Three-layer co-extrusion polyethylene heavy packaging film

Abstract

The invention belongs to the technical field of heavy packaging films, 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, and the inner layer comprises high-pressure polyethylene resin, metallocene polyethylene resin 2, a propenyl elastomer and maleimide oxide; the middle layer comprises metallocene polyethylene resin 1, metallocene polyethylene resin 2, allyl elastomer and calcium hexahydrophthalate; and the outer layer comprises high-pressure polyethylene resin, metallocene polyethylene resin 2, a propenyl elastomer and maleimide oxide. According to the three-layer polyethylene packaging film, the low-density metallocene polyethylene resin with a specific molecular structure is selected and matched with a small amount of elastomer, so that the thickness of the film is reduced, the low-temperature resistance of the film can be improved, the low-temperature resistance is mainly tear resistance and puncture resistance, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy packaging films, and in particular relates to a three-layer co-extruded polyethylene heavy packaging film. Background Art

[0002] Polyethylene heavy packaging film is a new type of packaging film. Usually, the packaging film that can carry 10-50kg of solid particles or powdered materials is called heavy packaging film. Generally, 25kg packaging bags are used. Polyethylene heavy packaging bags have the advantages of high packaging automation, good sealing, excellent moisture and anti-fouling performance, good aging resistance, and extended storage time of goods.

[0003] The temperature in northern my country is low in winter. When the film is exposed to low temperatures, it will become hard and brittle, resulting in an increase in the rate of broken packages, which affects product packaging and transportation. Patent CN115635750A discloses a low-temperature resistant three-layer co-extruded heavy packaging film. The heavy packaging film has high strength, but the film thickness in its embodiment is 160μm, which makes the material and cost high during the production process, and also generates more waste after use; in addition, the invention adds a high content of low-density polyethylene resin (LDPE) and linear low-density polyethylene resin (LLDPE), which will reduce the mechanical properties of the film. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a three-layer co-extruded polyethylene heavy packaging film, which can reduce the thickness of the film while improving the low-temperature resistance of the film, mainly the tear resistance and puncture resistance, thereby reducing production costs.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The co-extruded polyethylene heavy packaging film comprises 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 elastomer, 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 2, 10-20 parts of propylene 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 110-130 μm, preferably 120 μm; the thickness ratio of the inner layer, the middle layer and the 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 / cm 3 , preferably 0.924 g / cm 3 , the melt index is 0.3-0.8g / 10min, preferably 0.5g / 10min.

[0012] The metallocene polyethylene resin comprises metallocene polyethylene resin 1 and metallocene polyethylene resin 2, wherein the density of the metallocene polyethylene resin 1 is 0.933-0.938 g / cm 3 , preferably 0.936 g / cm 3 , the melt 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 / cm 3 , preferably 0.914 g / cm 3 , the melt index is 0.7-0.9 g / 10 min, preferably 0.8 g / 10 min.

[0013] The crystallization heat fractionation analysis of the metallocene polyethylene resin 2 was performed using DSC, wherein the content of the lamellae with a thickness of more than 9 nm was 25-35%, and the content of the lamellae with a thickness of less than 6 nm was 45-55%.

[0014] GPC was used to test the molecular weight and distribution of metallocene polyethylene resin 2, and its weight average molecular weight was greater than 130,000, of which the portion with a weight average molecular weight greater than 1,000,000 accounted for more than 0.40%. The higher the molecular weight and the greater the content of the high molecular weight portion, the more conducive it is to improving the mechanical properties of the material.

[0015] The comonomer and terminal methyl content in the metallocene polyethylene resin 2 were analyzed by carbon nuclear magnetic resonance, and the molar percentage of the comonomer was 3.30-3.80 mol%.

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

[0017] The maleimide oxide is preferably 4-maleimide-tetramethylpiperidin oxide. Through experiments, it is found that maleimide oxides and polyethylene resins can undergo micro-crosslinking reactions in the screw, increase the branching degree of polyethylene resin, and increase the content of long chain branches in the molecular structure, which can have three beneficial effects: first, increase the entanglement effect between molecular chains, improve the puncture resistance and tear resistance of the film, and have a low temperature resistance effect; second, the increase in branching degree reduces the crystallinity of the resin, increases the toughness of the material, and has a low temperature resistance effect; third, increasing the branching degree, especially the increase in the content of long chain branches, can reduce the content of thick lamellae, achieve the effect of reducing the melting temperature of the resin, and can reduce the heat sealing temperature when used in heavy packaging film packaging.

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

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The three-layer co-extruded polyethylene heavy packaging film of the present invention is prepared from a composition consisting of high-pressure polyethylene resin, metallocene polyethylene, propylene-based elastomer, maleimide oxide and calcium hexahydrophthalate, and the prepared heavy packaging film has reduced thickness and improved mechanical properties. By selecting a low-density metallocene polyethylene resin with a specific molecular structure, although its comonomer content is low, it has the particularity of different thickness lamella distribution and molecular weight distribution, breaking the rule that the same index resin has low comonomer content and poor mechanical properties. The film processed with the resin has higher comprehensive performance, exceeding the level of the resin with high comonomer content of the same index. When used in conjunction with a propylene-based elastomer, the tear resistance and puncture resistance of the film can be improved. When producing a low-temperature resistant FFS film, the production cost is reduced and the low-temperature resistance is improved, thereby reducing the breakage rate of the heavy packaging film in a low-temperature environment. It can be widely used in the packaging field of synthetic resins and other products, and has good economic and social benefits. DETAILED DESCRIPTION

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

[0022] Unless otherwise specified, the raw materials used in the examples and comparative examples are conventional commercial products. Among them, high-pressure polyethylene resin can be referred to as LDPE, metallocene polyethylene resin can be referred to as mPE, linear low-density polyethylene resin can be referred to as LLDPE, and the propylene-based elastomer is Vistamaxx 6102FL from ExxonMobil, with a density of 0.862 g / cm 3 , the melt index is 1.4g / 10min.

[0023] Example 1

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

[0025] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

[0026] The middle layer includes the following components by weight: mPE1 25 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0027] The outer layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

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

[0029] Example 2

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

[0031] The inner layer includes the following components by weight: 20 parts of LDPE1, density 0.922g / cm 3 , melt index 0.3g / 10min; mPE2 60 parts, density 0.913g / cm 3 , melt index 0.7g / 10min, 25% flake content with thickness above 9nm, 53% flake content with thickness below 6nm, weight average molecular weight 133000, 0.40% content of the part with molecular weight above 1000000, comonomer content 3.57mol%; Vistamaxx 6102FL 20 parts; 0.1 parts of 4-maleimide-tetramethylpiperidinoxide.

[0032] The middle layer includes the following components by weight: mPE1 15 parts, density 0.937g / cm 3 , melt index 0.7g / 10min; mPE2 70 parts, density 0.913g / cm 3 , melt index 0.7g / 10min, 25% flake content with thickness above 9nm, 53% flake content with thickness below 6nm, weight average molecular weight 133000, 0.40% content of molecular weight above 1000000, comonomer content 3.57mol%; Vistamaxx 6102FL 15 parts; 0.08 parts calcium hexahydrophthalate.

[0033] The outer layer includes the following components by weight: 20 parts of LDPE1, density 0.922g / cm 3 , melt index 0.3g / 10min; mPE2 60 parts, density 0.913g / cm 3 , melt index 0.7g / 10min, 25% flake content with thickness above 9nm, 53% flake content with thickness below 6nm, weight average molecular weight 133000, 0.40% content of the part with molecular weight above 1000000, comonomer content 3.57mol%; Vistamaxx 6102FL 20 parts; 0.1 parts of 4-maleimide-tetramethylpiperidinoxide.

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

[0035] Example 3

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

[0037] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.926g / cm 3, melt index 0.8g / 10min; mPE2 80 parts, density 0.915g / cm 3 , melt index 0.9g / 10min, 30% content of flakes with a thickness of 9nm or more, 46% content of flakes with a thickness of less than 6nm, weight average molecular weight 137000, 0.44% content of the part with a molecular weight of more than 1000000, comonomer content 3.40mol%; Vistamaxx 6102FL 10 parts; 0.05 parts of 4-maleimide-tetramethylpiperidinoxide.

[0038] The middle layer includes the following components by weight: mPE1 30 parts, density 0.933g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.915g / cm 3 , melt index 0.9g / 10min, 30% content of flakes with a thickness above 9nm, 46% content of flakes with a thickness below 6nm, weight average molecular weight 137000, 0.44% content of the part with a molecular weight above 1000000, comonomer content 3.40mol%; 10 parts of Vistamaxx 6102FL; 0.08 parts of calcium hexahydrophthalate.

[0039] The outer layer includes the following components by weight: 10 parts of LDPE1, density 0.926 g / cm 3 , melt index 0.8g / 10min; mPE2 80 parts, density 0.915g / cm 3 , melt index 0.9g / 10min, 30% content of flakes with a thickness of 9nm or more, 46% content of flakes with a thickness of less than 6nm, weight average molecular weight 137000, 0.44% content of the part with a molecular weight of more than 1000000, comonomer content 3.40mol%; Vistamaxx 6102FL 10 parts; 0.05 parts of 4-maleimide-tetramethylpiperidinoxide.

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

[0041] Comparative Example 1

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

[0043] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0044] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3, melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 28% flake content above 9nm, 51% flake content below 6nm, weight average molecular weight 138000, 0.38% content of molecular weight above 1000000, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts.

[0045] The middle layer includes the following components by weight: mPE1 25 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0046] The outer layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 28% flake content above 9nm, 51% flake content below 6nm, weight average molecular weight 138000, 0.38% content of molecular weight above 1000000, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts.

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

[0048] Comparative Example 2

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

[0050] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0051] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3, melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

[0052] The middle layer includes the following components by weight: mPE1 25 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 28% flake content above 9nm, 51% flake content below 6nm, weight average molecular weight 138000, 0.38% content of molecular weight above 1000000, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts.

[0053] The outer layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm3, melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

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

[0055] Comparative Example 3

[0056] The difference from Example 1 is that 4-maleimide-tetramethylpiperidinoxide and calcium hexahydrophthalate are not added.

[0057] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0058] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3, melt index 0.8g / 10min, 28% flake content above 9nm, 51% flake content below 6nm, weight average molecular weight 138000, 0.38% content of molecular weight above 1000000, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts.

[0059] The middle layer includes the following components by weight: mPE1 25 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 28% flake content above 9nm, 51% flake content below 6nm, weight average molecular weight 138000, 0.38% content of molecular weight above 1000000, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts.

[0060] The outer layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 28% flake content above 9nm, 51% flake content below 6nm, weight average molecular weight 138000, 0.38% content of molecular weight above 1000000, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts.

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

[0062] Comparative Example 4

[0063] The difference from Example 1 is that mPE2 is replaced by mPE with different thickness lamella distribution, molecular weight distribution and comonomer content, which is recorded as mPE3.

[0064] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0065] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE3 80 parts, density 0.914g / cm 3, melt index 0.8g / 10min, 50% content of flakes with a thickness of 9nm or more, 27% content of flakes with a thickness of less than 6nm, weight average molecular weight 138000, 0.07% content of the part with a molecular weight of more than 1000000, comonomer content 4.15mol%; Vistamaxx 6102FL 10 parts; 0.08 parts of 4-maleimide-tetramethylpiperidinoxide.

[0066] The middle layer includes the following components by weight: mPE1 25 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE3 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 50% flake content above 9nm, 27% flake content below 6nm, weight average molecular weight 138000, 0.07% content of molecular weight above 1000000, comonomer content 4.15mol%; Vistamaxx 6102FL 10 parts; 0.06 parts calcium hexahydrophthalate.

[0067] The outer layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE3 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, 50% content of flakes with a thickness of 9nm or more, 27% content of flakes with a thickness of less than 6nm, weight average molecular weight 138000, 0.07% content of the part with a molecular weight of more than 1000000, comonomer content 4.15mol%; Vistamaxx 6102FL 10 parts; 0.08 parts of 4-maleimide-tetramethylpiperidinoxide.

[0068] The thickness of the heavy packaging film is 120μm, and the thickness ratio of the inner, middle and outer layers is 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 recorded as LDPE2.

[0071] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0072] The inner layer includes the following components by weight: LDPE2 10 parts, density 0.918g / cm 3 , melt index 1g / 10min; mPE2 80 parts, density 0.914g / cm 3, melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

[0073] The middle layer includes the following components by weight: mPE1 25 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0074] The outer layer includes the following components by weight: LDPE2 10 parts, density 0.918g / cm 3 , melt index 1g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

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

[0076] Comparative Example 6

[0077] The difference from Example 1 is that mPE with different density and melt index is used to replace mPE1, which is recorded as mPE4.

[0078] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0079] The inner layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3, melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

[0080] The middle layer includes the following components by weight: mPE4 25 parts, density 0.940g / cm 3 , melt index 0.2g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; calcium hexahydrophthalate 0.06 parts.

[0081] The outer layer includes the following components by weight: LDPE1 10 parts, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of platelets with thickness above 9nm 28%, content of platelets with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; Vistamaxx 6102FL 10 parts; 4-maleimide-tetramethylpiperidinoxide 0.08 parts.

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

[0083] Comparative Example 7

[0084] The difference from Example 1 is that the formulation components and weight parts are different, the mPE used is recorded as mPE5, and the propylene-based elastomer used is 1881G from Dow Chemical, with a density of 0.904 g / cm 3 , the melt index is 1g / 10min.

[0085] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

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

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

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

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

[0090] Comparative Example 8

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

[0092] The heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein:

[0093] The inner layer includes the following components by weight: 20 parts of LDPE1, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; 0.08 parts of 4-maleimide-tetramethylpiperidinoxide.

[0094] The middle layer includes the following components by weight: mPE1 35 parts, density 0.935g / cm 3 , melt index 0.5g / 10min; mPE2 60 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; 0.06 parts of calcium hexahydrophthalate.

[0095] The outer layer includes the following components by weight: 20 parts of LDPE1, density 0.924g / cm 3 , melt index 0.5g / 10min; mPE2 80 parts, density 0.914g / cm 3 , melt index 0.8g / 10min, content of flakes with thickness above 9nm 28%, content of flakes with thickness below 6nm 51%, weight average molecular weight 138000, content of part with molecular weight above 1000000 0.38%, comonomer content 3.48mol%; 0.08 parts of 4-maleimide-tetramethylpiperidinoxide.

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

[0097] Detection method:

[0098] Film tensile properties: According to GB / T 1040.3-2006, 5-type splines, tensile speed is 200mm / min.

[0099] Film tear resistance: According to GB / T 11999-1989, using rectangular specimens.

[0100] Dart impact strength: according to GB / T 9639-2008.

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

[0102] Table 1

[0103]

[0104] Table 2

[0105]

[0106] It can be seen from the above test data 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 particularity of different thickness lamellae distribution and molecular weight distribution, breaking the rule that resins with the same index have low comonomer content and poor mechanical properties. The film processed using the resin has higher comprehensive performance, which exceeds the level of resins with high comonomer content with the same index. When used in combination with a propylene-based elastomer, the tear resistance and puncture resistance of the film can be improved, and it has a better effect in the production of low-temperature resistant FFS film.

Claims

1. A three-layer co-extruded polyethylene heavy packaging film, characterized in that: It includes inner layer, middle layer and 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 2, 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, 240-80 parts of metallocene polyethylene resin, 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 2, 10-20 parts of propylene elastomer, and 0.05-0.1 parts of maleimide oxide.

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

1.

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

4. The three-layer co-extruded polyethylene heavy packaging film according to claim 1, characterized in that: The density of the metallocene polyethylene resin 1 is 0.933-0.938 g / cm 3 , the melt index is 0.3-0.7g / 10min; the density of metallocene polyethylene resin 2 is 0.913-0.915g / cm 3 , the melt index is 0.7-0.9g / 10min.

5. The three-layer co-extruded polyethylene heavy packaging film according to claim 1, characterized in that: The content of the lamellae with a thickness of more than 9 nm in the metallocene polyethylene resin 2 is 25-35%, and the content of the lamellae with a thickness of less than 6 nm is 45-55%.

6. The three-layer co-extruded polyethylene heavy packaging film according to claim 1, characterized in that: The weight average molecular weight of the metallocene polyethylene resin 2 is greater than 130,000, wherein the portion with a weight average molecular weight greater than 1,000,000 accounts for more than 0.40%.

7. The three-layer co-extruded polyethylene heavy 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%.

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

9. The three-layer co-extruded polyethylene heavy packaging film according to claim 1, characterized in that: The three-layer co-extruded polyethylene heavy packaging film is produced by blow molding using a three-layer co-extruded film blowing machine.

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