A method for preparing an epoxy resin precursor using polycarbonate and its application

Abstract

The present invention discloses a method for preparing an epoxy resin precursor using polycarbonate and its application, belonging to the technical field of solid waste recycling. The method includes: using bisphenol A polycarbonate and a bromide with an epoxy group as raw materials, an inorganic base as a catalyst, and carrying out a depolymerization and upgrading reaction in an organic solvent system under an air atmosphere. The temperature of the depolymerization and upgrading reaction is ≥130 °C, and the time is ≥10 min. After the reaction, a bisphenol A-type epoxy resin precursor is separated; the organic solvent is 1,4-dioxane, toluene, tetrahydrofuran, acetonitrile, acetone or methyltetrahydrofuran; the inorganic base is a carbonate or hydroxide of an alkali metal or an alkaline earth metal. The method of the present invention has mild reaction conditions and a fast reaction rate, and can directionally and highly value-added upgrade waste polycarbonate plastics to obtain an epoxy resin precursor.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste recycling and utilization, and specifically relates to a method for preparing an epoxy resin precursor from polycarbonate and its application. Background Art

[0002] As a basic material for modern industry, plastics have currently been widely used in various fields of human production and life, and waste plastic pollution has become an environmental problem that cannot be ignored. As one of the general engineering plastics, polycarbonate has a high annual output and is widely used in fields such as electronics and electrical appliances, plates, films, building materials, and automotive parts. Most of the waste polycarbonate is disposed of by landfilling or incineration, resulting in serious waste of resources and potentially causing certain harm to the environment and human health. Recycling and utilization of waste polycarbonate is a key measure to address "white pollution". Through technological innovation, waste polycarbonate can be converted into high-value recycled materials for manufacturing new products.

[0003] A variety of methods for efficiently decomposing and recycling bisphenol A from PC have been reported in the prior art. For example, the Chinese patent document with the publication number CN117024255A reports a method for catalytic degradation of polycarbonate using a phosphazene base system. In this invention, a phosphazene base with a tert-butyl substituent is used as the catalyst, and substituted phenol is used as the reaction reagent. Under the catalysis of the phosphazene base catalyst, the substituted phenol attacks the polycarbonate molecular chain to depolymerize, obtaining the products bisphenol A and substituted diphenyl carbonate. The Chinese patent document with the publication number CN113861117A reports a method for catalytic ammonolysis of aromatic polycarbonate using a zinc catalyst. In this method, under mild conditions and in an argon atmosphere, a transition metal Zn catalyst is used to catalyze the reaction of aromatic polycarbonate with an amine, and bisphenol A, urea, and its derivatives are recovered from the reaction products. There are also research reports on methods for efficiently decomposing and recycling bisphenol A dimethyl ether from PC (such as the Chinese patent document with the publication number CN117986094A, etc.). This method uses a green ionic liquid catalyst to catalyze the methylation reaction of PC with dimethyl carbonate (which acts as both a depolymerization reagent and a methylation reagent), and realizes the high-value conversion of waste PC plastics to bisphenol A dimethyl ether through a "one-pot two-step method" under relatively mild conditions.

[0004] Epoxy resins have excellent mechanical properties, adhesiveness, chemical resistance, and insulation properties, and are widely used in industries such as industry, construction, electronics, and aerospace. Epoxy resin precursors generally refer to low-molecular-weight compounds that can generate epoxy resins through chemical reactions. The most common bisphenol A-type epoxy resin precursor is BADGE (bisphenol A diglycidyl ether), and its synthesis method mainly uses bisphenol A and epichlorohydrin as raw materials and undergoes ring-opening polymerization reaction under the action of an alkaline catalyst. A preparation method of a polyester-based glycidyl ether has been reported in the literature (a Chinese patent document with the publication number CN118459741A). This method uses polybasic acid, polyhydric alcohol, capping agent, epichlorohydrin, and sodium hydroxide as raw materials, first synthesizes a series of hydroxyl-terminated polyesters with different molecular weights and softening points, and then epoxidizes them to prepare glycidyl ether. However, the above method has high requirements for the purity of raw materials and there are side reactions. There is currently no report on the preparation of epoxy resin precursors using waste polycarbonate plastics.

[0005] Therefore, how to upgrade waste polycarbonate plastics into epoxy resin precursors in a targeted and high-value manner is an urgent problem to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing epoxy resin precursors using polycarbonate, which has a simple process flow and low production cost, can realize the upgrading and high-value utilization of waste polycarbonate plastics into epoxy resin precursors, and has good application prospects in waste plastic treatment and epoxy resin synthesis.

[0007] The specific technical solutions adopted are as follows:

[0008] A method for preparing epoxy resin precursors using polycarbonate, comprising: using bisphenol A polycarbonate and a bromide with an epoxy group as raw materials, an inorganic base as a catalyst, and carrying out a depolymerization and upgrading reaction in an organic solvent system under an air atmosphere. The temperature of the depolymerization and upgrading reaction is ≥130 °C and the time is ≥10 min. After the reaction is completed, bisphenol A-type epoxy resin precursors are separated.

[0009] The organic solvent is 1,4-dioxane (Diox), toluene (Tol), tetrahydrofuran (THF), acetonitrile (CH3CN), acetone (ACE), or methyltetrahydrofuran (MeTHF);

[0010] The inorganic base is a carbonate or hydroxide of an alkali metal or alkaline earth metal.

[0011] The core of the present invention lies in the depolymerization-functionalization upgrade reaction of bisphenol A polycarbonate. By using polar aprotic solvents (such as ACE, CH3CN, etc.), PC can be effectively dissolved, promoting the homogeneous progress of the depolymerization reaction. It can also form a solvation effect with inorganic bases, enhancing the catalytic activity of the bases and promoting the cleavage of the ester bonds of PC. The bromide with an epoxy group provides an epoxy group for the synthesis of the precursor of bisphenol A-type epoxy resin. At the same time, bromine (Br) is easily substituted by the phenoxy group of bisphenol A under alkaline conditions to form a Ph-O-R (epoxy group) structure. Compared with chlorides, the reaction rate of bromides is faster, while iodides have a high cost and may undergo reduction side reactions. In addition, the present invention selects inorganic bases as base additives. The base attacks the carbonate bond of PC, causing it to break to generate bisphenol A (BPA) and carbonate (or CO2); at the same time, the base deprotonates the phenolic hydroxyl group (-OH) of bisphenol A to generate a phenoxide anion (PhO - ), and the latter attacks the carbon-bromine bond of the bromide to complete the introduction of the epoxy group.

[0012] Preferably, the bromide with an epoxy group includes epibromohydrin, (2-bromoethyl) ethylene oxide or 2-(-3-bromopropyl) ethylene oxide; the obtained precursor of bisphenol A-type epoxy resin includes bisphenol A diglycidyl ether, 2,2-bis[4-(3,4-epoxybutoxy)phenyl]propane or 2,2-bis[4-(4,5-epoxypentyloxy)phenyl]propane.

[0013] More preferably, the molar ratio of bisphenol A polycarbonate to the bromide with an epoxy group is 1:1:2-5, and even more preferably 1:2.3-3.5.

[0014] Preferably, the inorganic base is selected from potassium carbonate, sodium hydroxide, potassium hydroxide, cesium acetate or cesium carbonate. The above inorganic bases can efficiently catalyze the progress of the depolymerization upgrade reaction.

[0015] More preferably, the molar ratio of bisphenol A polycarbonate to the inorganic base is 1:1-5, and even more preferably 1:2.2-3. Two moles of OH are consumed for the depolymerization of each mole of PC - (because each PC chain segment contains two phenolic ester bonds), and the generated carbonic acid (H2CO3) or CO2 will consume the base, and the excess base is used to maintain the reaction pH.

[0016] Preferably, the dosage of the organic solvent is 0.5-5 mL / mmol based on the molar amount of bisphenol A polycarbonate.

[0017] Preferably, in order to balance the reaction efficiency and product yield, the temperature of the depolymerization upgrade reaction is 130-180 °C and the time is 10-60 min.

[0018] The present invention also provides an application of the method for preparing an epoxy resin precursor using polycarbonate in the treatment of waste plastics.

[0019] Specifically, the waste plastics are waste materials made of bisphenol A polycarbonate, including but not limited to waste optical discs, waste water buckets, waste films, waste bottle materials, waste plates, waste sheets, waste lamp tubes, etc.

[0020] The method of the present invention is applicable to various forms of waste bisphenol A polycarbonate samples, and the recovery rate of the bisphenol A type epoxy resin precursor is ≥90%, further ≥95%, with high efficiency. Moreover, the prepared bisphenol A type epoxy resin precursor can be further used for the synthesis of epoxy resins, realizing the high-value utilization of waste plastics.

[0021] When the waste plastics are upgraded and transformed, they need to be pre-crushed into centimeter-sized or millimeter-sized flakes, granules or powders to ensure their resource utilization effect, so as to obtain the bisphenol A type epoxy resin precursor with high yield through directional upgrading.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) In the traditional process, bisphenol A (BPA) is often directly used to synthesize epoxy resins, which requires the consumption of petroleum-based raw materials and has high energy consumption. However, the present invention uses waste bisphenol A polycarbonate (such as optical discs, plates, etc.) as raw materials, and realizes resource recycling through depolymerization-functionalization upgrading. At the same time, it avoids environmental pollution and health risks during the BPA synthesis process, meeting the requirements of green chemistry and sustainable development.

[0024] (2) The present invention synchronously completes depolymerization and the introduction of epoxy groups in a single reaction system, and can efficiently react at ≥130 °C in an air atmosphere. The reaction path is short, the equipment requirements and energy consumption are low, and the yield of the bisphenol A type epoxy resin precursor product is high. At the same time, inorganic bases (such as KOH, Cs2CO3, etc.) are inexpensive, and the solvent can be recycled, significantly reducing costs compared with noble metal catalysts or organic base systems (such as triethylamine). Description of the Drawings

[0025] Figure 1 It is a reaction route diagram for preparing an epoxy resin precursor using polycarbonate.

[0026] Figure 2 It is a gas chromatogram of bisphenol A diglycidyl ether BADGE obtained in Example 1. Detailed Embodiments

[0027] To make the objectives, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description through specific embodiments. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflict.

[0028] For the operation methods without specific conditions noted in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0029] Example 1

[0030] Add 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol), and 1.5 mL of acetone into a glass tube. Place the glass tube on a collecting heat type constant temperature heating magnetic stirrer, turn on the stirring and heating, and heat the reaction system to 150 °C under an air atmosphere and react at this temperature for 30 min (the reaction route equation is as Figure 1 shown). After the reaction is completed, cool it to room temperature to obtain a mixed solution. The obtained mixed solution is analyzed by gas chromatography GC (the GC spectrum is as Figure 2 shown). Mesitylene is used as an internal standard. The results show that the yield of bisphenol A diglycidyl ether BADGE in this example is 99%.

[0031] The method for separating BADGE and incompletely reacted products is column chromatography; use a silica gel column or an alumina column with a particle size of 40 - 63 μm; first elute low-polarity impurities (such as unreacted BPA) with a non-polar solvent (such as petroleum ether), gradually increase the proportion of the polar solvent (such as ethyl acetate) to elute the mono-epoxy product, and finally elute BADGE with a polar mixed solvent (such as ethyl acetate:methanol = 9:1); monitor the fractions by TLC or HPLC and collect the target components.

[0032] Example 2

[0033] 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 2.5 mmol of different base additives (potassium carbonate, sodium hydroxide, potassium hydroxide, cesium acetate), and 1.5 mL of acetone were respectively added into different glass tubes. The different glass tubes were respectively placed on a thermostatic heating magnetic stirrer with heat collection. Stirring and heating were started, and the reaction system was heated to 150 °C under an air atmosphere and reacted at this temperature for 30 min. After the reaction was completed, the temperature was lowered to room temperature to obtain a mixed solution. The obtained mixed solution was analyzed by gas chromatography GC with mesitylene as the internal standard. The results showed that under the action of different base additives, the yields of bisphenol A diglycidyl ether BADGE in this example were 24%, 35%, 45%, and 11% respectively.

[0034] Example 3

[0035] 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), different amounts of cesium carbonate (2 mmol, 2.2 mmol, 2.3 mmol, 3 mmol, 4 mmol, 5 mmol), and 1.5 mL of acetone were respectively added into different glass tubes. The different glass tubes were respectively placed on a thermostatic heating magnetic stirrer with heat collection. Stirring and heating were started, and the reaction system was heated to 150 °C under an air atmosphere and reacted at this temperature for 30 min. After the reaction was completed, the temperature was lowered to room temperature to obtain a mixed solution. The obtained mixed solution was analyzed by gas chromatography GC with mesitylene as the internal standard. The results showed that under different dosages of inorganic base catalysts, the yields of bisphenol A diglycidyl ether BADGE in this example were 90%, 92%, 96%, 99%, 99%, and 99% respectively.

[0036] Example 4

[0037] 0.254 g of PC powder with CR purity (1 mmol), different amounts of epibromohydrin (2 mmol, 2.3 mmol, 2.5 mmol, 2.7 mmol, 3.5 mmol), 0.8146 g of cesium carbonate (2.5 mmol), and 1.5 mL of acetone were respectively added into different glass tubes. The different glass tubes were respectively placed on a thermostatic heating magnetic stirrer with heat collection. Stirring and heating were started, and the reaction system was heated to 150 °C under an air atmosphere and reacted at this temperature for 30 min. After the reaction was completed, the temperature was lowered to room temperature to obtain a mixed solution. The obtained mixed solution was analyzed by gas chromatography GC with mesitylene as the internal standard. The results showed that under different dosages of epibromohydrin, the yields of bisphenol A diglycidyl ether BADGE in this example were 75%, 91%, 98%, 99%, and 99% respectively.

[0038] Example 5

[0039] Add 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol) and 1.5 mL of acetone into a glass tube. Place the glass tube on a magnetic stirrer with a heat - collecting type constant - temperature heater, turn on stirring and heating, and under an air atmosphere, raise the temperature of the reaction system to 130 °C, 140 °C, 160 °C, 170 °C, 180 °C respectively, and react at this temperature for 30 min. After the reaction is completed, cool down to room temperature to obtain a mixed solution. The obtained mixed solution is analyzed by gas chromatography GC with mesitylene as the internal standard. The results show that at different reaction temperatures, the yields of bisphenol A diglycidyl ether BADGE in this example are 74%, 99%, 99%, 99%, 99% respectively.

[0040] Example 6

[0041] Add 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol) and 1.5 mL of acetone into a glass tube. Place the glass tube on a magnetic stirrer with a heat - collecting type constant - temperature heater, turn on stirring and heating, and under an air atmosphere, raise the temperature of the reaction system to 150 °C, and react at this temperature for 10 min, 20 min, 40 min, 50 min, 60 min respectively. After the reaction is completed, cool down to room temperature to obtain a mixed solution. The obtained mixed solution is analyzed by gas chromatography GC with mesitylene as the internal standard. The results show that at different reaction times, the yields of bisphenol A diglycidyl ether BADGE in this example are 88%, 96%, 99%, 99%, 99% respectively.

[0042] Example 7

[0043] 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol) and 1.5 mL of different organic solvents (1,4-dioxane Diox, toluene Tol, tetrahydrofuran THF, acetonitrile CH3CN, methyltetrahydrofuran MeTHF) were added to different glass tubes respectively. The different glass tubes were placed on a heating magnetic stirrer with heat collection and constant temperature. Stirring and heating were started. The reaction system was heated to 150 °C under an air atmosphere and reacted at this temperature for 30 min. After the reaction was completed, the temperature was cooled to room temperature to obtain a mixed solution. The obtained mixed solution was analyzed by gas chromatography GC, and mesitylene was used as an internal standard. The results showed that the yields of bisphenol A diglycidyl ether BADGE in this example were 75%, 50%, 68%, 96% and 69% respectively in different organic solvents.

[0044] Comparative Example 1

[0045] 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol) and 1.5 mL N -methylpyrrolidone were added to a glass tube. The glass tube was placed on a heating magnetic stirrer with heat collection and constant temperature. Stirring and heating were started. The reaction system was heated to 150 °C under an air atmosphere and reacted at this temperature for 30 min. After the reaction was completed, the temperature was cooled to room temperature to obtain a mixed solution. The obtained mixed solution was analyzed by gas chromatography GC, and mesitylene was used as an internal standard. The results showed that the yield of bisphenol A diglycidyl ether BADGE in this comparative example was 0.

[0046] Comparative Example 2

[0047] 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol) and 1.5 mL of dimethyl sulfoxide were added to a glass tube. The glass tube was placed on a heating magnetic stirrer with heat collection and constant temperature. Stirring and heating were started. The reaction system was heated to 150 °C under an air atmosphere and reacted at this temperature for 30 min. After the reaction was completed, the temperature was cooled to room temperature to obtain a mixed solution. The obtained mixed solution was analyzed by gas chromatography GC, and mesitylene was used as an internal standard. The results showed that the yield of bisphenol A diglycidyl ether BADGE in this comparative example was 0.

[0048] Comparative Example 3

[0049] Add 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.8146 g of cesium carbonate (2.5 mmol) and 1.5 mL N,N -dimethylformamide into a glass tube. Place the glass tube on a heating magnetic stirrer with heat collection and constant temperature. Turn on the stirring and heating. Under an air atmosphere, heat the reaction system to 150 °C and react at this temperature for 30 min. After the reaction is completed, cool it to room temperature to obtain a mixed solution. The obtained mixed solution is analyzed by gas chromatography GC with mesitylene as the internal standard. The results show that the yield of bisphenol A diglycidyl ether BADGE in this comparative example is 0.

[0050] Comparative Example 4

[0051] Add 0.254 g of PC powder with CR purity (1 mmol), 0.4109 g of epibromohydrin (3 mmol), 0.2503 g of potassium bicarbonate (2.5 mmol) and 1.5 mL of acetone into a glass tube. Place the glass tube on a heating magnetic stirrer with heat collection and constant temperature. Turn on the stirring and heating. Under an air atmosphere, heat the reaction system to 150 °C and react at this temperature for 30 min. After the reaction is completed, cool it to room temperature to obtain a mixed solution. The obtained mixed solution is analyzed by gas chromatography GC with mesitylene as the internal standard. The results show that the yield of bisphenol A diglycidyl ether BADGE in this comparative example is 0.

[0052] The above embodiments have described the technical solutions of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements or similar replacements made within the principle scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an epoxy resin precursor using polycarbonate, characterized in that, Comprising: Using bisphenol A polycarbonate and a bromide with an epoxy group as raw materials, an inorganic base as a catalyst, and carrying out a depolymerization and upgrading reaction in an organic solvent system under an air atmosphere. The temperature of the depolymerization and upgrading reaction is ≥130 °C, and the time is ≥10 min. After the reaction, a bisphenol A-type epoxy resin precursor is separated; The organic solvent is 1,4-dioxane, toluene, tetrahydrofuran, acetonitrile, acetone, or methyltetrahydrofuran; The inorganic base is cesium carbonate; The obtained bisphenol A-type epoxy resin precursor includes bisphenol A diglycidyl ether, 2,2-bis[4-(3,4-epoxybutoxy)phenyl]propane, or 2,2-bis[4-(4,5-epoxypentyloxy)phenyl]propane.

2. The method for preparing an epoxy resin precursor using polycarbonate according to claim 1, wherein The bromide with an epoxy group includes epibromohydrin, (2-bromoethyl)ethylene oxide, or 2-(-3-bromopropyl)ethylene oxide.

3. The method for preparing an epoxy resin precursor using polycarbonate according to claim 1, wherein The molar ratio of bisphenol A polycarbonate to the bromide with an epoxy group is 1:2 - 5.

4. The method for preparing an epoxy resin precursor using polycarbonate according to claim 1, wherein The molar ratio of bisphenol A polycarbonate to the inorganic base is 1:1 - 5.

5. The method for preparing an epoxy resin precursor using polycarbonate according to claim 1, characterized in that, The dosage of the organic solvent is 0.5 - 5 mL / mmol based on the molar amount of bisphenol A polycarbonate.

6. The method for preparing an epoxy resin precursor using polycarbonate according to claim 1, wherein The temperature of the depolymerization and upgrading reaction is 130 - 180 °C, and the time is 10 - 60 min.

7. Use of the method for preparing an epoxy resin precursor from polycarbonate according to any one of claims 1-6 in waste plastic treatment, characterized in that, The waste plastic is a waste of bisphenol A polycarbonate material.

8. The application according to claim 7, wherein The waste plastic needs to be pre-crushed into centimeter-sized or millimeter-sized flakes, granules, or powders during the upgrading transformation.

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