KR100360559B1 - Process for the production of extra fine powder of Cobalt - Google Patents

Abstract

The present invention relates to a method for producing cobalt metal powder which can be used for powder metallurgy, carbide tools, diamond tools, and powder metallurgy.

The present invention relates to a method for producing a high-purity ultrafine, high specific surface area cobalt metal powder which is used as a cobalt hydroxide (CoOOH) cobalt raw material, as a binder material for cemented carbide tools, diamond tools or powder metallurgy. (1) Cobalt hydroxide oxide is added to an acid such as hydrochloric acid, sulfuric acid, or nitric acid so that the cobalt ion concentration in the solution is within 5 to 25% and heated and dissolved at a temperature in the range of 50 to 100 ° C. Addition melting step; (2) a precipitation step of generating a carboxylic acid-transition metal salt by adding a carboxylic acid salt consisting of an alkali metal salt or an alkaline earth metal salt of carboxylic acid, such as oxalic acid or formic acid, to the solution obtained in the addition dissolution step; (3) sediment recovery step of separating and filtering the precipitate obtained in the precipitation step; And (4) reducing the dried precipitate by heating it in multiple stages of three to five stages in a temperature range of 200 to 800 ° C. in an inert or reducing atmosphere.

Therefore, the present invention has the effect of providing a method for producing a high purity, high specific surface area ultra fine cobalt metal powder from cobalt hydroxide oxide, and is particularly expensive cobalt metal suitable for use in carbide tools, diamond tools and powder metallurgy. It is effective to make powder.

Description

Process for the production of extra fine powder of Cobalt}

The present invention relates to a method for producing cobalt metal powder which can be used for powder metallurgy, carbide tools, diamond tools, and powder metallurgy. More specifically, the present invention provides a high-purity ultrafine, high specific surface area cobalt metal powder which is used as a cobalt hydroxide (CoOOH) cobalt raw material as a cemented carbide tool, a binder material of diamond tool or an additive element powder of powder metallurgy. It is about. Here, the binder material means an adhesive used to firmly bond cemented carbide tools to each other, and ultrafine cobalt metal powder of high purity is used. In addition, the powder of metallurgical added element powder may be used to produce a carbide tool made of diamond, and although the quality is somewhat lower than that of a pure carbide tool, it is very economically advantageous.

Cobalt metal powder that can be used in such carbide tools, diamond tools and powder metallurgy has not been used until now, and is used in some fields, but for this purpose, the method of manufacturing pure cobalt metal powder has been developed. It is not reported much because it belongs to and belong to some parts of the world. In addition, in order to enhance the solid-solid reactivity of the cobalt metal powder, ultrafine particle size of less than 1 micron and specific surface area having a diameter ratio of 5 or more are required. Since the proper ratio must be maintained, the optimal manufacturing process has not yet been established.

Known methods for producing cobalt metal powders include a method of directly heating and reducing cobalt oxide in a hydrogen atmosphere, a method of preparing a cobalt salt by dissolving cobalt metal and reacting with oxalic acid or formic acid, and then thermally decomposing it in a neutral atmosphere. The process for preparing basic cobalt carbonate and hydrogen reduction is known. The production method for directly reducing the cobalt oxide in a hydrogen atmosphere is not only high in manufacturing cost but also high production cost because the high temperature holding is required for oxide reduction. The average particle size of the cobalt metal powder is 5 microns or more, and the particle shape also exhibits a spherical shape, and thus, the solid-solid reactivity between the cobalt metal powder and other metal powders is inferior. In addition, it is difficult to maintain a proper ratio of α phase and β phase, which are crystal structures of cobalt metal. Second, a method of preparing a cobalt salt by dissolving cobalt metal and reacting with oxalic acid or formic acid and heating and decomposing it in a neutral atmosphere The ultrafine cobalt metal powder of 1 micron or less can be manufactured, but the purity of the ultrafine cobalt metal powder that is finally manufactured is because the purity of the cobalt metal used as a raw material is low and it contains a lot of impurities such as Si, Ni, and K. The method of preparing the basic cobalt carbonate salt and reducing the hydrogen has problems in safety during operation such as the use of carbon dioxide gas to prepare the basic cobalt carbonate salt, and the basic cobalt carbonate salt is extremely fine in the intermediate stage of synthesis. Due to the possibility of precipitation onto the cake, the process is difficult and yields There is a point.

The purpose of the present invention is to change the titration ratios of α and β phases, which are crystal structures of cobalt metal, by using high-purity cobalt hydroxide oxide raw materials and high-purity ultrafine particles, and having a diameter-to-length ratio of 5 or more. The present invention provides an optimal method for producing high purity ultrafine, high specific surface area cobalt metal powder suitable for cemented carbide, diamond tool, and powder metallurgy, which improves the solid-solid reactivity between cobalt metal powder and other metal powders.

In the cobalt hydroxide oxide (CoOOH) according to the present invention, a method for producing cobalt metal powder having high purity and ultrafine high specific surface area includes (1) adding cobalt hydroxide oxide in an aqueous solution by adding an acid such as hydrochloric acid, sulfuric acid, or nitric acid. An addition dissolution step of dissolving the cobalt ion concentration in 5 to 25% and heating at a temperature in the range of 50 to 100 ° C; (2) a precipitation step of generating a carboxylic acid-transition metal salt by adding a carboxylic acid salt consisting of an alkali metal salt or an alkaline earth metal salt of carboxylic acid, such as oxalic acid or formic acid, to the solution obtained in the addition dissolution step; (3) sediment recovery step of separating and filtering the precipitate obtained in the precipitation step; And (4) reducing the dried precipitate by heating it in multiple stages of 3 to 5 steps in a temperature range of 200 to 800 ° C. in an inert or reducing atmosphere.

Hereinafter, the present invention will be described in detail with reference to specific examples.

The cobalt hydroxide oxide used as the cobalt powder raw material can be liquefied by adding and dissolving an acidic aqueous solution. This liquefaction allows the preparation of intermediates in the cobalt metal powder preparation by precipitating the cobalt metal salt in subsequent precipitation steps. In this addition dissolution step, one selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid or a mixture of two or more thereof may be used, and an appropriate amount of water calculated to adjust the cobalt ion concentration in the solution to be prepared may be added. In addition, the mixture of cobalt hydroxide oxide and acid may be heated to a temperature in the range of 50 to 100 ℃ to promote dissolution. The amount of acid used in the addition dissolution step may be 1.0 to 2.0 equivalents, preferably 1.0 to 1.5 equivalents in the valence equivalent ratio of the cobalt metal. When the amount of the acid is less than 1.0 equivalent in the valence equivalent ratio of the cobalt metal, there may be a problem that the metal components including cobalt is not sufficiently dissolved, on the contrary, more than 2.0 equivalent is added to the excess acid is precipitated step Inhibit precipitation and reduce the recovery rate of cobalt metal and increase the acidity of the remaining reaction filtrate to complicate the wastewater treatment process of the reaction filtrate.

In the precipitation step, a carboxylic acid salt such as oxalic acid or formic acid is added to the solution obtained in the acid dissolution step to generate a cobalt-carboxylate by adding a carboxylic acid composed of an alkali metal salt or an alkaline earth metal salt of an acid. In order to increase the recovery of cobalt-carboxylate, an aqueous ammonia solution may be added at 0 to 50%, preferably 2 to 15%. The mixture of the two solutions in this step is maintained at a temperature in the range of 20 to 120 ° C., preferably 40 to 100 ° C. to induce a sufficient reaction of cobalt-carboxylate, and then the reaction filtrate is sufficiently cooled to room temperature. The recovery rate of cobalt ions remaining in the reaction filtrate can be increased. At this time, when the temperature is below 40 ° C, cobalt compounds such as cobalt hydroxides precipitate and inhibit the reactivity. If the temperature is above 100 ° C, the concentration of cobalt, organic acid, and ammonia water in the aqueous solution increases, resulting in low reactivity. There may be problems.

In the precipitation recovery step, the precipitated cobalt-carboxylate precipitate is filtered, washed, separated, and dried, which is the same as or similar to a conventional precipitate recovery method, and is easy for a person having ordinary knowledge in the art. It can be understood. At this time, the cleaning operation is usually enough about two times, but in order to further reduce the impurities incorporated into the product, it may be performed by increasing the number of cleaning.

The precipitate obtained in the precipitation recovery step is reduced by heating in two to four stages in a range of 200 to 800 ° C., preferably 300 to 600 ° C., in an inert atmosphere or a reducing component atmosphere, thereby reducing the cobalt metal having a desired particle size and crystal structure. You get a powder. At this time, when the reduction temperature is less than 200 ℃, the pyrolysis reaction is difficult to occur and difficult to recover as a metal powder. On the contrary, when the reduction temperature is higher than 800 ℃, a powder having a large particle size is obtained by the cross-linking reaction between the reduced metal powders. In addition, the crystal structure of the cobalt metal powder is all composed of β phase which is a high temperature phase, and thereafter, there may be a problem in that it cannot be used as a desired carbide tool or diamond tool. Therefore, reducing the pyrolytic reduction temperature of cobalt-carboxylate in two to four steps in the range of 300 to 600 ° C. is cobalt when used as a cemented carbide or diamond tool for cobalt metal powders obtained by reduction of cobalt-carboxylate. This is to adjust the composition ratio of the low-temperature α phase and the high-temperature phase β, which are crystal structures of metals, at an appropriate ratio. Pyrolytic reduction of cobalt-carboxylate can be sufficiently cobalt metal powder by pyrolytic reduction in the range of 350 to 800 ° C. The cobalt metal powder pyrolyzed and reduced by the single stage treatment may have a low temperature or a high temperature single phase crystal. In particular, the reduction of the first stage to a temperature of less than 350 ℃ has the disadvantage that the surface activity of the pyrolytically reduced cobalt metal powder is turned on and easily re-oxidized, and the thermal decomposition reduction of cobalt-carboxylate when the first stage pyrolysis is reduced to a temperature above 700 ℃ Although the speed is high, the grain size of the cobalt metal powder obtained is large and the shape is easily changed to spherical shape.

Cobalt hydroxide oxide used in the present invention is a high-purity cobalt raw material containing a minimum of impurity components in the raw material state, the addition dissolution is easier than other raw materials, and is particularly suitable for the production of cobalt metal powder.

Hereinafter, preferred examples and comparative examples of the present invention will be described. The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

<Example 1>

300 g of cobalt hydroxide oxide was added to a 3 L reactor together with 950 ml of 35% aqueous hydrochloric acid solution and dissolved for a sufficient time while heating to 90 ° C. to prepare a cobalt chloride aqueous solution having a cobalt concentration of 20% in an aqueous solution. Meanwhile, 400 g of oxalic acid and 400 ml of ammonium hydroxide were added to 900 ml of water, and dissolved in a sufficient time while heating to 90 ° C. to prepare a neutralized oxalic acid solution. After the two solutions were mixed, the reaction was carried out at 90 ° C. for a sufficient time to precipitate cobalt oxalate, which was filtered, washed, and dried to obtain a pink powder. The cobalt oxalate obtained was placed in an electric furnace and pyrolyzed and reduced in four steps at 300 ° C. 0.5 hour, 350 ° C. 0.5 hour, 400 ° C. 1 hour, and 500 ° C. 1 hour in a hydrogen atmosphere to obtain a cobalt metal powder. The obtained cobalt metal powder was subjected to elemental analysis, particle size analysis, granularity analysis and the like, and the results are shown in Table 1 below. Here, elemental analysis is conducted using Inductively Coupled Plasma Atomic Absorption Spectroscopy (ICP-AAS), model name JY38S, Jobinyvon, France. Particle size analysis is based on Fischer Air Permeation Measurement (FSSS: Fisher Sub Sieve Sizer, model name MK200, The manufacturer, Fisher Science), and the granularity analysis was performed using an image analyzer.

<Example 2>

300 g of cobalt hydroxide oxide was added to a 3 L reactor together with 300 ml of 100% sulfuric acid, 30 ml of methyl alcohol, and 900 ml of water. The mixture was reacted with a sufficient time while heating to 90 ° C. to prepare a cobalt sulfide aqueous solution having a cobalt concentration of 20%. Oxalic acid aqueous solution prepared in the same manner as in Example 1 was added thereto to obtain cobalt oxalate. The obtained cobalt oxalate was subjected to pyrolysis reduction and elemental analysis in the same manner as in Example 1, and the results are shown in Table 1 below.

<Example 3>

300 g of cobalt hydroxide oxide was added to a 3 L reactor together with 200 ml of 100% nitric acid, 30 ml of methyl alcohol, and 900 ml of water. The mixture was reacted with a sufficient time while heating at 90 ° C. to prepare a cobalt nitride aqueous solution having a cobalt concentration of 20%. Oxalic acid aqueous solution prepared in the same manner as in Example 1 was added thereto to obtain cobalt oxalate. The obtained cobalt oxalate was subjected to pyrolysis reduction and elemental analysis in the same manner as in Example 1, and the results are shown in Table 1 below.

<Comparative Example 1>

Cobalt oxalate obtained in the same manner as in Example 1 was put in an electric furnace and pyrolytically reduced to 500 ° C. under hydrogen atmosphere for 1 hour to obtain a cobalt metal powder. Elemental analysis of the obtained cobalt metal powder in the same manner as in Example 1 and the results are shown in Table 1 below.

<Comparative Example 2>

Cobalt oxalate obtained in the same manner as in Example 2 was put in an electric furnace and pyrolytically reduced to 500 ° C. under a hydrogen atmosphere for 1 hour to obtain a cobalt metal powder. Elemental analysis of the obtained cobalt metal powder in the same manner as in Example 1 and the results are shown in Table 1 below.

<Comparative Example 3>

Cobalt oxalate obtained in the same manner as in Example 3 was put in an electric furnace and pyrolytically reduced to 500 ° C. under hydrogen atmosphere for 1 hour to obtain a cobalt metal powder. Elemental analysis of the obtained cobalt metal powder in the same manner as in Example 1 and the results are shown in Table 1 below.

<Comparative Example 4>

350 ml of 35% aqueous hydrochloric acid solution was added to 100 gr of cobalt oxide (Co 3 O 4) used for industrial purposes and completely dissolved. Oxalic acid prepared in the same manner as in Example 1 was added to obtain cobalt oxalate. The obtained cobalt oxalate was placed in an electric furnace and thermally reduced at 500 ° C. under hydrogen atmosphere for 1 hour to obtain a cobalt metal powder. Elemental analysis of the obtained cobalt metal powder in the same manner as in Example 1 and the results are shown in Table 1 below.

<Comparative Example 5>

30 gr of cobalt metal granulated powder (Co powder) was completely dissolved by adding 100 ml of 35% aqueous hydrochloric acid solution. Oxalic acid prepared in the same manner as in Example 1 was added to obtain cobalt oxalate. The obtained cobalt oxalate was placed in an electric furnace and thermally reduced at 500 ° C. under hydrogen atmosphere for 1 hour to obtain a cobalt metal powder. Elemental analysis of the obtained cobalt metal powder in the same manner as in Example 1 and the results are shown in Table 1 below.

As a result of the analysis of the above embodiments, it was found that ultrafine cobalt metal powder having a high purity and specific surface area suitable for cemented carbide or diamond tools can be obtained, and added by using cobalt hydroxide as a raw material. It was easy to dissolve and it was confirmed that the process operation could be simplified.

Therefore, according to the present invention, there is an effect of providing a method for preparing ultrafine cobalt metal powder of high purity and high specific surface area from cobalt hydroxide oxide, and is particularly expensive cobalt metal suitable for carbide tools, diamond tools and powder metallurgy. It is effective to make powder.

Although the present invention has been described in detail only with respect to the embodiments described, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention and that such modifications and modifications belong to the appended claims.

Claims (8)

(1) Cobalt hydroxide oxide (CoOOH) is added to an acid solution selected from the group consisting of a mixture of two or more of hydrochloric acid, sulfuric acid and nitric acid, so that the cobalt ion concentration in the solution is within 5 to 25%. An addition dissolution step of dissolving by heating at a temperature in a range of from 100 ° C .; (2) a precipitation step of generating a cobalt-carboxylate by adding a carboxylate consisting of alkali metal salts or alkaline earth metal salts of carboxylic acids such as oxalic acid and formic acid to the solution obtained in the addition dissolution step; (3) a precipitate recovery step of filtering and separating the precipitate obtained in the precipitation step, washing at least two times, and then drying; (4) high purity, high specific surface area from cobalt hydroxide, characterized in that it comprises reducing steps of heating the dried precipitate in an inert or reducing atmosphere at a temperature ranging from 300 to 600 ° C. in multiple stages. Ultrafine cobalt metal powder production method. delete delete delete delete delete delete The ultrafine particles having high purity and high specific surface area from the cobalt hydroxide, characterized in that the reduction step is carried out through the multi-stage reduction heating of three to five stages in the temperature range of 300 to 600 ℃. Cobalt metal powder production method.