Readily recyclable PETG copolyester, heat-shrinkable film containing same and recycling method therefor

Abstract

Disclosed in the present application are an readily recyclable PETG copolyester, a heat-shrinkable film containing same and a recycling method therefor. In the present application, a certain proportion of a fourth monomer is introduced during the synthesis of the PETG copolyester, and a certain proportion of a plastic degradation masterbatch is introduced in each layer during the preparation of a PETG heat-shrinkable film; and by flexibly controlling the chemical alcoholysis process of the heat‑shrinkable film and in combination with a three‑step alcoholysis process, deep chemical alcoholysis of the heat‑shrinkable film can be achieved, facilitating better closed loop recycling within the PETG industrial chain, thereby realizing the free production of a high-performance recyclable heat-shrinkable film, reducing the recycling costs of PETG heat-shrinkable films, and producing a PETG heat-shrinkable film with great aging resistance, and thus significantly enhancing the efficiency of enterprises.

Description

Recyclable petg copolyester, heat-shrinkable film containing the same and recycling method thereof

[0001] The present application claims priority to the Chinese patent application No. CN202411252502.3, filed on September 9, 2024, and entitled "Recyclable PETG copolyester, heat-shrinkable film containing the same and recycling method thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of polymer synthesis and processing, in particular to a recyclable PETG copolyester, a heat-shrinkable film containing the same and a recycling method thereof. BACKGROUND

[0003] The heat-shrinkable film refers to a label used for wrapping around the outer periphery of a container, including plastic bottles, glass bottles, etc. The heat-shrinkable film has good gloss, adhesion and shrinkage properties, and due to the gloss and shrinkage of the heat-shrinkable film, the packaging patterns on the container are more vivid, and the image on the supermarket shelf is more prominent, producing an unexpected shelf effect, and the heat-shrinkable film is widely used for packaging containers.

[0004] The materials of the existing heat-shrinkable film for labels mainly include polyvinyl chloride (PVC), polyethylene terephthalate-1, 4-cyclohexane dimethanol (PETG), oriented polystyrene (OPS), etc. Among them, the PETG heat-shrinkable film has high shrinkage, good transparency, no toxicity, no odor, good mechanical properties, excellent printing performance, and relatively low self-shrinkage, and is relatively storage-resistant, especially in line with environmental protection, etc. In developed countries, the PETG heat-shrinkable film has successfully replaced the polyvinyl chloride heat-shrinkable film and become the most ideal heat-shrinkable packaging material. However, with the large-scale use of PETG copolyester materials, effective recycling and reuse of the materials has become an urgent demand.

[0005] At present, the recycling methods of PETG copolyester materials mainly include physical recycling, biological enzymatic recycling and chemical recycling, etc. Among them, the chemical recycling method is considered to have the highest value in the industry. This method usually uses alcoholysis or thermal cracking method to heat treat the polyester materials to produce terephthalate glycol monomer (BHET), and then regenerate by feeding glycol. The process technology is relatively mature, and the defects such as serious degradation and color yellowing of the polyester materials after multiple recycling and processing are solved.

[0006] The cracking process is carried out in a cracking kettle. The large amount of raw material makes it difficult to ensure that all polyester fragments are uniformly heated and cracked into BHET. Therefore, a large proportion of BHET dimers, trimers or even multimers will replace BHET monomers in the cracking process. The dimers or multimers will have a lot of thermal stress due to long-time heating, which will be transmitted to the newly generated products during the polymerization process. If no improvement is made, the mechanical properties of the produced film products will be poor, which cannot meet the use requirements. Therefore, the recycled polyester material cannot be effectively utilized in product processing, especially in the heat shrinkable film industry. Therefore, how to solve the above problems has become a key technical problem for high-value recycling and utilization of recycled polyester materials in the heat shrinkable film industry. SUMMARY

[0007] In view of the defects of the prior art, the purpose of the present application is to provide an easily recyclable PETG copolyester with high cracking degree, which can be recycled and utilized, and has strong mechanical properties and aging resistance after recycling, and a heat shrinkable film containing the same and a recycling method thereof.

[0008] Technical scheme:

[0009] An easily recyclable PETG copolyester is prepared by copolymerizing 35-40% of terephthalic acid, 45-50% of ethylene glycol, 5-15% of neopentyl glycol and 5-15% of a fourth monomer, based on a molar content of 100%.

[0010] Further, the fourth monomer is selected from at least one of polypropylene glycol, polyethylene glycol, polyether glycol, polybutylene glycol, polyhexylene glycol, dodecyl glycol and octanediol.

[0011] By introducing a certain proportion of the fourth monomer in the process of synthesizing the PETG copolyester, the present application can absorb heat during thermal cracking, improve the cracking degree of the PETG copolyester, and thus reduce the content of BHET dimers, trimers or even multimers after thermal cracking, and reduce the influence of the dimers or multimers on the material properties and the subsequent recycling ability after recycling. The recycling ability of the PETG copolyester can be effectively improved.

[0012] Further, the easily recyclable PETG copolyester is prepared by the following steps:

[0013] (1) Esterification: In a reactor, terephthalic acid, ethylene glycol, neopentyl glycol and the fourth monomer are added in proportion, and esterification is carried out at a temperature of 245-265℃. The reaction time is 2-3 hours. After the reaction is completed, the excess reactants are distilled to obtain an esterification product;

[0014] (2) polycondensation: the esterification product is subjected to polycondensation at 270-285℃ under catalyst conditions at a pressure of 0.1-10kPa, the reaction time is 3-5 hours, after the reaction, cooling, filtration, washing, and drying, the easily recyclable PETG copolyester is obtained.

[0015] The heat-shrinkable film comprises the easily recyclable PETG copolyester, and has a three-layer composite structure comprising a surface film layer and a core film layer sandwiched between two surface film layers.

[0016] The total thickness of the heat-shrinkable film is 20-50μm, and the thickness of the surface film layer is 2-5μm.

[0017] The heat-shrinkable film has a longitudinal shrinkage of 1-30% and a transverse shrinkage of 50-80%.

[0018] The surface film layer material comprises, by weight fraction, 80-95 parts of the easily recyclable PETG copolyester, 5-10 parts of a plastic degradation masterbatch, and 2-6 parts of an opening agent.

[0019] The core film layer material comprises, by weight fraction, 55-75 parts of the easily recyclable PETG copolyester, 20-30 parts of a white masterbatch, and 5-10 parts of a plastic degradation masterbatch.

[0020] Further, the opening agent is silicon dioxide, the white masterbatch is titanium dioxide, and the plastic degradation masterbatch is selected from one of polylactic acid or a polylactic acid derivative.

[0021] The present application can make the heat-shrinkable film disintegrate during thermal cracking by introducing a certain proportion of plastic degradation masterbatch into each layer of the heat-shrinkable film, thereby significantly improving the cracking degree of the PETG copolyester, improving the recyclability, and the product after cracking is uniform and stable, which can effectively improve the stability of the PETG copolyester produced again, and improve the aging resistance.

[0022] Further, the plastic degradation masterbatch is prepared by graft copolymerization of polylactic acid and itaconic acid under the condition of an initiator, and the initiator is selected from one of benzoyl peroxide or dibenzoyl peroxide.

[0023] The present application can improve the mechanical properties of the PETG copolyester by using the itaconic acid-modified polylactic acid as a plastic degradation masterbatch, and can improve the disintegration ability of the heat-shrinkable film, thereby further improving the recyclability of the PETG copolyester.

[0024] Further, the heat shrinkable film is prepared by the following steps: by a three-layer co-extrusion biaxial stretching production process, the core film layer material and the surface film layer material are respectively supplied, mixed, melted and plasticized, and filtered and extruded, and then the heat shrinkable film is prepared after casting, longitudinal stretching, transverse stretching, edge cutting and winding.

[0025] Further, the core film layer filtering extrusion temperature is 240-260℃, and the surface film layer filtering extrusion temperature is 245-265℃.

[0026] In the longitudinal stretching, the preheating temperature is 90-100℃, the longitudinal stretching temperature is 80-90℃, the longitudinal stretching ratio is 1.0-3.0, the longitudinal stretching setting temperature is 70-85℃, and the longitudinal stretching setting time is 2-5 seconds.

[0027] In the transverse stretching, the preheating temperature is 100-120℃, the transverse stretching temperature is 80-100℃, the transverse stretching ratio is 4-5.5 times, the transverse stretching setting temperature is 70-85℃, and the transverse stretching setting time is 5-10 seconds.

[0028] The recycling method of the heat shrinkable film containing the easily recyclable PETG copolyester according to any one of the above, comprising the following steps:

[0029] (1) The waste heat shrinkable film containing the easily recyclable PETG copolyester is pyrolyzed in the first kettle, and after being treated by the filtering system, it is transported to the second kettle, then the fourth monomer in the easily recyclable PETG copolyester is pyrolyzed in the second kettle, and after being treated by the filtering system, it is transported to the third kettle, and finally the second kettle reaction component is deeply pyrolyzed in the third kettle;

[0030] (2) According to the molar content of 100%, 35-40% of the product of step (1) deep pyrolysis, 45-50% of ethylene glycol, 5-15% of neopentyl glycol and 5-15% of the fourth monomer are esterified and polycondensed to prepare the easily recyclable PETG copolyester;

[0031] (3) The easily recyclable PETG copolyester prepared in step (2) is made into a heat shrinkable film containing the easily recyclable PETG copolyester according to claims 4-8 again, and after being discarded, it is recycled and subjected to step (1) again.

[0032] The present application can realize the recycling and reuse of PETG copolyester material by preparing the easily recyclable PETG copolyester, preparing the heat shrinkable film containing the same, and the corresponding pyrolysis recycling method, reduce the recycling and reuse cost of PETG heat shrinkable film, and the recycled heat shrinkable film has excellent mechanical properties and aging resistance, which can greatly improve the efficiency of enterprises.

[0033] Further, the thermal cracking temperature of the first kettle in step (1) is 220-240°C, and the time is 1-2 hours; the thermal cracking temperature of the second kettle is 250-270°C, and the time is 1-2 hours; the thermal cracking temperature of the third kettle is 280-300°C, and the time is 1-2 hours.

[0034] The thermal cracking in step (1) is carried out in an ethylene glycol environment with the introduction of inert gas and a pressure of 1-10 kPa. Beneficial effects:

[0035] (1) The easily recyclable PETG copolyester and the heat-shrinkable film containing the same and the recycling method thereof provided in the present application introduce a certain proportion of a fourth monomer in the process of synthesizing the PETG copolyester and introduce a certain proportion of plastic degradation masterbatch in each layer in the process of preparing the PETG heat-shrinkable film, flexibly control the chemical alcoholysis process of the heat-shrinkable film, and realize deep chemical alcoholysis of the heat-shrinkable film by means of a three-step alcoholysis method, better breaking through the recycling process of the PETG industrial chain, realizing free preparation of high-performance recyclable heat-shrinkable film, reducing the recycling cost of the PETG heat-shrinkable film, and the PETG heat-shrinkable film prepared by the process has good aging resistance, greatly improving the efficiency of enterprises.

[0036] (2) In the easily recyclable PETG copolyester provided in the present application, a certain proportion of a fourth monomer is introduced in the process of synthesizing the PETG copolyester, which can absorb heat in the thermal cracking process, improve the cracking degree of the PETG copolyester, and thus reduce the content of BHET dimers, trimers or even polymers after thermal cracking, reduce the influence of the dimers or polymers after recycling on the material performance and the subsequent recycling ability, and effectively improve the recycling ability of the PETG copolyester.

[0037] (3) In the easily recyclable PETG copolyester provided in the present application, a certain proportion of plastic degradation masterbatch is introduced into each layer of the heat-shrinkable film, which can make the heat-shrinkable film disintegrate in the thermal cracking process, thereby significantly improving the cracking degree of the PETG copolyester, improving its recyclability, and the material quality of the cracked product is uniform and stable, which can effectively improve the stability of the PETG copolyester prepared again, and improve the aging resistance.

[0038] (4) In the easily recyclable PETG copolyester provided in the present application, the polylactic acid is modified with itaconic acid as a plastic degradation masterbatch, which can improve the mechanical properties of the PETG copolyester after being added to the PETG copolyester, and can improve the disintegration ability of the polylactic acid to the heat-shrinkable film, further improving the recyclability of the PETG copolyester.

[0039] (5) The application provides a recycling method of the easy-to-recycle PETG copolyester and the heat-shrinkable film containing the same. The recycling method of the PETG copolyester material can be realized by preparing the easy-to-recycle PETG copolyester, preparing the heat-shrinkable film containing the same, and the corresponding thermal cracking recycling method, the recycling cost of the PETG heat-shrinkable film is reduced, the heat-shrinkable film recycled has excellent mechanical properties and aging resistance, and the efficiency of enterprises can be greatly improved. DETAILED DESCRIPTION

[0040] The application will be described below in combination with specific embodiments. It should be noted that the following examples are examples of the application and are only used to illustrate the application, but not to limit the application. Other combinations and various modifications within the concept of the application can be made without departing from the spirit or scope of the application. The reagents and equipment in the application are conventional reagents and equipment in the technical field.

[0041] Preparation of itaconic acid grafted polylactic acid

[0042] The itaconic acid grafted polylactic acid is prepared by the following steps:

[0043] 10 g of polylactic acid and 50 mL of dimethylbenzene are added to a reactor, nitrogen is introduced, heated to 90℃, and after stirring until the polylactic acid is completely dissolved, 4 g of itaconic acid and 0.3 g of benzoyl peroxide are added. After 8 hours of reaction, cooling, washing and drying are carried out to obtain the itaconic acid grafted polylactic acid.

[0044] Example 1

[0045] S1. The easy-to-recycle PETG copolyester is prepared by the following steps:

[0046] (1) Esterification: in a reactor, 35% of terephthalic acid, 45% of ethylene glycol, 10% of neopentyl glycol and 10% of polyethylene glycol are added according to a molar content of 100%, and an esterification reaction is carried out at a temperature of 250℃. The reaction time is 2.5 hours. After the reaction is completed, the excess reactants are distilled to obtain an esterification product;

[0047] (2) Polycondensation: the esterification product is polycondensed at 275℃ under the condition of a catalyst and within a pressure range of 5kPa. The reaction time is 4 hours. After the reaction is completed, cooling, filtration, washing and drying are carried out to obtain the easy-to-recycle PETG copolyester;

[0048] S2. The heat-shrinkable film containing the easy-to-recycle PETG copolyester is prepared by the following steps:

[0049] The core film layer material and the surface film layer material are respectively supplied, mixed, melted and plasticized, and filtered and extruded by a three-layer co-extrusion biaxial stretching production process, and then the heat-shrinkable film is obtained after casting, longitudinal stretching, transverse stretching, edge cutting and winding;

[0050] The surface film layer material comprises 92 parts of the recyclable PETG copolyester, 6 parts of itaconic acid grafted polylactic acid and 2 parts of silicon dioxide by weight;

[0051] The core film layer material comprises 69 parts of the recyclable PETG copolyester, 25 parts of titanium dioxide and 6 parts of itaconic acid grafted polylactic acid by weight;

[0052] Further, the filtering extrusion temperature of the core film layer material is 260℃, and the filtering extrusion temperature of the surface film layer material is 265℃;

[0053] In the longitudinal stretching, the preheating temperature is 95℃, the longitudinal stretching temperature is 81℃, the longitudinal stretching ratio is 1.01, the longitudinal stretching setting temperature is 85℃, and the setting time is 3 seconds;

[0054] In the transverse stretching, the preheating temperature is 105℃, the transverse stretching temperature is 90℃, the transverse stretching ratio is 4.8 times, the transverse stretching setting temperature is 85℃, and the transverse stretching setting time is 8 seconds;

[0055] The recyclable PETG copolyester-containing heat-shrinkable film prepared has a three-layer composite structure with a layer thickness of 40μm, wherein the surface film layer has a thickness of 5μm, the longitudinal shrinkage rate is 20%, and the transverse shrinkage rate is 60%;

[0056] S3. Recycling the waste recyclable PETG copolyester-containing heat-shrinkable film:

[0057] (1) The waste recyclable PETG copolyester-containing heat-shrinkable film is subjected to thermal cracking in the first kettle at a temperature of 230℃ for 1.5 hours, and then is transported to the second kettle after being treated by a filtering system, and then the fourth monomer in the recyclable PETG copolyester is subjected to thermal cracking in the second kettle at a temperature of 260℃ for 2 hours, and then is transported to the third kettle after being treated by a filtering system, and finally the reaction components in the second kettle are subjected to deep thermal cracking in the third kettle at a temperature of 280℃ for 2 hours, all the cracking processes are carried out in ethylene glycol, inert gas is introduced in all stages, and the pressure is 8kPa, wherein the inert gas is nitrogen;

[0058] (2) The recyclable PETG copolyester is prepared by esterification and polycondensation of 35% of the deep thermal cracking product of step (1), 45% of ethylene glycol, 10% of neopentyl glycol and 10% of polyethylene glycol based on a molar content of 100%;

[0059] (3) The recyclable PETG copolyester prepared in step (2) is used to prepare the recyclable PETG copolyester-containing heat-shrinkable film again according to step S2.

[0060] Example 2

[0061] The same as example 1, except that the molar ratio of polyethylene glycol in step S1 is adjusted to 5%, terephthalic acid accounts for 37.5%, ethylene glycol accounts for 47.5%, and neopentyl glycol accounts for 10%.

[0062] Example 3

[0063] The same as example 1, except that the surface film layer material in step S2 includes 89 parts of recyclable PETG copolyester, 9 parts of polylactic acid, and 2 parts of silicon dioxide; and the core film layer material includes 66 parts of recyclable PETG copolyester, 25 parts of titanium dioxide, and 9 parts of polylactic acid.

[0064] Example 4

[0065] The same as example 1, except that in step S3, two-kettle alcoholysis preparation is adopted, the first kettle is controlled at a temperature of 260°C for 3.5 hours, and after being treated by a filtering system, it is delivered to the second kettle; the second kettle performs deep thermal cracking on the reaction components of the first kettle, and the temperature is controlled at 280°C for 2 hours.

[0066] Comparative Example 1

[0067] The same as example 1, except that in step S1, the components and contents are changed to 40% terephthalic acid, 50% ethylene glycol, and 10% neopentyl glycol; and in step S3, two-kettle alcoholysis preparation is adopted, the first kettle is controlled at a temperature of 260°C for 3.5 hours, and after being treated by a filtering system, it is delivered to the second kettle; the second kettle performs deep thermal cracking on the reaction components of the first kettle, and the temperature is controlled at 280°C for 2 hours.

[0068] Comparative Example 2

[0069] The same as example 1, except that in step S2, the surface film layer material includes 98 parts of recyclable PETG copolyester and 2 parts of silicon dioxide; and the core film layer material includes 75 parts of recyclable PETG copolyester and 25 parts of titanium dioxide; and in step S3, two-kettle alcoholysis preparation is adopted, the first kettle is controlled at a temperature of 260°C for 3.5 hours, and after being treated by a filtering system, it is delivered to the second kettle; the second kettle performs deep thermal cracking on the reaction components of the first kettle, and the temperature is controlled at 280°C for 2 hours.

[0070] Comparative Example 3

[0071] The same as example 1, except that in step S1, the components and contents are changed to 40% terephthalic acid, 50% ethylene glycol and 10% neopentyl glycol; in step S2, the surface film layer material comprises 98 parts of recyclable PETG copolyester and 2 parts of silicon dioxide; the core film layer material comprises 75 parts of recyclable PETG copolyester and 25 parts of titanium dioxide; in step S3, a one-pot glycolysis process is used to prepare, and the heat shrinkable film is placed in an ethylene glycol environment at a temperature of 280°C for 5.5 hours.

[0072] Performance test

[0073] The heat shrinkable films containing recyclable PETG copolyester prepared in step S3 of examples 1-4 and comparative examples 1-3 are respectively aged and stored in an aging oven at 55°C and 60% humidity for 7 days, and then the mechanical property test is performed using a universal testing machine, and the time when the fracture occurs is recorded.

[0074] The test results are as follows:

[0075] According to the comparison of the test results of examples 1-4 and comparative examples 1-3, it can be seen that the recyclable PETG copolyester and the heat shrinkable film containing the same and the recycling method provided by the present application, by introducing a certain proportion of the fourth monomer in the synthesis of PETG copolyester, and introducing a certain proportion of plastic degradation masterbatch in each layer during the preparation of PETG heat shrinkable film, the flexible control of the chemical glycolysis process of the heat shrinkable film, the three-step glycolysis method realizes the deep chemical glycolysis of the heat shrinkable film, better connects the recycling process of the PETG industry chain, realizes the free preparation of high-performance recyclable heat shrinkable film, reduces the recycling cost of PETG heat shrinkable film, and the PETG heat shrinkable film prepared by the process has good aging resistance and mechanical properties.

[0076] The above embodiments are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application, any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A recyclable PETG copolyester characterized in that, The fourth monomer is selected from at least one of polypropylene glycol, polyethylene glycol, polyether glycol, polybutylene glycol, polyhexylene glycol, dodecyl glycol, and octanediol.

2. The recyclable PETG copolyester of claim 1, wherein, The fourth monomer is selected from at least one of polypropylene glycol, polyethylene glycol, polyether glycol, polybutylene glycol, polyhexylene glycol, dodecyl glycol, and octanediol.

3. The recyclable PETG copolyester of claim 1, wherein, The easily recyclable PETG copolyester is prepared by the following steps: (1) esterification: in a reactor, terephthalic acid, ethylene glycol, neopentyl glycol, and the fourth monomer are added in proportion, and esterification is carried out at a temperature of 245-265°C, the reaction time is 2-3 hours, after the reaction is completed, the excess reactants are distilled to obtain an esterification product; (2) polycondensation: the esterification product is subjected to polycondensation under the condition of a catalyst at a temperature of 270-285°C and a pressure of 0.1-10 kPa, the reaction time is 3-5 hours, after the reaction is completed, cooling, filtration, washing, and drying are carried out to obtain the easily recyclable PETG copolyester.

4. A heat shrinkable film comprising the recyclable PETG copolyester of any one of claims 1-3, characterized in that, The heat-shrinkable film is a three-layer composite structure, comprising a surface film layer and a core film layer sandwiched between two surface film layers; The total thickness of the heat-shrinkable film is 20-50 μm; the thickness of the surface film layer is 2-5 μm; The longitudinal shrinkage rate of the heat-shrinkable film is 1-30%, and the transverse shrinkage rate is 50-80%; The surface film layer material comprises, by weight fraction, 80-95 parts of the easily recyclable PETG copolyester, 5-10 parts of a plastic degradation masterbatch, and 2-6 parts of an opening agent; The core film layer material comprises, by weight fraction, 55-75 parts of the easily recyclable PETG copolyester, 20-30 parts of a white masterbatch, and 5-10 parts of a plastic degradation masterbatch.

5. The heat shrinkable film according to claim 4, characterized in that, The opening agent is silicon dioxide; the white masterbatch is titanium dioxide; and the plastic degradation masterbatch is selected from one of polylactic acid or a polylactic acid derivative.

6. The heat shrinkable film according to claim 5, characterized in that, The plastic degradation masterbatch is prepared by graft copolymerization of polylactic acid and itaconic acid under the condition of an initiator; the initiator is selected from one of benzoyl peroxide or dibenzoyl peroxide.

7. The heat shrinkable film according to claim 4, wherein, The heat-shrinkable film is prepared by the following steps: the core film layer material and the surface film layer material are respectively fed, mixed, melt-plasticized, and filtered and extruded by a three-layer co-extrusion biaxial stretching production process, and then the heat-shrinkable film is obtained after casting, longitudinal stretching, transverse stretching, edge cutting, and winding.

8. The heat shrinkable film according to claim 7, characterized in that, The filtering and extruding temperature of the core film layer is 240°C-260°C, and the filtering and extruding temperature of the surface film layer is 245°C-265°C; In the longitudinal stretching, the preheating temperature is 90-100°C, the longitudinal stretching temperature is 80°C-90°C, the longitudinal stretching ratio is 1.0-3.0, the longitudinal stretching setting temperature is 70°C-85°C, and the longitudinal stretching setting time is 2-5 seconds; In the transverse stretching, the preheating temperature is 100-120°C, the transverse stretching temperature is 80°C-100°C, the transverse stretching ratio is 4-5.5 times, the transverse stretching setting temperature is 70°C-85°C, and the transverse stretching setting time is 5-10 seconds.

9. The recycling method of the heat-shrinkable film containing the recyclable PETG copolyester according to any one of claims 4 to 8, characterized in that, The method comprises the following steps: (1) the waste heat-shrinkable film containing the recyclable PETG copolyester is pyrolyzed in the first kettle, and after being treated by a filtering system, is delivered to the second kettle, then the fourth monomer in the recyclable PETG copolyester is pyrolyzed in the second kettle, and after being treated by a filtering system, is delivered to the third kettle, and finally the reaction components in the second kettle are deeply pyrolyzed in the third kettle; (2) the product of the deep pyrolysis in step (1) is 35-40% by molar content, 45-50% of ethylene glycol, 5-15% of neopentyl glycol and 5-15% of the fourth monomer are esterified and polycondensed to obtain the recyclable PETG copolyester; (3) the recyclable PETG copolyester obtained in step (2) is made into the heat-shrinkable film containing the recyclable PETG copolyester again according to claims 4-8, and after being discarded, is recycled and subjected to step (1) again.

10. The method of recycling a heat-shrinkable film containing recyclable PETG copolyester according to claim 9, characterized in that, The pyrolysis temperature of the first kettle in step (1) is 220-240℃, and the time is 1-2 hours; the pyrolysis temperature of the second kettle is 250-270℃, and the time is 1-2 hours; the pyrolysis temperature of the third kettle is 280-300℃, and the time is 1-2 hours; The pyrolysis in step (1) is carried out in an ethylene glycol environment with inert gas being introduced and the pressure being 1-10 kPa.

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