Polyethylene heavy duty packaging film

Abstract

The application discloses a polyethylene heavy packaging film and belongs to the technical field of polyethylene heavy packaging films.The technical scheme is as follows: the film comprises three layers of an inner layer, a middle layer and an outer layer, the inner layer comprises the following components in parts by weight: 10-25 parts of high-pressure polyethylene resin, 20-40 parts of metallocene polyethylene resin I and 50-70 parts of metallocene polyethylene resin II; the middle layer comprises the following components in parts by weight: 10-40 parts of high-density polyethylene resin, 10-50 parts of metallocene polyethylene resin I, 20-50 parts of metallocene polyethylene resin II and 0.06-0.1 parts of a metal salt compound of hexahydrophthalic acid; and the outer layer comprises the following components in parts by weight: 10-25 parts of high-pressure polyethylene resin, 20-40 parts of metallocene polyethylene resin I and 50-70 parts of metallocene polyethylene resin II.The polyethylene heavy packaging film realizes the reduction of the thickness of the polyethylene heavy packaging film and the improvement of the comprehensive performance of the polyethylene heavy packaging film without adding an elastomer.

Description

Technical Field

[0001] This invention relates to the field of polyethylene heavy-duty packaging film technology, and specifically to a polyethylene heavy-duty packaging film. Background Technology

[0002] Polyethylene heavy-duty packaging film is a new type of packaging film. Generally, packaging films capable of holding 10-50 kg of solid granules or powdered materials are called heavy-duty packaging films, typically in 25 kg bags. Polyethylene heavy-duty packaging bags offer advantages such as high automation in packaging, good sealing, excellent moisture and dirt resistance, good aging resistance, and extended shelf life. Early polyethylene heavy-duty packaging bags were mainly made from blends of general-purpose linear polyethylene and low-density polyethylene resin, but they were relatively thick, around 150-200 μm, resulting in higher production costs and a higher total amount of waste after unpacking and using the materials.

[0003] Chinese invention patent CN111483196B discloses a method for preparing a three-layer co-extruded heavy-duty packaging film, providing a heavy-duty packaging film with good mechanical properties. However, its formulation includes a high content of polyolefin elastomer. Currently, the average price of polyolefin elastomer is over 20,000 yuan / ton, while the average price of polyethylene resin is less than 10,000 yuan / ton. Therefore, the addition of a high content of polyolefin elastomer significantly increases production costs. Furthermore, this patent does not specify the thickness of the prepared heavy-duty packaging film. Chinese invention patent CN115635750A discloses a low-temperature resistant three-layer co-extruded heavy-duty packaging film, providing a high-strength heavy-duty packaging film. However, the film thickness is 160μm, and the addition of a high content of polyolefin elastomer results in higher material usage and costs during production, and also generates more waste after use. Additionally, the addition of a high content of LDPE and LLDPE resins in this invention reduces the mechanical properties of the film.

[0004] Therefore, in order to address the aforementioned problems with existing polyethylene heavy-duty packaging films, it is necessary to develop a new formulation for three-layer co-extruded polyethylene heavy-duty packaging films, which can produce polyethylene heavy-duty packaging films with high overall performance without adding polyolefin elastomers, which have high production costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a polyethylene heavy packaging film. Through the formulation design of the inner, middle and outer three layers and the optimization of each component in the formulation, the thickness of the polyethylene heavy packaging film is reduced and its overall performance is improved without adding elastomer.

[0006] The technical solution of this invention is as follows:

[0007] A polyethylene heavy-duty packaging film comprises three layers: an inner layer and an outer layer. The inner layer comprises the following components in parts by weight: 10-25 parts of low-density polyethylene resin (LDPE), 20-40 parts of metallocene polyethylene resin I (mPE1), and 50-70 parts of metallocene polyethylene resin II (mPE2). The middle layer comprises the following components in parts by weight: 10-40 parts of high-density polyethylene resin (HDPE), 10-50 parts of metallocene polyethylene resin I, 20-50 parts of metallocene polyethylene resin II, and 0.06-0.1 parts of a metal hexahydrophthalic acid (HEPA) salt compound, preferably 0.06 parts of the HEPA metal salt compound. The outer layer comprises the following components in parts by weight: 10-25 parts of low-density polyethylene resin, 20-40 parts of metallocene polyethylene resin I, and 50-70 parts of metallocene polyethylene resin II.

[0008] Preferably, the high-density polyethylene resin is a copolymer of ethylene and 1-hexene with a density of 0.952-0.956 g / cm³. 3 The melt index is 8-12 g / 10 min; preferably, the density of the high-density polyethylene resin is 0.954 g / cm³. 3 The melt index is 10g / 10min.

[0009] Preferably, the density of the high-pressure polyethylene resin is 0.920-0.926 g / cm³. 3 The melt index is 0.3-0.8 g / 10 min; preferably, the density of the high-pressure polyethylene resin is 0.924 g / cm³. 3 The melt index is 0.5 g / 10 min.

[0010] Preferably, the density of the metallocene polyethylene resin is 0.917-0.921 g / cm³. 3 The melt index is 0.8-1.1 g / 10 min; preferably, the density of the metallocene polyethylene resin is 0.918 g / cm³. 3 The melt index is 1.0 g / 10 min; the density of metallocene polyethylene resin II is 0.913-0.915 g / cm³. 3 The melt index is 0.7-0.9 g / 10 min; preferably, the density of the metallocene polyethylene resin II is 0.914 g / cm³. 3 The melt index is 0.8 g / 10 min.

[0011] Preferably, the metallocene polyethylene resin 2 is subjected to crystallization thermal classification analysis using DSC, wherein the content of lamellar crystals with a thickness of 9 nm or more is 22-30%, and the content of lamellar crystals with a thickness of 6 nm or less is 48-55%.

[0012] Preferably, the molecular weight and distribution of metallocene polyethylene resin II are tested using GPC. Its weight-average molecular weight is greater than 130,000, and the content of the portion with a weight-average molecular weight of more than 1,000,000 is greater than 0.35%. The higher the molecular weight and the greater the content of the high molecular weight portion, the better it is to improve the mechanical properties of the material.

[0013] Preferably, the comonomers of metallocene polyethylene resin II are analyzed using carbon NMR spectroscopy, and the molar percentage of the comonomers is 3.20-3.60 mol.

[0014] Preferably, the hexahydrophthalic acid metal salt compound is calcium hexahydrophthalate. Experiments have shown that adding the hexahydrophthalic acid metal salt compound can improve the tear resistance and puncture resistance of polyethylene heavy packaging film.

[0015] Preferably, the polyethylene heavy packaging film of the present invention is a three-layer co-extruded film with a thickness ratio of 1:(2-3):1 for the inner, middle and outer layers, and a total thickness of 120μm for the polyethylene heavy packaging film.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This invention provides a three-layer polyethylene heavy packaging film. Through the formulation design of the inner, middle and outer layers and the optimization of each component in the formulation, the thickness of the polyethylene heavy packaging film is reduced and its overall performance is improved without adding elastomers. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments.

[0019] Example 1

[0020] The polyethylene heavy-duty packaging film of this embodiment comprises three layers: inner, middle, and outer. The inner layer comprises the following components in parts by weight: 20 parts LDPE resin with a density of 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38%, comonomer molar percentage 3.38 mol.

[0021] The middle layer comprises the following components in parts by weight: 30 parts HDEP resin, density 0.954 g / cm³. 3 Melt index 10 g / min; mPE1 resin content 30 parts, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 40 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol%, calcium hexahydrophthalate 0.06 parts.

[0022] The outer layer comprises the following components in parts by weight: 20 parts LDPE resin, density 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol.

[0023] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0024] Example 2

[0025] The polyethylene heavy-duty packaging film of this embodiment comprises three layers: inner, middle, and outer. The inner layer comprises the following components in parts by weight: 15 parts LDPE resin with a density of 0.926 g / cm³. 3 Melt index 0.5 g / 10 min; 30 parts of mPE1 resin, density 0.921 g / cm³ 3 Melt index 1.0 g / 10 min; 55 parts of mPE2 resin, density 0.913 g / cm³ 3 Melt index 0.7 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.40 mol.

[0026] The middle layer comprises the following components in parts by weight: 20 parts HDEP resin, density 0.952 g / cm³. 3Melt index 8 g / min; mPE1 resin content 30 parts, density 0.921 g / cm³ 3 Melt index 1.0 g / 10 min; 50 parts of mPE2 resin, density 0.913 g / cm³ 3 Melt index 0.7 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.40 mol%, calcium hexahydrophthalate 0.08 parts.

[0027] The outer layer comprises the following components in parts by weight: 15 parts LDPE resin, density 0.926 g / cm³. 3 Melt index 0.5 g / 10 min; 30 parts of mPE1 resin, density 0.921 g / cm³ 3 Melt index 1.0 g / 10 min; 55 parts of mPE2 resin, density 0.913 g / cm³ 3 Melt index 0.7 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.40 mol.

[0028] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0029] Example 3

[0030] The polyethylene heavy-duty packaging film of this embodiment comprises three layers: inner, middle, and outer. The inner layer comprises the following components in parts by weight: 25 parts LDPE resin with a density of 0.920 g / cm³. 3 Melt index 0.3 g / 10 min; 20 parts of mPE1 resin, density 0.917 g / cm³ 3 Melt index 1.1 g / 10 min; 55 parts of mPE2 resin, density 0.915 g / cm³ 3 Melt index 0.9 g / 10 min, lamellar content 29% for thicknesses above 9 nm, lamellar content 50% for thicknesses below 6 nm, weight average molecular weight 148,000, content of the portion with molecular weight above 1,000,000 0.42, comonomer molar percentage 3.26 mol.

[0031] The middle layer comprises the following components in parts by weight: 40 parts HDEP resin, density 0.956 g / cm³. 3 Melt index 12 g / 10 min; mPE1 resin content 10 parts, density 0.917 g / cm³ 3Melt index 1.1 g / 10 min; 50 parts of mPE2 resin, density 0.915 g / cm³ 3 Melt index 0.9 g / 10 min, lamellar content 29% for thicknesses above 9 nm, lamellar content 50% for thicknesses below 6 nm, weight average molecular weight 148,000, content of the portion with molecular weight above 1,000,000 0.42, comonomer molar percentage 3.26 mol%; calcium hexahydrophthalate 0.1 parts.

[0032] The outer layer comprises the following components in parts by weight: 25 parts LDPE resin, density 0.920 g / cm³. 3 Melt index 0.3 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 55 parts of mPE2 resin, density 0.915 g / cm³ 3 Melt index 0.9 g / 10 min, lamellar content 29% for thicknesses above 9 nm, lamellar content 50% for thicknesses below 6 nm, weight average molecular weight 148,000, content of the portion with molecular weight above 1,000,000 0.42, comonomer molar percentage 3.26 mol.

[0033] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0034] Comparative Example 1

[0035] The difference from Example 1 is that calcium hexahydrophthalate is not added to the middle layer.

[0036] Comparative Example 2

[0037] Comparative Example 2's polyethylene heavy-duty packaging film comprises three layers: inner, middle, and outer. The inner layer includes the following components in parts by weight: 20 parts LDPE resin with a density of 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of low-density mPE resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 50% for thicknesses above 9 nm, lamellar content 27% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.07, comonomer molar percentage 4.15 mol.

[0038] The middle layer comprises the following components in parts by weight: 30 parts HDEP resin, density 0.954 g / cm³. 3 Melt index 10 g / min; mPE1 resin content 30 parts, density 0.918 g / cm³3 Melt index 1.0 g / 10 min; 40 parts of low-density mPE resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 50% for thicknesses above 9 nm, lamellar content 27% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.07, comonomer molar percentage 4.15 mol%; calcium hexahydrophthalate 0.06 parts.

[0039] The outer layer comprises the following components in parts by weight: 20 parts LDPE resin, density 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of low-density mPE resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 50% for thicknesses above 9 nm, lamellar content 27% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.07, comonomer molar percentage 4.15 mol.

[0040] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0041] Comparative Example 3

[0042] Comparative Example 3's polyethylene heavy-duty packaging film comprises three layers: inner, middle, and outer. The inner layer includes the following components in parts by weight: 20 parts LDPE resin with a density of 0.917 g / cm³. 3 Melt index 1.0 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38%, comonomer molar percentage 3.38 mol.

[0043] The middle layer comprises the following components in parts by weight: 30 parts HDEP resin, density 0.954 g / cm³. 3 Melt index 10 g / min; mPE1 resin content 30 parts, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 40 parts of mPE2 resin, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol%, calcium hexahydrophthalate 0.06 parts.

[0044] The outer layer comprises the following components in parts by weight: 20 parts LDPE resin, density 0.917 g / cm³, melt index 1.0 g / 10 min; 20 parts mPE1 resin, density 0.918 g / cm³. 3 Melt index 1.0 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol.

[0045] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0046] Comparative Example 4

[0047] Comparative Example 4's polyethylene heavy-duty packaging film comprises three layers: inner, middle, and outer. The inner layer includes the following components in parts by weight: 20 parts LDPE resin with a density of 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.924 g / cm³. 3 Melt index 0.6 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38%, comonomer molar percentage 3.38 mol.

[0048] The middle layer comprises the following components in parts by weight: 30 parts HDEP resin, density 0.954 g / cm³. 3 Melt index 10 g / min; mPE1 resin content 30 parts, density 0.924 g / cm³ 3 Melt index 0.6 g / 10 min; 40 parts of mPE2 resin, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol%, calcium hexahydrophthalate 0.06 parts.

[0049] The outer layer comprises the following components in parts by weight: 20 parts LDPE resin, density 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.924 g / cm³. 3 Melt index 0.6 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol.

[0050] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0051] Comparative Example 5

[0052] Comparative Example 5: A polyethylene heavy-duty packaging film comprising three layers, inner, middle, and outer, wherein the inner layer comprises the following components in parts by weight: 20 parts LDPE resin, density 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38%, comonomer molar percentage 3.38 mol.

[0053] The middle layer comprises the following components in parts by weight: 30 parts HDEP resin, density 0.950 g / cm³. 3 Melt index 14 g / min; mPE1 resin content 30 parts, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 40 parts of mPE2 resin, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol%, calcium hexahydrophthalate 0.06 parts.

[0054] The outer layer comprises the following components in parts by weight: 20 parts LDPE resin, density 0.924 g / cm³. 3 Melt index 0.5 g / 10 min; 20 parts of mPE1 resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 60 parts of mPE2 resin, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of the portion with molecular weight above 1,000,000 0.38, comonomer molar percentage 3.38 mol.

[0055] The three-layer co-extrusion has a thickness ratio of 1:2:1 for the inner, middle, and outer layers, and the total thickness of the polyethylene heavy packaging film is 120μm.

[0056] Comparative Example 6 (Example 1 in CN114454578A)

[0057] Outer layer of polyethylene heavy-duty packaging film: 50 parts mPE resin, density 0.924 g / cm³ 3 Melt index 1.1 g / 10 min, relative content of lamellar crystals thicker than 9 nm 15%; 25 parts of ultra-low density polyethylene resin, density 0.910 g / cm³ 3 Melt index 1.0 g / 10 min; 25 parts of LDPE resin, density 0.920 g / cm³ 3 Melt index 1.0g / 10min.

[0058] Middle layer of polyethylene heavy packaging film: 80 parts mPE resin, density 0.924 g / cm³ 3 Melt index 1.1 g / 10 min, relative content of lamellar crystals thicker than 9 nm 15%; 20 parts LDPE resin, density 0.920 g / cm³ 3 Melt index 1.0g / 10min.

[0059] Inner layer of polyethylene heavy-duty packaging film: 16.7 parts ultra-low density polyethylene resin, density 0.910 g / cm³ 3 Melt index 1.0 g / 10 min; 50 parts of LDPE resin, density 0.920 g / cm³. 3 Melt index is 1.0 g / 10 min; mPE resin 33.3 parts, density 0.924 g / cm³3 Melt index 1.1 g / 10 min, relative content of lamellar crystals with a thickness of 9 nm or more 15%.

[0060] The thickness ratio of the inner, middle and outer layers is 1:1:1, with a total thickness of 120μm.

[0061] Comparative Example 7 (Example 1 in CN115635750A)

[0062] Inner layer of polyethylene heavy-duty packaging film: 25 parts LDPE resin, density 0.920 g / cm³ 3 Melt index 1.0 g / 10 min; 39 parts of mLLDPE resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 30 parts LLDPE resin, 0.920 g / cm³, melt index 0.5 g / 10 min; 5 parts acrylic elastomer, density 0.900 g / cm³. 3 Melt index 0.5 g / 10 min; 1 part processing aid.

[0063] Middle layer of polyethylene heavy packaging film: 20 parts LDPE resin, density 0.920 g / cm³ 3 Melt index 1.0 g / 10 min; 50 parts of mLLDPE resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; LLDPE resin 0.920 g / cm³ 3 Melt index 0.5g / 10min.

[0064] Outer layer of polyethylene heavy-duty packaging film: 20 parts LDPE resin, density 0.920 g / cm³ 3 Melt index 1.0 g / 10 min; 40 parts of mLLDPE resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 29 parts of LLDPE resin, density 0.920 g / cm³ 3 Melt index 0.5g / 10min; 1 part color masterbatch.

[0065] The thickness ratio of the inner, middle and outer layers is 1:2:1, and the total thickness is 160μm.

[0066] Comparative Example 8 (Example 6 in CN115635750A)

[0067] Inner layer of polyethylene heavy-duty packaging film: 39 parts mPE resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 25 parts of LLDPE resin, density 0.920 g / cm³ 3 Melt index 1.0 g / 10 min; 20 parts of LDPE resin, density 0.924 g / cm³ 3Melt index 0.8 g / 10 min; 10 parts of propylene-based elastomer, density 0.900 g / cm³ 3 Melt index 0.5g / 10min.

[0068] Middle layer of polyethylene heavy packaging film: 50 parts mPE resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 20 parts of LLDPE resin, density 0.920 g / cm³ 3 Melt index 1.0 g / 10 min; 20 parts of LDPE resin, density 0.924 g / cm³ 3 Melt index 0.8 g / 10 min; 15 parts of propylene-based elastomer, density 0.900 g / cm³ 3 Melt index 0.5 g / 10 min; 1 part processing aid.

[0069] Outer layer of polyethylene heavy-duty packaging film: 40 parts mPE resin, density 0.918 g / cm³ 3 Melt index 1.0 g / 10 min; 25 parts of LLDPE resin, density 0.920 g / cm³ 3 Melt index 1.0 g / 10 min; 20 parts of LDPE resin, density 0.924 g / cm³ 3 Melt index 0.8 g / 10 min; 15 parts of propylene-based elastomer, density 0.900 g / cm³ 3 Melt index 0.5g / 10min.

[0070] The thickness ratio of the inner, middle and outer layers is 1:2:1, and the total thickness is 120μm.

[0071] The performance of the polyethylene heavy packaging films prepared in Examples 1-3 and Comparative Examples 1-8 was evaluated according to the following methods:

[0072] Tensile properties: tested according to GB / T 1040.3-2006, using type 5 specimens, with a tensile speed of 200 mm / min;

[0073] Tear resistance: Tested according to GB / T 11999-1989, using rectangular specimens;

[0074] Drop impact strength: conducted according to GB / T 9639-2008.

[0075] The test results are shown in Table 1-2:

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080] As shown in Tables 1-2, the absence of calcium hexahydrophthalate in the middle layer of the packaging film in Comparative Example 1 results in lower tear resistance and drop weight impact strength of the prepared polyethylene heavy-duty packaging film. This is mainly because the addition of calcium hexahydrophthalate in the examples increased the crystallization orientation of polyethylene during film processing, thereby improving the tear and puncture resistance of the film. Comparative Example 2 used a density of 0.914 g / cm³. 3 Compared to mPE2 in the examples, the resin in Comparative Example 2 has a higher comonomer content. Theoretically, for resins with similar properties, a higher comonomer content should result in better puncture and tear resistance in the processed film. However, structural analysis revealed that the mPE2 resin in Comparative Example 2 had a low polymer content and a low content of high-molecular-weight comonomers, resulting in no improvement in the final film performance despite its high comonomer content. The LDPE resin used in Comparative Example 3 had a low density and a high melt index, leading to a decrease in the mechanical properties of the film. The mPE1 resin used in Comparative Example 4 had an increased density, resulting in a decrease in the longitudinal tear and drop dart impact strength of the film. The HDPE resin used in Comparative Example 5 had a decreased density, resulting in a decrease in the transverse tear and transverse tensile properties of the film. Comparative Example 6 did not add HDPE resin, resulting in low tensile strength and transverse tear resistance of the film. Comparative Examples 7 and 8 added propylene-based elastomers, but due to the addition of a large amount of LLDPE resin, the drop dart impact strength was low. Additionally, the film thickness of Comparative Example 7 was high, increasing production costs and making thinning and reinforcement impossible.

[0081] This invention utilizes a low-density metallocene polyethylene resin with a specific molecular structure. Although its comonomer content is relatively low, it possesses unique characteristics such as different thickness lamellar distributions and molecular weight distributions. This breaks the rule that resins with the same specifications have poor mechanical properties when the comonomer content is low. Packaging films processed using this resin have higher comprehensive performance, exceeding the level of resins with the same specifications but higher comonomer content.

Claims

1. A polyethylene heavy-duty packaging film, characterized in that, It consists of three layers: inner, middle and outer. The inner layer comprises the following components in parts by weight: 10-25 parts of high-pressure polyethylene resin, 20-40 parts of metallocene polyethylene resin I, and 50-70 parts of metallocene polyethylene resin II. The middle layer comprises the following components in parts by weight: 10-40 parts of high-density polyethylene resin, 10-50 parts of metallocene polyethylene resin I, 20-50 parts of metallocene polyethylene resin II, and 0.06-0.1 parts of hexahydrophthalic acid metal salt compound. The outer layer comprises the following components in parts by weight: 10-25 parts of high-pressure polyethylene resin, 20-40 parts of metallocene polyethylene resin I, and 50-70 parts of metallocene polyethylene resin II. The density of the metallocene polyethylene resin is 0.917-0.921 g / cm³. 3 The melt index is 0.8-1.1 g / 10 min; the density of metallocene polyethylene resin II is 0.913-0.915 g / cm³. 3 The melt index is 0.7-0.9 g / 10 min; In the metallocene polyethylene resin II, the content of lamellar crystals with a thickness of 9 nm or more is 22-30%, and the content of lamellar crystals with a thickness of 6 nm or less is 48-55%. The metallocene polyethylene resin II has a weight-average molecular weight greater than 130,000, wherein the content of the portion with a weight-average molecular weight greater than 1,000,000 is greater than 0.35%. The comonomer molar percentage of the metallocene polyethylene resin II is 3.20-3.60 mol.

2. The polyethylene heavy-duty packaging film as described in claim 1, characterized in that, The high-density polyethylene resin is a copolymer of ethylene and 1-hexene, with a density of 0.952-0.956 g / cm³. 3 The melt index is 8-12 g / 10 min.

3. The polyethylene heavy-duty packaging film as described in claim 1, characterized in that, The density of the high-pressure polyethylene resin is 0.920-0.926 g / cm³. 3 The melt index is 0.3-0.8 g / 10 min.

4. The polyethylene heavy-duty packaging film as described in claim 1, characterized in that, The hexahydrophthalic acid metal salt compound is calcium hexahydrophthalic acid.

5. The polyethylene heavy-duty packaging film as described in claim 1, characterized in that, The thickness ratio of the inner, middle and outer layers of the polyethylene heavy packaging film is 1:(2-3):1, and the total thickness of the polyethylene heavy packaging film is 120μm.

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