JPH07304019A - Manufacture of glassy carbon molding - Google Patents

Abstract

PURPOSE:To manufacture glassy carbon molding, which as extremely few pores and homogeneous and dense constitutional structure, at favorable production yield. CONSTITUTION:In the manufacturing method of glassy carbon molding, in which thermosetting resin solution is put in a mold for forming and hardening and, after that, fired and carbonized at 800 deg.C or higher under non-oxidizing atmosphere, the mold is made of porous fluoroplastic having the air permeability of 0.05-1.0cm/seccmAq and the average pore diameter of 5-60mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glassy carbon molded body which is homogeneous and dense, and particularly has a structural structure having extremely few internal pores, with a good product yield and high productivity.

[0002]

2. Description of the Related Art A glassy carbon material is a heterogeneous carbon material having a glassy dense structure, and is gas impermeable, wear resistant, corrosion resistant, self-lubricating, and has a smooth surface as compared with general carbon materials. Because of its excellent properties and fastness, it is utilized for various industrial members in various fields, such as battery electrodes, electrolysis electrodes, semiconductor manufacturing crucibles, by taking advantage of its characteristics.
In recent years, attention has been paid to the non-contaminating material properties in which minute particles do not separate from the tissue, and practical application in the semiconductor field, such as electrodes for plasma etching of silicon wafers and members for ion implantation equipment, where contamination is averse ing.

Usually, a glassy carbon molded product is molded by putting a thermosetting resin liquid having a high carbonization residual ratio such as phenol-based and / or furan-based into a molding die, and after hardening, firing and carbonization in a non-oxidizing atmosphere. It is manufactured by the method. The curing reaction of the thermosetting resin in this process proceeds by forming a cross-linked structure by the polycondensation reaction of the thermosetting resin initial condensate, but the condensation water and decomposition gas generated at this time must be discharged and removed, In the subsequent calcination and carbonization process, bound water and decomposed gas remain in the structure and cause pores to be generated in the glassy carbon molded body, which further causes material defects such as swelling and cracking. This tendency becomes remarkable as the thickness of the molded body increases.

As a means for solving such a problem,
For example, in JP-A-60-131816, when a thermosetting resin is placed in a mold and cured, a material having a critical surface energy of 70 dyn / cm or less is formed on the surface of the mold that contacts the thermosetting resin. There has been proposed a method for producing a glassy carbon material by using. However, this method eliminates the pool of condensation water and the like in the resin by using a material having a small critical surface energy, that is, a water-repellent material, and cures the thermosetting resin in a dispersed state. It is not intended to remove condensed water and the like by discharge.

The applicant of the present invention also added an acid catalyst having an acidity (PKa) of 0 to 1 as a curing agent to the thermosetting resin initial condensate in order to allow the curing reaction to proceed slowly and uniformly. A method of primary curing under reduced pressure and then secondary curing by heating was proposed (Japanese Patent Publication No. 4-55122). According to this method, the condensed water and the decomposition gas generated as the curing reaction proceeds are removed by degassing under reduced pressure during the curing process, so that glassy carbon with few pores can be obtained.

Further, the applicant of the present invention, in a method of molding a thermosetting resin liquid having a composition mainly composed of a phenolic resin, heating and curing it, and then firing and carbonizing it at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere, A method has been developed in which the steps from molding of a thermosetting resin liquid to heat curing are performed in an oxidizing atmosphere with an oxygen concentration of 10 to 70% (Japanese Patent Application No. 5-174834). According to this method, by heat-curing in an oxygen atmosphere, the polycondensation reaction of the thermosetting resin proceeds at a relatively early stage of the resin curing process, and the condensed water and the generated gas are smoothly volatilized and removed. It is possible to prevent the generation of pores inside the tissue.

[0007]

However, in the above-mentioned prior art, no consideration is given to the discharge of the condensed water at the interface between the thermosetting resin and the inner surface of the mold, so that it is generated as the curing reaction proceeds. It is difficult for the condensed water to be smoothly discharged and removed to the outside of the system at the side surface portion and the bottom surface portion which are in contact with the inner surface of the mold, and the curing reaction inside and outside is often uneven. Therefore, where there is a difference in the degree of curing, the amount of shrinkage between the inner surface and the outer surface of the molded body is different in the curing and firing carbonization steps, which causes warpage, shape distortion, or cracking.

The object of the present invention is to solve the above problems, to smoothly remove condensed water during curing, and to obtain a glassy carbon molded product having a structure structure which is always homogeneous and dense and has few internal pores. It is to provide a manufacturing method for manufacturing with good and high productivity.

[0009]

In order to achieve the above-mentioned object, a method for producing a glassy carbon molded article according to the present invention comprises a thermosetting resin liquid, which is molded into a molding die and cured, and then a non-oxidizing agent. In a method for producing a glassy carbon molded article that is calcined and carbonized at a temperature of 800 ° C. or higher in an atmosphere,
Air permeability of the mold is 0.05-1.0 cm / sec cmAq,
It is characterized in that it is made of a fluororesin having a porosity with an average pore diameter of 5 to 60 μm.

The thermosetting resin liquid is a resin having a high carbonization residual ratio, such as a phenol resin, a furan resin, or the like, which is carbonized by heating in a non-oxidizing atmosphere and converted into glassy carbon. An initial condensate of a mixed resin or the like is used. These thermosetting resin liquids are put into a molding die having a desired shape and molded, and then heated and cured.

The present invention has a key point in that the molding die is made of a fluorine-based resin having air permeability and excellent releasability from the resin molding. As the fluorine-based resin, polytetrafluoroethylene, polytrifluoroethylene,
Polyvinylidene fluoride and the like can be mentioned. These fluororesins have the property of being converted into fine fibrous form by applying an appropriate shearing force or compressing force. The mold having the porosity used in the present invention is produced by utilizing this property.

That is, the molding die of the present invention is made into a sheet by forming a fine fiber by applying a shearing force to a fluororesin such as fibrous polytetrafluoroethylene, polytrifluoroethylene, polyvinylidene fluoride, etc. It is formed by molding the sheet into a predetermined shape. Specifically, for example, glycerin, solvent naphtha, a low-viscosity epoxy resin and other kneading aids are added to the above-mentioned fluororesin, and the kneading machine is subjected to shearing force such as a rotary blade kneader and sufficiently kneaded. To fiberize. The kneaded product is formed into a sheet by roll rolling or the like, and then washed in an appropriate solvent to remove the kneading aid component and dried. Using the sheet thus obtained, a forming die is obtained by forming into a desired container shape such as a cylindrical shape or a square shape. At this time, by controlling the powder particle size of the fluororesin, the addition amount of the kneading aid, the shearing force and the time during kneading, and changing the thickness of the fiber diameter, the length and the entangled state of the fibers, the resin molding The air permeability is adjusted to 0.05 to 1.0 cm / sec cmAq and the average pore diameter is adjusted to 5 to 60 μm.

The porosity of the molding die functions as a discharge passage for condensed water, decomposed gas, etc., but if the air permeability is below 0.05 cm / sec cmAq and the average pore diameter is less than 5 μm. Condensed water, etc. are not discharged smoothly, while the air permeability exceeds 1.0 cm / sec cmAq and the average pore diameter is 60.
If it exceeds μm, the sheet becomes brittle and it becomes difficult to make a mold. Therefore, by setting the pore characteristics in the above range, it is possible to pass only a gas without passing a high-viscosity liquid such as a resin, so that vapor of condensed water and decomposition gas are easily discharged out of the system, It becomes possible to uniformly proceed the curing reaction.

The structure of the mold is more effective as long as it has water absorption as well as fine pores that serve as discharge channels for condensed water. Since the fluororesin inherently has excellent water repellency and releasability, by spreading a filter paper having water absorbability on the outer surface of the above-mentioned molding die, it is possible to further facilitate the discharge and removal of the condensed water. . As a means for spreading the filter paper on the molding die, a method of laminating the filter paper on a fibrous sheet of fluororesin and molding it into the molding die under pressure bonding, or adhering a moistened filter paper to the outer surface of the preformed molding die A method of encapsulating and then drying is applied.

After the thermosetting resin liquid is injected into the mold thus produced, it is heat-cured in a temperature range of 350 ° C. or lower. If the heating temperature is higher than 350 ° C., the curing reaction will proceed rapidly, causing distortion in the structure of the molded body and causing cracks or damage during firing and carbonization. The preferable curing temperature is 100 to 200 ° C., but when the filter paper is spread on the outer surface of the mold, it is necessary to cure in a temperature range around 100 ° C.

The heat-cured resin molded product is packed in a heating furnace maintained in a non-oxidizing atmosphere and subjected to firing carbonization treatment at a temperature of 800 ° C. or higher, preferably 900 to 1200 ° C. The material after firing and carbonization is subjected to graphitization treatment at a temperature of 2000 ° C. or higher in a non-oxidizing atmosphere, if necessary, to obtain a glassy carbon molded body.

[0017]

[Function] Generally, in the curing reaction of a thermosetting resin, a decomposition condensation reaction of a methylol group, a dimethylene ether bond, etc. occurs in an initial low temperature region, and then a hydroxyl group, a methylene bond, etc. are thermally decomposed. Most of the condensation reaction proceeds with the generation of condensed water and while generating decomposition gas. According to the present invention, by forming the molding die with a fluororesin having a specific porosity, condensed water and decomposition gas generated during this curing reaction are passed through the pores of the molding die from all sides of the resin molding. It can be discharged evenly and smoothly. In particular, it is possible to smoothly discharge and remove a relatively large amount of gas components such as low boiling point components and unreacted components in addition to condensed water and decomposition gas generated in the initial stage of the curing reaction. Further, the fluorine-based resin is also excellent in the releasing property of the thermosetting resin, and when the molded product is taken out from the molding die, the releasing action is exhibited well.

Further, when the filter paper is spread on the outer surface of the mold, the condensed water that has passed through the pores of the mold is absorbed by the filter paper on the outer surface, so that the curing reaction is accelerated and the pores are evenly distributed. It is possible to obtain a vitreous carbon molded body.

As described above, the resin molded product finally becomes a glassy carbon molded product having no tissue defect due to the action of uniformly and smoothly discharging condensed water and decomposed gas from all the surfaces in contact with the inner surface of the molding die. It becomes possible to manufacture efficiently.

[0020]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 4 and Comparative Examples 1 to 3 Phenol purified by vacuum distillation and formalin are subjected to an addition condensation reaction in the presence of ammonia to prepare a phenol resin initial condensation product, and then furfuryl alcohol is added and mixed. The viscosity was adjusted to 70 centipoise (25 ° C).

Particle size-adjusted polytetrafluoroethylene (PTFE) [manufactured by Mitsui DuPont Fluorochemicals,
K10-J] 100 parts with glycerin 10 as a kneading aid
Parts were added and kneading was carried out at a temperature of 100 ° C. with a blast mill kneading machine while changing the rotation speed and kneading time. Next, the kneaded product was passed through rolls to form a sheet having a thickness of 0.2 mm, and the formed sheet was immersed in warm water at 60 ° C. to remove glycerin and then dried. The sheets thus obtained having different pore characteristics were compression-molded to prepare a cylindrical molding die having a diameter of 80 mm and a height of 350 mm. The air permeability of the mold was measured according to JIS K7126A method.

Phenol resin initial condensate was poured into this mold, deaerated under a reduced pressure of 10 torr for 1 hour, and then transferred to a clean electric oven at a temperature of 100 ° C. for 48 hours.
After time-curing, a cylindrical resin-cured molded product having a diameter of 80 mm and a height of 300 mm was obtained. The resin-cured molded body was taken out from the molding die and sliced into a disk shape having a thickness of 1.2 mm with a diamond cutter.

Then, 20 disk-shaped resin-cured moldings were
High-purity graphite plate with impurities less than 5 ppm [Tokai Carbon Co., Ltd.
Manufactured by G347SS] and set in a packingless high-temperature heating furnace equipped with a high-purity graphite heater [TP150 manufactured by Tokai High-Temperature Industry Co., Ltd.], and the atmosphere in the furnace is high-purity argon containing less than 10 ppm of impurities. While holding in gas 1
The mixture was heated to 200 ° C. to be carbonized by firing. The obtained glassy carbon molded product had a diameter of 60 mm and a thickness of 1 mm.

Various characteristics of each glassy carbon molded body thus obtained were measured and shown in Table 1 in comparison with the pore characteristics of the molding die. For comparison, an example in which a cylindrical container made of a gas impermeable polypropylene was used, and molding, curing and baking were performed under the same conditions as those of the examples is also shown in Table 1 (Comparative Example 3). The number of pores is the number of glassy carbon moldings for each maximum pore size observed within a field of view of 2 mm by observing the texture of the polished surface with an optical microscope after polishing the surface of glassy carbon.

[0026]

[Table 1]

From the results shown in Table 1, the glass-like carbon moldings produced in the examples satisfying the requirements of the present invention have extremely few pores as compared with the comparative examples which deviate from the requirements of the present invention, and particularly, large pores of 5 μm or more. It is clearly recognized that the pores have a homogeneous and dense tissue structure that is rarely present. Further, the yield of calcination and carbonization is high, and the strength characteristics are excellent. Further, the effect of the present invention is more apparent when compared with Comparative Example 3 in which a polypropylene mold having no pores is used.

Example 5 A filter paper having a thickness of 0.1 mm was laminated on the surface corresponding to the outer surface of a sheet prepared under the same conditions as in Example 1 and compression-molded to prepare a mold having the same shape as in Example 1. . Using this mold, a glassy carbon molded body was manufactured under the same conditions as in Example 1. The properties of the obtained glassy carbon molded product were as follows: bulk density 1.50 g / cm ³ , bending strength 1150 kgf / cm ³ , firing yield 95% (19 non-defective products), and 19 pores There wasn't. In addition, the appearance also showed a smooth glassy quality, and no irregularities were observed.

[0029]

As described above, according to the present invention, by using a molding die made of a fluororesin having a specific porosity, condensed water and the like produced during the curing reaction can be smoothly discharged and removed from the system. In addition, it becomes possible to extremely reduce the generation of pores due to the condensed water remaining during the firing and carbonization. Also,
Since the curing reaction is accelerated and the composition is uniformly cured, the structural structure of the glassy carbon molded body is homogenized and densified, and the strength characteristics, product yield, and productivity are improved. Therefore, it is extremely useful as a method for producing a glassy carbon molded article for industrial members in various fields including the semiconductor field.

Claims (3)

[Claims] 1. A thermosetting resin liquid is placed in a molding die for molding.
In the method for producing a glass-like carbon molded product which is hardened and then fired and carbonized at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere, the mold has an air permeability of 0.05 to 1.0 cm /
A method for producing a glass-like carbon molded article, characterized by comprising a fluorocarbon resin having a sec cmAq and an average pore diameter of 5 to 60 μm. 2. A filter paper is spread on the outer surface of the mold.
A method for producing the glass-like carbon molded article described. 3. A molding die is made into fine fibers by applying shearing force to polytetrafluoroethylene, polytrifluoroethylene or polyvinylidene fluoride capable of being formed into fibers, and then formed into a sheet, and the sheet is formed into a processed shape. The method for producing a glassy carbon molded article according to claim 1 or 2, which is obtained.