JP2011201753A - Method for producing carbon film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon film, in which the number of times of film formation is reduced to reduce the number of steps, and a homogeneous carbon film is formed.SOLUTION: The method for producing a carbon film includes dipping a porous support into a suspension of a phenol resin or of a precursor of the phenol resin, drying the applied suspension to form a film composed of the phenol resin or the precursor of the phenol resin, and then heating the formed film to carbonize it.

Description

  The present invention relates to a method for producing a carbon film. More specifically, the present invention relates to a method for producing a carbon film used for selectively separating a specific component from a mixed component.

  In recent years, zeolite membranes and carbon membranes have been used to separate specific components from mixed components from the viewpoint of environmental protection and effective utilization of base materials. In particular, the carbon membrane has better acid resistance than the zeolite membrane, and can be used for separation of mixed components containing organic acids. As such a carbon film, a liquid thermosetting resin is applied to the surface of the ceramic porous body to form a polymer film, and then heat-treated at 550 to 1100 ° C. in a non-oxidizing atmosphere to obtain a carbon content. Has disclosed a molecular sieving carbon membrane in which a large number of pores having a pore diameter of 1 nm or less are present (see Patent Document 1).

  Moreover, the separation membrane porous body composite aiming at improving a flux (permeation | transmission flow rate) and selectivity is disclosed (refer patent document 2). This separation membrane porous body composite has a porous body and a carbon membrane, and a composite layer having a thickness of 1 nm or less is formed at the interface between the porous body and the carbon membrane, and at least a part of the composite layer Is made of the same material as the separation membrane. As a method for producing this separation membrane porous body composite, Patent Document 2 discloses a solution for forming a separation membrane while supplying pressurized gas into the pores of the porous body. Disclosed is a method comprising the step of contacting the substrate.

  Furthermore, it is possible to uniformly dry or imidize a membrane made of the precursor solution of the separation membrane formed on the surface in the through hole of the monolith substrate, and to monolith into the dryer. A method of manufacturing a separation membrane that is excellent in productivity and does not require a complicated process such as installation of a substrate has been disclosed (see Patent Document 3).

Japanese Patent No. 3647985 Specification International Publication No. 2008/056803 International Publication No. 2008/078442

  When the precursor solution of the separation membrane is applied to the porous support, a highly viscous precursor solution such as polyimide can be applied uniformly by the methods disclosed in Patent Documents 2 and 3. However, when applying a precursor solution having a low viscosity such as a phenol resin, it is difficult to apply the precursor solution uniformly, and the number of film formation may increase.

  The separation performance of a carbon membrane using polyimide as a precursor may be lowered depending on conditions when an acidic solution is separated. Therefore, although it is necessary to use a phenol resin as a precursor of a carbon film, the improvement was desired from the above-mentioned problem.

  The present invention has been made in view of such problems of the prior art, and the problem is that the number of film formation can be reduced, the number of processes can be reduced, and a uniform carbon film can be formed. An object of the present invention is to provide a carbon film manufacturing method capable of forming a film.

  As a result of intensive studies to achieve the above-described problems, the present inventors have immersed the porous support in the precursor suspension of the separation membrane when applying the separation membrane precursor to the surface of the porous support. As a result, the present inventors have found that the above-described problems can be achieved, and have completed the present invention.

  That is, according to the present invention, the following carbon film manufacturing method is provided.

  [1] After immersing the porous support in a suspension of a phenol resin or a suspension of a precursor of a phenol resin and drying to form a film made of the phenol resin or the precursor of the phenol resin A carbon film manufacturing method for obtaining a carbon film by heat treatment and carbonization.

  [2] The method for producing a carbon film according to [1], wherein the phenol resin or the precursor of the phenol resin is a powdery substance.

  [3] The method for producing a carbon film according to [1] or [2], wherein the turbidity of the suspension is 1 to 1000 degrees.

  [4] The method for producing a carbon film according to any one of [1] to [3], wherein the turbidity of the suspension is 100 to 1000 degrees.

  [5] The method for producing a carbon film according to any one of [1] to [4], wherein the solvent of the suspension is N-methyl-2-pyrrolidinone.

  [6] The carbon membrane according to any one of [1] to [5], wherein the porous support includes a porous base material on which a plurality of cells communicating from one end face to the other end face are formed. Production method.

  [7] The porous support further includes a layer composed of particles having an average particle diameter smaller than the particles constituting the porous substrate, and the average pore diameter of the outermost layer of the porous support is 0. The method for producing a carbon film according to [6], which is 01 to 1 μm.

  According to the carbon film manufacturing method of the present invention, it is possible to reduce the number of times of film formation and reduce the number of steps.

1 is a schematic perspective view showing an embodiment of a porous support according to the present invention. It is a schematic diagram which expands and shows a part of cross section of the inner wall surface of the cell of the porous support body which concerns on this invention.

  Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. It is understood that the scope of the present invention includes modifications, improvements, and the like as appropriate to the following embodiments based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Should.

  In the method for producing a carbon membrane of the present invention, a porous support is immersed in a suspension of a phenol resin or a suspension of a precursor of a phenol resin and dried to form a membrane made of a phenol resin or a precursor of a phenol resin. Is a method of obtaining a carbon film by heat treatment and carbonization. This manufacturing method uses a so-called dip coating method, but differs in that a suspension of a phenol resin or a precursor of a phenol resin is used when the porous support is immersed. .

  In dip coating, since it is usually necessary to apply uniformly to the surface of a porous support, a solution in which raw materials are uniformly dissolved is used when immersed. However, when a solution using a phenol resin or a precursor of a phenol resin as a raw material is used, it is difficult to apply uniformly because the viscosity of the solution is low, and the number of film formation increases (that is, the number of processes increases). Problem). However, in the carbon film manufacturing method of the present invention, a suspension in which the raw material is suspended without being completely dissolved is used. Therefore, even if the viscosity of the suspension is low, the phenol resin or the precursor of the phenol resin is used. Can be deposited on the surface of the porous support to prevent permeation, and a uniform film can be formed. Therefore, the number of film formations can be reduced, and the number of processes can be reduced.

(Porous support)
The shape of the porous support is not particularly limited and can be appropriately selected according to the purpose of use. For example, as shown in FIG. 1, a lotus-like columnar body (hereinafter referred to as “monolith shape”) including a porous substrate 2 in which a plurality of cells 3 communicating from one end surface 5 to the other end surface 6 is formed. There is. In addition, there are a honeycomb shape, a disk shape, a polygonal plate shape, a cylinder shape such as a cylinder and a square tube, and a column shape such as a column and a prism. Since the ratio of the membrane area to the volume and weight is large, a monolith shape or a honeycomb shape is preferable, and a monolith shape is more preferable.

  The size of the porous support is not particularly limited, and can be appropriately selected according to the purpose as long as the strength required for the support is satisfied and the permeability of the component to be separated is not impaired. Moreover, it is preferable that the average pore diameter of a porous support body is 0.01-50 micrometers. Furthermore, the porosity of the porous support is preferably 25 to 55% from the viewpoint of the strength and permeability of the porous support itself.

  As shown in FIG. 2, the porous support 1 includes a porous substrate 2 and a plurality of layers composed of particles 17 and 18 having an average particle diameter smaller than the particles 12 constituting the porous substrate 2. 7 and 8 are preferable. In FIG. 2, the porous support 1 has the intermediate layer 7 and the outermost layer 8, but may further have layers as necessary. By having such layers 7 and 8, the surface on which the separation membrane 10 of the porous support 1 is disposed becomes smooth, and a uniform membrane can be formed.

  The particles constituting the porous support are preferably ceramic materials such as alumina, silica, cordierite, mullite, titania, zirconia, and silicon carbide from the viewpoint of strength and chemical stability. In addition, it is preferable that the average particle diameter of the particle | grains which comprise a porous support body is 0.03-200 micrometers.

  This porous support can be prepared by a conventionally known method. For example, there is a method in which a porous base material is formed by extrusion molding using particles constituting the porous support and fired. In the case where the porous support has a plurality of layers, particles having an average particle diameter smaller than the particles constituting the porous support are deposited on the surface of the porous substrate by a filtration film forming method and fired. A plurality of layers can be formed. As a kind of particle | grains, the same kind of particle | grains as the particle | grains which comprise a porous support body can be used.

(Phenolic resin or phenolic resin precursor)
It does not specifically limit as a phenol resin, A conventionally well-known thing can be used. For example, the product names “Bellepearl S899”, S890, S870 (above, manufactured by Air Water), the product name “Sumilite Resin PR53056” (manufactured by Sumitomo Bakelite), the product name “Resitop PSK2320”, the product name “Marilyn” HF "(manufactured by Gunei Chemical Co., Ltd.). Among these, it is preferable to use Belpearl S899, S890, and S870 which are powdery substances.

  The weight average molecular weight of the phenol resin is preferably 3000 to 10,000, and more preferably 4000 to 10,000. When the weight average molecular weight is in such a range, a highly selective membrane can be obtained. If the weight average molecular weight exceeds 10,000, defects are likely to occur due to shrinkage of the film during heat treatment or carbonization, and the selectivity may be lowered.

  Moreover, the precursor of a phenol resin is not specifically limited, A conventionally well-known thing can be used. For example, there is a resole resin. Among these, it is preferable to use Belpearl S series which is a powdery substance.

(Suspension)
The suspension of the phenol resin or the precursor of the phenol resin used for the immersion is not particularly limited. The turbidity of the suspension is preferably 1 to 1000 degrees, more preferably 100 to 1000 degrees, and particularly preferably 300 to 1000 degrees. The turbidity of the suspension can be measured using a trade name “TR-55” manufactured by Kasahara Kagaku Kogyo Co., Ltd. using a transmission scattered light measurement method.

  The solvent for preparing the suspension of the phenol resin or the precursor of the phenol resin is not particularly limited. Specific examples include N-methyl-2-pyrrolidinone and ethanol.

  The method for preparing the suspension of the phenol resin or the precursor of the phenol resin is not particularly limited, and the raw material and the solvent are mixed and stirred and filtered using a predetermined filter paper or a predetermined opening. It is possible to prepare by removing raw material particles having an excessive average particle diameter through a sieve.

  In the method for producing a carbon film of the present invention, the porous support is immersed in the suspension and dried to form a film made of a phenol resin or a phenol resin precursor, and then heat-treated. In this method, a carbon film is obtained by carbonization. As a dipping method, a conventionally known dipping method can be used. In addition, it is preferable to carry out by what is called a pressure dip method of immersing while applying pressure in the pores of the porous support. In this case, the pressure is preferably 1 to 1000 kPa, more preferably 10 to 500 kPa, and particularly preferably 50 to 100 kPa.

  A drying process is not specifically limited, It can carry out by a conventionally well-known method. More specifically, it can be heat-treated and dried at 90 to 300 ° C. for 0.5 to 60 hours.

  The conditions for carbonization by heat treatment are not particularly limited, but it is preferable to perform the heat treatment in a non-oxidizing atmosphere. The non-oxidizing atmosphere refers to an atmosphere in which a film made of a phenol resin or a precursor of a phenol resin is not oxidized even when heated in a temperature range during heat treatment. Specifically, in an inert gas such as nitrogen or argon, An atmosphere such as a vacuum.

  Specifically, the heat treatment condition is preferably 400 to 1200 ° C, and more preferably 600 to 900 ° C. When it is lower than 400 ° C., carbonization is insufficient, pores are not formed, and separation performance may not be exhibited. On the other hand, when the temperature is higher than 1200 ° C., the strength may be decreased, or the membrane may be excessively densified, resulting in a decrease in separation performance.

  In addition, it is preferable that the average pore diameter of a carbon film is 0.2-1.0 nm. When the average pore diameter is less than 0.2 nm, the supported component may block the pores and the permeation amount of the component to be separated may decrease. On the other hand, if it exceeds 1.0 nm, the effect of improving selectivity may be reduced.

  The thickness of the carbon film is preferably 0.01 to 10 μm, and more preferably 0.01 to 0.5 μm. If the thickness is less than 0.01 μm, the selectivity may be lowered or the strength may be lowered. On the other hand, if it is thicker than 10 μm, the permeability of the component to be separated may decrease.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, the measuring method of various physical-property values and the evaluation method of various characteristics are shown below.

  [Turbidity (degree)]: Measured using a trade name “TR-55” manufactured by Kasahara Kagaku Kogyo Co., Ltd. using a transmission scattered light measurement method.

[Separation coefficient α]: The separation coefficient was calculated by substituting each concentration into the following equation.
Separation factor α = ((ethanol concentration in permeate) / (water concentration in permeate)) / ((ethanol concentration in feed) / (water concentration in feed))

[Permeation flow rate (Flux) (kg / m ² h)]: In the water-acetic acid permeation vaporization separation test, the permeate from the side of the porous support was collected with a liquid nitrogen trap, and the mass of the collected permeate was measured The permeability coefficient was calculated by dividing by the sampling time and membrane area.

Example 1
The raw material phenol resin powder (trade name “Bellpearl S899”, manufactured by Air Water) was mixed with N-methyl-2-pyrrolidone at a mass ratio of 10:90 and stirred at 25 ° C. for 24 hours. . While 27 kg of N-methyl-2-pyrrolidone was stirred with a propeller stirrer, 3 kg of phenol resin powder was slowly added at a charging rate of 10 g / min. A part of the obtained suspension was filtered with a filter paper No. 1 manufactured by Advantech. The undissolved residue was removed by passing through 5A (pore diameter 7 μm).

  Alumina particles having an average particle size of 3 μm are deposited on a monolithic alumina porous support having a diameter of 3 cm, a length of 16 cm, an average particle size of 50 μm, and an average pore size of 12 μm, and then fired. Thus, an intermediate layer having a thickness of 200 μm and an average pore diameter of 0.6 μm was formed. On this intermediate layer, titania particles having an average particle size of 0.3 μm were further deposited by a filtration film forming method, followed by firing to form an outermost layer having a thickness of 30 μm and an average pore size of 0.1 μm. On this porous support, a suspension of the above-mentioned precursor of the phenol resin was formed into a film by a pressure dipping method and dried. The dried film was further heat-treated at 200 to 350 ° C. in an air atmosphere, and a film was formed on the porous support by thermal curing. The airtightness of the film after thermosetting was evaluated by the amount of gas permeation, and the film formation was repeated until a predetermined airtightness was exceeded. Then, it carbonized at 700 degreeC in the vacuum, and formed the carbon film on the surface of the porous support body. The obtained carbon film was pervaporated at 50 ° C. using a 50/50% solution of water and ethanol, and then heat-treated at 80 ° C. for 100 hours.

  The separation performance of the obtained carbon membrane was evaluated by a water-acetic acid pervaporation separation test (test conditions: water / acetic acid = 30/70%, supply liquid temperature 70 ° C., permeation side pressure 6.7 kPa). The results are shown in Table 1.

(Examples 2 to 10 and comparative examples)
The raw materials, solvents, and filtration methods described in Table 1 were used as raw materials to prepare suspensions or solutions. Using the prepared suspension or solution, a carbon film was formed on the porous support with the number of film formation, the drying conditions, and the supporting conditions shown in Table 1. The turbidity of the suspension or solution and the evaluation results of the separation performance of the obtained carbon membrane are also shown in Table 1.

  In addition, the kind of raw material described in Table 1 and the detail of the filtration method are described below.

(material)
Bell Pearl S890 (trade name “Bell Pearl S890”, manufactured by Air Water)
PR53056 (trade name “Sumilite Resin PR53056”, manufactured by Sumitomo Bakelite Co., Ltd., liquid)
U-Varnish A (trade name “U-Varnish A”, manufactured by Ube Industries, polyamic acid solution)

(Filtration method)
25 μm sieve: A sieve having an opening of 25 μm was passed.
100 μm sieve: A sieve having an opening of 100 μm was passed.

  When PR53056 was used as a raw material, the suspension was adjusted so that the concentration was 10%.

  As can be seen from Table 1, the carbon membranes (Examples 1 and 5) formed using the suspension having a turbidity of 1.5 degrees were filtered using a sieve. Compared to the carbon membranes formed using the suspension (Examples 2, 3, 6, and 7), the separation factor α was low and the number of film formations was large. On the other hand, in the carbon membrane (Example 8) formed using the suspension whose turbidity exceeded 1000 degrees and could not be measured, the separation coefficient α was low. Moreover, in the carbon film (Example 9) formed using a suspension using ethanol as a solvent, the number of film formations was increased, and the permeation flow rate (Flux) was slightly low. Furthermore, the carbon film (Example 10) formed using a suspension using a liquid phenol resin as a raw material had a large number of film formation and a low permeation flow rate (Flux). Moreover, the carbon film (comparative example) which made the precursor the polyimide resin formed using the solution which used U-varnish A as a raw material compared with the carbon film (Examples 1-10) which made the phenol resin the precursor. The separation factor α was as low as 7, and the permeation flow rate (Flux) was also low.

  The carbon film manufactured by the carbon film manufacturing method of the present invention can be used for a filter that selectively separates a specific component from a mixed component containing an acid.

1: porous support, 2 :: porous substrate, 3: cell, 5: one end face, 6: the other end face, 7: intermediate layer, 8: outermost layer, 10: carbon film, 11: porous Base material, 12, 17, 18: particles.

Claims (7)

  The porous support is immersed in a suspension of a phenol resin or a suspension of a precursor of a phenol resin and dried to form a film made of the phenol resin or the precursor of the phenol resin, followed by heat treatment. A carbon film manufacturing method for obtaining a carbon film by carbonization.   The method for producing a carbon film according to claim 1, wherein the phenol resin or the precursor of the phenol resin is a powdery substance.   The carbon film manufacturing method according to claim 1, wherein the turbidity of the suspension is 1 to 1000 degrees.   The method for producing a carbon film according to any one of claims 1 to 3, wherein the turbidity of the suspension is 100 to 1000 degrees.   The method for producing a carbon film according to claim 1, wherein a solvent of the suspension is N-methyl-2-pyrrolidinone.   The method for producing a carbon film according to any one of claims 1 to 5, wherein the porous support includes a porous base material on which a plurality of cells communicating from one end surface to the other end surface are formed. The porous support further comprises a layer composed of particles having an average particle size smaller than the particles constituting the porous substrate;
The method for producing a carbon film according to claim 6, wherein an average pore diameter of an outermost layer of the porous support is 0.01 to 1 μm.

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