A polyethylene film with high puncture resistance and impact strength, and a preparation method and application thereof

Abstract

The application belongs to the technical field of soft package composite film materials, and particularly relates to a polyethylene film with high puncture resistance and impact strength, and a preparation method and application thereof. The application comprises a film body, which is prepared through a bidirectional stretching process of a surface layer, a subsurface layer, an intermediate layer, a subsurface inner layer and a corona layer connected in sequence. The polyethylene composite film has excellent optical and mechanical properties, good thickness uniformity, high puncture strength, good low-temperature toughness and high impact strength, and can meet the production requirements of a high-speed printing machine.

Description

Technical Field

[0001] This invention belongs to the technical field of flexible packaging composite film materials, and particularly relates to a polyethylene film with high puncture resistance and impact resistance, its preparation method, and its application. Background Technology

[0002] Currently, most flexible plastic packaging used in the market is made by laminating multiple films of different materials with adhesives. The demand and production of packaging materials are constantly increasing, but after use, packaging is difficult to separate and classify, making recycling challenging. To date, no country has an effective method to separate and decompose packaging materials of different materials for recycling.

[0003] Polyethylene is a widely used general-purpose plastic. Biaxially oriented polyethylene (BEE) film, produced using a multi-layer co-extrusion bi-stretching process, possesses characteristics such as high gloss, few crystal points, high transparency, and low haze. This allows for thinner composite films, meeting the requirements of my country's low-carbon society development, making this type of polyethylene film more competitive in the market than ordinary polyethylene film. While the longitudinal and transverse stretching process of BEE film results in high physical and mechanical strength, it also makes the film more prone to embrittlement and less tough, thus limiting its development. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a polyethylene film with high puncture and impact resistance, its preparation method, and its applications. The polyethylene film of this invention possesses excellent optical and mechanical properties, good thickness uniformity, high puncture strength, good low-temperature toughness, and high impact resistance, meeting the production requirements of high-speed printing presses.

[0005] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0006] A polyethylene film with high puncture resistance and impact resistance includes a film body, which is made by a biaxial stretching process from a surface layer, a sub-surface layer, an intermediate layer, a sub-inner layer and a corona layer connected in sequence.

[0007] The surface layer comprises linear low-density polyethylene resin and anti-blocking resin in a mass ratio of (97-99):(1-3);

[0008] The sub-layer comprises linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of (50-90):(10-50).

[0009] The intermediate layer comprises linear low-density polyethylene resin, first metallocene linear low-density polyethylene resin, and antistatic resin in a mass ratio of (42.5-59.5):(40-55):(0.5-2.5);

[0010] The inner layer comprises linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of (45-75):(25-55).

[0011] The corona layer comprises a second metallocene linear low-density polyethylene resin, a linear low-density polyethylene resin, and an anti-blocking resin in a mass ratio of (50-77):(21-45):(2-5).

[0012] Preferably, the surface layer comprises linear low-density polyethylene resin and anti-blocking resin in a mass ratio of 98:2; the sub-surface layer comprises linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of 65:35; the intermediate layer comprises linear low-density polyethylene resin, a first metallocene linear low-density polyethylene resin, and an antistatic resin in a mass ratio of 53.2:45:1.8; the sub-inner layer comprises linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of 65:35; and the corona layer comprises a second metallocene linear low-density polyethylene resin, linear low-density polyethylene resin, and anti-blocking resin in a mass ratio of 73:25:2.

[0013] Preferably, the polyethylene film has a thickness of 25-40 μm, wherein the thickness of the surface layer is 1-4 μm, the thickness of the sub-surface layer is 1-4 μm, the thickness of the intermediate layer is 9-36 μm, the thickness of the sub-inner layer is 1-4 μm, and the thickness of the corona layer is 1-4 μm.

[0014] Preferably, the polyethylene film has a thickness of 25 μm, wherein the thickness of the surface layer is 2 μm, the thickness of the sub-surface layer is 2 μm, the thickness of the intermediate layer is 17 μm, the thickness of the sub-inner layer is 2 μm, and the thickness of the corona layer is 2 μm.

[0015] Preferably, the linear low-density polyethylene is INNATE TF80 manufactured by Dow Chemical Company, the anti-blocking resin is EAZ-10 manufactured by Primacy Corporation, the low-pressure high-density polyethylene is XUS59910.18 manufactured by Dow Chemical Company, the first metallocene linear low-density polyethylene is Evolue SP3530 manufactured by Primacy Corporation, the antistatic resin is CONSTAB AT431LD manufactured by Constance Corporation, and the second metallocene linear low-density polyethylene is Evolue SP2020 manufactured by Primacy Corporation.

[0016] To achieve the second objective mentioned above, the present invention provides a method for preparing a polyethylene film with high puncture resistance and impact resistance. The specific steps are as follows: weigh the materials contained in the surface layer, sub-surface layer, intermediate layer, sub-inner layer and corona layer of the polyethylene film respectively, and add them into a multi-layer co-extrusion biaxial stretching machine. The polyethylene film with high puncture resistance and impact resistance is obtained through a five-layer co-extrusion biaxial stretching process.

[0017] To achieve the third objective mentioned above, the present invention provides an application of a polyethylene film with high puncture resistance and impact resistance, comprising the following steps:

[0018] S1. A benzene-free ink is gravure printed onto the corona layer surface of a polyethylene film, and then dried and cured to form an ink layer.

[0019] S2. Apply the composite adhesive evenly to the ink layer using a dry or solvent-free lamination method. After being heated and pressed by a laminating roller, it is then laminated with a blown polyethylene film to obtain a polyethylene composite film.

[0020] Preferably, the polyethylene composite film is composed of a film body, an ink layer, an adhesive layer and a blown polyethylene film connected in sequence; the initial sealing temperature of the blown polyethylene film is 90℃-110℃; the adhesive layer is formed by curing a two-component polyurethane adhesive resin.

[0021] Preferably, in step S1, the printing speed of gravure printing is 180-220 m / min, and the drying temperature is 55-75℃.

[0022] Preferably, the two-component polyurethane adhesive includes a polyurethane base agent and a curing agent, with a mass ratio of 5:1, both of which are products of Coim, Italy.

[0023] The advantages of this invention are:

[0024] (1) The polyethylene film of this invention possesses excellent optical and mechanical properties, good thickness uniformity, high puncture strength, good low-temperature toughness, and high impact resistance, making it suitable for use in liquid packaging. It significantly reduces the risk of breakage from drops, meets the production requirements of high-speed printing presses, and exhibits low haze, good transparency, and high gloss, effectively showcasing the printing effect. It can also be used for transparent packaging products, allowing consumers to observe the contents in real time and attracting their attention. The good thickness uniformity of the polyethylene film facilitates subsequent printing and lamination, effectively reducing appearance quality problems.

[0025] (2) The present invention obtains biaxially oriented polyethylene film by five-layer extrusion biaxial stretching, and then produces composite film by dry lamination or solvent-free lamination. The composite film has high low-temperature toughness. Because the polyethylene film of the present invention is puncture resistant, has good vacuum bonding effect, and good bag forming effect, the prepared composite film is made of PE polyethylene material, which facilitates the unified recycling of plastics in the later stage of the product, prevents pollution from multiple types of resins, and can significantly reduce the recycling cost. Moreover, it has good heat sealing effect and strong anti-pollution heat sealing ability, which can meet the requirements of modern high-speed packaging products, improve product quality, and reduce packaging loss.

[0026] (3) The high puncture and impact resistance biaxially oriented polyethylene film provided by this invention is produced by a five-layer co-extrusion process. Compared with the traditional three-layer co-extrusion structure, it adds a sub-surface layer and a sub-inner layer, which increases the intermolecular interaction between polyethylene chains in adjacent layers. The molecular chains conjugate with each other to form a network structure, which expands the buffering effect when the film is under stress, thereby enhancing the toughness of the film. Since the embrittlement temperature of the linear low-density polyethylene resin and the low-pressure high-density polyethylene resin selected in the formula are both below -50℃, the polyethylene molecular chains still maintain a certain degree of entanglement and unentanglement activity at low temperatures, resulting in a significant improvement in low-temperature puncture and impact resistance. Due to the difference in cooling rate, the two layers of polyethylene resin have different crystallization in their microstructure. After biaxial stretching, the crystals in the crystalline region of the two layers are more orderly arranged, and the molecular entanglement in the amorphous region is significantly reduced, effectively improving the impact and puncture resistance of the film. Moreover, the five-layer structure is more symmetrical, which effectively reduces the curl of the film and increases the oxygen and moisture barrier properties of the film to a certain extent. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention.

[0028] The meanings of the symbols in the diagram are as follows:

[0029] 1-Polyethylene composite film, 2-Film body, 3-Top layer, 4-Secondary top layer, 5-Intermediate layer, 6-Secondary inner layer, 7-Corona layer, 8-Ink layer, 9-Adhesive layer, 10-Blown polyethylene film. Detailed Implementation

[0030] 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 accompanying drawings and 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.

[0031] A polyethylene film with high puncture resistance and impact resistance includes a film body 2, which is composed of a surface layer 3, a sub-surface layer 4, an intermediate layer 5, a sub-inner layer 6 and a corona layer 7 connected in sequence.

[0032] Surface layer 3 comprises linear low-density polyethylene resin and anti-blocking resin in a mass ratio of (97-99):(1-3);

[0033] The subsurface layer 4 comprises linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of (50-90):(10-50).

[0034] The intermediate layer 5 comprises linear low-density polyethylene resin, first metallocene linear low-density polyethylene resin, and antistatic resin in a mass ratio of (42.5-59.5):(40-55):(0.5-2.5);

[0035] The innermost layer 6 comprises linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of (45-75):(25-55).

[0036] The corona layer 7 comprises a second metallocene linear low-density polyethylene resin, a linear low-density polyethylene resin, and an anti-blocking resin in a mass ratio of (50-77):(21-45):(2-5).

[0037] The polyethylene film has a thickness of 25-40 μm, wherein the thickness of the surface layer 3 is 1-4 μm, the thickness of the sub-surface layer 4 is 1-4 μm, the thickness of the intermediate layer 5 is 9-36 μm, the thickness of the sub-inner layer 6 is 1-4 μm, and the thickness of the corona layer 7 is 1-4 μm.

[0038] A method for preparing a polyethylene film with high puncture resistance and impact resistance includes the following steps: weighing the materials contained in the surface layer 3, sub-surface layer 4, intermediate layer 5, sub-inner layer 6 and corona layer 7 of the polyethylene film, and then adding them into a multi-layer co-extrusion biaxial stretching machine to obtain a polyethylene film with high puncture resistance and impact resistance through a five-layer co-extrusion biaxial stretching process.

[0039] The processing parameters of this preparation method are shown in Table 1 below:

[0040] Table 1

[0041]

[0042]

[0043] A polyethylene composite film 1 with high puncture and impact resistance is composed of a film body 2, an ink layer 8, an adhesive layer 9, and a blown polyethylene film 10 connected in sequence. The preparation method is as follows:

[0044] S1. The benzene-free ink is gravure printed on the surface of the corona layer 7 of the polyethylene film, and after drying and curing, an ink layer 8 is formed. The gravure printing speed is 180-220m / min, and the drying temperature is 55-75℃.

[0045] S2. Apply the composite adhesive evenly to the ink layer 8 using a dry or solvent-free lamination method. After being heated and pressed by the laminating roller, it is then laminated with the blown polyethylene film 10 to obtain the polyethylene composite film 1.

[0046] The blown polyethylene film 10 has a sealing temperature of 90℃-110℃; the adhesive layer 9 is formed by curing a two-component polyurethane adhesive resin.

[0047] Example 1

[0048] A polyethylene film with high puncture resistance and impact resistance is prepared according to the above preparation method. The formulation of polyethylene film one is shown in Table 2 below.

[0049] Example 2

[0050] A polyethylene film with high puncture resistance and impact resistance is prepared according to the above preparation method. The formulation of polyethylene film II is shown in Table 2 below.

[0051] Example 3

[0052] A polyethylene film with high puncture resistance and impact resistance is prepared according to the above preparation method. The formulation of polyethylene film III is shown in Table 2 below.

[0053] Example 4

[0054] A polyethylene film with high puncture resistance and impact resistance is prepared according to the above preparation method. The formulation of polyethylene film four is shown in Table 2 below.

[0055] Table 2

[0056]

[0057]

[0058] Comparative Example 1

[0059] 25μm biaxially oriented polyethylene film purchased from the market (manufactured by Guangdong Deguan Film).

[0060] The performance of polyethylene films I to IV prepared in Examples 1-4 and the biaxially oriented polyethylene film of Comparative Example 1 were tested, and the results are shown in Table 3 below:

[0061] Table 3

[0062]

[0063]

[0064] As can be seen from the test data in Table 3, the biaxially oriented polyethylene films produced in Examples 1-4 all exhibit a low-temperature puncture strength that is more than 90.5% higher than that of Comparative Example 1, demonstrating excellent puncture performance under low-temperature conditions. The dart impact strength of Examples 1-4 is also more than 42.6% higher than that of Comparative Example 1, indicating that the resin compounding design of the biaxially oriented polyethylene films prepared by this invention is more rational.

[0065] The heat shrinkage rates of Examples 1-4 under a fixed high-temperature environment were all lower than those of Comparative Example 1. Since heat shrinkage rate reflects the film's performance on a printing press, this indicates that the biaxially oriented polyethylene film prepared by this invention is more suitable for high-speed printing. The thickness uniformity of Examples 1-4 was better than that of Comparative Example 1, controlled within ±1%. The longitudinal and transverse elongation at break of Examples 1-4 were close to or greater than that of Comparative Example 1, indicating that the film has good toughness and can be applied to multiple industries, achieving both overall packaging safety and reliability.

[0066] 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 polyethylene film having high puncture resistance and impact strength, characterized by: The film body (2) is made by biaxial stretching of a surface layer (3), a sub-surface layer (4), an intermediate layer (5), a sub-inner layer (6) and a corona layer (7) connected in sequence. The surface layer (3) is composed of linear low-density polyethylene resin and anti-blocking resin in a mass ratio of (97-99):(1-3); The subsurface layer (4) is composed of linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of (50-90):(10-50); The intermediate layer (5) is composed of linear low-density polyethylene resin, first metallocene linear low-density polyethylene resin and antistatic resin in a mass ratio of (42.5-59.5):(40-55):(0.5-2.5); The innermost layer (6) is composed of linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of (45-75):(25-55); The corona layer (7) is composed of a second metallocene linear low-density polyethylene resin, a linear low-density polyethylene resin and an anti-adhesion resin in a mass ratio of (50-77):(21-45):(2-5).

2. The polyethylene film according to claim 1, wherein: The outer layer (3) is composed of linear low-density polyethylene resin and anti-blocking resin in a mass ratio of 98:2; the sub-outer layer (4) is composed of linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of 65:35; the middle layer (5) is composed of linear low-density polyethylene resin, first metallocene linear low-density polyethylene resin and antistatic resin in a mass ratio of 53.2:45:1.8; the inner layer (6) is composed of linear low-density polyethylene resin and low-pressure high-density polyethylene resin in a mass ratio of 65:35; and the corona layer (7) is composed of second metallocene linear low-density polyethylene resin, linear low-density polyethylene resin and anti-blocking resin in a mass ratio of 73:25:

2.

3. The polyethylene film with high puncture resistance and impact resistance according to claim 1, characterized in that: The polyethylene film has a thickness of 25-40 μm, wherein the thickness of the surface layer (3) is 1-4 μm, the thickness of the sub-surface layer (4) is 1-4 μm, the thickness of the intermediate layer (5) is 9-36 μm, the thickness of the sub-inner layer (6) is 1-4 μm, and the thickness of the corona layer (7) is 1-4 μm.

4. A polyethylene film with high puncture resistance and impact resistance according to claim 3, characterized in that: The polyethylene film has a thickness of 25 μm, of which the thickness of the surface layer (3) is 2 μm, the thickness of the sub-surface layer (4) is 2 μm, the thickness of the intermediate layer (5) is 17 μm, the thickness of the sub-inner layer (6) is 2 μm, and the thickness of the corona layer (7) is 2 μm.

5. A polyethylene film with high puncture resistance and impact resistance according to claim 1 or 2, characterized in that: The linear low-density polyethylene is INNATE TF80 manufactured by Dow Chemical Company, the anti-blocking resin is EAZ-10 manufactured by Primavis, the low-pressure high-density polyethylene is XUS 59910.18 manufactured by Dow Chemical Company, the first metallocene linear low-density polyethylene is Evolue SP3530 manufactured by Primavis, the antistatic resin is CONSTAB AT431LD manufactured by Constance, and the second metallocene linear low-density polyethylene is Evolue SP2020 manufactured by Primavis.

6. A method for preparing a polyethylene film with high puncture resistance and impact resistance as described in any one of claims 1-5, characterized in that, The specific steps are as follows: Weigh the materials contained in the surface layer (3), sub-surface layer (4), middle layer (5), sub-inner layer (6) and corona layer (7) of the polyethylene film respectively, and add them into the multi-layer co-extrusion biaxial stretching machine. A polyethylene film with high puncture resistance and impact resistance is obtained through the five-layer co-extrusion biaxial stretching process.

7. The application of a polyethylene film with high puncture resistance and impact resistance as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. The corona layer (7) of a polyethylene film is gravure printed with benzene-free ink and dried and cured to form an ink layer (8). S2. Apply the composite adhesive evenly to the ink layer (8) using a dry or solvent-free lamination method. After being heated and pressed by the lamination roller, it is then laminated with the blown polyethylene film (10) to obtain a polyethylene composite film (1).

8. The application of the polyethylene film with high puncture resistance and impact resistance according to claim 7, characterized in that, The polyethylene composite film (1) is composed of a film body (2), an ink layer (8), an adhesive layer (9) and a blown polyethylene film (10) connected in sequence; the initial sealing temperature of the blown polyethylene film (10) is 90℃-110℃; the adhesive layer (9) is formed by curing a two-component polyurethane adhesive resin.

9. The application of the polyethylene film with high puncture resistance and impact resistance according to claim 7, characterized in that, In step S1, the printing speed of gravure printing is 180-220 m / min, and the drying temperature is 55-75℃.

10. The application of the polyethylene film with high puncture resistance and impact resistance according to claim 8, characterized in that, The two-component polyurethane adhesive comprises a polyurethane base agent and a curing agent, wherein the mass ratio of the polyurethane base agent to the curing agent is 5:1.

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