A copper protecting agent for copper surface tin stripping and a process for achieving full recycling of tail water

Abstract

The present invention belongs to the technical field of copper surface tin stripping, and specifically relates to a copper protecting agent for copper surface tin stripping and a process for realizing full recycling of tail water. The composition of the copper protecting agent includes one or more of benzotriazole, toluene triazole, and benzimidazole; preferably, a combination of benzotriazole and toluene triazole is used, and the compound copper protecting agent makes the speed of copper surface tin stripping more stable, and a protective film is formed on the copper surface during the tin stripping process, which reduces the erosion rate of the copper surface by the tin stripping water, and the copper surface after tin stripping is smoother, and the waste water after tin stripping is more conducive to the sedimentation and reuse of tin mud; reducing the concentration of the complexing agent allows the supersaturated tin nitrate to precipitate quickly, and adopts a multi-stage sedimentation method to allow the tin nitrate to fully settle, and adopts oxalic acid and polyacrylamide to fully settle the free tin ions and copper ions in the solution, and recover nitric acid to the greatest extent, so as to achieve the effect of saving reagents and system circulation balance.

Description

Technical Field

[0001] The invention belongs to the technical field of copper surface tin stripping, and specifically relates to a copper protecting agent used for copper surface tin stripping and a process for realizing full circulation reuse of tail water. Background Art

[0002] The traditional copper surface tin stripping process is to purchase tin stripping water to strip the metal tin layer on the copper surface. When the tin stripping water dissolves the metal tin to saturation, the manufacturer transfers the waste tin stripping water to a hazardous waste disposal company. The hazardous waste disposal company extracts the metal tin in the waste tin stripping water in the form of tin mud through neutralization, filtration and other processes, and finally treats the generated wastewater harmlessly. The above process has several disadvantages: 1. Using a large amount of alkali to neutralize the acid in the tin stripping wastewater causes a double waste of alkali and acid; 2. The wastewater after filtration of the tin mud contains a large amount of nitrate ions, which has a high disposal cost. The cost of disposing of each ton of wastewater is more than 1,500 yuan, which is a great waste of social resources.

[0003] Patent CN201910428326.7 discloses a method for regenerating and reusing PCB nitric acid type tin stripping waste liquid, which is 1) using a metal ion capture agent to precipitate tin, copper, and divalent iron ions; 2) using an impurity remover to remove impurities; 3) using nitric acid, a promoter, a tin complexing agent, and a copper protecting agent to prepare a regenerated tin stripping solution; 4) using hydrochloric acid to dissolve tin, copper, and iron precipitation; 5) electrolytic recovery of tin and copper, and the copper protecting agent is selected from thiourea and benzotriazole; Patent CN202110377364.1 discloses a tin stripping water and its production process, the tin stripping water includes nitric acid solution, ferric nitrate, a metal ion complexing agent, a copper protecting agent, and a soluble chloride salt, and the copper protecting agent used is one of benzotriazole, methylbenzotriazole, and tropine, and the resulting tin stripping water can be used in the tin stripping process of PCB boards. However, the tin stripping effect is still not ideal. In addition to the requirements for the tin stripping rate, the copper surface after tin stripping must be well protected.

[0004] Therefore, in order to solve the above-mentioned drawbacks and truly achieve energy conservation and emission reduction and maximize the utilization of resources, a technical study on the full recycling of wastewater from direct chemical tin extraction at the production site of copper surface tin stripping was proposed. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a copper protecting agent for tin stripping of copper surface and a process for achieving full recycling of tail water.

[0006] The technical contents of the present invention are as follows:

[0007] The present invention provides a copper protecting agent for copper surface tin stripping, wherein the composition of the copper protecting agent includes one or more of benzotriazole, tolyltriazole and benzimidazole;

[0008] The copper protecting agent is used at a concentration of 0 to 20 g / L, preferably 8 to 12 g / L;

[0009] Among them, the combination of benzotriazole and toluenetriazole is preferred, and the mixing ratio is (1:9) to (9:1), preferably (4:6) to (6:4).

[0010] The present invention also provides a process for stripping tin from a copper surface and realizing full recycling of tail water, comprising the following steps:

[0011] 1) Tin stripping

[0012] In the production tank, a tin stripping liquid is used to strip the tin-plated copper surface to obtain a tin stripping solution and a copper surface;

[0013] The tin stripping solution comprises a copper protecting agent, nitric acid, ferric nitrate, ferric chloride, sodium chloride and citric acid;

[0014] The copper protecting agent comprises one or more of benzotriazole, tolyltriazole and benzimidazole, and the concentration is 0-20g / L;

[0015] The concentration of nitric acid used is 10-25%;

[0016] The use concentration of the ferric nitrate is 5-40 g / L;

[0017] The use concentration of the ferric chloride is 1-15 g / L;

[0018] The use concentration of the sodium chloride is 2-20 g / L;

[0019] The concentration of citric acid used is 5-40 g / L. The low concentration of citric acid (complexing agent) in the tin stripping solution can quickly precipitate the supersaturated tin nitrate.

[0020] 2) Multi-stage sedimentation

[0021] The liquid flow rate in the production tank is about 200 L / min. The tin stripping solution in the production tank flows to the sedimentation tank through the liquid level difference. Three or more sedimentation tanks are set. There is a height difference from the production tank to the sedimentation tank, so that the solution flows naturally through the liquid level difference. The tin salt (tin nitrate) in the tin stripping solution entering the sedimentation tank settles to the bottom of the tank due to its own gravity to form tin mud.

[0022] 3) Recycling

[0023] The tin stripping liquid that has passed through the sedimentation tank is returned to the production tank for copper surface tin stripping;

[0024] Extract the tin mud at the bottom of the sedimentation tank, add oxalic acid and polyacrylamide to reduce the acidity of the tin mud to below 3.0 equivalents, fully precipitate the free tin ions and copper ions in the tin mud solution, make the precipitated tin mud particles larger, more conducive to subsequent filter pressing, and maximize the recovery of nitric acid;

[0025] The concentration of oxalic acid in the tin mud is 5-25 g / L;

[0026] The average molecular weight of the polyacrylamide is 200w, and the concentration in the tin mud is 50-200 ppm.

[0027] Beneficial effects of the present invention:

[0028] The copper protecting agent for tin stripping of copper surface of the present invention comprises one or more of benzotriazole, tolyltriazole and benzimidazole. The compounded copper protecting agent makes the speed of tin stripping of copper surface more stable. During the tin stripping process, a protective film is formed on the copper surface, which reduces the corrosion rate of tin stripping water on the copper surface. The copper surface after tin stripping is smoother, and the wastewater after tin stripping is more conducive to the sedimentation and reuse of tin mud.

[0029] The process for stripping tin from copper surface and realizing full recycling of tail water of the present invention reduces the concentration of the complexing agent in the adopted tin stripping solution so that the supersaturated tin nitrate is quickly precipitated, a multi-stage sedimentation method is adopted to fully precipitate the tin nitrate, and oxalic acid and polyacrylamide are adopted to fully precipitate free tin ions and copper ions in the solution, and nitric acid is recovered to the maximum extent, so as to achieve the effects of saving reagents and balancing the system cycle, change the traditional disposal mode of waste tin stripping water, no longer use the neutralization method for treatment, and retain the residual nitric acid in the waste water to the maximum extent, so that the neutralization alkali is saved and the nitric acid is reused, so as to achieve two-way saving, and the tin stripping solution can be reused in the whole process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the effect of benzotriazole as copper protecting agent on copper biting rate;

[0031] Figure 2 This is the effect of methylbenzotriazole on the copper biting rate when the copper protecting agent is methylbenzotriazole;

[0032] Figure 3 This is the effect of benzoimidazole as copper protecting agent on copper biting rate;

[0033] Figure 4 This is the effect of the copper protecting agent, benzotriazole and benzoimidazole, on the copper biting rate;

[0034] Figure 5 This is the effect of the copper protecting agent, benzotriazole and toluenetriazole, on the copper biting rate;

[0035] Figure 6This is the effect of copper protecting agent, which is a compound of methylbenzotriazole and benzoimidazole, on the copper biting rate;

[0036] Figure 7 The present invention is a schematic diagram of the process flow for stripping tin from copper surface and achieving full recycling of tail water. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below through specific implementation cases and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art are all within the scope of the claims attached to this application.

[0038] Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents from the conventional market.

[0039] Example

[0040] A copper protecting agent for stripping tin from copper surface

[0041] The copper protecting agent comprises one or more of benzotriazole, tolyltriazole and benzimidazole, and the use concentration is 0-20g / L.

[0042] Table 1 Copper Protective Agent

[0043] Example Copper Protector Example 1 Benzotriazole Example 2 Methylbenzotriazole Example 3 Benzoimidazole Example 4 Compound of benzotriazole and benzoimidazole Example 5 Compound of benzotriazole and methylbenzotriazole Example 6 Compound of methylbenzotriazole and benzoimidazole

[0044] The effects of different copper protecting agents used in Examples 1 to 6 on the copper biting rate were tested, and the results are as follows:

[0045] like Figure 1 , Figure 2 and Figure 3 The results of the effects of the single copper protecting agents benzotriazole, methylbenzotriazole and benzimidazole on the copper biting rate at different concentrations shown in Examples 1-3 respectively show that the copper biting rate decreases significantly with the increase of the concentration of the copper protecting agent in the solution. When the concentration reaches 8 g / L or 10 g / L, the copper biting rate is 1-2 μm / min, and the concentration above 10 g / L has no obvious effect on the copper biting rate, and the rate is maintained.

[0046] Considering both the effect and the economic cost, the concentration of the copper protecting agent was set at 10 g / L, and the compound copper protecting agents of Examples 4-6 were designed, and two of them were compounded, and the total concentration of the copper protecting agent was set at 10 g / L. The copper biting rate was tested by changing the compounding ratio. The results are as follows: Figure 4 , Figure 5 and Figure 6As shown in the figure, the copper protectors are compounded with benzotriazole and benzoimidazole, compounded with benzotriazole and toluene triazole, and compounded with toluene triazole and benzoimidazole. It can be seen that the copper biting rate is the lowest when benzotriazole and toluene triazole are compounded in a ratio of 5:5. When the copper biting rate of the tin stripping water is low enough, the copper surface after tin stripping can be well protected, and the surface roughness of the copper surface after tin stripping is small and the brightness is better.

[0047] As can be seen from the above, the copper protecting agent is preferably used at a concentration of 8 to 12 g / L, wherein a combination of benzotriazole and tolyltriazole is preferred, with a mixing ratio of (1:9) to (9:1), preferably (4:6) to (6:4).

[0048] Example 7

[0049] A process for stripping tin from copper surface and realizing full recycling of tail water

[0050] 1) Tin stripping

[0051] In the production tank, a tin stripping liquid is used to perform a tin stripping reaction on the tin-plated copper surface to obtain a tin stripping solution and a tin stripped copper surface;

[0052] The tin stripping solution includes 10 g / L copper protector (benzotriazole: methylbenzotriazole = 5:5), 15% nitric acid, 20 g / L ferric nitrate, 10 g / L ferric chloride, 15 g / L sodium chloride and 20 g / L citric acid, all of which are working concentrations;

[0053] The low concentration of citric acid (complexing agent) in the tin stripping solution can quickly precipitate the supersaturated tin nitrate;

[0054] 2) Multi-stage sedimentation

[0055] The liquid flow rate in the production tank is about 200 L / min. In the production tank, the tin stripping solution flows to the sedimentation tank through the liquid level difference. Three sedimentation tanks are set. There is a height difference from the production tank to the sedimentation tank, so that the solution flows naturally through the liquid level difference. The tin salt (tin nitrate) in the tin stripping solution entering the sedimentation tank settles to the bottom of the tank due to its own gravity to form tin mud.

[0056] 3) Recycling

[0057] The tin stripping liquid that has passed through the sedimentation tank is returned to the production tank for copper surface tin stripping;

[0058] Extract the tin mud at the bottom of the sedimentation tank, add oxalic acid and polyacrylamide to reduce the acidity of the tin mud to below 3.0 equivalents, fully precipitate the free tin ions and copper ions in the tin mud solution, make the precipitated tin mud particles larger, more conducive to subsequent filter pressing, and maximize the recovery of nitric acid;

[0059] The concentration of oxalic acid in the tin mud is 18-25 g / L;

[0060] The average molecular weight of the polyacrylamide is 200w, and the concentration in the tin mud is 50-110 ppm.

[0061] The above process flow is as follows Figure 7 As shown, the present invention changes the traditional disposal mode of waste tin stripping water, no longer uses the neutralization method for treatment, and retains the residual nitric acid in the wastewater to the maximum extent, which not only saves the neutralization alkali but also reuses the nitric acid, achieving two-way savings. The multi-stage water washing is adopted. After the first stage of water washing reaches saturation, it is reused in new medicine, the second stage of water washing is reused in the first stage, the third stage of water washing is reused in the second stage, and so on until the last stage of water washing adds new tap water. This water washing method not only saves a lot of water for washing, but also follows the principle of small amount and multiple washing, ensuring the quality of the product.

[0062] Example 8

[0063] A process for stripping tin from copper surface and realizing full recycling of tail water

[0064] 1) Tin stripping

[0065] In the production tank, a tin stripping liquid is used to perform a tin stripping reaction on the tin-plated copper surface to obtain a tin stripping solution and a tin stripped copper surface;

[0066] The tin stripping solution includes 10 g / L copper protector (benzotriazole: methylbenzotriazole = 4:6), 10% nitric acid, 10 g / L ferric nitrate, 15 g / L ferric chloride, 10 g / L sodium chloride and 40 g / L citric acid, all of which are working concentrations;

[0067] The low concentration of citric acid (complexing agent) in the tin stripping solution can quickly precipitate the supersaturated tin nitrate;

[0068] 2) Multi-stage sedimentation

[0069] The liquid flow rate in the production tank is about 200 L / min. In the production tank, the tin stripping solution flows to the sedimentation tank through the liquid level difference. Three sedimentation tanks are set. There is a height difference from the production tank to the sedimentation tank, so that the solution flows naturally through the liquid level difference. The tin salt (tin nitrate) in the tin stripping solution entering the sedimentation tank settles to the bottom of the tank due to its own gravity to form tin mud.

[0070] 3) Recycling

[0071] The tin stripping liquid that has passed through the sedimentation tank is returned to the production tank for copper surface tin stripping;

[0072] Extract the tin mud at the bottom of the sedimentation tank, add oxalic acid and polyacrylamide to reduce the acidity of the tin mud to below 3.0 equivalents, fully precipitate the free tin ions and copper ions in the tin mud solution, make the precipitated tin mud particles larger, more conducive to subsequent filter pressing, and maximize the recovery of nitric acid;

[0073] The concentration of oxalic acid in the tin mud is 10-18 g / L;

[0074] The average molecular weight of the polyacrylamide is 200w, and the concentration in the tin mud is 150-200 ppm.

[0075] Example 9

[0076] A process for stripping tin from copper surface and realizing full recycling of tail water

[0077] 1) Tin stripping

[0078] In the production tank, a tin stripping liquid is used to perform a tin stripping reaction on the tin-plated copper surface to obtain a tin stripping solution and a tin stripped copper surface;

[0079] The tin stripping solution includes 10 g / L copper protector (benzotriazole: methylbenzotriazole = 4.5:5.5), 25% nitric acid, 40 g / L ferric nitrate, 5 g / L ferric chloride, 20 g / L sodium chloride and 10 g / L citric acid, all of which are working concentrations;

[0080] The low concentration of citric acid (complexing agent) in the tin stripping solution can quickly precipitate the supersaturated tin nitrate;

[0081] 2) Multi-stage sedimentation

[0082] The liquid flow rate in the production tank is about 200 L / min. In the production tank, the tin stripping solution flows to the sedimentation tank through the liquid level difference. Three sedimentation tanks are set. There is a height difference from the production tank to the sedimentation tank, so that the solution flows naturally through the liquid level difference. The tin salt (tin nitrate) in the tin stripping solution entering the sedimentation tank settles to the bottom of the tank due to its own gravity to form tin mud.

[0083] 3) Recycling

[0084] The tin stripping liquid that has passed through the sedimentation tank is returned to the production tank for copper surface tin stripping;

[0085] Extract the tin mud at the bottom of the sedimentation tank, add oxalic acid and polyacrylamide to reduce the acidity of the tin mud to below 3.0 equivalents, fully precipitate the free tin ions and copper ions in the tin mud solution, make the precipitated tin mud particles larger, more conducive to subsequent filter pressing, and maximize the recovery of nitric acid;

[0086] The concentration of oxalic acid in the tin mud is 5-15 g / L;

[0087] The average molecular weight of the polyacrylamide is 200w, and the concentration in the tin mud is 80-140 ppm.

[0088] The present invention is used in the treatment process of tin stripping of copper surface and realizing full recycling of tail water, so that the speed of tin stripping of copper surface is more stable and the copper surface after tin stripping is smoother. In addition, due to the low copper biting rate, the low copper ion concentration in the tin stripping wastewater is conducive to the sedimentation of tin mud and the subsequent wastewater recycling.

Claims

1. A process for stripping tin from copper surface and realizing full recycling of tail water, characterized in that: The steps include: 1) Tin stripping In the production tank, a tin stripping liquid is used to strip the tin-plated copper surface to obtain a tin stripping solution and a copper surface; The tin stripping solution includes a copper protecting agent, and the composition of the copper protecting agent includes one or more of benzotriazole, tolyltriazole, and benzimidazole; 2) Multi-stage sedimentation In the production tank, the tin stripping solution flows into the sedimentation tank through the liquid level difference. Three or more sedimentation tanks are set. There is a height difference from the production tank to the sedimentation tank, so that the solution flows naturally through the liquid level difference. The tin salt in the tin stripping solution entering the sedimentation tank settles to the bottom of the tank due to its own gravity to form tin mud. 3) Recycling The tin stripping liquid that has passed through the sedimentation tank is returned to the production tank for copper surface tin stripping; Extract the tin sludge at the bottom of the sedimentation tank, add oxalic acid and polyacrylamide to reduce the acidity of the tin sludge to below 3.0 equivalents, fully precipitate the free tin ions and copper ions in the tin sludge solution, make the precipitated tin sludge particles larger, more conducive to subsequent filter pressing, and maximize the recovery of nitric acid.

2. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The copper protecting agent is used at a concentration of 0-20 g / L.

3. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The copper protecting agent is used at a concentration of 8-12 g / L.

4. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The copper protecting agent is a combination of benzotriazole and toluenetriazole, and the mixing ratio is (1:9) to (9:1).

5. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The copper protecting agent is a combination of benzotriazole and toluenetriazole, and the mixing ratio is (4:6) to (6:4).

6. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The tin stripping solution also includes nitric acid, ferric nitrate, ferric chloride, sodium chloride and citric acid; the concentration of the nitric acid is 10-25%; The use concentration of the ferric nitrate is 5-40 g / L; The use concentration of the ferric chloride is 1-15 g / L; The use concentration of the sodium chloride is 2-20 g / L; The citric acid is used at a concentration of 5-40 g / L.

7. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The concentration of oxalic acid in the tin mud is 5-25 g / L.

8. The process for stripping tin from copper surface and realizing full recycling of tail water according to claim 1 is characterized in that: The average molecular weight of the polyacrylamide is 200w, and the concentration in the tin mud is 50-200 ppm.

Images