm using a mechanical stirrer. An aqueous solution prepared by dissolving 1.23 g (5.41 mmol) of ammonium persulfate in ion-exchanged water (9.60 ml) was added dropwise to the resulting aqueous solution while heating to 35° C. and stirring at 200 rpm under a nitrogen atmosphere. A polymerization reaction was carried out at 70° C. for 150 minutes. After that, the solution temperature was raised to 90° C. over 30 minutes, and the polymerization reaction was continued at this solution temperature for 60 minutes. After cooling the resulting aqueous solution to room temperature, it is poured into methanol to precipitate a copolymer, which is recovered, vacuum dried at 100° C. for 12 hours, and further vacuum dried at 120° C. for 3 hours. , a carbon material precursor consisting of a water-soluble acrylamide/acrylonitrile/acrylic acid copolymer (AAm/AN/AAc copolymer) was obtained.

(Example 3)
Acrylamide (AAm) 24.96 g (351 mmol), acrylonitrile (AN) 7.17 g (135 mmol), acrylic acid (AAc) 3.89 g (54.0 mmol) and tetramethylethylenediamine 1.57 g (13.5 mmol) were ion-exchanged. It was dissolved in water (194 ml) and stirred at 200 rpm using a mechanical stirrer. An aqueous solution prepared by dissolving 1.23 g (5.41 mmol) of ammonium persulfate in ion-exchanged water (9.60 ml) was added dropwise to the resulting aqueous solution while heating to 35° C. and stirring at 200 rpm under a nitrogen atmosphere. A polymerization reaction was carried out at 70° C. for 150 minutes. After that, the solution temperature was raised to 90° C. over 30 minutes, and the polymerization reaction was continued at this solution temperature for 60 minutes. After cooling the resulting aqueous solution to room temperature, it is poured into methanol to precipitate a copolymer, which is recovered, vacuum dried at 100° C. for 12 hours, and further vacuum dried at 120° C. for 3 hours. , a carbon material precursor consisting of a water-soluble acrylamide/acrylonitrile/acrylic acid copolymer (AAm/AN/AAc copolymer) was obtained.

(Comparative example 1)
8.52 g (120 mmol) of acrylamide (AAm) was dissolved in ion-exchanged water (190 ml) and stirred at 800 rpm using a magnetic stirrer. 336 mg (1.20 mmol) of 4,4′-azobis(4-cyanovaleric acid) was added as a polymerization initiator to the obtained aqueous solution, and the polymerization reaction was carried out at a solution temperature of 70° C. for 180 minutes under nitrogen atmosphere. After cooling the resulting aqueous solution to room temperature, it is poured into methanol to precipitate a copolymer, which is recovered, vacuum dried at 100° C. for 12 hours, and further vacuum dried at 120° C. for 3 hours. , to obtain a carbon material precursor composed of water-soluble polyacrylamide (PAAm).

(Comparative example 2)
96.0 g (1.35 mol) of acrylamide (AAm), 23.9 g (0.45 mol) of acrylonitrile (AN) and 6.75 ml (0.045 mol) of tetramethylethylenediamine were dissolved in deionized water (470.6 ml), Stirred at 200 rpm using a mechanical stirrer. Under a nitrogen atmosphere, while heating to 45° C. and stirring at 200 rpm, an aqueous solution obtained by dissolving 2.52 g (0.11 mol) of ammonium persulfate in ion-exchanged water (9.40 ml) was added dropwise to the resulting aqueous solution. A polymerization reaction was carried out at 78° C. for 120 minutes. After that, the solution temperature was raised to 90° C. over 30 minutes, and the polymerization reaction was continued at this solution temperature for 60 minutes. After cooling the resulting aqueous solution to room temperature, it is poured into methanol to precipitate a copolymer, which is recovered, vacuum dried at 100° C. for 12 hours, and further vacuum dried at 120° C. for 3 hours. , a carbon material precursor comprising a water-soluble acrylamide/acrylonitrile copolymer (AAm/AN copolymer) was obtained.

(Comparative Example 3)
16.82 g (237 mmol) acrylamide (AAm), 4.30 g (81.1 mmol) acrylonitrile (AN), 0.560 g (6.50 mmol) methyl acrylate (MA) and 0.940 g (8.09 mmol) tetramethylethylenediamine was added to deionized water (116.4 ml) and stirred at 200 rpm using a mechanical stirrer. An aqueous solution prepared by dissolving 0.741 g (3.25 mmol) of ammonium persulfate in ion-exchanged water (5.76 ml) was added dropwise to the resulting aqueous solution while heating to 35° C. and stirring at 200 rpm under a nitrogen atmosphere. A polymerization reaction was carried out at 70° C. for 150 minutes. After that, the solution temperature was raised to 90° C. over 30 minutes, and the polymerization reaction was continued at this solution temperature for 60 minutes. After cooling the resulting aqueous solution to room temperature, it is poured into methanol to precipitate a copolymer, which is recovered, vacuum dried at 100° C. for 12 hours, and further vacuum dried at 120° C. for 3 hours. , a carbon material precursor consisting of a water-soluble acrylamide/acrylonitrile/methyl acrylate copolymer (AAm/AN/MA copolymer) was obtained.

<Measurement of composition ratio of copolymer>
AAm/AN/AAc copolymers (Examples 1 to 3), AAm/AN copolymers (Comparative Example 2), or AAm/AN/MA copolymers (Comparative Example 3 ) were each dissolved in heavy water (or in deuterated dimethyl sulfoxide if insoluble in heavy water), and ¹³ C-NMR measurement was performed on each of the obtained solutions at room temperature and a frequency of 100 MHz. In the obtained ¹³ C-NMR spectrum, a peak derived from the carbon of the acrylamide carbonyl group appearing at about 177 ppm to about 182 ppm, and a peak derived from the carbon of the cyano group of acrylonitrile appearing at about 121 ppm to about 122 ppm, Based on the integrated intensity ratio of the peak derived from the carbon of the carbonyl group of acrylic acid appearing from about 179 ppm to about 182 ppm and the peak derived from the carbon of the carbonyl group of methyl acrylate appearing from about 176 ppm to about 179 ppm, The molar ratio of acrylamide (AAm) units and acrylic acid (AAc) units to acrylonitrile (AN) units in the AAm/AN/AAc copolymer ((AAm+AAc)/AN), acrylamide (AAm ) units and acrylonitrile (AN) units (AAm/AN) and the moles of acrylamide (AAm) units, acrylonitrile (AN) units and methyl acrylate (MA) units in the AAm/AN/MA copolymer A ratio (AAm/AN/MA) was calculated. Furthermore, the AAm/AN/AAc copolymer was subjected to infrared spectroscopy (IR). In the obtained IR spectrum, the intensity ratio of the peak derived from acrylamide appearing at about 1678 cm ⁻¹ , the peak derived from acrylonitrile appearing at about 2239 cm ⁻¹ , and the peak derived from acrylic acid appearing at about 1715 cm ⁻¹ Based on this, the molar ratio (AAm/AAc) between the acrylamide (AAm) units and the acrylic acid (AAc) units in the AAm/AN/AAc copolymer was calculated, and the (AAm+AAc)/AN and the AAm/AAc The molar ratio (AAm/AN/AAc) of acrylamide (AAm) units, acrylonitrile (AN) units and acrylic acid (AAc) units in the AAm/AN/AAc copolymer was obtained from the above. Those results are shown in Table 1.

<Measurement of weight average molecular weight Mw>
AAm/AN/AAc copolymers (Examples 1 to 3), PAAm (Comparative Example 1), AAm/AN copolymer (Comparative Example 2) and AAm/AN/MA constituting the obtained carbon material precursors The weight average molecular weight Mw of the copolymer (Comparative Example 3) was measured using gel permeation chromatography ("HLC-8220GPC" manufactured by Tosoh Corporation) under the following conditions. Table 1 shows the results.
〔Measurement condition〕
Column: TSKgel GMPW _XL x 2 + TSKgel G2500PW _XL x 1.
Eluent: 100 mM sodium nitrate aqueous solution/acetonitrile = 80/20.
Eluent flow rate: 1.0 ml/min.
Column temperature: 40°C.
Molecular Weight Standards: Standard Polyethylene Oxide/Standard Polyethylene Glycol.
Detector: Differential refractive index detector.

<Measurement of flameproofing yield>
1 to 2 mg of each of the carbon material precursors obtained in Examples and Comparative Examples was weighed, and a differential thermal balance (“TG8120” manufactured by Rigaku Co., Ltd.) was used to measure the rate of temperature increase under an air atmosphere with an air flow rate of 500 ml/min. It was heated from room temperature to 350°C at 10°C/min and held at 350°C for 10 minutes (flameproofing treatment) to obtain a flameproof carbon material precursor. Considering the influence of water adsorbed on the carbon material precursor after vacuum drying, the mass retention rate of the carbon material precursor before and after the flameproofing treatment (flameproofing yield of the carbon material precursor) was calculated at 150°C. Based on the mass of the following formula:
Flameproofing yield [%] of carbon material precursor = _M350 / _M150 x 100
[M ₃₅₀ : mass of carbon material precursor (flame-resistant material) after heating at 350° C. for 10 minutes in air atmosphere, M ₁₅₀ : mass of carbon material precursor at 150° C.]
obtained by Table 1 shows the results.

<Measurement of carbonization yield>
Using a differential thermal balance (“TG8120” manufactured by Rigaku Co., Ltd.), the flame-resistant carbon material precursor is heated from room temperature to 1150° C. at a temperature elevation rate of 20° C./min in a nitrogen atmosphere with a nitrogen flow rate of 500 ml/min ( carbonization) to obtain a carbon material. Considering the influence of water adsorbed on the flame-resistant material, the mass retention rate of the flame-resistant material when heated to 1000°C (the carbonization yield of the flame-resistant material at 1000°C) is calculated as follows based on the mass of the flame-resistant material at 150°C. formula:
Carbonization yield [%] of flameproof material = M1000/ _M150 x ₁₀₀
[M1000: mass of flame-resistant material (carbon material) after heating to ₁₀₀₀ °C in nitrogen atmosphere, M150: mass of flame-resistant material at ₁₅₀ °C]
obtained by Table 1 shows the results.

<Calculation of the total yield of flameproofing and carbonization>
The total yield of flameproofing and carbonization of the carbon material precursors obtained in Examples and Comparative Examples is calculated by the following formula:
Total yield of flameproofing and carbonization [%] = (flameproofing yield/100) x (carbonization yield/100) x 100
obtained by Table 1 shows the results.

As is clear from the results shown in Table 1, acrylamide (AAm) was homopolymerized by copolymerizing acrylonitrile (AN) and acrylic acid (AAc) (Examples 1 to 3). Compared to the case (Comparative Example 1), the flameproofing yield of the carbon material precursor is higher, and when acrylamide (AAm) is copolymerized with acrylonitrile (AN) (Comparative Example 2) or acrylonitrile Compared to the case where (AN) and methyl acrylate (MA) are copolymerized (Comparative Example 3), the carbonization yield of the flame-resistant material is higher, and as a result, the AAm/AN/AAc copolymer is formed. The carbon material precursors (Examples 1 to 3) are a carbon material precursor made of PAAm (Comparative Example 1), a carbon material precursor made of AAm/AN copolymer (Comparative Example 2) and AAm/AN/MA co-polymer. It was found that the total yield of flameproofing and carbonization was improved compared to the carbon material precursor (Comparative Example 3) composed of a polymer.

On the other hand, when acrylonitrile (AN) was copolymerized with acrylamide (AAm) (Comparative Example 2) or when acrylonitrile (AN) and methyl acrylate (MA) were copolymerized (Comparative Example 3), Compared to the case of homopolymerization of acrylamide (AAm) (Comparative Example 1), it was found that the carbonization yield of the flame-resistant substance was greatly reduced, although the flame-proofing yield of the carbon material precursor was higher.

Further, when acrylonitrile (AN) is copolymerized with acrylamide (AAm) (Comparative Example 2), the weight average molecular weight is lower than when acrylamide (AAm) is homopolymerized (Comparative Example 1). It was found that the molding workability of the carbon material precursor was improved. Such a decrease in weight-average molecular weight is also observed when acrylamide (AAm) is copolymerized with acrylonitrile (AN) and acrylic acid (AAc) (Examples 1 to 3). It was confirmed that the molding processability of the carbon material precursor can be ensured by further copolymerizing acrylonitrile (AN) even when the acid (AAc) is copolymerized.

As described above, according to the present invention, an acrylamide-based copolymer having a high flameproofing yield, a high carbonization yield, and a high flameproofing/carbonization total yield can be obtained without adding an additive component such as an acid. It becomes possible to obtain a carbon material precursor composed of a polymer.

Therefore, in the method for producing a carbon material of the present invention, the carbon material precursor used has a high yield of flameproofing, a high yield of carbonization, and a high total yield of flameproofing and carbonization. It is useful as a method capable of producing a carbon material by

Claims (3)

Acrylamide/vinyl cyanide/ A precursor material for producing a carbon material , comprising an unsaturated carboxylic acid-based copolymer. The molar ratio of the unsaturated carboxylic acid-based monomer unit to the vinyl cyanide-based monomer unit (unsaturated carboxylic acid-based monomer unit/vinyl cyanide-based monomer unit) is 0.01/1 to 1/1. The precursor material for carbon material production according to claim 1. 3. A method for producing a carbon material, comprising subjecting the precursor material for manufacturing a carbon material according to claim 1 or 2 to a flameproofing treatment and then to a carbonizing treatment.