JP2012036061A - Method for producing nanocarbon film and nanocarbon film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nanocarbon film and a nanocarbon film which ensures a high filtration rate and high durability, can be utilized as an ultrafiltration membrane, a nanofiltration membrane or a reverse osmosis membrane, and exhibits high mechanical strength in spite of its ultra-thin thickness.SOLUTION: The method for producing a nanocarbon film includes: a step S1 of forming a sacrificial film comprising nanofibers on a microfiltration membrane by a filtration process; a step S2 where a carbon filled layer in which carbon is filled into the gaps among the nanofibers is formed by a high-frequency plasma process, and then a carbon flat film having a flat surface is formed so as to cover the sacrificial film; and a step S3 where the nanofibers in the carbon filled layer are removed with an acid or alkali solution to form a carbon backing layer having a network cavity, thereby forming a nanocarbon film comprising the carbon flat film and the backing layer and having a film thickness of ≤100 nm.

Description

The present invention relates to a method for producing a nanocarbon film and a nanocarbon film.

A carbon film with a thickness of nanometer scale (referred to here as a nanocarbon film) is effective not only for wear resistance, but also for improving surface slippage and preventing internal corrosion. Used frequently.
For example, a carbon film of about 100 nm is coated on the inside of a PET bottle of carbonated drink water. The high gas barrier property of the carbon coating is used to prevent carbon dioxide from leaking from the bottle. In such an application, the nanocarbon film is required to be dense and strong, and the carbon atoms constituting the film must be closely bonded to each other.
This film is often called a DLC (diamond-like carbon) film.

Nanocarbon membranes have high mechanical strength, so if pores of several nanometers or less are formed inside, they can be expected to be used as ultra-thin filtration membranes, and have significant characteristics such as filtration speed, durability, and chemical resistance. Improvement can be expected.
Examples of the filtration membrane include an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane (Reverse Osmosis membrane: RO membrane).

An ultrafiltration membrane is generally a filtration membrane having pores of 100 nm or less and 1 nm or more, and is widely used in the manufacturing process of drinking water, ultrapure water for semiconductors, foods and cosmetics, etc. It is also used in the manufacture of pharmaceuticals or filters for artificial dialysis.
The nanofiltration membrane has pores of less than 2 nm and is used for softening water by purifying drinking water and removing multivalent ions.
Further, the reverse osmosis membrane has a pore size of 0.5 nm or less and can remove small ions such as sodium.
These membranes are widely used today for seawater desalination. The reverse osmosis membrane is also expected as a membrane for future osmotic pressure power generation.

Reverse osmosis membranes were put to practical use by cellulose acetate membranes in the 1960s, and at present, crosslinked polyamide membranes developed around 1970 have become mainstream. This is because the process for producing a reverse osmosis membrane using a crosslinked polyamide membrane has been improved, and performances such as filtration speed and durability have been remarkably improved.
In recent crosslinked polyamide membranes, a thin film of several tens of nanometers is formed, and 99% or more of sodium chloride can be removed with a flux of about 50 L / m ² h even at a pressure difference of about 10 atmospheres. it can.

On the other hand, many researches on reverse osmosis membranes using nanocarbon membranes were conducted in the 1970s. For example, as research on nanocarbon films in the 1970s, there is a paper by Hollahan and Wydeven (Non-Patent Document 1).
Non-Patent Document 1 discloses that a carbon film having a thickness of 800 nm to 1600 nm was produced by plasma polymerization of polyallylamine on a polymer filter (ultrafiltration membrane) having an average pore diameter of 25 nm, and vice versa. According to the performance evaluation of the osmotic membrane, it is described that this membrane has a performance capable of removing 90% or more of sodium chloride with a flux of about 10 L / m ² h at a pressure difference of 40 atm.

As another research on nanocarbon films, there is a paper by Yasuda and Lamaze (Non-Patent Document 2).
In Non-Patent Document 2, 4-vinylpyridine was vapor-deposited by plasma polymerization on a polymer filter (ultrafiltration membrane) having 25 nm pores similar to the above to form a carbon film thicker than 100 nm. According to the performance evaluation of a reverse osmosis membrane, it is described that this membrane has a performance capable of removing 99% of sodium chloride with a flux of 65 L / m ² h at a pressure difference of 81 atm.
In this research by Yasuda et al., The amount of carbon film deposited is described in terms of weight, and assuming that the density is 1 g / cm ³ , an ultrathin carbon film of 100 nm or less is not formed.

However, research using nanocarbon films has not been put to practical use. This is because the superiority was not shown over the crosslinked polyamide film. As a result, the application of nanocarbon membranes to separation membranes has not received much attention for a long time.

In addition, it is technically easy to manufacture an extremely thin carbon film having a thickness of 100 nm or less among the nanocarbon films. For example, in a plasma CVD (or plasma polymerization) method using high frequency or microwave, a nanocarbon film having a thickness of about 10 nanometers is manufactured, and an ultrathin nanocarbon film can also be manufactured by a PVD method.

However, the performance required for filtration membranes is not only extremely thin, but also requires the mechanical strength of the membrane, high porosity and high blocking performance against solute molecules (or ions), all of which must be satisfied. Is not easy.
In order to effectively block solute molecules (or ions), it is necessary to build pores of the same scale as the molecules (or ions) to be blocked inside the carbon film. When it is made thin, there is a problem that even if it is a strong carbon film, mechanical strength cannot be expected.
Note that the permeation rate (flux) of the liquid increases in inverse proportion to the thickness of the carbon film. Therefore, when the carbon film is extremely thin, the above problem becomes a larger problem.
In previous studies, a homogeneous nanocarbon membrane could not be produced as a “self-supporting membrane” on a microfiltration membrane having pores of about 1 μm.

Japanese Patent No. 4314362

Hollahan, et al. Science, 179, 500-501, 1973. “Synthesis of Reverse Osmosis Membranes by Plasma Polymerization of Allylamine” Yasuda, et al. , Journal of Applied Polymer Science, 17, 201-222, 1973 “Preparation of Reverse Osmosis by Plasma Polymerization of Organic Compounds”.

The present invention is a membrane that can be used for ultrafiltration membranes, nanofiltration membranes or reverse osmosis membranes having a high filtration rate and high durability, and is a very thin but high mechanical strength nanocarbon membrane. It is an object to provide a method and a nanocarbon film.

The researchers repeated trial and error to produce nanocarbon membranes with high filtration speed and high durability. Excellent filtration performance by providing a backing structure that can withstand high pressures, that is, by lining one side of a very thin porous carbon membrane with a smooth surface with a network of carbon fibers And mechanical strength were found to be compatible. The nanocarbon film having such a structure could be formed by forming a film on a nonwoven fabric (sacrificial film) made of ultrafine nanofibers. This method succeeded in producing a nanocarbon film having an overall thin film thickness of 100 nm or less but high mechanical strength.

It has been found that this membrane can be used as a filtration membrane having a high filtration rate and high durability.
Moreover, it discovered that it could utilize for an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane (RO membrane) etc. by changing the kind of raw material of a nanocarbon membrane, and film-forming conditions.
Furthermore, when such a nanocarbon membrane is used as a self-supporting membrane and formed on a microfiltration membrane (generally having submicron pores) having a large porosity, a highly permeable ultrafiltration membrane suitable for practical use. It was found to be a nanofiltration membrane or a reverse osmosis membrane.
The present invention has the following configuration.

The method for producing a nanocarbon membrane of the present invention includes a step of forming a sacrificial membrane made of nanofibers on a microfiltration membrane by a filtration method, and a carbon-filled layer in which carbon is filled in the gaps of the nanofibers by a high-frequency plasma method. Forming a carbon flat film having a flat surface so as to cover the sacrificial film, and removing the nanofibers of the carbon-filled layer with an acid or alkali solution to form a network-like cavity Forming a carbon backing layer having a portion to form a nanocarbon film having a film thickness of 100 nm or less, comprising the carbon flat film and the backing layer.

In the method for producing a nanocarbon film of the present invention, the high frequency plasma method generates carbon plasma by generating a high frequency plasma in a state where a gas containing an organic compound having a vapor pressure of 8 Pa or more at room temperature is circulated inside the chamber. A method of forming a film is preferred.

In the method for producing a nanocarbon film of the present invention, the organic compound is selected from the group consisting of acetylene, butadiene, pyridine, benzene, hexafluorobenzene, cyclohexane, hexamethyldisiloxane, 4-vinylpyridine, propylamine, and allylamine. It is preferable that it is an organic compound.

In the method for producing a nanocarbon film of the present invention, the diameter of the nanofiber is preferably 10 nm or less.
In the method for producing a nanocarbon film of the present invention, the nanofiber is preferably a nanostrand.
In the method for producing a nanocarbon film of the present invention, it is preferable that an aqueous solution of an organic salt is passed through the sacrificial film made of the nanostrand to improve the stability of the nanostrand under a medium vacuum.

The nanocarbon film of the present invention has a hole penetrating one surface side and the other surface side, and is formed on the other surface side of the carbon flat film having a flat surface and a mesh-like cavity. A film having a thickness of 100 nm or less.

In the nanocarbon film of the present invention, the pore diameter is preferably 5 nm or less.
In the nanocarbon film of the present invention, the pore area ratio of the carbon flat film is preferably 1% or more, and more preferably 3% or more.
In the nanocarbon film of the present invention, the diameter of the cavity is preferably 10 nm or less.

The nanocarbon membrane of the present invention is preferably formed on one side of the microfiltration membrane.

The method for producing a nanocarbon membrane of the present invention includes a step of forming a sacrificial membrane made of nanofibers on a microfiltration membrane by a filtration method, and a carbon-filled layer in which carbon is filled in the gaps of the nanofibers by a high-frequency plasma method. Forming a carbon flat film having a flat surface so as to cover the sacrificial film, and removing the nanofibers of the carbon-filled layer with an acid or alkali solution to form a network-like cavity Forming a carbon backing layer having a portion and forming a nanocarbon film having a film thickness of 100 nm or less, comprising the carbon flat film and the backing layer, and has a hole of about 1 μm. A homogeneous and extremely thin carbon film can be produced as a “self-supporting film” on the microfiltration membrane via a sacrificial film. Further, by using a smooth nonwoven fabric made of nanofibers such as nanostrands as a sacrificial film, a flat and homogeneous carbon film can be produced as a “self-supporting film” on the sacrificial film. In addition, by inserting carbon into the gap between the nanofibers of the sacrificial membrane and forming a backing layer on the other side of the carbon membrane, the mechanical strength of the carbon membrane can be increased, and the durability of the filtration membrane Can be improved. Further, the backing layer can be easily formed by dissolution and removal. Furthermore, the nanocarbon membrane of the present invention can be formed on a microfiltration membrane and used as it is as a separation membrane. However, when the nanofibers are dissolved and removed, the nanocarbon membrane is separated from the microfiltration membrane to obtain other porous materials. It is also possible to transfer it onto other materials. With the above configuration, the nanocarbon membrane has a high filtration rate and high durability, and can be used as an ultrafiltration membrane, a nanofiltration membrane or a reverse osmosis membrane, and is extremely thin but has high mechanical strength. The manufacturing method of can be provided.

The nanocarbon film of the present invention has a hole penetrating one surface side and the other surface side, and is formed on the other surface side of the carbon flat film having a flat surface and a mesh-like cavity. Since the film has a thickness of 100 nm or less, it can be used for a filtration membrane having a high filtration rate. By providing the backing layer on the other surface side of the carbon flat membrane, the mechanical strength of the carbon flat membrane can be increased and used for a highly durable filtration membrane. Furthermore, by setting the size of the pores in various ways, the membrane can be used as an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.

It is a flowchart which shows an example of the manufacturing method of the nano carbon film | membrane of this invention. It is a figure which shows an example of the manufacturing method of the nano carbon membrane of this invention, Comprising: FIG. 2 (a) is a figure which shows the filtration process of a nano strand solution, FIG.2 (b) is a microfiltration membrane on a filtration method. It is a figure which shows the sacrificial film formed in. It is the schematic which shows an example of a high frequency plasma apparatus. It is a figure which shows an example of the carbon film formed by the high frequency plasma method, Comprising: Fig.4 (a) is sectional drawing, FIG.4 (b) is an expanded sectional view of the A section of Fig.4 (a). It is a figure which shows an example of the nanocarbon film | membrane of this invention, Comprising: Fig.5 (a) is a top view, FIG.5 (b) is sectional drawing of the B section of Fig.5 (a). It is a scanning electron micrograph of the surface of the nonwoven fabric (sacrificial film) of Example 1 (F-05). FIG. 7A is a scanning electron micrograph of the nanocarbon film of Example 1 (NC-07), and FIG. 7A is a photograph in which a part of the nanocarbon film is pulled up on alumina, and FIG. Is an enlarged photograph of a nanocarbon film. FIG. 8A is a transmission electron micrograph of the nanocarbon film of Example 1 (NC-08), FIG. 8A is a photograph of the bent nanocarbon film, and FIG. 8B is FIG. 8A. It is an enlarged photograph of the part surrounded by the square. It is a scanning electron micrograph of the nanocarbon film of Example 2 (NC-23). It is a scanning electron micrograph of the nanocarbon film of Example 2 (NC-32).

(Embodiment of the present invention)
Hereinafter, a method for producing a nanocarbon film and a nanocarbon film according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a flowchart showing an example of a method for producing a nanocarbon film according to an embodiment of the present invention. As shown in FIG. 1, the method for producing a nanocarbon film according to an embodiment of the present invention includes a sacrificial film forming step S1, a carbon film forming step S2, and a sacrificial film removing step S3.

(Sacrificial film forming step S1)
First, a solution containing nanofibers is prepared. Nanofibers are highly dispersed in solution.
Next, as shown in FIG. 2 (a), a funnel 34 having a disk-shaped microfiltration membrane 2 sandwiched in a suction bottle 33 is attached, and a solution 32 containing nanofibers is poured from a beaker 31 into the funnel 34. Filter.

FIG. 2B is a diagram showing an example of the sacrificial film 3 formed on the microfiltration membrane 2 by the filtration, and a smooth and disc-shaped sacrificial film 3 is formed on the microfiltration membrane 2. .
The sacrificial film 3 is formed by integrating fibrous nanofibers.

The thickness of the sacrificial film 3 is preferably in the range of 20 nm to 1000 nm. If the thickness of the sacrificial film 3 is greater than 1000 nm, the surface of the sacrificial film 3 is likely to crack during the drying process of the sacrificial film 3. On the contrary, when the thickness of the sacrificial film 3 is made thinner than 20 nm, it is difficult to uniformly cover the holes of the microfiltration membrane 2.
For example, when cadmium hydroxide nanostrands are used as the nanofibers, the thickness of the sacrificial film 3 is preferably about 100 nm.

The microfiltration membrane 2 may be any one having pores of a size that can be filtered by blocking nanofibers.
The pore diameter of the microfiltration membrane 2 is preferably in the range of 50 nm to several μm. Further, the area of pores on the surface of the microfiltration membrane 2 (open area ratio: porosity) is preferably 10% or more. By setting the aperture area ratio to 10% or more, the filtration step can be performed in a short time.

As the microfiltration membrane 2, for example, an anodized porous alumina membrane that penetrates in the direction perpendicular to the membrane surface and has a hole with a diameter of about 100 nm can be used.
Since the alumina film is rigid, even when the carbon film is formed on the alumina film via the sacrificial film 3 in the carbon film forming step S2 described later, the warp of the alumina film is suppressed and the flatness of the carbon film is achieved. Can be maintained.

As long as the polymer has rigidity, a polymer microfiltration membrane may be used. Examples of the polymer microfiltration membrane include a polycarbonate membrane filter having submicron pores.
Further, the carbon film may be prevented from warping by being reinforced with a material having rigidity. For example, another microfiltration membrane may be used in an overlapping manner.

The nanofibers preferably have a diameter of 10 nm or less. By making the diameter of the nanofibers 10 nm or less, a flat surface can be formed on the sacrificial film 3 made of nanofibers, and a carbon film was formed on the sacrificial film 3 in the carbon film forming step S2 described later. Sometimes the flatness of the carbon film can be improved.

The length of the nanofiber is preferably at least twice the diameter of the pores of the microfiltration membrane 2. For example, when the pore diameter of the microfiltration membrane 2 is 1 μm or less, the length of the nanofiber is preferably 2 μm or more, and more preferably several tens of μm or more.
The sacrificial membrane 3 can be formed on the microfiltration membrane 2 even when nanofibers having the same length as the pore diameter of the microfiltration membrane 2 are used. However, in this case, since most of the nanofibers pass through the microfiltration membrane 2, a large amount of nanofiber solution is required to form the sacrificial membrane 3.

The nanofiber is preferably soluble in an aqueous solution of acid or alkali. Thereby, the sacrificial film 3 can be easily dissolved and removed in the sacrificial film removing step S3 described later. If necessary, the nanocarbon film can be separated as a single unit and easily on other porous materials. Can be moved.

As the nanofiber, for example, a metal hydroxide nanostrand can be used.
A nanostrand is a nanofiber formed by adding an alkali to a dilute aqueous solution of a metal salt, and its surface is highly positively charged, so that it exists dispersed in water.
Nanostrands have already been granted as positively charged nanofibers (Patent Document 1). For example, Patent Document 1 relates to a metal oxide nanofiber and a method for producing the same, and describes a nanocomposite using nanofibers and nanostrands that are extremely positively charged ultrafine nanofibers. Yes.

Specific examples of the nanostrand include nanostrands such as cadmium hydroxide (Cd (OH) ₂ ), zinc hydroxide (Zn (OH) ₂ ), and copper hydroxide (Cu (OH) ₂ ). Can do. These can be nanostrands having a diameter of several nanometers or less and reaching several tens of micrometers, and can be easily decomposed with an acid. Moreover, these metal hydroxides can be formed under pH conditions near neutrality.

The solution 32 containing nanostrands is preferably an aqueous solution used for the preparation of nanostrands, and examples thereof include an aqueous solution of nanostrands of cadmium hydroxide, copper hydroxide, or zinc hydroxide.

The nanostrand sacrificial film 3 is preferably passed through an aqueous organic salt solution immediately after formation. For example, an aqueous solution of parastyrene sulfonic acid sodium salt (PSS-Na) is filtered by the sacrificial film 3.
A sacrificial film (nonwoven fabric) made of nanostrands is placed under medium vacuum (100 Pa to 0.1 Pa) in a carbon film forming process using a high-frequency plasma method. If left under such a reduced pressure for a long time, a part of the nanostrand is decomposed, which causes a defect when an extremely thin carbon film is formed. However, by filtering an aqueous solution of anionic organic molecules such as PSS-Na through the sacrificial film 3, if the negatively charged PSS-Na is adsorbed on the nanostrand surface, the nanostrand is removed under medium vacuum. Can be stabilized. Thereby, the damage (cracking etc.) of the surface in the drying process of the sacrificial film 3 can be prevented.
The surface of the nanostrand is extremely positively charged, and electrostatically adsorbs the organic molecules in the process of filtering an aqueous solution of anionic organic molecules such as PSS-Na.
On the other hand, nanostrands are weak in high-temperature and high-humidity environments, and when left in a high-humidity environment, some of them are decomposed to precipitate crystals. However, if anionic organic molecules are electrostatically adsorbed, crystal precipitation can be prevented.

(Carbon film forming step S2)
Next, the production of the carbon film by the high frequency plasma method will be described.
FIG. 3 is a schematic diagram of the high-frequency plasma apparatus 40.
As shown in FIG. 3, the high-frequency plasma apparatus 40 is schematically configured to include a chamber 41, pipes 46 and 47, electrode portions 42 a and 42 b, and a gas introduction pipe 43.
The upper and lower electrode portions 42a and 42b function as a pair of electrode portions, and an electric field can be applied between them. The lower electrode portion 42b also has a function of holding the substrate.
The pipe 46 is connected to a gas supply unit (not shown), and is used as a gas introduction pipe for introducing the gas G ₁ stored in the gas supply unit into the chamber 41.
The pipe 47 is connected to a vacuum pump (not shown), and can reduce the pressure in the chamber 41 to a predetermined degree of vacuum, and is used as a gas discharge pipe for discharging the gas G ₁ introduced into the chamber 41. Yes.

First, as shown in FIG. 3, a substrate 39 made of a microfiltration membrane 2 on which a sacrificial film 3 is formed is placed inside a chamber 41 so that one surface 3a of the sacrificial film 3 faces a gas outlet 43a. It attaches to the part 42b.
Next, the inside of the chamber 41 is depressurized to a predetermined degree of vacuum.
Next, a gas G ₁ containing an organic compound is introduced into the chamber 41 from the gas supply unit.

The organic compound is preferably an organic compound having a vapor pressure of 8 Pa or more in a range of 10 ° C. before and after room temperature.
The organic compound may contain not only hydrocarbons but also oxygen, nitrogen, silicon, phosphorus, boron, and other elements.
The organic compound is not particularly limited. For example, the organic compound is selected from the group consisting of acetylene, butadiene, pyridine, benzene, hexafluorobenzene, cyclohexane, hexamethyldisiloxane, 4-vinylpyridine, propylamine, and allylamine. The organic compound can be mentioned.

The organic compound may be introduced into the chamber 41 as a single gas after being in a gas state, or may be introduced into the chamber 41 as a mixed gas with other organic compound or inert gas. For example, a highly reactive gas such as acetylene or butadiene is preferably introduced by mixing with an argon gas.
When a liquid having a relatively high boiling point, such as hexamethyldisiloxane, is used, a decompression container for gasifying the liquid is provided outside the chamber 41, and the pressure inside the chamber 41 is increased to 8 Pa or more in the decompression container. May be introduced.

Then, into the chamber 41, while being circulated gas G ₁ containing an organic compound, the upper and lower electrode portions 42a, by applying an electric field between the 42b, the high-frequency plasma between the electrode portions 42a, 42b 48 is generated.
The film forming conditions are not particularly limited, but for example, the substrate temperature is −20 to 30 ° C., the output is 2 to 100 W, the pressure is 1 to 8 Pa, and the film forming time is 1 to 120 seconds. With the film forming conditions, it is possible to plasma gas G ₁ containing an organic compound.
By holding the high-frequency plasma 48 so as to be in contact with the one surface 3a of the sacrificial film 3 for a predetermined time, a carbon film can be formed on the one surface 3a side of the sacrificial film 3.

More specifically, the carbon film is formed by the following process.
First, the carbonized carbon or the like in the high-frequency plasma 48 enters the gap (gap) between the nanofibers of the sacrificial film 3. This is because the sacrificial film 3 is composed of fibrous nanofibers integrated in a network, and there are gaps (voids) between the nanofibers.
Depending on the degree of integration of the nanofibers, the depth at which the carbonized carbon or the like enters varies. When the degree of nanofiber integration is low, or when the sacrificial film 3 is thin, plasmaized carbon or the like enters so as to fill the entire sacrificial film 3. However, when the degree of integration of nanofibers is high or the sacrificial film 3 is thick, carbonized carbon or the like enters only from the one surface 3a of the sacrificial film 3 to a certain depth.
Carbonized carbon or the like in contact with the nanofiber adheres to the nanofiber.

Next, carbon or the like that has been turned into plasma so as to surround each nanofiber adheres one after another. As the amount of carbon or the like attached to the surface of each nanofiber increases, the gap (gap) between the nanofibers gradually decreases. Then, after a certain period of time, the nanofiber gaps (voids) are completely eliminated.

After the gaps (voids) between the nanofibers have completely disappeared, the plasmaized carbon or the like is successively deposited on a film mainly made of carbon. As this deposition continues, the film thickness mainly of carbon increases. The film mainly made of carbon does not contain nanofibers, but may contain elements (hydrogen, nitrogen, silicon, etc.) contained in the plasma gas.
A carbon film is formed by the above steps.

4A and 4B are diagrams showing a carbon film laminate formed by a high-frequency plasma method, in which FIG. 4A is a schematic cross-sectional view, and FIG. 4B is an enlarged view of a portion A in FIG. It is sectional drawing.
As shown in FIG. 4A, the carbon film laminate 19 is formed on the microfiltration membrane 2, the sacrificial film 3 formed on the one surface 2a of the microfiltration membrane 2, and the one surface 3a of the sacrificial film 3. It is generally composed of a carbon flat film 12 mainly made of carbon. The sacrificial film 3 is composed of a carbon filled layer 8 and a carbon unfilled layer 9.

As shown in FIG. 4B, the sacrificial film 3 is a film in which a plurality of fibrous nanofibers 3d form a network structure in the form of a mesh.
As a result of filling with plasma or the like, a carbon-filled layer 8 in which the voids 3e of the nanofibers 3d having a network structure are filled with carbon or the like 81 is provided on the one surface 3a side of the sacrificial film 3. In addition, the gap 3e on the other surface 3b side of the sacrificial film 3 is not filled with carbon but is a carbon unfilled layer 9.

A carbon flat film 12 is formed on one surface 3 a of the sacrificial film 3.
Since the sacrificial film 3 is made of nanofibers having a diameter of 10 nm or less, the flatness of the one surface 3a of the sacrificial film 3 is kept high. Therefore, depending on the flatness, the flatness of the one surface 12a of the carbon flat film 12 mainly made of carbon formed by being deposited on the one surface 3a of the sacrificial film 3 is also increased.

Moreover, the carbon flat film 12 has a hole 10c, and the hole 10c communicates from the one surface 12a side to the carbon filling layer 8 side.

(Sacrificial film removal step S3)
Next, the sacrificial film removal step S3 will be described.
The sacrificial film removal step S3 is a step of dissolving and removing the sacrificial film 3 with an acid or alkali solution. For example, by floating the carbon film laminate 19 in an acid or alkaline solution for a predetermined time, the nanofibers 3d of the carbon filling layer 8 can be removed to form a carbon backing layer having a network-like cavity. . In addition, the carbon backing layer can be separated from the microfiltration membrane 2 with an acid or alkali solution.
Thereby, it is possible to form a nanocarbon film composed of the flat carbon film and the backing layer and having a film thickness of 100 nm or less.

FIG. 5 is a view showing an example of a nanocarbon film according to an embodiment of the present invention, in which FIG. 5 (a) is a plan view, and FIG. 5 (b) is a cross-section at a portion B in FIG. FIG.
As shown in FIG. 5A, the nanocarbon film 10 has a substantially disc shape. In addition, it has a plurality of holes 10c (not shown).

As shown in FIG. 5B, the nanocarbon film 10 includes a carbon flat film 12 and a backing layer 11. The carbon flat film 12 is also called an S layer, and the backing layer 11 is also called an N layer.
The film thickness of the nanocarbon film 10 is 100 nm or less. Thereby, when the nanocarbon membrane 10 is used as a filtration membrane, the filtration rate can be increased.
The film thickness of the nanocarbon film 10 varies depending on the film forming conditions, but can be reduced to about 5 nm. When the film thickness of the nanocarbon film 10 is reduced to about 5 nm, the filtration rate can be made very fast.

The carbon flat film 12 is a film mainly made of carbon, and one surface 12a, that is, one surface 10a of the nanocarbon film 10 is a flat surface. Further, the film thickness is extremely thin and is at least 100 nm or less.

The backing layer 11 is made of carbon or the like 81 formed so as to cover the entire other surface 12b side of the carbon flat film 12 and to form a highly crosslinked structure. Note that the carbon or the like 81 may include an element (hydrogen, nitrogen, silicon, or the like) contained in the plasma gas.
The backing layer 11 is provided with a plurality of cavities 11c in a mesh shape. The hollow part 11c is a part formed by dissolving and removing the nanofibers 3d formed in the network form, and thus is provided in the network form. Further, the diameter of the hollow portion 11c is set to 10 nm or less similarly to the diameter of the used nanofiber 3d.
In addition, when the nanofiber 3d with a small diameter is used, the backing layer 11 having the cavity 11c with a small diameter can be formed.
The size of the hole 10c controls the filtration performance of the nanocarbon membrane 10, and the diameter of the cavity 11c does not hinder the filtration performance of the carbon flat membrane 12.

Since the backing layer 11 is a layer that backs the carbon flat film 12, the mechanical strength of the carbon film can be increased. Thereby, the durability of the nanocarbon membrane 10 as a filtration membrane can be improved.
Specifically, by providing the backing layer 11, the nanocarbon film 10 can have a Young's modulus in the range of 50 to 300 GPa, and can be a film that can withstand a pressure of 30 atm or more.

Furthermore, since the nanocarbon membrane 10 has a highly crosslinked structure of the backing layer 11, it can be used as a stable filtration membrane in various organic solvents (methanol, ethanol, chloroform, benzene, acetonitrile, hexene, etc.). Can be used to separate these solvents.

As shown in FIG. 5B, the carbon flat film 12 has a plurality of holes 10c. The hole 10c communicates with a hole (mainly the cavity 11c) formed in the backing layer 11, and as a result, communicates from the one surface 10a side of the nanocarbon film 10 to the other surface 10b side. The size of the hole 10 c controls the filtration performance of the nanocarbon membrane 10.
The hole area ratio of the carbon flat film 12 can be 1% or more, and can also be 3% or more. By increasing the aperture area ratio, the filtration step when used as a filtration membrane can be carried out in a short time.

The diameter of the hole 10c of the nanocarbon film 10 can be set variously by selecting various organic compounds used in the high-frequency plasma method. The diameter of the hole 10c is 100 nm or less, 1 nm or more, and an ultrafiltration membrane of 2 nm Less than nanofiltration membrane, 0.5 nm or less RO membrane, etc. can be obtained.

When the nanocarbon film is formed using hexamethyldisiloxane as the organic compound, the diameter of the hole 10c can be made relatively large. This is because the basic skeleton of the organic compound introduced into the nanocarbon film 10 remains, and the nanocarbon film containing silicon becomes a porous film. Thereby, it is easy to form an ultrafiltration membrane or a nanofiltration membrane.
On the other hand, when the nanocarbon film 10 is formed using acetylene, the crosslink density of the nanocarbon film 10 can be increased, so that a nanofiltration membrane can be formed.
Further, when the nanocarbon film 10 is formed using propylamine, a dense nanocarbon film is formed, and the diameter of the hole 10c can be made relatively small. For this reason, it is easy to form the RO film.

Further, in the nanocarbon film 10 manufactured using butadiene, the filtration rate of the organic solvent (hexane or the like) can be remarkably increased. In general, the nanocarbon membrane of the present invention has a remarkably large filtration rate of an organic solvent compared to water, and is suitable for use as a filtration membrane for an organic solvent.

The performance of the nanocarbon membrane 10 as a separation membrane can be further improved by post-processing. Specifically, for example, the water permeability of the nanocarbon film 10 can be improved by filtering hot water or the like into the nanocarbon film 10. Further, by allowing hexane to pass through the nanocarbon film 10, the ethanol permeability of the nanocarbon film 10 can be improved.
Furthermore, by treating the nanocarbon film 10 with water or an organic solvent to which an acid, a base, an oxidizing agent or the like is added, the liquid permeability or solute rejection of the nanocarbon film 10 can be further adjusted.

In addition, it can be set as the filtration membrane which changed the variation of the filtration speed and durability further by mounting the said various nanocarbon membrane 10 in the microfiltration membrane from which the diameter of a hole differs. The nanocarbon membrane 10 of the present invention can be separated from the microfiltration membrane in the sacrificial membrane removal step S3 and copied onto another microfiltration membrane or the like. However, when the nanocarbon membrane 10 and the microfiltration membrane are bonded in the process of dissolving and removing the nanofibers, a separation membrane having the nanocarbon membrane 10 on one side of the microfiltration membrane can be more easily manufactured.
The nanocarbon membrane 10 according to an embodiment of the present invention can be formed as a “self-supporting membrane” on the microfiltration membrane 2, and has structural stability as a “self-supporting membrane” alone, and has other porous properties. It can also be transferred onto the substance. For this reason, various applications as a separation membrane are possible.

In the present embodiment, as a method for dissolving and removing the nanofibers of the sacrificial film 3, a method of floating the carbon film laminate 19 in an acid or alkali solution for a predetermined time is used, but the present invention is not limited to this. Other removal methods may be used.
For example, when the nanocarbon film 10 suitable for an ultrafiltration membrane or a nanofiltration membrane is formed, the nanofibers 3d of the sacrificial membrane 3 can be dissolved and removed by passing a weakly acidic aqueous solution.
When the nanocarbon film 10 suitable for the RO film is formed, the nanofibers 3d of the sacrificial film 3 can be removed by a method of immersing (floating) the microfiltration membrane 2 on which the nanocarbon film 10 is formed in a weakly acidic aqueous solution. .
Further, when nanostrands are used as the nanofibers 3d of the sacrificial film 3, the nanofibers of the sacrificial film 3 can be removed by allowing water to permeate for a long time.

The method for producing a nanocarbon film according to an embodiment of the present invention includes a step of forming a sacrificial film 3 made of nanofibers 3d on a microfiltration membrane 2 by a filtration method, and a gap ( A step of forming a carbon flat film 12 having a flat surface so as to cover the sacrificial film 3 after forming the carbon-filled layer 8 filled with carbon 81 or the like in the gap 3e), and an acid or alkali solution, By removing the nanofibers 3d of the carbon-filled layer 8 to form a carbon backing layer 11 having a network-like cavity 11c, a nano-layer having a carbon thickness of 100 nm or less, which is composed of the carbon flat film 12 and the backing layer 11. A step of forming the carbon film 10, and a uniform ultrathin carbon on the microfiltration membrane 2 having pores of about 1 μm through the sacrificial film 3. The can be manufactured as a "self-supporting film". Further, by using a smooth nonwoven fabric made of nanofibers 3d such as nanostrands as the sacrificial film 3, a flat and homogeneous carbon film can be produced as a “self-supporting film” on the sacrificial film 3. Further, carbon etc. 81 is inserted into the gap (gap portion 3e) between the nanofibers 3d of the sacrificial film 3 to form the backing layer 11 on the other surface side of the carbon film, thereby increasing the mechanical strength of the carbon film. And the durability of the filtration membrane can be improved. In addition, the backing layer 11 can be easily formed and the nanocarbon film 10 can be separated from the microfiltration membrane 2 by dissolution and removal. With the above configuration, the nanocarbon membrane has a high filtration rate and high durability, and can be used as an ultrafiltration membrane, a nanofiltration membrane or a reverse osmosis membrane, and is extremely thin but has high mechanical strength. Ten manufacturing methods can be provided.

In the method for producing a nanocarbon film according to an embodiment of the present invention, the high-frequency plasma method is a method in which a high-frequency plasma is produced in a state where a gas containing an organic compound having a vapor pressure of 8 Pa or higher at normal temperature is circulated inside a chamber. Since the structure is a method for forming a carbon film by generating the carbon film, the plasma-filled carbon or the like enters the void 3e of the nanofiber 3d on the one surface 3a side of the sacrificial film 3 to form the carbon filling layer 8. The flat carbon film 12 made of an extremely thin carbon film can be formed on the one surface 3a of the sacrificial film 3.

In the method for producing a nanocarbon film according to an embodiment of the present invention, the organic compound is a group of acetylene, butadiene, pyridine, benzene, hexafluorobenzene, cyclohexane, hexamethyldisiloxane, 4-vinylpyridine, propylamine, and allylamine. Therefore, it is possible to produce various ultra-thin nanocarbon membranes 10 with different pore quality and with different membrane quality, such as ultrafiltration membranes, nanofiltration membranes or vice versa. A membrane that can be used as an osmotic membrane can be produced.

Since the nanocarbon film manufacturing method according to the embodiment of the present invention has a configuration in which the diameter of the nanofiber 3d is 10 nm or less, the carbon flat film 12 with improved flatness of the one surface 12a (10a) can be formed.

The nanocarbon film manufacturing method according to an embodiment of the present invention can form the sacrificial film 3 having a network structure with a diameter of 2.5 nm or less because the nanofibers are nanostrands. The nanostrands associate with each other to form thicker nanofibers. Even in such a case, the sacrificial film 3 having a network structure with a diameter of 10 nm or less is provided. In addition, the sacrificial film 3 having the gap 3e can be formed, and the carbon filling layer 8 can be formed by filling the gap 3e with carbon or the like. Further, the carbon flat film 12 can be formed on the flat surface 3a of the sacrificial film 3, and the flatness of the one surface 12a (10a) of the carbon flat film 12 can be improved. Further, the nanostrand can be easily removed with an acid or alkali solution.

Since the nanocarbon film manufacturing method according to an embodiment of the present invention is configured to pass an aqueous solution of an organic salt through the sacrificial film made of the nanostrand and improve the stability of the nanostrand under a medium vacuum, In the carbon film forming step S2 by the method, the stability of the sacrificial film 3 can be improved, and a nanocarbon film having excellent flatness and a uniform pore diameter can be formed.

In the nanocarbon film 10 according to the embodiment of the present invention, the hole 10c formed in the carbon flat film 12 having the flat surface 12a is formed in the backing layer 11 on the other surface 12b side of the carbon flat film 12. A film having a thickness of 100 nm or less and having a hole penetrating the one surface 10a side and the other surface 10b side of the carbon film 10 as a result of communicating with the hole portion (mainly the mesh-shaped cavity portion 11c). Therefore, the nanocarbon film 10 can be used for a filtration membrane having a high filtration rate by making the film thickness of the nanocarbon film 10 as extremely thin as 100 nm or less. By providing the backing layer 11 on the other surface 12b side of the carbon flat film 12, the mechanical strength of the carbon flat film 12 can be increased and used for a highly durable filter membrane. Furthermore, by setting various sizes of the hole 10c, it is possible to obtain a membrane that can be used for an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.
In addition, since the nanocarbon film 10 according to the embodiment of the present invention is a film made of carbon or the like (which may include an element contained in a plasma gas), it can be used as a film having high permeability of an organic solvent. In addition, the nanocarbon membrane 10 according to the embodiment of the present invention has the same performance as a nanofiltration membrane for water treatment or an RO membrane as an existing membrane such as a crosslinked polyamide membrane, but is similar to a crosslinked polyamide membrane. It can be used for acid, alkali, and corrosive liquids that are difficult to use with existing films, and can be used as a film with excellent chemical stability.

Since the nanocarbon membrane which is an embodiment of the present invention has a configuration in which the diameter of the hole 10c is 5 nm or less, it can be used for any of ultrafiltration membranes, nanofiltration membranes or reverse osmosis membranes.
Since the nanocarbon film which is an embodiment of the present invention has a configuration in which the open area ratio of the carbon flat film 12 is 1% or more, more preferably 3% or more, the filtration rate can be increased.

Since the nanocarbon film according to the embodiment of the present invention has a configuration in which the diameter of the cavity portion 11c is 10 nm or less, the carbon flat film 12 is reinforced by the backing layer having the mesh-like cavity portion 11c. The mechanical strength of the filter can be increased, and the durability as a filtration membrane can be improved.

Since the nanocarbon membrane which is an embodiment of the present invention is formed on the one surface 2a side of the microfiltration membrane 2, a filtration membrane in which variations in filtration speed and durability are changed by selecting an ultrafiltration membrane It can be.

The method for producing a nanocarbon film and the nanocarbon film which are embodiments of the present invention are not limited to the above-described embodiments, and can be implemented with various modifications within the scope of the technical idea of the present invention. . Specific examples of this embodiment are shown in the following examples. However, the present invention is not limited to these examples.

Example 1
In Example 1, nanostrand nonwoven fabrics (sacrificial membranes) were formed on various microfiltration membranes, and nanocarbon membranes were produced using acetylene as a raw material.

(Sacrificial film formation process)
First, an aqueous solution (30 mL) of 2.66 mM cadmium chloride (CdCl ₂ ) and an aqueous solution of 0.2 mM aminoethanol (30 mL) were mixed with vigorous stirring, and the mixture was allowed to stand at room temperature for 60 minutes. An aqueous solution of nanostrands was prepared.

Predetermined amounts of this aqueous solution were added to anodized porous alumina filters (diameter 2.5 cm, porosity 50%) having pores of 20 nm, 100 nm and 200 nm or polycarbonate (PC) membranes (diameter 2.5 cm) having 200 nm pores. , Under reduced pressure at a pressure difference of 80 kPa.

In some cases, the nanostrand non-woven fabric thus produced was filtered with an aqueous solution of 2 mM sodium parastyrene sulfonate (PSS-Na).
The production conditions of the nanostrand nonwoven fabric are shown in Table 1.

The thickness of the nonwoven fabric was measured by scanning electron microscope observation of the cross section. Moreover, the depth of the unevenness | corrugation of the surface formed when nanostrands overlap was estimated, changing the observation angle of a scanning electron microscope.
FIG. 6 is a scanning electron micrograph of the surface of the nonwoven fabric (sacrificial film) of Example 1 (F-05). The photo was taken with about 3 nm of platinum deposited to prevent charge-up. Therefore, the diameter of the nanostrand has been observed to be larger than actual.
The nonwoven fabric (sacrificial film) of F-05 is a nonwoven fabric produced by filtering the nanostrand aqueous solution on a anodic porous alumina filter having 100 nm pores under reduced pressure and filtering the PSS-Na aqueous solution. As shown in FIG. 6, unevenness having a depth of 4 to 5 nm is present on the surface due to overlapping of nanostrands.

(Carbon film forming process)
The microfiltration membrane having the nanostrand nonwoven fabric prepared in this way is placed inside the vacuum chamber, acetylene gas is introduced, the internal pressure is 4-8 Pa, the frequency is 13.6 MHz, and the output is 30-100 W. The AC was applied for 20 to 60 seconds.
A similar experiment was performed using a mixed gas of acetylene and argon (mixing ratio 20:80, 10:90).

(Sacrificial film removal process)
Thereafter, the nanofiltration membrane formed on the nanofiltration membrane is floated in a 10 mM hydrochloric acid aqueous solution for 10 minutes to remove the nanostrand sacrificial membrane. Or washed with ethanol. The nanocarbon membrane was then scooped on a different anodized porous alumina filter.
As a result, a nanocarbon membrane that was present as a free-standing membrane on the microfiltration membrane pores was obtained. Detailed experimental conditions are shown in Table 2.
In addition, NC-01 and NC-07 in Table 2 were used for the filtration experiment described later, and the nanofiltration membrane was formed on a 10 mM hydrochloric acid aqueous solution for 10 minutes to remove the nanostrand sacrificial membrane. A sample washed with water or ethanol without peeling from the microfiltration membrane was also prepared.

The nanocarbon film thus produced is composed of a network-like carbon fiber layer (N layer) and a smooth and extremely thin carbon layer (S layer).
The thicknesses of the two layers were measured by cross-sectional observation with a scanning electron microscope.

FIG. 7 is a scanning electron micrograph of the nanocarbon film of Example 1 (NC-07), and FIG. 7A is a photograph of a part of the nanocarbon film pulled up on alumina. 7 (b) is an enlarged photograph of the nanocarbon film. This nanocarbon film is scooped and photographed on a different anodized porous alumina filter for electron microscope observation.
The nanocarbon film shown in FIG. 7 is a film manufactured from a mixed gas GM1 (20:80) of acetylene and argon.

In the cross-sectional view of FIG. 7, a portion where the free-standing film is bent is photographed. The film thickness was measured to be 35 nm. When observed from the surface, it can be confirmed that a network-like structure reflecting the structure near the surface of the nanostrand nonwoven fabric is formed inside the nanocarbon film.
The thickness of this layer was about twice the depth of the unevenness (4-5 nm) on the surface of the nonwoven fabric.

FIG. 8 is a transmission electron micrograph of the nanocarbon film of Example 1 (NC-08), FIG. 8A is a photograph of the bent nanocarbon film, and FIG. It is an enlarged photograph of the part enclosed by the square of 8 (a). The nanocarbon film is transferred onto a copper grid for an electron microscope and photographed for observation with a transmission electron microscope.
As shown in FIG. 8B, the thickness of the nanocarbon film is 30 nm, and it is clear that a network-like structure is formed inside.
The nanocarbon film shown in FIG. 8 is a film manufactured from a mixed gas GM1 (20:80) of acetylene and argon.

(Example 2)
In Example 2, a nanocarbon film was produced on a nanostrand non-woven fabric using various organic compounds as raw materials.
(Sacrificial film formation process)
First, a nanostrand nonwoven fabric having a thickness of 80 nm was formed on an anodized porous alumina filter having 100 nm pores by the method shown in Example 1.

(Carbon film forming process)
Next, a microfiltration membrane (anodized porous alumina filter) having nanostrand non-woven fabric was placed inside the vacuum chamber, and various organic compounds were introduced into the chamber as gases to produce nanocarbon membranes.

The organic compounds used are butadiene, pyridine, benzene, hexafluorobenzene, cyclohexane, hexamethyldisiloxane, 4-vinylpyridine, propylamine, and allylamine.
These organic compounds were introduced as gases, and the pressure inside the chamber was adjusted to 1 to 8 Pa. The application conditions of the high-frequency plasma were a frequency of 13.6 MHz and an output of 2 to 100 W. The film formation time was between 5 seconds and 370 seconds.

(Sacrificial film removal process)
Thereafter, the microfiltration membrane on which the nanocarbon membrane was formed was floated in a 10 mM hydrochloric acid aqueous solution for 10 minutes to remove the sacrificial membrane of nanostrands, and was washed with water or ethanol without peeling off the microfiltration membrane.
Detailed experimental conditions are shown in Table 3.

With all organic compounds except for hexafluorobenzene whose film growth rate is slightly high, it was possible to produce a nanocarbon film of 100 nm or less. With hexafluorobenzene, a 120 nm nanocarbon film was obtained in a film formation time of 20 seconds.
As is apparent from Table 3, the nanocarbon film becomes thinner as the film formation time is shortened.
The thickness of the N layer was 10 nm in all cases because F-05 was used as the nanostrand nonwoven fabric. The thickness of the S layer reaches 5 nm when it is thin.

As typical examples of the nanocarbon film formed on the anodized porous alumina filter having 100 nm pores, FIGS. 9 and 10 show NC-23 (source gas: pyridine) and NC-32 (source gas). : A scanning electron micrograph of the cross section of the nanocarbon film of hexamethyldisiloxane.
FIG. 9 is a scanning electron micrograph of the nanocarbon film of Example 2 (NC-23). A cross section of a nanocarbon membrane made from pyridine is shown.
FIG. 10 is a scanning electron micrograph of the nanocarbon film of Example 2 (NC-32). A cross section of a nanocarbon film made from hexamethyldisiloxane is shown.
From these photographs, it is clear that a nanocarbon film having a total film thickness of 35 nm is formed as a self-supporting film on the anodized porous alumina filter.

(Example 3)
In Example 3, in order to show that the nanocarbon film of the present invention is formed by crosslinking of the radicals of the organic compound used, the structure of the nanocarbon film is analyzed, and the mechanical and chemical properties are obtained. evaluated.
Here, NC-07 (source gas: acetylene), NC-23 (source gas: pyridine), and NC-32 (source gas: hexamethyldisiloxane) were selected as representative nanocarbon films.

First, FT-IR measurement of these nanocarbon films was performed.
In the NC-07 film, a peak derived from the C—H bond is observed in the vicinity of 2920 cm ⁻¹ , indicating that a nanocarbon film containing hydrogen formed by crosslinking of acetylene radicals is formed. It was done.
On the other hand, in the film of NC-23, in addition to the peak derived from the C—H bond, a peak derived from the N—H bond was also observed in the vicinity of 3368 cm ⁻¹ , and the radical of pyridine was cross-linked, so that hydrogen and nitrogen It was shown that a carbon film containing was formed.
Furthermore, in the film of NC-32, in addition to the peak derived from the C—H bond, a peak derived from the Si—H bond is observed in the vicinity of 2140 cm ⁻¹ , and the hydrogen of the hexamethyldisiloxane radical is crosslinked. It was shown that a nanocarbon film containing silicon and silicon was formed.

Next, the composition of the nanocarbon film was confirmed by XPS measurement.
For the NC-23 film, the carbon to nitrogen ratio was estimated to be 11: 1. Since the ratio of carbon to nitrogen in the raw material pyridine was 5: 1, it became clear that about half of the nitrogen molecules in the raw material were introduced into the nanocarbon film.
On the other hand, in the NC-32 film, the ratio of carbon to silicon was estimated to be 5: 3. Since the ratio of carbon to silicon in the raw material hexamethyldisiloxane was 3: 1, it was suggested that about one third of carbon atoms were lost during the formation of the nanocarbon film in this case.

Next, the density of the nanocarbon film was calculated from the weight and thickness of the film formed on the electrode of the crystal oscillator. In addition, the mechanical strength of the nanocarbon film was measured by the nanoindentation method,
The density of the NC-07 film was 1.22 g / cm ³ , and the Young's modulus and hardness were 170 GPa and 20.1 GPa, respectively. The NC-23 film had a density of 1.04 g / cm ³ and Young's modulus and hardness of 106 GPa and 12.3 GPa. Furthermore, the density of the NC-32 film was 0.98 g / cm ³ , and the Young's modulus and hardness were 91.8 GPa and 10.1 GPa.
As described above, the density of the nanocarbon film depends on the raw material gas, and as described later, the smaller the density, the higher the liquid permeability.

Next, an NC-40 nanocarbon film was formed on an anodized porous alumina filter having 100 nm pores, and after removing nanostrands, a pressure resistance test was performed. Although the thickness of the S layer of this membrane was 30 nm, it was confirmed that the membrane was not broken even when a water pressure of 30 atm was applied on the anodized porous alumina filter.

Example 4
In Example 4, in order to show that the nanocarbon membrane of the present invention can be used as an ultrafiltration membrane, a nanofiltration membrane, or an RO membrane, a filtration experiment was performed on the nanocarbon membranes prepared in Example 1 and Example 2. went. The results are shown in Table 4.

The nanocarbon membrane formed on the microfiltration membrane was installed in the filtration device together with the microfiltration membrane, and the permeation rate (flux) and the blocking rate of solute molecules were evaluated.
In the present embodiment, the permeation rate of the liquid is indicated by a unit area and a flow rate (flux) per unit time, and the applied pressure is indicated separately.
The flux is calculated from the effective area of the membrane, which is multiplied by the porosity of the microfiltration membrane.
The rejection rate of the solute was calculated from the ultraviolet / visible absorption spectrum measurement of the solution that passed through the membrane.

First, when a pressure of 80 kPa (0.08 MPa) was applied to the nanocarbon film of NC-01 to allow ethanol, methanol, and water to pass therethrough, a remarkably large flux was observed. This nanocarbon film can block 19.5% of azozensen in ethanol, 61.2% of protoporphyrin in ethanol, and 100% of 5 nm gold nanoparticles in ethanol. I was able to stop. The total thickness of this nanocarbon film is 10 nm, the thickness of the N layer is 10 nm, and the thickness of the S layer is 0 nm. Since the S layer does not exist, the flux when used as a filtration membrane is remarkably large, showing a value of 300 L / hm ² or more.
When the thickness of the nanocarbon film is 10 nm or less, the flux in the filtration experiment is remarkably increased. This indicates that the S layer is formed after the N layer has a thickness of 10 nm. Further, since the 5 nm gold nanoparticles were completely blocked, it can be concluded that the diameter of the cavity in the N layer of this nanocarbon film is 5 nm or less. Furthermore, this result shows that the N layer alone can be used as an ultrafiltration membrane that can withstand a filtration operation of 80 kPa.

Next, when a pressure of 80 kPa was applied to the NC-07 nanocarbon film to allow hexane, chloroform, benzene, 2-propanol, acetonitrile, ethanol, methanol, and water to pass through, the higher the hydrophobicity, the larger the flux. There was a trend. Water molecules are the smallest of the solvents, but the flux is small. This result shows that the NC-07 nanocarbon membrane is useful for filtration using an organic solvent.
Note that the nanocarbon film is not deteriorated by the organic solvent. This nanocarbon film was able to block 87.2% of azozensen in ethanol and 100% of phloroglucinol, fluorescein-4-isothiocyanate, and protoporphyrin in ethanol. Moreover, 100% of ferricyan potassium in water could be blocked.

The NC-23 nanocarbon membrane has low ethanol permeability and increased water permeability. Therefore, the film is more hydrophilic than the NC-07 nanocarbon film. A blocking rate of 90% or more was confirmed for azozensen and fluorescein-4-isothiocyanate even in the NC-23 film. This result indicates that the NC-23 nanocarbon membrane can be used as a nanofiltration membrane.

In the NC-32 nanocarbon film, the flux of water and ethanol is large, and the rejection of azobenzene and the like is small. This membrane has a blocking rate of 27% for gold nanoparticles with a diameter of 2 nm and a blocking rate of gold nanoparticles with a diameter of 5 nm is 99.8%, indicating that it can be used as an ultrafiltration membrane.

The NC-40 nanocarbon membrane has a water flux of only 0.7 L / hm ² when filtered with a pressure difference of 80 kPa (0.08 MPa). On the other hand, when a pressure of 2.4 MPa was applied and a 34 mM sodium chloride aqueous solution was permeated, it was possible to block 68.5% of sodium chloride with a flux of 4.7 L / hm ² . This result shows that the nanocarbon film of NC-40 has performance as an RO film.

The nanocarbon membrane production method and nanocarbon membrane of the present invention have a high filtration rate and high durability, and can be used for ultrafiltration membranes, nanofiltration membranes or reverse osmosis membranes, and are extremely thin. However, the present invention relates to a method for producing a nanocarbon membrane having high mechanical strength and a nanocarbon membrane, and is applicable to industries such as a filtration membrane production industry and an analysis industry using a filtration membrane.
Since the nanocarbon membrane of the present invention is a self-supporting membrane, it can also be used as a highly permeable RO membrane for osmotic pressure power generation. The performance as the RO membrane is still slightly inferior compared with the existing crosslinked polyamide membrane. However, the high permeability of organic solvents is a notable feature and has great applicability for industrial applications such as recovery of functional organic materials and solid-liquid separation in chemical processes.

2 ... microfiltration membrane, 2a ... one side, 3 ... sacrificial membrane (nonwoven fabric), 3a ... one side, 3b ... other side, 3d ... nanofiber, 3e ... void, 8 ... carbon filled layer, 9 ... carbon unfilled layer, DESCRIPTION OF SYMBOLS 10 ... Nanocarbon film, 10a ... One side, 10b ... Other side, 10c ... Hole, 11 ... Backing layer (N layer), 11a ... One side, 11b ... Other side, 11c ... Hollow part, 12 ... Carbon flat film (S Layer), 12a ... one side, 12b ... other side, 19 ... carbon film laminate, 31 ... beaker, 32 ... nanofiber solution, 33 ... suction bottle, 34 ... funnel, 39 ... substrate, 40 ... high frequency plasma film forming apparatus, 41 ... chamber, 42a, 42b ... electrode portion, 43 ... gas inlet, spout of 43a ... gas, 46, 47 ... pipe, 48 ... high frequency plasma, 81 ... carbon, etc., G 1 _... gas, S1 ... sacrificial film made Membrane process, S2 ... Carbon The film-forming process, S3 ... sacrificial layer removing step.

Claims (11)

A step of forming a sacrificial film made of nanofibers on the microfiltration membrane by a filtration method and a carbon-filled layer in which carbon is filled in the gaps of the nanofibers by a high-frequency plasma method and then covering the sacrificial membrane Forming a carbon flat film having a flat surface, and forming a carbon backing layer having a network-like cavity by removing the nanofibers of the carbon-filled layer with an acid or alkaline solution. And a step of forming a nanocarbon film having a film thickness of 100 nm or less, comprising the carbon flat film and the backing layer. The high-frequency plasma method is a method of forming a carbon film by generating a high-frequency plasma in a state where a gas containing an organic compound having a vapor pressure of 8 Pa or higher at normal temperature is circulated in a chamber. The method for producing a nanocarbon film according to claim 1. The organic compound is one organic compound selected from the group consisting of acetylene, butadiene, pyridine, benzene, hexafluorobenzene, cyclohexane, hexamethyldisiloxane, 4-vinylpyridine, propylamine, and allylamine. Item 3. A method for producing a nanocarbon film according to Item 2. The diameter of the said nanofiber is 10 nm or less, The manufacturing method of the nanocarbon film of any one of Claims 1-3 characterized by the above-mentioned. The method for producing a nanocarbon film according to claim 4, wherein the nanofiber is a nanostrand. 6. The method for producing a nanocarbon film according to claim 5, wherein an aqueous solution of an organic salt is passed through the sacrificial film made of the nanostrand to improve the stability of the nanostrand under a medium vacuum. A carbon flat film having a flat surface and having a hole penetrating one surface side and the other surface side, and a backing layer formed on the other surface side of the carbon flat film and having a mesh-like cavity. A nanocarbon film having a thickness of 100 nm or less.   The nanocarbon film according to claim 7, wherein a diameter of the hole is 5 nm or less.   The nanocarbon film according to claim 7 or 8, wherein a hole area ratio of the flat carbon film is 1% or more. The nanocarbon film according to any one of claims 7 to 9, wherein a diameter of the hollow portion is 10 nm or less. The nanocarbon membrane according to any one of claims 7 to 10, wherein the nanocarbon membrane is formed on one side of a microfiltration membrane.