Easy-to-recycle PETG copolyester and heat shrinkable film containing the same and recycling method thereof

Abstract

The present invention discloses an easily recyclable PETG copolyester and a heat shrinkable film containing the same and a recycling method thereof. The present invention introduces a certain proportion of the fourth monomer in the process of synthesizing the PETG copolyester, and introduces a certain proportion of plastic degradation masterbatch in each layer in the process of preparing the PETG heat shrinkable film, flexibly controls the chemical alcoholysis process of the heat shrinkable film, and realizes deep chemical alcoholysis of the heat shrinkable film by using a three-step alcoholysis method, better opens up the circulation process of the PETG industrial chain, realizes the free preparation of high-performance recyclable heat shrinkable films, reduces the recycling cost of the PETG heat shrinkable film, and the PETG heat shrinkable film prepared by the process has good aging resistance, which greatly improves the benefits of the enterprise.

Description

Technical Field

[0001] The invention relates to the technical field of polymer synthesis and processing, and in particular to an easily recyclable PETG copolyester and a heat shrinkable film containing the same and a recycling method thereof. Background Art

[0002] Heat shrink film refers to the label used to wrap around the outer circumference of the container, including plastic bottles, glass bottles, etc. Heat shrink film has good gloss, fit and shrinkage properties, and due to the gloss and shrinkage of heat shrink film, the packaging pattern on the container is more vivid, which can better highlight the image on the supermarket shelves, creating an unexpected container effect, and is widely used in container packaging.

[0003] The existing heat shrinkable film materials for labels mainly include polyvinyl chloride (PVC), polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG), oriented polystyrene (OPS), etc. Among them, PETG heat shrinkable film has successfully replaced polyvinyl chloride heat shrinkable film in developed countries and become the most ideal heat shrinkable packaging material because of its high shrinkage rate, good transparency, non-toxicity, odorlessness, good mechanical properties, excellent printing performance, low self-shrinkage rate, relatively durable storage, and especially environmental protection. However, with the large-scale use of PETG copolyester materials, it has become an urgent need to effectively recycle and reuse them.

[0004] At present, the recycling and reuse methods of PETG copolyester materials are mainly divided into physical recycling, bio-enzymatic recycling and chemical recycling. Among them, the chemical recycling method is recognized by the industry as the most valuable. This method usually uses alcoholysis or thermal cracking to heat treat the polyester material to produce ethylene terephthalate monomer (BHET), and then add diol for regeneration. The process technology is relatively mature, and it can solve the defects of severe degradation and yellowing of polyester materials after multiple recycling and processing.

[0005] The cracking process is carried out in a cracking kettle. The large amount of raw materials makes it difficult to ensure that all polyester fragments are heated uniformly and cracked into BHET. Therefore, a large proportion of BHET dimers, trimers or even polymers will replace BHET monomers during the cracking process. Due to long-term heating, dimers or polymers will have more thermal stress, and this thermal stress will be transmitted to the newly generated products during the repolymerization process. If no improvement is made, the produced film products will have poor mechanical properties and cannot meet the use requirements. Therefore, the recycled polyester materials cannot be effectively used in product processing, especially in the heat shrink film industry. Therefore, how to solve the above problems has become a key technical problem for the high-value recycling and utilization of recycled polyester materials in the heat shrink film industry. Summary of the invention

[0006] In view of the defects of the prior art, the object of the present invention is to provide an easily recyclable PETG copolyester with a high degree of cracking, which can be recycled and reused, and has strong mechanical properties and aging resistance after recycling, and a heat shrinkable film containing the same and a recycling method thereof.

[0007] Technical solution:

[0008] The invention discloses an easily recyclable PETG copolyester, which 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%.

[0009] Furthermore, the fourth monomer is selected from at least one of polypropylene glycol, polyethylene glycol, polyether glycol, polybutylene glycol, polyhexylene glycol, dodecane glycol and octanediol.

[0010] The present invention introduces a certain proportion of the fourth monomer 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 further reduce the content of BHET dimers, trimers and even polymers after the thermal cracking, reduce the influence of the recovered dimers or polymers on the material properties and the subsequent recycling and reuse capacity, and can effectively improve the recycling capacity of the PETG copolyester.

[0011] Further, the easily recyclable PETG copolyester is prepared by the following steps:

[0012] (1) Esterification: Add terephthalic acid, ethylene glycol, neopentyl glycol and the fourth monomer in proportion to the reactor, and carry out esterification reaction at a temperature of 245-265°C for 2-3 hours. After the reaction is completed, distill off the excess reactants to obtain the esterification product;

[0013] (2) Polycondensation: The esterification product is subjected to polycondensation at 270-285°C under catalyst conditions and within a pressure range of 0.1-10 kPa for a reaction time of 3-5 hours. After the reaction is completed, the easily recyclable PETG is obtained by cooling, filtering, washing and drying.

[0014] A heat shrinkable film comprising any one of the above-mentioned easily recyclable PETG copolyesters, wherein the heat shrinkable film is a three-layer composite structure, including a surface film layer and a core film layer sandwiched between two surface film layers;

[0015] The total thickness of the heat shrinkable film is 20-50 μm; the thickness of the surface film layer is 2-5 μm;

[0016] The longitudinal shrinkage rate of the heat shrinkable film is 1-30%, and the transverse shrinkage rate is 50-80%;

[0017] The surface film layer material comprises 80-95 parts of easily recyclable PETG, 5-10 parts of plastic degradation masterbatch and 2-6 parts of anti-blocking agent by weight;

[0018] In terms of weight, the core film layer material comprises 55-75 parts of easily recyclable PETG, 20-30 parts of white masterbatch and 5-10 parts of plastic degradation masterbatch.

[0019] Furthermore, 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 polylactic acid derivatives.

[0020] The invention introduces a certain proportion of plastic degradation masterbatch into each layer of the heat shrinkable film, so that the heat shrinkable film can be disintegrated in the thermal cracking process, thereby significantly improving the cracking degree of PETG copolyester and improving its recyclability. The material of the cracked product is uniform and stable, which can effectively improve the stability of the PETG copolyester made again and improve the aging resistance.

[0021] Furthermore, the plastic degradation masterbatch is prepared by graft copolymerization of polylactic acid and itaconic acid under initiator conditions; the initiator is selected from one of benzoyl peroxide and dibenzoyl peroxide.

[0022] The invention uses itaconic acid to modify polylactic acid as a plastic degradation masterbatch, and after adding it to PETG copolyester, the mechanical properties of the masterbatch can be improved, and the disintegration ability of the polylactic acid on the heat shrinkable film can be improved, thereby further improving the recyclability of the PETG copolyester.

[0023] Furthermore, the heat shrinkable film is prepared by the following steps: through a three-layer co-extrusion biaxial stretching production process, the core film layer material and the surface film layer material are respectively fed, mixed, melt-plasticized and filtered and extruded, and then the heat shrinkable film is obtained after cast film, longitudinal stretching, transverse stretching, trimming and winding.

[0024] Furthermore, the filtration extrusion temperature of the core film layer is 240°C-260°C, and the filtration extrusion temperature of the surface film layer is 245°C-265°C;

[0025] The preheating temperature in the longitudinal stretching 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;

[0026] 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.

[0027] Any of the above-mentioned methods for recycling heat shrinkable films containing easily recyclable PETG copolyester comprises the following steps:

[0028] (1) In the first kettle, the discarded heat shrinkable film containing easily recyclable PETG copolyester is thermally cracked, and after being treated by a filtration system, it is transported to a second pyrolysis kettle, and then in the second kettle, the fourth monomer in the easily recyclable PETG copolyester is thermally cracked, and after being treated by a filtration system, it is transported to a third pyrolysis kettle, and finally, in the third kettle, the reaction components in the second kettle are deeply thermally cracked;

[0029] (2) based on a molar content of 100%, 35-40% of the product of the deep thermal cracking of step (1) is esterified and polycondensed with 45-50% of ethylene glycol, 5-15% of neopentyl glycol and 5-15% of a fourth monomer to obtain an easily recyclable PETG copolyester;

[0030] (3) The easily recyclable PETG copolyester obtained in step (2) is made into a heat shrinkable film containing the easily recyclable PETG copolyester again according to claims 4-8, and then the film is discarded and recycled to perform step (1) again.

[0031] The invention prepares easily recyclable PETG copolyester, prepares a heat shrinkable film containing the same and a corresponding thermal cracking recovery method, so that the recycling and reuse of the PETG copolyester material can be realized, and the recycling cost of the PETG heat shrinkable film is reduced. In addition, the recycled heat shrinkable film has excellent mechanical properties and aging resistance, and can greatly improve the benefits of enterprises.

[0032] Furthermore, in step (1), the thermal cracking temperature of the first kettle 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;

[0033] The thermal cracking in step (1) is carried out in an ethylene glycol environment with an inert gas at a pressure of 1-10 kPa.

[0034] Beneficial effects:

[0035] (1) The easily recyclable PETG copolyester and the heat shrinkable film containing the same and the recycling method thereof in the present invention introduce a certain proportion of the 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 achieve deep chemical alcoholysis of the heat shrinkable film by using a three-step alcoholysis method, so as to better open up the circulation process of the PETG industrial chain, realize the free preparation of high-performance recyclable heat shrinkable film, reduce the recycling cost of the PETG heat shrinkable film, and the PETG heat shrinkable film prepared by this process has good aging resistance, which greatly improves the benefits of the enterprise.

[0036] (2) In the easily recyclable PETG copolyester provided by the present invention, by introducing a certain proportion of the fourth monomer in the process of synthesizing the PETG copolyester, heat can be absorbed during the thermal cracking process, thereby increasing the degree of cracking of the PETG copolyester, thereby reducing the content of BHET dimers, trimers and even polymers after the thermal cracking, reducing the influence of the recovered dimers or polymers on the material properties and the subsequent recycling and reuse capabilities, and effectively improving the recycling capacity of the PETG copolyester.

[0037] (3) In the easily recyclable PETG copolyester provided by the present invention, by introducing a certain proportion of plastic degradation masterbatch into each layer of the heat shrinkable film, the heat shrinkable film can be disintegrated during the thermal cracking process, thereby significantly improving the cracking degree of the PETG copolyester and improving its recyclability. In addition, the material of the cracked product is uniform and stable, which can effectively improve the stability of the PETG copolyester made again and improve its aging resistance.

[0038] (4) In the easily recyclable PETG copolyester provided by the present invention, polylactic acid is modified with itaconic acid and used as a plastic degradation masterbatch. After adding it to PETG copolyester, its mechanical properties can be improved, and the disintegration ability of polylactic acid on heat shrinkable film can be improved, thereby further improving the recyclability of PETG copolyester.

[0039] (5) The method for recycling the easily recyclable PETG copolyester and the heat shrinkable film containing the same provided by the present invention can realize the recycling of PETG copolyester materials by preparing the easily recyclable PETG copolyester, preparing the heat shrinkable film containing the same and the corresponding thermal cracking recovery method, thereby reducing the recycling cost of the PETG heat shrinkable film. In addition, the recycled heat shrinkable film has excellent mechanical properties and aging resistance, which can greatly improve the benefits of the enterprise. DETAILED DESCRIPTION

[0040] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are examples of the present invention and are only used to illustrate the present invention, but are not used to limit the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention may be carried out. Reagents and equipment in the present invention are conventional reagents and equipment in the art.

[0041] Preparation of itaconic acid grafted polylactic acid

[0042] Itaconic acid grafted polylactic acid was prepared by the following steps:

[0043] 10 g of polylactic acid and 50 mL of xylene were added to the reactor, nitrogen was introduced, and the mixture was heated to 90° C. After stirring until the polylactic acid was completely dissolved, 4 g of itaconic acid and 0.3 g of benzoyl peroxide were added. After reacting for 8 hours, the mixture was cooled, washed, and dried to obtain the itaconic acid grafted polylactic acid.

[0044] Example 1

[0045] S1. Prepare easily recyclable PETG copolyester by the following steps:

[0046] (1) Esterification: Based on a molar content of 100%, 35% of terephthalic acid, 45% of ethylene glycol, 10% of neopentyl glycol and 10% of polyethylene glycol were added to a reactor, and an esterification reaction was carried out at a temperature of 250°C for 2.5 hours. After the reaction was completed, the excess reactants were distilled off to obtain an esterification product;

[0047] (2) polycondensation: polycondensing the esterification product at 275°C under a catalyst and within a pressure range of 5 kPa for 4 hours. After the reaction is completed, the easily recyclable PETG is obtained by cooling, filtering, washing and drying.

[0048] S2. Prepare a heat shrinkable film containing easily recyclable PETG copolyester by the following steps:

[0049] Through a three-layer co-extrusion biaxial stretching production process, the core film layer material and the surface film layer material are respectively mixed, melt-plasticized and filtered and extruded, and then cast, longitudinally stretched, transversely stretched, trimmed and rolled to obtain the heat shrinkable film;

[0050] In terms of weight, the surface film layer material includes 92 parts of easily recyclable PETG, 6 parts of itaconic acid grafted polylactic acid and 2 parts of silicon dioxide;

[0051] In terms of weight, the core film layer material includes 69 parts of easily recyclable PETG, 25 parts of titanium dioxide and 6 parts of itaconic acid grafted polylactic acid;

[0052] Further, the filtration extrusion temperature of the core film layer material is 260°C, and the filtration extrusion temperature of the surface film layer material is 265°C;

[0053] The preheating temperature in the longitudinal stretching is 95°C, the longitudinal stretching temperature is 81°C, the longitudinal stretching ratio is 1.01, the longitudinal stretching setting temperature is 85°C, and the setting time is 3 seconds;

[0054] The preheating temperature in transverse stretching is 105°C, the transverse stretching temperature is 90°C, the transverse stretching ratio is 4.8 times, the transverse stretching setting temperature is 85°C, and the transverse stretching setting time is 8 seconds;

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

[0056] S3. Recycling of discarded heat shrinkable films containing easily recyclable PETG copolyester:

[0057] (1) In the first kettle, the waste heat shrink film containing easily recyclable PETG copolyester is thermally cracked at a temperature of 230°C for 1.5 hours, and then the waste heat shrink film is treated by a filtration system and then transported to the second pyrolysis kettle. Then, in the second kettle, the fourth monomer in the easily recyclable PETG copolyester is thermally cracked at a temperature of 260°C for 2 hours, and then the waste heat shrink film is transported to the third pyrolysis kettle after being treated by a filtration system. Finally, in the third kettle, the reaction components in the second kettle are deeply thermally cracked at a temperature of 280°C for 2 hours. All the pyrolysis processes are carried out in ethylene glycol. Inert gas is introduced in all stages at a pressure of 8 kPa, wherein the inert gas is nitrogen.

[0058] (2) based on a molar content of 100%, 35% of the product of the deep thermal cracking of step (1) is esterified and polycondensed with 45% of ethylene glycol, 10% of neopentyl glycol and 10% of polyethylene glycol to obtain an easily recyclable PETG copolyester;

[0059] (3) The easily recyclable PETG copolyester prepared in step (2) is again made into a heat shrinkable film containing the easily recyclable PETG copolyester according to step S2.

[0060] Example 2

[0061] The method is basically the same as Example 1, except that in step S1, the molar ratio of polyethylene glycol 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 method is basically the same as Example 1, except that in step S2, the surface film layer material includes 89 parts of easily recyclable PETG, 9 parts of polylactic acid and 2 parts of silicon dioxide; the core film layer material includes 66 parts of easily recyclable PETG, 25 parts of titanium dioxide and 9 parts of polylactic acid.

[0064] Example 4

[0065] The method is basically the same as Example 1, except that two kettles are used for alcoholysis preparation in step S3, the temperature of the first kettle is controlled at 260°C for 3.5 hours, and the mixture is transported to the second cracking kettle after being treated by the filtration system; 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 method is basically the same as Example 1, except that the components and contents in step S1 are changed to 40% terephthalic acid, 50% ethylene glycol and 10% neopentyl glycol; in step S3, two-kettle alcoholysis is adopted, the temperature of the first kettle is controlled at 260° C., the time is 3.5 hours, and the mixture is transported to the second cracking kettle after being treated by the filtration system; the second kettle performs deep thermal cracking on the reaction components of the first kettle, the temperature is controlled at 280° C., and the time is 2 hours.

[0068] Comparative Example 2

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

[0070] Comparative Example 3

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

[0072] Performance Testing

[0073] The heat shrinkable film containing easily recyclable PETG copolyester was prepared again in step S3 of Example 1-4 and Comparative Example 1-3, respectively, and aged for 7 days at 55° C. and 60% humidity in an aging box, and then the mechanical properties were tested using a universal tensile machine, and the time when the fracture began to occur was recorded.

[0074] The test results are shown in the following table:

[0075] Stretching without breaking time (h) Example 1 24 Example 2 17 Example 3 20 Example 4 11 Comparative Example 1 5.5 Comparative Example 2 4.5 Comparative Example 3 3

[0076] According to the comparison of the test results of Examples 1-4 and Comparative Examples 1-3, the easily recyclable PETG copolyester and the heat shrinkable film containing the same provided by the present invention and the recycling method thereof, by introducing a certain proportion of the fourth monomer in the process of synthesizing the PETG copolyester, and introducing a certain proportion of plastic degradation masterbatch in each layer in the process of preparing the PETG heat shrinkable film, the chemical alcoholysis process of the heat shrinkable film is flexibly controlled, and the three-step alcoholysis method is used to achieve deep chemical alcoholysis of the heat shrinkable film, so as to better open up the circulation process of the PETG industrial chain, realize the free preparation of high-performance recyclable heat shrinkable film, reduce the recycling cost of the PETG heat shrinkable film, and the PETG heat shrinkable film prepared by the process has good aging resistance and mechanical ability.

[0077] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A heat shrinkable film containing easily recyclable PETG copolyester, characterized in that: The heat shrinkable film is a three-layer composite structure, including 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 80-95 parts of easily recyclable PETG copolyester, 5-10 parts of plastic degradation masterbatch and 2-6 parts of anti-blocking agent by weight; The core film layer material comprises, by weight, 55-75 parts of easily recyclable PETG copolyester, 20-30 parts of white masterbatch and 5-10 parts of plastic degradation masterbatch; Based on a molar content of 100%, the 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; The fourth monomer is polyethylene glycol; 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 and dibenzoyl peroxide; The heat shrinkable film containing the easily recyclable PETG copolyester can be recycled by the following steps: (1) In the first kettle, the waste heat shrink film containing easily recyclable PETG copolyester is thermally cracked, and after being treated by the filtration system, it is transported to the second kettle cracking kettle, and then in the second kettle, the fourth monomer in the easily recyclable PETG copolyester is thermally cracked, and after being treated by the filtration system, it is transported to the third cracking kettle, and finally, the reaction components in the second kettle are deeply thermally cracked in the third kettle; (2) based on a molar content of 100%, 35-40% of the product of the deep thermal cracking of step (1) is esterified and polycondensed with 45-50% of ethylene glycol, 5-15% of neopentyl glycol and 5-15% of a fourth monomer to obtain an easily recyclable PETG copolyester; (3) The easily recyclable PETG copolyester obtained in step (2) is made into a heat shrinkable film containing the easily recyclable PETG copolyester according to the above formula, and then the film is recycled and step (1) is performed again after being discarded.

2. The heat shrinkable film containing easily recyclable PETG copolyester according to claim 1, characterized in that: The easily recyclable PETG copolyester is prepared by the following steps: (1) Esterification: Add terephthalic acid, ethylene glycol, neopentyl glycol and the fourth monomer in proportion to the reactor, and carry out esterification reaction at a temperature of 245-265°C for 2-3 hours. After the reaction is completed, distill off the excess reactants to obtain the esterification product; (2) Polycondensation: The esterification product is subjected to polycondensation at 270-285° C. and a catalyst under a pressure range of 0.1-10 kPa for a reaction time of 3-5 hours. After the reaction is completed, the easily recyclable PETG copolyester is obtained by cooling, filtering, washing and drying.

3. The heat shrinkable film containing easily recyclable PETG copolyester according to claim 1, 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 polylactic acid derivatives.

4. The heat shrinkable film containing easily recyclable PETG copolyester according to claim 1, characterized in that: The heat shrinkable film containing easily recyclable PETG copolyester is prepared by the following steps: through a three-layer co-extrusion biaxial stretching production process, the core film layer material and the surface film layer material are respectively fed, mixed, melt-plasticized and filtered and extruded, and then the heat shrinkable film is obtained after cast film, longitudinal stretching, transverse stretching, trimming and winding.

5. The heat shrinkable film containing easily recyclable PETG copolyester according to claim 4, characterized in that: The filtration extrusion temperature of the core film layer is 240°C-260°C, and the filtration extrusion temperature of the surface film layer is 245°C-265°C; The preheating temperature in the longitudinal stretching 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.

6. The heat shrinkable film containing easily recyclable PETG copolyester according to claim 1, characterized in that: In the method for recycling heat shrinkable film containing easily recyclable PETG copolyester, the thermal cracking temperature of the first kettle in step (1) is 220-240°C for 1-2 hours; the thermal cracking temperature of the second kettle is 250-270°C for 1-2 hours; the thermal cracking temperature of the third kettle is 280-300°C for 1-2 hours; The thermal cracking in step (1) is carried out in an ethylene glycol environment with an inert gas at a pressure of 1-10 kPa.