A method for recycling waste polycarbonate to produce recycled polycarbonate

Abstract

The application discloses a method for recycling waste polycarbonate to produce regenerated polycarbonate, and belongs to the technical field of depolymerization and recycling of high polymer composite materials. The waste polycarbonate is degraded into low-molecular-weight polycarbonate short chains by using phenol first, and then new polycarbonate material is obtained by polymerization at high temperature, so that the closed-loop circulation between chemical monomers and polymers is realized, and the polycarbonate chemical recycling, degradation and recycling in a true sense are realized. In addition, the catalyst used in the degradation and polymerization process is common and relatively inexpensive, and a small amount of polymerization monomer is added in the polymerization process, so that the preparation of the regenerated polycarbonate new material is realized, the polymerization cost is greatly reduced, the sustainable development of the polycarbonate industry is realized, and the pollution of plastics to the environment can be eliminated.

Description

TECHNICAL FIELD

[0001] The application relates to a method for recycling waste polycarbonate to produce regenerated polycarbonate, and belongs to the technical field of depolymerization and recycling of high polymer composite materials. BACKGROUND

[0002] Poly(bisphenol A carbonate), commonly known as polycarbonate, is a thermoplastic polymer produced by the condensation reaction of bisphenol A (BPA) and a carbonyl source (usually phosgene or diphenyl carbonate), and was first produced by General Electric Company and Bayer Company in 1950. Polycarbonate materials have a high glass transition temperature of about 150 DEG C and exhibit amorphous characteristics, and polycarbonate is classified as an engineering plastic with many ideal properties, such as high impact resistance, ductility, good optical clarity, flame retardancy and low production cost. Polycarbonate materials have been widely used in building boards, optical storage media, containers, safety products, electronic products, automobiles and many other fields. The production of polycarbonate materials is gradually increasing to 5 million tons / year.

[0003] At present, scientists have carried out a large amount of research on the recycling of plastics. And the recycling of polycarbonate is summarized in detail. The recycling methods include physical recycling and chemical recycling, and the chemical recycling method can convert the used polycarbonate into high-value chemical raw materials or retain the original polymer monomer, which does not realize the true sense of closed-loop recycling. Therefore, by developing a new process, a method for recycling waste polycarbonate to produce regenerated polycarbonate is provided, the closed-loop recycling between chemical monomers and polymers is realized, and the sustainable development of the polycarbonate industry is realized, which is expected to eliminate the pollution of plastics to the environment. SUMMARY

[0004] The application aims to recycle waste polycarbonate to produce regenerated polycarbonate, and provides a method for recycling waste polycarbonate to produce regenerated polycarbonate.

[0005] The technical scheme of the application is as follows:

[0006] One of the purposes of the application is to provide a method for recycling waste polycarbonate to produce regenerated polycarbonate, which comprises the following steps:

[0007] S1, under normal pressure and a certain temperature, waste polycarbonate is degraded into polycarbonate short chains by using phenol and a depolymerization catalyst;

[0008] S2, under normal pressure and high temperature conditions, polycarbonate short chains are polymerized with bisphenol A and diphenyl carbonate under the action of a catalyst to obtain regenerated polycarbonate polymer.

[0009] Further limited, the temperature in S1 is 90-230 DEG C, and the degradation time is 3-6 h.

[0010] Further limit, the depolymerization catalyst in S1 is one or more of ZnCl2, Zn(OAc)2, Zn(HMDS)2, ZnEt2, ZnI2, ZnBr2.

[0011] Further limit, the amount of the depolymerization catalyst in S1 is 0.2-50wt% of the waste polycarbonate.

[0012] Further limit, the amount of the phenol in S1 is 10-200wt% of the waste polycarbonate.

[0013] Further limit, the waste polycarbonate in S1 is commercial polycarbonate.

[0014] Further limit, the high temperature in S2 is 200-350℃.

[0015] Further limit, the catalyst in S2 is one or more of KOH, NaOH, LiOH, Na2CO3.

[0016] Further limit, the amount of the catalyst in S2 is 0.2-40wt% of the waste polycarbonate.

[0017] Further limit, the ratio of the total moles of bisphenol A and diphenyl carbonate to the moles of the waste polycarbonate in S2 is 1:(1-5).

[0018] Further limit, the molar ratio of bisphenol A to diphenyl carbonate is 1:1.1.

[0019] Further limit, the molecular weight of the regenerated polycarbonate is 19-23kg / mol.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application adopts the strategy of first degrading and then polymerizing the waste polycarbonate. First, phenol is used to degrade the waste polycarbonate into low molecular weight polycarbonate short chains, and then new polycarbonate materials are obtained by polymerization at high temperature, thereby realizing the closed-loop recycling between chemical monomers and polymers and achieving true chemical recycling and degradation of polycarbonate. In addition, the catalyst used in the first degradation and then polymerization process is common and relatively inexpensive. A small amount of polymerization monomer is added during the polymerization process to realize the preparation of regenerated polycarbonate new materials, greatly reducing the polymerization cost, realizing the sustainable development of the polycarbonate industry, and hopefully eliminating the pollution of plastics to the environment. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0023] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0024] Example 1:

[0025] The reaction process for recycling and manufacturing recycled polycarbonate in this embodiment is as follows:

[0026]

[0027] The specific recycling and manufacturing recycled polycarbonate process is as follows:

[0028] (1) Take 120 mL of pressure-resistant bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 9.34 mL (100 wt%) of phenol, followed by adding 2 wt% of ZnCl2 catalyst, heat to 150°C and stir for 6 hours to complete the degradation.

[0029] (2) Then, the low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added with an appropriate amount of methanol, and then centrifuged to obtain the product low molecular weight polycarbonate short chains, with a total yield of 49.2%. Dry the product at 40°C under vacuum to constant weight, and measure the molecular weight of the dried product by gel permeation chromatography (GPC) to be 2 kg / mol.

[0030] (3) The obtained low molecular weight polycarbonate short chains are polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:1.1:1) at 260°C, and 2 wt% of KOH catalyst is added, and the polymerization is complete after 3h of reaction detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer are measured by gel permeation chromatography (GPC), with a molecular weight of 20 kg / mol and a molecular weight distribution of 1.26. The molecular weight of the recycled new polycarbonate polymer is basically unchanged.

[0031] Example 2:

[0032] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 9.34 mL (100 wt%) of phenol, followed by 2 wt% of ZnBr2 catalyst, and complete degradation after stirring at 170°C for 3 hours.

[0033] (2) Then, the low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains are obtained by centrifugation, with a total yield of 51.2%. The dried product is obtained by vacuum drying at 40°C until the weight is constant, and the molecular weight is 2 kg / mol by gel permeation chromatography (GPC).

[0034] (3) The obtained low molecular weight polycarbonate short chains are polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:1:1.1) at 260°C, 0.5 w% of NaOH catalyst is added, and the polymerization is complete after 3h of reaction, which is detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer are measured by gel permeation chromatography (GPC), the molecular weight is 20.2 kg / mol, and the molecular weight distribution is 1.25. The molecular weight of the recovered new polycarbonate polymer is basically unchanged.

[0035] Example 3:

[0036] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 9.34 mL (100 wt%) of phenol, followed by 1.5 wt% of Zn(HMDS)2 catalyst, and complete degradation after stirring at 160°C for 3.3 hours to obtain low molecular weight polycarbonate short chains.

[0037] (2) Then, the low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains are obtained by centrifugation, with a total yield of 51.2%. The dried product is obtained by vacuum drying at 40°C until the weight is constant, and the molecular weight is 2 kg / mol by gel permeation chromatography (GPC).

[0038] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1 : 1.1 : 1) at 260 °C, 2 wt% LiOH catalyst was added, and the polymerization was complete after 3 h detected by NMR. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), the molecular weight was 19.5 kg / mol, and the molecular weight distribution was 1.14. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0039] Example 4:

[0040] (1) A 120 mL pressure bottle was taken, 20 g of waste polycarbonate (waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuumed and placed under inert gas, then 9.34 mL (50 wt%) of phenol was added, followed by the addition of 3 wt% ZnI2 catalyst, and the temperature was raised to 160 °C for stirring reaction for 3.3 hours to complete the degradation.

[0041] (2) Then the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added to an appropriate amount of methanol and centrifuged to obtain the product low molecular weight polycarbonate short chains, with a total yield of 25.4%. The dried product was obtained by drying under vacuum at 40 °C to constant weight, and the molecular weight was 2 kg / mol measured by gel permeation chromatography (GPC).

[0042] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1 : 1.1 : 1) at 270 °C, 2.5 wt% LiOH catalyst was added, and the polymerization was complete after 3 h detected by NMR. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), the molecular weight was 22 kg / mol, and the molecular weight distribution was 1.20. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0043] Example 5:

[0044] (1) A 120 mL pressure bottle was taken, 20 g of waste polycarbonate (waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuumed and placed under inert gas, then 9.34 mL (50 wt%) of phenol was added, followed by the addition of 3 wt% ZnI2 catalyst, and the temperature was raised to 160 °C for stirring reaction for 3.3 hours to complete the degradation.

[0045] (2) Subsequently, the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains were obtained by centrifugation, with a total yield of 60.1%. The dried product was obtained by drying under vacuum at 40°C until the weight was constant, and the molecular weight was 2 kg / mol as measured by gel permeation chromatography (GPC).

[0046] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:1.1:1) at 260°C, 1.5 wt% LiOH catalyst was added, and the polymerization was complete after 3h as detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), with a molecular weight of 20.4 kg / mol and a molecular weight distribution of 1.16. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0047] Example 6:

[0048] (1) 120 mL of a pressure-resistant bottle was taken, 10 g of waste polycarbonate (waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuum was applied and placed under inert gas, then 11.21 mL (80 wt%) of phenol was added, followed by the addition of 2.2 wt% ZnEt2 catalyst, and the reaction was complete after 3 hours of stirring at 170°C.

[0049] (2) Subsequently, the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains were obtained by centrifugation, with a total yield of 60.1%. The dried product was obtained by drying under vacuum at 40°C until the weight was constant, and the molecular weight was 2 kg / mol as measured by gel permeation chromatography (GPC).

[0050] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:2.2:2) at 290°C, 5 wt% KOH catalyst was added, and the polymerization was complete after 3h as detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), with a molecular weight of 19.8 kg / mol and a molecular weight distribution of 1.30. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0051] Example 7:

[0052] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 16.05 mL (150 wt%) of phenol, followed by adding 4 wt% of ZnCl2 and ZnBr2 mixed catalyst (mass ratio of ZnCl2 and ZnBr2 is 1:1), and complete degradation after stirring at 165°C for 3 hours.

[0053] (2) Then, low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains are obtained by centrifugation, and the yield is 75.7%. The dried product is obtained by drying under vacuum at 40°C until the weight is constant, and the molecular weight is 2 kg / mol by gel permeation chromatography (GPC).

[0054] (3) The obtained low molecular weight polycarbonate short chains are polymerized with diphenyl carbonate and bisphenol A (molar amount ratio is 1:2.2:2) at 270°C, 1.2 wt% of KOH catalyst is added, and the polymerization is complete after 3h of reaction, which is detected by nuclear magnetic resonance, and the molecular weight and molecular weight distribution of the new polycarbonate polymer are measured by gel permeation chromatography (GPC), the molecular weight is 20.1 kg / mol, and the molecular weight distribution is 1.19. The molecular weight of the recovered new polycarbonate polymer is basically unchanged.

[0055] Example 8:

[0056] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 18.7 mL (200 wt%) of phenol, followed by adding 4 wt% of ZnBr2 and ZnI2 mixed catalyst (mass ratio of ZnBr2 and ZnI2 is 1:3), and complete degradation after stirring at 150°C for 3 hours.

[0057] (2) Then, low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains are obtained by centrifugation, and the yield is 75.7%. The dried product is obtained by drying under vacuum at 40°C until the weight is constant, and the molecular weight is 2 kg / mol by gel permeation chromatography (GPC).

[0058] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1 : 1.1 : 1) at 300 °C, 2.3 wt% NaOH catalyst was added, and the polymerization was complete after 3 h detected by NMR. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), the molecular weight was 21.2 kg / mol, and the molecular weight distribution was 1.26. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0059] Example 9:

[0060] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the raw material of the waste polycarbonate was derived from processing leftover scraps, the molecular weight was 21 kg / mol, and the molecular weight distribution was 1.25) was added, vacuumized and placed under inert gas, then 18.7 mL (200 wt%) of phenol was added, followed by the addition of 2 wt% of ZnCl2 catalyst, and the temperature was raised to 150 °C for stirring reaction for 3 hours to complete the degradation.

[0061] (2) Then the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added to an appropriate amount of methanol and centrifuged to obtain the product low molecular weight polycarbonate short chains, the yield was 99.6%. The dried product was obtained by vacuum drying at 40 °C until the weight was constant, and the molecular weight was 2 kg / mol measured by gel permeation chromatography (GPC).

[0062] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1 : 1.1 : 1) at 280 °C, 0.9 wt% of LiOH and NaOH mixed catalyst (mass ratio of LiOH and NaOH was 1 : 2) was added, and the polymerization was complete after 3 h detected by NMR. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), the molecular weight was 22.4 kg / mol, and the molecular weight distribution was 1.45. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0063] Example 10:

[0064] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the raw material of the waste polycarbonate was derived from processing leftover scraps, the molecular weight was 21 kg / mol, and the molecular weight distribution was 1.25) was added, vacuumized and placed under inert gas, then 4.67 mL (50 wt%) of phenol was added, followed by the addition of 1.5 wt% of ZnI2 and Zn(HMDS)2 mixed catalyst (mass ratio of ZnI2 and Zn(HMDS)2 was 1 : 2), and the temperature was raised to 180 °C for stirring reaction for 3 hours to complete the degradation.

[0065] (2) Subsequently, the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains were obtained by centrifugation, with a total yield of 77.3%. The dried product was obtained by drying under vacuum at 40°C until the weight was constant, and the molecular weight was 2 kg / mol as measured by gel permeation chromatography (GPC).

[0066] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:5.5:5) at 300°C, 0.6 wt% of KOH catalyst was added, and the polymerization was complete after 3h as detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), with a molecular weight of 22.8 kg / mol and a molecular weight distribution of 1.24. The molecular weight of the recovered new polycarbonate polymer was basically unchanged.

[0067] Example 11:

[0068] (1) 120 mL of a pressure-resistant bottle was taken, 10 g of waste polycarbonate (the source of the waste polycarbonate raw material was processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuum was applied and it was placed under inert gas, then 18.7 mL (200 wt%) of phenol was added, followed by the addition of 2.1 wt% of Zn(HMDS)2 catalyst, and the degradation was completed after 3 hours of stirring at 150°C.

[0069] (2) Subsequently, the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added to an appropriate amount of methanol, and the product low molecular weight polycarbonate short chains were obtained by centrifugation, with a total yield of 99.1%. The dried product was obtained by drying under vacuum at 40°C until the weight was constant, and the molecular weight was 2 kg / mol as measured by gel permeation chromatography (GPC).

[0070] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:1.1:1) at 290°C, 1.5 wt% of a mixed catalyst of KOH and NaOH (mass ratio of KOH to NaOH was 1:2) was added, and the polymerization was complete after 3h as detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), with a molecular weight of 21.5 kg / mol and a molecular weight distribution of 1.18. The molecular weight of the recovered new polycarbonate polymer was basically unchanged.

[0071] Example 12:

[0072] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 9.34 mL (100 wt%) of phenol, and then add 6 wt% of ZnEt2 catalyst, heat to 150°C, and stir for 6 hours to complete degradation.

[0073] (2) Then, low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added to an appropriate amount of methanol, and centrifugation is performed to obtain the product low molecular weight polycarbonate short chains, and the yield is 58.2%. The dried product is obtained by vacuum drying at 40°C until the constant weight, and the molecular weight is 2 kg / mol by gel permeation chromatography (GPC).

[0074] (3) The obtained low molecular weight polycarbonate short chains are polymerized with diphenyl carbonate and bisphenol A (molar amount ratio is 1:1.1:1) at 260°C, 15 wt% of Na2CO3 catalyst is added, and the polymerization is completed after 3h by nuclear magnetic resonance detection, and the molecular weight and molecular weight distribution of the new polycarbonate polymer are measured by gel permeation chromatography (GPC), the molecular weight is 20.2 kg / mol, and the molecular weight distribution is 1.20. The molecular weight of the recovered new polycarbonate polymer is basically unchanged.

[0075] Example 13:

[0076] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 9.34 mL (100 wt%) of phenol, and then add 3 wt% of Zn(HMDS)2 catalyst, heat to 150°C, and stir for 6 hours to complete degradation.

[0077] (2) Then, low molecular weight polycarbonate short chains in the reaction system are separated, the solution is added to an appropriate amount of methanol, and centrifugation is performed to obtain the product low molecular weight polycarbonate short chains, and the yield is 58.2%. The dried product is obtained by vacuum drying at 40°C until the constant weight, and the molecular weight is 2 kg / mol by gel permeation chromatography (GPC).

[0078] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1 : 1.1 : 1) at 260 °C, 3 wt% Na2CO3 and LiOH catalysts (mass ratio of Na2CO3 and LiOH is 1 : 6) were added, and the polymerization was complete after 3 h detected by NMR. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), the molecular weight was 22 kg / mol, and the molecular weight distribution was 1.31. The molecular weight of the recovered new polycarbonate polymer was basically unchanged.

[0079] Example 14:

[0080] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the raw material of the waste polycarbonate was derived from processing leftover scraps, the molecular weight was 21 kg / mol, and the molecular weight distribution was 1.25) was added, vacuumized and placed under inert gas, then 9.34 mL (100 wt%) of phenol was added, followed by the addition of 2 wt% of ZnCl2 catalyst, and the temperature was raised to 150 °C for stirring reaction for 6 hours to complete the degradation.

[0081] (2) Then the low molecular weight polycarbonate short chains in the reaction system were separated, the solution was added with an appropriate amount of methanol, and centrifugation was performed to obtain the product low molecular weight polycarbonate short chains, and the yield was 55.7%. The dried product was obtained by vacuum drying at 40 °C until the weight was constant, and the molecular weight was 2 kg / mol measured by gel permeation chromatography (GPC).

[0082] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1 : 1.1 : 1) at 260 °C, 4 wt% of a mixed catalyst of KOH and Na2CO3 (mass ratio of KOH and Na2CO3 is 3: 1) was added, and the polymerization was complete after 3 h detected by NMR. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), the molecular weight was 21.3 kg / mol, and the molecular weight distribution was 1.16. The molecular weight of the recovered new polycarbonate polymer was basically unchanged.

[0083] Example 15:

[0084] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the raw material of the waste polycarbonate was derived from processing leftover scraps, the molecular weight was 21 kg / mol, and the molecular weight distribution was 1.25) was added, vacuumized and placed under inert gas, then 9.34 mL (100 wt%) of phenol was added, followed by the addition of 2 wt% of Zn(HMDS)2 catalyst, and the temperature was raised to 150 °C for stirring reaction for 6 hours to complete the degradation.

[0085] (2) Subsequently, low molecular weight polycarbonate short chains in the reaction system were separated, and the solution was added to an appropriate amount of methanol, and then centrifuged to obtain the product low molecular weight polycarbonate short chains, with a total yield of 53.1%. The dried product was obtained by drying under vacuum at 40°C until the weight was constant, and the molecular weight was 2 kg / mol as measured by gel permeation chromatography (GPC).

[0086] (3) The obtained low molecular weight polycarbonate short chains were polymerized with diphenyl carbonate and bisphenol A (molar ratio of 1:2.2:2) at 260°C, with the addition of 15 wt% Na2CO3 catalyst, and the polymerization was complete after 3h of reaction as detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), with a molecular weight of 19.8 kg / mol and a molecular weight distribution of 1.25. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0087] Example 16:

[0088] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuum was applied and it was placed under inert gas, then 9.34 mL (100 wt%) of phenol was added, followed by the addition of 2 wt% Zn(HMDS)2 catalyst, and the temperature was raised to 150°C for stirring reaction for 6 hours to complete the degradation.

[0089] (2) The obtained depolymerization product was subjected to re-polymerization at 260°C, with the addition of 2 wt% KOH catalyst during the polymerization process, and the polymerization was complete after 3h of reaction as detected by nuclear magnetic resonance. The molecular weight and molecular weight distribution of the new polycarbonate polymer were measured by gel permeation chromatography (GPC), with a molecular weight of 22.9 kg / mol and a molecular weight distribution of 1.18. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0090] Example 17:

[0091] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuum was applied and it was placed under inert gas, then 9.34 mL (100 wt%) of phenol was added, followed by the addition of 2 wt% Zn(HMDS)2 catalyst, and the temperature was raised to 150°C for stirring reaction for 6 hours to complete the degradation.

[0092] (2) The obtained depolymerization product was placed at 300 °C for re-polymerization, and 1.5 wt% of NaOH catalyst was added during the polymerization process for reaction. After 3 h of reaction, nuclear magnetic resonance detection showed that the polymerization was complete. Gel permeation chromatography (GPC) was used to measure the molecular weight and molecular weight distribution of the new polycarbonate polymer, which had a molecular weight of 20.6 kg / mol and a molecular weight distribution of 1.24. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0093] Example 18:

[0094] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuum was applied and the bottle was placed under inert gas, then 9.34 mL (100 wt%) of phenol was added, followed by the addition of a 5 wt% Zn(OAc)2 catalyst, and the temperature was raised to 150 °C for stirring reaction for 6 hours to complete the degradation.

[0095] (2) The obtained depolymerization product was placed at 300 °C for re-polymerization, and 1.5 wt% of NaOH catalyst was added during the polymerization process for reaction. After 3 h of reaction, nuclear magnetic resonance detection showed that the polymerization was complete. Gel permeation chromatography (GPC) was used to measure the molecular weight and molecular weight distribution of the new polycarbonate polymer, which had a molecular weight of 20.6 kg / mol and a molecular weight distribution of 1.24. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0096] Example 19:

[0097] (1) A 120 mL pressure-resistant bottle was taken, 10 g of waste polycarbonate (the waste polycarbonate raw material was derived from processing leftover scraps, with a molecular weight of 21 kg / mol and a molecular weight distribution of 1.25) was added, vacuum was applied and the bottle was placed under inert gas, then 9.34 mL (100 wt%) of phenol was added, followed by the addition of a 5 wt% Zn(OAc)2 catalyst, and the temperature was raised to 150 °C for stirring reaction for 6 hours to complete the degradation.

[0098] (2) The obtained depolymerization product was placed at 300 °C for re-polymerization, and 1.5 wt% of NaOH catalyst was added during the polymerization process for reaction. After 3 h of reaction, nuclear magnetic resonance detection showed that the polymerization was complete. Gel permeation chromatography (GPC) was used to measure the molecular weight and molecular weight distribution of the new polycarbonate polymer, which had a molecular weight of 20.6 kg / mol and a molecular weight distribution of 1.24. The molecular weight of the recovered new polycarbonate polymer was essentially unchanged.

[0099] Example 20:

[0100] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 9.34 mL (100 wt%) of phenol, followed by adding 3 wt% of Zn(OAc)2 and Zn(HMDS)2 mixed catalyst (mass ratio of Zn(OAc)2 and Zn(HMDS)2 is 1:2), and complete degradation after stirring at 150°C for 6 hours.

[0101] (2) The obtained depolymerization product is placed at 260°C for re-polymerization, 4 wt% of Na2CO3 and KOH mixed catalyst (mass ratio of Na2CO3 and KOH is 1:3) is added during the polymerization process for reaction, and the polymerization is completely detected by nuclear magnetic resonance after 3h of reaction. The molecular weight and molecular weight distribution of the new polycarbonate polymer are measured by gel permeation chromatography (GPC), and the molecular weight is 22.5 kg / mol and the molecular weight distribution is 1.24. The molecular weight of the recovered new polycarbonate polymer is basically unchanged.

[0102] Example 21:

[0103] (1) Take 120 mL of pressure bottle, add 10 g of waste polycarbonate (waste polycarbonate raw material is derived from processing leftover materials, molecular weight is 21 kg / mol, and molecular weight distribution is 1.25), vacuumize and place under inert gas, then add 11.21 mL (120 wt%) of phenol, followed by adding 4 wt% of ZnEt2 and Zn(HMDS)2 mixed catalyst (mass ratio of ZnEt2 and Zn(HMDS)2 is 1:1), and complete degradation after stirring at 150°C for 6 hours.

[0104] (2) The obtained depolymerization product is placed at 300°C for re-polymerization, 2 wt% of LiOH and KOH mixed catalyst (mass ratio of LiOH and KOH is 1:1) is added during the polymerization process for reaction, and the polymerization is completely detected by nuclear magnetic resonance after 3h of reaction. The molecular weight and molecular weight distribution of the new polycarbonate polymer are measured by gel permeation chromatography (GPC), and the molecular weight is 21.5 kg / mol and the molecular weight distribution is 1.25. The molecular weight of the recovered new polycarbonate polymer is basically unchanged.

[0105] Among them, the hardness of part of the recovered polycarbonate is as follows:

[0106] Test Item Example 1 Example 2 Example 3 Example 4 Original Polycarbonate Hardness / Shore D 86 85 90 92 95

[0107] The hardness of the recovered polycarbonate is comparable to that of the original polycarbonate, and has good performance.

[0108] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for recycling waste polycarbonate to produce recycled polycarbonate, characterized in that, include: S1, under normal pressure and a certain temperature, waste polycarbonate is degraded into short polycarbonate chains using phenol and a depolymerization catalyst, and short polycarbonate chains with a molecular weight of 2 kg / mol are obtained by adding methanol to the solution obtained from the degradation and centrifuging. The depolymerization catalyst in S1 is one or a mixture of ZnCl2, Zn(OAc)2, Zn(HMDS)2, ZnEt2, ZnI2, and ZnBr2; The temperature in S1 is 90–230℃, and the degradation time is 3–6 hours; S2, under normal pressure and high temperature conditions, short chains of polycarbonate are polymerized with bisphenol A and diphenyl carbonate in the presence of a catalyst to obtain a recycled polycarbonate polymer. The catalyst in S2 is one or a mixture of KOH, NaOH, LiOH, and Na2CO3. The high temperature in S2 is 200–350℃.

2. The method for recycling waste polycarbonate to produce recycled polycarbonate according to claim 1, characterized in that, The amount of depolymerization catalyst used in S1 is 0.2 to 50 wt% of the waste polycarbonate.

3. The method for recycling waste polycarbonate to produce recycled polycarbonate according to claim 1, characterized in that, The amount of phenol used in S1 is 10-200 wt% of the waste polycarbonate.

4. The method for recycling waste polycarbonate to produce recycled polycarbonate according to claim 1, characterized in that, The amount of catalyst used in S2 is 0.2 to 40 wt% of the waste polycarbonate.

5. The method for recycling waste polycarbonate to produce recycled polycarbonate according to claim 1, characterized in that, The ratio of the total molar amount of bisphenol A and diphenyl carbonate in S2 to the molar amount of waste polycarbonate is 1:(1-5).

6. A recycled polycarbonate prepared by the method of claim 1, characterized in that, The molecular weight of recycled polycarbonate is 19–23 kg / mol.

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