JPH06663B2 - Method for producing glassy carbon composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is used for producing a glassy carbon composite material.
More specifically, the present invention relates to a method for producing a composite material containing glassy carbon as a main component and having excellent wear resistance and a small friction coefficient, which is excellent as a material for precision processed parts.

〔Overview〕

The present invention provides a method for producing a composite material containing glassy carbon as a main component, in which a whisker as a reinforcing fiber component is uniformly mixed with a hardening precursor of a liquid thermosetting resin so that friction with a mating material in sliding contact is obtained. It is intended to provide a glassy carbon composite material which has low resistance, does not damage a counterpart material, and has excellent wear resistance and durability of itself.

[Conventional technology]

At present, various devices for recording and reproducing by using a sheet or film having a magnetic layer or paper as a recording medium are commercially available. These recording / reproducing devices include a large number of parts which are constantly or temporarily slidably in contact with the recording medium. As parts of this kind, flexible disk head slider, hard disk flying slider,
There are thermal print heads, magnetic heads and the like. These parts are required to have characteristics of excellent durability and not damaging a recording medium which is in sliding contact with the parts. Further, these parts, especially the magnetic head, require ultra-precision processing of several microns to several tens of microns, and the precision processing characteristics of the material are required.

Materials for such parts include silicon dioxide, alumina, silicon carbide, hard glass, alumina-based ceramics,
Ferrite, calcium titanate, barium titanate and the like are commonly used. However, although these materials are suitable for precision parts, they have high hardness and poor slidability with respect to the recording medium, and therefore may damage the recording medium.

Further, a graphite material is known as a material having extremely good slidability, but it has a large abrasion property and it is difficult to maintain the same shape stably for a long period of time. In addition, because of the constituent grains, sufficient denseness cannot be obtained, which is not suitable for use as a precision part.

Therefore, the present inventors have conducted various studies in order to solve the above-mentioned drawbacks, and have found that glassy carbon can solve the above-mentioned drawbacks, and filed a patent application earlier. This application is published as Japanese Patent Application Laid-Open Nos. 59-84325 and 59-144019.

Glassy carbon is a material having an appropriate antifriction property, and when it slides on a mating material, the glassy carbon itself has a property of being worn before it is damaged.

[Problems to be solved by the invention]

However, as a result of further tests, it was found that the glass-like carbon alone may cause insufficient wear resistance due to the roughness and hardness of the surface of the mating material.

The present invention has a low frictional resistance with a mating material, does not damage the mating material, without applying a lubricant to the surface of the mating material in sliding contact and without providing a protective film on the surface of the mating material. It is an object of the present invention to provide a method for producing a composite material capable of producing a sliding contact component having excellent wear resistance and durability.

[Means for solving problems]

The manufacturing method of the glassy carbon composite material of the present invention, a curing precursor of a thermosetting resin, silicon carbide whiskers, silicon nitride whiskers and one or more whiskers selected from graphite whiskers are mixed, and the resin is cured, Furthermore, in the method for producing a glassy carbon composite material, which is carbonized and baked at a temperature of 800 ° C. or higher, preferably 1000 ° C. or higher in an inert atmosphere, the precursor before curing is characterized in that it is in a liquid state.

The present invention uses a liquid thermosetting resin to uniformly disperse the whiskers in the glassy carbon. As the thermosetting resin, a liquid resin is selected from furan resin, phenol resin, phenol-furan resin and the like. In particular,
It is desirable to use a thermosetting resin that can contain 20% by weight or more of water in the form of an initial condensate.

According to the method of the present invention, whiskers are added to the liquid thermosetting resin, and the whiskers are uniformly dispersed in the resin by physically high shearing force. In order to obtain a physical high shearing force, for example, a ball mill, a kneader, a sand mill or the like is used, but a sand mill is particularly preferable.

Furthermore, by adding a water-soluble surfactant at the time of mixing the whiskers, the whiskers can be more uniformly dispersed in the resin.

Water-soluble surfactants include nonionic surfactants and polyvinylpyrrolidrin. Nonionic surfactants include polyethylene glycol type nonionic surfactants and polyhydric alcohol type nonionic surfactants.

Specific surfactants include polyethylene glycol, oxyethylene oxypropylene block polymer,
Polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, and polyvinyl pyrrodrine are used.

These water-soluble surfactants have an ether bond, and a water molecule is hydrogen-bonded to an oxygen atom of an ether bond in an aqueous solution to exhibit hydrophilicity. Therefore, the increase in the number of moles of ethylene oxide contributes to the increase in hydrophilicity.

Further, it is possible to use a surfactant that absorbs water molecules and exhibits hydrophilicity, such as polyvinylporolidone, even if it does not contain ethylene oxide.

The water absorption curing of the surfactant increases the viscosity of the entire system when the water-soluble surfactant is added to the liquid thermosetting resin, and prevents whiskers from settling and aggregating. Further, it is desirable to evenly disperse the whiskers by physically high shearing forces.

The glassy carbon as the main component in the glassy carbon composite material produced by the present invention is a glassy carbon obtained by carbonizing a thermosetting resin such as a furan resin or a phenol resin, or a thermosetting resin such as a phenol resin. It is a glassy carbon obtained by carbonizing a resin modified by such copolymerization or cocondensation.

In particular, non-porous glassy carbon obtained from a thermosetting resin containing 20% or more of water in the state of an initial condensation product as a raw material,
That is, the glassy carbon disclosed in JP-A-60-171208, JP-A-60-171209, JP-A-60-171210 and JP-A-60-171211 is preferable.

These glassy carbons are amorphous materials,
It is a material that has an appropriate level of antifriction property and that, when the recording medium slides, it self-wears before the surface film of the recording medium is damaged.

Also, whisker here means natural growth from solid,
It is a needle-like crystal that grows by vapor condensation, chemical reaction, eutectic unidirectional solidification, electrodeposition, etc., and is also called whiskers. It is known that its thickness ranges from 0.05 μm or less to about 10 μm. The biggest feature of whiskers is that there are very few dislocations and defects inside the crystal,
Some have nothing. Therefore, the whisker strength is close to the ideal value of the crystal.

Although the aspect ratio (ratio between thickness and length) of whiskers is not particularly specified, generally, the higher the aspect ratio, the higher the strength of the composite material containing it. In the glassy carbon composite material of the present invention, the effect was obtained when the whiskers having an aspect ratio of 10 or more, further 50 or more were used.

The content of whiskers is preferably in the range of 0.005 to 0.2, and more preferably in the range of 0.005 to 0.1, by volume ratio with respect to the glassy carbon. Within this range, precision workability, wear resistance and friction coefficient are excellent. If the whisker content is low, the effect of mixing cannot be obtained.
On the other hand, if the amount is too large, the precision workability is deteriorated and the friction coefficient is increased.

[Action]

By mixing whiskers with liquid thermosetting resin,
A glassy carbon composite material in which whiskers are uniformly dispersed can be manufactured. Furthermore, when a water-soluble surfactant is added at the time of mixing the whiskers, the whiskers can be dispersed more uniformly. According to the manufacturing method of the present invention, the bending strength of the glassy carbon composite material can be increased, and the reliability in breaking the material can be increased. That is, it is possible to prevent breakage of the material such as chipping and chipping.

The glassy carbon composite material obtained by the method of the present invention is a material in which inorganic whiskers are dispersed in glassy carbon to improve wear resistance while maintaining the low friction property of glassy carbon. Therefore, by using this composite material, it is possible to manufacture a sliding contact component that has a low frictional resistance with the mating material, does not damage the mating material, and has excellent wear resistance and durability of itself.

The mating material differs depending on the application of the sliding contact part. For example, when the sliding contact part is used with a magnetic head, a head slider of a floppy disk, or a flying slider of a hard disk, the mating material is a floppy disk, a hard disk, a magnetic tape, etc. The material is paper or polymer sheet, and when used as a ball retainer for bearings, SUJ2
Etc. steel. In this way, the mating material may have any shape such as a flat surface, a curved surface or a thread shape, and even if the shape does not change,
It may be flexible.

When this material is used, for example, in a sliding contact part with a recording medium, it is possible to maintain the lubricity for a long time without using a lubricant between the recording medium and to damage the surface of the recording medium. Moreover, there is an advantage that the wear of the material itself is small.

In addition, the conductivity of the glassy carbon does not generate static electricity, and dust is less likely to adhere to the portion in contact with the disk recording medium and the recording medium itself.

The glassy carbon composite material of the present invention is specifically, a sliding contact part such as a flexible disk head slider, a hard disk floating slider, a thermal print head, a magnetic head, a ball retainer of a bearing, and a ring for high-speed twisting. Available for vane pump blades, various bobbins and guides. These parts may be entirely composed only of the glassy carbon composite material of the present invention,
Alternatively, only the sliding contact portion with a mating material such as a recording medium may be made of the glassy carbon composite material of the present invention.

Furthermore, since the glassy carbon composite material of the present invention is excellent in strength, it can be used for fuel cell separators, machine parts, various value jigs and the like.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The following example is merely an example and does not limit the technical scope of the present invention. Further, "parts" in the examples all mean "parts by weight".

(Comparative Example 1) Furfuryl alcohol 500 parts and 92% paraformaldehyde 480 were stirred and dissolved at 80 ° C, and a mixed liquid of phenol 520 parts, sodium hydroxide 8.8 parts and water 45 was added dropwise under stirring. After completion of dropping, the mixture was reacted at 80 ° C. for 3 hours. This is followed by 80 parts phenol, 8.8 parts sodium hydroxide and 4 parts water.
A mixed solution of 5 parts was further added, and the mixture was reacted at 80 ° C. for 4.5 hours. After cooling to 30 ° C., it was neutralized with 70% paratoluenesulfonic acid. The neutralized product was dehydrated under reduced pressure to remove 150 parts of water, and 500 parts of furfuryl alcohol was added. The viscosity of the obtained resin was 680 cps at 25 ° C. The amount of water that this resin can contain was measured and found to be 38%.

This thermosetting resin initial condensate has a β-type silicon carbide whisker having a diameter of 0.05 to 1.5 μm, a length of 20 to 200 μm and a specific gravity of 3.18 (silicon carbide whisker SCW manufactured by Tateho Chemical Industry Co., Ltd.).
Was added at a ratio of 2% by weight and 5% by weight, and dispersed and mixed by a sand mill. The viscosity of the resulting mixture was 25 ° C., 700 cps with 2% by weight of whiskers and 800 cps with 5% by weight. This mixture was poured into a strip-shaped mold having a thickness of 5 mm and degassed under reduced pressure. Then, at 50-60 ° C for 3 hours,
It was further heated at 900 ° C. for 5 days. The strip-shaped material obtained by this is put into a tubular furnace, and 2-5 hourly in a nitrogen stream.
It was heated to 1200 ° C. at a temperature rising rate of ° C., held at this temperature for 2 hours, and then cooled. When the obtained sample was measured by X-ray diffraction, it was a complex of β-type silicon carbide and glassy carbon.

(Example 1) To the thermosetting resin obtained in Comparative Example 1, β-type silicon carbide whiskers were added at a ratio of 2% by weight and 5% by weight. further,
As a water-soluble surfactant, polyethylene oxide (molecular weight: 600 to 1.1 million) was added at a ratio of 0.25% by weight, and dispersed and mixed by a sand mill. The viscosity of the obtained mixture at 25 ° C. was 3200 cps when 2% by weight of whiskers were added and 3600 cps when 5% by weight was added. After this, Comparative Example 1
This material was cured and calcined at 1200 ° C.

(Example 2) To the thermosetting resin obtained in Comparative Example 1, β-type silicon carbide whiskers were added in a proportion of 2% by weight and 5% by weight. further,
As a water-soluble surfactant, oxyethylene oxypropylene block polymer (molecular weight 10800, EO mole number 8550)
Was added at a ratio of 1.0% by weight and dispersed and mixed by a sand mill. The viscosity of the resulting mixture at 25 ° C was 2500 cps with 2% by weight of whiskers and 2 with 5% by weight of whiskers.
It was 800 cps. Then, as in Comparative Example 1, the material was cured and then baked at 1200 ° C.

(Example 3) To the thermosetting resin obtained in Comparative Example 1, β-type silicon carbide whiskers were added at a ratio of 2% by weight and 5% by weight. further,
As a water-soluble surfactant, polyoxyethylene sorbitan fatty acid ester (HLB16.7) was added at a ratio of 1.0% by weight, and dispersed and mixed by a sand mill. The viscosity of this mixture at 25 ° C is 2400 cp when 2% by weight of whisker is added.
s, 5% by weight was 2600 cps. Then, as in Comparative Example 1, the material was cured and then baked at 1200 ° C.

(Example 4) To the thermosetting resin obtained in Comparative Example 1, β-type silicon carbide whiskers were added at a ratio of 2% by weight and 5% by weight. further,
As a water-soluble surfactant, polyvinylpyrrolidone (MW4
0000) was added at a ratio of 1.0% by weight, and dispersed and mixed by a sand mill. The viscosity of the obtained mixture at 25 ° C. was 2500 cps when 2% by weight of whiskers were added and 2700 cps when 5% by weight of whiskers were added. Then, as in Comparative Example 1, the material was cured and then baked at 1200 ° C.

Comparative Example 2 To 100 parts of a mixture of spherical semi-cured phenol resin powder (Bellpearl manufactured by Kanebo Co., Ltd.) and novolac resin powder, 2 parts by weight and 5 parts by weight of the β-type silicon carbide whisker used in Comparative Example 1 were mixed. Then, it was heat-molded by a heat press machine to obtain a strip-shaped composite cured resin. The composite cured resin is heated to 1200 ° C. at a heating rate of 2 to 5 ° C./hour in a nitrogen stream,
It was kept at this temperature for 2 hours and then cooled.

(Test Example) Regarding the glassy carbon composite materials obtained in the above Examples 1 to 4 and Comparative Examples 1 and 2, whisker dispersibility in glassy carbon, bending strength, Weibull coefficient, friction coefficient of material and wear. The quantity was tested.

(i) Dispersibility, bending strength and Weibull coefficient To investigate the dispersibility of whiskers in glassy carbon,
Polishing the sample, observing with a microscope and observing the distribution of Si atoms (contained in silicon carbide or silicon nitride whiskers) by X-ray microanalyzer (XMA),
The surface property was investigated.

Furthermore, regarding bending strength and Weibull coefficient, JIS
It was measured by the method of K7203.

(ii) Coefficient of friction Fig. 1 shows the shape of the test piece used to measure the coefficient of friction.
For these test pieces, the samples obtained in the above Examples 1 to 4 and Comparative Examples 1 and 2 were cut into a rectangular parallelepiped having a length a of 4.0 mm, a width b of 6.0 mm, and a height h of 3.0 mm, and sliding. The surface A was gradually polished from fine to fine, and finally mirror-finished with emery paper # 15000. Further, the ridge portion surrounding the sliding contact surface A of this rectangular parallelepiped is chamfered with a fixed number of emery paper, and then gradually increased to a radius of 0.2 to 0.3 mm using high number emery paper.
A test piece for measuring the coefficient of friction was provided by rounding off.

Using these test pieces, the so-called "pin disk method"
The friction coefficient was measured by. That is, a test piece for measuring the friction coefficient was attached to a gimbal spring used in a floppy disk drive, and a load of about 20 g was applied from the test piece to the floppy disk attached to a spindle and a rotating plate that rotate at an arbitrary speed. And frictionally slid it. At this time, the frictional force μ was calculated by obtaining the frictional force with a strain gauge attached to the arm of this device.

(iii) Amount of Wear FIG. 2 shows the shape of the test piece used for measuring the amount of wear. These test pieces have a width w of 0 in the lateral direction on the sliding surface A of the sample piece used for measuring the coefficient of friction by a slicing machine.
A groove having a depth d of 5 μm and a depth of several μm was formed. The distance r from the end of this groove is 2.0 mm. Using a precision roughness measuring instrument (HIPOSS ET-10 manufactured by Kosaka Laboratory Ltd.), the sectional curve of the groove was obtained and the groove depth was measured. This test piece was attached to a gimbal spring and attached to the head portion of a floppy disk drive. A load of 20 g was applied to this test piece to cause frictional sliding with the floppy disk, and the head was moved one track per rotation of the floppy disk to wear the test piece.

The wear depth was measured by measuring the groove depth of the test piece over time.

The floppy disk is a Co-Cr sputter disk,
Regarding the amount of wear, the depth of wear after 100 hours was measured.

(Test Results) Tables show the test results of the glassy carbon composite materials containing 5% by weight of whiskers in Examples 1 to 4 and Comparative Examples 1 and 2.

As shown in the table, by mixing the whiskers in the liquid thermosetting resin, the surface properties are improved and the Weibull coefficient is increased. In particular, by adding a water-soluble surfactant, a large strength and Weibull coefficient can be obtained, and the amount of wear is also reduced.

[Effects of the Invention] The method for producing the glassy carbon composite material of the present invention comprises the use of a liquid thermosetting resin and a water-soluble surfactant,
Whiskers can be uniformly dispersed in glassy carbon.

The dispersibility of whiskers in glassy carbon affects flexural strength and Weibull modulus. Bending strength increases with more uniform distribution. Further, the Weibull coefficient shows the variation of the fracture probability. The larger this coefficient is, the smaller the variation of the maximum value of the non-destructive stress of the material is. That is, the better the dispersibility is, the more the Weibull coefficient is increased. Therefore, by increasing the dispersibility, the Weibull coefficient is increased, and the reliability in breaking the material can be increased.

Further, by uniformly dispersing the whiskers, it is possible to improve the wear property of the glassy carbon and reduce the wear amount.

The glassy carbon composite material produced by the present invention,
It is a material with excellent wear resistance, a small wear coefficient, and precision processing. It is also excellent in strength.

When a sliding contact part is manufactured using this glassy carbon composite material, the lubricity can be maintained for a long time without using a lubricant between the mating material and the surface of the mating material is damaged. In addition, the excellent effect of less wear of the material itself can be obtained. In addition, since the glassy carbon as the main component has conductivity, static electricity is not generated, and dust is less likely to adhere to the mating material and its contacting portion.

Further, the glassy carbon composite material produced according to the present invention can be used for fuel separators, machine parts, various jigs, etc. by utilizing its strength.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape of a test piece used for measuring a friction coefficient. FIG. 2 is a diagram showing the shape of a test piece used for measuring the amount of wear.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuyuki Kishine 2990 2990 Ishii-cho, Utsunomiya City, Tochigi Prefecture (56) References JP 62-108768 (JP, A) JP 58-194777 (JP, A) JP-A-60-145952 (JP, A) JP-A-59-169915 (JP, A)

Claims (1)

[Claims] 1. A liquid thermosetting resin curing precursor is mixed with one or more whiskers selected from silicon carbide whiskers, silicon nitride whiskers, and graphite whiskers, and the resin is cured, and then 1000 wt% in an inert atmosphere. In the method for producing a glassy carbon composite material which is carbonized and baked at a temperature of ℃ or higher, at least one water-soluble surfactant selected from the group consisting of a nonionic surfactant and polyvinylpyrrolidrin is added when whiskers are mixed. A method for producing a glassy carbon composite material, comprising: