JP5071837B2 - Method for producing graphite porous body - Google Patents

Description

The present invention has a structure in which open pores having a high pore size and a large pore diameter are three-dimensionally penetrated, such as sliding materials such as oil-free bearings, filters for air purification and water purification, catalyst carriers, etc. The present invention relates to a method for producing a graphite porous body that can be suitably used.

  Carbon materials have excellent heat resistance and high temperature strength in a non-oxidizing atmosphere, and have high conductivity, thermal conductivity, and chemical stability, and are used as various industrial materials. In addition, a carbon material obtained by making a carbon material porous is lightweight and widely used as a filter, a catalyst carrier, a heat insulating material, an electrochemical industrial member, or the like.

  Oil-free bearings require a material with a low coefficient of friction so as not to damage the mating material when sliding, and oil-free bearings consisting of a composite of an alloy and graphite in which an alloy is infiltrated into a porous graphite body have been developed. Yes. In this case, in order for the molten alloy to be injected into the open pores of the graphite material and smoothly enter, the open pores preferably have a pore diameter of about 1 to several mm.

  In addition, air purification filters, water purification filters, catalyst carriers, and the like are required to have a porous body with low pressure loss and good contact efficiency with fluids, and have high porosity and large pore diameter and high strength. A large porous body is desired. Furthermore, since chemical resistance, high thermal conductivity, and the like are also required, the porous material is preferably a carbonaceous material, particularly a graphite porous material.

  As a technique for producing a porous carbon material, a method of impregnating a sheet obtained by papermaking carbon fiber together with pulp with a thermosetting resin solution, forming a laminate, and firing and carbonizing (for example, Patent Document 1) is known. ing. However, since this method uses expensive carbon fibers, the manufacturing cost increases, and it is difficult to control the pore properties.

  In view of this, a method has been developed in which a thermosetting resin solution is impregnated into an inexpensive paper-making sheet made of an organic substance mainly composed of α-cellulose, and the resin-impregnated sheet is laminated to perform hot pressing. For example, Patent Document 2 discloses a step of making a sheet by making a thermally volatile material containing α-cellulose as a main component, a step of impregnating the sheet with a thermosetting resin solution, and heating and semi-curing the impregnated sheet. There is disclosed a method for producing a porous carbon material comprising a step, a step of laminating a semi-cured sheet and compressing while heating, and a step of firing and carbonizing.

  However, in these methods, a porous body is formed by voids in which fibers are entangled, so that the pore structure is different between the surface direction and the thickness direction of the plate-like molded body, and the strength characteristics such as bending strength are also anisotropic. There are drawbacks such as occurrence and delamination easily. Furthermore, when trying to obtain a product with a high porosity, the strength decreases and it is difficult to obtain a product with a large pore diameter.

  Further, as a method for producing a carbon porous body, a method of firing and carbonizing a resin foam such as melamine, urethane, or phenol resin is known, but has a disadvantage that strength is low. Therefore, Patent Document 3 proposes a carbon porous body obtained by carbonizing a resin foam such as a melamine resin foam, a urethane resin foam, and a phenol resin foam having continuous pores and impregnated with a polycarbodiimide resin.

However, the porosity and pore diameter are small, and it is not sufficient for use in sliding materials such as the above oil-free bearings, filters for air purification and water purification, catalyst carriers, and the like.
JP 61-236664 A Japanese Patent Laid-Open No. 03-183672 Japanese Patent Application Laid-Open No. 06-032677

  Therefore, the inventors have conducted extensive research to produce a porous graphite body having a high porosity, a large open pore diameter, and excellent strength characteristics. It has come.

That is, an object of the present invention is to provide a structure in which open pores having a high pore diameter and a large pore diameter are three-dimensionally penetrated, for example, sliding materials such as oil-free bearings, filters for air purification and water purification, etc. Another object of the present invention is to provide a method for producing a graphite porous body that can be suitably used as a catalyst carrier.

In order to achieve the above object, a method for producing a porous graphite material according to claim 1 has a structure in which the open porosity is 60 to 85% and the open pores having a pore diameter of 1 to 5 mm are three-dimensionally penetrated. A porous graphite body having a graphite density of 1.0 to 1.6 g / cm ³ , a porosity of 10 to 50%, and a pore diameter of 1 to 5 μm. A method of manufacturing, wherein graphite is mixed at a ratio of 15 to 100 parts by weight of a thermosetting resin, 50 to 300 parts by weight of a dispersion medium, and 0.5 to 5 parts by weight of a dispersant with respect to 100 parts by weight of graphite powder. A step of preparing a slurry, a step of pouring the graphite slurry into a preform made of a spherical pore former having a particle diameter of 1 to 6 mm placed in a molding vessel , drying to volatilize and remove the dispersion medium, and then 120 to 200 Heat to ℃ to cure resin component, and further heat to 200-250 ℃ After forming the pores by volatilization the pore forming material to be a non-oxidizing atmosphere step fired carbonization is heat-treated at 800 ° C. or higher temperatures during or further characterized by comprising a step of graphitization.

The method for producing a graphite porous body according to claim 2 is replaced with the method of injecting the graphite slurry into a preform made of a spherical pore-forming material having a particle diameter of 1 to 6 mm placed in a forming container in claim 1. The graphite slurry is mixed with a spherical pore former having a particle size of 1 to 6 mm and compressed into a gypsum mold .

The method for producing a graphite porous body according to claim 3 is characterized in that, in claim 1 or 2, the graphite powder is previously coated with a silane coupling agent .

According to the present invention, it has a structure in which open pores with a high open pore size and a large pore diameter are three-dimensionally penetrated, such as sliding materials such as oil-free bearings, various types of materials such as air purification and water purification. A method for producing a porous graphite material that can be suitably used as a filter, a catalyst carrier, and the like is provided.

  A graphite sliding material such as an oil-free bearing requires about 30% of the graphite portion exposed on the sliding surface, which depends on the porosity of the graphite porous body. In addition, the pore property greatly affects the oil occluded in the pores to ooze out to the surface and maintain the slidability.

  In addition, the filter and catalyst carrier used for air purification and water purification have a low fluid resistance and a porous body with a high open porosity and a large open pore diameter in order to increase the contact efficiency with the fluid. Is preferred. Further, graphite porous bodies are useful from the standpoint of material properties such as corrosion resistance, strength characteristics and thermal conductivity.

The porous graphite material obtained by the present invention has a structure in which open porosity is 60 to 85% and three-dimensionally open pores having a pore diameter of 1 to 5 mm are suitable for these applications. It is characterized by.

  When the porosity of the open pores is less than 60%, for example, the ventilation resistance is increased. On the other hand, when the porosity is more than 85%, the strength is decreased and the voids are easily lost during use. On the other hand, when the pore diameter of the open pores is less than 1 mm, the wall of the skeleton forming the porous body becomes thin, the strength is lowered, and the ventilation resistance is also increased. However, when the pore diameter exceeds 5 mm, the contact area with the skeleton portion is reduced, so that the reaction efficiency is lowered.

  Thus, the graphite porous body of the present invention, which is composed of graphite excellent in heat resistance, corrosion resistance, thermal conductivity, slidability, etc., and whose porosity is specified, is a sliding material such as an oil-free bearing, air It is extremely useful as a filter and catalyst carrier for cleaning and water purification.

In this case, it is preferable that the density of the graphite forming the skeleton portion of the graphite porous body is 1.0 to 1.6 g / cm ³ . When the density of the graphite in the skeletal part is less than 1.0 g / cm ³ , the strength is insufficient, but when the density is greater than 1.6 g / cm ³ , for example, the occlusion and holding of oil necessary for an oil-free bearing cannot be sufficiently performed. . For the same reason, the porosity of graphite forming the skeleton is 10 to 50%, and the pore diameter is preferably 1 to 5 μm.

  The graphite porous body having these pore properties is prepared by preparing a graphite slurry and injecting and molding the graphite slurry into a preform made of a spherical pore former, and then volatilizing and removing the pore former, or the graphite slurry is spherical. After the pore former is mixed and filled into a gypsum mold, it can be produced by a method of volatilizing and removing the pore former.

  Graphite slurry is blended in a proportion of 15 to 100 parts by weight of thermosetting resin, 50 to 300 parts by weight of a dispersion medium, and 0.5 to 5 parts by weight of a dispersing agent with respect to 100 parts by weight of graphite powder, and thoroughly mixed To prepare. In order to remove air entrained during the mixing and generated bubbles, it is preferable to remove bubbles by degassing under reduced pressure.

  As the graphite powder, natural graphite powder, artificial graphite powder, mixed powder thereof, and the like can be used. In order to obtain a slurry having high fluidity, graphite powder having a particle size distribution of several μm to several tens of μm is preferable. An isotropic artificial graphite pulverized product that is cheaper and easier to pulverize than natural graphite powder produced in the form of a powder is preferred.

  In order to obtain a graphite slurry having a high density and fluidity and to allow the slurry to smoothly enter the voids between the spherical pore formers, it is preferable to adjust the particle size of the graphite powder. For example, the average particle size is 30 to 70 μm, 5 A mixed graphite powder in which graphite powders of 10 μm and 1 μm are mixed at an appropriate ratio is used.

  In this case, the graphite powder is mixed with a solution in which a silane coupling agent is dissolved in an organic solvent such as ethanol, dried, and coated with the silane coupling agent, so that the wettability with the thermosetting resin as a binder is improved. preferable.

  The thermosetting resin is used as a binder for binding graphite powder having no self-sintering property, and an epoxy resin, a phenol resin, a mixed resin thereof, pitch, or the like is used. A phenol resin or pitch having a charcoal rate of 40% or more is used.

  The mixing ratio of the graphite powder and the thermosetting resin is set to a ratio of 15 to 100 parts by weight of the thermosetting resin with respect to 100 parts by weight of the graphite powder. When the amount of the thermosetting resin is less than 15 parts by weight, the strength is insufficient, and when it exceeds 100 parts by weight, the graphite skeleton of the graphite porous body is densified and it is difficult to form fine pores.

  The dispersion medium for preparing the graphite slurry is water or an organic solvent such as acetone, methyl ethyl ketone, ethanol, and methanol. The dispersion medium is mixed and dispersed at a ratio of 50 to 300 parts by weight with respect to 100 parts by weight of the graphite powder. Let

  The dispersant is used for the flowability of the graphite slurry and the dispersion stability of the graphite powder. In consideration of a decrease in strength due to burning during firing or graphitization, 0.5 to 5 parts by weight of the graphite powder is used. Add in proportions. A surfactant is used as the dispersant, and any of anionic, nonionic, and cationic surfactants can be used. In the case where water or a ketone solvent is used as the dispersion medium, polycarboxylic acid type polymer surfactants and polyoxyethylene derivative surfactants are suitable.

  The graphite slurry is prepared by sufficiently stirring and mixing the above graphite powder, thermosetting resin, dispersion medium, and dispersing agent in a predetermined quantitative ratio with a stirrer, a universal mixer, a mixer, or the like. At this time, since air is entrained or bubbles are generated, it is preferable to perform defoaming treatment.

  Using the graphite slurry thus prepared, the first method for producing a porous graphite body according to the present invention is to use a spherical pore former having a particle size of 1 to 6 mm by using an adhesive or thermocompression bonding. Are joined together to produce a preform having a desired shape, and this preform is placed in a molding container, and graphite slurry is poured into the preform to invade well into the gap of the preform.

  The material of the spherical pore former is thermoplastic such as polyethylene, polystyrene, polyester, nylon, acrylic rubber, and can be used as long as it can be heat-sealed and heated and evaporated at a relatively low temperature. Foamed styrene beads that are heat-fused and thermally evaporate at a low temperature are preferably used. In addition, since the particle size of the spherical pore-forming material affects the porosity of the graphite porous body to be produced, it is used by appropriately adjusting the particle size within the range of 1 to 6 mm depending on the application. .

  After allowing the graphite slurry to penetrate into the preform, the dispersion medium is volatilized and removed by an appropriate means such as natural drying, hot air drying, reduced pressure drying, etc., and then heated at a temperature of 120 to 200 ° C. to cure the resin component. Holes are formed by heating to a temperature of ˜250 ° C. to volatilize and remove the pore former. In this case, by adjusting the particle size and distribution of the spherical pore former that is volatilized and removed by heating, the porosity property of the produced graphite porous body can be controlled and adjusted.

  After volatilizing and removing the spherical pore former, the resin component is calcined by heating at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere, or is further graphitized by heating to a temperature of about 3000 ° C. Thus, a graphite porous body can be produced. In this manufacturing process, by setting the mixing ratio of the graphite powder and the thermosetting resin, the particle size and volume ratio of the spherical pore former forming the preform, the open porosity and the open pore diameter are controlled. A graphite porous body having a pore property in which pores penetrate three-dimensionally is produced.

  The second method for producing a porous graphite material according to the present invention is to add and mix a spherical pore former having a particle size of 1 to 6 mm in the graphite slurry prepared by the above method while adjusting the volume mixing ratio. Is poured into a gypsum mold and lightly compressed to absorb and discharge the dispersion medium from the slurry into the gypsum mold. The spherical pore former can be brought into close contact with each other by this compression.

  After molding, the molded body taken out from the gypsum mold is further dried to volatilize the dispersion medium, and then the resin component is cured by the same method as in the first manufacturing method, and heated to volatilize the pore former to remove the pores. After forming, it is calcined and further graphitized to produce a porous graphite body.

  Hereinafter, although the Example of this invention is described concretely compared with a comparative example, this invention is not restrict | limited to this Example at all.

Example 1
As the graphite powder, isotropic graphite was pulverized and then the particle size was adjusted to obtain 70 parts by weight of graphite powder having an average particle diameter of 50 μm, 10 parts by weight of graphite powder having an average particle diameter of 7 μm, and 20 parts by weight of graphite powder having an average particle diameter of 4 μm. A graphite powder was prepared. 100 parts by weight of this graphite powder and 25 parts by weight of a resol type phenol resin powder are placed in a dispersion prepared by mixing 70 parts by weight of water as a dispersion medium and 2 parts by weight of a nonionic surfactant in a dispersant, and stirred. The mixture was sufficiently stirred and mixed with an ultrasonic disperser. Thereafter, the degassing treatment under reduced pressure was performed to degas the bubbles entrained during dispersion to prepare a graphite slurry.

  A spherical polystyrene foam bead having a particle diameter of 3 to 5 mm was tap-filled into a plastic molded container having a diameter of 50 mm and a height of 100 mm so as to have a height of 50 mm, and a light load was applied from above to compress it by 20 vol%. This compressed body was heated in a drying furnace at 110 ° C. for 1 minute to fuse the polystyrene, thereby producing a preform.

  A graphite slurry was poured into a molding container on which this preform was placed, and the slurry was sufficiently and evenly infiltrated into the gaps of the preform, followed by drying at 50 ° C. for one day. Next, the resin was cured by heat treatment at 150 ° C. for 2 hours, and then placed in an oven at 250 ° C. for 30 minutes to volatilize and remove the polystyrene beads to form pores. A pore was formed. afterwards. The graphite porous body was produced by placing in a firing furnace maintained in a nitrogen gas atmosphere and firing and carbonizing at a temperature of 1000 ° C.

Example 2
The graphite slurry prepared by the same method as in Example 1 was mixed with spherical polystyrene foam beads having a particle diameter of 3 to 5 mm in a volume ratio of 4 times the volume of the bulk molded product, and mixed with gypsum having a diameter of 50 mm and a height of 100 mm. It was poured into a mold and dried at a temperature of 50 ° C. for 1 day under a compression load. Thereafter, the dried molded body was taken out from the gypsum mold, and the resin component was cured and the polystyrene beads were volatilized and removed by the same method as in Example 1 to form pores and calcined to produce a graphite porous body.

Example 3
In Example 1, 100 parts by weight of graphite powder was dispersed in a solution in which 1 part by weight of an amine-based silane coupling agent was dissolved in ethanol, filtered and dried to remove ethanol, and then dried at a temperature of 120 ° C. to give an amine. A graphite porous body was produced by the same method as in Example 1 except that graphite powder surface-treated (coated) with a silane coupling agent was used.

Comparative Examples 1 and 2
In Example 1, a graphite porous body was produced in the same manner as in Example 1 except that the amount of resin in the graphite slurry was 10 parts by weight (Comparative Example 1) and 120 parts by weight (Comparative Example 2).

Comparative Example 3
In Example 2, instead of the spherical polystyrene foam beads, polystyrene crushed to a particle size of 0.2 to 0.8 mm was used and added to the graphite slurry. At this time, the addition amount could only be mixed up to 55%. Thereafter, a graphite porous body was produced in the same manner as in Example 2.

About these graphite porous bodies, the compressive strength, the open porosity, and the pore diameter ( open pore diameter ) of the open pores were measured. Further, the density, pore diameter, and porosity of the graphite serving as the skeleton part of the graphite porous body were measured . The obtained results are shown in Table 1.

  The graphite porous bodies of Examples 1 to 3 have a high compressive strength, a favorable open pore ratio and open pore diameter, a high open porosity, and a structure in which large open pores are three-dimensionally penetrated. The graphite of the skeleton part also has fine pores, and can be suitably used as a sliding material such as an oil-free bearing, a filter for air purification or water purification, a catalyst carrier, and the like.

  In Example 3, the graphite powder was coated with an amine-based silane coupling agent, so that the wettability with the resin was improved and the compression strength was improved.

  On the other hand, in Comparative Example 1, since the resin amount was as small as 10 parts by weight, the graphite porous body was brittle and the compressive strength was remarkably low. On the other hand, in Comparative Example 2, since the amount of resin was as large as 120 parts by weight, the open pore diameter was small, and the pores in the skeleton portion were few and could not be used as a sliding material. In Comparative Example 3, the pore former was indefinite, and could not be added in a large amount to the graphite slurry, and both the open porosity and the open pore diameter were small.

Claims (3)

A graphite porous body having a structure in which open porosity is 60 to 85% and open pores having a pore diameter of 1 to 5 mm are three-dimensionally penetrated, and the density of graphite forming the skeleton of the graphite porous body is 1. A method for producing a graphite porous body having 0 to 1.6 g / cm ³ , a porosity of 10 to 50%, and a pore diameter of 1 to 5 μm, comprising 100 parts by weight of graphite powder and a thermosetting resin 15 to 100 parts by weight, the dispersion medium 50 to 300 parts by weight, preparing a graphite slurry is mixed in a ratio of dispersant 0.5 to 5 parts by weight, particle size 1 placing the graphite slurry into molding vessel A process of pouring into a preform made of a spherical pore former of ˜6 mm, drying to volatilize and remove the dispersion medium, then heating to 120 to 200 ° C. to cure the resin component, and further heating to 200 to 250 ° C. After forming the pores by evaporating the pore material, in a non-oxidizing atmosphere at 800 ° C or higher Step firing carbonization is heat-treated at a temperature above or method of manufacturing a graphite porous body, characterized by comprising the step of graphitization. Instead of injecting the graphite slurry into a preform made of a spherical pore former having a particle diameter of 1 to 6 mm placed in a molding vessel, the spherical slurry having a particle diameter of 1 to 6 mm is mixed with the graphite slurry. 2. The method for producing a graphite porous body according to claim 1 , wherein the step of compressing and filling the gypsum mold is performed . The method for producing a porous graphite material according to claim 1 or 2, wherein the graphite powder is previously coated with a silane coupling agent.