Preparation process of environment-friendly PE stretching and wrapping film

Abstract

The invention relates to the technical field of stretch wrapping films, in particular to a preparation process of an environment-friendly PE stretch wrapping film which comprises the following components: polyethylene glycol terephthalate, linear low-density polyethylene, bio-based polyethylene, starch-based plastic, nanocellulose, plant polyphenol, a tackifier, an anti-ultraviolet agent and an antistatic agent. By adopting a bio-based material and a degradable material, high performance is realized, and meanwhile, the environment-friendly requirement is also met. Due to material selection, carbon emission in the production process is reduced, and the wrapping film can be degraded by the natural environment more easily after being used.

Description

Technical Field

[0001] The invention relates to the technical field of stretch wrapping films, and in particular to a preparation process of an environmentally friendly PE stretch wrapping film. Background Art

[0002] With the continuous development of the global economy and the continuous improvement of people's living standards, plastic products are increasingly used in packaging, logistics, agriculture and other fields. Among them, stretch wrap film, as an important packaging material, is widely used in the packaging and transportation of various products due to its excellent stretchability, resilience, transparency and self-adhesion, to provide stable protection and convenient packaging solutions.

[0003] Traditional stretch wrapping films are mostly made of petroleum-based plastics, which not only consume a lot of resources, but also are difficult to degrade after use, causing serious pollution to the ecological environment. In addition, traditional stretch wrapping films often have difficulty in taking into account the tensile strength, resilience, weather resistance and anti-static requirements in terms of performance, which limits their application in certain specific fields.

[0004] Therefore, we proposed a preparation process of an environmentally friendly PE stretch wrap film to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a preparation process of an environmentally friendly PE stretch wrap film.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An environmentally friendly PE stretch wrap film comprises the following components in parts by weight: 20-30 parts of polyethylene terephthalate, 20-30 parts of linear low-density polyethylene, 10-20 parts of bio-based polyethylene, 5-15 parts of starch-based plastic, 2-5 parts of nanocellulose, 1-3 parts of plant polyphenols, 3-8 parts of a thickener, 1-3 parts of an anti-ultraviolet agent, and 1-3 parts of an antistatic agent.

[0008] As the preferred technical solution:

[0009] The environmentally friendly PE stretch wrap film as described above comprises the following components in parts by weight: 24 parts of polyethylene terephthalate, 25 parts of linear low-density polyethylene, 14 parts of bio-based polyethylene, 8 parts of starch-based plastic, 3 parts of nanocellulose, 2 parts of plant polyphenols, 5 parts of thickener, 2 parts of anti-ultraviolet agent, and 2 parts of antistatic agent.

[0010] The environmentally friendly PE stretch wrapping film as described above, wherein the particle ellipticity of the polyethylene terephthalate is ≤0.1, and the molecular weight of the polyethylene terephthalate is 18,000-25,000 g / mo l, the particle size is 100-300 microns; the median particle size of the particle size distribution of the linear low-density polyethylene is 200-400 microns, and the number of branches per 1000 carbon atoms in the molecular chain branching degree is 3-10; the molecular weight distribution of the bio-based polyethylene is not wider than 4.0, and the bio-based carbon content of the bio-based polyethylene is 50%-80%; the average particle size of the starch particles of the starch-based plastic is 10-50μm, and natural corn starch or potato starch is used in the starch-based plastic; the nanocellulose is 1-100 nanometers, and the dispersion uniformity of nanocellulose in the film substrate is 95%-99%; the thickener is one of polybutene and acrylic acid, the anti-ultraviolet agent is one of hindered amine light stabilizer and benzotriazole ultraviolet absorber, and the antistatic agent is one of glyceryl acyl ester and ethoxyamine.

[0011] As described above, in the environmentally friendly PE stretch wrap film, in the polyethylene terephthalate, the PET molecular chains are arranged linearly in the film to ensure the tensile properties and resilience of the film; the molecular chains of the linear low-density polyethylene are arranged in three rows parallel to each other in the film to form a layered structure; active ingredients are embedded in the starch-based plastic, and the active ingredients include antibacterial agents and mildew inhibitors. The active ingredients can be gradually released during the use of the wrap film to provide additional protection for the contents of the package.

[0012] In the environmentally friendly PE stretch wrap film as described above, the polyethylene terephthalate adopts a three-dimensional conformation design and presents a twisted or spiral shape in space; the linear low-density polyethylene has a long-chain branched structure, which enhances the entanglement between molecules while maintaining the flexibility of the linear main chain; the bio-based polyethylene adopts biological monomers for polymerization, which can interact with starch-based plastics to promote the biocompatibility and degradability of the overall film; the starch-based plastic forms a multi-level crystalline structure in the film, wherein the crystallinity of the outer layer is 2-3 times that of the inner layer, the outer layer is oriented, and the inner layer is disordered; the plant polyphenols are polyphenol-polymer conjugated structures, and the plant polyphenols form a conjugated structure with the polymer in the film, and the binding force between the two is enhanced by electronic interaction.

[0013] The second aspect of the present invention provides a preparation process of an environmentally friendly PE stretch wrap film, comprising the following steps:

[0014] S1: Using a staged mixing technology, polyethylene terephthalate and linear low-density polyethylene are first preheated separately, and then polyethylene terephthalate and linear low-density polyethylene are preliminarily mixed in a high-speed mixer. At the end of the preliminary mixing stage, starch-based plastics are gradually added to form a basic blend;

[0015] S2: adding bio-based polyethylene to the base blend, and melt blending through a screw extruder to ensure that the components are evenly dispersed to obtain a melt blend;

[0016] S3: Using nano-scale dispersion technology, nanocellulose and plasticizer are pre-dispersed under ultrasonic action to form a uniform suspension, which is then added to the molten blend by spraying to enhance the tensile properties and toughness of the film;

[0017] S4: Then, plant polyphenols are added to the molten blend to improve the service life of the membrane by utilizing its antioxidant properties;

[0018] S5: A multi-channel injection system is used to accurately inject the tackifier, UV inhibitor and antistatic agent into the downstream area of ​​the extruder through different channels;

[0019] S6: The fully mixed and modified molten material is extruded through the die head of the extruder to form a continuous film. The film is quickly cooled by a cooling roller, and then shaped and wound by a trimming and winding device. After slitting, an environmentally friendly PE stretch wrap film is obtained.

[0020] As the preferred technical solution:

[0021] As described above, in the preparation process of an environmentally friendly PE stretch wrap film, in S2, bio-based polyethylene is added to the basic blend, and melt blending is performed through a screw extruder. Dynamic mixing elements, including torsion elements and shear elements, are introduced into the screw extruder to improve the dispersion uniformity and mixing efficiency of the molten blend, ensure that each component is evenly dispersed, and obtain a molten blend.

[0022] In the preparation process of an environmentally friendly PE stretch wrap film as described above, in S4, the plant polyphenols are encapsulated in tiny capsules using microcapsule technology, and these microcapsules are evenly added to the blend through a feeding system, and their antioxidant properties are used to improve the service life of the film.

[0023] In the preparation process of an environmentally friendly PE stretch wrap film as described above, in S6, the molten material that has been fully mixed and modified is extruded through the die head of the extruder, and an airflow assist technology is introduced at the die head of the extruder. By controlling the direction and intensity of the airflow, the cooling and shaping effects of the film are optimized to form a continuous film. The film is quickly cooled by a cooling roller, and then shaped and wound by a trimming and winding device, and the environmentally friendly PE stretch wrap film is obtained after slitting.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] By synergistically mixing materials such as polyethylene terephthalate, linear low-density polyethylene, bio-based polyethylene and starch-based plastics, starch-based plastics themselves have good biodegradability and can be gradually decomposed under the action of microorganisms. Although bio-based polyethylene is also made from renewable resources, its biodegradability is relatively weak. When starch-based plastics are combined with bio-based polyethylene, starch-based plastics can "guide" the biodegradation process of bio-based polyethylene, thereby accelerating the biodegradation rate of the entire film.

[0026] The addition of nanocellulose further enhances the tensile properties and toughness of the membrane. Nanocellulose enhances the mechanical strength and wear resistance of the membrane, while starch-based plastic improves the biodegradability of the membrane. The synergistic effect of the two not only ensures the performance of the membrane, but also enhances its environmental value. The addition of starch-based plastic can also reduce the cost of the membrane and improve its market competitiveness.

[0027] The introduction of plant polyphenols not only improves the antioxidant properties of the stretch film and extends its service life, but also forms a conjugated structure with the polymer in the film, enhancing the bonding force between the two, making the film more uniform and stable when subjected to force. The precise injection of tackifiers, anti-ultraviolet agents and antistatic agents enables the stretch film to exhibit more comprehensive and excellent performance in response to different environments and usage requirements. The synergistic effect of these functional ingredients greatly improves the practicality and adaptability of the stretch film.

[0028] By using bio-based and degradable materials, the stretch film not only achieves high performance, but also takes environmental protection into account. This material selection not only reduces carbon emissions during the production process, but also makes the stretch film more easily degraded by the natural environment after use.

[0029] In summary, the environmentally friendly PE stretch wrap film of the present invention exhibits excellent performance and broad application prospects through the synergistic effects of materials, functional components, and environmental protection and sustainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a surface SEM photograph of the wrapping film of Example 4 of the present invention;

[0031] Figure 2 It is a data line chart of the embodiments and comparative examples of the present invention. DETAILED DESCRIPTION

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. In the event of a conflict, the definitions in the specification shall prevail. "When mass, concentration, temperature, time, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed separately. For example, a range of 1-50 should be understood to include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 6, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, any number, combination of numbers, or subrange, and all decimal values ​​between the above integers, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to subranges, "nested subranges" extending from any endpoint within the range are specifically contemplated. For example, nested subranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in the other direction."

[0033] The present invention is further explained below in conjunction with specific examples. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0034] An environmentally friendly PE stretch wrap film comprises the following components in parts by weight: 20-30 parts of polyethylene terephthalate, 20-30 parts of linear low-density polyethylene, 10-20 parts of bio-based polyethylene, 5-15 parts of starch-based plastic, 2-5 parts of nanocellulose, 1-3 parts of plant polyphenols, 3-8 parts of a thickener, 1-3 parts of an anti-ultraviolet agent, and 1-3 parts of an antistatic agent.

[0035] Specifically, the particle ellipticity of polyethylene terephthalate is ≤0.1, and the molecular weight of polyethylene terephthalate is 18,000-25,000 g / mo l. The particle size is 100-300 microns; the median particle size of the linear low-density polyethylene particle size distribution is 200-400 microns, and the number of branches per 1000 carbon atoms in the molecular chain branching degree is 3-10; the molecular weight distribution of bio-based polyethylene is not wider than 4.0, and the bio-based carbon content of bio-based polyethylene is 50%-80%; the average particle size of starch particles in starch-based plastics is 10-50μm, and natural corn starch or potato starch is used in starch-based plastics; the particle size of nanocellulose is 1-100 nanometers, and the dispersion uniformity of nanocellulose in the film substrate is 95%-99%; the thickener is one of polybutene and acrylic acid, the anti-ultraviolet agent is one of hindered amine light stabilizer and benzotriazole ultraviolet absorber, and the antistatic agent is one of glyceryl acyl ester and ethoxyamine.

[0036] Among them, in polyethylene terephthalate, the PET molecular chains are arranged linearly in the film, ensuring the tensile properties and resilience of the film; the molecular chains of linear low-density polyethylene are arranged in three rows parallel to each other in the film to form a layered structure; active ingredients are embedded in starch-based plastics, including antibacterial agents and mildew inhibitors. The active ingredients can be gradually released during the use of the stretch film to provide additional protection for the contents of the package.

[0037] The above-mentioned limitation is explained by an example: Preparation of environmentally friendly PE stretch wrap film

[0038] 1. Material Preparation

[0039] Polyethylene terephthalate (PET): Select PET materials with particle ellipticity ≤ 0.1, molecular weight of 18,000-25,000 g / mol, and particle size of 100-300 microns. Linear low-density polyethylene (LLDPE): Select LLDPE materials with a median particle size distribution of 200-400 microns and a molecular chain branching degree of 3-10 branches per 1000 carbon atoms. Starch-based plastics: Starch-based plastics prepared from natural corn starch or potato starch with an average particle size of 10-50 μm, and embedded with antibacterial and antifungal agents as active ingredients.

[0040] 2. Preparation process

[0041] a. Preliminary mixing of PET and LLDPE: Preheat PET and LLDPE to appropriate temperatures respectively. Preliminary mix the preheated PET and LLDPE in a high-speed mixer to ensure that the two are evenly dispersed.

[0042] b. Melt blending and layered structure formation: The preliminarily mixed PET and LLDPE are added to the screw extruder for melt blending. By adjusting the temperature and screw speed of the extruder, the LLDPE molecular chains are controlled to be arranged in three rows parallel to each other in the film to form a layered structure.

[0043] c. Addition of starch-based plastics and active ingredients: During the melt blending process, starch-based plastics are gradually added and ensured to be evenly dispersed in the PET and LLDPE matrix. The antibacterial and mildew-proof agents in the starch-based plastics, as active ingredients, can be gradually released during the use of the wrapping film to provide additional protection for the contents of the package.

[0044] d. Extrusion molding and cooling and shaping: After being fully mixed, the molten material is extruded through the die head of the extruder to form a continuous film. The film is quickly cooled by the cooling roller, and then shaped and wound by the trimming and winding device.

[0045] Results and data:

[0046] Through the tensile performance test, the tensile strength and elongation at break of this environmentally friendly PE stretch wrap film meet or exceed the industry standards.

[0047] Through microstructural observation, we can clearly see the layered structure formed by the LLDPE molecular chains in the film and the linear arrangement of the PET molecular chains.

[0048] Through antibacterial and anti-mildew performance tests, it is proved that the active ingredients embedded in the starch-based plastic can be gradually released during the use of the stretch film and provide effective protection for the contents of the package.

[0049] In summary, by selecting materials, controlling the preparation process and introducing active ingredients, the linear arrangement of PET molecular chains, the layered structure of LLDPE molecular chains and the embedding of active ingredients in starch-based plastics in environmentally friendly PE stretch wrapping films can be successfully achieved. These structural features jointly improve the stretching properties, resilience and protection of the wrapping film for the contents of the package.

[0050] Specifically, polyethylene terephthalate adopts a three-dimensional conformation design, presenting a twisted or spiral shape in space; linear low-density polyethylene has a long-chain branched structure, which enhances the entanglement between molecules while maintaining the flexibility of the linear main chain; bio-based polyethylene uses biological monomers for polymerization, which can interact with starch-based plastics to promote the biocompatibility and degradability of the overall film; starch-based plastics form a multi-level crystalline structure in the film, in which the crystallinity of the outer layer is 2-3 times that of the inner layer, the outer layer is oriented, and the inner layer is disordered; plant polyphenols are polyphenol-polymer conjugated structures, and plant polyphenols form a conjugated structure with the polymer in the film, and the binding force between the two is enhanced through electronic interaction.

[0051] In the environmentally friendly PE stretch wrap film, in order to realize the stereo conformation design of the polyethylene terephthalate (PET), the long chain branching structure of the linear low density polyethylene (LLDPE), the polymerization of the bio-source monomer of the bio-based polyethylene, the multi-level crystal structure of the starch-based plastic, and the conjugated structure of the plant polyphenols and the polymer in the film, the following examples can be used for illustration:

[0052] Example: Specific implementation of environmentally friendly PE stretch wrap film:

[0053] 1. Stereo conformation design of polyethylene terephthalate (PET)

[0054] Select PET raw materials with stereo conformation potential.

[0055] During the polymerization process, 0.8% of a stereo conformation regulator (such as a chiral catalyst: the metal center includes noble metals such as rhodium (Rh), ruthenium (Ru), and iridium (Ir). These metals can provide active centers in the catalytic reaction and synergize with the ligand to form a catalytic complex with a specific spatial configuration. The ligand is an organic molecule with chirality (i.e., asymmetry), such as chiral phosphine ligands, nitrogen heterocyclic ligands, etc. They can coordinate with the metal center to form a stable complex and affect the enantioselectivity of the catalytic reaction through their spatial structure) is added to induce the PET molecular chain to form a twisted or helical form.

[0056] X-ray diffraction analysis confirmed that the PET molecular chain presented a conformation with a twist angle of 45°±5° in space.

[0057] 2. Long chain branching structure of linear low density polyethylene (LLDPE)

[0058] The LLDPE raw material with a branching degree of 10 branches per 1000 carbon atoms was selected. Melt blending was carried out at 170°C to ensure that LLDPE was evenly mixed with other components while maintaining its long-chain branching structure. Rheological tests verified that the long-chain branching structure of LLDPE enhanced the intermolecular entanglement and improved the tensile properties of the film by about 20%.

[0059] 3. Polymerization of bio-sourced monomers for bio-based polyethylene

[0060] The polymerization reaction was carried out using ethylene monomer with a purity of 98.5% extracted from renewable resources. During the polymerization process, a biocatalyst was used, and the reaction temperature was controlled at 100°C and the pressure was 3MPa to ensure the high molecular weight of the bio-based polyethylene. Through infrared spectroscopy analysis, it was confirmed that the bio-based polyethylene interacted with the starch-based plastic, which improved the biocompatibility and degradability of the film.

[0061] 4. Multi-level crystalline structure of starch-based plastics

[0062] A starch-based plastic material with a crystallinity of 80% was selected. During the film preparation process, the crystallization temperature and time were controlled (such as crystallization at 95°C for 15 minutes) to achieve an outer layer crystallinity that was 2.5 times that of the inner layer. X-ray diffraction technology verified that the outer layer crystal orientation arrangement reached 85%, while the inner layer crystal was in a disordered state.

[0063] 5. Conjugated structure of plant polyphenols and polymers in membranes

[0064] Tea polyphenols with a purity of 96% were selected as raw materials. During the membrane preparation process, tea polyphenols and polymer solution were mixed in a ratio of 1:15 and reacted at 70°C to form a stable conjugated structure. UV-visible spectroscopy analysis verified that the conjugated structure between tea polyphenols and the polymer in the membrane enhanced the electronic interaction and increased the binding force between the two by about 20%.

[0065] In summary, this embodiment, through specific data and operation steps, elaborates in detail how to achieve the specific structure and performance of each component in the environmentally friendly PE stretch wrap film. These optimization measures jointly improve the stretching performance, resilience, biocompatibility and degradability of the wrap film, meeting the dual requirements of environmental protection and practicality.

[0066] Embodiment 1

[0067] An environmentally friendly PE stretch wrap film comprises the following components in parts by weight: 20 parts of polyethylene terephthalate, 20 parts of linear low-density polyethylene, 10 parts of bio-based polyethylene, 5 parts of starch-based plastics, 2 parts of nanocellulose, 1 part of plant polyphenols, 3 parts of a thickener (polybutene), 1 part of an anti-ultraviolet agent (hindered amine light stabilizer), and 1 part of an antistatic agent (glyceryl acyl ester).

[0068] The embodiment also provides a preparation process of an environmentally friendly PE stretch wrap film, comprising the following steps: S1: using a segmented mixing technology, first preheating polyethylene terephthalate to 120° C. and preheating linear low-density polyethylene to 80° C., and then preliminarily mixing polyethylene terephthalate and linear low-density polyethylene in a high-speed mixer, the speed of the high-speed mixer is set to 800 rpm, the mixing time is 10 minutes, and in the last 3 minutes of mixing, gradually adding starch-based plastic to form a basic blend;

[0069] S2: adding bio-based polyethylene to the basic blend, and melt blending through a screw extruder, the screw speed is set to 100 rpm, the screw extruder temperature is set to 160°C, and a dynamic mixing element is introduced into the screw extruder, including a torsion element and a shear element, the torsion element angle is 45°, and the shear element gap is 0.5 mm, so as to improve the dispersion uniformity and mixing efficiency of the molten blend, ensure that each component is evenly dispersed, and obtain a molten blend;

[0070] S3: Using nano-scale dispersion technology, nanocellulose and plasticizer were pre-dispersed under ultrasonic wave with ultrasonic power of 200W and dispersion time of 30 minutes to form a uniform suspension, which was then added to the molten blend by spraying with a spray pressure of 0.5MPa to enhance the tensile properties and toughness of the film;

[0071] S4: Using microencapsulation technology, plant polyphenols are encapsulated in tiny capsules with a diameter of 5 μm. These microcapsules are evenly added to the blend through a feeding system, and their antioxidant properties are used to increase the service life of the membrane;

[0072] S5: Use a multi-channel injection system, preheat to 80°C before injection, control the diameter of each channel to 2mm, and accurately inject the tackifier, anti-ultraviolet agent and antistatic agent into the downstream area of ​​the extruder through different channels;

[0073] S6: The fully mixed and modified molten material is extruded through the die of the extruder. The temperature of the extruder die is 180°C. Airflow assist technology is introduced at the die of the extruder. The airflow temperature is controlled at 20°C and the airflow speed is 5m / s. By controlling the direction and intensity of the airflow, the cooling and shaping effects of the film are optimized to form a continuous film. The film is quickly cooled by a cooling roller. The temperature of the cooling roller is set to 20°C, and then it is shaped and wound by a trimming and winding device. The trimming width is controlled within the range of ±1mm. After slitting, an environmentally friendly PE stretch wrapping film is obtained.

[0074] Embodiment 2

[0075] An environmentally friendly PE stretch wrap film comprises the following components in parts by weight: 22 parts of polyethylene terephthalate, 24 parts of linear low-density polyethylene, 13 parts of bio-based polyethylene, 7 parts of starch-based plastic, 3 parts of nanocellulose, 2 parts of plant polyphenols, 4 parts of a thickener, 2 parts of an anti-ultraviolet agent, and 2 parts of an antistatic agent.

[0076] The embodiment also provides a preparation process of an environmentally friendly PE stretch wrap film, comprising the following steps: S1: using a segmented mixing technology, first preheating polyethylene terephthalate to 130° C. and preheating linear low-density polyethylene to 85° C., and then preliminarily mixing polyethylene terephthalate and linear low-density polyethylene in a high-speed mixer, the speed of the high-speed mixer is set to 900 rpm, the mixing time is 12 minutes, and in the last 4 minutes of mixing, gradually adding starch-based plastic to form a basic blend;

[0077] S2: adding bio-based polyethylene to the basic blend, and melt blending through a screw extruder, the screw speed is set to 120 rpm, the screw extruder temperature is set to 170°C, and a dynamic mixing element is introduced into the screw extruder, including a torsion element and a shear element, the torsion element angle is 50°, and the shear element gap is 0.8 mm, so as to improve the dispersion uniformity and mixing efficiency of the molten blend, ensure that each component is evenly dispersed, and obtain a molten blend;

[0078] S3: Using nano-scale dispersion technology, nanocellulose and plasticizer were pre-dispersed under ultrasonic wave with ultrasonic power of 250W and dispersion time of 40 minutes to form a uniform suspension, which was then added to the molten blend by spraying with a spray pressure of 0.9MPa to enhance the tensile properties and toughness of the film;

[0079] S4: Using microencapsulation technology, plant polyphenols are encapsulated in tiny capsules with a diameter of 8μm. These microcapsules are evenly added to the blend through a feeding system, and their antioxidant properties are used to increase the service life of the membrane;

[0080] S5: Use a multi-channel injection system, preheat to 85°C before injection, control the diameter of each channel to 3mm, and accurately inject the tackifier, anti-ultraviolet agent and antistatic agent into the downstream area of ​​the extruder through different channels;

[0081] S6: The fully mixed and modified molten material is extruded through the die of the extruder. The temperature of the extruder die is 190°C. Airflow assist technology is introduced at the die of the extruder. The airflow temperature is controlled at 25°C and the airflow speed is 11m / s. By controlling the direction and intensity of the airflow, the cooling and shaping effects of the film are optimized to form a continuous film. The film is quickly cooled by a cooling roller. The temperature of the cooling roller is set to 22°C, and then it is shaped and wound by a trimming and winding device. The trimming width is controlled within the range of ±1mm. After slitting, an environmentally friendly PE stretch wrapping film is obtained.

[0082] Embodiment 3

[0083] An environmentally friendly PE stretch wrap film comprises the following components in parts by weight: 28 parts of polyethylene terephthalate, 27 parts of linear low-density polyethylene, 18 parts of bio-based polyethylene, 13 parts of starch-based plastic, 4 parts of nanocellulose, 2 parts of plant polyphenols, 6 parts of a thickener, 2 parts of an anti-ultraviolet agent, and 2 parts of an antistatic agent.

[0084] The embodiment also provides a preparation process of an environmentally friendly PE stretch wrap film, comprising the following steps: S1: using a segmented mixing technology, first preheating polyethylene terephthalate to 130° C. and preheating linear low-density polyethylene to 90° C., and then preliminarily mixing polyethylene terephthalate and linear low-density polyethylene in a high-speed mixer, the speed of the high-speed mixer is set to 1100 rpm, the mixing time is 13 minutes, and in the last 4 minutes of mixing, gradually adding starch-based plastic to form a basic blend;

[0085] S2: adding bio-based polyethylene to the basic blend, and melt blending through a screw extruder, the screw speed is set to 180 rpm, the screw extruder temperature is set to 190°C, and a dynamic mixing element is introduced into the screw extruder, including a torsion element and a shear element, the torsion element angle is 80°, and the shear element gap is 1.7 mm, so as to improve the dispersion uniformity and mixing efficiency of the molten blend, ensure that each component is evenly dispersed, and obtain a molten blend;

[0086] S3: Using nano-scale dispersion technology, nanocellulose and plasticizer were pre-dispersed under ultrasonic wave with ultrasonic power of 300W and dispersion time of 50 minutes to form a uniform suspension, which was then added to the molten blend by spraying with a spray pressure of 1.3MPa to enhance the tensile properties and toughness of the film;

[0087] S4: Using microencapsulation technology, plant polyphenols are encapsulated in tiny capsules with a diameter of 17 μm. These microcapsules are evenly added to the blend through a feeding system, and their antioxidant properties are used to increase the service life of the membrane;

[0088] S5: Use a multi-channel injection system, preheat to 90°C before injection, control the diameter of each channel to 4mm, and accurately inject the tackifier, anti-ultraviolet agent and antistatic agent into the downstream area of ​​the extruder through different channels;

[0089] S6: The fully mixed and modified molten material is extruded through the die of the extruder. The temperature of the extruder die is 210°C. Airflow assist technology is introduced at the die of the extruder. The airflow temperature is controlled at 30°C and the airflow speed is 12m / s. By controlling the direction and intensity of the airflow, the cooling and shaping effects of the film are optimized to form a continuous film. The film is quickly cooled by a cooling roller. The temperature of the cooling roller is set to 28°C, and then it is shaped and wound by a trimming and winding device. The trimming width is controlled within the range of ±1mm. After slitting, an environmentally friendly PE stretch wrapping film is obtained.

[0090] Embodiment 4

[0091] An environmentally friendly PE stretch wrap film comprises the following components in parts by weight: 30 parts of polyethylene terephthalate, 30 parts of linear low-density polyethylene, 20 parts of bio-based polyethylene, 15 parts of starch-based plastic, 5 parts of nanocellulose, 3 parts of plant polyphenols, 8 parts of a thickener, 3 parts of an anti-ultraviolet agent, and 3 parts of an antistatic agent.

[0092] The embodiment also provides a preparation process of an environmentally friendly PE stretch wrap film, comprising the following steps: S1: using a segmented mixing technology, first preheating polyethylene terephthalate to 140° C. and preheating linear low-density polyethylene to 100° C., then preliminarily mixing polyethylene terephthalate and linear low-density polyethylene in a high-speed mixer, the speed of the high-speed mixer is set to 1200 rpm, the mixing time is 15 minutes, and in the last 5 minutes of mixing, gradually adding starch-based plastic to form a basic blend;

[0093] S2: adding bio-based polyethylene to the basic blend, and melt blending through a screw extruder, the screw speed is set to 200 rpm, the screw extruder temperature is set to 200°C, and a dynamic mixing element is introduced into the screw extruder, including a torsion element and a shear element, the torsion element angle is 90°, and the shear element gap is 2 mm, so as to improve the dispersion uniformity and mixing efficiency of the molten blend, ensure that each component is evenly dispersed, and obtain a molten blend;

[0094] S3: Using nano-scale dispersion technology, nanocellulose and plasticizer were pre-dispersed under ultrasonic wave with ultrasonic power of 400W and dispersion time of 60 minutes to form a uniform suspension, which was then added to the molten blend by spraying with a spray pressure of 1.5MPa to enhance the tensile properties and toughness of the film;

[0095] S4: Using microencapsulation technology, plant polyphenols are encapsulated in tiny capsules with a diameter of 20 μm. These microcapsules are evenly added to the blend through a feeding system, and their antioxidant properties are used to increase the service life of the membrane;

[0096] S5: Use a multi-channel injection system, preheat to 100°C before injection, control the diameter of each channel to 5mm, and accurately inject the tackifier, anti-ultraviolet agent and antistatic agent into the downstream area of ​​the extruder through different channels;

[0097] S6: The fully mixed and modified molten material is extruded through the die of the extruder. The temperature of the extruder die is 220°C. Airflow assist technology is introduced at the die of the extruder. The airflow temperature is controlled at 40°C and the airflow speed is 15m / s. By controlling the direction and intensity of the airflow, the cooling and shaping effects of the film are optimized to form a continuous film. The film is quickly cooled by a cooling roller. The temperature of the cooling roller is set to 30°C, and then it is shaped and wound by a trimming and winding device. The trimming width is controlled within the range of ±1mm. After slitting, an environmentally friendly PE stretch wrapping film is obtained.

[0098] Comparative Example 1

[0099] A preparation process of an environmentally friendly PE stretch wrap film is basically the same as that of Example 4, except that nanocellulose is omitted.

[0100] Comparative Example 2

[0101] A preparation process of an environmentally friendly PE stretch wrap film is basically the same as that of Example 4, except that the starch-based plastic is omitted.

[0102] Comparative Example 3

[0103] A preparation process of an environmentally friendly PE stretch wrap film is basically the same as that of Example 4, except that plant polyphenols are omitted.

[0104] Comparative Example 4

[0105] A preparation process of an environmentally friendly PE stretch wrap film is basically the same as that of the fourth embodiment, except that the dynamic mixing element step is omitted.

[0106] The stretch wrapping films prepared in the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 4 were tested:

[0107] Tensile strength: Tested in accordance with GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for films and sheets". This standard specifies the method for determining the tensile properties of plastic films and sheets, including tensile strength, elongation at break, etc.

[0108] Biodegradation rate: can be determined by referring to GB / T 19277.1-2011 "Determination of the ultimate aerobic biodegradability of materials under controlled composting conditions by determination of released carbon dioxide method Part 1: General method". This standard is used to evaluate the biodegradability of materials under controlled composting conditions.

[0109] Oxidation induction time: Determined in accordance with GB / T 19466.2-2004 / I SO 6272:1993 "Plastics Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) Part 2: Determination of Oxidation Induction Time (Isothermal OIT) and Oxidation Induction Temperature (Dynamic OIT)". This standard is used to determine the oxidation stability of plastic materials.

[0110] Transparency: It can be measured according to GB / T 2410-2008 / I SO 14782:1999 "Determination of light transmittance and haze of transparent plastics". This standard specifies the method for measuring light transmittance and haze of transparent plastics.

[0111] The results are shown in Table 1:

[0112] Table 1

[0113]

[0114] From the above Table 1, it can be directly determined that the environmentally friendly PE stretch wrapping films of Examples 1 to 4 all perform better in terms of four key indicators: tensile strength, biodegradation rate, oxidation induction time and transparency:

[0115] Tensile strength is a key indicator for measuring the material's ability to resist tensile damage. The tensile strengths of the four embodiments are all at a high level, and embodiment four performs best. Biodegradation rate is an important indicator for measuring the environmental performance of materials. All four embodiments show good biodegradability, indicating that the added starch-based plastics and other components effectively promote the biodegradation process of the film. The slight rate difference is related to the uniformity of the dispersion of the components or the subtle differences in the preparation process. Oxidation induction time is a key parameter for evaluating the antioxidant properties of materials. All four embodiments show a long oxidation induction time, indicating that the added antioxidant components such as plant polyphenols effectively improve the oxidative stability of the film. The slight difference between embodiment three and other embodiments is due to factors such as the dispersion state of the antioxidant components or the temperature control during the preparation process. Transparency is an important indicator for measuring the visual effect of the film material. All four embodiments show high transparency, indicating that the preparation process and component ratio adopted are conducive to maintaining the clarity and visual effect of the film. The excellent performance of embodiment four is related to the uniform dispersion of nanocellulose and the optimization of the membrane structure.

[0116] Reference Figure 1-2 , in Example 4 and Comparative Example 1 where other conditions are the same:

[0117] The tensile strength of Example 4 is 27.5 MPa, while the tensile strength of Comparative Example 1 (nanocellulose omitted) is only 18.5 MPa. At the same time, the transparency of Comparative Example 1 also decreases from 93.5% of Example 4 to 88%.

[0118] Nanocellulose plays a significant reinforcing role in the membrane. Its nanoscale size and excellent mechanical properties help to improve the tensile strength and toughness of the membrane. Therefore, after omitting nanocellulose, the mechanical properties and wear resistance of the membrane are significantly reduced, and the transparency is also affected.

[0119] In Example 4 and Comparative Example 2, the biodegradation rate of Example 4 is 85%, while the biodegradation rate of Comparative Example 2 (starch-based plastic omitted) is greatly reduced to 55%. Starch-based plastic, as a biodegradable material, plays a role in promoting biodegradation in the film. Therefore, after omitting starch-based plastic, although the tensile properties of the film remain basically unchanged, its biodegradability is significantly reduced, which is not conducive to the realization of environmental protection goals.

[0120] Example 4 and Comparative Example 3: The oxidation induction time of Example 4 is 35 minutes, while the oxidation induction time of Comparative Example 3 (omitted plant polyphenols) is significantly shortened to 25 minutes. Plant polyphenols, as a natural antioxidant, play a role in improving the oxidation stability in the film. After omitting plant polyphenols, the antioxidant performance of the film is significantly reduced, which causes the film to oxidatively age earlier during use, thereby affecting its service life.

[0121] Comparative Example 4 omits the step of the dynamic mixing element. The dynamic mixing element plays a key role in the melt blending process and can improve the dispersion uniformity and mixing efficiency of each component. After omitting this step, the mixing quality of the melt blend is reduced, resulting in the tensile strength and transparency of the film being affected. This shows that the dynamic mixing element is of great significance for optimizing the preparation process and improving the performance of the film.

[0122] The synergy of starch-based plastics and bio-based polyethylene: Starch-based plastics themselves have good biodegradability and can be gradually decomposed under the action of microorganisms. Although bio-based polyethylene is also made from renewable resources, its biodegradability is relatively weak. When starch-based plastics are combined with bio-based polyethylene, starch-based plastics can "guide" the biodegradation process of bio-based polyethylene, thereby accelerating the biodegradation rate of the entire film. The specific process is:

[0123] Microbial effects:

[0124] Microbial invasion: The starch component in starch-based plastics will first be invaded by microorganisms (such as bacteria and fungi) as a food source. This process will greatly increase the surface area of ​​the plastic, thus providing favorable conditions for further biodegradation.

[0125] Enzymatic hydrolysis: When microorganisms invade starch, they secrete enzymes to break down starch. These enzymes can enter the active sites of polymers, causing the strength of polymers to decrease, laying the foundation for subsequent degradation processes.

[0126] Breakage of polymer chains:

[0127] The role of auto-oxidants: Some auto-oxidants (such as unsaturated fatty acids, etc.) can be added to starch-based plastics. These oxidants can react with metal salts in the soil or water to generate peroxides, which can cut off the long chains of polymers and reduce the molecular weight of polymers.

[0128] Promote degradation: When the molecular weight of polyolefin polymers is reduced to a certain extent, they can be more easily decomposed by bacteria or enzymes. The low molecular weight substances produced by the starch component in starch-based plastics during the degradation process can be further degraded by microorganisms into small molecular compounds such as carbon dioxide and water.

[0129] Synergistic degradation:

[0130] Synergy between starch and polyethylene: In the composite use of starch-based plastics and bio-based polyethylene, the degradation process of starch will "guide" the degradation of polyethylene. Due to the degradation of starch, the surface of the composite material becomes porous and the specific surface area increases, which is conducive to the further action of microorganisms and enzymes on the polyethylene part, accelerating its degradation process.

[0131] Continuous biodegradation: As starch continues to degrade, the polyethylene part of the composite material will also gradually be degraded by microorganisms and enzymes. This continuous degradation process makes the entire composite material completely biodegradable in the end.

[0132] In addition, nanocellulose enhances the mechanical strength and wear resistance of the membrane, while starch-based plastic improves the biodegradability of the membrane. The synergistic effect of the two not only ensures the performance of the membrane, but also improves its environmental value. The addition of starch-based plastic can also reduce the cost of the membrane and improve its market competitiveness.

[0133] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An environmentally friendly PE stretch wrap film, characterized in that: The invention comprises the following components in parts by weight: 20-30 parts of polyethylene terephthalate, 20-30 parts of linear low-density polyethylene, 10-20 parts of bio-based polyethylene, 5-15 parts of starch-based plastic, 2-5 parts of nanocellulose, 1-3 parts of plant polyphenols, 3-8 parts of thickener, 1-3 parts of anti-ultraviolet agent and 1-3 parts of antistatic agent.

2. The environmentally friendly PE stretch wrap film according to claim 1, characterized in that: The invention comprises the following components in parts by weight: 24 parts of polyethylene terephthalate, 25 parts of linear low-density polyethylene, 14 parts of bio-based polyethylene, 8 parts of starch-based plastic, 3 parts of nanocellulose, 2 parts of plant polyphenols, 5 parts of thickener, 2 parts of anti-ultraviolet agent and 2 parts of antistatic agent.

3. The environmentally friendly PE stretch wrap film according to claim 1, characterized in that: The particle ellipticity of the polyethylene terephthalate is ≤0.1, the molecular weight of the polyethylene terephthalate is 18,000-25,000 g / mol, and the particle size is 100-300 microns; The median particle size of the linear low-density polyethylene particles is 200-400 microns, and the number of branches per 1000 carbon atoms in the molecular chain branching degree is 3-10; The molecular weight distribution of the bio-based polyethylene is no wider than 4.0, and the bio-based carbon content of the bio-based polyethylene is between 50% and 80%; The average particle size of starch particles in the starch-based plastic is 10-50 μm, and natural corn starch or potato starch is used in the starch-based plastic; The nanocellulose has a size of 1-100 nanometers, and the dispersion uniformity of the nanocellulose in the film substrate is 95%-99%; The tackifier is one of polybutene and acrylic acid, the anti-ultraviolet agent is one of hindered amine light stabilizer and benzotriazole ultraviolet absorber, and the antistatic agent is one of glyceryl acyl ester and ethoxyamine.

4. The environmentally friendly PE stretch wrap film according to claim 1, characterized in that: In the polyethylene terephthalate, the PET molecular chains are arranged linearly in the film, ensuring the tensile properties and resilience of the film; The molecular chains of the linear low-density polyethylene are arranged in three rows parallel to each other in the film to form a layered structure; Active ingredients are embedded in the starch-based plastic, and the active ingredients include antibacterial agents and mildew inhibitors. The active ingredients can be gradually released during the use of the stretch film to provide additional protection for the package contents.

5. The environmentally friendly PE stretch wrap film according to claim 1, characterized in that: The polyethylene terephthalate adopts a three-dimensional conformation design and presents a twisted or spiral shape in space; The linear low-density polyethylene has a long-chain branched structure, which enhances the entanglement between molecules while maintaining the flexibility of the linear main chain; The bio-based polyethylene is polymerized using monomers from biological sources, and can interact with starch-based plastics to promote the biocompatibility and degradability of the overall film; The starch-based plastic forms a multi-level crystalline structure in the film, wherein the crystallinity of the outer layer is 2-3 times that of the inner layer, the outer layer is oriented, and the inner layer is disordered; The plant polyphenols are polyphenol-polymer conjugated structures. The plant polyphenols and the polymers in the membrane form a conjugated structure, and the binding force between the two is enhanced through electronic interaction.

6. A process for preparing the environmentally friendly PE stretch wrap film according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Using a staged mixing technology, polyethylene terephthalate and linear low-density polyethylene are first preheated separately, and then polyethylene terephthalate and linear low-density polyethylene are preliminarily mixed in a high-speed mixer. At the end of the preliminary mixing stage, starch-based plastics are gradually added to form a basic blend; S2: adding bio-based polyethylene to the base blend, and performing melt blending through a screw extruder to ensure that the components are evenly dispersed to obtain a melt blend; S3: Using nano-scale dispersion technology, nanocellulose and plasticizer are pre-dispersed under ultrasonic action to form a uniform suspension, which is then added to the molten blend by spraying to enhance the tensile properties and toughness of the film; S4: Then, plant polyphenols are added to the molten blend to improve the service life of the membrane by utilizing its antioxidant properties; S5: A multi-channel injection system is used to accurately inject the tackifier, UV inhibitor and antistatic agent into the downstream area of ​​the extruder through different channels; S6: The fully mixed and modified molten material is extruded through the die head of the extruder to form a continuous film. The film is quickly cooled by a cooling roller, and then shaped and wound by a trimming and winding device. After slitting, an environmentally friendly PE stretch wrap film is obtained.

7. The process for preparing an environmentally friendly PE stretch wrap film according to claim 6, characterized in that: In S2, bio-based polyethylene is added to the basic blend, and melt blending is performed through a screw extruder. Dynamic mixing elements, including torsion elements and shear elements, are introduced into the screw extruder to improve the dispersion uniformity and mixing efficiency of the molten blend, ensure that each component is evenly dispersed, and obtain a molten blend.

8. The process for preparing an environmentally friendly PE stretch wrap film according to claim 6, characterized in that: In S4, the plant polyphenols are encapsulated in tiny capsules using microcapsule technology, and these microcapsules are evenly added to the blend through a feeding system, so as to improve the service life of the membrane by utilizing its antioxidant properties.

9. The process for preparing an environmentally friendly PE stretch wrap film according to claim 6, characterized in that: In S6, the molten material that has been fully mixed and modified is extruded through the die head of the extruder, and airflow assist technology is introduced at the die head of the extruder. By controlling the direction and intensity of the airflow, the cooling and shaping effects of the film are optimized to form a continuous film. The film is quickly cooled by a cooling roller, and then shaped and wound by a trimming and winding device, and the environmentally friendly PE stretch wrapping film is obtained after slitting.

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