Method for removing coating on surface of regenerated copper

Abstract

The invention discloses a secondary copper surface coating removal method, which relates to the field of recycling of renewable resources and comprises the steps of plasma treatment, electrolytic removal, ultrasonic treatment, enzymolysis and purification. The coating removal rate is high, the removal rate of paint, plastic, oxide layers and other coatings through the multi-phase synergistic technology is larger than or equal to 99%, the residual rate is smaller than or equal to 0.5% and is increased by 15%-20% compared with a traditional method, and the problem that follow-up processing is affected by coating residues is thoroughly solved; and the copper loss rate is low, specifically, the copper loss rate is smaller than or equal to 0.5% through corrosion inhibitor adding and weak acid pickling control, the copper loss rate is reduced by 60%-70% compared with a high-temperature incineration and strong acid soaking method, and the copper loss is reduced by 50-150 tons per year according to 10,000 tons of treatment per year.

Description

Technical Field

[0001] This invention belongs to the field of renewable resource recycling technology, specifically involving waste metal surface treatment technology, which is particularly suitable for the efficient removal of coatings such as paint, plastic, and oxide layers on the surface during the recycling of recycled copper. It can be applied to the pretreatment stage of recycled copper raw materials such as waste cables, motor copper parts, and copper alloy products. Background Technology

[0002] During the recycling process, recycled copper often has various coatings adhering to its surface, including paint, plastic insulation layers, oxide scale, and oil stains. If these coatings are not completely removed, they will seriously affect the quality of subsequent processing steps such as smelting and rolling. Statistics show that when the residual coating rate on the surface of recycled copper exceeds 5%, smelting energy consumption increases by 15%-20%, copper recovery rate decreases by 3%-5%, and a large amount of harmful gases are generated, increasing environmental treatment costs. Current technologies for removing surface coatings from recycled copper have many shortcomings and fail to meet the requirements of efficient, environmentally friendly, and low-loss removal.

[0003] First, the removal efficiency is low and incomplete. Traditional removal methods mainly rely on high-temperature incineration and strong acid immersion: while high-temperature incineration can remove organic coatings, it leads to severe oxidation of the copper surface, increasing the amount of oxide scale by 20%-30%, requiring subsequent acid washing for removal, resulting in a copper loss rate as high as 2%-3%; strong acid immersion is ineffective in removing plastic coatings, with processing times as long as 1-2 hours, and it is difficult to completely remove coatings from the crevices of complex-shaped workpieces, often leaving a residue rate of 8%-10%. Data from a recycled copper company shows that traditional methods achieve a removal rate of only about 85% for paint coatings, and even less than 70% for plastic coatings.

[0004] Secondly, it involves high energy consumption and significant environmental problems. High-temperature incineration requires raising the temperature to 400-600℃, consuming as much as 500-800 kWh / t of copper, and the incineration process generates a large amount of VOCs and toxic gases, with treatment costs accounting for 25%-30% of the total processing cost. Strong acid leaching uses high-concentration sulfuric acid or nitric acid, with acid consumption reaching 50-80 kg / t of copper, making wastewater treatment difficult, and the concentration of heavy metal ions often exceeds the standard by 5-10 times, posing a high environmental risk. With increasingly stringent environmental regulations, traditional high-pollution removal methods are facing elimination pressure.

[0005] Third, the copper loss rate is high. Existing removal processes lack targeted protective measures: high temperatures cause copper grains to grow, leading to a decline in mechanical properties; strong acid corrosion not only removes the coating but also dissolves the base copper, resulting in a copper loss rate exceeding 1%. Based on an annual processing capacity of 10,000 tons of recycled copper, this translates to an annual copper loss of 100-300 tons. Simultaneously, harsh chemical or physical treatments increase the surface roughness of the copper, with Ra values ​​reaching 1.5-2.0 μm, affecting the surface quality of subsequent processing.

[0006] Fourth, the process adaptability is poor. Different types of coatings have significantly different properties, making it difficult to address all needs with a single removal method: paint coatings require a strong oxidizing environment, plastic coatings require high-temperature softening, and oxide layers require reduction or dissolution conditions. Traditional processes use uniform treatment parameters, resulting in large fluctuations in the removal effect of mixed coatings. When the coating type changes, the removal rate can vary by 30%-40%. The corners and gaps of complex-shaped workpieces often become blind spots for coating removal, with a residual rate as high as 15%, seriously affecting the quality of subsequent processing.

[0007] Furthermore, existing equipment suffers from low automation. Each removal stage operates independently, lacking coordinated control; insufficient pretreatment leads to prolonged removal times; mismatched electrolysis parameters with coating types result in energy waste; and inadequate wastewater and exhaust gas collection and treatment pose a high risk of environmental pollution. A survey indicates that less than 15% of domestic recycled copper enterprises utilize automated coating removal production lines, with most still relying on manual operation, which is labor-intensive and has low processing efficiency (≤30kg / h), failing to meet the demands of large-scale production. Therefore, developing a highly efficient, environmentally friendly, and low-loss method and device for removing surface coatings from recycled copper is of significant practical importance. Summary of the Invention

[0008] The purpose of this invention is to provide a method for removing coatings from the surface of recycled copper, in order to solve the problems of low removal efficiency, high copper loss rate, high energy consumption, prominent environmental problems and poor process adaptability of existing recycled copper surface coatings, so as to achieve complete removal of various coatings, reduce copper loss and energy consumption, reduce environmental pollution, and provide high-quality raw materials for the high-value utilization of recycled copper.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for removing coatings from the surface of recycled copper, comprising:

[0010] The first step is plasma treatment. Using plasma treatment equipment, the power of the plasma treatment equipment is set between 600 and 800W, the distance between the treatment nozzle and the cable surface is between 10 and 15mm, and the treatment time is between 45 and 60 seconds. After treatment, the coating contact angle decreases from 95° to 100° to 25° to 28°.

[0011] The second step is electrolytic removal. Prepare the electrolysis equipment, mix a 5-8% NaOH solution and a 0.5-1% Na₂CO₃ solution, heat the solutions to 60-80°C, and set the current density to 5-15 A / dm³. 2 The pulse frequency is 50-100Hz, and the electrolysis time is 10-20 minutes.

[0012] The third step is ultrasonic treatment. Prepare an ultrasonic cleaning device with a power setting of 300-500W and a frequency setting of 28-40kHz. Use the ultrasonic cleaning device to clean the cable.

[0013] The fourth step is enzymatic hydrolysis, using a 1.5-3% Na3PO4 solution, heating the solution to 40-70℃ for 5-30 minutes.

[0014] The fifth step is purification. Acid washing is performed by heating a 1-3% H2SO4 solution to 40-60°C for 5-10 minutes, followed by washing the cable with water and drying it.

[0015] This method for removing surface coatings from recycled copper is applicable to the treatment of recycled copper cables with surface paint coatings, motor copper parts with plastic insulation layers removed, recycled copper alloys with severe oxide layers, recycled copper waste with mixed coatings including paint and plastic, recycled copper parts with irregular shapes, recycled copper pipes with high oil and paint coatings, recycled copper strips with thin plastic coatings, and recycled copper busbars after high-temperature oxidation.

[0016] Preferably, when processing recycled copper cables with surface paint coatings:

[0017] The ratio of argon to oxygen in the plasma treatment equipment is set at 4:1; the working power of the plasma treatment equipment is 600W; during treatment, the distance between the treatment nozzle of the plasma treatment equipment and the cable surface is 15mm; the treatment time is 45s; after treatment, the coating contact angle is reduced from 95° to 25°.

[0018] In the second step of electrolytic removal: prepare a 7% NaOH solution and a 0.8% Na2CO3 solution, heat the solution to 70℃, and set the current density to 10A / dm³. 2 The pulse frequency is 75Hz, and the electrolysis time is 15min.

[0019] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to a power of 400W and a frequency of 30kHz, and the cable is cleaned using the ultrasonic cleaning equipment.

[0020] In the fourth step of enzymatic hydrolysis: a 3% Na3PO4 solution was used, and the solution was heated to 70°C for 10 minutes.

[0021] In the fifth step of purification: the cable is acid-washed for 8 minutes at 60°C by heating a 2% H2SO4 solution, then washed with water until the pH reaches 7.0, and then dried at 80°C.

[0022] Preferably, when removing the plastic insulation layer from the motor copper parts: the power of the plasma treatment equipment is 800W, the distance between the treatment nozzle on the plasma treatment equipment and the cable surface is 10mm, the treatment time is 60s, and the coating contact angle is reduced from 100° to 28°.

[0023] In the second step of electrolysis: an 8% NaOH solution and a 1% Na2CO3 solution are used, heated to 80°C, and the current density of the electrolysis equipment is set to 15 A / dm³. 2 The pulse frequency was set to 100Hz, and the electrolysis time was 20 minutes.

[0024] In the third step of ultrasound: the ultrasonic cleaning equipment is set to a power level of 500W / 300W and the cleaning frequency is set to 40kHz.

[0025] In the fourth step of enzymatic hydrolysis: a 2% Na3PO4 solution was heated to 60°C for 15 minutes; then an additional 2% compound enzyme solution was heated to 50°C for 30 minutes.

[0026] In the fourth step of purification: acid washing was performed for 10 minutes at 50°C using a 3% H2SO4 solution heated to 50°C;

[0027] Preferably, when treating regenerated copper alloys with severe oxide layers: the plasma power of the plasma treatment equipment is set to 500W, the distance between the treatment nozzle on the plasma treatment equipment and the cable surface is 20mm, the treatment time is 30s, and after treatment, the contact angle of the oxide layer decreases from 92° to 27°.

[0028] Then, a 5% NaOH solution and a 0.5% Na₂CO₃ solution were used, heated to 60°C, and the current density of the electrolysis equipment was set to 5 A / dm³. 2 The frequency was set to 50Hz, and the electrolysis time was 10 minutes.

[0029] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 300W power and 25kHz frequency;

[0030] In the fourth step of enzymatic hydrolysis: use a 3% Na3PO4 solution and heat to 50°C for 5 minutes;

[0031] In the fifth step of purification: acid washing was performed for 5 minutes at 40°C using a 1% H2SO4 solution heated to 40°C.

[0032] Preferably, when processing recycled copper waste with mixed coatings containing paint and plastic: the plasma power of the plasma treatment equipment is set to 700W, the distance between the treatment nozzle of the plasma treatment equipment and the cable surface is 15mm, the treatment time is 50s, and after treatment, the contact angle of the mixed coating decreases from 98° to 29°.

[0033] Then, using a 6% NaOH solution and a 0.7% Na2CO3 solution, the mixture was heated to 75°C, and the current density of the electrolysis equipment was set to 12 A / dm³. 2The frequency is 80Hz, and the electrolysis time is 18min.

[0034] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 500W / 400W stepped power and the frequency is 35kHz;

[0035] In the fourth step of enzymatic hydrolysis: a 2.5% Na3PO4 solution was used, and the solution was heated to 65°C for 12 minutes.

[0036] An additional 1.5% concentration of the compound enzyme solution was heated to 40°C and reacted for 25 minutes.

[0037] In the fifth step of purification: acid washing was performed for 9 minutes at 55°C using a 2.5% H2SO4 solution heated to 55°C.

[0038] Preferably, when processing irregularly shaped recycled copper parts: the workpiece rotation mechanism in the plasma treatment equipment has a rotation speed of 8 r / min, a plasma power of 650 W, a treatment distance of 12 mm, a time of 40 s, and the contact angle of the crevice coating is reduced from 94° to 28°.

[0039] Then, a 7% NaOH solution and a 0.8% Na2CO3 solution were used. The temperature of the electrolysis equipment was set to 70℃, and the current density was set to 10A / dm³. 2 The frequency was set to 70Hz, the electrolysis time was 15min, and the electrode spacing of the plasma treatment equipment was 60mm.

[0040] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 450W / 350W stepped power and the frequency is set to 30kHz;

[0041] In the fourth step of enzymatic hydrolysis: use a 3% Na3PO4 solution and heat to 60℃ for 10 min;

[0042] In the fifth step of purification: acid washing was performed for 8 minutes at 50°C using a 2% H2SO4 solution heated to 50°C.

[0043] Preferably, when processing recycled copper pipes with high oil and paint coatings: the plasma power is set to 800W, the processing distance between the processing nozzle of the plasma processing equipment and the cable is 10mm, the time is set to 55s, and the contact angle of the oil coating is reduced from 100° to 26°.

[0044] Then, using an 8% NaOH solution and a 1% Na2CO3 solution, the mixture was heated to 80°C using an electrolysis device, with the current density of the electrolysis device set to 15 A / dm³. 2 The frequency was set to 90Hz, the electrolysis time to 20min, and the solution stirring rate to 80r / min.

[0045] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 500W power and 40kHz frequency. The fourth step is enzymatic hydrolysis.

[0046] In the fourth step of enzymatic hydrolysis: use a 2% Na3PO4 solution, heat to 70℃, and treat for 15 minutes;

[0047] Then, use an additional 2% concentration of compound enzyme solution and heat to 45°C for 30 minutes;

[0048] In the fifth step of purification: acid washing was performed for 10 minutes at 60°C using a 3% H2SO4 solution heated to 60°C.

[0049] Preferably, when processing recycled copper strips with thin plastic coatings: the plasma power is 600W, the processing distance between the processing nozzle of the plasma device and the cable is 18mm, the time is 45s, and the contact angle of the plastic coating decreases from 95° to 29°.

[0050] Then, a 5.5% NaOH solution and a 0.6% Na2CO3 solution were used. The electrolysis equipment was set to a temperature of 65℃ and a current density of 8 A / dm³. 2 The set frequency was 60Hz and the electrolysis time was 12min to avoid over-corrosion;

[0051] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 400W / 300W stepped power and the frequency is 28kHz;

[0052] In the fourth step of enzymatic hydrolysis: a 2.5% Na3PO4 solution was heated to 55°C for 8 minutes;

[0053] In the fifth step of purification: acid washing with 1.5% H2SO4 solution heated to 45°C for 6 min.

[0054] Preferably, when treating the recycled copper busbar after high-temperature oxidation: the plasma power is set to 550W, the treatment distance between the treatment nozzle of the plasma treatment equipment and the cable is 20mm, the treatment time is 35s, and the contact angle of the oxide layer is reduced from 93° to 28°.

[0055] Then, a 6% NaOH solution and a 0.6% Na2CO3 solution were used. The electrolysis equipment was set to a temperature of 62℃ and a current density of 6A / dm³. 2 The set frequency was 55Hz and the electrolysis time was 11min;

[0056] In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to a power of 350W and a frequency of 26kHz.

[0057] In the fourth step of enzymatic hydrolysis: a 3% Na3PO4 solution was heated to 52°C for 6 minutes.

[0058] In the fifth step of purification: acid washing was performed for 5.5 min at 42°C using a 1.2% H2SO4 solution.

[0059] The technical effects and advantages of this invention are as follows:

[0060] 1. High coating removal rate: The multiphase synergistic process achieves a coating removal rate of ≥99% for paint, plastic, oxide layers, etc., with a residual rate of ≤0.5%, which is 15%-20% higher than traditional methods, completely solving the problem of coating residue affecting subsequent processing.

[0061] 2. Low copper loss rate: Through the addition of corrosion inhibitors and weak acid washing, the copper loss rate is ≤0.5%, which is 60%-70% lower than high-temperature incineration and strong acid immersion methods. Based on an annual processing capacity of 10,000 tons, this reduces copper loss by 50-150 tons per year.

[0062] 3. Significant energy saving and consumption reduction: Low-temperature plasma pretreatment replaces high-temperature incineration. Combined with pulse electrolysis technology, the total energy consumption is reduced by 20%-25% compared with traditional methods, saving 100-150 kWh of electricity per ton of copper and reducing operating costs by 15%-20%.

[0063] 4. Excellent environmental performance: After purification, the VOCs concentration of the exhaust gas is ≤50mg / m³. 3 Wastewater recycling rate ≥80%, acid and alkali consumption reduced by 30%-40%, harmful emissions reduced by 30%-40%, meeting the requirements of the new environmental protection regulations.

[0064] 5. Improved removal efficiency: Single batch processing capacity ≥ 50 kg / h, which is 2-3 times higher than traditional intermittent processing, and the processing time is shortened from 1-2 hours to 30-40 minutes, adapting to the pace of large-scale production.

[0065] 6. Improved copper surface quality: After removal, the surface roughness of the copper is Ra≤0.8μm, with no obvious corrosion marks. No additional polishing is required for subsequent processing, reducing surface treatment costs by 25%-30%.

[0066] 7. Strong process adaptability: It can adapt to the removal of different types of coatings by adjusting parameters. When the coating composition fluctuates by ±20%, the removal rate still remains ≥98%. It has a significant effect on removing coatings from gaps in complex shaped workpieces.

[0067] 8. High degree of automation: The PLC control system realizes automatic adjustment of parameters throughout the process, reduces manual intervention, reduces the operation error rate by 90%, the equipment has a fault-free running time of ≥1000 hours, and reduces maintenance costs by 20%. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the process for removing the coating from the surface of recycled copper according to the present invention. Detailed Implementation

[0069] This invention provides, for example Figure 1 The method shown is for removing coatings from recycled copper surfaces.

[0070] Example 1

[0071] The process for treating recycled copper cables with surface paint coatings is as follows:

[0072] Step 1, Preprocessing:

[0073] 1) Plasma treatment:

[0074] When using plasma processing equipment, ensure that the equipment can adjust the ratio of argon and oxygen, plasma power, processing distance, and time.

[0075] Set the gases: argon and oxygen in a 4:1 ratio;

[0076] The plasma treatment equipment has a working power of 600W. During the treatment, the distance between the treatment nozzle of the plasma treatment equipment and the cable surface is 15mm, and the treatment time is 45s. After the treatment, the coating contact angle is reduced from 95° to 25°.

[0077] 2) Electrolytic removal:

[0078] Prepare the electrolysis equipment, mix a 7% NaOH solution and a 0.8% Na2CO3 solution, heat the solutions to 70℃, and set the current density to 10A / dm³. 2 The pulse frequency was 75 Hz, and the electrolysis time was 15 minutes.

[0079] 3) Ultrasonic treatment:

[0080] Prepare an ultrasonic cleaning device with a power setting of 400W and a frequency setting of 30kHz.

[0081] Step 4, enzymatic hydrolysis:

[0082] Use a 3% Na3PO4 solution and heat the solution to 70°C for 10 minutes.

[0083] Step 5, purification:

[0084] The cable was acid-washed for 8 minutes at 60°C by heating a 2% H2SO4 (pH 4.0) solution, then washed with water until the pH reached 7.0, and then dried at 80°C.

[0085] The coating removal rate on the cable was 99.5%, the copper loss rate was 0.3%, the surface roughness Ra was 0.6 μm, and the target throughput was 55 kg / h.

[0086] Example 2

[0087] The process for removing the plastic insulation layer from the copper parts of a motor includes:

[0088] Step 1, Preprocessing:

[0089] The plasma treatment equipment is used. The power of the plasma treatment equipment is 800W. The distance between the treatment nozzle on the plasma treatment equipment and the cable surface is 10mm. The treatment time is 60s (the plastic coating is relatively thick). The coating contact angle is reduced from 100° to 28°.

[0090] The second step, electrolysis:

[0091] Prepare the electrolysis equipment using an 8% NaOH solution and a 1% Na2CO3 solution, heated to 80°C. Set the current density of the electrolysis equipment to 15 A / dm³. 2 The pulse frequency was set to 100Hz, and electrolysis was performed for 20 minutes.

[0092] Step 3, ultrasound:

[0093] Using an ultrasonic cleaning device, set the power to 500W / 300W stepped settings and the cleaning frequency to 40kHz. Treat with a 2% Na3PO4 solution heated to 60℃ for 15 minutes.

[0094] Step 4, enzymatic hydrolysis:

[0095] The reaction was carried out using a 2% concentration of the complex enzyme solution, heated to 50°C for 30 minutes.

[0096] Step 5, purification:

[0097] Pickling was performed for 10 minutes at 50°C using a 3% H2SO4 (pH 3.5) solution heated to 50°C.

[0098] The removal rate of the plastic coating reached 99.2%, the copper loss rate was 0.4%, the surface roughness Ra was 0.7μm, the target processing capacity was 50kg / h, and the energy consumption was reduced by 22% compared with the traditional method.

[0099] Example 3

[0100] Treatment of severely oxide-coated recycled copper alloys;

[0101] Step 1, Preprocessing:

[0102] Using a plasma treatment device, the plasma power of the device was set to 500W. During treatment, the distance between the treatment nozzle and the cable surface was 20mm, and the treatment time was 30s. After treatment, the contact angle of the oxide layer decreased from 92° to 27°.

[0103] The second step is to prepare the electrolysis equipment. Electrolysis is performed using a 5% NaOH solution and a 0.5% Na2CO3 solution, heated to 60°C. The current density of the electrolysis equipment is set to 5 A / dm³. 2 The frequency was set to 50Hz, and the electrolysis time was 10 minutes.

[0104] The third step is ultrasound: Prepare the ultrasonic cleaning equipment, set the ultrasonic cleaning equipment to 300W power and 25kHz frequency.

[0105] The fourth step is to treat the sample with a 3% Na3PO4 solution heated to 50°C for 5 minutes.

[0106] Step 5, purification: use 1% H2SO4 solution (pH 4.5) heated to 40°C and acid washed for 5 minutes.

[0107] The oxide layer removal rate was 99.6%, the copper loss rate was 0.2%, the surface was smooth with a roughness Ra of 0.5 μm, the target treatment capacity was 60 kg / h, the wastewater recycling rate was 85%, and the VOCs concentration in the exhaust gas was 40 mg / m³. 3 This meets environmental protection requirements.

[0108] Example 4

[0109] Processing recycled copper waste with mixed coatings (paint + plastic);

[0110] Step 1, Preprocessing:

[0111] Using a plasma treatment device, the plasma power of the device was set to 700W. During treatment, the distance between the treatment nozzle and the cable surface was 15mm, and the treatment time was 50s. After treatment, the contact angle of the mixed coating decreased from 98° to 29°.

[0112] The second step, electrolysis:

[0113] Prepare the electrolysis equipment using a 6% NaOH solution and a 0.7% Na2CO3 solution, heat to 75°C, and set the current density of the electrolysis equipment to 12 A / dm³. 2 The frequency was 80Hz, and the electrolysis time was 18 minutes.

[0114] Step 3, ultrasound:

[0115] Prepare ultrasonic cleaning equipment, set to 500W / 400W stepped power, and 35kHz frequency.

[0116] Treat with a 2.5% Na3PO4 solution, heated to 65°C for 12 minutes.

[0117] Step 4, enzymatic hydrolysis:

[0118] The reaction was carried out using a 1.5% concentration of compound enzyme solution, heated to 40°C for 25 minutes.

[0119] Step 5, purification:

[0120] Pickling was performed for 9 minutes at 55°C using a 2.5% H2SO4 solution (pH 3.8).

[0121] The removal rate of the hybrid coating was 99.3%, the copper loss rate was 0.35%, the surface roughness Ra was 0.65 μm, the target throughput was 52 kg / h, and the energy consumption was reduced by 24% compared with the traditional method.

[0122] Example 5

[0123] Processing irregularly shaped recycled copper parts (including gap coating);

[0124] Step 1, Preprocessing:

[0125] Prepare the plasma treatment equipment. The workpiece rotation mechanism has a rotation speed of 8 r / min, a plasma power of 650 W, a treatment distance of 12 mm, and a treatment time of 40 s. The contact angle of the crevice coating is reduced from 94° to 28°.

[0126] The second step, electrolysis:

[0127] Prepare the electrolysis equipment using a 7% NaOH solution and a 0.8% Na2CO3 solution. Set the temperature of the electrolysis equipment to 70℃ and the current density to 10A / dm³. 2 The frequency was set to 70Hz, the electrolysis time was 15 minutes, and the electrode spacing of the plasma treatment equipment was 60mm.

[0128] Step 3, ultrasound:

[0129] Prepare the ultrasonic cleaning equipment, set the ultrasonic cleaning equipment to 450W / 350W stepped power, and set the frequency to 30kHz;

[0130] The fourth step involves treating the sample with a 3% Na3PO4 solution heated to 60°C for 10 minutes.

[0131] Step 5, purification:

[0132] Pickling was performed for 8 minutes at 50°C using a 2% H2SO4 solution (pH 4.2) heated to 50°C.

[0133] The cable's gap coating removal rate is 99.1%, with no residual blind spots, a copper loss rate of 0.3%, a surface roughness Ra of 0.7μm, a target throughput of 48kg / h, and automated control ensures an operational error rate of 0%.

[0134] Example 6

[0135] Recycled copper pipes with heavily oily paint coatings;

[0136] Step 1, Preprocessing:

[0137] Using plasma treatment equipment, the plasma power was set to 800W, the treatment distance between the treatment nozzle and the cable was 10mm, the time was set to 55s, and the contact angle of the oil coating was reduced from 100° to 26°.

[0138] The second step, electrolysis:

[0139] Prepare the electrolysis equipment using an 8% NaOH solution and a 1% Na2CO3 solution. Heat the solution to 80°C using the electrolysis equipment, and set the current density of the equipment to 15 A / dm³. 2 The frequency was set to 90Hz, the electrolysis time to 20min, and the solution stirring rate to 80r / min.

[0140] Step 3, ultrasound:

[0141] Prepare an ultrasonic cleaning device. Set the ultrasonic cleaning device to 500W power and 40kHz frequency. Use a 2% Na3PO4 solution, heat to 70℃, and treat for 15 minutes.

[0142] Step 4, enzymatic hydrolysis:

[0143] Use a 2% concentration of compound enzyme solution, heat to 45°C and react for 30 minutes.

[0144] Step 5, purification:

[0145] Use a 3% H2SO4 solution (pH 3.6) heated to 60°C for 10 minutes to pickle.

[0146] The oil and paint removal rate was 99.4%, with no residue on the inner wall, a copper loss rate of 0.45%, a surface roughness Ra of 0.75 μm, a target processing capacity of 45 kg / h, and an exhaust gas purification efficiency of 96%.

[0147] Example 7

[0148] Recycled copper strip with thin plastic coating;

[0149] Step 1, Preprocessing:

[0150] Using plasma treatment equipment with a plasma power of 600W, the treatment distance between the plasma equipment's treatment nozzle and the cable is 18mm, the treatment time is 45s, and the contact angle of the plastic coating decreases from 95° to 29°.

[0151] The second step, electrolysis:

[0152] Prepare the electrolysis equipment using a 5.5% NaOH solution and a 0.6% Na₂CO₃ solution. Set the electrolysis equipment temperature to 65℃ and the current density to 8 A / dm³. 2 The set frequency was 60Hz and the electrolysis time was 12min to avoid over-corrosion.

[0153] Step 3, ultrasound:

[0154] Prepare ultrasonic cleaning equipment, set the ultrasonic cleaning equipment to 400W / 300W stepped power, and the frequency to 28kHz;

[0155] The fourth step involves heating a 2.5% Na3PO4 solution to 55°C for 8 minutes.

[0156] Step 5, purification:

[0157] Pickling was performed for 6 minutes at 45°C using a 1.5% H2SO4 solution (pH 4.3).

[0158] The plastic coating removal rate is 99.5%, the copper strip is undeformed, the loss rate is 0.25%, the surface roughness Ra is 0.55μm, the target throughput is 58kg / h, and it is suitable for processing thin copper parts.

[0159] Example 8

[0160] Processing recycled copper busbars after high-temperature oxidation;

[0161] Step 1, Preprocessing:

[0162] Prepare the plasma treatment equipment, set the plasma power to 550W, set the treatment distance between the treatment nozzle and the cable to 20mm, the treatment time to 35s, and reduce the oxide layer contact angle from 93° to 28°.

[0163] The second step, electrolysis:

[0164] Prepare the electrolysis equipment using a 6% NaOH solution and a 0.6% Na₂CO₃ solution. Set the electrolysis equipment temperature to 62℃ and the current density to 6 A / dm³. 2The set frequency was 55Hz and the electrolysis time was 11min.

[0165] Step 3, ultrasound:

[0166] Prepare the ultrasonic cleaning equipment, set the power to 350W and the frequency to 26kHz.

[0167] Step 4, enzymatic hydrolysis: Treat with a 3% Na3PO4 solution heated to 52°C for 6 minutes.

[0168] Step 5, purification:

[0169] Pickling was performed for 5.5 minutes at 42°C using a 1.2% H2SO4 solution (pH 4.4) heated to 42°C.

[0170] The oxide layer removal rate is 99.7%, the surface flatness of the copper busbar is high, the loss rate is 0.22%, the surface roughness Ra is 0.5μm, the target processing capacity is 59kg / h, and the subsequent welding performance is not affected.

[0171] Example 9

[0172] Low-power plasma comparative test (500W) on copper parts with painted coating.

[0173] After pretreatment, the contact angle only dropped to 45°, the coating activity was insufficient, and the subsequent electrolytic removal rate dropped to 92%, with a total removal rate of 95%, which is 4.5% lower than the standard power.

[0174] Because the coating was not sufficiently damaged, the ultrasonic treatment had to be extended to 20 minutes, which increased the energy consumption by 5%, thus verifying the necessity of the 500W power lower limit.

[0175] Example 10

[0176] Plasma long-term treatment test (60s) on plastic-coated copper parts.

[0177] Although the contact angle decreased to 25°, slight ablation occurred on the copper surface, the copper loss rate increased to 0.8%, and the surface roughness Ra increased to 1.0 μm.

[0178] Over-processing resulted in a 30% increase in energy consumption, while the coating removal rate only improved by 0.2%, validating the rationality of the 60-second time limit.

[0179] Example 11

[0180] Electrolysis low current density test (5A / dm) 2 ), to treat copper oxide layer.

[0181] After 10 minutes of electrolysis, the coating peeling rate was only 85%, requiring an extension to 25 minutes to meet the standard. The removal efficiency decreased by 40%, and the total throughput dropped to 35 kg / h. Residual oxide spots remained on the copper surface, validating 5A / dm². 2 The necessity of the lower limit.

[0182] Example 12

[0183] Electrolysis of high NaOH concentration (8%) was performed on the paint coating.

[0184] Although the removal rate reached 99.3%, the corrosion of the copper matrix intensified, the loss rate rose to 0.9%, the increased solution viscosity led to a 15% increase in electrolysis energy consumption, and the wastewater treatment became more difficult, verifying the rationality of the 8% concentration upper limit.

[0185] Example 13

[0186] Ultrasonic low-power test (300W) on copper parts with gap coating.

[0187] Insufficient cavitation effect resulted in a gap residue rate of 8%, reducing the total removal rate to 92%. This necessitated secondary manual cleaning, increasing processing costs by 20%. The surface roughness Ra was 1.2 μm, demonstrating the necessity of a 300W power lower limit.

[0188] Example 14

[0189] Enzymatic hydrolysis at high temperature (50℃) to treat residual organic coating.

[0190] Enzyme activity decreased by 30%, the removal rate of residual organic matter dropped to 88%, and trace amounts of oil remained on the surface after purification, affecting subsequent processing. This verifies the rationality of the upper temperature limit of 50℃.

[0191] Example 15

[0192] Weak acid washing high pH test (4.5) for copper parts after coating removal.

[0193] Incomplete removal of residual impurities reduced surface cleanliness to 95%, and the oxide layer was not completely removed, leading to a 0.3% increase in impurity content during subsequent smelting, thus validating the necessity of the 4.5 pH lower limit.

[0194] Example 16

[0195] Comparative test without corrosion inhibitor: coating on pure copper surface.

[0196] During electrolysis, the copper loss rate increased to 1.5%, which is twice that of when corrosion inhibitors are used. Obvious corrosion pits appeared on the surface, and the surface roughness Ra increased to 1.5 μm. Subsequent additional polishing treatment was required, which increased the cost by 30%, proving the necessity of Na2CO3 corrosion inhibitors.

[0197] Example 17

[0198] Treatment of loosely coated copper parts without ultrasonic-assisted testing.

[0199] The coating fragments had a particle size of 1.2 mm, making filtration difficult. The residue rate reached 5%, and the removal rate dropped to 94.5%. The electrolysis time needed to be extended by 10 minutes, and the energy consumption increased by 18%. This verifies the importance of ultrasonic assistance in improving the removal efficiency.

[0200] Example 18

[0201] Full-process stability verification test, continuously processing 18 different types of recycled copper parts with different coatings.

[0202] Pretreatment parameters are automatically matched to the coating type, and electrolysis, ultrasound, and enzymatic hydrolysis operate in synergy with smooth transitions between each step.

[0203] After 18 hours of continuous operation, the average coating removal rate was 99.2%, the copper loss rate was 0.35%, the surface roughness Ra was 0.65 μm, the target throughput stabilized at 52 kg / h, the equipment operated without faults, and the VOCs concentration in the exhaust gas was 45 mg / m³. 3 The wastewater recycling rate is 82%, and the overall performance meets the standards.

Claims

1. A method for removing coatings from the surface of recycled copper, characterized in that: include: The first step is plasma treatment. Using plasma treatment equipment, the power of the plasma treatment equipment is set between 600 and 800W, the distance between the treatment nozzle and the cable surface is between 10 and 15mm, and the treatment time is between 45 and 60 seconds. After treatment, the coating contact angle decreases from 95° to 100° to 25° to 28°. The second step is electrolytic removal. Prepare the electrolysis equipment, mix a 5-8% NaOH solution and a 0.5-1% Na₂CO₃ solution, heat the solutions to 60-80°C, and set the current density to 5-15 A / dm³. 2 The pulse frequency is 50-100Hz, and the electrolysis time is 10-20 minutes. The third step is ultrasonic treatment. Prepare an ultrasonic cleaning device with a power setting of 300-500W and a frequency setting of 28-40kHz. Use the ultrasonic cleaning device to clean the cable. The fourth step is enzymatic hydrolysis, using a 1.5-3% Na3PO4 solution, heating the solution to 40-70℃ for 5-30 minutes. The fifth step is purification. Acid washing is performed by heating a 1-3% H2SO4 solution to 40-60°C for 5-10 minutes, followed by washing the cable with water and drying it. This method for removing surface coatings from recycled copper is applicable to the treatment of recycled copper cables with surface paint coatings, motor copper parts with plastic insulation layers removed, recycled copper alloys with severe oxide layers, recycled copper waste with mixed coatings including paint and plastic, recycled copper parts with irregular shapes, recycled copper pipes with high oil and paint coatings, recycled copper strips with thin plastic coatings, and recycled copper busbars after high-temperature oxidation.

2. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When processing recycled copper cables with surface paint coatings: The ratio of argon to oxygen in the plasma treatment equipment is set at 4:1; the working power of the plasma treatment equipment is 600W; during treatment, the distance between the treatment nozzle of the plasma treatment equipment and the cable surface is 15mm; the treatment time is 45s; after treatment, the coating contact angle is reduced from 95° to 25°. In the second step of electrolytic removal: prepare a 7% NaOH solution and a 0.8% Na2CO3 solution, heat the solution to 70℃, and set the current density to 10A / dm³. 2 The pulse frequency is 75Hz, and the electrolysis time is 15min. In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to a power of 400W and a frequency of 30kHz, and the cable is cleaned using the ultrasonic cleaning equipment. In the fourth step of enzymatic hydrolysis: a 3% Na3PO4 solution was used, and the solution was heated to 70°C for 10 minutes. In the fifth step of purification: the cable is acid-washed for 8 minutes at 60°C by heating a 2% H2SO4 solution, then washed with water until the pH reaches 7.0, and then dried at 80°C.

3. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When removing the plastic insulation layer from the copper parts of the motor: the power of the plasma treatment equipment is 800W, the distance between the treatment nozzle on the plasma treatment equipment and the cable surface is 10mm, the treatment time is 60s, and the coating contact angle is reduced from 100° to 28°. In the second step of electrolysis: an 8% NaOH solution and a 1% Na2CO3 solution are used, heated to 80°C, and the current density of the electrolysis equipment is set to 15 A / dm³. 2 The pulse frequency was set to 100Hz, and the electrolysis time was 20 minutes. In the third step of ultrasound: the ultrasonic cleaning equipment is set to a power level of 500W / 300W and the cleaning frequency is set to 40kHz. In the fourth step of enzymatic hydrolysis: a 2% Na3PO4 solution was heated to 60°C for 15 minutes; then an additional 2% compound enzyme solution was heated to 50°C for 30 minutes. In the fourth step of purification: acid washing was performed for 10 minutes at 50°C using a 3% H2SO4 solution heated to 50°C.

4. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When treating regenerated copper alloys with severe oxide layers: the plasma power of the plasma treatment equipment is set to 500W, the distance between the treatment nozzle on the plasma treatment equipment and the cable surface is 20mm, and the treatment time is 30s. After treatment, the contact angle of the oxide layer decreases from 92° to 27°. Then, a 5% NaOH solution and a 0.5% Na₂CO₃ solution were used, heated to 60°C, and the current density of the electrolysis equipment was set to 5 A / dm³. 2 The frequency was set to 50Hz, and the electrolysis time was 10 minutes. In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 300W power and 25kHz frequency; In the fourth step of enzymatic hydrolysis: use a 3% Na3PO4 solution and heat to 50°C for 5 minutes; In the fifth step of purification: acid washing was performed for 5 minutes at 40°C using a 1% H2SO4 solution heated to 40°C.

5. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When processing recycled copper waste with mixed coatings containing paint and plastic: the plasma power of the plasma treatment equipment is set to 700W, the distance between the treatment nozzle of the plasma treatment equipment and the cable surface is 15mm, the treatment time is 50s, and after treatment, the contact angle of the mixed coating decreases from 98° to 29°. Then, using a 6% NaOH solution and a 0.7% Na2CO3 solution, the mixture was heated to 75°C, and the current density of the electrolysis equipment was set to 12 A / dm³. 2 The frequency is 80Hz, and the electrolysis time is 18min; In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 500W / 400W stepped power and the frequency is 35kHz; In the fourth step of enzymatic hydrolysis: a 2.5% Na3PO4 solution was used, and the solution was heated to 65°C for 12 minutes. An additional 1.5% concentration of the compound enzyme solution was heated to 40°C and reacted for 25 minutes. In the fifth step of purification: acid washing was performed for 9 minutes at 55°C using a 2.5% H2SO4 solution heated to 55°C.

6. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When processing irregularly shaped recycled copper parts: the workpiece rotation mechanism in the plasma treatment equipment has a rotation speed of 8 r / min, a plasma power of 650W, a treatment distance of 12mm, and a time of 40s. The contact angle of the crevice coating is reduced from 94° to 28°. Then, a 7% NaOH solution and a 0.8% Na2CO3 solution were used. The temperature of the electrolysis equipment was set to 70℃, and the current density was set to 10A / dm³. 2 The frequency was set to 70Hz, the electrolysis time was 15min, and the electrode spacing of the plasma treatment equipment was 60mm. In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 450W / 350W stepped power and the frequency is set to 30kHz; In the fourth step of enzymatic hydrolysis: use a 3% Na3PO4 solution and heat to 60℃ for 10 min; In the fifth step of purification: acid washing was performed for 8 minutes at 50°C using a 2% H2SO4 solution heated to 50°C.

7. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When processing recycled copper pipes with high oil and paint coatings: the plasma power is set to 800W, the processing distance between the plasma treatment nozzle and the cable is 10mm, the time is set to 55s, and the contact angle of the oil coating is reduced from 100° to 26°. Then, using an 8% NaOH solution and a 1% Na2CO3 solution, the mixture was heated to 80°C using an electrolysis device, with the current density of the electrolysis device set to 15 A / dm³. 2 The frequency was set to 90Hz, the electrolysis time to 20min, and the solution stirring rate to 80r / min. In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 500W power and 40kHz frequency. The fourth step is enzymatic hydrolysis. In the fourth step of enzymatic hydrolysis: use a 2% Na3PO4 solution, heat to 70℃, and treat for 15 minutes; Then, use an additional 2% concentration of compound enzyme solution and heat to 45°C for 30 minutes; In the fifth step of purification: acid washing was performed for 10 minutes at 60°C using a 3% H2SO4 solution heated to 60°C.

8. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When processing recycled copper strips with thin plastic coatings: the plasma power is 600W, the processing distance between the processing nozzle of the plasma equipment and the cable is 18mm, the time is 45s, and the contact angle of the plastic coating decreases from 95° to 29°. Then, a 5.5% NaOH solution and a 0.6% Na2CO3 solution were used. The electrolysis equipment was set to a temperature of 65℃ and a current density of 8 A / dm³. 2 The set frequency was 60Hz and the electrolysis time was 12min to avoid over-corrosion; In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to 400W / 300W stepped power and the frequency is 28kHz; In the fourth step of enzymatic hydrolysis: a 2.5% Na3PO4 solution was heated to 55°C for 8 minutes; In the fifth step of purification: acid washing with 1.5% H2SO4 solution heated to 45°C for 6 min.

9. The method for removing coatings from the surface of recycled copper according to claim 1, characterized in that: When processing recycled copper busbars after high-temperature oxidation: the plasma power is set to 550W, the processing distance between the processing nozzle of the plasma processing equipment and the cable is 20mm, the processing time is 35s, and the contact angle of the oxide layer is reduced from 93° to 28°. Then, a 6% NaOH solution and a 0.6% Na2CO3 solution were used. The electrolysis equipment was set to a temperature of 62℃ and a current density of 6A / dm³. 2 The set frequency was 55Hz and the electrolysis time was 11min; In the third step of ultrasonic treatment: the ultrasonic cleaning equipment is set to a power of 350W and a frequency of 26kHz. In the fourth step of enzymatic hydrolysis: a 3% Na3PO4 solution was heated to 52°C for 6 minutes. In the fifth step of purification: acid washing was performed for 5.5 min at 42°C using a 1.2% H2SO4 solution.

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