Method for synthesizing regenerated polymer from waste polyester, polycarbonate and / or polyether and regenerated polymer

Abstract

The invention provides a method for synthesizing a regenerated polymer by using waste polyester, polycarbonate and / or polyether and the regenerated polymer, the method comprises two steps: the first step is to prepare a precursor through a chain exchange reaction, and the second step is to prepare the regenerated polymer through a ring formation reaction. Obviously, the method does not need to separate the waste polyester, polycarbonate and / or polyether, but directly synthesizes the regenerated polymer with excellent performance through chain exchange and cyclization reaction, does not introduce an organic solvent, meets the national environmental protection requirements, and provides basic conditions for subsequent large-scale recycling of the polymers.

Description

Technical Field

[0001] The invention belongs to the technical field of waste polymer recycling, and specifically relates to a method for synthesizing a recycled polymer by utilizing waste polyester, polycarbonate and / or polyether, and also relates to the recycled polymer synthesized by the method. Background Art

[0002] With the growing global environmental protection requirements and the increasing shortage of oil resources, China, as one of the world's largest plastic producers and consumers, has been actively promoting the development of green, low-carbon economy and circular economy in recent years. As a result, the demand for the recycling of polymers, especially the recycling of waste plastics, has become more and more urgent and has become a domestic requirement. In particular, how to recycle polyester, polycarbonate and polyether, the three most widely used polymers, has become a top priority in research.

[0003] Polyester is a class of thermoplastic polymer compounds formed by polycondensation of dibasic acid and diol, among which polyethylene terephthalate (PET) is the representative. Currently, PET is one of the most widely used polymer materials in the world, and is widely used in textile, packaging and bottling and other fields. Polycarbonate is a general term for polymer compounds containing carbonate structure in the molecular chain and various materials made based on it, with bisphenol A polycarbonate being the most important. Its three major application fields are glass assembly industry, automobile industry and electronics and electrical industry. It is also widely used in industrial machinery parts, office equipment, medical and health care, film, leisure and protective equipment, etc. Polyether is a linear polymer synthesized by ring-opening homopolymerization or copolymerization of epoxy compounds under the action of catalysts. This material has excellent mechanical properties, thermal stability and chemical corrosion resistance, and is widely used in construction, automobile, electronics and electrical appliances, and biomedicine and other fields.

[0004] So far, the main methods for recycling and reusing waste plastics are physical recycling and chemical conversion. Among them, the physical recycling method involves treating waste polymers through physical means such as crushing, washing, sorting, and weighing, and then processing them into usable materials. However, it has defects such as degradation of recycled product performance, low recycling efficiency, and high recycling cost; the chemical recycling method is a recycling method that uses chemical conversion (including alcoholysis, phenololysis, hydrolysis, acidolysis, aminolysis, etc.) to convert waste polymers into monomers or oligomers for reuse. Specifically, the current chemical recovery of waste polyester and polycarbonate mainly relies on small molecule alcohols, acids or amines to exchange with ester bonds or carbonate bonds to depolymerize them into monomer raw materials for reuse to achieve recovery. For example, CN117586486A discloses a continuous manufacturing process for recycled PET using waste polyester bottles as raw materials, and adopts a continuous manufacturing method of continuous alcoholysis and polycondensation, in which a large amount of ethylene glycol is used for depolymerization; CN116535316A discloses a method for recovering bisphenol A and carbonate by catalytic alcoholysis of polycarbonate, which uses alcohol degradation agents to depolymerize polycarbonate. After the reaction is completed, bisphenol A and carbonate can be obtained at the same time after separation. However, since small molecules such as water, alcohol, and amine can react with polyester or polycarbonate at the same time, and not only monomers will be formed during the depolymerization process, but also oligomers with different polymerization degrees will be produced, which inevitably leads to difficulties in product separation and purification, significantly reducing the utilization efficiency of waste polymers. In addition, there is still a lack of effective chemical recovery methods for the chemical recovery of waste polyethers at this stage.

[0005] However, polyester, polycarbonate, and polyether usually exist in the form of a mixture because they have similar physical and chemical properties. Traditional recycling methods often have difficulty in achieving complete separation of these three types of polymers, resulting in mutual interference during the recycling process. In addition, traditional recycling methods are usually only suitable for recycling a single type of plastic and are not suitable for processing mixtures of waste polymers. Therefore, in order to solve this problem, it is urgent to develop an efficient and low-cost method for preparing recycled polymers, which can directly utilize specific reactions to achieve efficient recycling of waste polyester, polycarbonate, and polyether mixtures and achieve the synthesis of high-performance recycled polymers without separating the polyester, polycarbonate, and polyether mixtures. Summary of the invention

[0006] In order to solve the above problems, the inventors of the present invention have developed a method for synthesizing recycled polymers using waste polyester, polycarbonate and / or polyether after a large number of experiments. The method can directly synthesize high-performance recycled polymers from waste polyester, polycarbonate and polyether through cyclization reaction without separation, and the method has relatively low cost and high recovery efficiency. The whole process is simple and easy to operate and the post-processing is simple, which provides the basic conditions for the subsequent large-scale recycling of these waste polymers.

[0007] In a first aspect of the present invention, there is provided a method for synthesizing a recycled polymer using waste polyester, polycarbonate and / or polyether, comprising the steps of:

[0008] S1. Preparing a precursor: melting the waste polymer mixture and then performing a chain exchange reaction under the action of a catalyst to obtain a precursor;

[0009] S2. Preparation of regenerated polymer: subjecting the precursor prepared in step S1 to a cyclization reaction and removing cyclic small molecules to obtain a regenerated polymer,

[0010] The waste polymer mixture comprises a mixture of two or more of polyester, polycarbonate and / or polyether.

[0011] In the present invention, the chain exchange reaction of obtaining the first precursor from waste polyester, polycarbonate and polyether under the action of a catalyst in step S1 is based on the exchange of ester bonds, carbonate bonds and ether bonds at any position in the polyester, polycarbonate and polyether molecular chains, and the general reaction formula is as follows:

[0012]

[0013] It can be seen from the above reaction formulas (I)-(III) that the chain exchange reaction in step S1 does not change the number of molecules. In addition, these waste polyesters, polycarbonates, and polyether mixtures usually contain moisture absorbed from the air. The presence of these small molecules of water leads to the occurrence of hydrolysis reactions in the system, thereby reducing the overall molecular weight of these waste polymer systems. Therefore, the precursor obtained in step S1 is a low molecular weight oligomer.

[0014] In step S2, the precursor obtained in step S1 is continuously catalyzed by a catalyst through a cyclization reaction of the following general formula (IV)-(VII) under high temperature, reduced pressure conditions to generate cyclic small molecules and then produce new polymers and cyclic small molecules. At the same time, accompanied by the removal of small molecule water, i.e., the reverse reaction of step S1 and the removal of cyclic small molecules, the generated polymer molecular chain continues to grow, and finally a high-performance regenerated polymer is obtained.

[0015]

[0016] It should be noted that in the above reaction formulas (I)-(V), X, Y, Z, and L only represent repeating units in the raw material waste polymer mixture and the polyester, polycarbonate and / or polyether in the product precursor in step S1, and are not specific, nor do they have a one-to-one correspondence. The above reaction formulas (I)-(V) are only for illustrative purposes to better understand the entire recycling process of the present invention.

[0017] Obviously, the method of the present invention can directly recycle the waste polymer mixture containing polyester, polycarbonate and polyether with similar physical and chemical properties into high-performance recycled polymer without separation.

[0018] Preferably, in the above method, the waste polymer mixture comprises a first composition, which comprises a polyester having a first repeating unit derived from a dibasic acid, dibasic ester and / or dibasic acid anhydride represented by the following formula (U1) and / or (U2) and a polycarbonate and / or polyether having a second repeating unit derived from a diol and / or diol ester represented by the following formula (U3) and / or (U4),

[0019]

[0020] Among them, R1, R2, R3, R4, R5, R 16 , R 19 , R 20 may be the same or different and are independently selected from hydrogen, alkyl, 15 , R 17 , R 18 , R 21 may be the same or different and are each independently selected from hydrogen and / or acyl.

[0021] In the method of the present invention, the polyester having a first repeating unit derived from a dibasic acid, dibasic ester and / or dibasic anhydride as shown in the following formula (U1) and / or (U2) and the polycarbonate and / or polyether having a second repeating unit derived from a diol and / or diol ester as shown in the following formula (U3) and / or (U4) can be commercially available polymers commonly found in the art, such as polypropylene oxalate, polybutylene oxalate, polypropylene malonate, polybutylene malonate, polypropylene methyl malonate, polypropylene glycol oxalate, polypropylene glycol oxalate, polybutylene glycol oxalate, polypropylene ... , poly(butylene methyl malonate), etc.; the polycarbonate may be one or more of bisphenol A polycarbonate, polypropylene carbonate, polyethylene carbonate, etc.; the polyether may be one or more of polyoxymethylene, polyethylene glycol, poly(1,2-propylene glycol), etc., and the five / six-membered ring diesters produced by these polyesters, polycarbonates and / or polyethers in the method of the present invention are not only easy to be removed from the recycled polymer to increase the molecular weight of the recycled polymer, but the removed ring diesters can also be used as by-products for chemical raw materials.

[0022] More preferably, the alkyl group is an unsubstituted or substituted straight chain, branched chain or cyclic alkyl group consisting of 1 to 18 carbon atoms.

[0023] More preferably, the unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 18 carbon atoms is an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms, more preferably an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms, in particular an unsubstituted or halogen (such as fluorine, chlorine, bromine, etc.) mono- or poly-substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms, such as methyl, trifluoromethyl, ethyl, propyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.

[0024] More preferably, the acyl group is the remaining part after removing the hydroxyl group from the oxygen-containing acid, and its structural formula is the following formula (XI):

[0025]

[0026] Wherein R is an alkyl group having no more than 4 carbon atoms, further an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms, more preferably an unsubstituted or halogen (such as fluorine, chlorine, bromine, etc.) mono- or poly-substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopropane, cyclobutane, etc.

[0027] In the present invention, the first composition comprising a polyester having a structure derived from repeating units of a dibasic acid, dibasic ester and / or dibasic acid anhydride represented by the following formula (U1) and / or (U2) and a polycarbonate and / or polyether having a structure derived from repeating units of a diol and / or diol ester represented by the following formula (U3) and / or (U4) can be specifically: (1a) a polyester having a structure derived from repeating units of a dibasic acid, dibasic ester and / or dibasic acid anhydride represented by the following formula (U1) and / or (U2) and a polycarbonate and / or polyether having a structure derived from repeating units of a diol and / or diol ester represented by the following formula (U3) and / or (U4) (1b) a polyester having a structure derived from repeating units of a dibasic acid, dibasic ester and / or dibasic acid anhydride as shown in the following formula (U1) and / or (U1) and a polyether having a structure derived from repeating units of a diol and / or diol ester as shown in the following formula (U3) and / or (U4); or, (1c) a mixture of a polycarbonate and a polyether having a structure derived from repeating units of a dibasic acid, dibasic ester and / or dibasic acid anhydride as shown in the following formula (U1) and / or (U1) and a diol and / or diol ester as shown in the following formula (U3) and / or (U4).

[0028] When the waste polymer mixture contains the first composition, the general reaction formula of the cyclization reaction of the precursor prepared in step S1 in step S2 is as shown in the above reaction formulas (IV)-(V), and the cyclic small molecules produced by the cyclization reaction are cyclic diesters, and their corresponding structures are shown in the following formulas (C1)-(C3).

[0029]

[0030] Furthermore, when the first composition contains a polyester having repeating units of a dibasic acid, a dibasic ester and / or a dibasic acid anhydride as shown in formula (U1) and a polycarbonate and / or a polyether having repeating units of a diol and / or a diol ester as shown in formula (U3), the cyclic small molecule produced by the cyclization reaction is a cyclic diester and has a structure as shown in formula (C1). When the first composition contains a polyester having repeating units of a dibasic acid, a dibasic ester and / or a dibasic acid anhydride as shown in formula (U1) and a diol as shown in formula (U4), the cyclic small molecule produced by the cyclization reaction is a cyclic diester and has a structure as shown in formula (C1). When the first composition contains a polyester with repeating units of a dibasic acid, dibasic ester and / or dibasic anhydride as shown in formula (U2) and a polycarbonate and / or polyether with repeating units of a dibasic alcohol and / or diol ester as shown in formula (U3), the cyclic small molecule produced by the ring-forming reaction is a cyclic diester and has a structure as shown in formula (C3). However, it should also be noted that when the first composition contains polyesters with repeating units of dibasic acids, dibasic esters and / or dibasic acid anhydrides as shown in formula (U2) and polycarbonates and / or polyethers with repeating units of diols and / or diol esters as shown in the above formula (U4), the cyclic small molecules produced by the annulation reaction are seven-membered ring cyclic diesters, which are inferior to five- / six-membered ring cyclic diesters in terms of stability and use, and the relatively unstable seven-membered ring is not conducive to formation and removal at high temperatures, and is not conducive to the formation of recycled polymers.

[0031] Preferably, in the above method, the waste polymer mixture comprises a second composition comprising a polycarbonate having a carbonate group and a polyester and / or a polyether having a third repeating unit derived from a diol and / or a diol ester represented by the following formula (U5) and / or (U6):

[0032]

[0033] Among them, R7, R8, R 11 , R 12 , R 13 may be the same or different and are independently selected from hydrogen, alkyl, R6, R9, R 10 , R 14 may be the same or different and are each independently selected from hydrogen and / or acyl.

[0034] In the method of the present invention, the polycarbonate contained in the second composition and the polyester and / or polyether whose structure is derived from the third repeating unit of the diol and / or diol ester shown in the following formula (U5) and / or (U6) are commercially available polymers commonly found in the art, such as the polyester can be one or more of polyethylene terephthalate, polyethylene succinate, polypropylene terephthalate, etc., and the polyether can be one or more of polyethylene glycol, poly(1,2-propylene glycol), poly(1,3-propylene glycol), etc. The five / six-membered cyclic esters produced by these polyesters, polycarbonates and / or polyethers in the method of the present invention are not only easy to be removed from the recycled polymer to increase the molecular weight of the recycled polymer, but the removed cyclic esters can also be used as by-products for chemical raw materials.

[0035] More preferably, the alkyl group is an unsubstituted or substituted straight chain, branched chain or cyclic alkyl group consisting of 1 to 18 carbon atoms.

[0036] More preferably, the unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 18 carbon atoms is an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms, more preferably an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms, in particular an unsubstituted or halogen (such as fluorine, chlorine, bromine, etc.) mono- or poly-substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms, such as methyl, trifluoromethyl, ethyl, propyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.

[0037] More preferably, the acyl group is the remaining part after removing the hydroxyl group from the oxygen-containing acid, and its structural formula is the following formula (XI):

[0038]

[0039] Wherein R is an alkyl group having no more than 4 carbon atoms, further an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms, more preferably an unsubstituted or halogen (such as fluorine, chlorine, bromine, etc.) mono- or poly-substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopropane, cyclobutane, etc.

[0040] In the present invention, the second composition comprising a polycarbonate having a carbonate group and a polyester and / or a polyether whose structure is derived from repeating units of a diol and / or a diol ester as shown in the following formula (U5) and / or (U6) can specifically be: (2a) a polycarbonate having a carbonate group and a polyester whose structure is derived from repeating units of a diol and / or a diol ester as shown in the following formula (U5) and / or (U6); (2b) a polycarbonate having a carbonate group and a polyether whose structure is derived from repeating units of a diol and / or a diol ester as shown in the following formula (U5) and / or (U6); or (2c) a mixture of a polycarbonate having a carbonate group and a polyester and a polyether whose structure is derived from repeating units of a diol and / or a diol ester as shown in the following formula (U5) and / or (U6).

[0041] When the waste polymer mixture contains the second composition, the general reaction formula of the cyclization reaction of the precursor prepared in step S1 in step S2 is as shown in the above reaction formulas (VI)-(VII), and the cyclic small molecule produced by the cyclization reaction is a cyclic carbonate, and its corresponding structure is shown in the following formulas (10)-(11).

[0042]

[0043] Obviously, when the second composition contains a polycarbonate having a carbonate group and a polyester and / or a polyether having repeating units of a diol and / or a diol ester as shown in the above formula (U5), the cyclic small molecules produced by the cyclization reaction are cyclic carbonates and have a structure as shown in the above formula (C4); when the second composition contains a polycarbonate having a carbonate group and a polyester and / or a polyether having repeating units of a diol and / or a diol ester as shown in the above formula (U6), the cyclic small molecules produced by the cyclization reaction are cyclic carbonates and have a structure as shown in the above formula (C5).

[0044] In the waste polymer mixture containing the first composition, the cyclization reaction is based on the reaction of ester bonds at specific positions in the polyester molecular chain with carbonate bonds or ether bonds at specific positions in the polycarbonate and / or polyether molecular chains to produce removable five-membered or six-membered ring diester small molecules, but in the waste polymer mixture containing the second composition, the cyclization reaction is based on the reaction of carbonate bonds at specific positions in the polycarbonate with ester bonds or ether bonds at specific positions in the polyester and / or polyether molecular chains to produce removable five-membered or six-membered ring carbonate small molecules. These obtained stable five-membered or six-membered cyclic small molecules are not only easy to be removed from the recycled polymer to increase the molecular weight of the recycled polymer, but can also be used as high-value chemical raw materials after simple purification.

[0045] It can be seen from the above reaction formula (IV)-formula (VII) that step S2 needs to achieve continuous removal of cyclic small molecules by reducing pressure and increasing temperature, so that the reaction proceeds more thoroughly to the right. Therefore, in step S2, the pressure of the system reacting gradually decreases from standard atmospheric pressure (101.325 kPa) to 1000 Pa-1 Pa, thereby obtaining a high molecular weight regenerated polymer, that is, the absolute pressure condition for the cyclization reaction in step S2 is 1 Pa-1000 Pa, and other reaction conditions are: temperature of 200-300 ° C, and reaction time of 0.5-24 hours.

[0046] Further optimized, in the above method, the conditions of the cyclization reaction in step S2 are: temperature of 250-280°C, pressure of 10-100Pa, and reaction time of 3-6 hours. At this temperature, the equilibrium constant of the cyclization reaction is large, it is easier to remove cyclic small molecules, and the molecular weight of the obtained regenerated polymer is relatively high.

[0047] In the step S2, as the cyclic small molecules are continuously removed, new polyester, polycarbonate or polyether units are continuously formed during the reaction process and their proportion is continuously increasing, thereby changing the original chemical structure of the polyester, polycarbonate and polyether, and the mechanical properties and thermal properties of the regenerated polymer change accordingly as the reaction proceeds. In addition, in the present invention, since the ring tension of the five-membered and six-membered ring molecules is relatively small, it is easier to complete the ring-closing reaction in the ring-forming reaction of step S2. Specifically, the smaller ring tension makes these cyclic molecules more stable during the reaction process, so that they can be effectively removed from the reaction system in the S2 reaction stage, and this removal process is conducive to promoting the formation of the regenerated polymer and improving the molecular weight and yield of the regenerated polymer.

[0048] In the example, the main components of the waste polymer mixture of polyethylene terephthalate and bisphenol A polycarbonate can be regenerated into high-strength, high-temperature resistant polyarylate (PAR) by controlling the appropriate reaction ratio of the two for conversion. Therefore, in the present invention, the mechanical properties and thermal properties of the final recycled polymer can be selectively regulated by controlling the reaction conditions according to the different fields and purposes of the recycled product. Obviously, the present invention can achieve better recycling of waste polymers, and the generated recycled polymers also have good application prospects.

[0049] In the present invention, the specific composition of the waste polymer mixture is affected by the source of the waste, but the specific composition can be artificially regulated through later detection. Since the rate of the cyclization reaction is affected by the specific composition of the waste polymer mixture, after a large number of experimental optimization and regulation, in the waste polymer mixture containing the first composition, the molar ratio of the first repeating unit to the second repeating unit is 1: (0.1-10), and in the waste polymer mixture containing the second composition, the molar ratio of the second repeating unit to the third repeating unit is 1: (0.1-10). In this case, with the continuous removal of cyclic small molecules, the proportion of the generated new polymer in the original cyclization reaction system gradually increases until it reaches 100%, and then the obtained recycled polymer is significantly different from the original waste polymer mixture in both chemical structure and physical properties.

[0050] Preferably, in the above method, the catalyst used for the chain exchange reaction in step S1 is the same as the catalyst used for the cyclization reaction in step S2, which can be a Lewis acid of tin, zinc, magnesium, titanium, antimony, scandium, iron, cobalt, or nickel, and can be specifically selected from but not limited to at least one of stannous chloride, stannous octoate, zinc chloride, zinc oxide, magnesium chloride, magnesium sulfate, titanium tetraisopropoxide, tetraphenyl titanate, acetylacetonoxytitanium, antimony glycol, antimony trioxide, scandium trifluoromethanesulfonate, iron acetate, iron oxide, cobalt acetate, and nickel chloride. It has been verified that this type of metal Lewis can effectively catalyze the exchange reaction between ester group-carbonate group, ester group-ester group, and carbonate group-carbonate group, thereby ensuring the smooth progress of the chain exchange reaction and cyclization reaction between waste polyester and polycarbonate, avoiding repeated addition of catalysts, saving operations, and avoiding the problem that the introduction of too much material has an adverse effect on the performance of subsequent recycled polymers.

[0051] Preferably, in the above method, the weight of the catalyst accounts for 0.05-1% of the total weight of the waste polymer mixture to ensure a significant catalytic effect.

[0052] Preferably, in the above method, the conditions for the chain exchange reaction in step S1 are: an inert atmosphere, a temperature of 150-300°C, and a time of 0.5-24 hours. More preferably, the temperature is 200-280°C, and the reaction time is 1-3 hours. This is because the degree of chain exchange reaction is affected by its reaction equilibrium constant. The higher the temperature, the larger the reaction equilibrium constant (i.e., the easier the reaction is), so high reaction temperature is conducive to the reaction.

[0053] Further preferably, the inert atmosphere is achieved by introducing an inert gas such as nitrogen or argon to prevent oxygen or water in the air from producing side reactions such as oxidation and hydrolysis, which may adversely affect the chain exchange reaction, such as monomer oxidation and ester hydrolysis.

[0054] It should be noted that both step S1 and step S2 are carried out under stirring, and the purpose of stirring is to make the various substances in the corresponding reaction system uniformly dispersed, while increasing the contact area of ​​the reactants and improving the reaction rate. There is no strict limit on the stirring speed, such as in step S1, the rotation speed can be 10-200 rpm, and in step S2, the rotation speed can be 50-200 rpm.

[0055] In a second aspect of the present invention, there is provided a recycled polymer obtained by the above-mentioned method of synthesizing a recycled polymer using waste polyester, polycarbonate and polyether.

[0056] In the method for synthesizing recycled polymers from waste polyesters, polycarbonates, and polyethers of the present invention, the cyclization reaction can be controlled to proceed to the right by continuously removing cyclic small molecules, thereby continuously increasing the molecular weight of the newly generated polymer, and finally making the recycled polymer of the present invention have good mechanical properties. In addition, the performance of the recycled polymer can be regulated in the process of recycling the waste polymer mixture according to specific use requirements, that is, the recycled polymer can be specifically customized according to specific use requirements.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The method for synthesizing a regenerated polymer from waste polyester, polycarbonate and / or polyether of the present invention does not require separation of waste polyester, polycarbonate and / or polyether, and can directly synthesize a regenerated polymer with excellent performance through chain exchange and cyclization reaction. The method does not introduce an organic solvent, meets national environmental protection requirements, and is simple and easy to operate, simple to post-process, high in recovery efficiency, and relatively low in cost, providing basic conditions for subsequent large-scale recovery and utilization of these polymers. In addition, the regenerated polymer synthesized from waste polyester, polycarbonate and / or polyether of the present invention can regulate its performance according to the purpose of use and field specificity, and the generated cyclic small molecule product can be used as a chemical raw material after purification, thereby realizing the sustainable recycling of waste polymers and meeting the atomic economy principle of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The hydrogen and carbon nuclear magnetic resonance spectra of the polyethylene terephthalate raw material used in Inventive Example 1;

[0060] Figure 2 The hydrogen and carbon nuclear magnetic resonance spectra of the bisphenol A polycarbonate raw material used in Inventive Example 1;

[0061] Figure 3 The hydrogen and carbon nuclear magnetic resonance spectra of the precursor prepared in step S1 of Inventive Example 1;

[0062] Figure 4 The hydrogen and carbon nuclear magnetic resonance spectra of the regenerated polymer prepared in Inventive Example 1;

[0063] Figure 5 The hydrogen and carbon nuclear magnetic resonance spectra of the cyclic small molecule removed in step S2 of Inventive Example 1. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and drawings, but the protection scope of the present invention is not limited to the embodiments.

[0065] Unless otherwise specified, the raw materials used in the following examples are all commercially available. In addition, the waste polymers polyester, polycarbonate and polyether used in the following examples are all obtained by simple physical screening from mixed wastes, and the number average molecular weight is detected by a molecular weight analyzer, and the obtained recycled polymers are analyzed and detected by nuclear magnetic resonance spectroscopy and molecular weight analysis instruments, wherein the nuclear magnetic resonance spectroscopy and molecular weight analysis are performed in the following manner.

[0066] MRI test steps: 1 H. 13 C NMR spectra were performed on a Bruker AVANCE NEO 600 MHz spectrometer. Deuterated chloroform was usually used as a solvent. For samples that were insoluble in chloroform, such as the prepared regenerated polymer, a mixed solvent of deuterated chloroform / trifluoroacetic acid (v / v, 2:1) was used as a solvent.

[0067] Molecular weight test steps: The number average molecular weight is measured by a PL-GPC 220 instrument, wherein the solvent for polyester raw materials and their regenerated products uses hexafluoroisopropanol as the mobile phase, the flow rate is 1.0 mL / min, the test temperature is 40°C, and a monodisperse polymethyl methacrylate standard sample is used for calibration; the solvent for polycarbonate or polyether raw materials and their regenerated products uses chloroform, the flow rate is 1.0 mL / min, the test temperature is 25°C, and a monodisperse polystyrene standard sample is used for calibration.

[0068] Invention Example 1

[0069] S1 Preparation of precursors

[0070] 19.9g of polyethylene terephthalate (PET) and 30g of bisphenol A polycarbonate (PC) (the molar ratio of the repeating unit of PET to the repeating unit of PC is 1:1) were added to a 250mL reactor, wherein the number average molecular weight of PET was 26.5kDa after separation (the test solvent was phenol / 1,1,2,2-tetrachloroethane with a mass ratio of 60 / 40, the same below unless otherwise specified); the number average molecular weight of PC was 22.6kDa after separation; then 0.025g of stannous chloride was added, an inert argon gas flow was introduced for anti-oxidation protection, and the precursor was heated to 270°C under normal pressure and stirring conditions for chain exchange reaction for 3 hours to obtain a precursor. After testing, the number average molecular weight of the precursor was 15.2kDa.

[0071] Comparison of raw material PET( Figure 1 , the test solvent is deuterated chloroform / trifluoroacetic acid mixed solvent), PC( Figure 2 , the test solvent is deuterated chloroform) and the precursor ( Figure 3 The nuclear magnetic resonance spectrum of the precursor (test solvent is deuterated chloroform) shows that the chemical shift of the benzene ring peaks in the original PET and PC in the precursor has changed significantly, proving that the chain exchange reaction has been successfully carried out. In addition, since the PET raw material cannot be dissolved in a simple deuterated chloroform solvent, the fact that the precursor can be dissolved in deuterated chloroform also proves that the reaction has occurred.

[0072] S2 Preparation of recycled polymer

[0073] The precursor obtained in step S1 was evacuated to 100 Pa in a reactor, and a cyclization reaction was carried out to remove cyclic small molecules at a temperature of 250° C. and a rotation speed of 120 r / min. The reaction lasted for 4 hours to obtain a regenerated polymer, which was recorded as A1.

[0074] The number average molecular weight of the obtained regenerated polymer A1 was 28.1 kDa, and the results of nuclear magnetic resonance spectroscopy were shown in Figure 4 , which shows that the molar ratio of the terephthalic acid units in the new polyarylate formed in the final product A1, namely poly(bisphenol A terephthalate), to the repeating units of the residual PET is 0.61:0.39, that is, 61% of the terephthalic acid units in the original PET have been converted into new polyarylate units. In addition, the collected liquid substance, namely the cyclic small molecule substance, was dried over anhydrous sodium sulfate and separated and then analyzed by nuclear magnetic resonance spectroscopy. The specific results are shown in Figure 5 In the experiment, the test solvent was deuterated chloroform. Obviously, the collected cyclic small molecule substance was ethylene carbonate.

[0075] Invention Example 2

[0076] Inventive Example 2 was carried out according to the method of Inventive Example 1, with the only difference being that the polyethylene terephthalate (PET) in step S1 was replaced by polytrimethylene terephthalate (PTT, with a number average molecular weight of 25.7 kDa as detected), and the obtained recycled polymer was denoted as A2.

[0077] According to the test, in this embodiment of the invention, the number average molecular weight of the precursor obtained in step S1 is 16.3 kDa. The number average molecular weight of the regenerated polymer A2 obtained in step S2 is 29.3 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the terephthalic acid unit in the formed new polyarylate to the repeating unit of the residual PTT is 0.71:0.29, that is, 71% of the terephthalic acid units in the original PTT have been converted into new polyarylate units.

[0078] Invention Example 3

[0079] Inventive Example 2 was carried out according to the method of Inventive Example 1, with the only difference being that the polyethylene terephthalate (PET) in step S1 was replaced by polybutylene oxalate (the number average molecular weight was 29.6 kDa after detection), and the obtained recycled polymer was recorded as A3.

[0080] After testing, in this embodiment of the invention, the number average molecular weight of the precursor obtained in step S1 is 20.6 kDa. The number average molecular weight of the regenerated polymer A3 obtained in step S2 is 30.2 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the succinic acid unit in the formed new polyarylate to the repeating unit of the residual polybutylene oxalate is 0.79:0.21, that is, 79% of the succinic acid units in the original PBS have been converted into new polyarylate units.

[0081] Invention Example 4

[0082] Inventive Example 4 was carried out according to the method of Inventive Example 1, with the only difference being that the polyethylene terephthalate (PET) in step S1 was replaced by polybutylene oxalate, and the bisphenol A type polycarbonate (PC) was replaced by polyethylene glycol (the number average molecular weight was detected to be 30.4 kDa), and the obtained recycled polymer was recorded as A4.

[0083] After testing, in this embodiment of the invention, the number average molecular weight of the precursor obtained in step S1 is 21.6 kDa. The number average molecular weight of the regenerated polymer A2 obtained in step S2 is 32.6 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the ethylene glycol unit in the formed new polyether to the repeating unit of the residual polyethylene glycol is 0.84:0.16, that is, 84% of the ethylene glycol units in the original polyethylene glycol have been converted into new polyether units.

[0084] Invention Example 5

[0085] Inventive Example 2 was carried out according to the method of Inventive Example 1, with the only difference being that the polyethylene terephthalate (PET) in step S1 was replaced by polybutylene oxalate, and the bisphenol A type polycarbonate (PC) was replaced by polyoxymethylene (the number average molecular weight was detected to be 24.3 kDa), and the obtained recycled polymer was recorded as A5.

[0086] According to the test, in this embodiment of the invention, the number average molecular weight of the precursor obtained in step S1 is 14.8 kDa. The number average molecular weight of the regenerated polymer A5 obtained in step S2 is 26.3 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the formaldehyde unit in the formed new polyether to the repeating unit of the residual polyformaldehyde is 0.64:0.36, that is, 64% of the formaldehyde units in the original polyformaldehyde have been converted into new polyether units.

[0087] Invention Example 6

[0088] Inventive Example 2 was carried out according to the method of Inventive Example 1, with the only difference being that the polyethylene terephthalate (PET) in step S1 was replaced by polyethylene glycol (the number average molecular weight was 30.4 kDa after detection), and the obtained regenerated polymer was denoted as A6.

[0089] After testing, in this embodiment of the invention, the number average molecular weight of the precursor obtained in step S1 is 18.6 kDa. The number average molecular weight of the regenerated polymer A6 obtained in step S2 is 30.5 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the ethylene glycol unit in the formed new polyether to the repeating unit of the residual polyethylene glycol is 0.67:0.33, that is, 67% of the ethylene glycol units in the original polyethylene glycol have been converted into new polyether units.

[0090] Invention Example 7

[0091] Inventive Example 2 was carried out according to the method of Inventive Example 1, with the only difference being that the polyethylene terephthalate (PET) in step S1 was replaced by poly(1,2-propylene glycol) (the number average molecular weight was detected to be 21.3 kDa), and the obtained recycled polymer was recorded as A7.

[0092] After testing, in this embodiment of the invention, the number average molecular weight of the precursor obtained in step S1 is 16.8 kDa. The number average molecular weight of the regenerated polymer A7 obtained in step S2 is 25.8 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the 1,2-propylene glycol unit in the formed new polyether to the repeating unit of the residual poly(1,2-propylene glycol) is 0.65:0.35, that is, 65% of the 1,2-propylene glycol units in the original poly(1,2-propylene glycol) have been converted into new polyether units.

[0093] Inventive Examples 8 and 9

[0094] Inventive Examples 8 and 9 were carried out according to the method of Inventive Example 1, with the only difference being that the catalyst stannous chloride in step S1 was replaced by antimony trioxide (Inventive Example 8) and ferric acetate (Inventive Example 9), respectively. The obtained regenerated polymers were recorded as A8 and A9, respectively.

[0095] According to the test, in Inventive Example 8, the number average molecular weight of the precursor obtained in step S1 is 20.9 kDa. The number average molecular weight of the regenerated polymer A8 obtained in step S2 is 35.6 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the terephthalic acid unit in the formed new polyarylate to the repeating unit of the residual PET is 0.80:0.20, that is, 80% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0096] In Inventive Example 9, the number average molecular weight of the precursor obtained in step S1 is 19.8 Da. The number average molecular weight of the recycled polymer A9 obtained in step S2 is 31.0 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.66:0.34, that is, 66% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0097] Invention Examples 10-12

[0098] Inventive Examples 10-12 were respectively carried out according to the method of Inventive Example 1, with the only difference being that the molar ratio of the repeating units of PET and PC in step S1 was 1:1 and replaced with 2:3 (Inventive Example 10), 3:2 (Inventive Example 11), and 1:5 (Inventive Example 12), respectively, and the recycled polymers obtained in Inventive Examples 10-12 were denoted as A10, A11, and A12, respectively.

[0099] According to the test, in the inventive example 10, the number average molecular weight of the precursor obtained in step S1 is 18.3 kDa. The number average molecular weight of the recycled polymer A10 obtained in step S2 is 29.3 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the repeating units of terephthalic acid in the formed new polyarylate to the residual PET units is 0.63:0.37, that is, 63% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0100] In Inventive Example 11, the number average molecular weight of the precursor obtained in step S1 is 21.6 kDa. The number average molecular weight of the recycled polymer A11 obtained in step S2 is 33.8 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.70:0.30, that is, 70% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0101] In Inventive Example 12, the number average molecular weight of the precursor obtained in step S1 is 16.1 kDa. The number average molecular weight of the recycled polymer A12 obtained in step S2 is 34.9 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.83:0.17, that is, 83% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0102] Invention Example 13

[0103] Inventive Example 13 was carried out according to the method of Inventive Example 1, with the only difference being that the reaction temperature in step S1 was replaced with 290° C., and the obtained regenerated polymers were respectively denoted as A13.

[0104] After testing, in Inventive Example 13, the number average molecular weight of the precursor obtained in step S1 is 14.3 kDa. The number average molecular weight of the regenerated polymer A13 obtained in step S2 is 33.7 kDa, and the nuclear magnetic resonance spectrum test shows that the molar ratio of the terephthalic acid unit in the formed new polyarylate to the repeating unit of the residual PET is 0.72:0.28, that is, 72% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0105] Invention Example 14

[0106] Inventive Example 14 was carried out according to the method of Inventive Example 1, with the only difference being that the reaction temperature in step S2 was replaced with 280° C., and the obtained regenerated polymers were respectively denoted as A14.

[0107] After testing, in Inventive Example 14, the number average molecular weight of the recycled polymer A14 obtained in the step S2 is 38.2 kDa, and nuclear magnetic resonance spectroscopy detection shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.68:0.32, that is, 68% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0108] Invention Examples 15-17

[0109] Inventive Examples 15-17 were carried out according to the method of Inventive Example 1, with the only difference being that the reaction time of 4 hours in step S2 was replaced by 6 hours (Inventive Example 15), 8 hours (Inventive Example 16), and 12 hours (Inventive Example 17), respectively. The regenerated polymers obtained in Inventive Examples 15-17 were recorded as A15, A16, and A17, respectively.

[0110] In Inventive Example 15, the number average molecular weight of the recycled polymer A15 obtained in step S2 is 29.4 kDa, and nuclear magnetic resonance spectroscopy detection shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.69:0.31, that is, 69% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0111] After testing, in Inventive Example 16, the number average molecular weight of the recycled polymer A16 obtained in the step S2 is 32.9 kDa, and nuclear magnetic resonance spectroscopy detection shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.78:0.22, that is, 78% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0112] In Inventive Example 17, the number average molecular weight of the recycled polymer A17 obtained in step S2 is 39.4 kDa, and nuclear magnetic resonance spectroscopy detection shows that the molar ratio of the terephthalic acid units in the formed new polyarylate to the repeating units of the residual PET is 0.91:0.09, that is, 91% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0113] It is obvious from the above embodiments that the method of the present invention can effectively reuse waste polyester, polycarbonate and / or polyether, and can adjust the molecular weight of the recycled polymer by adjusting the reaction time, temperature, composition of the waste polymer and other reaction parameters, thereby obtaining a recycled polymer with practical application value.

[0114] In addition, compared with the traditional recycling method, the waste polymer recycling method of the present invention can directly use the mixture of waste polyester, polycarbonate and polyether to realize the synthesis of recycled polymer, without the need to separate polyester, polycarbonate and polyether in advance, and the whole recycling process is relatively simple, controllable and efficient, and the recycled polymer can be prepared at low cost. In addition, the method of preparing high-performance recycled polymer using waste polyester, polycarbonate and polyether of the present invention can react under solvent-free conditions, overcoming the problems of difficult removal of small molecules, low degree of polymerization and insufficient product molecular weight in the traditional melt polymerization method, and the generated cyclic small molecules can be collected for reuse, realizing recyclable recycling, which is in line with the atomic economy principle of green chemistry.

[0115] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for synthesizing recycled polymers using waste polyester, polycarbonate and / or polyether, characterized in that: The steps include: S1. Preparing a precursor: melting the waste polymer mixture and then performing a chain exchange reaction under the action of a catalyst to obtain a precursor; S2. Preparation of regenerated polymer: subjecting the precursor prepared in step S1 to a cyclization reaction and removing cyclic small molecules to obtain a regenerated polymer, The waste polymer mixture comprises a mixture of two or more of polyester, polycarbonate and / or polyether.

2. The method according to claim 1, characterized in that The waste polymer mixture comprises a first composition, which comprises a polyester having a first repeating unit derived from a dibasic acid, dibasic ester and / or dibasic anhydride represented by the following formula (U1) and / or (U2) and a polycarbonate and / or polyether having a second repeating unit derived from a diol and / or diol ester represented by the following formula (U3) and / or (U4), Among them, R1, R2, R3, R4, R5, R 16 , R 19 , R 20 may be the same or different and are each independently selected from hydrogen, alkyl, 15 , R 17 , R 18 , R 21 may be the same or different and are each independently selected from hydrogen and / or acyl.

3. The method according to claim 1, characterized in that: The waste polymer mixture comprises a second composition, which comprises a polycarbonate having a carbonate group and a polyester and / or a polyether whose structure is derived from a third repeating unit of a diol and / or a diol ester represented by the following formula (U5) and / or (U6), Among them, R7, R8, R 11 , R 12 , R 13 may be the same or different and are independently selected from hydrogen, alkyl, R6, R9, R 10 , R 14 may be the same or different and are each independently selected from hydrogen and / or acyl.

4. The method according to claim 2 or 3, characterized in that: The alkyl group is an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 18 carbon atoms. Further preferably, the unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 18 carbon atoms is an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms, more preferably an unsubstituted or substituted straight chain, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms, in particular an unsubstituted or halogen-mono- or poly-substituted straight chain, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms.

5. The method according to claim 1, characterized in that The conditions for the chain exchange reaction in step S1 are: an inert atmosphere, a temperature of 150-300° C., and a time of 0.5-24 hours.

6. The method according to claim 2, characterized in that In the waste polymer mixture comprising the first composition, the molar ratio of the first repeating unit to the second repeating unit is 1:(0.1-10).

7. The method according to claim 3, characterized in that In the waste polymer mixture comprising the second composition, the molar ratio of the second repeating unit to the third repeating unit is 1:(0.1-10).

8. The method according to claim 1, characterized in that: The pressure condition for the cyclization reaction in step S2 is 1000Pa-1Pa, the temperature condition is 200-300°C, and the reaction time is 0.5-24 hours.

9. The method according to claim 1, characterized in that: The catalyst used for the chain exchange reaction in step S1 is the same as the catalyst used for the cyclization reaction in step S2, and can be a Lewis acid of tin, zinc, magnesium, titanium, antimony, scandium, iron, cobalt, or nickel, and can be specifically selected from but not limited to at least one of stannous chloride, stannous octoate, zinc chloride, zinc oxide, magnesium chloride, magnesium sulfate, titanium tetraisopropoxide, tetraphenyl titanate, titanium acetylacetonate, antimony glycol, antimony trioxide, scandium trifluoromethanesulfonate, ferric acetate, ferric oxide, cobalt acetate, and nickel chloride.

10. A recycled polymer, characterized in that The method is prepared by any one of claims 1 to 10.

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