Three layer coextruded polyethylene heavy duty packaging film

Abstract

The present application belongs to the technical field of heavy packaging film, and particularly relates to a three-layer co-extrusion polyethylene heavy packaging film. The three-layer co-extrusion polyethylene heavy packaging film comprises an inner layer, a middle layer and an outer layer. The inner layer comprises high-pressure polyethylene resin, metallocene polyethylene resin 2, propylene-based elastomer and maleimide-based oxide. The middle layer comprises metallocene polyethylene resin 1, metallocene polyethylene resin 2, propylene-based elastomer and calcium hexahydrophthalate. The outer layer comprises high-pressure polyethylene resin, metallocene polyethylene resin 2, propylene-based elastomer and maleimide-based oxide. The three-layer polyethylene packaging film can reduce the thickness of the film and improve the low-temperature resistance of the film, mainly the tear resistance and puncture resistance, and reduce the production cost by selecting low-density metallocene polyethylene resin with a specific molecular structure and matching a small amount of elastomer.

Description

Technical Field

[0001] This invention belongs to the field of heavy-duty packaging film technology, specifically relating to a three-layer co-extruded polyethylene heavy-duty packaging film. Background Technology

[0002] Polyethylene heavy-duty packaging film is a new type of packaging film. Films capable of holding 10-50 kg of solid granules or powdered materials are generally called heavy-duty packaging films, typically using 25 kg bags. Polyethylene heavy-duty packaging bags offer advantages such as high automation in packaging, excellent sealing, superior moisture and dirt resistance, good aging resistance, and extended shelf life.

[0003] In northern my country, winter temperatures are low, causing films to harden and become brittle, leading to increased breakage rates and impacting product packaging and transportation. Patent CN115635750A discloses a low-temperature resistant three-layer co-extruded heavy-duty packaging film. While this film boasts high strength, its 160μm thickness in certain embodiments results in higher material usage and costs during production, and also generates significant waste after use. Furthermore, the invention incorporates high levels of low-density polyethylene resin (LDPE) and linear low-density polyethylene resin (LLDPE), which reduces the film's mechanical properties. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a three-layer co-extruded polyethylene heavy packaging film that can improve the film's low-temperature resistance, mainly its tear and puncture resistance, while reducing film thickness and lowering production costs.

[0005] The technical solution adopted in this invention is as follows:

[0006] The aforementioned co-extruded polyethylene heavy-duty packaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0007] The inner layer comprises the following components in parts by weight: 5-20 parts of high-pressure polyethylene resin, 260-80 parts of metallocene polyethylene resin, 10-20 parts of propylene-based elastomer, and 0.05-0.1 parts of maleimide oxide, preferably 0.08 parts.

[0008] The middle layer comprises the following components in parts by weight: 10-30 parts of metallocene polyethylene resin 1, 40-80 parts of metallocene polyethylene resin 2, 10-20 parts of propylene-based elastomer, and 0.06-0.1 parts of calcium hexahydrophthalate, preferably 0.06 parts.

[0009] The outer layer comprises the following components in parts by weight: 5-20 parts of high-pressure polyethylene resin, 60-80 parts of metallocene polyethylene resin, 10-20 parts of propylene-based elastomer, and 0.05-0.1 parts of maleimide oxide, preferably 0.08 parts.

[0010] The total thickness of the three-layer co-extruded polyethylene heavy packaging film is 110-130μm, preferably 120μm; the thickness ratio of the inner layer, middle layer and outer layer is 1:(2-3):1, preferably 1:2:1.

[0011] The density of the high-pressure polyethylene resin is 0.920-0.926 g / cm³. 3 The preferred value is 0.924 g / cm³. 3 The melt flow index is 0.3-0.8 g / 10 min, preferably 0.5 g / 10 min.

[0012] The metallocene polyethylene resin comprises metallocene polyethylene resin 1 and metallocene polyethylene resin 2, wherein the density of metallocene polyethylene resin 1 is 0.933-0.938 g / cm³. 3 The preferred value is 0.936 g / cm³. 3 The melt flow index is 0.3-0.7 g / 10 min, preferably 0.5 g / 10 min; the density of metallocene polyethylene resin 2 is 0.913-0.915 g / cm³. 3 The preferred value is 0.914 g / cm³. 3 The melt index is 0.7-0.9 g / 10 min, preferably 0.8 g / 10 min.

[0013] The crystallization thermal classification analysis of metallocene polyethylene resin 2 was performed using DSC, and the content of lamellar crystals with a thickness of more than 9 nm was 25-35%, while the content of lamellar crystals with a thickness of less than 6 nm was 45-55%.

[0014] The molecular weight and distribution of metallocene polyethylene resin 2 were tested using GPC. Its weight average molecular weight was greater than 130,000, and the proportion of the portion with a weight average molecular weight greater than 1,000,000 was greater than 0.40%. The higher the molecular weight and the greater the content of the high molecular weight portion, the more beneficial it is to improving the mechanical properties of the material.

[0015] The content of comonomers and terminal methyl groups in metallocene polyethylene resin 2 was analyzed by carbon NMR spectroscopy, and the molar percentage of comonomers was 3.30-3.80 mol%.

[0016] The density of the propylene-based elastomer is 0.85-0.87 g / cm³. 3 The melt flow index is 1.3-1.6 g / 10 min, preferably Vistamaxx 6102FL, purchased from ExxonMobil.

[0017] The maleimide oxides mentioned are preferably 4-maleimide-tetramethylpiperidine oxide. Experiments have shown that maleimide oxides can undergo a micro-crosslinking reaction with polyethylene resin within the screw, increasing the branching degree of the polyethylene resin and the content of long-chain branches in the molecular structure. This has three beneficial effects: first, it increases the entanglement effect between molecular chains, improving the puncture and tear resistance of the film and thus achieving low-temperature resistance; second, the increased branching degree reduces the crystallinity of the resin, increasing the material's toughness and achieving low-temperature resistance; and third, the increased branching degree, especially the increased content of long-chain branches, can reduce the content of thick flake crystals, thereby lowering the resin melting temperature and reducing the heat-sealing temperature when used in heavy-duty packaging films.

[0018] The aforementioned three-layer co-extruded polyethylene heavy packaging film is produced by blow molding using a three-layer co-extruded blown film machine.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The three-layer co-extruded polyethylene heavy-duty packaging film of this invention is prepared from a composition of high-pressure polyethylene resin, metallocene polyethylene, propylene-based elastomer, maleimide oxide, and calcium hexahydrophthalate. The prepared heavy-duty packaging film has reduced thickness and improved mechanical properties. By selecting low-density metallocene polyethylene resin with a specific molecular structure, although its comonomer content is relatively low, it possesses the unique characteristics of lamellar distribution and molecular weight distribution with different thicknesses. This breaks the rule that resins with low comonomer content have poor mechanical properties. The film processed using this resin has higher comprehensive performance, exceeding the level of resins with high comonomer content for the same specifications. When used in conjunction with propylene-based elastomer, it can improve the tear resistance and puncture resistance of the film. When producing low-temperature resistant FFS film, the production cost is reduced and the low-temperature resistance is improved, thereby reducing the breakage rate of heavy-duty packaging film in low-temperature environments. It can be widely used in the packaging of synthetic resins and other products, with good economic and social benefits. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0022] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products. High-density polyethylene resin can be abbreviated as LDPE, metallocene polyethylene resin as mPE, and linear low-density polyethylene resin as LLDPE. The propylene-based elastomer used is ExxonMobil's Vistamaxx 6102FL, with a density of 0.862 g / cm³. 3 The melt flow index is 1.4 g / 10 min.

[0023] Example 1

[0024] The aforementioned three-layer co-extruded polyethylene heavy-duty packaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0025] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts Vistamaxx 6102FL; 0.08 parts 4-maleimide-tetramethylpiperidine oxide.

[0026] The middle layer comprises the following components in parts by weight: mPE1 25 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0027] The outer layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

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

[0029] Example 2

[0030] The aforementioned three-layer co-extruded polyethylene heavy-duty packaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0031] The inner layer comprises the following components in parts by weight: 20 parts LDPE1, density 0.922 g / cm³. 3 Melt flow index 0.3 g / 10 min; mPE2 60 parts, density 0.913 g / cm³ 3 Melt index 0.7 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 53% for thicknesses below 6 nm, weight average molecular weight 133,000, content of molecular weight above 1,000,000 0.40%, comonomer content 3.57 mol%; Vistamaxx 6102FL 20 parts; 4-maleimide-tetramethylpiperidine oxide 0.1 parts.

[0032] The middle layer comprises the following components in parts by weight: mPE1 15 parts, density 0.937 g / cm³. 3 Melt flow index 0.7 g / 10 min; mPE2 70 parts, density 0.913 g / cm³ 3 Melt index 0.7 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 53% for thicknesses below 6 nm, weight average molecular weight 133,000, content of molecular weight above 1,000,000 0.40%, comonomer content 3.57 mol%; Vistamaxx 6102FL 15 parts; calcium hexahydrophthalate 0.08 parts.

[0033] The outer layer comprises the following components in parts by weight: 20 parts LDPE1, density 0.922 g / cm³. 3 Melt flow index 0.3 g / 10 min; mPE2 60 parts, density 0.913 g / cm³ 3 Melt index 0.7 g / 10 min, lamellar content 25% for thicknesses above 9 nm, lamellar content 53% for thicknesses below 6 nm, weight average molecular weight 133,000, content of molecular weight above 1,000,000 0.40%, comonomer content 3.57 mol%; Vistamaxx 6102FL 20 parts; 4-maleimide-tetramethylpiperidine oxide 0.1 parts.

[0034] The three-layer co-extruded polyethylene heavy packaging film has a thickness of 125μm, with the thickness ratio of the inner, middle, and outer layers being 1:2.5:1.

[0035] Example 3

[0036] The aforementioned three-layer co-extruded polyethylene heavy-duty packaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0037] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.926 g / cm³. 3Melt flow index 0.8 g / 10 min; mPE2 80 parts, density 0.915 g / cm³ 3 Melt index 0.9 g / 10 min, lamellar content 30% for thicknesses above 9 nm, lamellar content 46% for thicknesses below 6 nm, weight average molecular weight 137,000, content of molecular weight above 1,000,000 0.44%, comonomer content 3.40 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.05 parts.

[0038] The middle layer comprises the following components in parts by weight: mPE1 30 parts, density 0.933 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.915 g / cm³ 3 Melt index 0.9 g / 10 min, lamellar content 30% for thicknesses above 9 nm, lamellar content 46% for thicknesses below 6 nm, weight average molecular weight 137,000, content of molecular weight above 1,000,000 0.44%, comonomer content 3.40 mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.08 parts.

[0039] The outer layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.926 g / cm³. 3 Melt flow index 0.8 g / 10 min; mPE2 80 parts, density 0.915 g / cm³ 3 Melt index 0.9 g / 10 min, lamellar content 30% for thicknesses above 9 nm, lamellar content 46% for thicknesses below 6 nm, weight average molecular weight 137,000, content of molecular weight above 1,000,000 0.44%, comonomer content 3.40 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.05 parts.

[0040] The three-layer co-extruded polyethylene heavy packaging film has a thickness of 115μm, with the thickness ratio of the inner, middle, and outer layers being 1:3:1.

[0041] Comparative Example 1

[0042] The difference from Example 1 is that 4-maleimide-tetramethylpiperidine oxide was not added.

[0043] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0044] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts of Vistamaxx 6102FL.

[0045] The middle layer comprises the following components in parts by weight: mPE1 25 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0046] The outer layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts of Vistamaxx 6102FL.

[0047] The heavy-duty packaging film is 120μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0048] Comparative Example 2

[0049] The difference from Example 1 is that calcium hexahydrophthalate was not added.

[0050] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0051] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0052] The middle layer comprises the following components in parts by weight: mPE1 25 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts of Vistamaxx 6102FL.

[0053] The outer layer comprises the following components in parts by weight: LDPE1 10 parts, density 0.924 g / cm3, melt index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm3. 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0054] The heavy-duty packaging film is 120μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0055] Comparative Example 3

[0056] The difference from Example 1 is that 4-maleimide-tetramethylpiperidine oxide and calcium hexahydrophthalate were not added.

[0057] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0058] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts of Vistamaxx 6102FL.

[0059] The middle layer comprises the following components in parts by weight: mPE1 25 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts of Vistamaxx 6102FL.

[0060] The outer layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 10 parts of Vistamaxx 6102FL.

[0061] The heavy-duty packaging film is 120μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0062] Comparative Example 4

[0063] The difference from Example 1 is that mPE2 is replaced with mPE3, which has different thicknesses of lamellar distribution, molecular weight distribution and comonomer content.

[0064] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0065] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE3 80 parts, density 0.914 g / cm³ 3Melt 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 molecular weight above 1,000,000 0.07%, comonomer content 4.15 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0066] The middle layer comprises the following components in parts by weight: mPE1 25 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE3 60 parts, 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 molecular weight above 1,000,000 0.07%, comonomer content 4.15 mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0067] The outer layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE3 80 parts, 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 molecular weight above 1,000,000 0.07%, comonomer content 4.15 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0068] The heavy-duty packaging film is 120μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0069] Comparative Example 5

[0070] The difference from Example 1 is that the density and melt index of the LDPE used are different, and it is referred to as LDPE2.

[0071] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0072] The inner layer comprises the following components in parts by weight: 10 parts LDPE2, density 0.918 g / cm³. 3 Melt flow index 1 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0073] The middle layer comprises the following components in parts by weight: mPE1 25 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0074] The outer layer comprises the following components in parts by weight: 10 parts LDPE2, density 0.918 g / cm³. 3 Melt flow index 1 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0075] The heavy-duty packaging film is 120μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0076] Comparative Example 6

[0077] The difference from Example 1 is that mPE1 is replaced with mPE4, which has a different density and melt index.

[0078] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0079] The inner layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0080] The middle layer comprises the following components in parts by weight: 25 parts mPE4, density 0.940 g / cm³. 3 Melt flow index 0.2 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0081] The outer layer comprises the following components in parts by weight: 10 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidine oxide 0.08 parts.

[0082] The heavy-duty packaging film is 120μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0083] Comparative Example 7

[0084] The difference from Example 1 lies in the composition and weight percentage of the formulation. The mPE used is designated as mPE5, and the propylene-based elastomer used is Dow Chemical's 1881G with a density of 0.904 g / cm³. 3 The melt flow index is 1 g / 10 min.

[0085] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0086] The inner layer comprises the following components in parts by weight: mPE5 39 parts, density 0.918 g / cm³. 3Melt index 1 g / 10 min; LLDPE 25 parts, density 0.920 g / cm³ 3 Melt index 1 g / 10 min; LDPE3 20 parts, density 0.924 g / cm³ 3 Melt index 0.8 g / 10 min; 1881G 10 parts.

[0087] The middle layer comprises the following components in parts by weight: 50 parts mPE5, density 0.918 g / cm³. 3 Melt index 1 g / 10 min; LLDPE 20 parts, density 0.920 g / cm³ 3 Melt index 1 g / 10 min; LDPE3 20 parts, density 0.924 g / cm³ 3 Melt index 0.8 g / 10 min; 1881G 15 parts.

[0088] The outer layer comprises the following components in parts by weight: 40 parts mPE5, density 0.918 g / cm³. 3 Melt index 1 g / 10 min; LLDPE 25 parts, density 0.920 g / cm³ 3 Melt index 1 g / 10 min; LDPE3 20 parts, density 0.924 g / cm³ 3 Melt index 0.8 g / 10 min; 1881G 15 parts.

[0089] The heavy-duty packaging film is 160μm thick, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0090] Comparative Example 8

[0091] The difference from Example 1 is that no propylene-based elastomer was added, and the proportions of inner LDPE1, middle mPE1, and outer LDPE1 were increased respectively.

[0092] The aforementioned repackaging film includes an inner layer, a middle layer, and an outer layer, wherein,

[0093] The inner layer comprises the following components in parts by weight: 20 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 0.08 parts of 4-maleimide-tetramethylpiperidine oxide.

[0094] The middle layer comprises the following components in parts by weight: mPE1 35 parts, density 0.935 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 60 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%, calcium hexahydrophthalate 0.06 parts.

[0095] The outer layer comprises the following components in parts by weight: 20 parts LDPE1, density 0.924 g / cm³. 3 Melt flow index 0.5 g / 10 min; mPE2 80 parts, density 0.914 g / cm³ 3 Melt index 0.8 g / 10 min, lamellar content 28% for thicknesses above 9 nm, lamellar content 51% for thicknesses below 6 nm, weight average molecular weight 138,000, content of molecular weight above 1,000,000 0.38%, comonomer content 3.48 mol%; 0.08 parts of 4-maleimide-tetramethylpiperidine oxide.

[0096] The three-layer co-extruded polyethylene heavy packaging film has a thickness of 120μm, with the thickness ratio of the inner, middle, and outer layers being 1:2:1.

[0097] Detection method:

[0098] Thin film tensile properties: tested according to GB / T 1040.3-2006, using type 5 specimens, with a tensile speed of 200 mm / min.

[0099] Tear resistance of film: tested according to GB / T 11999-1989, using rectangular specimens.

[0100] Impact strength of dart: as per GB / T 9639-2008.

[0101] The test results of the examples and comparative examples are shown in Tables 1 and 2.

[0102] Table 1

[0103]

[0104] Table 2

[0105]

[0106] The test data above shows that the present invention uses a low-density metallocene polyethylene resin with a specific molecular structure. Although its comonomer content is relatively low, it has the special characteristics of different thickness lamellar distribution and molecular weight distribution. This breaks the rule that resins with the same index have poor mechanical properties when the comonomer content is low. The film processed using this resin has higher comprehensive performance, exceeding the level of resins with the same index and high comonomer content. When used in combination with propylene-based elastomers, it can improve the tear resistance and puncture resistance of the film, and has a good effect in the production of low-temperature resistant FFS film.

Claims

1. A three-layer co-extruded polyethylene heavy-duty packaging film, characterized in that, It includes an inner layer, a middle layer, and an outer layer, among which, The inner layer comprises the following components in parts by weight: 5-20 parts of high-pressure polyethylene resin, 60-80 parts of metallocene polyethylene resin, 10-20 parts of propylene-based elastomer, and 0.05-0.1 parts of maleimide oxide. The middle layer comprises the following components in parts by weight: 10-30 parts of metallocene polyethylene resin 1, 40-80 parts of metallocene polyethylene resin 2, 10-20 parts of propylene-based elastomer, and 0.06-0.1 parts of calcium hexahydrophthalate. The outer layer comprises the following components in parts by weight: 5-20 parts of high-pressure polyethylene resin, 60-80 parts of metallocene polyethylene resin, 10-20 parts of propylene-based elastomer, and 0.05-0.1 parts of maleimide oxide. The density of the metallocene polyethylene resin 1 is 0.933-0.938 g / cm³. 3 The melt flow index is 0.3-0.7 g / 10 min; the density of metallocene polyethylene resin 2 is 0.913-0.915 g / cm³. 3 The melt flow index is 0.7-0.9 g / 10 min; The metallocene polyethylene resin 2 contains 25-35% lamellar crystals with a thickness of 9 nm or more, and 45-55% lamellar crystals with a thickness of 6 nm or less. The metallocene polyethylene resin 2 has a weight-average molecular weight greater than 130,000, of which the portion with a weight-average molecular weight greater than 1,000,000 accounts for more than 0.40%.

2. The three-layer co-extruded polyethylene heavy-duty packaging film according to claim 1, characterized in that, The total thickness of the three-layer co-extruded polyethylene heavy packaging film is 110-130μm, and the ratio of the thickness of the inner layer, middle layer and outer layer is 1:(2-3):

1.

3. The three-layer co-extruded polyethylene heavy-duty packaging film according to claim 1, characterized in that, The density of the high-pressure polyethylene resin is 0.920-0.926 g / cm³. 3 The melt flow index is 0.3-0.8 g / 10 min.

4. The three-layer co-extruded polyethylene heavy-duty packaging film according to claim 1, characterized in that, The molar percentage of the comonomer in the metallocene polyethylene resin 2 is 3.30-3.80 mol.

5. The three-layer co-extruded polyethylene heavy-duty packaging film according to claim 1, characterized in that, The density of the propylene-based elastomer is 0.85-0.87 g / cm³. 3 The melt flow index is 1.3-1.6 g / 10 min.

6. The three-layer co-extruded polyethylene heavy-duty packaging film according to claim 1, characterized in that, The aforementioned three-layer co-extruded polyethylene heavy packaging film is produced by blow molding using a three-layer co-extruded blown film machine.

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