JPH0159994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an impermeable hollow carbon molded body.

Hollow carbon molded bodies with multiple through holes facing each other are mainly used for applications such as block heat exchangers due to carbon's excellent properties such as heat resistance, corrosion resistance, and thermal conductivity. . A block type heat exchanger is a main parallelepiped or rectangular parallelepiped impermeable graphite block with a large number of through holes provided at every other stage so that the fluid to be heat exchanged mainly flows crosswise. It is known for its great value in places where installation space is limited, as it can exchange the same amount of heat with approximately 1/2 to 1/3 the volume of a conventional container.

Conventional manufacturing methods for this block type heat exchanger include drilling holes in an impermeable graphite block, or cutting grooves on the surface of an impermeable graphite block and then bonding them together. Alternatively, a mixture of carbon powder and thermosetting resin binder is filled into a mold together with a metal plate or rod with a limited coefficient of thermal expansion (18x10 ^-6 [1/℃] or more). There is a method such as hot-press molding, hardening of the binder, cooling, and drawing out a metal plate or rod (Japanese Patent Application Laid-open No. 148726/1983).

However, with methods using conventional processing machines, it is difficult to obtain hollow carbon molded bodies with through holes with excellent dimensional accuracy, and it also requires a large amount of man-hours, such as chips being emitted during cutting and tool wear and tear. It is fraught with many problems such as. Special publication 1978-
Although the method of drawing out a metal plate or rod in No. 148726 can obtain through holes with excellent dimensional accuracy, it does not include a carbonization firing process after hardening the resin by heat treatment, so it has poor heat resistance, corrosion resistance, and thermal conductivity. Its use temperature is severely restricted.

By the way, general carbon materials are permeable to fluids because they retain a large number of fine pores that are generated when the binder is carbonized during the firing process.
Therefore, when manufacturing an impermeable graphite block, the artificial graphite block is impregnated with a thermosetting synthetic resin or pitch under pressure, and then heat treated to harden the resin to make it impermeable. Alternatively, there is a method in which a synthetic resin or pitch is impregnated under pressure and then fired again, and this operation is repeated until the desired density is reached. However, in the former case, although it depends on the type of synthetic resin to be impregnated, the heat resistance and corrosion resistance are generally inferior, and the temperature of use is also limited. In the latter case, although it has excellent heat resistance and corrosion resistance, it requires a large number of man-hours and is disadvantageous in terms of cost.

In view of the above-mentioned drawbacks, the inventors of the present application have conducted intensive research and have placed a pipe-shaped molded body made of carbon powder and a thermosetting resin binder that exhibits a high residual yield after firing in a mold, and A liquid composition consisting of a liquid pitch showing carbon residue after firing or a thermosetting resin binder is filled into the gap of a pipe-shaped molded body placed in a mold, and after hardening, it is placed in an inert gas atmosphere. Through carbonization treatment, it has through holes with excellent dimensional accuracy and is heat resistant.
The idea was to obtain a high-strength impermeable hollow carbon molded body that has excellent corrosion resistance, thermal conductivity, and impermeability, and does not require any secondary processing after carbonization firing.

By using the method of the present invention, it has become possible to form through holes using a simpler method than in the past. Furthermore, it is worth noting that conventional methods can only produce straight through holes in any case, but the pipe-shaped molded product can be molded into a curved or spiral shape in a green state where it can be easily deformed. As a result, it has become possible to produce a hollow carbon molded body having curved or spiral through holes, which could not be obtained by conventional methods.

In the present invention, the term carbon includes carbonaceous and graphitic substances. In addition, the state in which carbon powder and thermosetting resin are mixed and kneaded and then molded into an arbitrary shape is called a green state, and the carbon precursor state is a state in which a green state molded product is used with a carbonization accelerating catalyst, a crosslinking agent, or a polymer. Methods such as adding an initiator, oxidation treatment, heating crosslinking at 50 to 500℃ in an atmosphere such as air, or crosslinking and curing by irradiating with ultraviolet rays, electron beams, or other radiation, etc. Therefore, it refers to the state that has been treated to make it insoluble and infusible.

The method for manufacturing the impermeable hollow carbon molded body of the present invention will be specifically explained below.

First, if necessary, a curing agent is added to a mixture of one or more carbon powders and a thermosetting resin that shows a high residual yield after firing.
Mix evenly with a mixer such as a Henschel mixer,
A kneaded material that has become semi-molten through polymerization using a kneader that can apply a high shearing force such as a pressure kneader, co-kneader, two-roll, or three-roll kneader, and heating operation as necessary. By molding into a pipe shape using an extrusion molding machine, a pipe-shaped molded product in a green state that can be fired in an inert atmosphere to obtain a carbon pipe is obtained. This pipe-shaped molded body is molded in an easily deformable green state into a rod shape as shown in FIG. 1, a curved shape as shown in FIG. 2, or a spiral shape as shown in FIG. 3. By subjecting this green-state molded body to a carbon precursor treatment, a molded body in a carbon precursor state can be obtained. The obtained rod-shaped, curved or spiral pipe-shaped molded product in a green state or a carbon precursor state is cut into an appropriate size that can be accommodated in a mold.

The carbon powder to be used is selected from one or more of natural graphite, artificial graphite, carbon black, coke powder, etc., and the total amount of the powdered carbon powder with an average particle size of 2 mm or less, preferably 1 mm or less is added to the mixture. It is added in an amount of 10 to 90% by weight, preferably 20 to 80% by weight. Further, as the thermosetting resin showing a high carbon residue yield after firing to be used as a binder, one or more of phenol resin, furan resin, epoxy resin, etc. is selected.

In addition, the most suitable weight of carbon powder and binder to make the green pipe-shaped molded product obtained after extrusion molding into a curved or spiral shape is determined by the type of carbon powder and binder selected. It varies depending on the

Next, a liquid composition consisting of carbon powder to be filled into the mold, liquid pitch showing carbon residue after firing, a thermosetting resin binder, etc. is prepared. This is a mixture of one or more types of carbon powder and a mixture of liquid pitch that shows carbon residue after firing, or a thermosetting resin binder, etc., and a hardening agent is added as necessary, and a Henschel mixer is used. ,
It is obtained by uniformly mixing at room temperature with a mixer such as a water mixer or a pony mixer.

The carbon powder used is, for example, one or more selected from natural graphite, artificial graphite, carbon black, and coke powder, and has an average particle diameter of 2 mm or less.
Preferably, powdered carbon powder of 1 mm or less is added in an amount of 10 to 30% by weight based on the total amount of the blend. Further, as the liquid pitch used as the binder, petroleum asphalt, coal tar pitch, naphtha cracked pitch, petroleum asphalt-coal tar pitch, etc. are used. As the thermosetting resin, phenol resin, furan resin, epoxy resin, etc. are used. One or more of these liquid pitches, thermosetting resins, etc. are selected.

Further, the viscosity of the liquid composition when filling into the mold is set to 5000 cp or less, preferably 1000 cp or less, in view of problems such as its fluidity, filling property, and inclusion of air bubbles. Further, if necessary, a method of lowering the viscosity by heating the liquid composition to a temperature below the resin curing start temperature may be adopted.

The obtained liquid composition is vacuum defoamed using a vacuum defoaming device, if necessary. This is done to remove air bubbles remaining in the liquid composition, which cause thermal expansion during carbonization and firing, which causes spalling and internal cracks in the fired product. be.

Next, the previously obtained rod-shaped, curved or spiral pipe molded body in the green state or carbon precursor state is placed in a mold as shown in FIG. 4, FIG. 5, or FIG. 6. , the gap in the pipe is filled with the obtained liquid composition. This green hollow molded body is subjected to carbon precursor treatment to make it insoluble and infusible, and then heated to 800°C or higher, preferably 1000°C or higher in an inert gas atmosphere to perform carbonization treatment. . After cooling, an impermeable hollow carbon molded body is obtained.

Examples will be described below, but the present invention is not limited to these examples.

Example 1 Furan resin initial condensate (Hitafuran VF302 manufactured by Hitachi Chemical) 70wt% scaly graphite powder (CSP manufactured by Nippon Graphite, average particle size 7μ)
Materials containing 30 wt% or more were uniformly dispersed using a Henschel mixer. Then roll the mixture at a surface temperature of 70
After thorough bank kneading by passing through two mixing rolls kept at ~80°C, the roll interval was set to zero and the mixture was collected in the form of a film. This recovered film-like composition was extruded into a pipe shape using a pipe-forming die using a plunger extruder at a die temperature of 80°C, and then cut to form a pipe with an outer diameter of 13 mm.
We prepared 25 pieces with the dimensions of φ, inner diameter 9mmφ, and length 65mm. These pipe shapes are shown in Figure 4.
In a mold of 65 mm x 65 mm x 65 mm, 5 tubes were placed in each stage, and a total of 5 stages were arranged so that each stage had a cross-counter flow. Next, the same materials as above were mixed using a Henschel mixer to obtain a liquid composition, and after vacuum defoaming, the liquid composition was filled into the spaces between the pipe-shaped objects in the mold. This hollow molded body was heated to 150℃ in air for 10 days.
After pre-oxidation by treating at 180℃ for 10 hours,
Raise the temperature at a heating rate of 30℃/h in a nitrogen atmosphere.
After holding at 1050℃ for 3 hours, it is naturally cooled and the dimensions are
An impermeable hollow carbon molded body having dimensions of 60 mm x 60 mm x 60 mm and 25 through holes with a hole diameter of 8 mm was obtained.

The obtained impermeable hollow carbon molded body has a compressive strength of 3 Kg/mm ² and an air permeability of 5.0×10 ^-10 cm ² /sec thermal conductivity.
0.03 cal/cm. It had excellent properties of s.℃.

Example 2 A green pipe-shaped molded product obtained using the same raw materials and the same conditions as in Example 1 was molded into two types of curved pipe-shaped products with radiuses of 26 mm and R13 mm from the center of the pipe as shown in Fig. 2. Five bottles of each were prepared.
Next, as shown in Fig. 5, in a mold of 65 mm x 65 mm x 65 mm, all 5 of the previously obtained two types of curved pipe shapes were placed in a cross-circuit manner, one at each stage.
Arranged in tiers.

The following is 60mmx60mmx60mm under the same conditions as Example 1.
An impermeable hollow carbon molded body having a pore diameter of 8 mm, 20 through holes, and curved through holes was obtained.

Example 3 A green pipe-shaped molded product obtained using the same raw materials and under the same conditions as in Example 1 was wound around a ceramic pipe (diameter 50.0 mmφ) having a smooth surface. This was done in air at 150℃ for 10 hours at 180℃.
After being preoxidized by treatment at 10° C. for 10 hours, the mold was released from the ceramic pipe (support) to obtain a spiral pipe-shaped product having an outer diameter of 13 mmφ, an inner diameter of 9 mmφ, and a length of 80 mm as shown in FIG. 3. This is 80mmx80 as shown in Figure 6.
It was placed in a mold of mmx80mm.

The following is 74mmx74mmx74mm under the same conditions as Example 1.
An impermeable hollow carbon molded body having a pore diameter of 8 mm, one through hole, and a spiral through hole was obtained.

[Brief explanation of drawings]

FIG. 1 shows a pipe-shaped molded product extruded into a pipe shape. 2 and 3 show curved and spiral pipe-shaped molded products obtained by molding the rod-shaped pipe-shaped molded product shown in FIG. 1 into a curved shape and a spiral shape, respectively, in a green state. Figures 4, 5 and 6
The figure is a schematic diagram in which a rod-shaped pipe-shaped molded product, a curved pipe-shaped molded product, and a spiral pipe-shaped molded product are placed in a mold, and the gap between them is filled with a liquid composition. Figures 7, 8, and 9 show a hollow carbon molded body with linear through-holes, a hollow carbon molded body with curved through-holes, and a spiral through-hole obtained after carbonization firing, respectively. FIG.

Claims (1)

[Scope of Claims] 1 A composite composition of carbon powder and a thermosetting resin binder that exhibits a high carbon residue yield after firing is mixed and kneaded and then molded into a pipe shape. After being placed in a mold in a carbon precursor state and filled with a liquid composition consisting of carbon powder and a liquid pitch or thermosetting resin binder that exhibits a high carbon residue yield after firing into the mold and hardening, A method for producing an impermeable hollow carbon molded body, characterized by performing carbonization treatment in an inert atmosphere. 2. The impermeable hollow carbon molded product according to claim 1, wherein the pipe-shaped molded product is a curved pipe-shaped molded product that is molded into a curved shape in a green state where it can be easily deformed after being molded into a pipe shape. How the body is manufactured. 3. The pipe-shaped molded product is formed by forming it into a pipe shape and then spirally winding it around a round bar or pipe having a smooth surface of a desired diameter and dimensions as a support in an easily deformable green state. A method for producing an impermeable hollow carbon molded body according to claim 1, which is a spiral pipe-shaped molded body.