JP6333601B2 - Method for producing flaky carbon using plant extract - Google Patents

Description

  The present invention relates to a method for producing flaky carbon using a plant extract. In particular, flaky carbon, flaky carbon composition for use in conductive materials, heat transfer materials, power storage devices such as transistors and capacitors, sensors, piezoelectric materials, antibacterial materials, filtration materials, resin additives, optical materials, Alternatively, the present invention relates to a method for producing a flaky carbon dispersion.

The graphene sheet is a two-dimensional single-layer sheet in which carbon atoms are arranged in a honeycomb lattice shape, and is also a structural unit such as graphite, fullerene, and carbon nanotube. The flaky carbon in which the graphene sheet is laminated to a thickness of about 10 nm or less (in the present invention, the concept including the graphene sheet) has its unique properties (for example, a Young's modulus of 1.0 in the case of a single-layer graphene sheet). TPa, carrier mobility 200000 cm ² V ^-1 s ^-1, electrical conductivity 30 · □ ^-1, since it has a thermal conductivity 5000 Wm ^-1 K ^-1, etc.), conductive material, the heat transfer material It is attracting attention as a new material used for power storage devices such as transistors and capacitors, sensors, piezoelectric materials, antibacterial materials, filtration materials, resin additives, optical materials and the like.

As a method for producing flaky carbon,
(1) Mechanical exfoliation method using tape, etc. (2) Formation on metal foil by CVD (3) Heating of SiC substrate (4) Delamination by oxidation of graphite and reduction of graphene oxide obtained ing.

  Among these, the methods (1) to (3) have a problem in mass productivity and are difficult to isolate because flaky carbon is obtained on the substrate or attached to the tape. In particular, in the case of flaky carbon having a small thickness, it is almost impossible to isolate the flaky carbon by peeling off from these substrates or tapes. Moreover, even if it can be isolated, the flaky carbon obtained by these methods is very easily aggregated, and it is very difficult to isolate it in a dispersed state. It is also very difficult to peel off the agglomerated flaky carbon.

  On the other hand, the method (4) is a process in which graphite oxide generated by oxidizing graphite is delaminated by ultrasonic treatment or the like to obtain graphene oxide, which is then reduced to graphene. When this method is employed, if graphene oxide is reduced in the liquid, aggregation occurs and film formation cannot be performed. Moreover, it is difficult to peel the aggregated graphene on a sheet-by-sheet basis. In order to prevent agglomeration after reduction, the coexistence of a surfactant such as sodium dodecylbenzenesulfonate has been studied (Non-patent Document 1). However, since intense oxidation and reduction are performed, it is very difficult to obtain flaky carbon while maintaining the graphene structure, and there is also a problem in safety. Furthermore, even if this method is adopted, flaky carbon is precipitated, and dispersion stabilization in the liquid has not been achieved.

  Thus, although flaky carbon has excellent physical properties, it is very difficult to isolate it in a dispersed state, and a method for this is required.

  On the other hand, in food factories, energy and transportation costs are required for the treatment of residues containing a lot of moisture, and it is desired to effectively utilize these. In tea and coffee, excessive crushing and extraction causes quality problems such as taste and problems such as extraction efficiency. Therefore, excessive crushing and extraction are usually not performed in order to increase commercial value. Therefore, many unused components remain in the extraction residue of tea and coffee. Furthermore, for foods extracted with water, it is considered that the components that are soluble only in organic solvents remain.

Adv. Funct. Mater. 2010, 20, 2893-2902

  An object of the present invention is to provide a method that can be obtained in a state in which flaky carbon can be stably dispersed using an inexpensive material and a simple process. Another object of the present invention is to provide a flaky carbon, a flaky carbon composition and a flaky carbon dispersion obtained by using this method.

  As a result of intensive studies to achieve the above object, the present inventors have performed a powerful ultrasonic treatment and / or high pressure treatment on a carbonaceous material having a layered structure in the presence of a plant extract. Thus, it has been found that flaky carbon can be obtained in a state where it can be stably dispersed despite the use of an inexpensive material and a simple process. The inventors of the present invention have further studied based on the findings and have completed the present invention. That is, this invention includes the following structures. That is, this invention includes the following structures.

Item 1. A method for producing flaky carbon,
In the presence of plant extracts, carbonaceous materials with a layered structure
The manufacturing method which performs at least 1 process of (1) pressurization of 30 Mpa or more and (2) ultrasonic dispersion process of 100 W or more.

Item 2. For a carbonaceous material dispersion having a layered structure, a plant extract, and a solvent,
Item 2. The manufacturing method according to Item 1, wherein at least one of (1) pressurization of 30 MPa or more and (2) ultrasonic dispersion treatment of 100 W or more is performed.

  Item 3. Item 3. The production method according to Item 2, wherein the solvent contains water, and the content of the water is 70% by weight or more in the solvent.

  Item 4. Item 4. The production method according to any one of Items 1 to 3, wherein the plant extract contains polyphenol.

  Item 5. Item 5. The production method according to Item 4, wherein the plant extract further contains a heterocyclic ring-containing compound.

  Item 6. Item 6. The production method according to Item 5, wherein the heterocyclic ring-containing compound is a compound containing in the molecule at least one selected from the group consisting of a tetrapyrrole ring, a pyrrole ring, a pyrazine ring, a pyridine ring, and a xanthine skeleton. .

  Item 7. Item 7. The production method according to any one of Items 1 to 6, wherein the plant extract is an extract obtained by extracting an extraction residue obtained by extracting a plant with water with a solvent.

  Item 8. Item 8. The method according to Item 7, wherein the solvent contains 50% by weight or more of an organic solvent.

  Item 9. Item 9. The method according to Item 8, wherein the extract is treated with at least one selected from the group consisting of organic ammonium, alkali metal, ammonium, and polyalkylene oxide.

Item 10. By pressurizing (1) above,
(I) causing two or more carbonaceous material dispersions to collide with each other; (ii) causing the carbonaceous material dispersion to collide with a metal or ceramic material; and (iii) isolating the carbonaceous material dispersion. Item 10. The production method according to any one of Items 2 to 9, wherein at least one treatment selected from the group consisting of passing through a space having an area of 1 cm ² or less is performed.

  Item 11. Item 11. The production method according to any one of Items 1 to 10, wherein the carbonaceous material having a layered structure is contained at a concentration of 10% by weight or less.

  Item 12. Item 12. A flaky carbon obtained by the production method according to any one of items 1 to 11.

  Item 13. Item 13. The flaky carbon according to Item 12, having a thickness of 10 nm or less.

Item 14. A method for producing a flaky carbon dispersion,
For a carbonaceous material dispersion having a layered structure, a plant extract, and a solvent,
The manufacturing method which performs at least 1 process of (1) pressurization of 30 Mpa or more and (2) ultrasonic dispersion process of 100 W or more.

  Item 15. Item 15. A flaky carbon dispersion obtained by the production method according to Item 14.

  Item 16. Item 15. A method for producing a flaky carbon composition containing flaky carbon and a plant extract, comprising obtaining a flaky carbon dispersion by the production method according to Item 14, and drying the solvent.

  Item 17. Item 17. A flaky carbon composition obtained by the production method according to item 16.

  Item 18. Item 18. The flaky carbon composition according to Item 17, wherein the content of the plant extract is 1 part by weight or more with respect to 100 parts by weight of the flaky carbon.

  Item 19. Item 17. A method for producing flaky carbon, comprising washing a flaky carbon composition obtained by the production method according to Item 16 with water or an organic solvent to remove a plant extract.

  Item 20. Item 20. A flaky carbon obtained by the production method of Item 19.

  According to the present invention, flaky carbon can be obtained in a state where it can be stably dispersed using an inexpensive material and a simple process.

  Further, according to the present invention, the flaky carbon is a flaky carbon-containing material of any aspect of the flaky carbon alone, the flaky carbon composition, and the flaky carbon dispersion, while suppressing aggregation. Can be obtained. That is, the versatility is high because the form to be used can be appropriately set according to the application. In particular, since the flaky carbon can be easily isolated and the flaky carbon can be uniformly mixed with other materials, application to a nanocomposite containing the flaky carbon is also expected.

The SEM observation image of Test Example 1 is shown.

1. Method for producing flaky carbon dispersion In the method for producing flaky carbon of the present invention, a carbonaceous material having a layered structure is obtained in the presence of a plant extract.
At least one of (1) pressurization of 30 MPa or more and (2) ultrasonic dispersion treatment of 100 W or more is performed.

The method of coexisting the carbonaceous material having a lamellar structure and the plant extract is not particularly limited, but a lamellar carbon dispersion in which flaky carbon is stably dispersed can be obtained and is easily applied to various applications. For a carbonaceous material dispersion containing a carbonaceous material, a plant extract, and a solvent,
It is preferable to perform at least one of (1) pressurization of 30 MPa or more and (2) ultrasonic dispersion treatment of 100 W or more.

The carbonaceous material having a carbonaceous material layered structure having a layered structure is not particularly limited, natural graphite, artificial graphite, expanded graphite, earthy graphite, graphite oxide, and the like. As the graphite oxide, for example, graphite oxidized with one or more oxidizing agents such as sulfuric acid, nitric acid, potassium permanganate, hydrogen peroxide and the like can be used. For example, when obtaining graphite oxide by the Hammers method, after immersing graphite in concentrated sulfuric acid, adding potassium permanganate to oxidize graphite, the reaction is quenched with dilute sulfuric acid and / or hydrogen peroxide, Thereafter, by washing with distilled water or the like, oxygen atoms are bonded to carbon atoms, and oxygen atoms are introduced between layers to obtain graphite oxide.

  In particular, when obtaining flaky carbon having a high purity that does not contain hetero atoms such as oxygen, graphite is preferably used as a raw material, and natural graphite and expanded graphite are more preferable. In addition, when using expanded graphite, it is preferable to employ | adopt expanded graphite with little oxidation of a graphene structure.

  In addition, graphite oxide may be used when importance is attached to manufacturing. By using graphite oxide, it is easy to insert solvent molecules between layers, it is easy to peel only in the layer direction, and the thinning efficiency and dispersibility are improved, so the processing time can be shortened. is there. However, when graphite oxide is used, reduction treatment is necessary later, and from the viewpoint of maintaining the graphene structure, conductivity and strength, other materials (natural graphite, artificial graphite, expanded graphite, earthy graphite) Is preferred.

  On the other hand, in order to further improve dispersibility, earth graphite can be employed. However, from the viewpoint of crystallinity and structure maintenance, other materials (natural graphite, artificial graphite, expanded graphite, graphite oxide) are preferable.

  In addition, artificial graphite may be used when importance is attached to the crystallinity, strength, structure maintenance, etc. of the flaky carbon obtained. However, since the treatment time tends to be longer, other materials (natural graphite, artificial graphite, expanded graphite, earth graphite, graphite oxide) are preferable for further efficiency.

  From the above, natural graphite or expanded graphite is particularly preferable in consideration of the balance of purity, ease of production, graphene structure maintenance, conductivity, strength, and the like.

  In the present invention, the content of the carbonaceous material having a layered structure in the system when performing ultrasonic treatment and / or pressure treatment is not particularly limited, but is preferably 10% by weight or less, and 0.0001 to 7% by weight. More preferably, 0.001 to 5% by weight is even more preferable. In addition, the content of the carbonaceous material having a layered structure tends to make flaky carbon more efficient because thinning (delamination) is more likely to occur, and there is a tendency that the number of treatments can be reduced, There is a tendency to easily perform ultrasonic treatment, pressurization treatment, etc. while maintaining the viscosity appropriately. On the other hand, the higher the content of the carbonaceous material having a layered structure, the better the productivity. For this reason, it is preferable to appropriately set the content of the carbonaceous material having a layered structure from the viewpoint of the balance of flaking efficiency, viscosity, productivity, and the like. In the production method of the present invention, when a carbonaceous material dispersion is used, the content of the carbonaceous material having a layered structure in the dispersion is preferably within the above range.

Plant extracts Conventionally, when flaky carbon is produced by a wet method, a water dispersion containing graphene oxide and an aqueous solvent is subjected to a reduction treatment, but it is difficult to maintain the graphene structure by this method. At the same time, since the obtained flaky carbon agglomerates vigorously, it was difficult to obtain a graphene sheet aqueous dispersion. There was also a problem in terms of safety. On the other hand, in the present invention, by using a plant extract, it is possible to obtain flaky carbon in a uniformly dispersed state (flaky carbon dispersion or the like) without agglomerating the flaky carbon maintaining the graphene structure. it can. At this time, the plant extract can also function as a dispersant for uniformly dispersing the flaky carbon.

  The plant extract is not particularly limited as long as it is an extract obtained by extracting plant material with a solvent.

  The plant material is not particularly limited as long as it is a plant-derived material, and examples thereof include the plant itself, an extraction residue obtained by extracting the plant with a solvent, and the like. From the viewpoint that the residue that is usually discarded can be effectively used, an extraction residue obtained by extracting a plant with a solvent is preferable. Examples of the solvent include organic solvents such as ethanol and acetone, water, and the like.

  The plant used as the plant material is not particularly limited as long as it is a plant containing a polyphenol and / or a heterocyclic compound.

  The polyphenol is not particularly limited as long as it is a compound having two or more phenolic hydroxyl groups in the molecule. Specific examples of polyphenols include catechin, anthocyanin, tannin, rutin, isoflavone, chlorogenic acid, ellagic acid, lignan, curcumin, coumarin, and lignin degradation products.

  The heterocyclic ring-containing compound is not particularly limited as long as it is a compound containing a heterocyclic ring in the molecule and is not classified into the above polyphenol. Examples of the heterocyclic ring-containing compound include compounds containing in the molecule at least one selected from the group consisting of a tetrapyrrole ring, a pyrrole ring, a pyrazine ring, a pyridine ring, and a xanthine skeleton. More specifically, tetrapyrroles such as chlorophyll, alkaloids such as caffeine and nicotine, and the like can be mentioned.

  Examples of plants that can be used as plant materials include camellia plants such as tea tree, coffee genus plants such as coffee, grape genus plant, apple genus plant, genus genus plant such as blueberry, oyster genus plant such as camellia, and banana etc. Genus plants, artichokes and other genus plants, eye and other genus plants, irises and other iris plants, ashitaba and other genus plants, avocado and other crocodile plants, achacha and other hydrangea plants Genus plants, hollyhock genus plants such as Altea, Hanamyoga genus plants such as Alpinia katsudai, aloe genus plants such as aloe, ginkgo genus plants such as ginkgo, genus genus plants such as fennel, turmeric genus plants such as turmeric, ages Rose genus plants, purple pear genus plants such as Echinacea, Ogon Of the genus Pleurotus genus, the yellow genus plant such as the apricot, the auren genus plant such as the apricot, the troollae genus plant such as the okra, the genus Olysium plant such as the apricot, the citrus genus plant such as orange and grapefruit, the brown algae, the red algae and the green algae Seaweeds, cucumbers such as kakonm, deer plants such as chamomile, carrots such as carrots, mugworts such as strawberries, raspberries such as raspberry, matabies such as kiwi, cucumbers such as cucumber Gardenia plants such as Gardenia, Sasa plants such as Kumazasa, Clara plants such as Clara, Sennin plants such as Clematis, Chlorella plants such as Chlorella, Gentian plants such as Gentiana, and Saracia plants such as Kotara Himubutu , Rice genus plants such as rice, and genus Cypress , Plants such as cherry, cherry blossoms such as cherry, maple genus such as sugar maple, genus genus plants such as savonso, hawthorn plants such as hawthorn and hawthorn, salamander plants such as salam Plants of the genus Shea butter, etc., plants of the genus Acacia, such as Diou, plants of the genus Murasaki, such as Sicon, plants of the genus of Perilla such as Perilla, plants of the genus Shobu, such as honeysuckle, plants of the genus Papaver such as Psyllium Pear genus plants such as pears, Yarrow genus plants such as Achillea millefolium, Clam genus plants such as nematodes, Soybean genus plants such as soybean, Thymus genus plants such as thyme, Futomo genus plants such as clove, Eggplant genus plants such as tomatoes , Rose genus plants such as roses, polya genus plants such as beechweeds, And safflower plants such as na. Among these, preferably camellia genus plants such as tea tree, coffee genus plant such as coffee, grape genus plant, apple genus plant, genus genus plant such as blueberry, oyster genus plant such as strawberry, and genus plant such as banana. More preferable examples include camellia plants such as tea tree and coffee plant such as coffee. Moreover, the part of the plant used as plant material is not particularly limited, and leaves, stems, flowers, roots and the like can be used.

  From the viewpoint of transportation, it is desirable to use a dried plant material. However, since the extraction efficiency may be deteriorated and the water-soluble component may be insolubilized, it remains in a wet state or moisture. It is preferable to use a material that has been subjected to the minimum necessary drying to reduce the amount of water.

  The plant material is preferably finely pulverized from the viewpoint of increasing the extraction efficiency and extracting many components having low solubility. The means for pulverization is not particularly limited, and examples thereof include a mixer, a mill, a grinder, and a homogenizer. The mode of pulverization is not particularly limited, but for example, it is more preferable to add water or a solvent to the wet plant material and pulverize with a mixer or the like. The pulverization is preferably performed until the average particle size of the pulverized product is, for example, 1 mm or less, preferably 100 μm or less.

  One kind of plant material may be used alone, or two or more kinds of combinations may be used.

  The extraction solvent for the plant material is not particularly limited as long as it can extract polyphenols, heterocycle-containing compounds and the like in the plant. Examples of the extraction solvent include water and organic solvents. As an organic solvent, alcohol (for example, methanol, ethanol, propanol, butanol etc.), acetone, toluene etc. can be mentioned, for example. From the viewpoint that polyphenols and nitrogen-containing heterocyclic compounds can be extracted more efficiently, alcohols (particularly ethanol), acetone and the like are preferably cited as extraction solvents.

  One type of extraction solvent may be used alone, or two or more types may be used in combination. When it is a mixed solvent, it may be in a completely mixed state or in a separated state. Further, for example, in the case of a mixed solvent of water and an organic solvent, the content of the organic solvent is preferably 50% by weight or more, more preferably from the viewpoint that polyphenols and nitrogen-containing heterocyclic compounds can be extracted more efficiently. May be 70 wt% or more, more preferably 90 wt% or more.

  The extraction method is not particularly limited as long as polyphenols, heterocycle-containing compounds and the like in plants can be extracted. For example, a method in which the plant material is immersed in an extraction solvent and left (or stirred) can be mentioned.

  The extraction time is not particularly limited as long as polyphenols, heterocyclic compounds and the like in plants can be extracted. For example, it can be about 1 minute to 24 hours. By setting it longer, more plant components are extracted, but the extraction efficiency may be lowered. Therefore, from the viewpoint of extraction efficiency, it is preferably about 1 minute to 3 hours, more preferably about 1 minute to 30 minutes.

  The extraction temperature is not particularly limited as long as polyphenols, heterocyclic compounds and the like in plants can be extracted, and for example, a temperature of about room temperature to about 100 ° C. can be adopted.

  The obtained extract may be used as a plant extract as it is, or a dried, concentrated, or diluted product as a plant extract. From the viewpoint of transportation and storage, a dried product is preferable. However, when the drying temperature is high, the polymer may be polymerized and the water solubility may be lowered. Therefore, the drying means is preferably a means capable of instantaneous drying such as reduced pressure drying or spray drying.

  Moreover, when performing the manufacturing method of this invention using water as a solvent, it is desirable that the water solubility of more polyphenols and heterocyclic containing compounds in a plant extract is higher. Therefore, from this viewpoint, the plant extract is preferably water-solubilized according to a conventional method using organic ammonium, alkali metal hydroxide, ammonium, or polyalkylene oxide.

  As said organic ammonium, organic ammonium, such as quaternary ammonium, is used suitably, For example, tetraalkylammonium, such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, is preferable.

  Examples of the alkali metal include sodium, potassium, and lithium salts.

  Examples of the polyalkylene oxide include polyethylene oxide and polypropylene oxide.

  In the present invention, the content of the plant extract in the system when performing ultrasonic treatment and / or pressure treatment is not particularly limited, but is preferably 0.1 to 30% by weight in terms of dry weight of the plant extract, 0.5-25 weight% is more preferable and 1-20 weight% is further more preferable. On the other hand, in the present invention, the content of the plant extract to be input before the treatment is preferably 1 to 100,000 parts by weight in terms of the dry weight of the plant extract with respect to 100 parts by weight of the carbonaceous material having a layered structure, More preferred is 10 to 10,000 parts by weight.

Solvent In the present invention, as described above, the carbonaceous material having a layered structure is subjected to specific treatment in the presence of a plant extract. From the viewpoint of versatility of carbon and the like, it is preferable to perform a specific treatment on the carbonaceous material having a layered structure and the carbonaceous material dispersion containing the plant extract.

  The carbonaceous material dispersion may be formed as a dispersion or may be formed as a coating on the substrate.

  At this time, as a solvent used for preparing a dispersion (dispersion or coating film), it is preferable to use water as a main solvent from the viewpoint of the exfoliation efficiency of a carbonaceous material having a layered structure.

  The water content in the dispersion is not particularly limited, but is preferably 70% by weight or more (70 to 100% by weight), and preferably 75 to 99% by weight from the viewpoint of thinning efficiency of the carbonaceous material having a layered structure. Is more preferable.

  In the present invention, as the solvent, only water may be used and the organic solvent is not necessarily used. However, the solubility of the poorly water-soluble component in the plant extract to water is further improved. Therefore, alcohols such as methanol, ethanol, 2-propanol and t-butyl alcohol; glycols such as ethylene glycol; glycerin; and organic solvents such as 2-methoxyethanol may be used.

  The content of the organic solvent in the solvent to be used is preferably 50% by weight or less (0 to 50% by weight), more preferably 0 to 30% by weight, from the viewpoint of thinning efficiency of the carbonaceous material having a layered structure. .

  In the present invention, when a specific treatment is performed using a carbonaceous material dispersion using a solvent, the total amount of the solvent in the carbonaceous material dispersion (the total amount of liquid components in the plant extract and other solvents). Is not particularly limited, but is preferably 60 to 99.9998% by weight, more preferably 65 to 99.998% by weight, and still more preferably 75 to 99.98% by weight from the viewpoint of thinning efficiency of the carbonaceous material having a layered structure.

  In the present invention, when a specific treatment is performed using a carbonaceous material dispersion using a solvent, the carbonaceous material dispersion may be charged with a carbonaceous material having a layered structure in a plant extract dispersion. Alternatively, the plant extract may be put into a carbonaceous material dispersion having a layered structure. Further, the carbonaceous material having a layered structure and the plant extract may be simultaneously added to the solvent.

Other components In the present invention, when performing a specific treatment, the carbonaceous material having a layered structure may coexist with other components in addition to the plant extract. That is, another component may be included in the carbonaceous material dispersion before the specific treatment. Thereby, these other components can be contained also in the flaky carbon dispersion and flaky carbon composition finally obtained. Examples of such other components include carbon fibers (particularly carbon nanofibers having a fiber diameter of 500 nm or less), activated carbon, carbon black (acetylene black, oil furnace black, etc .; ketjen black having particularly high conductivity and a large specific surface area). , Glassy carbon, carbon microcoil, fullerene, biomass-based carbon materials (bagasse, sorghum, wood waste, sawdust, bamboo, bark, rice straw, rice husk, oak, rice straw, pulp waste, etc .; from lignin You may use the manufactured carbon fiber etc. in the range which does not impair the effect of this invention.

Treatment In the present invention, as described above, the carbonaceous material having a layered structure is subjected to a specific pressure treatment and / or a specific ultrasonic dispersion treatment in the presence of a plant extract. In addition, when using a carbonaceous material dispersion, a specific pressurization process and / or a specific ultrasonic dispersion process are performed with respect to a carbonaceous material dispersion.

  By applying pressure treatment, the carbonaceous material having a layered structure is atomized, and depending on the conditions, the graphene structure may not be maintained. However, the carbonaceous material having the layered structure can be thinned efficiently. And the processing time can be reduced. The pressure level at the time of performing such pressure treatment is not particularly limited as long as the carbonaceous material having a layered structure can be sufficiently thinned, but is 30 MPa or more, preferably 50 to 400 MPa. More preferably, it is 100 to 300 MPa. Such pressure treatment can be performed using a high-pressure dispersion device or the like.

By such pressurization, for example,
(I) causing two or more carbonaceous material dispersions to collide with each other;
(Ii) colliding the carbonaceous material dispersion with a metal or ceramic material;
(Iii) It is preferable to perform a treatment such as passing the carbonaceous material dispersion through a space having a cross-sectional area of 1 cm ² or less.

  According to the above (i) and (ii), it is possible to make the pressurization condition stronger, the thinning of the carbonaceous material having a layered structure can be performed more efficiently, and the processing time is further reduced. be able to. According to the above (iii), the carbonaceous material having a layered structure can be more appropriately thinned while maintaining the graphene structure. This pressurizing operation may be performed once or more, preferably 10 times or more.

  The pressurizing temperature is not particularly limited, and may be a temperature at which thinning of the carbonaceous material having a layered structure can be sufficiently performed.

  By applying the ultrasonic dispersion treatment, the carbonaceous material having a layered structure can be gradually thinned while further maintaining the graphene structure. As will be described later, the ultrasonic dispersion treatment may be performed as a pretreatment of the pressure treatment. The output when performing such ultrasonic dispersion treatment is not particularly limited, but is more powerful than the usual ultrasonic dispersion treatment (about 40 to 50 W) from the viewpoint of thinning the carbonaceous material having a layered structure. Preferably. Specifically, the output of the ultrasonic dispersion process is 100 W or more, preferably 300 to 20000 W, more preferably 400 to 18000 W.

  The ultrasonic dispersion temperature is not particularly limited, and may be set to a temperature at which thinning of the carbonaceous material having a layered structure can be sufficiently performed, and may be 0 to 80 ° C., particularly 10 to 70 ° C. The ultrasonic dispersion time is not particularly limited, and may be a time that allows the carbonaceous material having a layered structure to be sufficiently thinned, and may be 1 to 600 minutes, particularly 3 to 120 minutes.

  In addition, the said pressurization process and ultrasonic dispersion process may be performed independently, and may be performed in combination. In particular, when the pressure treatment is performed, it is preferable to perform an ultrasonic dispersion treatment described later as a preliminary treatment (pretreatment) to atomize the carbonaceous material having a layered structure.

  According to the above (i) and (ii), it is possible to make the pressurization condition stronger, the thinning of the carbonaceous material having a layered structure can be performed more efficiently, and the processing time is further reduced. be able to. According to the above (iii), the carbonaceous material having a layered structure can be more appropriately thinned while maintaining the graphene structure.

  In the present invention, when graphite oxide is used as the carbonaceous material having a layered structure, a flaky carbon oxide is contained in the dispersion subjected to the pressure treatment and / or ultrasonic dispersion treatment. Exist as. For this reason, when graphite oxide is used as the carbonaceous material having a layered structure, it is preferable to perform a reduction treatment as a post-treatment. As the reduction treatment, various methods such as chemical reduction and electrochemical reduction can be adopted, but chemical reduction is preferable. Of these, chemical reduction with a reducing agent such as hydrazine and sodium borohydride is preferred. The amount of the reducing agent is preferably 1 to 1000 parts by weight, more preferably 10 to 500 parts by weight, and still more preferably 50 to 300 parts by weight with respect to 100 parts by weight of the flaky carbon oxide. Moreover, when it heats at the time of reduction | restoration, it will become easier to reduce | restore. The heating temperature is preferably 40 to 200 ° C, more preferably 50 to 150 ° C, and further preferably 60 to 120 ° C. The reduction time is preferably 10 minutes to 64 hours, more preferably 30 minutes to 48 hours, and even more preferably 1 to 24 hours. However, it is preferable that the graphene structure is not excessively destroyed.

2. Flaky carbon dispersion According to the production method of the present invention described above, desired flaky carbon can be obtained. In particular, according to the production method of the present invention, a flaky carbon dispersion in which desired flaky carbon is dispersed can be obtained.

  The flaky carbon thus obtained is preferably thin because of its excellent physical properties. However, flaky carbon having a thickness of 10 nm or less, particularly 0.3 to 5 nm can be obtained. Although flaky carbon having a very large thickness may be obtained, the thickness of many flaky carbon is within the above range.

  The flaky carbon thus obtained is preferably thin because of its excellent physical properties. However, flaky carbon having a layered structure in which ten or fewer layers (that is, 1 to 10 layers) of graphene are laminated can be obtained. Although flaky carbon having a very large number of layers may be obtained, the number of flaky carbon layers is within the above range. Since such flaky carbon has a planar shape with many convex angles and concave angles, its size cannot be defined unconditionally. In the present specification, the distance between the convex angles that are farthest in one piece of flaky carbon is defined as the size of the flaky carbon.

  As such flaky carbon, those having a size of 200 nm or more, preferably 300 nm or more, more preferably 500 nm or more can be obtained. Such a flaky carbon can provide sufficient conductivity. In addition, since it is known that the larger flaky carbon is better in various physical properties such as electrical properties, the upper limit of the size is not limited. The size of the flaky carbon is measured by observation with a microscope (such as a laser microscope).

  According to the production method of the present invention, the flaky carbon can be obtained as a flaky carbon dispersion. In the production method of the present invention, since the plant extract is contained, the plant extract is also contained in the flaky carbon dispersion. Since this plant extract can be adsorbed on the surface of the flaky carbon and disperse the flaky carbon in a high concentration in a solvent, it functions as a dispersant in the flaky carbon dispersion. Moreover, the said plant extract can use a commercial item, and has an advantage over the conventional product in both cost and dispersibility. Furthermore, even if this plant extract remains on the flaky carbon surface, it can maintain sufficient conductivity, and the plant extract can be easily removed from the flaky carbon. is there.

  In addition, in the conventional method of performing oxidation treatment and reduction treatment, the plastic substrate is hydrolyzed during the reduction treatment, and flaky carbon aggregates when subjected to the reduction treatment, so that it cannot exist as a dispersion. From the above, it was impossible to form a flaky carbon dispersion on a plastic substrate. However, in the present invention, polyethylene terephthalate (PET) or the like can be obtained by performing a specific treatment while containing the plant extract. It is also possible to form a flaky carbon dispersion on the substrate without subjecting the plastic substrate to hydrolysis. In addition, as described above, it is easy to separate and purify flaky carbon from this flaky carbon dispersion, and it is also possible to uniformly mix flaky carbon with other materials, so nanocomposites containing flaky carbon, etc. Applicable to. Further, the flaky carbon composition, which is a dried product of the flaky carbon dispersion, has excellent physical properties such as conductivity even if it contains a plant extract, and easily removes the remaining plant extract. Therefore, it can be applied to various uses such as conductive materials, heat transfer materials, power storage devices such as transistors and capacitors, sensors, piezoelectric materials, antibacterial materials, filtration materials, resin additives, and optical materials.

3. Flaky carbon composition and flaky carbon In the present invention, the flaky carbon composition is a dried product of the flaky carbon dispersion and contains flaky carbon and a plant extract. Although there is no restriction | limiting in particular as a shape of such a flaky carbon composition, A coating film, a sheet | seat, a lump, etc. can be mentioned.

  In order to obtain a dried product, in addition to drying the flaky carbon dispersion, a method of drying the flaky carbon dispersion on a substrate after spin coating or coating, the flaky carbon composition is recovered by ordinary solid-liquid separation. It can be implemented by a method or the like. As a method of performing this separation, for example, a method used for usual solid-liquid separation, for example, a method of filtering using a filter paper, a glass filter or the like; a method of filtering after centrifugation; a method of using a vacuum filter Can be illustrated. Next, it does not specifically limit as a drying method, For example, the method of drying for about 1 to 24 hours at about 50-200 degreeC using a warm air dryer etc. can be illustrated.

The flaky carbon composition thus obtained has not only sufficient conductivity but also excellent gas barrier properties. In the present invention, the flaky carbon composition has a plant extract remaining on the flaky carbon surface. However, the plant extract can be removed if necessary, although it may have various physical properties such as electrical conductivity. Specifically, the plant extract can be removed by washing the flaky carbon composition with water, an organic solvent or the like. The washing treatment can be removed by washing with a dilute acid or dilute alkali in addition to water and an organic solvent.

  Conventional dispersants are many types of surfactants used in so-called detergents. These are thought to be adsorbed by utilizing the hydrophobic interaction between dispersant molecules and flaky carbon, and the molecular weights are compared. Therefore, it is thought that its adsorption power is also large. On the other hand, polyphenols and heterocycle-containing compounds in the plant extract used in the present invention are adsorbed using π-π interaction with flaky carbon, and therefore can only be adsorbed in an aqueous medium and have a molecular weight. Therefore, the adsorption power is weak compared to the conventional products. Therefore, the plant extract used by this invention has the advantage that it is easier to remove from a flaky carbon composition than a conventional product.

  Washing for removing the plant extract can be performed by bringing the flaky carbon composition into contact with the washing liquid. As the washing liquid, water, various organic solvents, and the like can be used as long as they can dissolve the plant extract. As the organic solvent, for example, alcohols such as methanol, ethanol, isopropyl alcohol (IPA) (particularly lower alcohols having 1 to 6 carbon atoms), acetone, N-methylpyrrolidone, dimethylformamide and the like can be used. These may be used alone or in combination of two or more.

  Among these, an organic solvent that evaporates from the flaky carbon composition in a short time after washing is preferable. Examples of the organic solvent include those having a boiling point at normal pressure of about 50 to 250 ° C., particularly about 60 to 200 ° C., such as methanol, ethanol, acetone, N-methylpyrrolidone, dimethylformamide and the like.

  Moreover, you may perform washing | cleaning for removing a plant extract by making a flaky carbon composition and a dilute acid or a dilute alkali contact, and then washing with water as mentioned above. The diluted acid is preferably 0.1 to 5% hydrochloric acid, and the diluted alkali is preferably 0.1 to 3% aqueous ammonia.

  The cleaning operation may be performed by bringing the cleaning liquid into contact with the flaky carbon composition. For example, it is preferable that the flaky carbon composition recovered from the flaky carbon dispersion is gently immersed in the cleaning liquid at room temperature. The immersion time is preferably within 30 minutes, and more preferably within 20 minutes in order to maintain the shape of the flaky carbon composition.

  The amount of the cleaning liquid used is not particularly limited as long as it is an effective amount for cleaning, and can be appropriately selected from a wide range. In general, the cleaning liquid is 100 to 100000 parts by weight with respect to 100 parts by weight of the flaky carbon composition. Good results are obtained when about 1 part, especially about 1000 to 5000 parts by weight is used.

  Thus, the flaky carbon can be isolated, and the flaky carbon obtained at this time has the characteristics as described above.

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

Production Example 1
After 90 ° C. hot water was poured into the tea leaves and immersed for 3 hours, the extract was removed. 600 g of water was added to 58 g of wet tea leaves, and pulverized with a mixer for 1 minute. The solution was centrifuged at 18890 g for 10 minutes. The supernatant was filtered under reduced pressure using hydrophilized PTFE filter paper. Further, about 30 to 60 g of water was added to the centrifugal precipitate and mixed, followed by filtration under reduced pressure in the same manner as the supernatant. As a result, 580 g (solid content concentration 0.4%) of a green liquid was obtained as a filtrate. This solution was concentrated to prepare a solution having a solid content concentration of 1% (referred to as Dispersant 1).

  The weight of the residue obtained by filtration was 67 g, and the amount of adsorbed water increased as much as the specific surface area increased by pulverization. Ethanol 400g was added to this residue, and it stirred at normal temperature for 1 hour. When filtration was performed under reduced pressure, 420 g of a dark green transparent liquid (solid content concentration 0.4%) and 40 g of residue were obtained including ethanol used for washing. This solution was concentrated and subjected to solvent replacement with water to prepare a solution having a solid concentration of 1% (referred to as Dispersant 2).

Production Example 2
After 90 ° C. hot water was poured into the tea leaves and immersed for 1 hour, the extract was removed. 400 g of ethanol was added to 43 g of wet tea leaves, and pulverized with a mixer for 1 minute. By filtering the liquid under reduced pressure, 450 g of a dark green transparent liquid (solid content concentration 0.9%) and 26 g of a residue were obtained. This solution was concentrated, water and solvent substitution were performed, and a solution with a solid content concentration of 1% was prepared (referred to as Dispersant 3).

  To the residue obtained by filtration, 100 g of acetone was added and kept at 50 ° C. for 30 minutes. After filtration under reduced pressure, 127 g of a green transparent liquid including acetone used for washing (solid content concentration 0.2 %) And 9 g of residue were obtained. When this solvent was once dried and water was added again, it did not dissolve at all. However, when a 25% aqueous solution of tetramethylammonium hydroxide was added dropwise, the solid content was dissolved and a brown transparent aqueous solution was obtained. The concentration was not adjusted, and the weight was adjusted to 100 g (referred to as Dispersant 4).

Production Example 3
The residue obtained after paper drip was dried at room temperature to obtain 28 g of coffee extraction residue. Acetone 100g was added to this, and extraction was performed at 50 degreeC for 1 hour. Thereafter, filtration under reduced pressure resulted in 90 g of a dark brown liquid (solid content concentration 2.0%). When water was added to this and concentrated to remove the acetone content, an insoluble matter was generated and it became cloudy. To this heterogeneous liquid, a 25% aqueous solution of tetramethylammonium hydroxide was added dropwise until the solid content dissolved and a brown transparent aqueous solution was obtained, and finally the solid content concentration was adjusted to 1% (dispersant 5). And).

Production Example 4
The residue obtained after the paper drip was dried at room temperature to obtain 59 g of a coffee extraction residue. 200g of ethanol was added to this, and it heated up at 70 degreeC, and extracted for 1 hour. Thereafter, as a result of filtration under reduced pressure, 160 g (solid content concentration: 1.4%) of a dark brown liquid was obtained. Water was added to this solution and concentrated to remove ethanol, and the solution became cloudy. To this heterogeneous liquid, a 25% aqueous solution of tetramethylammonium hydroxide was added dropwise until a brown transparent aqueous solution was obtained, and the solid content concentration was finally adjusted to 1% (referred to as Dispersant 6).

Example 1
To 100 g of Dispersant 1, 0.01 g of expanded graphite (made by Ito Graphite) was added. This was subjected to a dispersion treatment for 30 minutes while cooling with ice at an output of about 400 W using an ultrasonic dispersion apparatus. As a result, a uniform dispersion was obtained. When the dispersion was applied to conductive glass and observed with SEM, flaky carbon (thickness of 10 nm or less, about 3 to 20 layers) was observed. This observation image is shown in FIG.

Example 2
To 100 g of Dispersant 1, 0.01 g of expanded graphite (made by Ito Graphite) was added. This was subjected to a dispersion treatment for 5 minutes while cooling with ice at an output of about 400 W using an ultrasonic dispersion apparatus. Furthermore, using a high-pressure dispersing device, a dispersion treatment was performed 40 times by colliding with an eccentric ceramic ball at a treatment pressure of about 250 MPa. As a result, a uniform dispersion was obtained. This maintained the dispersed state even after being left for one day. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM, TEM, and Raman spectroscopy. As a result, flaky (mainly several layers) carbon (thickness 5 nm or less) About 2 to 10 layers) was observed.

Example 3
The experiment was performed in the same manner as in Example 2 except that the dispersant 1 was changed to the dispersant 2. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM. As a result, flaky carbon (thickness 5 nm or less, about 2 to 10 layers) was observed.

Example 4
The experiment was performed in the same manner as in Example 2 except that the dispersant 1 was changed to the dispersant 3. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM. As a result, flaky carbon (thickness 5 nm or less, about 2 to 10 layers) was observed.

Example 5
The experiment was performed in the same manner as in Example 2 except that the dispersant 1 was changed to the dispersant 4 and the amount of expanded graphite was 0.003 g. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM. As a result, flaky carbon (thickness 5 nm or less, about 2 to 10 layers) was observed.

Example 6
The experiment was performed in the same manner as in Example 2 except that the dispersant 1 was changed to the dispersant 5. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM. As a result, flaky carbon (thickness 5 nm or less, about 2 to 10 layers) was observed.

Example 7
The experiment was performed in the same manner as in Example 2 except that the dispersant 1 was changed to the dispersant 6. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM. As a result, flaky carbon (thickness 5 nm or less, about 2 to 10 layers) was observed.

Example 8
To 100 g of Dispersant 1, 0.01 g of natural graphite (manufactured by Wako Pure Chemical Industries) was added. Using a 600 W ultrasonic dispersion apparatus, the dispersion treatment was performed at an output of about 400 W for 5 minutes while cooling with ice. Further, using a high-pressure dispersing device, a dispersion treatment of colliding with an eccentric ceramic ball at a treatment pressure of about 250 MPa was performed for 100 times. As a result, a uniform dispersion was obtained. This maintained the dispersed state even after being left for one day. The obtained dispersion was filtered, washed with acetone to remove the dispersant component, and analyzed by SEM. As a result, flaky carbon (thickness 7 nm or less, about 2 to 15 layers) was observed.

Claims (12)

A method for producing flaky carbon,
In the presence of plant extracts, carbonaceous materials with a layered structure
(1) 30 MPa or more pressure, and (2) have lines at least one processing of 100W or more ultrasonic dispersion treatment,
The manufacturing method in which the said plant extract contains the polyphenol and / or heterocyclic containing compound extracted from a plant . Carbonaceous material having a layered structure, the plant extracts, and with respect to the carbonaceous material dispersion containing a solvent,
The manufacturing method according to claim 1, wherein at least one of (1) pressurization of 30 MPa or more and (2) ultrasonic dispersion treatment of 100 W or more is performed. The production method according to claim 2, wherein the solvent contains water, and the content of the water is 70% by weight or more in the solvent. The heterocycle-containing compound, tetrapyrrole ring, a pyrrole ring, a pyrazine ring, a pyridine ring, and compounds containing at least one in the molecule selected from the group consisting of xanthine skeleton, any of claims 1 to 3 The production method according to claim 1 . The manufacturing method according to any one of claims 1 to 4 , wherein the plant extract is an extract obtained by extracting an extraction residue obtained by extracting a plant with water with a solvent. The manufacturing method of Claim 5 in which the said solvent contains 50 weight% or more of organic solvents. The production method according to claim 6 , wherein the extract is treated with at least one selected from the group consisting of organic ammonium, alkali metal, ammonium, and polyalkylene oxide. By pressurizing (1) above,
(I) causing two or more carbonaceous material dispersions to collide with each other; (ii) causing the carbonaceous material dispersion to collide with a metal or ceramic material; and (iii) isolating the carbonaceous material dispersion. at least one treatment is performed chosen from the group consisting of passing the area 1 cm ² or less space, process according to any one of claims 2-7. The content of the carbonaceous material having a layered structure is performed at a concentration of 10 wt% or less, the production method according to any one of claims 1-8. A method for producing a flaky carbon dispersion, comprising a carbonaceous material having a layered structure, a plant extract, and a carbonaceous material dispersion containing a solvent,
(1) 30 MPa or more pressure, and (2) have lines at least one processing of 100W or more ultrasonic dispersion treatment,
The manufacturing method in which the said plant extract contains the polyphenol and / or heterocyclic containing compound extracted from a plant . A method for producing a flaky carbon composition containing flaky carbon and a plant extract, comprising: obtaining a flaky carbon dispersion by the production method according to claim 10 ; and drying the solvent. A method for producing flaky carbon, comprising washing a flaky carbon composition obtained by the production method according to claim 11 with water or an organic solvent to remove a plant extract.

Images