JPH05254814A - Carbonaceous fine particle and its production - Google Patents

Abstract

PURPOSE:To provide a new carbonaceous material capable of exhibiting various useful physical properties such as large specific surface area and shape holding properties as a functional material and industrially and advantageously produce the new carbonaceous material capable of exhibiting the useful physical properties. CONSTITUTION:The objective carbonaceous fine particles are fine particles, composed of a carbonaceous substance and characterized by having hollow parts. The objective method for producing the carbonaceous fine particles is characterized by burning core-shell type polymer fine particles, consisting essentially of a polymer prepared by polymerizing a hydrophobic monomer having vinyl group and having a higher acrylonitrile monomer content in the outer shell part than that in the central part, thermally decomposing the central part and providing the hollow parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel carbonaceous fine particle and a method for producing the same, and more specifically, it has high performance including catalysts, conductive materials, battery electrode materials, magnetic materials and elastic materials. The present invention relates to carbonaceous fine particles useful as a material.

[0002]

2. Description of the Related Art Needless to say, carbon materials have been essential materials in human life since the beginning of "charcoal materials made by charcoal". Since it is rich in resources and can be transformed into various forms, it has been applied to a wide range of fields. In the history of carbon material development, especially 19
PAN-based carbon fibers made from polyacrylonitrile (PAN) that appeared around 1960 changed the role of carbon materials in various industries and human society.

In the form of CFRP, CFRC, C / C composite, it has become an indispensable structural material in the state of the art such as space, aviation, ocean, construction, high speed machinery and nuclear fusion. It can be said that this is because the carbon material in the form of carbon fiber is a material that can be transformed into various shapes and can be compounded with other materials such as plastic, cement, and ceramics. 198
Since the 0's, with the development of the computer industry, carbon materials have regained attention as magnetic materials, IC-related materials, capacitors, optical fiber materials, and secondary battery electrode materials. Graphite, diamond, C ₆₀ carbon clusters, etc. Application research as a new functional material is being carried out, mainly in the form of a thin film or in the form of a composite with a metal element.

[0004]

The carbon material according to the prior art is a fiber or a thin film formed on a substrate, or even if it is a sheet-like or granular one, it is a thin sheet having a large area. Not, not flexible,
Since the size of the particles is not small and the sizes are not uniform, there are restrictions on application and development as new functional materials, and improvements in terms of such morphology were desired. ..

The present inventors have paid attention to the problems that the above-mentioned conventional carbon materials cannot achieve, and as a result of diligent studies to solve the problems, as a result, acrylonitrile is used as a raw material for carbon fibers. Focusing on the fact that even among the hydrophobic monomers having a group, it does not burn off even if it is exceptionally baked, it is mainly composed of a polymer obtained by polymerizing a hydrophobic monomer having a vinyl group. In the polymer particles, the acrylonitrile monomer content of the outer shell part is higher than the acrylonitrile monomer content of the central part, and the core-shell polymer fine particles are tried to be calcined. The core with low content easily decomposes and disappears, while the shell with high content of acrylonitrile monomer remains as a relatively strong shell, resulting in hollow carbonaceous fine particles. watch the It was. Further, such hollow carbonaceous fine particles have various specific physical properties as a functional material, such as having a specific surface area larger than it looks because of being hollow and having a shape-retaining property, and are likely to be applicable to various applications. The present invention has been accomplished by finding that it can be used as a material having high cost.

That is, an object of the present invention is to provide a novel carbon material which has various useful physical properties as a functional material, such as a large specific surface area and shape retention. Another object of the present invention is to industrially produce a novel carbon material having useful physical properties.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is, therefore, to provide carbonaceous fine particles having a hollow portion, and carbonaceous fine particles, and a hydrophobic monolayer having a vinyl group. A polymer particle mainly composed of a polymer obtained by polymerizing a polymer, wherein the content of acrylonitrile monomer in the outer shell is higher than the content of acrylonitrile monomer in the central portion. This can be easily achieved by a method for producing fine carbonaceous particles which is characterized in that the central part is pyrolyzed to be hollow by firing.

The present invention will be described in more detail below. The carbonaceous fine particles of the present invention are characterized by being made of a carbonaceous substance and having a hollow portion. A carbonaceous substance is a substance mainly composed of carbon and has a carbon content of 8%.
It is a substance of 5% by weight or more, preferably 95% by weight or more. Examples thereof include graphite, amorphous carbon, carbon as a graphite precursor, and the like. In addition, as a copolymer monomer,
When acrylonitrile is used, nitrogen may be contained in an amount of 1 to 10% by weight in addition to carbon.

The fact that the carbonaceous fine particles of the present invention have a hollow portion means that the inside of the fine particles is a hollow portion having a size that can be clearly distinguished from ordinary pores, that is, about 20% of the diameter of the fine particles.
As described above, it means having a cavity having a diameter of preferably about 30 to 80%, whereby the carbonaceous fine particles of the present invention have a very large specific surface area, elasticity, flexibility and the like. , Shows various useful physical properties. The particle size of the carbonaceous fine particles themselves is not particularly limited, but if it is too large, the advantage as a functional material is lost in terms of the specific surface area and the like, so 10 μm or less, more preferably 5 μm or less, most preferably 1 μm or less. It is good to do. The lower limit of the particle size is not particularly limited, but is 0.01 μm or more, more preferably 0.1 μm or more.

The carbonaceous fine particles of the present invention are polymer particles mainly composed of a hydrophobic vinyl polymer containing an acrylonitrile monomer, wherein the content of acrylonitrile monomer in the outer shell is acrylonitrile in the central portion. The core-shell type polymer particles having a content higher than the content are calcined to thermally decompose the central part to make it hollow, whereby it can be easily produced. Further, the core-shell type polymer fine particles are obtained by emulsion-polymerizing a hydrophobic monomer having a vinyl group in water on the surface of a seed particle, and acrylonitrile or a derivative thereof as a main component is seed-polymerized. However, the carbonaceous fine particles of the present invention are not limited by the production method.

The hydrophobic monomer having a vinyl group, in the presence or absence of a usual emulsifier, is easily emulsified into microspheres in water due to its hydrophobicity, and is easily emulsified as seed particles for the subsequent seed polymerization. It becomes polymer fine particles. During the emulsification, by adjusting the temperature, the concentration of the monomer, the reaction time, etc.,
The particle size of the seed particles can be easily adjusted, and the particle size may be determined in consideration of shrinkage due to firing according to the desired particle size of the carbonaceous particles, but usually the average particle size is 0.001 to 50 μm, more preferably 0.1 to 10 μm
m, most preferably 0.2 to 1.0 μm. Generally, in order to form a sheet for applications such as electrodes, it is preferable that the particle size is small.

In this case, the hydrophobic monomer having a vinyl group to be used is not particularly limited, but styrene, methyl methacrylate, ethyl methacrylate, butyl methacrylate, vinyl acetate and the like can be used. Although acrylonitrile can be used, its content is preferably 50 mol% or less, more preferably 30 mol% or less.

Next, the polymer fine particles synthesized by the above-mentioned method are seed-polymerized by adding a predetermined amount of acrylonitrile-based monomer as a seed for polymer formation reaction, that is, as seed particles. In this way, fine particles of a core-shell type polyacrylonitrile copolymer having an outer shell containing polyacrylonitrile as a main component are produced. In addition to acrylonitrile, other hydrophobic monomers having a vinyl group may be added during the seed polymerization. In that case, it is preferable that the content of acrylonitrile is at least 50 mol% or more, more preferably 70 mol% or more in order to maintain the strength of the hollow carbonaceous fine particles.

As the polymerization initiator, it is preferable to use a general water-soluble polymerization initiator. Specifically, azo-based 2,2′-azobis (2-amidinopropane) hydrochloride, a peroxide salt or the like can be used. The amount of acrylonitrile added is such that the size of the resulting core-shell polymer particles is 0.01 to 50 μm in diameter, preferably 0.1 to 10 μm, and most preferably 0.2 to 1.0 μm.
It is better to adjust the amount added so that Further, the above-mentioned polymerization reaction is preferably carried out in an inert gas atmosphere such as argon, helium or nitrogen gas. The temperature of the polymerization reaction is 0 to 200 ° C., more preferably room temperature to 1
In the range of 00 ° C, the reaction time is preferably 1 second to 50 hours, more preferably 1 minute to 10 hours, and appropriately adjusted according to the desired particle size.

The core-shell type polymer fine particles thus synthesized are separated by a method such as filtration or centrifugation. If necessary, it is washed with water to remove impurities such as a polymerization initiator and then dried. By firing the obtained core-shell type polymer particles, hollow carbonaceous particles can be produced. The firing is usually argon, helium,
It is carried out in a stream of an inert gas such as nitrogen gas, but if the temperature is selected such that only the central part is burnt out and the outer shell part is not burnt out, it is possible to carry out the baking in air. The firing temperature is 200 to 32
It can be appropriately selected in the range of 50 ° C, preferably 300 to 2800 ° C.

Further, micropores were developed in the hollow carbonaceous fine particles which were calcined at 600 to 1300 ° C. in the atmosphere of steam, carbon dioxide gas or a mixed gas thereof, or a gas obtained by diluting these with an inert gas. It is also possible to obtain porous hollow carbonaceous fine particles. In the firing, the core-shell type polymer fine particles may be preliminarily applied with pressure to be molded, and then fired in the form of a molded body. In this case, it is possible to manufacture a structure in which hollow carbonaceous fine particles are in close contact with each other and which is sintered to some extent.

The structure manufactured in this manner is rich in elasticity and has flexibility. When it is formed into a sheet, it becomes a deformable carbon material that can be bent. Further, this structure has a property that it contracts and deforms when a pressing force is applied, but returns to its original shape when the pressure is released. Incidentally, at the time of the above-mentioned seed polymerization, as a monomer component to be added in addition to acrylonitrile, at least one kind of monomer having a functional group in which a metal compound is easily coordinated, which is a monomer copolymerizable with acrylonitrile, By adding and then reacting with a metal compound, it is possible to obtain polymer fine particles whose outer shell part is composed of a metal-complexed polyacrylonitrile copolymer. Then, by firing the polymer fine particles, the carbonaceous fine particles carrying the metal can be carved. Examples of the hydrophobic monomer having a functional group in which the other metal compound in this case is easily coordinated include acrylic acid, methacrylic acid, maleic acid, itaconic acid,
Styrene sulfonic acid, vinyl sulfonic acid, acrylamide, methacrylamide, acryloylmorpholine, dimethylaminoethyl acrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylamide, their salts and quaternary compounds, vinylpyrrolidone, vinylpyridine, vinylimidazole, etc. Can be mentioned.

The content of these monomers may be determined depending on the amount of the metal to be supported, but for the above-mentioned reasons of strength, at least 50 mol% of acrylonitrile,
It is more preferably 70 mol% or more.
Examples of the metal compound to be coordinated include Ti, V, C
r, Mn, Fe, Co, Ni, Cu, Zn, Ru, M
Examples thereof include compounds of transition metals such as o, Rh, Pd, Ag, Pt, and Au, and halides of these metals, thiolate compounds, cyano compounds, amine compounds, carbonyl compounds and the like can be used.

Further, the metal compound can be supported on the surface even when the outer shell is a polymer of acrylonitrile alone. By firing the core-shell type polymer fine particles coordinated with the metal complex, hollow carbonaceous fine particles carrying ultrafine metal particles are obtained.

[0020]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In each Example or Comparative Example, the particle size of the obtained carbonaceous fine particles and the diameter of the hollow portion were obtained from a transmission electron microscope photograph or a scanning electron microscope photograph.

(Example 1) 4.2 g of styrene and 200 g of water were charged into a 300 ml flask equipped with a reflux condenser, a thermometer, an Ar introduction tube and a stirrer, and the mixture was heated to 70 in an Ar stream.
Heated at ° C. Then, 0.054 g of potassium persulfate was added and polymerized for 30 minutes, and 8.5 g of acrylonitrile was added dropwise to the obtained polymer dispersion over 1 hour. Then, the reaction was carried out for 5 hours to obtain a polymer fine particle dispersion liquid. The average particle size of the obtained polymer fine particles was 0.36 μm. The obtained fine particle dispersion liquid is dried, and the temperature is 400 in a firing furnace under Ar flow.
As a result of firing at 4 ° C. for 4 hours, carbonaceous fine particles having an average hollow diameter of 0.17 μm and an average particle diameter of 0.25 μm were obtained. (Examples 2 to 8) Polymer fine particles and carbon fine particles were prepared in exactly the same manner as in Example 1 except that the monomer composition (total concentration was constant) and the firing temperature were changed as shown in Table 1. Obtained. Table 1 shows the average particle diameter of the polymer fine particles and the average hollow diameter of the carbonaceous fine particles. The particle structure of the carbonaceous fine particles obtained in Example 2 is shown in FIG.

[0022]

[Table 1] <Table 1> ───────────────────────────────── Implementation Monomer composition Polymer fine particles Firing Temperature Average hollow diameter Example No. (molar ratio) Average particle diameter (μm) (℃) (μm) ──────────────────────────── ────── 1 AN / St = 8/2 0.36 400 0.17 2 AN / St = 8/2 0.36 600 0.18 3 AN / St = 8/2 0.36 800 0. 18 4 AN / St = 9/1 0.29 600 0.15 5 AN / St = 7/3 0.40 600 0.27 6 AN / St = 6/4 0.28 400 0.20 7 AN / St = 6/4 0.28 600 0.20 8 AN / St = 6/4 0.28 800 0.20 ───────────────────────── ───────── AN: Acrylonitrile, St: Styrene

(Example 9) 2.1 g of styrene and 200 g of water were charged into a 300 ml flask equipped with a reflux condenser, a thermometer, an Ar introducing tube and a stirrer, and the mixture was heated to 70 under Ar flow.
Heated at ° C. Then, 0.0541 g of potassium persulfate was added and polymerized for 30 minutes, and 9.5 g of acrylonitrile was added dropwise to the obtained polymer dispersion over 1 hour. Then, the reaction was carried out for 5 hours to obtain a polymer fine particle dispersion liquid. The average particle size of the obtained polymer fine particles was 0.29 μm.

To 50 g of the polymer fine particle dispersion, 50 g of an aqueous solution containing 0.35 g of palladium chloride was added at room temperature.
After stirring for 1 hour, the dispersion was centrifuged and the supernatant was removed to obtain palladium-supporting fine particles. The palladium-supported fine particles are dried and then heated in a firing furnace under Ar flow for 10
As a result of firing at 00 ° C. for 4 hours, palladium-supporting carbonaceous fine particles having an average hollow diameter of 0.15 μm were obtained. (Examples 10 to 11) Polymer fine particles and metal were prepared in exactly the same manner as in Example 9 except that the monomer composition (total concentration was constant), firing temperature and metal compound were changed as shown in Table 2. Supported carbonaceous fine particles were obtained. Table 2 shows the average particle diameter of the polymer fine particles and the average hollow diameter of the carbonaceous fine particles.

[0025]

[Table 2] <Table 2> ──────────────────────────────────── Implementation Monomer composition Particles of coalesced metal compound Firing temperature Average hollow diameter Example No. (molar ratio) Average particle diameter (μm) (℃) (μm) ─────────────────────── ────────────── 9 AN / St = 9/1 0.29 PdCl ₂ 1000 0.15 10 AN / St = 9/1 0.29 AgNO ₃ 800 0.15 11 AN / St = 9/1 0.29 FeCl ₃・ 6H ₂ O 800 0.15 ──────────────────────────────── ───── AN: Acrylonitrile, St: Styrene

(Embodiment 12) Reflux condenser, thermometer, Ar
2.1 g (20 mmol) of styrene and 190 g of water were charged into a 300 ml flask equipped with an introduction tube and a stirrer, and heated at 70 ° C. under Ar flow. Then, 0.0541 g of potassium persulfate was added and polymerized for 30 minutes, and 8.5 g of acrylonitrile (160 g) was added to the obtained polymer dispersion.
mmol) and 1.5 g of acrylic acid were added dropwise over 1 hour. Then, the reaction was carried out for 5 hours to obtain a polymer fine particle dispersion liquid. The average particle size of the obtained polymer fine particles is 0.29μ.
It was m. 100 g of 0.1N aqueous sodium hydroxide solution was added to 100 g of the polymer fine particle dispersion, and the mixture was stirred at room temperature for 1 hour.
After stirring for a time, the liquid was redispersed in ethanol. 100 g of the dispersion is placed in a flask and 2.3 g of cobalt chloride.
Was added at room temperature. After stirring for 1 hour, the dispersion was centrifuged and the supernatant was removed to obtain cobalt-supporting carbonaceous fine particles. The cobalt-supported fine particles were dried and calcined at 800 ° C. for 2 hours in a firing furnace under an Ar stream, and as a result, cobalt-supported carbonaceous fine particles having an average hollow diameter of 0.15 μm and an average particle diameter of 0.24 μm were obtained. A transmission electron micrograph of the obtained cobalt-supporting carbonaceous fine particles is shown in FIG. It can be seen that metallic cobalt exists inside the fine particles. Further, the X-ray diffraction spectrum is shown in FIG. The diffraction spectrum corresponding to metallic cobalt is clearly visible.

(Examples 13 to 16) Polymers were prepared in the same manner as in Example 12 except that the monomer composition (total concentration was constant), firing temperature and metal compound were changed as shown in Table 3. Fine particles and metal-supported carbonaceous fine particles were obtained. Table 3 shows the average particle diameter of the polymer fine particles and the average hollow diameter of the carbonaceous fine particles. (Example 17) A 300-ml flask equipped with a reflux condenser, a thermometer, an Ar introduction tube, and a stirrer was charged with 2.0 g of methyl methacrylate and 200 g of water, and the mixture was heated to 70 under an Ar stream.
Heated at ° C. Then, 0.0541 g of potassium persulfate was added and polymerized for 30 minutes, and 9.5 g of acrylonitrile was added dropwise to the obtained polymer dispersion over 1 hour. Then, the reaction was carried out for 5 hours to obtain a polymer fine particle dispersion liquid. The average particle size of the obtained polymer fine particles was 0.30 μm. The obtained fine particle dispersion liquid is dried, and is dried in a firing furnace under an Ar stream.
As a result of firing at 0 ° C. for 4 hours, carbonaceous fine particles having an average hollow diameter of 0.15 μm and an average particle diameter of 0.25 μm were obtained.

[0028]

[Table 3] <Table 3> ─────────────────────────────────── Implementation Monomer Composition Polymer Fine particle metal compound Firing temperature Average hollow diameter Example No. (molar ratio) Average particle diameter (μm) (℃) (μm) ───────────────────────── ──────────── 12 AN / AA / St = 8/1/1 0.29 CoCl ₂・ 6H ₂ O 800 0.15 13 AN / AA / St = 8/1/1 0 _{.29 NiCl 2 · 6H 2 O 1000} 0.15 14 AN / AA / St = 85/5/10 0.29 CoCl 2 · 6H 2 O 800 0.15 15 AN / AA / St = 85/5/10 0 _{.29 NiCl 2 · 6H 2 O 1000} 0.15 16 AN / AA / St = 8/1/1 0.29 PdCl 2 1000 0.15 ───────────────── ────────────────── 17 AN / MMA = 8/2 0.30 ──── 400 0.15 ────────────── ──── ────────────────── AN: Acrylonitrile, AA: Acrylic acid, St: Styrene MMA: Methyl methacrylate

(Embodiment 18) Reflux condenser, thermometer, Ar
A 300 ml flask equipped with an introduction tube and a stirrer was charged with 8.32 g of styrene and 200 g of water, and heated at 70 ° C. under an Ar stream. Then potassium persulfate 0.0541
g was added thereto, the mixture was polymerized for 30 minutes, and 6.36 g of acrylonitrile was added dropwise to the obtained polymer dispersion over 1 hour. Then, the reaction was carried out for 5 hours to obtain a polymer fine particle dispersion liquid.
The average particle size of the obtained polymer fine particles was 0.28 μm. The obtained fine particle dispersion is dried, and 3 g thereof is pressed with a tablet press at 200 kg / cm ² for 1 minute, and then Ar
As a result of firing at 800 ° C. for 4 hours in a firing furnace, carbonaceous fine particles having an average hollow diameter of submicron size were obtained.

(Example 19) The polymer fine particles having an average particle size of 0.36 μm produced in Example 1 were dried, and then the diameter was 7 m.
The container was placed in a cylindrical container having a height of 3 mm and a height of 3 mm, and the container was baked at 800 ° C. for 2 hours in a baking furnace under an argon gas flow. As a result, a molded body having cylindrical carbon fine particles adhered thereto and having high elasticity was obtained. The compact elastically recovered to its original size when it was shrunk by applying compressive pressure. Further, when it was observed with a high resolution transmission electron microscope, it was confirmed that it was composed of carbonaceous fine particles having an average particle diameter of 0.2 μm and a hollow portion having an average diameter of 0.17 μm inside.

[0031]

EFFECTS OF THE INVENTION The carbonaceous fine particles of the present invention have a unique shape of being hollow, and thus exhibit various useful physical properties as a functional material such as a large specific surface area and shape retention. By previously containing a material having a functional group capable of easily coordinating a metal compound as a material for forming the outer shell, the metal compound can be easily and firmly supported, and the carbonaceous fine particles are magnetic. Materials, IC related materials,
It is expected to have various uses such as a capacitor, an electrode material for a secondary battery, and a catalyst, and provides a great industrial benefit. Further, according to the method for producing carbonaceous fine particles of the present invention, the carbonaceous fine particles exhibiting such useful physical properties can be easily produced.

[Brief description of drawings]

FIG. 1 is a drawing showing a particle structure of carbonaceous fine particles obtained in the present invention.

FIG. 2 is a transmission electron micrograph showing the particle structure of the cobalt-supporting carbonaceous fine particles obtained in the present invention.

FIG. 3 is a drawing showing an X-ray spectrum of the cobalt-supporting carbonaceous fine particles obtained in the present invention.

Claims (4)

[Claims] 1. Fine particles of a carbonaceous substance, which have a hollow portion. 2. The carbonaceous fine particles according to claim 1, which carry a metal. 3. Polymer particles mainly composed of a polymer obtained by polymerizing a hydrophobic monomer having a vinyl group, wherein the content of acrylonitrile monomer in the outer shell portion is acrylonitrile monomer in the central portion. A method for producing carbonaceous fine particles, characterized in that core-shell type polymer fine particles having a content higher than the content are fired to thermally decompose the central portion to make it hollow. 4. The core-shell type polymer microparticles are obtained by emulsion-polymerizing a hydrophobic monomer having a vinyl group in water, and seed particles are formed on the surface of acrylonitrile or a derivative thereof as a main component. 4. The method for producing carbonaceous fine particles according to claim 3, wherein the carbonaceous fine particles are seed-polymerized.