Method for recovering copper and PET from waste PET copper foil step by step

Abstract

The invention relates to the technical field of composite copper foil recovery, in particular to a method for recovering copper and PET (polyethylene terephthalate) from waste PET copper foil step by step, which comprises the following steps: 1) obtaining the waste PET copper foil; (2) the waste PET copper foil obtained in the step (1) is immersed in a leaching treatment solution containing H2SO4, CuSO4 and NaCl, and a leaching solution containing copper and a PET base material are obtained; 3) recovering copper from the leachate by adopting an electrochemical deposition method, and obtaining a copper deposit; 4) respectively pretreating a cross-linking agent DGEBA (bisphenol A diglycidyl ether), a catalyst Zn (acac) 2 (zinc acetylacetonate) and the PET base material separated in the step 2), and then mixing to obtain a mixed material; 5, PET is recycled from the mixed material in the step 4 through a Vitrimers chemical modification method.According to the method, the integrated process of selective leaching-electrodeposition cooperating with copper recycling and Vitrimers chemical modification PET regeneration is adopted, the treatment cost is low, the requirements for environmental protection and sustainable development are met, and it is possible that PET copper foil is efficiently recycled in an environment-friendly mode.

Description

Technical Field

[0001] This invention belongs to the field of composite copper foil recycling technology, and in particular relates to a method for stepwise recycling of copper and PET from waste PET copper foil. Background Technology

[0002] With the rapid development of new energy vehicles and the electronics industry, the demand for PET composite copper foil as a key material for lithium battery current collectors and electronic insulating coatings has surged. However, the defective and waste products generated during the production process are difficult to recycle efficiently through traditional physical sorting due to their complex structure (the copper layer is tightly bonded to the PET substrate).

[0003] In existing technologies, physical recycling largely relies on processes such as mechanical crushing and flotation, but these methods easily lead to the breakage of PET molecular chains, enabling only downgraded utilization (such as recycled fibers) and failing to separate high-purity copper resources. While chemical recycling can depolymerize PET, the integrated separation of composite copper foil still faces problems such as demanding reaction conditions, cumbersome processes, and secondary pollution. Therefore, solutions are urgently needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for stepwise recovery of copper and PET from waste PET copper foil. The method adopts an integrated process of selective leaching-electrodeposition synergistic copper recovery and Vitrimers chemical modification for PET recycling. It has low processing cost, meets the requirements of environmental protection and sustainable development, and makes efficient and environmentally friendly recycling of PET copper foil possible.

[0005] To achieve the aforementioned objective, the technical solution of the present invention is implemented as follows: a method for stepwise recycling of copper and PET from waste PET copper foil, comprising the following steps: 1) Obtain waste PET copper foil; 2) The obtained waste PET copper foil is immersed in a leaching solution containing H2SO4, CuSO4 and NaCl to obtain a copper-containing leaching solution and PET substrate. 3) The leachate is placed in a two-chamber electrolysis device, and copper is recovered from the leachate by electrochemical deposition to obtain copper deposits; 4) The crosslinking agent DGEBA (bisphenol A diglycidyl ether), the catalyst Zn(acac)2 (zinc acetylacetonate), and the PET substrate separated in step 2) are respectively pretreated; 5) The material from step 4) was recycled as PET using the Vitrimers chemical modification method.

[0006] Furthermore, in step 2), the concentration ratio of chloride to copper (Ccl / Ccu) in the leaching solution is not less than 8, the solid-liquid ratio is set to 1 / 8 to 1 / 15 (g / ml), and the leaching duration for each leaching treatment is 10 to 16 hours.

[0007] Furthermore, in step 2), during the dismantling and metal leaching process of the copper foil on the waste PET copper foil, air is continuously blown into the leaching solution to regenerate the oxidant in situ, so that the PET substrate obtained after the dismantling / leaching operation maintains structural integrity.

[0008] Furthermore, in step 3), the anode of the electrochemical deposition method uses a copper sheet with a purity of 99.8%, and the cathode uses a graphite block; the anode chamber and cathode chamber of the dual-chamber electrolysis device are separated by a ceramic membrane, and both the anode chamber and the cathode chamber are filled with the leachate, and the leachate in the cathode chamber is magnetically stirred.

[0009] Furthermore, the copper deposit from step 3) is immersed in a 2-8 M NaCl solution, and the pH of the NaCl solution is adjusted with HCl to control the pH of the NaCl solution to be 0.8-2. The immersion time of the copper deposit is 8-20 minutes to remove CuCl and CuO from the copper deposit.

[0010] Furthermore, the pretreatment in step 4) involves pulverizing the PET substrate and drying it in a vacuum environment at a temperature of 105~150℃ and a pressure of -700~-1000 mbar for at least 12 hours, and drying the DGEBA and Zn(acac)2 at 40~60℃ for at least 5 hours.

[0011] Furthermore, the Vitrimers chemical modification method for recycling PET in step 5) involves reactive melt blending of a mixture of PET substrate, DGEBA, and Zn(acac)2 using a co-rotating twin-screw extruder under specific operating conditions.

[0012] Further, the mixture in step 5) consists of 96.1-100 wt% PET substrate, 1.2-3.8 wt% DGEBA and 0.1-2 wt% Zn(acac)2.

[0013] Furthermore, the specific working conditions are as follows: the working atmosphere is nitrogen, and the working temperature is: first 230~260℃ and then increased to 270~300℃ for gradient heating; the screw speed is set to 40~70 rpm when the mixture is fed, and the screw speed is increased to 80~110 rpm when the mixture is finally extruded; the product is discharged when the normal force applied to the screw by the extruder reaches 5000~7500N, and recycled PET is obtained.

[0014] Furthermore, the process of obtaining the mixture includes: first mixing the DGEBA and Zn(acac)2 and then coating it onto the compressed PET film, and then folding the PET film to wrap the DGEBA and Zn(acac)2.

[0015] The beneficial effects of this invention are reflected in: (1) In copper recycling, this invention employs an H2SO4-CuSO4-NaCl leaching system and electrodeposition technology to achieve non-destructive stripping of copper foil (leaching rate > 98%) and high purification of electrolytic copper (> 99.5%), solving the problems of high energy consumption and strong acid corrosion in traditional high-temperature treatment. In PET recycling, based on the dynamic covalent cross-linking modification process of DGEBA / Zn(acac)2, a Vitrimer network is constructed through twin-screw extrusion and a gradient heating process, enabling recycled PET to possess both mechanical strength (tensile strength > 54 MPa) and high-temperature resistance to sag, breaking through the performance degradation bottleneck caused by chain breakage in traditional recycled materials.

[0016] (2) The method provided by the present invention achieves efficient stepwise regeneration of metal and polymer through the synergy of two technologies, which has both environmental protection and high efficiency characteristics, and provides a high-value recycling path for the resource utilization of waste PET copper foil. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] A method for stepwise recycling of copper and PET from waste PET copper foil includes the following steps: 1. Copper foil dismantling and selective leaching Waste PET copper foil is immersed in a multi-component solution system containing H2SO4, CuSO4, and NaCl, with the chloride to copper concentration ratio (Ccl / Ccu) controlled at ≥8, the solid-liquid ratio at 1 / 8 to 1 / 15 (g / mL), and the leaching time at 10 to 16 hours. In-situ regeneration of the oxidant is achieved by continuously aerating air, maintaining the structural integrity of the PET substrate while efficiently leaching the copper layer.

[0019] 2. Electrochemical deposition for copper purification A dual-chamber electrolysis apparatus was employed, using a 99.8% pure copper sheet as the anode and a graphite block as the cathode, with a ceramic membrane isolating the anode and cathode chambers. Electrodeposition was performed in the cathode chamber leachate under magnetic stirring (300-500 rpm) with a current density controlled at 200-400 A / m², yielding copper deposits with a purity >99.5%. The resulting deposits were then rinsed with 2-8M NaCl solution (pH adjusted to 0.8-2 with HCl) for 8-20 minutes to effectively remove impurities such as CuCl and CuO.

[0020] 3. Pretreatment and modification of PET substrate The separated PET substrate was pulverized and then vacuum dried at 105~150℃ and -700~-1000mbar for ≥12 hours. The crosslinking agent DGEBA and the catalyst Zn(acac)2 were dried at 40~60℃ for ≥5 hours. Using Vitrimers dynamic chemical modification technology, 96.1-100wt% PET substrate, 1.2-3.8wt% DGEBA and 0.1-2wt% Zn(acac)2 were reactively melt-blended using a co-rotating twin-screw extruder: DGEBA was first coated onto a PET film and folded and wrapped. Gradient heating (230~260℃→270~300℃) was carried out under nitrogen protection. The screw speed was increased from 40~70rpm in the feeding section to 80~110rpm in the mixing section. When the normal force reached 5000~7500N, the product was extruded to obtain recycled PET.

[0021] Example 1: Following the above method, 200g of waste PET copper foil was immersed in a solution containing H2SO4 (1.5mol / L), CuSO4 (0.2mol / L), and NaCl (1.8mol / L) (C Cl / C Cu =9), solid-liquid ratio 1:8 (g / mL), immersion time 10 hours, continuous air blowing, no cracks on the surface of PET substrate.

[0022] In the dual-chamber electrolysis unit, the cathode current density is 200 A / m 2 The mixture was magnetically stirred at 300 rpm for 6 hours. The sediment was then rinsed with 2M NaCl (pH=0.8) for 8 minutes.

[0023] The PET substrate was vacuum dried (105℃ / -700mbar / 12h), and after drying with DGEBA (1.2wt%) and Zn(acac)2 (0.1wt%), the product was obtained by gradient heating in a twin-screw extruder (230℃→270℃), screw speed 40→80rpm, and normal force 5000N.

[0024] Example 2: Following the above method, 150g of waste PET copper foil was immersed in a solution containing H2SO4 (2.0mol / L), CuSO4 (0.15mol / L), and NaCl (1.5mol / L) (C Cl / C Cu =10), solid-liquid ratio 1:12 (g / mL), leaching time 13 hours, continuous air blowing.

[0025] Cathode current density 300A / m 2 Stir magnetically at 400 rpm for 8 hours. Rinse with 4M NaCl (pH=1.5) for 15 minutes.

[0026] The product was obtained by drying PET (130℃ / -900mbar / 14h), mixing DGEBA (2.5wt%) and Zn(acac)2 (1.0wt%), and then heating it in a twin-screw gradient (245℃→285℃) at a speed of 55→95rpm and a normal force of 6500N.

[0027] Example 3: Following the above method, 180g of waste PET copper foil was immersed in a solution containing H2SO4 (3.0mol / L), CuSO4 (0.25mol / L), and NaCl (2.5mol / L) (C). Cl / C Cu =10), solid-liquid ratio 1:15 (g / mL), leaching time 16 hours, continuous air blowing.

[0028] Cathode current density 400 A / m 2 Stir magnetically at 500 rpm for 10 hours. Rinse with 8M NaCl (pH=2.0) for 20 minutes.

[0029] The product was obtained by drying PET (150℃ / -1000mbar / 16h), mixing DGEBA (3.8wt%) and Zn(acac)2 (2.0wt%), and then heating it in a twin-screw gradient (260℃→300℃) at a speed of 70→110rpm and a normal force of 7500N.

[0030] Comparative Example 1: The H2SO4-CuSO4-NaCl leaching system in the recovery process, wherein the concentration ratio of chloride to copper (Ccl / Ccu) is controlled at 7, and the remaining steps are the same as in Example 1.

[0031] Comparative Example 2: The product was obtained using DGEBA (5.0 wt%, exceeding the upper limit of 3.8 wt%) and Zn(acac)2 (3.0 wt%) with an extruder normal force of 8500 N.

[0032] In summary, the present invention provides a copper recovery process using an H2SO4-CuSO4-NaCl leaching system and an electrodeposition technology to achieve non-destructive stripping of copper foil (leaching rate > 98%) and high purification of electrolytic copper (> 99.5%), thus solving the problems of high energy consumption and strong acid corrosion in traditional high-temperature treatment.

[0033] In PET recycling, a dynamic covalent cross-linking modification process based on DGEBA / Zn(acac)2 is employed. This process utilizes twin-screw extrusion to construct a Vitrimer network and a gradient heating process, enabling recycled PET to possess both mechanical strength (tensile strength > 54 MPa) and high-temperature resistance to sag, overcoming the performance degradation bottleneck caused by chain breakage in traditional recycled materials. The synergistic use of these two technologies achieves efficient stepwise recycling of metals and polymers, combining environmental friendliness and high efficiency, providing a high-value recycling pathway for waste PET copper foil.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for stepwise recycling of copper and PET from waste PET copper foil, characterized in that, The steps are as follows: 1) Obtain waste PET copper foil; 2) The obtained waste PET copper foil is immersed in a leaching solution containing H2SO4, CuSO4 and NaCl to obtain a copper-containing leaching solution and PET substrate. 3) The leachate is placed in a two-chamber electrolysis device, and copper is recovered from the leachate by electrochemical deposition to obtain copper deposits; 4) Pretreatment is performed on the crosslinking agent DGEBA, the catalyst Zn(acac)2, and the PET substrate separated in step 2); 5) The material from step 4) was recycled as PET using the Vitrimers chemical modification method.

2. The method for stepwise recovery of copper and PET from waste PET copper foil according to claim 1, characterized in that, In step 2), the concentration ratio of chloride to copper in the leaching solution is not less than 8, the solid-liquid ratio is set to 1 / 8 to 1 / 15 g / ml, and the leaching duration for each leaching treatment is 10 to 16 hours.

3. The method for stepwise recovery of copper and PET from waste PET copper foil according to claim 2, characterized in that, In step 2), during the dismantling and metal leaching process of the copper foil on the waste PET copper foil, air is continuously bubbled into the leaching solution to regenerate the oxidant in situ.

4. The method for stepwise recovery of copper and PET from waste PET copper foil according to claim 1, characterized in that, In step 3), the anode of the electrochemical deposition method uses a copper sheet with a purity of 99.8%, and the cathode uses a graphite block; the anode chamber and cathode chamber of the dual-chamber electrolysis device are separated by a ceramic membrane, and both the anode chamber and the cathode chamber are filled with the leachate, and the leachate in the cathode chamber is magnetically stirred.

5. A method for stepwise recovery of copper and PET from waste PET copper foil according to claim 1, characterized in that, The copper deposit from step 3) is immersed in a 2-8 M NaCl solution, and the pH of the NaCl solution is adjusted with HCl to control the pH of the NaCl solution to 0.8-2. The immersion time of the copper deposit is 8-20 minutes to remove CuCl and CuO from the copper deposit.

6. A method for stepwise recovery of copper and PET from waste PET copper foil according to claim 1, characterized in that, The pretreatment in step 4) involves pulverizing the PET substrate and drying it in a vacuum environment at a temperature of 105~150℃ and a pressure of -700~-1000mbar for at least 12 hours, and drying the DGEBA and Zn(acac)2 at 40~60℃ for at least 5 hours.

7. A method for stepwise recovery of copper and PET from waste PET copper foil according to claim 1, characterized in that, The Vitrimers chemical modification method for recycling PET in step 5) involves reactive melt blending of a mixture of PET substrate, DGEBA, and Zn(acac)2 using a co-rotating twin-screw extruder under specific operating conditions.

8. A method for stepwise recovery of copper and PET from waste PET copper foil according to claim 7, characterized in that, The mixture consists of 96.1-100 wt% PET substrate, 1.2-3.8 wt% DGEBA and 0.1-2 wt% Zn(acac)2.

9. A method for stepwise recovery of copper and PET from waste PET copper foil according to claim 8, characterized in that, The specific working conditions are as follows: the working atmosphere is nitrogen; the working temperature is: first 230~260℃ and then raised to 270~300℃ for gradient heating; the screw speed of the extruder is set to 40~70 rpm when the mixture is fed, and the screw speed of the extruder is increased to 80~110 rpm when the mixture is finally extruded; the product is discharged when the normal force applied to the screw by the extruder reaches 5000~7500N, and recycled PET is obtained.

10. A method for stepwise recovery of copper and PET from waste PET copper foil according to claim 7, characterized in that, The process of obtaining the mixture includes: first, mixing DGEBA and Zn(acac)2 and then coating it onto the compressed PET film, and then folding the PET film to wrap DGEBA and Zn(acac)2.