Preparation Method of EBCPZ Copolymerized PBAT Film with Excellent Mechanical Properties

Abstract

The invention discloses a preparation method of an EBCPZ copolymerized PBAT film with excellent mechanical properties, belonging to the technical field of film processing. The invention is used to solve the technical problem that the existing PBAT copolymerized film has poor low-temperature resistance and the mechanical properties need to be further improved in a low-temperature environment. The preparation method of the EBCPZ copolymerized PBAT film with excellent mechanical properties includes the following steps: adding ethyl p-hydroxybenzoate and acetone into a three-necked flask protected by nitrogen and stirring until the system is clear; reducing the temperature of the three-necked flask to 10-20 °C, adding sodium into the three-necked flask, and carrying out a heat preservation reaction for 3-5 h, and then performing post-treatment to obtain intermediate I; adding intermediate I, hexachlorocyclotriphosphazene and petroleum ether into a three-necked flask protected by nitrogen and stirring. The invention not only effectively improves the tensile strength and elongation at break of the film, but also improves the low-temperature resistance and degradation performance of the film.

Description

Technical Field

[0001] The present invention relates to the technical field of film processing, and specifically relates to a preparation method of an EBCPZ copolymerized PBAT film with excellent mechanical properties. Background Art

[0002] With the development of the national economy, the food packaging industry has rapidly emerged, and the consumption of packaging materials has also been increasing continuously. For example, the usage amounts of bubble films, fresh-keeping films, fresh-keeping bags, etc. have also increased synchronously. Although recycling, crushing, and reusing methods are currently adopted to reduce plastic waste, thereby slowing down white pollution, this method only treats the symptoms but not the root cause.

[0003] PBAT is a completely biodegradable polyester material that can be metabolized and decomposed by microorganisms and ultimately become carbon dioxide and water. PBAT has good ductility and elongation at break, and it also has a certain strength after forming a film. However, pure PBAT has a low melt index, poor processing performance, and poor film opening property during blown film. To overcome this difficulty, PBAT is usually blended with polylactic acid. However, the glass transition temperature of polylactic acid is relatively high, resulting in poor low-temperature resistance of PBAT. In a low-temperature environment, the film easily transforms into a glassy state, leading to a significant decline in the mechanical properties of the film.

[0004] In view of the technical defects in this regard, a solution is now proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of an EBCPZ copolymerized PBAT film with excellent mechanical properties, aiming to solve the technical problems in the prior art that pure PBAT has a low melt index, poor processing performance, poor film opening property during blown film. To overcome this difficulty, PBAT is usually blended with polylactic acid, but after adding polylactic acid, the glass transition temperature of the film increases, and the mechanical properties of the film are poor in a low-temperature environment.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A preparation method of an EBCPZ copolymerized PBAT film with excellent mechanical properties includes the following steps:

[0008] S1. Add ethyl p-hydroxybenzoate and acetone into a three-necked flask under nitrogen protection and stir until the system becomes clear. Lower the temperature of the three-necked flask to 10 - 20°C, add sodium to the three-necked flask, keep the temperature for reaction for 3 - 5 h, and perform post-treatment to obtain intermediate I;

[0009] The synthesis reaction principle of intermediate I is:

[0010]

[0011] S2. Add the intermediate I, hexachlorocyclotriphosphazene, and petroleum ether into a three-necked flask under nitrogen protection and stir. Heat the temperature of the three-necked flask to 70 - 90 °C, and reflux for 4 - 6 h. After post-treatment, EBCPZ is obtained.

[0012] The synthesis reaction principle of EBCPZ is as follows:

[0013]

[0014] S3. Add PBAT, modified polylactic acid, EBCPZ, and additives into a twin-screw extruder, melt and blend, and pelletize to obtain copolymerized PBAT.

[0015] S4. Add the copolymerized PBAT into a single-screw blown film machine to process and obtain a film.

[0016] Furthermore, in step S1, the molar ratio of ethyl p-hydroxybenzoate to sodium is 1:1, and the amount of acetone used is 3 - 5 times the weight of ethyl p-hydroxybenzoate. The post-treatment operation includes: after the reaction is completed, raise the temperature of the three-necked flask to 40 - 50 °C, and distill off the solvent under reduced pressure to obtain the intermediate I.

[0017] Furthermore, in step S2, the molar ratio of the intermediate I to hexachlorocyclotriphosphazene is 6:1, the boiling range of the petroleum ether is 60 - 90 °C, and the amount of petroleum ether used is 3 - 5 times the weight of the intermediate I. The post-treatment operation includes: after the reaction is completed, lower the temperature of the three-necked flask to room temperature, add purified water to the three-necked flask, stir for 20 - 30 min, let it stand for liquid separation. After the organic phase is washed twice with purified water, dry it. Transfer the organic phase to a rotary evaporator, set the water bath temperature to 55 - 65 °C, and distill off the petroleum ether under reduced pressure to obtain EBCPZ.

[0018] Furthermore, the preparation method of the modified polylactic acid is as follows: Add polylactic acid and an impact modifier into a screw extruder, melt and blend at 190 - 200 °C at a rotation speed of 200 r / min, and then extrude at a rate of 8 kg / h. After post-treatment, the modified polylactic acid is obtained.

[0019] Furthermore, the weight ratio of polylactic acid to the impact modifier is 18:1, the model of the impact modifier is KT - 18, and the post-treatment operation includes: after the extruded sample is cooled by water, cut it into wet modified polylactic acid products by a pelletizer at a rotation speed of 200 r / min. Transfer the wet modified polylactic acid products to a drying oven at 75 - 85 °C and vacuum dry for 8 - 12 h to obtain the modified polylactic acid.

[0020] Further, in step S3, the weight ratio of PBAT, modified polylactic acid, EBCPZ, and the additive is 20:5:2:1.5. The temperatures of multiple temperature zones of the barrel of the twin-screw extruder from the feeding end to the discharging end are 190°C, 200°C, 200°C, 200°C, and 200°C in sequence, the screw speed is 16 r / min. After the sample is extruded by the twin-screw extruder and cooled by water, it is cut into copolymer PBAT wet products by a pelletizer at a speed of 200 r / min. The copolymer PBAT wet products are transferred to a drying oven at a temperature of 80 - 90°C and vacuum-dried for 8 - 12 h to obtain copolymer PBAT.

[0021] Further, the additive is composed of an antioxidant, a light stabilizer, an antistatic agent, and a dispersant in a ratio of 1:1:1:2. The antioxidant is one or more of tea polyphenols, butylated hydroxyanisole, dibutylhydroxytoluene, and tert-butylhydroquinone. The light stabilizer is one or more of zinc oxide, titanium dioxide, benzophenone, benzotriazole, and salicylate. The antistatic agent is one or more of antistatic agent SN, antistatic agent TM, and antistatic agent SP. The dispersant is polyethylene wax.

[0022] Further, in step S4, the aspect ratio of the single-screw blown film machine is 25:1. The temperatures of multiple temperature zones of the barrel on the single-screw blown film machine from the feeding end to the discharging end are 180°C, 185°C, 190°C, 190°C, and 190°C in sequence. The screw speed of the single-screw blown film machine is set to 38 r / min, the feeding rate of the blown film machine is 7 kg / h, the blow-up ratio is 3, the frost line height is 15 cm, and the winding speed is 7.0 m / min.

[0023] The present invention has the following beneficial effects:

[0024] 1. When preparing the film, in the present invention, ethyl p-hydroxybenzoate reacts with sodium in an acetone environment. The phenolic hydroxyl group on ethyl p-hydroxybenzoate reacts with sodium to generate intermediate I with sodium phenoxide. The sodium phenoxide on intermediate I undergoes substitution addition with the chlorine on hexachlorocyclotriphosphazene in a petroleum ether environment to generate EBCPZ; EBCPZ is a hexaphenoxy-substituted derivative of cyclic trimeric phosphazene, with a unique and compact molecular structure of alternating phosphorus and nitrogen arrangements. Due to containing elements such as phosphorus and nitrogen, it has a phosphorus-nitrogen compound structure similar to that required by common intumescent flame retardant systems, and is a type of halogen-free flame retardant with great development potential, making the film have excellent flame retardant effects; The ethyl benzoate grafted on EBCPZ has a structure similar to that of PBAT, improving the compatibility between EBCPZ and PBAT, reducing the weak interfacial properties of the film, and improving the mechanical properties of the film; The addition of EBCPZ also effectively reduces the melting temperature of PBAT and modified polylactic acid, facilitating the blown film processing of copolymer PBAT.

[0025] 2. When preparing the film of the present invention, poly(lactic acid) and an impact modifier are melt-blended at a high temperature. An impact modifier with a low glass transition temperature is added to poly(lactic acid) to modify poly(lactic acid), so as to reduce the glass transition temperature of poly(lactic acid) and improve the low-temperature resistance of poly(lactic acid). Both poly(lactic acid) and PBAT contain a large number of carbonyl groups and are similar in structure, resulting in good compatibility between the modified poly(lactic acid) and PBAT. Moreover, both the modified poly(lactic acid) and PBAT have a long straight-chain structure, and EBCPZ has a cyclic structure. The modified poly(lactic acid), PBAT and EBCPZ are blended, and the modified poly(lactic acid) and PBAT are crosslinked through EBCPZ, further reducing the weak interfacial property of the copolymerized PBATD. In addition, the modified poly(lactic acid) modified by the impact modifier has a low glass transition temperature, improving the low-temperature resistance of the copolymerized PBAT. Both PBAT and poly(lactic acid) are biodegradable materials, enabling the copolymerized PBAT to be degraded under biological soil, which is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is the electron micrograph of the film prepared in Example 3 of the present invention;

[0028] Figure 2 It is the bar graph of the elongation at break of the films prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention at 25°C and -15°C;

[0029] Figure 3 It is the bar graph of the tensile strength of the films prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention at 25°C and -15°C;

[0030] Figure 4 It is the line graph of the biodegradability of the films prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment provides a method for preparing an EBCPZ copolymerized PBAT film with excellent mechanical properties, comprising the following steps:

[0034] S1. Weigh by weight: 166 g of ethyl p-hydroxybenzoate and 498 g of acetone are added to a three-necked flask under nitrogen protection and stirred until the system becomes clear. The temperature of the three-necked flask is lowered to 10 °C, 23 g of sodium is added to the three-necked flask, and the reaction is carried out under insulation for 3 h. After the reaction is completed, the temperature of the three-necked flask is raised to 40 °C, and the solvent is removed by reduced pressure distillation to obtain intermediate I;

[0035] S2. Weigh by weight: 188 g of intermediate I, 57.9 g of hexachlorocyclotriphosphazene and 564 g of petroleum ether with a boiling range of 60-90 °C are added to a three-necked flask under nitrogen protection and stirred. The temperature of the three-necked flask is raised to 282 °C, and the reflux reaction is carried out for 4 h. After the reaction is completed, the temperature of the three-necked flask is lowered to room temperature. 94 g of purified water is added to the three-necked flask, stirred for 20 min, and left to stand for liquid separation. The organic phase is washed twice with purified water and then dried. The organic phase is transferred to a rotary evaporator, the water bath temperature is set to 55 °C, and the petroleum ether is removed by reduced pressure distillation to obtain EBCPZ;

[0036] S3. Weigh by weight: 900 g of polylactic acid and 50 g of an impact modifier of model KT-18 are added to a screw extruder, melt-blended at 190 °C at a rotation speed of 200 r / min, and then extruded at a rate of 8 kg / h. After the extruded sample is cooled by water, it is cut into modified polylactic acid wet products by a pelletizer at a rotation speed of 200 r / min. The modified polylactic acid wet products are transferred to a drying oven at 75 °C and vacuum-dried for 8 h to obtain modified polylactic acid.

[0037] S4. Weigh by weight: 1000 g of PBAT, 250 g of modified polylactic acid, 100 g of EBCPZ, 15 g of tea polyphenols, 15 g of zinc oxide, 15 g of antistatic agent SN and 30 g of polyethylene wax are mixed evenly and added to a twin-screw extruder. The temperatures of multiple temperature zones of the barrel of the twin-screw extruder from the feed end to the discharge end are 190 °C, 200 °C, 200 °C, 200 °C and 200 °C in sequence, and the screw rotation speed is 16 r / min. After the sample extruded by the twin-screw extruder is cooled by water, it is cut into copolymerized PBAT wet products by a pelletizer at a rotation speed of 200 r / min. The copolymerized PBAT wet products are transferred to a drying oven at 80-90 °C and vacuum-dried for 8 h to obtain copolymerized PBAT;

[0038] S5. Add the copolymerized PBAT into a single-screw blown film machine with a length-to-diameter ratio of 25:1. The temperatures of multiple temperature zones of the barrel on the single-screw blown film machine from the feed end to the discharge end are 180 °C, 185 °C, 190 °C, 190 °C, and 190 °C in sequence. Set the screw speed of the single-screw blown film machine to 38 r / min, the feed rate of the blown film machine to 7 kg / h, the blow-up ratio to 3, the frost line height to 15 cm, and the winding speed to 7.0 m / min, and process to obtain a film.

[0039] Example 2

[0040] This example provides a method for preparing an EBCPZ copolymerized PBAT film with excellent mechanical properties, including the following steps:

[0041] S1. Weigh by weight: 166 g of ethyl p-hydroxybenzoate and 664 g of acetone are added to a three-necked flask under nitrogen protection and stirred until the system is clear. The temperature of the three-necked flask is lowered to 15 °C, 23 g of sodium is added to the three-necked flask, and the reaction is carried out at a constant temperature for 4 h. After the reaction is completed, the temperature of the three-necked flask is raised to 45 °C, and the solvent is removed by reduced pressure distillation to obtain Intermediate I;

[0042] S2. Weigh by weight: 188 g of Intermediate I, 57.9 g of hexachlorocyclotriphosphazene, and 752 g of petroleum ether with a boiling range of 60 - 90 °C are added to a three-necked flask under nitrogen protection and stirred. The temperature of the three-necked flask is raised to 80 °C, and the reflux reaction is carried out for 5 h. After the reaction is completed, the temperature of the three-necked flask is lowered to room temperature. 376 g of purified water is added to the three-necked flask, stirred for 25 min, allowed to stand for liquid separation. The organic phase is washed twice with purified water and then dried. The organic phase is transferred to a rotary evaporator, the water bath temperature is set to 60 °C, and the petroleum ether is removed by reduced pressure distillation to obtain EBCPZ;

[0043] S3. Weigh by weight: 900 g of polylactic acid and 50 g of an impact modifier with the model number KT-18 are added to a screw extruder and melt-blended at 195 °C at a speed of 200 r / min, and then extruded at a rate of 8 kg / h. After the extruded sample is cooled by water, it is cut into modified polylactic acid wet products by a pelletizer at a speed of 200 r / min. The modified polylactic acid wet products are transferred to a drying oven at 80 °C and vacuum-dried for 10 h to obtain modified polylactic acid.

[0044] S4. Weigh by weight: 1000 g of PBAT, 250 g of modified polylactic acid, 100 g of EBCPZ, 15 g of butylated hydroxyanisole, 15 g of titanium dioxide, 15 g of antistatic agent TM, and 30 g of polyethylene wax. Mix them evenly and add them to a twin-screw extruder. The temperatures of multiple temperature zones of the barrel of the twin-screw extruder from the feeding end to the discharging end are 190 °C, 200 °C, 200 °C, 200 °C, and 200 °C in sequence. The screw speed is 16 r / min. After the sample extruded by the twin-screw extruder is cooled by water, it is cut into wet copoly PBAT by a pelletizer at a speed of 200 r / min. The wet copoly PBAT is transferred to a drying oven at 85 °C and vacuum dried for 10 h to obtain copoly PBAT;

[0045] S5. Add copoly PBAT to a single-screw blown film machine with a length-diameter ratio of 25:1. The temperatures of multiple temperature zones of the barrel on the single-screw blown film machine from the feeding end to the discharging end are 180 °C, 185 °C, 190 °C, 190 °C, and 190 °C in sequence. Set the screw speed of the single-screw blown film machine to 38 r / min, the feeding rate of the blown film machine to 7 kg / h, the blow-up ratio to 3, the frost line height to 15 cm, and the winding speed to 7.0 m / min to process and obtain a film.

[0046] Example 3

[0047] This example provides a preparation method of an EBCPZ copoly PBAT film with excellent mechanical properties, including the following steps:

[0048] S1. Weigh by weight: 166 g of ethyl p-hydroxybenzoate and 830 g of acetone. Add them to a three-necked flask under nitrogen protection and stir until the system is clear. Lower the temperature of the three-necked flask to 20 °C, add 23 g of sodium to the three-necked flask, and keep the reaction at this temperature for 5 h. After the reaction is completed, raise the temperature of the three-necked flask to 50 °C and distill off the solvent under reduced pressure to obtain Intermediate I;

[0049] S2. Weigh by weight: 188 g of Intermediate I, 57.9 g of hexachlorocyclotriphosphazene, and 940 g of petroleum ether with a boiling range of 60 - 90 °C. Add them to a three-necked flask under nitrogen protection and stir. Raise the temperature of the three-necked flask to 90 °C and reflux for 6 h. After the reaction is completed, lower the temperature of the three-necked flask to room temperature. Add 470 g of purified water to the three-necked flask, stir for 30 min, let it stand for liquid separation. After the organic phase is washed twice with purified water, it is dried. The organic phase is transferred to a rotary evaporator, set the water bath temperature to 65 °C, and distill off the petroleum ether under reduced pressure to obtain EBCPZ;

[0050] S3. Weigh by weight: 900 g of polylactic acid and 50 g of impact modifier of model KT-18 are added to a screw extruder, melt-blended at 200 °C with a rotation speed of 200 r / min, and then extruded at a rate of 8 kg / h. After the extruded sample is cooled by water, it is cut into wet modified polylactic acid pellets by a pelletizer at a rotation speed of 200 r / min. The wet modified polylactic acid pellets are transferred to a drying oven at 85 °C for vacuum drying for 12 h to obtain modified polylactic acid.

[0051] S4. Weigh by weight: 1000 g of PBAT, 250 g of modified polylactic acid, 100 g of EBCPZ, 15 g of tert-butylhydroquinone, 15 g of benzophenone, 15 g of antistatic agent SP, and 30 g of polyethylene wax are mixed evenly and added to a twin-screw extruder. The temperatures of multiple temperature zones of the barrel of the twin-screw extruder from the feeding end to the discharging end are 190 °C, 200 °C, 200 °C, 200 °C, and 200 °C in sequence, and the screw rotation speed is 16 r / min. After the sample extruded by the twin-screw extruder is cooled by water, it is cut into wet copolyester PBAT pellets by a pelletizer at a rotation speed of 200 r / min. The wet copolyester PBAT pellets are transferred to a drying oven at 90 °C for vacuum drying for 12 h to obtain copolyester PBAT;

[0052] S5. Add copolyester PBAT to a single-screw blown film machine with a length-diameter ratio of 25:1. The temperatures of multiple temperature zones of the barrel on the single-screw blown film machine from the feeding end to the discharging end are 180 °C, 185 °C, 190 °C, 190 °C, and 190 °C in sequence. Set the screw rotation speed of the single-screw blown film machine to 38 r / min, the feeding rate of the blown film machine to 7 kg / h, the blow-up ratio to 3, the frost line height to 15 cm, and the winding speed to 7.0 m / min to process and obtain a film.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 3 is that steps S1 and S2 are cancelled, and EBCPZ is not added in step S4.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 3 is that step S3 is cancelled, and the modified polylactic acid in step S4 is replaced by polylactic acid in equal amount.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 3 is that step S3 is cancelled, and the modified polylactic acid is not added in step S4.

[0059] Performance test:

[0060] The mechanical properties and biodegradability of the films prepared in Examples 1-3 and Comparative Examples 1-3 were tested. Among them, for the mechanical property test, referring to the standard GB / T 1040.1-2018 "Determination of Tensile Properties of Plastics - Part 1: General Principles", the tensile strength and elongation at break of the specimens were tested at room temperature and -15°C. For the biodegradability test, the specimens were cut into small pieces of 30 mm × 40 mm, and after drying, the original weight m of the specimens was weighed. 0 Then, all the specimens were placed in a container filled with soil, maintaining the same burial depth and burial interval. Under natural conditions, water was regularly and quantitatively added. After 90 days of burial, the specimens were taken out, repeatedly washed with distilled water and then dried, and the used weight m was weighed. t According to the formula the degradation rate of the specimens was obtained. The specific test data are shown in the following table:

[0061]

[0062] Data analysis:

[0063] In Comparative Example 1, due to the absence of EBCPZ, its mechanical properties were significantly different from those of Examples 1-3.

[0064] In Comparative Example 2, since the modified polylactic acid was replaced by polylactic acid in equal amounts, its low-temperature resistance was significantly different from that of Examples 1-3.

[0065] In Comparative Example 3, due to the absence of modified polylactic acid or polylactic acid, its low-temperature resistance and degradation rate were significantly different from those of Examples 1-3.

[0066] Through the data analysis of Comparative Examples 1-3 and Examples 1-3, it was found that in the present invention, by synthesizing EBCPZ and modified polylactic acid to modify PBAT, the tensile strength, elongation at break, low-temperature resistance and biodegradability of the film were effectively improved, with good mechanical properties and degradability.

[0067] The above content is only an example and explanation of the structure of the present invention. Those skilled in the art of this technology can make various modifications, supplements or use similar methods to replace the specific embodiments described, as long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

[0068] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0069] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments only. Obviously, according to the content of this specification, many modifications and changes can be made. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. Preparation method of EBCPZ copolymerized PBAT film with excellent mechanical properties, Characterized in that, It includes the following steps: S1. Add ethyl p-hydroxybenzoate and acetone into a three-necked flask under nitrogen protection and stir until the system becomes clear. Lower the temperature of the three-necked flask to 10 - 20 °C, add sodium into the three-necked flask, keep the temperature for reaction for 3 - 5 h, and perform post-treatment to obtain intermediate I; S2. Add intermediate I, hexachlorocyclotriphosphazene and petroleum ether into a three-necked flask under nitrogen protection and stir. Raise the temperature of the three-necked flask to 70 - 90 °C, reflux for reaction for 4 - 6 h, and perform post-treatment to obtain EBCPZ; S3. Add PBAT, modified polylactic acid, EBCPZ and additives into a twin-screw extruder, melt and blend, and pelletize to obtain copolymerized PBAT, where the weight ratio of PBAT, modified polylactic acid, EBCPZ and additives is 20:5:2:1.5; S4. Add copolymerized PBAT into a single-screw blown film machine to process and obtain a film; The preparation method of the modified polylactic acid is: Add polylactic acid and an impact modifier into a screw extruder, melt and blend at a rotation speed of 200 r / min at 190 - 200 °C, and then extrude at a rate of 8 kg / h, and perform post-treatment to obtain modified polylactic acid.

2. The preparation method of EBCPZ copolymerized PBAT film with excellent mechanical properties according to claim 1, Characterized in that, In step S1, the molar ratio of ethyl p-hydroxybenzoate to sodium is 1:1, and the amount of acetone used is 3 - 5 times the weight of ethyl p-hydroxybenzoate. The post-treatment operation includes: After the reaction is completed, raise the temperature of the three-necked flask to 40 - 50 °C, distill off the solvent under reduced pressure to obtain intermediate I.

3. The preparation method of EBCPZ copolymerized PBAT film with excellent mechanical properties according to claim 1, Characterized in that, In step S2, the molar ratio of intermediate I to hexachlorocyclotriphosphazene is 6:1, the boiling range of the petroleum ether is 60 - 90 °C, and the amount of petroleum ether used is 3 - 5 times the weight of intermediate I. The post-treatment operation includes: After the reaction is completed, lower the temperature of the three-necked flask to room temperature, add purified water into the three-necked flask, stir for 20 - 30 min, let it stand for liquid separation. After the organic phase is washed twice with purified water, dry it, transfer the organic phase to a rotary evaporator, set the water bath temperature to 55 - 65 °C, and distill off the petroleum ether under reduced pressure to obtain EBCPZ.

4. The preparation method of EBCPZ copolymerized PBAT film with excellent mechanical properties according to claim 1, Characterized in that, The weight ratio of polylactic acid to the impact modifier is 18:1, the model of the impact modifier is KT - 18, and the post-treatment operation includes: After the extruded sample is cooled by water, cut it into wet modified polylactic acid products by a pelletizer at a rotation speed of 200 r / min. Transfer the wet modified polylactic acid products to a drying oven at 75 - 85 °C for vacuum drying for 8 - 12 h to obtain modified polylactic acid.

5. The preparation method of EBCPZ copolymerized PBAT film with excellent mechanical properties according to claim 1, Characterized in that, In the step S3, the temperatures of multiple temperature zones of the barrel of the twin-screw extruder from the feeding end to the discharging end are 190 °C, 200 °C, 200 °C, 200 °C, and 200 °C in sequence, the screw rotation speed is 16 r / min. After the sample extruded by the twin-screw extruder is cooled by water, it is cut into wet copolyester PBAT particles by a pelletizer at a rotation speed of 200 r / min. The wet copolyester PBAT particles are transferred to a drying oven at a temperature of 80 - 90 °C for vacuum drying for 8 - 12 h to obtain copolyester PBAT.

6. The preparation method of the EBCPZ copolyester PBAT film with excellent mechanical properties according to claim 5, characterized in that, the additive is composed of an antioxidant, a light stabilizer, an antistatic agent, and a dispersant in a ratio of 1:1:1:

2. The antioxidant is one or more of tea polyphenols, butylated hydroxyanisole, dibutylhydroxytoluene, and tert-butylhydroquinone; the light stabilizer is one or more of zinc oxide, titanium dioxide, benzophenone, benzotriazole, and salicylate; the antistatic agent is one or more of antistatic agent SN, antistatic agent TM, and antistatic agent SP; and the dispersant is polyethylene wax.

7. The preparation method of the EBCPZ copolyester PBAT film with excellent mechanical properties according to claim 1, characterized in that, in the step S4, the ratio of the length to the diameter of the single-screw blown film machine is 25:

1. The temperatures of multiple temperature zones of the barrel on the single-screw blown film machine from the feeding end to the discharging end are 180 °C, 185 °C, 190 °C, 190 °C, and 190 °C in sequence. The screw rotation speed of the single-screw blown film machine is set to 38 r / min, the feeding amount of the blown film machine is 7 kg / h, the blow-up ratio is 3, the frost line height is 15 cm, and the winding speed is 7.0 m / min.

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