Multilayer film with low seal initiation temperature

Abstract

This invention relates to a multilayer film having a low sealing initiation temperature, comprising at least an outer layer, a core layer, and a sealing layer, wherein the sealing layer comprises: i) at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer relative to the total weight of the sealing layer; and ii) at least 10.0 wt% of a material with a density of 910 kg / m³ relative to the total weight of the sealing layer. 3 A first plastic body of or lower (ISO 1183); wherein the core layer comprises: a) a density of 910 kg / m³ at least 8.0 wt% relative to the total weight of the core layer. 3 or a lower (ISO 1183) second plastic body, or b) at least 8.0 wt% of multimodal linear low-density polyethylene (LLDPE) binary copolymer relative to the total weight of the sealing layer; and c) second multimodal polyethylene terpolymer.

Description

[0001] This patent application is a divisional application of the invention patent application filed on August 12, 2021, with application number 202180069161.4, publication number CN116323196A, and invention title "Multilayer Film with Low Sealing Start Temperature". Technical Field

[0002] This invention relates to packaging films with beneficial heat-sealing and heat-adhesive properties. In particular, this invention relates to a multilayer packaging film with improved properties, comprising a multimodal LLDPE terpolymer. Background Technology

[0003] Polymer films are widely used in packaging. These films must obviously protect the items inside from damage and environmental impact. Furthermore, the ability to form packages on high-speed packaging machines is crucial.

[0004] Polyethylene film is widely used in packaging, and is often laminated with a substrate such as PET film, which has relatively high heat resistance, to create flexible packaging. Because it contains two materials with different chemical properties, this laminate is not easily recyclable.

[0005] To address this issue, longitudinally stretched polyethylene (MDO PE) or biaxially stretched polyethylene (BOPE) films can be used instead of PET films. The resulting laminate contains only polyethylene and is therefore fully mechanically recyclable.

[0006] Once the material to be packaged has been placed inside the packaging material, the package is typically heat-sealed. It is important that the heat-resistant layer (e.g., MDO PE or BOPE) does not shrink or soften during the heat-sealing process. This is a particular concern when using vertical or horizontal fill and seal (FFS) operations. Due to the chemical properties of polyethylene, the possibilities for increasing the heat resistance of MDO PE or BOPE films are limited. Since the Vicat softening temperature of HDPE, commonly used in MDO PE and BOPE films, is around 125°C or lower, the preferred sealing temperature should be below 60°C or at least below 65°C to ensure sufficient temperature clearance (e.g., >60°C) between the heat-resistant MDO PE or BOPE film layer of the laminate and the sealing PE layer for faster packaging.

[0007] Another important property of laminates is their thermal tack strength at low sealing temperatures. In vertical FFS (VFFS) technology, the higher this strength, the heavier the contents of the package and the faster the packaging speed. Therefore, a polyethylene laminate with a seal initiation temperature (SIT) below 65°C and high thermal tack strength at low sealing temperatures is a solution to this problem.

[0008] WO2012 / 0611681 claims a sealing strength of 10 N / 25 mm at sealing temperatures >68°C. However, the claimed membrane is not 100% polyethylene because it contains propylene copolymer.

[0009] US7842770 discloses a blown film composition with high hot tack, wherein the sealing layer composition contains an ethylene-octene multiblock copolymer that exhibits a peak hot tack strength of 5 N / 25 mm at a temperature above or equal to 105 °C.

[0010] EP0575465 discloses a polyethylene film structure having a sealant layer containing a propylene-ethylene elastomer and an ethylene-octene plasticizer, which exhibits a sealing strength of 10 N / 25 mm at a sealing temperature equal to or higher than 110 °C.

[0011] The inventors have discovered that co-extruded multilayer polyethylene films containing certain carefully defined components provide films with low seal initiation temperatures (SITs) but high hot tack strength. In particular, the films of this invention can provide a seal at extremely low temperatures of 60°C or lower, and exhibit a maximum hot tack strength of >9 N / 25 mm at seal temperatures of 66°C or higher. The sealing time is short, and the resulting films possess good stiffness, puncture resistance, and impact resistance. Improved sealing performance is achieved without reducing haze or gloss. Summary of the Invention

[0012] From one perspective, the present invention provides

[0013] A multilayer polyethylene film, comprising at least an outer layer, a core layer, and a sealing layer, wherein the sealing layer includes: i) at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer relative to the total weight of the sealing layer; and ii) A density of 910 kg / m³ is present at least 10.0 wt% of the total weight of the sealing layer. 3 Or lower (ISO 1183) first plastic body; The core layer includes: a) A density of 910 kg / m³, representing at least 8.0 wt% of the total weight of the core layer. 3 Or a lower (ISO 1183) second plastic body, or b) At least 8.0 wt% of a multimodal linear low-density polyethylene (LLDPE) binary copolymer relative to the total weight of the sealing layer; and c) Second multimodal polyethylene terpolymer.

[0014] Specifically, the present invention provides a multilayer polyethylene film, which sequentially comprises at least an outer layer, a core layer, and a sealing layer, wherein the sealing layer comprises: i) at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer relative to the total weight of the sealing layer; and ii) A density of 910 kg / m³ is present at least 10.0 wt% of the total weight of the sealing layer. 3 Or lower (ISO 1183) first plastic body; The core layer includes: a) A density of 910 kg / m³, representing at least 8.0 wt% of the total weight of the core layer. 3 Or a lower (ISO 1183) second plastic body, or b) At least 8.0 wt% of multimodal linear low-density polyethylene (LLDPE) binary copolymer relative to the total weight of the core layer; and c) Second multimodal polyethylene terpolymer; and The outer layer includes: I) Low-density polyethylene; II) Multimodal linear low-density polyethylene (LLDPE) binary copolymer; and III) First multimodal linear low-density polyethylene terpolymer or second multimodal polyethylene terpolymer.

[0015] From another perspective, the present invention provides a method for preparing the multilayer polyethylene film as described above, comprising the following steps: i) Forming a first polymer composition comprising at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer; and ii) At least 10.0 wt% of the product has a density of 910 kg / m³. 3 Or a lower first plastic body; A second polymer composition is formed, comprising: a) At least 8.0 wt% of the product has a density of 910 kg / m³. 3 Or a lower second plastic body; or b) At least 8.0 wt% of multimodal linear low-density polyethylene (LLDPE) binary copolymer; and c) Second multimodal polyethylene terpolymer; Forming a third polymer composition; and (Together) extruding the first, second and third polymer compositions to form the sealing layer, core layer and outer layer, respectively. Attached Figure Description

[0016] Figure 1 The relationship between sealing temperature and sealing strength of the membrane of the present invention and the comparative membrane is described.

[0017] Figure 2 The relationship between sealing temperature and thermal adhesion of the membrane of the present invention and the comparative membrane is described. Detailed Implementation

[0018] The membrane of the present invention is a multilayer polyethylene membrane, which sequentially comprises at least an outer layer, a core layer, and a sealing layer. The membrane of the present invention has a wide sealing window, allowing for sealing at a variety of temperatures.

[0019] Furthermore, in a preferred embodiment, a very low sealing initiation temperature is achieved by blending a first multi-peak LLDPE terpolymer with a narrow molecular weight distribution in the sealing layer with a low-density plastomer.

[0020] Preferably, all polymer components of the membrane of the present invention are polyethylene polymers. The term polyethylene refers to a polymer containing more than 50.0 wt% ethylene monomer, preferably more than 60.0 wt% ethylene monomer.

[0021] sealing layer

[0022] The sealing layer comprises at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer; and at least 10.0 wt% of a material with a density of 910 kg / m³. 3 Or lower first plastic body. The weight percentage (wt%) values ​​of these components are relative to the total weight of the sealant.

[0023] Preferably, the presence of the first multimodal LLDPE terpolymer in the sealing layer is at least 35.0 wt%, for example at least 40.0 wt%, preferably at least 50.0 wt%, for example at least 60.0 wt%, relative to the total weight of the sealing layer.

[0024] Alternatively, the sealing layer may contain 30.0 to 80.0 wt%, for example, 30.0 to 70.0 wt%, of a first multimodal LLDPE terpolymer. In some embodiments, the sealing layer may contain 50.0 to 80.0 wt%, of a first multimodal LLDPE terpolymer.

[0025] Preferably, the sealing layer contains 15.0 to 45.0 wt%, for example 20.0 to 40.0 wt%, particularly 25.0 to 40.0 wt%, of a first plastic body.

[0026] The density of the first multimodal LLDPE terpolymer used in the sealing layer can be 910 to 930 kg / m³. 3 Preferably 915 to 925 kg / m3 .

[0027] The MFR2 of the first multimodal LLDPE terpolymer can be 0.1 to 20 g / 10 min, preferably 0.35 to 5.0 g / 10 min, and more preferably 0.4 to 3.0 g / 10 min.

[0028] The Mw / Mn ratio of the first multimodal linear low-density polyethylene terpolymer can be from 2.0 to 7.0, for example from 2.0 to 6.0, and ideally less than 5.0.

[0029] The first multimodal LLDPE terpolymer used in the sealing layer typically contains a lower molecular weight (LMW) component and a higher molecular weight (HMW) component.

[0030] The first multimodal LLDPE terpolymer used in the sealing layer must contain two comonomers. These may be present in the HMW component, i.e., it is a terpolymer component, or the comonomers may be distributed in both components. Furthermore, if the HMW component is a terpolymer, the lower molecular weight (LMW) component may be an ethylene homopolymer. In this case, the multimodal LLDPE is still a multimodal LLDPE terpolymer.

[0031] Therefore, the first multimodal LLDPE terpolymer of the present invention may be wherein the HMW component comprises ethylene-derived and at least two other C4-based copolymers. 4-12 α-olefin monomers such as 1-butene and a C 6-12 Polymers of repeating units of α-olefin monomers. Ethylene preferably forms the majority of the LMW or HMW component.

[0032] Alternatively, both LMW and HMW are composed of ethylene and at least one C 4-12 The copolymer of α-olefin monomers makes the entire first multimodal LLDPE terpolymer contain at least two C2O4 monomers. 4-12 α-olefin monomers.

[0033] The total monomer content in the first multimodal LLDPE terpolymer, on a molar basis, may be, for example, 0.5 to 8.0%, preferably 0.7 to 6.5%, more preferably 1.0 to 4.5%, and most preferably 1.5 to 4.0%.

[0034] On a molar basis, 1-butene may be present in an amount of 0.1% to 2.5%, for example 0.22% to 2.0%, more preferably 0.25% to 1.5%, and most preferably 0.25% to 1.0%.

[0035] On a molar basis, C6 to C12 α-olefins may be present in amounts of 0.3 to 5.5%, preferably 0.4 to 4.5%, more preferably 0.7 to 4.0%, and most preferably 1.0 to 3.5%, particularly 1.5 to 3.0%.

[0036] Preferably, C6 to C12 The α-olefin is 1-hexene.

[0037] In a preferred embodiment, the first multimodal LLDPE terpolymer may comprise two ethylene copolymers, such that at least two C4-12 copolymers are present. α-olefin comonomers, such as ethylene-butene copolymers (e.g., as LMW components) and ethylene-hexene copolymers (e.g., as HMW components). ethylene copolymer components and ethylene terpolymer components can also be combined such that at least two C4-12 α-olefin comonomers are present, such as ethylene-butene copolymers (e.g., as LMW components) and ethylene-butene-hexene terpolymers (e.g., as HMW components).

[0038] A suitable first multimodal LLDPE terpolymer preferably has the following characteristics: (i) Ethylene polymer components as lower molecular weight (LMW) components, with an MFR2 of 1.0 to 10.0 g / 10 min (according to ISO 1133, at 190 °C and a load of 2.16 kg) and (ii) The ethylene polymer component as the higher molecular weight (HMW) component has an MFR2 of 0.2 to 2.5 g / 10 min (according to ISO 1133, at 190 °C and 2.16 kg load). Furthermore, the density of ethylene polymer component (i) is higher than that of ethylene polymer component (ii); the density of ethylene polymer component (i) is between 930 and 950 kg / m³. 3 Within the range.

[0039] The HMW component of the first multimodal LLDPE terpolymer can, for example, have an MFR2 preferably less than 1.0 g / 10 min, preferably less than 0.9 g / 10 min, and particularly less than 0.8 g / 10 min. Its density can be less than 915 kg / m³. 3 For example, less than 910 kg / m 3 Preferably less than 905 kg / m 3 .

[0040] The first multi-peak LLDPE terpolymer can be formed using either single-point catalysis or Ziegler-Natta catalysts. Both types of catalysts are well known in the art.

[0041] In one embodiment, the first multimodal LLDPE terpolymer may comprise an ethylene homopolymer and an ethylene-butene-hexene copolymer component, and is ideally prepared via single-point catalysis, and is therefore a metallocene-catalyzed linear low-density polyethylene (mLLDPE). In a further embodiment, the first multimodal LLDPE terpolymer may comprise an ethylene-butene copolymer and an ethylene-hexene copolymer component, and is ideally prepared via single-point catalysis, and is therefore a metallocene-catalyzed linear low-density polyethylene (mLLDPE).

[0042] Metallocene-catalyzed linear low-density polyethylene (mLLDPE) is known in the art and is therefore not the subject of this invention. Reference is made in this regard to the examples of EP3257895A1, Example IE1 of EP3257895A1, or, for example, the second bimodal terpolymer of WO2020 / 136166, or Example 3 of WO 2019 / 081611.

[0043] An example of this metallocene-catalyzed linear low-density polyethylene (mLLDPE) is Anteo. TM FK1820 or FK1828, they have a density of 918 kg / m³. 3 MFR2 is a bimodal ethylene / 1-butene / 1-hexene terpolymer of 1.5 g / 10 min, commercially available from Borouge.

[0044] Multimodal (e.g., bimodal) polymers can typically be prepared by mechanical blending of two or more separately prepared polymer components or, preferably, by in-situ blending in a multi-stage polymerization process within the preparation of the polymer components. Both mechanical blending and in-situ blending are well known in the art.

[0045] Therefore, the preferred first multi-peak LLDPE terpolymer is prepared by in-situ blending in multi-stage, i.e., two-stage or more-stage polymerization or by using two or more different polymerization catalysts (including multi-site or dual-site catalysts) in one-stage polymerization.

[0046] Preferably, the first multimodal LLDPE terpolymer is prepared using the same catalyst, such as a unit spot or Ziegler-Natta catalyst, in at least two stages of polymerization. Therefore, for example, two slurry reactors or two gas-phase reactors or any combination thereof can be employed in any order. However, preferably, the multimodal polymer, such as LLDPE, is prepared by slurry polymerization in a circulating reactor followed by gas-phase polymerization in a gas-phase reactor.

[0047] The circulating reactor-gas phase reactor system is sold by Borealis as the BORSTAR reactor system. Therefore, any multimodal polymers, such as LLDPE, are preferably formed in a two-stage process comprising first slurry circulating polymerization followed by gas phase polymerization.

[0048] The conditions used in this process are well known. For slurry reactors, the reaction temperature is typically in the range of 60 to 110°C (e.g., 85-110°C), the reactor pressure is typically in the range of 5 to 80 bar (e.g., 50-65 bar), and the residence time is typically in the range of 0.3 to 5 hours (e.g., 0.5 to 2 hours). The diluent used is typically an aliphatic hydrocarbon with a boiling point in the range of -70 to +100°C. In such reactors, polymerization can be carried out under supercritical conditions if desired. Slurry polymerization can also be carried out in bulk, where the reaction medium is formed from the monomers being polymerized.

[0049] For gas-phase reactors, the reaction temperature is typically in the range of 60 to 115°C (e.g., 70 to 110°C), the reactor pressure is typically in the range of 10 to 25 bar, and the residence time is typically 1 to 8 hours. The gases used are typically non-reactive gases, such as nitrogen, or low-boiling hydrocarbons, such as propane and monomers (e.g., ethylene).

[0050] Preferably, the lower molecular weight polymer portion is generated in a continuously operating circulating reactor, wherein ethylene and optional comonomers are polymerized in the presence of a polymerization catalyst and chain transfer agent such as hydrogen as described above. The diluent is typically an inert aliphatic hydrocarbon, preferably isobutane or propane.

[0051] The same catalyst can then be used to form higher molecular weight components in a gas-phase reactor.

[0052] If a higher molecular weight component is the second most important component in a multi-stage polymerization process, its properties cannot be directly measured. However, those skilled in the art can determine the density, MFR2, etc., of the higher molecular weight component using the Kim McAuley equation. Therefore, both density and MFR2 can be derived using KK McAuley and J. F. McGregor's "On-line Inference of Polymer Properties in an Industrial Polyethylene Reactor," AIChE Journal, June 1991, Vol. 37, No. 6, pages 825–835.

[0053] The density was calculated according to McAuley Equation 37, where the final density and the density after the first reactor were known.

[0054] MFR2 was calculated using McAuley Equation 25, which calculates both the final MFR2 and the MFR2 after the first reactor. Using these equations to calculate polymer properties in multimodal polymers is common practice. However, the polymer used in this invention is a commercially available material.

[0055] First plastic body

[0056] The sealing layer further comprises a first plastic body. Preferably, at least 10.0 wt% of the first plastic body is present, for example, at least 15.0 wt% of the first plastic body. Preferably, the sealing layer contains 15.0 to 45.0 wt%, for example, 20.0 to 40.0 wt%, particularly 25.0 to 40.0 wt% of the first plastic body.

[0057] The first plastic body may be a copolymer of ethylene with 1-butene, 1-hexene, or 1-octene, wherein ethylene constitutes the major component. Preferably, the first plastic body is a copolymer of ethylene and 1-butene or ethylene and 1-octene, and more preferably, a copolymer of ethylene and 1-octene. The content of the comonomer such as 1-octene in the plastic body may be from 5.0 to 40.0 wt%, for example, from 15.0 to 30.0 wt%.

[0058] In one embodiment, the density of the first plastic component of the sealing layer can be between 870 and 895 kg / m³. 3 Between 875 and 890 kg / m³ 3 Between 875 and 885 kg / m³, further preferred. 3 between.

[0059] In one embodiment, the MFR2 of the first plastic body of the sealing layer can be between 0.1 and 5.0 g / 10 min, preferably between 0.5 and 3.0 g / 10 min, and more preferably between 0.6 and 2.0 g / 10 min.

[0060] A suitable molecular weight distribution for vinyl plastomers, Mw / Mn, is most often below 4, for example 3.8 or lower, but at least 1.7. It is preferably between 3.5 and 1.8.

[0061] Suitable vinyl first plastics can be any copolymer of ethylene and propylene or ethylene and 1-butene, 1-hexene or 1-octene having the properties defined above, which are commercially available, namely, from Borealis under the trade name Queo, from DOW Chemical Corp (USA) under the trade name Engage or Affinity, or from Mitsui Chemicals under the trade name Tafmer.

[0062] Alternatively, these vinyl plastics can be prepared in the presence of suitable catalysts known to those skilled in the art, such as vanadium oxide catalysts or unit site catalysts, such as metallocene or confined geometry catalysts, by known methods, including solution polymerization, slurry polymerization, gas-phase polymerization, or combinations thereof, in a one-stage or two-stage polymerization process.

[0063] Preferably, these vinyl plastomers are prepared by a one-stage or two-stage solution polymerization process, particularly by a high-temperature solution polymerization process at temperatures above 100°C.

[0064] This process is primarily based on the polymerization of monomers and suitable comonomers in a liquid hydrocarbon solvent, where the resulting polymer is soluble. Polymerization is carried out at a temperature above the polymer's melting point, thereby obtaining a polymer solution. This solution is flash-evaporated to separate the polymer from unreacted monomers and solvent. The solvent is then recovered and recycled within the process.

[0065] Preferably, the solution polymerization process is a high-temperature solution polymerization process, using a polymerization temperature higher than 100°C. More preferably, the polymerization temperature is at least 110°C, and more preferably at least 150°C. The polymerization temperature can reach a maximum of 250°C.

[0066] The pressure in this solution polymerization process is preferably between 10 and 100 bar, more preferably between 15 and 100 bar, and even more preferably between 20 and 100 bar.

[0067] The liquid hydrocarbon solvent used is preferably a C5-12-hydrocarbon, which may be unsubstituted or substituted with C1-4 alkyl groups, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, and hydrogenated naphtha. Unsubstituted C6-10-hydrocarbon solvents are more preferably used.

[0068] The known solution technique suitable for the method of this invention is Borceed. TM technology.

[0069] The plastic body of the present invention is ideally formed using a metallocene catalyst. The plastic body used in the present invention is commercially available, can be purchased from polymer suppliers, and contributes to the sealing of protective films.

[0070] Additional polymer components of the sealing layer

[0071] In one embodiment, the sealing layer further comprises a multi-peak LLDPE binary copolymer as defined in detail for the core layer.

[0072] If present, the multimodal LLDPE binary copolymer can form a sealing layer of 20.0 to 40.0 wt%. The combined amount of the first multimodal LLDPE terpolymer and the multimodal LLDPE binary copolymer in the sealing layer can be 60.0 to 80.0 wt%.

[0073] Core layer

[0074] The multilayer membrane of the present invention includes a core layer. The core layer is sandwiched between an outer layer and a sealing layer. Preferably, the core layer is in direct contact with the outer layer. Preferably, the core layer is in direct contact with the sealing layer. Preferably, the core layer is in direct contact with both the sealing layer and the outer layer. Therefore, ideally, the membrane of the present invention comprises only three layers.

[0075] The core layer includes: a) At least 8.0 wt% of the product has a density of 910 kg / m³. 3 Or a lower second plastic body, or b) At least 8.0 wt% of multimodal linear low-density polyethylene (LLDPE) binary copolymer; and c) Second multimodal polyethylene terpolymer.

[0076] The wt% of these components are relative to the total weight of the core layer.

[0077] The second plastic body of the core layer

[0078] In one embodiment, the core layer comprises a second plastic body. The second plastic body of the core layer may be the same as or different from the first plastic body of the sealing layer. The limitations provided above for the first plastic body in the sealing layer also apply to the plastic body of the core layer. The same preferences also apply. Preferably, the first plastic body of the sealing layer is the same as the second plastic body of the core layer.

[0079] Based on the weight of the core layer, the core layer may contain at least 8.0 wt% of a second plastic body, for example at least 10.0 wt%, preferably 10.0 to 40.0 wt%, for example 12.0 to 40.0 wt%.

[0080] Multimodal linear low-density polyethylene (LLDPE) binary copolymer

[0081] In a second embodiment, the core layer comprises at least one multimodal LLDPE binary copolymer. Ideally, it is a copolymer of ethylene and a C4-12α olefin (binary copolymer). Its density is preferably 910 to 940 kg / m³. 3 Preferably, it is 915 to 935 kg / m3 .

[0082] It preferably has an MFR2 content of 0.1 to 5.0 g / 10 min.

[0083] The polymer is preferably a multimodal LLDPE binary copolymer having a C4-12α olefin, comprising a lower molecular weight (LMW) component and a higher molecular weight (HMW) component.

[0084] In one embodiment, the multimodal LLDPE binary copolymer may be a Ziegler-Natta catalyzed LLDPE copolymer. In another embodiment, the multimodal LLDPE binary copolymer may comprise two ethylene-butene copolymers.

[0085] In another embodiment of the invention, in the multimodal LLDPE binary copolymer used in the core layer, the HMW component and the lower molecular weight (LMW) component are ethylene copolymers of ethylene and a C4-12α olefin, preferably copolymers of ethylene and 1-butene.

[0086] Ziegler-Natta catalyzed linear low-density polyethylene (znLLDPE) is also known in the art and is therefore not the subject of this invention. They are prepared, for example, using ZN catalysts disclosed in EP 688794, EP 835887, WO 2004 / 000933, WO 2004 / 000902, or WO 2004 / 106393.

[0087] An example of a Ziegler-Natta catalyzed multimodal LLDPE binary copolymer (znLLDPE) is FB2230, a bimodal ethylene / 1-butene copolymer with a density of 923 kg / m³. 3 MFR2 is 0.2g / 10min and is commercially available from Borealis.

[0088] The content of comonomers present in the multimodal LLDPE binary copolymer is preferably 0.5 to 12.0 mol%, for example 2.0 to 10.0 mol%, particularly 4.0 to 8.0 mol%.

[0089] Multimodal LLDPE binary copolymers suitable for the core layer may comprise a polyethylene homopolymer as the lower molecular weight fraction and a copolymer of ethylene and an α-olefin comonomer having 4-10 carbon atoms as the higher molecular weight fraction. However, if the HMW component and the lower molecular weight (LMW) component are preferably ethylene copolymers of ethylene and a C4-10 α-olefin, a copolymer of ethylene and 1-butene is preferred.

[0090] The core layer may contain at least 8.0 wt% of a multimodal linear low-density polyethylene (LLDPE) binary copolymer, for example at least 10.0 wt%, preferably 10.0 to 40.0 wt%, for example 20.0 to 40.0 wt% of the multimodal linear low-density polyethylene (LLDPE) binary copolymer.

[0091] Second multimodal ternary copolymer

[0092] The core layer also contains a second multimodal terpolymer. It is preferably a terpolymer of ethylene and at least two C4-12α olefins.

[0093] The second multimodal terpolymer preferably constitutes at least 50.0 wt%, more preferably at least 60.0 wt%, for example at least 65.0 wt%, and particularly at least 70.0 wt%, relative to the total weight of the core layer. In some embodiments, it constitutes 65.0 to 90.0 wt%, for example 70 to 90 wt%, of the core layer.

[0094] The second multimodal ethylene terpolymer may contain at least two C4-12 α-olefin comonomers. Ideally, the multimodal ethylene terpolymer contains only two comonomers. The comonomers are particularly selected from 1-butene, 1-hexene, or 1-octene. The amount of comonomer present in the multimodal ethylene terpolymer is preferably 0.5 to 12.0 mol%, for example 2.0 to 10.0 mol%, particularly 4.0 to 8.0 mol%.

[0095] The second multimodal ethylene terpolymer suitable for the membrane of the present invention preferably comprises a terpolymer of polyethylene homopolymer as the lower molecular weight portion and ethylene as the higher molecular weight portion and at least two α-olefin comonomers having 4-10 carbon atoms.

[0096] Therefore, preferably, the second multimodal ethylene terpolymer suitable for the membrane core layer of the present invention may include: (b-1) Lower molecular weight homopolymers of ethylene; and (b-2) A high molecular weight terpolymer of ethylene, 1-butene and C6-C10-α-olefin.

[0097] Preferably, the second comonomer of the higher molecular weight component is a C6-C10-α-olefin selected from 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene, especially a C6-C10-α-olefin of 1-hexene or 1-octene.

[0098] The second multimodal ethylene terpolymer preferably has a content of 920 to 940 kg / m³. 3 The density. Ideally, the density of a multimodal terpolymer is 930 to 940 kg / m³. 3 .

[0099] The MFR2 of the second multimodal ethylene terpolymer is preferably 0.1 to 3.0 g / 10 min, and more preferably 0.3 to 2.5 g / 10 min.

[0100] The second multimodal polyethylene terpolymer of the core layer may have a Mw / Mn ratio of 10 to 30, preferably 10 to 25.

[0101] Multimodal ethylene terpolymers can be produced by polymerization using conditions that produce multimodal (e.g., bimodal) polymer products, ideally using a Ziegler-Natta catalyst system. Typically, two- or more-stage, i.e., multi-stage polymerization processes use different process conditions (e.g., different temperatures, pressures, polymerization media, hydrogen partial pressures, etc.) in different stages or regions. Preferably, multimodal (e.g., bimodal) compositions are produced by multi-stage polymerization, for example using a series of reactors, with optional comonomers preferably added only in the reactor used to produce the higher / highest molecular weight component. A multi-stage process is defined as a polymerization process in which a polymer comprising two or more moieties is produced by producing each or at least two polymer moieties in separate reaction stages in the presence of the reaction products of a preceding stage containing a polymerization catalyst. The polymerization reaction used in each stage may involve conventional ethylene homopolymerization or copolymerization, such as gas-phase, slurry-phase, or liquid-phase polymerization, using conventional reactors, such as circulating reactors, gas-phase reactors, batch reactors, etc. (see, for example, WO97 / 44371 and WO96 / 18662). Terpolymers that meet the requirements of this invention are known and can be purchased from suppliers such as Borealis, for example, FX1002.

[0102] It is preferred when the second multimodal ethylene terpolymer of the core layer is different from the multimodal LLDPE terpolymer used in the sealing layer.

[0103] In a preferred embodiment, the multimodal linear low-density polyethylene terpolymer of the sealing layer comprises a lower molecular weight (LMW) copolymer component and a higher molecular weight (HMW) copolymer component; and

[0104] The multimodal polyethylene terpolymer in the core layer comprises a low molecular weight (LMW) homopolymer component and a high molecular weight (HMW) terpolymer component.

[0105] outer layer

[0106] The membrane of the present invention comprises an outer layer. The outer layer is different from the sealing layer. The outer layer is different from the core layer. In order to make the membrane have a distinguishable sealing layer, core layer and outer layer, those skilled in the art will understand that they are different.

[0107] The outer layer preferably comprises at least one low-density polyethylene homopolymer (LDPE). For example, the LDPE may have a density of 905 to 930 kg / m³. 3 The density. For example, LDPE can have an MFR2 of 0.1 to 4.0 g / 10min.

[0108] LDPE preferably forms at least 30.0 wt% of the outer layer. Preferably at least 35.0 wt%, for example 35.0 to 50.0 wt%. These wt% components are relative to the total weight of the outer layer.

[0109] The outer layer may also include multimodal polyethylene as defined above for the core layer or sealing layer. Therefore, it may contain a first multimodal linear low-density polyethylene terpolymer as defined for the sealing layer or a second multimodal polyethylene terpolymer as defined for the core layer.

[0110] The outer layer may include a multimodal linear low-density polyethylene (LLDPE) binary copolymer as defined in the core layer. It may also include mixtures of such polymers.

[0111] Preferably, in addition to LDPE, the outer layer also comprises a multimodal linear low-density polyethylene (LLDPE) binary copolymer as defined in the core layer and a second multimodal polyethylene terpolymer as defined in the core layer or a first multimodal linear low-density polyethylene terpolymer as defined in the sealing layer.

[0112] The outer layer may contain at least 20.0 wt%, for example 20.0 to 45.0 wt%, of a multimodal linear low-density polyethylene (LLDPE) binary copolymer, for example 25.0 to 35.0 wt%.

[0113] The outer layer may contain at least 20.0 wt%, such as 20.0 to 45.0 wt%, of a second multimodal polyethylene terpolymer as defined in the core layer or a first multimodal linear low-density polyethylene terpolymer as defined in the sealing layer, such as 25.0 to 35.0 wt%.

[0114] Specifically, the present invention provides a multilayer polyethylene film, which sequentially comprises at least an outer layer, a core layer, and a sealing layer, wherein the sealing layer comprises: i) at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer; and ii) At least 10.0 wt% of the product has a density of 910 kg / m³. 3 Or a lower first plastic body; The core layer includes: a) At least 8.0 wt% of the product has a density of 910 kg / m³. 3 Or a lower second plastic body, or b) At least 8.0 wt% of multimodal linear low-density polyethylene (LLDPE) binary copolymer; and c) At least 60.0 wt% of a second multimodal polyethylene terpolymer; and The outer layer includes: I) At least 30.0 wt% low-density polyethylene; II) At least 20.0 wt% of a multimodal linear low-density polyethylene (LLDPE) binary copolymer; and III) At least 20.0 wt% of a first multimodal linear low-density polyethylene terpolymer or a second multimodal polyethylene terpolymer.

[0115] Multilayer film

[0116] The membranes of the present invention can be prepared using blow molding extrusion techniques known in the art. Suitable mixtures of the required components for each layer can be blended and co-extruded. It should be understood that, if desired, any layer of the membrane of the present invention may also contain standard polymer additives.

[0117] The membrane of the present invention may have a thickness of 20 to 120 μm, preferably 30 to 100 μm, and more preferably 40 to 80 μm. The membrane of the present invention is preferably not stretched in the longitudinal, transverse, or biaxial directions.

[0118] For a three-layer structure, the sealing layer, outer layer, and core layer can all have the same thickness, or the core layer can be thicker than the outer and sealing layers. A practical membrane comprises an outer / sealing layer that forms 10.0 to 35.0%, preferably 15.0 to 30.0%, of the final total thickness of the three-layer membrane, and a core layer that forms the remaining thickness, for example, 30.0 to 80.0%, preferably 40.0 to 70.0%, of the final total thickness of the three-layer membrane.

[0119] The total thickness of the membrane is 100%, therefore the sum of all layers must be 100%.

[0120] The membrane structure of the present invention provides the sealing performance of a 100% polyethylene blown film without any further orientation processing steps at extremely low temperatures down to 57°C to achieve a sealing strength of 5N / 25mm, while having minimal stiffness trade-offs and good puncture resistance.

[0121] The sealing initiation temperature of the membrane of the present invention can be in the range of 50 to 70°C, preferably 55 to 65°C.

[0122] The upper limit for sealing is typically about 105 to 110°C. Therefore, the sealing window of the membrane of the present invention can be about 40 to 50°C, that is, roughly 55 to 105°C.

[0123] The hot-applied temperature is preferably in the range of 50 to 65°C, and more preferably 50 to 60°C.

[0124] The hot-tack strength is preferably 8.00 N / 25 mm or higher, for example 8.50 to 10 N / 25 mm.

[0125] Existing technologies disclose membrane structures with very low sealing initiation temperatures, but those membrane structures are not 100% polyethylene and have a minimum sealing temperature >68°C to achieve a sealing strength of 10N / 25mm.

[0126] The membrane structure of this invention also exhibits very high thermal tack strength of >9 N / 25 mm for a 100% PE blown film at low sealing temperatures of 66°C or higher. Such high thermal tack strength at such low sealing temperatures has not yet been claimed for protection.

[0127] The membrane of the present invention has a tensile modulus of 250 to 400 MPa in the longitudinal direction. The membrane of the present invention has a tensile modulus of 300 to 475 MPa in the transverse direction. The elongation at break is also very high.

[0128] The films of this invention maintain high gloss and low haze. They exhibit good dart drop and impact resistance as well as good puncture resistance.

[0129] The invention will now be defined with reference to the following non-limiting embodiments and accompanying drawings. Figure 1 The relationship between sealing temperature and sealing strength of the membrane of the present invention and the comparative membrane is depicted. Figure 2 The relationship between sealing temperature and thermal adhesion of the membrane of the present invention and the comparative membrane is described.

[0130] Determination methods

[0131] The density of the material was measured using isopropanol-water as the gradient liquid according to ISO 1183:1987(E) Method D. The cooling rate of the plaque was 15 °C / min during sample crystallization. The conditioning time was 16 hours.

[0132] Melt flow rate (MFR) or melt index (MI)

[0133] Melt flow rate (MFR) is determined according to ISO 1133 and expressed in g / 10 min. MFR represents the melt viscosity of the polymer. The MFR of PE is determined at 190°C, and that of PP at 230°C. The load used to determine the melt flow rate is usually indicated by a subscript, for example, MFR2 is measured under a load of 2.16 kg, MFR5 is measured under a load of 5 kg, or MFR... 21 It was measured under a load of 21.6 kg.

[0134] Molecular weight, molecular weight distribution, Mn, Mw, MWD

[0135] Weight-average molecular weight (Mw) and molecular weight distribution (MWD = Mw / Mn, where Mn is the number-average molecular weight and Mw is the weight-average molecular weight) were measured using a method based on ISO 16014-4:2003. A Waters 150CV plus instrument equipped with a refractive index detector and an online viscometer, and 3 x HT6E styragel columns (styrene-divinylbenzene) from Waters were used with 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol) as solvent, at a temperature of 140 °C and a flow rate of 1 mL / min. 500 μL of sample solution was injected for each analysis. The column set was calibrated using a universal calibration (according to ISO 16014-2:2003) with 10 narrow MWD polystyrene (PS) standards ranging from 1.05 kg / mol to 11600 kg / mol. Mark Houwink constants were used for polystyrene and polyethylene (K: 19 x 10⁻⁶ for PS). -3 dL / g and a: 0.655, for PE, K: 39 x 10 -3 dL / g and a: 0.725). All samples were prepared by dissolving 0.5–3.5 mg of polymer in 4 mL of stable TCB (same as the mobile phase) at 140 °C for 2 hours, and then holding the samples at 160 °C for another 2 hours with occasional shaking before transferring them to the GPC instrument.

[0136] The comonomer content (%wt and %mol) is determined by using methods as described in WO2020 / 064534. 13 C-NMR determination. 13 C-NMR spectra were recorded at 150 °C on a Bruker 500 MHz spectrometer. The conversion between %wt and %mol can be performed by calculation.

[0137] The impact strength depends on the dart drop (g / 50%). The dart drop was measured using ISO 7765-1 Method “A”. A hemispherical dart with a diameter of 38 mm was dropped from a height of 0.66 m onto a membrane sample clamped in a hole. If the sample failed, the weight of the dart was reduced; if it did not fail, the weight was increased. At least 20 samples were tested. The weight that caused 50% of the samples to fail was calculated, providing the dart drop impact (DDI) value (g). The relative DDI (g / μm) was then calculated by dividing the DDI by the membrane thickness.

[0138] Tensile modulus (secant modulus, 0.05-0.25%) and elongation at break were measured according to ISO 527-3 for membrane samples prepared according to the "Membrane Sample Preparation" procedure described below. The test speed was 200 mm / min. The test temperature was 23°C. The membrane width was 25 mm.

[0139] Hot viscosity

[0140] Hot tack was measured according to ASTM F1921-12 / Method B on a J&B model 4000 MB, flat, NIPTEF® coated sealing strip, 50 mm in length and 5 mm in width. Sealing time: 1 second; cooling time: 0.2 s; sealing pressure: 0.15 N / mm². Clamp separation rate: 200 mm / s; sample width: 25 mm; force range: 45 N. Energy calculation begins: 2 [%] Energy calculation complete: 20 [%] Gloss, clarity, and haze were measured on a 25 μm thick film sample according to ASTM D2457 (gloss) and ASTM D1003 (haze).

[0141] Puncture resistance was measured from the membrane sample using the ISO 7765-2 method.

[0142] Sealing start temperature (SIT); Sealing end temperature (SET); Sealing range: This method determines the sealing temperature range (sealing range) of polyethylene films, particularly blown or cast films. The sealing temperature range is the temperature range at which the film can be sealed according to the conditions given below.

[0143] The lower limit (heat seal initiation temperature (SIT)) is the sealing temperature at which a seal strength of ≥5 N is achieved. The upper limit (seal end temperature (SET)) is reached when the membrane adheres to the sealing device.

[0144] Measurements were performed according to a slightly modified version of ASTM F1921-12, which modified the test parameters for sealing pressure, cooling time, and test speed. The force / temperature profile was determined until the membrane underwent thermal failure.

[0145] The sealing range was measured on a J&B Universal Sealing Machine Model 4000, with a blown film thickness of 40µm. Further parameters are as follows: Adjustment time: >96 h Sample width: 25 mm Sealing pressure: 0.4 N / mm² (PE) Sealing time: 1 second Delay time: 30 seconds Sealing claw size: 50x5 mm Sealing claw shape: flat Sealing claw coating: Niptef Sealing temperature: ambient temperature -240℃ Sealing temperature interval: 5℃ Starting temperature: 50℃ Grip separation rate: 42 mm / s

[0146] Example: Materials used: Queo TM 8201LA: Vinyloctene plastide, MFR (190 / 2.16) 1.1 g / 10 min, single peak, density 883 kg / m³, produced by solution polymerization using a metallocene catalyst supplied by Borealis AG. It contains processing stabilizers.

[0147] Queo 0201FX: Vinyloctene plastomer, MFR (190 / 2.16) 1.1 g / 10 min, single peak, density 902 kg / m³, produced in a solution polymerization process using a metallocene catalyst (supplied by Borealis AG). It contains 3000 ppm anti-caking agent and 1200 ppm anti-slip agent, processing aids and stabilizers.

[0148] FX1002: A multimodal α-olefin terpolymer commercially available from Borealis AG, with a density of 937 kg / m³. 3 (Measured according to ISO 1183) The melt flow rate (190℃ / 2.15kg) is 0.4 g / 10min and the melt flow rate (190℃ / 21kg) is 42 g / 10min (measured according to ISO 1133).

[0149] FX1001: A multimodal α-olefin terpolymer commercially available from Borealis AG, with a density of 931 kg / m³. 3 (Measured according to ISO 1183), the melt flow rate (190℃ / 2.15kg) is 0.9 g / 10min.

[0150] Anteo TM FK1828: Bimodal ethylene / 1-butene / 1-hexene terpolymer, with a density of 918 kg / m³. 3 MFR2 is 1.5 g / 10 min and is available from Borouge.

[0151] FB2230: Density is 923 kg / m³ 3MFR2 is a bimodal ethylene / 1-butene copolymer of 0.2 g / 10 min, available from Borealis.

[0152] FT5236: Low-density polyethylene produced using tubular technology (supplied by Borealis AG). FT5230 has an MFR2 of 0.75 g / 10 min and a density of 923 kg / m³. 3 .

[0153] Membrane preparation

[0154] Three-layer blown film was produced on Dr. Colin's three-layer blown film production line. The melt temperature of the sealing layer (A) was 180 to 200°C, the melt temperature of the core layer (B) was 190 to 210°C, and the melt temperature of the outer layer (C) was 200°C. The total output of the extruder was 10 kg / h. The composition used for each layer is shown in Table 1.

[0155] Other parameters for the blown film production line are: Mold clearance: 1.5 mm Mold size: 60mm Drilling ratio: 1:3 Frost line height: 120 mm The total thickness of the formed films is 60 µm. Table 1 shows their properties:

[0156] Data shows that, for embodiments of the present invention, the sealing initiation temperature is reduced without loss of thermal tack. In fact, for all embodiments, thermal tack is actually increased relative to the comparative example. Data also shows that using the film of the present invention does not impair tensile modulus, elongation at break, haze, and gloss.

Claims

1. A multilayer polyethylene film, comprising at least an outer layer, a core layer, and a sealing layer, wherein the sealing layer comprises: i) at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer relative to the total weight of the sealing layer; and ii) A density of 910 kg / m³, measured according to ISO 1183, at least 10.0 wt% of the total weight of the sealing layer. 3 Or a lower first plastic body; The core layer includes: a) A density of 910 kg / m³, measured according to ISO 1183, at least 8.0 wt% of the total weight of the core layer. 3 Or a lower second plastic body, wherein the second plastic body is a copolymer of ethylene and a comonomer selected from 1-butene, 1-hexene or 1-octene; and b) Second multimodal polyethylene terpolymer.

2. The multilayer polyethylene film according to claim 1, wherein, The multi-peak linear low-density polyethylene terpolymer of the sealing layer comprises a low molecular weight copolymer component and a high molecular weight copolymer component. The lower molecular weight copolymer component is an ethylene copolymer of ethylene and one or more C4-C12 α-olefins, and the higher molecular weight copolymer component is an ethylene copolymer of ethylene and one or more C4-C12 α-olefins, such that at least two C4-C12 α-olefins are present.

3. The multilayer polyethylene film according to claim 1, wherein, The multimodal polyethylene terpolymer of the core layer comprises a low molecular weight homopolymer component and a high molecular weight ethylene and two or more C4-C12 α-olefin terpolymer components.

4. The multilayer polyethylene film according to any one of the preceding claims, wherein, The first multimodal linear low-density polyethylene terpolymer of the sealing layer has a strength of 910 to 930 kg / m³ as measured according to ISO 1183. 3 The density.

5. The multilayer polyethylene film according to any one of the preceding claims, wherein, The first multimodal linear low-density polyethylene terpolymer of the sealing layer has a Mw / Mn ratio of 2.0 to 7.0, for example 2.0 to 6.0, ideally less than 5.0, as measured by GPC.

6. The multilayer polyethylene film according to any one of the preceding claims, wherein, The MFR2 of the first multimodal linear low-density polyethylene terpolymer of the sealing layer or the multimodal terpolymer of the core layer, measured according to ISO 1133 at 190°C and 2.16 kg, is 0.1 to 20 g / 10 min, preferably 0.35 to 5.0 g / 10 min, and more preferably 0.4 to 3.0 g / 10 min.

7. The multilayer polyethylene film according to any one of the preceding claims, wherein, The first multimodal linear low-density polyethylene terpolymer of the sealing layer is present in an amount of at least 35.0 wt%, for example at least 40.0 wt%, preferably at least 50.0 wt%, for example at least 60.0 wt., relative to the total weight of the sealing layer.

8. The multilayer polyethylene film according to any one of the preceding claims, wherein, The second multimodal polyethylene terpolymer of the core layer has a strength of 920 to 940 kg / m³ as measured according to ISO 1183. 3 The density and / or the Mw / Mn ratio of the second multimodal polyethylene terpolymer of the core layer, as measured by GPC, is 10 to 30, preferably 10 to 25.

9. The multilayer polyethylene film according to any one of the preceding claims, wherein, The first plastic body and the second plastic body are independently copolymers of ethylene and 1-octene.

10. The multilayer polyethylene film according to any one of the preceding claims, wherein, The first plastic body is present in an amount of 15.0 to 45.0 wt%, for example 20.0 to 40.0 wt%, particularly 25.0 to 40.0 wt%, relative to the total weight of the sealing layer.

11. The multilayer polyethylene film according to any one of the preceding claims, wherein, The second plastic body is present in an amount of at least 10.0 wt%, preferably 10.0 to 40.0 wt%, for example 12.0 to 40.0 wt%, relative to the total weight of the core layer.

12. The multilayer polyethylene film according to any one of the preceding claims, wherein, The second multimodal polyethylene terpolymer of the core layer is present in an amount of at least 50.0 wt%, preferably at least 60.0 wt%, and for example at least 70.0 wt%, relative to the total weight of the core layer.

13. The multilayer polyethylene film according to any one of the preceding claims, wherein, The outer layer comprises a blend of multimodal polyethylene and low-density polyethylene, such as a blend of low-density polyethylene, a multimodal linear low-density polyethylene binary copolymer, and a blend of a first multimodal linear low-density polyethylene terpolymer or a second multimodal polyethylene terpolymer.

14. The multilayer polyethylene film according to any one of the preceding claims, wherein the sealing initiation temperature, measured according to ASTM F1921-12 at 5 N / 25 mm, is 70°C or lower, preferably 65°C or lower; and / or At temperatures of 65°C or higher, the maximum hot tack strength, as measured according to ASTM F1921-12 / Method B, is greater than 9 N / 25 mm.

15. The multilayer polyethylene film according to any one of the preceding claims, wherein, The MFR2 of the second plastic body is 0.1 to 5.0 g / 10 min, preferably 0.5 to 3.0 g / 10 min, and more preferably 0.6 to 2.0 g / 10 min.

16. The multilayer polyethylene film according to any one of the preceding claims, wherein, The molecular weight distribution of the second plastic body, Mw / Mn, is less than 4, preferably between 1.7 and 3.8, and more preferably between 1.8 and 3.

5.

17. The multilayer polyethylene film according to any one of the preceding claims, wherein, The first plastic body of the sealing layer is the same as the second plastic body of the core layer.

18. A method for preparing a multilayer polyethylene film as described in any one of claims 1 to 17, comprising the following steps: i) Forming a first polymer composition comprising at least 30.0 wt% of a first multimodal linear low-density polyethylene terpolymer; and ii) At least 10.0 wt% of a substance with a density of 910 kg / m³ as measured according to ISO 1183. 3 Or lower (first plastic body); A second polymer composition is formed, comprising: a) At least 8.0 wt% of a substance with a density of 910 kg / m³ as measured according to ISO 1183. 3 Or a lower second plastic body; wherein the second plastic body is a copolymer of ethylene and a comonomer selected from 1-butene, 1-hexene or 1-octene; and b) Second multimodal polyethylene terpolymer; Forming a third polymer composition; and The first, second and third polymer compositions are co-extruded to form the sealing layer, the core layer and the outer layer, respectively.

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