JPH05208876A - Production of cylindrical porous carbon molded product - Google Patents

Abstract

PURPOSE:To improve the homogeneity of the cylindrical porous carbon molded product by winding a binder-impregnated fiber aggregate on an inner mold used for cylindrical molded products, covering the combination with a bag-like article, compressing the fiber aggregate under vacuum, disposing the compressed fiber aggregate in an outer mold, releasing the compression of the compressed fiber aggregate, thermally curing the fiber aggregate and subsequently calcining the molded fiber aggregate. CONSTITUTION:A felt-like fiber aggregate using carbon fibers is impregnated with a binder solution such as a phenol resin and then dried to produce a binder-impregnated fiber aggregate 2. The fiber aggregate is wound on the outer side of an inner mold 1 used for molding cylindrical molded products in a thickness larger than the distance between the outside of the inner mold 1 and the inside of the outer mold 4. The combination is covered with a bag-like article made from PP, etc., and the inner part of the bag-like article is vacuumized to compress the binder-impregnated fiber aggregate 2, thereby bringing the fiber aggregate tightly into contact with the inner mold 1 to allow the wound fiber aggregate to contract into a thickness smaller than the distance between the molds. Subsequently, the combination is disposed in the outer mold 4, and the vacuum is released to tightly bring the wound fiber aggregate into contact with the outer mold 4. The fiber aggregate is thermally cured and demolded from the inner mold 1 and the outer mold 4. The molded product is calcined at a temperature of >=1000 deg.C under vacuum for the carbonization thereof or graphitized at a temperature of >=2000 deg.C to obtain a cylindrical porous carbon molded product or a cylindrical graphitized molded product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cylindrical porous carbon compact, and more particularly to a method for easily producing a homogeneous compact.

[0002]

2. Description of the Related Art Porous carbon moldings are used in various applications utilizing the characteristics of carbon materials such as chemical stability, heat resistance in an inert atmosphere, and electrical conductivity, such as heat insulating materials for ultrahigh temperatures and electrode materials. ,
It is used for filters.

As a method for producing a porous carbon molded body, there is generally a method in which a fibrous substance is used as a main material, and the fibrous substance is molded with a binder such as a resin and fired to carbonize or graphitize. In this method, organic fibers such as pulp, polyacrylonitrile and polyester, or inorganic fibers such as carbon fibers and graphite fibers are used alone or in combination as the fibrous substance. In the case of using organic fibers, in order to prevent the shrinkage of the material in the firing process, a so-called infusibilizing treatment such as forming an oxide film on the fiber surface is performed, or the carbon fiber does not shrink in the firing process. In many cases, measures such as compounding are taken.
Therefore, in the production of the porous carbon molded body, it can be said that the method using carbon fiber as the main material is the easiest general method.

[0004]

One of the methods for forming a porous carbon molded body into a predetermined shape is to use a mixture of milled or chopped short fibers and a powdery or liquid binder as a molding die. There is a method of filling or pouring into, and removing from the mold after thermosetting. In this method, when the shape of the molded body is complicated, it is difficult to uniformly fill or pour the mixture of the fiber and the resin into the mold, and since the short fiber is used, the molding with a low bulk density is performed. The body is very difficult to manufacture.

Another method is to impregnate a fibrous substance with a binder and compression-mold it. In this method, a low bulk density product is used as the fibrous substance, and if the degree of compression is changed, the bulk density of the molded product can be controlled in a wide range. However, this method can relatively easily manufacture a flat plate, a rectangular parallelepiped, or a convex body that can be manufactured by two pairs of molding dies. However, the tubular molded product becomes more difficult to manufacture as the low bulk density product is used for the fibrous substance. That is, in the molding of the tubular molded body, since it is necessary to wind the prepreg around the inner mold for molding and tighten and fix it with the outer mold for molding, the mold becomes a split mold, but in the process of tightening and fixing. Since the material cannot be compressed uniformly, the density distribution varies, and a good molded product cannot be molded. Therefore, conventionally, for a tubular product, a method may be adopted in which the tubular product is divided into vertical sections, each of which is separately molded, and then bonded by some method, but the mechanical characteristics of the bonded portion are
Non-uniformity of thermal characteristics or electrical characteristics is unavoidable.

[0006]

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have found that after winding a fiber aggregate impregnated with a binder around the inner mold of a mold for a cylindrical molded body. , The whole is covered with a bag, the inside of which is decompressed to compress the fiber assembly, which is placed in an outer mold for molding, and the compression is released, followed by heat curing to obtain a tubular molded body. It was found that a homogeneous tubular carbon compact can be easily obtained by carrying out the process, and completed the present invention.

That is, the present invention relates to the production of a tubular porous carbon molded article in which a tubular molded article is formed by using a fiber aggregate impregnated with a binder and then fired to carbonize or graphitize. After winding a fiber assembly in which a binder is impregnated on the outside of the molding inner die of the tubular molding body, over the gap between the outside of the molding inner die and the inside of the molding outer die,
This is covered with a bag-like material, and then the inside of the bag-like material is decompressed to make the winding wall thickness equal to or less than the gap between the outside of the molding inner die and the inside of the molding outer die. Placed inside, and then the vacuum of the bag-shaped material is released to bring the fiber assembly into close contact with the inner side of the outer mold, and after heat curing in this state, the mold is detached and then fired to remove carbon. The present invention provides a method for producing a cylindrical porous carbon molded body, which is characterized in that the carbonized or graphitized.

The fiber assembly used in the present invention includes carbonaceous fibers such as carbon fibers, graphite fibers, flame resistant fibers and activated carbon fibers, and other inorganic fibers such as silicon carbide fibers, silicon nitride fibers and pitch fibers, aramids and polypropylene. Fibers such as organic fibers such as cellulose, cellulose, and polyacrylonitrile are used. Above all, carbonaceous fibers that do not shrink in the firing step, especially those using carbon fibers are preferable. The raw material and manufacturing method for obtaining these fibers are not limited at all. Specific examples of the shape of these aggregates include mats, needle punched felts, and papers produced by a wet papermaking method. As will be described later, a mat that allows compression (reduction of bulk) of the fiber assembly due to depressurization in the bag and swelling (return of bulk) of the fiber assembly due to release of the decompression in a relatively wide range, The shape of felt or the like is preferable since a wide range of bulk density molded bodies can be easily molded, and felt is particularly preferable because it is easy to handle.

The binder in the present invention may be either organic or inorganic, or a combination thereof, and among them, those which are carbonized at 400 ° C. or higher are preferable, but the yield (residual amount remaining after carbonization by post-treatment is not always required. It does not have to have a high rate of charcoal. Specific examples of these binders include thermosetting resins such as epoxy resin, phenol resin, unsaturated polyester resin, furan resin, and polyimide resin, and rubber-like substances such as silicone, SBR, NBR, and pitches. Phenolic resin is preferable in terms of high residual carbon rate.

The amount of the binder used here is usually 1 to 100 parts of the total of the fiber aggregate and the binder.
Although it is in the range of 90 parts by weight, in order to have good handleability of the material in the molding step and to maintain the strength of the molded body,
70 parts is desirable.

Further, in the fiber assembly impregnated with the binder used in the present invention, various powders such as carbon black and graphite can be added for the purpose of price reduction and improvement of physical properties.

Various methods can be considered for impregnating the fiber assembly with the binder, but any method can be used as long as it does not deviate from the purpose, and the method is not particularly limited. For example, there are a hot melt method of impregnating a fiber assembly with a binder melted by heating, a method of impregnating a binder dispersed or dissolved in a solvent, and then drying the solvent. In either case, handling is improved if the binder is semi-cured by heat treatment to form a prepreg.

The method for molding a tubular molded body using a fiber aggregate impregnated with a binder is as follows.

That is, (1) a fiber aggregate impregnated with a binder is placed on the outer side of the inner mold of the molding die for the tubular molded body, and the gap between the outer side of the inner mold and the inner side of the outer mold (after molding). (Corresponding to the wall thickness of the cylindrical molded body in 1). At this time, the winding wall thickness can be changed depending on the bulk density of the fiber assembly, the impregnation concentration of the binder, and the like. In general, when a material having a low bulk density is used, the winding wall thickness is considerably larger than the gap between the outer side of the inner mold and the inner side of the outer mold (corresponding to the wall thickness of the tubular molded body after molding). It can be bigger,
When the bulk density is relatively high, a winding thickness that is slightly larger than the gap is sufficient. In the actual production of the molded body, the required amount of the binder-impregnated fiber aggregate calculated from the design bulk density of the final tubular molded body is weighed and wound around the inner mold for molding.

(2) The entire molding inner die around which the fiber assembly is wound is covered with a bag-like material, the interior is depressurized, and the fiber assembly is compressed to adhere the fiber assembly to the inner die. Then, the winding wall thickness is set to the gap or less.

(3) While keeping the state as it is, this is placed in the outer mold of the molding die for the tubular molded body, and then the depressurization of the bag-shaped object is released to remove the fiber assembly. Stick it to the mold.

(4) After thermosetting in this state, the inner mold and the outer mold are detached to obtain a molded body. The bag-like material attached to the outside of the molded body does not need to be removed unless there is a problem in the subsequent firing step. Of course, it does not matter if it is removed if necessary.

The cylindrical molded body molding die used in the above-mentioned method of the present invention is a molding die in which a gap between the outside of the molding inner die and the inside of the molding outer die is at least 10 mm on the outside of the molding inner die. .

The bag-like material used in the present invention has a size equal to or larger than the minimum size required to cover the inner mold for molding around which the binder-impregnated fiber aggregate is wound. Further, in order to uniformly compress the binder-impregnated fiber assembly when the inside of the bag is depressurized, a material having sufficient flexibility and having no air permeability is preferable. As such, for example, thermoplastic resin such as polyamide resin, fluororesin, polyester resin, polyolefin resin, polyacetal resin, silicone,
Examples thereof include rubber-like substances such as SBR and NBR. Further, the thickness of the bag-shaped material is preferably thin in order to maintain the dimensional accuracy of the molded product, and is preferably 1 mm or less.

The tubular molded product molded by such a method is then subjected to an inert gas atmosphere of nitrogen, argon or the like,
Alternatively, the desired porous carbon molded body can be obtained by firing in vacuum at a temperature of 1000 ° C. or higher.
Depending on the purpose, it may be graphitized by further firing at a temperature of 2000 ° C. or higher.

The obtained porous carbon molded article is used for various applications utilizing the characteristics of the carbon material such as chemical stability, heat resistance in an inert atmosphere, and conductivity, for example, a heat insulating material for ultrahigh temperature,
Used for electrode materials, filters, etc.

[0022]

EXAMPLES Next, the present invention will be further described with reference to examples. Incidentally,% in the examples is based on weight unless otherwise specified.

Example 1 Pitch-based general-purpose carbon fiber [DONACAR manufactured by Donac Co., Ltd.,
Fiber diameter 13.5 μm, average fiber length 12 cm],
A felt of 500 g / m ² was prepared by needle punching. This felt is made of novolac phenolic resin 60
% Resin solution impregnated and dried to 50% resin content
A prepreg sheet of was obtained. This sheet is 50 cm x 1
50c cut to 9m and coated with a fluorine-based release agent
It was wound around the outside of a FRP molding die (inner die) of mφ × 48 cmφ × 50 cm ^H. (Coil thickness: 19c
m)

Furthermore, this is 50 μ ^T × 120 cm ^W × 250
Cover with a cm ^L polypropylene bag and wrap the bag inside about 4
The pressure was reduced to 00 torr and the prepreg sheet was compression-adhered to the molding die. (Wall thickness when compressed: 7 cm)
This was put inside a FRP molding die (outer die) of 62 cmφ × 60 cmφ × 50 cm ^H , and then the reduced pressure was released. Since the prepreg sheet swelled and adhered to the outer mold for molding, the prepreg sheet was heat-cured at 150 ° C. for 60 minutes, and then the inner mold and the outer mold were pulled out. The obtained molded body is vacuumed to 2000
Bake for 1 hour at ℃, 60cmφ × 50cmφ × 50cm
A homogeneous cylindrical porous graphite compact having ^{H 2} and a bulk density of 0.16 g / cm ³ was obtained.

Comparative Example 1 In the same manner as in Example 1, the FRP mold was wound on the outside (molding inner mold). 60cmφ x 50cm
Place ^H inside the split mold for molding, which is split in two vertically.
The outer mold was used for compression, and the outer mold was used to compress the prepreg to bring the split mold into close contact. At this time, shrinkage wrinkles of the prepreg were generated in the split mold connection portion. Then, it was heat-cured in the same manner as in Example 1 and further fired to obtain a cylindrical porous graphite compact having a bulk density of 0.16 g / cm ³ . When the molded body was divided into pieces and inspected, an abnormally high bulk density portion was found in the vicinity of the connection portion of the split mold, and the measured value was 0.26 g / cm ³ .

Example 2 Pitch-based general-purpose carbon fiber [DONACAR manufactured by DONAC CORPORATION,
Fiber diameter 13.5 μm, average fiber length 12 cm],
A felt of 300 g / m ² was prepared by needle punching. This felt is made of novolac phenolic resin 60
% Resin solution impregnated and dried to 70% resin content
A prepreg sheet of was obtained. This sheet is 10 cm x
Cut to 4.7 m and apply a fluorine-based release agent on the surface 2
It was wound around the outside of a molding die (molding inner die) of 5 cmφ × 10 cm ^H. (Thickness of winding: 4.2 cm)

Furthermore 100μ this ^T × 45cm ^W × 100
Cover with a cm ^L polypropylene bag, and wrap the bag inside about 1
The pressure was reduced to 50 torr and the prepreg sheet was compression-adhered to the molding die. (Wall thickness when compressed: 1.8c
m) This was placed inside a 27 cmφ × φ × 10 cm ^H molding die (outer molding die), and then the reduced pressure was released. Since the prepreg sheet swelled and adhered to the outer mold for molding, 150
After heat-curing under the condition of ° C x 10 minutes, the inner mold and the outer mold were pulled out. The obtained molded body was fired in a vacuum at 1000 ° C. for 1 hour to obtain a homogeneous cylindrical porous carbon molded body having 27 cmφ × 25 cmφ × 10 cm ^H and a bulk density of 0.46 g / cm ³ .

Example 3 Pitch-based general-purpose carbon fiber [DONACAR manufactured by Donac Co., Ltd.,
A fiber having a fiber diameter of 13.5 μm and an average fiber length of 7.7 cm] was used to make a 100 g / m ² sheet by a wet papermaking method using an epoxy resin as a binder. This sheet was impregnated with a 70% methanol solution of novolac phenol resin and dried to obtain a prepreg sheet having a resin content of 50%. This sheet was cut into 30 cm × 21 m, and a fluorine-based release agent was applied on the surface. 25 cmφ × 30 cm ^H
It was wound around the outside of the molding die (inner molding). (Thickness of winding: 7.5 cm)

Furthermore 50μ ^T × 50cm ^W × 150c this
Cover with a polyethylene bag of ^mL , and the inside of the bag is about 400
The pressure was reduced to torr and the prepreg sheet was compression-adhered to the molding die. (Wall thickness when compressed: 2.8c
m) This was put inside a molding die (outer die) of 30 cmφ × 30 cm ^H , and then the reduced pressure was released. 150 ° C x 2 because the prepreg sheet swelled and adhered to the outer mold for molding
After thermosetting under the condition of 0 minutes, the inner mold and the outer mold were pulled out. The obtained molded body was fired in vacuum at 1000 ° C. for 1 hour to obtain a homogeneous cylindrical porous carbon molded body having a size of 30 cmφ × 25 cmφ × 30 cm ^H and a bulk density of 0.13 g / cm ³ .

[0030]

The tubular carbon molded body obtained by the method of the present invention is an integrally molded body having a uniform bulk density and no adhesive portion.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view taken along line AA ′ showing a state in which a binder-impregnated fiber assembly is wound around a molding inner die for a cylindrical molded body.

FIG. 2 is a cross-sectional view taken along the line AA ′ showing a state where a wound inner mold of the fiber assembly is covered with a bag.

FIG. 3 is a cross-sectional view taken along the line AA ′ showing a state immediately after releasing the reduced pressure in the bag-shaped material after the placement in the outer mold for molding.

FIG. 4 is a cross-sectional view taken along the line AA ′ showing a state in which the binder-impregnated fiber assembly is swollen and is in close contact with the outer mold.

[Explanation of symbols]

 1 Cylindrical Molding Inner Mold 2 Binder Impregnated Fiber Aggregate 3 Bag-like Material 4 Cylindrical Molding Outer Mold

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Claims (6)

[Claims] 1. A tubular molded body produced by molding a tubular molded body using a fiber aggregate impregnated with a binder and then carbonizing or graphitizing by firing. A fiber assembly impregnated with a binder on the outside of the molding inner die of the molding die is wound around a gap between the outside of the molding inner die and the inside of the molding outer die, and then covered with a bag-like material, Next, the inside of the bag-like material is decompressed so that the wall thickness of the winding becomes less than or equal to the gap between the outside of the molding inner die and the inside of the molding outer die, and then the bag is placed in the outer molding die, and then the bag It is characterized in that the reduced pressure of the shaped material is released to bring the fiber assembly into close contact with the inner side of the outer mold, and after heat curing in this state, the mold is detached and then fired to carbonize or graphitize. And a method for producing a tubular porous carbon molded body. 2. The method according to claim 1, wherein the fibers of the fiber assembly are carbon fibers. 3. The method according to claim 1, wherein the fiber assembly is a carbon fiber felt. 4. A fiber assembly impregnated with a binder,
The manufacturing method according to claim 1, which is a prepreg. 5. The production method according to claim 1, wherein the bag-shaped material is made of a thermoplastic resin. 6. The method according to claim 1, 2, 3, 4, or 5, wherein the mold is a molding die for a cylindrical porous carbon molded body.