JP2607397B2 - Method for producing porous glassy carbon material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mass-producing a porous glassy carbon material having good porosity and excellent skeletal strength.

[0002]

2. Description of the Related Art Porous carbon materials exhibiting excellent properties such as light weight, conductivity, heat resistance and corrosion resistance are useful in application fields such as industrial filters, battery electrodes and adsorbents.

Conventionally, a typical production technique of a porous carbon material includes a process in which coke powder having a uniform particle size is kneaded with a carbonizable binder such as tar pitch, followed by pulverization, molding and calcining. However, it is difficult to set conditions for providing a uniform and stable pore structure, and the material strength is low.

In this regard, a method of impregnating a thermosetting resin liquid into a carbon fiber mixed sheet obtained by paper-making carbon fibers together with pulp and a binder component, followed by calcining and carbonizing (Japanese Patent Application Laid-Open No. 50-25808) has been proposed. Since the carbon fibers form a reinforcing skeleton and the thermosetting resin is converted into a glassy carbon structure, the material strength can be effectively improved. However, in this method, bulk density, pore size,
There is a problem in controlling the porosity and the like, and in addition, there is a problem that the production cost rises because expensive carbon fiber is used as a raw material.

[0005] For this reason, organic fibers for carbon fiber production are used in place of carbon fibers, and pulp, carbonaceous powder, etc. are blended into the sheet and the organic polymer substance or carbonaceous powder is suspended in the sheet. (Japanese Patent Application Laid-Open Nos. 61-23664 and 61-23666)
No. 5) has been proposed. However, in this method, since a locally closed void portion is formed in the tissue, it is difficult to obtain a uniform and controlled pore structure.

The present inventors have attempted to solve the above-mentioned problems, and as a process for obtaining a vitreous carbonaceous porous material having both good porosity and high strength properties, α-cellulose is mainly used. Paper-making the heat-volatile substance into a sheet, impregnating the sheet with a thermosetting resin solution having a residual carbon ratio of 40% by weight or more, and semi-curing the impregnated sheet at a temperature of 50 to 150 ° C. Laminating the semi-cured sheets and compressing them so that the sheet thickness becomes 70 to 20% while uniformly heating the entire surface; and 800 ° C in a non-oxidizing atmosphere.
A method for producing a porous carbon material comprising a step of calcining and carbonizing at the above temperature has been developed and has already been proposed as Japanese Patent Application No. 1-321729.

[0007]

However, in the subsequent research, there are some new problems that must be solved when trying to carry out continuous processing steps for mass production in the prior art. Occurred. That is, when the continuous paper making method, which is regarded as a production line for industrial paper, is applied to the sheet forming process, troubles of sheet breakage occur frequently in the middle of the production line, and it is necessary to stop the line each time. The cause of sheet breakage is that the sheet immediately after papermaking contains a large amount of water, and the binder used is also water-soluble, so that an appropriate sheet strength cannot be secured at the papermaking stage. ) Is based on the phenomenon that a slight change in tension easily leads to tissue destruction. Such a phenomenon can be mitigated by controlling the papermaking conditions and increasing the sheet density.However, in this case, since the formation of a uniform pore structure is impaired, a continuous When the impregnation treatment is performed, uneven distribution of the impregnated resin occurs, so that it is not possible to obtain good pore properties.

An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a porous glassy carbon which always has good porosity and excellent skeletal strength without causing sheet breakage even in a continuous process. An object of the present invention is to provide a method for manufacturing a material with good mass productivity.

[0009]

In order to achieve the above-mentioned object, a method for producing a porous glassy carbon material according to the present invention comprises: Dispersed water of a raw material composition comprising 10 to 40 parts by weight of a binder and 1 to 10 parts by weight of a water-insoluble and heat-vaporizable binder is continuously formed into a sheet, and the sheet is subjected to a thermal effect of a residual carbon ratio of 40% or more. After continuous immersion in an aqueous resin solution, roll squeezing treatment is performed, the treated sheet is semi-cured, laminated and formed, and the formed body is calcined and carbonized at a temperature of 800 ° C or more in a non-acidic atmosphere. The feature of.

The organic material mainly composed of α-cellulose as a main raw material of the present invention is used as a filler component of a sheet during papermaking. In addition to ordinary pulp, rayon pulp containing 90% of α-cellulose Can be used. As the pulp properties, it is preferable to select a pulp having a fiber shape of 3 to 10 deniers and 5 to 10 mm in length from the viewpoint of ensuring papermaking properties and high pore structure.

The water-soluble papermaking binder is a component that functions as a binder for sheet formation in the papermaking process. For example, softwood pulp such as red pine, spruce pine, fir pine, larch, fir, and shiga is preferably used.

[0012] The water-insoluble and heat-volatile binder is:
A third component added to reinforce the function of the water-soluble binder and impart sufficient strength when the sheet is in a wet state, such as polyvinyl alcohol (vinylon), insoluble starch, and microfibrillated pulp. Etc. can be used. By using these binders in combination, the strength of the papermaking sheet when wet is increased,
Even when a continuous papermaking operation is applied, the breakage of the sheet does not occur.

The mixing ratio of the raw materials is 60 to 90 parts by weight mainly composed of α-cellulose, 10 to 10 parts of a water-soluble papermaking binder.
40 parts by weight and water-insoluble and heat-vaporizable binder 1
Set to ~ 10 parts by weight. If the amount of the binder component relative to the organic substance is below the above range, the papermaking moldability will be poor, while if the amount of the binder component exceeds the above range, it will be difficult to form a porous structure. Particularly, the amount of the water-insoluble and heat-vaporizable binder added as the third component is important. If the amount is less than 1 part by weight, it is not possible to secure an appropriate sheet strength in a wet state, and the sheet breaks. When the content exceeds 10 parts by weight, the porosity, the pore size, and the like decrease, and it becomes impossible to obtain a porous structure having a uniform target pore distribution.

The above three-component raw materials are mixed and uniformly dispersed in water, continuously made into paper using a continuous paper making apparatus, formed into a sheet, and wound around a drying roll.

The dried sheet is then set in a processing apparatus having a mechanism for continuously immersing it through a guide roll in a thermosetting resin solution having a residual carbon ratio of 40% or more, and immersion treatment is performed. The residual carbon ratio of a thermosetting resin is 80% under non-oxidizing atmosphere.
Refers to the weight of carbon remaining when fired at a temperature of 0 ° C. When the residual carbon ratio is less than 40%, it is extremely difficult to improve the strength of the resulting porous glassy carbon material to a practical level. Becomes Examples of the thermosetting resin having a residual carbon ratio of 40% by weight or more include a phenol resin, a furan resin, and a polyimide resin, all of which are converted to glassy carbon after firing and carbonization. The organic solvent used to form a solution of these thermosetting resins is selected depending on the type of the resin. Usually, organic solvents having a low viscosity, high permeability, and easily heat-evaporating properties such as methanol, ethanol, acetone, and methyl ethyl ketone are used. A solvent is selected. If the resin concentration in the solution is less than 5% by weight, the strength characteristics decrease, and if it exceeds 40% by weight, the viscosity increases, impairing the impregnation property, and the pores are blocked, and the porosity and the pore size are adjusted. It will be difficult. Therefore, it is preferable to set the resin concentration in the range of 5 to 40% by weight.

The immersed sheet is then passed between two rolls with a predetermined gap and subjected to roll squeezing to remove excess resin solution and homogenize the impregnated structure.

The processed sheet is passed through a dryer maintained at a temperature of 50 to 150 ° C. to volatilize and remove unreacted substances such as moisture and reaction products together with an organic solvent component, and simultaneously remove a resin component supported on the sheet. Semi-cured. Next, while laminating the required number of semi-cured sheets and uniformly heating the entire surface, the sheets are compressed and laminated and molded under conditions such that the sheet thickness is reduced to a range of 70 to 20% as compared with that before compression. At a low compression ratio such that the compression ratio exceeds 70%, practical strength performance is difficult to obtain,
At a high compression ratio of less than 20%, the structure becomes dense and the porosity is greatly reduced. It is industrial to use a flat heating plate with a built-in heater for the homogeneous heating and to use a hydraulic press or a pneumatic press for the compression means. The molding temperature varies slightly depending on the properties of the resin.
It is molded smoothly in the range of 80 to 200 ° C, and at the same time, the resin is completely cured.

[0018] The molded product thus formed by lamination is
It is baked in a non-oxidizing atmosphere at a temperature of 800 ° C. or higher to volatilize the heat-volatile component and carbonize the thermosetting resin component to be converted into a glassy carbon material. This carbonization step has an effect of preventing deformation such as warpage when the formed body is sandwiched between graphite plates having a smooth surface.

[0019]

According to the present invention, the water-insoluble and heat-vaporizable binder, which is the third component of the raw material, enhances the adhesive force between the main raw materials in the papermaking stage and withstands the roll tension in the continuous papermaking process. In the firing step, it is thermally decomposed to completely volatilize, and functions to secure a favorable porous structure. Further, the roll squeezing treatment performed as a step after the thermosetting resin solution is continuously immersed in the papermaking sheet has a function of removing excess resin and uniformly supporting the resin in the sheet structure.

These functions are combined with the essential functions of forming uniform pores and skeletons by an organic substance containing α-cellulose as a main component, and forming a glassy carbon structure by carbonization of a thermosetting resin. Thus, it is possible to continuously produce a porous glassy carbon material having excellent material strength while having uniform and fine air permeability.

[0021]

EXAMPLES Examples of the present invention and comparative examples will be described below.

Example 1 α-cellulose content of 90% or more, thickness 5 denier, length 25 mm
80 parts by weight of rayon pulp (manufactured by Daiwa Spinning Co., Ltd.), bleached softwood pulp (NBKP) as a water-soluble papermaking binder
20 parts by weight and 1 part by weight of a vinylon binder (VPB105 manufactured by Kuraray Co., Ltd.) as a water-insoluble and heat-vaporizable binder were mixed, stirred and mixed in water, homogeneously dispersed, and then averaged using a continuous paper machine. Pore diameter 110μm, thickness 0.23m
m, a continuous sheet having a width of 1300 mm was formed. The strength of the wet sheet before drying was 45 kgf / cm ² , continuous papermaking proceeded smoothly, and no breakage of the sheet occurred.

The dried sheet is set in a continuous resin dipping apparatus, and a phenol resin (Sumilite Resin PR940, manufactured by Sumitomo Durez Co., Ltd.) having a residual carbon ratio of 45% is passed through a guide roll.
It was immersed by continuously passing it through a tank filled with a 20% by weight acetone solution, followed by roll squeezing between two rolls adjusted to a gap of 0.2 mm.

Next, the sheet was passed through a drier maintained at 100 ° C., semi-cured, cut into squares of 1300 mm on a side, and 14 sheets were laminated to form a soaking plate adjusted to 120 ° C. The resin was completely cured by being compression-molded from above on a flat plate until the compression ratio reached 65%.

The obtained molded body was sandwiched between graphite plates having a smooth surface, transferred to an electric firing furnace, and the periphery thereof was covered with a coke packing material, and then fired and carbonized at a temperature of 1000 ° C.

Various properties of the porous glassy carbon material thus manufactured were measured.
0.49 g / cc, porosity (mercury intrusion method, the same applies hereinafter) 67%, average pore diameter (mercury intrusion method, the same applies hereinafter) 55 μm, bending strength 270 k
It exhibited good pore properties and material strength of gf / cm ^2, and it was confirmed by observation with a scanning electron microscope that it had a homogeneous porous structure. In addition, the product yield after 10 trial productions in this example was 100%.

Example 2 A porous glassy carbon material was produced under the same process conditions as in Example 1 except that the amount of the vinylon binder was changed to 3 parts by weight. In this case, the strength of the wet sheet was 49 kgf / cm ² , and no breakage of the sheet was observed in the continuous papermaking process.

The properties of the material obtained are: bulk density 0.48 g / cc,
The porosity was 65%, the average pore diameter was 54 μm, the bending strength was 250 kgf / cm ² , the pore structure and the material strength were good, and the same microscopic observation results as in Example 1 were obtained. The product yield after 10 trial productions was 100%.

Example 3 A porous glassy carbon material was produced under the same process conditions as in Example 1 except that the amount of the vinylon binder was changed to 10 parts by weight. In this case, the strength of the wet sheet was as high as 53 kgf / cm ^2, and there was no trouble in the continuous papermaking process.

The properties of the material obtained are: bulk density 0.49 / cc,
The porosity was 68%, the average pore diameter was 56 μm, the bending strength was 260 kgf / cm ² , the pore structure and the material strength were good, and it was confirmed by microscopic observation that the porous structure was homogeneous as in Example 1. The product yield after 10 trial productions was 100%.

Comparative Example 1 Continuous papermaking was carried out in the same process as in Example 1 without blending a vinylon binder as a water-insoluble and heat-volatile binder. . When the strength of the wet sheet in this case was measured, it was as low as 21 kgf / cm ² .

Comparative Example 2 Continuous papermaking was carried out under the same conditions as in Example 1 except that the amount of the vinylon binder was changed to 0.5 part by weight. As a result, the sheet was broken and production was difficult. When the strength of the wet sheet in this case was measured, 27 kgf /
It was cm ^2.

Comparative Example 3 A porous glassy carbon material was produced by the same process and conditions as in Example 1 except that the blending amount of the vinylon binder was 13 parts by weight and the roll drawing treatment was not applied.
In this case, the strength of the wet sheet was as high as 57 kgf / cm ^2, and the continuous paper making process proceeded smoothly.

As a result of measuring the properties of the obtained material, the bulk density was 0.51 g / cc, the porosity was 55%, the average pore diameter was 45 μm, and the bending strength was
The porosity and material strength were reduced to 230 kgf / cm ² as compared with the examples, and the structure was observed by scanning electron microscope. As a result, many pores were clogged, and it was confirmed that the structure was heterogeneous.

Comparative Example 4 A porous glassy carbon material was produced using the same process and conditions as in Example 1 except that the blending amount of the vinylon binder was 3 parts by weight and the roll drawing treatment was not applied. In this case, the strength of the wet sheet was 46 kgf / cm ² , and there was no trouble in the continuous papermaking process.

The obtained material has a bulk density of 0.49 g / cc and a porosity.
Although the measurement results were equivalent to those of the example with 67%, an average pore diameter of 53 μm, and a bending strength of 270 kgf / cm ² , the pores were often clogged by microscopic observation with a scanning electron microscope. There was a place where the rate was about 40%, and clear tissue heterogeneity was recognized.

[0037]

As described above, according to the present invention, a high quality porous glassy carbon material having both good porosity and excellent material strength is produced without trouble through a continuous paper making and dipping process. be able to.

Accordingly, since the production cost can be reduced by mass production curing, it is extremely effective for producing members for fuel cells and secondary batteries which require cost reduction in addition to heat resistance and corrosion resistance.

Claims (1)

(57) [Claims] An organic substance comprising α-cellulose as a main component.
~ 90 parts by weight, a water-soluble paper binder 10 to 40 parts by weight and a water-insoluble and heat-vaporizable binder 1 to 10 parts by weight of the dispersed water of the raw material composition to form a sheet by continuous paper making,
The sheet is continuously immersed in a thermosetting resin solution having a residual carbon ratio of 40% or more, and then subjected to roll squeezing treatment. The treated sheet is semi-cured to form a laminate, and the molded body is subjected to a non-oxidizing atmosphere.
A method for producing a porous glassy carbon material, characterized by firing and carbonizing at a temperature of 800 ° C or higher.