JPH0992292A - Manufacture of metal porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing the Fe material based metal porous body having the excellent sintering ability and the excellent strength characteristic. SOLUTION: After coating the surface of a frame of a porous resin core material with the binder resin, the mixture powder, which is formed of Fe powder and the second metal powder smaller than the mean grain diameter of the Fe powder and/or the metal oxide powder, is directly coated before the resin is dried for hardening. Thereafter, heating is performed in the non- oxidization atmosphere.

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 porous metal body mainly used for an electrode substrate of an alkaline secondary battery such as a nickel-cadmium battery, a nickel-zinc battery and a nickel-hydrogen battery.

[0002]

2. Description of the Related Art There are lead storage batteries and alkaline storage batteries as storage batteries used as various power sources. Among them, the alkaline storage battery has been widely used for various portable devices, and the large type for industrial purposes because it is expected to have high reliability and can be made compact and lightweight. In this alkaline storage battery, zinc, iron, hydrogen, etc. are targeted as the negative electrode in addition to cadmium. However, as the positive electrode, an air electrode, a silver oxide electrode, and the like are partially taken up, but in most cases, it is a nickel electrode. The characteristics have been improved from the pocket type to the sintering type, and the sealing has been made possible and the use has expanded.

However, in the ordinary powder sintering method, when the porosity of the substrate is 85% or more, the strength is significantly lowered, so that there is a limit to the filling of the active material, and therefore, there is a limit to increase the capacity of the battery. Therefore, as a substrate having a higher porosity of 90% or more, a foamed substrate or a fibrous substrate has been picked up and put into practical use instead of the sintered substrate. As a method for producing such a porous metal substrate having a high porosity, Japanese Patent Application Laid-Open No. S5-5200 is known.
There are a method by a plating method disclosed in JP-A-7-174484 and a method by a sintering method disclosed in JP-B-38-17554. In the plating method, carbon powder or the like is applied to the surface of the skeleton of a foamed resin such as urethane foam to perform a conductive treatment, and then Ni is electrodeposited by an electroplating method, and then the foamed resin and carbon are eliminated. The method is to obtain a metal porous body.
On the other hand, in the sintering method, slurry metal powder is impregnated onto the skeleton surface of foamed resin such as urethane foam and then heated to sinter the metal powder.

[0004]

As described in the prior art, the application of the metal porous body as the electrode plate for a battery makes a great contribution to the increase in the capacity of the battery. However, in the production of a metal porous body by a plating method as disclosed in JP-A-57-174484, it is necessary to apply carbon as a conductive treatment for electroplating a porous resin core, which is a production process. It is necessary only in the process and eventually burned out, and is not necessary as a porous metal body. Therefore, the application of carbon for the conductive treatment not only increases the cost of the product, but also may affect the quality due to the residual carbon, and therefore its improvement is desired. In addition, Japanese Examined Sho 38-
In the production of the porous metal body by the sintering method as disclosed in Japanese Patent No. 17554, there is no problem as described above, but the steps of slurrying and applying the metal powder and the sintering step are complicated steps. It is difficult to obtain the desired characteristics. There is also a problem that the manufacturing cost is high. Further, Japanese Patent Laid-Open No. 7-6765 proposes a method of obtaining a metal porous body by applying adhesiveness to the skeleton surface of a three-dimensional network structure, depositing metal powder thereon, and sintering the metal powder. ing. However, with this method as it is, it is difficult to densely sinter Fe having poor sinterability in the shape of a porous body, and it is also difficult to strictly control the amount of metal powder adhered. The present invention, in order to solve the above problems, in a method for producing a metal porous body by a sintering method,
It proposes a novel method for obtaining desired electrical characteristics and strength characteristics in a simple process.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventor was able to densely sinter Fe by using a combination of Fe powder and a second powder having a particle size smaller than that of Fe powder. Further, they have found that the amount of Fe deposited on the resin core can be controlled, and have reached the present invention. That is, the method for producing a porous metal body of the present invention is (1) after applying a binder resin to the skeleton surface of a porous resin core body and before the resin is dried and cured, an Fe powder and an average of the Fe powder. A method for producing a porous metal body, which comprises directly applying a mixed powder composed of a second metal powder and / or a metal oxide powder having a particle size smaller than the particle size, and performing heat treatment in a non-oxidizing atmosphere,
(2) Fe powder and Fe powder after the binder resin is applied to the skeleton surface of the porous resin core and before the resin is dried and cured.
A metal characterized by directly applying a mixed powder of a second metal powder and / or a metal oxide powder having a particle size smaller than the average particle diameter of the powder, performing heat treatment in a non-oxidizing atmosphere, and then performing electric Ni plating. A method for manufacturing a porous body.

Examples of the porous resin core used in the present invention include resin foam, resin nonwoven fabric, resin felt, resin mesh and the like. Here, as a method for applying the binder resin to the porous resin core, the porous resin core is impregnated in a liquid obtained by mixing the binder resin with a diluent such as water or an organic solvent, and then using a roll etc. It is possible to use a method of removing those adhering to the substrate, or a method of spraying the above mixed solution on the porous resin core body by a spray or the like. Further, as a method for directly applying the mixed powder composed of the Fe powder and the second metal powder, a method of spraying the mixed powder on the porous resin with an air gun or a method of rocking the porous resin core in the mixed powder, etc. Can be used. According to the method of directly applying the mixed powder as described above, the manufacturing process is significantly simplified as compared with the conventionally used method of applying the slurry in which the metal powder and the binder resin are kneaded. The particle size of the Fe powder used in the present invention is preferably 5 to 100 μm.

As the second metal powder, Fe,
It is preferable to use P, Ge, Si, Ti, Ni simple substance or an alloy powder containing two or more kinds. The second metal oxide powder may be Fe, P, Ge, Si, Ti, N.
It is preferably an oxide containing at least one or more of i. These second powders have a smaller particle size than the Fe powder, and the particle size is preferably 0.5 to 40 μm.
The particle size of the second powder is 1/2 to 1 of the particle size of the Fe powder.
/ 200 is preferable, and the weight ratio of Fe: second powder = 99.8: 0.2 to 0.2: 99.8 is preferable.
By using these second metal powders or metal oxide powders and their mixed powders, it is possible to coat the porous resin with the second powder so as to fill the voids of the Fe powder as shown in FIG. By doing so, the contact area between the powders is increased, so that the sinterability is improved. Furthermore, P, Ge, S
i, Ti, Ni or oxides thereof contribute to the improvement of sinterability by the effect of acting as a sintering aid. By controlling the addition amount of the second metal powder, the adhesion amount of Fe is controlled. It becomes possible.

When the Fe powder is sintered at atmospheric pressure as in the embodiment of the present invention, the sintering process that requires a high temperature and a long time is
According to the method of the present invention, it is possible to lower the temperature and sinter in a short time, which can greatly contribute to the reduction of the sintering cost. further,
Since an extremely dense sintered body can be obtained in the porous body skeleton, it has low electric resistance and excellent strength characteristics.
Usually, the metal porous body of the present invention is used as a battery electrode substrate of an alkaline battery or the like, but in that case, the weight per unit area of the metal porous body has a great influence on the battery performance, so that it can be controlled accurately. Is important. However, when the Fe powder alone is adhered to the porous resin core by the above method, the adhered amount is almost uniquely determined by the particle size of the Fe powder, and therefore the adhered amount cannot be strictly controlled. It will be quite difficult. Therefore, the present inventors have found that when a mixed powder of Fe powder and a second metal powder having an average particle size smaller than that of Fe powder is applied to the porous resin core, the amount of Fe powder deposited can be controlled. It is a thing. That is, by adjusting the ratio of the second metal powder powder in the mixed powder, it becomes possible to adjust the amount of Fe finally attached to the porous resin core. That is, if the amount of Fe deposited is increased by decreasing the mixing ratio of the second powder, the obtained porous metal becomes a porous metal having a low porosity, and the mixing ratio of the second powder is increased. Thus, if the amount of Fe deposited is reduced, the obtained metal porous body becomes a metal porous body having a high porosity.

Next, the porous resin core coated with the mixed powder thus obtained is heat-treated in a non-oxidizing atmosphere to sinter the metal and remove the resin component to obtain a metal porous body. . The heat treatment is 900 to 13
50 ° C. is preferred. If it is 900 ° C or lower, sufficient sintering cannot be achieved, and if it exceeds 1350 ° C, the porous structure cannot be maintained.

As another aspect of the present invention,
The metal porous body obtained by the above method is further charged with electric N
By forming a Ni film by i-plating, a metal porous body having strong corrosion resistance particularly in a strong alkaline solution in an alkaline secondary battery can be obtained. Further, preferably, by performing the heat treatment in a non-oxidizing atmosphere after the electric Ni plating, it is possible to improve the adhesion of the Ni film and reduce the residual stress due to the plating. Here, the heat treatment temperature is preferably 600 ° C. or lower.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 Polyurethane foam having a thickness of 2.5 mm and about 50 pores per inch is made of acrylic resin 60 wt% and water 4
After impregnating the binder resin liquid mixed with 0 wt%, the excess impregnated coating component was removed with a squeeze roll to prepare a binder-coated porous resin core. Next, a mixed powder was prepared by uniformly mixing Fe powder having an average particle size of 80 μm and Fe ₂ O ₃ powder having an average particle size of 1 μm at a weight ratio (%) of 95: 5.

Next, this mixed powder is directly sprayed onto the porous resin core body by an air gun, and the mixed powder is blown to 150 in the air.
It was dried at 0 ° C for 5 minutes. Next, in a hydrogen stream,
Sintering was performed by performing heat treatment for 10 minutes, and an Fe porous body was produced. In addition, as a comparative example, an Fe porous body using only Fe powder having an average particle size of 80 μm was also produced in the same procedure as above. As shown in Table 1 as a result of evaluating the properties of these Fe porous bodies, it is understood that the Fe porous body according to the present invention exhibits excellent properties.

[0013]

[Table 1]

Example 2 A polyurethane resin foam having a thickness of 2.0 mm and about 40 pores per inch was spray-coated with a binder resin solution prepared by mixing 60 wt% of phenol resin and 40 wt% of water, and the binder was applied. A porous resin core body was produced. Next, the porous resin core was shaken in various metal mixed powders shown in Table 2 to apply the metal powder, and then dried at 150 ° C. in the atmosphere for 10 minutes. Next, in a hydrogen stream 12
Heat treatment was carried out at 50 ° C. for 10 minutes to obtain a porous metal body.

[0015]

[Table 2]

Table 3 shows the results of evaluating the characteristics of the obtained porous metal body.

[0017]

[Table 3]

Example 3 Sample 9 of Example ² was plated with Ni at a current density of 10 A / dm ² in a watt bath for electric Ni plating,
A 100 g / m ² Ni coating was formed. After Ni plating, heat treatment was performed at 550 ° C. for 5 minutes in an N ₂ atmosphere. The characteristics of this sample are shown in Table 4.

[0019]

[Table 4]

Next, this sample was subjected to KOH having a specific gravity of 1.3.
Cyclic voltammetry measurements were performed to investigate the corrosion resistance in aqueous solution. The measurement conditions are as follows.

Working electrode: This sample Counter electrode: Ni plate Reference electrode: Hg / HgO Sweeping potential: 0 V (start) → -1.0 V → 0.5 V 0.5 V to -1.0 V (1000 cycles) Sweeping speed: 10 mV / Sec As a result of the measurement, except for the oxygen generation peak near 0.5 V,
Almost no current peak due to oxidation / reduction was observed, demonstrating that it is extremely stable in a strong alkaline solution.

[0022]

As described above, according to the manufacturing method of the present invention, the sintering process can be performed at a low temperature and in a short time, which can contribute to the reduction of the production cost. In addition, the sinterability is improved, and a metal porous body made of a dense sintered body can be formed. The porous metal body has low electric resistance and excellent strength characteristics, and is suitable as an electrode substrate for electricity. Furthermore, the metal porous body plated with Ni is stable in a strong alkaline solution, and is particularly useful as an electrode for alkaline secondary batteries.

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a state in which Fe powder and a second powder are attached to a porous resin core according to the present invention.

Claims (4)

[Claims] 1. A Fe powder after a binder resin is applied to the skeleton surface of a porous resin core and before the resin is dried and hardened, and a second metal powder having a smaller average particle size than the Fe powder and / Alternatively, the method for producing a porous metal body is characterized in that a mixed powder of metal oxide powder is directly applied and heat treatment is performed in a non-oxidizing atmosphere. 2. A Fe powder and a second metal powder having an average particle size smaller than that of the Fe powder after the binder resin is applied to the skeleton surface of the porous resin core and before the resin is dried and hardened. A method for producing a porous metal body, which comprises directly applying a mixed powder of metal oxide powder, performing heat treatment in a non-oxidizing atmosphere, and then performing electric Ni plating. 3. The second metal powder is Fe, P, Ge, S.
The method for producing a metal porous body according to claim 1 or 2, which is a powder of i, Ti, or Ni alone or an alloy powder containing two or more kinds. 4. The second metal oxide powder is Fe, P, G.
The method for producing a metal porous body according to claim 1 or 2, which is an oxide containing at least one of e, Si, Ti, and Ni.