An easy peel PE film and its preparation method and a heat-sealable PET easy peel composite film

Abstract

The present application relates to the technical field of composite film, and provides an easy-to-peel PE film, a preparation method thereof and a heat-sealable PET easy-to-peel composite film. The raw materials and the proportion of the outer layer, the middle layer and the inner layer of the easy-to-peel PE film are strictly controlled, and two kinds of easy-to-peel functional materials are compounded in the inner layer. The obtained easy-to-peel PE film is smooth and has no jumping during peeling, can meet the use under different conditions such as freezing and microwave, is safe and sanitary, and meets the health and safety requirements of different countries such as FDA, national standard, European Union, Japan and the like. The easy-to-peel PE film is used to prepare the heat-sealable PET easy-to-peel composite film by being compounded with the PET film, and the obtained composite film has moderate heat-seal strength, a wide heat-seal window, no jumping, no wire drawing and no residue during sealing and peeling and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite film, in particular to an easy-to-peel PE film, a preparation method thereof and a heat-sealable PET easy-to-peel composite film. BACKGROUND

[0002] PET film is also known as high-temperature-resistant polyester film, which has excellent physical properties, chemical properties and dimensional stability, and is widely used in various fields such as electronic and electrical, screen protection, food and drug packaging. Ordinary PET is a crystalline polymer, and after stretching and orientation, PET film will produce a large degree of crystallization, so ordinary PET film does not have heat-sealing performance and cannot be heat-sealed with other materials such as PP or PE.

[0003] Ordinary polyethylene (PE) material cannot be mixed with PET at all, and cannot be sealed. At present, in order to realize the heat-sealing and easy-to-peeling of PET cups, plates and boxes, a layer of PE film is generally coated on the surface of the PET film by means of coating, and then a heat-sealable easy-to-peel film for sealing PE is used to realize easy-to-peeling, which adds an additional process and increases the cost. At present, there are very few reports in the field about heat-sealable easy-to-peel films that can directly seal PET. SUMMARY

[0004] Therefore, the present application provides an easy-to-peel PE film, a preparation method thereof and a heat-sealable PET easy-to-peel composite film. The easy-to-peel PE film provided by the present application is easy to peel off, can be directly sealed with a PET film, has moderate heat-sealing strength, a wide heat-sealing window, and no jumping, no wire drawing and no residue during sealing and peeling.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] An easy-to-peel PE film is made of three layers of outer layer, middle layer and inner layer by co-extrusion and blowing film;

[0007] The preparation raw materials of the outer layer include, in mass fraction, 30-70 parts of low-density polyethylene, 10-50 parts of linear low-density polyethylene, 10-20 parts of linear metallocene low-density polyethylene and 0.5-1 part of processing aid;

[0008] The preparation raw materials of the middle layer include, in mass fraction, 20-65 parts of low-density polyethylene, 10-30 parts of linear low-density polyethylene, 10-50 parts of metallocene low-density polyethylene and 0.5-1 part of processing aid;

[0009] The preparation raw materials of the inner layer include 30-80 parts of the first easy-peeling functional material, 20-50 parts of the second easy-peeling functional material, and 0.5-1 part of the functional additive, in terms of mass fraction; the first easy-peeling functional material is Z325 easy-peeling resin produced by Mitsubishi Chemical Corporation of Japan; and the second easy-peeling functional material is Z100F easy-peeling resin produced by Mitsubishi Chemical Corporation of Japan.

[0010] The weight ratio of the outer layer, the middle layer and the inner layer is (1-2) :(1-4) :(1-2);

[0011] The processing aids used in the outer layer, the middle layer and the inner layer are functional master batches prepared from fluoropolymers and polyolefin resins.

[0012] Preferably, the melt index of the low-density polyethylene used in the outer layer is 1.5-2.5 g / 10 min, and the density is 0.920-0.930 g / cm 3 ; the melt index of the linear low-density polyethylene used in the outer layer is 1.5-2.5 g / 10 min, and the density is 0.912-0.925 g / cm 3 ; and the melt index of the linear metallocene low-density polyethylene used in the outer layer is 1.5-2.5 g / 10 min, and the density is 0.910-0.920 g / cm 3 .

[0013] Preferably, the melt index of the low-density polyethylene used in the middle layer is 1.5-2.5 g / 10 min, and the density is 0.920-0.930 g / cm 3 ; the melt index of the linear low-density polyethylene used in the middle layer is 1.5-2.5 g / 10 min, and the density is 0.910-0.925 g / cm 3 ; and the melt index of the metallocene low-density polyethylene used in the middle layer is 0.5-1.8 g / 10 min, and the density is 0.920-0.935 g / cm 3 .

[0014] Preferably, the melt index of the first easy-peeling functional material used in the inner layer is 6.0-7.5 g / 10 min, and the density is 0.910-0.930 g / cm 3 ; the melt index of the second easy-peeling functional material is 11-13 g / 10 min, and the density is 0.900-0.910 g / cm 3 .

[0015] Preferably, the melt index of the processing aid used in the outer layer, the middle layer and the inner layer is independently 4.0-5.0 g / 10 min, and the density is independently 0.910-0.930 g / cm 3 .

[0016] Preferably, the low-density polyethylene used in the outer, middle, and inner layers is low-density polyethylene of grade 2426H produced by Lanzhou Petrochemical Company of China National Petroleum Corporation; the linear low-density polyethylene used in the outer layer is linear low-density polyethylene of grade 1002AY produced by ExxonMobil; and the linear metallocene low-density polyethylene used in the outer layer is linear metallocene low-density polyethylene of grade SP1520 produced by Mitsui Chemicals, Ltd.

[0017] The linear low-density polyethylene used in the middle layer is KP7050 linear low-density polyethylene produced by Shell Petrochemicals, Inc. in China; the metallocene low-density polyethylene used in the middle layer is 1327MA metallocene low-density polyethylene produced by ExxonMobil.

[0018] The processing aids used in the outer, middle, and inner layers are processing aids of grade PE103-001 manufactured by Daikin Industries, Ltd.

[0019] The present invention also provides a method for preparing the easy-to-peel PE film described above, comprising the following steps:

[0020] The raw materials for the outer, middle, and inner layers are co-extruded in three layers to obtain the easy-to-peel PE film.

[0021] The present invention also provides a heat-sealable PET easy-peel composite film, comprising a heat-sealable layer and a printing layer stacked together; the heat-sealable layer is the easy-peelable PE film described in the above scheme or the easy-peelable PE film prepared by the preparation method described in the above scheme; the printing layer is a polyester film.

[0022] This invention also provides a method for preparing the heat-sealable PET easy-peel composite film described above, comprising the following steps:

[0023] Polyester film and easy-peel PE film are laminated with solvent-free adhesive and then cured to obtain heat-sealable PET easy-peel composite film.

[0024] Preferably, the curing temperature is 40±5℃ and the time is 24~48h.

[0025] The application provides an easy-to-peel PE film which is made of three layers of co-extrusion blown film, i.e. an outer layer, a middle layer and an inner layer; the preparation raw materials of the outer layer include low-density polyethylene 30-70 parts, linear low-density polyethylene 10-50 parts, linear metallocene low-density polyethylene 10-20 parts and processing aid 0.5-1 part in terms of mass fraction; the preparation raw materials of the middle layer include low-density polyethylene 20-65 parts, linear low-density polyethylene 10-30 parts, metallocene low-density polyethylene 10-50 parts and processing aid 0.5-1 part; the preparation raw materials of the inner layer include first easy-to-peel functional material 30-80 parts, second easy-to-peel functional material 20-50 parts and functional aid 0.5-1 part; the first easy-to-peel functional material is easy-to-peel resin with the trade name Z325 produced by Mitsubishi Chemical, the second easy-to-peel functional material is easy-to-peel resin with the trade name Z100F produced by Mitsubishi Chemical; the weight ratio of the outer layer, the middle layer and the inner layer is (1-2):(1-4):(1-2); the processing aid used in the outer layer, the middle layer and the inner layer is functional master batch prepared from fluoropolymer and polyolefin resin. The application adds two kinds of easy-to-peel functional materials in the inner layer of the easy-to-peel PE film, the easy-to-peel functional material is modified ethylene-acrylate resin, the acrylic resin has strong polarity and good compatibility with various materials, so that the acrylic resin can be sealed with PET, and the acrylic resin also contains ethylene, so that the PET can be peeled after heat sealing. Therefore, the PE film of the application can be heat sealed with PET, and has the effect of easy-to-peel; in addition, the application also strictly controls the raw materials and the ratio of each layer of the easy-to-peel PE film, the obtained easy-to-peel PE film has smooth peeling without jumping, can meet the use under different conditions such as freezing and microwave, is safe and sanitary, and meets the sanitary and safety requirements of different countries such as FDA, national standard, European Union, Japan and the like. Further, the application improves the composition of the easy-to-peel PE film, the outer layer uses linear low-density polyethylene with the trade name 1002AY, has the characteristics of good composite strength and easy processing, the middle layer uses metallocene low-density polyethylene with the trade name 1327MA, has the characteristics of high strength, good stiffness, high transparency and easy processing.

[0026] The application also provides a heat-sealed PET easy-to-peel composite film which comprises a heat-sealed layer and a printing layer arranged in layers; the heat-sealed layer is the easy-to-peel PE film in the above-mentioned scheme, and the printing layer is a polyester film. The application uses the above-mentioned easy-to-peel PE film to heat seal the PET film, and the obtained easy-to-peel composite film has the characteristics of moderate heat sealing strength, wide heat sealing window, no jumping, no stringing and no residue during sealing and peeling. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The test results of the heat sealing strength of the heat-sealed PET easy-to-peel composite film prepared in examples 1-3 after heat sealing with PET film at different temperatures. DETAILED DESCRIPTION

[0028] The application provides an easy-to-unfold PE film which is made of three layers of co-extrusion blown film, namely an outer layer, a middle layer and an inner layer.

[0029] The raw materials for preparing the outer layer include, in mass fraction, 30-70 parts of low-density polyethylene, 10-50 parts of linear low-density polyethylene, 10-20 parts of linear metallocene low-density polyethylene and 0.5-1 part of a processing aid.

[0030] The raw materials for preparing the middle layer include, in mass fraction, 20-65 parts of low-density polyethylene, 10-30 parts of linear low-density polyethylene, 10-50 parts of metallocene low-density polyethylene and 0.5-1 part of a processing aid.

[0031] The raw materials for preparing the inner layer include, in mass fraction, 30-80 parts of a first easy-to-unfold functional material, 20-50 parts of a second easy-to-unfold functional material and 0.5-1 part of a functional aid; the first easy-to-unfold functional material is a Z325 easy-to-unfold resin produced by Mitsubishi Chemical, and the second easy-to-unfold functional material is a Z100F easy-to-unfold resin produced by Mitsubishi Chemical.

[0032] The weight ratio of the outer layer, the middle layer and the inner layer is (1-2):(1-4):(1-2).

[0033] The processing aid used in the outer layer, the middle layer and the inner layer is a functional master batch prepared from a fluoropolymer and a polyolefin resin.

[0034] The raw materials for preparing the outer layer include, in mass fraction, 30-70 parts, preferably 40-60 parts, of low-density polyethylene. In the application, the melt index of the low-density polyethylene used in the outer layer is preferably 1.5-2.5 g / 10 min, more preferably 1.8-2.0 g / 10 min, and the density is preferably 0.920-0.930 g / cm 3 , more preferably 0.922-0.934 g / cm 3 , and the density is preferably 0.920-0.930 g / cm 3 In a specific embodiment of the application, the melt index of the low-density polyethylene used in the outer layer is 2.0 g / 10 min, and the density is 0.924 g / cm

[0035] The raw materials for preparing the outer layer include, in mass fraction, 30-70 parts, preferably 40-60 parts, of low-density polyethylene. In the application, the melt index of the low-density polyethylene used in the outer layer is preferably 1.5-2.5 g / 10 min, more preferably 1.8-2.0 g / 10 min, and the density is preferably 0.920-0.930 g / cm 3more preferably 0.913 to 0.918 g / cm3 3 In a specific embodiment of the present application, the linear low density polyethylene used in the outer layer has a melt index of 2.0 g / 10 min and a density of 0.918 g / cm3 3 Specifically, it is a linear low density polyethylene with the trade name 1002AY produced by Exxon Mobil Corporation, which has good composite strength and easy processability.

[0036] The outer layer is prepared from raw materials including 10 to 20 parts, preferably 13 to 15 parts, of linear metallocene low density polyethylene, in terms of mass fraction of the low density polyethylene used in the outer layer. In the present application, the linear metallocene low density polyethylene used in the outer layer has a melt index of preferably 1.5 to 2.5 g / 10 min, more preferably 1.8 to 2.1 g / 10 min, and a density of preferably 0.912 to 0.925 g / cm3 3 more preferably 0.913 to 0.914 g / cm3 3 In a specific embodiment of the present application, the linear metallocene low density polyethylene used in the outer layer has a melt index of 1.9 g / 10 min and a density of 0.913 g / cm3 3 Specifically, it is a linear metallocene low density polyethylene with the trade name SP1520 produced by Mitsui Chemicals, Inc., which has high composite strength, good transparency and easy processability.

[0037] The outer layer is prepared from raw materials including 0.5 to 1 part, preferably 0.6 to 0.7 part, of a processing aid, in terms of mass fraction of the low density polyethylene used in the outer layer. In the present application, the processing aid used in the outer layer is preferably a functional master batch prepared from a fluoropolymer and a polyolefin resin, which has a melt index of preferably 4.0 to 5.0 g / 10 min, more preferably 4.3 to 4.5 g / 10 min, and a density of preferably 0.915 to 0.930 g / cm3 3 more preferably 0.912 to 0.920 g / cm3 3 In a specific embodiment of the present application, the functional master batch used in the outer layer has a melt index of 4.5 g / 10 min and a density of 0.920 g / cm3 3 Specifically, it is a processing aid with the trade name PE103-001 produced by Daikin Industries, Ltd., which can effectively reduce die buildup, reduce crystal points, reduce extrusion pressure and improve production efficiency.

[0038] The middle layer is prepared from raw materials including 20 to 65 parts, preferably 30 to 50 parts, of low density polyethylene, in terms of mass fraction. In the present application, the low density polyethylene used in the middle layer has a melt index, a density and a specific trade name that are preferably the same as those of the low density polyethylene used in the outer layer, which will not be described herein again.

[0039] The raw material for preparing the middle layer includes linear low density polyethylene 10-30 parts, preferably 13-15 parts, based on the mass fraction of low density polyethylene used in the middle layer. In the present application, the melt index of the linear low density polyethylene used in the middle layer is preferably 1.5-2.5 g / 10 min, more preferably 1.8-2.0 g / 10 min, and the density is preferably 0.910-0.925 g / cm 3 , more preferably 0.912-0.918 g / cm 3 ; in a specific embodiment of the present application, the melt index of the linear low density polyethylene used in the middle layer is 2.0 g / 10 min, and the density is 0.918 g / cm 3 ; specifically, the linear low density polyethylene used in the middle layer is KP7050 produced by China Shell Petrochemical Co., Ltd., and has the property of easy processing.

[0040] The raw material for preparing the middle layer includes metallocene low density polyethylene 10-50 parts, preferably 20-30 parts, based on the mass fraction of low density polyethylene used in the middle layer. In the present application, the melt index of the metallocene low density polyethylene used in the middle layer is preferably 0.5-1.8 g / 10 min, more preferably 1.0-1.3 g / 10 min, and the density is preferably 0.920-0.935 g / cm 3 , more preferably 0.925-0.930 g / cm 3 ; in a specific embodiment of the present application, the melt index of the metallocene low density polyethylene used in the middle layer is 1.3 g / 10 min, and the density is 0.927 g / cm 3 ; specifically, the metallocene low density polyethylene used in the middle layer is 1327MA produced by Exxon Mobil Co. (Exxon Mobil Chemical Business Co., Ltd.), and has the properties of high strength, good stiffness, high transparency and easy processing.

[0041] The raw material for preparing the middle layer includes processing aid 0.5-1 part, preferably 0.6-0.8 part, based on the mass fraction of low density polyethylene used in the middle layer. In the present application, the melt index, density and specific brand of the processing aid used in the middle layer are preferably the same as those of the processing aid used in the outer layer, which will not be described herein.

[0042] The raw material for preparing the inner layer includes first easy-peeling functional material 30-80 parts, preferably 40-60 parts, based on the mass fraction. In the present application, the first easy-peeling functional material is Z325 easy-peeling resin produced by Mitsubishi Chemical, and specifically a modified ethylene-acrylate resin; the melt index of the first easy-peeling functional material is preferably 6.0-7.5 g / 10 min, more preferably 6.5-7.0 g / 10 min, and the density is preferably 0.910-0.930 g / cm 3more preferably 0.915-0.922 g / cm3 3 In a specific embodiment of the present application, the melt index of the easy-peel resin with the trade designation Z235 is 6.6 g / 10 min, and the density is preferably 0.920 g / cm3 3 The resin has high peel strength, a heat-seal strength of 13.5 N / 15 mm at 120°C, good sealing, a wide heat-seal window, a heat-seal strength stable in the range of 13.5-15.5 N / 15 mm within 120-200°C, smooth peel without jumping, and can meet different conditions of use such as freezing and microwave, is safe and sanitary, and meets the sanitary and safety requirements of FDA, national standards, the European Union, Japan and other countries.

[0043] The preparation raw materials of the inner layer include 20-50 parts, preferably 30-40 parts of the second easy-peel functional material, based on the mass fraction of the first easy-peel functional material used in the inner layer. In the present application, the second easy-peel functional material is a modified ethylene-acrylate resin with the trade designation Z100F produced by Mitsubishi Chemical, Japan; the melt index of the second easy-peel functional material is preferably 11-13 g / 10 min, more preferably 11.5-12 g / 10 min, and the density is preferably 0.900-0.910 g / cm3 3 more preferably 0.902-0.905 g / cm3 3 In a specific embodiment of the present application, the melt index of the easy-peel resin with the trade designation Z100F is preferably 12 g / 10 min, and the density is preferably 0.905 g / cm3 3 The resin has moderate peel strength, a heat-seal strength of 6.5 N / 15 mm at 100°C, a wide heat-seal window, a heat-seal strength stable in the range of 6.5-8.0 N / 15 mm within 100-200°C, smooth peel without jumping, and can meet different conditions of use such as freezing and microwave, is safe and sanitary, and meets the sanitary and safety requirements of FDA, national standards, the European Union, Japan and other countries. The present application compounding two kinds of easy-peel resins, the obtained PE easy-peel film has a wide heat-seal window and moderate heat-seal strength, and can also be adjusted according to the requirements of customers.

[0044] The preparation raw materials of the inner layer include 0.5-1 parts, preferably 0.6-0.8 parts of a processing aid, based on the mass fraction of the first easy-peel functional material used in the inner layer. In the present application, the melt index, density and specific trade designation of the processing aid used in the inner layer are preferably the same as those of the processing aid used in the outer layer, which will not be described here.

[0045] In the present application, the weight ratio of the outer layer, the middle layer and the inner layer is (1-2):(1-4):(1-2), preferably 3:4:3, 1:2:1 or 6:9:5; in the present application, the weight ratio of the outer layer, the middle layer and the inner layer is the thickness ratio thereof, in the specific embodiments of the present application, according to the total thickness of the target PE film and the thickness ratio of the three layers, the mass of the raw materials required for each layer can be determined; the total thickness of the PE film is preferably 40-100 μm, more preferably 50-80 μm, and further preferably 65 μm.

[0046] The present application also provides a preparation method of the easy-to-open PE film described in the above-mentioned scheme, comprising the following steps:

[0047] The preparation raw materials of the outer layer, the middle layer and the inner layer are subjected to three-layer co-extrusion to obtain the easy-to-open PE film.

[0048] In the specific embodiments of the present application, the process of three-layer co-extrusion specifically comprises: the preparation raw materials of the outer layer, the middle layer and the inner layer are respectively fed into the outer layer, middle layer and inner layer extruders for melt plasticization, the obtained glue solution is transported to a die head, a bubble is extruded and blown to obtain a film bubble, the film bubble is air-cooled and cooled, then passes through a stabilizing ring, a herringbone row to an upper traction rotation, the film bubble is flattened and then enters a corona treatment device through a guide roller for corona treatment, then the edges are cut, and then passes through a lower traction clamp roller to front and rear winding devices for front and rear winding, thereby obtaining the easy-to-open PE film.

[0049] In the present application, the outer layer extruder, the middle layer extruder and the inner layer extruder are each preferably provided with 5 heating zones, which are sequentially recorded as zone 1-zone 5 according to the passing order of raw materials; the die head is provided with 4 heating zones, which are sequentially recorded as zone 1-zone 4 according to the passing order of raw materials.

[0050] In the present application, the extrusion temperature of each zone of the outer layer extruder, the middle layer extruder, the inner layer extruder and the die head is shown in Table 1:

[0051] Table 1 Extrusion temperature of each zone of the outer layer, the middle layer, the inner layer extruder and the die head

[0052] Temperature (°C) Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Outer layer 165±5℃ 172±5℃ 178±5℃ 168±5℃ 165±5℃ Middle layer 170±5℃ 178±5℃ 180±5℃ 175±5℃ 172±5℃ Inner layer 158±5℃ 165±5℃ 168±5℃ 160±5℃ 155±5℃ Die 172±5℃ 185±5℃ 188±5℃ 180±5℃

[0053] In the present application, the extrusion pressure of the outer layer extruder is preferably 225-315 bar, the extrusion pressure of the middle layer extruder is preferably 235-360 bar, and the extrusion pressure of the inner layer extruder is preferably 220-310 bar.

[0054] The present application also provides a heat-sealable PET easy-to-open composite film, comprising a heat-sealable layer and a printing layer arranged in layers; the heat-sealable layer is the easy-to-open PE film described in the above-mentioned scheme or prepared by the preparation method described in the above-mentioned scheme; the printing layer is a polyester film.

[0055] In the present application, the thickness of the polyester film is preferably 12 μm, and the layer thickness ratio of the polyester film and the easy-to-peel PE film is preferably 12:65; the present application does not have special requirements for the source of the polyester film, and a commercially available polyester film can be used; the heat-sealing layer and the printing layer are bonded by an adhesive, and the outer layer of the PE film and the printing layer are in contact.

[0056] In the present application, the heat-sealing window of the heat-sealable PET easy-to-peel composite film is 110-200℃.

[0057] The present application also provides a preparation method of the heat-sealable PET easy-to-peel composite film according to the above-mentioned scheme, comprising the following steps:

[0058] The polyester film and the easy-to-peel PE film are compounded by a solvent-free adhesive and then aged to obtain the heat-sealable PET easy-to-peel composite film.

[0059] In the present application, the polyester film is preferably printed according to requirements before being bonded with the easy-to-peel PE film, and the present application does not have special requirements for the printing method, and a gravure printing process known to those skilled in the art can be used. In the present application, the solvent-free adhesive is preferably a two-component solvent-free polyurethane adhesive from Wanhua Chemical (Beijing) Co., Ltd., and the components include 6092A and 792B. The present application does not have special requirements for the specific process of compounding, and a solvent-free compounding process known to those skilled in the art can be used. In the specific embodiments of the present application, the adhesive solution is coated on the polyester film, and then the easy-to-peel PE film is compounded. In the specific embodiments of the present application, the operating parameters of the compounding process are preferably as follows: mixing temperature: 40℃ for both components A and B; coating temperature: the temperature of each steel roller of the adhesive coating system is 40℃; adhesive ratio: the mass ratio of component A (i.e. 6092A) to component B (i.e. 792B) is 100:75; and the amount of adhesive is 1.8-2.2 g / m 2 , preferably 2.0 g / m 2 .

[0060] In the present application, the temperature of the aging is preferably 40±5℃, and the time is preferably 24-48 h, more preferably 36 h. After the aging is completed, the heat-sealable PET easy-to-peel composite film is obtained by cooling for 12 h and then slitting. The present application does not have special requirements for the slitting, and the slitting can be performed according to the specific required specifications.

[0061] The technical solutions in the present application will be described clearly and completely in combination with the embodiments in the present application, but it should not be understood as a limitation on the protection scope of the present application.

[0062] The sources and performance parameters of the raw materials used in the embodiments are shown in Table 2.

[0063] Table 2 Sources and performance parameters of raw materials used in the embodiments

[0064]

[0065] Example 1

[0066] The raw material usage and layer thickness ratio of each layer are shown in Table 4, and the total thickness of the easy-to-peel PE film is 65 μm. The preparation method is as follows:

[0067] After the raw materials of the outer layer, the middle layer and the inner layer are mixed by the automatic batching system according to the proportion, they are sent into the outer layer, the middle layer and the inner layer extruders. The raw materials of the outer layer, the middle layer and the inner layer are melted and plasticized, and then sent into the die head. The film is extruded and air-cooled. After the stabilization ring and the herringbone arrangement, the cylinder is flattened by the upper traction rotation, and then enters the corona treatment device for corona treatment. After the edge cutting, it enters the front and rear winding devices for front and rear winding, and the 65 μm easy-to-peel PE film is obtained.

[0068] The temperature and pressure of the outer layer, the middle layer and the inner layer extruders and the die head are shown in Table 3:

[0069] Table 3 Extruder temperature and pressure

[0070] Conditions Zone 1 / °C Zone 2 / °C Zone 3 / °C Zone 4 / °C Zone 5 / °C Pressure / bar Outer layer 160 168 172 165 160 210-305 Middle layer 163 168 170 165 162 215-355 Inner layer 165 172 168 163 160 205-290 Die 175 180 185 183

[0071] The above easy-to-peel PE film is used to prepare a heat-sealable PET easy-to-peel composite film. The polyester film (PET) used is directly purchased from Kanghui New Material Technology Co., Ltd. 12 μm packaging polyester film; the preparation method is as follows:

[0072] The printing layer of the polyester film is printed according to customer requirements by gravure printing, and a conventional process is selected for printing.

[0073] The printed PET polyester film is compounded with the PE film by a solvent-free compounding process. A two-component solvent-free polyurethane adhesive from Wanhua Chemical (Beijing) Co., Ltd. is used, and the process parameters are as follows: adhesive mixing temperature: both A and B components are set to 40℃; coating temperature: all the steel rollers of the coating adhesive system are set to 40℃; adhesive ratio: the mass ratio of A component to B component is 100:75, and the adhesive amount is 2.0 g / m 2 .

[0074] After compounding, the obtained composite film is placed in a curing room at 40±5℃ for curing for 36 h, and then cut after cooling for 12 h to obtain the heat-sealable PET easy-to-peel composite film.

[0075] Examples 2-3

[0076] The raw material usage and layer thickness ratio of each layer are shown in Table 4, and the total thickness of the easy-to-peel PE film is 65 μm. The preparation method and Example 1 are the same, and the easy-to-peel PE film and the heat-sealable PET easy-to-peel composite film are obtained.

[0077] Table 4: Raw material usage (in mass parts) for Examples 1-3

[0078]

[0079]

[0080] Performance test:

[0081] The heat-sealable PET easy-peel composite films prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the test methods and test results are shown in Table 5. The heat-seal strength test was performed by heat-sealing the heat-sealable PET easy-peel composite film with a PET film, and then testing the heat-seal strength.

[0082] Table 5: Performance test results

[0083]

[0084] In addition, the heat-sealable PET easy-peel composite films prepared in Examples 1-3 were heat-sealed with a PET film at different temperatures (110-200℃, heat-seal pressure was 3 kg, and the time was 1 second), and the heat-seal strength was tested. The results are shown in Table 5. Figure 1 .

[0085] According to the data in Table 5, it can be seen that the heat-sealable PET easy-peel composite film prepared in the present application has good mechanical properties, and the heat-seal strength is moderate, the seal peeling is smooth without jumping and no stringing; at the same time, according to the data in Table 5, it can be seen that the heat-sealable PET easy-peel composite film has a moderate heat-seal strength under the conditions of 110-200℃, which indicates that it has a relatively wide heat-seal window. Figure 1

[0086] The above description is only the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.​

Claims

1. An easy-peel PE film, characterized in that, It is made of three layers: outer layer, middle layer and inner layer, through co-extrusion blown film. The outer layer is prepared by mass parts of 30-70 parts of low-density polyethylene, 10-50 parts of linear low-density polyethylene, 10-20 parts of linear metallocene low-density polyethylene, and 0.5-1 parts of processing aids. The raw materials for preparing the middle layer, by mass parts, include 20-65 parts of low-density polyethylene, 10-30 parts of linear low-density polyethylene, 10-50 parts of metallocene low-density polyethylene, and 0.5-1 parts of processing aids. The raw materials for preparing the inner layer, by mass, include 30-80 parts of a first easy-peel functional material, 20-50 parts of a second easy-peel functional material, and 0.5-1 parts of functional additives; the first easy-peel functional material is an easy-peel resin of grade Z325 produced by Mitsubishi Chemical Corporation of Japan, and the second easy-peel functional material is an easy-peel resin of grade Z100F produced by Mitsubishi Chemical Corporation of Japan. The weight ratio of the outer layer, middle layer and inner layer is (1-2):(1-4):(1-2); The processing aids used in the outer, middle, and inner layers are all functional masterbatches made from fluoropolymers and polyolefin resins; the linear low-density polyethylene used in the outer layer is linear low-density polyethylene with the grade 1002AY produced by ExxonMobil; and the linear low-density polyethylene used in the middle layer is linear low-density polyethylene with the grade KP7050 produced by Shell Petrochemicals China Limited.

2. The easy-peel PE film according to claim 1, characterized in that, The outer layer uses low-density polyethylene with a melt index of 1.5–2.5 g / 10 min and a density of 0.920–0.930 g / cm³. 3 The outer layer uses linear low-density polyethylene with a melt index of 1.5–2.5 g / 10 min and a density of 0.912–0.925 g / cm³. 3 The outer layer uses linear metallocene low-density polyethylene with a melt index of 1.5–2.5 g / 10 min and a density of 0.910–0.920 g / cm³. 3 .

3. The easy-peel PE film according to claim 1, characterized in that, The low-density polyethylene used in the middle layer has a melt index of 1.5–2.5 g / 10 min and a density of 0.920–0.930 g / cm³. 3 The linear low-density polyethylene used in the middle layer has a melt index of 1.5–2.5 g / 10 min and a density of 0.910–0.925 g / cm³. 3 The metallocene low-density polyethylene used in the middle layer has a melt index of 0.5–1.8 g / 10 min and a density of 0.920–0.935 g / cm³. 3 .

4. The easy-peel PE film according to claim 1, characterized in that, The first easily peelable functional material used in the inner layer has a melt index of 6.0–7.5 g / 10 min and a density of 0.910–0.930 g / cm³. 3 The second easily peelable functional material has a melt index of 11–13 g / 10 min and a density of 0.900–0.910 g / cm³. 3 .

5. The easy-peel PE film according to claim 1, characterized in that, The processing aids used in the outer, middle, and inner layers each have a melt index of 4.0–5.0 g / 10 min and a density of 0.910–0.930 g / cm³. 3 .

6. The easy-peel PE film according to any one of claims 1 to 5, characterized in that, The low-density polyethylene used in the outer, middle and inner layers is low-density polyethylene of grade 2426H produced by China National Petroleum Corporation Lanzhou Petrochemical Company, and the linear metallocene low-density polyethylene used in the outer layer is linear metallocene low-density polyethylene of grade SP1520 produced by Mitsui Chemicals Co., Ltd. The metallocene low-density polyethylene used in the middle layer is metallocene low-density polyethylene of grade 1327MA manufactured by ExxonMobil. The processing aids used in the outer, middle, and inner layers are processing aids of grade PE103-001 manufactured by Daikin Industries, Ltd.

7. The method for preparing the easy-peel PE film according to any one of claims 1 to 6, characterized in that, Includes the following steps: The raw materials for the outer, middle, and inner layers are co-extruded in three layers to obtain the easy-to-peel PE film.

8. A heat-sealable PET easy-peel composite film, characterized in that, It includes a heat-sealing layer and a printing layer stacked together; the heat-sealing layer is the easy-peel PE film according to any one of claims 1 to 6 or the easy-peel PE film prepared by the preparation method according to claim 7; the printing layer is a polyester film.

9. The method for preparing the heat-sealable PET easy-peel composite film according to claim 8, characterized in that, Includes the following steps: Polyester film and easy-peel PE film are laminated with solvent-free adhesive and then cured to obtain heat-sealable PET easy-peel composite film.

10. The preparation method according to claim 9, characterized in that, The ripening temperature is 40±5℃, and the time is 24 to 48 hours.

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