Recyclable polyethylene composite film bag for food packaging and preparation method therefor

Abstract

The present invention relates to a recyclable polyethylene composite film bag for food packaging. The composite film bag comprises at least two layers, i.e. a modified polyethylene layer for printing and a micro-foamed polyethylene layer. Optionally, the composite film bag further comprises an ultralow-temperature heat-sealable polyethylene layer. The micro-foamed polyethylene layer and the ultralow-temperature heat-sealable polyethylene layer each consists of three structural layers, each structural layer being made from a specific raw material in a specific ratio. Also provided in the present invention is a preparation method for the recyclable polyethylene composite film bag for food packaging. The polyethylene composite film bag for food packaging of the present invention has the functions of printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance and heat sealing, is low-cost and meets environmental protection requirements.

Description

Recyclable polyethylene composite film bag for food packaging and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to a composite film bag for food packaging and a preparation method thereof, in particular to a recyclable polyethylene composite film bag for food packaging and a preparation method thereof. BACKGROUND

[0002] Since the inner surface and the outer surface of the food secondary packaging composite film bag bear different functions respectively, such as printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance, and firm heat sealing, etc., the prior art usually uses a combination of two or more different polymer materials to prepare the food secondary packaging composite film bag, for example, polyethylene terephthalate (PET) / polyethylene (PE) composite film bag, polyethylene terephthalate (PET) / polypropylene (PP) composite film bag, polyethylene terephthalate (PET) / cast polypropylene (CPP) composite film bag, etc.

[0003] However, the food secondary packaging composite film bag prepared by the combination of different polymer materials has the problem of difficult recycling and recycling utilization, which is not conducive to environmental protection. Therefore, from the perspective of environmental protection, a single material composite packaging film bag is undoubtedly a better choice. However, the existing ordinary single material composite packaging film bag (such as a polyethylene composite packaging film bag) needs a large amount of polyethylene raw material to meet the requirements of commercial rigidity and toughness, especially for high weight food secondary packaging. The cost of the packaging film bag obtained therefrom is much higher than that of the food secondary packaging composite film bag prepared by the combination of different polymer materials.

[0004] In summary, the prior art single material composite packaging film bag cannot meet the requirements of low cost and environmental protection while having the functions of printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance, and firm heat sealing. Therefore, there is an urgent need for a recyclable polyethylene composite film bag for food packaging and a preparation method thereof, which has the functions of printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance, and firm heat sealing, and has low cost and meets environmental protection requirements. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art single material composite packaging film bag, which cannot meet the requirements of low cost and environmental protection while having the functions of printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance, and firm heat sealing. The present application provides a recyclable polyethylene composite film bag for food packaging and a preparation method thereof, which has the functions of printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance, and firm heat sealing, and has low cost and meets environmental protection requirements.

[0006] The application provides a recyclable polyethylene composite film bag for food packaging, wherein the composite packaging film bag comprises at least two layers of a modified polyethylene layer for printing and a micro-foamed polyethylene layer, and optionally the composite packaging film bag further comprises an ultra-low temperature heat-seal polyethylene layer,

[0007] wherein the micro-foamed polyethylene layer is composed of the following three structural layers:

[0008] the first structural layer I is formed by raw materials of LDPE, LLDPE and color master batch,

[0009] the second structural layer II is formed by raw materials including LDPE, LLDPE, HDPE and a foaming agent,

[0010] the third structural layer III is composed of raw materials including LDPE, MLLDPE and color master batch;

[0011] or wherein the micro-foamed polyethylene layer is composed of the following three structural layers:

[0012] wherein the first structural layer A is formed by raw materials of LDPE, LLDPE and color master batch,

[0013] the second structural layer B is formed by raw materials including LDPE, LLDPE, HDPE and a foaming agent,

[0014] the third structural layer C is composed of raw materials including LDPE, MLLDPE, an opening agent and color master batch;

[0015] optionally wherein the ultra-low temperature heat-seal polyethylene layer is composed of the following three structural layers:

[0016] the first structural layer a is formed by raw materials of LDPE and LLDPE,

[0017] the second structural layer b is formed by raw materials including LDPE, LLDPE, HDPE,

[0018] the third structural layer c is composed of raw materials including LDPE, MLLDPE, an opening agent and color master batch.

[0019] The application further provides a method for preparing the recyclable polyethylene composite film bag for food packaging, and the method comprises the following steps:

[0020] S1 blown film: the raw materials of the micro-foamed polyethylene layer defined in the present application are added into the suction channel of the extruder respectively according to the weight parts, melted and extruded to form a film bubble, which is blown, clamped into a film piece by a clamp plate and discharged of the air inside, the outer surface of the film is treated by a corona machine, and then wound to obtain a co-extruded film of the first structure layer I, the second structure layer II and the third structure layer III or a co-extruded film of the first structure layer A, the second structure layer B and the third structure layer C, i.e. the micro-foamed polyethylene layer;

[0021] Optionally S1' blown film: the raw materials of the ultra-low temperature heat-sealable polyethylene layer defined in the present application are added into the suction channel of the extruder respectively according to the weight parts, melted and extruded to form a film bubble, which is blown, clamped into a film piece by a clamp plate and discharged of the air inside, the outer surface of the film is treated by a corona machine, and then wound to obtain a co-extruded film of the first structure layer a, the second structure layer b and the third structure layer c, i.e. the ultra-low temperature heat-sealable polyethylene layer;

[0022] S2 printing: optionally gravure printing the modified polyethylene layer (preferably MDOPE), first placing the modified polyethylene layer on the unwinding part of the printing machine, using a metal gravure roller to print the alcohol-soluble polyurethane system ink according to the predetermined pattern on the modified polyethylene layer, and then drying it in an oven at 40-60°C to obtain a printed semi-finished product, i.e. a printed polyethylene layer;

[0023] S3 compounding: using an adhesive to coat the printed polyethylene layer, the coated film enters an oven at 60-80°C for drying, and after drying, the printed polyethylene layer is hot-bonded with the micro-foamed polyethylene layer alone, optionally with the micro-foamed polyethylene layer and the ultra-low temperature heat-sealable polyethylene layer at 45-55°C, preferably at 50°C, to form a compounded semi-finished product, wherein the micro-foamed polyethylene layer and the ultra-low temperature heat-sealable polyethylene layer are also coated with an adhesive;

[0024] and

[0025] S4 curing: placing the hot-bonded compounded semi-finished product in an oven at 40-45°C for 24-48 hours for adhesive curing.

[0026] Compared with the prior art, the recyclable polyethylene composite film bag for food packaging and the preparation method thereof greatly reduce the opening temperature of the heat-sealing layer, expand the operation window during the bag making of the composite film, make the appearance of the finished bag flat, and stabilize the size, because the specific micro-foamed polyethylene layer and at least two polyethylene types of raw materials for the modified polyethylene layer for printing are selected.

[0027] The recyclable polyethylene composite film bag for food packaging and the preparation method thereof not only have the functions of printing, bearing, moisture resistance, oxygen resistance, heat resistance, puncture resistance and heat sealing, but also have low cost and meet the environmental protection requirements. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 shows the preparation process diagram of the micro-foamed polyethylene layer of the present application;

[0029] Figure 2 shows the preparation process diagram of the ultra-low temperature heat-sealing polyethylene layer of the present application;

[0030] Figure 3 shows the preparation process diagram of the printing polyethylene layer of the present application;

[0031] Figure 4 shows the preparation process diagram of the two-layer composite semi-finished product of the recyclable polyethylene composite film bag for food packaging of the present application;

[0032] Figure 5 shows the preparation process diagram of the three-layer composite semi-finished product of the recyclable polyethylene composite film bag for food packaging of the present application;

[0033] Figure 6 shows the process diagram of the finished product after obtaining the two-layer or three-layer composite semi-finished product of the recyclable polyethylene composite film bag for food packaging of the present application;

[0034] Figure 7 shows a two-layer structure schematic diagram of the recyclable polyethylene composite film bag for food packaging of the present application;

[0035] Figure 8 shows a three-layer structure schematic diagram of the recyclable polyethylene composite film bag for food packaging of the present application. DETAILED DESCRIPTION

[0036] The recyclable polyethylene composite film bag for food packaging provided by the present application comprises at least two layers of a modified polyethylene layer for printing and a micro-foamed polyethylene layer, and optionally further comprises an ultra-low temperature heat-sealing polyethylene layer,

[0037] Wherein, the micro-foamed polyethylene layer is composed of the following three structure layers:

[0038] The first structure layer I is formed by raw materials of LDPE, LLDPE and color master batch,

[0039] The second structure layer II is formed by raw materials including LDPE, LLDPE, HDPE and foaming agent,

[0040] The third structure layer III is composed of raw materials including LDPE, MLLDPE and color master batch;

[0041] Or wherein, the micro-foamed polyethylene layer is composed of the following three structure layers:

[0042] Wherein, the first structure layer A is formed by raw materials of LDPE, LLDPE and color master batch,

[0043] The second structure layer B is formed by raw materials including LDPE, LLDPE, HDPE and foaming agent,

[0044] The third structure layer C is composed of raw materials including LDPE, MLLDPE, opening agent and color master batch;

[0045] Optionally, the ultra-low temperature heat-sealing polyethylene layer is composed of the following three structure layers:

[0046] The first structure layer a is formed by raw materials of LDPE and LLDPE,

[0047] The second structure layer b is formed by raw materials including LDPE, LLDPE and HDPE,

[0048] The third structure layer c is composed of raw materials including LDPE, MLLDPE, opening agent and color master batch.

[0049] The above LDPE refers to low density polyethylene, LLDPE refers to linear low density polyethylene, HDPE refers to high density polyethylene, MLLDPE refers to metallocene linear low density polyethylene, opening agent refers to a substance that can effectively improve the opening performance of the film, and color master batch refers to a special colorant for high molecular materials.

[0050] When the composite packaging film bag of the present application is composed of only two main structures of the outer printed modified polyethylene layer and the inner micro-foamed polyethylene layer, the inventors of the present application unexpectedly found that although there are only two main structures, the obtained composite packaging film bag can still meet various requirements, such as meeting the product packaging requirements of bearing weight of 1200g or less, moisture resistance ≤5.0g / m2.24h, oxygen resistance ≤1600cm3 / m2.24h.0.1Mpa, puncture strength ≥6.0N, heat sealing strength ≥15N / 15mm (heat sealing temperature 125℃, heat sealing time 1S, heat sealing pressure 0.3Mpa).

[0051] When the composite packaging film bag of the present application is composed of three main structures, the inner layer is an ultra-low temperature heat sealing polyethylene layer, the middle layer is a micro-foamed polyethylene layer, and the outer layer is a printed modified polyethylene layer, the functions of bearing weight, moisture resistance, oxygen resistance, heat resistance, puncture resistance, and heat sealing are more excellent, and still meet the requirements of low cost and environmental protection.

[0052] Preferably, the raw material of the modified polyethylene layer for printing is a mono-directional stretched polyethylene film (MDOPE) or a bi-directional stretched polyethylene film (BOPE).

[0053] Preferably, the first structure layer I of the micro-foamed polyethylene layer is formed by three raw materials, and the weight ratio of raw material I-1: raw material I-2: raw material I-3 is in the range of (25-35):(55-65):(7-13), and the raw material I-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russian Petrochemical 15303, Dow 640I, and Iran Petrochemical 2100TN00, the raw material I-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Primex 0134N, and Primex 0234N, and the raw material I-3 is selected from the group consisting of Di Color Master 80029, Basel 8001T, M&L W1039, and Kimura 7M3001A.

[0054] Preferably, the second structural layer II of the micro-foamed polyethylene layer is formed by four raw materials, the weight ratio of raw material II-1 : raw material II-2: raw material II-3: raw material III-4 ranges from (25-35):(40-50):(17-23):(3-7), and the raw material II-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material II-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Primex 0134N, Primex 0234N and Boruel 1810, the raw material II-3 is selected from the group consisting of Exxon HTA108, Exxon AL55, Sinopec 6098, Sinopec 6097 and Shell B53, and the raw material II-4 is selected from the group consisting of Keway CFE-2130L (manufacturer: Guangzhou Keway New Material Co., Ltd.) and Yikao BR355 (manufacturer: Shanghai Yikao Industry Co., Ltd.). Among them, the raw material II-4 is used to form a micro-porous structure in the polyethylene film layer, showing a foaming effect.

[0055] Preferably, the third structural layer III of the micro-foamed polyethylene layer is formed by three raw materials, the weight ratio of raw material III-1 : raw material III-2: raw material III-3 ranges from (20-30):(60-70):(7-13), and the raw material III-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia Petrochemical 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material III-2 is selected from the group consisting of Mitsui SP1520, Exxon 2012MA and Dow PL1881G, and the raw material III-3 is selected from the group consisting of Di Color Master 80029, Basel 8001T, M&L W1039 and Kimura 7M3001A;

[0056] or preferably, the first structural layer A of the micro-foamed polyethylene layer is formed from three raw materials, the weight ratio of raw material A-1 : raw material A-2: raw material A-3 is in the range of (25-35):(55-65):(7-13), and the raw material A-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia Petrochemical 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material A-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Primex 0134N and Primex 0234N, and the raw material A-3 is selected from the group consisting of DIC Color Master 80029, BASF 8001T, M&G W1039 and Kimica 7M3001A,

[0057] Preferably, the second structural layer B of the micro-foamed polyethylene layer is formed from three raw materials, the weight ratio of raw material B-1 : raw material B-2: raw material B-3 is in the range of (25-35):(45-55):(17-23), and the raw material B-1 is selected from the group consisting of Sinopec 2426H, Thai PTT 2426H, Shell 2426H and Dow 641I, the raw material B-2 is selected from the group consisting of Exxon 1001BU, Exxon 1002BU, Dow 2645.11G, Secco 0209KJ, Dow 2045.11G, Primex 0134M, Primex 0234CL and Boroujen 1818, and the raw material B-3 is selected from the group consisting of Exxon HTA108, Exxon AL55, Sinopec 6098, Sinopec 6097 and Shell B53,

[0058] Preferably, the third structural layer C of the micro-foamed polyethylene layer is formed from four raw materials, the weight ratio of raw material C-1 : raw material C-2: raw material C-3: C-4 is in the range of (21-25):(50-60):(1.0-2.0):(7-13), and the raw material C-1 is selected from the group consisting of Sinopec 2426H, Shell 2426H, Dow 641I and Iran Petrochemical 2100TN00, the raw material C-2 is selected from the group consisting of Mitsui SP1520, Exxon 2012MA and Dow PL1881G, the raw material C-3 is selected from the group consisting of BASF F15 and Anpal Color 1001476-K, and the raw material C-4 is selected from the group consisting of BASF 705HF and Anpal Color 1001526-K;

[0059] Preferably, the first structural layer a of the ultra-low temperature heat-seal polyethylene layer is formed from two raw materials, the weight ratio of raw material a-1 : raw material a-2 ranges from (25-35):(65-75), and the raw material a-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia 15303, Dow 640I and Iran Petrochemical 2100TN00, and the raw material a-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Primex 0134N and Primex 0234N,

[0060] Preferably, the second structural layer b of the ultra-low temperature heat-seal polyethylene layer is formed from three raw materials, the weight ratio of raw material b-1 : raw material b-2: raw material b-3 ranges from (25-35):(45-55):(17-23), and the raw material b-1 is selected from the group consisting of Sinopec 2426H, Thailand PTT Company 2426H, Shell 2426H and Dow 641I, the raw material b-2 is selected from the group consisting of Exxon 1001BU, Exxon 1002BU, Dow 2645.11G, Secco 0209KJ, Dow 2045.11G, Primex 0134M, Primex 0234CL and Borue 1818, and the raw material b-3 is selected from the group consisting of Exxon HTA108, Exxon AL55, Sinopec 6098, Sinopec 6097 and Shell B53.

[0061] Preferably, the third structural layer c of the ultra-low temperature heat-seal polyethylene layer is formed from four raw materials, the weight ratio of raw material c-1 : raw material c-2: raw material c-3: c-4 ranges from (20-25):(70-80):(1.0-2.0):(0.8-1.2), and the raw material c-1 is selected from the group consisting of Sinopec 2426H, Shell 2426H, Dow 641I and Iran Petrochemical 2100TN00, the raw material c-2 is selected from the group consisting of Mitsui SP1520H, Exxon 2012MK and Dow PL1881G, the raw material c-3 is selected from the group consisting of BASF F15 and Anqusheng 1001476-K, and the raw material c-4 is selected from the group consisting of BASF 705HF and Anqusheng 1001526-K.

[0062] Preferably, the weight ratio of the raw material I-1 : raw material I-2: raw material I-3 is in the range of (27-33):(57-63):(7-13); the weight ratio of the raw material II-1 : raw material II-2: raw material II-3: raw material III-4 is in the range of (27-33):(43-47):(19-21):(4-6); the weight ratio of the raw material III-1 : raw material III-2: raw material III-3 is in the range of (23-27):(63-67):(9-11); the weight ratio of the raw material A-1 : raw material A-2: raw material A-3 is in the range of (27-33):(57-63):(9-11); the weight ratio of the raw material B-1 : raw material B-2: raw material B-3 is in the range of (27-33):(47-53):(19-21); the weight ratio of the raw material C-1 : raw material C-2: raw material C-3: C-4 is in the range of (22-24):(58-61):(1.3-1.7):(9-11); the weight ratio of the raw material a-1 : raw material a-2 is in the range of (27-33):(67-73); the weight ratio of the raw material b-1 : raw material b-2: raw material b-3 is in the range of (27-33):(47-53):(18-22); or the weight ratio of the raw material c-1 : raw material c-2: raw material c-3: c-4 is in the range of (21-23):(73-77):(1.3-1.7):(0.9-1.1).

[0063] More preferably, the weight ratio of the raw material I-1 : raw material I-2: raw material I-3 is 30:60:10; the weight ratio of the raw material II-1 : raw material II-2: raw material II-3: raw material III-4 is in the range of 30:45:20:5; the weight ratio of the raw material III-1 : raw material III-2: raw material III-3 is in the range of 25:65:10; the weight ratio of the raw material A-1 : raw material A-2: raw material A-3 is in the range of 30:60:10; the weight ratio of the raw material B-1 : raw material B-2: raw material B-3 is in the range of 30:50:20; the weight ratio of the raw material C-1 : raw material C-2: raw material C-3: C-4 is in the range of 23.5:65:1.5:10; the weight ratio of the raw material a-1 : raw material a-2 is in the range of 30:70); the weight ratio of the raw material b-1 : raw material b-2: raw material b-3 is in the range of 30:50:20; or the weight ratio of the raw material c-1 : raw material c-2: raw material c-3: c-4 is in the range of 22.5:75:1.5:1.

[0064] Further preferably, the feedstock I-1 is selected from the group consisting of Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the feedstock I-2 is selected from the group consisting of Exxon 1001AV, Synergy 0209AA, Dow 2045G and Dow 2645G, and the feedstock I-3 is selected from the group consisting of DIColour Master 80029, BASF 8001T and Mobil W1039, the feedstock II-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the feedstock II-2 is selected from the group consisting of Exxon 1001AV, Synergy 0209AA, Dow 2045G and Borougtar Chemical 1810, the feedstock II-3 is selected from the group consisting of Exxon HTA108, Sinopec 6098, Sinopec 6097 and Shell B53, and the feedstock II-4 is selected from the group consisting of Kolon CFE-2130L and Lyondell BR355, the feedstock III-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the feedstock III-2 is selected from the group consisting of Mitsui SP1520 and Exxon 2012MA, and the feedstock III-3 is selected from the group consisting of DIColour Master 80029, BASF 8001T and Mobil W1039;

[0065] The feedstock A-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the feedstock A-2 is selected from the group consisting of Exxon 1001AV, Synergy 0209AA, Dow 2045G, Dow 2645G, and the feedstock A-3 is selected from the group consisting of DIC Color 80029, BASF 8001T, Mobil W1039 and Kimica 7M3001A, the feedstock B-1 is selected from the group consisting of Thai PTT 2426H, Shell 2426H and Dow 641I, the feedstock B-2 is selected from the group consisting of Exxon 1001BU, Dow 2645.11G, Synergy 0209KJ, Dow 2045.11G and Borealis 1818, the feedstock B-3 is selected from the group consisting of Exxon HTA108, Sinopec 6098, Sinopec 6097 and Shell B53, the feedstock C-1 is selected from the group consisting of Shell 2426H, Dow 641I and Iran Petrochemical 2100TN00, the feedstock C-2 is selected from the group consisting of Mitsui SP1520, Exxon 2012MA and Dow PL1881G, the feedstock C-3 is selected from the group consisting of BASF F15 and An Color 1001476-K, the feedstock C-4 is selected from the group consisting of BASF 705HF and An Color 1001526-K;

[0066] The feedstock a-1 is selected from the group consisting of Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the feedstock a-2 is selected from the group consisting of Exxon 1001AV, Synergy 0209AA, Dow 2045G and Dow 2645G, the feedstock b-1 is selected from the group consisting of Thai PTT 2426H, Shell 2426H and Dow 641I, the feedstock b-2 is selected from the group consisting of Exxon 1001BU, Dow 2645.11G, Synergy 0209KJ, Dow 2045.11G and Borealis 1818, the feedstock b-3 is selected from the group consisting of Exxon HTA108, Sinopec 6098, Sinopec 6097 and Shell B53, the feedstock c-2 is selected from the group consisting of Mitsui SP1520H, Exxon 2012MK and Dow PL1881G, the feedstock c-3 is selected from the group consisting of BASF F15 and An Color 1001476-K, the feedstock c-4 is selected from the group consisting of BASF 705HF and An Color 1001526-K.

[0067] More preferably, the modified polyethylene layer is a uniaxially stretched polyethylene film. The uniaxially stretched polyethylene film is produced by a specific blowing plus longitudinal stretching process which strengthens the molecular arrangement of the film in the longitudinal direction. The mechanical strength, barrier property, transparency, rigidity and other indicators of the film produced by this process are all greatly improved compared to ordinary polyethylene film. This film is more suitable for printing, and the overprint precision, printing speed and the rate of genuine products are all greatly improved compared to ordinary polyethylene film. In addition, the uniaxial stretching process combined with the specific formula described above makes the overall temperature resistance of the film increase by about 15°C compared to ordinary polyethylene film, making it more suitable as a surface layer of a composite film. Combined with good mechanical properties, its application range is expanded.

[0068] The thickness of the micro-foamed polyethylene layer is 60-90 microns, preferably 75-90 microns, more preferably 75-85 microns, and most preferably 80-85 microns. Theoretically, the thicker the mechanical properties are better, but considering the cost, the thickness of this layer will be adjusted according to the gram weight of the product being packaged. If it is necessary to reduce the thickness as much as possible for reasons such as texture, product gram weight, cost, etc., or to use lower-cost raw materials, minor adjustments can be made within the scope of the raw material composition of the present application, and then the performance is tested to determine whether it meets the requirements.

[0069] The thickness of the modified polyethylene layer is 20-30 microns, more preferably 23-27 microns, and most preferably 25 microns. Theoretically, the thicker the mechanical properties are better, but considering the cost, the thickness of this layer will be adjusted according to the gram weight of the product being packaged. If it is necessary to reduce the thickness as much as possible for reasons such as texture, product gram weight, cost, etc., or to use lower-cost raw materials, minor adjustments can be made within the scope of the raw material composition of the present application, and then the performance is tested to determine whether it meets the requirements.

[0070] Preferably, the thickness of the ultra-low temperature heat-sealable polyethylene layer is 20-60 microns, more preferably 25-45 microns, and most preferably 30 microns. Theoretically, the thicker the mechanical properties are better, but considering the cost, the thickness of this layer will be adjusted according to the gram weight of the product being packaged. If it is necessary to reduce the thickness as much as possible for reasons such as texture, product gram weight, cost, etc., or to use lower-cost raw materials, minor adjustments can be made within the scope of the raw material composition of the present application, and then the performance is tested to determine whether it meets the requirements.

[0071] The present application also provides a method for preparing the recyclable polyethylene food packaging composite film bag described in the present application, which comprises the following steps:

[0072] S1 blowing film: the raw materials of the micro-foamed polyethylene layer defined in the present application are respectively added into the suction channel into the extruder for melt extrusion, the film bubble is blown, the thickness is measured by a thickness gauge, the film piece is clamped by a clamp plate and the air inside is discharged, the outer surface of the film is treated by a corona machine, and then winding is performed to obtain a co-extruded film of the first structure layer I, the second structure layer II and the third structure layer III or a co-extruded film of the first structure layer A, the second structure layer B and the third structure layer C, i.e. the micro-foamed polyethylene layer;

[0073] Optionally S1' blowing film: the raw materials of the ultra-low temperature heat sealing polyethylene layer defined in the present application are respectively added into the suction channel into the extruder for melt extrusion, the film bubble is blown, the film piece is clamped by a clamp plate and the air inside is discharged, the outer surface of the film is treated by a corona machine, and then winding is performed to obtain a co-extruded film of the first structure layer a, the second structure layer b and the third structure layer c, i.e. the ultra-low temperature heat sealing polyethylene layer;

[0074] The blowing film machine can use the automatic feeding and automatic weighing metering system carried by itself to suck the granular raw materials according to the formula, and the pure materials sucked are mixed by the automatic mixing system.

[0075] S2 printing: the modified polyethylene layer (preferably MDOPE) is printed by gravure printing, the modified polyethylene layer is first placed on the unwinding part of the printing machine, the alcohol-soluble polyurethane system ink is printed on the modified polyethylene layer according to the predetermined pattern by using a metal gravure roller, and after drying in an oven at 40-60℃, a printed semi-finished product, i.e. a printed polyethylene layer, is obtained;

[0076] S3 compounding: the printed polyethylene layer is coated with an adhesive, the coated film is dried in an oven at 60-80℃, and after drying, the printed polyethylene layer is hot laminated with the micro-foamed polyethylene layer alone, or optionally with the micro-foamed polyethylene layer and the ultra-low temperature heat sealing polyethylene layer, at 45-55℃, preferably at 50℃, to form a compounded semi-finished product, wherein the micro-foamed polyethylene layer and the ultra-low temperature heat sealing polyethylene layer are also coated with an adhesive;

[0077] and

[0078] S4 curing: the two-layer or three-layer compounded semi-finished product after hot lamination is placed in an oven at 40-45℃ for 24-48 hours for adhesive curing.

[0079] In addition, the method of the present application further comprises one or more of the following steps:

[0080] S5: standing: the finished composite semi-finished product is placed in a standing area in a temperature environment of 15-28 DEG C to achieve stress release and cooling setting purposes;

[0081] S6: slitting: the finished semi-finished product is cut according to the layout setting and length setting, if the final product is a roll film product, it is wound to obtain a roll film product;

[0082] Optionally, if the final product is a bag product, the following S7 bag making step is performed:

[0083] The finished semi-finished product is bagged according to the layout and bag type setting, and the film material is heat sealed when passing through a hot knife at 130-150 DEG C, and the heat sealing site needs to be cold knife set at 15-25 DEG C to realize size stability, and then cut into bags according to the layout.

[0084] The adhesive used in the application can be selected from high alliance YH2000S / YH10, high alliance EA3050A / EA3050B, Huateng UK2850 / UK5015 and other food packaging field allowed adhesive, coating amount 2.0-3.0g / m2.

[0085] Optionally, after the S4 step, the step of inspecting the product is also included, the finished composite semi-finished product is inspected, the printing and composite defect products are marked and rejected by full splicing full width online product inspection camera, and all qualified products are retained.

[0086] The barrel of the extruder that can be used in the application is generally divided into 4 zones or more zones, preferably divided into 4 zones, and the raw material is preferably gradually heated after entering the extruder barrel, and the temperature difference span of two adjacent zones is generally 5-10 DEG C.

[0087] Preferably, in the step S1, the slot die temperature of the first structure layer I or A is 150±5℃, the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 190±5℃; the slot die temperature of the second structure layer II or B is 135±5℃, the die includes at least 1-4 zones, the temperature of die zone 1 is 140±5℃, the temperature of die zone 2 is 155±5℃, the temperature of die zone 3 and die zone 4 is 160±5℃, and the temperature of screen changing zone and flange zone is 160±5℃; and the filter screen of the second structure layer II or B adopts a structure of 80 mesh + 300 mesh + 80 mesh, and the back pressure is 19.5-32.5 MPa; and the slot die temperature of the third structure layer III or C is 150±5℃, the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 190±5℃; the temperature of the interface base of the first structure layer I or A, the second structure layer II or B and the third structure layer III or C is 195℃, and the temperature of the die head is 160±5℃. The die head outlet can form a tubular object of the micro-foamed polyethylene layer, the outer layer of the tubular object is the first structure layer I or A, and the inner layer is the third structure layer III or C.

[0088] Alternatively, in the step S1', the slot die temperature of the first structure layer a is 150±5℃, the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 180±5℃; the slot die temperature of the second structure layer b is 135±5℃, the die includes at least 1-4 zones, the temperature of die zone 1 is 150±5℃, the temperature of die zone 2 is 165±5℃, the temperature of die zone 3 and die zone 4 is 165±5℃, and the temperature of screen changing zone and flange zone is 170±5℃; the slot die temperature of the third structure layer c is 150±5℃, the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 180±5℃; the temperature of the interface base of the first structure layer a, the second structure layer b and the third structure layer c is 180℃, and the temperature of the die head is 170±5℃. The die head outlet can form a tubular object of the ultra-low temperature polyethylene layer, the outer layer of the tubular object is the first structure layer a, and the inner layer is the third structure layer c.

[0089] The above steps all temperature control with temperature control table, wherein the barrel 1 zone, 2 zone, 3 zone and 4 zone due to the frequency of screw rotation will produce high temperature, in this case will increase cooling fan control temperature, controllable temperature error range in ± 10 ℃.

[0090] Preferably, in the steps S1 and S1', the blow ratio can be 2.5-3.0; and the bubble film is cooled under the action of the cooling air of the air ring, the cold air temperature is 15-20℃, and the sizing cage position is adjusted to shape the film bubble. The tubular film after cooling and shaping is controlled according to the set film thickness by the automatic thickness control system, then is pulled up by the traction device and is pinched by the chevron plate, then is pinched by a traction roller to form two opposite micro-foamed polyethylene layers or super-low-temperature heat-sealed polyethylene layers (two third structure layers opposite to each other on the original inner surface of the tubular), and the outer surfaces (first structure layers) of the two opposite micro-foamed polyethylene layers or super-low-temperature heat-sealed polyethylene layers are subjected to corona treatment. The power range of the corona machine for surface treatment is 400-500V. Finally, the edges are cut and divided into pieces according to the set width by the cutting and winding device, and are wound under the action of the tension (70N-90N) of the winding shafts on both sides, to obtain the micro-foamed polyethylene layer or super-low-temperature heat-sealed polyethylene layer of the application.

[0091] Preferably, in the step S2, the modified polyethylene layer is first wound onto the unwinding part of the printing machine, and is pulled flat under the action of the unwinding tension of 50N-80N, the introduction tension of 130N-170N, the lead-out tension of 100N-150N and the winding tension of 50N-70N, and when printing by metal intaglio printing, the alcohol-soluble polyurethane system ink with a viscosity of 12 Pa.s to 15 Pa.s is printed on the modified polyethylene layer according to the predetermined pattern under the rubber roller with a pressure of 0.2-0.4Mpa, and the ink is dried by the oven at 40-60℃, to obtain the printed polyethylene layer. The ink accounts for about 2% of the entire finished film, which does not affect the recycling process, and the treated particles can be downgraded for use in non-food fields.

[0092] Further preferably, in step S3, the printing polyethylene layer and the micro-foamed polyethylene layer are respectively fed to the feeding position of the laminating machine, and the printing polyethylene layer and the micro-foamed polyethylene layer are respectively flattened under the action of a printing polyethylene layer feeding tension of 80N-100N and a micro-foamed polyethylene layer feeding tension of 40N-60N; an adhesive with a coating weight of 2.0-3.0g / m2 is coated on the side of the printing polyethylene layer carrying the ink, and the printing polyethylene layer after coating is fed into an oven at 60-80℃ for drying, and after drying, the side of the printing polyethylene layer coated with the adhesive is hot-bonded to the first structural layer of the micro-foamed polyethylene layer under the action of an oven tension of 45-55℃, preferably 50℃, and 90N-130N, and after bonding and cold treatment, the two-layer composite semi-product is wound under a winding tension of 140N-170N, or

[0093] Optionally, the two-layer composite semi-product and the ultra-low temperature heat-seal polyethylene layer are further fed to the feeding position of the laminating machine, and the two-layer composite semi-product and the ultra-low temperature heat-seal polyethylene layer are respectively flattened under the action of a two-layer composite semi-product feeding tension of 80N-100N and an ultra-low temperature heat-seal polyethylene layer feeding tension of 40N-60N, an adhesive with a coating weight of 2.0-3.0g / m2 is coated on one side of the micro-foamed polyethylene layer of the two-layer composite semi-product, and the two-layer composite semi-product after coating is fed into an oven at 60-80℃ for drying, and after drying, the first structural layer of the two-layer composite semi-product and the ultra-low temperature heat-seal polyethylene film are hot-bonded under the action of an oven tension of 45-55℃, preferably 50℃, and 100N-130N, and after bonding and cold treatment, the three-layer composite semi-product is wound under a winding tension of 140N-170N.

[0094] The composite packaging film bag of the present application at least comprises a micro-foamed polyethylene layer and a modified polyethylene layer for printing, and has the properties of stiffness, toughness, wide heat-sealing window, easy tearing and environmental protection. Good stiffness provides support for fast running, good toughness meets the packaging of heavy products, and easy tearing is achieved at a low cost. Another most significant advantage is a wide sealing window, and the bag body is flat and beautiful. The polyethylene content of the product is more than 95%, and recycling and secondary use can be easily realized.

[0095] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0096] Example 1 (25μm MDOPE / 80μm micro-foamed PE two-layer composite film)

[0097] This embodiment illustrates the preparation method of the recyclable polyethylene composite film bag with two-layer main structure for food packaging.

[0098] The raw materials used in the examples are shown in Table 1 below:

[0099] Table 1

[0100] (1) Preparation of micro-foamed polyethylene layer (blown film)

[0101] Raw materials and percentages of the first structural layer:

[0102] 30% of Shell 2420H + 60% of Dow 2045G + 10% of DIC Color Master 80029;

[0103] Raw materials and percentages of the second structural layer:

[0104] 30% of Shell 2420H + 45% of Dow 2045.11G + 20% of Exxon HTA108 + 5% of Covestro CFE-2130L;

[0105] Raw materials and percentages of the third structural layer:

[0106] 25% of Shell 2420H + 65% of Mitsui SP1520 + 10% of DIC Color Master 80029.

[0107] Step 1: Blown film: The raw materials of each layer are added into the suction channel into the extruder respectively, and the parameters of each extruder are as follows:

[0108] The slot barrel temperature of the first structural layer is 150°C, the barrel 1 zone temperature is 160°C, the barrel 2 zone temperature is 170°C, the barrel 3 zone and the barrel 4 zone temperature are both 180°C, and the screen changer zone and the flange zone temperature are both 190°C.

[0109] The slot barrel temperature of the second structural layer is 135°C, the barrel 1 zone temperature is 140°C, the barrel 2 zone temperature is 155°C, the barrel 3 zone and the barrel 4 zone temperature are both 160°C, and the screen changer zone and the flange zone temperature are both 160°C; the filter screen structure of the foaming layer uses 80 mesh + 300 mesh + 80 mesh, and the back pressure is 25 MPa.

[0110] The slot barrel temperature of the third structural layer is 150°C, the barrel 1 zone temperature is 160°C, the barrel 2 zone temperature is 170°C, the barrel 3 zone and the barrel 4 zone temperature are both 180°C, and the screen changer zone and the flange zone temperature are both 190°C.

[0111] The interface base temperature of the three structural layers is 195°C, and the die temperature is 160°C; the three-layer co-extruded film is co-extruded,

[0112] The shaped co-extruded film is blown, the blowing ratio is 2.6, the obtained bubble film is cooled under the action of cooling wind of the air ring, the temperature of the cooling wind is 18℃, the thickness is measured by a thickness gauge, the film is clamped by a clamp plate and the air inside is discharged, the outer surface (the surface of the first structure layer) of the film is treated by a corona machine under the power of 450V of the corona machine, the edge material is cut off, and then the micro-foamed polyethylene layer with a thickness of 80μm is obtained.

[0113] (2) Preparation of the printed polyethylene layer (printing)

[0114] Step 2 printing: the 25μm thick modified polyethylene layer (MDOPE) is printed by gravure printing, the modified polyethylene layer is first fed to the unwinding part of the printing machine (unwinding tension: 60N, introduction tension: 150N, lead-out tension: 110N, winding tension: 70N), the alcohol-soluble polyurethane system ink with an ink viscosity of 13 Pascal seconds is printed on the modified polyethylene layer by using a metal gravure 0.3Mpa rubber roller under a pressure, and the printed modified polyethylene layer is obtained after drying in a 50℃ oven.

[0115] (3) Compound of the printed modified polyethylene layer and the micro-foamed polyethylene layer

[0116] Step 3 compound: the adhesive YH2000S / YH10 of Gao Meng is coated on one side of the printed modified polyethylene layer, the coating amount is 2.5g / m2, the printed modified polyethylene layer after coating is dried in a 75℃ oven, and then the micro-foamed polyethylene layer is hot laminated at a temperature of 50℃ to obtain a two-layer compound semi-finished product. The compound parameters are as follows: the printed modified polyethylene layer is put into a tension (90N), the micro-foamed polyethylene layer is put into a tension (50N), the oven tension is (100N), and the winding tension is (150N).

[0117] (4) Aging of the two-layer compound semi-finished product

[0118] Step 4 aging: the two-layer compound semi-finished product after hot lamination is put into an oven at 45℃ for 36 hours for adhesive curing.

[0119] (5) Storage after aging

[0120] Step 5 storage: the two-layer compound semi-finished product after aging is put into a storage area for storage at a temperature of 20℃, so as to achieve the purpose of stress release and cooling and setting.

[0121] (6) Slitting after storage

[0122] The semi-finished product after storage is cut into a roll film with a width of 65cm.

[0123] (7) Bag making after slitting

[0124] The slit semi-finished product is made into a bag according to the layout and bag type setting. During bag making, the film material is heat sealed when passing through the 140℃ hot knife. The heat sealing position needs to be 15℃ cold knife setting to realize the size stability. Then, the bag is cut according to the layout.

[0125] Example 2 (25μm MDOPE / 80μm Micro-foamed PE / 30μm Low-temperature heat-seal PE)

[0126] This example illustrates the preparation method of the recyclable polyethylene food packaging composite film bag with a three-layer main structure.

[0127] (1) Preparation of micro-foamed polyethylene layer (blown film)

[0128] The micro-foamed polyethylene layer was prepared according to the method of Example 1.

[0129] (2) Preparation of ultra-low-temperature heat-seal polyethylene layer (blown film)

[0130] Raw materials and percentages of the first structure layer:

[0131] 30% of Shell 2420H + 70% of Dow 2645G;

[0132] Raw materials and percentages of the second structure layer:

[0133] 30% of Shell 2426H + 50% of Dow 2645.11G + 20% of Exxon HTA108;

[0134] Raw materials and percentages of the third structure layer:

[0135] 22.5% of Shell 2426H + 75% of Mitsui SP1520H + 1.5% of Basell F15 + 1% of Basell 705HF.

[0136] Step 1: Blown film: The raw materials of each layer are added to the suction channel into the extruder respectively, and the parameters of each extruder are as follows:

[0137] The slot barrel temperature of the first structure layer is 150℃, the barrel 1 zone temperature is 160℃, the barrel 2 zone temperature is 170℃, the barrel 3 zone and the barrel 4 zone temperature are both 180℃, and the screen changer zone and the flange zone temperature are both 190℃.

[0138] The slot barrel temperature of the second structure layer is 150℃, the barrel 1 zone temperature is 160℃, the barrel 2 zone temperature is 170℃, the barrel 3 zone and the barrel 4 zone temperature are both 160℃, and the screen changer zone and the flange zone temperature are both 190℃.

[0139] The third structural layer slot die temperature is 150°C, the die 1 zone temperature is 160°C, the die 2 zone temperature is 170°C, the die 3 zone and the die 4 zone temperature are both 180°C, and the screen change zone and the flange zone temperature are both 180°C.

[0140] The interface base temperature of the three structural layers is 180°C, and the die temperature is 170°C; the three-layer co-extruded film is co-extruded,

[0141] The co-extruded film is blown, the blowing ratio is 2.8, the obtained bubble film is cooled under the action of the cooling air of the air ring, the cooling air temperature is 17°C, the thickness is measured by a thickness gauge, the film piece is clamped by a clamp plate and the air inside is discharged, the outer surface (the first structural layer surface) of the film is treated by a corona machine at a corona machine power of 450V, the edge material is cut off, and then the 30μm-thick ultra-low-temperature polyethylene layer is wound.

[0142] (2) Preparation of the printed polyethylene layer (printing)

[0143] Step 2 printing: gravure printing of a 25μm-thick modified polyethylene layer (MDOPE), the modified polyethylene layer is first placed on the unwinding part of the printing machine (unwinding tension: 60N, introduction tension: 150N, lead-out tension: 110N, winding tension: 70N), an alcohol-soluble polyurethane system ink with an ink viscosity of 13 Pascal seconds is printed on the modified polyethylene layer by using a metal gravure 0.3Mpa rubber roller pressure according to a predetermined pattern, and the printed modified polyethylene layer is obtained after drying in a 50°C oven.

[0144] (3) Compound of the printed modified polyethylene layer and the micro-foamed polyethylene layer

[0145] Step 3 compound: one side of the printed modified polyethylene layer is coated with an adhesive, the adhesive manufacturer's brand: Gaomeng YH2000S / YH10, the coating amount is 2.5g / square meter, the coated printed modified polyethylene layer enters a 80°C oven for drying, and the dried printed modified polyethylene layer is hot-bonded with the micro-foamed polyethylene layer at a temperature of 50°C to obtain a two-layer compound semi-finished product. Compound parameters: printed modified polyethylene layer unwinding tension (90N), micro-foamed polyethylene layer unwinding tension (50N), oven tension (100N), and winding tension (150N).

[0146] One side of the two-layer compound semi-finished product micro-foamed polyethylene layer is coated with an adhesive, the adhesive manufacturer's brand: Gaomeng YH2000S / YH10, the coating amount is 2.5g / square meter, and the coated printed modified polyethylene layer enters a 70°C oven for drying.

[0147] The dried two-layer composite semi-finished product is placed on the unwinding part of the laminator, the ultra-low temperature heat-sealed polyethylene layer is placed on the second placing part of the laminator, and the two-layer composite semi-finished product is laminated again, i.e., the two-layer composite semi-finished product is heat-bonded with the ultra-low temperature heat-sealed polyethylene layer at a temperature of 50°C after drying, to obtain a three-layer composite semi-finished product. The second lamination parameters are as follows: the two-layer composite semi-finished product is placed in a tension of 100 N, the ultra-low temperature heat-sealed polyethylene layer is placed in a tension of 50 N, the drying channel tension is 120 N, and the winding tension is 170 N.

[0148] (4) Maturation of the three-layer composite semi-finished product

[0149] Step 4 maturation: the heat-bonded three-layer composite semi-finished product is placed in a drying room at 45°C for 36 hours for curing of the adhesive.

[0150] (5) Air setting after maturation

[0151] Step 5 air setting: the maturation-finished two-layer composite semi-finished product is placed in an air setting area in a temperature environment of 20°C for air setting to achieve stress release and cooling setting.

[0152] (6) Slitting after air setting

[0153] The air-set semi-finished product is cut into a roll film with a width of 65 cm.

[0154] (7) Bag making after slitting

[0155] The slitted semi-finished product is made into bags according to the layout and bag type settings. During bag making, the film material is heat-sealed when passing through a hot knife at 140°C, and the heat-sealed part needs to be cooled and set by a cold knife at 20°C to achieve size stability, and then the film is cut into bags according to the layout.

[0156] Comparative Example

[0157] The film bag of the present comparative example is prepared by a conventional lamination film preparation process, in which a 12 μm thick polyester film (PET) and a 70 μm thick polyethylene are compounded.

[0158] The present comparative example is prepared by the steps of PET graphic printing, dry lamination, maturation, air setting, slitting, and bag making. The PET printed film is coated with an adhesive, and the dry coating amount is 2.5 g / m2. The maturation condition is 45°C for 36 hours.

[0159] Effect Test Example

[0160] The food packaging film bags obtained in Examples 1-2 and the comparative example are tested by a conventional method. The specific results are shown in Table 2.

[0161] Table 2

[0162] Example 3 (25 μm MDOPE / 80 μm micro-foamed PE two-layer composite film)

[0163] This example illustrates the preparation method of the recyclable polyethylene composite film bag with two-layer main structure for food packaging according to the present application.

[0164] The sources of raw materials used in the example are shown in Table 3 below:

[0165] Table 3

[0166] (1) Preparation of the micro-foamed polyethylene layer (blown film)

[0167] Raw materials and percentages of the first structural layer:

[0168] 25% Exxon LD150BW + 68% Exxon 1001AV + 7% Basell 8001T;

[0169] Raw materials and percentages of the second structural layer:

[0170] 25% Exxon LD150BW + 55% Exxon 1001AV + 17% Sinopec 6097 + 3% Yikex BR355;

[0171] Raw materials and percentages of the third structural layer:

[0172] 20% Exxon LD150BW + 73% Exxon 2012MA + 7% Basell 8001T.

[0173] Step 1: Blown film: The raw materials of each layer are added into the suction channel into the extruder respectively, and the parameters of each extruder are as follows:

[0174] The slot die cylinder temperature of the first structural layer is 145°C, the cylinder 1 zone temperature is 155°C, the cylinder 2 zone temperature is 165°C, the cylinder 3 zone and the cylinder 4 zone temperature are both 175°C, and the screen changer zone and the flange zone temperature are both 185°C.

[0175] The slot die cylinder temperature of the second structural layer is 130°C, the cylinder 1 zone temperature is 135°C, the cylinder 2 zone temperature is 150°C, the cylinder 3 zone and the cylinder 4 zone temperature are both 155°C, and the screen changer zone and the flange zone temperature are both 155°C; the filter screen structure of the foaming layer uses 80 mesh + 300 mesh + 80 mesh, and the back pressure is 19.5 MPa.

[0176] The slot die cylinder temperature of the third structural layer is 145°C, the cylinder 1 zone temperature is 155°C, the cylinder 2 zone temperature is 165°C, the cylinder 3 zone and the cylinder 4 zone temperature are both 175°C, and the screen changer zone and the flange zone temperature are both 185°C.

[0177] The interface base temperature of the three structure layers is 190℃, and the die temperature is 155℃; the three-layer co-extruded film is co-extruded,

[0178] The co-extruded film is blown, the blowing ratio is 2.5, the obtained bubble film is cooled under the action of the cooling wind of the air ring, the cold wind temperature is 15℃, the thickness is measured by a thickness gauge, the film piece is clamped by a clamp plate and the air inside is discharged, the outer surface (the first structure layer surface) of the film is treated by a corona machine under the power of 400V of the corona machine, the edge material is cut off, and then the 80μm-thick micro-foamed polyethylene layer is wound.

[0179] (2) Preparation of the printed polyethylene layer (printing)

[0180] Step 2 printing: the 25μm-thick modified polyethylene layer (MDOPE) is printed by gravure printing, the modified polyethylene layer is first placed on the unwinding part of the printing machine (unwinding tension: 50N, introduction tension: 130N, lead-out tension: 100N, winding tension: 50N), the alcohol-soluble polyurethane system ink with an ink viscosity of 12 Pascal seconds is printed on the modified polyethylene layer by using a metal gravure 0.2Mpa rubber roller under a pressure, and the printed modified polyethylene layer is obtained after drying in a 40℃ oven.

[0181] (3) Compound of the printed modified polyethylene layer and the micro-foamed polyethylene layer

[0182] Step 3 compound: the printed ink on one side of the printed modified polyethylene layer is coated with an adhesive, the adhesive manufacturer's model is Gao Meng EA3050A / EA3050B, the coating amount is 2.0g / m2, the printed modified polyethylene layer after coating is dried in a 60℃ oven, and then the micro-foamed polyethylene layer is hot-bonded at a temperature of 45℃ to obtain a two-layer compound semi-finished product. The compound parameters are as follows: the printed modified polyethylene layer is placed into a tension (80N), the micro-foamed polyethylene layer is placed into a tension (40N), the oven tension is (90N), and the winding tension is (140N).

[0183] (4) Maturation of the two-layer compound semi-finished product

[0184] Step 4 maturation: the two-layer compound semi-finished product after hot-bonding is placed in a 40℃ drying room for 24 hours for adhesive curing.

[0185] (5) Air setting after maturation

[0186] Step 5 air setting: the two-layer compound semi-finished product after maturation is placed in an air setting area at a temperature of 15℃ for air setting, so as to achieve the purpose of stress release and cooling and setting.

[0187] (6) Slitting after air setting

[0188] The finished semi-product is cut into 65 cm wide roll film.

[0189] (7) Bag making after slitting

[0190] The finished semi-product is made into bags according to the layout and bag type setting. During bag making, the film material is heat sealed when passing through the hot knife at 130°C, and the heat sealed part needs to be cooled by the cold knife at 15°C to stabilize the size. Then, the bags are cut according to the layout.

[0191] The product performance index of Example 3 is close to that of Example 1.

[0192] Example 4 (25 μm MDOPE / 80 μm Micro-foamed PE / 30 μm Low-temperature heat-sealing PE)

[0193] This example illustrates the preparation method of a recyclable polyethylene composite film bag with a three-layer main structure for food packaging.

[0194] (1) Preparation of micro-foamed polyethylene layer (blown film)

[0195] The micro-foamed polyethylene layer is prepared according to the method of Example 3.

[0196] (2) Preparation of ultra-low temperature heat-sealing polyethylene layer (blown film)

[0197] Raw materials and percentages of the first structural layer:

[0198] 25% Exxon LD150BW + 75% Exxon 1001AV;

[0199] Raw materials and percentages of the second structural layer:

[0200] 25% Thai PTT2426H + 58% Exxon 1001BU + 17% Sinopec 6097;

[0201] Raw materials and percentages of the third structural layer:

[0202] 20% Thai PTT2426H + 78.5% Exxon 2012MK + 1.0% Anqusheng 1001476-K + 0.8% Anqusheng 1001526-K.

[0203] Step 1: Blown film: The raw materials of each layer are added to the suction channel and enter the extruder, and the parameters of each extruder are as follows:

[0204] The temperature of the first structural layer slot barrel is 145°C, the temperature of barrel 1 zone is 155°C, the temperature of barrel 2 zone is 165°C, the temperature of barrel 3 zone and barrel 4 zone is 175°C, and the temperature of screen changer zone and flange zone is 185°C.

[0205] The second structural layer slot die temperature is 145°C, the die 1 zone temperature is 155°C, the die 2 zone temperature is 165°C, the die 3 zone and the die 4 zone temperature are both 155°C, and the screen changer zone and the flange zone temperature are both 185°C.

[0206] The third structural layer slot die temperature is 145°C, the die 1 zone temperature is 155°C, the die 2 zone temperature is 165°C, the die 3 zone and the die 4 zone temperature are both 175°C, and the screen changer zone and the flange zone temperature are both 175°C.

[0207] The interface base temperature of the three structural layers is 180°C, and the die temperature is 165°C; the three-layer co-extruded film is co-extruded,

[0208] The co-extruded film is blown, the blowing ratio is 2.5, the obtained bubble film is cooled under the action of the cooling air of the air ring, the cooling air temperature is 15°C, the thickness is measured by a thickness gauge, the film piece is clamped by a clamp and the air inside is discharged, the outer surface (the first structural layer surface) of the film is treated by a corona machine under the power of 400V, the edge material is cut off, and then the 30μm-thick ultra-low-temperature polyethylene layer is wound.

[0209] (2) Preparation of the printed polyethylene layer (printing)

[0210] Step 2 printing: gravure printing of a 25μm-thick modified polyethylene layer (MDOPE), the modified polyethylene layer is first placed on the unwinding part of the printing machine (unwinding tension: 50N, introduction tension: 130N, lead-out tension: 100N, winding tension: 50N), the alcohol-soluble poly system ink with an ink viscosity of 12 Pascal seconds is printed on the modified polyethylene layer according to the predetermined pattern by using a metal gravure 0.2Mpa rubber roller pressure, and the printed modified polyethylene layer is obtained after drying in a 40°C oven.

[0211] (3) Compound of the printed modified polyethylene layer and the micro-foamed polyethylene layer

[0212] Step 3 compound: one side of the printed modified polyethylene layer is coated with an adhesive, the adhesive manufacturer's brand is Gao Meng EA3050A / EA3050B, the coating amount is 2.0g / m2, the printed modified polyethylene layer after coating is dried in a 60°C oven, and then the printed modified polyethylene layer is hot-bonded with the micro-foamed polyethylene layer at a temperature of 45°C to obtain a two-layer compound semi-finished product. The compound parameters are as follows: the printed modified polyethylene layer unwinding tension (90N), the micro-foamed polyethylene layer unwinding tension (50N), the oven tension (100N), and the winding tension (150N).

[0213] The one side of the two-layer composite semi-finished product micro-foamed polyethylene layer is coated with adhesive, and the adhesive manufacturer's brand is Gao Meng YH2000S / YH10, the coating amount is 2.5 g / m2, and the printed modified polyethylene layer after coating is dried in an oven at 60°C.

[0214] The dried two-layer composite semi-finished product is placed on the first unwinding part of the laminator, the ultra-low temperature heat-sealed polyethylene layer is placed on the second unwinding part of the laminator, and the two-layer composite semi-finished product is again laminated, i.e. the two-layer composite semi-finished product is heat-bonded with the ultra-low temperature heat-sealed polyethylene layer at a temperature of 45°C after drying, to obtain a three-layer composite semi-finished product. The second lamination parameters are: two-layer composite semi-finished product tension (80N), ultra-low temperature heat-sealed polyethylene layer tension (40N), oven tension (100N) and winding tension (140N).

[0215] (4) Maturation of the three-layer composite semi-finished product

[0216] Step 4 maturation: the heat-bonded three-layer composite semi-finished product is placed in an oven at 40°C for 24 hours for adhesive curing.

[0217] (5) Air setting after maturation

[0218] Step 5 air setting: the maturation completed two-layer composite semi-finished product is placed in an air setting area at a temperature of 15°C for air setting, to achieve the purpose of stress release and cooling setting.

[0219] (6) Slitting after air setting

[0220] The air set semi-finished product is cut into a roll film with a width of 65 cm.

[0221] (7) Bag making after slitting

[0222] The slitted semi-finished product is made into bags according to the layout and bag type setting, and the film material is heat-sealed when passing through a hot knife at 130°C during bag making, and the heat-sealed part needs to be cold knife set at 15°C to realize size stabilization, and then cut into bags according to the layout.

[0223] The product performance index of Example 4 is equivalent to that of Example 2.

[0224] Example 5 (25 μm MDOPE / 80 μm micro-foamed PE two-layer composite film)

[0225] This example illustrates the preparation method of a recyclable polyethylene food packaging composite film bag with a two-layer main structure.

[0226] The sources of raw materials used in the examples are shown in Table 4 below:

[0227] Table 4

[0228] (1) Preparation of micro-foamed polyethylene layer (blown film)

[0229] Raw materials and percentages of the first structural layer:

[0230] 35% of Iran Petrochemical 2100TN00 + 52% of Secco 0209AA + 13% of Mobil W1039;

[0231] Raw materials and percentages of the second structural layer:

[0232] 30% of Iran Petrochemical 2100TN00 + 55% of Secco 0209AA + 17% of Shell B53 + 7% of Yikuo BR355;

[0233] Raw materials and percentages of the third structural layer:

[0234] 30% of Iran Petrochemical 2100TN00 + 73% of Dow PL1881G + 7% of Mobil W1039.

[0235] Step 1 blown film: the raw materials of each layer are added into the suction channel into the extruder respectively, and the parameters of each extruder are as follows:

[0236] The groove barrel temperature of the first structural layer is 155℃, the barrel 1 zone temperature is 165℃, the barrel 2 zone temperature is 175℃, the barrel 3 zone and the barrel 4 zone temperature are both 185℃, and the screen changer zone and the flange zone temperature are both 195℃.

[0237] The groove barrel temperature of the second structural layer is 140℃, the barrel 1 zone temperature is 145℃, the barrel 2 zone temperature is 160℃, the barrel 3 zone and the barrel 4 zone temperature are both 165℃, and the screen changer zone and the flange zone temperature are both 165℃; the filter screen structure of the foaming layer adopts 80 mesh + 300 mesh + 80 mesh, and the back pressure is 32.5 MPa.

[0238] The groove barrel temperature of the third structural layer is 155℃, the barrel 1 zone temperature is 165℃, the barrel 2 zone temperature is 175℃, the barrel 3 zone and the barrel 4 zone temperature are both 185℃, and the screen changer zone and the flange zone temperature are both 195℃.

[0239] The interface base temperature of the three structural layers is 195℃, and the die temperature is 165℃; the three-layer co-extruded film is co-extruded,

[0240] The co-extruded film is blown, the blowing ratio is 3.0, the obtained bubble film is cooled under the action of the cooling air of the air ring, the cooling air temperature is 20℃, the thickness is measured by a thickness gauge, the film piece is clamped by a clamp plate and the air inside is discharged, the outer surface (the first structural layer surface) of the film is treated by a corona machine at a corona machine power of 500V, the edge material is cut off, and then the 80μm thick micro-foamed polyethylene layer is wound.

[0241] (2) Preparation of the printed polyethylene layer (printing)

[0242] Step 2 printing: printing a modified polyethylene layer (MDOPE) with a thickness of 25 μιη, first applying the modified polyethylene layer to the unwinding part of the printing machine (unwinding tension: 80 N, introduction tension: 170 N, lead-out tension: 150 N, winding tension: 70 N), using a metal gravure 0.4 Mpa rubber roller to print a 15 Pascal-second alcohol-soluble polyurethane system ink with a predetermined pattern onto the modified polyethylene layer under a pressure of 0.4 Mpa, and then drying the printed modified polyethylene layer in an oven at 60°C to obtain the printed modified polyethylene layer.

[0243] (3) Compound of the printed modified polyethylene layer and the micro-foamed polyethylene layer

[0244] Step 3 compound: applying an adhesive to one side of the printed modified polyethylene layer, adhesive manufacturer: Huateng UK2850 / UK5015, coating amount: 3.0 g / m2, and then drying the coated printed modified polyethylene layer in an oven at 80°C, and then hot bonding the dried printed modified polyethylene layer with the micro-foamed polyethylene layer at a temperature of 55°C to obtain a two-layer compound semi-finished product. Compound parameters: unwinding tension of the printed modified polyethylene layer (100 N), unwinding tension of the micro-foamed polyethylene layer (60 N), oven tension (130 N), and winding tension (170 N).

[0245] (4) Curing of the two-layer compound semi-finished product

[0246] Step 4 curing: placing the hot-bonded two-layer compound semi-finished product in an oven at 45°C for 36 hours to cure the adhesive.

[0247] (5) Air setting after curing

[0248] Step 5 air setting: placing the cured two-layer compound semi-finished product in an air setting area at a temperature of 28°C to release stress and cool and set the product.

[0249] (6) Slitting after air setting

[0250] The air-set semi-finished product is cut into a roll film with a width of 65 cm.

[0251] (7) Bag making after slitting

[0252] The slitted semi-finished product is made into bags according to the layout and bag type, and the film material is heat sealed when passing through a hot knife at 150°C, and the heat sealed part needs to be cold sealed at 25°C to stabilize the size, and then the film material is cut into bags according to the layout.

[0253] The product performance index of Example 5 is equivalent to that of Example 1.

[0254] Example 6 (25 μm MDOPE / 80 μm micro-foamed PE / 30 μm low temperature heat sealable PE)

[0255] This example illustrates the method of preparing a recyclable polyethylene food packaging bag with a three-layer main structure according to the present application.

[0256] (1) Preparation of the micro-foamed polyethylene layer (blown film)

[0257] The micro-foamed polyethylene layer was prepared according to the method of Example 5.

[0258] (2) Preparation of the ultra-low temperature heat sealable polyethylene layer (blown film)

[0259] Raw materials and percentages for the first structural layer:

[0260] 35% of Iran 2100TN00 + 65% of Secco 0209AA;

[0261] Raw materials and percentages for the second structural layer:

[0262] 35% of Dow 641I + 42% of Boroujet 1818 + 23% of Shell B53;

[0263] Raw materials and percentages for the third structural layer:

[0264] 25% of Dow 641I + 71.8% of Exxon 2012MK + 2.0% of Basell F15 + 1.2% of 1001526-K.

[0265] Step 1 blown film: the raw materials of each layer were added into the suction channel into the extruder, respectively, and the parameters of each extruder were as follows:

[0266] The slot die cylinder temperature of the first structural layer was 155°C, the cylinder 1 zone temperature was 165°C, the cylinder 2 zone temperature was 175°C, the cylinder 3 zone and cylinder 4 zone temperatures were both 185°C, and the screen changer zone and flange zone temperatures were both 195°C.

[0267] The slot die cylinder temperature of the second structural layer was 155°C, the cylinder 1 zone temperature was 165°C, the cylinder 2 zone temperature was 175°C, the cylinder 3 zone and cylinder 4 zone temperatures were both 165°C, and the screen changer zone and flange zone temperatures were both 195°C.

[0268] The slot die cylinder temperature of the third structural layer was 155°C, the cylinder 1 zone temperature was 165°C, the cylinder 2 zone temperature was 175°C, the cylinder 3 zone and cylinder 4 zone temperatures were both 185°C, and the screen changer zone and flange zone temperatures were both 185°C.

[0269] The interface base temperature of the three structural layers was 180°C, and the die temperature was 175°C; the three-layer co-extruded film was co-extruded,

[0270] The formed co-extruded film is blown, with a blow-up ratio of 3.0, and the obtained bubble film is cooled under the action of cooling air of a wind ring, with the temperature of the cooling air being 20°C. The thickness is measured by a thickness gauge. The film is clamped into a film sheet by a clamping plate and the air inside is discharged. The outer surface (the surface of the first structure layer) of the film is treated by a corona machine at a power of 500V. The edge material is cut off. Then, the 30μm-thick ultra-low-temperature polyethylene layer is obtained.

[0271] (2) Preparation of the printed polyethylene layer (printing)

[0272] Step 2 printing: the 25μm-thick modified polyethylene layer (MDOPE) is printed by gravure printing. The modified polyethylene layer is first placed on the unwinding part of the printing machine (unwinding tension: 80N, introduction tension: 170N, lead-out tension: 150N, winding tension: 70N). The alcohol-soluble poly system ink with an ink viscosity of 15 Pascal seconds is printed on the modified polyethylene layer by using a metal gravure 0.4Mpa rubber roller pressure. The printed modified polyethylene layer is obtained after drying in an oven at 60°C.

[0273] (3) Compound of the printed modified polyethylene layer and the micro-foamed polyethylene layer

[0274] Step 3 compound: the printed ink on one side of the printed modified polyethylene layer is coated with an adhesive. The adhesive is UK2850 / UK5015 from Huateng. The coating amount is 3.0g / m2. The printed modified polyethylene layer after coating is dried in an oven at 80°C. The dried printed modified polyethylene layer is hot-bonded with the micro-foamed polyethylene layer at a temperature of 55°C to obtain a two-layer compound semi-finished product. The compound parameters are as follows: the printed modified polyethylene layer unwinding tension (90N), the micro-foamed polyethylene layer unwinding tension (50N), the oven tension (100N) and the winding tension (150N).

[0275] The micro-foamed polyethylene layer of the two-layer compound semi-finished product is coated with an adhesive. The adhesive is UK2850 / UK5015 from Huateng. The coating amount is 3.0g / m2. The printed modified polyethylene layer after coating is dried in an oven at 60°C.

[0276] The dried two-layer compound semi-finished product is placed on the first unwinding part of the compound machine. The ultra-low-temperature heat-seal polyethylene layer is placed on the second unwinding part of the compound machine. The two-layer compound semi-finished product and the ultra-low-temperature heat-seal polyethylene layer are hot-bonded at a temperature of 55°C after drying to obtain a three-layer compound semi-finished product. The compound parameters are as follows: the two-layer compound semi-finished product unwinding tension (100N), the ultra-low-temperature heat-seal polyethylene layer unwinding tension (60N), the oven tension (130N) and the winding tension (170N).

[0277] (4) Maturation of the three-layer compound semi-finished product

[0278] Step 4: aging: the three-layer composite semi-finished product after heat bonding is placed in an oven at 45℃ for 36 hours for adhesive curing.

[0279] (5) aging after aging

[0280] Step 5: aging: the two-layer composite semi-finished product after aging is placed in an aging area at a temperature of 28℃ for the purpose of stress release and cooling and setting.

[0281] (6) cutting after aging

[0282] The semi-finished product after aging is cut into a roll film with a width of 65cm.

[0283] (7) bag making after cutting

[0284] The semi-finished product after cutting is made into bags according to the layout and bag type. During bag making, the film material is heat sealed when passing through a hot knife at 150℃, and the heat sealed part needs to be cooled and set by a cold knife at 25℃ to achieve size stability. Then, the film material is cut into bags according to the layout.

[0285] The product performance index of Example 6 is equivalent to that of Example 2.

[0286] From the above performance test results, it can be seen that the peeling and elongation at break of the composite film of the two embodiments of the present application are significantly higher than those of ordinary non-single-material composite films, and the moisture resistance is also greatly improved. Compared with ordinary non-single-material composite films, the composite film waste and process scraps of the present application can be completely recycled and reused, and are good easy-to-recycle environmentally friendly materials.

[0287] Those skilled in the art should understand that the above description is only some specific embodiments of the present application, not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications and improvements that do not exceed the scope of the claims should be considered as the protection scope of the present application.

Claims

1. A recyclable polyethylene composite film bag for food packaging, characterized by, The composite packaging film bag comprises at least two layers of modified polyethylene layer for printing and micro-foamed polyethylene layer, and optionally the composite packaging film bag further comprises an ultra-low temperature heat-seal polyethylene layer, The micro-foamed polyethylene layer is composed of the following three structure layers: The first structure layer I is formed by raw materials of LDPE, LLDPE and color master batch, The second structure layer II is formed by raw materials including LDPE, LLDPE, HDPE and foaming agent, The third structure layer III is composed of raw materials including LDPE, MLLDPE and color master batch; Or the micro-foamed polyethylene layer is composed of the following three structure layers: The first structure layer A is formed by raw materials of LDPE, LLDPE and color master batch, The second structure layer B is formed by raw materials including LDPE, LLDPE, HDPE and foaming agent, The third structure layer C is composed of raw materials including LDPE, MLLDPE, opening agent and color master batch; Optionally, the ultra-low temperature heat-seal polyethylene layer is composed of the following three structure layers: The first structure layer a is formed by raw materials of LDPE and LLDPE, The second structure layer b is formed by raw materials including LDPE, LLDPE and HDPE, The third structure layer c is composed of raw materials including LDPE, MLLDPE, opening agent and color master batch.

2. The composite film bag of claim 1, which is recyclable polyethylene food packaging, wherein The raw materials of the modified polyethylene layer for printing are uniaxially stretched polyethylene film or biaxially stretched polyethylene film; Wherein, The first structure layer I is formed by three raw materials, and the weight ratio of raw material I-1: raw material I-2: raw material I-3 is in the range of (25-35):(55-65):(7-13), and the raw material I-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russian Petrochemical 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material I-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Primex 0134N and Primex 0234N, and the raw material I-3 is selected from the group consisting of Di Color Master 80029, Basel 8001T, M&L W1039 and Kimura 7M3001A, The second structural layer II is formed from four raw materials, the weight ratio of raw material II-1 : raw material II-2: raw material II-3: raw material III-4 ranges from (25-35):(40-50):(17-23):(3-7), and the raw material II-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material II-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Premion 0134N, Premion 0234N and Boroujerd Chemical 1810, the raw material II-3 is selected from the group consisting of Exxon HTA108, Exxon AL55, Sinopec 6098, Sinopec 6097 and Shell B53, and the raw material II-4 is selected from the group consisting of Kowa CFE-2130L and Kowa BR355, The third structural layer III is formed from three raw materials, the weight ratio of raw material III-1 : raw material III-2: raw material III-3 ranges from (20-30):(60-70):(7-13), and the raw material III-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia Petrochemical 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material III-2 is selected from the group consisting of Mitsui SP1520, Exxon 2012MA and Dow PL1881G, and the raw material III-3 is selected from the group consisting of Di Color Master 80029, Basel 8001T, M&G W1039 and Kimica 7M3001A; wherein, The first structural layer A is formed from three raw materials, the weight ratio of raw material A-1 : raw material A-2: raw material A-3 ranges from (25-35):(55-65):(7-13), and the raw material A-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia Petrochemical 15303, Dow 640I and Iran Petrochemical 2100TN00, the raw material A-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Premion 0134N and Premion 0234N, and the raw material A-3 is selected from the group consisting of Di Color Master 80029, Basel 8001T, M&G W1039 and Kimica 7M3001A, The second structural layer B is formed from three raw materials, the weight ratio of raw material B-1 : raw material B-2 : raw material B-3 ranges from (25-35) : (45-55) : (17-23), and the raw material B-1 is selected from the group consisting of Sinopec 2426H, Thai PTT 2426H, Shell 2426H and Dow 641I, the raw material B-2 is selected from the group consisting of Exxon 1001BU, Exxon 1002BU, Dow 2645.11G, Secco 0209KJ, Dow 2045.11G, Premex 0134M, Premex 0234CL and Boruel 1818, and the raw material B-3 is selected from the group consisting of Exxon HTA108, Exxon AL55, Sinopec 6098, Sinopec 6097 and Shell B53, The third structural layer C is formed from four raw materials, the weight ratio of raw material C-1 : raw material C-2 : raw material C-3 : C-4 ranges from (21-25) : (50-60) : (1.0-2.0) : (7-13), and the raw material C-1 is selected from the group consisting of Sinopec 2426H, Shell 2426H, Dow 641I and Iran Petrochemical 2100TN00, the raw material C-2 is selected from the group consisting of Mitsui SP1520, Exxon 2012MA and Dow PL1881G, the raw material C-3 is selected from the group consisting of BASF F15 and Anqusheng 1001476-K, and the raw material C-4 is selected from the group consisting of BASF 705HF and Anqusheng 1001526-K; wherein, The first structural layer a is formed from two raw materials, the weight ratio of raw material a-1 : raw material a-2 ranges from (25-35) : (65-75), and the raw material a-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Shell 2420D, Shell 2420F, Exxon LD150BW, Russia 15303, Dow 640I and Iran Petrochemical 2100TN00, and the raw material a-2 is selected from the group consisting of Exxon 1001AV, Exxon 1002AY, Dow 2377, Secco 0209AA, Dow 2045G, Dow 2645G, Sinopec 7042, Premex 0134N and Premex 0234N, The second structural layer b is formed from three raw materials, the weight ratio of raw material b-1 : raw material b-2: raw material b-3 ranges from (25-35):(45-55):(17-23), and the raw material b-1 is selected from the group consisting of Sinopec 2426H, Thai PTT 2426H, Shell 2426H and Dow 641I, the raw material b-2 is selected from the group consisting of Exxon 1001BU, Exxon 1002BU, Dow 2645.11G, Secco 0209KJ, Dow 2045.11G, Premex 0134M, Premex 0234CL and Boroujene 1818, and the raw material b-3 is selected from the group consisting of Exxon HTA108, Exxon AL55, Sinopec 6098, Sinopec 6097 and Shell B53, The third structural layer c is formed from four raw materials, the weight ratio of raw material c-1 : raw material c-2: raw material c-3: c-4 ranges from (20-25):(70-80):(1.0-2.0):(0.8-1.2), and the raw material c-1 is selected from the group consisting of Sinopec 2426H, Shell 2426H, Dow 641I and Iran Petrochemical 2100TN00, the raw material c-2 is selected from the group consisting of Mitsui SP1520H, Exxon 2012MK and Dow PL1881G, the raw material c-3 is selected from the group consisting of BASF F15 and Anfacheng 1001476-K, and the raw material c-4 is selected from the group consisting of BASF 705HF and Anfacheng 1001526-K.

3. The recyclable polyethylene composite film pouch for food packaging according to claim 2, characterized by The weight ratio of raw material I-1 : raw material I-2: raw material I-3 ranges from (27-33):(57-63):(7-13); the weight ratio of raw material II-1 : raw material II-2: raw material II-3: raw material III-4 ranges from (27-33):(43-47):(19-21):(4-6); The weight ratio of raw material III-1 : raw material III-2: raw material III-3 ranges from (23-27):(63-67):(9-11); the weight ratio of raw material A-1 : raw material A-2: raw material A-3 ranges from (27-33):(57-63):(9-11); the weight ratio of raw material B-1 : raw material B-2: raw material B-3 ranges from (27-33):(47-53):(19-21); the weight ratio of raw material C-1 : raw material C-2: raw material C-3: C-4 ranges from (22-24):(58-61):(1.3-1.7):(9-11); the weight ratio of raw material a-1 : raw material a-2 ranges from (27-33):(67-73); the weight ratio of raw material b-1 : raw material b-2: raw material b-3 ranges from (27-33):(47-53):(18-22); or the weight ratio of raw material c-1 : raw material c-2: raw material c-3: c-4 ranges from (21-23):(73-77):(1.3-1.7):(0.9-1.1).

4. The recyclable polyethylene composite film pouch for food packaging according to claim 3, characterized by the weight ratio of the raw material I-1 : raw material I-2: raw material I-3 is 30:60:10; the weight ratio of the raw material II-1 : raw material II-2: raw material II-3: raw material III-4 is in the range of 30:45:20:5; the weight ratio of the raw material III-1 : raw material III-2: raw material III-3 is in the range of 25:65:10; the weight ratio of the raw material A-1 : raw material A-2: raw material A-3 is in the range of 30:60:10; the weight ratio of the raw material B-1 : raw material B-2: raw material B-3 is in the range of 30:50:20; the weight ratio of the raw material C-1 : raw material C-2: raw material C-3: C-4 is in the range of 23.5:65:1.5:10; the weight ratio of the raw material a-1 : raw material a-2 is in the range of 30:70); the weight ratio of the raw material b-1 : raw material b-2: raw material b-3 is in the range of 30:50:20; or the weight ratio of the raw material c-1 : raw material c-2: raw material c-3: c-4 is in the range of 22.5:75:1.5:

1.

5. The recyclable polyethylene composite film bag for food packaging according to any one of claims 1 to 4, characterized in that, The raw material I-1 is selected from the group consisting of Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the raw material I-2 is selected from the group consisting of Exxon 1001AV, Sinopec 0209AA, Dow 2045G and Dow 2645G, and the raw material I-3 is selected from the group consisting of DIColor Master 80029, BASF 8001T and Mobil W1039, The raw material II-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the raw material II-2 is selected from the group consisting of Exxon 1001AV, Sinopec 0209AA, Dow 2045G and Boroujet 1810, the raw material II-3 is selected from the group consisting of Exxon HTA108, Sinopec 6098, Sinopec 6097 and Shell B53, and the raw material II-4 is selected from the group consisting of Kao CF E-2130L and Kao BR355, The raw material III-1 is selected from the group consisting of Iran Petrochemical 2420H, Shell 2420H, Exxon LD150BW, Dow 640I and Iran Petrochemical 2100TN00, the raw material III-2 is selected from the group consisting of Mitsui SP1520, Exxon 2012MA and Dow PL1881G, and the raw material III-3 is selected from the group consisting of DIColor Master 80029, BASF 8001T and Mobil W1039; said feedstock A-1 is selected from the group consisting of Iran petrochemical 2420H, Shell 2420H, Exxon LD150BW, Dow 640I and Iran petrochemical 2100TN00, said feedstock A-2 is selected from the group consisting of Exxon 1001AV, Saco 0209AA, Dow 2045G and Dow 2645G, and said feedstock A-3 is selected from the group consisting of DIC Color 80029, BASF 8001T, Mobil W1039 and Kimica 7M3001A, said feedstock B-1 is selected from the group consisting of Thai PTT 2426H, Shell 2426H and Dow 641I, said feedstock B-2 is selected from the group consisting of Exxon 1001BU, Dow 2645.11G, Saco 0209KJ, Dow 2045.11G and Borealis 1818, said feedstock B-3 is selected from the group consisting of Exxon HTA108, Sinopec 6098, Sinopec 6097 and Shell B53, said feedstock C-1 is selected from the group consisting of Shell 2426H, Dow 641I and Iran petrochemical 2100TN00, said feedstock C-2 is selected from the group consisting of Mitsui SP1520H, Exxon 2012MK and Dow PL1881G, said feedstock C-3 is selected from the group consisting of BASF F15 and An Color 1001476-K, said feedstock C-4 is selected from the group consisting of BASF 705HF and An Color 1001526-K; said feedstock a-1 is selected from the group consisting of Shell 2420H, Exxon LD150BW, Dow 640I and Iran petrochemical 2100TN00, said feedstock a-2 is selected from the group consisting of Exxon 1001AV, Saco Saco 0209AA, Dow 2045G and Dow 2645G, said feedstock b-1 is selected from the group consisting of Thai PTT 2426H, Shell 2426H and Dow 641I, said feedstock b-2 is selected from the group consisting of Exxon 1001BU, Dow 2645.11G, Saco 0209KJ, Dow 2045.11G and Borealis 1818, said feedstock b-3 is selected from the group consisting of Exxon HTA108, Sinopec 6098, Sinopec 6097 and Shell B53, said feedstock c-2 is selected from the group consisting of Mitsui SP1520H, Exxon 2012MK and Dow PL1881G, said feedstock c-3 is selected from the group consisting of BASF F15 and An Color 1001476-K, said feedstock c-4 is selected from the group consisting of BASF 705HF and An Color 1001526-K.

6. The recyclable polyethylene composite film bag for food packaging according to any one of claims 1 to 5, characterized in that, The raw materials for producing the micro-foamed polyethylene layer and the ultra-low temperature heat-seal polyethylene layer are the raw materials shown in the following table.

7. A method of preparing the recyclable polyethylene food packaging composite film bag according to any one of claims 1-6, said method comprising the steps of: S1 blowing film: the raw materials of the micro-foamed polyethylene layer according to any one of claims 1-6 are added into the suction channel of the extruder for melt extrusion, the film bubble is blown, the film piece is clamped by the clamp plate and the air inside is discharged, the outer surface of the film is treated by a corona machine, and then winding is performed to obtain a co-extruded film of the first structure layer I, the second structure layer II and the third structure layer III or a co-extruded film of the first structure layer A, the second structure layer B and the third structure layer C, i.e. the micro-foamed polyethylene layer; Optionally, S1' blowing film: the raw materials of the ultra-low temperature heat-sealable polyethylene layer according to any one of claims 1-6 are added into the suction channel of the extruder for melt extrusion, the film bubble is blown, the film piece is clamped by the clamp plate and the air inside is discharged, the outer surface of the film is treated by a corona machine, and then winding is performed to obtain a co-extruded film of the first structure layer a, the second structure layer b and the third structure layer c, i.e. the ultra-low temperature heat-sealable polyethylene layer; S2 printing: optionally, the modified polyethylene layer is printed by gravure printing, the modified polyethylene layer is first placed on the unwinding part of the printing machine, the alcohol-soluble polyurethane system ink is printed on the modified polyethylene layer according to the predetermined pattern by using a metal gravure roll, and after drying in an oven at 40-60°C, a printed semi-finished product, i.e. a printed polyethylene layer, is obtained; S3 compounding: the printed polyethylene layer is coated with an adhesive, the coated film is dried in an oven at 60-80°C, and after drying, the printed polyethylene layer is hot-bonded with the micro-foamed polyethylene layer alone, optionally with the micro-foamed polyethylene layer and the ultra-low temperature heat-sealable polyethylene layer, at 45-55°C, preferably at 50°C, to form a compounded semi-finished product, wherein the micro-foamed polyethylene layer and the ultra-low temperature heat-sealable polyethylene layer are also coated with an adhesive; and S4 curing: the compounded semi-finished product after hot-bonding is placed in an oven at 40-45°C for 24-48 hours for adhesive curing.

8. The method of claim 7, further comprising one or more of the following steps: S5 standing: the cured compounded semi-finished product is placed in a standing area for standing at a temperature of 15-28°C for the purpose of stress release and cooling and setting; S6 slitting: the standing finished semi-finished product is cut according to the layout and length settings, and if the final product is a roll of film product, it is wound to obtain a roll of film product; Optionally, if the final product is a bag product, the following S7 bag making step is performed: The slitted semi-finished product is bagged according to the layout and bag type settings, and during bag making, the film material is heat-sealed by a hot knife at 130-150°C, and the heat-sealed part needs to be cold-knifed at 15-25°C for size stabilization, and then cut according to the layout to form a bag.

9. The method according to claim 7 or 8, characterized in that, In the step S1, the groove type barrel temperature of the first structure layer I or A is 150±5°C, the barrel includes at least 1-4 zones, the temperature of the first zone of the barrel is 160±5°C, the temperature of the second zone of the barrel is 170±5°C, the temperature of the third zone and the fourth zone of the barrel are both 180±5°C, and the temperature of the screen changing zone and the flange zone are both 190±5°C. The slot die temperature of the second structure layer II or B is 135±5℃, and the die includes at least 1-4 zones, the temperature of die zone 1 is 140±5℃, the temperature of die zone 2 is 155±5℃, the temperature of die zone 3 and die zone 4 is 160±5℃, and the temperature of screen changing zone and flange zone is 160±5℃; and the filter screen of the second structure layer II or B adopts a structure of 80 mesh + 300 mesh + 80 mesh, and the back pressure is 19.5-32.5 MPa; and The slot die temperature of the third structure layer III or C is 150±5℃, and the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 190±5℃; The temperature of the interface base of the first structure layer I or A, the second structure layer II or B and the third structure layer III or C is 195℃, and the temperature of the die head is 160±5℃. and Optionally, in the step S1', the slot die temperature of the first structure layer a is 150±5℃, and the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 180±5℃; The slot die temperature of the second structure layer b is 135±5℃, and the die includes at least 1-4 zones, the temperature of die zone 1 is 150±5℃, the temperature of die zone 2 is 165±5℃, the temperature of die zone 3 and die zone 4 is 165±5℃, and the temperature of screen changing zone and flange zone is 170±5℃; The slot die temperature of the third structure layer c is 150±5℃, and the die includes at least 1-4 zones, the temperature of die zone 1 is 160±5℃, the temperature of die zone 2 is 170±5℃, the temperature of die zone 3 and die zone 4 is 180±5℃, and the temperature of screen changing zone and flange zone is 180±5℃; The temperature of the interface base of the first structure layer a, the second structure layer b and the third structure layer c is 180℃, and the temperature of the die head is 170±5℃.

10. The method according to any one of claims 6-8, characterized in that, In the steps S1 and S1', the blow-up ratio is 2.5-3.0; and cooling is performed under the action of cooling air of the air ring, and the temperature of the cooling air is 15-20℃.

11. The method according to any one of claims 6-9, characterized in that, In the step S2, the modified polyethylene layer is first placed on the unwinding part of the printing machine, and the modified polyethylene layer is leveled under the action of unwinding tension of 50N-80N, introduction tension of 130N-170N, lead-out tension of 100N-150N and winding tension of 50N-70N, and when metal intaglio printing is performed, an alcohol-soluble polyurethane system ink with a viscosity of 12 Pascal seconds to 15 Pascal seconds is printed on the modified polyethylene layer according to a predetermined pattern under the action of a rubber roller with a pressure of 0.2-0.4 Mpa, the ink is dried by passing through an oven at 40-60℃, and the printed polyethylene layer is obtained.

12. The method according to any one of claims 6-10, characterized in that, In step S3, the printing polyethylene layer and the micro-foamed polyethylene layer are respectively placed on the feeding position of the laminating machine, and the printing polyethylene layer and the micro-foamed polyethylene layer are respectively stretched flat under the action of the printing polyethylene layer feeding tension of 80N-100N and the micro-foamed polyethylene layer feeding tension of 40N-60N; the adhesive with a coating weight of 2.0-3.0g / m2 is coated on the side of the printing polyethylene layer carrying the ink, the printing polyethylene layer after coating is dried in the oven at 60-80℃, and after drying, the side of the printing polyethylene layer coated with the adhesive is hot-bonded with the first structural layer of the micro-foamed polyethylene layer under the action of the oven tension of 45-55℃, preferably 50℃, 90N-130N, after bonding, the cold treatment is performed, and the two-layer composite semi-product is formed by winding under the winding tension of 140N-170N, or Optionally, the two-layer composite semi-product and the ultra-low temperature heat-sealing polyethylene layer are further placed on the feeding position of the laminating machine, the two-layer composite semi-product and the ultra-low temperature heat-sealing polyethylene layer are respectively stretched flat under the action of the two-layer composite semi-product feeding tension of 80N-100N and the ultra-low temperature heat-sealing polyethylene layer feeding tension of 40N-60N, the adhesive with a coating weight of 2.0-3.0g / m2 is coated on the side of the micro-foamed polyethylene layer of the two-layer composite semi-product, the two-layer composite semi-product after coating is dried in the oven at 60-80℃, and after drying, the first structural layer of the two-layer composite semi-product and the ultra-low temperature heat-sealing polyethylene film are hot-bonded under the action of the oven tension of 45-55℃, preferably 50℃, 100N-130N, after bonding, the cold treatment is performed, and the three-layer composite semi-product is formed by winding under the winding tension of 140N-170N.

Images