JP7137124B2 - Carbon material precursor, carbon material precursor composition containing same, and method for producing carbon material using same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon material precursor, a carbon material precursor composition containing the same, and a method for producing a carbon material using them.

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.

On the other hand, polyacrylamide is a water-soluble polymer, and water can be used as a solvent at the time of polymerization and molding (filming, sheeting, spinning, etc.), which is inexpensive and has a low environmental impact. A reduction in manufacturing costs is expected.

Japanese Patent Publication No. 37-4405 JP 2015-74844 A JP 2016-40419 A JP 2016-113726 A

However, conventional aqueous solutions containing polyacrylamide have a problem of extremely low moldability due to their extremely high viscosity.

The present invention has been made in view of the above-described problems of the prior art, and includes a carbon material precursor made of an acrylamide polymer, having a high carbonization yield and excellent moldability, and a carbon material containing the same. An object of the present invention is to provide a precursor composition and a method for producing a carbon material using them.

The present inventors have made intensive studies to achieve the above object, and as a result, in a carbon material precursor composed of an acrylamide-based polymer, by reducing the weight average molecular weight of the acrylamide-based polymer to a specific range, the above-mentioned An aqueous solution or an aqueous mixed solution containing a carbon material precursor made of an acrylamide polymer has a low viscosity, so that molding processability is improved, and the carbon material precursor has an improved carbonization yield. The discovery led to the completion of the present invention.

That is, the carbon material precursor of the present invention is characterized by comprising an acrylamide polymer having a weight average molecular weight of 10,000 to 160,000 . In such a carbon material precursor, the acrylamide-based polymer preferably contains vinyl cyanide-based monomer units.

Further, the carbon material precursor composition of the present invention is characterized by containing the carbon material precursor of the present invention and at least one additive component selected from the group consisting of acids and salts thereof. is. In such a carbon material precursor composition, the content of the additive component is preferably 0.1 to 40 parts by mass with respect to 100 parts by mass of the carbon material precursor.

Furthermore, the method for producing a carbon material of the present invention is characterized by subjecting the carbon material precursor of the present invention or the carbon material precursor composition of the present invention to a carbonization treatment. Moreover, in the method for producing a carbon material of the present invention, it is preferable that the carbon material precursor or the carbon material precursor composition is subjected to a flameproofing treatment before the carbonization treatment.

In the present invention, the aqueous solution is a solution containing an aqueous solvent (water, alcohol, etc., and a mixed solvent thereof) as a solvent, and the aqueous mixed solution is an aqueous mixed solvent (the aqueous solvent and It is a solution containing an organic solvent (mixed solvent with tetrahydrofuran, etc.). Moreover, the content of the organic solvent in the aqueous mixed solvent is not particularly limited as long as the acrylamide polymer, which is insoluble or sparingly soluble in the aqueous solvent, dissolves when mixed with the organic solvent.

Further, the reason why the viscosity of the aqueous solution or aqueous mixed solution containing the carbon material precursor of the present invention is low is not necessarily clear, but the present inventors speculate as follows. That is, in high-molecular-weight acrylamide-based polymers, entanglement between polymer chains and hydrogen bonding between polymer chains generate a pseudo-crosslinked structure, which is presumed to increase the viscosity of the aqueous solution or aqueous mixed solution. On the other hand, when the acrylamide-based polymer is made to have a low molecular weight, the entanglement between polymer chains and the hydrogen bonding between polymer chains are reduced, so it is difficult to generate a pseudo-crosslinked structure, and the viscosity of the aqueous solution or aqueous mixed solution is lowered. guessed. Further, when the acrylamide-based polymer contains vinyl cyanide-based monomer units, the ratio of acrylamide-based monomer units in the acrylamide-based polymer decreases. It is presumed that the viscosity of the solution or aqueous mixed solution will also be lower.

Furthermore, the reason why the carbon material precursor of the present invention exhibits a high carbonization yield is not necessarily clear, but the present inventors speculate as follows. That is, in the carbon material precursor of the present invention, since the weight average molecular weight is reduced to a specific range, the entanglement between the polymer chains of the acrylamide-based polymer and the hydrogen bonding between the polymer chains are reduced. Since the number of crosslinked structures is small, it is assumed that the heat treatment facilitates cyclization of the polymer molecules, forms a highly heat-resistant cyclic structure, and increases the carbonization yield. Further, when the acrylamide-based polymer contains vinyl cyanide-based monomer units, in the heat treatment, rather than the cyclization reaction between acrylamide-based monomer units, the acrylamide-based monomer unit and the vinyl cyanide-based monomer unit By preferentially proceeding the cyclization reaction and the cyclization reaction between vinyl cyanide-based monomer units, a rigid cyclic structure is introduced into the polymer chain to improve heat resistance. It is presumed that the thermal stability is improved by suppressing chain thermal decomposition from the end of the polymer chain, so that the carbonization yield is further improved. Furthermore, in the carbon material precursor composition of the present invention, the acid or its salt, which is an additive component, catalyzes the dehydration reaction of the acrylamide-based polymer to form a cyclic structure, and the acrylamide-based polymer has a structure with high heat resistance. It is presumed that the carbonization yield of the carbon material precursor is further increased due to the conversion.

According to the present invention, it is possible to obtain a carbon material precursor that is composed of an acrylamide polymer, has a high carbonization yield, and is excellent in moldability. Moreover, by using such a carbon material precursor of the present invention, it becomes possible to produce a carbon material efficiently and stably at low cost.

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 comprises an acrylamide polymer having a weight average molecular weight within the range of 10,000 to 200,000.

(acrylamide polymer)
The weight average molecular weight of the acrylamide polymer used in the present invention is 10,000 to 200,000. If the weight-average molecular weight of the acrylamide-based polymer exceeds the upper limit, the viscosity of the aqueous solution or aqueous mixed solution containing the carbon material precursor composed of the acrylamide-based polymer increases, resulting in a decrease in molding processability and the carbon material precursor. The carbonization yield of the body is not sufficiently improved. On the other hand, if the weight-average molecular weight of the acrylamide-based polymer is less than the lower limit, the strength of the carbon material precursor composed of the acrylamide-based polymer decreases. Furthermore, the upper limit of the weight-average molecular weight of the acrylamide-based polymer is such that the viscosity of the aqueous solution or aqueous mixed solution containing the carbon material precursor made of the acrylamide-based polymer is lowered to improve moldability, and the carbon material From the viewpoint of improving the carbonization yield of the precursor, it is preferably 150,000 or less, more preferably 100,000 or less, even more preferably 90,000 or less, even more preferably 80,000 or less, even more preferably 70,000 or less, and 60,000. The following is more preferable, 50,000 or less is particularly preferable, and 47,000 or less is most preferable. The lower limit of the weight-average molecular weight of the acrylamide-based polymer is preferably 10,000 or more, more preferably 20,000 or more, from the viewpoint of improving the strength of the carbon material precursor composed of the acrylamide-based polymer.

Such an acrylamide-based polymer may be a homopolymer of an acrylamide-based monomer or a copolymer of an acrylamide-based monomer and another polymerizable monomer. From the viewpoint that the viscosity of the aqueous solution or aqueous mixed solution containing the polymer is lowered to improve the molding processability and the carbonization yield of the carbon material precursor is improved, the acrylamide-based monomer and other polymerizable monomers are used together. is preferred.

The lower limit of the content of the acrylamide-based monomer unit in the copolymer of the acrylamide-based monomer and other polymerizable monomer is 50 mol% or more from the viewpoint of the solubility of the copolymer in an aqueous solvent or an aqueous mixed solvent. Preferably, 60 mol % or more is more preferable, and 70 mol % or more is particularly preferable. Further, the upper limit of the content of acrylamide-based monomer units is such that the viscosity of the aqueous solution or aqueous mixed solution containing the carbon material precursor made of the acrylamide-based polymer is lowered to improve moldability. From the viewpoint of improving the carbonization yield of the body, it is preferably 99.9 mol% or less, more preferably 99 mol% or less, still more preferably 95 mol% or less, particularly preferably 90 mol% or less, and 85 mol% or less. Most preferred.

The lower limit of the content of the other polymerizable monomer unit in the copolymer of the acrylamide-based monomer and the other polymerizable monomer is the viscosity of the aqueous solution or aqueous mixed solution containing the carbon material precursor composed of the acrylamide-based polymer. 0.1 mol % or more is preferable, 1 mol % or more is more preferable, and 5 mol % or more is preferable from the viewpoint of improving the molding processability by decreasing the carbon material precursor and improving the carbonization yield of the carbon material precursor. More preferably, 10 mol % or more is particularly preferable, and 15 mol % or more is most preferable. Further, the upper limit of the content of the other polymerizable monomer unit is preferably 50 mol% or less, more preferably 40 mol% or less, more preferably 30 mol, from the viewpoint of solubility of the copolymer in an aqueous solvent or an aqueous mixed solvent. % or less is particularly preferred.

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; dialkylacrylamide, methacrylamide, and dialkylmethacrylamide are preferred, and acrylamide is particularly preferred, from the viewpoint of high solubility in aqueous solvents or aqueous mixed solvents.

Examples of other polymerizable monomers include vinyl cyanide-based monomers, unsaturated carboxylic acids and salts thereof, unsaturated carboxylic anhydrides, unsaturated carboxylic acid esters, vinyl-based monomers, and olefin-based monomers. Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, 2-hydroxyethyl acrylonitrile, chloroacrylonitrile, chloromethacrylonitrile, methoxyacrylonitrile, methoxymethacrylonitrile and the like. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, and itaconic acid. Examples of the unsaturated carboxylic anhydride include maleic anhydride and itaconic anhydride. Examples thereof include methyl acrylate, methyl methacrylate, etc. Examples of the vinyl-based monomers include styrene, α-methylstyrene, vinyl chloride, vinyl alcohol, etc. Examples of the olefin-based monomers include ethylene, propylene, etc. is mentioned. These other polymerizable monomers may be used alone or in combination of two or more. In addition, among these other polymerizable monomers, the viscosity of an aqueous solution or aqueous mixed solution containing a carbon material precursor made of an acrylamide-based polymer is lowered to improve moldability. Vinyl cyanide-based monomers are preferred, and acrylonitrile is particularly preferred, from the viewpoint of improving the carbonization yield.

An aqueous solution or aqueous mixed solution containing the carbon material precursor of the present invention made of such an acrylamide polymer has a viscosity even when the concentration of the carbon material precursor is high (for example, 20% by mass or more). It is low and has excellent moldability. Specifically, for the aqueous solution or the aqueous mixed solution in which the concentration of the carbon material precursor is 30% by mass, a rotary rheometer (for example, a tee plate) equipped with a cone plate having a diameter of 25 mm and an angle of 0.04 rad is used. "ARES-G2" manufactured by A Instruments Co., Ltd.), the viscosity measured at room temperature and a shear rate of 10 s ^-1 is preferably 200 Pa s or less, and is preferably 100 Pa s or less. It is more preferably 20 Pa·s or less, and particularly preferably 2 Pa·s or less. As a result, for example, when a film is formed by a solution casting method using the aqueous solution or the aqueous mixed solution, it is possible to obtain a film with little unevenness in thickness and excellent surface appearance. In addition, the production efficiency (productivity) can be improved by increasing the concentration. When the viscosity of the aqueous solution or the aqueous mixed solution exceeds 20 Pa s, the surface appearance of the obtained film tends to deteriorate, and when it exceeds 100 Pa s, the thickness unevenness of the obtained film increases (10% If it exceeds 200 Pa s, the handling property at the time of casting is low, and a film cannot be obtained, or even if a film is obtained, the film contains air bubbles, and the thickness unevenness is further increased ( 20%).

As a method for producing such a carbon material precursor of the present invention, a known polymerization method such as solution polymerization, suspension polymerization, precipitation polymerization, dispersion polymerization, emulsion polymerization (e.g., inverse emulsion polymerization) may be employed. can be done. When solution polymerization is employed, the solvent is not particularly limited as long as it dissolves the raw material monomer and the obtained acrylamide polymer. Alcohols, etc., and mixed solvents thereof, etc.) or the above-mentioned aqueous mixed solvents (mixed solvents of the above-mentioned aqueous solvents and organic solvents (tetrahydrofuran, etc.)) are preferably used, and it is more preferable to use the above-mentioned aqueous solvents. is particularly preferred. Further, as the polymerization initiator, a conventionally known polymerization initiator can be used. ), ammonium persulfate, potassium persulfate, or the like, or a radical polymerization initiator soluble in the aqueous solvent or the aqueous mixed solvent (preferably the aqueous solvent, more preferably water).

The temperature of the polymerization reaction is not particularly limited, but is preferably 40°C or higher, more preferably 50°C or higher, and 60°C, from the viewpoint that the weight average molecular weight of the obtained acrylamide polymer is reduced and the moldability is improved. 65° C. or higher is even more preferred, 70° C. or higher is particularly preferred, and 75° C. or higher is most preferred.

[Carbon material precursor composition]
Next, the carbon material precursor composition of the present invention will be described. The carbon material precursor composition of the present invention contains the carbon material precursor of the present invention and at least one additive component selected from the group consisting of acids and salts thereof. By adding at least one additional component selected from the group consisting of acids and salts thereof to the carbon material precursor of the present invention, the carbonization yield is further improved.

In the carbon material precursor composition of the present invention, the content of such additive components is 0.1 to 40 parts by mass with respect to 100 parts by mass of the carbon material precursor from the viewpoint of further improving the carbonization yield. parts, more preferably 0.1 to 30 parts by mass, even more preferably 0.2 to 25 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. Among these additive components, phosphoric acid, polyphosphoric acid, boric acid, polyboric acid, sulfuric acid, and ammonium salts thereof are particularly preferable from the viewpoint of further improving the carbonization yield of the obtained carbon material precursor. Acids, polyphosphoric acids and their ammonium salts are particularly preferred.

Such an aqueous solution or aqueous mixed solution containing the carbon material precursor composition of the present invention has a low viscosity even when the concentration of the carbon material precursor is high (e.g., 20% by mass or more), and is suitable for molding. Excellent workability. Specifically, for the aqueous solution or the aqueous mixed solution in which the concentration of the carbon material precursor is 30% by mass, a rotary rheometer (for example, a tee plate) equipped with a cone plate having a diameter of 25 mm and an angle of 0.04 rad is used. "ARES-G2" manufactured by A Instruments Co., Ltd.), the viscosity measured at room temperature and a shear rate of 10 s ^-1 is preferably 200 Pa s or less, and is preferably 100 Pa s or less. It is more preferably 20 Pa·s or less, and particularly preferably 2 Pa·s or less. As a result, for example, when a film is formed by a solution casting method using the aqueous solution or the aqueous mixed solution, it is possible to obtain a film with little unevenness in thickness and excellent surface appearance. In addition, the production efficiency (productivity) can be improved by increasing the concentration. When the viscosity of the aqueous solution or the aqueous mixed solution exceeds 20 Pa s, the surface appearance of the obtained film tends to deteriorate, and when it exceeds 100 Pa s, the thickness unevenness of the obtained film increases (10% If it exceeds 200 Pa s, the handleability at the time of casting is low, and a film cannot be obtained, or even if a film is obtained, the film contains air bubbles or the thickness unevenness is further increased ( 20%).

Methods for producing such a carbon material precursor composition of the present invention 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. A method of dry 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 into a desired shape. It is also possible to adopt a method of immersing or passing the carbon material precursor formed into a (for example, film, sheet, or fibrous) shape. From the viewpoint that the additive component is soluble in the aqueous solvent or the aqueous mixed solvent, and the carbon material precursor and the additive component can be uniformly mixed, the carbon material precursor and the additive component are A method of mixing in the 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. Furthermore, by removing the solvent from the resulting solution, the carbon material precursor composition of the present invention can be recovered and used for the production of the carbon material described later. The resulting solution can be used as it is for the production of the carbon material 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 a method for producing the carbon material of the present invention, the carbon material precursor of the present invention or the carbon material precursor composition of the present invention may be directly carbonized. Then, it is preferable to perform a carbonization treatment.

In a preferred method for producing the carbon material of the present invention, first, the carbon material precursor or carbon material precursor composition of the present invention is subjected to heat treatment in an oxidizing atmosphere (for example, in air) (flameproof treatment). As a result, the structure of the acrylamide-based polymer constituting the carbon material precursor is converted into a structure with high heat resistance, so that the carbonization yield of the carbon material precursor is improved. In particular, in the carbon material precursor composition, the dehydration reaction of the acrylamide-based polymer is facilitated by the catalytic action of the acid or its salt, which is an additive component. is easily converted into a structure with high heat resistance, the carbonization yield of the carbon material precursor is further increased. The heating temperature in such a flameproofing treatment is preferably 500°C or less, more preferably 150 to 450°C, and even more preferably 200 to 400°C. 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 carbon material precursor) or the carbon material precursor composition (flame-resistant carbon material precursor composition) that has been subjected to the flameproofing treatment in this way is placed in an inert atmosphere ( In an inert gas such as nitrogen, argon, or helium), heat treatment is performed at a temperature higher than the heating temperature in the flameproofing treatment (carbonization treatment). As a result, the flame resistant carbon material precursor is carbonized to obtain the desired carbon material. 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 2000° 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 may 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. be.

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, meltblowing, centrifugal spinning), provided that the carbon material precursor or carbon material precursor composition of the present invention is soluble in the aqueous solvent or the aqueous mixed solvent. , from the viewpoint of enhancing 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, it is preferable to mold the solution of the carbon material precursor after polymerization or the solution of the carbon material precursor composition obtained by the wet mixing as it is or after adjusting it 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. Each acrylamide polymer used in the examples was synthesized by the following method.

(Synthesis example 1)
12.8 g (0.18 mol) of acrylamide (AAm, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 180 ml of deionized water, and 0.252 g (0.0011 mol) of ammonium persulfate and tetramethylethylenediamine were added to the resulting aqueous solution. 35 ml was added, and the polymerization reaction was carried out at 60° C. for 3 hours under nitrogen atmosphere. The resulting aqueous solution was poured into methanol to precipitate a polymer, which was collected and vacuum-dried to obtain water-soluble polyacrylamide (PAAm). The weight average molecular weight Mw of this PAAm was measured by gel permeation chromatography (manufactured by Tosoh Corporation "HLC-8220GPC", column: TSKgel GMPW _XL × 2 + TSKgel G2500PW _XL × 1, eluent: 100 mM sodium nitrate aqueous solution / acetonitrile = 80 /20, column temperature: 40°C, molecular weight standards: standard polyethylene oxide/standard polyethylene glycol), Mw = 130,000.

(Synthesis example 2)
12.8 g (0.18 mol) of acrylamide (AAm, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 180 ml of deionized water, and 0.252 g (0.0011 mol) of ammonium persulfate and tetramethylethylenediamine were added to the resulting aqueous solution. 35 ml was added, and the polymerization reaction was carried out at 80° C. for 3 hours under nitrogen atmosphere. The resulting aqueous solution was poured into methanol to precipitate a polymer, which was collected and vacuum-dried to obtain water-soluble polyacrylamide (PAAm). When the weight average molecular weight Mw of this PAAm was measured in the same manner as in Synthesis Example 1, it was found to be Mw=95,000.

(Synthesis Example 3)
96.0 g (1.35 mol) of acrylamide (AAm, manufactured by Wako Pure Chemical Industries, Ltd.) and 23.9 g (0.45 mol) of acrylonitrile (AN) are dissolved in 480 ml of ion-exchanged water, and 1 part of ammonium persulfate is added to the resulting aqueous solution. 0.03 g (0.0045 mol) and 6.75 ml of tetramethylethylenediamine were added, and a polymerization reaction was carried out at 50° C. for 3 hours under a nitrogen atmosphere. The resulting aqueous solution was poured into methanol to precipitate a copolymer, which was collected and vacuum-dried to yield a water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=75 mol %/25 mol %). Obtained. When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=160,000.

(Synthesis Example 4)
A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=75 mol %/25 mol %) was obtained in the same manner as in Synthesis Example 3, except that the amount of ammonium persulfate was changed to 1.52 g (0.0067 mol). When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=130,000.

(Synthesis Example 5)
A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=75 mol %/25 mol %) was obtained in the same manner as in Synthesis Example 3, except that the amount of ammonium persulfate was changed to 2.52 g (0.011 mol). When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=95,000.

(Synthesis Example 6)
A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=75 mol %/25 mol %) was obtained in the same manner as in Synthesis Example 3, except that the amount of ammonium persulfate was changed to 4.11 g (0.018 mol). When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=78,000.

(Synthesis Example 7)
A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN = 75 mol% /25 mol%) was obtained. When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=54,000.

(Synthesis Example 8)
The amount of acrylamide (AAm) was changed to 108.8 g (1.53 mol), the amount of acrylonitrile (AN) was changed to 14.3 g (0.27 mol), and the amount of ammonium persulfate was changed to 4.11 g (0.018 mol). A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=85 mol %/15 mol %) was obtained in the same manner as in Synthesis Example 3, except that the polymerization temperature was changed to 70.degree. When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=60,000.

(Synthesis Example 9)
The amount of acrylamide (AAm) was changed to 89.6 g (1.26 mol), the amount of acrylonitrile (AN) was changed to 28.7 g (0.54 mol), and the amount of ammonium persulfate was changed to 4.11 g (0.018 mol). A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=70 mol %/30 mol %) was obtained in the same manner as in Synthesis Example 3, except that the polymerization temperature was changed to 70.degree. When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=60,000.

(Synthesis Example 10)
A water-soluble acrylamide/acrylonitrile copolymer (AAm/AN=75 mol %/25 mol %) was obtained in the same manner as in Synthesis Example 6, except that the polymerization temperature was changed to 78.degree. When the weight average molecular weight Mw of this AAm/AN copolymer was measured in the same manner as in Synthesis Example 1, it was found to be Mw=44,000.

(Example 1)
PAAm (Mw=130000) obtained in Synthesis Example 1 was used as the carbon material precursor.

(Example 2)
As a carbon material precursor, PAAm (Mw=130000) obtained in Synthesis Example 1 was dissolved in ion-exchanged water so that the carbon material precursor concentration was 20% by mass. To the obtained aqueous solution, 2 parts by mass of diammonium hydrogen phosphate was added with respect to 100 parts by mass of the carbon material precursor, and completely dissolved. After water was distilled off from the obtained aqueous solution under reduced pressure, the obtained solid component was vacuum-dried to obtain a carbon material precursor composition containing PAAm and diammonium hydrogen phosphate.

(Example 3)
PAAm (Mw=95000) obtained in Synthesis Example 2 was used as a carbon material precursor.

(Example 4)
A carbon material precursor composition containing PAAm and diammonium hydrogen phosphate was obtained in the same manner as in Example 2, except that PAAm (Mw = 95000) obtained in Synthesis Example 2 was used as the carbon material precursor. .

(Example 5)
Carbon material precursor composition containing PAAm and phosphoric acid in the same manner as in Example 4 except that 2 parts by mass of phosphoric acid was added to 100 parts by mass of the carbon material precursor instead of diammonium hydrogen phosphate. got stuff

(Example 6)
The AAm/AN copolymer (AAm/AN=75 mol %/25 mol %, Mw=160000) obtained in Synthesis Example 3 was used as the carbon material precursor as it was.

(Example 7)
AAm/AN copolymer was prepared in the same manner as in Example 2 except that the AAm/AN copolymer obtained in Synthesis Example 3 (AAm/AN=75 mol%/25 mol%, Mw=160000) was used as the carbon material precursor. A carbon material precursor composition containing a polymer and diammonium hydrogen phosphate was obtained.

(Example 8)
The AAm/AN copolymer (AAm/AN=75 mol %/25 mol %, Mw=130000) obtained in Synthesis Example 4 was used as the carbon material precursor as it was.

(Example 9)
The AAm/AN copolymer obtained in Synthesis Example 4 (AAm/AN=75 mol%/25 mol%, Mw=130000) was used as the carbon material precursor, and the amount of diammonium hydrogen phosphate added was A carbon material precursor composition containing an AAm/AN copolymer and diammonium hydrogen phosphate was obtained in the same manner as in Example 2, except that the amount was changed to 3 parts by mass with respect to 100 parts by mass.

(Example 10)
As the carbon material precursor, the AAm/AN copolymer (AAm/AN=75 mol %/25 mol %, Mw=95000) obtained in Synthesis Example 5 was used as it was.

(Example 11)
AAm/AN copolymer was prepared in the same manner as in Example 2 except that the AAm/AN copolymer obtained in Synthesis Example 5 (AAm/AN=75 mol%/25 mol%, Mw=95000) was used as the carbon material precursor. A carbon material precursor composition containing a polymer and diammonium hydrogen phosphate was obtained.

(Example 12)
AAm/AN copolymer and diammonium hydrogen phosphate were added in the same manner as in Example 11 except that the amount of diammonium hydrogen phosphate added was changed to 20 parts by mass with respect to 100 parts by mass of the carbon material precursor. A carbon material precursor composition was obtained.

(Example 13)
The AAm/AN copolymer (AAm/AN=75 mol %/25 mol %, Mw=78000) obtained in Synthesis Example 6 was used as the carbon material precursor as it was.

(Example 14)
AAm/AN copolymer was prepared in the same manner as in Example 2 except that the AAm/AN copolymer (AAm/AN=75 mol%/25 mol%, Mw=78000) obtained in Synthesis Example 6 was used as the carbon material precursor. A carbon material precursor composition containing a polymer and diammonium hydrogen phosphate was obtained.

(Example 15)
AAm/AN copolymer and phosphoric acid are contained in the same manner as in Example 14 except that 2 parts by mass of phosphoric acid is added to 100 parts by mass of the carbon material precursor instead of diammonium hydrogen phosphate. A carbon material precursor composition was obtained.

(Example 16)
AAm/AN copolymer and boric acid were added in the same manner as in Example 14 except that 2 parts by mass of boric acid was added to 100 parts by mass of the carbon material precursor instead of diammonium hydrogen phosphate. A carbon material precursor composition was obtained.

(Example 17)
The AAm/AN copolymer (AAm/AN=75 mol %/25 mol %, Mw=54000) obtained in Synthesis Example 7 was used as the carbon material precursor as it was.

(Example 18)
The AAm/AN copolymer (AAm/AN=75 mol%/25 mol%, Mw=54000) obtained in Synthesis Example 7 was used as the carbon material precursor, and the amount of diammonium hydrogen phosphate added was A carbon material precursor composition containing an AAm/AN copolymer and diammonium hydrogen phosphate was obtained in the same manner as in Example 2, except that the amount was changed to 3 parts by mass with respect to 100 parts by mass.

(Example 19)
AAm/AN copolymer and phosphoric acid are added in the same manner as in Example 18 except that 3 parts by mass of phosphoric acid is added to 100 parts by mass of the carbon material precursor instead of diammonium hydrogen phosphate. A carbon material precursor composition was obtained.

(Example 20)
The AAm/AN copolymer (AAm/AN=85 mol %/15 mol %, Mw=60000) obtained in Synthesis Example 8 was used as the carbon material precursor as it was.

(Example 21)
The AAm/AN copolymer (AAm/AN=85 mol%/15 mol%, Mw=60000) obtained in Synthesis Example 8 was used as the carbon material precursor, and the amount of diammonium hydrogen phosphate added was A carbon material precursor composition containing an AAm/AN copolymer and diammonium hydrogen phosphate was obtained in the same manner as in Example 2, except that the amount was changed to 3 parts by mass with respect to 100 parts by mass.

(Example 22)
The AAm/AN copolymer (AAm/AN=70 mol %/30 mol %, Mw=60000) obtained in Synthesis Example 9 was used as the carbon material precursor as it was.

(Example 23)
The AAm/AN copolymer (AAm/AN=70 mol %/30 mol %, Mw=60000) obtained in Synthesis Example 9 was used as the carbon material precursor, and the amount of diammonium hydrogen phosphate added was A carbon material precursor composition containing an AAm/AN copolymer and diammonium hydrogen phosphate was obtained in the same manner as in Example 2, except that the amount was changed to 3 parts by mass with respect to 100 parts by mass.

(Example 24)
The AAm/AN copolymer (AAm/AN=75 mol %/25 mol %, Mw=44000) obtained in Synthesis Example 10 was used as the carbon material precursor as it was.

(Example 25)
The AAm/AN copolymer (AAm/AN=75 mol%/25 mol%, Mw=44000) obtained in Synthesis Example 10 was used as the carbon material precursor, and the amount of diammonium hydrogen phosphate added was A carbon material precursor composition containing an AAm/AN copolymer and diammonium hydrogen phosphate was obtained in the same manner as in Example 2, except that the amount was changed to 3 parts by mass with respect to 100 parts by mass.

(Example 26)
AAm/AN copolymer and phosphoric acid are added in the same manner as in Example 25 except that 3 parts by mass of phosphoric acid is added to 100 parts by mass of the carbon material precursor instead of diammonium hydrogen phosphate. A carbon material precursor composition was obtained.

(Example 27)
AAm/AN copolymer and boric acid were added in the same manner as in Example 25 except that 3 parts by mass of boric acid was added to 100 parts by mass of the carbon material precursor instead of diammonium hydrogen phosphate. A carbon material precursor composition was obtained.

(Comparative example 1)
A 10% aqueous solution of polyacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd., product code: A0140) was dried under vacuum to remove water and recover polyacrylamide (PAAm). When the weight average molecular weight Mw of this PAAm was measured in the same manner as in Synthesis Example 1, it was found to be Mw=580,000. This PAAm (Mw=580000) was used as it was as a carbon material precursor.

<Measurement of carbonization yield>
Carbon material precursors obtained in Examples and Comparative Examples (Examples 1, 3, 6, 8, 10, 13, 17, 20, 22, 24, Comparative Example 1) or carbon material precursor compositions (Example 2, 4-5, 7, 9, 11-12, 14-16, 18-19, 21, 23, 25-27) 3 mg was vacuum-dried at 80 ° C. for 12 hours, and then subjected to a differential thermal balance (manufactured by Rigaku Co., Ltd. "TG8120") was used to heat from room temperature to 1000° C. at a temperature elevation rate of 20° C./min in a nitrogen stream at a flow rate of 500 ml/min. The carbonization yield of the carbon material precursor at 500 ° C. and 1000 ° C. is calculated by the following formula, based on the mass of the carbon material precursor at 150 ° C., considering the influence of water adsorbed on the carbon material precursor after the vacuum drying.
Carbonization yield [%] = M _T /M ₁₅₀ × 100
[M _T : mass of carbon material precursor at temperature T (500° C. or 1000° C.), M ₁₅₀ : mass of carbon material precursor at 150° C.]
obtained by Table 1 shows the results.

<Evaluation of moldability>
Carbon material precursors (Examples 1, 3, 6, 8, 10, 13, 17, 20, 22, 24, Comparative Example 1) or carbon material precursor compositions (Examples 2, 4 to 5, 7, 9 , 11-12, 14-16, 18-19, 21, 23, 25-27) were dissolved in ion-exchanged water so that the carbon material precursor concentration was 30 mass %. The viscosity of the resulting aqueous solution was measured using a rotary rheometer (“ARES-G2” manufactured by TA Instruments) equipped with a cone plate with a diameter of 25 mm and an angle of 0.04 rad at room temperature and a shear rate of 10 s. It was measured under the condition of ^-1 and evaluated according to the following criteria. Table 1 shows the results.
5: When the viscosity is 2 Pa·s or less.
4: When the viscosity exceeds 2 Pa·s and is 20 Pa·s or less.
3: When the viscosity exceeds 20 Pa·s and is 100 Pa·s or less.
2: When the viscosity exceeds 100 Pa·s and is 200 Pa·s or less.
1: When the viscosity exceeds 200 Pa·s.

As shown in Table 1, the carbon material precursors (Examples 1 and 3) of the present invention composed of acrylamide-based polymers having a predetermined weight-average molecular weight consist of acrylamide-based polymers with weight-average molecular weights exceeding a predetermined range. Compared to the carbon material precursor (Comparative Example 1), it was confirmed that the carbonization yield was high at both heating temperatures of 500°C and 1000°C, the viscosity of the aqueous solution was low, and the moldability was excellent. was done. This is because the entanglement between polymer molecular chains is reduced by reducing the molecular weight of the acrylamide-based polymer, and the fluidity at the time of heating is improved, promoting the intramolecular cyclization reaction and forming a highly heat-resistant cyclic structure. It is presumed that it was formed quickly and efficiently.

Further, as is clear from comparing Example 8 with Example 1, and Example 10 with Example 3, a carbon material precursor made of an acrylamide/acrylonitrile copolymer obtained by copolymerizing acrylamide with a predetermined amount of acrylonitrile. In (Examples 8 and 10), compared with carbon material precursors (Examples 1 and 3) composed of acrylamide homopolymers having the same weight-average molecular weight, the viscosity of the aqueous solution is low, and the moldability is improved. I found out.

Furthermore, Example 2 and Example 1, Example 4-5 and Example 3, Example 7 and Example 6, Example 9 and Example 8, Example 11-12 and Example 10, Example 14- 16 and Example 13, Examples 18-19 and Example 17, Example 21 and Example 20, Example 23 and Example 22, and Examples 25-27 and Example 24. Carbon material precursor compositions (Examples 2, 4 to 5, 7, 9 , 11 to 12, 14 to 16, 18 to 19, 21, 23, 25 to 27) when the additive component was not added (Examples 1, 3, 6, 8, 10, 13, 17, 20 , 22, 24), the carbonization yield is greatly increased.

(Production example 1)
The carbon material precursor obtained in Example 13 was dissolved in ion-exchanged water to a concentration of 30% by mass. After casting the obtained aqueous solution on a petri dish, the water was evaporated to form a film composed of the carbon material precursor. This film had a uniform thickness and an excellent surface appearance.

The obtained film made of the carbon material precursor was subjected to a heat treatment (flameproof treatment) at 350° C. for 10 minutes in an air atmosphere to obtain a film made of the flameproof carbon material precursor. The film made of this flame-resistant carbon material precursor was subjected to a heat treatment (carbonization treatment) at 1000° C. for 10 minutes in a nitrogen gas atmosphere to obtain a film made of a carbon material.

(Production example 2)
The carbon material precursor composition obtained in Example 14 was dissolved in ion-exchanged water so that the carbon material precursor concentration was 30 mass % to prepare an aqueous solution. A film of the carbon material precursor composition was obtained in the same manner as in Production Example 1, except that this aqueous solution was used. This film had a uniform thickness and an excellent surface appearance. A film made of the carbon material was obtained by carrying out the flameproofing treatment and the carbonization treatment in the same manner as in Production Example 1, except that the film made of the obtained carbon material precursor composition was used.

(Production example 3)
The carbon material precursor obtained in Example 24 was dissolved in ion-exchanged water so that the concentration of the carbon material precursor was 40% by mass to prepare an aqueous solution. A film composed of a carbon material precursor was obtained in the same manner as in Production Example 1, except that this aqueous solution was used. This film is made of the carbon material precursor obtained in Production Example 1, although the concentration of the carbon material precursor is increased from the viewpoint of further improving production efficiency (productivity) compared to Production Example 1. Like the film, it had a uniform thickness and an excellent surface appearance. A film made of a carbon material was obtained by carrying out the flameproofing treatment and the carbonization treatment in the same manner as in Production Example 1, except that the obtained film made of the carbon material precursor was used.

(Production example 4)
The carbon material precursor composition obtained in Example 25 was dissolved in ion-exchanged water so that the carbon material precursor concentration was 40% by mass to prepare an aqueous solution. A film of the carbon material precursor composition was obtained in the same manner as in Production Example 1, except that this aqueous solution was used. This film is the carbon material precursor composition obtained in Production Example 2, although the carbon material precursor concentration is increased from the viewpoint of further improving production efficiency (productivity) compared to Production Example 2. The film had a uniform thickness and an excellent surface appearance. A film made of the carbon material was obtained by carrying out the flameproofing treatment and the carbonization treatment in the same manner as in Production Example 1, except that the film made of the obtained carbon material precursor composition was used.

As described above, according to the present invention, it is possible to obtain a carbon material precursor that is composed of an acrylamide polymer, has a high carbonization yield, and is excellent in moldability.

Therefore, in the method for producing a carbon material of the present invention, the carbon material precursor used has a high carbonization yield and is excellent in moldability, so that the carbon material can be produced efficiently and stably at low cost. It is useful as a method.

Claims (6)

A carbon material precursor comprising an acrylamide polymer having a weight average molecular weight of 10,000 to 160,000 . 2. The carbon material precursor according to claim 1, wherein the acrylamide-based polymer contains a vinyl cyanide-based monomer unit. 3. A carbon material precursor composition comprising the carbon material precursor according to claim 1 and at least one additive component selected from the group consisting of acids and salts thereof. 4. The carbon material precursor composition according to claim 3, wherein the content of said additive component is 0.1 to 40 parts by mass with respect to 100 parts by mass of said carbon material precursor. 5. A method for producing a carbon material, wherein the carbon material precursor according to claim 1 or 2 or the carbon material precursor composition according to claim 3 or 4 is carbonized. 6. The method for producing a carbon material according to claim 5, wherein the carbon material precursor or the carbon material precursor composition is subjected to a flameproofing treatment before the carbonization treatment.