JP2016059856A - Adsorption material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorption material using a porous carbon material excellent in adsorptivity and improved in internal fluidity of liquid and gas because of a co-continuous porous structure composed of carbon skeletons and cavities, and a large surface area.SOLUTION: The adsorption material comprises a porous carbon material having co-continuous structure parts in which carbon skeletons and cavities make respectively continuous structures and which has a structural pitch of 0.002-20 μm, and having pores with an average diameter of 0.01-10 nm on a surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adsorbing material for adsorbing a specific substance contained in a liquid or gas.

  As an application example of the adsorbing material, adsorption removal of trihalomethane or the like in a domestic water purifier can be mentioned. Chlorine used for disinfection of tap water at water purification plants reacts with dissolved organic substances in water to produce harmful substances such as trihalomethane, and these are removed by activated carbon in small household water purifiers. Yes.

  In addition to the above, the adsorbent is used as a deodorant to adsorb the odors of various foods in the refrigerator, as well as household air purifiers for the purpose of adsorbing the odors of tobacco and pets and building materials. Also used for machine filters. Adsorbents are widely used not only for household equipment, but also for water and sewage treatment, pharmaceutical purification, raw water treatment for soft drinks and beer, factory exhaust gas treatment, solvent recovery, etc. Yes.

  As such a gas or liquid adsorbing material, an activated carbon having a porous structure mainly composed of carbon and having a property of adsorbing a substance on the surface pores is widely used at present. Generally, activated carbon is obtained by forming pores by activating a carbon material obtained by carbonizing cellulose or resin. However, due to the recent increase in awareness of environmental sanitation, research and development of adsorbent materials that can remove harmful substances and environmental pollutants with high efficiency are widely performed.

  For example, Patent Document 1 discloses an adsorbent using porous carbon obtained by activating a carbonaceous material obtained from fullerene or the like. The adsorbent described in Patent Document 1 has a pore diameter of 20 to 100 angstroms, so that the dynamic adsorptive power is considered to be improved over conventional activated carbon.

2006-247527

  However, in the activation process, pores are formed in one direction from the surface to the inside of the carbon material. Therefore, even when activation is advanced and a high specific surface area material is obtained, there is a problem that the fluidity in the pores of the material to be adsorbed is low and it takes time for the adsorbed substance or the like to reach the surface. The adsorbing material described in Patent Document 1 also uses activation treatment, and does not solve such a problem.

  An object of the present invention is to provide an adsorbing material having high fluidity of an adsorbed material inside and excellent in substance adsorbing property.

  The present invention comprises porous carbon having a co-continuous structure portion having a structure period of 0.002 μm to 20 μm in which a carbon skeleton and voids each have a continuous structure, and having pores having an average diameter of 0.01 to 10 nm on the surface. Adsorption material.

  Since the adsorbing material of the present invention has a large surface area in the co-continuous structure portion, the area on which the adsorbing substance can act increases, and it is possible to exhibit high performance as an adsorbing material used in water treatment, medical treatment, and the like. . Moreover, when the parts other than the carbon skeleton are continuous as voids, the internal fluidity is improved, and the adsorption efficiency of the adsorbed material on the carbon surface can be improved. Furthermore, since the carbon skeletons are continuous, the carbon skeletons support each other and thus have some resistance to deformation such as tension and compression.

2 is a scanning electron micrograph of the porous carbon material of Example 1. FIG.

<Porous carbon material>
[Co-continuous structure part]
The porous carbon material used for the adsorbing material of the present invention (hereinafter sometimes referred to as “the porous carbon material of the present invention” for convenience) has a co-continuous structure portion in which the carbon skeleton and the voids each form a continuous structure. . Specifically, for example, when the surface of the powder obtained by crushing a sample sufficiently cooled in liquid nitrogen with tweezers or the like or pulverized with a mortar or the like is observed with a scanning electron microscope (SEM) or the like. As illustrated in the scanning electron micrograph of the porous carbon material of Example 1 in FIG. 1, the carbon skeleton and the voids have a portion observed as a continuous and intertwined structure.

  In the porous carbon material of the present invention, it is possible to exhibit characteristics such as adsorption and desorption of substances by filling and / or flowing a fluid in the voids of the co-continuous structure portion. In addition, when heated or boiled for reuse or the like, it is possible to exhibit high temperature uniformity by taking advantage of the continuous carbon skeleton. In addition, due to the effect that the carbon parts support each other in the structure, a material having great resistance against deformation such as tension and compression can be obtained.

  These co-continuous structures include a lattice shape and a monolith shape, and are not particularly limited. However, a monolith shape is preferable in that the above effect can be exhibited. Monolithic form refers to a form in which the carbon skeleton forms a three-dimensional network structure in a co-continuous structure, and is formed by removing aggregated and connected template particles, or a structure in which individual particles are aggregated and connected. A distinction is made between irregular structures such as those formed by voids and surrounding skeletons.

  Moreover, the co-continuous structure part in the porous carbon material of the present invention has a periodic structure. In the present invention, having a periodic structure can be confirmed by making X-rays incident on the porous carbon material and having a peak value of the scattering intensity.

  Moreover, the structural period of the co-continuous structure portion in the porous carbon material of the present invention is 0.002 μm to 20 μm. In the present invention, the structural period is calculated by the following formula from the scattering angle 2θ at the position where the X-ray is incident and the scattering intensity has a peak value with respect to the porous carbon material sample of the present invention. is there.

Structure period: L, λ: wavelength of incident X-rays However, there are cases where the structure period is large and scattering at small angles cannot be observed. In that case, the structural period is obtained by X-ray computed tomography (X-ray CT). Specifically, after performing a Fourier transform on a three-dimensional image photographed by X-ray CT, the two-dimensional spectrum is averaged to obtain a one-dimensional spectrum. The characteristic wavelength corresponding to the position of the peak top in the one-dimensional spectrum is obtained, and the structural period is calculated from the reciprocal thereof.

  When the structural period of the co-continuous structure portion is 0.002 μm or more, it is possible to efficiently fill and / or flow a fluid in the void portion, and to improve thermal conductivity through the carbon skeleton. The structural period is preferably 0.01 μm or more, and more preferably 0.1 μm or more. Moreover, a high surface area and physical property can be acquired as a structural period is 20 micrometers or less. The structural period is preferably 10 μm or less, and more preferably 1 μm or less.

  Furthermore, by having a uniform continuous structure, it is possible to reduce resistance when gas and liquid flow inside, and in all processes related to production, such as the production process of porous carbon materials and the column packing process, tension and compression are performed. It is possible to use a material having a great resistance to deformation. The uniformity of the continuous structure of the porous carbon material of the present invention can be determined by the half width of the peak of the scattering intensity when X-rays are incident on the porous carbon material of the present invention. The full width at half maximum of the X-ray scattering peak of the porous carbon material of the present invention is preferably 5 ° or less, more preferably 3 ° or less, and particularly preferably 1 ° or less. The half width of the peak in the present invention is the peak A at the point A, a straight line parallel to the vertical axis of the graph is drawn from the point A, and the intersection of the straight line and the spectrum baseline is the point B. This is the width of the peak at the midpoint (point C) of the line segment connecting points A and B. In addition, the width | variety of the peak said here is a width | variety on the straight line which is parallel to a base line and passes along the point C. FIG.

  In the analysis of the structural period by X-rays, the part having no co-continuous structure described later has no influence on the analysis because the structural period is outside the above range, and the structural period calculated by the above method is used. , And the structural period of the co-continuous structure portion.

  The smaller the structure period, the finer the structure, the larger the surface area per unit volume or unit weight, and the higher the contact efficiency between the fluid and the porous carbon material. In addition, the larger the structural period, the more the pressure loss is reduced, and a larger amount of fluid can be filled and / or flowed. From these things, the structure period of a co-continuous structure part can be suitably adjusted according to the use and conditions to be used.

  The co-continuous structure portion preferably has an average porosity of 10 to 80%. The average porosity is an enlargement ratio adjusted to be 1 ± 0.1 (nm / pixel) of a cross section in which an embedded sample is precisely formed by a cross section polisher method (CP method). The image is calculated by the following expression from an image observed at a resolution of at least a pixel, where the area of interest required for calculation is set in 512 pixels square, the area of the area of interest is A, and the area of the hole is B.

Average porosity (%) = B / A × 100
The higher the average porosity, the smaller the pressure loss as a gas or liquid flow path, and the higher the flow rate, while the lower the porosity, the stronger the compression and bending, the more advantageous for handling and use under pressurized conditions. . Considering these, the average porosity of the co-continuous structure portion is preferably in the range of 15 to 75%, more preferably in the range of 18 to 70%.

〔pore〕
Furthermore, the porous carbon material of the present invention has pores having an average diameter of 0.01 to 10 nm on the surface. The surface refers to a contact surface with any outside of the porous carbon material including the surface of the carbon skeleton in the co-continuous structure portion of the carbon material. The pores can be formed on the surface of the carbon skeleton in the co-continuous structure portion and / or in the portion substantially not having the co-continuous structure described later, but at least formed on the surface of the carbon skeleton in the portion having the co-continuous structure. It is preferable to do.

  When the average diameter of the pores is 0.01 nm or more, an adsorption action can be exerted on the substance. Moreover, an adsorption function can be efficiently expressed by being 10 nm or less. The average diameter of such pores is preferably 0.1 nm or more, and more preferably 0.5 nm or more. Moreover, it is preferable that it is 5 nm or less, and it is more preferable that it is 2 nm or less. From the viewpoint of adsorption efficiency, the pore diameter is preferably appropriately adjusted to about 1.1 to 2.0 times the diameter of the target adsorbent.

The pore volume is preferably 0.1 cm ³ / g or more, more preferably 1.0 cm ³ / g or more, and further preferably 1.5 cm ³ / g or more. When the pore volume is 0.1 cm ³ / g or more, the adsorption performance is further improved. The upper limit is not particularly limited, but if it exceeds 10 cm ³ / g, the strength of the porous carbon material is lowered or the bulk density is remarkably lowered, so that the handleability tends to be deteriorated.

  In addition, in this specification, the average diameter of a pore means the measured value by any method of BJH method or MP method. That is, if either one of the measured values by the BJH method or the MP method falls within the range of 0.01 to 10 nm, it is determined that the surface has pores having an average diameter of 0.01 to 10 nm. The same applies to the preferable range of the pore diameter. The BJH method and the MP method are widely used as a pore size distribution analysis method, and can be obtained based on a desorption isotherm obtained by adsorbing and desorbing nitrogen on a porous carbon material. The BJH method is a method of analyzing the pore volume distribution with respect to the pore diameter assumed to be cylindrical according to the Barrett-Joyner-Halenda standard model, and can be applied mainly to pores having a diameter of 2 to 200 nm. (For details, see J. Amer. Chem. Soc., 73, 373, 1951 etc.). The MP method is based on the external surface area and adsorption layer thickness (corresponding to the pore radius because the pore shape is cylindrical) obtained from the change in the tangential slope at each point of the adsorption isotherm. This is a method for obtaining the pore volume and plotting it against the thickness of the adsorption layer to obtain a pore size distribution (for details, refer to Junealod Colloid and Interface Science, 26, 45, 1968, etc.). Applicable to pores having a diameter. In the present invention, all values obtained by rounding off the second decimal place to the first decimal place are used.

In the porous carbon material of the present invention, the voids in the co-continuous structure portion may affect the pore size distribution and pore volume measured by the BJH method or the MP method. That is, there is a possibility that these measured values may be obtained as values that reflect not only the pores but also the presence of voids. Even in this case, the measured values obtained by these methods are used in the present invention. Assume that the average diameter and the pore volume of the pores. Moreover, if the pore volume measured by BJH method or MP method is less than 0.05 cm < ³ > / g, it will be judged that the pore is not formed in the material surface.

In addition, the porous carbon material of the present invention preferably has a BET specific surface area of 50 m ² / g or more. The BET specific surface area is more preferably 200 m ² / g or more, further preferably 500 m ² / g or more, and further preferably 1000 m ² / g or more. When the BET specific surface area is 50 m ² / g or more, the area that can act on the adsorbed material is increased, and the performance is improved. Although an upper limit is not specifically limited, When it exceeds 4500 m < ² > / g, there exists a tendency for the intensity | strength of a porous carbon material to fall or for a bulk density to become remarkably low, and for handleability to worsen. The BET specific surface area in the present invention can be calculated based on the BET equation by measuring the adsorption isotherm by adsorbing and desorbing nitrogen to and from the porous carbon material according to JISR 1626 (1996). it can.

[Parts having substantially no co-continuous structure]
It is also a preferred embodiment that the porous carbon material of the present invention includes a portion that does not substantially have a co-continuous structure (hereinafter, simply referred to as “portion that does not have a co-continuous structure”). The portion having substantially no co-continuous structure is a portion below the resolution when a cross section formed by the cross section polisher method (CP method) is observed at an enlargement ratio of 1 ± 0.1 (nm / pixel). This means that a part where no clear air gap is observed exists in an area equal to or larger than a square region corresponding to three times the structural period L calculated from the X-ray described later.

  Since the portion having no co-continuous structure is densely filled with carbon, the thermal conductivity can be maintained at a certain level or higher. In addition, since there is a portion that does not have a co-continuous structure, it is possible to increase resistance to compression fracture.

  The proportion of the portion not having the co-continuous structure can be adjusted as appropriate. For example, when the portion not having the co-continuous structure is used as the outer wall of the gas or liquid flow path, 5% by volume or more is the co-continuous structure. It is preferable to use a portion that does not have a fluid because it is possible to prevent the fluid from leaking from the co-continuous structure portion or to maintain the thermal conductivity at a high level.

  When the portion that does not have the co-continuous structure is configured to cover the portion of the co-continuous structure, it is possible to more efficiently fill and / or flow fluid into the voids that form the co-continuous structure. Hereinafter, in the porous carbon material of this form, the co-continuous structure portion is referred to as a core layer, and the portion that does not substantially have the co-continuous structure formed so as to cover the core layer is referred to as a skin layer. By having an asymmetric structure composed of a skin layer and a core layer, efficient adsorption is possible with the skin layer as an outer wall of a gas or liquid flow channel and the core layer as a fluid flow channel and an adsorption function part.

  The continuous structure of the core layer is preferably formed such that the structural period in the center is 0.002 μm to 20 μm. Similarly, it is preferable that the average porosity in the central portion is 10 to 80%. Here, the central portion refers to the center of gravity when the mass distribution in the cross-section of the material is assumed to be uniform in the porous carbon material. For example, in the case of powder, the center is the center of gravity, and the form of the material is round. In the case of a fiber having a cross section, it refers to a point where the distance from the fiber surface is the same in a cross section perpendicular to the fiber axis. However, in the case of a film shape in which it is difficult to clearly define the center of gravity, a perpendicular line is drawn from the film surface in a cross section orthogonal to the TD or MD direction, and the set of points that are one-half the film thickness on the perpendicular line Is the center. Similarly, in the case of a hollow fiber in which the center of gravity does not exist in the material, a perpendicular line is drawn from the tangent line of the outer surface of the hollow fiber, and a set of points on the perpendicular line that is one-half the thickness of the material is used as the central part. The structural period can be measured by the X-ray described above.

  The skin layer is a portion substantially not having a co-continuous structure formed so as to cover the core layer around the core layer. The thickness of the skin layer is not particularly limited, and can be appropriately selected according to the use of the material. However, if the thickness is too thick, the porosity tends to decrease as a porous carbon material, so that the thickness is 100 μm or less. Preferably, it is 50 μm or less, and most preferably 20 μm or less. Although it does not specifically limit about a lower limit here, It is preferable that it is 1 nm or more from a viewpoint of maintaining the form of material and exhibiting the function distinguished from the core layer.

[Shape of porous carbon material]
The shape of the porous carbon material of the present invention is not particularly limited, and examples thereof include a lump shape, a hollow fiber shape, a rod shape, a flat plate shape, a disc shape, and a spherical shape. Among these, a particulate shape or a fibrous shape is preferable.

  The particulate form is preferably used, for example, in a method of filling a column or cartridge. The part that does not have a co-continuous structure occupies a part of one particle, so that it is possible to increase the thermal conductivity in the particle, and also increase the compressive strength of the particle itself and degrade the performance under high pressure. This is preferable because an effect such as a reduction in the number of particles can be expected.

  The diameter of the particles is not particularly limited and can be appropriately selected depending on the application. However, the range of 10 nm to 10 mm is preferable because it is easy to handle. In particular, the particle size is preferably 10 μm or less because the packing rate of particles is improved when packed in a column or module. On the other hand, when it is 0.1 μm or more, the gap between particles becomes large at the time of filling, and pressure loss can be suppressed when flowing gas or liquid, and further, when filling into a mesh bag or container, Since the outflow of the particle | grains from a mesh can be suppressed, it is preferable.

  The fibrous form refers to those having an average length of 100 times or more with respect to the average diameter, and may be a filament, a long fiber, a staple, a short fiber, or a chopped fiber. Further, the shape of the cross section is not limited at all, and can be an arbitrary shape such as a multi-leaf cross section such as a round cross section or a triangular cross section, a flat cross section or a hollow cross section.

  In particular, in the case of a fiber having a core layer having a co-continuous structure as a core and a skin layer substantially free of the co-continuous structure formed around the core layer, the core layer may be filled with fluid and / or flowed. In particular, when filling and / or flowing gas or liquid at high pressure, the carbon skeletons of the co-continuous structure parts have a structure that supports each other, so that they exhibit high compression resistance and efficiently fill and / or fluid. It becomes possible to flow.

  The average diameter of the fiber is not particularly limited and can be arbitrarily determined, but is preferably 10 nm or more from the viewpoint of maintaining handleability and porosity. Moreover, it is preferable that it is 5000 micrometers or less from a viewpoint of ensuring bending rigidity and improving a handleability.

<Use form of adsorbent material>
Although the usage form of the porous carbon material of this invention is not limited at all, it can be processed into a nonwoven fabric or a woven fabric from a fiber shape, or can be used as a sheet-like adsorbing material in a film shape itself. In addition, it can be used in the form of particles, fibers, and films filled in columns, cartridges, and bags that can pass liquids and gases. If the fiber layer or hollow fiber shape has a core layer and / or a hollow part having a co-continuous structure as a core and a skin layer substantially free of the co-continuous structure is formed around the core layer, a module This is a preferred embodiment because it can be easily incorporated into a membrane separation process or the like.

  In any use form, the porous carbon material of the present invention can be used in a state of being shaped into a desired shape. Examples of the shaping method include a method using a binder and a method of pressurizing. In any form of use, it may be used after a hydrophilic treatment or a hydrophobic treatment.

<Application of adsorption material>
The adsorbing material of the present invention can be used by being incorporated in a known purification device, for example, a water purifier, and as a type of water purifier, a continuous water purifier, a batch water purifier, a reverse osmosis membrane water purifier, etc. Can be mentioned. In addition, the water purifier model is a faucet direct connection type that attaches the water purifier body directly to the tip of a water faucet, a desktop type, a faucet integrated type that has a water purifier built into the faucet, and is installed in the kitchen sink Undersink type, pot type with a water purifier installed in a container such as a pot, central type directly attached to the water pipe after the water meter, portable type, straw type, etc. A well-known configuration and structure can be adopted.

  Further, the adsorbing material using the porous carbon material of the present invention has an excellent adsorption function for gas and can be used in various fields. As a gas recovery purpose, it is used for an automotive canister, a transpiration prevention application during refueling, or a solvent recovery application of methyl ethyl ketone, cyclohexanone, carbon disulfide, chlorofluorocarbon, trichloroethylene, or the like. Deodorizing purposes include air purifiers, refrigerator deodorants, shoe insoles, anesthetic gas removal in hospitals, photocopiers, and ozone decomposition in printers. For the purpose of gas concentration separation, it is used for separation of nitrogen, rare gas, and the like. Further, for water treatment purposes, it is used for industrial wastewater, sewage purification, trihalomethane, humic acid, chlorine removal applications, etc., and for purification purposes, it can be used for sugar, chemicals, liquor decolorization purification applications, etc.

<Method for producing porous carbon material>
As an example, the porous carbon material of the present invention includes a step (Step 1) in which 10% to 90% by weight of carbonizable resin and 90% to 10% by weight of the disappearing resin are mixed to form a resin mixture, It can be produced by a production method having a step of phase separation and immobilization of the resin mixture (step 2), a step of carbonization by heating and baking (step 3), and a step of activating the carbide (step 4).

[Step 1]
Step 1 is a step in which 10 to 90% by weight of the carbonizable resin and 90 to 10% by weight of the disappearing resin are compatible to form a resin mixture.

  Here, the carbonizable resin is a resin that is carbonized by firing and remains as a carbon material, and preferably has a carbonization yield of 40% or more. For example, both a thermoplastic resin and a thermosetting resin can be used, and examples of the thermoplastic resin include polyphenylene oxide, polyvinyl alcohol, polyacrylonitrile, phenol resin, wholly aromatic polyester, and thermosetting resin. Examples of these include unsaturated polyester resins, alkyd resins, melamine resins, urea resins, polyimide resins, diallyl phthalate resins, lignin resins, urethane resins, and the like. In view of cost and productivity, polyacrylonitrile and phenol resin are preferable, and polyacrylonitrile is more preferable. Particularly in the present invention, polyacrylonitrile is a preferred embodiment because a high specific surface area can be obtained. These may be used alone or in a mixed state. The carbonization yield here is the difference between the weight at room temperature and the weight at 800 ° C. by measuring the change in weight when the temperature is raised at 10 ° C./min in a nitrogen atmosphere by the thermogravimetry (TG) method. Is divided by the weight at room temperature.

  Further, the disappearing resin is a resin that can be removed after Step 2 described later, and is preferably a resin that can be removed at least in any stage of the infusibilization treatment, the infusibilization treatment, or the firing. . The removal rate is preferably 80% by weight or more, and more preferably 90% by weight or more when finally becoming a porous carbon material. The method for removing the disappearing resin is not particularly limited, and is a method of chemically removing the polymer by depolymerizing it with a chemical, a method of removing the disappearing resin with a solvent that dissolves, or by thermal decomposition by heating. A method of removing the lost resin by reducing the molecular weight is preferably used. These methods can be used singly or in combination, and when implemented in combination, each may be performed simultaneously or separately.

  As a method of chemically removing, a method of hydrolyzing with an acid or an alkali is preferable from the viewpoints of economy and handleability. Examples of the resin that is susceptible to hydrolysis by acid or alkali include polyester, polycarbonate, and polyamide.

  As a method of removing the disappearing resin with a solvent that dissolves, the mixed carbonizable resin and the disappearing resin are continuously supplied with a solvent to dissolve and remove the disappearing resin, or mixed in a batch system. A suitable example is a method of dissolving and removing the disappearing resin.

  Specific examples of the disappearing resin suitable for the method of removing with a solvent include polyolefins such as polyethylene, polypropylene and polystyrene, acrylic resins, methacrylic resins, polyvinylpyrrolidone, aliphatic polyesters, polycarbonates and the like. Among these, an amorphous resin is more preferable because of its solubility in a solvent, and examples thereof include polystyrene, methacrylic resin, polycarbonate, and polyvinylpyrrolidone.

  As a method of removing the lost resin by reducing the molecular weight by thermal decomposition, a method in which the mixed carbonizable resin and the lost resin are heated in a batch manner to thermally decompose, or a continuously mixed carbonized resin and the lost resin are removed. A method of heating and thermally decomposing while continuously supplying to a heat source.

  Among these, the disappearing resin is preferably a resin that disappears by thermal decomposition when carbonizing the carbonizable resin by firing in Step 3 described later, and is large during the infusibilization treatment of the carbonizable resin described later. A resin that does not cause a chemical change and has a carbonization yield after firing of less than 10% is preferable. Specific examples of such disappearing resins include polyolefins such as polyethylene, polypropylene and polystyrene, acrylic resins, methacrylic resins, polyacetals, polyvinylpyrrolidones, aliphatic polyesters, aromatic polyesters, aliphatic polyamides, polycarbonates and the like. These may be used alone or in a mixed state.

  In step 1, the carbonizable resin and the disappearing resin are mixed to form a resin mixture (polymer alloy). “Compatibilized” as used herein refers to creating a state in which the phase separation structure of the carbonizable resin and the disappearing resin is not observed with an optical microscope by appropriately selecting the temperature and / or solvent conditions.

  The carbonizable resin and the disappearing resin may be compatible by mixing only the resins, or may be compatible by adding a solvent or the like.

  A system in which a plurality of resins are compatible includes a phase diagram of an upper critical eutectic temperature (UCST) type that is in a phase separation state at a low temperature but has one phase at a high temperature, and conversely, a phase separation state at a high temperature. However, there is a system showing a lower critical solution temperature (LCST) phase diagram that becomes one phase at a low temperature. In particular, when a system in which at least one of the carbonizable resin and the disappearing resin is dissolved in a solvent, those in which phase separation to be described later is induced by permeation of the non-solvent are also preferable examples.

  The solvent to be added is not particularly limited, but the absolute value of the difference from the average value of the solubility parameter (SP value) of the carbonizable resin and the disappearing resin, which is a solubility index, is within 5.0. It is preferable. Since it is known that the smaller the absolute value of the difference from the average value of SP values, the higher the solubility, it is preferable that there is no difference. Further, the larger the absolute value of the difference from the average SP value, the lower the solubility, and it becomes difficult to take a compatible state between the carbonizable resin and the disappearing resin. Therefore, the absolute value of the difference from the average value of SP values is preferably 3.0 or less, and most preferably 2.0 or less.

  Specific examples of combinations of carbonizable resins and disappearance resins that are compatible are polyphenylene oxide / polystyrene, polyphenylene oxide / styrene-acrylonitrile copolymer, wholly aromatic polyester / polyethylene as long as they do not contain solvents. Examples include terephthalate, wholly aromatic polyester / polyethylene naphthalate, wholly aromatic polyester / polycarbonate. Specific examples of combinations of systems containing solvents include polyacrylonitrile / polyvinyl alcohol, polyacrylonitrile / polyvinylphenol, polyacrylonitrile / polyvinylpyrrolidone, polyacrylonitrile / polylactic acid, polyvinyl alcohol / vinyl acetate-vinyl alcohol copolymer, polyvinyl Examples include alcohol / polyethylene glycol, polyvinyl alcohol / polypropylene glycol, and polyvinyl alcohol / starch.

  The method for mixing the carbonizable resin and the disappearing resin is not limited, and various known mixing methods can be adopted as long as they can be mixed uniformly. Specific examples include a rotary mixer having a stirring blade and a kneading extruder using a screw.

  It is also a preferred aspect that the temperature (mixing temperature) when mixing the carbonizable resin and the disappearing resin is equal to or higher than the temperature at which the carbonizable resin and the disappearing resin are both softened. Here, the softening temperature may be appropriately selected as the melting point if the carbonizable resin or disappearing resin is a crystalline polymer, and the glass transition temperature if it is an amorphous resin. By setting the mixing temperature to be equal to or higher than the temperature at which both the carbonizable resin and the disappearing resin are softened, the viscosity of the both can be lowered, so that more efficient stirring and mixing are possible. Although the upper limit of the mixing temperature is not particularly limited, it is preferably 400 ° C. or lower from the viewpoint of preventing deterioration of the resin due to thermal decomposition and obtaining a precursor of a porous carbon material having excellent quality.

  Further, in step 1, 90 to 10% by weight of the disappearing resin is mixed with 10 to 90% by weight of the carbonizable resin. It is preferable that the carbonizable resin and the disappearing resin are within the above-mentioned range since an optimum void size and void ratio can be arbitrarily designed. If the carbonizable resin is 10% by weight or more, it is possible to maintain the mechanical strength of the carbonized material and improve the yield. Further, if the carbonizable material is 90% by weight or less, it is preferable because the lost resin can efficiently form voids.

  The mixing ratio of the carbonizable resin and the disappearing resin can be arbitrarily selected within the above range in consideration of the compatibility of the respective materials. Specifically, in general, the compatibility between resins deteriorates as the composition ratio approaches 1: 1, so when a system that is not very compatible is selected as a raw material, the amount of carbonizable resin is increased. It is also preferable to improve the compatibility by reducing it so that it approaches a so-called uneven composition.

  It is also a preferred embodiment to add a solvent when mixing the carbonizable resin and the disappearing resin. Addition of a solvent lowers the viscosity of the carbonizable resin and the disappearing resin to facilitate molding, and facilitates compatibilization of the carbonizable resin and the disappearing resin. The solvent here is not particularly limited as long as it is a liquid at room temperature that can dissolve and swell at least one of carbonizable resin and disappearing resin. Any resin that dissolves the resin is more preferable because the compatibility between the two can be improved.

  The addition amount of the solvent should be 20% by weight or more based on the total weight of the carbonizable resin and the disappearing resin from the viewpoint of improving the compatibility between the carbonizable resin and the disappearing resin and reducing the viscosity to improve the fluidity. preferable. On the other hand, from the viewpoint of costs associated with recovery and reuse of the solvent, it is preferably 90% by weight or less based on the total weight of the carbonizable resin and the disappearing resin.

[Step 2]
Step 2 is a step of phase-separating the resin mixture dissolved in Step 1 to form a fine structure and immobilize it.

  Phase separation of mixed carbonizable resin and disappearing resin can be induced by various physical and chemical methods, for example, by thermally induced phase separation method that induces phase separation by temperature change, by adding non-solvent Examples include a non-solvent induced phase separation method that induces phase separation, a reaction induced phase separation method that induces phase separation using a chemical reaction, a flow induced phase separation method, and an orientation induced phase separation method. Among these, a method that does not involve a chemical reaction during phase separation, such as a thermally induced phase separation method or a non-solvent induced phase separation method, is preferable in that the porous carbon material of the present invention can be easily produced.

  These phase separation methods can be used alone or in combination. Specific methods for use in combination include, for example, a method in which non-solvent induced phase separation is caused through a coagulation bath and then heated to cause heat-induced phase separation, or a temperature in the coagulation bath is controlled to control a non-solvent induced phase. Examples thereof include a method of causing separation and thermally induced phase separation at the same time, a method of bringing the material discharged from the die into cooling and causing thermally induced phase separation, and then contacting with a non-solvent.

  “No chemical reaction during the phase separation” means that the mixed carbonizable resin or disappearing resin does not change its primary structure before and after mixing. The primary structure refers to a chemical structure that constitutes a carbonizable resin or a disappearing resin. By not involving a chemical reaction such as polymerization during phase separation, it is possible to suppress a change in characteristics such as a significant improvement in elastic modulus and easily form an arbitrary structure such as a fiber or a film. The production method of the present invention excludes phase separation accompanied by a chemical reaction from the viewpoint of stable production at a lower cost, but the porous carbon material of the present invention is limited to the production method of the present invention. What has not been described is as described above.

[Removal of disappearing resin]
It is preferable that the resin mixture in which the microstructure after phase separation is fixed in Step 2 is subjected to the removal treatment of the lost resin before being subjected to the carbonization step (Step 3), simultaneously with the carbonization step, or both. The method for the removal treatment is not particularly limited as long as the disappearing resin can be removed. Specifically, the method of removing the lost resin by chemically decomposing and reducing the molecular weight using acid, alkali or enzyme, the method of removing by dissolving with a solvent that dissolves the lost resin, electron beam, gamma ray, ultraviolet ray, infrared ray A method of decomposing and removing the disappearing resin using radiation or heat such as is suitable.

  In particular, when the disappearance resin can be removed by thermal decomposition, a heat treatment can be performed at a temperature at which 80% by weight or more of the disappearance resin disappears in advance, and a carbonization step (step 3) or infusibilization described later. In the treatment, the lost resin can be removed by pyrolysis and gasification. From the viewpoint of increasing the productivity by reducing the number of steps, it is more preferable to select a method in which the lost resin is thermally decomposed and gasified and removed simultaneously with the heat treatment in the carbonization step (step 3) or infusibilization treatment described later. It is.

[Infusibilization]
The precursor material, which is a resin mixture in which the microstructure after phase separation is fixed in step 2, is preferably subjected to an infusibilization treatment before being subjected to the carbonization step (step 3). The infusible treatment method is not particularly limited, and a known method can be used. Specific methods include a method of causing oxidative crosslinking by heating in the presence of oxygen, a method of forming a crosslinked structure by irradiating high energy rays such as electron beams and gamma rays, and impregnating a substance having a reactive group, Examples thereof include a method of forming a crosslinked structure by mixing, and a method of causing oxidative crosslinking by heating in the presence of oxygen is preferable because the process is simple and the production cost can be kept low. These methods may be used singly or in combination, and each may be used simultaneously or separately.

  The heating temperature in the method of causing oxidative crosslinking by heating in the presence of oxygen is preferably 150 ° C. or higher from the viewpoint of efficiently proceeding with the crosslinking reaction, and it can be recovered from weight loss due to thermal decomposition, combustion, etc. of carbonizable resin. From the viewpoint of preventing rate deterioration, the temperature is preferably 350 ° C. or lower.

  Further, the oxygen concentration during the treatment is not particularly limited, but it is preferable to supply a gas having an oxygen concentration of 18% or more, in particular, air as it is because manufacturing costs can be kept low. The method for supplying the gas is not particularly limited, and examples thereof include a method for supplying air directly into the heating device and a method for supplying pure oxygen into the heating device using a cylinder or the like.

  As a method of forming a crosslinked structure by irradiating a high energy beam such as an electron beam or gamma ray, the carbonizable resin is irradiated with an electron beam or gamma ray using a commercially available electron beam generator or gamma ray generator. And a method of inducing cross-linking. The lower limit of the irradiation intensity is preferably 1 kGy or more from the efficient introduction of a crosslinked structure by irradiation, and is preferably 1000 kGy or less from the viewpoint of preventing the material strength from being lowered due to the decrease in molecular weight due to cleavage of the main chain.

  A method of forming a crosslinked structure by impregnating and mixing a substance having a reactive group is a method in which a low molecular weight compound having a reactive group is impregnated in a resin mixture, and a crosslinking reaction is advanced by irradiation with heat or high energy rays. And a method in which a low molecular weight compound having a reactive group is mixed in advance and the crosslinking reaction is advanced by heating or irradiation with high energy rays.

  In addition, it is also preferable to remove the lost resin at the same time during the infusibilization treatment because a cost reduction due to a reduction in the number of steps can be expected.

[Step 3]
In step 3, the resin mixture in which the microstructure after phase separation is fixed in step 2 or, if the disappearing resin has already been removed, the remaining portion made of carbonizable resin is fired and carbonized to form the carbide. It is a process to obtain.

  Firing is preferably performed by heating to 600 ° C. or higher in an inert gas atmosphere. Here, the inert gas refers to one that is chemically inert during heating, and specific examples include helium, neon, nitrogen, argon, krypton, xenon, carbon dioxide, and the like. Of these, nitrogen and argon are preferably used from the economical viewpoint. When the carbonization temperature is 1500 ° C. or higher, argon is preferably used from the viewpoint of suppressing nitride formation.

  The flow rate of the inert gas may be an amount that can sufficiently reduce the oxygen concentration in the heating device, and an optimal value can be selected as appropriate depending on the size of the heating device, the amount of raw material supplied, the heating temperature, and the like. preferable. The upper limit of the flow rate is not particularly limited, but is preferably set appropriately in accordance with the temperature distribution and the design of the heating device, from the viewpoint of economy and the temperature change in the heating device being reduced. Further, if the gas generated during carbonization can be sufficiently discharged out of the system, a porous carbon material excellent in quality can be obtained, which is a more preferable embodiment. From this, the generated gas concentration in the system is 3,000 ppm. It is preferable to determine the flow rate of the inert gas so as to be as follows.

  Although the upper limit of the temperature to heat is not limited, if it is 3000 degrees C or less, since a special process is not required for an installation, it is preferable from an economical viewpoint. Moreover, in order to raise a BET specific surface area, it is preferable that it is 1500 degrees C or less, and it is more preferable that it is 1000 degrees C or less.

  About the heating method in the case of continuously performing carbonization treatment, it is a method to take out the material while continuously supplying the material using a roller, a conveyor, or the like in a heating device maintained at a constant temperature. It is preferable because it can be increased.

  On the other hand, the lower limit of the rate of temperature rise and the rate of temperature drop when performing batch processing in the heating device is not particularly limited, but productivity can be increased by shortening the time required for temperature rise and temperature drop, and 1 ° C. It is preferable that the speed is at least 1 minute. Moreover, although the upper limit of the temperature increase rate and the temperature decrease rate is not particularly limited, it is preferable to make it slower than the thermal shock resistance of the material constituting the heating device.

[Step 4]
Step 4 is a step of forming pores on the surface by further activating the carbide obtained in Step 3. The activation method is not particularly limited, such as a gas activation method or a chemical activation method. The gas activation method is a method of forming pores by heating at 400 to 1500 ° C., preferably 500 to 900 ° C. for several minutes to several hours, using oxygen, water vapor, carbon dioxide gas, air or the like as an activator. It is. Also, the chemical activation method is one or two kinds of activator such as zinc chloride, iron chloride, calcium phosphate, calcium hydroxide, potassium hydroxide, magnesium carbonate, sodium carbonate, potassium carbonate, sulfuric acid, sodium sulfate, potassium sulfate, etc. This is a method of heat treatment for several minutes to several hours using the above, and after washing with water or hydrochloric acid as necessary, the pH is adjusted and dried.

  Generally, the BET specific surface area increases and the pore diameter tends to increase by further promoting the activation or increasing the mixing amount of the activator. The mixing amount of the activator is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more, and further preferably 4 parts by weight or more with respect to the target carbon raw material. Although an upper limit is not specifically limited, 10 weight part or less is common. In addition, the pore diameter tends to be larger in the chemical activation method than in the gas activation method.

  In the present invention, the chemical activation method is preferably employed because the pore diameter can be increased or the BET specific surface area can be increased. Among them, a method of activating with an alkaline agent such as calcium hydroxide, potassium hydroxide, potassium carbonate is preferably employed.

  When activated with an alkaline agent, the amount of acidic functional groups tends to increase, which may be undesirable depending on the application. At this time, it is also preferable to reduce by performing a heat treatment in a nitrogen atmosphere.

[Crushing treatment]
The porous carbon material that has been activated through the step 4 is pulverized into a particulate porous carbon material, or is pulverized at any stage before the post-process 4 in the step 2 The porous carbon material subjected to the activation treatment in the subsequent step 4 is also an embodiment of the porous carbon material of the present invention. Examples of the pulverization method include a ball mill, a bead mill, and a jet mill. The pulverization may be continuous or batch, but is preferably continuous from the viewpoint of production efficiency. The filler to be filled in the ball mill is selected as appropriate, but for adsorbent materials where mixing of metal materials is not preferred, it is made of metal oxides such as alumina, zirconia, titania, or nylon with stainless steel, iron, etc. as the core. It is preferable to use a material coated with polyolefin, fluorinated polyolefin or the like. For other uses, metals such as stainless steel, nickel and iron are preferably used.

  In addition, it is also a preferable aspect to use a grinding aid in terms of increasing grinding efficiency during grinding. The grinding aid is arbitrarily selected from water, alcohol or glycol, ketone and the like. As the alcohol, ethanol and methanol are preferable from the viewpoint of availability and cost, and in the case of glycol, ethylene glycol, diethylene glycol, propylene glycol and the like are preferable. In the case of a ketone, acetone, ethyl methyl ketone, diethyl ketone and the like are preferable.

  Carbide that has been pulverized has a uniform particle size and can be improved in packing efficiency by classification. About a particle size, it is preferable to select suitably according to the use of adsorption material.

  Examples of preferred embodiments of the present invention will be described below, but these descriptions do not limit the present invention.

<Evaluation method>
[With or without co-continuous structure]
The surface of the powder obtained by grinding with a mortar was observed with a scanning electron microscope. At that time, the presence or absence of the co-continuous structure was determined based on whether or not the carbon skeleton and the voids had a portion observed as a continuous and intertwined structure.

[Structure period of continuous structure part]
A porous carbon material was sandwiched between sample plates, and the positions of the light source, sample, and two-dimensional detector were adjusted so that information with a scattering angle of less than 10 degrees was obtained from an X-ray source obtained from a CuKα ray light source. From the image data (luminance information) obtained from the two-dimensional detector, the central portion affected by the beam stopper is excluded, a moving radius is provided from the beam center, and a luminance value of 360 ° is obtained for each angle of 1 °. The scattering intensity distribution curve was obtained by summing up. From the scattering angle 2θ at a position having a peak in the obtained curve, the structural period of the continuous structure portion was obtained by the following equation.

Structure period: L, λ: wavelength of incident X-ray [average porosity]
The porous carbon material is embedded in a resin, and then the cross section of the porous carbon material is exposed with a razor or the like, and the sample surface is irradiated with an argon ion beam at an acceleration voltage of 5.5 kV using JEOL SM-09010. Etching is performed. The cross section of the obtained porous carbon material is observed with a scanning secondary electron microscope at a magnification of 700,000 pixels or more at an enlargement ratio adjusted so that the central portion of the material becomes 1 ± 0.1 (nm / pixel). From the obtained image, the area of interest required for the calculation is set by 512 pixels square, and the area of the area of interest, the area of the hole portion or the disappearing resin portion is B, and is calculated by the following formula.

Average porosity (%) = B / A × 100
[BET specific surface area, pore diameter]
After degassing under reduced pressure at 300 ° C. for about 5 hours, nitrogen adsorption / desorption at a temperature of 77 K was measured by a multi-point method using “BELSORP-18PLUS-HT” manufactured by Bell Japan Co., Ltd. using liquid nitrogen. The surface area was measured by the BET method, and the pore distribution analysis (pore diameter, pore volume) was performed by the MP method.

[Chloroform adsorption measurement]
A porous carbon material sample was weighed, sealed in a vial, sealed, and then chloroform standard gas was injected into the vial and shaken lightly. A sample was taken out after 30 minutes, and a gas generated by heating was measured by a TPD-MS (Temperature Programmed Desorption-Mass Spectrometry) method under the following conditions to examine the amount of chloroform generated. This generated amount was defined as the amount of chloroform adsorbed on the sample. The result was 2 significant figures.

  The TPD-MS method is a method in which an MS (mass spectrometry) device is directly connected to a heating device with a temperature controller, and the concentration change for each mass number of gas generated from a sample during heating is tracked as a function of temperature and time. The experimental conditions are as follows.

Device: Shimadzu GC / MS QP2010Ultra
Heating conditions: Room temperature to 300 ° C. (Temperature increase rate: 10 ° C./min)
MS sensitivity: Gain 1.50kV
Mass number range: m / z = 10-300
Atmosphere: He flow (50 ml / min)
[Example 1]
70 g of polyacrylonitrile (MW 150,000, carbon yield 58%), 70 g of polyvinyl pyrrolidone (MW 40,000) manufactured by Sigma-Aldrich, and 400 g of dimethyl sulfoxide (DMSO) manufactured by Waken Pharmaceutical as a solvent are separated. A uniform and transparent solution was prepared at 150 ° C. while stirring and refluxing for 3 hours. At this time, the concentration of polyacrylonitrile and the concentration of polyvinylpyrrolidone were 13% by weight, respectively.

  After cooling the obtained DMSO solution to 25 ° C., the solution is discharged at a rate of 3 ml / min from a 0.6 mmφ 1-hole cap and led to a pure water coagulation bath maintained at 25 ° C., and then 5 m / min. The yarn was taken up at a speed and deposited on the bat to obtain a raw yarn. At this time, the air gap was 18 mm, and the immersion length in the coagulation bath was 15 cm. The obtained raw yarn was translucent and caused phase separation.

  The obtained yarn is dried for 1 hour in a circulation drier kept at 25 ° C. to dry the moisture on the surface of the yarn, followed by vacuum drying at 25 ° C. for 5 hours. Raw material yarn was obtained.

  Thereafter, the raw yarn as a precursor material was put into an electric furnace maintained at 250 ° C., and infusible treatment was performed by heating in an oxygen atmosphere for 1 hour. The raw yarn that had been infusibilized changed to black.

  Carbon fiber having a co-continuous structure is obtained by carbonizing the obtained infusible raw material under the conditions of a nitrogen flow rate of 1 liter / min, a heating rate of 10 ° C./min, an ultimate temperature of 850 ° C., and a holding time of 1 min. did. When the cross section was analyzed, the fiber diameter was 150 μm, and the thickness of the skin layer, which is a portion having no co-continuous structure, was 5 μm. In addition, a uniform co-continuous structure was formed at the center of the fiber.

Subsequently, after pulverizing using a ball mill, potassium hydroxide was mixed with an amount 4 times that of carbide, charged into a rotary kiln, and heated to 800 ° C. under a nitrogen flow. After the activation treatment for 1 hour and 30 minutes, the temperature was lowered, and then washing was performed using water and dilute hydrochloric acid until the washing solution reached pH7. The obtained particulate porous carbon material had a uniform co-continuous structure as shown in FIG. 1, and the average porosity of the co-continuous structure portion was 43% and the structure period was 75 nm. Moreover, it had the structure which included the part which does not have a co-continuous structure in some particle | grains. The BET specific surface area was 2480 m ² / g, the average pore diameter by the MP method was 0.6 nm, the pore volume was 2.0 cm ³ / g, and the chloroform adsorption amount was 490 wtppm. The results are summarized in Table 1.

[Example 2]
The activation treatment was performed in the same manner as in Example 1 except that sodium hydroxide was used instead of potassium hydroxide. In the obtained particulate porous carbon material, the average porosity of the co-continuous structure portion was 43%, and the structural period was 74 nm. Moreover, it had the structure which included the part which does not have a co-continuous structure in some particle | grains. The BET specific surface area was 2530 m ² / g, the average pore diameter by the MP method was 1.3 nm, the pore volume was 1.8 cm ³ / g, and the chloroform adsorption amount was 500 wtppm. The results are summarized in Table 1.

[Example 3]
In Example 1, water vapor activation was performed instead of alkali activation. That is, the carbon fiber obtained in the same manner as in Example 1 was pulverized with a ball mill, then charged into a rotary kiln and heated to 850 ° C. under a nitrogen flow. After reaching 850 ° C., steam was supplied into the rotary kiln together with nitrogen, and steam activation was performed for 2 hours. After the activation treatment, washing was performed in the same manner as in Example 1. In the obtained particulate porous carbon material, the average porosity of the co-continuous structure portion was 44%, and the structural period was 74 nm. Moreover, it had the structure which included the part which does not have a co-continuous structure in some particle | grains. The BET specific surface area was 420 m ² / g, the average pore diameter by the MP method was 0.3 nm, the pore volume was 0.2 cm ³ / g, and the chloroform adsorption amount was 55 wtppm. The results are summarized in Table 1.

[Comparative Example 1]
It carried out similarly to Example 1 except not performing an activation process. In the obtained particulate porous carbon material, the average porosity of the co-continuous structure portion was 41%, and the structural period was 75 nm. Moreover, it had the structure which included the part which does not have a co-continuous structure in some particle | grains. The BET specific surface area was 37 m ² / g, and pores by the MP method could not be confirmed. The amount of chloroform adsorbed was 4.1 wtppm. The results are summarized in Table 1.

[Comparative Example 2]
The coconut husk was vacuum dried at 110 ° C. for 24 hours, carbonized under the conditions of a nitrogen flow rate of 1 liter / minute, a heating rate of 10 ° C./minute, an ultimate temperature of 550 ° C., and a holding time of 3 hours, and allowed to cool naturally. . Next, the temperature was raised to a nitrogen flow rate of 1 liter / min, a temperature increase rate of 10 ° C./min, and an ultimate temperature of 850 ° C., and nitrogen containing water vapor was passed for 40 minutes as an activation treatment, followed by natural cooling. The obtained porous carbon material was not uniform in pore shape and size in the cross section, and we tried to calculate the structural period, but there was no peak in the obtained spectrum, and the structure was uniform. It was inferior. The BET specific surface area was 950 m ² / g, the average pore diameter by the MP method was 1.1 nm, and the pore volume was 1.8 cm ³ / g. The amount of chloroform adsorbed was 21 wtppm. The results are summarized in Table 1.

Claims (6)

An adsorbing material comprising a porous carbon material having a co-continuous structure portion having a structure period of 0.002 μm to 20 μm in which a carbon skeleton and a void each form a continuous structure, and having pores having an average diameter of 0.01 to 10 nm on the surface. The adsorbent material according to claim 1, wherein the BET specific surface area is 50 m ² / g or more. The adsorbent material according to claim 1, wherein the pores are formed at least in the carbon skeleton of the co-continuous structure portion. The adsorbent material according to any one of claims 1 to 3, wherein a half-value width of a peak of scattering intensity obtained by incidence of X-rays is 5 ° or less. Pore volume of the porous carbon material measured by the BJH method or MP method is 0.1 cm ³ / g or more, the adsorption material according to any one of claims 1 to 4. The adsorbent material according to any one of claims 1 to 5, wherein the porous carbon material further has a portion substantially not having a co-continuous structure.