PE gasket film, composite film, preparation method and application

Abstract

The invention relates to the technical field of composite membranes, and provides a PE gasket membrane, a composite membrane, a preparation method and application. The PE gasket film comprises an outer layer, a middle layer and an inner layer, the outer layer is prepared from low-density polyethylene, metallocene low-density polyethylene and a processing aid, and the middle layer is prepared from low-density polyethylene, high-density polyethylene and a processing aid. The preparation raw materials of the inner layer comprise low-density polyethylene, metallocene low-density polyethylene and a processing aid. The PE gasket film provided by the invention has few crystal point impurities, is safer and more sanitary, can avoid deterioration of contents caused by heat-sealing air leakage, is easy to die-cut, does not have a wiredrawing phenomenon during slicing, and can meet the use requirements of high-end bottled beverages, medicine bottles and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of composite films, and particularly relates to a PE gasket film, a composite film, a preparation method and an application thereof. Background Art

[0002] A bottle cap gasket is a component used inside a bottle cap to play roles such as sealing and buffering. The gasket film is an important component of the bottle cap gasket. Currently, the commonly used gasket film is a PE film, which has good heat sealability, flexibility and certain barrier properties, and is often used as a heat seal layer.

[0003] However, currently, there are many crystal point impurities in the gasket film. After preparing the gasket, it is easy to cause air leakage at the seal, reducing the shelf life. There are also some gasket films that are not easy to die cut, resulting in the gasket drawing and falling into the bottle during capping, posing a safety hazard and not meeting the usage requirements of high-end bottled beverages, medicine bottles, etc. Summary of the Invention

[0004] In view of this, the present invention provides a PE gasket film, a composite film, a preparation method and an application thereof. The PE gasket film provided by the present invention has few crystal points and is easy to die cut. When it is used in the gasket, it can avoid heat seal air leakage, and the cut slices do not draw, and can meet the usage requirements of high-end bottled beverages, medicine bottles, etc.

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

[0006] A PE gasket film includes an outer layer, a middle layer and an inner layer which are laminated in sequence;

[0007] By mass, the preparation raw materials of the outer layer include: 30 - 80 parts of low-density polyethylene, 10 - 30 parts of metallocene low-density polyethylene, and 0.3 - 0.8 part of processing aid;

[0008] By mass, the preparation raw materials of the middle layer include: 20 - 70 parts of low-density polyethylene, 10 - 50 parts of high-density polyethylene, and 0.5 - 1 part of processing aid;

[0009] By mass, the preparation raw materials of the inner layer include: 30 - 80 parts of low-density polyethylene, 10 - 30 parts of metallocene low-density polyethylene, and 0.5 - 1 part of processing aid.

[0010] Preferably, the melt index of the low-density polyethylene used in the outer layer, the middle layer and the inner layer is 1.5 - 2.5 g / 10min, and the density is 0.92 - 0.93 g / cm 3 .

[0011] Preferably, the melt index of the metallocene low-density polyethylene used in the outer layer and the inner layer is 1.5 - 2.5 g / 10min, and the density is 0.908 - 0.92 g / cm 3。

[0012] Preferably, the melt index of the high-density polyethylene used in the middle layer is 6-8.5 g / 10 min, and the density is 0.955-0.965 g / cm 3 ; the melt index of the processing aid used in the outer layer, middle layer and inner layer is 1.5-3 g / 10 min, and the density is 0.91-0.925 g / cm 3 。

[0013] Preferably, the grade of the low-density polyethylene used in the outer layer, middle layer and inner layer is 2420H; the grades of the metallocene low-density polyethylene used in the outer layer and inner layer are SP1520 or SP2320; the grade of the high-density polyethylene used in the middle layer is H377C; the grade of the processing aid used in the outer layer, middle layer and inner layer is PA0895LD.

[0014] The present invention also provides a method for preparing the PE gasket film described in the above solution, including the following steps:

[0015] Co-extrude the preparation raw materials of the outer layer, middle layer and inner layer to obtain the PE gasket film.

[0016] The present invention also provides a composite film, including a printing layer, a barrier layer and a heat-sealing layer laminated in sequence; the heat-sealing layer is the PE gasket film described in the above solution or the PE gasket film prepared by the preparation method described in the above solution.

[0017] Preferably, the printing layer is a polyester film; the barrier layer is an aluminum foil.

[0018] The present invention also provides a method for preparing the composite film described in the above solution, including the following steps:

[0019] Compound the printing layer and the barrier layer with an adhesive and carry out the first curing to obtain a printing layer / barrier layer composite film;

[0020] Compound the printing layer / barrier layer composite film and the PE gasket film with an adhesive and carry out the second curing to obtain the composite film.

[0021] The present invention also provides the application of the PE gasket film described in the above solution or the composite film described in the above solution in a bottle cap gasket.

[0022] The present invention provides a PE gasket film, which comprises an outer layer, a middle layer and an inner layer stacked in sequence; by mass parts, the preparation raw materials of the outer layer include: 30-80 parts of low-density polyethylene, 10-30 parts of metallocene low-density polyethylene, and 0.3-0.8 parts of processing aids; by mass parts, the preparation raw materials of the middle layer include: 20-70 parts of low-density polyethylene, 10-50 parts of high-density polyethylene, and 0.5-1 part of processing aids; by mass parts, the preparation raw materials of the inner layer include: 30-80 parts of low-density polyethylene, 10-30 parts of metallocene low-density polyethylene, and 0.5-1 part of processing aids. The present invention controls the types and ratios of the raw materials of the outer layer, the middle layer and the inner layer to obtain a PE gasket film with few crystal point impurities, good die-cutting performance and good mechanical properties; further, the raw materials adopted by the present invention are all raw materials with low crystal points and good die-cutting performance, which can further ensure the characteristics of low crystal points and good die-cutting performance of the PE gasket film. The results of the examples show that the PE gasket film provided by the present invention has few crystal point impurities, is safer and more hygienic, can avoid the deterioration of the contents caused by heat-sealing air leakage, and will not show wire drawing phenomenon during slicing, and can meet the use requirements of high-end bottled beverages, medicine bottles, etc.

[0023] The present invention also provides a composite film, which comprises a printing layer, a barrier layer and a heat-sealing layer stacked in sequence; the heat-sealing layer is the PE gasket film described in the above solution or the PE gasket film prepared by the preparation method described in the above solution. The composite film provided by the present invention has the characteristics of few crystal points, good die-cutting performance, low density and good barrier property, and has broad application prospects in bottle cap gaskets. Detailed Embodiments

[0024] The present invention provides a PE gasket film, which comprises an outer layer, a middle layer and an inner layer stacked in sequence;

[0025] By mass parts, the preparation raw materials of the outer layer include: 30-80 parts of low-density polyethylene, 10-30 parts of metallocene low-density polyethylene, and 0.3-0.8 parts of processing aids;

[0026] By mass parts, the preparation raw materials of the middle layer include: 20-70 parts of low-density polyethylene, 10-50 parts of high-density polyethylene, and 0.5-1 part of processing aids;

[0027] By mass parts, the preparation raw materials of the inner layer include: 30-80 parts of low-density polyethylene, 10-30 parts of metallocene low-density polyethylene, and 0.5-1 part of processing aids.

[0028] Unless otherwise specified, all raw materials adopted by the present invention are commercially available.

[0029] By mass fraction, the raw materials for preparing the outer layer include 30 to 80 parts of low-density polyethylene, specifically 30 parts, 45 parts, 55 parts, 60 parts, 68 parts or 80 parts; the melt index of the low-density polyethylene used in the outer layer is preferably 1.5 to 2.5 g / 10 min, more preferably 2 g / 10 min, and the density is preferably 0.92 to 0.93 g / cm 3 , more preferably 0.924 to 0.925 g / cm 3 ; the grade of the low-density polyethylene is preferably 2420H, and the manufacturers are CNOOC Shell, Lanzhou Petrochemical or Maoming Petrochemical. In the specific embodiments of the present invention, the low-density polyethylene of grade 2420H used comes from CNOOC Shell, with a melt index of 2 g / 10 min and a density of 0.924 g / cm 3 . The low-density polyethylene used in the present invention has the characteristics of few crystal points and good processability.

[0030] Based on the weight fraction of the low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 10 to 30 parts of metallocene low-density polyethylene, specifically 12 parts, 18 parts, 20 parts, 25 parts, 28 parts or 30 parts; the melt index of the metallocene low-density polyethylene used in the outer layer is preferably 1.5 to 2.5 g / 10 min, more preferably 1.9 to 2 g / 10 min, and the density is preferably 0.908 to 0.920 g / cm 3 , more preferably 0.913 to 0.915 g / cm 3 ; the grade of the metallocene low-density polyethylene is preferably SP1520 or SP2320, and the manufacturers are both Mitsui Chemicals; in the specific embodiments of the present invention, the grade of the metallocene low-density polyethylene used is SP1520, with a melt index of 1.9 g / 10 min and a density of 0.913 g / cm 3 . The metallocene low-density polyethylene used in the present invention has the characteristics of few crystal points and high composite fastness.

[0031] Based on the weight fraction of the low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 0.3 to 0.8 parts of processing aids, specifically 0.3 parts, 0.5 parts or 0.8 parts; the melt index of the processing aids is preferably 1.5 to 3 g / 10 min, more preferably 2 to 2.1 g / 10 min, and the density is preferably 0.91 to 0.925 g / cm 3 , more preferably 0.915 to 0.920 g / cm 3 ; in the specific embodiments of the present invention, the grade of the processing aids is preferably PA0895LD, with a melt index of 2.1 g / 10 min and a density of 0.915 g / cm 3, and the manufacturer is Suzhou Konstamp Engineering Plastics Co., Ltd. The processing aids used in the present invention can effectively reduce crystal points, reduce die build-up, lower extrusion pressure, and improve production efficiency.

[0032] By mass, the preparation raw materials of the middle layer include 20-70 parts of low-density polyethylene, specifically 20 parts, 25 parts, 35 parts, 43 parts, 45 parts or 70 parts; the melt index, density and grade of the low-density polyethylene used in the middle layer are preferably the same as those of the outer layer, which will not be elaborated here.

[0033] Based on the weight of the low-density polyethylene used in the middle layer, the preparation raw materials of the middle layer include 10-50 parts of high-density polyethylene, specifically 15 parts, 22 parts, 35 parts, 42 parts, 48 parts or 50 parts; the melt index of the high-density polyethylene is preferably 6-8.5 g / 10 min, more preferably 7.5-8 g / 10 min, and the density is preferably 0.955-0.965 g / cm 3 , more preferably 0.961-0.963 g / cm 3 ; in a specific embodiment of the present invention, the grade of the high-density polyethylene is preferably H377C, its melt index is 7.5 g / 10 min, and the density is 0.961 g / cm 3 , and the manufacturer is SCG of Thailand. The high-density polyethylene used in the present invention has the characteristics of few crystal points, high stiffness, good die-cutting performance and good processability.

[0034] Based on the weight of the low-density polyethylene used in the middle layer, the preparation raw materials of the middle layer include 0.5-1 part of processing aids, specifically 0.5 part, 0.8 part or 1 part; the melt index, density and grade of the processing aids used in the middle layer are preferably the same as those of the outer layer, which will not be elaborated here.

[0035] By mass, the preparation raw materials of the inner layer include 30-80 parts of low-density polyethylene, specifically 30 parts, 45 parts, 55 parts, 70 parts, 72 parts or 80 parts; the melt index, density and grade of the low-density polyethylene used in the inner layer are preferably the same as those of the outer layer, which will not be elaborated here.

[0036] Based on the weight of the low-density polyethylene used in the inner layer, the preparation raw materials of the inner layer include 10-30 parts of metallocene low-density polyethylene, specifically 12 parts, 15 parts, 18 parts, 20 parts, 25 parts or 28 parts; the melt index, density and grade of the metallocene low-density polyethylene used in the inner layer are preferably the same as those of the outer layer, which will not be elaborated here.

[0037] Based on the parts by weight of the low-density polyethylene used in the inner layer, the preparation raw materials of the inner layer include 0.5 to 1 part of processing aids, specifically 0.5 part, 0.8 part or 1 part; the melt index, density and grade of the processing aids used in the middle layer are preferably the same as those of the outer layer, which will not be elaborated here.

[0038] In the present invention, calculated based on the total mass of the raw materials used in the outer layer, middle layer and inner layer being 100%, the mass fraction of the outer layer raw materials is preferably 20 to 30%, the mass fraction of the middle layer is preferably 45 to 55%, and the mass fraction of the inner layer is preferably 25 to 30%.

[0039] In the present invention, the thickness of the PE gasket film is preferably 150 to 190 μm, more preferably 170 μm, and the thickness ratio of the outer layer, middle layer and inner layer is preferably 1 to 3:2 to 4:1 to 3, specifically 3:4:3, 1:2:1, 1:3:1 or 1:4:1.

[0040] In the present invention, the longitudinal tensile strength of the PE gasket film is preferably 22 to 23.5 MPa, the transverse tensile strength is preferably 20 to 21.5 MPa, the longitudinal elongation rate is preferably 410% to 435%, the transverse tensile strength is preferably 535% to 555%, the longitudinal elastic modulus is preferably 330 to 350%, the transverse elastic modulus is preferably 335 to 365 MPa, the wetting tension is preferably 40 to 50 mN / 15 mm, more preferably 46 mN / 15 mm; the number of crystal points larger than 0.6 mm is 0 per 1000 m 2 , the number of crystal points larger than or equal to 0.3 mm and less than 0.6 mm is less than 20 per 1000 m 2 , the number of crystal points larger than or equal to 0.2 mm and less than 0.3 mm is less than 40 per 1000 m 2 .

[0041] The present invention also provides a method for preparing the PE gasket film described in the above solution, including the following steps:

[0042] Co-extrude the preparation raw materials of the outer layer, middle layer and inner layer to obtain the PE gasket film.

[0043] In the present invention, the process of the three-layer co-extrusion specifically includes: feeding the preparation raw materials of the outer layer, middle layer and inner layer into the outer layer, middle layer and inner layer extruders respectively for melting and plasticizing, conveying the obtained glue solution to the die head, extruding and blowing to obtain a film bubble, cooling the film bubble by air cooling, then passing it through a stabilizing ring, a chevron arrangement to the upper traction and rotation, flattening the film bubble and then measuring the thickness by guiding roller traction, then performing corona treatment and edge trimming, and then entering the front and rear winding devices through the lower traction pinch rollers for front and rear winding to obtain the PE gasket film.

[0044] In the present invention, the outer layer extruder, the middle layer extruder, and the inner layer extruder are all preferably provided with 5 heating zones, which are sequentially denoted as Zone 1 to Zone 5 in the order of raw material passing; the die head is provided with 4 heating zones, which are sequentially denoted as Zone 1 to Zone 4 in the order of raw material passing.

[0045] In the present invention, the temperature of Zone 1 of the outer layer extruder is preferably 160 - 175 °C, more preferably 165 - 170 °C; the temperature of Zone 2 is preferably 165 - 180 °C, more preferably 170 - 175 °C; the temperature of Zone 3 is preferably 165 - 180 °C, more preferably 170 - 175 °C; the temperature of Zone 4 is preferably 160 - 170 °C, more preferably 165 °C; the temperature of Zone 5 is preferably 155 - 165 °C, more preferably 160 °C; the temperature of Zone 1 of the middle layer extruder is preferably 160 - 180 °C, more preferably 165 - 175 °C; the temperature of Zone 2 is preferably 165 - 185 °C, more preferably 170 - 180 °C; the temperature of Zone 3 is preferably 160 - 180 °C, more preferably 165 - 175 °C; the temperature of Zone 4 is preferably 157 - 175 °C, more preferably 162 - 170 °C; the temperature of Zone 5 is preferably 155 - 170 °C, more preferably 160 - 165 °C; the temperature of Zone 1 of the inner layer extruder is preferably 165 - 180 °C, more preferably 170 - 175 °C; the temperature of Zone 2 is preferably 173 - 183 °C, more preferably 175 - 178 °C; the temperature of Zone 3 is preferably 167 - 177 °C, more preferably 170 - 172 °C; the temperature of Zone 4 is preferably 160 - 175 °C, more preferably 163 - 170 °C; the temperature of Zone 5 is preferably 160 - 170 °C, more preferably 165 °C.

[0046] In the present invention, the die head is preferably provided with 4 heating zones, which are sequentially denoted as Zone 1 to Zone 4 in the order of raw material passing; the temperature of Zone 1 of the die head is preferably 180 - 190 °C, more preferably 180 - 185 °C; the temperature of Zone 2 is preferably 185 - 195 °C, more preferably 185 - 190 °C; the temperature of Zone 3 is preferably 180 - 190 °C, more preferably 185 - 188 °C; the temperature of Zone 4 is preferably 177 - 187 °C, more preferably 182 °C.

[0047] In the present invention, the extrusion pressure of the outer layer extruder is preferably 205 - 265 bar, more preferably 208 - 245 bar; the extrusion pressure of the middle layer extruder is preferably 280 - 345 bar, more preferably 320 - 345 bar; the extrusion pressure of the inner layer extruder is preferably 255 - 325 bar, more preferably 265 - 295 bar.

[0048] In the present invention, the PE gasket film is preferably produced in a class 10,000 dust-free workshop.

[0049] The present invention also provides a composite film, which comprises a printing layer, a barrier layer and a heat-sealing layer laminated in sequence; the heat-sealing layer is the PE gasket film described in the above solution or the PE gasket film prepared by the preparation method described in the above solution.

[0050] In the present invention, the printing layer is preferably a polyester (PET) film; the barrier layer is preferably an aluminum foil.

[0051] In the present invention, the thickness of the polyester film is preferably 12 μm, and the thickness of the aluminum foil is preferably 15-40 μm, more preferably 25 μm.

[0052] The present invention also provides a preparation method of the composite film described in the above solution, which comprises the following steps:

[0053] The printing layer and the barrier layer are compounded with an adhesive and then subjected to the first aging to obtain a printing layer / barrier layer composite film;

[0054] The printing layer / barrier layer composite film and the PE gasket film are compounded with an adhesive and then subjected to the second aging to obtain the composite film.

[0055] In the present invention, the printing layer and the barrier layer are compounded with an adhesive (denoted as the first compounding) and then subjected to the first aging to obtain a printing layer / barrier layer composite film. In the present invention, before the printing layer is compounded with the barrier layer, it is preferably printed according to requirements first. The present invention has no special requirements for the printing method, and the well-known gravure printing process in the art can be adopted. In the present invention, the first compounding is preferably dry compounding, and the adhesive used in the first compounding is preferably a dry compounding glue with low solvent residue. Specifically, the two-component aluminum foil glue YH3066 / YH3066B of Beijing GaoMeng New Materials Co., Ltd. can be used; when in use, YH3066, YH3066B and ethyl acetate are mixed, and the mass ratio of YH3066, YH3066B and ethyl acetate is preferably 10:1:10.8; the coating amount of the first compounding is preferably 3.0-3.8 g / m 2 ; the temperature of the first aging is preferably 50±5°C, and the time is preferably 72 h.

[0056] After obtaining the printed layer / barrier layer composite film, the present invention composites the printed layer / barrier layer composite film and the PE gasket film with an adhesive (denoted as the second composite) and then performs a second curing to obtain the composite film. In the present invention, the adhesive used in the second composite is preferably a solvent-free adhesive. Specifically, a commercially available two-component solvent-free polyurethane composite adhesive SF10M (A + B) can be used. When in use, SF10MA and SF10MB are mixed, and the mass ratio of SF10MA to SF10MB is preferably 100:50. The operating conditions of the second composite preferably include: the mixing temperature: SF10MA: 40 °C, SF10MB: 35 °C (i.e., heating SF10MA to 40 °C, heating SF10MB to 35 °C, and then mixing the two); the coating temperature is 42 °C, specifically, the temperature of each steel roller of the coating and gluing system is controlled at 42 °C; the amount of glue applied is 1.5 - 2.5 g / m 2 .

[0057] In the present invention, the temperature of the second curing is preferably 50 ± 5 °C, and the time is preferably 72 h. After the second curing is completed, it is preferably to place the obtained composite film at room temperature for 12 h and then slit it.

[0058] The present invention also provides the application of the PE gasket film or the composite film described in the above scheme in the bottle cap gasket; the PE gasket film or composite film provided by the present invention can be specifically used in the bottle cap gaskets of packaging bottles for fruit juices, wines, dairy products, water, liquid foods, health products, medicines, etc. The present invention has no special requirements for the application, and those well-known to those skilled in the art can be adopted.

[0059] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0060] In the following examples and comparative examples, the sources and indexes of the raw materials used are shown in Table 1.

[0061] Table 1 Sources and indexes of raw materials

[0062]

[0063] Example 1

[0064] 1. Preparation of PE gasket film

[0065] The PE gasket film in this example has a three-layer structure, namely an outer layer, a middle layer and an inner layer. The weight percentages of the raw materials of each layer are: 20% for the outer layer, 55% for the middle layer, and 25% for the inner layer.

[0066] By mass fraction, the preparation raw materials for each layer are as follows: Outer layer: Low-density polyethylene 2420H: 80 parts, Metallocene low-density polyethylene SP1520: 12 parts, Processing aid PA0895LD: 0.8 part;

[0067] Middle layer: Low-density polyethylene 2420H: 25 parts, High-density polyethylene H377C: 50 parts, Processing aid PA0895LD: 0.5 part;

[0068] Inner layer: Low-density polyethylene 2420H: 80 parts, Metallocene low-density polyethylene SP1520: 12 parts, Processing aid PA0895LD: 0.8 part.

[0069] The preparation method of the PE gasket film is as follows: After mixing the raw materials of the outer layer, middle layer, and inner layer in proportion through an automatic batching system, they are sent into the outer layer, middle layer, and inner layer extruders. Under the push of the screw, the raw materials are heated by the barrel to the molten state. At the same time, the shear force of the screw promotes the full mixing and plasticization of the raw materials. The molten and plasticized raw materials are sent into the die head, and a tubular film blank is formed through the annular die head. Compressed air is introduced to blow it into a tubular film bubble, and then it is cooled by air cooling to fix its shape and size. It passes through the stabilizing ring and the herringbone arrangement to be flattened by the upper traction rotation and is pulled by the guide roller. The on-line thickness gauge monitors the thickness in real time, and the automatic air ring automatically adjusts the parameters to control the thickness; then it enters the corona treatment device for corona treatment, is divided into sides and enters the front and rear winding devices through the lower traction pinch rollers for front and rear winding, and a 170-μm PE gasket film can be obtained. Among them, the temperatures and pressures of the outer layer, middle layer, and inner layer extruders, as well as the temperature of the die head, are shown in Table 2.

[0070] Table 2 Temperatures and pressures of the extruders and temperature of the die head

[0071] Temperature Zone 1 / °C Zone 2 / °C Zone 3 / °C Zone 4 / °C Zone 5 / °C Pressure / bar Outer layer 165 170 175 165 160 208 Middle layer 175 180 175 170 165 345 Inner layer 170 175 170 163 160 265 Die head 185 190 185 182 / /

[0072] 2. Preparation of the composite film

[0073] The composite film of this embodiment is composed of a polyester film (printing layer), an aluminum foil (barrier layer), and a PE gasket film (heat-sealing layer) laminated in sequence.

[0074] Among them, the polyester film (PET) used is purchased from Anhui Guofeng Plastics Co., Ltd. and has a thickness of 12 μm; the aluminum foil used is purchased from Shanghai Shenhuo Aluminum Foil Co., Ltd. and has a thickness of 25 μm.

[0075] The preparation method of the composite film is as follows: After the printing layer polyester film is gravure-printed according to requirements, it is compounded with the aluminum foil by the dry compounding process. The glue selected is the low-solvent-residue dry compounding glue of YH8950 / YH8950B from Beijing GaoMeng New Materials Co., Ltd., and the weight ratio is YH8950:YH8950B:Ethyl acetate = 10:1:10.8, and the coating amount is 3.5 g / m2 , after compounding, it is placed in a curing room at 50°C ± 5°C for 72 hours to obtain a PET / AL composite film.

[0076] The cured PET / AL composite film is compounded with the PE gasket film prepared in the previous step using a solvent-free adhesive. The adhesive is a two-component solvent-free polyurethane composite adhesive SF10M (A + B), and the glue ratio of SF10MA / SF10MB is 100:50 (mass ratio). The mixing temperature: SF10MA: 40°C, SF10MB: 35°C; the steel rollers of the coating and gluing system are set at 42°C, and the glue application amount is 2 g / m 2 ; after compounding, it is placed in a curing room at 50°C ± 5°C for 72 hours, taken out, placed at room temperature for 12 hours, and then slit.

[0077] Example 2

[0078] 1. Preparation of PE gasket film

[0079] The PE gasket film in this example is a three-layer structure, namely an outer layer, a middle layer, and an inner layer. The weight percentages of the raw materials for each layer are: 25% for the outer layer, 45% for the middle layer, and 30% for the inner layer.

[0080] In terms of parts by mass, the preparation raw materials for each layer are as follows: Outer layer: 68 parts of low-density polyethylene 2420H, 20 parts of metallocene low-density polyethylene SP1520, 0.8 part of processing aid PA0895LD;

[0081] Middle layer: 70 parts of low-density polyethylene 2420H, 15 parts of high-density polyethylene H377C, 0.5 part of processing aid PA0895LD;

[0082] Inner layer: 68 parts of low-density polyethylene 2420H, 20 parts of metallocene low-density polyethylene 1520, 0.8 part of processing aid PA0895LD.

[0083] The preparation method is the same as that in Example 1.

[0084] 2. Using the PE gasket film prepared in Example 2 to prepare a composite film, the preparation method is the same as that in Example 1.

[0085] Example 3

[0086] 1. Preparation of PE gasket film

[0087] The PE gasket film in this example is a three-layer structure, namely an outer layer, a middle layer, and an inner layer. The weight percentages of the raw materials for each layer are: 30% for the outer layer, 40% for the middle layer, and 30% for the inner layer.

[0088] In parts by mass, the raw materials for preparing each layer are as follows: Outer layer: Low-density polyethylene 2420H: 30 parts, Metallocene low-density polyethylene SP1520: 28 parts, Processing aid PA0895LD: 0.8 part;

[0089] Middle layer: Low-density polyethylene 2420H: 35 parts, High-density polyethylene H377C: 22 parts, Processing aid PA0895LD: 0.5 part;

[0090] Inner layer: Low-density polyethylene 2420H: 30 parts, Metallocene low-density polyethylene 1520: 28 parts, Processing aid PA0895LD: 0.8 part.

[0091] The preparation method is the same as that of Example 1.

[0092] 2. Prepare a composite film using the PE gasket film prepared in Example 3, and the preparation method is the same as that of Example 1.

[0093] Example 4

[0094] 1. Preparation of PE gasket film

[0095] The PE gasket film of this example has a three-layer structure, namely an outer layer, a middle layer and an inner layer. The weight percentages of the raw materials for each layer are: outer layer 25%, middle layer 50%, and inner layer 25%.

[0096] In parts by mass, the raw materials for preparing each layer are as follows: Outer layer: Low-density polyethylene 2420H: 45 parts, Metallocene low-density polyethylene SP1520: 25 parts, Processing aid PA0895LD: 0.8 part;

[0097] Middle layer: Low-density polyethylene 2420H: 58 parts, High-density polyethylene H377C: 42 parts, Processing aid PA0895LD: 0.5 part;

[0098] Inner layer: Low-density polyethylene 2420H: 45 parts, Metallocene low-density polyethylene 1520: 25 parts, Processing aid PA0895LD: 0.8 part.

[0099] The preparation method is the same as that of Example 1.

[0100] 2. Prepare a composite film using the PE gasket film prepared in Example 4, and the preparation method is the same as that of Example 1.

[0101] Example 5

[0102] 1. Preparation of PE gasket film

[0103] The PE gasket film of this example has a three-layer structure, namely an outer layer, a middle layer and an inner layer. The weight percentages of the raw materials for each layer are: outer layer 20%, middle layer 60%, and inner layer 20%.

[0104] In parts by mass, the preparation raw materials of each layer are as follows: Outer layer: Low-density polyethylene 2420H: 55 parts, Metallocene low-density polyethylene SP1520: 18 parts, Processing aid PA0895LD: 0.8 part;

[0105] Middle layer: Low-density polyethylene 2420H: 43 parts, High-density polyethylene H377C: 35 parts, Processing aid PA0895LD: 0.5 part;

[0106] Inner layer: Low-density polyethylene 2420H: 55 parts, Metallocene low-density polyethylene 1520: 18 parts, Processing aid PA0895LD: 0.8 part.

[0107] The preparation method is the same as that of Example 1.

[0108] 2. Using the PE gasket film prepared in Example 5 to prepare a composite film, the preparation method is the same as that of Example 1.

[0109] Example 6

[0110] 1. Preparation of PE gasket film

[0111] The PE gasket film of this example has a three-layer structure, namely an outer layer, a middle layer and an inner layer, and the weight percentages of the raw materials of each layer are: outer layer 25%, middle layer 45%, and inner layer 30%.

[0112] In parts by mass, the preparation raw materials of each layer are as follows: Outer layer: Low-density polyethylene 2420H: 60 parts, Metallocene low-density polyethylene SP1520: 30 parts, Processing aid PA0895LD: 0.8 part;

[0113] Middle layer: Low-density polyethylene 2420H: 20 parts, High-density polyethylene H377C: 48 parts, Processing aid PA0895LD: 0.5 part;

[0114] Inner layer: Low-density polyethylene 2420H: 72 parts, Metallocene low-density polyethylene 1520: 15 parts, Processing aid PA0895LD: 0.8 part.

[0115] The preparation method is the same as that of Example 1.

[0116] 2. Using the PE gasket film prepared in Example 6 to prepare a composite film, the preparation method is the same as that of Example 1.

[0117] Comparative Example 1

[0118] 1. Preparation of PE gasket film

[0119] The PE gasket film of this comparative example has a three-layer structure, namely an outer layer, a middle layer, and an inner layer. The weight percentages of the raw materials for each layer are as follows: 30% for the outer layer, 40% for the middle layer, and 30% for the inner layer. The sources and dosages of the raw materials used in the outer layer, middle layer, and inner layer are shown in Table 3.

[0120] Table 3 Sources and Dosages of Raw Materials for Comparative Example 1

[0121]

[0122] The preparation method is the same as that of Example 1. Among them, the temperatures and pressures of the extruders for the outer layer, middle layer, and inner layer, as well as the temperature of the die head, are shown in Table 4.

[0123] Table 4 Temperatures and Pressures of Extruders, Temperature of Die Head

[0124] Temperature Zone 1 / °C Zone 2 / °C Zone 3 / °C Zone 4 / °C Zone 5 / °C Pressure / bar Outer layer 168 175 170 164 160 235 Middle layer 170 175 172 165 160 295 Inner layer 167 172 165 160 160 330 Die head 183 188 182 180 / /

[0125] 2. Preparation of Composite Film

[0126] The composite film is prepared using the PE film prepared in Comparative Example 1, and the preparation method is the same as that of Example 1.

[0127] Comparative Example 2

[0128] 1. Preparation of PE Gasket Film

[0129] The PE gasket film of this example has a three-layer structure, namely an outer layer, a middle layer, and an inner layer. The weight percentages of the raw materials for each layer are as follows: 30% for the outer layer, 40% for the middle layer, and 30% for the inner layer.

[0130] In parts by mass, the preparation raw materials for each layer are as follows: Outer layer: 25 parts of low-density polyethylene 2420H, 52 parts of metallocene low-density polyethylene SP1520, 0.8 part of processing aid PA0895LD;

[0131] Middle layer: 42 parts of low-density polyethylene 2420H, 8 parts of high-density polyethylene H377C, 0.5 part of processing aid PA0895LD;

[0132] Inner layer: 28 parts of low-density polyethylene 2420H, 65 parts of metallocene low-density polyethylene SP1520, 0.8 part of processing aid PA0895LD.

[0133] The preparation method is the same as that of Example 1.

[0134] 2. The composite film is prepared using the PE gasket film prepared in Comparative Example 2, and the preparation method is the same as that of Example 1.

[0135] Performance Testing

[0136] The mechanical properties, wetting tension, and number of crystal points of the PE gasket films prepared in Examples 1-6 and Comparative Examples 1-2 were tested. The test methods and results are shown in Table 5.

[0137] Table 5 Test Results of PE Gasket Film Properties

[0138]

[0139] From the data in Table 1, it can be seen that the PE gasket films prepared by the present invention have good mechanical properties and wetting tension, and few crystal points. In Comparative Example 1, the raw materials for preparation were changed. Although the obtained PE film has good mechanical properties, the number of crystal points increased significantly and there were more impurities. In Comparative Example 2, the dosage of SP1520 in the outer layer increased and the dosage of H377C in the middle layer decreased. The number of crystal points of the obtained PE gasket film also increased significantly, indicating that the raw material ratio has a great influence on the performance of the PE gasket film.

[0140] The mechanical and die-cutting properties of the composite films prepared in Examples 1-6 and Comparative Examples 1-2 were tested. The test methods and results are shown in Table 6.

[0141] Table 6 Test Results of Composite Film Properties

[0142]

[0143] From the data in Table 6, it can be seen that the composite film provided by the present invention has good mechanical properties and does not draw wires during die-cutting. The composite film in Comparative Example 1 seriously draws wires, and the composite film in Comparative Example 2 also shows wire-drawing phenomenon, which cannot meet the requirements of the bottle cap gasket.

[0144] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A PE gasket film, characterized in that, It includes an outer layer, a middle layer and an inner layer which are stacked in sequence; By mass parts, the raw materials for preparing the outer layer include: 30 - 80 parts of low density polyethylene, 10 - 30 parts of metallocene low density polyethylene, and 0.3 - 0.8 parts of processing aid; By mass parts, the raw materials for preparing the middle layer include: 20 - 70 parts of low density polyethylene, 10 - 50 parts of high density polyethylene, and 0.5 - 1 part of processing aid; By mass parts, the raw materials for preparing the inner layer include: 30 - 80 parts of low density polyethylene, 10 - 30 parts of metallocene low density polyethylene, and 0.5 - 1 part of processing aid.

2. The PE gasket film according to claim 1, wherein, The melt index of the low-density polyethylene used for the outer layer, middle layer and inner layer is 1.5 to 2.5 g / 10 min, and the density is 0.92 to 0.93 g / cm 3 .

3. The PE gasket film according to claim 1, wherein The melt index of the metallocene linear low density polyethylene used for the outer layer and the inner layer is 1.5 to 2.5 g / 10 min, and the density is 0.908 to 0.92 g / cm 3 .

4. The PE gasket film according to claim 1, wherein The melt index of the high-density polyethylene used for the middle layer is 6 to 8.5 g / 10 min, and the density is 0.955 to 0.965 g / cm 3 ; the melt index of the processing aids used for the outer layer, middle layer and inner layer is 1.5 to 3 g / 10 min, and the density is 0.91 to 0.925 g / cm 3 .

5. The PE gasket film according to claim 1, characterized in that, The grade of the low density polyethylene used in the outer layer, middle layer and inner layer is 2420H; the grade of the metallocene low density polyethylene used in the outer layer and inner layer is SP1520 or SP2320; the grade of the high density polyethylene used in the middle layer is H377C; the grade of the processing aid used in the outer layer, middle layer and inner layer is PA0895LD.

6. The preparation method of the PE gasket film according to any one of claims 1 to 5, characterized in that, It includes the following steps: Co - extrude the raw materials for the outer layer, middle layer and inner layer in three layers to obtain the PE gasket film.

7. A composite film, characterized in that, It includes a printed layer, a barrier layer and a heat - seal layer which are stacked in sequence; the heat - seal layer is the PE gasket film described in any one of claims 1 - 5 or the PE gasket film prepared by the preparation method described in claim 6.

8. The composite film according to claim 7, wherein The printed layer is a polyester film; the barrier layer is an aluminum foil.

9. The method for preparing the composite film according to claim 7 or 8, characterized in that, It includes the following steps: Compound the printed layer and the barrier layer with an adhesive and then carry out the first aging to obtain a printed layer / barrier layer composite film; Compound the printed layer / barrier layer composite film and the PE gasket film with an adhesive and then carry out the second aging to obtain the composite film.

10. Application of the PE gasket film described in any one of claims 1 - 5 or the composite film described in claim 7 or 8 in a bottle cap gasket.

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