Biological antibacterial biaxially oriented polyethylene film and preparation method thereof

Abstract

The present application belongs to the technical field of soft packaging materials, in particular to a biologically antibacterial biaxially oriented polyethylene film and a preparation method thereof. The polyethylene film is composed of a corona layer, a subsurface layer, an intermediate layer, a subsurface inner layer and a heat sealing layer. The polyethylene film has good biocompatibility, controllable function and various structural designs, can inhibit and kill bacteria through physical barrier, membrane permeation and metabolic interference, and can be more widely applied to antibacterial.

Description

Technical Field

[0001] This invention belongs to the field of flexible packaging materials technology, and particularly relates to a bio-antibacterial biaxially oriented polyethylene film and its preparation method. Background Technology

[0002] In recent years, microbial infections and the global spread of viruses have had a tremendous impact on human life, health, and production. Food safety is of paramount importance, and the need to maintain food freshness, slow spoilage, and inhibit bacterial growth has led to a continuous increase in demand for antimicrobial materials.

[0003] After years of development, various inorganic and organic antibacterial materials have been developed and widely used. Among them, inorganic antibacterial film materials are mostly composed of metals or metal oxides, which have good thermal stability and bactericidal properties, but they also have certain biotoxicity and potential environmental impacts. Organic antibacterial film materials are mainly synthesized from small organic molecules as antibacterial substances, but due to their low bioavailability and short antibacterial shelf life, their antibacterial effect is difficult to achieve as expected when used alone.

[0004] Therefore, there is an urgent need for a biological antibacterial biaxially oriented polyethylene film and its preparation method to solve the above problems. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a bio-antibacterial biaxially oriented polyethylene film and its preparation method. The polyethylene film of this invention exhibits excellent antibacterial effects, improving the freshness and shelf life of the contents.

[0006] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0007] A bio-antibacterial biaxially oriented polyethylene film, comprising a corona layer, a sub-surface layer, an intermediate layer, a sub-inner layer, and a heat-sealing layer; the corona layer comprises 95-99 wt% linear low-density polyethylene resin and 1-5 wt% silica resin; the sub-surface layer comprises 60-80 wt% high-density polyethylene resin and 20-40 wt% linear low-density polyethylene resin; the intermediate layer comprises 60-80 wt% high-density polyethylene resin, 19.5-37.5 wt% linear low-density polyethylene resin, and 0.5-2.5 wt% antistatic resin; the sub-inner layer comprises 60-80 wt% high-density polyethylene resin, 19-37 wt% linear low-density polyethylene resin, and 1-3 wt% chitosan; and the heat-sealing layer comprises 95-98 wt% metallocene linear low-density polyethylene resin, 1-2 wt% chitosan, and 1-3 wt% slip agent resin.

[0008] Preferably, the corona layer comprises 97.5 wt% linear low-density polyethylene resin and 2.5 wt% silica resin, the sub-surface layer comprises 75 wt% high-density polyethylene resin and 25 wt% linear low-density polyethylene resin, the intermediate layer comprises 75 wt% high-density polyethylene resin, 33.4 wt% linear low-density polyethylene resin and 1.6 wt% antistatic resin, the sub-inner layer comprises 74 wt% high-density polyethylene resin, 24 wt% linear low-density polyethylene resin and 2 wt% chitosan, and the heat-sealing layer comprises 97 wt% metallocene linear low-density polyethylene resin, 1.5 wt% chitosan and 1.5 wt% slip agent resin.

[0009] Preferably, the polyethylene film has a thickness of 18-38 μm, the corona layer has a thickness of 1-5 μm, the subsurface layer has a thickness of 1-5 μm, the intermediate layer has a thickness of 15-30 μm, the innermost layer has a thickness of 1-5 μm, and the heat-sealing layer has a thickness of 5-8 μm.

[0010] Preferably, the polyethylene film has a thickness of 30 μm, the corona layer has a thickness of 2 μm, the subsurface layer has a thickness of 2 μm, the intermediate layer has a thickness of 18 μm, the innermost layer has a thickness of 2 μm, and the heat-sealing layer has a thickness of 6 μm.

[0011] Preferably, the linear low-density polyethylene resin has a density of 0.926 g / cm³. 3 The melt index is 1.7 g / 10 min; the density of the silica resin is 0.93 g / cm³. 3 The melt index is 3.5 g / 10 min; the density of high-density polyethylene is 0.953 g / cm³. 3 The melt index is 3.0 g / 10 min; the density of the antistatic resin is 0.912 g / cm³. 3 The melt index was 2.8 g / 10 min; the degree of deacetylation of chitosan was 98%, and the molecular weight was 50,000 Da; the density of metallocene linear low-density polyethylene resin was 0.916 g / cm³. 3 The melt index is 2.3 g / 10 min; the density of the slip resin is 0.92 g / cm³. 3 The melt index is 2.5 g / 10 min.

[0012] To achieve the second objective mentioned above, the present invention provides a method for preparing a bio-antibacterial biaxially oriented polyethylene film, the specific steps of which are as follows: weigh the materials of the corona layer, sub-surface layer, intermediate layer, sub-inner layer and heat-sealing layer respectively, and then put them into each extruder of the co-extrusion biaxial production line, and melt-form them to obtain a bio-antibacterial biaxially oriented polyethylene film.

[0013] Preferably, the production speed of the biaxial stretching production line is 520 m / min.

[0014] The advantages of this invention are:

[0015] (1) The polyethylene film of the present invention has good biocompatibility, functional controllability and diverse structural design. It can inhibit and kill bacteria through physical barrier, membrane permeation and metabolic interference, and can be more widely used in antibacterial applications.

[0016] (2) The polyethylene film of the present invention incorporates chitosan in the innermost layer and the heat-sealing layer. After biaxial stretching co-extrusion, the chitosan macromolecules are arranged in an orderly manner. Due to the van der Waals forces between the two layers, the chitosan molecules alter the permeability of the bacterial cell membrane, inhibit bacterial RNA synthesis, and disrupt bacterial metabolism, thereby interfering with the growth and reproduction of microorganisms. It has a good inhibitory effect on Escherichia coli and Staphylococcus aureus, with an antibacterial rate of up to 98% or more, thus improving the preservation and shelf life of the contents. Chitosan is a natural polymer obtained from chitin through deacetylation. It has the characteristics of biodegradability, broad-spectrum antibacterial properties, non-toxicity, and low cost, and is widely used in the pharmaceutical, food packaging, and cosmetic industries.

[0017] (3) In the five-layer structure of the polyethylene film of the present invention, a low proportion of chitosan is added to the innermost layer and the heat-sealing layer. Since chitosan is a natural hydrophilic polymer, it interacts with the hydrogen bonds in the molecular chains of metallocene polyethylene and low-density polyethylene in this layer and adjacent layers to form an entangled conjugated network structure at the microscopic level, thereby effectively improving the barrier properties of the film, increasing the difficulty for bacteria to penetrate into the contents, delaying the invasion of bacteria and microorganisms, and improving the antibacterial properties of the film. The five-layer co-extrusion stretching process of the present invention is different from the traditional three-layer structure. It adds a sub-surface layer and a sub-inner layer, which increases the interaction force between each layer, thereby making the film have excellent toughness and mechanical properties. The formulation ratio of the five layers is reasonably designed so that the internal and external stresses of the film can be effectively released, making the film flatter and reducing the occurrence of bending and curling.

[0018] (4) In the corona layer, subsurface layer and intermediate layer of the present invention, after co-extrusion and biaxial stretching of linear polyethylene resin and high-density polyethylene resin, the cooling speed is fast and the cooling efficiency is high, which reduces the crystallinity of the film, greatly reduces the proportion of crystalline area, and has a large number of irregularly distributed non-crystalline areas, thereby increasing the resistance of external bacteria from the outside to the inside and reducing the number of invading bacteria.

[0019] (5) The heat-sealing layer of the present invention uses metallocene linear polyethylene resin, which has a low initial sealing temperature, high heat adhesion strength, good anti-contamination heat-sealing ability, and a wide processing window, thus being able to adapt to the ever-evolving needs of rapid packaging.

[0020] (6) The polyethylene film of the present invention forms a composite film after being bonded together with adhesive. It has a low heat sealing temperature, high heat bonding strength, and a wide processing range. It can quickly adapt to the high-speed packaging of fruits and vegetables, and extend the freshness and shelf life of the contents. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] A bio-antibacterial biaxially oriented polyethylene film, comprising a corona layer, a sub-surface layer, an intermediate layer, a sub-inner layer, and a heat-sealing layer; the corona layer comprises 95-99 wt% linear low-density polyethylene resin (LLDPE) and 1-5 wt% silica resin (SiO2); the sub-surface layer comprises 60-80 wt% high-density polyethylene resin (HDPE) and 20-40 wt% linear low-density polyethylene resin (LLDPE); the intermediate layer comprises 60-80 wt% high-density polyethylene resin (HDPE) and 19.5-3 wt% silica resin (SiO2). The innermost layer comprises 7.5 wt% linear low-density polyethylene resin (LLDPE) and 0.5-2.5 wt% antistatic resin (ATPE), the second innermost layer comprises 60-80 wt% high-density polyethylene resin (HDPE), 19-37 wt% linear low-density polyethylene resin (LLDPE) and 1-3 wt% chitosan (CS), and the heat-sealing layer comprises 95-98 wt% metallocene linear low-density polyethylene resin (MLLDPE), 1-2 wt% chitosan (CS) and 1-3 wt% slip agent resin (SLIP).

[0023] The polyethylene film has a thickness of 18-38 μm, the corona layer has a thickness of 1-5 μm, the subsurface layer has a thickness of 1-5 μm, the intermediate layer has a thickness of 15-30 μm, the innermost layer has a thickness of 1-5 μm, and the heat-sealing layer has a thickness of 5-8 μm.

[0024] The density of linear low-density polyethylene resin is 0.926 g / cm³. 3 The melt index is 1.7 g / 10 min; the density of the silica resin is 0.93 g / cm³. 3 The melt index is 3.5 g / 10 min; the density of high-density polyethylene is 0.953 g / cm³. 3 The melt index is 3.0 g / 10 min; the density of the antistatic resin is 0.912 g / cm³. 3The melt index was 2.8 g / 10 min; the degree of deacetylation of chitosan was 98%, and the molecular weight was 50,000 Da; the density of metallocene linear low-density polyethylene resin was 0.916 g / cm³. 3 The melt index is 2.3 g / 10 min; the density of the slip resin is 0.92 g / cm³. 3 The melt index is 2.5 g / 10 min.

[0025] A method for preparing a bio-antibacterial biaxially oriented polyethylene film includes the following steps: Materials for the corona layer, subsurface layer, intermediate layer, subinner layer, and heat-sealing layer are weighed separately and then fed into each extruder of a co-extrusion biaxial production line. After melt molding, the bio-antibacterial biaxially oriented polyethylene film is obtained. The specific processing technology is shown in Table 1 below.

[0026] Table 1

[0027]

[0028]

[0029] Example 1

[0030] A bio-antibacterial biaxially oriented polyethylene film is prepared according to the above preparation method. The formulation of polyethylene film 1 is shown in Table 2 below.

[0031] Example 2

[0032] A bio-antibacterial biaxially oriented polyethylene film is prepared by the above preparation method. The formulation of polyethylene film 2 is shown in Table 2 below.

[0033] Example 3

[0034] A bio-antibacterial biaxially oriented polyethylene film is prepared according to the above preparation method. The formulation of polyethylene film 3 is shown in Table 2 below.

[0035] Table 2

[0036]

[0037] Comparative Example 1

[0038] The antibacterial cast polyethylene film was purchased from an external supplier (manufacturer: Yongxin Packaging (Huangshan) Co., Ltd.).

[0039] The performance of polyethylene films 1-3 prepared in Examples 1-3 and the polyethylene film of Comparative Example 1 were tested, and the results are shown in Table 3 below:

[0040] Table 3

[0041]

[0042]

[0043] As shown in Table 3, the biaxially oriented polyethylene films produced in Examples 1-3 all exhibited higher antibacterial rates than Comparative Example 1, with antibacterial rates against Escherichia coli and Staphylococcus aureus exceeding 98%, demonstrating strong antibacterial properties. With the increase in chitosan content, the antibacterial rates of Examples 2 and 3 were higher than those of Example 1. However, due to the rigidity and crystallinity of chitosan, Examples 2 and 3 were inferior to Example 1 in terms of optical properties such as gloss, haze, and light transmittance. The biaxially oriented polyethylene films produced in Examples 1-3 also possessed long-lasting antibacterial properties; after 30 days of storage, the antibacterial rate against both types of bacteria remained above 95%, significantly extending the film's service life. After further storage of the polyethylene films from Examples 1-3 for 3 months, the entanglement between chitosan molecules and polyethylene molecules tended to stabilize, and the network structure developed certain pores due to oxidation. However, the antibacterial rate against both types of bacteria remained above 92%, indicating good antibacterial properties.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biological antibacterial biaxially oriented polyethylene film, characterized in that: The polyethylene film comprises a corona layer, a sub-surface layer, an intermediate layer, a sub-inner layer, and a heat-sealing layer. The corona layer comprises 95-99 wt% linear low-density polyethylene resin and 1-5 wt% silica resin. The sub-surface layer comprises 60-80 wt% high-density polyethylene resin and 20-40 wt% linear low-density polyethylene resin. The intermediate layer comprises 60-80 wt% high-density polyethylene resin, 19.5-37.5 wt% linear low-density polyethylene resin, and 0.5-2.5 wt% antistatic resin. The sub-inner layer comprises 60-80 wt% high-density polyethylene resin, 19-37 wt% linear low-density polyethylene resin, and 1-3 wt% chitosan. The heat-sealing layer comprises 95-98 wt% metallocene linear low-density polyethylene resin, 1-2 wt% chitosan, and 1-3 wt% slip agent resin.

2. The antibacterial biaxially oriented polyethylene film according to claim 1, characterized in that: The polyethylene film has a thickness of 18-38 μm, the corona layer has a thickness of 1-5 μm, the subsurface layer has a thickness of 1-5 μm, the intermediate layer has a thickness of 15-30 μm, the innermost layer has a thickness of 1-5 μm, and the heat-sealing layer has a thickness of 5-8 μm.

3. The antibacterial biaxially oriented polyethylene film according to claim 1, characterized in that: The polyethylene film has a thickness of 30 μm, the corona layer has a thickness of 2 μm, the subsurface layer has a thickness of 2 μm, the intermediate layer has a thickness of 18 μm, the innermost layer has a thickness of 2 μm, and the heat-sealing layer has a thickness of 6 μm.

4. The antibacterial biaxially oriented polyethylene film according to claim 1, characterized in that: The density of linear low-density polyethylene resin is 0.926 g / cm³. 3 The melt index is 1.7 g / 10min; the density of the silica resin is 0.93 g / cm³. 3 The melt index is 3.5 g / 10min; the density of high-density polyethylene is 0.953 g / cm³. 3 The melt index is 3.0 g / 10min; the density of the antistatic resin is 0.912 g / cm³. 3 The melt index was 2.8 g / 10min; the degree of deacetylation of chitosan was 98%, and the molecular weight was 50,000 Da; the density of metallocene linear low-density polyethylene resin was 0.916 g / cm³. 3 The melt index is 2.3 g / 10min; the density of the slip resin is 0.92 g / cm³. 3 The melt index is 2.5 g / 10min.

5. A method for preparing a bio-antibacterial biaxially oriented polyethylene film as described in any one of claims 1-4, characterized in that, The specific steps are as follows: Weigh the materials of the corona layer, sub-surface layer, intermediate layer, sub-inner layer and heat-sealing layer respectively, and then put them into the extruders of the co-extrusion biaxial stretching production line. After melt molding, a bio-antibacterial biaxially oriented polyethylene film is obtained.

6. The method for preparing a bio-antibacterial biaxially oriented polyethylene film according to claim 5, characterized in that: The production speed of the biaxial stretching production line is 520 m / min.

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