Biological antibacterial biaxially oriented polyethylene film and preparation method thereof

Abstract

The invention belongs to the technical field of flexible packaging materials, and particularly relates to a biological antibacterial biaxially oriented polyethylene film and a preparation method thereof. The polyethylene film is composed of a corona layer, a secondary surface layer, a middle layer, a secondary inner layer and a heat sealing layer. The polyethylene film disclosed by the invention has good biocompatibility, function controllability and diversified structural design, can generate inhibition and killing effects on bacteria in manners of physical barrier, membrane permeation, interference metabolism and the like, and can be more widely applied to antibiosis.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible packaging materials, and in particular relates to a biological antibacterial biaxially oriented polyethylene film and a preparation method thereof. Background Art

[0002] In recent years, microbial infection and global virus transmission have had a huge impact on human health and production. Food safety is as important as Mount Tai. How to keep food fresh, slow down spoilage and inhibit the formation of bacteria has led to an increasing demand for antibacterial materials.

[0003] After years of development, a variety of inorganic and organic materials have been developed and widely used. Among them, inorganic antibacterial film materials are mostly composed of metals or metal oxides, with good thermal stability and bactericidal properties, but they have certain biological toxicity and potential environmental impacts; organic antibacterial film materials are mainly synthetic materials with organic small molecules as antibacterial substances, but due to their low bioavailability and short antibacterial effective period, the antibacterial effect is difficult to achieve the expected when used alone.

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

[0005] In order to overcome the above defects in the prior art, the present invention provides a biological antibacterial biaxially oriented polyethylene film and a preparation method thereof. The polyethylene film of the present invention has good antibacterial effect and improves the effect of keeping the contents fresh and the shelf life.

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

[0007] A biological antibacterial biaxially oriented polyethylene film, which consists of a corona layer, a subsurface layer, an intermediate layer, a subinner layer and a heat-sealing layer; the corona layer comprises 95-99wt% of a linear low-density polyethylene resin and 1-5wt% of a silicon dioxide resin, the subsurface layer comprises 60-80wt% of a high-density polyethylene resin and 20-40wt% of a linear low-density polyethylene resin, the intermediate layer comprises 60-80wt% of a high-density polyethylene resin, 19.5-37.5wt% of a linear low-density polyethylene resin and 0.5-2.5wt% of an antistatic resin, the subinner layer comprises 60-80wt% of a high-density polyethylene resin, 19-37wt% of a linear low-density polyethylene resin and 1-3wt% of chitosan, and the heat-sealing layer comprises 95-98wt% of a metallocene linear low-density polyethylene resin, 1-2wt% of chitosan and 1-3wt% of a lubricant resin.

[0008] Preferably, the corona layer comprises 97.5wt% of a linear low density polyethylene resin and 2.5wt% of a silicon dioxide resin, the sub-surface layer comprises 75wt% of a high density polyethylene resin and 25wt% of a linear low density polyethylene resin, the middle layer comprises 75wt% of a high density polyethylene resin, 33.4wt% of a linear low density polyethylene resin and 1.6wt% of an antistatic resin, the sub-inner layer comprises 74wt% of a high density polyethylene resin, 24wt% of a linear low density polyethylene resin and 2wt% of chitosan, and the heat sealing layer comprises 97wt% of a metallocene linear low density polyethylene resin, 1.5wt% of chitosan and 1.5wt% of a lubricant resin.

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

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

[0011] Preferably, the density of the linear low-density polyethylene resin is 0.926 g / cm 3 , the melt index is 1.7g / 10min; the density of silica resin is 0.93g / cm 3 , melt index is 3.5g / 10min; the density of high-density polyethylene is 0.953g / cm 3 , melt index is 3.0g / 10min; density of antistatic resin is 0.912g / cm 3 , the melt index is 2.8g / 10min; the deacetylation degree of chitosan is 98%, the molecular weight is 50000Da; the density of metallocene linear low-density polyethylene resin is 0.916g / cm 3 , the melt index is 2.3g / 10min; the density of the lubricant resin is 0.92g / cm 3 , the melt index is 2.5g / 10min.

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

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

[0014] The advantages of the present invention are:

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

[0016] (2) The polyethylene film of the present invention adds chitosan material to the sub-inner layer and the heat-sealing layer. After the biaxial stretching co-extrusion process, the chitosan macromolecules are arranged in an orderly manner. Due to the interaction of the chitosan molecules between the two layers due to the van der Waals force, the permeability of the bacterial cell membrane will be changed, the RNA synthesis of the bacteria will be inhibited, and the bacterial metabolism will be disordered, thereby interfering with the growth and reproduction of microorganisms. It has a good inhibitory effect on both Escherichia coli and Staphylococcus aureus, and the antibacterial rate can be as high as 98% or more, thereby improving the preservation and shelf life of the contents. Chitosan is a natural polymer obtained by deacetylation of chitin, and has the characteristics of biodegradability, broad-spectrum antibacterial type, non-toxicity and low cost, and is widely used in the pharmaceutical, food packaging, cosmetics and other 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 sub-inner layer and the heat-sealing layer. Since chitosan is a natural high molecular hydrophilic substance, it interacts with the hydrogen bonds in the metallocene polyethylene and low-density polyethylene molecular chains 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 bacterial microorganisms, and enhancing 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, and the sub-surface layer and the sub-inner layer are added, and the interaction force between the layers is increased, so that the film has excellent toughness and mechanical properties; and the formula ratio of the five layers is reasonably designed, so that the stress inside and outside the film is effectively released, making the film smoother and reducing the occurrence of bending and curling.

[0018] (4) After the linear polyethylene resin and the high-density polyethylene resin in the corona layer, sub-surface layer and intermediate layer of the present invention are co-extruded and biaxially stretched, the cooling speed is fast and the cooling efficiency is high, which reduces the crystallinity of the film, greatly reduces the proportion of the crystalline area, and a large number of non-crystalline areas are irregularly distributed, 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 a metallocene linear polyethylene resin, which has a low sealing temperature, high hot tack strength, good anti-pollution heat-sealing ability, and a wide processing window, thereby being able to meet the evolving needs of rapid packaging.

[0020] (6) The polyethylene film of the present invention is bonded to form a composite film, which has a low heat sealing temperature, high hot adhesive strength, and a wide processing range. It can quickly adapt to high-speed packaging of fruit and vegetable foods, and extend the shelf life of the contents. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0022] A biological antibacterial biaxially oriented polyethylene film, which consists of a corona layer, a subsurface layer, an intermediate layer, a subinner layer and a heat-sealing layer; the corona layer comprises 95-99wt% of a linear low-density polyethylene resin (LLDPE) and 1-5wt% of a silicon dioxide resin (SiO2), the subsurface layer comprises 60-80wt% of a high-density polyethylene resin (HDPE) and 20-40wt% of a linear low-density polyethylene resin (LLDPE), the intermediate layer comprises 60-80wt% of a high-density polyethylene resin (HDPE), 19.5-3 7.5wt% of linear low density polyethylene resin (LLDPE) and 0.5-2.5wt% of antistatic resin (ATPE), the sub-inner layer includes 60-80wt% of high density polyethylene resin (HDPE), 19-37wt% of linear low density polyethylene resin (LLDPE) and 1-3wt% of chitosan (CS), and the heat sealing layer includes 95-98wt% of metallocene linear low density polyethylene resin (MLLDPE), 1-2wt% of chitosan (CS) and 1-3wt% of slip agent resin (SLIP).

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

[0024] The density of linear low-density polyethylene resin is 0.926 g / cm 3 , the melt index is 1.7g / 10min; the density of silica resin is 0.93g / cm 3 , melt index is 3.5g / 10min; the density of high-density polyethylene is 0.953g / cm 3 , melt index is 3.0g / 10min; density of antistatic resin is 0.912g / cm 3, the melt index is 2.8g / 10min; the deacetylation degree of chitosan is 98%, the molecular weight is 50000Da; the density of metallocene linear low-density polyethylene resin is 0.916g / cm 3 , the melt index is 2.3g / 10min; the density of the lubricant resin is 0.92g / cm 3 , the melt index is 2.5g / 10min.

[0025] A method for preparing a biological antibacterial biaxially oriented polyethylene film, the specific steps are as follows: respectively weigh the materials of the corona layer, the sub-surface layer, the middle layer, the sub-inner layer and the heat-sealing layer, and then respectively put them into each extruder of the co-extrusion double-stretching production line, and melt-form them to obtain a biological antibacterial biaxially oriented polyethylene film. The specific processing technology is shown in Table 1 below:

[0026] Table 1

[0027]

[0028]

[0029] Example 1

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

[0031] Example 2

[0032] A biological antibacterial biaxially oriented polyethylene film is prepared according to the above preparation method. The formula of the polyethylene film 2 is shown in Table 2 below.

[0033] Example 3

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

[0035] Table 2

[0036]

[0037] Comparative Example 1

[0038] Purchased antibacterial cast polyethylene film (manufacturer is Yongxin Co., Ltd. (Huangshan) Packaging Co., Ltd.).

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

[0040] Table 3

[0041]

[0042]

[0043] As can be seen from Table 3, the biaxially oriented polyethylene films produced in Examples 1-3 have a higher antibacterial rate than that of Comparative Example 1, and the antibacterial rates against Escherichia coli and Staphylococcus aureus are as high as more than 98%, which have strong antibacterial properties. With the increase of the proportion of chitosan, the antibacterial rates of Examples 2 and 3 are improved compared with those of Example 1. Since chitosan has certain rigidity and crystallinity, Examples 2 and 3 are inferior to Example 1 in optical properties such as gloss, haze and transmittance. The biaxially oriented polyethylene films produced in Examples 1-3 also have long-lasting antibacterial properties. After being placed for 30 days, the antibacterial rates against the two bacteria are still maintained at more than 95%, which greatly increases the service life of the film. After the polyethylene films of Examples 1-3 are placed for another 3 months, the entanglement between the chitosan molecules and the polyethylene molecules tends to be stable, and its mesh structure has certain pores due to oxidation, but its antibacterial rate against the two types of bacteria is more than 92%, and it still has good antibacterial properties.

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

Claims

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

2. The bio-antibacterial biaxially oriented polyethylene film according to claim 1, characterized in that: The corona layer comprises 97.5wt% of a linear low-density polyethylene resin and 2.5wt% of a silicon dioxide resin, the sub-surface layer comprises 75wt% of a high-density polyethylene resin and 25wt% of a linear low-density polyethylene resin, the middle layer comprises 75wt% of a high-density polyethylene resin, 33.4wt% of a linear low-density polyethylene resin and 1.6wt% of an antistatic resin, the sub-inner layer comprises 74wt% of a high-density polyethylene resin, 24wt% of a linear low-density polyethylene resin and 2wt% of chitosan, and the heat-sealing layer comprises 97wt% of a metallocene linear low-density polyethylene resin, 1.5wt% of chitosan and 1.5wt% of a lubricant resin.

3. The bio-antibacterial biaxially oriented polyethylene film according to claim 1, characterized in that: The thickness of the polyethylene film is 18-38 μm, the thickness of the corona layer is 1-5 μm, the thickness of the subsurface layer is 1-5 μm, the thickness of the middle layer is 15-30 μm, the thickness of the sub-inner layer is 1-5 μm, and the thickness of the heat-sealing layer is 5-8 μm.

4. A biological antibacterial biaxially oriented polyethylene film according to claim 1 or 3, characterized in that: The thickness of the polyethylene film is 30 μm, the thickness of the corona layer is 2 μm, the thickness of the subsurface layer is 2 μm, the thickness of the middle layer is 18 μm, the thickness of the sub-inner layer is 2 μm, and the thickness of the heat-sealing layer is 6 μm.

5. The bio-antibacterial biaxially oriented polyethylene film according to claim 1 or 2, characterized in that: The density of linear low-density polyethylene resin is 0.926 g / cm 3 , the melt index is 1.7g / 10min; the density of silica resin is 0.93g / cm 3 , melt index is 3.5g / 10min; the density of high-density polyethylene is 0.953g / cm 3 , melt index is 3.0g / 10min; density of antistatic resin is 0.912g / cm 3 , the melt index is 2.8g / 10min; the deacetylation degree of chitosan is 98%, the molecular weight is 50000Da; the density of metallocene linear low-density polyethylene resin is 0.916g / cm 3 , the melt index is 2.3g / 10min; the density of the lubricant resin is 0.92g / cm 3 , the melt index is 2.5g / 10min.

6. A method for preparing a biological antibacterial biaxially oriented polyethylene film according to any one of claims 1 to 5, characterized in that: The specific steps are as follows: weigh the materials of the corona layer, sub-surface layer, middle layer, sub-inner layer and heat-sealing layer respectively, and then put them into each extruder of the co-extrusion double-drawing production line respectively, and obtain a biological antibacterial biaxially oriented polyethylene film through melt molding.

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

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