JPH0234902B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a hard carbon precision molded body. Specifically, the present invention relates to a method for easily and quickly manufacturing a hard carbonaceous precision molded body having a dense, homogeneous, high mechanical strength, precision, and complex shape, essentially without the need for secondary processing.

Conventionally, carbon molded products are generally made by using petroleum coke, pitch coke, graphite, carbon black, etc. as raw materials as aggregates, using a viscous material such as petroleum-based or coal-based pitch as a binder, and heating and kneading these. It is manufactured by molding and firing or graphitizing under heat.

Therefore, in order to obtain a dense and highly accurate carbon molded product, the raw material aggregate is pulverized to 10 microns or less, the above-mentioned binder is added to this, and the above procedure is followed, but if the aggregate is pulverized, As you can see, uniform dispersion and kneading with the binder becomes difficult. In particular, when carbon black has an aggregate particle size of several microns or less and has a structure in which the particles aggregate secondary to each other, uniform dispersion with the binder is nearly impossible, and a large amount of solvent must be used or Not only is it extremely complicated and economically undesirable, as it does not require a spray drying process, but
A large amount of vapor from volatile tar components and solvents is generated, which contaminates the working environment and is unfavorable in terms of occupational health.

In addition, in order to obtain high density and high strength in terms of quality, it is necessary to
After firing at around 1000°C, the material is impregnated under pressure with a viscous component such as a synthetic resin solution, tar, or soft pitch, and fired again. This operation is repeated until the target density is reached.

In order to improve this situation, petroleum pitch, coal tar pitch, etc. are heat treated at a temperature of about 200 to 500 degrees Celsius to remove low volatile matter, and then pulverized to form a powder with an average particle size of about 100 μm. A method was proposed in which the material is heated and pressed and then fired without adding a binder.

However, even with this method, delicate temperature and time management is required during the heat treatment process of pituti, which not only causes great difficulty in the subsequent crushing work, but also causes the crushed particles to heat-fuse again. There were drawbacks such as clumping and significantly deteriorating grinding efficiency.

Furthermore, although carbon yield and stability against deformation improve when the heat treatment temperature becomes high, the thermoplasticity of the material is poor and it does not flow, making it extremely difficult to form complex and precise shapes using molds, etc. On the other hand, while pressure is required, the powder has poor cohesive power and the resulting compact does not exhibit its strength, making it inconvenient to handle.On the other hand, if the heat treatment temperature is low, residual volatile components tend to form into agglomerates during re-grinding, resulting in a failure in the fired product. The structure became coarse and the deformation was large, making it difficult to obtain precision molded products.

Recently, Mezzoface. New carbon materials have been developed using microbeads or mesophase-coated semi-coke, which are directly molded and then fired. In addition to being expensive and difficult to shape, there are no easy processing methods like plastics or general metal materials, so they are usually produced in large blocks, and in order to make the final product, cutting is required depending on the purpose. Various types of processing such as drilling, thread cutting, etc. must be performed secondary processing using processing machines used for metal materials, and in this case, carbon blocks have poor cutting properties and the grinding mechanism is mainly used for crushing Chips scatter, reducing accuracy and increasing tool wear. Furthermore, stress acts on the surface of the workpiece, creating countless scratches, which causes a significant decrease in the mechanical strength of carbon products, which are inherently brittle. However, in the case of general carbon materials (soft carbon), it was possible to use the above secondary processing method, but in the case of hard carbon materials (hard carbon), the shore hardness reached 100 to 120, making it hard and brittle. Therefore, secondary precision machining was completely difficult.

The purpose of the present invention is to easily and quickly produce a hard carbonaceous precision molding having a precise and complex shape, which is dense and homogeneous without cavities or cracks, has strong mechanical strength, and essentially requires no secondary processing. The purpose is to provide a method.

In order to achieve this objective, the inventors of the present application have considered the above-mentioned circumstances to obtain a secondary carbon material that has excellent formability at room temperature and does not require difficult pre-treatment during carbonization, maintains its shape precisely in the final stage, and We are conducting research to obtain a molding composition that can produce high-density, high-strength carbon molded products that do not require processing. A material obtained by applying a high degree of mechanical energy to a homogeneously dispersed mixture of binders has a property that differs from the properties exhibited by the initial simple material, and has a high degree of moldability at room temperature and becomes infusible by simple air oxidation. Based on this knowledge, we realized that the fired product is homogeneous, has high mechanical strength, and has the desired dimensional accuracy.
Further, as a result of intensive research, it was found that the fine carbon powder of the present invention was combined with monomers, prepolymers, or low polymers of high molecular compounds, which are substances that exhibit a high carbon residue yield after firing and are relatively easily thermally polymerizable, as a binder. A mixture of one or more of these is uniformly dispersed, and mechanical energy is applied to induce a mechanochemical phenomenon to uniformly physicochemically distribute the binder onto the surface of the primary particles of the fine powder. A hard carbonaceous precision molded article that essentially does not require secondary processing, characterized by obtaining a strongly bonded molding composition, shaping the composition, subjecting it to infusibility treatment, and then firing it. He came up with the invention of a manufacturing method.

That is, one or more of monomers, prepolymers, and low polymers of polymer compounds that can be thermally polycondensed relatively easily and that exhibit a high carbonaceous residue yield after firing are selected as the binder. To this, fine carbon particles (graphite, carbon black, coke powder, etc. with a particle size of 10 μm or less) are added as aggregates, and a high degree of mechanical energy is applied in the coexistence of fine carbon powder (adding a polymerization catalyst as necessary). Distortion, disturbance and amorphous crystal lattice caused by structural destruction of aggregate powder, generation of lattice defects and active points on the surface,
Using the generation of local high temperature and high pressure conditions, the effect of exoelectrons, and the generation of fresh cross sections with high potential fields, the above-mentioned binder material is made into finely dispersed particles that are highly bonded physicochemically by mechanochemical phenomena. A carbon gel based on aggregate powder is obtained and used as a composition for manufacturing carbon products.

In the molding composition according to the present invention, the binder resin is uniformly dispersed and coated even in the primary particle state of the aggregate, and exhibits thermoplasticity or thermosetting property depending on the resin used. Any suitable conventional molding means may be used.

In addition, during carbonization, the entire composition is fixed by the aggregate and exhibits a designed uniform shrinkage rate.
It has become possible to obtain a thick, complex, and precise hard carbon molded body with high density and high strength without extensive secondary processing, which was previously unobtainable.

In particular, the molding composition pellets of the present invention, in which a thermoplastic resin monomer or low polymer is selected as a binder component and composited with ultrafine graphite (2 μm or less), are prepared by using a solvent such as tetrahydrofuran (THF). It shows extremely good colloidal dispersibility, the solution has a black ink-like appearance, and it shows dispersion stability that does not easily precipitate even when left standing). It has the characteristic of being able to employ simple and quick molding methods similar to those used in the normal plastics industry, such as the conventional hollow extrusion method, injection molding method, and blow molding method.
During carbonization, carbon products are stabilized by the action of fine aggregate and maintain their original shape to a high degree without being significantly deformed even by the usual method of firing in an inert air stream by simply performing preliminary oxidation in air. is obtained.

In addition, the molding composition powder of the present invention, in which a thermosetting resin prepolymer is selected as a binder and carbon black (20 μm) is composited with this as an aggregate, can be compressed by compression molding using a conventional mold or by hot pressing. By shaping it by molding or extrusion, post-curing if necessary, and firing it in an inert air stream, it becomes extremely homogeneous and isotropic, with a glass-like fracture surface, high strength and hard material with low porosity. A carbon molded article is obtained. Furthermore, as a binder, a thermoplastic resin component and a thermosetting resin component are selected to form a mixed resin,
By compounding this with fine graphite and subjecting it to a mechanochemical reaction, it can be made into a composition for extrusion molding or vacuum molding.

The device used in the present invention basically applies mechanical energy to fine powder such as graphite, carbon black, or coke powder, and grinds it to induce radical generation by breaking bonds on the surface. Any model that can increase the number of unpaired electrons may be used, such as a mixing roll, Banbury mixer, vibrating ball mill, rotary ball mill, ring roll mill, attrition mill, etc.
A grinder or the like may be used, but for efficiency, it is preferable to use a mixing roll, a Banbury mixer, and a rotary ball mill that exert a high degree of shearing force.

Types of thermoplastic monomers or low molecular weight polymers suitable as binders for making the compositions of the invention include acrolein, acrylonitrile, styrene, benzaldehyde, vinyl chloride, which are susceptible to thermal or friction polymer formation; Although methyl methacrylate is available, vinyl chloride and acrylonitrile are suitable due to moldability and carbonization process conditions.

In addition, as monomers or prepolymers for thermosetting resins, we handle divinylbenzene, methyl vinyl ketone, phenol resin, furan resin initial condensate, bismaleimide triazine resin, diallyl phthalate, diphenyl oxide, epoxy novolac, etc. Furan resin initial condensates, phenolic resins, bismaleimide triazine resins, and diallyl phthalate are suitable from the viewpoint of ease and moldability.

Further, as the binder that can be mixed with these resin components, lignin, violanthrone, naphtha cracked pitch, and vinyl chloride pitch, which exhibit a high carbon residue yield after firing, are preferably selected and used depending on the purpose.

Next, the present invention will be specifically explained using examples.

Example 1 Polyvinyl chloride (polymerization degree 700) (Vinicron #4000. Manufactured by Mitsui Toatsu Co., Ltd.) 20wt% Furan resin initial condensate (Hitafuran VF-302. Manufactured by Hitachi Chemical Co., Ltd.) 50wt% Graphite (average particle size 2.0 μm) 30wt % or more were uniformly dispersed by stirring at high speed with a Henschel mixer, and then a high shearing force was applied using a pressurized kneader (Banbury) keeping the temperature inside the tank at 50℃, and the binder resin component was dispersed. Knead with graphite powder until homogeneously combined by mechanochemical phenomenon.
As the reaction progresses, the binder resin component polymerizes and thickens. When the whole material becomes a mochi-like (hard putty-like), the material is thoroughly kneaded through two mixing rolls with the roll surface temperature kept below 70℃, and the roll gap is reduced to zero to form a film. to recover.

The film-like composition loses its colloidal dispersibility in THF, and even if it is left in a solvent, the dispersibility is not restored, leaving insoluble components behind and taking on a carbon gel-like appearance. Further, this composition is still in an uncured state and is rich in thermoplasticity.

This recovered film-like composition is pelletized using a pelletizer, and then the outer diameter is
A continuous pipe with an inner diameter of 10m/m and an inner diameter of 8m/m was molded.

The molded body is pre-oxidized by treating it in air at 150℃ for 10 hours and 200℃ for 10 hours, then gradually raising the temperature in a nitrogen gas phase, holding it at 1000℃ for 3 hours, and then cooling it naturally to produce the product. I got it.

The obtained carbonaceous pipe has an outer diameter of 8 m/m〓 and an inner diameter of
The dimensions of 6m/m〓 were maintained with high precision, and the surface was hard and extremely smooth. The bending strength of the pipe is
The weight was 2ton/cm ² and the bulk density was 1.5g/cm ³ .

Example 2 Furan resin initial condensate (Hitafuran VF-302 manufactured by Hitachi Chemical Co., Ltd.) 60 wt% Carbon black (20 μm) (Diablack manufactured by Mitsubishi Chemical Co., Ltd.) 40 wt% or more of the materials were stirred at high speed with a Henschel mixer to uniformly disperse them. After that, it is sufficiently bank-kneaded using two mixing rolls whose surface temperature is kept below 50℃, and then passed through the two rolls with zero gap while keeping the surface temperature below 100℃, and this process is repeated several times to form a film. Let's do it. At this stage, the condensation of the furan resin progresses, and at the same time, carbon gelation, in which the furan resin homogeneously reacts with the new active cross section based on the structure destruction of carbon black, progresses, so the roll is cooled and hardened when the viscosity has risen to an appropriate level. Collect as fragments.

Next, the recovered composition fragments are ground in a ceramic ball mill. A molding composition powder having an average particle size of 10 μm is obtained by grinding for 40 hours.

This fine powder for molding is already a good solvent.
Although it does not disperse in THF, it still has thermoplasticity and caking, so the mold temperature is kept at 150℃ and 150Kg/cm ²
A hardened molded product was obtained by powder compression molding.

This molded product was treated in air at 180℃ for 20 hours,
After post-curing, the temperature was raised to 1000°C in a nitrogen gas phase, held for 3 hours, and then allowed to cool naturally to obtain a product.

The obtained carbon molded product has a diameter of 50m/m and a thickness of
It was a 20m/m gear, and the molded product had no distortion or cracks, and the shape of the mold was traced with high precision. Although there is about 20% shrinkage throughout, it is uniform over all parts, which has the advantage of making it easier to design the final object and of increasing the density during firing.

The surface condition was very hard and showed a glass-like wave cross section.

The bulk specific gravity was 1.64gr/cm ³ and the compressive strength was 2Kg/mm ² . Bitkers hardness 200Kg/mm ^2Example 3 Naphtha decomposition pitch 50wt% Diallyl phthalate prepolymer 20wt% Diallyl phthalate monomer 10wt% Graphite (1μm) 20wt% Benzoyl peroxide (external 1%) The above materials were prepared in the same manner as in Example 1. After dispersion using a Henschel mixer, shearing force is applied using a pressure kneader that maintains the tank internal temperature below 100°C, and when the entire product polymerizes and thickens into a hard putty, the roll surface temperature is lowered to 100°C. The film is passed through two mixing rolls kept at a temperature of 0.degree.

Next, this recovered material is ground in a ceramic ball mill. A molding composition powder with an average particle size of 20 μm is obtained by grinding for 40 hours. This fine powder still has thermoplasticity and exhibits sufficient caking action, but once heated to 150°C or higher, it immediately hardens and becomes an insoluble and infusible substance.

This molding powder was press-molded using a die in a hydraulic plunger type extruder to form a continuous round bar with a diameter of 3.3 m/m. (Temperature 130℃,
The molded product was treated at 180°C for 20 hours and then fired at 1000°C in a nitrogen gas phase to obtain a hard carbonaceous round bar. The diameter of the round bar was 3.0 m/m, and the bending strength was 2.5 ton/ ^cm2 .

As described above, the carbon material produced by the method of the present invention was significantly superior in physical properties, especially mechanical strength, compared to conventional commercially available carbon materials.

The surface is extremely smooth and beautiful, maintains high precision with respect to design dimensions, and does not require any secondary machining.
Furthermore, the molding means can be any of the general methods used in the conventional plastics industry.

Claims (1)

[Claims] 1 Fine carbon powder, as a binder, a mixture of one or more monomers, prepolymers, or low polymers of polymer compounds that exhibit a high carbon residue yield after firing and are relatively easily thermally polymerizable. is uniformly dispersed, and a high degree of mechanical energy is applied to induce a mechanochemical phenomenon, whereby the binder is uniformly and firmly physicochemically bonded to the surface of the primary particles of the fine powder. 1. A method for producing a hard carbonaceous precision molded body that essentially does not require secondary processing, the method comprising: obtaining a composition for use, shaping the composition, subjecting it to infusibility treatment, and then firing it.