A polymer thin film and a manufacturing method thereof

Abstract

This invention relates to the field of thin film technology, specifically providing a polymer thin film and its manufacturing method, comprising the following raw materials in parts by weight: 48-52 parts of recycled polypropylene (rPP), 38-42 parts of polybutylene adipate-butylene terephthalate (PBAT), 7-9 parts of surface-aminated modified nanocellulose whiskers (CNC, diameter 20-30 nm), and 1.2-1.8 parts of bio-based interface stabilizer. This invention utilizes maleic anhydride grafted lignin to form a three-dimensional hydrogen bond network with rPP / PBAT. DSC measurements show a phase separation temperature difference ΔT = 35℃ and an interfacial peel strength of 13.2 N / cm. The synergistic effect of the epoxy-functionalized castor oil ring-opening reaction and the release of reactive oxygen free radicals from mesoporous zinc oxide (6-10 nm) increases the gel content to 72%. Hindered amine additives are released slowly through the mesoporous zinc oxide nanopores, blocking the PBAT ester hydrolysis chain reaction, resulting in a 60% reduction in the measured hydrolysis rate. A temperature path of 155℃→210℃→160℃ is used, with a melt viscosity fluctuation rate of ±2.5%, solving the problem of a narrow processing window caused by the heat sensitivity of PBAT.

Description

Technical Field

[0001] This invention relates to the field of thin film technology, and in particular to a polymer thin film and its manufacturing method. Background Technology

[0002] Currently, polymer films are thin films made from organic polymer materials. With the development of the petroleum industry and technology, the application fields of polymer films have been continuously expanding, evolving from initial packaging films to intelligent polymer films, functional polymer films, and so on. Among these, selective separation membranes, such as ion exchange membranes, microporous filtration membranes, ultrafiltration membranes, liquid membranes, and liquid crystal membranes, are used in various fields including nuclear fuel and metal refining, gas separation, seawater desalination, ultrapure water preparation, wastewater treatment, artificial organ manufacturing, medicine, food, agriculture, and chemicals. These products have brought great convenience to people's lives. With the widespread application of polymer films in various fields, coating their surfaces with modified coatings also has significant application prospects. Modified coatings can not only endow polymer films with new functions but also improve their durability, further enhancing the application value of polymer films.

[0003] Regarding the aforementioned technologies, the inventors believe that the following defects exist: existing polymer films have insufficient thermal stability during high-temperature extrusion processing, resulting in uneven film thickness and discrete mechanical properties. The introduction of recycled components further exacerbates the problem of weak interfacial bonding, leading to low product qualification rate and limited environmental adaptability. Summary of the Invention

[0004] To address the shortcomings of existing polymer films in terms of thermal stability during high-temperature extrusion processing, which leads to uneven film thickness and discrete mechanical properties, and the further exacerbation of weak interfacial bonding by the introduction of recycled components, resulting in low product yield and limited environmental adaptability, this application provides a polymer film and its manufacturing method.

[0005] This application provides a polymer film and its manufacturing method, which adopts the following technical solution: A polymer film comprising the following raw materials in parts by weight: 48-52 parts of recycled polypropylene (rPP), 38-42 parts of polybutylene adipate-butylene terephthalate (PBAT), 7-9 parts of surface-aminated modified nanocellulose whiskers (CNC, diameter 20-30nm), and 1.2-1.8 parts of bio-based interface stabilizer.

[0006] Further, the bio-based interface stabilizer is composed of the following raw materials in parts by weight: 68-72 parts maleic anhydride grafted lignin, 22-28 parts epoxy-functionalized castor oil (epoxy value 0.75-0.85 mol / 100g), 6-10 parts mesoporous zinc oxide (pore size 6-10 nm), and 0.5-1.0 parts anti-hydrolysis agent.

[0007] Further, the formula also includes the following raw materials in parts by weight: 0.5-1.5 parts antioxidant and 0.5-1.5 parts light stabilizer.

[0008] Furthermore, the antioxidant is a hindered phenolic antioxidant.

[0009] Furthermore, the light stabilizer is an ultraviolet absorber.

[0010] Further, the following raw materials are also included by weight: 5-10 parts of filler.

[0011] The filler is at least one of talc, calcium carbonate, or diatomaceous earth.

[0012] Further, the following raw materials are also included by weight: 2-5 parts plasticizer.

[0013] A method for preparing a polymer film includes the following steps: S1. A negative pressure vacuum conveying system is used to accurately deliver each component raw material to the dual-station metering chamber according to the formula ratio. A near-infrared spectrometer is equipped to detect and remove impurities in real time (detection limit ≤0.04mm). At the same time, the magnetic levitation sorting module is started to separate metal particles to ensure that the purity of the raw materials reaches more than 99.9%. S2. Differentiated homogenization is achieved through a four-stage variable frequency vortex mixer: low-speed stage I maintains 55 rpm for initial dispersion, medium-speed stage II increases to 140 rpm for enhanced mixing, high-speed stage III accelerates to 230 rpm to refine particles, and ultra-high-speed stage IV reaches 280 rpm to achieve microscopic homogenization. The built-in ultrasonic crushing head (frequency 25 kHz) works in conjunction with the shear ring assembly to effectively break up agglomeration, reducing mixing time to 55% of conventional processes, and achieving a component distribution uniformity CV value of <3%. S3. Melt extrusion utilizes a specialized equipment with a screw length-to-diameter ratio (L / D) of 40:1, implementing precise eight-zone temperature control: Zone I (155℃) preheats and softens rPP; Zone II (180℃) promotes initial melting of PBAT; Zone III (200℃) deeply plasticizes the composite system; Zone IV (210℃) achieves complete melting; Zone V (205℃) homogenizes melt viscosity; Zone VI (190℃) regulates pressure stability; Zone VII (170℃) cools down to reduce thermal history; and Zone VIII (160℃) stabilizes output. The melt pressure is controlled within 14-16 MPa throughout the process, with a fluctuation rate of ±2.5%. After extrusion through S4 and T-type dies, the film passes through three temperature gradient environments in sequence: the front section is rapidly cooled by a quenching roller (8℃ ice water spray) at a rate of 45℃ / s to quickly set the film and suppress the formation of large spherulites; the middle section is cooled by a slow cooling air knife (30℃ constant temperature airflow) at a rate of 10℃ / s to eliminate internal stress; and the rear section is cooled by a constant humidity setting table (RH=70%) to regulate the crystal morphology, resulting in a final product curvature ≤0.08mm / m. S5. It adopts a shaftless air shaft combined with a mechanical tension feedback arm to dynamically adjust the winding speed and pressure by monitoring the film tension change in real time (accuracy ±0.1N). This achieves precise control of tension fluctuation amplitude ≤±1.5N, ensuring film winding flatness and reducing subsequent processing loss rate to <0.5%. S6. The internal structure of the film is strengthened through a three-step chemical reaction. The basic adhesive layer involves adding maleic anhydride-grafted lignin to the melt. The active groups on its molecular chain form hydrogen bonds with recycled polypropylene (rPP) and non-polar polybutylene adipate-butylene terephthalate (PBAT), constructing a three-dimensional network structure. Differential scanning calorimetry (DSC) shows that this structure increases the phase separation temperature difference to 35°C and improves the interfacial peel strength to 13.2. N / cm (equivalent to a tensile force of 13.2 Newtons per centimeter of width); Dynamic cross-linking layer: Epoxy-functionalized castor oil undergoes a ring-opening reaction during high-temperature processing, generating hydroxyl and ether bonds. These bonds synergistically interact with the reactive oxygen free radicals on the surface of mesoporous zinc oxide, promoting in-situ cross-linking and curing of polymer segments. The final gel content reaches 72%, significantly improving the solvent resistance and mechanical strength of the material; Long-lasting protective layer: Hindered amine anti-hydrolysis additives are slowly released through the nanopores (6-10nm) of mesoporous zinc oxide, continuously capturing free radicals and blocking the hydrolysis chain reaction of PBAT ester groups. Experimental results show that this design can reduce the hydrolysis rate of PBAT by 60% and extend the service life of the film; S7. By using a reverse temperature control curve, high-temperature decomposition of plastics is avoided, and viscosity is kept stable. A temperature gradient design that first increases and then decreases (155℃→210℃→160℃) is adopted to precisely control the risk of PBAT degradation, reducing the melt viscosity fluctuation rate to ±2.5%. Through a stepped cooling system, the surface layer cools and hardens rapidly, while the inner layer crystallizes slowly, creating a flexible film suitable for packaging. Differential cooling of 45℃ / s→10℃ / s→RH=70% optimizes the crystallinity distribution (surface crystallinity 18%-22%, core layer crystallinity 35%-40%), meeting the requirements of high-precision packaging applications.

[0014] Compared with related technologies, the polymer film and its manufacturing method provided by the present invention have the following beneficial effects: This invention provides a polymer film and its fabrication method. A three-dimensional hydrogen bond network is formed by grafting lignin with maleic anhydride onto rPP / PBAT. DSC measurements show a phase separation temperature difference ΔT = 35℃ and an interfacial peel strength of 13.2 N / cm. The synergistic effect of the epoxy-functionalized castor oil ring-opening reaction and the release of reactive oxygen species from mesoporous zinc oxide (6-10 nm) increases the gel content to 72%. Hindered amine auxiliaries are released slowly through the mesoporous zinc oxide nanopores, blocking the PBAT ester hydrolysis chain reaction. The measured hydrolysis rate was reduced by 60%. Using a temperature path of 155℃→210℃→160℃, the melt viscosity fluctuation rate was ±2.5%, solving the problem of narrow processing window caused by the heat sensitivity of PBAT. Through the synergistic effect of bio-based interface stabilizers and CNC, a balance was achieved simultaneously in terms of reinforcement (tensile strength ≥28MPa), toughening (elongation at break ≥450%), and transparency (haze ≤3%). The proportion of recycled rPP material reached 48-52 parts. Combined with a fully degradable PBAT matrix, it meets the GB 4806.7-2016 food contact material standard. Replacing traditional petroleum-based plastics can reduce the carbon footprint by about 32%.

[0015] This invention provides a polymer film and its manufacturing method. By integrating a near-infrared spectrometer (detection limit ≤0.04mm) and a magnetic levitation sorting module into a negative pressure vacuum conveying system, the purity of the raw materials is increased to over 99.9%, reducing the film's porosity / crack defect rate by 58% and achieving a finished product qualification rate of 99.5%. Simultaneously, a four-stage variable frequency eddy current mixer (55-280rpm) combined with a 25kHz ultrasonic crushing head and shear ring assembly breaks down nanocellulose whisker (CNC) aggregates through a gradient shear force field, shortening the mixing time to that of conventional processes. With 55% of the process, the component distribution CV value is <3%, the L / D=40:1 length-to-diameter ratio screw implements eight-zone precise temperature control (zone I 155℃ → zone IV 210℃ → zone VIII 160℃), melt pressure fluctuation rate ±2.5%, inhibiting PBAT high-temperature degradation, and a triple cooling system (front section 8℃ ice water spray 45℃ / s rapid cooling → middle section 30℃ air knife 10℃ / s slow cooling → rear section RH 70% constant humidity shaping) to form a gradient distribution of crystallinity between the surface layer (18%-22%) and the core layer (35%-40%), with a curvature ≤0.08mm / m. Attached Figure Description

[0016] Figure 1 This is a flowchart of a preferred embodiment of a polymer film and its manufacturing method provided by the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to the accompanying drawings. Typical embodiments of the present invention are shown in the drawings. Example 1

[0018] like Figure 1As shown, the present invention provides a polymer film and its manufacturing method, comprising the following raw materials in parts by weight: 48 parts of recycled polypropylene (rPP), 38 parts of polybutylene adipate-butylene terephthalate (PBAT), 7 parts of surface-aminated modified nanocellulose whiskers (CNC, diameter 20-30 nm), and 1.2 parts of bio-based interface stabilizer.

[0019] like Figure 1 As shown, the bio-based interface stabilizer is composed of the following raw materials in parts by weight: 68 parts maleic anhydride grafted lignin, 22 parts epoxy-functionalized castor oil (epoxy value 0.75-0.85 mol / 100g), 6 parts mesoporous zinc oxide (pore size 6-10 nm), and 0.5 parts anti-hydrolysis agent.

[0020] like Figure 1 As shown, it also includes the following raw materials in parts by weight: 0.5 parts antioxidant and 0.5 parts light stabilizer.

[0021] like Figure 1 As shown, the antioxidant is a hindered phenolic antioxidant.

[0022] like Figure 1 As shown, the light stabilizer is an ultraviolet absorber.

[0023] like Figure 1 As shown, it also includes the following raw materials in parts by weight: 5 parts filler.

[0024] like Figure 1 As shown, the filler is at least one of talc, calcium carbonate, or diatomaceous earth.

[0025] like Figure 1 As shown, it also includes the following raw materials in parts by weight: 2 parts plasticizer.

[0026] A method for preparing a polymer film includes the following steps: S1. A negative pressure vacuum conveying system is used to accurately deliver each component raw material to the dual-station metering chamber according to the formula ratio. A near-infrared spectrometer is equipped to detect and remove impurities in real time (detection limit ≤0.04mm). At the same time, the magnetic levitation sorting module is started to separate metal particles to ensure that the purity of the raw materials reaches more than 99.9%. S2. Differentiated homogenization is achieved through a four-stage variable frequency vortex mixer: low-speed stage I maintains 55 rpm for initial dispersion, medium-speed stage II increases to 140 rpm for enhanced mixing, high-speed stage III accelerates to 230 rpm to refine particles, and ultra-high-speed stage IV reaches 280 rpm to achieve microscopic homogenization. The built-in ultrasonic crushing head (frequency 25 kHz) works in conjunction with the shear ring assembly to effectively break up agglomeration, reducing mixing time to 55% of conventional processes, and achieving a component distribution uniformity CV value of <3%. S3. Melt extrusion utilizes a specialized equipment with a screw length-to-diameter ratio (L / D) of 40:1, implementing precise eight-zone temperature control: Zone I (155℃) preheats and softens rPP; Zone II (180℃) promotes initial melting of PBAT; Zone III (200℃) deeply plasticizes the composite system; Zone IV (210℃) achieves complete melting; Zone V (205℃) homogenizes melt viscosity; Zone VI (190℃) regulates pressure stability; Zone VII (170℃) cools down to reduce thermal history; and Zone VIII (160℃) stabilizes output. The melt pressure is controlled within 14-16 MPa throughout the process, with a fluctuation rate of ±2.5%. After extrusion through S4 and T-type dies, the film passes through three temperature gradient environments in sequence: the front section is rapidly cooled by a quenching roller (8℃ ice water spray) at a rate of 45℃ / s to quickly set the film and suppress the formation of large spherulites; the middle section is cooled by a slow cooling air knife (30℃ constant temperature airflow) at a rate of 10℃ / s to eliminate internal stress; and the rear section is cooled by a constant humidity setting table (RH=70%) to regulate the crystal morphology, resulting in a final product curvature ≤0.08mm / m. S5. It adopts a shaftless air shaft combined with a mechanical tension feedback arm to dynamically adjust the winding speed and pressure by monitoring the film tension change in real time (accuracy ±0.1N). This achieves precise control of tension fluctuation amplitude ≤±1.5N, ensuring film winding flatness and reducing subsequent processing loss rate to <0.5%. S6. The internal structure of the film is strengthened through a three-step chemical reaction. The basic adhesive layer involves adding maleic anhydride-grafted lignin to the melt. The active groups on its molecular chain form hydrogen bonds with recycled polypropylene (rPP) and non-polar polybutylene adipate-butylene terephthalate (PBAT), constructing a three-dimensional network structure. Differential scanning calorimetry (DSC) shows that this structure increases the phase separation temperature difference to 35°C and improves the interfacial peel strength to 13.2. N / cm (equivalent to a tensile force of 13.2 Newtons per centimeter of width); Dynamic cross-linking layer: Epoxy-functionalized castor oil undergoes a ring-opening reaction during high-temperature processing, generating hydroxyl and ether bonds. These bonds synergistically interact with the reactive oxygen free radicals on the surface of mesoporous zinc oxide, promoting in-situ cross-linking and curing of polymer segments. The final gel content reaches 72%, significantly improving the solvent resistance and mechanical strength of the material; Long-lasting protective layer: Hindered amine anti-hydrolysis additives are slowly released through the nanopores (6-10nm) of mesoporous zinc oxide, continuously capturing free radicals and blocking the hydrolysis chain reaction of PBAT ester groups. Experimental results show that this design can reduce the hydrolysis rate of PBAT by 60% and extend the service life of the film; S7. By using a reverse temperature control curve, high-temperature decomposition of plastics is avoided, and viscosity is kept stable. A temperature gradient design that first increases and then decreases (155℃→210℃→160℃) is adopted to precisely control the risk of PBAT degradation, reducing the melt viscosity fluctuation rate to ±2.5%. Through a stepped cooling system, the surface layer cools and hardens rapidly, while the inner layer crystallizes slowly, creating a flexible film suitable for packaging. Differential cooling of 45℃ / s→10℃ / s→RH=70% optimizes the crystallinity distribution (surface crystallinity 18%-22%, core layer crystallinity 35%-40%), meeting the requirements of high-precision packaging applications. Example 2

[0027] like Figure 1 As shown, based on Example 1, the present invention provides a technical solution: a polymer film comprising the following raw materials in parts by weight: 52 parts of recycled polypropylene (rPP), 42 parts of polybutylene adipate-butylene terephthalate (PBAT), 9 parts of surface-aminated modified nanocellulose whiskers (CNC, diameter 20-30nm), and 1.8 parts of bio-based interface stabilizer.

[0028] like Figure 1 As shown, the bio-based interface stabilizer is composed of the following raw materials in parts by weight: 72 parts maleic anhydride grafted lignin, 28 parts epoxy-functionalized castor oil (epoxy value 0.75-0.85 mol / 100g), 10 parts mesoporous zinc oxide (pore size 6-10 nm), and 1.0 part anti-hydrolysis agent.

[0029] like Figure 1 As shown, it also includes the following raw materials in parts by weight: 1.5 parts antioxidant and 1.5 parts light stabilizer.

[0030] like Figure 1 As shown, the antioxidant is a hindered phenolic antioxidant.

[0031] like Figure 1 As shown, the light stabilizer is an ultraviolet absorber.

[0032] like Figure 1 As shown, it also includes the following raw materials in parts by weight: 10 parts filler.

[0033] like Figure 1 As shown, the filler is at least one of talc, calcium carbonate, or diatomaceous earth.

[0034] like Figure 1 As shown, it also includes the following raw materials in parts by weight: 5 parts plasticizer.

[0035] A method for preparing a polymer film includes the following steps: S1. A negative pressure vacuum conveying system is used to accurately deliver each component raw material to the dual-station metering chamber according to the formula ratio. A near-infrared spectrometer is equipped to detect and remove impurities in real time (detection limit ≤0.04mm). At the same time, the magnetic levitation sorting module is started to separate metal particles to ensure that the purity of the raw materials reaches more than 99.9%. S2. Differentiated homogenization is achieved through a four-stage variable frequency vortex mixer: low-speed stage I maintains 55 rpm for initial dispersion, medium-speed stage II increases to 140 rpm for enhanced mixing, high-speed stage III accelerates to 230 rpm to refine particles, and ultra-high-speed stage IV reaches 280 rpm to achieve microscopic homogenization. The built-in ultrasonic crushing head (frequency 25 kHz) works in conjunction with the shear ring assembly to effectively break up agglomeration, reducing mixing time to 55% of conventional processes, and achieving a component distribution uniformity CV value of <3%. S3. Melt extrusion utilizes a specialized equipment with a screw length-to-diameter ratio (L / D) of 40:1, implementing precise eight-zone temperature control: Zone I (155℃) preheats and softens rPP; Zone II (180℃) promotes initial melting of PBAT; Zone III (200℃) deeply plasticizes the composite system; Zone IV (210℃) achieves complete melting; Zone V (205℃) homogenizes melt viscosity; Zone VI (190℃) regulates pressure stability; Zone VII (170℃) cools down to reduce thermal history; and Zone VIII (160℃) stabilizes output. The melt pressure is controlled within 14-16 MPa throughout the process, with a fluctuation rate of ±2.5%. After extrusion through S4 and T-type dies, the film passes through three temperature gradient environments in sequence: the front section is rapidly cooled by a quenching roller (8℃ ice water spray) at a rate of 45℃ / s to quickly set the film and suppress the formation of large spherulites; the middle section is cooled by a slow cooling air knife (30℃ constant temperature airflow) at a rate of 10℃ / s to eliminate internal stress; and the rear section is cooled by a constant humidity setting table (RH=70%) to regulate the crystal morphology, resulting in a final product curvature ≤0.08mm / m. S5. It adopts a shaftless air shaft combined with a mechanical tension feedback arm to dynamically adjust the winding speed and pressure by monitoring the film tension change in real time (accuracy ±0.1N). This achieves precise control of tension fluctuation amplitude ≤±1.5N, ensuring film winding flatness and reducing subsequent processing loss rate to <0.5%. S6. The internal structure of the film is strengthened through a three-step chemical reaction. The basic adhesive layer involves adding maleic anhydride-grafted lignin to the melt. The active groups on its molecular chain form hydrogen bonds with recycled polypropylene (rPP) and non-polar polybutylene adipate-butylene terephthalate (PBAT), constructing a three-dimensional network structure. Differential scanning calorimetry (DSC) shows that this structure increases the phase separation temperature difference to 35°C and improves the interfacial peel strength to 13.2. N / cm (equivalent to a tensile force of 13.2 Newtons per centimeter of width); Dynamic cross-linking layer: Epoxy-functionalized castor oil undergoes a ring-opening reaction during high-temperature processing, generating hydroxyl and ether bonds. These bonds synergistically interact with the reactive oxygen free radicals on the surface of mesoporous zinc oxide, promoting in-situ cross-linking and curing of polymer segments. The final gel content reaches 72%, significantly improving the solvent resistance and mechanical strength of the material; Long-lasting protective layer: Hindered amine anti-hydrolysis additives are slowly released through the nanopores (6-10nm) of mesoporous zinc oxide, continuously capturing free radicals and blocking the hydrolysis chain reaction of PBAT ester groups. Experimental results show that this design can reduce the hydrolysis rate of PBAT by 60% and extend the service life of the film; S7. By using a reverse temperature control curve, high-temperature decomposition of plastics is avoided, and viscosity is kept stable. A temperature gradient design that first increases and then decreases (155℃→210℃→160℃) is adopted to precisely control the risk of PBAT degradation, reducing the melt viscosity fluctuation rate to ±2.5%. Through a stepped cooling system, the surface layer cools and hardens rapidly, while the inner layer crystallizes slowly, creating a flexible film suitable for packaging. Differential cooling of 45℃ / s→10℃ / s→RH=70% optimizes the crystallinity distribution (surface crystallinity 18%-22%, core layer crystallinity 35%-40%), meeting the requirements of high-precision packaging applications.

[0036] This technical solution utilizes a negative pressure vacuum conveying system (S1) equipped with a near-infrared spectrometer (detection limit ≤0.04mm) and a magnetic levitation sorting module to ensure raw material purity of 99.9%, reduce film porosity and crack defects, and improve the finished product qualification rate to 99.5%. A four-stage variable frequency eddy current mixer (low speed I 55rpm, medium speed II 140rpm, high speed III 230rpm, ultra-high speed IV 280rpm) with a built-in ultrasonic crushing head (25kHz) and shear ring assembly work together to break up agglomerates, ensuring uniform component distribution (CV value <3%) and eliminating local mechanical property fluctuations. A screw length-to-diameter ratio of [missing information] is employed. The L / D=40:1 equipment implements eight-zone precise temperature control (Zone I 155℃ for softening rPP, Zone II 180℃ for initial melting of PBAT, Zone III 200℃ for plasticizing the composite system, Zone IV 210℃ for complete melting, Zone V 205℃ for viscosity homogenization, Zone VI 190℃ for pressure stabilization, Zone VII 170℃ for transition, and Zone VIII 160℃ for output) to control melt pressure fluctuation rate by ±2.5% and avoid high-temperature degradation. A triple cooling system (front-end rapid cooling roller 8℃ ice water spray 45℃ / s to suppress spherulites, middle-end slow cooling air knife 30℃ airflow 10℃ / s to relieve stress, and rear-end constant humidity shaping table RH=70% to regulate crystallization) achieves a curvature ≤0.0. With an 8mm / m diameter, it meets the high-precision hot-pressing requirements of packaging boxes. Utilizing a shaftless air shaft in conjunction with a mechanical tension feedback arm (monitoring accuracy ±0.1N), it dynamically adjusts the winding speed and pressure, ensuring tension fluctuations are ≤±1.5N, reducing subsequent processing losses to <0.5%. Based on a three-step chemical reaction, it constructs a basic adhesive layer (maleic anhydride grafted lignin forms a hydrogen bond network with rPP / PBAT; DSC measurement shows a phase separation temperature difference ΔT=35℃, with an interfacial peel strength reaching 13.2N / cm) and a dynamic cross-linking layer (epoxy functionalized castor oil ring-opening reaction and mesoporous zinc oxide active oxygen free radical synergistic curing). The film's internal structure is enhanced by increasing the adhesive content to 72% and adding a long-lasting protective layer (a hindered amine anti-hydrolysis agent is released slowly through mesoporous zinc oxide pores of 6-10nm to block the hydrolysis of PBAT ester groups, with a measured hydrolysis rate reduction of 60%). A reverse temperature control curve (155℃→210℃→160℃) is used to suppress PBAT decomposition and maintain stable melt viscosity fluctuations of ±2.5%. A stepped cooling process (45℃ / s→10℃ / s→RH=70%) optimizes the crystallinity distribution (surface layer 18%-22%, core layer 35%-40%) to obtain a flexible and transparent film that meets food-grade packaging application standards.

[0037] The above are merely exemplary embodiments of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described in this disclosure.

Claims

1. A polymer film, characterized in that, The raw materials include the following parts by weight: 48-52 parts of recycled polypropylene (rPP), 38-42 parts of polybutylene adipate-butylene terephthalate (PBAT), 7-9 parts of surface-aminated modified nanocellulose whiskers (CNC, diameter 20-30nm), and 1.2-1.8 parts of bio-based interface stabilizer.

2. The polymer film according to claim 1, characterized in that, The bio-based interface stabilizer is composed of the following raw materials in parts by weight: 68-72 parts maleic anhydride grafted lignin, 22-28 parts epoxy-functionalized castor oil (epoxy value 0.75-0.85 mol / 100g), 6-10 parts mesoporous zinc oxide (pore size 6-10 nm), and 0.5-1.0 parts anti-hydrolysis agent.

3. A polymer film according to claim 1 or 2, characterized in that, It also includes the following raw materials in parts by weight: 0.5-1.5 parts antioxidant and 0.5-1.5 parts light stabilizer.

4. A polymer film according to claim 3, characterized in that, The antioxidant is a hindered phenolic antioxidant.

5. A polymer film according to claim 3, characterized in that, The light stabilizer is an ultraviolet absorber.

6. A polymer film according to any one of claims 1-5, characterized in that, It also includes the following raw materials by weight: 5-10 parts of filler.

7. The method for preparing a polymer film according to claim 6, characterized in that, The filler is at least one of talc, calcium carbonate, or diatomaceous earth.

8. A polymer film according to claims 1-7, characterized in that, It also includes the following raw materials by weight: 2-5 parts plasticizer.

9. A method for preparing a polymer film according to claims 1-8, characterized in that, Includes the following steps: S1. A negative pressure vacuum conveying system is used to accurately deliver each component raw material to the dual-station metering chamber according to the formula ratio. A near-infrared spectrometer is equipped to detect and remove impurities in real time (detection limit ≤0.04mm). At the same time, the magnetic levitation sorting module is started to separate metal particles to ensure that the purity of the raw materials reaches more than 99.9%. S2. Differentiated homogenization is achieved through a four-stage variable frequency vortex mixer: low-speed stage I maintains 55 rpm for initial dispersion, medium-speed stage II increases to 140 rpm for enhanced mixing, high-speed stage III accelerates to 230 rpm to refine particles, and ultra-high-speed stage IV reaches 280 rpm to achieve microscopic homogenization. The built-in ultrasonic crushing head (frequency 25 kHz) works in conjunction with the shear ring assembly to effectively break up agglomeration, reducing mixing time to 55% of conventional processes, and achieving a component distribution uniformity CV value of <3%. S3. Melt extrusion utilizes a specialized equipment with a screw length-to-diameter ratio (L / D) of 40:1, implementing precise eight-zone temperature control: Zone I (155℃) preheats and softens rPP; Zone II (180℃) promotes initial melting of PBAT; Zone III (200℃) deeply plasticizes the composite system; Zone IV (210℃) achieves complete melting; Zone V (205℃) homogenizes melt viscosity; Zone VI (190℃) regulates pressure stability; Zone VII (170℃) cools down to reduce thermal history; and Zone VIII (160℃) stabilizes output. The melt pressure is controlled within 14-16 MPa throughout the process, with a fluctuation rate of ±2.5%. After extrusion through S4 and T-type dies, the film passes through three temperature gradient environments in sequence: the front section is rapidly cooled by a quenching roller (8℃ ice water spray) at a rate of 45℃ / s to quickly set the film and suppress the formation of large spherulites; the middle section is cooled by a slow cooling air knife (30℃ constant temperature airflow) at a rate of 10℃ / s to eliminate internal stress; and the rear section is cooled by a constant humidity setting table (RH=70%) to regulate the crystal morphology, resulting in a final product curvature ≤0.08mm / m. S5. It adopts a shaftless air shaft combined with a mechanical tension feedback arm to dynamically adjust the winding speed and pressure by monitoring the film tension change in real time (accuracy ±0.1N). This achieves precise control of tension fluctuation amplitude ≤±1.5N, ensuring film winding flatness and reducing subsequent processing loss rate to <0.5%. S6. The internal structure of the film is strengthened through a three-step chemical reaction. The basic adhesive layer involves adding maleic anhydride-grafted lignin to the melt. The active groups on its molecular chain form hydrogen bonds with recycled polypropylene (rPP) and non-polar polybutylene adipate-butylene terephthalate (PBAT), constructing a three-dimensional network structure. Differential scanning calorimetry (DSC) shows that this structure increases the phase separation temperature difference to 35°C and improves the interfacial peel strength to 13.

2. N / cm (equivalent to a tensile force of 13.2 Newtons per centimeter of width); Dynamic cross-linking layer: Epoxy-functionalized castor oil undergoes a ring-opening reaction during high-temperature processing, generating hydroxyl and ether bonds. These bonds synergistically interact with the reactive oxygen free radicals on the surface of mesoporous zinc oxide, promoting in-situ cross-linking and curing of polymer segments. The final gel content reaches 72%, significantly improving the solvent resistance and mechanical strength of the material; Long-lasting protective layer: Hindered amine anti-hydrolysis additives are slowly released through the nanopores (6-10nm) of mesoporous zinc oxide, continuously capturing free radicals and blocking the hydrolysis chain reaction of PBAT ester groups. Experimental results show that this design can reduce the hydrolysis rate of PBAT by 60% and extend the service life of the film; S7. By using a reverse temperature control curve, high-temperature decomposition of plastics is avoided, and viscosity is kept stable. A temperature gradient design that first increases and then decreases (155℃→210℃→160℃) is adopted to precisely control the risk of PBAT degradation, reducing the melt viscosity fluctuation rate to ±2.5%. Through a stepped cooling system, the surface layer cools and hardens rapidly, while the inner layer crystallizes slowly, creating a flexible film suitable for packaging. Differential cooling of 45℃ / s→10℃ / s→RH=70% optimizes the crystallinity distribution (surface crystallinity 18%-22%, core layer crystallinity 35%-40%), meeting the requirements of high-precision packaging applications.

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