JPS5854082B2 - Manufacturing method of carbon porous material - Google Patents

Description

Detailed Description of the Invention The present invention involves impregnating a polyvinyl acecool-based synthetic resin porous body with a resin that can be converted into glassy carbon by thermal decomposition, and then firing it in a non-oxidizing atmosphere to at least partially convert it into glassy carbon. The present invention relates to a method for producing a porous carbon material having continuous pores made of carbon-like carbon.

Conventionally, a method for manufacturing porous carbon bodies has been to mix irregularly or spherical carbon or graphite with resin, cool, or pitch, mold the mixture, and then sinter it.

(Japanese Unexamined Patent Publication No. 48-67'188, etc.) However, the carbon porous bodies produced by these methods have a relatively large apparent specific gravity (1,00 to 1.30) and therefore a small porosity.

In addition, a method for producing porous bodies (Japanese Patent Publication No. 19999-1999) has been proposed in which carbonaceous micro hollow bodies are molded using a binder and then fired; however, with this method, the apparent specific gravity is relatively small (0 , 05 to 1.00), most of the pores are independent pores, and the air permeability is extremely small.

Furthermore, a method for producing a carbon porous body (Japanese Patent Publication No. 49 Sho.
-26196, etc.), but in this case, it is difficult to freely control the pore size to a desired size and produce a carbon porous body having continuous pores with a narrow pore size distribution. Ta.

In order to improve the shortcomings of these conventional carbon porous materials production methods and to produce porous materials with high porosity and continuous pores, we impregnated and hardened polyurethane foam with a resin that can be converted into glass or sliver carbon when heated. A method has been proposed in which carbonization is carried out at a high temperature after carbonization.

In addition, if a phenol resin or epoxy resin dissolved in a solvent such as acetone or methanol is applied to a polystyrene or cellulose porous material and then carbonized, the porous material of the base material becomes gasified, and the thermosetting resin coated on its surface becomes carbonized. The carbonized resin is carbonized to obtain a carbon porous body that has a yin and yang relationship with the porous body of the base material, but these porous bodies have a problem in terms of strength.

U.S. Pat. No. 3,922,334 discloses that a polyurethane foam having an open-pore network polyurethane structure from which thin partition walls have been removed is infiltrated with a phenolic resin solution using tetrahydrofuran as a solvent, and then carbonized over a relatively long period of time. A carbon porous body is disclosed in which the skeleton of the network polyurethane structure of the base material becomes a carbon skeleton as it is when fired.

Further, US Pat. No. 3,927,186 discloses a carbon porous body that utilizes the skeleton of a network polyurethane structure by impregnating the network polyurethane structure with a liquid furan resin and carbonizing it.

Although the methods using polyurethane foams described in these US patents are excellent, great care is required to remove excessively permeated resin from the surface of the polyurethane after resin impregnation.

Furthermore, depending on the solvent, when polyurethane foam is impregnated with resin, the resin may begin to dissolve the foam, and the foam may collapse during heat curing, and this tendency is particularly noticeable in flexible polyurethane foams.

For this reason, in JP-A-51-70207, liquid epoxide resin or
A complicated process of impregnation with an aqueous polyvinyl alcohol solution is introduced.

Furthermore, JP-A-53-125289 discloses that a flammable gas is introduced into a thermosetting resin foam obtained by directly reacting a mixture of a polyisocyanate and a phenol resin, a furan resin, or a precursor thereof. , a method for manufacturing a porous carbon material having continuous pores by igniting a flammable gas to destroy cell membranes and then carbonizing and firing is disclosed, but this method has the drawback that the manufacturing process is complicated. .

Polyurethane foam is originally a closed-pore foam, and in order to obtain a network structure with completely open pores, special treatment must be performed to remove the pore partition walls, or
Similar treatment is required after resin impregnation.

As mentioned above, although the carbon porous body using polyurethane foam has excellent properties, it has the disadvantage that the manufacturing method is complicated.

By the way, polyvinyl acecool-based porous materials are made by cross-linking and molding a mixture of polyvinyl alcohol and aldehydes as cross-linking agents, as well as starch, water-soluble salts, etc., and solidifying and eluting the water-soluble substances with water to impart continuous pores. It is a hydrophilic porous body with extremely high continuous porosity.

As a method for producing a carbon porous body that takes advantage of the excellent properties of the porous body, a method has been proposed in which the porous body is carbonized and fired in a non-oxidizing atmosphere.

(Japanese Patent Application No. 53-70069 (Japanese Patent Application No. 16057-1983)
No. 9)) However, when the above-mentioned polyvinyl acecool porous material is carbonized and fired in a non-oxidizing atmosphere, the weight loss during firing is extremely large, and when fired to 1000'C, the fired weight usually decreases to the initial value. Less than 20% of the weight.

Furthermore, the size decreases significantly, and by firing at 1000°C, the size decreases to about 52% of the initial size.

Such extreme weight and size reductions, as well as non-uniform deformation during shrinkage, are serious drawbacks in producing porous carbon materials.

Furthermore, since the porous body is made of easily graphitizable carbon, it has drawbacks such as poor oxidation resistance and chemical resistance.

The present inventors have completed the present invention as a result of intensive research to improve the above-mentioned drawbacks found in existing methods for producing porous carbon materials. The object of the present invention is to provide a new method for producing a carbon porous body with high porosity.

Other objects and advantages of the invention will become apparent from the description below.

The above purpose is to impregnate a polyvinyl acecool-based synthetic resin porous body with continuous pores with a resin that can be converted into glassy carbon by thermal decomposition, or a resin whose main component is resin, and then harden it and sinter it in a non-oxidizing atmosphere. This is achieved by

The polyvinyl acecool synthetic resin porous body used in the present invention is cross-linked by mixing starch, water-soluble salts, etc. in addition to polyvinyl alcohol and aldehydes as a cross-linking agent, and then solidified and eluted water-soluble substances with water. It is obtained by imparting continuous pores.

In addition, other synthetic resins such as epoxy resins, mixtures of vinyl polymers and divinyl compounds, urea resins, unsaturated polyester resins, melamine resins, pitch cool, etc. It is preferable to use a cool synthetic resin porous body coated with a resin that imparts shape retention.

In the present invention, the term "polyvinyl acecool-based synthetic resin porous body" refers not only to the polyvinyl acecool-based synthetic resin porous body, but also to the resin that imparts the shape retention properties to the polyvinyl acecool-based synthetic resin porous body. This term also includes porous bodies to which the term is applied.

The polyvinyl alcohol used for producing the above-mentioned polyvinyl acecool synthetic resin porous body preferably has a degree of polymerization of 100.
5,000 and a saponification degree of 70% or more, and those partially modified with carboxyl groups etc. are also preferably used.

Examples of the aldehydes used as crosslinking agents include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, octylaldehyde, 2-ethylhexylaldehyde, glyoxal, acrolein, and benzaldehyde.

As the powder or granule for providing continuous pores, starch or other organic fine powder, water-soluble metal salt, or the like may be used, and the powder or granule may be appropriately selected so as to provide the desired pore size.

These are added as an aqueous solution or dispersion to a heated aqueous solution of polyvinyl alcohol.

Next, an aldehyde as a crosslinking agent and a catalyst such as sulfuric acid are added to this mixed solution, and the mixture is poured into a reaction vessel capable of giving the desired shape and heated to react.

The shape of the molded product can be freely selected from plate-like, wavy, cylindrical, etc. depending on the purpose, use, and required performance.

As mentioned above, the polyvinyl acecool-based synthetic resin porous material used in the present invention can be easily obtained by a known method, but polyvinyl formal-based synthetic resin porous material having a specific network structure or pyrvinyl benzal-based synthetic resin porous material can be used in the present invention. A porous resin material is suitable.

Examples of resins that can be converted into glassy carbon that can be impregnated into the polyvinyl acecooled porous material of the present invention include resol resins, phenolic resins such as novolac resins, furan resins, etc., and these may be used alone or in combination. However, when considering aspects such as resin curing treatment operations, resol resins are most suitable, followed by novolak resins.

Resole resins are initial products produced by reacting phenols with aldehydes in the presence of basic catalysts, and are typically self-thermal crosslinking resols with molecular weights up to about 600 that are rich in methylol groups. It is.

Phenols used in the production of resol resins most commonly include phenol and cresol.

However, other phenols can also be used, such as phenol, υ-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,5-xylenol, 2,4- Xylenol, 2,6-xylenol, 3,4-xylenol, 3.
5-xylenol, υ-ethylphenol, m-ethylphenol, p-ethylphenol, p-phenylphenol, p-tert-butylphenol, p-ter
Examples include t-aminophenol, bisphenol A1 resorcinol, and mixtures of these phenols.

Formaldehyde is the most common aldehyde used for polycondensation with this phenol.

However, monoaldehydes and dialdehydes such as paraformaldehyde, hexamethylenetetramine, furfural and glutaraldehyde, acetaldehyde and glyoxal may also be used.

Basic catalysts used in the resol resin synthesis reaction include caustic alkali, alkali carbonate, barium hydroxide, calcium hydroxide, ammonia, quaternary ammonium compounds,
Known amines may be used, and caustic soda or ammonia is most commonly used.

The novolac resin is prepared by combining the same phenols used in the production of the resol resin and the same aldehydes used in the production of the resol resin with oxalic acid,
Produced by reaction with heating in the presence of an acidic catalyst such as organic acids such as formic acid, acetic acid, halogenated acid, and para-toluenesulfonic acid, and inorganic acids such as hydrochloric acid, sulfuric acid, perchloric acid, and phosphoric acid. It is an uncured and meltable thermoplastic resin with a molecular weight of about 300 to 2,000.

Examples of the furan resin include furfuryl alcohol resin, brifuryl alcohol phenol resin, furfural resin, furfural phenol resin, and furfural ketone resin.

Examples of curing agents for these resins include aniline hydrochloride,
Organic acids such as para-toluenesulfonic acid can be used.

Various known methods can be applied to apply a synthetic resin that can be converted into glassy carbon to a polyvinyl acecool-based synthetic resin porous body. A polyvinyl acetal synthetic resin porous body with continuous pores in shape, size, pore diameter, and porosity.
It may be immersed in a solution prepared by dissolving the above-mentioned phenol resin or furan resin in a solvent.

A phenol resin solution such as a resol resin or a novolak resin can be dissolved in an appropriate amount in a solvent such as methanol or acetone to prepare a phenol resin solution with a predetermined concentration.

Further, as the resol resin, a water-soluble resol resin can also be used.

In the case of a resol resin, if necessary, a small amount of an organic acid such as paratoluenesulfonic acid or phthalic acid may be added in advance to the solution as an acid catalyst for curing.

In the case of novolak resin, methanol,
A solution of a predetermined concentration obtained by dissolving an appropriate amount in a solvent such as acetone may be used.

As the crosslinking agent, hexamethylenetetramine is most commonly used, but aldehydes such as paraformaldehyde, glutaraldehyde, adipaldehyde, and glyoxal, and acids or alkalis may also be used in combination.

Alternatively, after a porous body is impregnated with a novolak resin in advance, it may be cured by heating in an aqueous solution containing hexamethylenetetramine, an acid or an alkali, and an aldehyde.

In the case of furan resin, use a solution in which the furan resin is dissolved in a solvent such as acetone or benzene, and a curing agent such as aniline hydrochloride or paratoluenesulfonic acid is mixed in at about 0.2 to 1% of the resin solid content. good.

There is no particular restriction on the concentration of the above resin solution to be impregnated into the polyvinyl acecool synthetic resin porous body, and the pore size of the porous body,
Although it may be selected as appropriate depending on the shape, amount of resin attached, etc., the preferred solution concentration for working is 5 to 60% by weight, more preferably 10 to 40% by weight.

As mentioned above, when a polyvinyl acecool synthetic resin porous body is impregnated with a phenolic resin or a furan resin dissolved in a solvent, the porous body swells due to the unique properties of the polyvinyl acecool synthetic resin, and the phenol resin or furan resin dissolves in the solvent. At the same time, it penetrates into the inside of the polyacetal synthetic resin.

The time required for this infiltration varies depending on the pore size of the porous body and the degree of acetalization, but is usually about ten to one hour.

The synthetic resin that has penetrated into the polyvinyl acecool-based synthetic resin porous body in this way is integrated with the polyvinyl acecool-based synthetic resin porous body through the drying process described later, and the network structure of the polyvinyl acecool-based synthetic resin porous body is maintained as it is by carbonization firing. The remaining carbon porous material remains.

The polyvinyl acecool synthetic resin porous body impregnated with phenol resin or furan resin is taken out of the solution, dried at room temperature or under heat to remove the solvent, and then heated to a high temperature of 120 to 180°C. Harden the impregnated resin.

Usually, after drying at 40-60°C for 3-5 hours,
By raising the temperature to 20 to 180°C and holding it for about 30 minutes to 2 hours, it is possible to dry and harden while maintaining a uniform resin adhesion state.

Further, in the case of a plate-shaped body, after being impregnated with resin, it can be dried at a temperature of 60°C or lower, and then pressure molded by applying a small amount of pressure at a temperature in the range of 100 to 180°C.

The content of thermosetting resin in the synthetic resin porous body dried and cured by the above method is usually 25 to 90% by weight, preferably 30 to 75% by weight, and most preferably 40 to 70% by weight.

If the content of the thermosetting resin porous body in the synthetic resin porous body is extremely low, weight loss and size reduction during the carbonization firing process in a non-oxidizing atmosphere tend to be large. creates a problem.

If the content of the thermosetting resin is excessive, exceeding 90% by weight, the porosity of the porous body tends to decrease, and the feature of the porous body having continuous pores tends to be lost. When the content of the thermosetting resin is 40 to 70% by weight, the amount of shrinkage during carbonization firing is small, and a high-strength carbon porous body with a large continuous porosity can be obtained.

In addition, other synthetic resins such as epoxy resins, mixtures of vinyl polymers and divinyl compounds, urea resins, unsaturated polyester resins, melamine resins, pitch tar, etc. are applied to the polyvinyl acecool synthetic resin porous body. When added, shape retention is improved.

These resins can be easily applied, for example, by impregnating a polyvinyl acecool-based synthetic resin porous body with a resin liquid or a mixed solution of these resins and a resin that can be converted into glassy carbon by thermal decomposition.

In short, it is sufficient that these resins are applied to the polyvinyl acecool-based synthetic resin porous body during firing.

The synthetic resin porous body impregnated with resin and cured in this way is then heated under a non-oxidizing atmosphere, that is, under reduced pressure, or with an inert gas such as argon gas or helium gas, or hydrogen gas.
At least 800' in nitrogen gas, halogen gas, etc.
C, preferably heated to 1000° C. or higher and carbonized and fired.

There is no upper limit to the firing temperature; it can be increased to 3000℃ if necessary.
It may be heated to a certain extent.

According to the research conducted by the present inventors, gaseous compounds such as H20, HCHO, etc.
, CO, CH4, etc. begin to be released from the porous body,
The generation of this thermal decomposition gas is most noticeable in the temperature range of 350 to 600°C, and weight loss and shrinkage of the resin composition proceed significantly in this temperature range.

However, in the carbonization firing process of the present invention, there is no particular restriction on the temperature increase rate, and it is usually 50'C/hr -50
It is possible to perform firing in a relatively short time at about 0'C/hr.

The carbon porous material obtained according to the above method is a reticulated carbon material that is at least partially made of glassy carbon, in which the skeleton constituting the network structure of the polyvinyl acecool synthetic resin porous material used as the base material is the carbon skeleton as it is. is a structure,
This porous body has continuous pores with a uniform pore size distribution, high porosity, and excellent oxidation resistance and chemical resistance.

In addition, by selecting a polyvinyl acecool-based synthetic resin porous body as a base material and combining it with a resin that can be converted into glassy carbon by thermal decomposition, such as a phenol resin or a furan resin, the carbon pores according to the present invention can be obtained by firing. The body has a network structure of polyvinyl acecool-based synthetic resin porous material.
In addition, it is firmly integrated with the above-mentioned phenol resin, furan resin, etc., and becomes rigid and high strength.

A carbon porous body having such excellent properties is suitable for the following uses.

That is, it is suitable for various filters such as separation of solids such as dust and impurities in gases and solids in liquids, especially filters with excellent corrosion resistance or heat resistance.

In addition, it is suitable as a catalyst carrier that takes advantage of its good air permeability.

Furthermore, the porous material can be used as a panel heater by making use of its conductivity and passing an electric current through the porous material.

Furthermore, it can be used for lightweight structural materials, heat insulating materials, battery electrodes, aeration equipment, chemical adsorbents, surface heating elements, radio wave shielding materials, etc.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Degree of polymerization 1700. Polyvinyl alcohol with a saponification degree of 99% is dispersed in water, then heated and dissolved, and when the temperature reaches 50°C, an aqueous dispersion of wheat flour starch is added and mixed uniformly.
It was heated to 75-80°C with stirring.

After cooling this mixed solution to 35°C, 37% formalin and sulfuric acid were added and mixed uniformly.
%, starch 4%, formalin 9%, and sulfuric acid 13%.

The solution was poured into a hollow cylindrical mold with an outer diameter of 707n7Itφ, an inner diameter of 30mmφ, and a height of 250mm, and was heated at 60°C for 1
After heating for 8 hours, the mixture was washed with water to elute starch and unreacted substances to obtain a polyvinyl formal porous body having continuous pores.

The average pore diameter of the porous body is 100μ, and the apparent specific gravity is 0.136.
, the continuous porosity was 91%.

The above polyvinyl formal porous material was immersed in a commercially available molding resol resin API06GK (manufactured by Crowd Chemical Co., Ltd.) dissolved in methanol solvent for 10 minutes, then gradually heated from room temperature to 100°C over 5 hours, dried, and then heated to 150°C. The resol was cured for 1 hour at ℃.

The amount of resol attached to the polyvinyl formal porous body was adjusted by varying the amount of resol in the methanol solvent from 5% by weight to 60% by weight.

When the concentration of the resol solution was 30% by weight or less, para-toluenesulfonic acid was added in an amount of 5% of the solid weight of the resol to shorten the drying and curing time.

The synthetic resin porous body obtained as described above was placed in an electric furnace and carbonized by heating at 200°C/hr in a nitrogen atmosphere,
It was maintained at 1000°C for 1 hour and then cooled.

Table 1 shows the properties of the obtained porous carbon material.

From Table 1, it can be seen that when polyvinyl formal porous bodies are used alone, the weight loss and dimensional change due to firing are extremely large, and the carbon porous bodies obtained exhibit a shape that is significantly more distorted than the cylindrical shape.

In particular, the resol content in the synthetic resin porous body is 25 to 25%.
In the range of 90% by weight, a carbon porous body with a porosity of 50% or more and good shape retention during firing was obtained.

Example 2 A polyvinyl butyral porous body was prepared in the same manner as in Example 1 by using n-butyraldehyde instead of formalin.

The porous body was molded into a flat plate by carrying out a butyralization reaction in a 1010×100×200 mold.

Furthermore, by adjusting the particle size of wheat starch added to polyvinyl alcohol, the average pore diameter of the polyvinyl butyral porous material was varied from 1 μm to 150 μm.

The obtained polyvinyl butyral porous material was immersed for 10 minutes in frifuryl alcohol to which 2% by weight of para-toluenesulfonic acid was added as a catalyst, and then heated from room temperature to io
The temperature was gradually raised to 0° C. over 8 hours to dry and harden.

In order to increase the amount of furan resin deposited, the porous body after drying and hardening was immersed again in frifuryl alcohol, and the same process was repeated.

The synthetic resin porous body thus obtained was further cured at 150°C for 2 hours and then placed in an electric furnace at 50°C in a nitrogen atmosphere.
Carbonization was carried out by increasing the temperature at 900° C./hr for 1 hour, and then cooling.

The properties of the carbon porous body thus obtained are shown in Table 2.

Table 2 shows that by selecting the furan resin content within an appropriate range, it is possible to obtain a carbon porous body with a large continuous porosity using a polyvinyl acecool synthetic resin porous body with an average pore diameter of 1 μ to 150 μ. .

Furthermore, when the amount of furan resin attached is small, the deformation is large and the average pore diameter of the carbon porous body also tends to become small.

Example 3 In the same manner as in Example 1, a two-thick plate-shaped polyvinylbenzal porous body was prepared by using benzaldehyde instead of formalin.

The porous body had an average pore diameter of 3 μm, an apparent specific gravity of 0.145, and a continuous porosity of 91%.

Methanol is used as a solvent for the polyvinylbenzal porous material in the upper air.

Resole: Novolak-2:1 (Phenol resin AP-106 and 1XAP-1062 manufactured by Komazu Kagaku Kogyo Co., Ltd.)
1 in a phenolic resin solution consisting of a proportion of
It was immersed for 0 minutes.

Para-toluenesulfonic acid was added to the phenol resin solution in an amount of 5% of the solid content of the phenol resin.

After taking out the porous body from the phenol resin solution, it is kept at room temperature to io
It was dried and cured by gradually raising the temperature to o'c over 6 hours, and further cured at 150°C for 1 hour.

The synthetic resin porous body thus obtained was placed in an electric furnace and heated at a rate of 300° C./hr in a nitrogen atmosphere, maintained at a predetermined temperature for 1 hour, and then cooled.

The carbon porous material thus obtained was mixed with concentrated nitric acid/concentrated hydrochloric acid 4/1 (
The sample was immersed in a mixed solution (volume ratio) at 90°C for 72 hours.

The results are shown in Table 3. Table 3 shows that when the phenol resin content is high and the firing temperature is 800° C. or higher, the obtained porous carbon material has excellent chemical resistance.

Example 4 Epoxy resin (Epomic, manufactured by Mitsui Petrochemical Industries, Ltd.) containing a curing agent (HN-2200, manufactured by Hitachi Chemical Co., Ltd.) at a resin concentration of 5 weight □ in the same polyvinyl formal porous body used in Example 1 After impregnating with an acetone solution of R140) and squeezing out the excess solution, it was dried and hardened in a dryer heated to 80°C.

10.5% of epoxy resin was attached to the obtained porous body.

Next, the porous body was impregnated with a methanol solution having a resol resin concentration of 20% by weight in the same manner as in Example 1, and dried and hardened.

The amount of resol resin adhered to the porous body was 57.4%.

In this case, since the epoxy resin was attached to the polyvinyl formal porous material, it did not soften even when impregnated with the resol resin solution, and the drying and curing operation was easy.

Then, it was fired to 1000° C. in the same manner as in Example 1 to obtain a carbon porous body with an apparent specific gravity of 0.235 and a porosity of 81%.

Claims (1)

[Scope of Claims] 1. A resin that can be converted into glassy carbon by thermal decomposition or a resin containing it as a main component is applied to a polyvinyl acecool-based synthetic resin porous body having continuous pores, and then cured, and a non-acid [
A method for producing a porous carbon material, characterized by firing in an arsenic atmosphere. 2. The method for producing a carbon porous body according to claim 1, wherein the polyvinyl acecool based synthetic resin porous body is a polyvinyl formal based synthetic resin porous body or a polyvinyl benzal based synthetic resin porous body. 3. The method for producing a porous carbon material according to claim 1, wherein the resin that can be converted into glassy carbon by thermal decomposition is a phenol resin or a furan resin. 4 The content of vine resin that is converted into glassy carbon by thermal decomposition in the synthetic resin porous body after resin impregnation is 25 to 90% by weight □
A method for producing a porous carbon material according to claim 1. 5. The method for producing a carbon porous body according to claim 1, which comprises firing at 800° C. or higher in a non-oxidizing atmosphere.