A machine for the production of a longitudinal easy-cut PE film

Abstract

The application relates to the technical field of high polymer materials, and particularly discloses a longitudinal easy-to-cut PE film and a preparation method thereof. The longitudinal easy-to-cut PE film comprises an outer layer, a middle layer and an inner layer which are sequentially contacted; the inner layer comprises the following raw materials in parts by weight: first low-density polyethylene, linear low-density polyethylene, metallocene ultra-low-density polyethylene, a PPA additive, a slip agent, an antioxidant and an opening agent; the middle layer comprises the following raw materials in parts by weight: high-density polyethylene, second low-density polyethylene, polypropylene, a cyclic olefin copolymer, a PPA additive, a filler and an antioxidant; and the outer layer comprises the following raw materials in parts by weight: second low-density polyethylene, linear low-density polyethylene, a PPA additive and an antioxidant. The longitudinal easy-to-cut PE film has the advantages of small tensile strength, longitudinal tear strength and impact strength, easy cutting, and no burr and wire drawing in the cut.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and more particularly to a longitudinal easy-to-cut PE film and a preparation method thereof. BACKGROUND

[0002] Polyethylene film, also known as PE film, is a colorless, odorless, odorless, translucent, non-toxic insulating material. One of the main uses of polyethylene (HDPE, MDPE, LLDPE and LDPE) is film application, such as grocery bags, public institutions and consumer can liners, merchandise bags, shopping bags, food packaging film, multi-walled bag liners, display bags, deli wraps, elastic outer packaging film and shrink outer packaging film. Key physical properties of polyethylene film include tear strength, impact strength, tensile strength, stiffness and transparency.

[0003] In the prior art, the Chinese patent application file with the application number CN107323053 discloses a tear-resistant polyethylene film, a composite film and a preparation method thereof. The tear-resistant polyethylene film comprises a corona layer, an intermediate layer and a heat-sealing layer. The corona layer and the intermediate layer are respectively composed of first metallocene PE, octacarbon LLDPE and processing aid with a mass ratio of (45-55):(45-55):(0.1-0.5). The heat-sealing layer is composed of first metallocene PE, second metallocene PE, silicone, slip agent and opening agent with a mass ratio of (45-55):(20-30):(1.9-2.3):(2.3-2.7):(1.5-1.9). The first metallocene PE has a melt index of 1.0 g / 10 min, and the second metallocene PE has a melt index of 1.9 g / 10 min.

[0004] The above-mentioned tear-resistant polyethylene film has strong toughness, tensile resistance and good tear resistance. However, when the film is longitudinally cold-cut, the film is easily cut and the cut edge has burrs and is not smooth, which cannot meet the customer's use requirements. SUMMARY

[0005] In order to reduce the longitudinal tear strength and tensile strength of the PE film, make it easy to cut when processing and cutting bags, and make the cut smooth and without burrs, the present application provides a longitudinal easy-to-cut PE film and a preparation method thereof.

[0006] In the first aspect, the present application provides a longitudinal easy-to-cut PE film, which adopts the following technical scheme:

[0007] A longitudinal easy-to-cut PE film, comprising an outer layer, a middle layer and an inner layer in contact with each other in sequence.

[0008] The inner layer comprises the following raw materials by weight: 30-60 parts of first low-density polyethylene, 30-50 parts of linear low-density polyethylene, 15-25 parts of metallocene ultra-low-density polyethylene, 0.1-0.5 parts of PPA additive, 0.2-0.6 parts of slip agent, 0.1-0.5 parts of antioxidant, 2.4-3.9 parts of opening agent;

[0009] The middle layer comprises the following raw materials by weight: 15-25 parts of high-density polyethylene, 20-40 parts of second low-density polyethylene, 10-30 parts of polypropylene, 15-25 parts of cyclic olefin copolymer, 0.1-0.5 parts of PPA additive, 40-60 parts of filler, 0.1-0.5 parts of antioxidant; and the outer layer comprises the following raw materials by weight: 30-50 parts of second low-density polyethylene, 50-70 parts of linear low-density polyethylene, 0.1-0.5 parts of PPA additive, 0.1-0.5 parts of antioxidant.

[0010] By using the above technical solution, different proportions of second low-density polyethylene with lower strength are used in the outer layer and the inner layer, the first low-density polyethylene material with longitudinal tear strength is added in the outer layer, linear low-density polyethylene and metallocene ultra-low-density polyethylene are additionally added therein, and the filler and COC (cyclic olefin copolymer) are used in the middle layer, so that the mechanical strength of the film is greatly reduced, the longitudinal tear strength of the film is low, the film is extremely easy to be slitted, and the cut is smooth and without burrs.

[0011] Optionally, the film comprises an outer layer, a middle layer and an inner layer which are sequentially contacted;

[0012] The inner layer comprises the following raw materials by weight: 35-40 parts of first low-density polyethylene, 35-40 parts of linear low-density polyethylene, 20-23 parts of metallocene ultra-low-density polyethylene, 0.2-0.3 parts of PPA additive, 0.3-0.4 parts of slip agent, 0.2-0.3 parts of antioxidant, 3-3.9 parts of opening agent;

[0013] The middle layer comprises the following raw materials by weight: 15-20 parts of high-density polyethylene, 25-30 parts of second low-density polyethylene, 15-20 parts of polypropylene, 20-25 parts of cyclic olefin copolymer, 0.1-0.3 parts of PPA additive, 45-50 parts of filler, 0.2-0.3 parts of antioxidant; and the outer layer comprises the following raw materials by weight: 35-40 parts of second low-density polyethylene, 55-60 parts of linear low-density polyethylene, 0.1-0.3 parts of PPA additive, 0.1-0.3 parts of antioxidant.

[0014] By using the above technical solution, the raw materials of each layer are more accurate, and the polyethylene film made is more easy to be slitted, and the slitting is smooth and flat.

[0015] Optionally, the high-density polyethylene in the middle layer has a melt index of 0.8-1.2 g / 10 min and a density of 0.949-0.953 g / cm 3 .

[0016] By adopting the above technical solution, the high-density polyethylene with the above melt index and density has high rigidity, high impact resistance and high flowability, and has a relatively low longitudinal tear strength, so that the longitudinal tear strength of the polyethylene film is small and the polyethylene film is easy to be cut.

[0017] Optionally, the first low-density polyethylene in the inner layer has a melt index of 1.7-2.2 g / 10 min and a density of 0.922-0.926 g / cm 3 .

[0018] By adopting the above technical solution, the first low-density polyethylene has a high melt index, a low molecular weight and a low strength, and is easy to be cut.

[0019] Optionally, the metallocene ultra-low-density polyethylene in the inner layer has a melt index of 1-1.2 g / 10 min and a density of 0.918-0.922 g / cm 3 .

[0020] By adopting the above technical solution, the metallocene ultra-low-density polyethylene can improve the heat-sealability of the polyethylene film and facilitate the opening effect.

[0021] Optionally, the second low-density polyethylene in the outer layer and the middle layer has a melt index of 3.4-4.6 g / 10 min and a density of 0.922-0.926 g / cm 3 .

[0022] By adopting the above technical solution, the second low-density polyethylene with a high melt index, a low molecular weight and a low strength can reduce the tear strength of the polyethylene film and improve the easy-to-cut effect.

[0023] Optionally, the linear low-density polyethylene in the inner layer and the outer layer has a melt index of 20-50 g / 10 min and a density of 0.922-0.926 g / cm 3 .

[0024] By adopting the above technical solution, the linear low-density polyethylene has a high melt index and a low strength, and can improve the heat-seal strength and the easy-to-cut effect.

[0025] Optionally, the polyethylene in the middle layer is selected from at least one of block copolymerized polypropylene, homopolymerized polypropylene and random copolymerized polypropylene.

[0026] By adopting the technical scheme, the molecular chain of the homopolymer polypropylene does not contain ethylene monomer, so the regularity of the molecular chain is high, the crystallinity is high, and the impact performance is low, so that the polyethylene film has good brittleness, is easy to cut open, and is not easy to produce wire drawing or burr; the size stability of the random copolymer polypropylene is good, and the rigidity of the block copolymer polypropylene is strong, so that the addition of any kind of polypropylene can reduce the toughness of the polyethylene film and improve the easy cutting effect.

[0027] Optionally, the melt index of the block copolymer PP in the inner layer and the outer layer is 2.5-3.5 g / 10 min, and the density is 0.9-1 g / cm 3 .

[0028] By adopting the technical scheme, the block copolymer PP with the above density and melt index has high rigidity, high flowability and high impact resistance, so that the polyethylene film has high rigidity and low toughness, and is easy to cut off.

[0029] Optionally, the melt index of the random copolymer PP in the inner layer and the outer layer is 18-19 g / 10 min, and the density is 0.89-0.91 g / cm 3 .

[0030] By adopting the technical scheme, the random copolymer PP with the above melt index and density has high impact resistance, and the elongation at break is less than 500%, and the tensile resistance is small.

[0031] Optionally, the melt index of the homopolymer PP in the inner layer and the outer layer is 9.5-10 g / 10 min, and the density is 0.9-0.92 g / cm 3 .

[0032] By adopting the technical scheme, the homopolymer PP with the above density and melt index has high rigidity and high flexibility, and can enhance the easy cutting effect of the polyethylene film.

[0033] Optionally, the opening agent includes silica with a particle size of 7-8 μm and silica with a particle size of 3-4 μm in a mass ratio of 1:2-2.5.

[0034] By adopting the technical scheme, the silica with different particle sizes is used as the opening agent, which can reduce the friction coefficient in the inner layer and prevent adhesion, and the opening agent with a small particle size is difficult to disperse in the inner layer, which hinders the transparency and strength of the polyethylene film.

[0035] Optionally, the filler is selected from at least one of calcium carbonate, talc powder, mica powder and montmorillonite powder.

[0036] By adopting the technical scheme, after the filler is added, the raw materials are mixed and hot-melted in the middle layer, and then blown into a film, and after stretching, the middle layer is separated from the surface of the filler and forms interconnected microporous channels between the filler particles, so that the tensile strength of the polyethylene film is reduced.

[0037] In a second aspect, the application provides a preparation method of the longitudinal easy-cut PE film, which adopts the following technical scheme:

[0038] The preparation method of the longitudinal easy-cut PE film comprises the following steps:

[0039] The raw materials of the inner layer, the outer layer and the middle layer are mixed according to the raw material ratio, and then extruded into a film bubble after melting and plasticizing, and then wound after cooling and corona treatment.

[0040] In summary, the application has the following beneficial effects:

[0041] 1. Since the second low-density polyethylene is used in the outer layer and the inner layer, the first low-density polyethylene is used in the inner layer, and the linear low-density polyethylene is added in the outer layer and the inner layer, the tensile strength and the tear strength of the polyethylene film prepared thereby are reduced, the polyethylene film is easy to cut when processing the bag, and the cut is smooth and without burrs.

[0042] 2. In the application, the linear low-density polyethylene and the metallocene ultra-low-density polyethylene are preferably used in the inner layer, which can improve the heat sealing strength while reducing the longitudinal tear strength, thereby facilitating the longitudinal cutting.

[0043] 3. In the application, the high-density polyethylene is preferably added in the middle layer, so that the longitudinal tear strength of the polyethylene film is relatively low, the polyethylene film is easy to cut, and the cut is neat and without burrs. DETAILED DESCRIPTION

[0044] EMBODIMENT

[0045] Table 1: Raw material sources in the embodiment

[0046]

[0047]

[0048] Embodiment 1: A longitudinal easy-cut PE film, comprising an outer layer, a middle layer and an inner layer in contact in sequence, the thickness of the film is 65 μm, the thickness ratio of the outer layer, the middle layer and the inner layer is 0.5:1:0.5, the raw material sources of the outer layer, the middle layer and the inner layer are shown in Table 1, the raw materials and the amounts are shown in Table 2, the melt index of the first low-density polyethylene in the outer layer is 1.9 g / 10 min, the density is 0.924 g / cm 3 , the model is 2420H, the melt index of the linear low-density polyethylene in the outer layer and the inner layer is 50 g / 10 min, the density is 0.926 g / cm 3 , the model is 6101XR, and the melt index of the second low-density polyethylene in the outer layer and the middle layer is 4 g / 10 min, the density is 0.924 g / cm 3, the outer layer contains 1:2 mass ratio of 8 μm diameter silica and 4 μm diameter silica, the inner layer contains metallocene ultra-low density polyethylene with a melt index of 1 g / 10 min and a density of 0.918 g / cm 3 , the middle layer contains polypropylene with a melt index of 3.5 g / 10 min, a tensile strength of 33.6 MPa, a heat distortion temperature of 104 °C, and the COC has a density of 1.02 g / cm 3 , the melt flow rate is 1 g / 10 min, the filler is calcium carbonate, the high-density polyethylene has a melt index of 0.9 g / 10 min and a density of 0.95 g / cm 3 , the antioxidant in the outer layer, the middle layer, and the inner layer is antioxidant 1010.

[0049] The preparation method of the above longitudinal easy-to-cut PE film comprises the following steps:

[0050] The raw materials of the inner layer, the outer layer, and the middle layer are mixed according to the raw material ratio, melted by the respective extruders, filtered, and the impurity-free molten resin is co-extruded into a film bubble from a die, cooled, and corona treated, and then wound up, the corona treatment is 38 dyn / cm, the temperature of each zone of the extruder is shown in Table 3, the middle layer is 52 r / min, the inner layer is 35 r / min, and the outer layer is 42 r / min.

[0051] Table 2 Raw materials and amounts of the longitudinal easy-to-cut PE film in Examples 1-4

[0052]

[0053]

[0054] Table 3 Temperature of each zone of the extruder

[0055] Temperature / °C Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Outer Layer 50 160 160 165 170 170 160 Middle Layer 50 160 160 165 170 170 160 Inner Layer 50 160 160 165 170 170 160 Die 150 155 160 165 160 160 /

[0056] Example 5: A longitudinal easy-to-cut PE film, which is different from Example 1 in that the polypropylene is random copolymer PP with a melt index of 19 g / 10 min and a density of 0.9 g / cm 3 , model 6019.

[0057] Example 6: A longitudinal easy-to-cut PE film, which is different from Example 1 in that the polypropylene is homopolymer PP with a melt index of 10 g / 10 min and a density of 0.905 g / cm 3 , model K1008.

[0058] Example 7: A longitudinal easy-to-cut PE film, which is different from Example 1 in that a melt index of 4 g / 10 min and a density of 0.924 g / cm3 LDPE, model 2420K, is used to replace the first low density polyethylene in the inner layer.

[0059] Example 8: A machine direction easy cut PE film, which is different from Example 1 in that a melt index of 2 g / 10 min and a density of 0.918 g / cm 3 LLDPE, model 1002KW, is used to replace the linear low density polyethylene in the inner layer.

[0060] Example 9: A machine direction easy cut PE film, which is different from Example 1 in that a melt index of 3.5 g / 10 min and a density of 0.918 g / cm 3 MLLDPE, model 3518CB, is used to replace the metallocene ultra low density polyethylene in the inner layer.

[0061] Example 10: A machine direction easy cut PE film, which is different from Example 1 in that a melt index of 2 g / 10 min and a density of 0.9225 g / cm 3 LDPE, model LD100AC, is used to replace the second low density polyethylene in the outer layer.

[0062] Example 11: A machine direction easy cut PE film, which is different from Example 1 in that a melt index of 1.9 g / 10 min and a density of 0.924 g / cm 3 The first low density polyethylene in the middle layer is replaced by high density polyethylene.

[0063] Comparative Example

[0064] Comparative Example 1: A machine direction easy cut PE film, which is different from Example 1 in that the first low density polyethylene is not added in the inner layer.

[0065] Comparative Example 2: A machine direction easy cut PE film, which is different from Example 1 in that the linear low density polyethylene is not added in the inner layer.

[0066] Comparative Example 3: A machine direction easy cut PE film, which is different from Example 1 in that the linear low density polyethylene and the metallocene ultra low density polyethylene are not added in the inner layer.

[0067] Comparative Example 4: A machine direction easy cut PE film, which is different from Example 1 in that the second low density polyethylene is not added in the outer layer.

[0068] Comparative Example 5: A machine direction easy cut PE film, which is different from Example 1 in that the cyclic olefin copolymer is not added in the middle layer.

[0069] Comparative Example 6: A machine direction easy cut PE film, which is different from Example 1 in that the polypropylene is not added in the middle layer.

[0070] Comparative Example 7: A machine direction easy tear PE film, which is different from Example 1 in that high density polyethylene is not added in the middle layer.

[0071] Comparative Example 8: A bidirectional easy tear film having a three-layer structure, which is respectively an outer layer, a middle layer and an inner layer, and the weight percentage of the three layers is respectively: 30% for the outer layer, 40% for the middle layer and 30% for the inner layer, and each layer is composed of the following components, the outer layer: high pressure low density polyethylene 55%, high density polyethylene 22%, linear low density polyethylene 15%, ethylene-acrylic acid copolymer (EAA) 8%; the weight percentage of each component in the middle layer: high pressure low density polyethylene 20%, metallocene high density polyethylene 15%, ethylene-methacrylic acid polymer 20%, high polymer 45%; the weight percentage of each component in the inner layer: high pressure low density polyethylene 40%, metallocene low density polyethylene 15%, linear low density polyethylene 26.5%, ethylene-octene copolymer 15%, opening agent (silicon dioxide) 1%, antistatic agent 2%, fluoropolymer (PPA) 0.5%; the method for preparing the bidirectional easy tear film is: the raw materials of the outer layer, the middle layer and the inner layer are mixed by the automatic mixing system according to the above weight percentage, and then the raw materials of each layer are respectively added into the outer layer extruder, the middle layer extruder and the inner layer extruder for melting and plasticizing, and then sent into the die head to co-extrude into a film bubble, and then cooled by the automatic air ring, treated by the corona and wound up, so as to obtain the bidirectional easy tear film; wherein the temperature of the outer layer extruder is 165℃, the extrusion pressure is 200bar; the temperature of the middle layer extruder is 145℃, the extrusion pressure is 450bar; the temperature of the inner layer extruder is 160℃, the extrusion pressure is 220bar; the die head temperature is 200℃.

[0072] Comparative Example 9: A high-strength and tear-resistant PE film, which sequentially comprises an inner layer, a middle layer and an outer layer, and the thickness of each layer is respectively 15μm, 30μm and 15μm.

[0073] The inner layer comprises the following raw materials in weight percentage: linear low density polyethylene 43.2 parts, low density polyethylene 20 parts, first metallocene polyethylene 35 parts, opening (slip) agent 1.5 parts, polyphthalamide (PPA) 0.3 parts; the middle layer comprises the following raw materials in weight percentage: second metallocene polyethylene 19.5 parts, medium density polyethylene 30 parts, high density polyethylene 50 parts, polyphthalamide (PPA) 0.5 parts; the outer layer comprises the following raw materials in weight percentage: second metallocene polyethylene 29.5 parts, medium density polyethylene 50 parts, low density polyethylene 20 parts, polyphthalamide (PPA) 0.5 parts. The brand of the first metallocene polyethylene is MLLDPE 1018MF, the density is 0.918g / cm 3 , and the melt index is 1.0g / 10min; the brand of the second metallocene polyethylene is MLLDPE 1327CA, the density is 0.927g / cm3 LLDPE 1002BU, density 0.918 g / cm 3 LDPE 2426K, density 0.924 g / cm 3 MDPE FB2230, density 0.923 g / cm 3 HDPE 7000F, density 0.956 g / cm 3 SF-002; PPA A1058.

[0074] The method for preparing the high-strength, tear-resistant PE film comprises the following steps:

[0075] The raw material for preparing the inner layer is put into the inner layer hopper of the three-layer co-extrusion film blowing machine, and the temperature of the inner layer main machine (inner layer screw extrusion structure) corresponding to the inner layer hopper is set to 210°C; the raw material for preparing the middle layer is put into the middle layer hopper of the three-layer co-extrusion film blowing machine, and the temperature of the middle layer main machine (middle layer screw extrusion structure) corresponding to the middle layer hopper is set to 200°C; the raw material for preparing the outer layer is put into the outer layer hopper of the three-layer co-extrusion film blowing machine, and the temperature of the outer layer main machine (outer layer screw extrusion structure) corresponding to the outer layer hopper is set to 210°C; the temperature of the die flow channel is set to 210°C; the film blowing is performed by using the three-layer co-extrusion film blowing machine, air is introduced into the extrusion die for blowing and cooling, and the PE film with a thickness of 60 μm is formed after traction, rolling and winding.

[0076] Performance detection test

[0077] The plastic films are prepared according to the above examples and comparative examples, and the performances of the plastic films are detected by referring to the following methods, and the detection results are recorded in Table 4.

[0078] 1. Tensile strength at break: detected according to GB / T13022 "Plastic film tensile property test method", 3 groups of samples are detected for each example or comparative example, and the average value is taken as the detection result;

[0079] 2. Elongation at break: detected according to GB / T13022-1991 "Plastic film tensile property test method", 3 groups of samples are detected for each example or comparative example, and the average value is taken as the detection result;

[0080] 3. Tear strength: according to GB / T 16578-1996 "Plastic film and sheet resistance to tear test method - trouser tear method" for detection, 3 groups of samples were detected for each example or comparative example, and the average value was taken;

[0081] 4. Heat sealing temperature: according to QB / T 2358-1998 "Plastic film packaging bag heat sealing strength test method" for detection;

[0082] 5. Cut edge condition: 10-column roll film was taken as the detection object, longitudinal cutting test was carried out, and whether the cut edge was easy to cut off, whether there was burr and other phenomena were observed.

[0083] Table 4 Performance test results of polyethylene film

[0084]

[0085]

[0086] As can be seen from the data in Table 4, in Examples 1-4, high-melt-index low-density polyethylene is used in the outer layer and the middle layer, and high-melt-index and low-strength linear low-density polyethylene is used in the inner layer and the outer layer, low-longitudinal tear strength first low-density polyethylene and metallocene linear low-density polyethylene are used in the inner layer, and block copolymer polypropylene and cyclic olefin copolymer are used in the middle layer, so that the tensile strength and tear strength of the polyethylene film prepared thereby are small, especially the longitudinal tear strength, which is easy to separate and cut off when processing the bag, and the cut edge is not smooth, neat and burr-free.

[0087] Compared with Example 1, random copolymer PP and homopolymer PP are used in Examples 5 and 6, respectively, the tensile strength and elongation at break, tear strength of the polyethylene film prepared in Examples 5 and 6 are increased, although it is easy to cut off, but the flatness of the cut edge is not as good as that of Example 1.

[0088] Compared with Example 1, the second low-density polyethylene 2420K is used in the outer layer and the middle layer instead of the first low-density polyethylene 2420H in the inner layer in Example 7, as shown in Table 4, the tensile strength, tear strength and other mechanical strength of the polyethylene film prepared in Example 7 are increased, the longitudinal tear strength is increased, which makes the film not easy to cut off, and burr appears at the cut edge.

[0089] In Example 8, LLDPE with low melt index is used to replace linear low-density polyethylene 6101XR in the inner layer, and in Example 9, MLLDPE with increased density is used to replace metallocene ultra-low-density polyethylene 2012MA in the inner layer, compared with Example 1, the tensile strength and tear strength of the polyethylene film prepared in Examples 8 and 9 are increased, and burr appears at the cut edge.

[0090] Example 10 compared with Example 1, the LDPE in the outer layer is replaced by the same amount of LDPE with reduced melt index, the tensile strength, elongation at break and tear strength of the polyethylene film are increased, and burrs and roughness occur at the cut.

[0091] Example 11 uses the first low-density polyethylene to replace the high-density polyethylene, compared with Example 1, the tear strength is increased, and the burrs are increased.

[0092] Comparative Example 1 does not add the first low-density polyethylene 2420H in the inner layer, compared with Example 1, the tensile strength and tear strength of the polyethylene film prepared in the comparative example are increased, burrs are prone to occur at the cut, and it is not easy to cut.

[0093] Comparative Example 2 does not add linear low-density polyethylene 6101XR in the inner layer compared with Example 1, and Comparative Example 3 does not add linear low-density polyethylene 6101XR and metallocene ultra-low-density polyethylene 2012MA in the inner layer, the mechanical strength of the polyethylene film prepared in Comparative Example 3 is greater than that in Comparative Example 2, and the tensile strength and other properties of the polyethylene film prepared in Comparative Example 2 are higher than those in Example 1, and there are more burrs at the cut.

[0094] Comparative Example 4 does not add the second low-density polyethylene 2420K in the outer layer, compared with Example 1, the mechanical properties are enhanced, and the amount of burrs at the cut is increased.

[0095] Comparative Example 5 and Comparative Example 6 do not add cyclic olefin copolymer and polypropylene respectively in the middle layer compared with Example 1, the tensile strength and elongation at break of the polyethylene film prepared in Comparative Example 5 and Comparative Example 6 are increased, the longitudinal tear strength is enhanced, it is not easy to cut, and there are more burrs at the cut.

[0096] Comparative Example 7 does not add high-density polyethylene in the middle layer compared with Example 1, the tensile strength and tear resistance of the polyethylene film are increased, and the easy cutting effect is decreased.

[0097] Comparative Example 8 is a bidirectional easy-to-tear film, and Comparative Example 9 is a high-strength tear-resistant film. Although the easy-to-tear film prepared in Comparative Example 8 has a lower tear strength, its tensile strength is large, and burrs still occur at the cut when cutting longitudinally. The plastic film prepared in Comparative Example 9 is difficult to cut, and there are more burrs.

[0098] The specific embodiments are merely an explanation of the present application, which is not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A longitudinally easy-to-cut PE film, characterized in that, Including the outer layer, middle layer and inner layer that come into contact in sequence; The inner layer comprises the following raw materials in parts by weight: 30-60 parts of first low-density polyethylene, 30-50 parts of linear low-density polyethylene, 15-25 parts of metallocene ultra-low-density polyethylene, 0.1-0.5 parts of PPA additive, 0.2-0.6 parts of slip agent, 0.1-0.5 parts of antioxidant, and 2.4-3.9 parts of opening agent; The middle layer comprises the following raw materials in parts by weight: 15-25 parts high-density polyethylene, 20-40 parts low-density polyethylene, 10-30 parts polypropylene, 15-25 parts cyclic olefin copolymer, 0.1-0.5 parts PPA additive, 40-60 parts filler, and 0.1-0.5 parts antioxidant. The outer layer comprises the following raw materials in parts by weight: 30-50 parts of second low-density polyethylene, 50-70 parts of linear low-density polyethylene, 0.1-0.5 parts of PPA additive, and 0.1-0.5 parts of antioxidant; The first low-density polyethylene in the inner layer has a melt index of 1.9 g / 10 min and a density of 0.924 g / cm³. 3 The model number is 2420H; The inner layer contains metallocene ultra-low density polyethylene with a melt flow index of 1 g / 10 min and a density of 0.918 g / cm³. 3 The brand name is 2012MA; The second low-density polyethylene in the outer and middle layers has a melt index of 4 g / 10 min and a density of 0.924 g / cm³. 3 The grade is 2420K; The linear low-density polyethylene in the inner and outer layers has a melt index of 50 g / 10 min and a density of 0.926 g / cm³. 3 The brand name is 6101XR.

2. The longitudinally cut PE film according to claim 1, characterized in that: Including the outer layer, middle layer and inner layer that come into contact in sequence; The inner layer comprises the following raw materials in parts by weight: 35-40 parts of first low-density polyethylene, 35-40 parts of linear low-density polyethylene, 20-23 parts of metallocene ultra-low-density polyethylene, 0.2-0.3 parts of PPA additive, 0.3-0.4 parts of slip agent, 0.2-0.3 parts of antioxidant, and 3-3.9 parts of opening agent; The middle layer comprises the following raw materials in parts by weight: 15-20 parts high-density polyethylene, 25-30 parts low-density polyethylene, 15-20 parts polypropylene, 20-25 parts cyclic olefin copolymer, 0.1-0.3 parts PPA additive, 45-50 parts filler, and 0.2-0.3 parts antioxidant; The outer layer comprises the following raw materials in parts by weight: 35-40 parts of second low-density polyethylene, 55-60 parts of linear low-density polyethylene, 0.1-0.3 parts of PPA additive, and 0.1-0.3 parts of antioxidant.

3. The longitudinally cut PE film according to claim 1, characterized in that, The inner polyethylene layer is selected from at least one of block copolymer polypropylene, homopolymer polypropylene, and random copolymer polypropylene.

4. The longitudinally cut PE film according to claim 1, characterized in that, The opening agent comprises silica with a particle size of 7-8 μm and silica with a particle size of 3-4 μm in a mass ratio of 1:2-2.

5.

5. The longitudinally cut PE film according to claim 1, characterized in that, The filler is selected from at least one of calcium carbonate, talc, mica powder, and montmorillonite powder.

6. The method for preparing the longitudinally cut PE film according to any one of claims 1-5, characterized in that, Includes the following steps: The raw materials for the inner, outer, and middle layers are mixed separately according to the raw material ratio, and after being melted and plasticized, they are extruded into film bubbles, cooled, corona-treated, and then wound up.

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