JPH06235033A - Production of three-dimensional network structural body - Google Patents

Abstract

PURPOSE:To provide the process for production of the three-dimensional network structural body which consists of metals, ceramics, etc., and is used for filters, catalyst carriers, batteries, current collectors, etc. CONSTITUTION:A urethane foam having about 3mm thickness is immersed into a tacky adhesive soln. of an acrylic ease of about 5% resin component contg. methyl ethyl ketone as a solvent and after the solvent is removed therefrom by drying for about 10 minutes at about 100 deg.C, a base body is inserted into carbonyl Ni powder and is oscillated, by which the Ni powder is deposited thereon. The base body is thereafter held for about 10 minutes in an atm. atmosphere to dissolve away the urethane foam. the base body is in succession held in a reducing atmosphere where gaseous hydrogen is passed for about 20 minutes at about 1200 deg.C. As a result, the three-dimensional network structural body of the Ni having the shape transferred with the polyurethane foam by sintering of the Ni powder is obtd. The porosity is about 96%. As a result, the three- dimensional network structural body having high strength, less apertures and good air permeability is produced without depending on materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a three-dimensional network structure made of metal, ceramics or the like used for filters, catalyst carriers, battery current collectors and the like.

[0002]

2. Description of the Related Art Methods for producing a three-dimensional network structure include a metal plating method and a powder slurry impregnation / application method. The plating method is disclosed in Japanese Examined Patent Publication No. 47-10524, and synthetic resin foam having a three-dimensional network structure such as urethane foam is subjected to a conductive treatment with carbon or the like, and then a metal such as Ni is plated in a plating tank. The layer is electrodeposited and then fired to decompose and burn off the resin to obtain a three-dimensional network structure of electrodeposited metal on which the shape of the foamed resin is transferred.

The powder slurry impregnation / coating method is disclosed in JP-B-61-534.
No. 17, the synthetic resin foam having a three-dimensional network structure such as urethane foam is immersed in a slurry prepared by mixing a metal powder, a thickening polymer and a solvent, and the metal powder is added to the skeleton of the foam. Is applied and then heat-treated to decompose and burn out the synthetic resin foam and sinter the metal powder to obtain a three-dimensional network structure of metal in which the shape of the foamed resin is transferred. In addition, in the powder slurry coating method, JP-A-62-269
As disclosed in Japanese Patent No. 724, it is possible to obtain a three-dimensional network structure with a non-conductive material such as ceramics by the same method.

[0004]

The plating method is currently used as a practical method. However, when plating an insulating material such as foamed resin, a conductive treatment or a seeder treatment is used as a pretreatment for the plating. The process is complicated because it is necessary. Further, there is a problem that a non-conductive substance such as ceramics and a substance composed of two or more kinds of alloys cannot be obtained, and the material of the three-dimensional network structure is limited to a part of a metal such as Ni or Cu which can be plated. .

The slurry coating method is generally a method in which a powder is suspended in a solution of a high molecular weight organic substance to prepare a slurry and the slurry is impregnated into a substrate. However, if the slurry is not sufficiently stirred, the powder will settle. There was a problem, and when the mixture was agitated too much, the management of the slurry was complicated, such as the inclusion of bubbles. The powder is not limited to metal, but it has the advantage that it can be formed of a material having no conductivity such as ceramics, but the surface tension of the applied slurry makes it easier for the powder to collect from the skeleton of the base to the joint of the skeleton, It is difficult to uniformly impregnate the substrate with the powder. This phenomenon seriously affects the strength of the finished three-dimensional network structure. That is, when a certain amount of powder is applied, the skeleton is thin and the strength is weak. Therefore, in order to thicken the skeleton, a method of increasing strength by increasing the amount of slurry to be impregnated and applied is adopted.

A further problem is that it is easy to form a thin film-like portion (closed portion) that closes the network structure of the substrate. This is a phenomenon that occurs because the slurry tends to form a film and depends largely on the viscosity of the slurry, but even when the polymer in the slurry is removed and the substrate is impregnated with the mixture of powder and solvent, the Aggregation occurs and a closed part is generated.

The present invention provides a novel method for producing a three-dimensional network structure which is not dependent on the material, has a large strength, has a small closed portion, and has good air permeability.

[0008]

According to the present invention, a method for producing a three-dimensional network structure is characterized in that a powder is deposited on the skeleton surface of the three-dimensional network structure to be a substrate, and then heat treatment is performed. Is. That is, the powder is directly applied to the surface of the substrate by a dry method.

The three-dimensional network structure serving as a substrate is a foaming resin having an open cell structure such as urethane foam, or a non-woven fabric, a woven fabric, etc., and the shape is appropriately selected according to the purpose of use. The material is not limited to flammable materials such as resin, but may be metals or ceramics.

Facilitating the deposition of powder on the surface of the base skeleton,
It is preferable to impart tackiness for the purpose of preventing peeling. The tackiness is imparted by applying an acrylic or rubber adhesive solution or an adhesive resin solution such as a phenol resin, an epoxy resin, or a furan resin. In addition, in the case of a resin substrate, it is possible to give tackiness to the substrate itself by plasma treatment or the like.

After imparting tackiness to the skeleton surface of the substrate, the powder is deposited on the skeleton surface by a method such as rocking the substrate in the powder or spraying the powder onto the substrate. This allows the dry powder to be applied directly to the surface of the substrate. The powder is instantly fixed on the surface of the substrate, and unlike the slurry method, the powder does not move on the surface of the substrate during the drying process, so that the powder does not collect at the joint portion of the substrate skeleton. Further, since the powder deposition occurs on the surface of the substrate and does not depend on the thickness of the adhesive layer, the powder deposition amount is uniform over the entire substrate, and when a constant weight of powder is deposited, the strength is high. A three-dimensional mesh structure is obtained. Further, the powder is selectively adhered only to the portion to which tackiness is imparted, and since no solvent is used, agglomeration of the powder particles does not occur, so that a closed portion is not formed unlike the slurry method.

The material of the powder may be any material such as metal, ceramics, carbon and the like, or may be a mixture thereof. The particle size of the powder may be in the range that can be adhered to the surface of the substrate, and is preferably in the range of 0.01 to 100 microns. Further, the shape of the powder is not particularly limited. The deposited powder forms a coating layer, but depending on the application the powder may be partially discontinuous.

After depositing the powder on the substrate, heat treatment is performed. The heat treatment is mainly for the purpose of sintering the powder, but when a foamed resin is used for the substrate, the decomposition temperature of the resin is generally lower than the sintering temperature of the powder, so the substrate is decomposed. To be removed. As the heat treatment conditions, the treatment temperature, time and atmosphere are appropriately selected depending on the substrate used and the properties of the powder. When a material such as foamed resin that is burnt down by heating is used for the substrate and a metal is used for the powder, it is preferable to change the atmosphere between the burning atmosphere of the substrate and the reducing atmosphere when sintering the metal powder. When oxide ceramics or platinum powder is used as the powder, there is no problem of oxidation, so heat treatment can be performed in an oxidizing atmosphere.

Further, a three-dimensional network structure having an arbitrary skeleton thickness can be obtained by repeating the step of imparting tackiness and the step of applying powder.

After the powder is deposited and before the heat treatment, the substrate is wetted with a liquid and then dried, whereby the powder can be densely deposited on the substrate skeleton. Therefore, after heat treatment, a three-dimensional network structure having high strength can be obtained. This is to wet the powder on the surface of the substrate with a liquid and to agglomerate the powder by the surface tension of the liquid in the drying process. The method for wetting the powder is performed by immersing the substrate in a liquid, spraying the liquid on the substrate, or the like. Any kind of liquid may be used as long as it does not reduce the adhesive force between the substrate and the powder, but water is the most practical. Further, by adding a binder such as a thickening polymer such as methyl cellulose or polyvinyl alcohol to this liquid, the strength after firing can be further improved.

[0016]

【Example】

Example 1 As a substrate having a three-dimensional network structure, a polyurethane foam having a thickness of 3 mm (trade name: Everlite SF, manufactured by Bridgestone Corporation) was used. This polyurethane foam was dipped in an acrylic adhesive solution containing methyl ethyl ketone as a solvent and having a resin content of 5%, and then the excess solution was removed through a roll and the adhesive was applied to give a stickiness to the surface of the substrate skeleton. . After drying at 100 ° C. for 10 minutes to remove the solvent, the substrate was inserted into the carbonyl Ni powder and shaken to deposit the Ni powder. Then 500 ° C, 10
The substrate was kept for 1 minute in the air atmosphere to decompose and remove the polyurethane foam of the substrate. Then, it was kept at 1200 ° C. for 20 minutes in a reducing atmosphere in which hydrogen gas was passed. As a result, Ni powder is sintered and Ni having a shape in which polyurethane foam is transferred
A three-dimensional network structure a of The porosity was 96%.

Example 2 A Ni three-dimensional network structure b was obtained in the same manner as in Example 1 except that the step of immersing in an aqueous solution after the deposition of the carbonyl Ni powder and drying at 100 ° C. for 30 minutes was added. 96% porosity
Met.

Comparative Example The same polyurethane foam as in Example 1 was used, and this polyurethane foam was dip-coated with a Ni powder slurry prepared by mixing a composition having the following composition for 30 minutes in a ball mill to remove excess Ni powder slurry. . After drying at 100 ° C. for 30 minutes to remove water, the substrate was kept at 500 ° C. for 10 minutes in the air atmosphere to decompose and remove the polyurethane foam as the base material. Then, the atmosphere was maintained in a reducing atmosphere in which hydrogen gas was flown at 1200 ° C. for 20 minutes. As a result, a Ni three-dimensional network structure c having a shape in which Ni powder was sintered and polyurethane foam was transferred was obtained. The porosity was 96%. Slurry composition Powder (carbonyl Ni powder) 50% by weight Binder (methylcellulose) 2% by weight Water 48% by weight

FIG. 1 shows the relationship between tensile stress and elongation of the Ni three-dimensional network structures a, b and c obtained in Examples 1, 2 and Comparative Example. The end of the curve in the figure is the break point.
The three-dimensional network structures of Examples 1 and 2 have a tensile strength more than doubled as compared with the three-dimensional network structures produced in Comparative Example, and according to the present invention, a method of applying a powder slurry. It can be seen that a three-dimensional mesh structure having a higher strength than that of Example 1 can be obtained. Further, comparing Examples 1 and 2, the tensile strength of Example 2 is increased by about 20%, and it can be seen that the strength is further improved by wetting with the liquid after the powder deposition.

The Ni three-dimensional network structures obtained in Example 1 and the comparative example were compared by a surface morphological observation photograph by a scanning electron microscope. The three-dimensional network structure obtained in Example 1 was a comparative example. The thickness of the skeleton was more uniform than that of the obtained three-dimensional network structure. According to the present invention, it is considered that the number of minute defects is small and the strength is higher than that of the slurry method. The three-dimensional network structure obtained in Comparative Example had many closed parts, but the three-dimensional network structure obtained in the present invention had few closed parts and had good air permeability, and when used in a filter or the like, pressure The loss can be reduced.

Example 3 The same polyurethane foam as in Example 1 was used. This urethane foam was dipped in an acrylic pressure-sensitive adhesive solution having a resin content of 5%, and the pressure-sensitive adhesive was applied to the surface of the base skeleton to give tackiness. After drying at 100 ° C. for 10 minutes, zinc oxide was applied. Then, it was held at 1300 ° C. for 2 hours in an oxidizing atmosphere under the atmosphere. As a result, a three-dimensional network structure of zinc oxide having a shape in which zinc oxide powder was sintered and urethane foam was transferred was obtained. This three-dimensional mesh structure 10
ZnO: Zn after reduction for 1 hour in a hydrogen-containing atmosphere at 00 ° C
A three-dimensional network structure of phosphor was obtained. When the structure was irradiated with ultraviolet rays, the surface area was large, and when the ultraviolet rays reached the inside of the structure, uniform blue-green light emission was obtained with high efficiency.

[0022]

As described above, according to the present invention, not only metals but also non-conductive ceramics have high strength and high porosity by a simple method of depositing powder on a substrate and then performing heat treatment. It is possible to obtain a three-dimensional mesh structure of

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between tensile stress and elongation of three-dimensional network structures obtained in Examples and Comparative Examples.

Claims (6)

[Claims] 1. A method for producing a three-dimensional network structure, characterized in that a powder is deposited on the skeleton surface of the three-dimensional network structure as a substrate and heat treatment is performed. 2. The production of a three-dimensional network structure according to claim 1, wherein the three-dimensional network structure to be the base is burned and removed by heat treatment, and the three-dimensional network structure to be the base is burned and removed by heat treatment. Method. 3. The powder is adhered to the surface of a skeleton of a three-dimensional network structure, which is a substrate, after the tackiness is imparted.
Alternatively, the method for producing the three-dimensional network structure according to the item 2. 4. The method for producing a three-dimensional network structure according to claim 2 or 3, wherein the heat treatment includes removing the three-dimensional network structure serving as a substrate in an oxidizing atmosphere. 5. The method for producing a three-dimensional network structure according to claim 1, wherein the heat treatment includes sintering the powder in a reducing atmosphere. 6. The method for producing a three-dimensional network structure according to claim 1, wherein the deposited powder is wetted with a liquid after the powder deposition and before the heat treatment.