Alcoholysis method of plastic mixture

Abstract

The invention relates to a method for the alcoholysis of a plastic mixture, said plastic mixture comprising a polycarbonate and a further polymer, said alcoholysis method comprising the following steps: mixing the plastic mixture with a specific catalyst and an alcoholysis agent, polycarbonate in the plastic mixture is subjected to an alcoholysis reaction at the polycarbonate alcoholysis temperature; and carrying out solid-liquid separation on a reaction system obtained by the alcoholysis reaction to obtain a liquid containing an alcoholysis product of polycarbonate and a solid containing other polymers. According to the alcoholysis method of the plastic mixture disclosed by the invention, while the polycarbonate is selectively alcoholyzed, other components are still kept in a solid state, so that the polycarbonate alcoholysis product can be easily separated from other components, and the selective chemical recovery of the polycarbonate is realized.

Description

Technical Field

[0001] This invention belongs to the field of plastic mixture processing and separation, and specifically relates to a method for the alcoholysis of plastic mixtures. Background Technology

[0002] Polycarbonate (PC), one of the five major general-purpose engineering plastics, is widely used in electronic and electrical enclosures, automotive parts, and building materials due to its impact resistance, high-temperature resistance, and excellent electrical insulation properties. However, polycarbonate plastics have poor resistance to chemical solvents and poor fatigue resistance. In practical applications, polycarbonate is often blended with polyester, polyamide, and polyolefins to obtain plastic products with ideal performance characteristics. However, the disposal of these high-performance plastic blends after disposal becomes a challenge.

[0003] Although chemical recycling routes for single types of plastics have been extensively studied, the challenges of chemical recycling of these plastic blends remain unresolved, and methods for handling complex blended plastic waste urgently need to be established.

[0004] Furthermore, real plastic products are often discarded together after use, and obtaining individual materials requires further separation using industrial methods such as magnetic separation, infrared spectroscopy, and flotation, which increases the sorting costs at the front end of chemical recycling. Therefore, the development of selective chemical recycling routes for actual plastic waste is also very important.

[0005] Currently, the main chemical methods for degrading plastics include hydrolysis, alcoholysis, and sugar alcoholysis. For example, Patent Document 1 discloses a plastic hydrolysis method that uses a binuclear metal complex as a catalyst to cause the hydrolysis reaction in an alkaline aqueous solution. Patent Document 2 discloses a method for catalytically degrading and recycling waste polyurethane into polyether polyols. First, under alcoholysis conditions, a metal-organic framework (MOF) is used as a catalyst to catalyze the degradation of waste polyurethane into polyether polyols and low-molecular-weight amide compounds at a certain temperature. After the alcoholysis reaction is completed, the mixture is cooled to room temperature and quenched with water. The reaction system is then further post-treated to obtain recycled polyether polyols.

[0006] References:

[0007] Patent Document 1: CN114377726A;

[0008] Patent document 2: CN118271702A. Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Neither of the methods for catalytic degradation of plastics disclosed in the aforementioned patent documents 1 and 2 involve the treatment of plastic mixtures containing polycarbonate.

[0011] The technical problem to be solved by the present invention is to provide a method for alcoholysis of plastic mixtures, which can selectively alcoholyze the polycarbonate contained in the plastic mixtures and can easily separate the polycarbonate alcoholysis products from other components.

[0012] Solution for solving the problem

[0013] To address the aforementioned problems, the inventors conducted extensive and in-depth research and discovered that by using a specific catalyst to treat a plastic mixture containing polycarbonate at a specific temperature, the polycarbonate in the mixture can be selectively alcoholyzed, thus completing this invention.

[0014] Specifically, the present invention solves the problems of the present invention through the following solutions.

[0015] [1] A method for alcoholysis of a plastic mixture, wherein the plastic mixture comprises polycarbonate and other polymers, wherein the other polymers are one or more selected from a second polymer, a third polymer, and a fourth polymer, wherein the second polymer is one or more selected from polyester and polyurethane, the third polymer is one or more selected from polyamide, and the fourth polymer is one or more selected from polyolefin;

[0016] The alcoholysis method includes the following steps:

[0017] (a) The plastic mixture is mixed with a catalyst and an alcoholysis agent, and the polycarbonate in the plastic mixture is subjected to an alcoholysis reaction at the polycarbonate alcoholysis temperature;

[0018] (a') The reaction system obtained in step (a) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of polycarbonate and a solid containing the other polymers;

[0019] The catalyst has the structure shown in the following general formula (I):

[0020]

[0021] Where M1 and M2 represent metal atoms, M1 is Mn, and M2 is selected from Mn, Fe, Co, Ni, or Cu, and the distance between the two atoms of M1 and M2 is [missing information]. M1 and M2 can be the same or different.

[0022] Y is selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O– or SO4 2– ,

[0023] n is 2 or 3

[0024] m represents the quantity of Y, which can be 1, 2, or 3.

[0025] R2 is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group, or a carboxyl group, or R2 is fused with R1 or R1' to form a ring structure, wherein the hydrocarbon group is a C1-C6 alkyl group, preferably a C1-C4 alkyl group.

[0026] R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms.

[0027] R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms.

[0028] X is either O or S;

[0029] The alcoholysis agent is one or more selected from monohydric alcohols and dihydric alcohols;

[0030] The polycarbonate alcoholysis temperature is below 150°C;

[0031] Preferably, in step (a), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent, the ratio of the number of moles of the alcoholysis agent to the total number of moles of the polycarbonate structural units in the plastic mixture is 100:1 to 8:1, and the alcoholysis reaction time is 0.5 h to 10 h.

[0032] [2] According to the alcoholysis method of [1], wherein the other polymer comprises a second polymer and optionally a third polymer and / or a fourth polymer, the alcoholysis method further comprises the following steps:

[0033] (b) The solid obtained in step (a') is mixed with a catalyst and an alcoholysis agent, and the second polymer is subjected to an alcoholysis reaction at a second temperature;

[0034] In cases where the other polymers comprise a third polymer and / or a fourth polymer, the alcoholysis method further includes the following steps:

[0035] (b') The reaction system obtained in step (b) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the second polymer and a solid containing the third polymer and / or the fourth polymer;

[0036] The second temperature is higher than the polycarbonate alcoholysis temperature, preferably a temperature higher than 150°C and lower than 195°C;

[0037] Preferably, in step (b), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent, the ratio of the number of moles of the alcoholysis agent to the number of moles of the structural units of the second polymer in the solid obtained in step (a') is 100:1 to 8:1, and the alcoholysis reaction time is 0.5 h to 10 h.

[0038] [3] The alcoholysis method according to [2], wherein the other polymer comprises a third polymer and optionally a fourth polymer, the alcoholysis method further comprises the following steps:

[0039] (c) The solid obtained in step (b') is mixed with a catalyst and an alcoholysis agent, and the third polymer is subjected to an alcoholysis reaction at a third temperature;

[0040] In the case that the other polymers include a fourth polymer, the alcoholysis method further includes the following steps:

[0041] (c') The reaction system obtained in step (c) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the third polymer and a solid containing the fourth polymer.

[0042] The third temperature is higher than the second temperature, preferably a temperature higher than 195°C;

[0043] Preferably, in step (c), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent; the ratio of the number of moles of the alcoholysis agent to the number of moles of the structural units of the third polymer in the solid obtained in step (b') is 100:1 to 8:1; and the alcoholysis reaction time is 0.5 h to 10 h.

[0044] [4] According to the alcoholysis method of [1], wherein the other polymer comprises a third polymer but not a second polymer, and optionally a fourth polymer, the alcoholysis method further comprises the following steps:

[0045] (c-1) The solid obtained in step (a') is mixed with a catalyst and an alcoholysis agent, and the third polymer is subjected to an alcoholysis reaction at a third temperature.

[0046] In the case that the other polymers include a fourth polymer, the alcoholysis method further includes the following steps:

[0047] (c'-1) The reaction system obtained in step (c-1) is subjected to solid-liquid separation to obtain a liquid containing the hydrolysis product of the third polymer alcohol and a solid containing the fourth polymer.

[0048] The third temperature is higher than the polycarbonate alcoholysis temperature, preferably a temperature higher than 195°C;

[0049] Preferably, in step (c-1), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent; the ratio of the number of moles of the alcoholysis agent to the number of moles of the structural units of the third polymer in the solid obtained in step (a') is 100:1 to 8:1; and the alcoholysis reaction time is 0.5 h to 10 h.

[0050] [5] The alcoholysis method according to any one of [1] to [4], wherein in general formula (1), M2 is Mn and Y is selected from NO3. – Cl – ,Br – ClO4 – CH3O – HOCH2CH2O – n is 2, m is 2, R2 represents H, R3 is selected from H, C1-C6 alkyl, and R1 and R1' are propylidene or 1,2-phenylene;

[0051] Preferably, the catalyst has the structure shown in the following general formula (II):

[0052]

[0053] [6] The alcoholysis method according to any one of [1] to [4], wherein the monohydric alcohol is an aliphatic monohydric alcohol, preferably an aliphatic monohydric alcohol with 1 to 6 carbon atoms, more preferably methanol, ethanol, or propanol; and the dihydric alcohol is an aliphatic dihydric alcohol, preferably an aliphatic dihydric alcohol with 2 to 6 carbon atoms, more preferably ethylene glycol, propylene glycol, or butanediol.

[0054] [7] The alcoholysis method according to any one of [1] to [4], wherein the polycarbonate is a bisphenol A type polycarbonate.

[0055] [8] The alcoholysis method according to any one of [1] to [4], wherein the polyester is one or more selected from the polymer obtained by polycondensation of polyols and polyacids, polymer obtained by ring-opening polymerization of lactones, and polymer obtained by polycondensation of compounds having both hydroxyl and carboxyl groups;

[0056] Preferably, the polyol is an aliphatic polyol, more preferably an aliphatic polyol with 2 to 6 carbon atoms; the lactone is an aliphatic lactone, more preferably an aliphatic lactone with 6 to 10 carbon atoms; and the compound having both hydroxyl and carboxyl groups is lactic acid.

[0057] More preferably, the polyester is one or more selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), and polybutylene terephthalate adipate (PBAT);

[0058] The polyurethane is selected from one or more of polyester-type polyurethane and polyether-type polyurethane.

[0059] [9] The alcoholysis method according to any one of [1] to [4], wherein the polyamide is one or more selected from aliphatic polyamides and aromatic polyamides;

[0060] Preferably, the polyamide is one or more selected from polyamide 6 (Nylon 6), polyamide 66 (Nylon 66), polyamide 46, polyamide 12, polyamide 69 and polyamide 6-10.

[0061]

[10] The alcoholysis method according to any one of [1] to [4], wherein the polyolefin is one or more selected from polyethylene (PE), polypropylene (PP), acrylonitrile-styrene-butadiene copolymer (ABS) and polystyrene (PS).

[0062] The effects of the invention

[0063] The alcoholysis method for plastic mixtures of the present invention can selectively alcoholyze polycarbonate while other components remain in solid form, thereby easily separating the polycarbonate alcoholysis products from other components and achieving selective chemical recycling of polycarbonate.

[0064] Furthermore, when the plastic mixture contains one or more of the second to fourth polymers, the separation of these polymer components can also be achieved. Attached Figure Description

[0065] Figure 1 The graph shows the yield of BPA and BHET over time in steps 1) and 2) of Example 1.

[0066] Figure 2 The 1H NMR spectrum of the BPA product obtained in step 3) of Example 1 is compared with the 1H NMR spectrum of commercially sourced BPA.

[0067] Figure 3 The infrared spectrum of the BPA product obtained in step 3) of Example 1 is compared with the infrared spectrum of commercially sourced BPA.

[0068] Figure 4 This is a graph showing the yield of BPA and BHET over time in steps 1) and 2) of Example 2.

[0069] Figure 5 The graph shows the yield of BPA and BDO over time in steps 1) and 2) of Example 3.

[0070] Figure 6 This is a schematic diagram of the reaction process in Example 6;

[0071] Figure 7 This is a schematic diagram of the reaction process in Example 7. Detailed Implementation

[0072] The present invention will now be described in detail. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0073] <Terminology and Definitions>

[0074] In this instruction manual, "room temperature" refers to a temperature range of 20 to 30°C, such as 25°C.

[0075] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0076] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0077] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0078] In this specification, the terms "optionally" or "optionally" are used to indicate the use or non-use of certain substances, components, procedures, application conditions, etc.

[0079] All unit names used in this manual are international standard unit names, and unless otherwise stated, the "%" used refers to weight or mass percentage content.

[0080] In this specification, references to "preferred embodiments," "implementation methods," etc., mean that a specific element (e.g., feature, structure, property, and / or characteristic) related to that embodiment is included in at least one of the embodiments described herein, and may or may not be present in other embodiments. Furthermore, it should be understood that the elements may be combined in any suitable manner in various embodiments.

[0081] One object of the present invention is to provide a method for alcoholysis of a plastic mixture, wherein the plastic mixture comprises polycarbonate and other polymers, said other polymers being one or more selected from a second polymer, a third polymer, and a fourth polymer, wherein the second polymer is one or more selected from polyesters and polyurethanes, the third polymer is one or more selected from polyamides, and the fourth polymer is one or more selected from polyolefins;

[0082] The alcoholysis method includes the following steps:

[0083] (a) The plastic mixture is mixed with a catalyst and an alcoholysis agent, and the polycarbonate in the plastic mixture is subjected to an alcoholysis reaction at the polycarbonate alcoholysis temperature;

[0084] (a') The reaction system obtained in step (a) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of polycarbonate and a solid containing the other polymers.

[0085] The alcoholysis method of the present invention, by using a specific catalyst and at a specific polycarbonate alcoholysis temperature, enables only the polycarbonate in the plastic mixture to undergo alcoholysis, while other polymers remain unreacted and exist in solid form. After the alcoholysis reaction, the polycarbonate alcoholysis products can be separated from other polymers through simple solid-liquid separation, achieving the purpose of selectively chemically treating and recovering polycarbonate from the plastic mixture.

[0086] The alcoholysis method of the present invention may include other steps depending on the composition of other polymers.

[0087] In one embodiment, the other polymer comprises a second polymer and optionally a third and / or a fourth polymer, and in addition to steps (a) and (a'), the alcoholysis method further comprises the following steps:

[0088] (b) The solid obtained in step (a') is mixed with a catalyst and an alcoholysis agent, and the second polymer is subjected to an alcoholysis reaction at a second temperature;

[0089] In cases where the other polymers comprise a third polymer and / or a fourth polymer, the alcoholysis method further includes the following steps:

[0090] (b') The reaction system obtained in step (b) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the second polymer and a solid containing the third polymer and / or the fourth polymer.

[0091] In this embodiment, after the polycarbonate in the plastic mixture has been alcoholyzed and the alcoholysis products separated from other polymers through steps (a) and (a'), the second polymer among the other polymers is further alcoholyzed at a second temperature higher than the polycarbonate alcoholysis temperature, while the third and / or fourth polymers that may be contained in the other polymers do not react and remain in solid form. After the alcoholysis reaction of the second polymer, the alcoholysis products of the second polymer can be separated from the third and / or fourth polymers that may be contained in the other polymers through simple solid-liquid separation, achieving the purpose of selectively chemically treating and recycling the second polymer in the plastic mixture.

[0092] In one aspect of this embodiment, the other polymers include a third polymer in addition to the second polymer, and the alcoholysis method further includes the following steps in addition to steps (a), (a'), (b), and (b'):

[0093] (c) The solid obtained in step (b') is mixed with a catalyst and an alcoholysis agent, and the third polymer is subjected to an alcoholysis reaction at a third temperature;

[0094] In the case that the other polymers include a fourth polymer, the alcoholysis method further includes the following steps:

[0095] (c') The reaction system obtained in step (c) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the third polymer and a solid containing the fourth polymer.

[0096] In this aspect, the third polymer is further subjected to alcoholysis at a third temperature higher than the second temperature, while the fourth polymer, which may be contained in other polymers, does not react, thereby achieving the purpose of selectively chemically treating and recycling the third polymer in the plastic mixture.

[0097] In one embodiment, the other polymers comprise a third polymer but not the second polymer, and optionally a fourth polymer, and in addition to steps (a) and (a'), the alcoholysis method further comprises the following steps:

[0098] (c-1) The solid obtained in step (a') is mixed with a catalyst and an alcoholysis agent, and the third polymer is subjected to an alcoholysis reaction at a third temperature.

[0099] In the case that the other polymers include a fourth polymer, the alcoholysis method further includes the following steps:

[0100] (c'-1) The reaction system obtained in step (c-1) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the third polymer and a solid containing the fourth polymer.

[0101] In this embodiment, since the other polymers do not contain the second polymer, the alcoholysis of the third polymer can be carried out directly at the third temperature after the alcoholysis of polycarbonate and the separation of alcoholysis products are completed (i.e., steps (a) and (a') are performed).

[0102] The various aspects of the alcoholysis method of the present invention are described in detail below.

[0103] <Catalyst>

[0104] The catalyst used in the alcoholysis reaction of this invention is a binuclear metal complex having the structure shown in the following general formula (I):

[0105]

[0106] In general formula (I), M1 and M2 represent metal atoms, M1 is Mn, and M2 is selected from Mn, Fe, Co, Ni, or Cu, and the interatomic distance between M1 and M2 is [missing information]. M1 and M2 can be the same or different.

[0107] Y is an anion, which can be selected from NO3. – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– Preferred from NO3 – Cl – ,Br – ClO4 – CH3O – HOCH2CH2O – More preferably Cl – Y – It can be axially coordinated at the center of a metal atom.

[0108] n can be 2 or 3, preferably 2.

[0109] m represents the quantity of Y, which can be 1, 2, or 3, preferably 2.

[0110] R2 is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group, or a carboxyl group, or R2 is fused with R1 or R1' to form a ring structure, wherein the hydrocarbon group is a C1-C6 alkyl group, preferably a C1-C4 alkyl group. Preferably, R2 represents H.

[0111] R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms, preferably from H, C1-C6 alkyl, and more preferably from methyl or ethyl.

[0112] R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms, preferably propylene or 1,2-phenylene, and more preferably propylene.

[0113] X is either O (oxygen atom) or S (sulfur atom), preferably O.

[0114] In a preferred embodiment, the catalyst has the structure shown in the following general formula (II):

[0115]

[0116] The catalyst used in this invention can selectively catalyze the alcoholysis reaction of different types of plastics at different temperatures without affecting other plastics, thus enabling selective chemical treatment and recycling of plastic mixtures.

[0117] <Alcohololysis temperature>

[0118] In the alcoholysis method of this invention, the alcoholysis temperature varies for different plastics, and the alcoholysis temperatures from low to high are as follows:

[0119] Polycarbonate < Second polymer < Third polymer

[0120] Under the conditions involved in the method of the present invention, the fourth polymer does not undergo alcoholysis.

[0121] Preferably, the polycarbonate alcoholysis temperature is below 150°C, more preferably below 140°C, even more preferably below 130°C, and still more preferably below 120°C. From the perspective of reaction efficiency, it is generally above 60°C, preferably above 70°C, more preferably above 80°C, and still more preferably above 90°C, such as above 100°C or above 110°C.

[0122] Preferably, the alcoholysis temperature of the second polymer, i.e. the second temperature, is above 150°C and below 195°C, more preferably 160-185°C, and even more preferably 170-180°C.

[0123] Preferably, the alcoholysis temperature of the third polymer, i.e., the third temperature, is above 195°C, more preferably above 200°C, even more preferably above 210°C, and further preferably above 220°C. From the perspective of energy conservation, it is generally below 280°C, preferably below 270°C, more preferably below 260°C, and even more preferably below 250°C, for example below 240°C or below 230°C.

[0124] <Alcohololysis agent>

[0125] The alcoholysis agent used in this invention is one or more selected from monohydric alcohols and dihydric alcohols.

[0126] Preferably, the monohydric alcohol is an aliphatic monohydric alcohol, more preferably an aliphatic monohydric alcohol with 1 to 6 carbon atoms, and more preferably methanol, ethanol, or propanol.

[0127] Preferably, the diol is an aliphatic diol, more preferably an aliphatic diol with 2 to 6 carbon atoms, and even more preferably ethylene glycol, propylene glycol, or butanediol.

[0128] <Alcohololysis reaction>

[0129] In the alcoholysis method of the present invention and its preferred embodiments, steps (a), (b), (c), and (c-1) are steps for carrying out the alcoholysis reaction of the corresponding polymer.

[0130] In steps (a), (b), (c), and (c-1), the alcoholysis reaction is carried out by mixing the catalyst, alcoholysis agent, and plastic mixture or solid obtained from solid-liquid separation, and adjusting the temperature of the mixture to the alcoholysis temperature of the corresponding polymer described above.

[0131] In this invention, there are no particular limitations on the time of the alcoholysis reaction in steps (a), (b), (c), and (c-1), and it can be selected according to the amount of materials, etc. Generally, the alcoholysis reaction time can be 0.5 to 10 hours, preferably 0.6 to 8 hours, more preferably 0.8 to 7 hours, and even more preferably 1 to 6 hours.

[0132] In one embodiment, in steps (a), (b), (c), and (c-1), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent; preferably 0.08 g / L to 0.8 g / L; more preferably 0.1 g / L to 0.7 g / L.

[0133] In one embodiment, in steps (a), (b), (c), and (c-1), the ratio of the molar number of the alcoholysis agent to the total molar number of the structural units of the polymer to be alcoholyzed in the plastic mixture is 100:1 to 8:1, preferably 90:1 to 20:1, and more preferably 80:1 to 40:1.

[0134] In the above text, "the polymer to be alcoholyzed" is polycarbonate in step (a), the second polymer in step (b), and the third polymer in steps (c) and (c-1).

[0135] In the above text, the "total number of moles of structural units" used to describe polymers refers to the sum of the moles of all structural units in the polymer. In the case of polymer mixtures and copolymers, it refers to the sum of the moles of structural units of each polymer in the mixture. In this text, the structural unit of a polymer has its usual meaning in the art and is used synonymously with a repeating unit.

[0136] Generally, for polycarbonate, the number of moles of its structural units is basically the same as the number of moles of carbonate groups; for polyester, the number of moles of its structural units is basically the same as the number of moles of ester groups; for polyurethane, the number of moles of its structural units is basically the same as the number of moles of urethane groups; for polyamide, the number of moles of its structural units is basically the same as the number of moles of amide groups; and for polyolefin, the number of moles of its structural units is the total number of moles of monomer units.

[0137] In one embodiment, the alcoholysis reactions in steps (a), (b), (c), and (c-1) are carried out in an inert gas (e.g., nitrogen or argon).

[0138] In one embodiment, the alcoholysis reaction in steps (a), (b), (c), and (c-1) is carried out under stirring conditions, preferably at a stirring rate of 300 r / min to 600 r / min, more preferably at 350 r / min to 500 r / min, for example at 400 r / min.

[0139] Solid-liquid separation

[0140] In the method of the present invention, in steps (a'), (b'), (c') and (c'-1), the system after the alcoholysis reaction is subjected to solid-liquid separation to separate the liquid containing the alcoholysis product from the unreacted solid.

[0141] The present invention does not particularly limit the method of solid-liquid separation, and it can be any suitable solid-liquid separation method known in the art, such as decantation, filtration, centrifugation and gravity sedimentation, etc., with filtration being preferred.

[0142] The solids obtained from filtration can be used directly in the next alcoholysis step (if any), or they can be used in the next alcoholysis step after post-treatment. Post-treatment includes, but is not limited to, washing, drying, and crushing.

[0143] The filtered liquid may contain alcoholysis products that can be separated and purified using methods conventional in the art.

[0144] Composition of Plastic Compounds

[0145] polycarbonate

[0146] In this invention, the polycarbonate can be aliphatic polycarbonate, aromatic polycarbonate, or aliphatic-aromatic polycarbonate.

[0147] In one embodiment, the polycarbonate is an aromatic polycarbonate, more preferably a bisphenol A type polycarbonate. Bisphenol A type polycarbonate can be synthesized by reacting bisphenol A with carbonyl chloride (COCl2). Currently, the most commonly used method is the melt transesterification method, which involves the synthesis of bisphenol A with diphenyl carbonate through transesterification and polycondensation.

[0148] In one embodiment, the polycarbonate has a weight-average molecular weight of 10,000 to 50,000, preferably 20,000 to 40,000.

[0149] Bisphenol A type polycarbonate has the following structure (end groups not shown):

[0150]

[0151] Where n represents the number of structural units within the brackets, typically 80 to 200.

[0152] Second polymer

[0153] The second polymer is one or more selected from polyester and polyurethane.

[0154] In this invention, the polyester can be a polymer obtained by polycondensation of a polyol and a polyacid, or a polymer obtained by ring-opening polymerization of a lactone, or a polymer obtained by polycondensation of a compound having both hydroxyl and carboxyl groups. The polyol is preferably an aliphatic polyol, more preferably an aliphatic polyol with 2 to 6 carbon atoms. The lactone is preferably an aliphatic lactone, preferably an aliphatic lactone with 6 to 10 carbon atoms. Compounds having both hydroxyl and carboxyl groups are also preferably aliphatic, such as lactic acid (lactide).

[0155] In one embodiment, the polyester is a linear polymer obtained by polycondensation of a diol and a diacid. The diol is preferably one or more selected from aliphatic diols, more preferably one or more selected from aliphatic diols having 2 to 6 carbon atoms, such as one or more selected from ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol. The diacid can be one or more selected from aliphatic or aromatic diacids, preferably including aromatic diacids, for example, diacids that simultaneously include aromatic and aliphatic diacids. Aromatic diacids include terephthalic acid, phthalic acid, etc. Aliphatic diacids include succinic acid, glutaric acid, adipic acid, etc.

[0156] In one embodiment, the polyester is a polymer obtained by ring-opening polymerization of a lactone, such as polycaprolactone.

[0157] In one embodiment, the polyester is a polymer obtained by polycondensation of a compound having both hydroxyl and carboxyl groups, such as polylactic acid (polylactide).

[0158] In a preferred embodiment, the polyester is one or more selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), and polybutylene terephthalate adipate (PBAT).

[0159] In one embodiment, the weight-average molecular weight of the polyester is 10,000 to 200,000, preferably 15,000 to 150,000.

[0160] In this invention, polyurethane refers to "polyurethane," a polymer obtained by polycondensation of polyols and polyisocyanates. The polyurethane can be a polyether-type polyurethane or a polyester-type polyurethane, preferably a polyester-type polyurethane.

[0161] Polyether polyurethane is a reaction product of polyether polyol and polyisocyanate, wherein the polyether polyol is preferably an aliphatic diol, such as polyethylene glycol, polypropylene glycol, polybutanediol, and their block or random copolymers.

[0162] Polyester-type polyurethane is a reaction product of polyester polyol and polyisocyanate, wherein the polyester polyol is preferably an aliphatic polyester polyol, such as an oligomer of aliphatic diol and aliphatic dicarboxylic acid, specific examples include polyethylene adipate diol (PEA), polyethylene adipate-propylene adipate diol, polyethylene adipate-diethylene adipate diol (PDA), polybutylene adipate diol, polyhexane adipate diol, polyethylene succinate diol, polypropylene succinate diol, polybutylene succinate diol, etc.

[0163] The aforementioned polyisocyanate is selected from one or more of aliphatic and aromatic polyisocyanates. Preferably, the aforementioned polyisocyanate is a diisocyanate, more preferably selected from one or more of aliphatic and aromatic diisocyanates. Particularly preferably, the diisocyanate is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, and dicyclohexylmethane diisocyanate.

[0164] In a preferred embodiment, the polyurethane is the reaction product of polybutylene succinate diol and diphenylmethane diisocyanate.

[0165] In one embodiment, the polyurethane has a weight-average molecular weight of 100,000 to 500,000, preferably 200,000 to 400,000.

[0166] Third polymer

[0167] The third polymer is one or more selected from polyamides.

[0168] Polyamides can be aliphatic polyamides, aromatic polyamides, and semi-aromatic polyamides.

[0169] Examples of polyamides include, but are not limited to, polyamide 6 (Nylon 6), polyamide 66 (Nylon 66), polyamide 46, polyamide 12, polyamide 69 and polyamide 6-10.

[0170] In one embodiment, the polyamide has a weight-average molecular weight of 5,000 to 20,000, preferably 8,000 to 16,000.

[0171] Fourth polymer

[0172] The fourth polymer is one or more selected from polyolefins.

[0173] In this invention, polyolefin has a broad meaning, referring to polymers obtained by polymerizing monomers having olefinic unsaturated groups. Monomers having olefinic unsaturated groups are selected from one or more of olefins and their derivatives, such as one or more of C2-8 olefins (ethylene, propylene, butene, pentene, etc.), styrene and its derivatives (styrene, 4-methylstyrene, 4-chlorostyrene, 4-vinylbenzyl chloride, etc.), and acrylonitrile.

[0174] Examples of polyolefins include, but are not limited to, polyethylene (PE), polypropylene (PP), acrylonitrile-styrene-butadiene copolymer (ABS), and polystyrene (PS).

[0175] In one embodiment, the polyolefin has a weight-average molecular weight of 8,000 to 150,000, preferably 10,000 to 140,000, and more preferably 11,000 to 130,000.

[0176] Example

[0177] The following specific embodiments further illustrate the present invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by this invention.

[0178] The raw materials used in the following examples are described below:

[0179] Catalyst: The binuclear Mn catalyst shown in formula (2) above;

[0180] Bisphenol A type polycarbonate (BPA-PC, hereinafter referred to as PC): Mw≈26,000, crystallinity 10%, brand name: Maclean.

[0181] Polyethylene terephthalate (PET): Mw≈20,000, crystallinity 38%. Brand: Maclean.

[0182] Polybutylene terephthalate (PBT): Mw≈100,000, crystallinity 30%, brand name: Maclean.

[0183] Polyurethane (PU): Polyester-type polyurethane is a polymer of diphenylmethane diisocyanate (MDI) and polyester-type polyol. The polyester-type polyol is an oligomer of butanediol and adipic acid, with Mw≈260,000. The structure is shown below:

[0184]

[0185] Where m = 3, n ≈ 270.

[0186] Polyamide 6 (Nylon 6): Mw≈12,000, brand name: Goodfellow.

[0187] Acrylonitrile-styrene-butadiene copolymer (ABS): Mw≈14,000, brand name Alfa Aesar.

[0188] Polypropylene (PP): Mw≈13,000, brand name: Sigma-Aldrich.

[0189] Low-density polyethylene (PE): Mw≈100,000, brand name: McLean.

[0190] Polystyrene (PS): Mw≈14,000, brand name Alfa Aesar.

[0191] In the above explanation, "Mw" represents the weight-average molecular weight.

[0192] The alcoholysis in the following examples was carried out as follows: a certain amount of catalyst and mixed plastic (or the separated solid) were added to ethylene glycol, heated to a specified reaction temperature under nitrogen atmosphere, and stirred at a speed of 400 rpm / min.

[0193] The conversion rate and yield in the following examples are calculated according to the following formula:

[0194] Plastic conversion rate % = (1 - amount of unreacted plastic / initial amount of plastic) * 100

[0195] The amount of unreacted plastic was determined based on the amount of solids after hot filtration.

[0196] Plastic recycling rate % = (Amount of unreacted plastic / Initial amount of plastic added) * 100

[0197] The amount of unreacted plastic was determined based on the amount of solids after hot filtration.

[0198] The amount of solid obtained after hot filtration was determined by the following method: the reaction system was filtered while hot after the reaction was completed, and the obtained solid was dried and weighed.

[0199] Monomer yield % = Amount of monomer in actual reaction solution / Amount of monomer after complete conversion of plastic

[0200] The amount of monomer in the actual reaction solution is determined by liquid chromatography or nuclear magnetic resonance spectroscopy, and the amount of monomer after complete conversion of the plastic is calculated based on the molar mass of the plastic.

[0201] The liquid chromatography instruments and testing conditions used are as follows:

[0202] The liquid chromatograph model is Agilent 1260 Infinity II.

[0203] C18 reversed-phase chromatographic column,

[0204] The detector is an ultraviolet detector.

[0205] The detection wavelength for BHET is 254nm, and the detection wavelength for BPA is 210nm.

[0206] The mobile phase for detecting BHET is 40 v% water + 60 v% methanol, and the mobile phase for detecting BPA is 40 v% water + 60 v% acetonitrile.

[0207] The flow rate of the mobile phase was 0.5 mL / min when detecting BHET and 1.0 mL / min when detecting BPA.

[0208] The nuclear magnetic resonance spectrometer used was a Bruker AVANCEⅢ400M.

[0209] The sample was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) for testing.

[0210] In the following examples, the molar amounts given for polymers are the total molar amounts of structural units (repeating units) in the polymer. For details, please refer to the specific descriptions of various polymers above.

[0211] Example 1

[0212] The plastic mixture processed in this embodiment is a mixture of PC and PET.

[0213] 1) PC component in alcoholysis plastic mixture

[0214] Alcohololysis conditions: 2 mmol PC powder, 2 mmol PET powder, 9 mL ethylene glycol, catalyst concentration of 0.11 g / L. Reaction temperature: 110℃, reaction time: 320 min. After the reaction, the reaction system was filtered to separate the filtrate and unreacted PET.

[0215] 2) PET component in alcoholysis plastic mixtures

[0216] Alcohololysis conditions: Unreacted PET was added to 9 mL of ethylene glycol, with a catalyst concentration of 0.11 g / L. The reaction temperature was 180 °C, and the reaction continued until the yield of the monomer product (BHET) no longer increased.

[0217] 3) Monomer product recovery and characterization

[0218] Separation of PC alcoholysis products: Extraction was performed by adding diethyl ether to the filtrate obtained in step 1). The BPA product entered the diethyl ether solution, and the diethyl ether solution was dried by rotary evaporation to obtain the BPA product.

[0219] Separation of PET alcoholysis products: The reaction solution after step 2) was cooled to room temperature and allowed to stand for 2 hours. Some BHET precipitated as white crystals. The BHET product was obtained by filtration and its purity was determined to be 99.0% by liquid chromatography.

[0220] Testing and Evaluation

[0221] During the alcoholysis reactions in steps 1) and 2), trace amounts of the reaction solution were taken at certain time intervals and the amounts of bisphenol A (BPA), a monomeric product of PC ethylene glycolation, and bis(2-hydroxyethyl) terephthalate (BHET), a monomeric product of PET ethylene glycolation, were detected by liquid chromatography, and the yields of BPA and BHET were calculated as described above.

[0222] The yield changes of BPA and BHET over time are as follows: Figure 1 As shown. By Figure 1 It can be seen that when PC is completely depolymerized to monomer BPA at 110℃, the conversion rate of PET is 0. After step 1), PET is completely recovered in solid form, and then PET is alcoholyzed at 180℃ to obtain monomer BHET.

[0223] The 1H NMR spectrum of the BPA product obtained in step 3) is as follows: Figure 2 As shown, the infrared spectrum is as follows Figure 3 As shown. By Figure 2 and Figure 3 It can be seen that the 1H NMR spectrum and infrared spectrum of the obtained BPA product are exactly the same as those of commercially available BPA.

[0224] Furthermore, both the 1H NMR and 1C NMR spectra of the BHET products indicate that the recovered BHET has high purity and no obvious signal of BHET dimer.

[0225] Example 2

[0226] The plastic mixture processed in this embodiment is a mixture of PC and PBT.

[0227] 1) PC component in alcoholysis plastic mixture

[0228] Alcohololysis conditions: 2 mmol PC powder, 2 mmol PET powder, 9 mL ethylene glycol, catalyst concentration of 0.11 g / L. Reaction temperature: 110 °C, reaction time: 320 min. After the reaction, the reaction system was filtered to separate the filtrate and unreacted PBT.

[0229] 2) PBT component in alcoholysis plastic mixtures

[0230] Alcohololysis conditions: Unreacted PBT was added to 9 mL of ethylene glycol, with a catalyst concentration of 0.11 g / L. The reaction temperature was 180 °C, and the reaction continued until the yield of the monomer product (BHET) no longer increased.

[0231] 3) Monomer product recovery and characterization

[0232] The separation method for PC alcoholysis products is the same as that described in Example 1, and high-purity BPA is obtained.

[0233] The method for separating the PBT alcoholysis products is the same as the method for separating the PET products in Example 1, and high-purity BHET is recovered.

[0234] Testing and Evaluation

[0235] During the alcoholysis reactions in steps 1) and 2), trace amounts of the reaction solution were taken at certain time intervals and the amounts of BPA (as a monomer product of PC ethylene glycolation) and bis(2-hydroxyethyl) terephthalate (BHET) (as a monomer product of PBT ethylene glycolation) were detected by liquid chromatography, and the yields of BPA and BHET were calculated as described above.

[0236] The yield changes of BPA and BHET over time are as follows: Figure 4 As shown. By Figure 4 It can be seen that when PC is completely depolymerized to monomer BPA at 110℃, the conversion rate of PBT is 0. After step 1), PBT is completely recovered in solid form, and then PBT is alcoholyzed at 180℃ to obtain monomer BHET.

[0237] Example 3

[0238] The plastic mixture processed in this embodiment is a mixture of PC and PU.

[0239] 1) PC component in alcoholysis plastic mixture

[0240] Alcohololysis conditions: 2 mmol PC powder, 2 mmol PU powder, 9 mL ethylene glycol, catalyst concentration 0.3 g / L. Reaction temperature 120℃, reaction time 60 min. After the reaction, the reaction system was filtered to separate the filtrate and unreacted PU.

[0241] 2) PU component in alcoholysis plastic mixture

[0242] Alcohololysis conditions: Unreacted PU was added to 9 mL of ethylene glycol, with a catalyst concentration of 0.3 g / L. The reaction temperature was 180 °C, and the reaction continued until the yield of the monomer product (BDO) no longer increased.

[0243] During the alcoholysis reactions in steps 1) and 2), a small amount of the reaction solution was taken at certain time intervals and the amount of BPA, which is the monomer product of PC ethylene glycolation, was detected by liquid chromatography. The amount of butanediol (BDO), which is the monomer product of polyester PU ethylene glycolation, was quantified by nuclear magnetic resonance hydrogen spectroscopy. The yields of BPA and BDO were calculated as described above.

[0244] The yield changes of BPA and BDO over time are as follows: Figure 5 As shown. By Figure 5 It can be seen that when PC is completely depolymerized to monomer at 120℃, the conversion rate of PU is 0. After step 1), PBT is completely recovered in solid form and then alcoholyzed at 180℃.

[0245] Example 4

[0246] The plastic mixture processed in this embodiment is a mixture of PC and Nylon6.

[0247] 1) PC component in alcoholysis plastic mixture

[0248] Alcohololysis conditions: 2 mmol PC powder, 2 mmol Nylon6 powder, 9 mL ethylene glycol, catalyst concentration of 0.3 g / L, reaction temperature of 120 °C, and reaction time of 1 h. After the reaction, the reaction system was filtered to separate the filtrate and unreacted Nylon6.

[0249] 2) Nylon6 component in alcoholysis plastic mixtures

[0250] Alcohololysis conditions: Unreacted Nylon 6 was added to 9 mL of ethylene glycol, with a catalyst concentration of 0.6 g / L. The reaction temperature was 210 °C, and the reaction was carried out until the solid in the system was completely eliminated, which took 2 h.

[0251] 3) Characterization of monomer products

[0252] The PC product separation method follows the same steps as described in Example 1, resulting in the separation of high-purity BPA.

[0253] The components of the Nylon 6 alcoholysis product are caprolactam (CPL) and 6-aminohexanoic acid-2-hydroxyethyl ester, the contents of which were determined by liquid chromatography.

[0254] The conversion rates of PC and Nylon 6 are shown in Table 1.

[0255] Table 1

[0256] PC Nylon 6 Conversion rate at 120℃ for 1 hour 100％ 0％ Conversion rate at 210℃ for 2 hours / 100％

[0257] As shown in Table 1, when PC is completely depolymerized to monomer at 120℃, the conversion rate of Nylon6 is 0. After step 1), Nylon6 is completely recovered in solid form and then alcoholyzed at a higher temperature.

[0258] Example 5

[0259] The plastic mixtures processed in this embodiment are mixtures of PC with ABS, PP, PE and PS respectively.

[0260] Alcohololysis conditions: 2 mmol PC powder, 2 mmol polyolefin (ABS, PP, PE, or PS) powder, 9 mL ethylene glycol, catalyst concentration of 0.3 g / L, reaction temperature of 120 °C, and reaction time of 1 h. After the reaction, the reaction system was filtered to separate the filtrate and unreacted solid (polyolefin).

[0261] The recovery rates of polyolefins are shown in Table 2.

[0262] Table 2

[0263] Types of plastics ABS PS PP PE Recovery rate (%) 100 99.5 99.8 99.7

[0264] As shown in Table 2, when PC is completely depolymerized at 120℃, the polyolefin can be recycled in solid form, maintaining the polymer morphology.

[0265] Example 6

[0266] The plastic mixture processed in this embodiment is a ternary mixture of PC, PET, and Nylon 6. A schematic diagram of the reaction process is shown below. Figure 6 As shown.

[0267] 1) PC component in alcoholysis plastic mixture

[0268] Alcohololysis conditions: 2 mmol each of PC, PET, and Nylon6 powder, 9 mL of ethylene glycol, and a catalyst concentration of 0.3 g / L. The reaction temperature was 120 °C, and the reaction time was 1 h. After the reaction was completed, the reaction system was filtered to separate the filtrate and unreacted solid (PET + Nylon6).

[0269] 2) PET component in alcoholysis plastic mixtures

[0270] Alcohololysis conditions: Unreacted solid was added to 9 mL of ethylene glycol, with a catalyst concentration of 0.3 g / L. The reaction temperature was 180 °C, and the reaction time was 1 h. After the reaction was completed, the reaction system was filtered to separate the filtrate and unreacted solid (Nylon 6).

[0271] The conversion and recovery rates of each plastic component are shown in Table 3.

[0272] Table 3

[0273] Types of plastics PC PET Nylon6 Conversion rate (%) 100 (Step 1) 100 (Step 2) 0 Polymer recovery rate (%) - - 100

[0274] As shown in Table 3, PC and PET in the ternary mixture can be converted into monomer products by alcoholysis at different temperatures, and polyamide can be completely recycled in solid form, maintaining the polymer morphology.

[0275] Example 7

[0276] The plastic mixture processed in this embodiment is a ternary mixture of PC, PBT, and ABS. A schematic diagram of the reaction process is shown below. Figure 7 As shown.

[0277] 1) PC component in alcoholysis plastic mixture

[0278] Alcohololysis conditions: 2 mmol each of PC, PET, and ABS powder, 9 mL of ethylene glycol, and a catalyst concentration of 0.3 g / L. The reaction temperature was 120 °C, and the reaction time was 1 h. After the reaction was completed, the reaction system was filtered to separate the filtrate and unreacted solid (PET + ABS).

[0279] 2) PBT component in alcoholysis plastic mixtures

[0280] Alcohololysis conditions: Unreacted solids were added to 9 mL of ethylene glycol, with a catalyst concentration of 0.3 g / L. The reaction temperature was 180 °C, and the reaction time was 3 h. After the reaction was completed, the reaction system was filtered to separate the filtrate and unreacted solids (PBT).

[0281] The conversion and recovery rates of each component are shown in Table 4.

[0282] Table 4

[0283] Types of plastics PC PBT ABS Conversion rate (%) 100 100 0 Polymer recovery rate (%) - - 100

[0284] As shown in Table 4, PC and PBT in the ternary mixture can be converted into monomer products by alcoholysis at different temperatures, and ABS can be completely recycled in polymer form.

[0285] As can be seen from the above embodiments, the method of the present invention can easily and selectively alcoholyze PC in a plastic mixture containing PC, thereby achieving selective chemical treatment and recycling of the PC component. Simultaneously, when the plastic mixture contains a second polymer and / or a third polymer, the second and / or third polymers can also be selectively alcoholyzed, thereby achieving selective chemical treatment and recycling of the second and / or third polymer components. Furthermore, since the fourth polymer does not undergo alcoholysis, it is also possible to separate the fourth polymer from the polycarbonate, the second polymer, and the third polymer.

[0286] Industrial availability

[0287] The alcoholysis method for plastic mixtures of the present invention can be widely used in industry for the treatment of plastic mixtures containing polycarbonate.

Claims

1. A method for the alcoholysis of a plastic mixture, characterized in that, The plastic mixture comprises polycarbonate and other polymers, wherein the other polymers are one or more selected from a second polymer, a third polymer, and a fourth polymer, wherein the second polymer is one or more selected from polyester and polyurethane, the third polymer is one or more selected from polyamide, and the fourth polymer is one or more selected from polyolefin; The alcoholysis method includes the following steps: (a) The plastic mixture is mixed with a catalyst and an alcoholysis agent, and the polycarbonate in the plastic mixture is subjected to an alcoholysis reaction at the polycarbonate alcoholysis temperature; (a') The reaction system obtained in step (a) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of polycarbonate and a solid containing the other polymers; The catalyst has the structure shown in the following general formula (I): Where M1 and M2 represent metal atoms, M1 is Mn, and M2 is selected from Mn, Fe, Co, Ni, or Cu, and the distance between the two atoms of M1 and M2 is [missing information]. M1 and M x They can be the same or different. Y is selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– , n is 2 or 3 m represents the quantity of Y, which can be 1, 2, or 3. R2 is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group, or a carboxyl group, or R2 is fused with R1 or R1' to form a ring structure, wherein the hydrocarbon group is a C1-C6 alkyl group, preferably a C1-C4 alkyl group. R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms. R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms. X is either O or S; The alcoholysis agent is one or more selected from monohydric alcohols and dihydric alcohols; The polycarbonate alcoholysis temperature is below 150°C; Preferably, in step (a), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent, the ratio of the number of moles of the alcoholysis agent to the total number of moles of the polycarbonate structural units in the plastic mixture is 100:1 to 8:1, and the alcoholysis reaction time is 0.5 h to 10 h.

2. The alcoholysis method according to claim 1, characterized in that, The other polymers include a second polymer, and optionally a third polymer and / or a fourth polymer, and the alcoholysis method further includes the following steps: (b) The solid obtained in step (a') is mixed with a catalyst and an alcoholysis agent, and the second polymer is subjected to an alcoholysis reaction at a second temperature; In cases where the other polymers comprise a third polymer and / or a fourth polymer, the alcoholysis method further includes the following steps: (b') The reaction system obtained in step (b) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the second polymer and a solid containing the third polymer and / or the fourth polymer; The second temperature is higher than the polycarbonate alcoholysis temperature, preferably a temperature higher than 150°C and lower than 195°C; Preferably, in step (b), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent, the ratio of the number of moles of the alcoholysis agent to the number of moles of the structural units of the second polymer in the solid obtained in step (a') is 100:1 to 8:1, and the alcoholysis reaction time is 0.5 h to 10 h.

3. The alcoholysis method according to claim 2, characterized in that, The other polymers include a third polymer and optionally a fourth polymer, and the alcoholysis method further includes the following steps: (c) The solid obtained in step (b') is mixed with a catalyst and an alcoholysis agent, and the third polymer is subjected to an alcoholysis reaction at a third temperature; In the case that the other polymers include a fourth polymer, the alcoholysis method further includes the following steps: (c') The reaction system obtained in step (c) is subjected to solid-liquid separation to obtain a liquid containing the alcoholysis product of the third polymer and a solid containing the fourth polymer. The third temperature is higher than the second temperature, preferably a temperature higher than 195°C; Preferably, in step (c), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent; the ratio of the number of moles of the alcoholysis agent to the number of moles of the structural units of the third polymer in the solid obtained in step (b') is 100:1 to 8:1; and the alcoholysis reaction time is 0.5 h to 10 h.

4. The alcoholysis method according to claim 1, characterized in that, The other polymers include a third polymer but not the second polymer, and optionally include a fourth polymer, and the alcoholysis method further includes the following steps: (c-1) The solid obtained in step (a') is mixed with a catalyst and an alcoholysis agent, and the third polymer is subjected to an alcoholysis reaction at a third temperature. In the case that the other polymers include a fourth polymer, the alcoholysis method further includes the following steps: (c'-1) The reaction system obtained in step (c-1) is subjected to solid-liquid separation to obtain a liquid containing the hydrolysis product of the third polymer alcohol and a solid containing the fourth polymer. The third temperature is higher than the polycarbonate alcoholysis temperature, preferably a temperature higher than 195°C; Preferably, in step (c-1), the amount of catalyst used is 0.05 g / L to 1.0 g / L based on the volume of the alcoholysis agent; the ratio of the number of moles of the alcoholysis agent to the number of moles of the structural units of the third polymer in the solid obtained in step (a') is 100:1 to 8:1; and the alcoholysis reaction time is 0.5 h to 10 h.

5. The alcoholysis method according to any one of claims 1 to 4, characterized in that, In general formula (1), M2 is Mn, and Y is selected from NO3. – Cl – ,Br – ClO4 – CH3O – HOCH2CH2O – n is 2, m is 2, R2 represents H, R3 is selected from H, C1-C6 alkyl, and R1 and R1' are propylidene or 1,2-phenylene; Preferably, the catalyst has the structure shown in the following general formula (II):

6. The alcoholysis method according to any one of claims 1 to 4, characterized in that, The monohydric alcohol is an aliphatic monohydric alcohol, preferably an aliphatic monohydric alcohol with 1 to 6 carbon atoms, more preferably methanol, ethanol, or propanol; the dihydric alcohol is an aliphatic dihydric alcohol, preferably an aliphatic dihydric alcohol with 2 to 6 carbon atoms, more preferably ethylene glycol, propylene glycol, or butanediol.

7. The alcoholysis method according to any one of claims 1 to 4, characterized in that, The polycarbonate is bisphenol A type polycarbonate.

8. The alcoholysis method according to any one of claims 1 to 4, characterized in that, The polyester is one or more selected from polymers obtained by polycondensation of polyols and polyacids, polymers obtained by ring-opening polymerization of lactones, and polymers obtained by polycondensation of compounds having both hydroxyl and carboxyl groups. Preferably, the polyol is an aliphatic polyol, more preferably an aliphatic polyol with 2 to 6 carbon atoms; the lactone is an aliphatic lactone, more preferably an aliphatic lactone with 6 to 10 carbon atoms; and the compound having both hydroxyl and carboxyl groups is lactic acid. More preferably, the polyester is one or more selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), and polybutylene terephthalate adipate (PBAT); The polyurethane is selected from one or more of polyester-type polyurethane and polyether-type polyurethane.

9. The alcoholysis method according to any one of claims 1 to 4, characterized in that, The polyamide is selected from one or more aliphatic polyamides and aromatic polyamides; Preferably, the polyamide is one or more selected from polyamide 6 (Nylon 6), polyamide 66 (Nylon 66), polyamide 46, polyamide 12, polyamide 69 and polyamide 6-10.

10. The alcoholysis method according to any one of claims 1 to 4, characterized in that, The polyolefin is selected from one or more of polyethylene (PE), polypropylene (PP), acrylonitrile-styrene-butadiene copolymer (ABS), and polystyrene (PS).

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