CN111100363A - Polyethylene composition and film thereof - Google Patents

Polyethylene composition and film thereof Download PDF

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CN111100363A
CN111100363A CN201811258196.9A CN201811258196A CN111100363A CN 111100363 A CN111100363 A CN 111100363A CN 201811258196 A CN201811258196 A CN 201811258196A CN 111100363 A CN111100363 A CN 111100363A
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component
film
polyethylene
polyethylene composition
weight
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CN111100363B (en
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邵静波
张师军
高达利
白弈青
徐萌
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/08—Copolymers of ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/04—Homopolymers or copolymers of ethene
    • C08J2423/08—Copolymers of ethene

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Abstract

The invention relates to the field of polyethylene materials, and discloses a polyethylene composition which is characterized by comprising a component A, a component B, a component C, a component D and a component E; wherein the MI of component A is determined at a temperature of 190 ℃ and a load of 2.16kgAIs 0.01 to 3.5g/10min, rhoA0.880-0.936g/cm3(ii) a MI of component BBIs 3.6-9.9g/10min, rhoBIs 0.910 to 0.930g/cm3(ii) a MI of component CCIs 16-80g/10min, rhoCIs 0.880-0.930g/cm3(ii) a MI of component DDIs 10-15g/10min, rhoDIs 0.880-0.930g/cm3(ii) a The component E is obtained by extruding and granulating the ethylene-octene copolymer, the polyethylene glycol and the aerogel through double screws. The polyethylene composition obtained by combining the component A, the component B, the component C, the component D and the component E with specific melt index and density is used for preparing the polyethylene film by adopting a flat film drawing methodAnd meanwhile, the composite material has the advantages of large stretching ratio, high film forming rate, high mechanical strength and excellent barrier property, and has great industrial application prospect.

Description

Polyethylene composition and film thereof
Technical Field
The invention relates to the field of polyethylene materials, in particular to a polyethylene composition and a film thereof.
Background
The Biaxially Oriented Polyethylene (BOPE) film is a film material formed by Biaxially stretching Polyethylene (PE) resin with a special molecular structure. In the forming and processing process of the BOPE film, after the film is stretched, the PE macromolecular chains and the crystalline structure are highly oriented, so that the tensile strength of the film is obviously improved, the tensile breaking elongation is reduced, and the film has lower haze, higher glossiness and better transparency. In addition, compared with polyethylene film products prepared by the extrusion blow molding process and the extrusion casting process in the prior art, the BOPE film has the advantages of high mechanical strength, good puncture resistance and impact resistance, excellent optical performance, energy conservation, environmental protection and the like. Therefore, the BOPE film can be widely used in packaging bags, heavy packaging bags, vacuum heat sealing films, low-temperature packaging films, composite films, medical and sanitary products, agricultural films and the like.
The two-way stretching processing method of the plastic film adopted at present comprises a flat film stretching method and a tube bubble stretching method. The flat film stretching method is already applied to the Processing of Polypropylene (PP), Polyamide (PA), polyethylene terephthalate (PET) and other film materials, and the process is mature. Compared with a tube bubble stretching method, the flat film stretching method has the advantages of large stretching ratio (the transverse stretching ratio can reach more than 10 times), high forming speed (the highest rolling speed can reach hundreds of meters per minute), high production efficiency, better mechanical strength, optical performance and thickness uniformity of the obtained film, obvious influence of process condition fluctuation on film forming, large film stretching processing difficulty and higher requirements on film raw materials. The existing biaxially oriented polyethylene raw materials are basically only suitable for preparing the BOPE film by a tube bubble stretching method, and when the existing biaxially oriented polyethylene raw materials are used for preparing the BOPE film by a flat film stretching method, the defects of poor film forming property (low stretching speed and stretching ratio) and easy film breakage exist, namely, the biaxially oriented polyethylene raw materials are basically not suitable for preparing the film by the flat film stretching method.
Therefore, in order to fully utilize the above advantages of the flat film stretching method, it is required to develop a polyethylene raw material suitable for preparing a BOPE film by the flat film stretching method, which has good film forming property, good barrier property and less film cracking.
Disclosure of Invention
The invention aims to overcome the problems of poor film forming property and easy film cracking of the conventional polyethylene film prepared by adopting a flat film drawing method as a raw material, and provides a novel polyethylene composition and a film prepared from the polyethylene composition.
In order to achieve the above object, the first aspect of the present invention provides a polyethylene composition, wherein the polyethylene composition comprises a component A, a component B, a component C, a component D and a component E, wherein the component A is ethylene- α olefin copolymerized linear low density polyethylene having a melt index MI at 190 ℃ under a load of 2.16kgA0.01-3.5g/10min, density rhoA0.880-0.936g/cm3The component B is linear low-density polyethylene copolymerized by ethylene- α olefin and having a melt index MI (melt index) of 2.16kg at the temperature of 190 ℃ under the load ofB3.6-9.9g/10min, density rhoBIs 0.910 to 0.930g/cm3The component C is linear low-density polyethylene copolymerized by ethylene- α olefin and having the temperature of 190 ℃ and the load of 2.16kgMelt index MIC16-80g/10min, density rhoCIs 0.880-0.930g/cm3The component D is linear low-density polyethylene copolymerized by ethylene- α olefin and having a melt index MI of 2.16kg at the temperature of 190 ℃ and under the loadDIs 10-15g/10min, density rhoDIs 0.880-0.930g/cm3(ii) a The POE component is a barrier master batch prepared by melting and mixing ethylene-octene copolymer, polyethylene glycol and aerogel.
In a second aspect, the present invention provides a polyethylene film, wherein said film comprises at least one polyethylene layer formed from said polyethylene composition.
The inventor of the invention finds that the strength of the prepared polyethylene film can be improved by adding the POE master batch with high barrier property, namely the component E, in the process of preparing the film, and moreover, the application field of the polyethylene film material is widened by adopting aerogel and polyethylene glycol to prepare the component E, and the efficiency is improved in the processing process of the polyethylene film material; in addition, after intensive research, the inventors of the present invention unexpectedly found that when a polyethylene film is prepared from the polyethylene composition obtained by using the component a, the component B, the component C, the component D and the component E having specific melt index and density in combination by a flat film stretching method, the polyethylene film has the advantages of large stretching ratio and high film forming rate, can meet the high requirements of the flat film stretching method on polyethylene raw materials, and the polyethylene film prepared from the polyethylene film also has excellent barrier property, and has great industrial application prospects.
According to a preferred embodiment of the invention, when the mass fraction W of the component A in the polyethylene composition is WA25 to 90 weight portions of the component B, the weight portion W of the component BB0.1 to 10 parts by weight of the component C, the mass part of the component C, WCWhen the weight ratio is 10-75 parts, the weight part W of the component DDWhen the content is 5-30 parts by weight, the polyethylene composition has good film forming property, and a film prepared from the polyethylene composition also has the advantages of large stretching ratio, high film forming rate and excellent barrier property.
According to the inventionIn another preferred embodiment, when the molecular weight distribution indexes of the component A, the component B, the component C and the component D all satisfy Mw/MnWhen the film forming rate is less than or equal to 8.0, the polyethylene composition has good film forming property, and a film prepared from the polyethylene composition also has the advantages of large stretching ratio, high film forming rate and excellent barrier property.
According to another preferred embodiment of the invention, when the polyethylene composition has a density ρ of component A, component B, component C and component DA、ρB、ρCAnd ρDThe relationship between them satisfies-0.04 ≤ rhoA-ρBNot more than 0.02, and-0.04 not more than rhoA-ρCNot more than 0.02, and-0.04 not more than rhoA-ρDWhen the film forming rate is less than or equal to 0.02, the polyethylene composition has good film forming property, and a film prepared from the polyethylene composition also has the advantages of large stretching ratio, high film forming rate and excellent barrier property.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of a multiple reactor parallel arrangement for producing polyethylene compositions.
Description of the reference numerals
1-a first reactor; 2-a second reactor; 3-a third reactor; 7-a fourth reactor;
4-a solid/liquid (gas) separator; 5-homogenizing stock bin; 6-melting granulation system.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a polyethylene composition, wherein the polyethylene composition comprises a component A, a component B, a component C, a component D and a component E, wherein the component A is ethylene- α olefin copolymerized linear low density polyethylene and has a melt index MI (melt index) of 2.16kg at the temperature of 190 ℃ and under the load of 2.16kgA0.01-3.5g/10min, density rhoA0.880-0.936g/cm3The component B is linear low-density polyethylene copolymerized by ethylene- α olefin and having a melt index MI (melt index) of 2.16kg at the temperature of 190 ℃ under the load ofB3.6-9.9g/10min, density rhoBIs 0.910 to 0.930g/cm3The component C is linear low-density polyethylene copolymerized by ethylene- α olefin and having a melt index MI (melt index) of 2.16kg at the temperature of 190 ℃ under the loadC16-80g/10min, density rhoCIs 0.880-0.930g/cm3The component D is linear low-density polyethylene copolymerized by ethylene- α olefin and having a melt index MI of 2.16kg at the temperature of 190 ℃ and under the loadDIs 10-15g/10min, density rhoDIs 0.880-0.930g/cm3(ii) a The component E is a barrier master batch prepared by melting and mixing an ethylene-octene copolymer, polyethylene glycol and aerogel.
According to the present invention, the component E may be present in an amount of 0.5 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the total of the components a, B, C and D.
According to the invention, the component E can be prepared from ethylene-octene copolymer (POE), aerogel and polyethylene glycol through blending, extruding, granulating and drying.
Wherein the melt index MI of the ethylene octene copolymer (POE) at 190 ℃ under a load of 2.16kg may be 1-3g/10 min.
Among them, aerogel is a solid substance form, and is one of the solids with very low density in the world, the density is 3 kg per cubic meter, and the common aerogel is silica aerogel, and there are many kinds of aerogels, including silica system, carbon system, sulfur system, metal oxide system, metal system, and so on. Aerogels are sometimes referred to as "solid smoke" or "frozen smoke" because of their translucent color and ultra-light weight. The new material seems fragile and durable and can bear the high temperature of 1400 ℃. In the present invention, the aerogel preferably has a density of 3 kg per cubic meter, the particle size of the aerogel may be in the nanometer level, and the aerogel is a silica aerogel, and is commercially available, for example, from the beijing huarui new city company, model number 2500.
The selected polyethylene glycol can be used as a lubricating auxiliary agent in the material to reduce the friction between the material and equipment in the preparation process of the material, so that the extrusion efficiency is improved.
According to the present invention, the content of the polyethylene glycol may be 3 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the ethylene octene copolymer; the content of the aerogel may be 1 to 30 parts by weight, preferably 10 to 30 parts by weight.
In the present invention, Polyolefin elastomers (POE) are thermoplastic elastomers with narrow relative molecular mass distribution and uniform short chain branch distribution using metallocene catalysts from DOW chemical company, usa. The inventors of the present invention have surprisingly found that: the soft chain curling structure of the octene and the crystallized ethylene chain are used as physical crosslinking points, so that the octene plastic has excellent toughness and good processability, does not have unsaturated double bonds in the molecular structure of the plastic, and has excellent aging resistance; in addition, the POE plastic has narrow molecular weight distribution, better fluidity and good compatibility with polyolefin; the good fluidity can improve the dispersion effect of the filler and simultaneously can improve the weld mark strength of the product.
According to the invention, preferably, the component A has a melt index MI at a temperature of 190 ℃ and a load of 2.16kgAIs 0.01-3g/10min, and the melt index MI of the component B at the temperature of 190 ℃ and the load of 2.16kg isBIs 4-8g/10min, and the melt index MI of the component C at the temperature of 190 ℃ and the load of 2.16kgC16-60g/10 min; said component D having a temperature of 1Melt index MI at 90 ℃ under a load of 2.16kgDIs 11-15g/10 min; more preferably, the component A has a melt index MI at a temperature of 190 ℃ and a load of 2.16kgAIs 0.01-2g/10min, and the melt index MI of the component B at the temperature of 190 ℃ and the load of 2.16kg isBIs 4-5g/10min, and the melt index MI of the component C at the temperature of 190 ℃ and the load of 2.16kgC16-40g/10 min; the component D has a melt index MI at a temperature of 190 ℃ and a load of 2.16kgDIs 12-15g/10 min.
In the present invention, the melt index is measured according to the method specified in GB/T3682-2000, wherein the test conditions include a temperature of 190 ℃ and a load of 2.16 kg.
According to the invention, preferably, the density ρ of the component AAIs 0.910 to 0.930g/cm3Density p of said component BBIs 0.913-0.928g/cm3Density p of said component CCIs 0.905-0.928g/cm3Density p of said component DDIs 0.910 to 0.925g/cm3(ii) a More preferably, the density ρ of the component AAIs 0.915-0.926g/cm3Density p of said component BBIs 0.913-0.924g/cm3Density p of said component CCIs 0.910 to 0.926g/cm3Density p of said component DDIs 0.911-0.923g/cm3. Particularly preferably, the polyethylene composition has a density ρ of component A, component B, component C and component DA、ρB、ρCAnd ρDThe relationship between them satisfies-0.04 ≤ rhoA-ρBNot more than 0.02, and-0.04 not more than rhoA-ρCNot more than 0.02, and-0.04 not more than rhoA-ρDLess than or equal to 0.02, so that the obtained polyethylene composition has better film forming performance, and a film prepared from the polyethylene composition also has excellent mechanical strength.
The component A, the component B, the component C and the component D are all linear low-density polyethylene copolymerized by ethylene- α olefin, wherein the linear structure means that a molecular chain only contains a short branched chain structure but does not contain a long branched chain structure and a crosslinking structure, and the linear structure is determined by a polymerization monomer and polymerization process conditions, is known to those skilled in the art and is not described herein in detail.
In order to obtain a polyethylene composition having good film-forming properties and excellent mechanical properties, it is preferred that the component A is present in the polyethylene composition in a mass fraction WA25 to 90 weight portions of the component B, the weight portion W of the component BB0.1 to 10 parts by weight of the component C, the mass part of the component C, WC10 to 75 weight portions of the component D, the weight portion W of the component DD5-30 parts by weight; more preferably, in the polyethylene composition, the mass fraction W of the component AA30-80 parts by weight of the component B, WB0.5 to 8 weight portions of the component C, the weight portion W of the component CC20 to 70 parts by weight of the component D, the mass part W of the component DD20-30 parts by weight; particularly preferably, the mass fraction W of the component AAAnd part by mass W of component CCMelt index MI with component AASatisfies the relationship of (1) 4.6 XlgMIA+10.4≥WA/WC≥0.18×lgMIA+0.7, preferably 1.8 XlgMIA+4.7≥WA/WC≥0.22×lgMIA+0.9, which enables the polyethylene composition to have a greater draw ratio and higher draw rate in the flat film process biaxial stretching process.
According to the invention, the polyethylene composition has a melt index at a temperature of 190 ℃ and a load of 2.16kg of 0.1 to 20g/10min, preferably 0.5 to 10g/10 min. When the component a, the component B, the component C and the component D having the above-mentioned specific melt index and density are used in combination, the melt index of the polyethylene composition as a whole is controlled within the preferable range, and the resulting polyethylene composition can have both of very excellent film formability and tensile strength.
According to the invention, preferably, the molecular weight distribution indexes of the component A, the component B, the component C and the component D all satisfy Mw/Mn8.0 or less, preferably 3.5 or less Mw/MnLess than or equal to 6.0. In particular, in order to obtain a composition havingThe component A, the component B, the component C and the component D with the molecular weight distribution are obtained by adopting Ziegler-Natta catalyst polymerization. The kind of the ziegler-natta catalyst can be selected conventionally in the art, and it generally consists of a magnesium/titanium compound and an organic aluminum compound, and optionally an electron donor, and is well known to those skilled in the art, and will not be described herein. After intensive research, the inventor of the present invention finds that when the component A, the component B and the component C which are obtained by adopting Ziegler-Natta catalyst polymerization and have the above-mentioned melt index and density are used together, the obtained film has good film forming performance, and the film prepared from the polyethylene composition also has the advantage of excellent mechanical performance.
The amount of α olefin comonomer in the components A, B, C and D is not particularly limited in the present invention, for example, the molar amount of α olefin comonomer in the components A, B, C and D may each independently be 0.2 to 15 mol%, preferably 1.5 to 10 mol%3-C20And α olefin in the component A, the component B and the component C is preferably at least one of propylene, 1-butene, 2-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3-dimethyl-1-pentene, 3, 4-dimethyl-1-pentene, 4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 5-methyl-1-hexene, 1-heptene, 2-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene, and more preferably at least one of 1-butene, 1-hexene and 1-octene, from the viewpoint of raw material availability.
In addition, the polyethylene composition may also contain various other conventional additives commonly used in polyethylene resins and polyethylene films, and the other additives do not adversely affect the stretch film forming property, the mechanical property and the barrier property of the polyethylene composition provided by the invention. Such other adjuvants include, but are not limited to: at least one of antioxidant, slipping agent, and anti-sticking agent. In addition, the amount of the other additives can be selected conventionally in the art, and those skilled in the art can know the amount of the other additives, and the details are not described herein.
The polyethylene composition can be prepared according to various existing methods, for example, the component A, the component B, the component C and the component D are prepared respectively, and then the component A, the component B, the component C, the component D and the component E are mechanically mixed in a mechanical mixing device according to the proportion, and then are added into a melt blending device for melt blending. The mechanical mixing device may be, for example, a high-speed stirrer, a kneader, or the like. The melt blending equipment may be, for example, a twin screw extruder, a single screw extruder, an open mill, an internal mixer, or the like.
According to a preferred embodiment of the present invention, the polyethylene composition is produced in a multi-reactor parallel apparatus as shown in fig. 1, the multi-reactor parallel apparatus comprises a first reactor 1, a second reactor 2, a third reactor 3, a fourth reactor 7, a solid/liquid (gas) separator 4, a homogenization silo 5 and a melt granulation system 6, wherein the first reactor 1, the second reactor 2, the third reactor 3 and the fourth reactor 7 are connected in parallel, the number of the solid/liquid (gas) separator 4 is four, the solid/liquid (gas) separator 4 is respectively communicated with the first reactor 1, the second reactor 2, the third reactor 3 and the fourth reactor 7, the phase separation of the component a produced by the first reactor 1, the component B produced by the second reactor 2, the component C produced by the third reactor 3 and the component D produced by the fourth reactor 7 is respectively carried out in different solid/liquid (gas) separators 4, then, the component A, the component B, the component C and the component D which are subjected to phase separation are conveyed into a homogenizing silo 5 in proportion and are uniformly mixed with the component E and other additives, and then the mixture is conveyed into a melting granulation system 6 for extrusion granulation. The polymerization in each reactor may be a batch polymerization or a continuous polymerization. When multiple reactors are used in parallel polymerization, W is hereinafterA、WB、WC、WDThe unit time yields of the components in the respective reactors.
In a second aspect, the present invention provides a polyethylene film, wherein said film comprises at least one polyethylene layer formed from said polyethylene composition.
The barrier film may have a single-layer structure or a multi-layer structure. When the high performance barrier polyethylene film is a multilayer structure, at least the core layer (typically the layer of greatest thickness) is a polyethylene layer formed from the polyethylene composition. For example, the barrier film may have a composite structure of an upper skin layer, a core layer, and a lower skin layer, and at least the core layer is a polyethylene layer formed of the polyethylene composition. Generally, the thickness of the barrier film may be 10 to 200 μm, preferably 10 to 100 μm. Further, when the barrier film has a composite structure of an upper skin layer, a core layer, and a lower skin layer, the thicknesses of the upper skin layer and the lower skin layer are each independently 1 to 25% of the thickness of the barrier film.
The barrier film may be a uniaxially stretched film or a biaxially stretched film, preferably a biaxially stretched film, more preferably a biaxially stretched film produced by a flat film biaxially stretching method.
The process of making biaxially oriented films using flat film biaxial stretching is well known to those skilled in the art. Specifically, the polyethylene composition is added into a casting device to be extruded and cast into a sheet, and then the obtained cast sheet is stretched and formed in a film biaxial stretching device. In the extrusion casting, the cast sheet die may be selected according to the structure of a film to be obtained, for example, when a film having a single layer structure is to be obtained, a single layer die may be used; when it is desired to obtain a film having a multilayer structure (a film having a three-layer structure of an upper skin layer, a core layer and a lower skin layer), a multilayer-structure composite die may be used, and at least one layer (core layer) of the multilayer-structure composite die is communicated with an extruder hopper containing the above-mentioned polyethylene composition, so that at least one layer (core layer) of the obtained film is a polyethylene layer formed of the above-mentioned polyethylene composition. In the extrusion process, the extrusion temperature may be 150 ℃ to 255 ℃, preferably 165 ℃ to 255 ℃, and the temperature of the casting chill roll may be 20 ℃ to 80 ℃. In addition, the biaxial stretching may be performed by a simultaneous faradaic stretching process (i.e., stretching in the Machine Direction (MD) and the Transverse Direction (TD)) or a stepwise stretching process (i.e., stretching in the machine direction and then stretching in the transverse direction). The synchronous stretching process comprises the following specific steps: the cast sheet is fully preheated and simultaneously stretched in the longitudinal direction and the transverse direction, wherein the preheating temperature can be 80-160 ℃, the stretching temperature can be 70-165 ℃, preferably 80-155 ℃, the longitudinal (MD) stretching ratio is more than or equal to 4 times, the Transverse (TD) stretching ratio is more than or equal to 5 times, and the transverse stretching rate is more than or equal to 50%/s. The step-by-step stretching process comprises the following specific steps: the cast sheet is fully preheated, and then longitudinally stretched and transversely stretched, wherein the preheating temperature can be 65-160 ℃, preferably 70-155 ℃, the stretching temperature can be 65-155 ℃, preferably 70-150 ℃, the longitudinal (MD) stretching ratio is more than or equal to 4 times, the Transverse (TD) stretching ratio is more than or equal to 5 times, and the transverse stretching rate is more than or equal to 50%/s. After the stretch-molding of the film, the film may be subjected to annealing and setting treatment without being subjected to setting treatment. When the annealing setting treatment is performed, the film setting treatment temperature may be 80 to 165 deg.C, preferably 85 to 160 deg.C. And finally, performing surface corona treatment, edge cutting and rolling treatment on the film to finally obtain the barrier film.
The high-performance barrier film provided by the invention has the advantages of good film forming property, large stretching multiplying power, high stretching speed and excellent high barrier property. In the process of preparing the biaxially oriented film by a flat film stretching method, as described above, the longitudinal (MD) stretching ratio of the barrier film is not less than 4 times, and the Transverse (TD) stretching ratio is not less than 5 times. The larger the stretch ratio, the higher the mechanical strength of the barrier film. The Transverse Direction (TD) stretching rate of the barrier film is more than or equal to 50%/s, and preferably 60-150%/s, so that industrial continuous production can be guaranteed.
The barrier film provided by the invention has higher mechanical strength and better temperature barrier property. The performance of the biaxial stretching film can meet the following requirements: the longitudinal (MD) tensile strength is more than or equal to 50MPa, preferably more than or equal to 55 MPa; the Transverse Direction (TD) tensile strength is more than or equal to 55MPa, preferably more than or equal to 60 MPa; the tensile elongation at break is less than or equal to 350 percent, preferably less than or equal to 300 percent; the oxygen index is not less than 20%, preferably not less than 22%. In the present invention, the machine direction tensile strength, the transverse direction tensile strength and the tensile elongation at break are measured according to the method specified in GB/T1040.3-2006. The oxygen index was measured according to the method specified in GB/T2406-2008.
In addition, the barrier film provided by the invention can have a thickness of 10-200 μm, preferably 10-100 μm.
The present invention will be described in detail below by way of examples.
In the following examples and comparative examples:
the film biaxial stretching apparatus was purchased from Br ü ckner, Germany, and was of the type KaroIV.
The polyethylene composition and film properties were tested according to the following methods:
(1) molecular weight distribution index (M)w/Mn): measuring by using a PL-GPC 220 type gel permeation chromatograph of Polymer Laboratories, UK, combined with an IR5 type infrared detector, wherein the chromatographic columns are 3 series-connected Plgel 10 mu m MIXED-B columns, the solvent and mobile phase are 1,2, 4-trichlorobenzene, the column temperature is 150 ℃, the flow rate is 1.0mL/min, and the general calibration is carried out by adopting EasiCalPS-1 narrow-distribution polystyrene standard sample of PL;
(2) melt Index (MI): the measurement is carried out according to the method specified in GB/T3682-2000, wherein the test temperature is 190 ℃, and the load is 2.16 kg;
(3) density: the measurement was carried out according to the method specified in GB/T1033.2-2010 and by the density gradient column method.
And the component E (POE barrier master batch P1) is a self-made material of a North chemical hospital, 100 parts by weight of POE, 10 parts by weight of aerogel and 10 parts by weight of polyethylene glycol are blended for three minutes at 60 ℃, and are added into a double-screw extruder for mixing and extrusion, wherein the extrusion temperature is 180 ℃ and 200 ℃, and the mixture is hereinafter referred to as P1.
And the component E (POE barrier master batch P2) is a self-made material of a North chemical hospital, 100 parts by weight of POE, 20 parts by weight of aerogel and 10 parts by weight of polyethylene glycol are blended for three minutes at 60 ℃, and are added into a double-screw extruder for mixing and extrusion, wherein the extrusion temperature is 180 ℃ and 200 ℃, and the mixture is hereinafter referred to as P2.
And the component E (POE barrier master batch P3) is a self-made material of a North chemical hospital, 100 parts by weight of POE, 30 parts by weight of aerogel and 10 parts by weight of polyethylene glycol are blended for three minutes at 60 ℃, and then the mixture is added into a double-screw extruder for mixing and extrusion, wherein the extrusion temperature is 180 ℃ and 200 ℃, and the mixture is hereinafter referred to as P3.
Example 1
This example illustrates the polyethylene composition and barrier film provided by the instant invention.
(1) Preparation of polyethylene composition:
the polyethylene composition provided in this example is composed of component a, component B, component C, component D and component E, where component a, component B, component C and component D are all Linear Low Density Polyethylene (LLDPE) copolymerized with ethylene- α olefin, and are all prepared by using the same catalyst system (ziegler-natta catalyst, which is the ziegler-natta catalyst system prepared in CN101838351A example 1, the following) and polymerization process, except that the amount of hydrogen added and the kind and molar content of α olefin comonomer are different when preparing different components, and component E is POE barrier masterbatch p1, which has the following specific steps:
ethylene, α olefin, hydrogen and nitrogen (ethylene, α olefin, hydrogen and nitrogen are all polymer grades, are used after water and oxygen are removed, the same is applied below) are added into a fluidized bed gas phase reactor, then a Ziegler-Natta catalyst system is added, and then polymerization is carried out under the conditions that the temperature is 84-88 ℃ and the pressure is 1.8-2.0MPa, so as to respectively obtain a component A, a component B, a component C and a component D, wherein the control of the melt index of the component A, the component B, the component C and the component D is realized by adjusting the adding amount of hydrogen, and the control of the density is realized by adjusting the type and the adding amount of α olefin, α olefin used in the preparation of the component A is 1-hexene, α olefin used in the preparation of the component B is 1-hexene, α olefin used in the preparation of the component C is 1-butene, and α olefin used in the preparation of the component D is 1-butene.
Through detection, the properties of the component A, the component B, the component C and the component D prepared by the method are as follows:
melt index MI of component AA2.0g/10min, density ρA＝0.92g/cm3Molecular weight distribution index Mw/Mn6.4, α molar content of olefin comonomer 8.9 mol%;
melt index MI of component BB4.0g/10min, density ρB＝0.91g/cm3Molecular weight distribution index Mw/Mn5.7, α molar content of olefin comonomer 8.9 mol%;
melt index MI of component CC16g/10min, density ρC＝0.905g/cm3Molecular weight distribution index Mw/MnThe molar content of the olefin comonomer was 10.1 mol% for 4.6 and α.
Melt index MI of component DD10g/10min, density ρD＝0.902g/cm3Molecular weight distribution index Mw/MnThe molar content of the olefin comonomer was 9.1 mol% for 4.8 and α.
Weighing and mixing the components according to the proportion, wherein the weight part W of the component AA40 parts by weight of component B, WB10 parts by weight of component C, WC10 parts by weight of the component D, WBIs 10 parts by weight of WA/WC4 (satisfy 4.6 × lgMI)A+10.4≥WA/WC≥0.18×lgMIA+0.7, also satisfying 1.8 XlgMIA+4.7≥WA/WC≥0.22×lgMIA+0.9), and the amount of the component E is 10 parts by weight based on 100 parts by weight of the total weight of the component A, the component B, the component C and the component D, then the mixture is added into a high-speed stirrer to be uniformly mixed, and the mixed material is added into W&In a feeder of a double-screw extruder manufactured by company P, materials enter the double screws through the feeder, the temperature of the screws is kept between 160 ℃ and 200 ℃ in the processing process, the materials are melted and mixed uniformly through the screws, and then the materials are extruded, granulated and dried to obtain polyethylene composition granules, and the melt index MI of the polyethylene composition granules is detected to be 3.1g/10 min.
(2) Preparing a barrier film:
drying the polyethylene composition granules prepared in the step (1), adding the dried polyethylene composition granules into a core layer extruder of a multilayer extrusion casting machine of a Labtech company, Sweden, of which the model is LCR400, and upper and lower surface layer extruders for melt extrusion and casting, wherein inorganic anti-sticking agents (nano silicon dioxide, purchased from QS-L150, the same as below) are also required to be added into the upper and lower surface layer extruders, the weight ratio of the anti-sticking agents added into the upper and lower surface layer extruders to the polyethylene composition granules is 0.005:1, and in the process of casting, the temperature of a casting chill roll is set to be 25 ℃ to prepare a polyethylene thick casting sheet which consists of an upper surface layer, a core layer and a lower surface layer.
Placing the polyethylene thick cast sheet into a stretching clamp of film biaxial stretching equipment, and forming by adopting a biaxial step-by-step stretching process of stretching in a longitudinal direction (MD) and then stretching in a Transverse Direction (TD), wherein the process conditions of each step are as follows: the MD preheating temperature is 105 ℃, the MD stretching temperature is 110 ℃, and the MD stretching magnification is 4 times; TD preheating temperature is 105 ℃, TD stretching temperature is 115 ℃, TD stretching ratio is 5 times, and TD stretching speed of the film is 160%/s; the film setting temperature was 120 ℃ to obtain a film having an average thickness of 25 μm, which was composed of an upper skin layer, a core layer, and a lower skin layer, each of which was made of the polyethylene composition according to this example, and further containing an antiblocking agent, and both of which had a thickness of 0.5 μm.
Example 2
This example illustrates the polyethylene composition and barrier film provided by the instant invention.
(1) Preparation of polyethylene composition:
the polyethylene composition provided in this example is composed of component a, component B, component C, component D, and component E, where component a, component B, component C, and component D are all Linear Low Density Polyethylene (LLDPE) copolymerized with ethylene- α olefin, and are all prepared using the same catalyst system (ziegler-natta catalyst) and polymerization process, except that the amount of hydrogen added and the type and molar content of α olefin comonomer are different when preparing different components, component E is POE barrier masterbatch p1, the specific steps are as follows:
adding ethylene, α olefin, hydrogen and nitrogen into a fluidized bed gas phase reactor, then adding a Ziegler-Natta catalyst system, and then polymerizing under the conditions that the temperature is 84-88 ℃ and the pressure is 1.8-2.0MPa to respectively obtain a component A, a component B, a component C and a component D, wherein the control of the melt index of the component A, the component B, the component C and the component D is realized by adjusting the adding amount of hydrogen, and the control of the density is realized by adjusting the type and the adding amount of α olefin, the α olefin used in the preparation of the component A is 1-butene, the α olefin used in the preparation of the component B is 1-butene, the α olefin used in the preparation of the component C is 1-hexene, and the α olefin used in the preparation of the component D is 1-hexene.
Through detection, the properties of the component A, the component B, the component C and the component D prepared by the method are as follows:
melt index MI of component AA0.01g/10min, density ρA＝0.930g/cm3Molecular weight distribution index Mw/Mn5.5, α molar content of olefin comonomer 2.1 mol%;
melt index MI of component BBDensity ρ of 9.0g/10minB＝0.920g/cm3Molecular weight distribution index Mw/Mn4.8, α molar content of olefin comonomer 2.8 mol%;
melt index MI of component CC40g/10min, density ρC＝0.922g/cm3Molecular weight distribution index Mw/Mn4.4, α the molar content of olefin comonomer was 4.0 mol%.
Melt index MI of component DD12g/10min, density ρD＝0.923g/cm3Molecular weight distribution index Mw/Mn4.8, α molar content of olefin comonomer 4.1 mol%.
Weighing and mixing the components according to the proportion, wherein the weight part W of the component AA45 parts by weight of the component B, WBIs 5 parts by weight, the mass part W of the component CC45 parts by weight of the component D, WDIs 5 parts by weight of WA/WC1 (satisfies 4.6 × lgMI)A+10.4≥WA/WC≥0.18×lgMIA+0.7, also satisfying 1.8 XlgMIA+4.7≥WA/WC≥0.22×lgMIA+0.9), and the amount of the barrier master batch P1 is 20 parts by weight based on 100 parts by weight of the total weight of the component A, the component B, the component C and the component D, then the mixture is added into a high-speed stirrer to be uniformly mixed, and the mixed material is added into W&In a feeder of a double-screw extruder manufactured by company P, materials enter the double screws through the feeder, the temperature of the screws is kept between 180 ℃ and 200 ℃ in the processing process, the materials are melted and mixed uniformly through the screws, and then the materials are extruded, granulated and dried to obtain polyethylene composition granules, and the melt index MI of the polyethylene composition granules is detected to be 3g/10 min.
(2) Preparing a barrier film:
drying the polyethylene composition granules prepared in the step (1), adding the dried polyethylene composition granules into a core layer extruder and upper and lower surface layer extruders of a multilayer extrusion casting machine of Labtech company, Sweden, of which the model is LCR400, for melt extrusion and casting sheets, wherein inorganic anti-sticking agents are also required to be added into the upper and lower surface layer extruders, the weight ratio of the anti-sticking agents added into the upper and lower surface layer extruders to the polyethylene composition granules is 0.005:1, and in the process of casting the sheets, the temperature of a casting chill roll is set to be 85 ℃ to prepare the polyethylene thick casting sheets which comprise the upper surface layer, the core layer and the lower surface layer.
Placing the polyethylene thick cast sheet into a stretching clamp of film biaxial stretching equipment, and forming by adopting a biaxial step-by-step stretching process of stretching in a longitudinal direction (MD) and then stretching in a Transverse Direction (TD), wherein the process conditions of each step are as follows: the MD preheating temperature is 130 ℃, the MD stretching temperature is 126 ℃, and the MD stretching magnification is 4 times; TD preheating temperature is 140 ℃, TD stretching temperature is 128 ℃, TD stretching ratio is 6 times, and TD stretching speed of the film is 110%/s; the film setting temperature was 130 ℃ to obtain a film having an average thickness of 25 μm, which was composed of an upper skin layer, a core layer, and a lower skin layer, each of which was made of the polyethylene composition according to this example, and further containing an antiblocking agent, and both of which had a thickness of 1 μm.
Example 3
This example illustrates the polyethylene composition and barrier film provided by the instant invention.
(1) Preparation of polyethylene composition:
the polyethylene composition provided in this example was polymerized by using the multiple reactor parallel apparatus shown in fig. 1, wherein the first reactor 1 was polymerized to prepare component a, the second reactor 2 was polymerized to prepare component B, the third reactor 3 was polymerized to prepare component C, and the fourth reactor 7 was polymerized to prepare component D, and component a, component B, component C, and component D were all Linear Low Density Polyethylene (LLDPE) copolymerized with ethylene- α olefin, and were all prepared by using the same catalyst system (ziegler-natta catalyst) and polymerization process, except that the amount of hydrogen added for preparing the different components, the type and molar content of α olefin comonomer, and the unit time yield of each reactor were different.
α olefin, normal hexane and hydrogen are added into a batch kettle type polymerization reactor, the batch kettle type polymerization reactor is heated to a preset polymerization temperature, then ethylene monomer and a catalyst system are simultaneously added into the batch kettle type polymerization reactor, and polymerization is carried out for 60 minutes under the conditions that the temperature is 240 ℃ and the pressure is 14.8MPa, so as to respectively obtain a component A, a component B, a component C and a component D, wherein the control of the melt index of the component A, the component B, the component C and the component D is realized by adjusting the adding amount of hydrogen, and the control of the density is realized by adjusting the type and the adding amount of α olefin, α olefin used in the process of preparing the component A is 1-octene, α olefin used in the process of preparing the component B is 1-butene, α olefin used in the process of preparing the component C is 1-butene, and α olefin used in the process of preparing the component D is 1-butene.
The production per unit time W of component A in the first reactor 1 during the preparationAThe yield per unit time W of component B in the second reactor 2BWith the yield per unit time W of component C in the third reactor 3CIs maintained at WA：WB：WC75: 2: 35 wherein WA/WC2.1 (satisfy 4.6 × lg)MIA+10.4≥WA/WC≥0.18×lgMIA+0.7, also satisfying 1.8 XlgMIA+4.7≥WA/WC≥0.22×lgMIA+0.9)。
Through detection, the properties of the component A, the component B, the component C and the component D prepared by the method are as follows:
melt index MI of component AADensity p of 0.1g/10minA＝0.90g/cm3Molecular weight distribution index Mw/Mn5.8, α molar content of olefin comonomer 2.5 mol%;
melt index MI of component BBDensity p of 6.0g/10minB＝0.920g/cm3Molecular weight distribution index Mw/Mn4.5, α molar content of olefin comonomer 5.3 mol%;
melt index MI of component CC25g/10min, density ρC＝0.920g/cm3Molecular weight distribution index Mw/MnThe molar content of olefin comonomer was 5.7 mol% for 4.2 and α.
Melt index MI of component DD15g/10min, density ρD＝0.910g/cm3Molecular weight distribution index Mw/MnThe molar content of the olefin comonomer was 5.7 mol% at 4.5 and α.
The prepared components are respectively conveyed into different solid/liquid (gas) separators 4 according to the production ratio per unit time for phase separation and then conveyed into a homogenizing silo 5 with stirring, and then POE barrier master batch P2 is added according to the proportion. Wherein, the component E (P2 of POE barrier master batch) is used in 10 parts by weight based on 100 parts by weight of the sum of the components A, B, C and D, then the mixture homogenized by the homogenizing silo 5 is added into a feeder of a twin-screw extruder manufactured by W & P company, the material enters into the twin-screw extruder through the feeder, the temperature of the screw is kept between 170 and 200 ℃ during the processing process, the polyethylene composition granules are obtained by melting, mixing, extruding, granulating and drying through the screw, and the melt index MI of the polyethylene composition granules is detected to be 2.8g/10 min.
(2) Preparing a barrier film:
drying the polyethylene composition granules prepared in the step (1), adding the dried polyethylene composition granules into a multilayer extrusion casting machine of a Labtech company in Sweden, wherein the model of the LCR400 is the model of the LCR400, carrying out melt extrusion, and casting a cast sheet, wherein in the process of casting the cast sheet, the temperature of a casting chill roll is set to be 35 ℃, so that a thick polyethylene cast sheet is prepared, and the cast sheet is of a single-layer structure.
Placing the polyethylene thick cast sheet into a stretching clamp of film biaxial stretching equipment, and forming by adopting a biaxial step-by-step stretching process of stretching in a longitudinal direction (MD) and then stretching in a Transverse Direction (TD), wherein the process conditions of each step are as follows: the MD preheating temperature is 116 ℃, the MD stretching temperature is 118 ℃, and the MD stretching magnification is 4 times; TD preheating temperature is 120 ℃, TD stretching ratio is 5 times, and TD stretching speed of the film is 110%/s; the film setting temperature was 122 ℃ to give a monolayer film having an average thickness of 25 μm.
Example 4
This example illustrates the polyethylene composition provided by the invention and a barrier film incorporating a barrier masterbatch, P2.
A polyethylene composition and a barrier film were prepared according to the method of example 1, except that P1 was replaced with P2, and 20 parts by weight of the POE barrier master batch P2 was added, based on 100 parts by weight of the total weight of component a, component B, component C and component D, to obtain a film having an average thickness of 25 μm, which was composed of an upper skin layer, a core layer and a lower skin layer, each of which was the polyethylene composition of the present example, and further containing an antiblocking agent in the upper and lower skin layers, each of which had a thickness of 0.5 μm.
Example 5
This example illustrates the polyethylene composition provided by the invention and a barrier film incorporating a barrier masterbatch, P3.
A polyethylene composition and a barrier film were prepared as in example 1, except that P1 was replaced with P3 and component A was used in an amount WA80 parts by weight of component BBIs 1 part by weight, the amount W of the component CC19 parts by weight of component DD10 parts by weight of POE barrier master batch P220 parts by weight of WA/WC4.21 (satisfy 4.6 × lgMI)A+10.4≥WA/WC≥0.18×lgMIA+0.7, also satisfying 1.8 XlgMIA+4.7≥WA/WC≥0.22×lgMIA+0.9, wherein MIA2.0g/10min) to obtain a film having an average thickness of 25 μm, which was composed of an upper skin layer, a core layer, and a lower skin layer, each of which was made of the polyethylene composition of the present example, and further containing an antiblocking agent, and both of which had a thickness of 0.5 μm.
Comparative example 1
This comparative example serves to illustrate the polyethylene feed and film barrier properties of the reference.
(1) Polyethylene raw material:
the film grade linear low density polyethylene produced by the Chinese petrochemical Yanshan petrochemical company used in the comparative example is the No. 7042, the catalyst is a Ziegler-Natta catalyst, the melt index MI is 2.0g/10min, and the density rho is 0.920g/cm3Molecular weight distribution index Mw/Mn＝4.5。
(2) Preparing a barrier film:
a barrier film was prepared as in example 1, except that the polyethylene composition pellets were replaced with the same weight part of the polyethylene raw material of step (1) of this comparative example, and the film was not stretched into a film in the case of tensile rupture after many attempts. In addition, after the TD stretching rate in the preparation process of the barrier film is reduced to 50%/s, the situation of stretching and film breaking still occurs after a plurality of attempts, and the film cannot be stretched to form.
Comparative example 2
This comparative example serves to illustrate the polyethylene composition of the reference as well as the film barrier properties.
A polyethylene composition and a barrier film were produced in the same manner as in example 1, except that component E, i.e., POE barrier masterbatch P1, was not added to the polyethylene composition, to obtain a film having an average thickness of 25 μm, which was composed of an upper skin layer, a core layer, and a lower skin layer, each of which was the polyethylene composition of the present comparative example, and further containing an antiblocking agent therein, both of which had a thickness of 0.5 μm.
Comparative example 3
This comparative example serves to illustrate a reference polyethylene feedstock and film thereof.
(1) Polyethylene raw material:
the polyethylene feedstock used in this comparative example was the same as that of comparative example 1.
(2) Preparing a barrier film:
the barrier film of this comparative example was obtained by extrusion blow molding using an up-blowing film blowing apparatus of dr.collin, germany, in the following specific manner: adding the polyethylene raw material selected in the step (1) into a hopper of an extruder of an up-blowing film blowing device, fully melting and plasticizing the raw material by the extruder, extruding the raw material by an annular die of a machine head to prepare a melt film tube, blowing by compressed air (blowing ratio is 2.5 times), and cooling by an air ring to prepare the barrier film, wherein the film is of a single-layer structure with the average thickness of 25 mu m.
Test example
Test examples are used to illustrate the performance tests of the films of examples 1-5 and the films of comparative examples 1-3.
(1) Film tensile strength and tensile elongation at break: the results obtained by measurement according to the method specified in GB/T1040.3-2006 are shown in Table 1;
(2) coefficient of thermal conductivity: the results obtained according to the method defined in GB 3399-1982 are shown in Table 1.
TABLE 1
Figure BDA0001843247270000211
Remarking: the thermal conductivity is the heat transferred in watts/meter.degree (W/(m.K) or (W/(m.DEG C.) through an area of 1 square meter in 1 second (1S) under a stable heat transfer condition, with a temperature difference of 1m thick material at both side surfaces of 1K or 1 ℃.
From the results in table 1, it can be seen that the biaxially oriented PE films prepared from the polyethylene composition provided by the present invention in examples 1-5 all can satisfy the requirements of longitudinal (MD) tensile strength not less than 50MPa, Transverse (TD) tensile strength not less than 55MPa, and tensile elongation at break not more than 350%, especially the thermal conductivity coefficient of the biaxially oriented PE films prepared from the polyethylene composition provided by the present invention in examples 1-5 is less than 0.16W/m.k, compared with the films in the prior art, the biaxially oriented PE films prepared from the polyethylene composition have the advantages of large film forming rate, fast stretching speed, and high mechanical strength, and have excellent barrier properties, and have great industrial application prospects.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (18)

1. The polyethylene composition is characterized by comprising a component A, a component B, a component C, a component D and a component E, wherein the component A is linear low-density polyethylene copolymerized by ethylene- α olefin, and the melt index MI of the component A at the temperature of 190 ℃ and the load of 2.16kgA0.01-3.5g/10min, density rhoA0.880-0.936g/cm3The component B is linear low-density polyethylene copolymerized by ethylene- α olefin, and the melt index MI of the component B is at the temperature of 190 ℃ and under the load of 2.16kgB3.6-9.9g/10min, density rhoBIs 0.910 to 0.930g/cm3The component C is linear low-density polyethylene copolymerized by ethylene- α olefin, and the melt index MI of the component C is 190 ℃ under the condition of temperature and 2.16kg under loadC16-80g/10min, density rhoCIs 0.880-0.930g/cm3The component D is linear low-density polyethylene copolymerized by ethylene- α olefin, and the melt index MI of the component D is 190 ℃ under the condition of the temperature and the load of 2.16kgDIs 10-15g/10min, density rhoDIs 0.880-0.930g/cm3(ii) a The component E is a barrier master batch prepared by melting and mixing an ethylene-octene copolymer, polyethylene glycol and aerogel.
2. The polyethylene composition according to claim 1, wherein the component E is present in an amount of 0.5 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the total amount of the components a, B, C and D.
3. The polyethylene composition according to claim 1, wherein in the component E, the polyethylene glycol is contained in an amount of 3 to 30 parts by weight and the aerogel is contained in an amount of 1 to 30 parts by weight, based on 100 parts by weight of the ethylene octene copolymer; preferably, the content of the polyethylene glycol is 10-20 parts by weight, and the content of the aerogel is 10-30 parts by weight.
4. Polyethylene composition according to claim 1 wherein the component A has a melt index MI at a temperature of 190 ℃ under a load of 2.16kgAIs 0.01-3g/10min, and the melt index MI of the component B at the temperature of 190 ℃ and the load of 2.16kg isBIs 4-8g/10min, and the melt index MI of the component C at the temperature of 190 ℃ and the load of 2.16kgC16-60g/10 min; the component D has a melt index MI at a temperature of 190 ℃ and a load of 2.16kgDIs 11-15g/10 min;
preferably, the component A has a melt index MI at a temperature of 190 ℃ and a load of 2.16kgAIs 0.01-2g/10min, and the melt index MI of the component B at the temperature of 190 ℃ and the load of 2.16kg isBIs 4-5g/10min, and the melt index MI of the component C at the temperature of 190 ℃ and the load of 2.16kgC16-40g/10 min; the component D has a melt index MI at a temperature of 190 ℃ and a load of 2.16kgDIs 12-15g/10 min.
5. Polyethylene composition according to claim 1, wherein the component A has a density pAIs 0.910 to 0.930g/cm3Density p of said component BBIs 0.913-0.928g/cm3Density p of said component CCIs 0.905-0.928g/cm3Density p of said component DDIs 0.910-0.925g/cm3；
Preferably, the density ρ of the component AAIs 0.915-0.926g/cm3Density p of said component BBIs 0.913-0.924g/cm3Density p of said component CCIs 0.910 to 0.926g/cm3Density p of said component DDIs 0.911-0.923g/cm3。
6. Polyethylene composition according to claim 1 or 5, wherein the polyethylene composition has a density p, of component A, component B, component C and component DA、ρB、ρCAnd ρDThe relationship between them satisfies-0.04 ≤ rhoA-ρBNot more than 0.02, and-0.04 not more than rhoA-ρCNot more than 0.02, and-0.04 not more than rhoA-ρD≤0.02。
7. Polyethylene composition according to any of claims 1 to 6, wherein the mass fraction W of component A in the polyethylene compositionA25 to 90 weight portions of the component B, the weight portion W of the component BB0.1 to 10 parts by weight of the component C, the mass part of the component C, WC10 to 75 weight portions of the component D, the weight portion W of the component DD5-30 parts by weight;
preferably, in the polyethylene composition, the mass fraction W of the component AA30-80 parts by weight of the component B, WB0.5 to 8 weight portions of the component C, the weight portion W of the component CC20 to 70 parts by weight of the component D, the mass part W of the component DD20 to 30 portions by weight.
8. The polyethylene composition according to claim 7, wherein the mass fraction W of component AAComponent C, part by mass WCComponent A, melt index MIAThe relationship between them satisfies:
4.6×lgMIA+10.4≥WA/WC≥0.18×lgMIA+0.7，
preferably 1.8 XlgMIA+4.7≥WA/WC≥0.22×lgMIA+0.9。
9. The polyethylene composition according to any of claims 1 to 8, wherein the polyethylene composition has a melt index at a temperature of 190 ℃ and a load of 2.16kg of from 0.1 to 20g/10min, preferably from 0.5 to 10g/10 min.
10. The polyethylene composition according to any of claims 1-5, wherein the molecular weight distribution indices of component A, component B, component C and component D all satisfy Mw/Mn8.0 or less, preferably 3.5 or less Mw/Mn≤6.0。
11. The polyethylene composition according to claim 10, wherein component a, component B, component C and component D are all polymerized using a ziegler-natta catalyst.
12. Polyethylene composition according to any of claims 1 to 5, wherein the molar content of α olefin in component A, component B, component C and component D each independently is from 0.2 to 15 mol%, preferably from 1.5 to 10 mol%.
13. The polyethylene composition according to claim 12, wherein the α olefin in component a, component B, component C, and component D is each independently C3-C20At least one olefin, preferably α olefin selected from propylene, 1-butene, 2-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3-dimethyl-1-pentene, 3, 4-dimethyl-1-pentene, 4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 5-methyl-1-hexene, 1-heptene, 2-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene, more preferably at least one olefin selected from 1-butene, 1-hexene and 1-octene.
14. A polyethylene film, characterized in that it comprises at least one polyethylene layer formed from a polyethylene composition according to any one of claims 1 to 13.
15. The film of claim 14, wherein the film has a composite structure of an upper skin layer, a core layer, and a lower skin layer, and at least the core layer is a polyethylene layer formed of the polyethylene composition; preferably, when the film has a composite structure of an upper skin layer, a core layer and a lower skin layer, the thicknesses of the upper skin layer and the lower skin layer are each independently 1 to 25% of the thickness of the film.
16. The film of claim 14 or 15, wherein the film is a biaxially oriented film prepared by a flat film biaxial orientation process; preferably, in the process of preparing the biaxially oriented film by using a flat film biaxially oriented method, the longitudinal stretching ratio is more than or equal to 4 times, the transverse stretching ratio is more than or equal to 5 times, the transverse stretching rate is more than or equal to 50%/s, and more preferably, the transverse stretching rate is 60-150%/s.
17. A film according to claim 14 or 15, wherein the thickness of the film is 10-200 μm, preferably 10-100 μm.
18. The film according to any one of claims 14 to 17, wherein the biaxially oriented film has a tensile strength of 50MPa or more in the machine direction and 55MPa or more in the transverse direction; the tensile elongation at break of the biaxially oriented film is less than or equal to 350 percent, preferably less than or equal to 300 percent; the oxygen index of the biaxial stretching film is more than or equal to 20 percent, and preferably more than or equal to 22 percent.
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