Production process and application of branched-chain PPC-based ultrathin full-biodegradable mulching film photolysis-resistant master batch

Abstract

The invention relates to a branched-chain PPC-based ultrathin full-biodegradable mulching film photolysis-resistant master batch as well as a preparation method and application thereof. The photolysis-resistant master batch comprises a photolysis-resistant auxiliary agent and branched chain PPC in a weight ratio of 1: (7-7.5), wherein the photolysis-resistant auxiliary agent is prepared from silicon dioxide, biomass calcium powder, a KH560 silane coupling agent, a phosphite ester auxiliary antioxidant, an ultraviolet light absorber, corn oil and water; the preparation method comprises the following steps: adding the raw materials into water, stirring to form a honeycomb-shaped raw material, carrying out cold-pressing extrusion granulation, and modifying with branched-chain PPC on a double-screw thermoplastic extruder; the full-biodegradable mulching film is prepared from branched-chain PPC, PBAT and branched-chain PPC photolysis-resistant master batch according to the mass ratio of (1-1.2): (2-2.5): (1-1.2). The weather-proof period of the full-biodegradable mulching film can be remarkably prolonged to 100 days or above, the longitudinal and transverse right-angle tearing strength of the ultrathin mulching film with the thickness of 0.006 mm + / -0.0002 mm can reach 1.0 N, and meanwhile the thickness of the mulching film and the use amount cost per mu are reduced by about 40%.

Description

Technical Field

[0001] This invention belongs to the field of agricultural plastic molding technology, and specifically relates to a branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch. It also relates to the preparation method of the branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch and the application method of using the masterbatch to prepare fully biodegradable mulch film. Background Technology

[0002] In recent years, the area covered by PE mulch film in my country has exceeded 300 million mu (approximately 20 million hectares). However, mulch film residue causes ground-source pollution in cultivated land, making the replacement of PE mulch film with fully biodegradable mulch film an inevitable trend. Currently, although fully biodegradable mulch film products made from biodegradable materials such as PBAT, PLA, PPC, and PCU are available on the market, these products generally suffer from problems such as large thickness, high price, and short weather resistance, making their promotion in agricultural production extremely difficult. The relevant standard for fully biodegradable mulch film, GB / T35795-2017 "Fully Biodegradable Farmland Covering Film," stipulates that fully biodegradable mulch film can be marketed after 60 days of weather resistance. However, in actual agricultural production, mulch film with a weather resistance of less than 90 days will prematurely lose its water retention and weed-blocking functions, failing to meet production needs and leading to reduced yields. The stretched area of ​​a 0.01mm fully biodegradable mulch film is 79.36m². 2 / kg, compared to 135.87 m³ of 0.008mm PE mulch film. 2 / kg / square meter less 56.5 m 2 / kg. The dosage of 0.01mm fully biodegradable mulch film is 6.72kg / mu, with a cost of 168 yuan / mu, which is much greater than the dosage of 0.008mm PE mulch film, which is 4.9kg / mu, with a cost of 54 yuan / mu.

[0003] To address the aforementioned issues in existing technologies, a PPC-based polypropylene carbonate biodegradable permeable mulch film has been developed. This film can produce a 0.007mm thick fully biodegradable mulch film and maintain a 60-day weather resistance period (see the article "Development and Performance Analysis of Polypropylene Carbonate Biodegradable Permeable Mulch Film" published in the October 2021 issue of *China Plastics*, DOI: 10.19491 / j.issn.1001-9278.2021.10.004 for relevant evidence). Simultaneously, an ultra-thin fully biodegradable permeable mulch film product with a thickness of 0.006mm ± 0.0002mm has also been developed, extending the weather resistance period to 86 days while maintaining a lower thickness (see the article "Development and Performance Analysis of Ultra-Thin Fully Biodegradable Permeable Mulch Film" published in the October 2025 issue of *China Plastics*, DOI: 10.19491 / j.issn.1001-9278.2025.05.015 for relevant evidence). The aforementioned technologies, while reducing the thickness of fully biodegradable mulch films, also decrease their weather resistance, thus expanding their applicability to a certain extent. However, the weather resistance of these films still cannot meet the planting needs of some crops or regions. For example, in spring maize planting in the North China Plain, the main function of the mulch film is to increase soil temperature, retain moisture, and promote early emergence and growth of maize. The actual usage time of the mulch film is about 60-70 days. However, when planting maize in arid areas of Northwest China, the mulch film needs to additionally perform water retention. To ensure that the mulch film does not break throughout the entire maize growth period, a weather resistance period of more than 100 days is required. The aforementioned biodegradable mulch films cannot be applied to planting under these circumstances. In existing technologies, the addition of light calcium carbonate and talc powder of about 800-1500 mesh (particle size 0.018mm-0.010mm) is usually done to improve the rigidity of the biodegradable mulch film. However, this method can only produce 0.01 mm biodegradable mulch films and cannot effectively reduce the film thickness. Furthermore, the calcination temperature of light calcium carbonate is around 900℃, so the calcined calcium carbonate does not have organic groups and cannot be linked with the epoxy and carboxyl groups of the resin, resulting in poor mechanical properties of the mulch film.

[0004] To address these issues, this invention develops a photodegradation-resistant masterbatch for branched PPC-based ultrathin films. Summary of the Invention

[0005] The purpose of this invention is to provide a production process and application of a branched PPC-based ultrathin fully biodegradable mulch film masterbatch that is resistant to photolysis. The mulch film produced has a small thickness, a long weather resistance period, and good mechanical properties.

[0006] To achieve the above objectives, the technical solution adopted in this invention is a branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch, comprising a photodegradation resistant agent and branched PPC. The photodegradation resistant agent is composed of silica, biomass calcium powder, KH560 silane coupling agent, corn oil, phosphite-based auxiliary antioxidants, ultraviolet absorbers, and water.

[0007] The weight ratio of the photodegradation resistant agent to branched PPC is 1:7.

[0008] The photodegradation resistant additive uses 3000 mesh silica with a particle size of no more than 0.005 mm and 2500 mesh biomass calcium powder with a particle size of no more than 0.006 mm.

[0009] Each 50 kg of silica corresponds to 45 kg to 50 kg of biomass calcium powder, 50 ml to 60 ml of KH560 silane coupling agent, 50 ml to 60 ml of corn oil, 1.0 kg to 1.2 kg of phosphite-based auxiliary antioxidant, 3.5 kg to 4.0 kg of ultraviolet absorber, and 50 L to 55 L of water.

[0010] The biomass calcium powder is produced from oyster shells, seashells, and legally cultured corals using a wet grinding process, followed by sedimentation and stratification. The KH560 silane coupling agent is γ-glycidoxypropyltrimethoxysilane, the phosphite-based auxiliary antioxidant is RIANOX 168 reagent produced by Lianlong, and the ultraviolet absorber is RIANOX UV-234 reagent produced by Lianlong.

[0011] Another technical solution of the present invention is a method for preparing a photodegradation resistant masterbatch of branched PPC-based ultrathin fully biodegradable mulch film, which is carried out according to the following steps:

[0012] Step 1: Select silica, biomass calcium powder, KH560 silane coupling agent, corn oil, phosphite-based auxiliary antioxidants, and ultraviolet absorbers according to the specified proportions.

[0013] Step 2: Add KH560 silane coupling agent, phosphite auxiliary antioxidant, ultraviolet absorber and corn oil to water in sequence and stir until they are fully mixed;

[0014] Step 3: After stirring, add silica and biomass calcium powder to the solution in sequence, and stir again to form a honeycomb-like raw material with alternating dry and wet phases;

[0015] Step 4: After granulation and drying of the honeycomb raw material in a cold extruder, a photodegradation resistant agent is formed;

[0016] Step 5: Select the photodegradation accelerator and branched PPC according to the weight ratio;

[0017] Step 6: Mix the selected photodegradation auxiliaries and branched PPC and feed them into a twin-screw thermoplastic extruder;

[0018] Step 7: After the mixture is extruded from a twin-screw thermoplastic extruder, it is drawn into fibers, cooled in water, and pelletized to obtain branched PPC-based photodegradation resistant masterbatch.

[0019] In step 6, a twin-screw thermoplastic extruder is used for granulation modification, wherein the heating temperature of the feeding zone is 135°C, the heating temperature of the front zone is 165°C, the heating temperature of the middle zone is 168°C, the heating temperature of the rear zone is 170°C, and the heating temperature of the outlet zone is 170°C.

[0020] The branched PPC-based ultrathin fully biodegradable mulch film masterbatch obtained after pelleting in step 7 has a particle size of 2mm to 5mm, and the masterbatch needs to be stored in the dark at an ambient temperature below 30℃.

[0021] Another technical solution of the present invention is a fully biodegradable mulch film, which is made of branched PPC, PBAT and branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch, and the mass ratio between branched PPC, PBAT and branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch is (1~1.2):(2~2.5):(1~1.2).

[0022] Another technical solution of the present invention is a method for preparing a branched PPC-based ultrathin fully biodegradable mulch film, the specific preparation method of which is as follows:

[0023] Step 1: Select branched PPC, PBAT and branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch in sequence according to weight ratio;

[0024] Step 2: Feed various raw materials into the blow molding machine and set the blow ratio to blow into a film;

[0025] Step 3: Cut the film to form the finished mulch film.

[0026] In step 2, after the raw material is fed into the blow molding machine, the heating temperature of the feeding zone is adjusted to 165°C, the heating temperature of the front zone is 165°C, the heating temperature of the middle zone is 168°C, the heating temperature of the rear zone is 170°C, and the heating temperature of the die head is 168°C.

[0027] In step 2, the blow-up ratio of the blow molding machine is set to a bubble diameter: die diameter = 2.8 to 4.0: 1, resulting in a film thickness of 0.006 mm ± 0.0002 mm.

[0028] In step 1, when selecting raw materials, biodegradable black masterbatch can be added according to the light-dissipating requirements. The amount added is 6% to 7% of the total mass of all the above raw materials, including branched PPC, PBAT, and branched PPC-based ultra-thin fully biodegradable mulch film photodegradation masterbatch. The content of 3000 mesh carbon black powder in the biodegradable black masterbatch used is 25% to 30%, thus obtaining black branched PPC-based ultra-thin fully biodegradable mulch film.

[0029] The present invention has the following advantages compared with the prior art:

[0030] The neutral epoxy groups in the KH560 silane coupling agent used in this invention can not only couple with ultrafine silica and ultrafine biomass calcium, but also react with branched PPC, carboxyl groups, amino groups, etc. to form chemical bonds. Simultaneously, the addition of corn oil prevents silica and biomass calcium powder from clumping, facilitating dispersion and crosslinking with branched PPC. The biomass calcium powder retains organic groups, which, through hydrogen bonding with branched PPC and PBAT via carboxyl or hydroxyl groups, form a mechanically based linkage system […KH560-SiO2-CaCO3-branched PPC…PBAT…], increasing the compatibility between the composite materials. This results in a comprehensive improvement in the longitudinal and transverse right-angle tear strength, tensile strength, etc., of the prepared film, while also enhancing the film's weather resistance. The fully biodegradable farmland cover film based on branched PPC with the mechanical structure of […KH560-SiO2-CaCO3-branched PPC…PBAT…] has improved tensile load, elongation at break and right-angle tear load in both the transverse and longitudinal directions. The weather resistance period has been extended from 60 days to more than 100 days, and the thickness has been reduced from 0.01mm to 0.006mm, resulting in a 40% reduction in usage cost.

[0031] The silica in this invention achieves efficient, stable, and safe ultraviolet protection through the coordinated effects of reflection, scattering, and absorption, making it a high-performance ultraviolet reduction material. SiO2 has high transmittance for long-wave ultraviolet radiation (UVA 315-400nm) and primarily absorbs short-wave ultraviolet radiation (UVB and UVC, <300nm). The 3000-mesh SiO2 in the ultra-thin, fully biodegradable mulch film photodegradation masterbatch, belonging to fumed silica, has a large specific surface area. After modification, it exhibits high dispersibility in branched PPC-based ultra-thin, fully biodegradable farmland cover films, acting like countless tiny mirrors to scatter and reflect ultraviolet radiation from all directions, greatly reducing the absorption and degradation of the polyester film, thereby extending the film's weather resistance.

[0032] The branched PPC-based ultrathin fully biodegradable mulch film masterbatch of this invention contains ether bonds, carbonyl groups, ester groups, and alkylene groups, which are easily decomposed into carbon dioxide and water under the action of microorganisms, sunlight, or catalysis by alkalis or acids. Therefore, it belongs to biodegradable or environmentally degradable materials. Among the photodegradable additives, silica is a harmless inorganic mineral, and the products of biomass calcium powder degradation are also harmless inorganic minerals. Corn oil and KH560 silane coupling agent are also environmentally friendly materials. The hydroxyl and ester groups on the surface of biomass calcium powder are functional additives that increase the affinity between polyester molecules. KH560 silane coupling agent can couple biomass calcium and corn oil ester and hydroxyl groups, as well as polyester materials, significantly increasing the longitudinal and transverse tear strength of the film and extending its safe and effective service life and weather resistance. This allows for a reduction in film thickness, providing the necessary conditions for branched PPC-based ultrathin fully biodegradable farmland covering film. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation process of the branched PPC-based photodegradation resistant agent in this invention.

[0034] Figure 2 This is a flowchart illustrating the preparation process of the branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch in this invention.

[0035] Figure 3 This is a flowchart illustrating the preparation process of the branched PPC-based fully biodegradable mulch film of this invention.

[0036] Figure 4 The reflectance of the black branched PPC-based fully biodegradable mulch film prepared according to the present invention in the laboratory;

[0037] Figure 5 The image shows the reflectance of the black branched PPC-based fully biodegradable mulch film prepared according to the present invention in a field.

[0038] Figure 6 Here is the molecular formula of the branched PPC used in this invention;

[0039] Figure 7 The molecular formula of the KH560 silane coupling agent used in this invention is shown below. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1:

[0042] A preparation process for a branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch, such as... Figure 1 As shown:

[0043] 100 ml of KH560 silane coupling agent, 2.0 kg of phosphite-based auxiliary antioxidant, 6.6 kg of ultraviolet absorber, and 100 ml of corn oil were added sequentially to 100 liters of water and stirred. Then, 100 kg of 3000-mesh silica and 100 kg of biomass calcium powder with a particle size ≤0.006 mm (equivalent to passing through 2500 mesh) were added sequentially and stirred to form a honeycomb structure with alternating dry and wet phases. The mixture was then loaded into a cold-press extruder funnel and granulated into particles with a diameter of 2 mm to 5 mm. After drying the particles, they were weighed and packed into moisture-proof bags and stored in a sealed container away from light at an ambient temperature below 30°C to produce 200 kg of photodegradation resistant additive.

[0044] The biomass calcium powder was purchased directly from Yanda Mineral Products Processing Enterprise in Lingshou County, Hebei Province. It was produced through wet ball milling using a 325-mesh sieve. The total batch size was 2000 kg, with shells and oysters each accounting for 50% of the raw materials. After purchase, the powder was slowly rinsed with tap water into a deep pit in the brickwork surface, covered with a windproof cover to keep it clean, and left to stand for 3 weeks until the moisture seeped out. Samples were then taken in layers, dried, and the particle size was determined under a microscope. Dry powder with a particle size ≤0.006 mm was obtained for preparation. 3000-mesh silica powder and KH560 silane coupling agent were purchased from Shanxi Tongde Chemical Co., Ltd. Phosphite-based auxiliary antioxidants and UV absorbers were purchased from RIANOX 168 reagent and RIANOX UV-234 reagent, respectively, produced by Lialon. The molecular structure of KH560 silane coupling agent is as follows: Figure 7 As shown.

[0045] Then, 200 kg of photodegradation resistant additive and 1400 kg of branched PPC were selected at a weight ratio of 1:7 and modified on a ∮30 twin-screw thermoplastic extruder. The temperature settings were: feeding zone heating temperature 135℃, front zone heating temperature 165℃, middle zone heating temperature 168℃, rear zone heating temperature 170℃, and outlet heating temperature 170℃. After drawing, water cooling, pelletizing, and drying, 1600 kg of branched PPC-based ultra-thin fully biodegradable mulch film photodegradation resistant masterbatch with a particle size of 2mm-5mm was produced. After weighing, it was sealed in a moisture-proof bag and stored away from light at an ambient temperature below 30℃. The molecular formula of branched PPC is as follows. Figure 6 As shown.

[0046] Example 2:

[0047] The branched PPC-based ultrathin fully biodegradable mulch film prepared in Example 1 was used to prepare a fully biodegradable mulch film. Figure 2 As shown:

[0048] 250 kg of branched PPC resin, 500 kg of PBAT resin, and 250 kg of ultra-thin, fully biodegradable, photodegradable mulch film masterbatch were selected and added to a blow molding machine with a die diameter of 180 mm. The heating temperatures were set as follows: feeding zone 165℃, front zone 168℃, middle zone 168℃, rear zone 170℃, and die head 168℃. The blow-up ratio was set to 2.8:1. The resulting agricultural mulch film was blown to a thickness of 0.006 mm and a width of 800 mm, and then wound into 5 kg rolls. The branched PPC resin had a number-average molecular weight of 100,000 and a weight-average molecular weight of 250,000, and was purchased from Zhejiang Huafeng Company (internal code HF902). The PBAT resin had a number-average molecular weight of 60,000 and a weight-average molecular weight of 140,000, and was purchased from Shanghai Tongcheng Company (internal code RA-WR290).

[0049] Mechanical testing was conducted on the prepared 0.006 mm branched PPC-based fully biodegradable mulch film. The CMA testing institution was the Polymer Materials Research Center of Taiyuan City, Shanxi Province. The test results are as follows: Report No. WJD202503009.

[0050]

[0051] The aging resistance of the prepared 0.006 mm branched PPC-based fully biodegradable mulch film was tested, and the results are as follows:

[0052]

[0053] Example 3:

[0054] The branched PPC-based ultrathin fully biodegradable mulch film prepared in Example 1 was used to prepare a fully biodegradable mulch film. Figure 3 As shown:

[0055] 250 kg of branched PPC resin, 500 kg of PBAT resin, and 250 kg of ultra-thin fully biodegradable mulch film photodegradation resistant masterbatch were selected and added to a blow molding machine with a die diameter of 250 mm. The heating temperatures were set as follows: feeding zone 165℃, front zone 168℃, middle zone 168℃, rear zone 170℃, and die head 168℃. The blow-up ratio was 3.3:1. The film was blown into a farmland covering film with a thickness of 0.007 mm and a width of 1300 mm, and then rolled into 10 kg sheets.

[0056] The prepared 0.007 mm branched PPC-based fully biodegradable mulch film was tested by the CMA testing institution, Taiyuan Polymer Materials Research Center, Shanxi Province. The test results are as follows: Report No. WJD20252004.

[0057]

[0058] The original method yielded a 0.01mm PPC-PBAT-based fully biodegradable mulch film. The CMA testing institution was the Taiyuan Plastics Research Institute of Shanxi Province, and the test results are as follows: Report No. WJX202003010

[0059]

[0060] By comparing the mulch films prepared in Examples 2 and 3 with existing mulch films, it can be seen that the mulch films obtained according to this method have significantly improved tensile load, elongation at break, and right-angle tear load in both the transverse and longitudinal directions.

[0061] Practical applications:

[0062] A 0.006 mm thick fully biodegradable mulch film was produced using branched PPC-based ultrathin fully biodegradable mulch film photodegradation-resistant masterbatch and a corresponding formula. It was applied in Lucheng District of Changzhi City in southern Shanxi Province, Yangqu County of Taiyuan City in central Shanxi Province, Shanyin County of Shuozhou City and Hequ County of Xinzhou City in northern Shanxi Province, and Fugu County and Jiaxian County of Yulin City in northern Shaanxi Province. The decomposition rate was tested under different climatic, soil, and vegetation conditions. A 0.01 mm thick PPC-PBAT-based fully biodegradable mulch film was prepared using the original formula as a control (CK). The test results are as follows:

[0063]

[0064] The test results show that the branched PPC-based ultrathin fully biodegradable mulch film prepared by this invention can maintain its integrity for a long time under different climate and soil conditions. The film prepared by this method can still remain undamaged for more than 103 days, while the mulch film of the control group will break after 65 days.

[0065] At the same time, by the appendix Figure 4 and attached Figure 5 It can be seen that the black branched PPC fully biodegradable mulch film prepared by adding carbon black in this invention appears white under strong light in the laboratory and field, and the whitening is more obvious with stronger light, proving that the film has a significant light-masking effect on strong light, which further improves the weather resistance of the mulch film.

Claims

1. A branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch, characterized in that, It includes a photodegradation resistant agent and branched PPC. The photodegradation resistant agent is composed of silica, biomass calcium powder, KH560 silane coupling agent, corn oil, phosphite-based auxiliary antioxidants, ultraviolet absorbers, and water. The weight ratio of the photodegradation resistant agent to branched PPC is 1:7 to 7.

5.

2. The branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch according to claim 1, characterized in that, The photodegradation resistant additive uses 3000 mesh silica with a particle size of no more than 0.005 mm and 2500 mesh biomass calcium powder with a particle size of no more than 0.006 mm. Each 50 kg of silica corresponds to 45 kg to 50 kg of biomass calcium powder, 50 ml to 60 ml of KH560 silane coupling agent, 50 ml to 60 ml of corn oil, 1.0 kg to 1.2 kg of phosphite-based auxiliary antioxidant, 3.5 kg to 4.0 kg of ultraviolet absorber, and 50 L to 55 L of water.

3. The branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch according to claim 2, characterized in that, The biomass calcium powder is produced by wet grinding, sedimentation, and stratification of oyster shells, seashells, and artificially cultivated corals. The KH560 silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

4. A method for preparing a photodegradable masterbatch for branched PPC-based ultrathin fully biodegradable mulch film, characterized in that, The formulation of the photodegradable masterbatch for branched PPC-based ultrathin fully biodegradable mulch film as described in claim 3 is carried out according to the following steps: Step 1: Select silica, biomass calcium powder, KH560 silane coupling agent, corn oil, phosphite-based auxiliary antioxidants, and ultraviolet absorbers according to the specified proportions. Step 2: Add KH560 silane coupling agent, phosphite auxiliary antioxidant, ultraviolet absorber and corn oil to water in sequence and stir until the five are fully mixed; Step 3: After stirring, add silica and biomass calcium powder to the solution in sequence, and stir again to form a honeycomb-like raw material with alternating dry and wet phases; Step 4: After granulation and drying of the honeycomb raw material in a cold extruder, a photodegradation resistant agent is formed; Step 5: Select the photodegradation accelerator and branched PPC according to the weight ratio; Step 6: Mix the selected photodegradation auxiliaries and branched PPC and feed them into a twin-screw thermoplastic extruder; Step 7: After the mixture is extruded from a twin-screw thermoplastic extruder, it is drawn into fibers, cooled in water, and pelletized to obtain branched PPC-based photodegradation resistant masterbatch.

5. The method for preparing the photodegradable masterbatch of branched PPC-based ultrathin fully biodegradable mulch film according to claim 4, characterized in that, In step 6, the heating temperature of the twin-screw thermoplastic extruder is 135°C in the feeding zone, 165°C in the front zone, 168°C in the middle zone, 170°C in the rear zone, and 170°C in the outlet zone.

6. The method for preparing the photodegradable masterbatch of branched PPC-based ultrathin fully biodegradable mulch film according to claim 4, characterized in that, The branched PPC-based ultrathin fully biodegradable mulch film masterbatch obtained after pelleting in step 7 has a particle size of 2mm to 5mm, and the masterbatch needs to be stored in the dark at an ambient temperature below 30℃.

7. A branched PPC-based ultrathin fully biodegradable mulch film, characterized in that, The branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch prepared using PPC, PBAT and any one of claims 4 to 6, wherein the mass ratio between branched PPC, PBAT and branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch is (1 to 1.2): (2 to 2.5): (1 to 1.2).

8. A method for preparing a branched PPC-based ultrathin fully biodegradable mulch film, characterized in that, The specific preparation method using the branched PPC-based ultrathin fully biodegradable mulch film formulation described in claim 7 is as follows: Step 1: Select branched PPC, PBAT and branched PPC-based ultrathin fully biodegradable mulch film photodegradation resistant masterbatch in sequence according to weight ratio; Step 2: Feed various raw materials into the blow molding machine and set the blow ratio to blow into a film; Step 3: Cut the film to form the finished mulch film.

9. The method for preparing branched PPC-based ultrathin fully biodegradable mulch film according to claim 8, characterized in that, In step 2, after the raw material is fed into the blow molding machine, the heating temperature of the feeding zone is adjusted to 165°C, the heating temperature of the front zone is 165°C, the heating temperature of the middle zone is 168°C, the heating temperature of the rear zone is 170°C, and the heating temperature of the die head is 168°C.

10. The method for preparing branched PPC-based ultrathin fully biodegradable mulch film according to claim 8, characterized in that, In step 2, the blow-up ratio of the blow molding machine is set to a bubble diameter: die diameter = 2.8 to 4.0: 1, resulting in a film thickness of 0.006 mm ± 0.0002 mm. In step 1, when selecting raw materials, biodegradable black masterbatch can be added according to the light-dissipating requirements. The amount added is 6% to 7% of the total mass of all the above raw materials, including branched PPC, PBAT, and branched PPC-based ultra-thin fully biodegradable mulch film photodegradation masterbatch. The content of 3000 mesh carbon black powder in the biodegradable black masterbatch used is 25% to 30%, thus obtaining black branched PPC-based ultra-thin fully biodegradable mulch film.

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