KR20170055049A - Method for separating valuable metals and resin from pb-free waste solder - Google Patents

Abstract

The present invention relates to a method for retrieving resins and valuable metal from waste leadfree solder, in an attempt to recycle waste cream solder including bismuth, copper, tin as well as resin components. To this end, the resin components are separated first through a swelling process, and then each metal is separated and retrieved individually using a difference in leaching mobility for bismuth, copper, tin. By recycling a leaching agent used for leaching out metal, circulation process can be achieved.

Description

METHOD FOR SEPARATING VALVE METALS AND RESIN FROM PB-FREE WASTE SOLDER BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a recycling technique, and in particular to a method for recovering useful components from waste free lead free solder.

As the life cycle of electronic products becomes shorter, the amount of waste such as waste electronic devices is rapidly increasing. These wastes contain precious metals such as gold and silver as well as valuable metals such as copper, zinc and tin, and research for recovering valuable metals from these wastes has been actively conducted.

On the other hand, the use of lead-free solder, which is mainly composed of tin, copper and silver, is increasing, as the EU regulations on WEEE & RoHS (Restriction of Hazardous Substances such as lead) are strengthened. Lead-free solder has been used in the chip bonding process of printed circuit boards in the manufacture of almost all electronic products in place of lead.

However, almost all of the waste lead-free solder generated after the use of the lead-free solder in the manufacturing process of the electronic product is disused. Recently, researches have been conducted to regenerate waste lead-free solder with lead-free solder or to recover useful metals from waste lead-free solder.

In Korea, dry solder melting process is used to partially recycle the waste lead-free solder, but harmful gas is generated in the melting process. In addition, although solder to solder method, which is mainly used as solder, is preferred, there is no consumer even in the domestic market where a home appliance manufacturing plant that needs solder is transferred overseas and produces solder.

On the other hand, the demand for tin in the domestic plating industry is soaring that the domestic plating industry is experiencing difficulties due to the rise in tin prices. Therefore, in Korea, technology for recovering tin from waste solder is required.

In order to recover the tin metal from the waste lead-free solder, a wet smelting process free from the generation of harmful gas as described above is suitable. In conventional wet smelting processes, tin is leached from waste lead-free solders using acids.

One of the reasons for lowering the yield in the conventional process of leaching tin from waste lead-free solder using acid is due to the resin component. Waste lead-free solder (especially in paste form) contains resin components to increase bonding strength. In order to increase the acid leaching efficiency, tin needs to have a larger area in contact with the acid. Since the resin encapsulates (coating) the tin metal, the acid leaching efficiency is lowered.

In order to solve this problem, there has been an attempt to remove the resin component by treating the solder paste at a high temperature in the conventional process. However, this technology has a limitation in that it is not only possible to generate gas in the heat treatment process, but also to recover the useful metals from the waste solder by heat treatment.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for recovering tin from a lead-free solder by separating a valuable metal and a resin from each other.

On the other hand, other unspecified purposes of the present invention will be further considered within the scope of the following detailed description and easily deduced from the effects thereof.

According to an aspect of the present invention, there is provided a method for separating valuable metal and resin in a waste solder, the method comprising: (a) placing a waste solder containing a metal component including tin, copper, and bismuth and a resin component in an organic solvent Swelling the resin component in the waste solder by forming pulp to form a colloid state and precipitating the metal component in the waste solder; (b) separating the metal component and the resin component from each other through solid-liquid separation with respect to the pulp; (c) recovering each of the metal component and the resin component separated by solid-liquid separation. The organic solvent is preferably a polar organic solvent.

In one embodiment of the present invention, water is added to the colloidal solution containing the resin component and the organic solvent to precipitate the resin component in a solid state.

The organic solvent and the resin component precipitated in a solid state are subjected to solid-liquid separation, and then the water and the organic solvent are separated from each other and the organic solvent is used again. More specifically, the organic solvent may be separated from water by adding sodium chloride in a state where the organic solvent and water are mixed.

Meanwhile, in an embodiment of the present invention, the method further comprises separating copper from the metal component by selectively leaching only copper from the metal component using a copper dissolution agent, in the solid state metal component separated through solid-liquid separation. More specifically, it is preferable to use a tetraamine copper (Cu (NH ₃ ) ₄ ^{2 +} ) solution as the copper dissolution agent.

The tin and bismuth can be separated from each other by selectively leaching only tin from the tin and bismuth. In order to selectively leach the tin, tin and bismuth are added to the tetra-tin solution to leach the solid tin into the dendritic tin. At this time, it is preferable to supply a solubility enhancer containing chlorine ions.

Finally, the solution in which the divalent tin is dissolved and the solid state bismuth are subjected to solid-liquid separation, and a solution in which the divalent tin is dissolved is recovered by electrolytic recovery to reduce a part of the divalent tin to a solid state tin, It is preferable to oxidize the remainder of the divalent tin to tetravalent tin and recycle it as a tetravalent tin solution.

In the present invention, first, the resin component is separated from the waste cream solder, and the leaching efficiency is improved by leaching according to the characteristics of the individual metal in a state where the metal component is exposed to the outside due to the separation of the resin component. Through this process, the resin component, tin, copper, and bismuth can be individually recovered. As a result, there is an advantage in that the waste solder can be recycled as a pure metal without recycling it as a solder.

Further, in the present invention, the material charging ratio can be minimized by realizing the circulation process. That is, the polar organic solvent necessary for the swelling process is recovered again, and the tetra-tin solution used for leaching tin is recovered again.

Above all, in the present invention, there is a great advantage in that it is safe to remove the method for heating the resin component in the recycling of the conventional waste solder, and the recovery rate of useful components is improved.

On the other hand, even if the effects are not explicitly mentioned here, the effect described in the following specification, which is expected by the technical features of the present invention, and its potential effects are treated as described in the specification of the present invention.

1 is a schematic flow chart of a method for collecting and recovering valuable metal and resin in a waste solder according to an embodiment of the present invention.
2 is a photograph of a waste cream solder, which is a main application of the present invention.
3 is a table showing compositional components of a waste cream solder.
4 is a photograph for explaining the swelling process.
Figs. 5 and 6 are SEM photographs before swelling, and photographs showing different colors by metal components, respectively.
FIGS. 7 and 8 are SEM photographs and color photographs of solid components (metal components) separated by solid-liquid separation after the swelling process. FIG.
9 is a table showing the form of the compound according to the pH and oxidation-reduction potential (E / V) of the copper compound
10 is a graph showing a leaching rate of a metal component with respect to a copper dissolution agent.
The graph of FIG. 11 is a graph comparing the leaching rates of tin and bismuth with respect to the tetravalent tin oxidizing agent.
12 is a schematic view of an electrolytic cell for reducing tin.
The graphs of FIGS. 13 and 14 show the leaching efficiency of the metal component in the case where the swelling process is not performed (FIG. 12) and the roughness (FIG. 13).
* The accompanying drawings illustrate examples of the present invention in order to facilitate understanding of the technical idea of the present invention, and thus the scope of the present invention is not limited thereto.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.

The present invention aims at recycling waste solders including copper, tin, bismuth and resin, but the application is not limited to waste solder, and can be applied to various alloys including them. Further, the present invention is mainly applied to paste solders and alloys in paste form.

Hereinafter, with reference to the accompanying drawings, a method for separating and recovering valuable metal and resin in a waste solder according to an embodiment of the present invention will be described in detail.

1 is a schematic flow chart of a method for collecting and recovering valuable metal and resin in a waste solder according to an embodiment of the present invention. 2 is a waste solder (paste type) which is a main object of the present invention.

As shown in the table of FIG. 3, the components of the waste solder, which is a main application object of the present invention, include a metal component of 47% copper, 17% tin, 20% bismuth and 16% resin component (mainly epoxy).

Referring to FIG. 1, in the present invention, a resin component and a metal component are separated from a waste solder. As described in the prior art, one of the reasons for the lowering of efficiency when lean metal is leached from waste solder is due to the resin component. In the solder, the resin encapsulates the outer surface of the metal, so that the metal component can not be brought into smooth contact with the agent. In the present invention, the resin component is first removed. In the past, heat treatment was performed to remove the resin component, but this is harmful due to gas generation. The first feature of the present invention is that it uses a swelling process.

In the swelling process, pulp (light liquid) is formed by injecting waste solder into an organic solvent, particularly a polar organic solvent, so that the solid resin in the waste solder is converted into a colloidal state. Swelling is a phenomenon in which a material absorbs (binds) to a solvent and swells up. The extent of the swelling is determined by what is called "bridging degree "," kind of exchange ion ", "concentration of solution" and the like. In the swelling process, the polar organic solvent is connected to the resin component by ion exchange or bridging. However, since the resin component (polymer) mainly composed of epoxy is not completely dissolved in the polar organic solvent but is loosely drawn toward the organic solvent in a long chain form, the resin component exists in a colloid form in the organic solvent.

In this embodiment, MEK (Methyl Ethyl Ketone) is used as the polar organic solvent, and other polar organic solvents such as THF (Tetrahydrofuran) may be used. The ratio of the polar organic solvent to the waste solder, that is, the pulp (light liquid) concentration, was set at 50 g / L. Considering other embodiments, the concentration of the light can be used in the range of 1 g / L to 300 g / L. If the concentration of the light liquid is less than the above range, the amount of the solvent is unnecessarily large, which is uneconomical. If the concentration exceeds the above range, the swelling process is not smoothly performed. The swelling process does not require heating and is performed at room temperature.

FIG. 4 shows photographs of a pulsed cream solder and a pulping process before the swelling process. The turbidity of the pulp during the swelling process is very poor because the resin component is dispersed in the colloidal state in the solution. For reference, the last photograph in Fig. 4 is a metal component separated through solid-liquid separation.

In the present invention, SEM photographs of waste cream solder before and after swelling were compared. 5 is an SEM photograph of a waste cream solder before swelling, and FIG. 6 is a color representation of each metal component. Similarly, FIG. 7 is an SEM photograph of the metal component separated after swelling, and FIG. 8 is a color display of each component. In the photographs of FIGS. 6 and 7, blue Cu, yellow, Bi, pink, and green are O, respectively.

Referring to FIGS. 6 and 7, it can be seen that in the original state of the waste cream solder, the metallic particles, which look like granules, are deeply embedded in the resin. In other words, since the metallic components are surrounded by the resin, it is seen that the color is not clearly separated but spreads calmly even in Fig. 7 in which the components are different in color. Therefore, the leaching rate of the metal is lowered. However, when looking at the SEM photographs after swelling (Figs. 7 and 8), the granules are clearly visible and the hue is clearly separated. This shows that the resin components are separated from the metal components. In this way, the resin component is separated from the metal component, and the subsequent leaching process for the metal component is effectively ensured.

As described above, once the swelling process is completed, the resin component in the waste solder is released toward the polar organic solvent, and the metal component is precipitated in the pulp in a solid state. In this state, solid-liquid separation is performed. When the pulp is subjected to solid-liquid separation using a known centrifugal separator or the like, the polar organic solvent containing the solid state metal component and the resin component is separated from each other.

Now we move on to the individual processing steps for metal and resin components.

First, the processing and recovery of the resin component will be described.

After the solid-liquid separation, the resin component is still contained in the polar organic solvent in a colloidal state. In this state, when water is added to the polar organic solvent, the colloidal resin component is precipitated again as a solid state. This is because the connection between the resin component and the polar organic solvent is broken by supplying water to the polar organic solvent. Although the colloid is not in a dissolved state, it may be likened to a case where the solubility of the resin is lowered. The amount of water to be supplied may vary depending on the concentration of the liquid, and the resin may be supplied to such an extent that the resin component can be sufficiently precipitated.

After the resin component is precipitated in a solid state in the organic solvent, the solid component and the liquid component are separated from each other by solid-liquid separation. The resin components separated in the solid state can be recycled again. The liquid component is a mixture of water and a polar organic solvent. In order to recycle the polar organic solvent, the water and the organic solvent must be separated from each other. Organic solvents do not mix well with water, but polar organic solvents have a relatively good ability to mix well with water as compared to nonpolar organic solvents. However, when sodium chloride is added to the mixed solution, the polar organic solvent and the water are separated from each other, and they can be separated from each other. This is because the solubility of the organic solvent decreases due to the addition of sodium chloride.

In the process of treating the resin component, it is important that the resin be separated and recovered and reused, but more importantly, the separation and reuse of the polar organic solvent. Since polar organic solvents are expensive, they account for a large portion of the material input cost of the entire process of the waste solder. Therefore, if the polar organic solvent can be recycled again, the economical efficiency of the process can be improved.

Now, the treatment of metal components through solid-liquid separation will be explained.

As described above, the metal components in the waste solder are composed of tin, bismuth, and copper. Separation of each metal is carried out using the difference in the leaching behavior between them.

First, copper is separated from the metal components.

Waste solder is put into a copper dissolving agent so that only copper is selectively leached (dissolved), and tin and bismuth are kept in a solid state. As the copper dissolving agent, tetraamine copper (Cu (NH ₃ ) ₄ ^{2 +} ) solution is used. The tetraamine copper solution elutes copper in a metallic state with a monovalent metal ion as shown in the following reaction formula (1).

Cu + Cu (NH 3) ₂ ⁺ = ₂ Cu (NH 3) ₂ ⁺ ... Reaction formula (1)

The form of the compound according to the pH and oxidation-reduction potential (E / V) of the copper compound is shown in the table of FIG. Referring to the table of FIG. 9, it can be seen that the tetraamine copper solution (bivalent) in the solid state copper forms a mono-valent tetraamine copper (monovalent) solution at the intermediate point.

The tetraamine copper solution used as the copper dissolution agent in this example was prepared by mixing 5M NH ₃ solution, 1M (NH ₄ ) CO ₃ solution and 0.1M CuCO ₃ solution. And the amount of metal component to copper dissolving agent was 2 g / 20 ml. In the present embodiment, the mixed solution can be prepared in the range of NH ₃ 1 to 5M, (NH ₄ ) CO ₃ 1 to 5M, CuCO ₃ 0.1 to 1M, and the concentration of the light can be adjusted to 1 to 5% .

The graph of FIG. 10 shows the result of leaching with the metal component added to the copper dissolution agent. The leaching of the metal components was carried out at 50 캜 under stirring at 300 rpm for 180 minutes.

Referring to the graph of FIG. 10, it can be seen that copper (green triangle) dissolves 100% within 30 minutes after the start of leaching, while tin and bismuth are not dissolved regardless of the passage of time.

After the copper is leached as described above, the copper component can be recovered through solid-liquid separation. Copper in solution is monovalent and can be reused as an oxidizing agent if it is electrically oxidized.

Now, only tin is selectively separated and recovered from tin and bismuth remaining as a solid component in solid-liquid separation.

The number of selective separations of tin is used as the oxidizing agent for tetravalent tin ions. That is, when a metal component composed of tin and bismuth is put into an aqueous solution of tetravalent tin, the solid tin is dissolved in the divalent tin as shown in the following reaction formula (2).

Sn ^{4 + 2} = 2Sn + Sn ^+, E ⁰ = 0.29V ... ... Reaction formula (2)

If the standard oxidation-reduction potential (E ⁰ ) is positive in the above reaction (2), it means that the reaction proceeds to the right. As a result, the solid tin is dissolved and leached into the aqueous solution. However, since bismuth has a lower ionization tendency than tin, it does not dissolve and remains in a solid state.

In this embodiment, an aqueous solution of tin chloride (SnCl ₄ ) is used to provide tetravalent tin ions.

As described above, after the tin is oxidized to the divalent ion and leached into the solution, the dissolved divalent tin ion should be stably kept in the ionic state and not be combined with other components and precipitated. For this purpose, it is necessary to improve the solubility of the divalent tin ions. In the present invention, a solubility enhancer is used. As the solubility enhancing agent, sulfuric acid or the like may be used, but it is preferable to use chlorine ions. Chloride ions can help the tin bivalent ions remain stable in the solvent. In this embodiment, in order to supply chlorine ions, a tin chloride (SnCl4) aqueous solution is mixed with the above hydrochloric acid solution and used as a solvent.

FIG. 11 shows the results of experiments on the leaching rates of tin and bismuth with different concentrations of tetravalent tin. In the experiment, tetravalent tin was supplied to 0.5 M hydrochloric acid solution, and the concentration of light was adjusted to 10 g / L. And the mixture was stirred at 300 rpm at a temperature of 50 캜 for 180 minutes. The experiment was repeated while increasing the concentration of tetravalent tin to 1,000 ~ 5000PPM.

From the experimental results, the precipitation rate increases sharply as the concentration of tetravalent tin ion used as an oxidizer increases. When leaching at a concentration of 5,000PPM for 60 minutes, 99% of tin was leached out. However, in the case of bismuth, no elution occurred at all regardless of the concentration of tetravalent tin. That is, when tetravalent tin is used as an oxidizing agent, only tin can be selectively dissolved and separated from a metal component in which tin and bismuth are mixed.

As described above, after the tin is oxidized and dissolved by the tetravalent tin ion, the metal component is dissolved in the liquid tin and solid state bismuth by supplying chlorine ions so that the divalent tin ion can be stably maintained in the solvent Separated. These can also be separated and recovered through solid-liquid separation. Bismuth remaining in the solid state is recycled again.

After the solid-liquid separation, the tin is recovered from the divalent tin ions in a solid state. In this embodiment, an electrowinning method using an ion-exchange membrane is used. An iontophoretic electrolyzer for implementing the electrolytic recovery method according to this embodiment is shown in FIG.

Referring to Fig. 12, an anion exchange membrane (b), through which divalent tin ions can not pass, is provided in the center of the electrolytic cell (k). A solvent containing divalent tin ions is contained in the electrolytic cell k and an anode electrode a and a cathode electrode c connected to the power source p are installed with the ion exchange membrane b interposed therebetween.

When power is supplied, divalent tin ions lose electrons around the anode electrode and are oxidized to quaternary tin ions. At the cathode electrode, divalent tin ions get electrons and precipitate as solid tin on the surface of the cathode electrode. As a result, pure tin in a solid state can be recovered from the cathode electrode.

In order to increase the efficiency of the electrolytic recovery, the concentration of tin 2 -valent ions should be 5,000 ppm or more, preferably 8,000 ppm or more. The concentration of divalent tin ions is related to the solubility enhancer. For example, when a sulfuric acid solution is used as a solubility enhancer, a concentration of 5,000 ppm or more can be ensured, and an electrolytic recovery process is possible, but a concentration of 8,000 ppm or more is unlikely. When the chloride ion is used as the solubility enhancer as in the present embodiment, the concentration of the divalent tin ions can be maintained at several tens of thousands of ppm or more, which can improve the tin recovery efficiency in the mass production process.

On the other hand, in this embodiment, the circulating process is realized by recycling the tetravalent ions reduced at the anode electrode (a) to the oxidant at the tin circulating means. That is, after separating the cathode electrode (c) from the electrolytic cell (k), the solvent remaining in the electrolytic cell (k) (including the tetravalent tin ion) is utilized again for the tin precipitating. Therefore, in the method for recovering the useful metals in the waste-free solder according to the present invention, it is possible to economically process the tin tetrachloride ion and the chlorine ion generated in the process by supplying the tin chloride and the hydrochloric acid solution only at the start of the process .

As described above, in the present invention, the resin component is firstly separated from the waste cream solder, and the leaching is performed according to the characteristics of the individual metals in a state where the metal component is exposed to the outside due to the separation of the resin component, Improves efficiency. Through this process, the resin component, tin, copper, and bismuth can be individually recovered. As a result, there is an advantage in that the waste solder can be recycled as a pure metal without recycling it as a solder. Further, in the present invention, the material charging ratio can be minimized by realizing the circulation process. That is, the polar organic solvent necessary for the swelling process is recovered again, and the tetra-tin solution used for leaching tin is recovered again.

Above all, in the present invention, there is a great advantage in that it is safe to remove the method for heating the resin component in the recycling of the conventional waste solder, and the recovery rate of useful components is improved.

The inventors of the present invention have conducted experiments to compare the leaching / recovery rates of metal components with and without the swelling process. In other words, all the processes and conditions are the same and the effect of the swelling process is tested. The results are shown in the graphs of FIG. 12 and FIG.

13 and 14, approximately 30% of tin, 3.6% of copper and 0.5% of bismuth were leached without swelling, whereas when swelled, tin 82.3%, copper 21.6%, bismuth 1.2% and the leaching efficiency was remarkably increased. This difference is attributed to whether or not the resin component was removed through swelling.

Although the present invention has been described above with respect to the waste cream solder, the present invention can be applied to a material containing a resin component and a different metal in addition to the waste cream solder.

The scope of protection of the present invention is not limited to the description and the expression of the embodiments explicitly described in the foregoing. It is again to be understood that the present invention is not limited by the modifications or substitutions that are obvious to those skilled in the art.

Claims (11)

(a) forming waste into a colloidal state by swelling the resin component in the waste solder by forming a pulp into an organic solvent, the waste solder containing a metal component including a tin, copper, and a bis component, and a resin component; Depositing a metal component in the solder;
(b) separating the metal component and the resin component from each other through solid-liquid separation with respect to the pulp;
(c) recovering each of the metal component and the resin component separated by solid-liquid separation; and recovering the metal component and the resin component in the waste solder. The method according to claim 1,
Wherein the organic solvent is a polar organic solvent. The method according to claim 1,
Further comprising the step of injecting water into the colloidal solution containing the resin component and the organic solvent to precipitate the resin component into a solid state. The method of claim 3,
The organic solvent and the resin component precipitated in a solid state are subjected to solid-liquid separation,
Separating the water and the organic solvent from each other and using the organic solvent again. 5. The method of claim 4,
Wherein the organic solvent is separated from the water by adding sodium chloride in a state where the organic solvent and water are mixed. The method according to claim 1,
Further comprising the step of selectively leaching only copper from the metal component by using a copper dissolution agent to separate copper from the solid metal component separated through the solid-liquid separation, thereby separating the copper from the valuable metal and resin in the waste solder Way. The method according to claim 6,
Wherein the copper dissolving agent is a tetraamine copper (Cu (NH ₃ ) ₄ ^{2 +} ) solution. The method according to claim 6,
And separating the tin and bismuth from each other by selectively leaching only tin from the tin and bismuth to separate the tin and bismuth from each other. 9. The method of claim 8,
In order to selectively leach the tin,
Wherein tin and bismuth are added to the tetravalent tin solution to leach the solid tin into the divalent tin. 10. The method of claim 9,
Wherein the solubility enhancer containing chlorine ions is supplied when the tin is leached. 10. The method of claim 9,
The solution in which the divalent tin is dissolved and the solid state bismuth are subjected to solid-liquid separation,
The solution in which the divalent tin is dissolved is recovered by reducing some of the divalent tin to solid state tin through electrolytic recovery and at the same time the remainder of the divalent tin is oxidized with the tetravalent tin to be recycled as a tetravalent tin solution And the resin is separated from the waste solder.

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