Film composition and application thereof, intermediate layer material for film and FFS (fringe field switching) heavy packaging film

Abstract

The invention relates to the field of plastic film modification, in particular to a film composition and application thereof, a middle layer material for a film and an FFS heavy packaging film, and discloses a film composition which comprises, by weight, 40-60 parts of linear low density polyethylene, 40-60 parts of ultra-low density polyethylene, 5-10 parts of polytetrafluoroethylene and 1-2.5 parts of polyethylene glycol. The film composition is used as an FFS heavy packaging film of a middle layer, the thickness of the film is reduced, the comprehensive performance can be improved at the same time, the thickness of an FFS heavy packaging film product with the middle layer is larger than or equal to 118 micrometers, the tearing strength is larger than or equal to 35 N, the falling standard impact strength is larger than or equal to 800 g, the heat sealing temperature of the film can be reduced by not more than 120 DEG C or higher when the FFS heavy packaging film product is used, the packaging capacity is larger than or equal to 950 bags per hour, and the service life of the FFS heavy packaging film product is prolonged. The heat sealing strength is not less than 47N / 15mm when not higher than 160, the recovery rate is not less than 87%, the processability is excellent, the thickness of the film is reduced, and the production cost of a user can be saved.

Description

Technical Field

[0001] The invention relates to the field of plastic film modification, and in particular to a film composition and application thereof, an intermediate layer material for the film and an FFS heavy packaging film. Background Art

[0002] With the development, environmental protection and energy conservation have put forward higher requirements for packaging materials, such as lightweight, fast processing efficiency, high yield and low consumption. In the existing technology, the performance of heavy packaging film decreases due to the change of external environmental temperature. For example, in winter, the temperature in northern China is low, which makes the film brittle and the toughness decreases, which easily causes the packaging film to break and leak. In summer, when the climate in the north and south is as high as 30≯, the plastic rebound elasticity deteriorates, the film strength decreases, and the adhesion between layers is poor. Early polyethylene heavy packaging film was mainly processed by blending general linear polyethylene and low-density polyethylene (LDPE) resin, but the thickness was relatively thick, about 150-200μm, the production cost was high, and the production equipment and process conditions were required to be high, and the processing was difficult. The general method is to add LDPE to improve the processing capacity of the overall raw materials. However, the addition of LDPE greatly reduces the strength of the heavy packaging film.

[0003] CN106079768B discloses a heavy packaging film and provides a heavy packaging film composition. Although the film has good mechanical properties, the thickness is between 140-250 μm, which cannot reduce the production and use costs.

[0004] CN103059402B discloses a FFS single-layer heavy-duty packaging film and a preparation method thereof. A preparation method for a single-layer heavy-duty packaging film is provided. Due to the use of single-layer extrusion processing, a film with reduced thickness and high mechanical properties cannot be obtained, and the tear resistance and drop impact strength of the prepared film are relatively low.

[0005] CN103029388.B discloses a three-layer co-extruded heavy packaging film and a preparation method thereof, but does not specify the thickness of the film and the tear resistance of the film is relatively low.

[0006] CN102452204B discloses an FFS film for heavy packaging. This technology uses a large amount of LDPE, which affects the overall strength of the film. At the same time, HDPE has strict requirements on equipment, which increases the difficulty of the production process of the heavy packaging film and is difficult to promote and use.

[0007] CN103029388B discloses a three-layer co-extruded heavy packaging film. This technology has excellent mechanical properties, good stiffness, and a moderate film surface friction coefficient, but the heat sealing temperature is high and the energy consumption is large.

[0008] CN103059402A discloses a FFS single-layer heavy packaging film and a preparation method thereof, which improves the mechanical properties of the FFS single-layer heavy packaging film by using ethylene-vinyl acetate copolymer, metallocene linear low-density polyethylene and ultra-low-density polyethylene. Since the technology uses a certain amount of EVA, the high temperature resistance of the film deteriorates, and adhesion is easily generated during the film processing. Since the heavy packaging film is mainly used for 25 kg of plastic particle packaging, it not only requires strength, but also requires it to be able to adapt to the operation of an automatic high-speed packaging production line. The above technologies do not involve content on processing efficiency, and the good processability of the film is conducive to improving production efficiency. Summary of the invention

[0009] The purpose of the present invention is to overcome the problems of low processing efficiency, poor mechanical strength, heat sealing performance, and rigid-toughness balance of FFS heavy packaging films in the prior art, and to provide a film composition and its application, an intermediate layer material for the film, and an FFS heavy packaging film. The film composition of the present invention is used for the FFS heavy packaging film as an intermediate layer, and the comprehensive performance can be improved at the same time. The FFS heavy packaging film product with the intermediate layer of the present invention has a thickness of ≯118μm, a tear resistance of ≮35N, and a drop impact strength of ≮800g. When used, the heat sealing temperature of the film can be reduced by ≯120≯, the packaging capacity is ≮950 bags / hour, the heat sealing strength is ≮47N / 15mm at 160≯, the recovery rate is ≮87%, the processability is excellent, and the film thickness is reduced, which can save the user's production cost.

[0010] In order to achieve the above objectives, the present invention provides a film composition, which comprises: 40-60 parts by weight of linear low-density polyethylene, 40-60 parts by weight of ultra-low-density polyethylene, 5-10 parts by weight of polytetrafluoroethylene, and 1-2.5 parts by weight of polyethylene glycol.

[0011] The second aspect of the present invention provides use of the composition of the present invention in preparing a film intermediate layer.

[0012] The third aspect of the present invention provides an intermediate layer material for a film formed from the raw material of the composition of the present invention.

[0013] A fourth aspect of the present invention provides an FFS heavy packaging film, wherein the intermediate layer of the FFS heavy packaging film contains the intermediate layer material of the present invention.

[0014] Through the above technical solution, the present invention has the following beneficial effects:

[0015] The present invention proposes a film composition for the first time, the composition comprising: 40-60 parts by weight of linear low-density polyethylene, 40-60 parts by weight of ultra-low-density polyethylene, 5-10 parts by weight of polytetrafluoroethylene, and 1-2.5 parts by weight of polyethylene glycol; the FFS heavy packaging film product having the intermediate layer of the present invention has a thickness of ≯118μm, a tear resistance of ≮35N, a drop impact strength of ≮800g, can reduce the heat sealing temperature of the film by ≯120≯ when used, has a packaging capacity of ≮950 bags / hour, and a heat sealing strength of ≯160≯ 47N / 15mm, recovery rate ≮87%, excellent processability, and reduced film thickness, which can save users' production costs; it is speculated that due to the synergistic effect of ultra-low density polyethylene and polytetrafluoroethylene, and the effect of polyethylene glycol dispersant, the linear molecules can be connected to each other to form a network structure, so that the molecular chains are more closely entangled with each other, which increases the adhesion between the film layers, improves the film's puncture resistance, tear resistance and resilience, and at the same time improves the film's toughness and gives the film a suitable friction coefficient.

[0016] The FFS heavy packaging film of the present invention has uniform thickness and good performance in use. It can produce a thinned FFS heavy packaging film with a thickness of 110-115 μm, which is much thinner than the common FFS heavy packaging film on the market and has the advantages of thin thickness, light weight and low cost.

[0017] In a preferred embodiment of the present invention, the present invention uses a metallocene polyethylene with a specific molecular structure, an ultra-low density polyethylene with a specific molecular structure, and ultrafine polytetrafluoroethylene powder and polyethylene glycol to blend, and the processing obtains a polyethylene heavy packaging film with reduced film thickness and improved comprehensive performance. The thickness of the film product is the thickness of the heavy packaging film ≯118μm, the tear strength is ≮35N, the drop impact strength is ≮800g, and the film heat sealing temperature can be reduced by ≯120≯ when used, the packaging capacity is ≮950 bags / hour, the heat sealing strength is ≮47N / 15mm at 160≯, the recovery rate is ≮87%, the processability is excellent, and the film thickness is reduced, which can save users' production costs. DETAILED DESCRIPTION

[0018] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0019] The present invention proposes a film composition for the first time, the composition comprising: 40-60 parts by weight of linear low-density polyethylene, 40-60 parts by weight of ultra-low-density polyethylene, 5-10 parts by weight of polytetrafluoroethylene, and 1-2.5 parts by weight of polyethylene glycol; the film composition of the present invention is used for an FFS heavy-duty packaging film as an intermediate layer, which can reduce the thickness of the film while improving the comprehensive performance at the same time; the FFS heavy-duty packaging film product having the intermediate layer of the present invention has a thickness of ≯118μm, a tear resistance of ≮35N, and a drop impact strength of ≮800g; when used, the heat sealing temperature of the film can be reduced by ≯120°C. The packaging capacity is ≮950 bags / hour, the heat sealing strength is ≮47N / 15mm at 160≯, the recovery rate is ≮87%, the processability is excellent, and the film thickness is reduced, which can save users' production costs; it is speculated that due to the synergistic effect of ultra-low density polyethylene and polytetrafluoroethylene, and the effect of polyethylene glycol dispersant, the linear molecules can be connected to each other to form a network structure, so that the molecular chains are more closely entangled with each other, which increases the adhesion between the film layers, improves the film's puncture resistance, tear resistance and resilience, and at the same time improves the film's toughness and gives the film a suitable friction coefficient.

[0020] In the present invention, the density of the linear low-density polyethylene can be a conventional choice in the art. According to a preferred embodiment of the present invention, the density of the linear low-density polyethylene is 0.92-0.93 g / cm 3 , preferably 0.923-0.926 g / cm 3 By adopting the above-mentioned preferred embodiments, the puncture resistance, tear resistance, processability and resilience of the film can be further improved, and the thickness can be further reduced to improve the stability of the film bubble.

[0021] In the present invention, the density of the ultra-low density polyethylene can be a conventional choice in the art. According to a preferred embodiment of the present invention, the density of the ultra-low density polyethylene is 0.885-0.909 g / cm 3 , preferably 0.886-0.903 g / cm 3 By adopting the above-mentioned preferred embodiments, the puncture resistance, tear resistance, processability and resilience of the film can be further improved, and the thickness can be further reduced to improve the stability of the film bubble.

[0022] In the present invention, the melt mass flow rate of the linear low-density polyethylene at 190≯ / 2.16kg can be a conventional choice in the art. According to a preferred embodiment of the present invention, the melt mass flow rate of the linear low-density polyethylene at 190≯ / 2.16kg is 3.1-4.0g / 10min, preferably 3.2-3.6g / 10min. By adopting the aforementioned preferred embodiment, the heat sealing temperature of the film can be further reduced.

[0023] In the present invention, the melt mass flow rate of the ultra-low density polyethylene at 190≯ / 2.16kg can be a conventional choice in the art. According to a preferred embodiment of the present invention, the melt mass flow rate of the ultra-low density polyethylene at 190≯ / 2.16kg is 0.8-3.2g / 10min, preferably 1.5-2.1g / 10min. By adopting the aforementioned preferred embodiment, the heat sealing temperature of the film can be further reduced.

[0024] In the present invention, the molecular weight distribution of the ultra-low density polyethylene can be a conventional choice in the art. According to a preferred embodiment of the present invention, the molecular weight distribution of the ultra-low density polyethylene is 3.8-5.0. By adopting the aforementioned preferred embodiment, the tear resistance of the film can be further improved.

[0025] In the present invention, the ultra-low density polyethylene described in the middle layer is a vinyl linear copolymer, and 4-20% of a high-grade alpha olefin comonomer is added during the polymerization process using a metallocene catalyst. The ultra-low density polyethylene contains a structural unit a provided by an ethylene monomer and a structural unit b provided by a comonomer. According to a preferred embodiment of the present invention, the molar content of the ultra-low density polyethylene structural unit b is 8-10mol%, and the comonomer is selected from at least one of propylene, butene, hexene and octene, preferably hexene. By adopting the aforementioned preferred embodiment, the tear resistance of the film can be further improved.

[0026] In the present invention, the mass percentage of the ultra-low density polyethylene with a crystallization heat fractionation analysis thickness of less than 6.2 nm lamellae can be a conventional choice in the art. According to a preferred embodiment of the present invention, the mass percentage of the ultra-low density polyethylene with a crystallization heat fractionation analysis thickness of less than 6.2 nm lamellae is 7.1-8.9%, preferably 7.5-8.5%. By adopting the aforementioned preferred embodiment, the tear resistance of the film can be further improved.

[0027] In the present invention, the crystallization heat grading test method has no special requirements and can be performed according to the prior art, which will not be described in detail in the present invention.

[0028] In the present invention, the number of branches of the ultra-low density polyethylene can be a conventional choice in the art. According to a preferred embodiment of the present invention, the number of branches of the ultra-low density polyethylene is 17.1-18.0 / 1000C. By adopting the above preferred embodiment, the tear resistance of the film can be further improved.

[0029] In the present invention, the molecular weight of the polytetrafluoroethylene can be a conventional choice in the art. According to a preferred embodiment of the present invention, the molecular weight of the polytetrafluoroethylene is 6000-8000. By adopting the above preferred embodiment, the tear resistance of the film can be further improved.

[0030] In the present invention, the particle size of the polytetrafluoroethylene can be a conventional choice in the art. According to a preferred embodiment of the present invention, the particle size of the polytetrafluoroethylene is 0.5-2 μm. By adopting the above preferred embodiment, the tear resistance of the film can be further improved.

[0031] In the present invention, the molecular weight of the polyethylene glycol can be a conventional choice in the art. According to a preferred embodiment of the present invention, the molecular weight of the polyethylene glycol is 2000-6000. By adopting the above preferred embodiment, the tear resistance of the film can be further improved.

[0032] The present invention has no special requirements on the physical and chemical parameters of polytetrafluoroethylene. According to the present invention, the polytetrafluoroethylene is preferably modified polytetrafluoroethylene treated with a modifier.

[0033] In the present invention, the method of treating polytetrafluoroethylene with a modifier can be a conventional choice in the art. According to a preferred embodiment of the present invention, the method of treating polytetrafluoroethylene with a modifier comprises: immersing in the presence of a modifier, washing, solid-liquid separation, and drying. By adopting the aforementioned preferred embodiment, the fusion between the components can be further improved, which is conducive to further improving the performance of the film.

[0034] In the present invention, the modifier may be a conventional one in the art.

[0035] According to a preferred embodiment of the present invention, the modifier is selected from at least one of tributyl methyl ether, tetrahydrofuran, dioxane, isopropanol and chloroform.

[0036] According to a preferred embodiment of the present invention, the modifier is selected from a mixture of tetrahydrofuran and isopropanol.

[0037] According to a preferred embodiment of the present invention, the ratio of tetrahydrofuran to isopropanol in the modifier is (7-9): (1-2.5).

[0038] By adopting the aforementioned preferred implementation, the fusion between the components can be further improved, which is beneficial to further improve the performance of the film.

[0039] In the present invention, the organic solvent used for washing can be a conventional choice in the art. According to a preferred embodiment of the present invention, the organic solvent is selected from propanol and / or acetone, preferably acetone. By adopting the aforementioned preferred embodiment, the fusion between the components can be further improved, which is conducive to further improving the performance of the film.

[0040] In the present invention, there is no special requirement for the washing time of the organic solvent, and it can be carried out according to actual operation.

[0041] In the present invention, after washing with an organic solvent and before solid-liquid separation, a step of dispersing the cells with an ultrasonic cell crusher (power 500 W) for 20 minutes is required.

[0042] In the present invention, the conditions for the drying process may be conventionally selected in the art.

[0043] According to a preferred embodiment of the present invention, the drying temperature is 55-85°C.

[0044] According to a preferred embodiment of the present invention, the drying time is 20-30 hours.

[0045] By adopting the aforementioned preferred embodiment, the fusion between the components can be further improved.

[0046] In the present invention, after the drying operation step, a crushing and grinding step is required.

[0047] In the present invention, the conditions for the immersion treatment may be conventionally selected in the art.

[0048] According to a preferred embodiment of the present invention, the temperature of the immersion treatment is -5--10≯.

[0049] According to a preferred embodiment of the present invention, the immersion time is 5-10 minutes.

[0050] By adopting the above-mentioned preferred embodiment, it is possible to further improve the guarantee that the modified filler powder is uniform and fine and fully reacts with the base resin.

[0051] The present invention provides use of the film composition of the present invention in preparing a film middle layer, preferably in a FFS heavy packaging film middle layer.

[0052] The present invention provides an intermediate layer material for a film according to the present invention, which is formed from the raw materials of the composition according to the present invention, and has very good processing performance and good rigidity-toughness balance performance. By adopting the above preferred embodiments, the tear resistance and nominal strain can be further improved.

[0053] The present invention provides a FFS heavy packaging film, the middle layer of which contains the middle layer material described in the present invention. According to a preferred embodiment of the present invention, the FFS heavy packaging film contains an outer layer, an inner layer and the middle layer. The FFS heavy packaging film of the present invention rationally distributes the outer mold, the inner film and the middle layer film, and while giving full play to the advantageous performance of each layer of the film, it can play a synergistic role, improve the adhesion between the film layers, and improve the overall performance of the film. Heavy packaging bags require not only strength, but also heat sealing, crispness, and stacking performance. The present invention realizes each performance one by one through co-extrusion of the outer layer, the middle layer, and the inner layer. The film has very good processing performance and good rigidity-toughness balance performance, good tear resistance, and low heat sealing temperature. The structure of the outer layer, the middle layer, and the inner layer of the present invention can replace the traditional four-layer material, greatly reducing production costs.

[0054] In the present invention, the thickness ratio of the composite structure of the outer layer, the middle layer and the inner layer can be a conventional choice in the art. According to a preferred embodiment of the present invention, the thickness ratio of the composite structure of the outer layer, the middle layer and the inner layer is (1-2.0): (1-2.0): 1. By adopting the aforementioned preferred embodiment, the overall performance of the film can be further improved, and the film can be thinned while having excellent mechanical properties.

[0055] According to a preferred embodiment of the present invention, the thickness of the FFS heavy packaging film is ≯118 μm.

[0056] According to a preferred embodiment of the present invention, the tear strength of the FFS heavy packaging film is ≮35N.

[0057] According to a preferred embodiment of the present invention, the drop impact strength of the FFS heavy packaging film is ≮800g.

[0058] According to a preferred embodiment of the present invention, the FFS heavy packaging film can reduce the heat sealing temperature of the film by ≯120≯ when used.

[0059] According to a preferred embodiment of the present invention, the packaging capacity of the FFS heavy packaging film is ≮950 bags / hour.

[0060] According to a preferred embodiment of the present invention, the heat sealing strength of the FFS heavy packaging film is 160≯≮47N / 15mm.

[0061] According to a preferred embodiment of the present invention, the recovery rate of the FFS heavy packaging film is ≮87%.

[0062] By adopting the aforementioned preferred implementation, the mechanical properties of the film can be further improved.

[0063] In the present invention, there is no special requirement for the weight composition of the outer layer of the FFS heavy packaging film. According to a preferred embodiment of the present invention, the weight composition of the outer layer of the FFS heavy packaging film includes: 70-90 weight parts of metallocene linear polyethylene, 10-30 weight parts of ultra-low density polyethylene, and 0.2-1.0 weight parts of polyethylene glycol. By adopting the aforementioned preferred embodiment, the tensile strength and dart drop impact strength can be further improved.

[0064] In the present invention, there is no special requirement for the weight composition of the inner layer of the FFS heavy packaging film. According to a preferred embodiment of the present invention, the weight composition of the inner layer of the FFS heavy packaging film includes: 70-90 weight parts of metallocene linear polyethylene, 10-30 weight parts of ultra-low density polyethylene, and 1-3 weight parts of TiO2 masterbatch. By adopting the aforementioned preferred embodiment, the tensile strength and dart drop impact strength can be further improved.

[0065] In the present invention, there is no special requirement for the properties of the metallocene linear polyethylene in the inner layer and the outer layer. According to a preferred embodiment of the present invention, the physical and chemical properties of the metallocene linear polyethylene in the inner layer and the outer layer include: a melt mass flow rate at 190≯ / 2.16kg of

[0066] 2.02 g / 10min-3.2 g / 10min, preferably 2.02-2.23 g / 10min.

[0067] According to a preferred embodiment of the present invention, the physical and chemical properties of the metallocene linear polyethylene in the inner layer and the outer layer include: a density of 0.920-0.935 g / cm 3 , preferably 0.921-0.930 g / cm 3 .

[0068] According to a preferred embodiment of the present invention, the physicochemical properties of the metallocene linear polyethylene in the inner layer and the outer layer include: molecular weight distribution 3.3-3.8, weight average molecular weight 120,000-160,000, preferably 130,000-150,000.

[0069] According to a preferred embodiment of the present invention, the physicochemical properties of the metallocene linear polyethylene in the inner layer and the outer layer include: the relative content of lamellar crystals with a thickness of more than 9.6 nm according to crystallization thermal fractionation analysis is more than 12%-16%, preferably 13-15%.

[0070] According to a preferred embodiment of the present invention, the physicochemical properties of the metallocene linear polyethylene in the inner layer and the outer layer include: the number of branches is 11.8-13.5 / 1000C.

[0071] By adopting the aforementioned preferred implementation, the mechanical properties of the film can be further improved and the strength of the film can be ensured.

[0072] In the present invention, there is no special requirement for the properties of the outer layer of ultra-low density polyethylene. According to a preferred embodiment of the present invention, in the outer layer, the physicochemical parameters of the ultra-low density polyethylene include:

[0073] The melt mass flow rate at 190≯ / 2.16 kg is 0.5-2.5 g / 10 min, preferably 0.8-1.6 g / 10 min.

[0074] According to a preferred embodiment of the present invention, in the outer layer, the physicochemical parameters of the ultra-low density polyethylene include: density of 0.908-0.915 g / cm 3 , preferably 0.909-0.912 g / cm 3 .

[0075] According to a preferred embodiment of the present invention, in the outer layer, the physicochemical parameters of the ultra-low density polyethylene include: molecular weight distribution 3.8-4.1, and the mass percentage of 9.4 nm thick lamellae analyzed by crystallization thermal fractionation is 8.0-9.2%, preferably 8.5-8.9%.

[0076] According to a preferred embodiment of the present invention, in the outer layer, the physicochemical parameters of the ultra-low density polyethylene include: branching number 14.5-17.0 / 1000C.

[0077] By adopting the above-mentioned preferred embodiment, the strong combination of ultra-low density polyethylene and metallocene linear polyethylene with this specific structure can further improve the strength of the film.

[0078] In the present invention, the outer layer ultra-low density polyethylene is a vinyl linear copolymer, and 4-20% of a high-grade alpha olefin comonomer is added during the polymerization process using a metallocene catalyst, and the ultra-low density polyethylene contains a structural unit a provided by an ethylene monomer and a structural unit b provided by a comonomer. According to a preferred embodiment of the present invention, the molar content of the ultra-low density polyethylene structural unit b is 4.2-5.5 mol%, and the comonomer is selected from at least one of propylene, butene, hexene and octene, preferably hexene. By adopting the aforementioned preferred embodiment, the tear resistance of the film can be further improved.

[0079] In the present invention, there is no special requirement for the molecular weight of the polyethylene glycol in the outer layer. According to a preferred embodiment of the present invention, the molecular weight of the polyethylene glycol in the outer layer is 2000-6000. By adopting the above preferred embodiment, the tear resistance of the film can be further improved.

[0080] In the present invention, there is no special requirement for the properties of the ultra-low density polyethylene in the inner layer. According to a preferred embodiment of the present invention, the physicochemical parameters of the ultra-low density polyethylene in the inner layer include: the melt mass flow rate of the ultra-low density polyethylene at 190≯ / 2.16kg is 0.8-3.2g / 10min, preferably 0.886-0.903g / cm 3 .

[0081] According to a preferred embodiment of the present invention, in the inner layer, the physicochemical parameters of the ultra-low density polyethylene include: molecular weight distribution 3.8-5.0.

[0082] According to a preferred embodiment of the present invention, in the inner layer, the physicochemical parameters of the ultra-low density polyethylene include: the mass percentage of lamellae with a thickness of less than 6.2 nm according to crystallization thermal fractionation analysis is 7.1-8.9%, preferably 7.5-8.5%.

[0083] According to a preferred embodiment of the present invention, in the inner layer, the physicochemical parameters of the ultra-low density polyethylene include: branching number 17.1-18.0 / 1000C.

[0084] By adopting the above-mentioned preferred embodiment, the strength of the film can be further improved.

[0085] In the present invention, the metallocene linear polyethylene in the inner layer and / or outer layer is a copolymer of ethylene and α-olefin (such as 1-butene, 1-hexene or 1-octene) under the action of a metallocene catalyst system. Preferably, the metallocene linear polyethylene is a copolymer of ethylene and 1-hexene.

[0086] In the present invention, the preparation of each layer of the film generally includes the steps of raw material mixing, extrusion, and kneading. The present invention has no special requirements on the raw material mixing, extrusion, and kneading techniques, and the existing techniques can be used.

[0087] According to a preferred embodiment of the present invention, the FFS heavy packaging film method comprises the following steps:

[0088] (1.1) Preparation of inner film raw materials:

[0089] The inner layer components were weighed by weight, put into a high-speed mixer for mixing, the mixing temperature was 15≯, the mixing speed was 860rpm, and the mixing time was 16min; then they were sent to a first single-screw extruder (diameter 50mm, aspect ratio 32:1) for mixing, the screw temperature of the first single-screw extruder was 180≯, the head temperature of the first single-screw extruder was 210≯, the screw speed was 110 rpm, and the extrusion processing pressure was 58MPa to obtain the inner layer film raw material;

[0090] (1.2) Preparation of intermediate film raw materials:

[0091] Polytetrafluoroethylene is first immersed in a frozen tetrahydrofuran and isopropanol solution (4:1 by weight) for 10 minutes, then rinsed with acetone for 8 minutes, and then dispersed with an ultrasonic cell crusher (power 500W) for 20 minutes. The solvent is removed by a rotary evaporator, filtered, and vacuum dried at 70°C for 24 hours until constant weight. The obtained powder will have a small amount of lumps. It should be ground with a small crusher for 1 hour and set aside.

[0092] Weigh polytetrafluoroethylene powder, ultra-low density polyethylene and polyethylene glycol powder by weight, put them into a high-speed mixer for mixing, the mixing temperature is 38≯, the mixing speed is 1100rpm, the mixing time is 15min, and then add metallocene linear polyethylene for mixing for 8min; then send them into a second single-screw extruder (diameter 55mm, aspect ratio 35:1) for mixing, the screw temperature of the second single-screw extruder is 218≯, the head temperature of the second single-screw extruder is 210≯, the screw speed is 109 rpm, and the extrusion processing pressure is 37MPa to obtain an intermediate layer film raw material;

[0093] (1.3) Preparation of outer film raw materials:

[0094] The outer layer components were weighed by weight, and put into a high-speed mixer for mixing, with a mixing temperature of 16°C, a mixing speed of 800 rpm, and a mixing time of 17 min; the mixture was then sent to a third single-screw extruder (diameter 65 mm, aspect ratio 36:1) for mixing, with a screw temperature of 190°C, a die head temperature of 210°C, a screw speed of 110 rpm, and an extrusion processing pressure of 40 MPa to obtain an outer film raw material;

[0095] (2) Extrusion molding: The fluid inner layer film raw material, the middle layer film raw material and the outer layer film raw material are simultaneously transported to a three-layer co-extruder for fusion at a fusion temperature of 230°C, and then converged to a film blowing die head at a die head temperature of 230°C, and formed into film bubbles after being extruded through the die head;

[0096] (3) Cooling and shaping:

[0097] The film bubble is cooled and shaped by 18≯ cooling air, and then rolled up to obtain heavy packaging film.

[0098] The present invention will be described in detail below through examples.

[0099] The preparation steps and conditions of the inner layer, outer layer and middle layer materials of the embodiment are as follows:

[0100] (1.1) Preparation of inner film raw materials:

[0101] The inner layer components were weighed by weight, put into a high-speed mixer for mixing, the mixing temperature was 15≯, the mixing speed was 860rpm, and the mixing time was 16min; then they were sent to a first single-screw extruder (diameter 50mm, aspect ratio 32:1) for mixing, the screw temperature of the first single-screw extruder was 180≯, the head temperature of the first single-screw extruder was 210≯, the screw speed was 110 rpm, and the extrusion processing pressure was 58MPa to obtain the inner layer film raw material;

[0102] (1.2) Preparation of intermediate film raw materials:

[0103] PTFE modification:

[0104] Polytetrafluoroethylene is first immersed in a mixed solution of frozen tetrahydrofuran and isopropanol (ratio 4:1) for 10 minutes, then rinsed with acetone for 8 minutes, and then dispersed with an ultrasonic cell crusher (power 500W) for 20 minutes. The solvent is removed by a rotary evaporator, filtered, and dried in a vacuum at 70°C for 24 hours until constant weight. The obtained powder will have a small amount of lumps. It should be ground with a small crusher for 1 hour and set aside.

[0105] Weigh polytetrafluoroethylene, ultra-low density polyethylene and polyethylene glycol powder by weight, put them into a high-speed mixer for mixing, the mixing temperature is 35≯, the mixing speed is 1100rpm, the mixing time is 15min, and then LLDPE is added for mixing for 8min; then send them into a second single-screw extruder (diameter 55mm, aspect ratio 35:1) for mixing, the screw temperature of the second single-screw extruder is 210≯, the head temperature of the second single-screw extruder is 220≯, the screw speed is 110 rpm, and the extrusion processing pressure is 40MPa to obtain an intermediate layer film raw material;

[0106] (1.3) Preparation of outer film raw materials:

[0107] The outer layer components were weighed by weight, and put into a high-speed mixer for mixing, with a mixing temperature of 16°C, a mixing speed of 800 rpm, and a mixing time of 15 min; the mixture was then sent to a third single-screw extruder (diameter 65 mm, aspect ratio 36:1) for mixing, with a screw temperature of 190°C, a die head temperature of 210°C, a screw speed of 110 rpm, and an extrusion processing pressure of 40 MPa to obtain an outer film raw material;

[0108] (2) Extrusion molding: The fluid inner layer film raw material, the middle layer film raw material and the outer layer film raw material are simultaneously transported to a three-layer co-extruder for fusion at a fusion temperature of 230°C, and then converged to a film blowing die head at a die head temperature of 230°C, and formed into film bubbles after being extruded through the die head;

[0109] (3) Cooling and shaping:

[0110] The film bubble is cooled and shaped by 15≯ cooling air, and then rolled up to obtain heavy packaging film.

[0111] In the present invention

[0112] Heavy packaging film performance testing standards:

[0113] Tensile strength and nominal strain at break: in accordance with GB / T1040.3-2006.

[0114] Drop impact strength: according to GB / T9639-2008.

[0115] Tear resistance: According to GB / T11999-1989, using rectangular specimens.

[0116] Heat sealing temperature / ≯: according to YBB00122003.

[0117] Heat seal strength: according to YBB00122003-2015.

[0118] Friction coefficient: in accordance with GB / T10006-1988.

[0119] Resilience: According to GB / T10006-1988.

[0120] Density: Compression molding sample preparation, according to method A in GB / T 1033.1-2010.

[0121] Melt mass flow rate (MFR): According to GB / T 3682.1-2008, the test temperature is 190°C, the nominal load is 2.16Kg, 50g of sample is dried in a vacuum oven at 90°C for 4h, and the test is carried out immediately after taking it out.

[0122] This experimental crystallization heat classification test method:

[0123] Weigh about 6 mg of the sample and seal it in a crucible, then place it in a differential scanning calorimeter (DSC). First, heat the sample to 165°C at a rate of 50≯ / min and keep it constant for 5 minutes to eliminate the thermal history; then cool the sample to 0°C at a rate of 25≯ / min and keep it constant for 3 minutes; then heat the sample to the set self-nucleation temperature at a rate of 25≯ / min and keep it constant for 5 minutes, then cool it to 25≯ at a rate of 25≯ / min, and then heat it to the next self-nucleation temperature at a rate of 25≯ / min, and repeat this cycle. The self-nucleation temperature points are (135, 125, 115, 115, 110, 105, 100)≯. Finally, cool it from 80°C to 25≯ at a rate of 25≯ / min and keep it constant for 3 minutes; then heat the sample to 160°C at a rate of 25≯ / min. The last DSC temperature rise curve was recorded; Q20 differential scanning calorimeter, TA Company, USA.

[0124] The performance test results of FFS heavy packaging film are shown in Table 1.

[0125] Example 1

[0126] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are as follows:

[0127] The outer layer is composed of the following components in parts by weight:

[0128] Metallocene linear polyethylene MFR (190≯, 2.16kg) is 2.02g / 10min, density is 0.921g / cm 3 , molecular weight distribution 3.35, weight average molecular weight 140,000, using crystallization thermal fractionation (SSA) analysis, the relative content of platelets with a thickness of more than 9.6nm is 13.2%, and the number of branches is 11.9 / 1000C; 70 parts.

[0129] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.6g / 10min, density 0.909g / cm 3 , molecular weight distribution 4.0, hexene molar content 4.6 mol%, branch number 14.7 / 1000C, and the mass percentage of 9.4 nm thick platelets analyzed by crystallization thermal fractionation (SSA) was 8.6%; 30 parts.

[0130] Polyethylene glycol molecular weight 2100; 0.3 parts.

[0131] The middle layer is composed of the following components in parts by weight:

[0132] Linear low-density polyethylene MFR (190≯, 2.16kg) is 3.2g / 10min, density is 0.923g / cm 3 ; 40 copies.

[0133] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.5g / 10min, density is 0.902g / cm 3 , molecular weight distribution 4.0, hexene molar content 8.2 mol%, branch number 17.4 / 1000C. The mass percentage of platelets with a thickness of less than 6.2 nm was analyzed by crystallization thermal fractionation (SSA) and was 7.5%; 50 parts.

[0134] Polytetrafluoroethylene molecular weight 6500, particle size 0.8μm; 10 parts.

[0135] Polyethylene glycol molecular weight 5100; 1.4 parts.

[0136] The inner layer is composed of the following components in parts by weight:

[0137] Metallocene linear polyethylene (same as outer layer); 70 parts.

[0138] Ultra-low density polyethylene (same as middle layer); 30 parts.

[0139] TiO2 masterbatch: 1.5 parts.

[0140] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0141] Example 2

[0142] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are as follows:

[0143] The outer layer is composed of the following components in parts by weight:

[0144] Metallocene linear polyethylene MFR (190≯, 2.16kg) is 2.20g / 10min, density is 0.924g / cm 3 The molecular weight distribution is 3.55, the weight average molecular weight is 145,000, and the relative content of platelets with a thickness of more than 9.6 nm is 13.6% by SSA analysis, and the number of branches is 12.3 / 1000C; 85 parts.

[0145] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 0.8g / 10min, density 0.910g / cm 3 , molecular weight distribution 3.84, hexene molar content 4.2 mol%, branch number 15.6 / 1000C, and the mass percentage of 9.4 nm thick platelets analyzed by crystallization thermal fractionation (SSA) was 8.8%; 15 parts.

[0146] Polyethylene glycol molecular weight 3000; 0.2 parts.

[0147] The middle layer is composed of the following components in parts by weight:

[0148] Linear low-density polyethylene MFR (190≯, 2.16kg) is 3.6g / 10min, density is 0.926g / cm 3 ; 42 copies.

[0149] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.64g / 10min, density is 0.889g / cm 3, molecular weight distribution 4.5, hexene molar content 9.5 mol%, branch number 17.8 / 1000C. The mass percentage of platelets with a thickness of less than 6.2 nm was analyzed by crystallization thermal fractionation (SSA) and was 7.6%; 50 parts.

[0150] Polytetrafluoroethylene molecular weight 7000, particle size 1.0μm; 8 parts.

[0151] Polyethylene glycol molecular weight 4000; 1.5 parts.

[0152] The inner layer is composed of the following components in parts by weight:

[0153] Metallocene linear polyethylene (same as outer layer); 75 parts.

[0154] Ultra-low density polyethylene (same as middle layer); 25 parts.

[0155] TiO2 masterbatch: 1.3 parts.

[0156] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1.5:2:1, and the performance test is shown in Table 1.

[0157] Example 3

[0158] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are as follows:

[0159] The outer layer is composed of the following components in parts by weight:

[0160] Metallocene linear polyethylene MFR (190≯, 2.16kg) is 2.1g / 10min, density is 0.930g / cm 3 The molecular weight distribution is 3.7, the weight average molecular weight is 138,000, and the relative content of platelets with a thickness of more than 9.6 nm is 13.9% by SSA analysis, and the number of branches is 12 / 1000C; 88 parts.

[0161] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.2g / 10min, density 0.906g / cm 3 , molecular weight distribution 3.91, hexene molar content 5.2 mol%, branch number 16.4 / 1000C, the mass percentage of 9.4 nm thick platelets analyzed by crystallization thermal fractionation (SSA) is 8.7%; 12 parts.

[0162] Polyethylene glycol molecular weight 2500; 0.4 parts.

[0163] The middle layer is composed of the following components in parts by weight:

[0164] Linear low-density polyethylene MFR (190≯, 2.16kg) is 3.3g / 10min, density is 0.924g / cm 3 ; 50 copies.

[0165] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 2.0g / 10min, density is 0.887g / cm 3 Molecular weight distribution 4.2, hexene molar content 9.0 mol%, branch number 18.0 / 1000C. The mass percentage of platelets with a thickness of less than 6.2 nm according to SSA analysis was 8.5%; 45 parts.

[0166] Polytetrafluoroethylene molecular weight 7500, particle size 1.5μm; 5 parts.

[0167] Polyethylene glycol molecular weight 4500; 1.6 parts.

[0168] The inner layer is composed of the following components in parts by weight:

[0169] Metallocene linear polyethylene (same as outer layer); 85 parts.

[0170] Ultra-low density polyethylene (same as middle layer); 15 parts.

[0171] TiO2 masterbatch: 1.8 parts.

[0172] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1.5:1.5:1, and the performance test is shown in Table 1.

[0173] Example 4

[0174] The FFS heavy packaging film provided in this embodiment includes three parts, an intermediate layer and an inner layer, which are arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are as follows:

[0175] Wherein the MFR and density of the metallocene linear polyethylene of the outer layer are not within the preferred range of the present invention, and the outer layer is composed of the following components in parts by weight:

[0176] Metallocene linear polyethylene MFR (190≯, 2.16kg) is 3.0g / 10min, density is 0.920g / cm 3 The molecular weight distribution is 3.62, the weight average molecular weight is 135,000, and the relative content of platelets with a thickness of more than 9.6 nm is 14.4% by SSA analysis, and the number of branches is 13 / 1000C; 75 parts.

[0177] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 0.9g / 10min, density 0.911g / cm 3, molecular weight distribution 4.1, hexene molar content 5.0 mol%, branch number 14.5 / 1000C, the mass percentage of 9.4 nm thick platelets analyzed by crystallization thermal fractionation (SSA) is 8.75%; 25 parts.

[0178] Polyethylene glycol molecular weight 2700; 0.25 parts.

[0179] The middle layer is composed of the following components in parts by weight:

[0180] Linear low-density polyethylene MFR (190≯, 2.16kg) is 3.4g / 10min, density is 0.925g / cm 3 ; 55 copies.

[0181] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.8g / 10min, density is 0.900g / cm 3 Molecular weight distribution 4.7, hexene molar content 10 mol%, branch number 17.5 / 1000C. The mass percentage of platelets with a thickness of less than 6.2 nm according to SSA analysis is 8.2%; 40 parts.

[0182] Polytetrafluoroethylene molecular weight 6800, particle size 2.0μm; 7 parts.

[0183] Polyethylene glycol molecular weight 4800; 2.0 parts.

[0184] The inner layer is composed of the following components in parts by weight:

[0185] Metallocene linear polyethylene (same as outer layer); 80 parts.

[0186] Ultra-low density polyethylene (same as middle layer); 20 parts.

[0187] TiO2 masterbatch: 1.6 parts.

[0188] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:1:1, and the performance test is shown in Table 1.

[0189] Example 5

[0190] The FFS heavy packaging film provided in this embodiment includes three parts, an intermediate layer and an inner layer, which are arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are as follows:

[0191] Wherein the outer layer metallocene linear polyethylene MFR is not within the preferred range of the present invention, and the outer layer is composed of the following components in parts by weight:

[0192] Metallocene linear polyethylene MFR (190≯, 2.16kg) is 2.6g / 10min, density is 0.923g / cm3 The molecular weight distribution is 3.46, the weight average molecular weight is 150,000, and the relative content of platelets with a thickness of more than 9.6 nm is 14.9% by SSA analysis, and the number of branches is 13.0 / 1000C; 88 parts.

[0193] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.4g / 10min, density 0.912g / cm 3 , molecular weight distribution 4.05, hexene molar content 4.8 mol%, branch number 17.0 / 1000C, and the mass percentage of 9.4 nm thick platelets analyzed by crystallization thermal fractionation (SSA) was 8.5%; 12 parts.

[0194] Polyethylene glycol molecular weight 2330; 0.35 parts.

[0195] The middle layer is composed of the following components in parts by weight:

[0196] Linear low-density polyethylene MFR (190≯, 2.16kg) is 3.5g / 10min, density is 0.92386g / cm 3 ; 60 copies.

[0197] Ultra-low density polyethylene MFR (190≯, 2.16kg) is 1.7g / 10min, density is 0.901g / cm 3 Molecular weight distribution: 5.0, hexene molar content: 8.5 mol%, branch number: 17.7 / 1000C. The mass percentage of platelets with a thickness of less than 6.2 nm according to SSA analysis is 8.0%; 48 parts.

[0198] Polytetrafluoroethylene molecular weight 8000, particle size 1.3μm; 9 parts.

[0199] Polyethylene glycol molecular weight 6000; 1.2 parts.

[0200] The inner layer is composed of the following components in parts by weight:

[0201] Metallocene linear polyethylene (same as outer layer); 90 parts.

[0202] Ultra-low density polyethylene (same as middle layer); 10 parts.

[0203] TiO2 masterbatch; 1.4 parts

[0204] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1.25:1.5:1, and the performance test is shown in Table 1.

[0205] Example 6

[0206] The FFS heavy packaging film provided in this embodiment includes an outer layer, an intermediate layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and their proportions of each layer are the same as those in Example 1, except that the density of the linear low-density polyethylene in the intermediate layer is 0.93 g / cm 3 , which is not within the preferred scope of the present invention.

[0207] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0208] Example 7

[0209] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and their proportions of each layer are the same as those in Example 1, except that the density of the ultra-low density polyethylene in the middle layer is 0.905 g / cm 3 , which is not within the preferred scope of the present invention.

[0210] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0211] Example 8

[0212] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are the same as those in Example 1, except that the thickness ratio of the outer layer, the middle layer, and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:0.8:1, which is not within the preferred range of the present invention. The performance test is shown in Table 1.

[0213] Comparative Example 1

[0214] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are the same as those in Example 1, except that the linear low-density polyethylene in the middle layer is 65 parts, which is not within the preferred range of the present invention.

[0215] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0216] Comparative Example 2

[0217] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are the same as those in Example 1, except that the middle layer has 36 parts of ultra-low density polyethylene, which is not within the preferred range of the present invention.

[0218] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0219] Comparative Example 3

[0220] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are the same as those in Example 1, except that the middle layer polytetrafluoroethylene is 12 parts, which is not within the preferred range of the present invention.

[0221] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0222] Comparative Example 4

[0223] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are the same as those in Example 1, except that the middle layer contains 2.7 parts of polyethylene glycol, which is not within the preferred range of the present invention.

[0224] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0225] Comparative Example 5

[0226] The FFS heavy packaging film provided in this embodiment includes an outer layer, a middle layer, and an inner layer arranged in sequence from the outside to the inside. The raw materials and proportions of each layer are the same as those in Example 1, except that no polytetrafluoroethylene is added to the middle layer.

[0227] The thickness ratio of the outer layer, the middle layer and the inner layer of the FFS heavy packaging film provided in this embodiment is 1:2:1, and the performance test is shown in Table 1.

[0228] Table 1

[0229]

[0230]

[0231] By comparing the test results of the embodiment and the comparative example, it can be seen that as long as the treated polytetrafluoroethylene in the embodiment is in the proportion within the range of the present invention, the tear strength of the film is improved, the processing efficiency of the film is improved, and the comprehensive performance of the film is excellent.

[0232] The above is only a preferred embodiment of the present invention, and does not limit the invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A film composition, characterized in that The composition comprises: 40-60 parts by weight of linear low-density polyethylene, 40-60 parts by weight of ultra-low-density polyethylene, 5-10 parts by weight of polytetrafluoroethylene, and 1-2.5 parts by weight of polyethylene glycol.

2. The composition according to claim 1, wherein In the composition, the density of the linear low-density polyethylene is 0.92-0.93 g / cm 3 , more preferably 0.923-0.926 g / cm 3 ; and / or The density of ultra-low density polyethylene is 0.885-0.909g / cm 3 , more preferably 0.886-0.903 g / cm 3 .

3. The composition according to claim 1 or 2, wherein The linear low-density polyethylene has a melt mass flow rate of 3.1-4.0 g / 10 min, preferably 3.2-3.6 g / 10 min at 190≯ / 2.16 kg; and / or The ultra-low density polyethylene has a melt mass flow rate of 0.8-3.2 g / 10 min, preferably 1.5-2.1 g / 10 min, a molecular weight distribution of 3.8-5.0, a mass percentage of lamellae with a thickness of less than 6.2 nm according to crystallization thermal fractionation analysis of 7.1-8.9%, preferably 7.5-8.5%, and a branch number of 17.1-18.0 / 1000C at 190≯ / 2.16 kg; and / or The polytetrafluoroethylene has a molecular weight of 6000-8000 and a particle size of 0.5-2 μm; and / or The polyethylene glycol has a molecular weight of 2000-6000; and / or The ultra-low density polyethylene contains structural unit a provided by ethylene monomer and structural unit b provided by comonomer, and preferably the molar content of structural unit b of the ultra-low density polyethylene is 8-10 mol%; and / or The comonomer is selected from at least one of propylene, butene, hexene and octene, more preferably hexene.

4. The film composition according to any one of claims 1 to 3, wherein The polytetrafluoroethylene is treated with a modifier, and the method for treating the polytetrafluoroethylene with a modifier comprises: immersing in the presence of a modifier, washing, solid-liquid separation, and drying; Preferably, the modifier is selected from at least one of tributyl methyl ether, tetrahydrofuran, dioxane, isopropanol and chloroform; More preferably, the modifier is selected from a mixture of tetrahydrofuran and isopropanol; It is further preferred that the mass ratio of tetrahydrofuran to isopropanol in the modifier is (7-9): (1-2.5); and / or The washing is performed using an organic solvent, wherein the organic solvent is selected from propanol and / or acetone, more preferably acetone; and / or The conditions of the drying process include: Temperature 55-85≯; and / or Time 20-30h; and / or The conditions of the immersion treatment include: temperature -5--10≯; and / or Time: 5-10 minutes.

5. Use of the film composition according to any one of claims 1 to 4 in preparing a film middle layer, preferably in a FFS heavy packaging film middle layer. 6 . An intermediate layer material for a film, the intermediate layer material being formed from a raw material containing the composition according to claim 1 .

7. A FFS heavy packaging film, wherein the middle layer of the FFS heavy packaging film comprises the middle layer material according to claim 6; Preferably, the FFS heavy packaging film comprises an outer layer, an inner layer and the middle layer; and / or The thickness ratio of the composite structure of the outer layer, the middle layer and the inner layer is (1-2.0):(1-2.0):1; and / or The FFS heavy packaging film product has a thickness of ≯118 μm, a tear resistance of ≮35N, a drop impact strength of ≮800g, can reduce the heat sealing temperature of the film by ≯120°C when in use, has a packaging capacity of ≮950 bags / hour, a heat sealing strength of ≮47N / 15mm at 160°C, and a recovery rate of ≮87%.

8. The FFS heavy packaging film according to claim 7, wherein: The outer layer contains: Metallocene linear polyethylene: 70-90 parts by weight; Ultra-low density polyethylene: 10-30 parts by weight; Polyethylene glycol PEG: 0.2-1.0 parts by weight; and / or The inner layer contains: Metallocene linear polyethylene: 70-90 parts by weight; Ultra-low density polyethylene: 10-30 parts by weight; TiO2 masterbatch: 1-3 parts by weight.

9. The FFS heavy packaging film according to claim 7, wherein: The physicochemical properties of the metallocene linear polyethylene in the inner layer and the outer layer include: The melt mass flow rate at 190≯ / 2.16kg is 2.02-3.2g / 10min, preferably 2.02-2.23g / 10min; and / or Density: 0.920-0.935 g / cm 3 , preferably 0.921-0.930 g / cm 3 ; and / or Molecular weight distribution 3.3-3.8, weight average molecular weight 120,000-160,000, preferably 130,000-150,000; and / or The relative content of platelets with a thickness of 9.6 nm or more is 12-16% or more, preferably 13-15% by crystallization thermal fractionation analysis; and / or The number of branches is 11.8-13.5 / 1000C.

10. The FFS heavy packaging film according to claim 7, wherein: In the outer layer, the physicochemical parameters of the ultra-low density polyethylene include: The melt mass flow rate at 190≯ / 2.16kg is 0.5g / 10-2.5g / 10min, preferably 0.8-1.6g / 10min; and / or Density: 0.908-0.915 g / cm 3 , preferably 0.909-0.912 g / cm 3 ; and / or Molecular weight distribution 3.8-4.1; and / or The mass percentage of the 9.4 nm thick platelets analyzed by thermal fractionation of crystallization is 8.0-9.2%, preferably 8.5-8.9%; and / or Number of branches: 14.5-17.0 / 1000C; and / or The ultra-low density polyethylene contains structural unit a provided by ethylene monomer and structural unit b provided by comonomer, and preferably the molar content of structural unit b of the ultra-low density polyethylene is 4.2-5.5%; and / or The comonomer is selected from at least one of propylene, butene, hexene and octene, more preferably hexene; and / or The polyethylene glycol has a molecular weight of 2000-6000; and / or In the inner layer, the physicochemical parameters of the ultra-low density polyethylene include: The melt mass flow rate at 190≯ / 2.16kg is 0.8-3.2g / 10min, preferably 0.886-0.903g / cm 3 ; and / or Molecular weight distribution 3.8-5.0; and / or The mass percentage of platelets with a thickness of less than 6.2 nm according to crystallization thermal fractionation analysis is 7.1-8.9%, preferably 7.5-8.5%; and / or Number of branches: 17.1-18.0 / 1000C.

Images