JPS60171210A - Manufacture of vitrified carbonaceous material - Google Patents

Abstract

PURPOSE:To obtain a practically nonporous vitrified carbonaceous material contg. no closed pores by providing a specified composition to a thermosetting resin as a starting material so that it can retain a specified wt% of water in the state of a precondensation product before curing. CONSTITUTION:A thermosetting resin capable of retaining >=20wt% water in the state of a precondensation product before curing is carbonized and calcined at >=800 deg.C in an inert atmosphere to manufacture a vitrified carbonaceous material. The composition of the thermosetting resin is composed of 70-100pts.wt. of one or more kinds of compounds selected among a monomer mixture consisting of phenol and/or furfuryl alcohol and formalin in 30:55-75:30 molar ratio, phenol resin, furan resin and a condensation product of phenol modified furan, 0-15pts.wt. of one or more kinds of compounds selected among lignin, modified rosin and modified cellulose, and 0-15pts.wt. of one or more kinds of compounds selected among a monomer mixture consisting of urea and/or melamine and formalin in 30:55-70:30 molar ratio, urea resin and melamine resin.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a method for manufacturing a glassy carbon material.

In particular, the present invention relates to a method for manufacturing a glassy carbon material whose surface after mirror polishing has extremely high smoothness.

[Description of prior art]

Generally, when a cured thermosetting resin that has a three-dimensional network structure and is insoluble and infusible is carbonized in an inert atmosphere, it has excellent gas impermeability, high hardness, and isotropic properties. A glassy carbon material with sexual tissue is obtained. This glassy carbon material has the light weight and
In addition to properties such as heat resistance, high electrical conductivity, corrosion resistance, thermal conductivity, mechanical strength, and lubricity, it is homogeneous and does not generate carbon powder even when used in sliding parts, making it suitable for the electronics industry. It is expected to be widely used in various fields including the nuclear power industry and the space industry.

Recently, attention has been paid to the characteristics of this glassy carbon material, and studies have been made to utilize the glassy carbon material as a substrate for a magnetic head. The performance required for a magnetic head substrate is not only lubricity and wear resistance, but also the ability to obtain a clean mirror surface by polishing. Furthermore, use as a Hent slider that supports a magnetic head is also being considered. The properties required for this are light weight in addition to lubricity and ease of mirror finishing. Therefore, by using a glassy carbon material, it can be used as a magnetic head base that also serves as a head slider.

When conventionally manufactured glassy carbon materials are observed under a microscope, they are found to have open pores.
pore ) and closed pore. Of these, the independent closed pores that exist inside the material do not affect the gas impermeability, but when the glassy carbon material is polished, it is
When applying to a field that uses the mirror surface,
If closed pores exist inside the material, the closed pores become open holes by polishing, making it impossible to obtain a mirror surface, resulting in a fatal defect.

In particular, when making thin-film magnetic heads, etc., it is necessary to evaporate or sputter metal onto a glassy carbon material as a basic material. However, with conventional glassy carbon materials, metal deposition cannot be achieved even after polishing for the reasons mentioned above. It was not possible to obtain a suitable mirror surface.

In the production of easily graphitizable carbon materials using ordinary pitch or the like as a raw material, the inclusion of air bubbles due to bubbling is unavoidable because the material undergoes a molten state in the process of carbonization. In order to avoid this contamination, carbonization under high pressure has been attempted, and although this carbonization has eliminated the contamination of bubbles to some extent, the gas impermeability has not yet reached a level where it can be said to be sufficient.

On the other hand, in the carbonization of thermosetting resins, when using phenolic resins and furan resins that have a high carbonization yield, low-boiling point substances such as water are used at the stage of obtaining the cured product, which is the precursor. This is unavoidable and accumulates in the resin during curing, causing closed pores on the order of μm or larger.

When thermosetting resins are cured, pores are created by ■ air trapped by the resin before curing, ■ low-boiling substances contained in the resin, unreacted components, condensed water during resin formation, and ■ during curing. This is caused by condensed water, cracked gas, etc. as by-products. The pre-contained air in (①) can be removed by defoaming, and the low-boiling substances, unreacted components, and condensed water contained in the resin in (①) during resin formation can be removed by heating under reduced pressure before curing. Part of the resulting condensed water and cracked gas can be removed very efficiently. Particularly when a highly hydrophobic resin is used, there is a drawback that condensed water accumulates and large pores remain in the carbon material after curing and subsequent carbonization.

Therefore, the present inventors conducted extensive research in order to obtain a glassy carbon material without closed pores, and as a result, the present inventors succeeded in curing the material while keeping the low-boiling substances produced as by-products during curing completely dispersed and dissolved in the base resin. The present inventors have discovered that a practically non-porous glass-free carbon material with almost no closed pores can be obtained by doing so, and have completed the present invention.

[Purpose of the invention]

An object of the present invention is to provide a thermosetting resin structure for producing a glassy carbon material that is practically non-porous, hard, dense, and gas-impermeable.

[Features of the invention]

The method for producing a glassy carbon material of the present invention involves carbonizing a thermosetting resin that can contain 20% by weight or more of water in the state of an initial condensate before curing at a temperature of 800°C or more in an inert atmosphere. In the method of producing a glassy carbon material by firing, the thermosetting resin is a monomer mixture of one or both of phenol and furfuryl alcohol and formalin in a molar ratio of 30:55 to 75:30. and,
Compound A is one or more compounds selected from a phenol resin, a furan resin, and a phenol-modified furan cocondensate, and one or more compounds selected from lignin, modified rosin, and modified cellulose. The compound is compound B, a monomer mixture of one or both of urea and melamine and formalin at a molar ratio of 30:55 to 75:30, and one or more types selected from urea resin and melamine resin. When the compound is Compound C, it is a resin composition consisting of 70 to 100 parts by weight of Compound A, 80 to 15 parts by weight of Compound, and 00 to 15 parts by weight of Compound, and having a viscosity of 300 to 8000 cps at 25°C. Features.

In the present invention, when a monomer mixture of both phenol and furfuryl alcohol and formalin at a predetermined ratio is used as compound A, or when a phenol-modified furan cocondensate is used, compound A is 70 to 10
However, when using a monomer mixture of formalin and one of phenol or furfuryl alcohol in a predetermined ratio as compound A, or a phenol resin or furan resin, 70 to 90 parts by weight of compound A is used. For use, compound B and compound C are added in a total of 10 to 3
It is preferable to use 0 parts by weight.

In the present invention, when a mixture of phenol and formalin is used as compound A, the ratio of phenol to formalin is preferably 1:3.5 to 1:0.5,
When a mixture of compound A, furfuryl alcohol and formalin is used, the ratio of furfuryl alcohol to formalin is preferably 1:1.2 to 1:0. Further, when a mixture of urea and formalin is used as compound C, the ratio of urea and formalin is 1:2.
The ratio of melamine to formalin is preferably from 1:6 to 1:0.5 when a mixture of melamine and formalin is used as compound C.

In the present invention, the resins used as Compound A and Compound C are in a solid state when forming the resin composition, as can be seen from the fact that the resin composition exhibits a viscosity of 300 to 8000 cps at 25°C. It exhibits fluidity at random, and is essentially in the state of an initial condensate.

In the present invention, formaldehyde polymers such as lantolelemaldehyde can also be used in place of formalin.

To provide a supplementary explanation of the present invention, the key point of the production method G of the present invention is to eliminate the accumulation of low-boiling substances within the thermosetting resin when the thermosetting resin is cured. In other words, in the initial condensate state with a high viscosity before the thermosetting resin hardens, the resin has hydrophilicity to the extent that it can dissolve 20% by weight or more of water, so that low boiling point substances are trapped in the resin. This can prevent it from being squeezed.

In the present invention, "inert atmosphere" refers to an atmosphere that does not contain oxygen and usually consists of at least -fffi gas selected from the group consisting of helium, argon, nitrogen, hydrogen, and halogen, or an atmosphere under reduced pressure or vacuum. Say something.

The type of raw material resin, degree of polymerization, and blending ratio determine the viscosity of the resin composition and whether or not almost no pores will be generated after curing if the water-soluble ability of the resin composition exceeds 20% by weight. As a result of the inventor's research, 3
It has been found that it is sufficient to have the above-mentioned water-soluble ability at a viscosity of 00 to 8000 cps/25°C.

Also, in practicing the present invention, filler (aggregate) can be added during the practice. Fillers include various carbon materials including thermosetting resins such as phenol resins, epoxy resins, unsaturated polyester resins, furan resins, urea resins, melamine resins, alkyd resins, and xylene resins, such as polyacrylonitrile carbon materials, and cellulose. carbon materials, rayon-based carbon materials, pi-nochi-based carbon materials, lignin-based carbon materials, phenolic-based carbon materials, furan-based carbon materials, epoxy resin-based carbon materials, alkyd resin-based carbon materials, unsaturated polyester-based carbon materials, In addition to xylene resin-based carbon materials,
There are various types of graphite, carbon black, etc., and carbon materials in all forms such as fibrous, particulate, powder, and lump can be used.

Before curing, the resin composition used in the present invention is put into a mold with a predetermined shape by various molding methods depending on the intended use of the glassy carbon material, and after becoming a predetermined molded product, it is inert. 800℃ or higher in the atmosphere, preferably 1000℃
The desired glassy carbon material is obtained by carbonization and firing at a temperature of 1200°C or higher, preferably 1200°C or higher. In this case, the carbonization firing time may be appropriately selected depending on the firing temperature.

If the heating temperature is lower than 800° C., carbonization will not be sufficient and the porosity will be large, making it difficult to impart the desired properties as a glass-like carbon material.

〔Effect of the invention〕

As described above, according to the method of the present invention, the resin composition as a starting material can contain 20% by weight or more of water at a stage before curing, so that when the resin composition is cured, it becomes an additive. Since the resulting low-boiling substances are cured while being completely dispersed and dissolved in the base resin, it is possible to obtain a practically non-porous glassy carbon material with almost no closed pores.

In particular, since a glass-like carbon material containing no closed pores in the internal structure can be obtained, the manufacturing method of the present invention can be used for manufacturing ultra-thin film substrates by thin film deposition or sputtering that takes advantage of specularity, such as magnetic head substrates. In addition to use in manufacturing methods for magnetic head sliders and thin film supports, it can also be used in wear-resistant sliding parts used in general precision electronic components, and for high integration and high density. It can greatly contribute to the use in manufacturing methods of electronic materials.

Further, since the glassy carbon material is substantially free of pores, the glassy carbon material obtained by the present invention can also be used as a separator for fuel cells.

(Explanation based on Examples) The present invention will be explained in more detail below using Examples, but the examples shown below are merely examples and do not limit the technical scope of the present invention. All "parts" and "-" herein mean "parts by weight."

(Example I) 100 parts of phenol to 1 part of 37% formaldehyde aqueous solution
57 parts and 15 parts of lignin are added under stirring, and
5 parts of 10% aqueous sodium hydroxide solution are added under stirring. This mixture was heated to 80 t', and at this temperature 2
Allow time to react. After this, the temperature of the reaction solution was lowered to 70°C, and 9 parts of melamine and 25 parts of a 37% formaldehyde aqueous solution were added.
After cooling the reaction solution to room temperature, it was neutralized or made weakly acidic with 85% lactic acid, and dehydrated under reduced pressure to remove 120 parts of water. The resin composition thus obtained was heated at 4°C at 25°C.
It had a viscosity of 800 cps and a water content of 30% or more.

Para-toluenesulfonic acid, water and glycol (weight ratio 7:2:1) were added to the resin composition obtained above.
4.5 parts of curing agent solution was added, stirred thoroughly, poured into a rectangular mold with a thickness of 3 mm, and reduced pressure. It bubbled. This was followed by heating at 50 to 60"C for 3 hours, and further heating at 90C for 1 day.The resulting cured resin strips were placed in a tube furnace and heated at 10C/hr in a nitrogen stream. The temperature was raised to 1200''C at a temperature rate, maintained for 2 hours, and then cooled to obtain a glassy carbon material.

This glassy carbon material #500~#8000
The surface pore structure and pore diameter of the inner polished surface were observed using a scanning electron microscope. On the polished surface, only a few pores with a diameter of 0.1 μm = 0.5 μm were observed per lion 2, and no pores with a larger diameter were observed.

(Example ■) 500 parts of furfuryl alcohol (manufactured by Acre), 483 parts of 80% paraformaldehyde (manufactured by Wako Pure Chemical Industries, Ltd.), and lignin (manufactured by Borregard, trade name: Ultrazine NA)
) and 305 parts of the mixture was heated to 80"C without stirring.Next, a mixture of 524 parts of carbolic acid (manufactured by Mitsui Toatsu) and 54 parts of a 16% sodium hydroxide aqueous solution was heated to 80"C without stirring.
Add dropwise while stirring at 0°C. After the addition was completed, it was aged at 80°C for 3 hours, and then a mixed solution of 81 parts of carbolic acid and 54 parts of 16% sodium hydroxide was added dropwise, and at this temperature,
Let rise for 2 hours. After cooling this liquid to room temperature,
Neutralize with 0% p-toluenesulfonic acid aqueous solution to weak acid (p
Adjust the temperature to H7~5), raise the liquid temperature to 80℃ again, and
120 parts of a 50% aqueous solution of urea and 90 parts of a 50% aqueous solution of urea
Drip the solution. After aging this for 1 hour, 290 parts of water is removed under reduced pressure, and 500 parts of furfuryl alcohol is added.

The resin composition thus obtained was heated to 290°C at 25°C.
It had a viscosity of 0 cps and a water content of 35% or more.

This resin was cured and carbonized in the same manner as in Example 2 to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material was observed in the same manner as in Example (2). As a result, the polished surface is glass-like and has a diameter of 0.
Only 10 or less pores with a diameter of 1 μm to 0.5 μm were observed per 2 cranes, and no pores with a larger diameter were observed.

(Example ■) A mixture of 500 parts of furfuryl alcohol, 483 parts of 80% paraformaldehyde, and 200 parts of lignin is heated to 80°C while stirring. Next, 8 parts of a mixture of 524 parts of carbolic acid and 54 parts of a 16% aqueous sodium hydroxide solution was added.
Add dropwise while stirring at 0°C. After the addition was completed, it was aged at 80°C for 3 hours, and then a mixed solution of 81 parts of carbolic acid and 54 parts of 16% sodium hydroxide was added dropwise, and at this temperature,
Let rise for 2 hours. After this, the liquid temperature is lowered to 70°C, 63 parts of melamine and 160 parts of a 37% formaldehyde aqueous solution are added, and the mixture is reacted at 70°C for 5 hours. Next, after cooling this liquid to room temperature, it was neutralized with a 70% aqueous para-toluenesulfonic acid solution, and 250 parts of water was dehydrated under reduced pressure.
Add 500 parts of furfuryl alcohol.

The resin composition thus obtained was heated to 380°C at 25°C.
It had a viscosity of 0 cps and a water content of 35% or more.

This resin composition was cured and carbonized in the same manner as in Example 2 to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material was observed in the same manner as in Example I. As a result, the polished surface is glass-like, and there are 10 pores with a diameter of 0.1 μm = 0.5 μm per 1 m2.
No pores with a larger diameter were observed.

(Test Example ■) The glassy carbon material obtained in Example ■ was cut into the shape and dimensions shown in the figure, and the sliding surface A with the recording medium and the surface B on which the thin film is formed were polished from coarse to gradually fine polishing. Finally, a mirror finish was performed using a polishing sheet #15000 to prepare a model base 1. When mirror-finished surface B was observed with a scanning electron microscope, no pores with a diameter of 0.5 μm or more were found on this surface, and no holes with a diameter of 0.
．． Only pores of 0.01 μm or less were observed.

This model substrate 1 was cut along the dashed line c-c' in the figure, and a Co-Zr layer with a thickness of 1 μm was placed on the B side of one of the cut pieces.
A -Nb alloy thin film was formed by sputtering, and a 0.3 μm thick Co -Zr film was formed on the B side of the other cut piece.
A -Nb alloy thin film was also formed by sputtering. After heat-treating these thin films in a rotating magnetic field,
The coercive force HC of each thin film was measured using a vibrating magnetic measuring device for soft magnetic thin films. The results are shown in the table.

(Test Example 1) Using the glassy carbon material obtained in Example ■,
A test similar to Test Example I was conducted. As a result, a good sputtered film was obtained.

(Test Example ■) Using the glassy carbon material obtained in Example ■,
A test similar to Test Example I was conducted. As a result, a good sputtered film was obtained.

(Test Results) As is clear from the table, the characteristics of the glassy carbon materials obtained in the Examples of the present invention as substrates for magnetic heads (Test Examples ■ to ■) are that the coercive force is small and the magnetic properties are excellent. I understand that.

[Brief explanation of drawings]

The figure is an external perspective view of a model base made of a material used in a magnetic head according to an embodiment of the present invention. l...Model base.

Claims (1)

[Scope of Claims]
In the method of producing a glassy carbon material by carbonizing and firing at a temperature of 00°C or higher, the thermosetting resin comprises one or both of phenol and furfuryl alcohol and formalin in a molar ratio of 30:55 to 75:30. a monomer mixture of, a phenolic resin, a furan resin,
70 to 100 M parts of one or more compounds selected from phenol-modified furan cocondensates, and 0 to 15 parts by weight of one or more compounds selected from lignin, modified rosin, and modified cellulose. a monomer mixture of one or both of urea and melamine and formalin at a molar ratio of 30:55 to 75:30, urea resin, and melamine resin.
1. A method for producing a glassy carbon material, characterized in that the resin composition is composed of 0 to 15 parts by weight of at least one compound, and has a viscosity of 300 to 8,000 cps at 25°C.