JPH04209773A - Method for manufacturing porous glassy carbon material - Google Patents

Abstract

PURPOSE:To provide the carbon material always having good porosity and excellent skeletal strength by continuously producing a sheet from an alpha-cellulose water dispersion containing a specific binder, treating the sheet with a thermosetting resin and subsequently calcination-carbonizing the treated product. CONSTITUTION:The water dispersion of a raw material composition comprising 60-90 pts.wt. of an organic substance containing alpha-cellulose as a main component, 10-40 pts.wt. of a water-soluble paper binder and 1-10 pts.wt. of a water-soluble and thermally volatile binder is continuously processed into a sheet. The sheet is continuously immersed in a thermosetting resin solution having a carbon residue degree of >=40% and subsequently squeezed with rolls. The treated sheet is semi-cured and subsequently calcination-carbonized at a temperature of >=800 deg.C in a non-oxidative atmosphere to provide the objective carbon material. Since the above production process permits the reduction in the cost for the production due to an mass production effect, the carbon material is extremely effective as a material for fuel batteries and secondary batteries requiring not only good heat resistance and corrosion resistance but also low costs.

Description

[Detailed description of the invention]

[00011

[Industrial Application Field] The present invention relates to a method for manufacturing a porous glassy carbon material having good pore properties and excellent skeletal strength with good mass productivity. [0002] [Prior Art] Lightweight, electrically conductive, Porous carbon materials exhibiting excellent properties such as heat resistance and corrosion resistance are useful in fields such as industrial filters, battery electrodes, and adsorbents. [0003] Conventionally, the typical manufacturing method for porous carbon materials has been a process of kneading coke powder with uniform particle size with a carbonizing binder such as tar pitch, followed by crushing, molding, and firing carbonization. However, it is difficult to set the conditions to provide a homogeneous and stable pore structure, and the material has the disadvantage of low strength. [0004] In this regard, a method (Japanese Unexamined Patent Publication No. 50-25808) in which a carbon fiber mixed sheet obtained by paper-making carbon fibers together with pulp and a binder component is impregnated with a thermosetting resin liquid and then subjected to firing carbonization treatment is 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, this method has difficulties in controlling bulk density, pore diameter, porosity, etc., and in addition, there is a problem in that the manufacturing cost increases because expensive carbon fiber is used as a raw material. [0005] For this reason, an organic polymer material or carbonaceous powder is suspended in a sheet made by using an organic fiber for manufacturing carbon fibers instead of carbon fibers and blending pulp, carbonaceous powder, etc. with this to make paper. A method has been proposed in which the material is impregnated with an organic polymeric material and then subjected to firing treatment (Japanese Patent Laid-Open Nos. 61-236664 and 61-236665). However, with this method, many locally occluded voids are formed within the tissue, making it difficult to obtain a homogeneous and controlled pore structure. [00061 The present inventors have attempted to solve the above-mentioned problems, and have developed a process for obtaining a glassy carbonaceous porous material that has both good pore properties and high strength properties. A process of paper-making volatile substances into a sheet, a process of impregnating the sheet with a thermosetting resin solution with a residual carbon content of 40% by weight or more, and a process of converting the sheet after the impregnation treatment into a sheet of 50 to 15% by weight.
A process of semi-curing at a temperature of 0℃, a process of laminating semi-cured sheets and compressing them to a sheet thickness of 70 to 20% while uniformly heating the entire surface, and a process of compressing the compressed sheets in a non-oxidizing atmosphere. We have developed a method for producing porous carbon material that involves a process of firing and carbonizing at a temperature of 800° C. or higher, and have already proposed it in Japanese Patent Application No. 1-321729. [0007]

[Problems to be Solved by the Invention] However, in subsequent research, it was discovered that the above-mentioned prior art has several new problems that must be solved when attempting to implement continuous processing steps for the purpose of mass production. Occurred. That is, when attempting to apply the continuous papermaking method used in industrial paper production lines to the sheeting process, problems with sheet breakage occur frequently during the production line, and the line must be stopped 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, making it impossible to ensure adequate sheet strength during the papermaking stage. ), a slight change in tension can easily lead to tissue destruction. This phenomenon can be alleviated by controlling the papermaking conditions and increasing the sheet density, but in this case, the formation of a homogeneous pore structure is impaired, so continuous resin liquid is added in the post-process. If the impregnation treatment is performed, the impregnated resin will be unevenly distributed, making it impossible to obtain good pore properties. [0008] The object of the present invention is to solve the above-mentioned problems in the prior art, and to create a porous glassy carbon that does not cause sheet breakage even in continuous processes and always has good pore properties and excellent skeletal strength. The purpose of the present invention is to provide a method for mass-producing materials. [0009]

[Means for Solving the Problems] A method for producing a porous vitreous carbon material according to the present invention to achieve the above-mentioned object comprises a method for producing a porous glassy carbon material containing 60 to 90% of an organic material containing α-cellulose as a main component.
A dispersion water having a raw material composition of 10 to 40 parts by weight of a water-soluble papermaking binder and 1 to 10 parts by weight of a water-insoluble and heat-volatile binder is continuously formed into a sheet, and the sheet is formed into a sheet with a residual carbon content. After continuous immersion in a thermosetting resin solution of 40% or more, the sheet is subjected to roll drawing treatment, the treated sheet is semi-cured and laminated, and the molded product is heated at a temperature of 800°C or more in a non-oxidizing atmosphere. [00101 The organic material mainly composed of α-cellulose, which is the main raw material of the present invention, is a filler component of the sheet during paper making, and can be used in addition to ordinary pulp. Rayon pulp containing 90% α-cellulose can be used. In terms of pulp properties, the thickness should be 3 to 10 deniers and the length should be 5 to 10 deniers in order to ensure paper formability and high pore structure.
It is preferable to select one having a fiber shape of mm. [00111 The water-soluble papermaking binder is a component that functions as a binding material for forming sheets in the papermaking process, and for example, softwood pulps such as Japanese red pine, rainbow pine, Sakhalin fir, Japanese fir, and hemlock are 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 provide sufficient strength when the sheet is wet, such as polyvinyl alcohol (vinylon), insoluble starch, microfibrillated pulp, etc. can be used. By using these binders in combination, the strength of the papermaking sheet when wet is increased, and even if continuous papermaking operation is applied, the phenomenon of sheet breakage does not occur. [0013] The blending ratio of the raw materials is 60 to 90 parts by weight of an organic substance mainly composed of α-cellulose, 10 to 40 parts by weight of a water-soluble papermaking binder, and 1 to 10 parts by weight of a water-insoluble and heat-volatile binder. If the blending amount of the binder component with respect to the organic substance is below the above range, paper formability will deteriorate, while if the binder component blend exceeds the above range, it will be difficult to form a porous structure. In particular, the amount of the water-insoluble, heat-volatile binder added as the third component is important; if it is less than 1 part by weight, it will not be possible to secure adequate sheet strength in a wet state, resulting in sheet breakage. It becomes easier and 1 again
If the amount exceeds 0 parts by weight, the porosity, pore diameter, etc. will decrease, making it impossible to obtain the desired porous structure with uniform pore distribution. [0014] The above three-component raw materials are mixed and uniformly dispersed in water, and then continuously formed into a sheet using a continuous paper machine and wound onto a drying roll. [0015] The dry sheet is then set in a processing device having a mechanism for continuously immersing it in a thermosetting resin solution having a residual carbon content of 40% or more via a guide roll, to perform an immersion treatment. The residual carbon content of a thermosetting resin refers to the weight of carbon that remains when the resin is fired at a temperature of 800°C in a non-oxidizing atmosphere. It becomes extremely difficult to improve the strength of the porous glassy carbon material to a practical level. Examples of thermosetting resins having a residual carbon content of 40% by weight or more include phenolic resins, furan resins, polyimide resins, etc. All of these resins are converted into glassy carbon after firing and carbonization, and these thermosetting resins The organic solvent used to make the resin into a solution is selected depending on the type of resin, but organic solvents such as methanol, ethanol, acetone, and methyl ethyl ketone, which have low viscosity, high permeability, and are easily vaporized by heat, are usually selected. be done. If the resin concentration in the solution is less than 5% by weight, the strength properties will deteriorate, and if it exceeds 40% by weight, the viscosity will increase and impregnating properties will be impaired, and pores will be blocked, making it difficult to adjust the porosity and pore diameter. It becomes difficult. Therefore, it is preferable to set the resin concentration in the range of 5 to 40% by weight. [0016] The sheet subjected to the immersion treatment is then passed between two rolls with a predetermined gap and subjected to a roll squeezing treatment to remove excess resin solution and homogenize the impregnated structure. [0017] The sheet after the treatment is Unreacted substances such as moisture and reaction products are volatilized and removed together with the organic solvent component through a dryer maintained at a temperature of 50 to 150°C, and at the same time the resin component supported on the sheet is semi-cured, and then semi-cured. The required number of sheets are laminated, the entire surface is heated uniformly, and the sheets are compressed and laminated under conditions such that the sheet thickness becomes 70 to 20% thinner than before compression, and the compression ratio is 70%.
If the compression ratio is as low as 20%, it is difficult to obtain practical strength performance, and if the compression ratio is as high as 20%, the structure becomes dense and the porosity significantly decreases. Further, it is industrially possible to use a flat heating plate with a built-in heater for homogeneous heating, and to use a hydraulic press or a pneumatic press for the compression means. Although the temperature during molding varies slightly depending on the properties of the resin, it is generally smoothly molded within the range of 80 to 200°C, and at the same time the resin is completely cured. [0018] The molded product laminated in this way is ,
Calcined at a temperature of 800°C or higher in a non-oxidizing atmosphere,
The heat-volatile component is volatilized, and the thermosetting resin component is carbonized and converted into a glassy carbon material. This carbonization process is effective in preventing deformation such as warping when the compact is sandwiched between graphite plates having smooth surfaces. [0019]

[Function] According to the present invention, the water-insoluble and heat-volatile binder, which is the third component of the raw material, increases the adhesive strength between the main raw materials during the papermaking stage and strengthens the sheet to withstand the roll tension of the continuous papermaking process. It completely volatilizes through thermal decomposition during the baking stage, and functions to ensure a good porous structure. The roll squeezing process performed functions to remove excess resin and uniformly support the resin within the sheet structure. [00201 These functions are combined with the inherent effects of forming homogeneous pores and skeletons by organic substances mainly composed of α-cellulose, and forming a glassy carbon structure by carbonizing the thermosetting resin. [00213

[Example] Examples and comparative examples of the present invention will be described below. [0022] Example 1 α-cellulose content 90% or more, thickness 5 denier, length 2
80 parts by weight of 5-city rayon pulp (manufactured by Daiwabo Co., Ltd.), bleached softwood pulp (NB) as a water-soluble papermaking binder
KP) 20 parts by weight and vinylon binder (manufactured by Kuraray Co., Ltd., VPB) as a water-insoluble and heat-volatile binder.
105) Mix 1 part by weight, stir and mix in water to homogeneously disperse, and then use a continuous paper machine to reduce the average pore size to 1.
A continuous sheet with a diameter of 10 μm, a thickness of 0°23 mm, and a width of 1300 μm was molded. The strength of the wet sheet before drying is 45kgf
/cm2, continuous paper making progressed smoothly and no sheet breakage occurred. [0023] The dry sheet is set in a continuous resin dipping device, and a phenol resin with a residual carbon content of 45% is applied via a guide roll.
Sumitomo Durez Co., Ltd., Sumilight Resin PR940]
The sample was continuously passed through a tank filled with a 20% by weight acetone solution for immersion treatment, and then passed between two rolls with a gap of 0.2 mm, and subjected to roll squeezing treatment. [00241Next, the sheet was passed through a dryer kept at 100°C to semi-cure, cut into squares of 1300mm on each side, and 14 sheets were stacked on top of a uniform heating plate adjusted to 120°C. The resin was compression-molded from above using a flat plate until the compression rate reached 65%, and the resin was completely cured. [0025] The obtained molded body was sandwiched between graphite plates having smooth surfaces, transferred to an electric firing furnace, and the surrounding area was covered with a coke backing material, and then fired and carbonized at a temperature of 1000°C. [0026] Various properties of the porous glassy carbon material produced in this way were measured, and the bulk density was 0.49 g/cc, and the porosity (mercury intrusion method, the same hereinafter) was 6.
7%, average pore diameter (mercury intrusion method, the same applies hereinafter) 55 μm,
It exhibited good pore properties and material strength with a bending strength of 270 kgf/cm2, and observation with a scanning electron microscope confirmed that it had a homogeneous porous structure. Further, the product yield in the 10th trial production according to this example was 100%. [0027] Example 2 A porous glassy carbon material was produced under the same process conditions as in Example 1, except that the amount of vinylon binder was changed to 3 parts by weight. The strength of the wet sheet in this case was 49 kgf/cm2, and no sheet breakage was observed during the continuous papermaking process. [0028] The properties of the obtained material are that the bulk density is 0.48 g
/c c, porosity 65%, average pore diameter 54 μm, bending strength 250 kgf/cm2, both the pore structure and material strength were good, and the same microscopic observation results as in Example 1 were obtained. Furthermore, the product yield during the 10th trial production was 100%. [0029] Example 3 A porous glassy carbon material was manufactured under the same process conditions as in Example 1, except that the amount of vinylon binder was changed to 10 parts by weight. The strength of the wet sheet in this case was as high as 53 kgf/c+++2, and there were no troubles during the continuous papermaking process. [00301 The properties of the obtained material are that the bulk density is 0.49g
/CC1 porosity 68%, average pore diameter 567B, bending strength 260 kgf/cm2, both the pore structure and material strength were good, and it was confirmed by microscopic observation that it was a homogeneous porous structure similar to Example 1. In addition, the product yield after 10 trials was 1
It was 00%. [0031] Comparative Example 1 When continuous paper making was carried out in the same process as in Example 1 without blending vinylon binder as a water-insoluble and heat-volatile binder, sheet breakage occurred frequently and paper production became impossible. Ta. When the strength of the wet sheet in this case was measured, it was as low as 21 kgf/cm2. [0032] Comparative Example 2 When the vinylon binder was blended in an amount of 0.5 parts by weight, continuous papermaking was carried out under the same conditions as in Example 1, but the sheet broke and production became difficult. When the strength of the wet sheet in this case was measured, it was 27 kg.
f. It was Cm2. [0033] Comparative Example 3 A porous glass-like carbon material was produced using the same process and conditions as in Example 1, except that the vinylon binder was blended in an amount of 13 parts by weight and the roll drawing process was not applied. The strength of the wet sheet in this case is 57 kgf/cm2
As a result, the continuous paper making process proceeded smoothly. [0034] As a result of measuring the properties of the obtained material, the degree of bulking was 0.51 g/cc, the porosity was 55%, and the average pore diameter was 45 μm.
m, bending strength of 230 kgf/cm2, which shows that the porosity and material strength are lower than those of the examples, and when the structure is observed using a scanning electron microscope, the structure is non-uniform with many pores being crowded. was confirmed. [0035] Comparative Example 4 A porous glass-like carbon material was produced using the same process and conditions as in Example 1, except that the vinylon binder was blended in an amount of 3 parts by weight and the roll drawing process was not applied. The strength of the wet sheet in this case was 46 kgf/cm2, and there were no troubles in the continuous papermaking process. [0036] The obtained material has a bulk density of 0.49 g/CC
1 pore friction 67%, average pore diameter 53μm, bending strength 270
The measurement results for kgf/cn+2 and characteristics were similar to those in the example, but when the structure was observed using a scanning electron microscope, the pores were often clogged, and there were some areas where the porosity was about 40%. Obvious coarse-grained heterogeneity was observed. [0037] [Effects of the Invention] As described above, according to the present invention, a high quality porous vitreous carbon material having both good pore properties and excellent material strength can be produced without trouble through continuous paper making and dipping processes. It can be manufactured without any [0038] Therefore, manufacturing costs can be reduced due to the mass production effect, which is extremely effective for manufacturing members for fuel cells and secondary batteries, which require not only heat and corrosion resistance but also low cost.

Claims (1)

[Claims] Claim 1: Organic substance 6 whose main component is α-cellulose
0 to 90 parts by weight, 10 to 40 parts by weight of a water-soluble papermaking binder, and 1 to 10 parts by weight of a water-insoluble and heat-volatile binder.
A dispersion water having a raw material composition of 2 parts by weight is continuously made into a sheet, and the sheet is continuously immersed in a thermosetting resin solution with a residual carbon content of 40% or more, and then subjected to a roll squeezing treatment. 1. A method for producing a porous glassy carbon material, which comprises semi-curing sheets, laminating them, and firing and carbonizing the molded product at a temperature of 800° C. or higher in a non-oxidizing atmosphere.