A PE light-sealing film and a preparation method thereof, and a light-sealing packaging bag composite film

Abstract

The present invention relates to the technical field of composite films, and provides a PE light-sealing film and a preparation method thereof, as well as a light-sealing packaging bag composite film. The present invention uses low-density polyethylene and linear low-density polyethylene to blend in the outer layer, which has the characteristics of good processing performance and high composite strength; the middle layer uses medium-density polyethylene and metallocene low-density polyethylene to blend, which has the characteristics of high strength, good stiffness and easy processing; polyolefin-modified α-olefin copolymer is added to the inner layer, and the polyolefin-modified α-olefin copolymer is blended with polyolefin as a modifier, which can achieve the effect of controlling the heat-sealing strength of the film and realize the light-sealing function. The PE light-sealing film of the present invention is used to prepare a light-sealing packaging bag composite film, and the obtained composite film has the characteristics of low heat-sealing strength, easy to tear the seal, no drawing, and no residue, and can be used for the packaging of common daily necessities such as nuts, milk powder and cosmetics.

Description

Technical Field

[0001] The invention relates to the technical field of composite films, and in particular to a PE light-sealing film and a preparation method thereof, and a light-sealing packaging bag composite film. Background Art

[0002] In the field of packaging bags, especially food packaging bags, as people have higher and higher requirements for food health and taste quality, and higher and higher requirements for the quality, quality and safety of raw materials in food, the requirements for packaging raw materials are becoming more and more stringent, and the requirements for packaging material performance are also diverse.

[0003] For example, some large packages must not only ensure the freshness and safety of food raw materials, but also need to withstand various external destructive forces during the transit transportation process. They also face many problems such as packaging damage and pollution of raw materials during transportation, stacking easily slipping and causing damage and pollution of raw materials, and slipping on the pulley and preventing normal transportation.

[0004] For some small packages, such as small bags of nuts, milk powder, cosmetics and other daily necessities, it is not necessary to further improve the anti-damage and high barrier properties of the packaging materials. These small packaging bags face another technical problem: due to the characteristics of the sealed items themselves, some need to be separated into dry and wet, and some need to be separated by category. The small packaging bags need to be double-cavity or multi-cavity heat-sealed. For users, the packaging bags need to be easily torn open. On the basis of maintaining the original performance, the tearing strength of the heat-sealed area is low so that it can be conveniently used. However, there are currently few PE films in the field that can meet the above requirements. Summary of the invention

[0005] In view of this, the present invention provides a PE light-sealing film and a preparation method thereof, and a light-sealing packaging bag composite film. The PE light-sealing film provided by the present invention has the characteristics of low heat-sealing strength on the basis of ensuring the principle mechanical properties of the PE film. The PE light-sealing film can be used to prepare a light-sealing packaging bag composite film, and the obtained composite film has the characteristics of low heat-sealing strength, easy to tear the seal, no drawing, and no residue.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A PE light sealing film, made of three layers of co-extruded blown film: outer layer, middle layer and inner layer;

[0008] The raw materials for preparing the outer layer include low-density polyethylene, linear low-density polyethylene and a first processing aid, and the mass ratio of the low-density polyethylene, linear low-density polyethylene and the first processing aid is (15-50):(50-90):(0.5-1);

[0009] The raw materials for preparing the middle layer include medium-density polyethylene, metallocene low-density polyethylene and a second processing aid, and the mass ratio of the medium-density polyethylene, metallocene low-density polyethylene and the second processing aid is (30-85): (20-45): (0.5-1);

[0010] The raw materials for preparing the inner layer include low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and a third processing aid; the mass ratio of the low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and the third processing aid is (20-60):(10-40):(10-25):(0.5-1);

[0011] The first processing aid, the second processing aid and the third processing aid are all functional masterbatches prepared from fluoropolymer and polyolefin resin, and the melt index of the first processing aid, the second processing aid and the third processing aid are independently 1.8-3.0 g / 10 min, and the density is independently 0.925-0.940 g / cm 3 .

[0012] Preferably, the low-density polyethylene used in the outer layer has a melt index of 1.5-2.5 g / 10 min and a density of 0.920-0.930 g / cm 3 ;

[0013] The linear low-density polyethylene used in the outer layer has a melt index of 1.5 to 2.5 g / 10 min and a density of 0.912 to 0.925 g / cm 3 .

[0014] Preferably, the medium-density polyethylene used in the middle layer has a melt index of 0.5-1.5 g / 10 min and a density of 0.925-0.935 g / cm 3 ;

[0015] The metallocene low-density polyethylene used in the middle layer has a melt index of 0.5-1.5 g / 10 min and a density of 0.912-0.925 g / cm 3 .

[0016] Preferably, the low-density polyethylene used in the inner layer has a melt index of 1.5-2.5 g / 10 min and a density of 0.920-0.930 g / cm 3 ;

[0017] The metallocene low-density polyethylene used in the inner layer has a melt index of 0.5-1.5 g / 10 min and a density of 0.912-0.925 g / cm 3 ;

[0018] The polyolefin modified α-olefin copolymer has a melt index of 0.5 to 1.5 g / 10 min and a density of 0.905 to 0.915 g / cm 3 .

[0019] Preferably, the thickness ratio of the outer layer, the middle layer and the inner layer is 1:(1.2-4):1; and the total thickness of the PE light sealing film is 30-160 μm.

[0020] The present invention also provides a method for preparing the PE light sealing film described in the above scheme, comprising the following steps:

[0021] The raw materials for the outer layer, the middle layer and the inner layer are co-extruded to obtain the PE light sealing film.

[0022] The present invention also provides a composite film for a light-sealing packaging bag, characterized in that it comprises a heat-sealing layer, a barrier layer and a printing layer which are stacked in sequence, and adjacent layers are compounded by an adhesive; the heat-sealing layer is the PE light-sealing film according to any one of claims 1 to 5 or the PE light-sealing film prepared by the preparation method according to claim 6.

[0023] Preferably, the printing layer is a polyester film; and the barrier layer is an aluminum film or a polyester aluminum-coated film.

[0024] The present invention also provides a method for preparing the composite film of the light-seal packaging bag described in the above scheme, comprising the following steps:

[0025] (1) compounding the printing layer and the barrier layer with a solvent-free adhesive and performing a first curing to obtain a printing layer / barrier layer composite film;

[0026] (2) Compounding the printed layer / barrier layer composite film and the PE light-sealing film with a solvent-free adhesive and then subjecting the composite film to a second curing step to obtain a light-sealing packaging composite film.

[0027] Preferably, the amount of the solvent-free adhesive applied in step (1) is 1.8 to 2.3 g / m 2 In step (2), the amount of the solvent-free adhesive applied is 1.3 to 1.8 g / m 2 ;

[0028] The temperature of the first ripening is 50±5°C, and the time is 2 to 3 days; the temperature of the second ripening is 40±5°C, and the time is 2 to 3 days.

[0029] The present invention provides a PE light sealing film, characterized in that it is made of a three-layer co-extruded blown film of an outer layer, a middle layer and an inner layer, wherein the raw materials for preparing the outer layer include low-density polyethylene, linear low-density polyethylene and a first processing aid, the raw materials for preparing the middle layer include medium-density polyethylene, metallocene low-density polyethylene and a second processing aid, and the raw materials for preparing the inner layer include low-density polyethylene, metallocene low-density polyethylene, a polyolefin-modified α-olefin copolymer and a third processing aid. The present invention adopts low-density polyethylene and linear low-density polyethylene as a blend for the outer layer, which has the characteristics of good processing performance and high composite strength; the middle layer adopts medium-density polyethylene and metallocene low-density polyethylene as a blend, which has the characteristics of high strength, good stiffness and easy processing; the inner layer adopts low-density polyethylene and metallocene low-density polyethylene as a blend, which has good strength and easy processing, and at the same time, polyolefin-modified α-olefin copolymer is added to the inner layer, and the polyolefin-modified α-olefin copolymer is used as a modifier and blended with polyolefin, which can achieve the effect of controlling the heat sealing strength of the film and realize the function of light sealing; in addition, the present invention also adds auxiliary agents to all three layers, which can effectively reduce die mouth material accumulation, reduce crystal points, reduce basic pressure, and improve production efficiency.

[0030] The present invention also provides a composite film for light-sealed packaging bags, comprising a heat-sealing layer, a barrier layer and a printing layer stacked in sequence, and the adjacent layers are composited by an adhesive; the heat-sealing layer is the PE light-sealing film described in the above scheme. The present invention uses the PE film described in the above scheme to prepare a composite film for light-sealed packaging bags, and the obtained composite film has the characteristics of low heat-sealing strength, easy to tear the seal, no drawing, and no residue. The composite film of the present invention can be used to prepare double-cavity or multi-cavity packaging bags, which are used for packaging common items in life such as nuts, milk powder and cosmetics. DETAILED DESCRIPTION

[0031] The present invention provides a PE light sealing film, which is made of a three-layer co-extruded blown film of an outer layer, a middle layer and an inner layer;

[0032] The raw materials for preparing the outer layer include low-density polyethylene, linear low-density polyethylene and a first processing aid, and the mass ratio of the low-density polyethylene, linear low-density polyethylene and the first processing aid is (15-50):(50-90):(0.5-1);

[0033] The raw materials for preparing the middle layer include medium-density polyethylene, metallocene low-density polyethylene and a second processing aid, and the mass ratio of the medium-density polyethylene, metallocene low-density polyethylene and the second processing aid is (30-85): (20-45): (0.5-1);

[0034] The raw materials for preparing the inner layer include low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and a third processing aid; the mass ratio of the low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and the third processing aid is (20-60):(10-40):(10-25):(0.5-1);

[0035] The first processing aid, the second processing aid and the third processing aid are all functional masterbatches prepared from fluoropolymer and polyolefin resin, and the melt index of the first processing aid, the second processing aid and the third processing aid are independently 1.8-3.0 g / 10 min, and the density is independently 0.925-0.940 g / cm 3 .

[0036] In the present invention, the raw materials for preparing the outer layer include low-density polyethylene, linear low-density polyethylene and a first processing aid, and the mass ratio of the low-density polyethylene, linear low-density polyethylene and the first processing aid is (15-50): (50-90): (0.5-1), preferably (25-45): (60-80): (0.6-0.8). In the present invention, the melt index of the low-density polyethylene used in the outer layer is preferably 1.5-2.5 g / 10min, more preferably 1.8-2.2 g / 10min, and the density is preferably 0.920-0.930 g / cm 3 , more preferably 0.922 to 0.925 g / cm 3 In a specific embodiment of the present invention, the grade of the low-density polyethylene is preferably 2426H, specifically a product produced by Maoming Petrochemical (Sinopec Group Maoming Petrochemical Co., Ltd.), with a melt index of 2.0 g / min and a density of 0.924 g / cm 3 The present invention adopts low-density polyethylene that meets the above indicators and has the characteristics of good processing.

[0037] In the present invention, the melt index of the linear low-density polyethylene used in the outer layer is preferably 1.5 to 2.5 g / 10 min, more preferably 1.8 to 2.2 g / 10 min, and the density is preferably 0.912 to 0.925 g / cm 3 , more preferably 0.915 to 0.920 g / cm 3 In a specific embodiment of the present invention, the grade of the linear low-density polyethylene is preferably KP7042, specifically a product produced by CNOOC Shell, with a melt index of 2.0 g / 10 min and a density of 0.918 g / cm 3 , with good composite strength and easy processing performance.

[0038] In the present invention, the melt index of the first processing aid is preferably 1.8 to 3.0 g / 10 min, more preferably 2.1 to 2.4 g / 10 min, and the density is preferably 0.925 to 0.940 g / cm 3 , more preferably 0.931 to 0.933 g / cm 3 In a specific embodiment of the present invention, the brand of the first processing aid is preferably PA0895LD, specifically a product produced by Konstanp (Suzhou Konstanp Engineering Plastics Co., Ltd.), with a melt index of 2.3 g / min and a density of 0.932 g / cm 3 The present invention adopts the above-mentioned processing aid, which can effectively reduce the die mouth material accumulation, reduce the crystal point, reduce the extrusion pressure, and improve the production efficiency.

[0039] In the present invention, the raw materials for preparing the middle layer include medium-density polyethylene, metallocene low-density polyethylene and a second processing aid, and the mass ratio of the medium-density polyethylene, metallocene low-density polyethylene and the second processing aid is (30-85): (20-45): (0.5-1), preferably (40-65): (25-35): (0.6-0.8). In the present invention, the melt index of the medium-density polyethylene used in the middle layer is preferably 0.5-1.5 g / 10 min, more preferably 0.8-1.2 g / 10 min, and the density is preferably 0.925-0.935 g / cm 3 , more preferably 0.927 to 0.932 g / cm 3 In a specific embodiment of the present invention, the grade of the medium density polyethylene is preferably 2042G, specifically a product produced by Dow Chemical, with a melt index of 1.0g / 10min and a density of 0.930g / cm 3 , with the characteristics of good stiffness and easy processing.

[0040] In the present invention, the melt index of the metallocene low-density polyethylene used in the middle layer is preferably 0.5 to 1.5 g / 10 min, more preferably 0.8 to 1.2 g / 10 min, and the density is preferably 0.912 to 0.925 g / cm 3 , more preferably 0.915 to 0.920 g / cm 3 In a specific embodiment of the present invention, the grade of the metallocene low-density polyethylene used in the middle layer is preferably 1018BA, specifically a product produced by LG Chemical, with a melt index of 1.0 g / 10 min and a density of 0.918 g / cm 3 , with the characteristics of high strength and easy processing.

[0041] In the present invention, the melt index, density and type of the second processing aid are preferably consistent with those of the first processing aid, which will not be described in detail herein.

[0042] In the present invention, the raw materials for preparing the inner layer include low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and a third processing aid; the mass ratio of the low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and the third processing aid is (20-60):(10-40):(10-25):(0.5-1), preferably (30-50):(20-30):(15-20):(0.6-0.8). In the present invention, the melt index, density and type of the low-density polyethylene used in the inner layer are preferably consistent with those of the outer layer, which will not be repeated here; the melt index, density and type of the low-density polyethylene used in the inner layer are preferably consistent with those of the outer layer, which will not be repeated here; the melt index, density and type of the third processing aid are preferably consistent with those of the first processing aid, which will not be repeated here; the melt index of the metallocene low-density polyethylene used in the inner layer is preferably 0.5-1.5g / 10min, more preferably 0.8-1.0g / 10min, and the density is preferably 0.912-0.925g / cm 3 , more preferably 0.915 to 0.918 g / cm 3 In a specific embodiment of the present invention, the grade of the metallocene low-density polyethylene used in the inner layer is preferably 5401G, specifically a product produced by Dow Chemical, with a melt index of 1.0 g / 10 min and a density of 0.918 g / cm 3 , with the characteristics of high strength and easy processing.

[0043] In the present invention, the melt index of the polyolefin-modified α-olefin copolymer is preferably 0.5 to 1.5 g / 10 min, more preferably 0.8 to 1.1 g / 10 min, and the density is preferably 0.905 to 0.915 g / cm 3 , more preferably 0.908 to 0.912 g / cm 3 In a specific embodiment of the present invention, the grade of the polyolefin-modified α-olefin copolymer is preferably BL3100, specifically a product produced by Mitsui Chemicals, with a melt index of 1.0 g / 10 min and a density of 0.910 g / cm 3 .

[0044] In the present invention, the thickness ratio of the outer layer, the middle layer and the inner layer is preferably 1:(1.2-4):1, specifically preferably 3:4:3, 1:2:1, 1:3:1 or 1:4:1; the total thickness of the PE light sealing film is preferably 30-160 μm, more preferably 50-120 μm.

[0045] The present invention also provides a method for preparing the PE light sealing film described in the above scheme, comprising the following steps:

[0046] The raw materials for the outer layer, the middle layer and the inner layer are co-extruded to obtain the PE light sealing film.

[0047] In the present invention, the three-layer co-extrusion process specifically includes: feeding the raw materials for the outer layer, the middle layer and the inner layer into the outer layer, the middle layer and the inner layer extruders respectively for melting and plasticization, conveying the obtained glue solution to the die head, extruding and blowing the film to obtain a film bubble, and cooling the film bubble with air, passing through a stabilizing ring and a herringbone arrangement to the upper traction rotation, flattening the film bubble and passing through a guide roller to enter a corona treatment device for corona treatment, and then trimming the edge, and then passing through a lower traction clamping roller to enter a front and rear winding device for front and rear winding, so as to obtain a PE light sealing film.

[0048] In the present invention, the outer layer extruder, the middle layer extruder and the inner layer extruder are preferably provided with 5 heating zones, which are recorded as zones 1 to 5 in the order in which the raw materials pass through; the die head is provided with 4 heating zones, which are recorded as zones 1 to 4 in the order in which the raw materials pass through.

[0049] In the present invention, the extrusion temperatures of the outer layer extruder, the middle layer extruder, the inner layer extruder and each zone of the die head are shown in Table 1:

[0050] Table 1 Extrusion temperatures of the outer layer, middle layer, inner layer extruders and each zone of the die head

[0051] Temperature(℃) Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Outer Layer 160±5℃ 170±5℃ 173±5℃ 165±5℃ 162±5℃ Middle level 170±5℃ 175±5℃ 179±5℃ 172±5℃ 165±5℃ Inner Layer 165±5℃ 170±5℃ 175±5℃ 165±5℃ 160±5℃ Die head 180±5℃ 185±5℃ 185±5℃ 180±5℃

[0052] In the present invention, the extrusion pressure of the outer layer extruder is preferably 205-280 bar, preferably 243-260 bar, the extrusion pressure of the middle layer extruder is preferably 245-460 bar, preferably 385-420 bar, and the extrusion pressure of the inner layer extruder is preferably 220-435 bar, preferably 300-335 bar.

[0053] The present invention also provides a light-sealing packaging bag composite film, comprising a heat-sealing layer, a barrier layer and a printing layer stacked in sequence, and adjacent layers are composited by an adhesive; the heat-sealing layer is the PE light-sealing film described in the above scheme or the PE light-sealing film prepared by the preparation method described in the above scheme.

[0054] In the present invention, the printing layer is the outer layer, and the heat-sealing layer is the inner layer; the printing layer is preferably a polyester film (PET); the barrier layer is preferably an aluminum film (Al) or a polyester aluminized film (VMPET); in the present invention, the polyester film, the aluminum film and the polyester aluminized film are all commercially available products; the polyester aluminized film is specifically a layer of aluminum plated on the surface of the polyester film by vacuum aluminizing technology. In the present invention, the thickness of the polyester film and the polyester aluminum-plated film is preferably 12 μm; the thickness of the aluminum film is preferably 7 μm.

[0055] The present invention also provides a method for preparing the composite film of the light-seal packaging bag described in the above scheme, comprising the following steps:

[0056] (1) compounding the printing layer and the barrier layer with a solvent-free adhesive and performing a first curing to obtain a printing layer / barrier layer composite film;

[0057] (2) Compounding the printed layer / barrier layer composite film and the PE light-sealing film with a solvent-free adhesive and then subjecting the composite film to a second curing step to obtain a light-sealing packaging composite film.

[0058] The present invention uses a solvent-free adhesive to compound the printing layer and the barrier layer and then performs a first aging to obtain a printing layer / barrier layer composite film. In the present invention, the printing layer is preferably printed according to demand before bonding with the barrier layer. The present invention has no special requirements for the printing method, and the gravure printing process familiar to those skilled in the art can be used. In the present invention, the solvent-free adhesive is preferably the new solvent-free polyurethane composite adhesive YH752A / YH752B of Beijing Gaomeng New Materials Co., Ltd., with a solid content of 100%; the present invention has no special requirements for the specific process of compounding in steps (1) to (2), and the solvent-free compounding process familiar to those skilled in the art can be used. In a specific embodiment of the present invention, the adhesive is specifically applied on the printing layer, and then the barrier layer is compounded. In a specific embodiment of the present invention, the operating parameters of the compounding process in step (1) preferably include: the mixing temperature is preferably 40°C, specifically the temperature of component A and component B are both controlled to 40°C; the coating temperature is preferably 40°C, specifically the temperature of each steel roller in the coating and gluing system is set to 40°C; the glue ratio: the mass ratio of component A to component B is 100:70; the glue amount is preferably 1.8-2.3 g / m 2 , more preferably 2.2 g / m 2 .

[0059] In the present invention, the temperature of the first aging is preferably 50° C., and the time is preferably 2 to 3 days.

[0060] After obtaining the printed layer / barrier layer composite film, the present invention uses a solvent-free adhesive to composite the printed layer / barrier layer composite film and the PE light-sealing film and then performs a second aging to obtain a light-sealing packaging composite film. In the present invention, the solvent-free adhesive is preferably the new solvent-free polyurethane composite adhesive YH752A / YH752B of Beijing Gaomeng New Materials Co., Ltd., with a solid content of 100%; the operating parameters of the composite process in step (2) preferably include: the mixing temperature is preferably 40°C, specifically, the temperature of component A and component B are both controlled to 40°C; the coating temperature is preferably 40°C, specifically, the temperature of each steel roller in the coating and gluing system is set to 40°C; glue ratio: the mass ratio of component A and component B is 100:60; the glue amount is preferably 1.3-1.8g / m 2 , more preferably 1.6 g / m 2In a specific embodiment of the present invention, when the PE film is bonded, the outer layer is in contact with the barrier layer.

[0061] In the present invention, the second aging temperature is preferably 40° C., and the time is preferably 2 to 3 days.

[0062] After the second aging is completed, the light-sealing packaging composite film of the present invention is obtained. The light-sealing packaging composite film of the present invention can be used to prepare double-cavity or multi-cavity light-sealing packaging bags, and can be prepared according to the bag-making process familiar to those skilled in the art, specifically: the aging light-sealing packaging composite film is cut and then bag-made; the process parameters of bag-making are preferably as follows: the horizontal sealing parameters include: temperature of 170-185°C, heat sealing pressure of 3.5-5kg, time of 0.5-1 second, and sealing line width of 8±1.5mm; the vertical sealing parameters include: temperature of 170-185°C, heat sealing pressure of 3.5-5kg, time of 0.5-1 second, and sealing line width of 8±1.5mm; the dividing line parameters include: temperature of 160-175°C, pressure of 1.5-3kg, time of 0.3-0.5 seconds, and sealing line width of 3±0.5mm.

[0063] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but this should not be construed as limiting the protection scope of the present invention.

[0064] Example 1

[0065] 1. Preparation of PE light sealing film: The PE light sealing film prepared in this embodiment has a three-layer structure, namely an outer layer, a middle layer and an inner layer, wherein the weight percentage of the outer layer is 30%, the weight percentage of the middle inner layer is 40%, and the weight percentage of the inner layer is 30%; the raw materials and proportions used in each layer are as follows:

[0066] Outer layer: low-density polyethylene 2426H, linear low-density polyethylene KP7042, processing aid PA0895LD, the mass ratio of low-density polyethylene, linear low-density polyethylene and processing aid is 15:88:0.5;

[0067] Middle layer: medium density polyethylene 2042G, metallocene low density polyethylene 1018BA, processing aid PA0895LD, the mass ratio of medium density polyethylene, metallocene low density polyethylene and processing aid is 33:45:0.6;

[0068] Inner layer: low-density polyethylene 2426H, metallocene low-density polyethylene 5401G, polyolefin-modified α-olefin copolymer BL3100, processing aid PA0895LD, the mass ratio of low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and processing aid is 55:13:10:0.5;

[0069] The preparation method is as follows:

[0070] The raw materials of the outer layer, middle layer and inner layer are mixed in proportion by an automatic batching system and sent to the outer layer, middle layer and inner layer extruders. The raw materials of the outer layer, middle layer and inner layer are melted and plasticized and then sent to the die head for extrusion and film blowing. Then, they are cooled by air cooling, and rotated by a stabilizing ring and a herringbone arrangement. The cylinder is flattened and sent to the corona treatment device through a guide roller for corona treatment. Then, the trimmed edges are sent to the front and rear winding device through the lower traction clamp roller for front and rear winding, and a PE light sealing film with a thickness of 60 μm can be obtained. The temperature and pressure of the extruder and the die head are shown in Table 2:

[0071] Table 2 Extruder temperature and pressure

[0072] condition Zone 1 / ℃ Zone 2 / ℃ Zone 3 / ℃ Zone 4 / ℃ Zone 5 / ℃ Pressure / bar Outer Layer 160 170 173 165 162 243 Middle level 170 175 179 172 165 385 Inner Layer 165 170 175 165 160 335 Die head 180 185 185 180

[0073] 2. Preparation of light-sealing packaging composite film: The light-sealing packaging composite film is prepared by using the PE light-sealing film prepared above. The outer layer of the composite film is a printing layer, which adopts DuPont Hongji 12μm printed PET, the middle layer is a barrier layer, which adopts Shancailong 12μm polyester aluminum-plated film, and the inner layer is the PE light-sealing film prepared above; the printing layer polyester film adopts gravure printing according to the needs, and conventional printing process is selected;

[0074] The printed PET polyester film and the polyester aluminum-plated film are compounded by a solvent-free compounding process. The glue used is the new solvent-free polyurethane composite adhesive YH752A / YH752B of Beijing Gaomeng New Materials Co., Ltd., with a solid content of 100%; the operating parameters of the compounding process are: mixing temperature: both A and B components are set to 40°C; coating temperature: each steel roller of the coating and gluing system is set to 40 degrees; glue ratio A / B = 100 / 70; glue amount is 2.2g / m 2 After compounding, the composite film was placed in a 50°C curing room for 2 days to obtain a PET / VMPET composite film;

[0075] The cured PET / VMPET composite film and PE light sealing film were compounded by solvent-free compounding process. The glue used was the new solvent-free polyurethane composite adhesive YH752A / YH752B of Beijing Gaomeng New Materials Co., Ltd. with a solid content of 100%. The operating parameters of the compounding process were as follows: mixing temperature: both A and B components were set to 40°C; coating temperature: each steel roller of the coating and gluing system was set to 40°C; glue ratio A / B = 100 / 60; glue amount was 1.6g / m 2 After compounding, it was placed in a curing room at 45°C for 2 days to obtain a light-sealing packaging composite film.

[0076] 3. Use the above-mentioned light-sealing packaging composite film to prepare double-cavity packaging bags: cut the matured light-sealing packaging composite film into bags; the bag making process is as follows: transverse sealing temperature: 180°C, heat sealing pressure 4.5kg, time 0.7 seconds, sealing line width 8.5mm; longitudinal sealing temperature: 180°C, heat sealing pressure 4.5kg, time 0.7 seconds, sealing line width 8.5mm; dividing line temperature: 163°C, pressure 2kg, time 0.4 seconds, sealing line width 3mm.

[0077] Example 2

[0078] The other conditions are the same as those in Example 1, except that: the weight percentage of the outer layer in the PE light sealing film is 25%, the weight percentage of the middle layer is 50%, and the weight percentage of the inner layer is 25%;

[0079] In the outer layer: the mass ratio of low-density polyethylene, linear low-density polyethylene and processing aid is 26:72:0.7;

[0080] In the middle layer: the mass ratio of medium density polyethylene, metallocene low density polyethylene and processing aid is 65:34:0.8;

[0081] In the inner layer: the mass ratio of low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and processing aid is 43:26:18:0.8;

[0082] The preparation method is the same as that of Example 1;

[0083] After the PE light-sealing film is prepared, a light-sealing packaging composite film is prepared according to the method of Example 1, and a double-cavity packaging bag is prepared.

[0084] Example 3

[0085] The other conditions are the same as those in Example 1, except that: the weight percentage of the outer layer in the PE light sealing film is 20%, the weight percentage of the middle layer is 60%, and the weight percentage of the inner layer is 20%;

[0086] In the outer layer: the mass ratio of low-density polyethylene, linear low-density polyethylene and processing aid is 37:51:0.8;

[0087] In the middle layer: the mass ratio of medium density polyethylene, metallocene low density polyethylene and processing aid is 83:22:0.8;

[0088] In the inner layer: the mass ratio of low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and processing aid is 27:40:23:1;

[0089] The preparation method is the same as that of Example 1;

[0090] After the PE light-sealing film is prepared, a light-sealing packaging composite film is prepared according to the method of Example 1, and a double-cavity packaging bag is prepared.

[0091] Comparative Example 1

[0092] The other conditions were the same as those in Example 1, except that the mass ratio of low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and processing aid in the inner layer was changed to 55:13:8:0.5, that is, the amount of polyolefin-modified α-olefin copolymer in the inner layer was reduced.

[0093] The preparation method is the same as that of Example 1;

[0094] After the PE light-sealing film is prepared, a light-sealing packaging composite film is prepared according to the method of Example 1, and a double-cavity packaging bag is prepared.

[0095] Comparative Example 2

[0096] The other conditions were the same as those in Example 3, except that the mass ratio of low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and processing aid in the inner layer was changed to 27:40:28:1, that is, the amount of polyolefin-modified α-olefin copolymer in the inner layer was increased.

[0097] The preparation method is the same as that of Example 1;

[0098] After the PE light-sealing film is prepared, a light-sealing packaging composite film is prepared according to the method of Example 1, and a double-cavity packaging bag is prepared.

[0099] Performance Test:

[0100] The tensile strength and elongation at break of the PE light sealing films prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested, and the heat sealing strength and sealing conditions of the double-cavity packaging bags prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested. The results are shown in Table 3.

[0101] Table 3 Performance test results

[0102]

[0103] According to the data in Table 3, it can be seen that the PE light sealing film provided by the present invention has good mechanical properties, low heat sealing strength, easy to tear the seal, no drawing, and is convenient to use; the amount of the polyolefin-modified α-olefin copolymer in the inner layer of the PE film in Comparative Example 1 is too low, resulting in too high heat sealing strength and difficulty in tearing, while the amount of the polyolefin-modified α-olefin copolymer in the inner layer of the PE film in Comparative Example 2 is too high, resulting in too low heat sealing strength and a problem of weak sealing.

[0104] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A PE light sealing film, characterized in that: Made of three layers of co-extruded blown film: outer layer, middle layer and inner layer; The outer layer is prepared from low-density polyethylene, linear low-density polyethylene and a first processing aid, and the mass ratio of the low-density polyethylene, linear low-density polyethylene and the first processing aid is (15-50):(50-90):(0.5-1); The raw materials for preparing the middle layer are medium-density polyethylene, metallocene low-density polyethylene and a second processing aid, and the mass ratio of the medium-density polyethylene, metallocene low-density polyethylene and the second processing aid is (30-85): (20-45): (0.5-1); The raw materials for preparing the inner layer are low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and a third processing aid; the mass ratio of the low-density polyethylene, metallocene low-density polyethylene, polyolefin-modified α-olefin copolymer and the third processing aid is (20-60):(10-40):(10-25):(0.5-1); the grade of the polyolefin-modified α-olefin copolymer is BL3100; The first processing aid, the second processing aid and the third processing aid are all functional masterbatches prepared from fluoropolymer and polyolefin resin, and the melt index of the first processing aid, the second processing aid and the third processing aid are independently 1.8-3.0 g / 10 min, and the density is independently 0.925-0.940 g / cm 3 .

2. The PE light sealing film according to claim 1, characterized in that: The low-density polyethylene used in the outer layer has a melt index of 1.5-2.5 g / 10 min and a density of 0.920-0.930 g / cm 3 ; The linear low-density polyethylene used in the outer layer has a melt index of 1.5 to 2.5 g / 10 min and a density of 0.912 to 0.925 g / cm 3 .

3. The PE light sealing film according to claim 1, characterized in that: The medium-density polyethylene used in the middle layer has a melt index of 0.5-1.5 g / 10 min and a density of 0.925-0.935 g / cm 3 ; The metallocene low-density polyethylene used in the middle layer has a melt index of 0.5-1.5 g / 10 min and a density of 0.912-0.925 g / cm 3 .

4. The PE light sealing film according to claim 1, characterized in that: The low-density polyethylene used in the inner layer has a melt index of 1.5-2.5 g / 10 min and a density of 0.920-0.930 g / cm 3 ; The metallocene low-density polyethylene used in the inner layer has a melt index of 0.5-1.5 g / 10 min and a density of 0.912-0.925 g / cm 3 ; The polyolefin modified α-olefin copolymer has a melt index of 0.5 to 1.5 g / 10 min and a density of 0.905 to 0.915 g / cm 3 .

5. The PE light sealing film according to claim 1, characterized in that: The thickness ratio of the outer layer, the middle layer and the inner layer is 1:(1.2-4):1; the total thickness of the PE light sealing film is 30-160 μm.

6. The method for preparing the PE light sealing film according to any one of claims 1 to 5, characterized in that: The following steps are involved: The raw materials for the outer layer, the middle layer and the inner layer are co-extruded to obtain the PE light sealing film.

7. A composite film for light-sealed packaging bags, characterized in that: It comprises a heat-sealing layer, a barrier layer and a printing layer which are stacked in sequence, and adjacent layers are compounded by an adhesive; the heat-sealing layer is the PE light-sealing film according to any one of claims 1 to 5 or the PE light-sealing film prepared by the preparation method according to claim 6.

8. The light-seal packaging bag composite film according to claim 7, characterized in that: The printing layer is a polyester film; the barrier layer is an aluminum film or a polyester aluminum-plated film.

9. The method for preparing the composite film for light-sealed packaging bags according to claim 7 or 8, characterized in that: The following steps are involved: (1) compounding the printing layer and the barrier layer with a solvent-free adhesive and performing a first curing to obtain a printing layer / barrier layer composite film; (2) Compounding the printed layer / barrier layer composite film and the PE light-sealing film with a solvent-free adhesive and then subjecting the composite film to a second curing step to obtain a light-sealing packaging composite film.

10. The preparation method according to claim 9, characterized in that: The amount of the solvent-free adhesive applied in step (1) is 1.8 to 2.3 g / m 2 In step (2), the amount of the solvent-free adhesive applied is 1.3 to 1.8 g / m 2 ; The temperature of the first ripening is 50±5°C, and the time is 2 to 3 days; the temperature of the second ripening is 40±5°C, and the time is 2 to 3 days.

Images