Pbst three-layer co-extrusion biodegradable film and preparation method thereof, biodegradable mulching film

Abstract

The application discloses a PBST three-layer co-extrusion biodegradable film and a preparation method and biodegradable mulching film thereof, and belongs to the technical field of biodegradable films.The biodegradable film comprises a core layer and surface layers, the surface layers comprise a first surface layer and a second surface layer located on the two sides of the core layer respectively; the preparation raw materials of the core layer comprise PBST 75-95 parts, heavy calcium 10-20 parts, other fillers 10-20 parts and toughening agents 1-2 parts by weight; and the preparation raw materials of the surface layers comprise PBST 65-90 parts, PBAT 10-35 parts and compatible toughening agents 0.5-2 parts.The main resin types / compositions of the core layer and the surface layers of the PBST three-layer co-extrusion biodegradable film are selected, so that the biodegradable film has excellent mechanical properties and heat and soil conservation properties.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable membrane technology, and particularly relates to a PBST three-layer co-extruded biodegradable membrane and its preparation method, as well as a biodegradable mulch film. Background Technology

[0002] Mulching technology is an important means of increasing agricultural production in arid and semi-arid regions. Traditional polyethylene (PE) mulch film is widely used in these regions, effectively solving problems such as moisture retention and temperature increase. However, PE mulch film is difficult to degrade naturally.

[0003] In recent years, fully biodegradable mulch films have become an important alternative to PE mulch films. Biodegradable materials such as polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) have been gradually applied in mulch film production. However, existing biodegradable mulch films have revealed significant shortcomings under extreme climatic conditions: firstly, their mechanical strength is relatively low, especially their tensile strength and resistance to wind and sand abrasion, making them unable to withstand the onslaught of strong winds and sandstorms in spring, and prone to tearing and damage during the covering period; secondly, their heat preservation and moisture retention performance needs improvement, making it difficult to fully realize their heat preservation and moisture retention functions.

[0004] Furthermore, cotton cultivation in Xinjiang requires approximately 140 days of mulch protection, but existing fully biodegradable mulch technology cannot achieve precise film breaking within this 140-day period in Xinjiang.

[0005] Therefore, how to develop a biodegradable membrane with improved mechanical properties, heat preservation and moisture retention properties, and even more importantly, the ability to achieve precise membrane rupture in Xinjiang within about 140 days, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention provides a PBST three-layer co-extruded biodegradable film, its preparation method, and a biodegradable mulch film, which at least solves the problems of poor mechanical properties and thermal insulation and moisture retention performance of biodegradable films. Specifically, this invention achieves excellent mechanical properties and thermal insulation and moisture retention performance of the biodegradable film by selecting the main resin types / compositions of the core layer and surface layer of the PBST three-layer co-extruded biodegradable film.

[0007] The first objective of this invention is to provide a PBST three-layer co-extruded biodegradable membrane, which includes a core layer and a surface layer, wherein the surface layer includes a first surface layer and a second surface layer located on both sides of the core layer;

[0008] By weight, the raw materials for preparing the core layer include 75-95 parts of PBST, 10-20 parts of heavy calcium carbonate, 10-20 parts of other fillers, and 1-2 parts of toughening agent; the raw materials for preparing the surface layer include 65-90 parts of PBST, 10-35 parts of PBAT, and 0.5-2 parts of compatibility toughening agent.

[0009] Furthermore, to ensure controllable rupture time of the biodegradable mulch film in Xinjiang, in some preferred embodiments of the present invention, the raw materials for preparing the core layer further include 1-4 parts of plant fiber, and the raw materials for preparing the surface layer further include 0.1-1 parts of UV stabilizer and 0.1-1 parts of antioxidant. By adding biodegradable plant fiber to the core layer and adding UV stabilizer and antioxidant components to the surface layer, the interaction between the two allows for controllable rupture time of the biodegradable mulch film in Xinjiang.

[0010] In some preferred embodiments of the present invention, for example, in the northern Xinjiang region with its distinctly cold and windy climate, the plant fiber is selected from bamboo powder and hemp stalk powder, with a preferred mass ratio of bamboo powder to hemp stalk powder of 1:0.1~1, more preferably 1:0.4~0.8. The UV stabilizer is selected from at least one of nano-titanium dioxide and nano-cerium oxide, and the antioxidant is selected from hindered phenols. In this invention, by selecting the types of plant fiber, UV stabilizer, and antioxidant, the invention adapts to the climate of northern Xinjiang, further achieving precise film breaking in approximately 140 days to meet the planting needs of crops such as cotton.

[0011] In some other preferred embodiments of the present invention, for example, in the high-temperature and high-UV-intensity southern Xinjiang region, the plant fiber is selected from bamboo powder and coconut shell powder, with the mass ratio of bamboo powder to coconut shell powder preferably being 1:1~2, more preferably 1:1.5~2. The UV stabilizer is selected from at least one of nano-titanium dioxide and nano-cerium oxide, and the antioxidant is selected from hindered phenols and phosphites, with the mass ratio of hindered phenols to phosphites preferably being 1:0.5~1. In the present invention, to adapt to the climate of the southern Xinjiang region, the types of the above-mentioned plant fiber, UV stabilizer, and antioxidant need to be adjusted to further achieve precise film breaking in about 140 days, meeting the planting needs of crops such as cotton.

[0012] In some embodiments of the present invention, the mesh size of the bamboo powder, the hemp stalk powder, and the coconut shell powder is independently 40 to 100 mesh.

[0013] In some embodiments of the present invention, the hindered phenolic antioxidant is selected from at least one of antioxidant 1010 and antioxidant 1076.

[0014] In some embodiments of the present invention, the phosphite antioxidant is selected from at least one of antioxidant 168 and antioxidant 9228.

[0015] In some embodiments of the present invention, the heavy calcium carbonate is selected from activated heavy calcium carbonate. It is understood that activated heavy calcium carbonate refers to heavy calcium carbonate that has undergone activation treatment, such as heavy calcium carbonate that has been surface-treated with silane coupling agents, fatty acids, etc.

[0016] In some embodiments of the present invention, the other filler is selected from at least one of talc, mica, kaolin, barium sulfate, zinc sulfide, aluminum sulfide, and calcium sulfide.

[0017] In some embodiments of the present invention, the toughening agent is selected from at least one of POE-g-GMA, POE-g-MAH, and TPEE.

[0018] In some embodiments of the present invention, the compatibility toughening agent is selected from at least one of POE-g-GMA and POE-g-MAH.

[0019] In some embodiments of the present invention, the raw materials for preparing the surface layer further include 0.5 to 3 parts of an opening slip agent. Preferably, the opening slip agent is selected from organic amides, and more preferably, it is selected from at least one of erucamide, oleamide, and stearamide.

[0020] In some embodiments of the present invention, the thickness ratio of the core layer to the surface layer is 1 to 1.2:1. Preferably, the thickness of the PBST three-layer co-extruded biodegradable film is 0.01 to 0.02 mm.

[0021] The second objective of this invention is to provide a method for preparing the above-mentioned PBST three-layer co-extruded biodegradable membrane, which includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, conveying them to the co-extrusion die, extruding, blowing and molding, drawing, and winding to obtain the PBST three-layer co-extruded biodegradable membrane.

[0022] In some embodiments of the present invention, for example, for biodegradable membranes used in northern Xinjiang, the heating and melting temperature is 120~160°C and the temperature of the co-extrusion die is 143~147°C.

[0023] In other embodiments of the present invention, for example, for biodegradable membranes used in southern Xinjiang, the heating and melting temperature is 125~165°C and the temperature of the co-extrusion die is 148~152°C.

[0024] In some embodiments of the present invention, the blow-up ratio of the blow-molding is 2.5 to 3.0.

[0025] In some embodiments of the present invention, the traction ratio of the traction is 3.5 to 4.2.

[0026] A third objective of this invention is to provide a PBST three-layer co-extruded biodegradable mulch film, comprising the aforementioned PBST three-layer co-extruded biodegradable film.

[0027] In some embodiments of the present invention, the PBST three-layer co-extruded biodegradable mulch film is composed of the above-mentioned PBST three-layer co-extruded biodegradable film.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The PBST three-layer co-extruded biodegradable film of the present invention has a mechanical strength increased by more than 20%, significantly enhanced wind resistance and tensile strength, and good heat preservation and moisture retention properties.

[0030] Furthermore, by adjusting the formulation of the core and surface layers of the PBST three-layer co-extruded biodegradable film, namely by adding biodegradable plant fibers to the core layer and adding UV-resistant and antioxidant components to the surface layer, this invention enables the mulch film formed by the biodegradable film to precisely break in about 140 days in both southern and northern Xinjiang, meeting the needs of planting crops such as cotton across the entire region. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0032] Unless otherwise specified, all raw materials used in this invention are commercially available. In the following examples and comparative examples, PBST and PBAT were obtained from Sinopec, and the activated calcium carbonate was stearic acid-treated calcium carbonate.

[0033] The following specific embodiments are the technical solutions for the PBST three-layer co-extruded biodegradable membrane of the present invention.

[0034] Example 1

[0035] This embodiment provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The PBST three-layer co-extruded biodegradable membrane includes a core layer and a surface layer. The surface layer includes a first surface layer and a second surface layer located on both sides of the core layer.

[0036] By weight, the raw materials for preparing the core layer include 75 parts PBST, 10 parts activated heavy calcium carbonate, 10 parts talc, and 1 part POE-g-GMA; the raw materials for preparing the surface layer include 75 parts PBST, 25 parts PBAT, and 1 part POE-g-GMA.

[0037] The preparation method includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, feeding them into the co-extrusion die, extruding, blow-forming, drawing, and winding to obtain a PBST three-layer co-extruded biodegradable film with a thickness of 0.015 mm; wherein, the thickness ratio of the core layer, the first surface layer, and the second surface layer is 1:0.5:0.5, the heating and melting temperatures of the core layer are 120 / 135 / 145 / 155 / 160 / 155℃ respectively, the heating and melting temperatures of the surface layer are 120 / 135 / 145 / 155 / 155 / 155℃ respectively, the temperature of the co-extrusion die is 145℃, the blow-up ratio is 2.5, and the drawing ratio is 4.

[0038] Example 2

[0039] This embodiment provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The PBST three-layer co-extruded biodegradable membrane includes a core layer and a surface layer. The surface layer includes a first surface layer and a second surface layer located on both sides of the core layer.

[0040] By weight, the raw materials for preparing the core layer include 85 parts PBST, 15 parts activated heavy calcium carbonate, 15 parts barium sulfate, and 2 parts POE-g-MAH; the raw materials for preparing the surface layer include 85 parts PBST, 15 parts PBAT, and 2 parts POE-g-MAH.

[0041] The preparation method includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, feeding them into the co-extrusion die, extruding, blowing, drawing, and winding to obtain a PBST three-layer co-extruded biodegradable film with a thickness of 0.015 mm; wherein, the thickness ratio of the core layer, the first surface layer, and the second surface layer is 1:0.5:0.5, the heating and melting temperatures of the core layer are 125 / 135 / 150 / 155 / 165 / 160℃, the heating and melting temperatures of the surface layer are 125 / 135 / 150 / 155 / 160 / 160℃, the temperature of the co-extrusion die is 150℃, the blowing ratio is 2.5, and the drawing ratio is 4.

[0042] Example 3

[0043] This embodiment provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The PBST three-layer co-extruded biodegradable membrane includes a core layer and a surface layer. The surface layer includes a first surface layer and a second surface layer located on both sides of the core layer.

[0044] By weight, the raw materials for preparing the core layer include 95 parts PBST, 20 parts activated heavy calcium carbonate, 20 parts calcium sulfide, and 2 parts TPEE; the raw materials for preparing the surface layer include 90 parts PBST, 10 parts PBAT, and 1.5 parts POE-g-GMA.

[0045] The preparation method includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, feeding them into the co-extrusion die, extruding, blowing, drawing, and winding to obtain a PBST three-layer co-extruded biodegradable film with a thickness of 0.015 mm; wherein, the thickness ratio of the core layer, the first surface layer, and the second surface layer is 1:0.5:0.5, the heating and melting temperatures of the core layer are 125 / 135 / 150 / 155 / 165 / 160℃, the heating and melting temperatures of the surface layer are 125 / 135 / 150 / 155 / 165 / 160℃, the temperature of the co-extrusion die is 150℃, the blowing ratio is 2.5, and the drawing ratio is 4.

[0046] Comparative Example 1

[0047] This comparative example provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The PBST three-layer co-extruded biodegradable membrane includes a core layer and a surface layer. The surface layer includes a first surface layer and a second surface layer located on both sides of the core layer.

[0048] By weight, the raw materials for preparing the core layer include 75 parts PBST, 25 parts PBAT, 10 parts activated heavy calcium carbonate, 10 parts talc, and 1 part POE-g-GMA; the raw materials for preparing the surface layer include 75 parts PBST and 1 part POE-g-GMA.

[0049] The preparation method includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, feeding them into the co-extrusion die, extruding, blow-forming, drawing, and winding to obtain a PBST three-layer co-extruded biodegradable film with a thickness of 0.015 mm; wherein, the thickness ratio of the core layer, the first surface layer, and the second surface layer is 1:0.5:0.5, the heating and melting temperatures of the core layer are 120 / 135 / 145 / 155 / 160 / 155℃ respectively, the heating and melting temperatures of the surface layer are 120 / 135 / 145 / 155 / 155 / 155℃ respectively, the temperature of the co-extrusion die is 145℃, the blow-up ratio is 2.5, and the drawing ratio is 4.

[0050] Comparative Example 2

[0051] This comparative example provides a PBAT three-layer co-extruded biodegradable membrane and its preparation method. The PBAT three-layer co-extruded biodegradable membrane includes a core layer and a surface layer. The surface layer includes a first surface layer and a second surface layer located on both sides of the core layer.

[0052] By weight, the raw materials for preparing the core layer include 75 parts of PBAT, 10 parts of activated heavy calcium carbonate, 10 parts of talc, and 1 part of POE-g-GMA; the raw materials for preparing the surface layer include 25 parts of PBST, 75 parts of PBAT, and 1 part of POE-g-GMA.

[0053] The preparation method includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, feeding them into the co-extrusion die, extruding, blow-forming, drawing, and winding to obtain a PBAT three-layer co-extruded biodegradable film with a thickness of 0.015 mm; wherein, the thickness ratio of the core layer, the first surface layer, and the second surface layer is 1:0.5:0.5, the heating and melting temperatures of the core layer are 120 / 135 / 145 / 155 / 160 / 155℃ respectively, the heating and melting temperatures of the surface layer are 120 / 135 / 145 / 155 / 155 / 155℃ respectively, the temperature of the co-extrusion die is 145℃, the blow-up ratio is 2.5, and the drawing ratio is 4.

[0054] The mechanical properties and heat preservation and moisture retention properties of the three-layer co-extruded biodegradable films obtained in Examples 1-3 and Comparative Examples 1-2 are tested below.

[0055] 1. Mechanical properties

[0056] Referring to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", the three-layer co-extruded biodegradable films obtained in Examples 1-3 and Comparative Examples 1-2 were cut into Type 2 strips with a width of 25 mm. Their mechanical properties and elongation at break (transverse) were tested at a test rate of 500 mm / min. The results are shown in Table 1.

[0057] 2. Thermal insulation performance

[0058] In an indoor environment with a temperature of 10°C, half the height of farmland soil was filled into an open acrylic box (20cm×10cm×10cm). An electronic thermometer was placed on the soil surface. The opening of the acrylic box was covered with the three-layer co-extruded biodegradable film obtained in Examples 1-3 and Comparative Examples 1-2, respectively. Then, the film surface was vertically irradiated with a 500W xenon lamp at a height of 1.5m. After irradiation for 1 hour, the irradiation was stopped, and the temperature inside the acrylic box was recorded 1 hour after the irradiation was stopped. The results are shown in Table 1.

[0059] 3. Moisture retention performance

[0060] Referring to the cup weight gain method in GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Weight Gain and Loss Method", the three-layer co-extruded biodegradable films obtained in Examples 1-3 and Comparative Examples 1-2 were sealed in a permeable cup containing desiccant and placed in an environment with a temperature of 38℃ ± 0.5℃ and a relative humidity of 90% ± 2%. The water vapor permeability (WVT) was determined based on the weight change after constant weight was achieved. The results are shown in Table 1. The smaller the WVT, the better the moisture retention performance.

[0061] Table 1: Performance of the three-layer co-extruded biodegradable films obtained in Examples 1-3 and Comparative Examples 1-2

[0062]

[0063] Furthermore, the rupture time of the PBST three-layer co-extruded biodegradable mulch film formed by the above-mentioned PBST three-layer co-extruded biodegradable film is controlled through the following specific implementation methods.

[0064] Example 4

[0065] This embodiment provides a PBST three-layer co-extruded biodegradable membrane. Its composition and preparation method differ from Example 1 only in that the core layer's raw materials also include 3 parts plant fiber (bamboo powder and hemp stalk powder in a 2:1 mass ratio, 60 mesh), and the surface layer's raw materials also include 0.5 parts nano-titanium dioxide and 0.5 parts antioxidant 1010. Everything else remains the same as in Example 1.

[0066] Example 5

[0067] This embodiment provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The only difference between this membrane and Example 2 is that the core layer is prepared by adding 2 parts of plant fiber (bamboo powder and hemp stalk powder in a 1:1 mass ratio, 60 mesh), and the surface layer is prepared by adding 0.5 parts of nano titanium dioxide and 0.5 parts of antioxidant 1076. Everything else remains the same as in Example 2.

[0068] Example 6

[0069] This embodiment provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The only difference between this membrane and Example 1 is that the core layer also includes 2.5 parts of plant fiber (bamboo powder and coconut shell powder in a mass ratio of 1:1.5, 60 mesh), and the surface layer also includes 0.5 parts of nano titanium dioxide, 0.5 parts of antioxidant 1010, and 0.3 parts of antioxidant 168. Everything else remains the same as in Example 1.

[0070] Example 7

[0071] This embodiment provides a PBST three-layer co-extruded biodegradable membrane and its preparation method. The only difference between this membrane and Example 2 is that the core layer also includes 3 parts of plant fiber (bamboo powder and coconut shell powder in a mass ratio of 1:2, 60 mesh), and the surface layer includes 0.5 parts of nano titanium dioxide, 0.5 parts of antioxidant 1076, and 0.3 parts of antioxidant 168. Everything else remains the same as in Example 2.

[0072] Referring to the above methods for testing mechanical properties and heat preservation and moisture retention properties, the above properties of the PBST three-layer co-extruded biodegradable films obtained in Examples 4 to 7 were tested, and the results are shown in Table 2.

[0073] Table 2: Performance of the three-layer co-extruded biodegradable membranes obtained in Examples 4-7

[0074]

[0075] Application Examples 1-4

[0076] The above application examples provide a PBST three-layer co-extruded biodegradable mulch film, which is formed from the PBST three-layer co-extruded biodegradable films obtained in Examples 4 to 7. That is, the PBST three-layer co-extruded biodegradable films obtained in Examples 4 to 7 are directly used as the PBST three-layer co-extruded biodegradable mulch films in Application Examples 1 to 4.

[0077] Below, the rupture time of the PBST three-layer co-extruded biodegradable mulch film obtained in Examples 1-4 was tested in the southern and northern Xinjiang regions respectively. The specific test method was as follows: The PBST three-layer co-extruded biodegradable mulch film (size 1.5m×20m) obtained in Examples 1-4 was laid in the fields of southern and northern Xinjiang respectively. After 60 days of laying, the mulch film was observed every 5 days to see if the phenomenon of natural rupture occurred. The time when natural rupture began to occur was recorded as the rupture time. The results are shown in Table 3.

[0078] Table 3: Break-up time of PBST three-layer co-extruded biodegradable mulch film obtained in Application Examples 1-4

[0079]

[0080] As can be seen, the PBST three-layer co-extruded biodegradable mulch film obtained in Application Examples 1-2 can achieve a film breaking time of about 140 days in the northern Xinjiang region, and the PBST three-layer co-extruded biodegradable mulch film obtained in Application Examples 3-4 can achieve a film breaking time of about 140 days in the southern Xinjiang region. That is, by adding plant fibers, UV stabilizers, and antioxidants, the present invention effectively further solves the problem of precisely controlling the film breaking time of the formed PBST three-layer co-extruded biodegradable mulch film to about 140 days in the Xinjiang region. The PBST three-layer co-extruded biodegradable mulch film of the present invention meets the needs of planting crops such as cotton in all regions.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A PBST three-layer co-extruded biodegradable membrane, characterized in that, It includes a core layer and a surface layer, wherein the surface layer includes a first surface layer and a second surface layer located on both sides of the core layer; By weight, the raw materials for preparing the core layer include 75-95 parts of PBST, 10-20 parts of heavy calcium carbonate, 10-20 parts of other fillers, and 1-2 parts of toughening agent; the raw materials for preparing the surface layer include 65-90 parts of PBST, 10-35 parts of PBAT, and 0.5-2 parts of compatibility toughening agent.

2. The PBST three-layer co-extruded biodegradable membrane according to claim 1, characterized in that, The raw materials for preparing the core layer also include 1 to 4 parts of plant fiber, and the raw materials for preparing the surface layer also include 0.1 to 1 part of UV protectant and 0.1 to 1 part of antioxidant.

3. The PBST three-layer co-extruded biodegradable membrane according to claim 2, characterized in that, The plant fiber is selected from bamboo powder and hemp stalk powder, the UV stabilizer is selected from at least one of nano titanium dioxide and nano cerium oxide, and the antioxidant is selected from hindered phenols.

4. The PBST three-layer co-extruded biodegradable membrane according to claim 2, characterized in that, The plant fiber is selected from bamboo powder and coconut shell powder, the UV stabilizer is selected from at least one of nano titanium dioxide and nano cerium oxide, and the antioxidant is selected from hindered phenols and phosphites.

5. The PBST three-layer co-extruded biodegradable membrane according to any one of claims 1 to 4, characterized in that, The heavy calcium carbonate is selected from activated heavy calcium carbonate; and / or, the other filler is selected from at least one of talc, mica, kaolin, barium sulfate, zinc sulfide, aluminum sulfide, and calcium sulfide; and / or, the toughening agent is selected from at least one of POE-g-GMA, POE-g-MAH, and TPEE; and / or, the compatibility toughening agent is selected from at least one of POE-g-GMA and POE-g-MAH.

6. The PBST three-layer co-extruded biodegradable membrane according to any one of claims 1 to 4, characterized in that, The raw materials for preparing the surface layer also include 0.5 to 3 parts of an opening slip agent; And / or, the ratio of the core layer thickness to the surface layer thickness is 1 to 1.2:

1.

7. The method for preparing the PBST three-layer co-extruded biodegradable membrane according to any one of claims 1 to 6, characterized in that, The process includes the following steps: heating and melting the raw materials for the core layer and the surface layer respectively, feeding them into a co-extrusion die, extruding, blowing, drawing, and winding to obtain the PBST three-layer co-extruded biodegradable membrane.

8. The preparation method according to claim 7, characterized in that, The heating and melting temperature is 120~160℃ and the co-extrusion die temperature is 143~147℃; or, the heating and melting temperature is 125~165℃ and the co-extrusion die temperature is 148~152℃.

9. The preparation method according to claim 7, characterized in that, The blow-up ratio of the blow-forming process is 2.5 to 3.0; and / or the traction ratio of the traction process is 3.5 to 4.

2.

10. A PBST three-layer co-extruded biodegradable mulch film, characterized in that, Includes the PBST three-layer co-extruded biodegradable membrane as described in any one of claims 1 to 6.

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