Alcoholysis method of plastic

Abstract

The present invention relates to a method for alcoholysis of a plastic, in which the plastic is subjected to an alcoholysis reaction using a specific binuclear metal complex catalyst in the presence of an alcoholysis agent to obtain a monomer, and the plastic is one or more selected from the group consisting of polyester, polycarbonate, polyamide and polyurethane. According to the alcoholysis method of the plastic, catalytic alcoholysis can be efficiently carried out, the purity of a monomer product is high, post-treatment is simple, and various plastics can be treated.

Description

TECHNICAL FIELD

[0001] The present application relates to a plastic alcoholysis method, belonging to the field of plastic recycling. BACKGROUND

[0002] Plastic products have become an indispensable part of human life and are widely used in food packaging, industrial production, electronics and electrical appliances, medical treatment, construction and other fields. Among the many types of plastics, polyesters, polyurethanes, polyamides, polycarbonates, polyethers and epoxy resins are common plastics containing C-N and / or C-O bonds, with an annual output of 110 million tons and still growing rapidly. However, less than 10% of the used plastics are recycled, and most of them exist in nature for a long time, polluting water, air and soil environment, and bringing great health risks to human society. How to handle the huge amount of waste plastics has become a global problem that has attracted attention from all walks of life.

[0003] Chemical recycling, as an emerging plastic recycling management method, can depolymerize waste plastics into monomers to realize the closed-loop recycling of plastics. This recycling method not only solves the problem of waste plastic pollution, but also reduces the consumption of fossil energy and carbon emissions required for the production of plastic monomers. At present, hydrolysis, alcoholysis and ammonolysis and other dissolution routes have been developed for polyesters, polycarbonates, polyurethane plastics containing C-N and / or C-O bonds to obtain their monomers and monomer derivatives. However, these methods currently often require harsh conditions such as high temperature (>190℃), high pressure (1.4-2.0 MPa), concentrated acid or strong base (1-5 M), which brings problems such as severe equipment corrosion and high cost, limiting the popularization and application of chemical recycling technology. Therefore, it is urgent to develop efficient catalysts to reduce the energy consumption and cost of catalytic plastic depolymerization process.

[0004] At present, there are many studies on alcoholysis catalysts for polyesters and polycarbonates, and various catalysts such as small molecule organic bases, deep eutectic solvents, ionic liquids, simple metal salts and metal oxides have been developed. For example, patent document 1 and patent document 2 disclose a method for alcoholysis of polyethylene terephthalate (PET) and its modified materials using K2CO3, Na2CO3, KOH, NaOH, zinc acetate, hydrotalcite, etc. as catalysts.

[0005] CITATIONS

[0006] Patent document 1: CN118251376A

[0007] Patent document 2: CN118234703A SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The alcoholysis method of plastics disclosed in the prior art also has problems such as low catalyst activity, difficulty in recovery, low monomer yield, and monomers being easily contaminated by metals. These can all lead to a decrease in the economics of chemical recycling. Furthermore, there is a lack of development of catalysts for alcoholysis of a wider range of plastic types.

[0010] In view of the above problems in the prior art, the technical problem to be solved by the present application is to provide an alcoholysis method of plastics, which can efficiently perform catalytic alcoholysis, has high purity of monomer products, and can handle a variety of plastics.

[0011] Solution for solving the problem

[0012] In view of the above problems, the present inventors have conducted long-term and in-depth research and found that alcoholysis of plastics such as polyesters, polycarbonates, polyamides, and polyurethanes using a specific dinuclear metal complex catalyst can solve the above technical problems.

[0013] Specifically, the present application solves the problems of the present application by the following solution.

[0014] [1] An alcoholysis method of plastics, wherein, in the presence of an alcoholysis agent, a dinuclear metal complex catalyst is used, and the plastics undergo an alcoholysis reaction, thereby obtaining a monomer,

[0015] the plastics are one or more selected from the group consisting of polyesters, polycarbonates, polyamides, and polyurethanes,

[0016] the dinuclear metal complex has a structure represented by the following general formula (1):

[0017]

[0018] In the general formula (1), M1 and M2 represent metal atoms, each independently selected from V, Cr, Mn, Fe, Co, Ni, or Cu, and the distance between the two atoms M1 and M2 is

[0019] Y is selected from NO3 - , Cl - , Br - , OAc - , ClO4 - , OH - , CH3O - , HOCH2CH2O - , or SO4 2- ,

[0020] n is 2 or 3,

[0021] m represents the number of Y and is 1, 2, or 3,

[0022] each X is independently selected from N, O, S or P,

[0023] R1and R1' are each independently selected from an alkylene group having 2 to 4 carbon atoms or an arylene group having 6 to 20 carbon atoms,

[0024] each R2is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group or a carboxyl group, or R2is fused with R1or R1'to form a ring,

[0025] each R3is independently selected from H, a halogen, a hydroxyl group, a nitro group, a carboxyl group and an alkyl group, an alkoxy group and an alkoxyalkyl group having 1 to 6 carbon atoms.

[0026] [2] The alcoholysis method of plastic according to [1], wherein the alcoholysis agent is one or more selected from monohydric alcohol and dihydric alcohol; preferably, the alcoholysis agent is dihydric alcohol, more preferably, the dihydric alcohol is one or more selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,2,2-tetramethyl-1,3-cyclobutanediol, 2-methyl-2,4-pentanediol and p-xylylene glycol.

[0027] [3] The alcoholysis method of plastic according to [1] or [2], wherein in the general formula (1), M1and M2are each independently selected from Mn, Fe, Co, Ni or Cu,

[0028] Y is selected from NO3 - , Cl - , Br - , ClO4 - , CH3O - or HOCH2CH2O - ,

[0029] n is 2,

[0030] m is 2,

[0031] each X is independently selected from O or S, preferably, each X is O,

[0032] R1and R1' are each independently selected from propylene or 1,2-phenylene, preferably, R1and R1' are each 1,3-propylene,

[0033] each R2is independently selected from H, C1-C6 alkyl, preferably, each R2is H,

[0034] each R3is independently selected from H, C1-C6 alkyl, preferably, each R3is independently selected from C1-C4 alkyl, more preferably, each R3is methyl.

[0035] [4] The alcoholysis method of plastic according to any one of [1] to [3], wherein the dinuclear metal complex has one or more of the structures represented by the following formulae (2-1) to (2-6):

[0036]

[0037] [5] The alcoholysis method of plastic according to any one of [1] to [4], wherein the ratio of the molar amount of the alcoholysis agent to the total molar amount of the structural units in the plastic is 100: 1 to 8: 1.

[0038] [6] The alcoholysis method of plastic according to any one of [1] to [5], wherein the amount of the catalyst is 0.1 g / L to 8.0 g / L, based on the volume of the alcoholysis agent.

[0039] [7] The alcoholysis method of plastic according to any one of [1] to [6], wherein the amount of the catalyst is 0.0006 to 0.13 times the mass of the plastic.

[0040] [8] The alcoholysis method of plastic according to any one of [1] to [7], wherein the temperature of the alcoholysis reaction is 50°C to 280°C, preferably 60°C to 240°C, more preferably 70°C to 210°C; the time of the alcoholysis reaction is 0.5 hours to 12 hours, preferably 0.8 hours to 10 hours, more preferably 1 hour to 8 hours; and stirring is performed during the alcoholysis reaction, the rate of the stirring being 300 r / min to 600 r / min.

[0041] [9] The alcoholysis method of plastic according to any one of [1] to [8], wherein,

[0042] the polyester is one or more selected from the group consisting of a polymer obtained by polycondensation of a polyhydric alcohol and a polybasic acid, a polymer obtained by ring-opening polymerization of a lactone, and a polymer obtained by polycondensation of a compound having both a hydroxyl group and a carboxyl group;

[0043] Preferably, the polyhydric alcohol is an aliphatic polyhydric alcohol, more preferably an aliphatic polyhydric alcohol having 2 to 6 carbon atoms; the lactone is an aliphatic lactone, more preferably an aliphatic lactone having 6 to 10 carbon atoms; and the compound having both a hydroxyl group and a carboxyl group is lactic acid.

[0044] the polycarbonate is a bisphenol A type polycarbonate;

[0045] the polyamide is one or more selected from the group consisting of an aliphatic polyamide and an aromatic polyamide;

[0046] the polyurethane is one or more selected from the group consisting of a polyester type polyurethane and a polyether type polyurethane.

[0047]

[10] The alcoholysis method of plastic according to any one of [1] to [9], wherein the plastic is one or more selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate-adipate, polybutylene adipate, polybutylene succinate, polyethylene adipate, polyethylene succinate, polycaprolactone, polylactic acid, polyamide 6, polyamide 66, polyamide 46, polyamide 12, polyamide 69, polyamide 6-10, and polyurethane formed by polymerization of polybutylene adipate diol and methylene diphenyl diisocyanate (MDI); preferably, the plastic is one or more selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyamide 6, polyamide 66, and polyurethane formed by polymerization of polybutylene adipate diol and methylene diphenyl diisocyanate (MDI).

[0048] Effects of the Invention

[0049] The alcoholysis method of plastic of the present application can efficiently perform catalytic alcoholysis, the purity of monomer product is high, post-treatment is simple, and various plastics can be treated. Therefore, the alcoholysis method of the present application significantly reduces the time cost of plastic decomposition, the post-treatment cost of product, etc., and has a wide range of applications, the alcoholysis product can be recycled, and is expected to bring huge development space and profit space for actual plastic chemical recycling. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 A graph showing the change in yield of BHET of Example 1 over time.

[0051] Figure 2 A liquid chromatogram of the BHET product obtained in Example 1 and a liquid chromatogram of commercially sourced BHET.

[0052] Figure 3 A nuclear magnetic carbon spectrum of the BHET product obtained in Example 1 and a nuclear magnetic carbon spectrum of commercially sourced BHET.

[0053] Figure 4 A nuclear magnetic hydrogen spectrum of the BHET product obtained in Example 1 and a nuclear magnetic hydrogen spectrum of commercially sourced BHET. DETAILED DESCRIPTION

[0054] Hereinafter, the content of the present application will be described in detail. The description of the technical features described below is based on representative embodiments, specific examples of the present application, but the present application is not limited to these embodiments, specific examples.

[0055] <TERMS AND DEFINITIONS>

[0056] In this instruction manual, "room temperature" refers to a temperature range of 20 to 30°C, such as 25°C.

[0057] 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.

[0058] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0059] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The purpose of this invention is to provide a method for the alcoholysis of plastics, wherein, in the presence of an alcoholysis agent, a binuclear metal complex catalyst is used to induce an alcoholysis reaction in the plastic, thereby yielding monomers.

[0064] The plastic is selected from one or more of polyester, polycarbonate, polyamide and polyurethane.

[0065] The alcoholysis method of the present invention uses a specific catalyst to efficiently alcoholyze plastics at the alcoholysis temperature, thereby enabling the plastics to be alcoholyzed into monomers. This achieves the objectives of efficient catalytic alcoholysis of plastics, high purity of monomer products, and a wide variety of plastics that can be alcoholyzed.

[0066] The various aspects of the alcoholysis method of the present invention are described in detail below.

[0067] Catalyst

[0068] The catalyst used in the alcoholysis reaction of the present invention is a binuclear metal complex having the structure shown in the following general formula (1):

[0069]

[0070] In general formula (1), M1and M2represent metal atoms, each independently selected from V, Cr, Mn, Fe, Co, Ni or Cu, and the distance between the two atoms of M1and M2is M1and M2may be the same or different, preferably, M1and M2are each independently selected from Mn, Fe, Co, Ni or Cu, and the distance between the two atoms of M1and M2is

[0071] Y is an anion, which can be selected from NO3 - , CI - , Br - , OAc - , CI04 - , OH - , CH30 - , HOCH2CH20 - or SO4 2- , preferably, Y is selected from NO3 - , CI - , Br - , CI04 - , CH30 - or HOCH2CH20 - . Y – may be axially coordinated at the center of the metal atom.

[0072] n is 2 or 3, preferably 2.

[0073] m represents the number of Y, and is 1, 2 or 3, preferably 2.

[0074] Each X is independently selected from N (nitrogen atom), O (oxygen atom), S (sulfur atom) or P (phosphorus atom), preferably, each X is independently selected from O or S, more preferably, each X is O.

[0075] R1and R1’ are each independently selected from an alkylene group having 2 to 4 carbon atoms or an arylene group having 6 to 20 carbon atoms, preferably, R1and R1’ are each independently selected from a propylene group or a 1,2-phenylene group, more preferably, R1and R1’ are each a 1,3-propylene group.

[0076] Each R2is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group or a carboxyl group, or R2is fused with R1or R1’ to form a ring, preferably, each R2is independently selected from H, a C1-C6 alkyl group, more preferably, each R2is H,

[0077] Each R3is independently selected from the group consisting of H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy and alkoxyalkyl groups having 1 to 6 carbon atoms, preferably each R3is independently selected from the group consisting of H, C1to C6alkyl, more preferably each R3is independently selected from the group consisting of C1to C4alkyl, still more preferably each R3is methyl.

[0078] In a preferred embodiment, the catalyst has one or more of the following formulae (2-1) to (2-6):

[0079]

[0080] <Alcoholysis agent>

[0081] The alcoholysis agent used in the present application is one or more selected from monohydric alcohols and dihydric alcohols.

[0082] Preferably, the monohydric alcohol is one or more of aliphatic monohydric alcohols, more preferably one or more of aliphatic monohydric alcohols having 2 to 6 carbon atoms, still more preferably one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol and t-butanol.

[0083] Preferably, the alcoholysis agent is one or more of dihydric alcohols, and the dihydric alcohol includes aliphatic dihydric alcohols, alicyclic dihydric alcohols, aromatic dihydric alcohols and the like, more preferably the dihydric alcohol is one or more selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,2,2-tetramethyl-1,3-cyclobutanediol, 2-methyl-2,4-pentanediol and p-xylylene glycol, still more preferably the dihydric alcohol is an aliphatic dihydric alcohol, in particular one or more selected from ethylene glycol, propylene glycol and butanediol.

[0084] <Alcoholysis temperature>

[0085] The alcoholysis method of the present application is applicable to plastics such as polyesters, polycarbonates, polyamides and polyurethanes, and the alcoholysis method can be performed in a wide alcoholysis temperature range of 50°C to 280°C, and the alcoholysis temperature can be adjusted depending on the kind of the plastic to be alcoholysed.

[0086] From the viewpoint of reaction efficiency, the alcoholysis temperature of the present application is usually preferably 50°C or higher, more preferably 60°C or higher, for example 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher.

[0087] Further, from the viewpoint of facilitating the operation, volatility of the alcoholysis agent, reduction of equipment requirements, and prevention of high-temperature carbonization of the plastic and alcoholysis product, the alcoholysis temperature of the present application is preferably 280°C or lower, more preferably 260°C or lower, still more preferably 240°C or lower, and further preferably 210°C or lower. Specifically, for example, 270°C or lower, 250°C or lower, 230°C or lower, 220°C or lower, or 200°C or lower.

[0088] In one embodiment, the alcoholysis temperature is 50°C to 280°C, preferably 60°C to 240°C, and more preferably 70°C to 210°C.

[0089] <Alcoholysis reaction>

[0090] In the alcoholysis method of the present application, the alcoholysis reaction can be performed by mixing the alcoholysis agent, the catalyst, and the plastic together, and heating the mixture to the alcoholysis temperature described above in a nitrogen atmosphere while stirring the mixture.

[0091] In the present application, the time for the alcoholysis reaction is not particularly limited, and can be selected depending on the amount of the material, the alcoholysis temperature, and the like. Generally, the time for the alcoholysis reaction can be 0.5 hours to 12 hours, preferably 0.8 hours to 10 hours, and more preferably 1 hour to 8 hours. Specifically, the time for the alcoholysis reaction can be, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours, and the like.

[0092] In one embodiment, the stirring rate of the mixture during the alcoholysis reaction is 300 r / min to 600 r / min, preferably 350 r / min to 500 r / min, and for example, 400 r / min.

[0093] In one embodiment, the ratio of the molar amount of the alcoholysis agent to the total molar amount of the structural units in the plastic is 100: 1 to 8: 1, preferably 90: 1 to 9: 1, and still more preferably 85: 1 to 10: 1.

[0094] In the above, the "total molar number of structural units" described for the plastic means the total of the molar numbers of all the structural units in the plastic (i.e., the polymer), and in the case of a polymer mixture and a copolymer, the total of the molar numbers of the structural units of the respective polymers in the mixture. Herein, the structural unit of a polymer has the generally accepted meaning in the art, and is used synonymously with the repeating unit.

[0095] Generally, the number of moles of the structural unit is substantially the same as the number of moles of the ester group in the case of a polyester; the number of moles of the structural unit is substantially the same as the number of moles of the carbonate group in the case of a polycarbonate; the number of moles of the structural unit is substantially the same as the number of moles of the amide group in the case of a polyamide; and the number of moles of the structural unit is substantially the same as the number of moles of the urethane group in the case of a polyurethane.

[0096] In one embodiment, the catalyst is used in an amount of 0.10 g / L to 8.0 g / L, preferably 0.2 g / L to 7.3 g / L, and more preferably 0.3 g / L to 7.2 g / L, based on the volume (25°C) of the alcoholysis agent.

[0097] In one embodiment, the catalyst is used in an amount of 0.0006 to 0.13 times, preferably 0.006 to 0.12 times, and more preferably 0.007 to 0.116 times, the mass of the plastic.

[0098] In one embodiment, the mass ratio of the alcoholysis agent to the plastic is 35:1 to 2:1, preferably 30:1 to 2:1, and more preferably 28:1 to 3:1.

[0099] <Separation of alcoholysis product>

[0100] In the alcoholysis method of the present application, the alcoholysis product is optionally separated from the reaction system after the alcoholysis reaction is completed. The method for separating the alcoholysis product is not particularly limited and can be any suitable separation method known in the art. In the case where the monomer produced by the alcoholysis is dissolved in the alcoholysis reaction system, for example, extraction or the like can be used. In the case where the monomer produced by the alcoholysis is precipitated from the alcoholysis reaction system and the polymer raw material has no solid residue, for example, decantation, filtration, centrifugal separation or the like can be used.

[0101] The separated monomer can be optionally washed several times (e.g., 3 times, 5 times) with a solvent, dried or the like to improve the purity of the monomer. The solvent used for the washing can be an alcohol such as methanol, ethanol or the like; an ether such as dimethyl ether, diethyl ether or the like.

[0102] <Plastic>

[0103] In the present application, the plastic is one or more selected from the group consisting of a polyester, a polycarbonate, a polyamide and a polyurethane.

[0104] Polyesters

[0105] In the present application, the polyester includes saturated polyesters and unsaturated polyesters. The polyester can be a polymer obtained by polycondensation of a polyhydric alcohol and a polybasic acid, or a polymer obtained by ring-opening polymerization of a lactone, or a polymer obtained by polycondensation of a compound having both a hydroxyl group and a carboxyl group. The polyhydric alcohol is preferably an aliphatic polyhydric alcohol, more preferably an aliphatic polyhydric alcohol having 2 to 6 carbon atoms. The lactone is preferably an aliphatic lactone, preferably an aliphatic lactone having 6 to 10 carbon atoms. The compound having both a hydroxyl group and a carboxyl group is preferably lactic acid (lactide) or the like.

[0106] In one embodiment, the polyester is a linear polymer obtained by polycondensation of a dihydric alcohol and a dibasic acid. The dihydric alcohol is preferably one or more selected from aliphatic dihydric alcohols, more preferably one or more selected from aliphatic dihydric alcohols having 2 to 6 carbon atoms, for example one or more selected from ethylene glycol, propylene glycol, butylene glycol, pentanediol and hexanediol. The dibasic acid can be one or more selected from aliphatic dibasic acids or aromatic dibasic acids, preferably the dibasic acid includes an aromatic dibasic acid, for example the dibasic acid includes both an aromatic dibasic acid and an aliphatic dibasic acid. The aromatic dibasic acid is, for example, terephthalic acid, phthalic acid or the like. The aliphatic dibasic acid is, for example, succinic acid, glutaric acid, adipic acid or the like.

[0107] In one embodiment, the polyester is a polymer obtained by ring-opening polymerization of a lactone, for example polycaprolactone.

[0108] In one embodiment, the polyester is a polymer obtained by polycondensation of a compound having both a hydroxyl group and a carboxyl group, for example polylactic acid (polylactide).

[0109] In a preferred embodiment, the polyester is one or more selected from polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate-adipate, polybutylene adipate, polybutylene succinate, polyethylene adipate, polyethylene succinate, polycaprolactone and polylactic acid; more preferably, the polyester is one or more selected from polyethylene terephthalate, polybutylene terephthalate, polylactic acid and polybutylene terephthalate-adipate.

[0110] In one embodiment, the weight average molecular weight of the polyester is 10,000 to 200,000, preferably 15,000 to 150,000.

[0111] Polycarbonates

[0112] In the present application, the polycarbonate can be an aliphatic polycarbonate, an aromatic polycarbonate, an aliphatic-aromatic polycarbonate.

[0113] In one embodiment, the polycarbonate is an aromatic polycarbonate, more preferably a bisphenol A type polycarbonate. Bisphenol A type polycarbonates can be synthesized by the reaction of bisphenol A and carbonyl chloride (COCl2), and the most commonly used synthesis method is melt transesterification, i.e. synthesis by ester exchange and polycondensation reaction of bisphenol A and diphenyl carbonate.

[0114] In one embodiment, the polycarbonate has a weight average molecular weight of 10,000 to 50,000, preferably 20,000 to 40,000.

[0115] Bisphenol A type polycarbonate has the following structure (end groups not shown):

[0116]

[0117] wherein n represents the number of structural units within the brackets, and is usually 80 to 200.

[0118] Polyamides

[0119] The polyamide can be an aliphatic polyamide, an aromatic polyamide and a semi-aromatic polyamide.

[0120] Examples of the polyamide include, but are not limited to, polyamide 6 (Nylon 6), polyamide 66 (Nylon 66), polyamide 46, polyamide 12, polyamide 69 and polyamide 6-10.

[0121] In one embodiment, the polyamide has a weight average molecular weight of 5,000 to 20,000, preferably 8,000 to 16,000.

[0122] Polyurethanes

[0123] The polyurethane refers to "polyurethane", and is a polymer obtained by polycondensation of a polyol and a polyisocyanate. The polyurethane can be a polyether type polyurethane or a polyester type polyurethane, and is preferably a polyester type polyurethane.

[0124] The polyether type polyurethane is a reaction product of a polyether polyol and a polyisocyanate, wherein the polyether polyol is preferably an aliphatic diol, such as polyethylene glycol, polypropylene glycol, polybutylene glycol, and block or random copolymers thereof.

[0125] The polyester polyurethane is a reaction product of a polyester polyol and a polyisocyanate, wherein the polyester polyol is preferably an aliphatic polyester polyol, such as an oligomer of an aliphatic diol and an aliphatic dicarboxylic acid, specific examples including polyethylene adipate diol (PEA), polyethylene-propylene adipate diol, polydiethylene adipate diol (PDA), polybutylene adipate diol, polyhexylene adipate diol, polyethylene succinate diol, polypropylene succinate diol, polybutylene succinate diol, and the like.

[0126] The polyisocyanate is one or more selected from the group consisting of aliphatic polyisocyanates and aromatic polyisocyanates. Preferably, the polyisocyanate is a diisocyanate, more preferably one or more selected from the group consisting of aliphatic diisocyanates and aromatic diisocyanates. Particularly preferably, the diisocyanate is one or more selected from the group consisting of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, dicyclohexylmethane diisocyanate.

[0127] In a preferred embodiment, the polyurethane is a reaction product of polybutylene adipate diol and diphenylmethane diisocyanate.

[0128] In one embodiment, the polyurethane has a weight average molecular weight of 100,000 to 500,000, preferably 200,000 to 400,000.

[0129] In one embodiment, the plastic is one or more selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate-adipate, polybutylene adipate, polybutylene succinate, polyethylene adipate, polyethylene succinate, polycaprolactone, polylactic acid, polyamide 6, polyamide 66, polyamide 46, polyamide 12, polyamide 69, polyamide 6-10, and polyurethane formed by polymerization of polybutylene adipate diol and diphenylmethane diisocyanate (MDI); preferably, the plastic is one or more selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyamide 6, polyamide 66, and polyurethane formed by polymerization of polybutylene adipate diol and diphenylmethane diisocyanate (MDI).

[0130] The alcoholysis method of the present application achieves efficient catalytic alcoholysis, is less likely to leave metals from the catalyst, has simple post-treatment, and has high purity of the monomer product, and is applicable to a wide variety of plastics, thereby significantly reducing the time cost of plastic decomposition, the post-treatment cost of the product, and the like, and the alcoholysis product can be recycled, thereby saving resources.

[0131] Examples

[0132] The present application is further described in the following examples. It should be understood that these examples are included merely to illustrate the present application and should not be considered limiting of the scope of the application. Furthermore, since numerous modifications and changes can be made in the examples by those having ordinary skill in the art, it is to be understood that this application includes all such modifications and changes and further scope thereof.

[0133] The raw materials used in the following examples are described as follows:

[0134] Polyethylene terephthalate (PET): Mw~20,000, crystallinity 38%, brand Macrolin.

[0135] Polybutylene terephthalate (PBT): Mw~100,000, crystallinity 30%, brand Macrolin.

[0136] Bisphenol A polycarbonate (BPA-PC, hereinafter PC): Mw~26,000, crystallinity 10%, brand Macrolin. The structure is shown as follows:

[0137]

[0138] wherein n~102.

[0139] Polyurethane (PU): polyester-based polyurethane (brand BASF), which is a polymer of diphenylmethane diisocyanate (MDI) and polyester-based polyol, which is an oligomer of butanediol and adipic acid. The Mw of this polyurethane is ~260,000, and the structure is shown as follows:

[0140]

[0141] wherein m=3, n~270.

[0142] Polyamide 6 (Nylon 6): Mw~12,000, brand Goodfellow.

[0143] Polyamide 66 (Nylon 66): Mw~30,000, brand DuPont.

[0144] "Mw" in the above description means weight average molecular weight.

[0145] The alcoholysis of the following examples was carried out as follows: a certain amount of catalyst and plastic were added to ethylene glycol, and the mixture was heated to the specified reaction temperature under nitrogen atmosphere while stirring the mixture at 400 rpm / min.

[0146] Test methods and evaluation criteria

[0147] The test methods and evaluation criteria involved in the following examples and comparative examples are described in detail below.

[0148] 1) Conversion, conversion rate, and yield

[0149] The conversion, conversion rate, and yield in the following examples are calculated according to the following test methods and calculation formula:

[0150] 1.1) Conversion of plastic

[0151] Conversion of plastic (%) = (1 - unreacted plastic amount / initial amount of plastic) x 100

[0152] In the above, the unreacted plastic amount is determined according to the solid amount after hot filtration.

[0153] The solid amount after hot filtration is measured by the following method: after the reaction is completed, the reaction system is filtered while hot, and the obtained solid is dried and weighed.

[0154] 1.2) Conversion rate of plastic

[0155] Unless otherwise specified, the conversion rate of plastic (mmol / h) in the following refers to the conversion rate in the first hour after the reaction starts.

[0156] Conversion rate of plastic (mmol / h) = molar amount of monomer product in the actual reaction solution after one hour of reaction.

[0157] In the above, the amount of monomer in the actual reaction solution is determined by liquid chromatography or nuclear magnetic hydrogen spectrum.

[0158] 1.2.1) Liquid chromatography

[0159] The amount of monomer in the actual reaction solution is determined by liquid chromatography.

[0160] The liquid chromatography instrument and test conditions used are as follows:

[0161] The liquid chromatography instrument used is Agilent 1260 Infinity II,

[0162] The chromatographic column is a C18 reverse phase chromatographic column,

[0163] The detector is an ultraviolet detector,

[0164] The detection wavelength is 254 nm,

[0165] The mobile phase is 40% water + 60% methanol,

[0166] The flow rate is 0.5 mL / min.

[0167] 1.2.2) Nuclear magnetic hydrogen spectroscopy

[0168] The amount of monomer in the actual reaction solution was determined using nuclear magnetic hydrogen spectrum.

[0169] The nuclear magnetic resonance spectrometer used was a Bruker AVANCE III 400M.

[0170] The sample was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) for testing.

[0171] 1.3) Monomer yield

[0172] Monomer yield % = amount of monomer in the actual reaction solution / theoretical amount of monomer after complete conversion of the plastic

[0173] The amount of monomer in the actual reaction solution was determined using liquid chromatography (the instrument and test conditions used were the same as those described above in 1.2.1) or nuclear magnetic hydrogen spectrum (the instrument and solvent used were the same as those described above in 1.2.2), and the theoretical amount of monomer after complete conversion of the plastic was calculated according to the molar mass of the plastic.

[0174] Specifically, during the alcoholysis reaction, a small amount of reaction solution was taken at certain time intervals (for example, in Example 1, samples were taken at intervals of 15 minutes, 15 minutes, 35 minutes, 35 minutes and 20 minutes, respectively) to detect the amount of monomer product of polymer alcoholysis by liquid chromatography, and the monomer yield was calculated according to the above formula.

[0175] 2) Measurement and characterization of purity

[0176] The purity of the monomer product in the examples and comparative examples was measured or characterized by one or more of liquid chromatography (the instrument and test conditions used were the same as those described above in 1.2.1), nuclear magnetic carbon spectrum (the instrument and solvent used were the same as those described above in 1.2.2), nuclear magnetic hydrogen spectrum (the instrument and solvent used were the same as those described above in 1.2.2), and the following inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0177] Inductively coupled plasma atomic emission spectroscopy (ICP-OES)

[0178] Whether there is residual Mn element in the monomer product was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0179] The plasma emission spectrometer used was a Thermo IRIS Intrepid II. The monomer product was detected after acid digestion.

[0180] The molar mass given for the polymer in the following examples is the total molar mass of the structural units (repeat units) in the polymer, which can be specifically referred to the specific description of each type of polymer above.

[0181] Example 1

[0182] The plastic processed in this embodiment is PET; the catalyst used is [Mn2L]Cl2 represented by the following formula (2-1):

[0183]

[0184] 1) Preparation of the catalyst [Mn2L]Cl2 represented by the above formula (2-1):

[0185] The synthesis of the catalyst [Mn₂L]Cl₂ was performed according to the method described in J. Chem. Soc., Dalton Trans., 1988, 1225-1235. A methanol solution (1 mL) of 1,3-diaminopropane (0.133 g, 1.8 mmol) was added to a methanol solution (9 mL) containing MnCl₂·4H₂O (0.178 g, 0.9 mmol) and Mn(OAc)₂·4H₂O (0.221 g, 0.9 mmol). Then, 4-methyl-2,6-xylenol (0.294 g, 1.8 mmol) was added with stirring. After reflux for 15 minutes, a deep yellow solid precipitated from the solution. The precipitate was filtered and collected, washed with hot methanol, and dried at 100 °C for 1 hour to give [Mn₂L]Cl₂ in 80% yield.

[0186] 2) Catalytic alcoholysis of PET:

[0187] Alcohololysis conditions: [Mn₂L]Cl₂ catalyst and 0.192 g of 100-mesh PET powder were added to 4.5 mL of ethylene glycol. The concentration of [Mn₂L]Cl₂ catalyst was 0.3 g / L. The reaction temperature was 180 °C, and the reaction time was 2 h. After the reaction was completed, the reaction system was cooled to room temperature. Bis(2-hydroxyethyl) terephthalate (BHET), the monomer product of PET alcoholysis, precipitated as white crystals. The crystals were filtered, washed three times with ethanol, and dried to obtain the BHET product. The alcoholysis process and the measurement results of the monomer product in this example are shown in Table 1 below. Figures 1 to 4 As shown in the image.

[0188] (1) Yield of BHET

[0189] The yield of BHET in this embodiment changes over time as follows: Figure 1 As shown. From Figure 1 It can be seen that the yield of BHET reaches 93% after 2 hours of reaction.

[0190] (2) Purity of BHET product

[0191] (2.1) Liquid Chromatography Analysis

[0192] The BHET product obtained in this embodiment (Figure 2 Figure 2 shows the chromatogram of the liquid chromatography of the BHET product of Example 1 (rBHET) and the BHET from commercial source (cBHET). Figure 2 Figure 3 shows the chromatogram of the liquid chromatography of the BHET product of Example 2 (rBHET) and the BHET from commercial source (cBHET). Figure 2 Figure 4 shows the chromatogram of the liquid chromatography of the BHET product of Example 3 (rBHET) and the BHET from commercial source (cBHET). Figure 2 As can be seen from Figure 4, the chromatogram of the liquid chromatography of the BHET product of Example 3 (rBHET) is identical to that of the BHET from commercial source (cBHET). Figure 2 The chromatogram of the liquid chromatography of the BHET product of Example 3 (rBHET) indicates that the recovered BHET product is of high purity, with no obvious signal of BHET dimer.

[0193] (2.2) Nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum analysis

[0194] The BHET product of Example 1 was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) to determine its nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum, which are shown in Figure 1 and Figure 2, respectively. Figure 3 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 4 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 3 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 4 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 2 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 3 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 3 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 4 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 3 As can be seen from Figure 1 and Figure 2, the nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 1 (rBHET) are identical to those of the BHET from commercial source (cBHET). Figure 4 The nuclear magnetic carbon spectrum and nuclear magnetic hydrogen spectrum of the BHET product of Example 3 (rBHET) both indicate that the recovered BHET product is of high purity, with no obvious signal of BHET dimer.

[0195] (2.3) Inductively coupled plasma atomic emission spectroscopy (ICP-OES) analysis

[0196] The results of the inductively coupled plasma atomic emission spectroscopy (ICP-OES) test show that no residual Mn element is found in the BHET product of Example 1 (Mn content is lower than 0.1 μg / mg, lower than its detection limit).

[0197] Comparative Example 1

[0198] The alcoholysis of PET was carried out in the same manner as Example 1 except that no catalyst was added.

[0199] Example 1 and Comparative Example 1 were measured in the same method and conditions, and the results are shown in Table 1 below.

[0200] Table 1

[0201]

[0202] As shown in Table 1, when [Mn2L]Cl2was used as the alcoholysis catalyst (Example 1), the conversion rate of PET and the conversion rate of PET at 2h and the yield of BHET at 2h were significantly higher than the conversion rate and the conversion rate of PET at 2h and the yield of BHET at 2h in the case of no catalyst (Comparative Example 1). In addition, the purity of the BHET product obtained after the above-mentioned ethanol washing and drying was as high as 99.0%.

[0203] In this example, for the alcoholysis reaction of PET, there is a reaction equilibrium between the BHET monomer and the dimer of BHET, and thus it is difficult to achieve a 100% BHET yield.

[0204] Example 2

[0205] The plastic treated in this example was PBT; the catalyst used was the same as in Example 1.

[0206] Alcoholysis conditions: 0.220 g of 100-mesh PBT powder was added to 6.0 mL of 1,4-butanediol, and the catalyst [Mn2L]Cl2was added to a concentration of 0.3 g / L, and the reaction temperature was 180°C, and the reaction time was 8h. After the reaction was completed, the reaction system was cooled to room temperature, and bis(2-hydroxybutyl) terephthalate (BHDT) as the monomer product of PBT alcoholysis was precipitated as white crystals, was filtered and washed with ethanol 3 times and dried to obtain the BHDT product.

[0207] Comparative Example 2

[0208] The alcoholysis of PBT was carried out in the same manner as in Example 2, except that no catalyst was added.

[0209] Example 2 and Comparative Example 2 were measured in the same manner and under the same conditions, and the results are shown in Table 2 below.

[0210] Table 2

[0211]

[0212] As shown in Table 2, when [Mn2L]Cl2was used as the alcoholysis catalyst (Example 2), the conversion rate of PBT and the conversion rate of PBT at 8h and the yield of BHDT at 8h were significantly higher than the conversion rate and the conversion rate of PBT at 8h and the yield of BHDT at 8h in the case of no catalyst (Comparative Example 2). In addition, the purity of the BHDT product obtained after the above-mentioned ethanol washing and drying was as high as 98.5% and no residual Mn element was found.

[0213] Similarly to Example 1, in the alcoholysis reaction of PBT, there is a reaction equilibrium between the BHDT monomer and the dimer of BHDT, and thus it is also difficult to achieve a 100% BHDT yield.

[0214] Example 3

[0215] The plastic treated in this example is PC; the catalyst used is [CuMnL](N03)2 represented by the following formula (2-2):

[0216]

[0217] 1) Preparation of the catalyst [CuMnL](N03)2 represented by the above formula (2-2):

[0218] The synthesis of the catalyst [CuMnL](N03)2 was performed according to the method given in the reference J. Am. Chem. Soc, 1981, 103, 4073-4081.

[0219] 2) Catalytic alcoholysis of PC:

[0220] Alcoholysis conditions: The catalyst [CuMnL](N03)2 and 0.25 g of PC powder of 100 mesh were introduced into 4.5 mL of ethylene glycol, the concentration of the catalyst [CuMnL](N03)2 was 6.45 g / L, the reaction temperature was 120°C, and the reaction time was 1 h.

[0221] Comparative Example 3-1

[0222] The alcoholysis of PC was performed in the same manner as in Example 3, except that the catalyst [CuMnL](N03)2 in Example 3 was replaced with the catalyst Mn(OAc)2.

[0223] Comparative Example 3-2

[0224] The alcoholysis of PC was performed in the same manner as in Example 3, except that the catalyst [CuMnL](N03)2 in Example 3 was replaced with the catalyst Zn(OAc)2.

[0225] Comparative Example 3-3

[0226] The alcoholysis of PC was performed in the same manner as in Example 3, except that no catalyst was added.

[0227] Example 3 and Comparative Examples 3-1 to 3-3 were measured in the same manner and under the same conditions, and the results are shown in Table 3 below.

[0228] Table 3

[0229]

[0230] As can be seen from Table 3, the conversion rate of PC and the conversion rate of PC at 1 h using [CuMnL](N03)2as the catalyst (Example 3) are significantly higher than the conversion rate of PC and the conversion rate of PC at 1 h using simple metal salts as the catalyst (Comparative Examples 3-1 and 3-2), and are much higher than the conversion rate of PC and the conversion rate of PC at 1 h without catalyst (Comparative Example 3-3).

[0231] Example 4

[0232] The plastics treated in this example are PU, PET, PBT, Nylon 6 and Nylon 66; the catalyst used is the same as in Example 3.

[0233] Example 4-1

[0234] Catalytic alcoholysis of PU

[0235] Alcoholysis conditions: 100 mesh PU powder with a total mole amount of structural units of 5 mmol was put into 4.5 mL of ethylene glycol with the catalyst [CuMnL](N03)2, the concentration of the catalyst [CuMnL](N03)2was 7.2 g / L, the reaction temperature of PU was 180°C, and the reaction time was 1 h.

[0236] Example 4-2

[0237] The alcoholysis of PET was carried out in the same way as in Example 4-1, except that 100 mesh PET powder with a total mole amount of structural units of 5 mmol was used instead of PU powder, and the reaction temperature of PET was 190°C.

[0238] Example 4-3

[0239] The alcoholysis of PBT was carried out in the same way as in Example 4-1, except that 100 mesh PBT powder with a total mole amount of structural units of 5 mmol was used instead of PU powder, and the reaction temperature of PBT was 190°C.

[0240] Example 4-4

[0241] The alcoholysis of Nylon 6 was carried out in the same way as in Example 4-1, except that 100 mesh Nylon 6 powder with a total mole amount of structural units of 5 mmol was used instead of PU powder, and the reaction temperature of Nylon 6 was 197°C.

[0242] Example 4-5

[0243] The alcoholysis of Nylon 66 was carried out in the same way as in Example 4-1, except that 100 mesh Nylon 66 powder with a total mole amount of structural units of 5 mmol was used instead of PU powder, and the reaction temperature of Nylon 66 was 190°C.

[0244] Comparative Examples 4-1 to 4-5

[0245] Comparative Examples 4-1 to 4-5 were subjected to alcoholysis in the same manner as Examples 4-1 to 4-5, respectively, except that no catalyst was added.

[0246] Examples 4-1 to 4-5 and Comparative Examples 4-1 to 4-5 were measured in the same manner and under the same conditions, and the results are shown in Table 4 below.

[0247] Table 4

[0248]

[0249] As can be seen from Table 4, when [CuMnL](NO3)2catalyzed the alcoholysis of polyesters, polyurethanes, and polyamides (Examples 4-1 to 4-5), the conversion rate of each polymer and the conversion rate at 1 h were much higher than those of the alcoholysis without catalyst (Comparative Examples 4-1 to 4-5).

[0250] Example 5

[0251] The plastic treated in this example was PC.

[0252] The catalysts [Fe2L]Cl2, [Co2L]Cl2, [Ni2L]Cl2, and [Cu2L]Cl2used in the following Examples 5-1 to 5-4 are represented by the following formulas (2-3), (2-4), (2-5), and (2-6), respectively:

[0253]

[0254] Preparation of catalysts [Fe2L]Cl2, [Co2L]Cl2, [Ni2L]Cl2, and [Cu2L]Cl2:

[0255] The synthesis of catalysts [Fe2L]Cl2, [Ni2L]Cl2, and [Cu2L]Cl2followed the method given in the reference J. Am. Chem. Soc., 2023, 145, 8, 4819-4827.

[0256] The catalyst [Co2L]Cl2was synthesized by following the method given in the reference J. Am. Chem. Soc., 2023, 145, 8, 4819-4827, except that Co(NO3)2·6H2O mentioned in the method was replaced with an equimolar amount of CoCl2·6H2O.

[0257] Example 5-1

[0258] Catalytic alcoholysis of PC:

[0259] Alcoholysis conditions: The catalyst [Fe2L]Cl2and 0.25 g of 100 mesh PC powder were put into 4.5 mL of ethylene glycol, the catalyst [Fe2L]Cl2concentration was 0.7 g / L, the reaction temperature was 120℃, and the reaction time was 4 h.

[0260] Example 5-2

[0261] The alcoholysis of PC was carried out in the same manner as in Example 5-1, except that the catalyst [Co2L]Cl2was used instead of the catalyst [Fe2L]Cl2.

[0262] Example 5-3

[0263] The alcoholysis of PC was carried out in the same manner as in Example 5-1, except that the catalyst [Ni2L]Cl2was used instead of the catalyst [Fe2L]Cl2.

[0264] Example 5-4

[0265] The alcoholysis of PC was carried out in the same manner as in Example 5-1, except that the catalyst [Cu2L]Cl2was used instead of the catalyst [Fe2L]Cl2.

[0266] Examples 5-1 to 5-4 were measured in the same manner and under the same conditions, and the results are shown in Table 5 below.

[0267] Table 5

[0268]

[0269] As can be seen from Table 5, each of the catalysts represented by formulae (2-3), (2-4), (2-5), and (2-6) can efficiently catalyze the alcoholysis reaction of PC.

[0270] As can be seen from the above examples, the alcoholysis method of the present application can efficiently catalyze the alcoholysis of plastics, the purity of the monomer product is high, the post-treatment is simple, and a wide variety of plastics can be treated.

[0271] Industrial applicability

[0272] The alcoholysis method of plastics of the present application can be widely used in the recycling treatment of plastics in industry, and further the monomers as alcoholysis products can be used in the production of plastics to realize recycling.

Claims

1. A method for the alcoholysis of plastics, characterized in that, In the presence of an alcoholysis agent and using a binuclear metal complex catalyst, the plastic undergoes an alcoholysis reaction to yield monomers. The plastic is selected from one or more of polyester, polycarbonate, polyamide, and polyurethane. The binuclear metal complex has the structure shown in the following general formula (1): In the general formula (1), M1 and M2 represent metal atoms, each independently selected from V, Cr, Mn, Fe, Co, Ni, or Cu, and the interatomic distance between M1 and M2 is [missing information]. 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. Each X is independently selected from N, O, S, or P. R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms. Each R2 group 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. Each R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms.

2. The method for alcoholysis of plastics according to claim 1, characterized in that, The alcoholysis agent is selected from one or more monohydric alcohols and dihydric alcohols; preferably, the alcoholysis agent is a dihydric alcohol, more preferably, the dihydric alcohol is selected from one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, 1,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, 1,4-cyclohexanediethanol, 2,2,2,2-tetramethyl-1,3-cyclobutanediol, 2-methyl-2,4-pentanediol, and p-xylenediol.

3. The method for alcoholysis of plastics according to claim 1 or 2, characterized in that, In the general formula (1), M1 and M2 are each independently selected from Mn, Fe, Co, Ni, or Cu. Y is selected from NO3 - Cl - ,Br - ClO4 - CH3O - or HOCH2CH2O - , n is 2, m is 2, Each X is independently selected from O or S; preferably, each X is O. R1 and R1' are independently selected from propylidene or 1,2-phenylene, preferably, both R1 and R1' are 1,3-propylidene. Each R2 is independently selected from H and C1-C6 alkyl groups; preferably, each R2 is H. Each R3 is independently selected from H, C1 to C6 alkyl groups, preferably, each R3 is independently selected from C1 to C4 alkyl groups, more preferably, each R3 is methyl.

4. The method for alcoholysis of plastics according to any one of claims 1 to 3, characterized in that, The binuclear metal complex has one or more of the structures shown in formulas (2-1) to (2-6):

5. The method for alcoholysis of plastics according to any one of claims 1 to 4, characterized in that, The molar ratio of the alcoholysis agent to the total molar ratio of the structural units in the plastic is 100:1 to 8:

1.

6. The method for alcoholysis of plastics according to any one of claims 1 to 5, characterized in that, Based on the volume of the alcoholysis agent, the amount of catalyst used is 0.1 g / L to 8.0 g / L.

7. The method for alcoholysis of plastics according to any one of claims 1 to 6, characterized in that, The amount of catalyst used is 0.0006 to 0.13 times the mass of the plastic.

8. The method for alcoholysis of plastics according to any one of claims 1 to 7, characterized in that, The temperature of the alcoholysis reaction is 50℃~280℃, preferably 60℃~240℃, more preferably 70℃~210℃; the time of the alcoholysis reaction is 0.5 hours to 12 hours, preferably 0.8 hours to 10 hours, more preferably 1 hour to 8 hours; the alcoholysis reaction is carried out by stirring at a rate of 300 r / min~600 r / min.

9. The method for alcoholysis of plastics according to any one of claims 1 to 8, characterized in that, The polyester is selected from one or more of the following: 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. The polycarbonate is bisphenol A type polycarbonate; The polyamide is selected from one or more aliphatic polyamides and aromatic polyamides; The polyurethane is selected from one or more types of polyester polyurethane and polyether polyurethane.

10. The method for alcoholysis of plastics according to any one of claims 1 to 9, characterized in that, The plastic is selected from one or more of polyethylene terephthalate, polybutylene terephthalate, polybutylene adipate, polybutylene adipate, polybutylene succinate, polyethylene adipate, polybutylene succinate, polycaprolactone, polylactic acid, polyamide 6, polyamide 66, polyamide 46, polyamide 12, polyamide 69, polyamide 6-10, and polyurethane formed by polymerizing polybutylene adipate diol with diphenylmethane diisocyanate (MDI); preferably, the plastic is selected from one or more of polyethylene terephthalate, polybutylene terephthalate, polyamide 6, polyamide 66, and polyurethane formed by polymerizing polybutylene adipate diol with diphenylmethane diisocyanate (MDI).

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