JPS6346004B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field to which the invention pertains] The present invention relates to a method for producing 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 the Prior Art] When a cured product of thermosetting resin, which is generally formed in a three-dimensional network structure and has insoluble and infusible properties, is carbonized in an inert atmosphere, it has excellent glass permeability and hardness. A glassy carbon material having a high and isotropic fiber structure is obtained. This glassy carbon material has the characteristics of light weight, heat resistance, high electrical conductivity, corrosion resistance, thermal conductivity, mechanical strength, lubricity, etc. of general carbon materials, and is homogeneous and can be used for sliding parts. It has the property of not producing carbon powder even when exposed to water, and is expected to be used in a wide range of fields including the electronics industry, nuclear power industry, and space industry. Recently, attention has been paid to the characteristics of this glassy carbon material, and the use of glassy carbon material as a substrate for magnetic heads has been studied. The properties required for a magnetic head substrate include lubricity and abrasion resistance, as well as the ability to polish to a clean mirror surface. Furthermore, use as a head slider to support 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 base for a magnetic head 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 and closed pores. Among these, the independent closed pores that exist inside the material have no effect on glass impermeability, but
When polishing a glass-like carbon material and applying it to a field where the mirror surface is to be used, such as the substrate for a magnetic head, if there are closed pores inside the material, the polishing will open the closed pores. This results in holes, and a mirror surface cannot be obtained, resulting in a fatal defect. In particular, when making thin-film magnetic heads, etc., it is necessary to evaporate or sputter-deposit metal onto a glassy carbon material as a basic material. It was not possible to obtain a suitable mirror surface. In the production of easily graphitizable carbon materials using general pitch as a raw material, the inclusion of air bubbles due to bubbling is unavoidable because the materials undergo 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, 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 so-called phenolic resins or furan resins that have a high carbonization yield, low-boiling point substances such as water can be This is unavoidable and accumulates in the resin during curing, causing closed pores on the order of μm or larger. Pores are created when thermosetting resins are cured due to air entrained by the resin before curing, low-boiling substances contained in the resin, reactive components, condensed water during resin production, and by-products produced during curing. water of condensation as a product,
The cause is decomposition gas, etc. The air pre-contained in the resin can be removed by defoaming, and the low-boiling substances, end-reaction components, and condensed water contained in the resin can be removed by heating under reduced pressure before curing. It is extremely difficult to remove some of the condensed water and cracked gas. Particularly when a highly hydrophobic resin is used, there is a disadvantage that condensed water accumulates and large pores remain in the carbon material after curing and subsequent carbonization. Therefore, the present inventors conducted intensive research to obtain a glassy carbon material without closed pores, and as a result,
This book was developed based on the discovery that a virtually non-porous glassy carbon material with almost no closed pores can be obtained by curing while keeping the low-boiling substances produced as by-products completely dispersed and dissolved in the base resin. The invention was completed. [Object of the invention] The present invention provides a thermosetting resin composite material for producing a glassy carbon material that is practically non-porous, hard, dense, and gas-impermeable. With the goal. [Features of the invention] The method for producing a glassy carbon material of the present invention includes the following steps:
In a method for producing a glassy carbon material by carbonizing and firing a thermosetting resin that can contain 20% by weight or more of water in an initial condensate state before curing at a temperature of 800°C or more in an inert atmosphere. , the above thermosetting resin is a resin composition obtained by co-condensing phenol, furfuryl alcohol, and formalin, and its composition is a molar ratio converted to monomers, in which phenol is 15 to 40, and furfuryl alcohol is 15-35
It is characterized by a formalin content of 30 to 55. In the present invention, formaldehyde polymers such as paraformaldehyde can be used in place of formalylin. To provide a supplementary explanation of the present invention, the key point of the production method 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 high viscosity before the thermosetting resin hardens, low boiling point substances are trapped within the resin because the resin has hydrophilicity to the extent that it can dissolve 20% by weight or more of water. It is possible to prevent this from occurring. In the present invention, the term "inert atmosphere" refers to an atmosphere that does not contain oxygen and usually consists of at least one gas selected from the group consisting of helium, argon, nitrogen, hydrogen, and halogen, or an atmosphere under reduced pressure or vacuum. Say something. The viscosity of the resin composition and the fact that if the water solubility of the resin composition exceeds 20% by weight will cause almost no pores after curing, depends on the type of raw resin, the degree of polymerization, and the blend. Although it varies depending on the ratio etc.
As a result of research by the present inventors, it was found that it is sufficient to have the above-mentioned water-soluble ability at a viscosity of 300 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, xylene resins, etc., such as polyacrylonitrile carbon materials, cellulose. Carbon material, rayon-based carbon material, pitch-based carbon material, lignin-based carbon material, phenol-based carbon material, furan-based carbon material, epoxy resin-based carbon material, alkyd resin-based carbon material, unsaturated polyester-based carbon material, xylene resin-based material In addition to carbon materials, there are various types of graphite, carbon black, and the like, and carbon materials in all forms such as fibrous, particulate, powder, and block forms 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℃ in atmosphere
or higher, preferably 1000°C or higher, more preferably
It is carbonized and fired at a temperature of 1,200°C or higher to become the desired glassy carbon material. 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, sufficient carbonization will not occur and the porosity will be large, making it difficult to impart the desired properties as a glassy carbon material. [Effects 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 before curing, so that the resin composition can be By curing while keeping the low boiling point substances produced as by-products completely dispersed and dissolved in the matrix resin, it is possible to obtain a practically non-porous glassy carbon material with almost no closed pores. It has excellent effects. 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 ultrathin film substrates by thin film deposition or sputtering that takes advantage of specularity, such as magnetic head substrates. In addition to being used 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 parts, and for high integration and density. It can greatly contribute to the use in the manufacturing method of associated 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 using Examples below, but the examples shown below are just examples.
This does not limit the technical scope of the present invention. In addition, all "parts" in the examples mean "parts by weight." Example 500 parts of furfuryl alcohol and 480 parts of 92% paraformaldehyde are stirred and dissolved at 80°C, and a liquid mixture of 520 parts of phenol, 8.8 parts of sodium hydroxide and 45 parts of water is added dropwise while stirring. After completion of the dropwise addition, the reaction was carried out at 80°C for 3 hours. Furthermore, a mixed solution of 80 parts of phenol, 8.8 parts of sodium hydroxide, and 45 parts is added, and the mixture is reacted at 80° C. for 4.5 hours.
This mixture is cooled to 30°C and neutralized with a 70% aqueous solution of para-toluenesulfonic acid. Thereafter, 150 parts of water are removed by dehydration under reduced pressure and 500 parts of furfuryl alcohol are added. The resin composition thus obtained has a molar ratio of phenol PhOH, furfuryl alcohol FFA, and formalin F, calculated as monomers, of 22:32:
46 composition and has a viscosity of 680 cps at 25 °C,
The moisture content was 38%. Table 1 shows the composition, viscosity, and water content of the resin composition. To the resin composition obtained above, 70 parts of para-toluenesulfonic acid and 3.5 parts of a solution of water and glycol (weight ratio 2:1) were added, and after thorough stirring, a strip of 3 mm thick was added. The mixture was poured into a mold and defoamed under reduced pressure. After this, it was heated at 50-60% for 3 hours and further heated at 90°C for 2 days. The obtained strip-shaped cured resin was placed in a tube furnace and heated at 10℃/hr in a nitrogen stream.
The temperature was raised to 1200° C. at a heating rate of 1,200° C., held for 2 hours, and then cooled to obtain a glassy carbon material. This glassy carbon material was polished with a #500 to #8000 polishing sheet, and the surface pore structure and pore diameter of the internally polished surface were observed using a scanning electron microscope. The polished surface is clearly glass-like and has a diameter of 0.5 μm ~
Only pores of 0.01 μm or less were observed. Example Furfuryl Alcohol (manufactured by Kao Quaker) 50
and 92% paraformaldehyde (manufactured by Mitsui Toatsu Co., Ltd.)
Put 483 parts of
Increase the temperature to. In this, carbolic acid (manufactured by Mitsui Toatsu Co., Ltd.)
A mixture of 525 parts and 54 parts of a 16.5% aqueous sodium hydroxide solution was added dropwise at 80°C over about 6 hours. Although paraform sublimes during the dropping reaction, stir the solution. After the dropwise addition was completed, the reaction was continued for an additional 3 hours.
After this, a mixture of 80.5 parts of phenol and 45 parts of 16.5% thorium hydroxide is added dropwise over 1 hour with stirring. After performing the aging reaction at 80℃ for 2 hours,
Cool to room temperature and neutralize with 50.8 parts of 70% para-toluenesulfonic acid aqueous solution. After this, under reduced pressure, approx.
Dehydrate 150 parts of water and add 400 parts of furfuryl alcohol. The resin composition thus obtained has a molar ratio of phenol, furfuryl alcohol, and formalin in terms of monomers of 20:29.5:50.5, and has a viscosity of 1750 cps at 25°C. and the moisture content is
It was 31%. This resin composition was cured and carbonized in the same manner as in the examples to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material is
Observations were made in the same manner as in Examples. As a result, the polished surface was glass-like, and less than 10 pores with a diameter of 0.1 μm to 0.5 μm were observed per mm ² , and no pores with a larger diameter were observed. Example Phenol, furfuryl alcohol, and formalin were co-condensed at a molar ratio of 32:32:36 in terms of monomers. The resin composition obtained by this is heated at 25°C.
It had a viscosity of 1600 cps and a water content of 30%. This resin composition was cured and carbonized in the same manner as in the examples to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material is
Observations were made in the same manner as in Examples. As a result,,
The polished surface is glass-like and has a diameter of 0.1 μm to 0.5 μm.
Only 10 or less pores were observed per mm ² , and no pores with a larger diameter were observed. Example Phenol, furfuryl alcohol, and formalin were co-condensed at a molar ratio of 24:20:55 in terms of monomers. The resin composition obtained by this is heated at 25°C.
It had a viscosity of 4250 cps and a water content of 35%. This resin composition was cured and carbonized in the same manner as in the examples to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material is
Observations were made in the same manner as in Examples. As a result, the polished surface was glass-like, and less than 10 pores with a diameter of 0.1 μm to 0.5 μm were observed per mm ² , and no pores with a larger diameter were observed. Example Phenol, furfuryl alcohol, and formalin were co-condensed at a molar ratio of 29:26:45 in terms of monomers. The resin composition obtained by this is heated at 25°C.
It had a viscosity of 1800 cps and a water content of 30%. This resin composition was cured and carbonized in the same manner as in the examples to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material is
Observations were made in the same manner as in Examples. As a result, the polished surface was glass-like, and less than 10 pores with a diameter of 0.1 μm to 0.5 μm were observed per mm ² , and no pores with a larger diameter were observed. Example The molar ratio of phenol, furfuryl alcohol, and formalin in terms of monomers is 25.5:
Cocondensation was carried out at a ratio of 36.5:38. The resin composition obtained by this is heated at 25°C.
It had a viscosity of 320 cps and a water content of 36%. This resin composition was cured and carbonized in the same manner as in the examples to obtain a glassy carbon material. The surface pore structure of the internally polished surface of this glassy carbon material is
Observations were made in the same manner as in Examples. As a result, the polished surface was glass-like, and less than 10 pores with a diameter of 0.1 μm to 0.5 μm were observed per mm ² , and no pores with a larger diameter were observed. Comparative Example Phenol, furfuryl alcohol, and formalin were co-condensed at a molar ratio of 19:41:40 in terms of monomers. The cocondensate thus obtained was heated at 25°C.
It had a viscosity of 420 cps and a water content of 26%. This co-condensate was cured and carbonized in the same manner as in the example to obtain a carbon material. The surface pore structure of the internally polished surface of this carbon material was observed in the same manner as in Examples. As a result, the diameter is 0.1 μm to 0.5 μm.
Approximately 20 pores were observed per ^mm2 . Comparative Example Phenol, furfuryl alcohol, and formalin were co-condensed at a molar ratio of 5:15:35 in terms of monomers. The cocondensate thus obtained has a viscosity of 2700 cps at 25°C and a water content of
It was 18%. This co-condensate was cured and carbonized in the same manner as in the example to obtain a carbon material. The surface pore structure of the internally polished surface of this carbon material was observed in the same manner as in Examples. As a result, approximately ¹⁰³ pores with a diameter of 0.1 μm to 0.5 μm were observed per 1 ^mm2 , and pores with a diameter of 0.5 μm were observed.
More pores were also observed. Comparative Example Phenol and formalin were co-condensed at a molar ratio of 30:70 in terms of monomers. The cocondensate thus obtained had a viscosity of 3200 cps at 25°C and a content of 19%. This co-condensate was cured and carbonized in the same manner as in the example to obtain a carbon material. The surface pore structure of the internally polished surface of this carbon material was observed in the same manner as in Examples. As a result, many pores with a diameter of 1 μm or more were observed. Comparative Example Furfuryl alcohol and formalin were co-condensed at a molar ratio of 59:41 in terms of monomers. The cocondensate thus obtained was heated to 25°C.
It had a viscosity of 350 cps and a water content of 15%. This co-condensate was cured and carbonized in the same manner as in the example to obtain a carbon material. The surface pore structure of the internally polished surface of this carbon material was observed in the same manner as in the example. As a result, many pores with a diameter of 1 μm or more were observed. Comparative Example Furfuryl alcohol alone had a viscosity of 390 cps at 25°C and a water content of 4%. This was cured and carbonized in the same manner as in the examples to obtain a carbon material. The surface pore structure of the internally polished surface of this carbon material was observed in the same manner as in the example. As a result, many pores with a diameter of 1 μm or more were observed.

[Table] Comparative example Hitafuran VF302 (furfuryl alcohol/furfural co-condensate, viscosity 200 cps at 25°C)
The amount of water that can be contained was determined as follows. That is, after vigorously mixing with approximately the same amount of water, this was left to stand, and the resin precipitated at the bottom was taken out and sampled, and the amount of water contained was determined by the Karl Fischer method. As a result, the water content is
It was 3.9%. This was cured and carbonized in the same manner as in the examples to obtain a carbon material. The surface pore structure of the internally polished surface of this carbon material was observed in the same manner as in Examples. As a result, pores with a diameter of 0.1 μm to 3 μm are 1 mm
10 ⁴ to ^{10 5} were seen per ² . Further, a good sputtering film was not obtained on this substrate, and the film peeled off during annealing due to poor adhesion of the film. Test Example The glassy carbon material obtained in Examples and Comparative Examples 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 was formed were The model substrate 1 was prepared by performing rough polishing, then gradually fine polishing, and finally mirror finishing with polishing sheet #15000. When mirror-finished surface B was observed with a scanning electron microscope, it was found that this surface had a diameter
No pores with a diameter of 0.5 μm or more were observed, and only pores with a diameter of 0.01 μm or less were observed. This model substrate 1 was cut along the dashed-dotted line C-C' in the figure, and a 1-μm-thick Co
A thin alloy film of -Zr-NB was formed by sputtering, and a thickness of 0.3 μm was formed on the B side of the other cut piece.
A Co-Zr-NB alloy thin film was also formed by sputtering. After heat-treating these thin films in a rotating magnetic field, the magnetic properties of each thin film, such as coercive force Hc, were evaluated using a vibrating magnetometer for soft magnetic thin films. Those with good magnetic properties are H-
If the B curve is a smooth hysteresis curve, and the magnetic properties are poor, the H-B curve becomes a multi-stage discontinuous line. Table 2 shows the state of the sputtered film and the evaluation of its magnetic properties. Test Results As is clear from Table 2, the properties of the glassy carbon materials obtained in the Examples of the present invention as substrates for magnetic heads (Examples or Examples) are the same as those of the glassy carbon materials obtained in the Comparative Examples. It can be seen that the coercive force is small and the magnetic properties are excellent compared to the properties as a head substrate (comparative examples).

【table】

【table】 [Brief explanation of the drawing]

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. 1...Model base.

Claims (1)

[Claims] 1. A thermosetting resin that can contain 20% by weight or more of water in the state of an initial condensate before curing is carbonized and fired at a temperature of 800°C or more in an inert atmosphere to produce glassy carbon. In the method for producing the material, the thermosetting resin is a resin composition obtained by co-condensation of phenol, furfuryl alcohol, and formalin, and the composition has a molar ratio of 15 to 40% of phenol in terms of monomers. and furfuryl alcohol is 15
35, and formalin is 30 to 55.