A method for synthesizing a recycled polymer using waste polyester, polycarbonate and / or polyether and the recycled polymer

Abstract

The application provides a method for synthesizing recycled polymers from waste polyester, polycarbonate and / or polyether and the recycled polymers, the method comprising two steps, a first step of preparing a precursor through a chain exchange reaction, and a second step of preparing the recycled polymers through a ring formation reaction. Obviously, the method does not need to separate the waste polyester, polycarbonate and / or polyether, but directly synthesizes the recycled polymers with excellent performance through the chain exchange and ring formation reactions, and does not introduce organic solvents, meets the national environmental protection requirements, and provides a basic condition for subsequent large-scale recycling of the polymers.

Description

Technical Field

[0001] This invention belongs to the field of waste polymer recycling technology, specifically relating to a method for synthesizing recycled polymers using waste polyester, polycarbonate and / or polyether, and also relating to the recycled polymers synthesized by the method. Background Technology

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

[0003] Polyesters are thermoplastic polymers formed by the polycondensation reaction of diacids and diols, with polyethylene terephthalate (PET) being the most representative. PET is currently one of the most widely used polymer materials in the world, with applications in textiles, packaging, and bottling. Polycarbonates are a class of polymers containing carbonate structures in their molecular chains, and a general term for various materials derived from them. Bisphenol A polycarbonate is the most important, with its three main application areas being glass assembly, the automotive industry, and the electronics and electrical appliance industry. It is also widely used in industrial machinery parts, office equipment, medical and healthcare products, films, leisure and protective equipment, etc. Polyethers are linear polymers formed by the ring-opening homopolymerization or copolymerization of epoxides under the action of a catalyst. These materials possess excellent mechanical properties, thermal stability, and chemical resistance, and are widely used in construction, automotive, electronics, and biomedical fields.

[0004] To date, the main methods for recycling and reusing waste plastics are physical recycling and chemical conversion. Physical recycling involves processing waste polymers through physical means such as crushing, washing, sorting, and weighing, and then processing them into usable materials. However, it suffers from drawbacks such as performance degradation of recycled products, low recycling efficiency, and high recycling costs. Chemical recycling is a recycling method that uses chemical conversion (including alcoholysis, phenolysis, hydrolysis, acid hydrolysis, ammonolysis, etc.) to convert waste polymers into monomers or oligomers for reuse. Specifically, current chemical recycling of waste polyester and polycarbonate mainly relies on the exchange reaction between small molecule alcohols, acids, or amines and ester or carbonate bonds to depolymerize them into monomer raw materials for reuse. For example, CN117586486A discloses a continuous manufacturing process for recycled PET using waste polyester bottles as raw materials, employing a continuous alcoholysis and polycondensation method, which uses a large amount of ethylene glycol for depolymerization. CN116535316A discloses a method for catalytic alcoholysis of polycarbonate to recover bisphenol A and carbonates, using alcohol-based degrading agents to depolymerize polycarbonate. After the reaction, bisphenol A and carbonates can be obtained simultaneously through separation. However, because small molecules such as water, alcohols, and amines can react with polyester or polycarbonate simultaneously, and not only monomers are formed during depolymerization, oligomers with different degrees of polymerization are also generated, inevitably leading to difficulties in product separation and purification, significantly reducing the utilization efficiency of waste polymers. Furthermore, there is currently a lack of effective chemical recycling methods for waste polyethers.

[0005] However, polyester, polycarbonate, and polyether often exist as mixtures due to their similar physical and chemical properties. Traditional recycling methods often struggle to completely separate these three polymers, leading to interference during the recycling process. Furthermore, traditional recycling methods are typically only suitable for recycling single types of plastics and not for processing mixtures of waste polymers. Therefore, there is an urgent need to develop an efficient and low-cost method for preparing recycled polymers that can directly utilize specific reactions to achieve the efficient recycling of waste polyester, polycarbonate, and polyether mixtures and synthesize high-performance recycled polymers without separating the polyester, polycarbonate, and polyether mixtures. Summary of the Invention

[0006] To address the aforementioned issues, the inventors of this invention have developed a method for synthesizing recycled polymers from waste polyester, polycarbonate, and / or polyether through extensive experimentation. This method enables the direct synthesis of high-performance recycled polymers from waste polyester, polycarbonate, and polyether via cyclization reactions without the need for separation. Furthermore, this method is cost-effective, highly efficient, simple to operate, and easy to process, providing a foundation for large-scale recycling of these waste polymers.

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

[0008] S1. Preparation of precursors: The waste polymer mixture is melted and then subjected to a chain exchange reaction under the action of a catalyst to obtain the precursors;

[0009] S2. Preparation of regenerated polymer: The precursor prepared in step S1 is subjected to a cyclization reaction and the cyclic small molecules are removed to obtain the regenerated polymer.

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

[0011] In this invention, the chain exchange reaction in step S1, in which waste polyester, polycarbonate, and polyether are reacted under the action of a catalyst to obtain the first precursor, is based on the pairwise exchange of ester bonds, carbonate bonds, and ether bonds at any position in the polyester, polycarbonate, and polyether molecular chains. The general reaction formulas are as follows: reaction formulas (I)-(III):

[0012]

[0013] As can be seen from the above reaction formulas (I)-(III), the chain exchange reaction in step S1 does not change the number of molecules. In addition, these waste polyester, polycarbonate and polyether mixtures usually contain moisture absorbed from the air. The presence of these small water molecules leads to hydrolysis in the system, which in turn reduces the overall molecular weight of these waste polymer systems. Therefore, the precursor obtained in step S1 is an oligomer with a low molecular weight.

[0014] In step S2, the precursor obtained in step S1 continuously generates cyclic small molecules through cyclization reactions under high temperature, reduced pressure and catalyst catalysis, as shown in reaction formulas (IV)-(VII) below, thereby producing new polymers and cyclic small molecules. At the same time, the removal of small molecule water, i.e. the reverse reaction of step S1 and the removal of cyclic small molecules, is accompanied by the continuous growth of polymer molecular chains, ultimately obtaining high-performance regenerated polymers.

[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 polyester, polycarbonate, and / or polyether in the raw material waste polymer mixture and product precursor in step S1. They are not specific and there is no one-to-one correspondence. Furthermore, 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 waste polymer mixtures containing polyester, polycarbonate and polyether with similar physicochemical properties into high-performance recycled polymers without separation.

[0018] Preferably, in the above method, the waste polymer mixture comprises a first composition comprising a polyester of a first repeating unit derived from a diacid, diester, and / or diacid anhydride of formula (U1) and / or (U2) and a polycarbonate and / or polyether of a second repeating unit derived from a diol and / or diol ester of formula (U3) and / or (U4).

[0019]

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

[0021] In the method of the present invention, the polyester whose structure is derived from the first repeating unit of a diacid, diester, and / or diacid anhydride represented by formula (U1) and / or (U2) and the polycarbonate and / or polyether whose structure is derived from the second repeating unit of a diol and / or diol ester represented by formula (U3) and / or (U4) can be commercially available polymers commonly used in the art. For example, the polyester can be polypropylene oxalate, polybutylene oxalate, polypropylene malonate, polybutylene malonate, or polymethyl propylene methyl malonate. 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-propanediol), etc. The five / six-membered cyclic diesters produced by these polyesters, polycarbonates and / or polyethers in the method of the present invention are not only easily removed from the regenerated polymer to increase the molecular weight of the regenerated polymer, but the removed cyclic diesters can also be used as by-products as chemical raw materials.

[0022] More preferably, the alkyl group is an unsubstituted or substituted straight-chain, branched 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, especially unsubstituted or halogen (such as fluorine, chlorine, bromine, etc.) monosubstituted or polysubstituted straight-chain, branched or cyclic alkyl groups 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 portion remaining after removing the hydroxyl group from an oxyacid, and its structural formula is as follows (XI).

[0025]

[0026] Wherein R is an alkyl group with no more than 4 carbon atoms, further comprising 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.) monosubstituted or polysubstituted 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 this invention, the first composition comprising a polyester comprising repeating units of a diacid, diester, and / or diacid anhydride represented by formula (U1) and / or (U1) and a polycarbonate and / or polyether comprising repeating units of a diol and / or diol ester represented by formula (U3) and / or (U4) can specifically be: (1a) a polyester comprising repeating units of a diacid, diester, and / or diacid anhydride represented by formula (U1) and / or (U1) and a polycarbonate and / or polyether comprising repeating units of a diol and / or diol ester represented by formula (U3) and / or (U4) (1b) A polyester whose structure is derived from repeating units of diacids, esters and / or diacid anhydrides as shown in (U1) and / or (U1) and a polyether whose structure is derived from repeating units of diols and / or diol esters as shown in (U3) and / or (U4); or, (1c) A mixture of a polyester whose structure is derived from repeating units of diacids, esters and / or diacid anhydrides as shown in (U1) and / or (U1) and a polycarbonate and polyether whose structure is derived from repeating units of diols and / or diol esters as shown in (U3) and / or (U4).

[0028] When the waste polymer mixture contains the first composition, the general reaction formula for 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 molecule produced by the cyclization reaction is a cyclic diester, the corresponding structure of which is shown in the following formulas (C1)-(C3).

[0029]

[0030] Further, when the first composition contains a polyester of repeating units of a diacid, diester, and / or diacid anhydride as shown in formula (U1) and a polycarbonate and / or polyether of repeating units of a diol and / or diol ester as shown in formula (U3), the cyclic small molecule generated by the cyclization reaction is a cyclic diester with the structure shown in formula (C1) above; the first composition contains a polyester of repeating units of a diacid, diester, and / or diacid anhydride as shown in formula (U4) above and a polycarbonate and / or polyether of repeating units of a diol and / or diol ester as shown in formula (U4). When the polycarbonate and / or polyether of repeating units of alcohol and / or diol ester is used, the cyclic small molecule produced by the cyclization reaction is a cyclic diester and has the structure shown in formula (C2) above; when the first composition contains a polyester of repeating units of diacid, diester and / or diacid anhydride as shown in formula (U2) and polycarbonate and / or polyether of repeating units of diol and / or diol ester as shown in formula (U3) above, the cyclic small molecule produced by the cyclization reaction is a cyclic diester and has the structure shown in formula (C3) above. However, it should also be noted that when the first composition contains a polyester of repeating units of diacid, diester and / or diacid anhydride as shown in formula (U2) and polycarbonate and / or polyether of repeating units of diol and / or diol ester as shown in formula (U4), the cyclic small molecules produced by the cyclization reaction are seven-membered ring cyclic diesters. These cyclic diesters are less stable and have fewer uses than five / six-membered ring cyclic diesters, and the less stable seven-membered ring is not conducive to the formation and removal at high temperatures, which is not conducive to the formation of regenerated polymers.

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

[0032]

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

[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 formula (U5) and / or (U6) are commercially available polymers commonly found in the art. For example, the polyester may be one or more of polyethylene terephthalate, polyethylene succinate, and polyethylene terephthalate, and the polyether may be one or more of polyethylene glycol, poly(1,2-propanediol), and poly(1,3-propanediol). The five / six-membered cyclic esters produced by these polyesters, polycarbonates, and / or polyethers in the method of the present invention are not only easily removed from the regenerated polymer to increase the molecular weight of the regenerated polymer, but the removed cyclic esters can also be used as byproducts as chemical raw materials.

[0035] More preferably, the alkyl group is an unsubstituted or substituted straight-chain, branched 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, especially unsubstituted or halogen (such as fluorine, chlorine, bromine, etc.) monosubstituted or polysubstituted straight-chain, branched or cyclic alkyl groups 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 portion remaining after removing the hydroxyl group from an oxyacid, and its structural formula is as follows (XI).

[0038]

[0039] Wherein R is an alkyl group with no more than 4 carbon atoms, further comprising 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.) monosubstituted or polysubstituted 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 this invention, the second composition comprising a polycarbonate having carbonate groups and a polyester and / or polyether having a structure derived from repeating units of diols and / or diol esters represented by formulas (U5) and / or (U6) can specifically be: (2a) a polycarbonate having carbonate groups and a polyester having a structure derived from repeating units of diols and / or diol esters represented by formulas (U5) and / or (U6); (2b) a polycarbonate having carbonate groups and a polyether having a structure derived from repeating units of diols and / or diol esters represented by formulas (U5) and / or (U6); or, (2c) a mixture of a polycarbonate having carbonate groups and a polyester and polyether having a structure derived from repeating units of diols and / or diol esters represented by formulas (U5) and / or (U6).

[0041] When the waste polymer mixture contains the second composition, the general reaction formula for 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 molecules produced by the cyclization reaction are cyclic carbonates, the corresponding structures of which are shown in the following formulas (10)-(11).

[0042]

[0043] Clearly, when the second composition contains polycarbonate with carbonate groups and polyester and / or polyether of repeating units of diol and / or diol ester as shown in formula (U5), the cyclic small molecule produced by the cyclization reaction is a cyclic carbonate with a structure as shown in formula (C4); when the second composition contains polycarbonate with carbonate groups and polyester and / or polyether of repeating units of diol and / or diol ester as shown in formula (U6), the cyclic small molecule produced by the cyclization reaction is a cyclic carbonate with a structure as shown in formula (C5).

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

[0045] As can be seen from the above general reaction formulas (IV) to (VII), step S2 requires reducing pressure and increasing temperature to achieve the continuous removal of cyclic small molecules, thereby making the reaction proceed more thoroughly to the right. Therefore, in step S2, the pressure of the reaction system is gradually reduced from standard atmospheric pressure (101.325 kPa) to 1000 Pa-1 Pa, thereby obtaining a high molecular weight regenerated polymer. That is to say, the absolute pressure condition for the cyclization reaction in step S2 is 1 Pa-1000 Pa, and other reaction conditions are: temperature 200-300 °C, and reaction time 0.5-24 hours.

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

[0047] In step S2, as cyclic small molecules are continuously released, new polyester, polycarbonate, or polyether units are continuously formed during the reaction, and their proportion continuously increases. This alters the original chemical structure of the polyester, polycarbonate, or polyether, and the mechanical and thermal properties of the regenerated polymer change accordingly as the reaction proceeds. Furthermore, in this invention, the relatively low ring strain of five- and six-membered ring molecules makes it easier to complete the ring-closing reaction in step S2. Specifically, the lower ring strain makes these cyclic molecules more stable during the reaction, allowing them to be effectively removed from the reaction system in the S2 reaction stage. This removal process promotes the formation of the regenerated polymer, increasing its molecular weight and yield.

[0048] In this example, the main components are a mixture of waste polymers of polyethylene terephthalate and bisphenol A type polycarbonate. By controlling the appropriate reaction ratio of the two, high-strength, high-temperature resistant polyarylate (PAR) can be generated for conversion. Therefore, in this invention, the mechanical and thermal properties of the final recycled polymer can be selectively controlled by adjusting the reaction conditions according to the different application fields and purposes of the recycled product. Clearly, this invention achieves good recycling of waste polymers, and the generated recycled polymers also have good application prospects.

[0049] In this invention, the specific composition of the waste polymer mixture is affected by the source of the waste, but can be artificially controlled through subsequent testing. Since the rate of the cyclization reaction is influenced by the specific composition of the waste polymer mixture, after extensive experimental optimization, 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), while 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). Under these conditions, with the continuous removal of cyclic small molecules, the proportion of the newly generated polymer in the original cyclization reaction system gradually increases until it reaches 100%, resulting in a regenerated polymer that 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, and can be a Lewis acid of tin, zinc, magnesium, titanium, antimony, scandium, iron, cobalt, or nickel. Specifically, it can be selected from, but is not limited to, at least one of stannous chloride, stannous octoate, zinc chloride, zinc oxide, magnesium chloride, magnesium sulfate, titanium tetraisopropoxide, tetraphenyl titanate, titanium oxyacetylacetone, antimony glycolate, antimony trioxide, scandium trifluoromethanesulfonate, iron acetate, iron oxide, cobalt acetate, and nickel chloride. It has been verified that this type of metal Lewis acid can effectively catalyze the exchange reactions between ester groups and carbonate groups, ester groups and ester groups, and carbonate groups and carbonate groups, thereby ensuring the smooth progress of the chain exchange reaction and cyclization reaction between waste polyester and polycarbonate, avoiding the repeated addition of catalysts, saving operation time, and avoiding the problem of excessive substances adversely affecting the performance of subsequent recycled polymers.

[0051] Preferably, in the above method, 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℃, and a time of 0.5-24 hours. More preferably, the temperature is 200-280℃ 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). Therefore, a high reaction temperature is conducive to the reaction.

[0053] More preferably, the inert atmosphere is achieved by introducing inert gases such as nitrogen or argon, so as to prevent side reactions such as oxidation and hydrolysis of oxygen or water in the air, which could have adverse effects on the chain exchange reaction, such as monomer oxidation and ester hydrolysis.

[0054] It should be noted that both steps S1 and S2 are carried out under stirring conditions. The purpose of stirring is to ensure that the various substances in the corresponding reaction system are evenly dispersed, while increasing the contact area of ​​the reactants and improving the reaction rate. The stirring speed is not strictly limited; for example, in step S1, the stirring speed can be 10-200 rpm, and in step S2, it can be 50-200 rpm.

[0055] In a second aspect of the invention, a recycled polymer obtained by the above-described method of synthesizing recycled polymers from waste polyester, polycarbonate, and polyether is provided.

[0056] In the method for synthesizing recycled polymers from waste polyester, polycarbonate, and polyether described in this invention, the cyclization reaction can be controlled to proceed continuously to the right by continuously removing small cyclic molecules, thereby increasing the molecular weight of the newly generated polymer and ultimately giving the recycled polymer of this invention better mechanical properties. Furthermore, the properties of the recycled polymer can be adjusted during the recycling of waste polymer mixtures according to specific application requirements; that is, the recycled polymer can be specifically customized according to specific application requirements.

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

[0058] This invention provides a method for synthesizing recycled polymers from waste polyester, polycarbonate, and / or polyether without separating these materials. The method directly synthesizes high-performance recycled polymers through chain exchange and cyclization reactions. Furthermore, this method does not introduce organic solvents, complying with national environmental protection requirements. It is also simple to operate, has easy post-processing, high recycling efficiency, and relatively low cost, providing a foundation for large-scale recycling of these polymers. In addition, the properties of the recycled polymers synthesized from waste polyester, polycarbonate, and / or polyether can be controlled according to the intended use and specific application. The resulting cyclic small molecule products can be purified and used as chemical raw materials, achieving sustainable recycling of waste polymers and conforming to the atom economy principle of green chemistry. Attached Figure Description

[0059] Figure 1 The 1H and 1C NMR spectra of the polyethylene terephthalate raw material used in Example 1 of the invention;

[0060] Figure 2 The 1H and 1C NMR spectra of the bisphenol A type polycarbonate raw material used in Example 1 of the invention;

[0061] Figure 3 The 1H and 1C NMR spectra of the precursor prepared in step S1 of Example 1 of the invention;

[0062] Figure 4 The proton and carbon NMR spectra of the regenerated polymer prepared in Example 1 of the invention;

[0063] Figure 5 The images show the 1H and 1C NMR spectra of the cyclic small molecules removed in step S2 of Example 1 of the invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. However, the scope of protection claimed by this invention is not limited to the embodiments.

[0065] Unless otherwise specified, all raw materials used in the following examples are commercially available. Furthermore, the waste polymers polyester, polycarbonate, and polyether used in the following examples were obtained from mixed waste through simple physical screening, and their number-average molecular weights were determined using a molecular weight analyzer. The resulting recycled polymers were analyzed using nuclear magnetic resonance spectroscopy and molecular weight analysis, which were performed as follows.

[0066] MRI test procedure: 1 H, 13 C10 NMR spectroscopy was performed on a Bruker AVANCE NEO 600MHz spectrometer. Deuterated chloroform was typically used as the solvent. For samples insoluble in chloroform, such as prepared regenerated polymers, a mixture of deuterated chloroform and trifluoroacetic acid (v / v, 2:1) was used as the solvent.

[0067] Molecular weight testing procedure: Number average molecular weight was measured using a PL-GPC 220 instrument. For polyester raw materials and their recycled products, hexafluoroisopropanol was used as the mobile phase at a flow rate of 1.0 mL / min and a test temperature of 40 °C. Monodisperse polymethyl methacrylate standard samples were used for calibration. For polycarbonate or polyether raw materials and their recycled products, chloroform was used as the solvent at a flow rate of 1.0 mL / min and a test temperature of 25 °C. Monodisperse polystyrene standard samples were used for calibration.

[0068] Invention Embodiment 1

[0069] S1 Preparation of precursors

[0070] 19.9 g of polyethylene terephthalate (PET) and 30 g of bisphenol A polycarbonate (PC) (the molar ratio of repeating units of PET to PC was 1:1) were added to a 250 mL reactor. The number-average molecular weight of PET was determined to be 26.5 kDa (the test solvent was phenol / 1,1,2,2-tetrachloroethane at a mass ratio of 60 / 40, unless otherwise specified); the number-average molecular weight of PC was determined to be 22.6 kDa. Then, 0.025 g of stannous chloride was added, and an inert argon gas flow was introduced for oxidation protection. The mixture was heated to 270 °C under normal pressure and stirring for 3 hours to carry out a chain exchange reaction, yielding the precursor. The number-average molecular weight of this precursor was determined to be 15.2 kDa.

[0071] Comparison of raw material PET ( Figure 1 The test solvent was a mixture of deuterated chloroform and trifluoroacetic acid, and PC ( Figure 2 The test solvent was deuterated chloroform) and the precursor ( Figure 3 The nuclear magnetic resonance (NMR) spectra of the precursor (using deuterated chloroform as the test solvent) showed significant changes in the chemical shifts of the benzene ring peaks in the original PET and PC, proving that the chain exchange reaction was successfully carried out. Furthermore, since PET raw materials are insoluble in deuterated chloroform, the fact that the precursor could dissolve in deuterated chloroform also demonstrates that the reaction occurred.

[0072] S2 Preparation of Regenerated Polymers

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

[0074] The obtained regenerated polymer A1 was found to have a number-average molecular weight of 28.1 kDa, and the nuclear magnetic resonance spectroscopy results showed that... Figure 4 The results show that the molar ratio of terephthalic acid units to repeating units in the new polyarylate (bisphenol A terephthalate) formed in the final product A1 is 0.61:0.39, meaning that 61% of the terephthalic acid units in the original PET have been converted into new polyarylate units. Furthermore, the collected liquid substance, i.e., the cyclic small molecule substance, was dried and separated using anhydrous sodium sulfate, and then subjected to nuclear magnetic resonance spectroscopy analysis. Specific results are shown in [Figure / Reference / Illustration]. Figure 5 In the test, the solvent was deuterated chloroform, and it is clear that the collected cyclic small molecule was ethylene carbonate.

[0075] Invention Embodiment 2

[0076] Example 2 of the invention is carried out according to the method of Example 1 of the invention, except that: polyethylene terephthalate (PET) in step S1 is replaced with polypropylene terephthalate (PTT, with a number average molecular weight of 25.7kDa as detected), and the resulting recycled polymer is denoted as A2.

[0077] According to the test results 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 nuclear magnetic resonance spectroscopy shows that the molar ratio of terephthalic acid units in the newly formed polyarylate to the repeating units 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 Embodiment 3

[0079] Example 2 of the invention is carried out according to the method of Example 1, except that the polyethylene terephthalate (PET) in step S1 is replaced with polybutylene oxalate (the number average molecular weight is 29.6 kDa). The resulting recycled polymer is denoted as A3.

[0080] Upon testing, in this embodiment of the invention, the number-average molecular weight of the precursor obtained in step S1 was 20.6 kDa. The number-average molecular weight of the regenerated polymer A3 obtained in step S2 was 30.2 kDa, and nuclear magnetic resonance spectroscopy showed that the molar ratio of succinic acid units to the repeating units of the residual polybutylene oxalate in the newly formed polyarylate was 0.79:0.21, meaning that 79% of the succinic acid units in the original PBS had been converted into new polyarylate units.

[0081] Invention Embodiment 4

[0082] Example 4 of the invention is carried out according to the method of Example 1 of the invention, except that: in step S1, polyethylene terephthalate (PET) is replaced with polybutylene oxalate, and bisphenol A type polycarbonate (PC) is replaced with polyethylene glycol (the number average molecular weight is 30.4 kDa). The resulting recycled polymer is denoted as A4.

[0083] Upon 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 nuclear magnetic resonance spectroscopy analysis shows that the molar ratio of ethylene glycol units in the newly formed polyether to the repeating units of the residual polyethylene glycol is 0.84:0.16, meaning that 84% of the ethylene glycol units in the original polyethylene glycol have been converted into new polyether units.

[0084] Invention Embodiment 5

[0085] Invention Example 2 is carried out according to the method of Invention Example 1, except that: in step S1, polyethylene terephthalate (PET) is replaced with polybutylene oxalate, and bisphenol A type polycarbonate (PC) is replaced with polyoxymethylene (with a number average molecular weight of 24.3 kDa). The resulting recycled polymer is denoted as A5.

[0086] According to the test results 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 nuclear magnetic resonance spectroscopy shows that the molar ratio of formaldehyde units in the newly formed polyether to the repeating units of the residual polyoxymethylene is 0.64:0.36, that is, 64% of the formaldehyde units in the original polyoxymethylene have been converted into new polyether units.

[0087] Invention Embodiment 6

[0088] Example 2 of the invention is carried out according to the method of Example 1 of the invention, except that: polyethylene terephthalate (PET) in step S1 is replaced with polyethylene glycol (the number average molecular weight is 30.4 kDa as detected), and the resulting recycled polymer is denoted as A6.

[0089] Upon 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 nuclear magnetic resonance spectroscopy analysis shows that the molar ratio of ethylene glycol units in the newly formed polyether to the repeating units of the residual polyethylene glycol is 0.67:0.33, meaning that 67% of the ethylene glycol units in the original polyethylene glycol have been converted into new polyether units.

[0090] Invention Embodiment 7

[0091] Invention Example 2 is carried out according to the method of Invention Example 1, except that: polyethylene terephthalate (PET) in step S1 is replaced with poly(1,2-propanediol) (the number average molecular weight is 21.3kDa). The resulting recycled polymer is denoted as A7.

[0092] Upon 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 nuclear magnetic resonance spectroscopy analysis shows that the molar ratio of 1,2-propanediol units in the newly formed polyether to the repeating units of the residual poly(1,2-propanediol) is 0.65:0.35, meaning that 65% of the 1,2-propanediol units in the original poly(1,2-propanediol) have been converted into new polyether units.

[0093] Embodiments 8 and 9 of the Invention

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

[0095] Upon testing, in Example 8 of the invention, the number-average molecular weight of the precursor obtained in step S1 was 20.9 kDa. The number-average molecular weight of the regenerated polymer A8 obtained in step S2 was 35.6 kDa, and nuclear magnetic resonance spectroscopy showed that the molar ratio of terephthalic acid units in the newly formed polyarylate to the repeating units of the residual PET was 0.80:0.20, meaning that 80% of the terephthalic acid units in the original PET had been converted into new polyarylate units.

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

[0097] Invention Examples 10-12

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

[0099] Upon testing, in Example 10 of the invention, the number-average molecular weight of the precursor obtained in step S1 was 18.3 kDa. The number-average molecular weight of the regenerated polymer A10 obtained in step S2 was 29.3 kDa, and nuclear magnetic resonance spectroscopy showed that the molar ratio of repeating terephthalic acid units to residual PET units in the newly formed polyarylate was 0.63:0.37, meaning that 63% of the terephthalic acid units in the original PET had been converted into new polyarylate units.

[0100] In Embodiment 11 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 A11 obtained in step S2 is 33.8 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of terephthalic acid units in the newly formed 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 Embodiment 12, the number-average molecular weight of the precursor obtained in step S1 is 16.1 kDa. The number-average molecular weight of the regenerated polymer A12 obtained in step S2 is 34.9 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of terephthalic acid units in the newly formed polyarylate to the repeating units in the residual PET is 0.83:0.17, meaning that 83% of the terephthalic acid units in the original PET have been converted into new polyarylate units.

[0102] Invention Embodiment 13

[0103] Example 13 of the invention is carried out according to the method of Example 1 of the invention, except that the reaction temperature in step S1 is replaced with 290°C, and the obtained regenerated polymer is referred to as A13.

[0104] Upon testing, in Example 13 of the invention, the number-average molecular weight of the precursor obtained in step S1 was 14.3 kDa. The number-average molecular weight of the regenerated polymer A13 obtained in step S2 was 33.7 kDa, and nuclear magnetic resonance spectroscopy showed that the molar ratio of terephthalic acid units in the newly formed polyarylate to the repeating units in the residual PET was 0.72:0.28, meaning that 72% of the terephthalic acid units in the original PET had been converted into new polyarylate units.

[0105] Invention Embodiment 14

[0106] Example 14 of the invention is carried out according to the method of Example 1 of the invention, except that the reaction temperature in step S2 is replaced with 280°C, and the obtained regenerated polymer is referred to as A14.

[0107] Upon testing, in Example 14 of the invention, the number-average molecular weight of the regenerated polymer A14 obtained in step S2 was 38.2 kDa, and nuclear magnetic resonance spectroscopy showed that the molar ratio of terephthalic acid units in the newly formed polyarylate to the repeating units in the residual PET was 0.68:0.32, meaning that 68% of the terephthalic acid units in the original PET had been converted into new polyarylate units.

[0108] Invention Examples 15-17

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

[0110] In Embodiment 15 of the invention, the number-average molecular weight of the regenerated polymer A15 obtained in step S2 is 29.4 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of terephthalic acid units in the newly formed 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] Upon testing, in Example 16 of the invention, the number-average molecular weight of the regenerated polymer A16 obtained in step S2 was 32.9 kDa, and nuclear magnetic resonance spectroscopy showed that the molar ratio of terephthalic acid units in the newly formed polyarylate to the repeating units of the residual PET was 0.78:0.22, meaning that 78% of the terephthalic acid units in the original PET had been converted into new polyarylate units.

[0112] In Embodiment 17 of the invention, the number-average molecular weight of the regenerated polymer A17 obtained in step S2 is 39.4 kDa, and nuclear magnetic resonance spectroscopy shows that the molar ratio of terephthalic acid units in the newly formed 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 evident from the above embodiments that the method of the present invention can effectively reuse waste polyester, polycarbonate and / or polyether, and the molecular weight of the recycled polymer can be controlled by adjusting a number of reaction parameters such as reaction time, temperature and composition of waste polymer, thereby obtaining recycled polymers with practical application value.

[0114] Furthermore, compared to traditional recycling methods, the waste polymer recycling method of this invention can directly utilize the mixture of waste polyester, polycarbonate, and polyether to synthesize recycled polymers without prior separation of polyester, polycarbonate, and polyether. The entire recycling process is simpler, more controllable, and more efficient, enabling the low-cost preparation of recycled polymers. In addition, the method of preparing high-performance recycled polymers from waste polyester, polycarbonate, and polyether can be carried out under solvent-free conditions, overcoming the problems of difficult removal of small molecules, low polymerization degree, and insufficient product molecular weight in traditional melt polymerization methods. Moreover, the generated cyclic small molecules can be collected for reuse, achieving recyclability and conforming to the atom economy principle of green chemistry.

[0115] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can 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 protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for synthesizing a recycled polymer using waste polyesters, polycarbonates and / or polyethers, characterized in that, Comprising the following steps: S1. Preparation of a precursor: a waste polymer mixture is subjected to a chain exchange reaction in the presence of a catalyst after being melted to obtain a precursor; S2. Preparation of a regenerated polymer: the precursor prepared in step S1 is subjected to a ring formation reaction and removal of cyclic small molecules to obtain a regenerated polymer, wherein the waste polymer mixture comprises a first composition comprising a polyester having a first repeating unit derived from a dibasic acid and / or a dibasic ester represented by the following formula (U1) and a polycarbonate and / or a polyether having a second repeating unit derived from a dibasic alcohol and / or a dibasic alcohol ester represented by the following formula (U3) and / or (U4), or a polyester having a first repeating unit derived from a dibasic acid and / or a dibasic ester represented by the following formula (U2) and a polycarbonate and / or a polyether having a second repeating unit derived from a dibasic alcohol and / or a dibasic alcohol ester represented by the following formula (U3), wherein R1, R2, R3, R4, R5, R 16 , R 19 , R 20 may be the same or different and are each independently selected from the group consisting of hydrogen, alkyl, R 15 , R 17 , R 18 , R 21 may be the same or different and are each independently selected from the group consisting of hydrogen, acyl; or, the waste polymer mixture comprises a second composition comprising a polycarbonate having a carbonate group per se and a polyester and / or a polyether having a third repeating unit derived from a dibasic alcohol and / or a dibasic alcohol ester represented by the following formula (U5) and / or (U6), wherein R7, R8, R 11 , R 12 , R 13 may be the same or different and are each independently selected from hydrogen, alkyl, R6, R9, R 10 , R 14 may be the same or different and are each independently selected from hydrogen, acyl.

2. The method of claim 1, wherein, the alkyl group is an unsubstituted or substituted linear, branched or cyclic alkyl group consisting of 1 to 18 carbon atoms.

3. The method of claim 1, wherein, the alkyl group is an unsubstituted or substituted linear, branched or cyclic alkyl group consisting of 1 to 6 carbon atoms.

4. The method of claim 1, wherein, the alkyl group is an unsubstituted or halogen mono- or poly-substituted linear, branched or cyclic alkyl group consisting of 1 to 4 carbon atoms.

5. The method of claim 1, wherein, The chain exchange reaction in step S1 is carried out under the following conditions: an inert atmosphere, a temperature of 150-300°C, and a time of 0.5-24 hours.

6. The method of claim 1, wherein, 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 of claim 1, wherein, 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 of claim 1, wherein, The ring formation reaction in step S2 is carried out under the following conditions: a pressure of 1000 Pa to 1 Pa, a temperature of 200-300°C, and a reaction time of 0.5-24 hours.

9. The method of claim 1, wherein, The catalyst used for the chain exchange reaction in step S1 is the same as the catalyst used for the ring formation reaction in step S2, which is a Lewis acid of tin, zinc, magnesium, titanium, antimony, scandium, iron, cobalt, nickel.

10. A recycled polymer characterized in that, Obtained by the method of any one of claims 1-9.

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