JPH0450108A - Production of high-density vitreous carbonaceous material - Google Patents

Abstract

PURPOSE:To obtain the title high-density carbonaceous material with excellent functionality up to ca.7mm thick, by forming an outer layer of a polyimide resin on the surface of a laminated, hot-pressed sheet from polyimide resin thin films followed by calcination. CONSTITUTION:Firstly, thin films of a polyimide resin <300 deg.C in glass transition temperature are mutually laminated and hot-pressed into a sheet of a specified thickness. Thence, an outer layer of another polyimide resin >=300 deg.C in glass transition temperature is formed on this sheet surface followed by calcination and carbonization at 800-2100 deg.C in a non-oxidative atmosphere, thus obtaining the objective carbonaceous material. With the present production process, the calcination and carbonization can be performed smoothly with the sheet form prior to calcination retained at all times, resulting in the conversion into the objective perfectly gas-impermeable, uniform, high-density vitreous carbonaceous material free from any texture damage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a glassy carbon material having a sheet shape and having a high density of up to about 71 mm in thickness.

[Conventional technology]

Glassy carbon material is a hard, densely structured carbonaceous material that exhibits a glass-like appearance and fractured surface, and is superior in terms of gas impermeability and chemical stability compared to ordinary carbon materials, so it is used for electronic purposes. It is used in a variety of fields including , machinery, and chemistry.

Conventionally, glassy carbon materials have been manufactured by molding a thermosetting resin with a high carbonization residual rate, such as furan resin or phenol resin, into a desired shape and then firing and carbonizing it in a non-oxidizing atmosphere. However, the present applicant has developed a method of using an aromatic polyimide resin film as a raw material resin as a means of efficiently producing a glassy carbon material that is thinner and has a higher density structure (Japanese Patent Application No. No. 149984, No. 1-303542).

Among these, the invention of Japanese Patent Application No. 1-303542 is used to press an aromatic polyimide resin film with a glass transition temperature (Tg) of 300'C or higher using a carbon pressure plate in order to produce a high-density glassy carbon film. This structure effectively prevents the polyimide resin film from adhering to the presser plate during the firing stage, making it possible to create a thin film of high-density glass-like garbon without structural damage. It becomes possible to obtain.

[Problems to be Solved by the Invention] However, although the above-mentioned prior art is effective as a method for manufacturing a glassy carbon material with a thin film of 0.2 mm, it cannot be used in a sheet shape having a constant thickness of 1M11 or more. It is not suitable as a means for producing glassy carbon materials. The reason for this is: - To obtain a glassy carbon material with a constant thickness, it is necessary to mold the raw material polyimide resin into a fairly thick sheet, but polyimide resin sheets have a glass transition temperature (Tg) of 300°C or higher. This is because when a resin component is used, integration by heat fusion does not proceed and molding becomes impossible.

The present invention was developed as a result of repeated research on the conditions for manufacturing a glass-like carbon material in the form of a sheet of constant thickness using a polyimide resin film as a raw material. It is an object of the present invention to provide a method for producing a glassy carbon material having properties with good yield.

[Means to solve the problem]

A method for producing a high-density glassy carbon material according to the present invention to achieve the above object is to heat-press thin films of polyimide resin having a glass transition temperature (Tg) of less than 300°C into a sheet of constant thickness. The sheet surface is heated to 300°C at the same time as the above-mentioned forming process or as a post-process.
After forming an outer layer of polyimide resin having a glass transition temperature (Tg) of 800 to 21
The structural feature is that the firing carbonization treatment is performed at a temperature of 00°C.

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The step of molding a polyimide resin sheet with a certain thickness is performed at a glass transition temperature (Tg) of less than 300°C, preferably 25°C.
This is done by laminating a large number of thin films made of aromatic polyimide resin at 0 to 295° C. and having a thickness of 0.02 to 0.13+-, and then hot-pressing them. The heat and pressure conditions are as follows:
Maintain the temperature in the range of 50 to 450℃ and the pressure to 5 kg/cm
It is desirable to set the value above. Under these conditions, it is possible to mold a polyimide resin sheet having a thickness of 0.1 to 9-1 and having an integrally fused structure.

On the surface of the molded polyimide resin sheet, an outer layer made of polyimide resin at a temperature of 300° C. or higher is formed simultaneously with the molding step or as a post-process.

In order to form this outer layer at the same time as the molding process, aromatic polyimide resin films with a glass transition temperature (Tg) of 300°C or higher are placed on both sides of a laminated film with a glass transition temperature (Tg) of lower than 300°C in the molding process. A method of applying heat and pressure at the same time is adopted. In addition, in order to form as a post-process of the molding process, the glass transition temperature (Tg) after imidization of the polyimide resin sheet formed by laminating and hot pressing is 30
A method is adopted in which a polyamic acid varnish (precursor of polyimide resin) that reaches a temperature of 0° C. or higher is applied, dried, and imidized. Application methods include doctor blade method,
Various methods such as a dipping method, a spray method, and a brush coating method can be applied. The drying process should be carried out at a temperature in the range of 60 to 120°C at which the solvent component (usually N-methyl-2-pyrrolidone or N,N-dimethylacetamide) evaporates, and the imidization should be carried out in the temperature range of 120 to 400°C. is suitable.

The calcination carbonization treatment is performed by heating to a temperature of 800 to 2100° C. using a furnace maintained in a non-oxidizing atmosphere such as nitrogen or argon.

Since the polyimide resin body obtained in the process of the present invention described above is a hard sheet having a certain thickness, it is not necessarily necessary to fill it into the furnace while being compressed with carbonaceous presser plates during firing, and it can be placed in the furnace as it is. can be set to .

The glassy carbon material produced through firing carbonization process is
It exhibits an amorphous crystal structure with a very dense structure with a thickness of 1 to 71 mm.

[For production]

According to the present invention, a polyimide resin film having a low melting point and a glass transition temperature (Tg) of less than 300°C is formed into a sheet portion of the inner layer, which is the main material, by laminating and hot pressing, and the sheet surface is coated with a polyimide resin film having a high melting point and a glass transition temperature (Tg) of less than 300°C. Tg) An outer layer made of polyimide resin having a temperature of 300° C. or higher is formed to form a raw resin body. Therefore, when forming the inner layer sheet, it is possible to easily form an integrally fused sheet with a desired thickness through lamination heat pressure of polyimide resin films, and the sheet is covered with an outer layer of high melting point polyimide resin formed on the surface. Fixed. In this structure, the polyimide resin layer that forms the outer layer with a glass transition temperature (Tg) of 300°C or higher has a thermal decomposition temperature lower than its melting point, so it may soften and deform during the heating stage of the firing carbonization process, or There is no phenomenon of fusion with other members.

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Due to this action, the sheet is smoothly fired and carbonized while always maintaining its sheet shape before firing, and is converted into a homogeneous and high-density glassy carbon material that is completely gas-impermeable and has no tissue damage.

Further, since there is no need to add a curing agent or other third component in the process before firing and carbonization, the material purity of the obtained glassy carbon is extremely high.

〔Example〕

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

Example 1 Glass transition temperature (Tg) having the following molecular structural formula (1)
) Polyimide resin film (“Ubilex R” manufactured by Ube Industries, Ltd., thickness 0.125 mm) at 285°C was heated at 20°C.
The sheets were laminated and pressed at a temperature of 300° C. and a pressure of 10 kg/cmz to form a sheet with a thickness of 2.5 m.

Next, on this sheet surface, a precursor polyamine citric acid varnish ["U-Varnish S" manufactured by Ube Industries, Ltd.] which is converted into a polyimide resin having a glass transition temperature (Tg) of 500° C. and the following molecular structure formula (2) after imide is applied. ”, concentration 20%
] was applied uniformly with a brush to a film thickness of approximately 50 μm.

Table 1 The sheet after coating was heated at 70°C and 120°C for 1 time each.
After drying for an hour, the coated resin was cured and imidized by heating at 200° C. and 300° C. for 2 hours each.

The resin sheet on which the outer layer was formed in this manner was transferred to a firing furnace maintained in a nitrogen gas atmosphere, and subjected to firing carbonization treatment at a temperature of 1500°C.

The obtained glassy carbon material had an amorphous crystal structure with a thickness of 21 mm, and various properties were measured and the results shown in Table 1 were obtained. For comparison, Table 1 also lists the characteristics of a commercially available glassy carbon material (manufactured by Tokai Carbon ■, CC20) manufactured using furan resin as a raw material.

From the results in Table 1, it is recognized that the glassy carbon materials according to the examples have functional properties such as higher density and superior strength characteristics than conventional products.

Example 2 Pyromellitic anhydride and 44-diaminodiphenyl ether were stirred in N-methyl-2-pyrrolidone solvent for 12 hours to prepare a polyamic acid cloth (concentration 20%). When imidized, this polyamic acid resin is converted into a polyimide resin having a glass transition temperature (Tg) of 420°C and having the following molecular structure formula (3).

A sheet of polyimide resin (glass transition temperature: 285°C) molded under the same conditions as in Example 1 was immersed in the second polyamide resin sheet to uniformly adhere to the surface, then dried in the same manner as in Example 1. It was subjected to carbonization and calcination carbonization treatments.

Ten glassy carbon sheets were manufactured through the above steps, and conditions such as cracking and deformation during the firing and carbonization process were investigated. The results are shown in Table 2.

Example 3 Eighteen polyimide resin films (glass transition temperature 285°C) identical to those in Example 1 were laminated, and a polyimide resin film with a thickness of 0°1251 and having a glass transition temperature (Tg) of 500°C on both sides [molecule Structural formula (2)] were stacked and pressed under hot pressure conditions of 300° C. and 10 kg/cm” of pressure to form a laminated polyimide sheet with a thickness of 2.5 mm.

This sheet was subjected to firing carbonization treatment in the same manner as in Example 1.
0 glassy carbon sheets were manufactured. In this case, conditions such as cracking and deformation during the calcination carbonization process were investigated, and the results are also listed in Table 2.

Comparative Example 1 A sheet of polyimide resin (glass transition temperature 285°C) molded under the same conditions as Example 1 was fired and carbonized at a temperature of 1500°C in a nitrogen gas atmosphere to produce 10 glassy carbon sheets. did. In this case, conditions such as cracking and deformation during the calcination carbonization process were investigated, and the results are also listed in Table 2.

Table 2 Comparative Example 2 Thickness 0°1 with glass transition temperature (Tg) 500°C
25+u+ polyimide resin film [Molecular structural formula (2
)] were laminated and pressed at a temperature of 300'C and 400°C under a pressure of 10kg/c@''.

However, in this case, the resin film does not soften or fuse, and
It was not possible to mold it in one piece.

〔Effect of the invention〕

As described above, according to the present invention, the glass transition temperature (Tg)
300°C on the outer surface of the polyimide resin sheet whose temperature is less than 300°C.
By firing and carbonizing a raw material resin body with a structure in which a polyimide resin layer of C or higher is formed, a glass-like carbon material having a sheet shape of up to 71 mm in thickness and having high density and excellent functional properties is produced. It can be produced with good yield. Therefore, it is extremely useful as a material for applications that require a high degree of gas impermeability, heat resistance, chemical stability, etc. at the same time.

Applicant: Tokai Carbon Co., Ltd. Agent: Patent attorney Tadashi Takahata and others

Claims (1)

[Claims] 1. Thin films of polyimide resin having a glass transition temperature (Tg) of less than 300°C are laminated and hot-pressed to form a sheet of a constant thickness, and the surface of this sheet is heated at 300°C or more at the same time as the above-mentioned forming process or as a post-process. Glass-transition temperature(
After forming an outer layer of polyimide resin having Tg),
A method for producing a high-density glassy carbon material, characterized by carrying out a firing carbonization treatment at a temperature of 800 to 2100°C in a non-oxidizing atmosphere.