High-purity copper formate

Abstract

To provide a high-purity copper formate which is usable for producing high-purity copper particles.SOLUTION: Provided is a copper formate having a purity of 99.999 wt.% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to high-purity copper formate and a method for producing the same.

Background Art

[0002] In recent years, functional liquid materials containing metal nanoparticles have attracted attention. In particular, materials using copper nanoparticles, which are more advantageous in terms of cost than silver nanoparticles, have attracted attention.

[0003] Generally, copper formate is used as a starting material for copper nanoparticles. High-purity copper formate is required for the production of high-purity copper nanoparticles.

[0004] Patent Document 1 (Japanese Patent Laid-Open No. 3-176455) discloses a method for producing copper formate by subjecting methyl formate to a hydrolysis reaction in the liquid phase in the presence of copper carbonate. The copper formate obtained by the production method of Patent Document 1 contains 100 to 1010 ppm of sodium and 5 to 420 ppm of sulfur as impurities, and the purity of the copper formate is estimated to be 99.86 to 99.98%.

[0005] Patent Document 2 (Patent No. 5045015) discloses a method for producing copper formate by reacting performic acid with copper. Patent Document 2 further discloses a method for producing copper particles from the copper formate thus obtained. The purity of the copper formate obtained by the production method of Patent Document 2 was estimated to be 99.5%.

[0006] Patent Document 3 (Patent No. 5205717) discloses a method for producing a copper formate complex by dissolving copper formate in an aliphatic amine, and further discloses a method for producing copper particles from the copper formate complex thus obtained.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] Therefore, an object of the present invention is to provide high-purity copper formate that can be used for the production of high-purity copper particles. [Means for Solving the Problems]

[0009] As a result of intensive research and development, the present inventor has achieved the production of high-purity copper formate and reached the present invention.

[0010] Therefore, the present invention includes the following (1): (1) Copper formate having a purity of 99.999 wt% or more. [Advantages of the Invention]

[0011] The present invention provides high-purity copper formate. [Brief Description of the Drawings]

[0012]

Figure 1

Figure 2

[0013] The present invention will be described in detail below with specific embodiments. The present invention is not limited to the specific embodiments disclosed below.

[0014] [High-Purity Copper Formate] The present invention relates to copper formate having a purity of 99.999 wt% or more.

[0015] Furthermore, in a preferred embodiment, the purity of the copper formate of the present invention can be, for example, 99.999 wt% or more, or 99.9990 wt% or more, 99.9991 wt% or more, 99.9992 wt% or more, 99.9993 wt% or more, 99.9994 wt% or more, 99.9995 wt% or more, 99.9996 wt% or more, 99.9997 wt% or more, 99.9998 wt% or more.

[0016] According to the copper formate of the present invention, high-purity copper particles can be easily produced.

[0017] [Purity] The purity of the copper formate was calculated by the means disclosed in the examples described below.

[0018] In a preferred embodiment, the purity of the copper formate of the present invention is the purity calculated by excluding hydrogen, carbon, oxygen, sulfur, chlorine, nitrogen, and phosphorus.

[0019] [Impurity content] In a preferred embodiment, in the high-purity copper formate of the present invention, the content of the following impurity elements can be the following contents respectively. The values of the impurity content can be measured by the means described below in the examples:

[0020] Na content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, less than 0.1 wtppm; Al content: 1 wtppm or less, 0.5 wtppm or less, 0.05 wtppm or less, less than 0.05 wtppm; K content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, less than 0.1 wtppm; Ca content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less; Cr content: 1 wtppm or less, 0.5 wtppm or less, 0.14 wtppm or less; Fe content: 1 wtppm or less, 0.5 wtppm or less, 0.2 wtppm or less; Content of Ni: 1 wtppm or less, 0.5 wtppm or less, 0.19 wtppm or less; Content of Ag: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, less than 0.05 wtppm; Content of Si: 1 wtppm or less, less than 1 wtppm; Content of S: 1 wtppm or less, less than 1 wtppm; Content of Cl: 100 wtppm or less, less than 100 wtppm;

[0021] Content of Li: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Content of Be: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Content of B: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Content of N: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, less than 0.01 wtppm; Content of Mg: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm;

[0022] Content of P: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Content of Ti: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less; V content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm;

[0023] Mn content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Co content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Zn content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, less than 0.005 wtppm; Ga content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, less than 0.01 wtppm; Ge content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, less than 0.005 wtppm; As content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, less than 0.005 wtppm;

[0024] Zr content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Nb content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Mo content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, less than 0.005 wtppm; Cd content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, less than 0.01 wtppm; Sn content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, less than 0.01 wtppm; Sb content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.002 wtppm or less, less than 0.002 wtppm; Ba content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; W content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm;

[0025] Au content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, less than 0.01 wtppm; Hg content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, less than 0.01 wtppm; Pb content: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.002 wtppm or less, less than 0.002 wtppm; Content of Bi: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, 0.05 wtppm or less, 0.01 wtppm or less, 0.005 wtppm or less, 0.001 wtppm or less, less than 0.001 wtppm; Content of Th: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, less than 0.1 wtppm; Content of U: 1 wtppm or less, 0.5 wtppm or less, 0.1 wtppm or less, less than 0.1 wtppm.

[0026] [Hydrate] In a preferred embodiment, the copper formate of the present invention can be in the form of a hydrate or an anhydride, or in the form of a mixture of a hydrate and an anhydride. As the form of the hydrate, for example, it can be a tetrahydrate, a dihydrate, or a mixture thereof. The number of water molecules of the hydrate can be measured and determined by the means disclosed in the examples described later.

[0027] In a preferred embodiment, the number of water molecules of the hydrate of the copper formate of the present invention can be controlled to a desired number of water molecules by drying with the drying means disclosed in the examples.

[0028] [Production of Copper Formate] The copper formate of the present invention can be produced by the production method described later in the examples. That is, by using the electrolytic dissolution apparatus and conditions disclosed in the examples, a step of electrolytically dissolving 6N-Cu as a raw material, a step of precipitating copper formate into an anolyte, and a step of recovering the obtained copper formate, it can be produced by a method including these steps.

[0029] [Preferred Embodiment of the Present Invention] As a preferred embodiment, the present invention includes the following (1) and below. (1) Copper formate with a purity of 99.999 wt% or more. (2) The copper formate according to (1), wherein the purity is the purity calculated excluding hydrogen, carbon, oxygen, sulfur, chlorine, nitrogen, and phosphorus. (3) Copper formate according to (1), having a sodium content of 1 wtppm or less. (4) Copper formate according to (1), having an aluminum content of 1 wtppm or less. (5) Copper formate according to (1), having a potassium content of 1 wtppm or less. (6) Copper formate according to (1), having a calcium content of 1 wtppm or less. (7) Copper formate according to (1), having a chromium content of 1 wtppm or less. (8) Copper formate according to (1), having an iron content of 1 wtppm or less. (9) Copper formate according to (1), having a nickel content of 1 wtppm or less. (10) Copper formate according to (1), having a silver content of 1 wtppm or less. (11) Copper formate according to (1), having a purity of 99.9995 wt% or more. (12) Copper formate according to (1), which is in the form of an anhydride or a hydrate.

Examples

[0030] The present invention will be described in detail below with reference to examples. The present invention is not limited to the examples illustrated below.

[0031] [Example 1: Example 1] [Electrolytic Dissolution Apparatus] An explanatory diagram of the apparatus used for electrolytic dissolution is shown in Fig. 1.

[0032] The electrolytic apparatus includes an electrolytic dissolution cell 1 and an external catholyte cell 19. The electrolytic dissolution cell 1 includes an anode 3 and a cathode box 11.

[0033] As the anode 3, 6N-Cu which is the raw material is formed and used. The anode 3 is immersed in the anolyte 7. Note that instead of the anode 3, an anode box (not shown) can be installed, and 6N-Cu which is the raw material can be stored inside and used.

[0034] Inside the cathode box 11, a titanium plate is used as the cathode 9 and is provided. The cathode 9 is immersed in the catholyte 13. The catholyte 13 is separated from the anolyte 7 outside the cathode box by an anion exchange membrane.

[0035] The electrolytic dissolution tank 1 is provided with a stirrer (not shown) and can be stirred throughout the electrolytic dissolution.

[0036] Inside the external catholyte tank 19, with the formic acid-resistant tube 17 as the flow path, the catholyte 13 in the cathode box 11 is introduced, and a circulation path is formed in which the introduced catholyte 13 is introduced back into the cathode box 11 again with the formic acid-resistant tube 17 as the flow path.

[0037] As the electrolytic dissolution progresses, copper formate precipitates, consuming the formic acid in the anolyte and catholyte. Therefore, by adding formic acid into the catholyte in the external catholyte tank 19, the amount of consumed formic acid can be supplemented, and the concentration of formic acid in the anolyte and catholyte can be maintained constant.

[0038] [Manufacture of Copper Formate Solution by Electrolytic Dissolution and Precipitation of Copper Formate] Using the electrolytic dissolution apparatus shown in Fig. 1, electrolytic dissolution was carried out. The conditions of electrolytic dissolution are as follows. Anolyte at the start of electrolysis: Dilute formic acid (concentration 16.0 - 18.4 wt%) Catholyte at the start of electrolysis: Formic acid (concentration 77.0 - 78.0 wt%) Anode: 6N-Cu Cathode: Titanium plate

[0039] The analytical values of 6N-Cu used as the anode by GDMS are shown in Table 1 below. In Table 1, the unit of the analytical values of the contained impurity elements is wtppm, and the values indicated by less than (<) indicate that the values were less than the detection limit.

[0040]

Table 1

[0041] By adding formic acid into the catholyte in the external catholyte tank 19, the concentration of formic acid in the anolyte was maintained within the range of 16.0 - 22.3 wt%. As the voltage, electrolytic dissolution was carried out at a constant voltage of 4.0 - 5.0 V. Electrification was carried out for 2 - 3 weeks to dissolve high-purity copper into the anolyte. When the dissolution of high-purity copper started, the color of the solution changed from colorless and transparent to blue. When the copper formate solution reached the saturation concentration, the precipitation of copper formate started in the anolyte solution. When visually observing the start of the precipitation of copper formate, it was determined that a sufficient amount of copper formate was generated, and the electrolytic dissolution was terminated. The precipitated copper formate was recovered. The recovery of the precipitated copper formate was carried out by collecting the anolyte solution and the precipitated crystals and performing solid-liquid separation by suction filtration. The copper formate crystals obtained thereby were used as Sample 1.

[0042] [Analysis of Copper Formate Crystals] The contained elements of the recovered copper formate crystals were analyzed. Na, Al, Si, K, Ca, Cr, Fe, Ni, Ag, S, Cl were analyzed by ICP-MS (Inductively Coupled Plasma Mass Spectrometry), and Cu was analyzed by ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry). The results obtained by the analysis are shown in Table 2. In Table 2, the unit of the analytical values of the contained impurity elements is wtppm, and the values indicated by less than (<) indicate that the values were less than the detection limit.

[0043]

Table 2

[0044] Based on the analysis results, for Sample 1, the purity of copper formate was calculated to be 99.9998 wt% or higher. In the calculation, the elements measured in Table 2 were used as impurities in the calculation, and for the elements not measured in Table 2, since they are elements that can be considered not to increase or decrease based on the principle of the experimental operation, for the 6N-Cu used as the anode, the element content measured in Table 1 was used for the calculation. However, among the elements in Table 1 and Table 2, hydrogen, carbon, oxygen, sulfur, chlorine, nitrogen, and phosphorus are removed as gas components when producing copper particles by reduction from copper formate, so they were not used in the purity calculation.

[0045] For the purity calculation, focusing on the impurity content of metal elements, among the elements in Table 1 and Table 2 above, excluding hydrogen, carbon, oxygen, sulfur, chlorine, nitrogen, and phosphorus, the elements were considered as impurities, and the impurity content was calculated by substituting it into the formula of 100 wt% - (total of metal impurity content in wtppm / 10000) wt%.

[0046] [Measurement of hydration number] The obtained copper formate crystals were found to be approximately tetrahydrate by XRD analysis under the following conditions.

[0047] XRD was performed under the following conditions using a Rigaku fully automatic horizontal multi-purpose X-ray diffractometer SmartLab: X-ray tube: Cu (measured with CuKα) Tube voltage: 40 kV, tube current: 30 mA, optical system: focusing type diffraction optical system Scan mode (2θ / θ): 10°, scanning range (2θ): 10° to 60° Measurement step (2θ): 10°, scan speed (2θ): 20° per minute Filter: CuKβ filter, divergence slit: 2 / 3° Incident slit: 0.150 mm, longitudinal limiting slit: 10.0 mm, Receiving slit 1: 1.000 mm, receiving slit 2: 0.150 mm.

[0048] The results obtained by XRD analysis of Sample 1 are shown in Fig. 2. In the chart of Fig. 2, for comparison, the chart of XRD analysis of copper formate tetrahydrate obtained from the database is also shown. From the comparison of characteristic peaks, it was found that more than 99 wt% of the copper formate crystals in Sample 1 exist in the form of tetrahydrate.

[0049] [Drying] Sample 1 was dried using a dryer under the following conditions. Drying temperature: 30 °C Drying time: 240 minutes Atmosphere: Air

[0050] As described above, more than 99 wt% of the copper formate crystals in Sample 1 were in the form of copper formate tetrahydrate. And when dried by the above operation, it became a mixture of copper formate tetrahydrate and dihydrate (tetrahydrate: dihydrate = 70 wt%: 30 wt%). Thus, by further drying the precipitated crystals, the content ratio of the hydrate could be controlled.

Industrial Applicability

[0051] The present invention provides high-purity copper formate that can be used for the production of high-purity copper particles. The present invention is an industrially useful invention.

Claims

1. Copper formate with a purity of 99.999 wt% or more.

2. The copper formate according to Claim 1, wherein the purity is the purity calculated excluding hydrogen, carbon, oxygen, sulfur, chlorine, nitrogen, and phosphorus.

3. The copper formate according to Claim 1, wherein the sodium content is 1 wtppm or less.

4. The copper formate according to Claim 1, wherein the aluminum content is 1 wtppm or less.

5. The copper formate according to Claim 1, wherein the potassium content is 1 wtppm or less.

6. The copper formate according to Claim 1, wherein the calcium content is 1 wtppm or less.

7. The copper formate according to Claim 1, wherein the chromium content is 1 wtppm or less.

8. The copper formate according to Claim 1, wherein the iron content is 1 wtppm or less.

9. The copper formate according to Claim 1, wherein the nickel content is 1 wtppm or less.

10. The copper formate according to Claim 1, wherein the silver content is 1 wtppm or less.

11. The copper formate according to Claim 1, wherein the purity is 99.9995 wt% or more.

12. The copper formate according to Claim 1, wherein the copper formate is in the form of an anhydride or a hydrate.

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