JP5245570B2 - Carbon porous body and method for producing the same - Google Patents

Description

  The present invention relates to a lightweight carbon porous body having high strength and high dimensional stability, and a method capable of producing the carbon porous body very easily.

Patent Documents 1 to 3 describe a polyimide foam as a heat-resistant foam and a method for producing the same. In Patent Document 4, a previously foamed polyimide resin mass is pulverized, mixed with a heat-resistant binder, and the mixture is put into a predetermined mold, and then pressed and fired to a predetermined density. A foamed polyimide molded body is disclosed. The binder specifically used here was a solution of polyamic acid which is a polyimide precursor.
As a method for producing a polyimide foam, such a method of mixing with a heat-resistant binder is not easy to uniformly mix the foam chip and the binder solution, and the solvent of the binder solution needs to be removed. There was room for improvement in workability.

On the other hand, as a method for producing a carbon porous body, there has been known a method of firing a resin foam such as melamine, urethane, phenol, etc. In these methods, in general, a resin foam is carbonized when it is fired. Since the yield is low, the resin foam, which is the starting material, undergoes a very large volume shrinkage due to firing, and there is a drawback that the strength cannot be obtained.
For this reason, in order to improve the drawbacks of the above conventional method of firing the resin foam as it is, a resin foam such as urethane foam is impregnated with a thermosetting resin (furan resin, phenol resin, imide resin, etc.) There has been proposed a method for producing a porous carbon body by firing a resin foam impregnated with this thermosetting resin (see Patent Documents 5 to 7).
These methods result in a porous carbon body that retains the shape of the original resin foam, but the dimensional change is reduced due to shrinkage of the foam and the shrinkage of carbonization of the thermosetting resin during heating up to carbonization. The effect is not enough. Furthermore, a method for uniformly impregnating a resin foam with an appropriate amount of a resin solution is not described, and it is difficult to produce a resin having a uniform density.

U.S. Pat. No. 4,241,193 JP-A-4-21440 JP 2002-12688 A JP 2004-323715 A Japanese Patent Publication No.53-7538 Japanese Patent No. 3233703 JP 2005-41748 A

An object of the present invention is to provide a lightweight carbon porous body having high strength and high dimensional stability, and a method capable of producing the carbon porous body very easily.
As a result of various studies, the inventors have made a high-density foam having a density of about 100 to 1000 kg / m ³ substantially formed of an aromatic polyimide, in particular, a foam formed substantially of an aromatic polyimide. A porous carbon body that achieves the above object by carbonizing a lightweight polyimide molded body having a density of about 100 to 1000 kg / m ³ obtained by pressure molding and heat treatment of the body chip without using a binder. Has been found to be easy to produce, and has reached the present invention.

The following section 5 is described for the carbon porous body manufactured by the manufacturing method of the present invention. In the following description, the carbon porous body produced by the production method of the present invention is also referred to as the carbon porous body of the present invention for convenience.
1. A lightweight, high-strength and high dimensional stability product obtained by carbonizing an aromatic polyimide foam having a density of 100 to 1000 kg / m ³ at a temperature of 600 ° C. or higher in an inert gas atmosphere or in a vacuum. Carbon porous body.
2. A lightweight carbon porous body with high strength and high dimensional stability, obtained by carbonizing a lightweight polyimide molded body formed of an aromatic polyimide foam in an inert gas atmosphere or in a vacuum at a temperature of 600 ° C. or higher. body.

3. Item 3. The porous carbon body according to Item 2, wherein the lightweight polyimide molded body is obtained by subjecting a foam chip formed of aromatic polyimide to pressure molding and heat treatment without using a binder.
4). Item 3. The porous carbon body according to item 2, wherein the lightweight polyimide molded body is obtained by compressing a foam formed of an aromatic polyimide.

  5. Item 2-4, wherein the weight retention is 55% or more and the dimensional retention is 75% or more obtained by carbonizing a lightweight polyimide molded body in an inert gas atmosphere or in a vacuum at a temperature of 800 ° C. or higher. The carbon porous body according to crab.

  6). Aromatic polyimide, the main component of tetracarboxylic acid component is biphenyltetracarboxylic acid and / or benzophenone tetracarboxylic acid, the main component of diamine component is p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenyl ether Aromatics comprising at least one aromatic diamine selected from the group consisting of 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 2,6-diaminopyridine Item 6. The porous carbon body according to any one of Items 1 to 5, which is a polyimide.

7. Item 7. The porous carbon body according to any one of Items 2 to 6, wherein the lightweight polyimide molded body has a density of 100 to 1000 kg / m ³ .
8). Item 4. The porous carbon body according to Item 3, wherein the maximum diameter of the foam chip is 50 mm or less.

Item 9 below is a description relating to the production method of the present invention.
9. A step of obtaining a lightweight polyimide molded body using a foam formed of aromatic polyimide, and a carbonization step of carbonizing the lightweight polyimide molded body at a temperature of 600 ° C. or higher in an inert gas atmosphere or in a vacuum. a method of manufacturing a non-carbon porous body,
The step of obtaining a lightweight polyimide molded body includes a step of obtaining a pressure molded body by placing a foam chip formed of an aromatic polyimide in a mold and performing pressure molding at a temperature of 100 ° C. or less, and the pressure molding. A method for producing a porous carbon body comprising a step of placing a body in a mold having a target shape and heat-treating the body at a temperature of 250 to 500 ° C.

The porous carbon body of the present invention has little dimensional change during carbonization, has high dimensional stability, has high strength, is lightweight, and has continuous pores.
According to the present invention, since carbonization can be performed while maintaining a three-dimensional shape in a carbonization process with little dimensional change, a carbon product having a shape as designed can be easily provided. Since a carbon molded product can be obtained without processing such as cutting a carbon material having poor workability, the effects are great, such as improvement in quality, reduction in manufacturing cost, realization of high-mix low-volume production.
In particular, since the density of the lightweight polyimide molded body is easy to adjust and the change in density in the carbonization process is small, the density of the carbon porous body of the present invention can be easily adjusted. For example, if the density of the carbon porous body is increased, the mechanical strength is increased, and if the density of the carbon porous body is decreased, the permeability of gas and liquid is improved. A porous body is obtained.

  In the present invention, the “lightweight polyimide molded body” is a term used for the purpose of distinguishing from a dense polyimide molded body obtained by, for example, heating and compressing polyimide powder. “Lightweight polyimide molded body” has a higher density due to a smaller proportion of bubble (pore) space than the foam chip of the raw material, but the molded body has a space due to bubbles in the foam chip. The polyimide molded body is lighter than the dense polyimide molded body as described above.

In the present invention, the aromatic polyimide forming the foam is composed of an aromatic tetracarboxylic acid as a tetracarboxylic acid component and an aromatic diamine as a diamine component, and has a glass transition temperature of 250 ° C. or higher, preferably 300 ° C. or higher, more preferably. Is preferably an aromatic polyimide having a temperature of 330 ° C. or higher, particularly preferably 350 ° C. or higher. When a foam formed of polyimide with a low glass transition temperature is used, the foam (pore) structure of the foam is easily softened during heat treatment, resulting in uneven deformation. Is not preferable and the shape is distorted.
Therefore, the aromatic polyimide forming the foam in the present invention is composed of aromatic tetracarboxylic acids and aromatic diamines and has the glass transition temperature. Minor components other than aromatic tetracarboxylic acids and aromatic diamines may be used for the purpose of improving plasticity during foam molding, for example. It is important that the glass transition temperature of the resulting polyimide does not fall below the above value. When using the said small amount component, it is about 10 mol% or less each independently in a tetracarboxylic-acid component and a diamine component, Preferably it is 5 mol% or less, More preferably, it is 2 mol% or less.

Examples of the tetracarboxylic acid component include 2,3,3 ′, 4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,2 ′, 3,3′-biphenyltetracarboxylic acid Biphenyl tetracarboxylic acids such as acids, pyromellitic acids, benzophenone tetracarboxylic acids such as 3,3 ′, 4,4′-benzophenone tetracarboxylic acids, 2,3,6,7-naphthalene tetracarboxylic acids, 1,2, Naphthalene tetracarboxylic acids such as 5,6-naphthalene tetracarboxylic acids, 1,2,4,5-naphthalene tetracarboxylic acids, 1,4,5,8-naphthalene tetracarboxylic acids, bis (3,4-dicarboxyphenyl) ) Bis (dicarboxyphenyl) ethers such as ethers, 2,2-bis (2,5-dicarboxyphenyl) Bis (dicarboxyphenyl) propanes such as propane, bis (dicarboxyphenyl) ethanes such as 1,1-bis (2,3-dicarboxyphenyl) ethane, 1,1-bis (3,4- Aromatic tetracarboxylic acids such as bis (dicarboxyphenyl) sulfones such as dicarboxyphenyl) sulfones can be suitably used alone or in combination. Among these, biphenyltetracarboxylic acids and / or benzophenonetetracarboxylic acids, particularly biphenyltetracarboxylic acids, can easily obtain a foam and have a high glass transition temperature. Therefore, the main component of the tetracarboxylic acid component (50 mol%) Or more, preferably 80 mol% or more).

Here, the tetracarboxylic acids mean tetracarboxylic acids that can form polyimides, such as tetracarboxylic acids, esterified products thereof, and anhydrides thereof, and derivatives thereof.
The minor component used in consideration of moldability and the like includes bis (dicarboxyphenyl) such as 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane. Cyclohexanetetracarboxylic acids such as tetramethyldisiloxanes, cyclopentanetetracarboxylic acids, 1,2,4,5-cyclohexanetetracarboxylic acid, 3-methyl-4-cyclohexene-1,2,4,5-tetracarboxylic acid Aliphatic tetracarboxylic acids such as acids can be mentioned.

  Examples of the diamine component include p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, aromatic diamine having one benzene nucleus such as 3,5-diaminobenzoic acid, An aromatic diamine having two benzene nuclei such as 4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 1,3-bis (3- Aromatic diamines having three benzene nuclei such as aminophenoxy) benzene and 1,3-bis (4-aminophenoxy) benzene, bis (4- (4-aminophenoxy) phenyl) sulfone, bis (4- (3- Aminophenoxy) phenyl) sulfone, 4,4′-bis (3-aminophenoxy) biphe Nyl, 4,4′-bis (4-aminophenoxy) biphenyl, aromatic diamine having four benzene nuclei such as 2,2-bis (4- (4-aminophenoxy) phenyl) propane, and naphthalene such as diaminonaphthalene An aromatic diamine having a ring, an aromatic diamine having a heterocyclic ring such as 2,6-diaminopyridine, and the like can be suitably used alone or in combination. Among these, p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and 2, It is preferable to use at least one aromatic diamine selected from the group consisting of 6-diaminopyridine as the main component (50 mol% or more, preferably 80 mol% or more).

  Minor components used in consideration of moldability and the like include diaminosiloxanes such as 1,3-bis (3-aminopropyl) tetramethylsilane, isophoronediamine, norbornenediamine, 1,2-diaminocyclohexane, 1, Examples include alicyclic diamines such as 3-diaminocyclohexane, 1,4-diaminocyclohexane, and bis (4-aminocyclohexyl) methane, and aliphatic diamines such as hexamethylenediamine and diaminododecane.

  The aromatic polyimide foam can be suitably produced by a conventionally known method. For example, a tetracarboxylic dianhydride and the lower alcohol are reacted in a lower alcohol solvent to form a tetracarboxylic ester solution, and a diamine is added and mixed to obtain a polyimide precursor solution composition. The alcohol solvent of the solution composition is removed by evaporation at a low temperature to obtain a powdered polyimide precursor composition. An aromatic polyimide foam can be suitably obtained by pre-molding the powdered polyimide precursor composition into a green body as necessary, and then heating and foaming by microwave heating or the like. Moreover, after adding lower alcohol to the polyimide precursor composition of the powder again to obtain a polyimide precursor composition of solution or suspension, the foam of aromatic polyimide is obtained by heating and foaming by microwave heating or the like. It can be suitably obtained.

  The polyimide precursor solution composition is prepared by mixing the tetracarboxylic acid component and the diamine component at a composition ratio such that the equimolar amounts of the tetracarboxylic acid component and the diamine component. In order to make the foam uniform, for example, diaminodisiloxane is added to the diamine. It is suitably used as a minor component of the component. As the lower alcohol of the solvent, methanol, ethanol, propanol or the like is used, and it may be mixed with other solvents. When a diamine is added to and mixed with the tetracarboxylic acid ester solution to obtain a polyimide precursor solution composition, the concentration of each component is preferably below the solubility limit of diamine, and the amount of non-volatile components is 3 in the total amount. It becomes about 50 mass%. This polyimide precursor solution composition includes 1,2-dimethylimidazole, benzimidazole, isoquinoline, substituted pyridine and other imidation catalysts, surfactants, or other known additives such as inorganic fillers. -Inorganic or organic pigments may be added.

  The polyimide precursor solution composition is evaporated to dryness and pulverized using an evaporator in the laboratory and a spray dryer in the industry. The temperature at this time is preferably 100 ° C. or less, particularly preferably 80 ° C. or less. When evaporating to dryness at a high temperature, the foamability of the polyimide precursor composition is extremely lowered. Evaporation to dryness may be performed under normal pressure, under pressure, or under reduced pressure.

  The green body is prepared by, for example, a method in which a powdered polyimide precursor composition is compression-molded at room temperature, a method in which it is cast and solidified as a slurry solution, and a microwave inactive to Teflon (registered trademark). It can be performed by a method of filling the container. If a green body having a substantially uniform state can be obtained, uniformization during foaming can be achieved.

Foaming of the polyimide precursor composition can be suitably performed by heating by microwave heating. At this time, the operation is generally performed at 2.45 GHz. This is based on Japanese domestic law (Radio Law). It is preferable to use the microwave output per weight of the powder as a guide. This should be defined by experimentation. For example, when microwaves of about 100 g / 1 kW are irradiated for about 1 minute, foaming starts, and foaming converges in 2 to 3 minutes.
Since the foamed foam is very brittle, it is preferable to immediately heat it using an oven or the like. Heating is preferably performed by gradually increasing the temperature from about 200 ° C. (as a guideline, a temperature increase rate of about 100 ° C./10 minutes). Finally, it is heated for 5 to 60 minutes, preferably about 10 minutes at a temperature of polyimide glass transition temperature + α (about 10 to 100 ° C.).
By the above production method, it is possible to suitably obtain an aromatic polyimide foam having a density of ³ to 20 kg / m ³ , a uniform foamed structure, and excellent elasticity and resilience. it can.

The lightweight polyimide molded body used in the present invention is formed of the above-mentioned aromatic polyimide foam.
The lightweight polyimide molded body used in the present invention is preferably obtained by pressure molding and heat-treating a predetermined amount of the above-mentioned aromatic polyimide foam chip without using a binder. In the present invention, the pressure molding and heat treatment steps may be performed in a single step, but a predetermined amount of the foam chip is placed in a mold and pressure molded at a temperature of 100 ° C. or lower to form a pressure molded body. A multi-stage method including a step of obtaining a pressure polyimide molded body in a mold having a desired shape and a heat treatment at a temperature of 250 to 500 ° C. It is preferable because it can be manufactured stably.

The said foam chip | tip can use suitably the chip | tip obtained by crushing and sizing the said aromatic polyimide foam using a crushing and sizing apparatus, for example. The density of the foam chip is preferably ³ to 20 kg / m ³ , particularly 5 to 20 kg / m ³ . The shape of the foam chip is not particularly limited, but a preferable shape is a shape close to a sphere that can be granulated when put into a predetermined mold. The maximum diameter of the foam chip is preferably 50 mm or less, and more preferably, the chip having the maximum diameter of 10 to 50 mm occupies 80% by volume or more with respect to the total volume. When the maximum diameter of the foam chip exceeds 50 mm, it is difficult to obtain a lightweight polyimide molded body having a uniform density, which is not preferable. It is also possible to use a chip with a minimum diameter of 5 mm or less, and there is no particular problem with the characteristics of the resulting lightweight polyimide molded body, but to crush the maximum diameter from a polyimide foam to 5 mm or less. It takes a considerable amount of time and is inefficient.

Hereinafter, the multistage manufacturing method will be described.
First, a predetermined amount of a foam chip is put into a mold and press-molded. The input amount is an amount calculated from the volume of the final lightweight polyimide molded body and the target density. This is pressure-molded by, for example, a press machine to obtain a pressure-molded body (green body) in which the foam chip is compressed. The density of the pressure-molded body must take into account the return of dimensions due to the springback that occurs after pressure molding. Therefore, at the time of pressure molding, it is 102 to 120%, preferably 105%, of the (target) density of the pressure-molded body. It is preferable to adjust the molding pressure, the mold dimensions, and the amount of foam chips introduced so that the density is ˜110%. By this springback, it becomes easy to eliminate the voids and obtain a more uniformly pressed body. Moreover, it is preferable that the shape and dimensions of the chip are as described above in order to obtain a pressure-molded body having a uniform density in the pressure-molding step.

The (target) density of the pressure-molded body is preferably set to a density of 85 to 115%, more preferably 90 to 100%, with respect to the (target) density of the lightweight polyimide molded body as the product.
In this step, there is no particular need for heating, and it is sufficient that the pressure-molded body is pressure-molded to such an extent that it can be integrated so that it can be easily taken out of the mold. That is, the pressurization temperature is 100 ° C. or less, preferably −10 to 100 ° C., more preferably 0 to 50 ° C., and still more preferably room temperature (about 15 to 30 ° C.). Is preferred.

In addition, since the polyimide foam is easily deformed, any special pressure can be used as long as it can apply a pressure that can be sufficiently compressed (usually 200 to 5000 kg / cm ² , preferably 500 to 2000 kg / cm ² ). Conditions are not required. Although the pressurization time is not particularly limited, a short time of about 1 second to 10 minutes is preferable, and it is preferable to repeat the pressurization for a short time a plurality of times.

  The mold used for the pressure molding is not particularly limited as long as a predetermined amount of the foam chip can be pressure molded. The shape is preferably a shape according to the shape of the final product (in the case of manufacturing a single product by combining a plurality of pressure-formed bodies, each partial shape). For example, if a plate-shaped product is to be manufactured, it can be suitably carried out by combining a mold that compresses a box-shaped container with an inner lid (punch) and a uniaxial hydraulic molding machine.

Subsequently, in order to heat-process, a press-molded body is moved to another metal mold | die normally equipped with a heating apparatus. In this mold, the pressure-molded body is heated to a target shape (target density) of the product and kept in the target shape. At this time, if the density of the press-molded body is smaller than the target density of the product, it is compressed into a mold and becomes high density. On the other hand, when the density of the press-molded body is larger than the target density of the product, the press-molded body expands due to heating, resulting in a low density. The heat treatment is preferably performed in the temperature range of 250 to 500 ° C. for about 0.1 to 10 hours. Note that springback may occur even after the heat treatment. In that case, it is preferable to determine the mold shape in consideration of the amount of springback required empirically. The lower limit of the temperature range of the heat treatment is preferably 300 ° C, more preferably 330 ° C, still more preferably 350 ° C, and particularly preferably 380 ° C. The upper limit of the temperature range of the heat treatment is preferably 450 ° C. The temperature at which heat treatment is performed is based on the glass transition temperature of the polyimide forming the foam chip. That is, it is −20 ° C. to + 100 ° C., preferably −10 ° C. to + 50 ° C., more preferably 0 to 50 ° C. with respect to the glass transition temperature of the polyimide forming the foam chip. When the glass transition temperature is not observed in the polyimide, it is preferable to carry out in a temperature range of 400 to 500 ° C.
When the temperature of the heat treatment is too low, the mechanical strength of the lightweight polyimide molded body is lowered, which is not preferable. In addition, if heat treatment is performed at a temperature higher than 500 ° C., the carbonization of polyimide starts, which is not preferable.

  The glass transition temperature of the polyimide forming the foam chip can be measured from the dynamic viscoelasticity of the foamed material using a dynamic viscoelasticity measuring device.

  The mold used in the heat treatment has the shape of a lightweight polyimide molded body whose product is a product. Accordingly, a metal that is not easily deformed is preferably used. When obtaining a plate-like lightweight polyimide molded body, a combination of metal spacers having a predetermined thickness between two metal plates can be suitably used. And if it can perform the pressurization function for adjusting a shape and heat processing, there will be no limitation in particular, It can use suitably combining a hot press apparatus with a metal plate and a spacer.

The lightweight polyimide molded body used in the present invention is suitably obtained by increasing the density to 10 to 330 times, preferably about 20 to 200 times the density of the foam chip to be used. The density of lightweight polyimide molded body used in the present invention, 100~1000kg / m ^3, preferably 300~1000kg / m ^3, more preferably 400~1000kg / m ^3, more preferably 500~900kg / m ^3, in particular Preferably, 550 to 850 kg / m ³ is suitable because it has excellent mechanical strength despite its light weight.

Carbonizing a lightweight polyimide molded body having a density lower than 100 kg / m ³ is not preferable because the shrinkage in the carbonization process is large and the shape is distorted. Further, the strength of the obtained carbon porous body is low, and when the surface is rubbed by hand, carbon powder comes out and collapses from the surface. A lightweight polyimide molded body having a density higher than 1000 kg / m ³ is not preferable because the pressure applied to the molding increases and the load increases and the lightness is lost.
The shape of the lightweight polyimide molded body used in the present invention may be any shape such as a sheet shape, a plate shape, a half pipe shape, a column shape, a cube shape, and a box shape.

In addition, as a lightweight polyimide molded body used in the present invention, in addition to a lightweight polyimide molded body formed by the foam chip, for example, a foam board formed by the aromatic polyimide is compressed. What was obtained can be used.
The board preferably has a density of 100 to 1000 kg / m ³ , preferably 300 to 1000 kg / m ³ and a thickness of about 0.5 to 50 mm.
The board is preferably compressed using a uniaxial press at a temperature of 200 to 450 ° C. and using a spacer having a predetermined thickness, preferably 3 to 200 times, more preferably 50 to 50 times the density before compression. It is suitably performed by applying pressure so as to increase the density to about 200 times.
In the present invention, an aromatic polyimide foam having a density in the range of 100 to 1000 kg / m ³ can be used as it is without being compressed.

The carbon porous body of the present invention is a high-density aromatic polyimide foam having a density of 100 to 1000 kg / m ³ typified by the light-weight polyimide molded body at 600 ° C. in an inert gas atmosphere or in vacuum. It was obtained by carbonizing at the above temperature.
The carbon porous body of the present invention does not need to be completely carbonized like graphite, and may be partially carbonized. The partially carbonized carbon porous body preferably has a carbon mass fraction of 60% by mass or more, more preferably a carbon mass fraction of 70% by mass or more, and still more preferably a carbon mass fraction. The rate is 80% by mass or more, particularly preferably the carbon mass fraction is 90% by mass or more.
The inert gas is, for example, helium gas, argon gas, nitrogen gas, or a mixed gas of these gases. Here, the “inert gas atmosphere” means that the atmosphere does not need to be an inert gas only, and the inert gas only needs to be present to the extent that oxidation by oxygen in the air is suppressed.
The vacuum is preferably 133 Pa or less, more preferably 1.3 × 10 ⁻² Pa or less.

The heating rate up to the carbonization temperature should be adjusted by the size, shape and weight of the lightweight polyimide molded body. Small molded bodies can be uniformly carbonized with little temperature difference between the edge and the center even if the heating rate is high, but with large molded bodies, the temperature difference is large and the degree of shrinkage during carbonization is also large. Because there is a difference, it warps or cracks. For this reason, in order to obtain a carbide having a large shape or a complicated shape, it is generally performed to raise the carbonization temperature at a very slow temperature increase rate.
The holding time at the carbonization temperature is to eliminate the temperature difference between the center part and the end part and make the degree of carbonization uniform, and the holding time is short for small things or those with a slow heating rate. It's okay.

The carbonization temperature is 600 ° C. or higher, preferably 800 ° C. or higher. When graphitization is performed, high-temperature treatment can be performed up to about 3000 ° C. The characteristics of the carbide vary depending on the carbonization temperature. If the surface area of the porous structure is important, a carbonization temperature of about 800 ° C. is preferable, and it is better to carbonize at a high temperature to increase conductivity.
When carbonizing, the foam may be pressurized for the purpose of reducing warpage and increasing temperature uniformity. If it is pressurized too much, it will shrink or crack in the pressing direction. The pressure is preferably about 1 to 300 g / cm ² . Further, when the foam is plate-shaped, a method of placing a weight is also acceptable.
After carbonization, for the purpose of increasing the surface area, surface treatment can be performed by activation with water vapor or carbon monoxide or by treatment under oxidizing conditions.

  The carbon porous body of the present invention obtained by such a carbonization process usually has a weight retention of 55% or more, a dimensional retention of 75% or more, and a three-dimensional structure having many continuous fine pores made of carbon Since it is a body, it can be used for a catalyst carrier, a filter, and the like, and can be suitably used for a gas adsorbent, a heat insulating material, a radio wave absorber, a heat dissipation material, and the like.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to a following example.

The measurement methods used in the following examples are as follows.
(Density measurement)
Measured according to ASTM D 3574 TEST A.

(Size measurement)
The dimensions of the lightweight polyimide molded body and the porous carbon body are the Z-axis in the direction (thickness direction) in which pressure was applied during molding of the lightweight polyimide molded body, and the X-axis represents one side of each 5 cm square cut out from the lightweight polyimide molded body. The Y axis was measured in 0.1 mm units with a caliper.
(Measurement of Shore hardness)
Measured according to ASTM D 2240.
(Measurement of pore diameter and porosity)
It measured using the mercury intrusion type porosimeter Auto Pore III (made by Shimadzu Corporation).

Reference Example 1 Preparation of Polyimide Foam In a 1 m ³ jacketed reactor equipped with a stirrer, 55.519 kg of 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride and 15.201 kg of 3, After charging 3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 139.7 kg of methanol and replacing the inside of the reaction vessel with nitrogen, the jacket was heated by circulating 90 ° C. warm water, and the reaction solution After the temperature reached 90 ° C., the mixture was refluxed for 90 minutes to carry out an esterification reaction. Then, after cooling a reaction liquid to 30 degrees C or less, 25.052 kg of p-phenylenediamine and 0.628 kg of 1,3-bis (3-aminopropyl) tetramethyldisiloxane were added to the reaction liquid. Further, 2.892 kg of 1,2-dimethylimidazole was added and stirred to make the reaction solution uniform. Next, using a spray dryer, the reaction solution was dried while adjusting the spray amount so that the drying temperature was 50 ° C. or less, thereby obtaining a dry powder of a foamed polyimide precursor. Next, 2 kg of this dried polyimide precursor powder was filled in a 300 mmφ × 200 mmt mold and pressed with a press to compress the green body. The obtained green body had a size of 300 mmφ × 15 mmt. This green body is put in a microwave irradiation apparatus, and irradiated with microwaves at an output of 5 kw for 10 minutes to obtain a foamed polyimide precursor foam, which is put into an oven heated to 120 ° C. and heated to 375 ° C. for 10 After raising the temperature at a rate of temperature increase of ° C./min, the temperature was maintained at 375 ° C. for 5 minutes and then cooled to room temperature to obtain a foamed polyimide. The obtained foamed polyimide was dense and uniform foaming, and the density was 7.5 kg / m ³ .

[Example 1]
The polyimide foam obtained in Reference Example 1 was put into a crushing apparatus (a crushing and granulating machine Fiore, manufactured by Kotokakusho Co., Ltd.) and crushed. A schematic diagram of the pulverization and sizing machine is shown in FIG. 530 g of a chip having a particle diameter of 30 mm or less that has passed through a screen with a hole diameter of 30 mm is placed in a 315 × 315 × 80 mm stainless steel mold, and a pressure of 1130 kg using a pressing device (single screw hydraulic molding machine, manufactured by Toho Machinery Co., Ltd.) The plate-shaped press-molded body was obtained by cold molding at room temperature for 10 seconds at / cm ² . A schematic cross-sectional view of this process is shown in FIG. The size of this press-molded body was 315 × 315 × 7.5 mmt, and the density was 710 kg / m ³ . The pressure-molded body is sandwiched between two stainless steel flat plates of 330 × 330 × 10 mm together with a spacer of 8 mm thickness, and squares are fixed with bolts as shown in FIG. And heated at 400 ° C. for 3 hours in a calcination furnace DF-200HS (manufactured by Futaba Kagaku Co., Ltd.) to obtain a lightweight polyimide molded body having dimensions of 315 × 315 × 8.1 mmt. This lightweight polyimide molded body had a density of 660 kg / m ³ .
This lightweight polyimide molded body was cut into about 5 cm square and carbonized in an electric furnace at 1000 ° C. for 1 hour in a nitrogen stream. The heating rate up to the carbonization temperature was 10 ° C./min from room temperature to 300 ° C., and 3 ° C./min from 300 ° C. to 1000 ° C.
The obtained porous carbon body has a weight of 7.5 g, a weight retention rate of 60%, a bulk density of 710 kg / m ³ , and a dimensional retention rate of about 82% (X-axis direction: 82%, Y-axis direction: 82%, Z-axis) Direction: 81%).

[Example 2]
Lightweight polyimide molding with dimensions of 315 × 315 × 8.1 mmt in the same manner as in Example 1 except that the amount of the foam chip was 620 g and the pressure at the time of producing the pressure-molded body was changed to 1400 kg / cm ^2. Got the body. This lightweight polyimide molded body had a density of 770 kg / m ³ .
This lightweight polyimide molded body was cut into about 5 cm square and carbonized in an electric furnace at 1000 ° C. for 1 hour in a nitrogen stream. The heating rate up to the carbonization temperature was 10 ° C./min from room temperature to 300 ° C., and 3 ° C./min from 300 ° C. to 1000 ° C.
The obtained porous carbon body has a weight of 8.6 g, a weight retention rate of 60%, a bulk density of 810 kg / m ³ , a dimensional retention rate of about 83% (X-axis direction: 84%, Y-axis direction: 84%, Z-axis) Direction: 80%).
Further, this carbon porous body has a Shore hardness of 70, and has a high strength considering that the bulk density is 810 kg / m ³ .

Example 3
A lightweight polyimide molded body with dimensions of 315 × 315 × 8.1 mmt was obtained in the same manner as in Example 1 except that the foam chip amount was 450 g and the molding pressure was 920 kg / cm ² . This lightweight polyimide molded body had a density of 560 kg / m ³ .
This lightweight polyimide molded body was cut into about 5 cm square and carbonized in an electric furnace at 1000 ° C. for 1 hour in a nitrogen stream. The heating rate up to the carbonization temperature was 10 ° C./min.
The obtained porous carbon body has a weight of 6.5 g, a weight retention rate of 60%, a bulk density of 600 kg / m ³ , and a dimension retention rate of about 84% (X-axis direction: 83%, Y-axis direction: 82%, Z-axis) Direction: 87%).
This carbon porous body had an average pore diameter of 13 μm and a porosity of 45% as measured by a mercury intrusion porosimeter.

Example 4
A lightweight polyimide molded body having dimensions of 315 × 315 × 8.1 mmt was obtained in the same manner as in Example 1 except that the foam chip amount was 490 g and the molding pressure was 1020 kg / cm ² . This lightweight polyimide molded body had a density of 610 kg / m ³ .
This lightweight polyimide molded body was cut into about 5 cm square and carbonized in an electric furnace at 800 ° C. for 1 hour in a nitrogen stream. The heating rate up to the carbonization temperature was 2.5 ° C./min from room temperature to 300 ° C., and 1.7 ° C./min from 300 ° C. to 800 ° C.
The obtained porous carbon body has a weight of 7.7 g, a weight retention rate of 62%, a bulk density of 660 kg / m ³ , a dimensional retention rate of about 83% (X-axis direction: 83%, Y-axis direction: 83%, Z-axis) Direction: 83%).

The carbon porous body obtained in Example 4 was further carbonized with an electric furnace at 1000 ° C. for 1 hour in a nitrogen stream. The heating rate up to the carbonization temperature was 6.5 ° C./min from room temperature to 800 ° C., and 1.7 ° C./min from 800 ° C. to 1000 ° C.
The obtained porous carbon body has a weight of 7.5 g, a weight retention rate of 60%, a bulk density of 640 kg / m ³ , a dimensional retention rate of about 83% (X-axis direction: 83%, Y-axis direction: 83%, Z-axis) Direction: 83%). However, the weight retention ratio and the dimension retention ratio were based on the weight and dimension of the lightweight polyimide molded body of Example 4.

  According to the present invention, the work forming process is simple, the density is easily adjusted, and various shapes of porous carbon bodies can be suitably obtained. This carbon porous body has good mechanical properties despite being relatively light. Further, according to the present invention, the remaining polyimide foam after being cut out from the polyimide foam bulk after foaming can be used effectively.

It is the schematic for demonstrating the crushing apparatus used in Example 1. FIG. In Example 1, it is the schematic for demonstrating the process for obtaining a press-molded body. In Example 1, it is the schematic for demonstrating the process of obtaining a lightweight polyimide molded object from a press-molded object.

Claims (1)

A step of obtaining a lightweight polyimide molded body using a foam formed of aromatic polyimide, and a carbonization step of carbonizing the lightweight polyimide molded body at a temperature of 600 ° C. or higher in an inert gas atmosphere or in a vacuum. a method of manufacturing a non-carbon porous body,
The step of obtaining a lightweight polyimide molded body includes a step of obtaining a pressure molded body by placing a foam chip formed of an aromatic polyimide in a mold and performing pressure molding at a temperature of 100 ° C. or less, and the pressure molding. A method for producing a porous carbon body comprising a step of placing a body in a mold having a target shape and heat-treating the body at a temperature of 250 to 500 ° C.

Images