JPS6344684B2 - - 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 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 gas impermeability and hardness. A glassy carbon material having a high isotropic structure and a high isotropic structure can be obtained. In addition to the properties of general carbon materials such as light weight, heat resistance, high electrical conductivity, corrosion resistance, thermal conductivity, mechanical strength, and lubricity, this glassy carbon material 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 do not have any effect on gas impermeability, but it is possible to polish the glassy carbon material and utilize its mirror surface as in the substrate for the magnetic head described above. When applied in the field, if there are closed pores inside the material, polishing will open the closed pores, 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, but conventional glassy carbon materials cannot be used for metal deposition 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 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 phenolic resins or 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. Pores are created when thermosetting resins are cured due to air entrained in the resin before curing, low-boiling substances contained in the resin, unreacted 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, unreacted components, and condensed water contained in the resin can be removed by heating under reduced pressure before curing, but by-products during curing can be removed. 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 aims to provide a thermosetting resin structure for producing a glassy carbon material that is practically non-porous, hard, dense, and gas-impermeable. purpose. [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 mixture of formalin and one or both of phenol and furfuryl alcohol in a ratio of 30 to 55.
Compound A is a monomer mixture with a molar ratio of 75:30, a phenolic resin, and one or more compounds selected from a furan resin and a phenol-modified furan cocondensate, lignin, a modified rosin, Compound B is one or more compounds selected from 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, and urea resin. When Compound C is one or more compounds selected from melamine resin, it consists of 70 to 100 parts by weight of Compound A, 0 to 15 parts by weight of Compound B, and 0 to 15 parts by weight of Compound C, and the viscosity at 25°C is It is characterized by being a resin composition of 300 to 8000 cps. In the present invention, when using a monomer mixture of both phenol and furfuryl alcohol and formalin at a predetermined ratio as compound A, or when using a phenol-modified furan cocondensate, compound A has a weight of 70 to 100%. Although some parts are used,
When using a monomer mixture of phenol or furfuryl alcohol and formalin in a predetermined ratio as compound A, or a phenol resin or furan resin, use 70 to 90 parts by weight of compound A, and compound B and C. It is preferable to use 10 to 30 parts by weight in total. In the present invention, when a mixture of compound A, phenol, and formalin is used, the ratio of phenol to formalin is preferably 1:3.5 to 1:0.5, and as compound A, a mixture of furfuryl alcohol and formalin is used. If the ratio of furfuryl alcohol to formalin is 1:1,
1.2 to 1:0 is preferred. Further, when a mixture of urea and formalin is used as compound C, the ratio of urea to formalin is 1:2 to 1:0.5.
is preferred, and when a mixture of melamine and formalin is used as compound C, the ratio of melamine to formalin is preferably 1:6 to 1:0.5. In the present invention, the resins used as Compound A and Compound C are not in solid form 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 and is essentially in the state of an initial condensate. In the present invention, formaldehyde polymers such as paraformaldehyde can also be used in place of formalin. 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 a 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. means. 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. It varies depending on the
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 phenolic resins, epoxy resins, unsaturated polyester resins, furan resins, urea resins, melamine resins, alkyd resins, and xylene resins;
For example, polyacrylonitrile-based carbon materials, cellulose-based carbon materials, rayon-based carbon materials, pitch-based carbon materials, lignin-based carbon materials, phenol-based carbon materials, furan-based carbon materials, epoxy resin-based carbon materials, alkyd resin-based carbon materials, non-carbon materials. In addition to saturated polyester-based carbon materials and xylene resin-based carbon materials, there are various types of graphite, carbon black, etc., and carbon materials in any form such as fibrous, particulate, powdered, or lumpy 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, carbonization will not be sufficient 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 Because it cures while keeping the low-boiling substances that are produced as by-products 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. It has a positive effect. 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 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 merely examples.
This does not limit the technical scope of the present invention. In addition, all "parts" in the examples mean "parts by weight." Example I 157 parts of a 37% aqueous formaldehyde solution and 15 parts of lignin are added to 100 parts of phenol under stirring, and further 5 parts of a 10% aqueous sodium hydroxide solution are added under stirring. This mixture is heated to 80°C and reacted at this temperature for 2 hours. Thereafter, the temperature of the reaction solution was lowered to 70°C, 9 parts of melamine and 25 parts of a 37% formaldehyde aqueous solution were added, and the mixture was allowed to react at 70°C for 5 hours. After cooling the reaction solution to room temperature, it is neutralized or made slightly acidic with 85% lactic acid and dehydrated under reduced pressure to remove 120 parts of water. The resin composition thus obtained had a viscosity of 4800 cps at 25°C and a water content of 30% or more. To the resin composition obtained above, 4.5 parts of a curing agent solution of para-toluenesulfonic acid, water and glycol (weight ratio 7:2:1) was added, and after thorough stirring, a strip of 3 mm thick was added. The mixture was poured into a shaped mold and defoamed under reduced pressure. This was followed by heating at 50-60°C for 3 hours and further heating at 90°C for 10 days. The obtained strip-shaped cured resin was placed in a tube furnace and heated to 1200°C at a rate of 10°C/hr in a nitrogen stream.
After holding for a period of time, the mixture was 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. On the polished surface, only a few pores with a diameter of 0.1 μm to 0.5 μm were observed per 1 mm ² , and no pores with a larger diameter were observed. Example Furfuryl Alcohol (manufactured by Kao Quaker)
500 parts and 80% paraformaldehyde (manufactured by Wako Pure Chemical Industries)
A mixture of 483 parts of lignin and 305 parts of lignin (manufactured by Borregard, trade name Ultrazine NA) is heated to 80°C while stirring. Next, carbolic acid (Mitsui Toatsu
Co., Ltd. and 54 parts of a 16% aqueous sodium hydroxide solution was added dropwise at 80°C while stirring. After dropping, mature at 80℃ for 3 hours, and
A mixed solution of 81 parts of carbolic acid and 54 parts of 16% sodium hydroxide is added dropwise, and the mixture is aged at this temperature for 2 hours. After cooling this liquid to room temperature, it was neutralized with a 70% aqueous solution of para-toluenesulfonic acid and adjusted to a weak acid (PH7-5), the temperature of the liquid was raised to 80°C again, and 120 parts of a 37% aqueous formalin solution and urea were added. Add 90 parts of a 50% aqueous solution dropwise. After aging this for 1 hour, under reduced pressure
Dehydrate 290 parts of water and add 500 parts of furfuryl alcohol. The resin composition obtained by this is heated at 25°C.
It had a viscosity of 2900 cps and a water content of 35% or more. This resin 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 was observed in the same manner as in Example I. 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 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, carbolic acid
A mixture of 524 parts and 54 parts of a 16% aqueous sodium hydroxide solution is added dropwise at 80°C with stirring. After dropping, it was aged at 80℃ for 3 hours, and then added with carbolic acid.
A mixed solution of 81 parts and 54 parts of 16% sodium hydroxide is added dropwise, and the mixture is aged at this temperature for 2 hours. After this, the liquid temperature was lowered to 70°C, 63 parts of melamine and 160 parts of a 37% formaldehyde aqueous solution were added, and the temperature was lowered to 70°C.
Allow time to react. Next, after cooling this liquid to room temperature, it is neutralized with a 70% aqueous para-toluenesulfonic acid solution, 250 parts of water is dehydrated under reduced pressure, and 500 parts of furfuryl alcohol is added. The resin composition obtained by this is heated at 25°C.
It had a viscosity of 3800 cps and a water content of 35% or more. This resin composition was cured and carbonized in the same manner as in Example I 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 Example I. As a result, the polished surface is glass-like, and less than 10 pores with a diameter of 0.1 μm to 0.5 μm can be seen per ¹ mm2.
No pores with larger diameters were observed. Test Example I The glassy carbon material obtained in Example I 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 roughly polished and then gradually finely polished. Finally, a mirror finish was applied using polishing sheet #15000, and model base 1 was created.
was created. When mirror-finished surface B was observed with a scanning electron microscope, it was found that this surface had a diameter
No pores larger than 0.5 μm were observed, and only pores smaller than 0.01 μm in diameter 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 Zr-Nb alloy thin film was formed by sputtering, and a 0.3 μm thick film 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 coercive force Hc of each thin film was measured using a vibrating magnetometer for soft magnetic thin films. The results are shown in the table. Test Example A test similar to Test Example I was conducted using the glassy carbon material obtained in Example. As a result, a good sputtered film was obtained. Test Example A test similar to Test Example I was conducted using the glassy carbon material obtained in Example. 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 I and above) are that the coercive force is small and the magnetic properties are excellent. I understand. 【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 comprises a monomer mixture of one or both of phenol and furfuryl alcohol and formalin in a molar ratio of 30:55 to 75:30, a phenol resin, and a furan resin. and one or more compounds selected from phenol-modified furan cocondensates 70 to 100
0 to 15 parts by weight, one or more compounds selected from lignin, modified rosin, and modified cellulose
parts by weight, a monomer mixture of one or both of urea and melamine and formalin in a molar ratio of 30:55 to 75:30, urea resin, and one or more compounds selected from melamine resin. 0 to 15 parts by weight, and a resin composition having a viscosity of 300 to 8000 cps at 25°C.