A method for degrading polycarbonate with a phenolic catalyst

Abstract

The application discloses a method for degrading polycarbonate by using a phenolic catalyst, and belongs to the technical field of organic material chemical recycling. In the method, a phenolic compound is used as a catalyst, and diphenyl carbonate is used as a reaction reagent. In a high-temperature normal-pressure reaction process, PC molecular chains are broken and depolymerized to obtain polycarbonate low-molecular-weight chains, i.e. polycarbonate oligomers. In the reaction process, no metal catalyst is added, which is helpful to reduce a post-processing step and realize green chemical recycling.

Description

Technical Field

[0001] This invention relates to a method for degrading polycarbonate using a phenolic catalyst, belonging to the field of organic material chemical recycling technology. Background Technology

[0002] Polycarbonate (PC) has a very broad application prospect. Due to its excellent durability, transparency, and very high mechanical properties, PC is used in everything from microelectronic components to stadium sunshades. However, recycling PC after use is usually difficult. Traditional physical recycling methods involve crushing the recycled PC to manufacture new plastic products, but this method is very inefficient. Currently, chemical recycling of PC has emerged as an emerging recycling method that has replaced traditional physical recycling methods. Chemical recycling can convert PC into its original monomer (bisphenol A); and at the same time, it can also extract carbonyl groups from the molecular chain to produce other high-value-added chemical substances. However, existing chemical recycling methods for waste PC usually use metal catalysts to catalyze the degradation of PC. Therefore, providing a new chemical recycling method for PC using organic matter as a catalyst is of great significance. Summary of the Invention

[0003] This invention addresses the common practice in existing chemical recycling of waste polycarbonate by using metal catalysts to catalyze its degradation. It provides a method for degrading polycarbonate using phenolic catalysts, which helps reduce post-processing steps and achieve green chemical recycling.

[0004] The technical solution of this invention:

[0005] One objective of this invention is to provide a method for degrading polycarbonate using a phenolic catalyst. The method involves using a phenolic compound as a catalyst, replacing diphenyl carbonate as a reaction reagent, under high temperature and normal pressure conditions to catalytically degrade polycarbonate and obtain a depolymerization solution containing polycarbonate oligomers.

[0006] Further specifying, the phenolic compound is one or a mixture of sodium phenolate, potassium phenolate, and sodium bisphenol A.

[0007] Further specified, the amount of catalyst used is 1 to 6 wt% of polycarbonate.

[0008] Further, the degradation temperature is specified as 150–280℃, and the time is specified as 5–10 hours.

[0009] Further specified, the alternative to diphenyl carbonate is one or more of the following: diphenyl carbonate, bis(pentafluorophenyl)carbonate, guaiacol carbonate, 4,4-methylthiodiphenyl carbonate, and di(p-nitrobenzene) carbonate.

[0010] Further specified, the amount of diphenyl carbonate used is 30–200 mol of the polycarbonate repeating unit.

[0011] Further, the depolymerization solution was neutralized by passing it through a Sigma acidic molecular sieve column to achieve a pH of 6–8, and then filtered to obtain polycarbonate oligomers.

[0012] Further specifying, polycarbonate is one or more PC granules with different molecular weights.

[0013] Further specifying, the molecular weight of PC granules is 12–20.5 kg / mol.

[0014] Furthermore, the molecular weight of the polycarbonate oligomer is below 6 kg / mol.

[0015] The advantages of this invention compared to the prior art are as follows:

[0016] This invention uses phenolic compounds as catalysts to replace diphenyl carbonate as a reaction reagent. During the high-temperature and atmospheric-pressure reaction, the PC molecular chains break down and depolymerize to obtain low molecular weight polycarbonate chains, namely polycarbonate oligomers. No metal catalyst is added during the reaction, which helps to reduce post-processing steps and achieve green chemical recycling. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0019] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0021] Example 1

[0022]

[0023] A. Depolymerization: The purchased PC granules (M n =12.3 kg / mol, PDI = 3.36) At 280℃ and standard atmospheric pressure, sodium phenolate was used as a catalyst, with the catalyst added at 3.3 wt% of the PC granules. Diphenyl carbonate was added at 50 mol% of the polycarbonate repeating unit, and the reaction time was 10 h, which caused the PC molecular chains to break down and depolymerize, obtaining the degradation products.

[0024] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.8 kg / mol.

[0025] Example 2

[0026]

[0027] A. Depolymerization: The purchased PC granules (M n =12.3 kg / mol, PDI=3.36) At 230℃ and standard atmospheric pressure, potassium phenolate was used as a catalyst, with the catalyst added at 2.5 wt% of the PC granules. Diphenyl carbonate was added at 50 mol% of the polycarbonate repeating unit, and the reaction time was 7 h, which caused the PC molecular chains to break down and depolymerize, obtaining the degradation products.

[0028] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.9 kg / mol.

[0029] Example 3

[0030]

[0031] A. Depolymerization: The purchased PC granules (M n =12.3 kg / mol, PDI = 3.36) At 200℃ and standard atmospheric pressure, sodium bisphenol A was used as a catalyst, with the catalyst added at 6 wt% of the PC granules. Diphenyl carbonate was added at 30 mol% of the polycarbonate repeating unit, and the reaction time was 9 h, which caused the PC molecular chains to break down and depolymerize, obtaining the degradation products.

[0032] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.3 kg / mol.

[0033] Example 4

[0034]

[0035] A. Depolymerization: The purchased PC granules (M n =12.3 kg / mol, PDI = 3.36) At 270℃ and standard atmospheric pressure, using sodium bisphenol A and sodium phenolate as a composite catalyst (the ratio of the composite catalyst is sodium phenolate:sodium bisphenol A = 1:1), the amount of catalyst added is 3 wt% of the mass fraction of PC granules. Diphenyl carbonate is added at an amount of 50 mol% of the repeating unit of polycarbonate, and the reaction time is 8.3 h, which causes the PC molecular chains to break down and depolymerize, obtaining degradation products.

[0036] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.6 kg / mol.

[0037] Example 5

[0038]

[0039] A. Depolymerization: The purchased PC granules (M n =17.7 kg / mol, PDI = 2.9) At 253℃ and standard atmospheric pressure, sodium phenolate was used as a catalyst, with the catalyst added at 4.2 wt% of the PC granules. Bis(pentafluorophenyl)carbonic acid was added at 50 mol% of the polycarbonate repeating unit, and the reaction time was 5.5 h, causing the PC molecular chains to break down and depolymerize, yielding the degradation products.

[0040] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.0 kg / mol.

[0041] Example 6

[0042]

[0043] A. Depolymerization: The purchased PC granules (M n =17.7 kg / mol, PDI = 2.9) At 260℃ and standard atmospheric pressure, potassium phenolate and sodium phenolate were used as a composite catalyst (the ratio of the composite catalyst was sodium phenolate:potassium phenolate = 1:1), and the amount of catalyst added was 4 wt% of the PC granules. Bis(pentafluorophenyl)carbonic acid was added at an amount of 100 mol% of the polycarbonate repeating unit, and the reaction time was 5.5 h, causing the PC molecular chains to break down and depolymerize, thus obtaining the degradation products.

[0044] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 4.6 kg / mol.

[0045] Example 7

[0046]

[0047] A. Depolymerization: The purchased PC granules (M n =15.5 kg / mol, PDI=2.7) At 250℃ and standard atmospheric pressure, sodium phenolate was used as a catalyst, with the catalyst added at 5.9 wt% of the PC granules. Bis(pentafluorophenyl)carbonic acid was added at 100 mol% of the polycarbonate repeating unit, and the reaction time was 5 h, which caused the PC molecular chains to break down and depolymerize, obtaining the degradation products.

[0048] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 4.1 kg / mol.

[0049] Example 8

[0050]

[0051] A. Depolymerization: The purchased PC granules (M n =15.5 kg / mol, PDI = 2.7) At 280℃ and standard atmospheric pressure, using sodium bisphenol A as a catalyst, the amount of catalyst added was 5.0 wt% of the PC granules. Guaiacin carbonate was added, the amount of which was 50 mol% of the polycarbonate repeating unit, and the reaction time was 6 h, so that the PC molecular chains were broken and depolymerized to obtain the degradation products.

[0052] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.3 kg / mol.

[0053] Example 9

[0054]

[0055] A. Depolymerization: The purchased PC granules (M n=15.5 kg / mol, PDI=2.7) At 270℃ and standard atmospheric pressure, potassium phenolate was used as a catalyst, with the catalyst added at 5.0 wt% of the PC granules. Guaiacin carbonate was added at 100 mol% of the polycarbonate repeating unit, and the reaction time was 6 h, which caused the PC molecular chains to break down and depolymerize, thus obtaining the degradation products.

[0056] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 3.3 kg / mol.

[0057] Example 10

[0058]

[0059] A. Depolymerization: The purchased PC granules (M n =20.5 kg / mol, PDI=2.5) At 270℃ and standard atmospheric pressure, potassium phenolate was used as a catalyst, with the catalyst added at 6.0 wt% of the PC granules. 4,4-Methylthiodiphenyl carbonate was added at 30 mol% of the polycarbonate repeating unit, and the reaction time was 8 h, causing the PC molecular chains to break down and depolymerize, thus obtaining the degradation products.

[0060] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 6.0 kg / mol.

[0061] Example 11

[0062]

[0063] A. Depolymerization: The purchased PC granules (M n =20.5 kg / mol, PDI = 2.5) At 260℃ and standard atmospheric pressure, sodium phenolate was used as a catalyst, with the catalyst added at 6.0 wt% of the PC granules. 4,4-Methylthiodiphenyl carbonate was added at 40 mol% of the polycarbonate repeating unit, and the reaction time was 9 h, causing the PC molecular chains to break down and depolymerize, thus obtaining the degradation products.

[0064] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.9 kg / mol.

[0065] Example 12

[0066]

[0067] A. Depolymerization: The purchased PC pellets (M n =18.3 kg / mol, PDI = 2.9) At 250℃ and standard atmospheric pressure, sodium phenolate was used as a catalyst, with the catalyst added at 5.0 wt% of the PC granules. Di(p-nitrobenzene) carbonate was added at 50 mol% of the polycarbonate repeating unit, and the reaction time was 10 h, causing the PC molecular chains to break down and depolymerize, thus obtaining the degradation products.

[0068] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 5.2 kg / mol.

[0069] Example 13

[0070]

[0071] A. Depolymerization: The purchased PC pellets (M n =18.5 kg / mol, PDI = 2.3) At 290℃ and standard atmospheric pressure, using sodium bisphenol A as a catalyst, the amount of catalyst added was 5.0 wt% of the PC granules. Di(p-nitrobenzene) carbonate was added, the amount of which was 60 mol% of the polycarbonate repeating unit, and the reaction time was 8 h, so that the PC molecular chains would break down and depolymerize to obtain the degradation products.

[0072] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 4.8 kg / mol.

[0073] Example 14

[0074]

[0075] A. Depolymerization: The purchased PC pellets (M n =16.2 kg / mol, PDI = 2.3) At 290℃ and standard atmospheric pressure, sodium phenolate and sodium bisphenol A were used as a composite catalyst (the mass ratio of the composite catalyst was sodium phenolate:sodium bisphenol A = 1:1), and the amount of catalyst added was 6.0 wt% of the PC granules. Di(p-nitrobenzene) carbonate was added at an amount of 80 mol% of the polycarbonate repeating unit, and the reaction time was 7.5 h, which caused the PC molecular chains to break down and depolymerize, obtaining the degradation products.

[0076] B. Neutralization: The depolymerized solution is neutralized by acid and base. After neutralization with an acidic molecular sieve and an alkaline catalyst in the solution, the solution is filtered to obtain the final product, polycarbonate oligomer, with a molecular weight of 4.7 kg / mol.

[0077] 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 degrading polycarbonate using a phenolic catalyst, characterized in that, Under high temperature and normal pressure conditions, using phenolic compounds as catalysts and diphenyl carbonate or substituted diphenyl carbonate as reactants, polycarbonate is catalytically degraded to obtain a depolymerization solution containing polycarbonate oligomers. The phenolic compounds are one or more of sodium phenolate, potassium phenolate, and sodium bisphenol A, and the amount of catalyst used is 1 to 6 times the weight of the polycarbonate. wt The degradation temperature is 150 ~ 280℃, and the time is 5 ~ 10 h. The substituted diphenyl carbonate is one or more of the following: bis(pentafluorophenyl)carbonate, guaiacol carbonate, 4,4-methylthiodiphenyl carbonate, and di(p-nitrobenzene) carbonate.

2. The method for degrading polycarbonate using a phenolic catalyst according to claim 1, characterized in that, The amount of diphenyl carbonate replaced is 30 to 200 mol of the polycarbonate repeating unit.

3. The method for degrading polycarbonate using a phenolic catalyst according to claim 1, characterized in that, The depolymerization solution was neutralized by passing it through a Sigma acidic molecular sieve column to bring the pH of the depolymerization solution to 6-8, and then filtered to obtain polycarbonate oligomers.

4. The method for degrading polycarbonate using a phenolic catalyst according to claim 1, characterized in that, Polycarbonate is one or more PC granules with different molecular weights.

5. The method for degrading polycarbonate using a phenolic catalyst according to claim 4, characterized in that, The molecular weight of PC granules is 12 ~ 20.5 kg / mol.

6. The method for degrading polycarbonate using a phenolic catalyst according to claim 1, characterized in that, The molecular weight of polycarbonate oligomers is below 6 kg / mol.

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