JPS626984B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a silicon carbide/glassy carbon composite porous body. Silicon carbide has high strength at high temperatures and excellent corrosion resistance and oxidation resistance, and its sintered body is attracting attention as a high temperature corrosion resistant material and a structural material. Various methods such as gas phase reaction method, reaction sintering method, and hot pressing method are being considered as methods for manufacturing silicon carbide sintered bodies having such characteristics, but it is difficult to easily obtain products with complex shapes. The current situation is that it is difficult. Furthermore, since silicon carbide has high strength and is hard, post-processing of the sintered body is difficult, and this is also a major factor preventing the expansion of its uses. Glassy carbon has also attracted attention as a material with high strength, excellent corrosion resistance, and heat insulation properties. 145108) has been proposed, but this manufacturing method has the disadvantage of large weight loss and deformation during firing and low productivity, and it is desirable to consider a more efficient manufacturing method. ing. Further, as a material suitable for applications requiring excellent heat insulation properties and resistance to corrosion-resistant fluids, a porous body having an appropriate porosity and consisting of minute pore diameters is desired. The present inventors have completed the present invention as a result of intensive research in view of the above-mentioned problems of existing methods. It is an object of the present invention to provide a method for producing a silicon carbide/glass-like carbon composite porous body which has excellent properties, excellent corrosion resistance, and good workability, and further reduces weight loss and deformation during the firing process during production. Other objects and advantages of the present invention will become apparent from the following description. The above object is to produce a silicon carbide/glassy carbon composite porous material, which is characterized in that silicon carbide fine powder and a thermosetting resin solution are mixed together with a pore-forming material, and then fired in a non-oxidizing atmosphere after a curing reaction treatment. This is achieved through manufacturing methods. The silicon carbide fine powder used in the present invention is α-
Either SiC or β-SiC may be used, and the particle size is 0.1
~100μm can be used, but
Particularly preferred is one in the range of 0.5 to 50 μm. Examples of the thermosetting resin used in the present invention include phenol resin, furan resin, melamine resin, urea resin, epoxy resin, and unsaturated polyester resin, and these may be used alone or in combination. Among the thermosetting resins mentioned above, phenolic resins and furan resins are particularly preferred because they have a high carbonization yield through thermal decomposition in a non-oxidizing atmosphere, and phenolic resins are most suitable in terms of ease of handling during resin curing operations. Furan resin is the next most preferred. Phenol resins are divided into two types: resol resins and novolac resins. Resole resins are initial products produced by reacting phenols with aldehydes in the presence of basic catalysts, and are usually rich in methylol groups and have a molecular weight of about
It is a self-thermal crosslinking resin up to 600%. In particular, water-soluble resols are obtained by reacting 1.5 to 3.5 moles of aldehydes per mole of phenol in the presence of a slightly excess alkali catalyst, and keeping the initial condensate in a stable water-soluble state. It is easy to handle and is the most desirable thermosetting resin for use in the present invention. Phenols used in the production of resol resins most commonly include phenols and cresols. However, other phenols can also be used, such as phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol,
2,5-xylenol, 2,4-xylenol,
2,6-xylenol, 3,4-xylenol,
3,5-xylenol, o-ethylphenol,
m-ethylphenol, p-ethylphenol,
Examples include p-phenylphenol, p-tert-butylphenol, p-tert-aminophenol, bisphenol A, resorcinol, and mixtures of these phenols. Formaldehyde is the most common aldehyde used for polycondensation with this phenol. However, monoaldehydes and dialdehydes such as paraformaldehyde, hexamethylenetetramine, furfural and glutaraldehyde, adipaldehyde and glyoxal may also be used. As the basic catalyst used in the resol resin synthesis reaction, known catalysts such as caustic alkali, alkali carbonate, barium hydroxide, calcium hydroxide, ammonia, quaternary ammonium compounds, and amines may be used. is most commonly used. The novolac resin is prepared by adding the same phenols used in the production of the resol resin and the same aldehydes used in the production of the resol resin to oxalic acid, formic acid, acetic acid, halogenated acid, and p-toluenesulfonic acid. Uncured and meltable with a molecular weight of about 300 to 2000, it can be produced by reacting while heating in the presence of an acid catalyst such as organic acids such as hydrochloric acid, sulfuric acid, perchloric acid, phosphoric acid, etc., and inorganic acids such as phosphoric acid. There are thermoplastic resins. Furan resins include furfuryl alcohol resin, furfuryl alcohol phenol resin, furfural resin, furfural phenol resin, furfur ketone resin, etc., and curing agents for these resins include, for example, aniline hydrochloride, para-toluenesulfonic acid, etc. Organic acids can be used. Urea resin and melamine resin are initial condensates of urea-formaldehyde and melamine-formaldehyde, respectively, and are water-soluble and therefore easy to handle. As these curing agents, inorganic acids such as hydrochloric acid and sulfuric acid, carboxylic acid esters such as dimethyl oxalate, and amine hydrochlorides such as ethylamine hydrochloride and triethanolamine hydrochloride can be used. The most commonly used epoxy resin is a liquid bisphenol type epoxy resin obtained by reacting bisphenol A and epichlorohydrin in the presence of an alkali. The epoxy resin may be used by diluting it to an appropriate concentration with a solvent such as methanol, toluene, or xylene, and adding amines, organic acids, or the like as a curing agent. As the pore-forming material used in the present invention, starch or other organic fine powder, or fine powder of a sublimable compound, etc. can be used. The type and size of the powder may be appropriately selected depending on the pore diameter of the intended porous body. When producing the silicon carbide/vitreous carbon composite porous body of the present invention, a thermosetting resin solution of a predetermined concentration and silicon carbide fine powder are mixed together with a pore-forming material, and if necessary, a curing agent is added. After performing the curing reaction, it may be washed and fired at 800° C. or higher in a non-oxidizing atmosphere. A phenolic resin such as a resol resin or a novolak resin may be dissolved in an appropriate amount in a solvent such as methanol or acetone to prepare a phenolic resin having a predetermined concentration before use. Further, as the resol resin, it is preferable to use a water-soluble resol because it is easy to handle. In the case of a resol resin, if necessary, a small amount of an organic acid such as paratoluenesulfonic acid or phthalic acid may be added in advance to the solution as an acid catalyst for curing. In the case of a novolac resin, a crosslinking agent may be further dissolved in a solution of a predetermined concentration in which an appropriate amount is dissolved in a solvent such as methanol or acetone. As the crosslinking agent, hexamethylenetetramine can be most commonly used, but aldehydes such as paraformaldehyde, glutaraldehyde, adipaldehyde and glyoxal, and acids or alkalis may also be used in combination. In the case of furan resin, a solution may be used in which the furan resin is dissolved in a solvent such as acetone or benzene, and further a curing agent such as aniline hydrochloride or paratoluenesulfonic acid is mixed in at about 0.2 to 1% of the solid content of the resin. In the case of urea resin or melamine resin, a solution prepared by mixing several percent of an acid catalyst or the like as a curing agent into an aqueous solution of the resin may be used. Furthermore, it is desirable to use epoxy resin, unsaturated polyester resin, etc. in combination with phenolic resin, furan resin, etc., considering the carbonization yield during firing. As mentioned above, silicon carbide fine powder and pore forming material are added to a thermosetting resin of a predetermined concentration dissolved in a solvent, stirred and mixed, transferred to a mold of a desired shape and heated to complete the curing reaction, The molded product taken out from the mold is washed with water. The shape of the molded product can be freely selected from plate-like, cylindrical, etc. depending on the purpose, use, and required performance. The silicon carbide/thermosetting resin porous body of the present invention is fired in a non-oxidizing atmosphere, that is, under reduced pressure, or using an inert gas such as argon gas or helium gas, hydrogen gas,
This is carried out by heating to at least 800°C, preferably 1000°C or higher in nitrogen gas or the like. The silicon carbide content in the silicon carbide/glassy carbon composite porous body obtained as described above is usually 60 to 90%.
% by weight, preferably 65-85%, most preferably 70-80. Further, the porosity of the silicon carbide/vitreous carbon composite porous body is usually 40 to 80% by weight, preferably 45 to 70% by weight. When producing the silicon carbide/glass-like carbon porous body, if the silicon carbide content is too low, weight loss and deformation during firing will increase, and production efficiency and yield of raw products will tend to decrease. Moreover, if the silicon carbide content is too large, the bond between the silicon carbide fine powder and the glassy carbon becomes weak, and the strength of the composite porous body decreases significantly, which is not preferable. The porosity of the silicon carbide/glass-like carbon composite porous material changes depending on the ratio of silicon carbide and thermosetting resin solid content to the solvent and the amount of pore-forming material, and the solid content of silicon carbide and thermosetting resin increases. The porosity decreases as the amount of solvent and the amount of pore-forming material increase. If the porosity of the silicon carbide/glass-like carbon composite porous body is too large, the strength tends to decrease significantly and the heat insulation properties tend to decrease. Furthermore, if the porosity is too low, workability during production is poor and it is difficult to mix the raw materials uniformly, making it impossible to obtain a good silicon carbide/glass-like carbon composite porous body. The pore diameter of the silicon carbide/glassy carbon porous material obtained by the present invention is usually distributed in the range of 0.1 to 50 μm,
In particular, most of the pores have a diameter of about 0.5 to 10 μm.
The silicon carbide/glass-like carbon composite porous body has extremely good corrosion resistance and heat insulation properties, and is suitable as a high-temperature heat insulating material, a shielding material for corrosive fluids, and a jig for an electric furnace. In addition to the above-mentioned uses, the silicon carbide/glass-like carbon porous body can also be used as a lightweight structural material, an abrasive material/heating element, and a heat treatment jig. Next, the present invention will be specifically explained with reference to Examples. Example 1 A water-soluble resol resin solution with a solid content concentration of 65% by weight (Sumitomo Durez Co., Ltd. product, Sumilite Resin)
PR961A) to a specified amount and when it reaches 60℃, add 200g of wheat flour starch that has been gelatinized at 70℃.
was added and stirred at 70 to 80°C for 15 minutes while stirring. After cooling this solution to 40℃, β-
A predetermined amount of silicon carbide fine powder was added and thoroughly stirred and mixed, and further, 20% by weight of para-toluenesulfonic acid was added as a hardening agent based on the water-soluble resol resin and stirred. The mixed solution was poured into a cylindrical mold, heated at 80°C for 24 hours to perform a curing reaction, then taken out from the mold, washed with a shower for 8 hours to wash away the acid catalyst, etc., and then dried. A silicon carbide/phenol resin composite porous body of 250 mm × 60 mm ^t was obtained. The composite porous body obtained as described above was placed in an electric furnace and heated at a rate of 20°C/hr in a nitrogen atmosphere to 1000°C.
The mixture was held for 1 hour and fired to obtain a silicon carbide/glassy carbon composite porous body. Table 1 shows the charged composition of the silicon carbide/vitreous carbon composite porous body, weight and volume changes due to firing, and properties of the obtained silicon carbide/vitreous carbon composite porous body. In Table 1, the SiC content in the silicon carbide/glassy carbon composite porous material is determined when the composite porous material is exposed to air.
It was determined by measuring the weight of silicon carbide after burning the glassy carbon by holding it at 900°C for 48 hours. In addition, the corrosion resistance of the silicon carbide/glassy carbon composite porous material is measured in a CO ₂ /H ₂ O mixed atmosphere (molar ratio CO ₂ /H 2 O).
H ₂ O = 1:1 flow rate 5/min) and the weight retention rate when held at 950°C for 4 hours was evaluated. As can be seen from Table 1, the silicon carbide/glassy carbon composite porous body had a silicon carbide content of 60 to 90% by weight, and a porous body with good workability and sample condition during manufacturing and excellent corrosion resistance was obtained. .

[Table] Example 2 A furan resin solution with a solid content concentration of 50% by weight (Hitafuran 302, a product of Hitachi Chemical Co., Ltd.) was added with an average particle size of 0.5μ.
A predetermined amount of α-silicon carbide fine powder (m) was added and thoroughly stirred, and further a predetermined amount of potato starch was added and mixed while being careful not to agglomerate. A curing agent for hitafuran corresponding to 0.2% of the furan resin was added to this mixed solution, and the mixture was further diluted with acetone so that the total liquid volume was 5%. The mixed solution was poured into a rectangular mold, held at 70°C for 48 hours to perform a curing reaction, and after demolding, washed with a shower for 8 hours and dried to form a 300 mm x 200 mm x 20 mm silicon carbide/furan. A resin composite porous body was obtained. The composite porous material was heated to 800℃ in an argon atmosphere.
The temperature was raised at 10° C./hr and then at 50° C./hr, and the temperature was maintained at 1500° C. for 1 hour for firing to obtain a silicon carbide/glassy carbon composite porous body. Table 2 shows the charging composition and properties of the glassy carbon composite porous material. As can be seen from Table 2, good silicon carbide/glassy carbon composite porous bodies were obtained with porosity in the range of 40 to 80%.

[Table] Example 3 In the same manner as in Example 1, a water-soluble resol resin solution with a solid content concentration of 65% by weight (product of Sumitomo Durez Co., Ltd.,
Sumilight Resin PR961A) 400g, solid content concentration
60% water-soluble melamine resin solution (Sumitomo Chemical Co., Ltd.)
Product, Sumitekus Resin M3, Curing Catalyst, Sumitekus ACX) 200g, Average Particle Size 10μm β-Sic
800 g of fine powder and 30 g of wheat flour starch were mixed, and water was further added to adjust the total amount of the mixed liquid to 1. The mixture was cast into a flat mold.
A 100mm x 200mm x 4mm ^t plate-shaped composite porous material was heated to 700℃ and 900℃ at a heating rate of 20℃/hr in a helium atmosphere.
The temperature was raised to 1500°C and 1500°C, respectively, and held at each temperature for 1 hour to create a silicon carbide/glassy carbon composite porous body. The silicon carbide/vitreous carbon composite porous material was added to a mixed solution of concentrated nitric acid/concentrated hydrochloric acid = 5/1 (volume ratio) at 90°C.
Soaked for 7 days. The results are shown in Table 3. Table 3 shows that when the firing temperature is 800°C or higher, the obtained silicon carbide/glassy carbon composite porous body has excellent chemical resistance.

【table】

Claims (1)

[Scope of Claims] 1. Silicon carbide/silicon carbide powder, which is characterized by mixing fine silicon carbide powder and a thermosetting resin solution together with a pore-forming material, and firing the mixture in a non-oxidizing atmosphere after a curing reaction treatment.
Manufacturing method of glassy carbon composite porous material. 2. The method for producing a silicon carbide/vitreous carbon composite porous body according to claim 1, wherein the silicon carbide content in the silicon carbide/vitreous carbon composite porous body is 60 to 90% by weight. 3. The method for producing a silicon carbide/glassy carbon composite porous body according to claim 1, wherein the silicon carbide/glassy carbon composite porous body has a porosity of 40 to 80%. 4. The method for producing a silicon carbide/glass-like carbon composite porous body according to claim 1, wherein the thermosetting resin is a phenolic resin or a furan resin. 5. A method for producing a silicon carbide composite porous body according to claim 1, which comprises firing at 800° C. or higher in a non-oxidizing atmosphere.