Biaxially oriented polypropylene-based multilayer film

Abstract

Biaxially oriented polypropylene-based multilayer film, method for the manufacture of the biaxially oriented multilayer film and use thereof in flexible packaging.

Description

Technical Field

[0001] This invention relates to a biaxially oriented polypropylene-based multilayer film, a method for preparing the biaxially oriented multilayer film, and its application in flexible packaging. Background Technology

[0002] Polypropylene-based resins are widely used in the food packaging industry due to their excellent tensile strength, rigidity, transparency, and the additional advantages of being non-toxic and odorless. Typically, polypropylene-based resins are used in the form of cast film (CPP), biaxially oriented polypropylene (BOPP), or water-quenched tubular polypropylene (TQPP).

[0003] Biaxially oriented polypropylene (BOPP) film is a film stretched simultaneously in the longitudinal and transverse directions, resulting in molecular chains oriented in both directions.

[0004] Biaxially oriented polypropylene (BOPP) multilayer films are commonly used in the packaging industry, including food packaging.

[0005] Typically, this application includes a sealing layer to provide the sealing performance required for the packaging system to close securely. However, since this sealing layer comes into direct contact with the packaged food, its cleanliness (e.g., low extractable content) is crucial.

[0006] Food packaging films are typically transparent, or more generally, they should also have good optical properties, such as low haze, to provide an aesthetically pleasing appearance.

[0007] According to state-of-the-art technology, polypropylene materials are based on Ziegler-Natta catalyst technology, namely, a titanium-centered heterogeneous catalyst activated by alkylaluminum. Therefore, the sealing layer is typically a Ziegler-Natta catalyzed propylene-ethylene-butene terpolymer.

[0008] For example, WO2009 / 019169A1 describes a method for producing Ziegler-Natta catalyst-derived PP terpolymers suitable for blown films using a 1,3-diether internal donor catalyst, said PP terpolymer comprising at least 8 wt% of comonomer units derived from ethylene and C4-C8 α-olefins. According to WO2009 / 019169A1, an optimal performance balance is observed when an ethylene content of less than 2.5 wt% is combined with a 1-butene content of more than 10 wt%; thus, when the ethylene content is greater than 2.5 wt%, the 1-butene content should be less than 10 wt%. A composition with an ethylene content of 1.2 wt% and a 1-butene content of 11.3 wt% (i.e., a C4 / C2 (wt / wt) ratio of 9.4) has a SIT of 107.4°C and a haze of 0.2% (on a 1 mm plate).

[0009] For decades, this solution has been sufficient to meet the needs. However, due to changes in market demands, such terpolymers have reached their limits to some extent, for example, due to insufficient sealing initiation temperatures and inadequate optical properties.

[0010] Metallocene catalyst-derived PP terpolymers have also been described for sealing applications.

[0011] For example, EP20193414A discloses a bimodal C2C3C4 terpolymer prepared by polymerization in a loop reactor followed by polymerization in a gas-phase reactor in the presence of a metallocene catalyst, wherein a fairly high polymer content is produced in the gas-phase reactor, namely 46.0% to 57.0% by weight of the final polymer.

[0012] The MFR2 (ISO 1133, 2.16 kg, 230 °C) of these terpolymers after polymerization reached 2.0 g / 10 min, and was adjusted to a final MFR2 (ISO 1133, 2.16 kg, 230 °C) in the range of 11.0 to 14.0 g / 10 min for the preparation of cast films.

[0013] BOPP membrane was mentioned in general, but this was not confirmed.

[0014] WO2022167368A discloses a membrane made from a blend of a C2C3C4 terpolymer and a C3C4 random copolymer modified resin.

[0015] The C2C3C4 terpolymer was prepared by polymerization in a loop reactor followed by polymerization in a gas-phase reactor in the presence of a metallocene catalyst, wherein the polymer yield was higher in the gas-phase reactor, accounting for 59.0% by weight of the final polymer.

[0016] According to claim 1, the xylene cold solubles (XCS) content of the terpolymer, as measured at 25°C according to ISO 16152, is in the range of 5.0 to 25.0% by weight, preferably 15.0 to 19.0% by weight.

[0017] The terpolymer used in the examples had a fairly high xylene cold soluble content (XCS), at 17.1% by weight.

[0018] As mentioned above, BOPP multilayer films are widely used in the packaging industry. Key requirements include sealing performance, optical properties (e.g., haze), and low extractable content.

[0019] Therefore, there is still a need for BOPP multilayer membranes with good sealing performance, low haze and low extractable content. Summary of the Invention

[0020] Therefore, one objective of the present invention is to provide a novel BOPP multilayer film with improved sealing performance (e.g., low seal initiation temperature (SIT) and wide processing window) and good optical performance (e.g., low haze).

[0021] Another issue is the recycling of BOPP multilayer films after their first use. Recycling BOPP multilayer films made from different materials (e.g., different types of polymers, such as polyamide, polyester, and polypropylene) is more challenging than recycling single-material solutions. On the other hand, different materials are often required to achieve acceptable performance (e.g., sealing performance and mechanical properties). Therefore, another object of the present invention is to provide a polypropylene-based single-material solution that exhibits good sealing behavior.

[0022] Therefore, the present invention relates to a biaxially oriented polypropylene-based multilayer film, comprising at least: a core layer (CL), a first outer layer (OL1), and a second outer layer (OL2), wherein,

[0023] The first outer layer (OL1) and the second outer layer (OL2) are blends comprising the following components:

[0024] i) Based on the total weight of the blend, 60.0 to 95.0% by weight of the metallocene-catalyzed ethylene-propylene-1-butene terpolymer base resin,

[0025] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene-propylene-1-butene terpolymer base resin is obtained through... 13 C-NMR analysis (as described in the experimental section) showed that the ethylene (C2) content ranged from 0.8 to 2.5% by weight.

[0026] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene-propylene-1-butene terpolymer base resin is obtained through... 13 The 1-butene (C4) content, as determined by C-NMR analysis (as described in the experimental section), ranged from 3.0 to 10.0% by weight.

[0027] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene-propylene-1-butene terpolymer base resin is obtained through... 13 The propylene (C3) content, as determined by C-NMR analysis (as described in the experimental section), ranged from 89.2% to 93.0% by weight.

[0028] The sum of units derived from ethylene, propylene, and butene is 100% by weight, and

[0029] The melt flow rate (MFR2) of the ethylene-propylene-1-butene terpolymer base resin, as measured according to ISO 1133 (230°C / 2.16 kg), is in the range of 3.0 to 35.0 g / 10 min.

[0030] The xylene cold solubles (XCS) content of the ethylene-propylene-1-butene terpolymer base resin, as measured at 25°C according to ISO 16152, is in the range of 1.0 to 4.5% by weight.

[0031] The melting temperature T of the ethylene-propylene-1-butene terpolymer base resin, as measured by DSC according to ISO 11357, is... m Within the range of 120 to 140°C;

[0032] The crystallization temperature T of the ethylene-propylene-1-butene terpolymer base resin, as measured by DSC according to ISO 11357, is... c Within the range of 80 to 115°C; and

[0033] The ethylene-propylene-1-butene terpolymer base resin is obtained through... 13 The number of defects in region 2,1, as determined by C-NMR analysis (as described in the experimental section) ranged from 0.10 to 1.0 mol%.

[0034] ii) Based on the total weight of the blend, 40.0 to 5.0% by weight of propylene-1-butene random copolymer,

[0035] The melting temperature T of the propylene-1-butene random copolymer was measured by differential scanning calorimetry (DSC). m The temperature is between 70 and 90 degrees Celsius.

[0036] Based on the total amount of propylene-1-butene random copolymer, the propylene-1-butene random copolymer is obtained through... 13 C-NMR analysis (as described in the experimental section) showed that the 1-butene content ranged from 20.0% to 35.0% by weight.

[0037] The sum of units derived from propylene and 1-butene is 100% by weight.

[0038] The melt flow rate (MFR2) of the propylene-1-butene random copolymer, measured according to ISO 1133 (230°C / 2.16 kg), is...

[0039] The concentration was 1.0 to 18.0 g / 10 min; and

[0040] Optionally, the elongation at break (ASTM D638) of the propylene-1-butene random copolymer is 100% to 900%.

[0041] The core layer (CL) is a polypropylene-based layer, and

[0042] Among them, the biaxially oriented polypropylene-based multilayer film has the following characteristics:

[0043] According to the experimental section, the sealing initiation temperature measured on a 25 μm biaxially stretched cast film was in the range of 50 to 90 °C.

[0044] According to ASTM D1003-00, the haze measured on a 25 μm thick biaxially oriented cast film is in the range of 0.5% to 1.5%.

[0045] Surprisingly, the biaxially oriented polypropylene-based multilayer film of the present invention provides improved sealing performance, such as a combination of particularly low seal initiation temperature (SIT) and low haze. Detailed Implementation

[0046] definition

[0047] When the term "comprising" is used in this specification and claims, it does not exclude other unspecified elements that are of primary or secondary functional importance. For the purposes of this invention, the term "consisting of" is considered a preferred embodiment of the term "comprising." If below a group is defined as comprising at least a certain number of embodiments, it should also be understood as disclosing a group preferably consisting only of these embodiments.

[0048] Whenever “includes” or “has” is used, these terms have the same meaning as “includes” as defined above.

[0049] When an indefinite or definite article, such as “a,” “a kind,” or “the / that”, is used to refer to a singular noun, this includes the plural form of the noun unless otherwise explicitly stated.

[0050] In this invention, the metallocene-catalyzed ethylene-propylene-1-butene terpolymer base resin is defined as an ethylene-propylene-1-butene terpolymer base resin prepared in the presence of a metallocene catalyst.

[0051] In this invention, "terpolymer" refers to a polymer composed of ethylene, propylene, and 1-butene monomers present in the polymer chain. The sum of the weight percentages of units derived from these monomers is 100% by weight. Pseudo-terpolymers made from mixtures of two copolymers are not included in the term "terpolymer" in this invention. Pseudo-terpolymers can be identified by coupled TREF-IR, coupled TREF-NMR, or similar methods. By definition, a terpolymer in this invention is not a mixture of two copolymers.

[0052] In this invention, a polypropylene-based layer is defined as a layer made solely of polypropylene polymer, i.e., with virtually no polymers other than polypropylene present.

[0053] Regional defects

[0054] Regional defects in propylene polymers can be classified into three types: 2,1-erythro (2,1e), 2,1-threo (2,1t), and 3,1 defects. A detailed description of the structure and formation mechanism of regional defects in polypropylene can be found in *Chemical Reviews*, 2000, 100(4), pp. 1316-1327. These defects employ… 13 The measurements were performed using C NMR, which will be described in more detail below.

[0055] The term "2,1-region defect" as used in this invention refers to the sum of 2,1-erythro-region defects and 2,1-threo-region defects. Propylene random copolymers or polypropylene homopolymers having the desired number of region defects in the propylene compositions of this invention are typically and preferably prepared in the presence of a single-site catalyst.

[0056] Catalysts have a significant impact on the microstructure of polymers. Therefore, polypropylene prepared using metallocene catalysts has a different microstructure compared to polypropylene prepared using Ziegler-Natta (ZN) catalysts. The most significant difference lies in the presence of regional defects in metallocene-catalyzed polypropylene, while polypropylene prepared using Ziegler-Natta (ZN) catalysts does not exhibit regional defects.

[0057] It should also be understood from the content of this disclosure that the embodiments described below can be used in combination.

[0058] Detailed description

[0059] Outer layers (OL1, OL2)

[0060] According to the present invention, the multilayer film includes a first outer layer (OL1) and a second outer layer (OL2), which comprises a metallocene-catalyzed ethylene-propylene-1-butene terpolymer base resin and a propylene-1-butene random copolymer.

[0061] Metallocene-catalyzed ethylene-propylene-1-butene terpolymer base resin

[0062] Metallocene-catalyzed ethylene-propylene-1-butene terpolymer base resins have the following properties:

[0063] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, through 13 C-NMR analysis (as described in the experimental section) showed that the ethylene (C2) content ranged from 0.8 to 2.5% by weight.

[0064] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, through 13 The 1-butene (C4) content, as determined by C-NMR analysis (as described in the experimental section), ranged from 3.0 to 10.0% by weight.

[0065] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, through 13 The propylene (C3) content, as determined by C-NMR analysis (as described in the experimental section), ranged from 89.2% to 93.0% by weight.

[0066] The sum of units derived from ethylene, propylene, and butene is 100% by weight, and

[0067] • The melt flow rate MFR2 (230℃ / 2.16kg) measured according to ISO 1133 is in the range of 3.0 to 35.0 g / 10min;

[0068] • The content of xylene cold solubles (XCS), as measured at 25°C according to ISO 16152, is in the range of 1.0 to 4.5% by weight;

[0069] • Melting temperature T measured by DSC according to ISO 11357 m Within the range of 120 to 140°C;

[0070] • Crystallization temperature T measured by DSC according to ISO 11357 c Within the range of 80 to 115°C, and

[0071] ·pass 13The number of defects in the 2,1 region, as determined by C-NMR analysis (as described in the experimental section), ranged from 0.10 to 1.0 mol%.

[0072] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene (C2) content of the ethylene-propylene-1-butene terpolymer base resin is preferably 0.9 to 2.2% by weight, more preferably 1.0 to 2.0% by weight, and even more preferably 1.0 to 1.8% by weight.

[0073] Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the 1-butene (C4) content of the ethylene-propylene-1-butene terpolymer base resin is preferably 5.0 to 9.5% by weight, more preferably 6.5 to 9.0% by weight.

[0074] In one embodiment of the present invention, based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the total content of the comonomers (i.e., C2 and C4 content) of the ethylene-propylene-1-butene terpolymer base resin is in the range of 7.0 to 10.8% by weight, preferably in the range of 7.5 to 10.5% by weight, and more preferably in the range of 8.0 to 10.0% by weight.

[0075] The melt flow rate MFR2 (230°C / 2.16 kg) measured according to ISO 1133 is preferably 3.5 to 20.0 g / 10 min, more preferably 3.8 to 15.0 g / 10 min, and even more preferably 4.0 to 10.0 g / 10 min.

[0076] Based on the weight of the ethylene-propylene-1-butene terpolymer base resin, the xylene cold solubles (XCS) content, as measured according to ISO 16152, is preferably 1.0 to 4.0 wt%, more preferably 1.3 to 3.5 wt%, and even more preferably 1.5 to 3.0 wt%.

[0077] The melting temperature T, as measured by DSC according to ISO 11357. m The temperature is preferably 122 to 135°C, and more preferably 125 to 130°C.

[0078] The crystallization temperature T, as measured by DSC according to ISO 11357, is... c Preferably, the temperature is 82 to 110°C, more preferably 85 to 100°C, and even more preferably 86 to 90°C.

[0079] pass 13 The number of defects in region 2,1 as determined by C-NMR analysis (as described in the experimental section) is preferably 0.15 to 0.90 mol%, more preferably 0.20 to 0.60 mol%.

[0080] According to another preferred embodiment of the invention, the ethylene-propylene-1-butene terpolymer base resin comprises two polymer components (TERPO-1) and (TERPO-2), more preferably composed of these two polymer components (TERPO-1) and (TERPO-2), wherein, based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the content of component (TERPO-1) is 50.0 to 80.0% by weight, preferably 60.0 to 78.0% by weight, more preferably 67.0 to 75.0% by weight; therefore, based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the content of component (TERPO-2) is 20.0 to 50.0% by weight, preferably 22.0 to 40.0% by weight, more preferably 25.0 to 33.0% by weight.

[0081] Optionally, a small amount of prepolymer component may also be present in the ethylene-propylene-1-butene terpolymer base resin, typically less than 5.0% by weight (based on the total weight of the ethylene-propylene-1-butene terpolymer base resin). Such prepolymer component (if present) is typically included in the TERPO-1 component content.

[0082] According to another embodiment of the present invention, the ethylene content of component (TERPO-1) of the ethylene-propylene-1-butene terpolymer base resin is 0.2 to 2.0 wt%, preferably 0.4 to 1.8 wt%, more preferably 0.5 to 1.5 wt%, and / or the ethylene content of component (TERPO-2) is 1.0 to 4.0 wt%, preferably 1.2 to 3.5 wt%, more preferably 1.3 to 3.0 wt%.

[0083] The ethylene content of component (TERPO-1) is preferably lower than that of component (TERPO-2).

[0084] The 1-butene content of component (TERPO-1) of the ethylene-propylene-1-butene terpolymer base resin is 2.5 to 10.0 wt%, preferably 3.5 to 9.0 wt%, more preferably 4.5 to 8.0 wt%, and / or the 1-butene content of component (TERPO-2) is 5.0 to 15.0 wt%, preferably 5.5 to 14.0 wt%, more preferably 6.0 to 13.0 wt%.

[0085] According to another preferred embodiment of the present invention, the ethylene-propylene-1-butene terpolymer base resin is prepared in the presence of a metallocene catalyst, preferably a metallocene catalyst comprising the complex in any of the embodiments described in WO2013 / 007650A1, WO2015 / 158790A2, WO2018 / 122134A1 or WO2019 / 179959.

[0086] Preferred complexes for the preparation of ethylene-propylene-1-butene terpolymer base resins are described, for example, in WO2019179959.

[0087] A more preferred complex is the complex shown in formula (I).

[0088]

[0089] In the formula, each R 1 Independently identical or different, and being hydrogen or straight-chain or branched C1-C6 alkyl groups, wherein each phenyl group contains at least one R 1 Not hydrogen;

[0090] R′ is C 1-10 Hydrocarbon group, preferably C 1-4 Hydrocarbon group, more preferably methyl; and

[0091] X can be independently a hydrogen atom, a halogen atom, or a C atom. 1-6 Alkoxy, C 1-6 Alkyl, phenyl, or benzyl.

[0092] Most preferably, X is chlorine, benzyl, or methyl. Preferably, the two X groups are identical. The most preferred configuration is two chlorine atoms, two methyl groups, or two benzyl groups, especially two chlorine atoms.

[0093] The metallocene catalyst complexes particularly preferred by this invention include:

[0094] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(4'-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4-(3',5'-dimethyl-phenyl)-5-methoxy-6-tert-butylindacen-1-yl]zirconium dichloride

[0095] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indan-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylindan-1-yl]zirconium dichloride

[0096] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indenman-1-yl][2-methyl-4-(3',5'-di-tert-butyl-phenyl)-5-methoxy-6-tert-butylindenman-1-yl]zirconium dichloride,

[0097] Or their corresponding dimethylzirconium analogues.

[0098] In another preferred embodiment of the invention, a cocatalyst system comprising a boron-containing cocatalyst (e.g., a borate cocatalyst) and an aluminoxane cocatalyst is used.

[0099] The catalyst can be used in supported or unsupported form, with supported form being preferred. The particulate support material used is preferably an organic or inorganic material, such as silica, alumina, or zirconium oxide, or a mixed oxide, such as silica-alumina, particularly silica, alumina, or silica-alumina. Silica support is preferred. Those skilled in the art understand the steps required for supporting metallocene catalysts.

[0100] Particularly preferred is that the carrier is a porous material so that the complex can be loaded into the pores of the carrier, for example using methods similar to those described in WO94 / 14856 (Mobil), WO95 / 12622 (Borealis) and WO2006 / 097497.

[0101] The average particle size of silica supports is typically 10 to 100 μm. However, it has been shown that if the average particle size of the support is 15 to 80 μm, preferably 18 to 50 μm, special advantages can be obtained.

[0102] The average pore size of the silica support can be in the range of 10 to 100 nm, and the pore volume can be in the range of 1 to 3 mL / g.

[0103] Examples of suitable support materials include ES757 manufactured and sold by PQ Corporation, Sylopol 948 manufactured and sold by Grace, or SUNSPERA DM-L-303 silica manufactured by AGC Si-Tech. The support may optionally be calcined prior to its use in catalyst preparation to achieve optimal silanol group content.

[0104] The use of these carriers is common practice in this field.

[0105] The ethylene-propylene-1-butene terpolymer base resin can be prepared by a single polymerization step comprising a single polymerization reactor (R1), or by a sequential polymerization process comprising at least two polymerization reactors (R1) and (R2), wherein a first component (TERPO-1) is generated in the first polymerization reactor (R1) and subsequently conveyed to the second polymerization reactor (R2). In the second polymerization reactor (R2), a second component (TERPO-2) is generated in the presence of the first component (TERPO-1).

[0106] Polymerization processes suitable for producing ethylene-propylene-1-butene terpolymer base resins typically include one or two polymerization stages, each of which can be carried out in solution, slurry, fluidized bed, bulk, or gas phase.

[0107] The term "polymerization reactor" should indicate the location where the main polymerization occurs. Therefore, if the process consists of one or two polymerization reactors, this definition does not exclude the possibility that the entire system includes a prepolymerization step, for example, in a prepolymerization reactor. The term "consisting of" is only a closed-ended statement referring to the main polymerization reactor.

[0108] The term "sequential polymerization process" indicates that the ethylene-propylene-1-butene terpolymer base resin is produced in at least two reactors connected in series. Therefore, such a polymerization system includes at least a first polymerization reactor (R1) and a second polymerization reactor (R2), and optionally a third polymerization reactor (R3).

[0109] The preferred multi-stage process is the "loop-gas phase" process, such as the one developed by Borealis. The technology has been described in patent documents, such as EP0887379, WO92 / 12182, WO2004 / 000899, WO2004 / 111095, WO99 / 24478, WO99 / 24479 or WO00 / 68315.

[0110] Another suitable slurry-gas phase process is that of Basell. Process.

[0111] In any embodiment, the ethylene-propylene-1-butene terpolymer base resin comprising the two components (TERPO-1) and (TERPO-2) is preferably prepared by a method comprising the following steps:

[0112] a) Polymerize propylene, ethylene and 1-butene in the first reactor (R1) to obtain polymer component (TERPO-1);

[0113] b) Transfer the polymer component (TERPO-1) and unreacted comonomer from the first reactor to the second reactor (R2);

[0114] c) Propylene, ethylene and 1-butene are fed into the second reactor (R2);

[0115] d) In the second reactor (R2), in the presence of the polymer component (TERPO-1), propylene, ethylene and 1-butene are polymerized to obtain a polymer component (TERPO-2) that is closely mixed with (TERPO-1), thereby obtaining the final ethylene-propylene-1-butene terpolymer base resin, wherein the polymerization is preferably carried out in the presence of the metallocene catalyst system in any of the embodiments described herein.

[0116] The ethylene-propylene-1-butene terpolymer base resin may contain one or more commonly used additives, preferably in a total amount of 0.01 to 5.0% by weight, more preferably 0.05 to 3.0% by weight (based on the total weight of the propylene-ethylene random copolymer). The additives are selected from slip agents, anti-sticking agents, UV stabilizers, antistatic agents, α-nucleating agents, antioxidants, and mixtures thereof. Preferably, the propylene-ethylene random copolymer of the present invention contains at least an antioxidant.

[0117] propylene-1-butene random copolymer

[0118] The random copolymer of propylene-1-butene is characterized by having at least the following properties:

[0119] • Melting temperature T measured by differential scanning calorimetry (DSC) according to ISO 11357 m Within the range of 70 to 90℃;

[0120] • Based on the total amount of propylene-1-butene random copolymer, through 13 C-NMR analysis (as described in the experimental section) showed that the 1-butene content ranged from 20.0% to 35.0% by weight.

[0121] The sum of units derived from propylene and butene is 100% by weight.

[0122] • The melt flow rate (MFR2) (230°C / 2.16 kg) measured according to ISO 1133 is in the range of 1.0 to 18.0 g / 10 min; and

[0123] • Optionally, the elongation at break (ASTM D638) is 100% to 900%.

[0124] The melting temperature is preferably in the range of 72 to 85°C, and more preferably in the range of 73 to 80°C.

[0125] The 1-butene content is preferably in the range of 22.0 to 34.5% by weight, more preferably in the range of 24.0 to 34.0% by weight.

[0126] The melt flow rate MFR2 (230°C / 2.16 kg) measured according to ISO 1133 is preferably in the range of 3.0 to 15.0 g / 10 min, more preferably in the range of 5.0 to 12.0 g / 10 min.

[0127] In a preferred embodiment, the elongation at break (ASTM D638) of the propylene-1-butene random copolymer is 100 to 900%, preferably 300 to 850%, and more preferably 500 to 800%.

[0128] In another embodiment, the propylene-1-butene random copolymer also has one or more of the following properties, preferably all of them:

[0129] a) The tensile strength at break (ASTM D638) is at least 15 MPa, preferably in the range of 16 to 50 MPa, more preferably in the range of 20 to 45 MPa, and even more preferably in the range of 25 to 40 MPa.

[0130] b) The tensile (Young's) modulus (according to ASTM D638) is at least 200 MPa, preferably in the range of 210 to 450 MPa, and more preferably in the range of 250 to 400 MPa;

[0131] c) The Shore D hardness (ASTM D2240) is at least 45, preferably in the range of 48 to 65, and more preferably in the range of 50 to 60.

[0132] These propylene-1-butene random copolymers with these properties are commercially available from companies such as Mitsui Chemicals, for example, the Tafmer XM series.

[0133] The outer layers (OL-1) and (OL-2) according to the invention are preferably composed of 70 to 95% by weight of an ethylene-propylene-1-butene terpolymer base resin relative to the total amount of the blend and 5 to 30% by weight of a propylene-1-butene random copolymer relative to the total amount of the blend. The ethylene-propylene-1-butene terpolymer base resin and the propylene-1-butene random copolymer preferably total at least 98% by weight, more preferably 100% by weight, for each outer layer, meaning that the resulting outer layer material is substantially free of other polymer components, and more preferably completely free of other polymer components.

[0134] More preferably, the amount of the ethylene-propylene-1-butene terpolymer base resin is 75 to 90% by weight, and the amount of the propylene-1-butene random copolymer is 10 to 25% by weight, based on the total amount of the blend.

[0135] Core layer

[0136] According to the present invention, the multilayer film further includes a core layer (CL), which is a polypropylene-based layer.

[0137] Suitable polypropylene polymers are propylene homopolymers or propylene random copolymers.

[0138] Propylene homopolymer is preferred.

[0139] Propylene homopolymer (H-PP)

[0140] In one embodiment of the invention, the core layer (CL) comprises propylene homopolymer (H-PP). More preferably, the core layer (CL) is composed of propylene homopolymer (H-PP).

[0141] As used in this invention, the term "propylene homopolymer" refers to polypropylene that is essentially composed of propylene units, that is, polypropylene composed of more than 98.0% by weight, preferably more than 99.0% by weight, more preferably more than 99.5% by weight, and even more preferably at least 99.8% by weight of propylene units. In a preferred embodiment, only propylene units are detectable in the propylene homopolymer (HPP).

[0142] Therefore, the xylene soluble content (XCS) of the preferred propylene homopolymer (H-PP) as measured according to ISO 16152 is less than 5.0 wt%, more preferably less than 4.0 wt%, and even more preferably less than 3.5 wt%.

[0143] Preferred propylene homopolymers (H-PP) have high isotactic regularity.

[0144] Therefore, the preferred propylene homopolymer (H-PP) has a pentagonal concentration of ≥85.0% as measured by NMR spectroscopy, preferably in the range of 85.0% to 98.0%, and / or is determined by... 13 The defects in the 2,1 red region, as measured by C-NMR spectroscopy, are less than 1.0%, preferably less than 0.5%, and more preferably less than 0.3%.

[0145] For Ziegler-Natta catalyzed propylene homopolymers, the suitable lower limit for regional defects is 0.0%, and for metallocene catalyzed propylene homopolymers, the suitable lower limit is 0.05%.

[0146] Particularly preferred is that the weight-average molecular weight Mw of the propylene homopolymer (H-PP) is in the range of 260 to 1000 kg / mol, more preferably in the range of 300 to 700 kg / mol, and even more preferably in the range of 380 to 650 kg / mol.

[0147] Furthermore, the propylene homopolymer (H-PP) preferably has a wide molecular weight distribution (Mw / Mn). Therefore, the molecular weight distribution (Mw / Mn) of the propylene homopolymer (H-PP) is preferably 3.5 to 10.0, more preferably 4.0 to 8.5, for example 4.5 to 7.5.

[0148] Furthermore, the propylene homopolymer (H-PP) preferably has a very low melt flow rate. Therefore, the melt flow rate (2.16 kg, 230 °C) of the propylene homopolymer (H-PP) measured according to ISO 1133 is preferably 0.1 to 15.0 g / 10 min, more preferably 1.5 to 10.0 g / 10 min, and even more preferably 2.5 to 4.0 g / 10 min.

[0149] In a preferred embodiment, the propylene homopolymer (H-PP) possesses thermomechanical stability. Therefore, the melting temperature T of the propylene homopolymer (H-PP) is... m Preferably at least 145°C, more preferably at least 150°C, and even more preferably at least 160°C. m The reasonable upper limit is 170℃.

[0150] Preferably, the propylene homopolymer (H-PP) according to the present invention is a propylene homopolymer known in the art.

[0151] Particularly preferred is the commercially available propylene homopolymer (H-PP) HC101BF from Borealis AG.

[0152] Membrane structure

[0153] According to the present invention, the multilayer film includes at least a first outer layer (OL1), a second outer layer (OL2), and a core layer (CL).

[0154] The outer layers (OL1) and (OL2) of the multilayer film of the present invention are used as sealing layers.

[0155] The term “sealing layer” is to be understood in this document as a term used in the field of packaging technology, meaning that the term “sealing layer” indicates that the layer is used for sealing purposes, i.e., sealing can occur on the surface of the layer or a portion thereof.

[0156] In a preferred embodiment, the multilayer biaxially oriented membrane comprises at least three layers, namely at least one core layer (CL) and two sealing layers (OL1 and OL2), namely a first sealing layer / outer layer (OL1) and a second sealing layer / outer layer (OL2), wherein the biaxially oriented polymer multilayer membrane has the following stacking order: first sealing layer / outer layer (OL1) - core layer (CL) - second sealing layer / outer layer (OL2).

[0157] The first sealing layer / outer layer (OL1) and the second sealing layer / outer layer (OL2) can be chemically different, i.e., different ethylene-propylene-1-butene terpolymer base resins and / or propylene-1-butene random copolymers as described above; or they can be the same, i.e., blends of the same ethylene-propylene-1-butene terpolymer base resin and propylene-1-butene random copolymer, with the latter being preferred.

[0158] The membrane of the present invention may further include one or two connecting layers (TL1) and (TL2). Optionally, the connecting layer is located between the core layer (CL) and one of the outer layers (OL1) and / or (OL2) or between the two outer layers.

[0159] Therefore, one possible membrane structure is OL1 / TL1 / CL / TL2 / OL2.

[0160] In one embodiment, the connecting layers (TL1) and (TL2) are made of a polypropylene-based polymer, preferably the same propylene-based polymer.

[0161] Suitable polypropylene-based polymers are as defined above for the core layer (CL).

[0162] In a preferred embodiment, the connecting layers (TL1) and (TL2) are made of the same polypropylene polymer as the core layer (CL), more preferably of the same propylene homopolymer (H-PP).

[0163] Preferably, the biaxially oriented polymer multilayer film is obtained by co-extrusion. Co-extrusion can be performed on a blown film production line or a cast film production line, the latter being preferred. After co-extrusion, the multilayer polymer film is biaxially stretched.

[0164] The multilayer membrane according to the present invention can be produced using conventional membrane manufacturing techniques. Typically, the membrane layers are co-extruded in a manner known in the art and then oriented to obtain a biaxially oriented (BOPP) multilayer membrane.

[0165] Therefore, after co-extruding each layer, the resulting multilayer film is oriented in the longitudinal direction (MDO) and in the transverse direction (TDO).

[0166] In the production of biaxially oriented polymer multilayer films using casting film technology, molten polymer is extruded through a flat extrusion die onto a cooling roller to cool the polymer into a solid film of at least three layers.

[0167] The production of biaxially oriented polymer multilayer films is carried out as follows: Melts of the polymer for the core layer (CL), melts of the propylene-ethylene random copolymer for the outer layers (OL1 and OL2), and optionally melts of the polymer for the connecting layers (TL1 and / or TL2) (corresponding to the individual layers of the biaxially oriented polymer multilayer film) are co-extruded through a flat die. The resulting polymer film is then removed from one or more rolls for curing. Following conventional co-extrusion methods, the polymer for each individual layer is first compressed and liquefied in an extruder. Any additives can be pre-added to the polymer or added at this stage via masterbatch. The melts are then simultaneously forced through a flat die (slit die), and the extruded multilayer polymer film is removed from one or more traction rolls, where it is cooled and cured.

[0168] It has been shown that retaining one or more traction rollers is particularly advantageous, through which the extruded film is cooled and cured. Orientation can be achieved by first stretching or pulling the film longitudinally (MD) and then orienting it transversely (TD), similar to the orientation process in a tenter frame. Orientation can be performed sequentially or simultaneously, depending on the desired film characteristics. Preferred orientation ratios are typically 3 to 6 longitudinally and 4 to 10 transversely.

[0169] Therefore, the thickness of each layer in a BOPP film can be as follows:

[0170] Each outer layer: 0.3 μm to 3.0 μm, preferably 0.5 μm to 2.0 μm, more preferably 0.8 μm to 1.5 μm.

[0171] Preferably, the two outer layers have the same thickness.

[0172] Core layer: 5μm to 40μm, preferably 10μm to 35μm, more preferably 15μm to 25μm.

[0173] Each connecting layer (if any): 1.0 μm to 5 μm, preferably 1.5 μm to 4.5 μm, more preferably 2.0 μm to 4.50 μm.

[0174] Preferably, the two connecting layers have the same thickness.

[0175] The total thickness of the BOPP film is 8 μm to 80 μm, preferably 10 μm to 60 μm, and more preferably 15 μm to 40 μm.

[0176] The thickness of the film can be determined using microscopy techniques known in the art, such as optical microscopy or electron microscopy. For example, a thin film is cut perpendicular to the film plane using a microtome blade, as shown below. The film is cooled with liquid nitrogen in a microtome holder. The microtome blade then cuts multiple slices with a thickness of approximately 10 to 15 μm. These slices are then observed using an optical microscope and projected onto an image. The thickness of each layer shown on the projected image can be measured using software programs known in the art. Measurements can be taken at different points on the image, and then an average value is determined. The film layers can be clearly distinguished by their different contrasts.

[0177] Alternatively, one or both sides of the biaxially oriented polymer multilayer film can be corona-treated or flame-treated using known methods. For corona treatment, the film is passed through two conductive elements serving as electrodes, and a high voltage, typically an alternating current voltage (approximately 10,000 V and 10,000 Hz), is applied between the electrodes to generate a spray or corona discharge. Due to the spray or corona discharge, air at the film surface is ionized and reacts with molecules on the film surface, thereby forming polar inclusions within the inherently nonpolar polymer matrix. The treatment intensity is typically within the range, preferably 38 to 45 dynes / cm after production.

[0178] The biaxially oriented polypropylene-based multilayer film of the present invention is characterized in that its sealing initiation temperature (as described in the experimental section, measured on a BOPP film with a thickness of 25 μm) is in the range of 50 to 90°C, preferably in the range of 65 to 88°C, and more preferably in the range of 70 to 85°C.

[0179] Furthermore, the haze of the biaxially oriented polypropylene-based multilayer film (measured according to ASTM D1003-00 on a BOPP film with a thickness of 25 μm) is in the range of 0.5% to 1.5%, preferably between 0.55% and 1.0%.

[0180] In addition, the longitudinal and transverse tensile moduli of the biaxially oriented polypropylene-based multilayer film (measured according to ISO 527-3, at 23°C on a BOPP film with a thickness of 25 μm) can be in the range of 1000 to 3000 MPa, preferably in the range of 1200 to 2800 MPa.

[0181] In one embodiment, the biaxially oriented polypropylene-based multilayer film according to the invention has an enlarged processing window, which is determined by the melting temperature T of the ethylene-propylene-1-butene terpolymer base resin by DSC analysis. m The difference between the membrane's sealing initiation temperature (SIT) and the membrane's sealing temperature is defined. This difference is preferably in the range of 30 to 70°C, more preferably in the range of 35 to 65°C, and even more preferably in the range of 40 to 60°C.

[0182] The biaxially oriented polymer multilayer film of the present invention is fully recyclable, thereby improving sustainability, as it is a “100% PP” solution containing no other polymers besides propylene-based polymers.

[0183] Furthermore, the present invention also relates to the use of the biaxially oriented polymer multilayer film of the present invention as a packaging material, particularly as a packaging material for food and / or non-food products (e.g., textiles, flowers, pet food, detergents) and as a protective film for cardboard boxes containing tobacco products or perfumes.

[0184] The invention will be further described with reference to the following non-limiting embodiments.

[0185] Experimental Section

[0186] Measurement methods

[0187] Unless otherwise defined, the following terms and measurement methods apply to the above general description of the invention and the following embodiments.

[0188] Melt flow rate of ethylene-propylene-1-butene terpolymer base resin

[0189] Melt flow rate (MFR) was determined according to ISO 1133 - Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics (Part 1: Standard methods), in units of g / 10 min. MFR indicates the fluidity of a polymer, and thus its processability. A higher melt flow rate generally indicates a lower polymer viscosity. The MFR2 for polypropylene was measured at 230°C and a load of 2.16 kg.

[0190] Comonomer content of the second polymer component (TERPO-2)

[0191] The comonomer content of the second polymer component (TERPO-2) is calculated according to formula (I).

[0192]

[0193] in

[0194] w(A-1) is the weight fraction of the first polymer component (TERPO-1) [in weight %].

[0195] w(A-2) is the weight fraction of the second polymer component (TERPO-2) [in weight %].

[0196] C(A-1) represents the comonomer content of the first polymer component (TERPO-1) [in weight %].

[0197] C(A) represents the comonomer content of the ethylene-propylene-1-butene terpolymer (TERPO) [in weight %].

[0198] C(A-2) is the calculated comonomer content of the second polymer component (TERPO-2) [in weight %].

[0199] Calculate the melt flow rate (MFR2) of the polymer component (TERPO-2).

[0200] The MFR of the second polymer component (RACO-2) is calculated according to formula (II).

[0201]

[0202] in

[0203] w(A1) represents the weight fraction of the polymer component TERPO-1 [in weight %].

[0204] w(A2) represents the weight fraction of the polymer component TERPO-2 [in weight %].

[0205] MFR(A1) is the melt flow rate MFR2 (230℃) of polymer component TERPO-1 [in g / 10min], and MFR(A) is the melt flow rate MFR2 (230℃) of the entire ethylene-propylene-1-butene terpolymer (TERPO) [in g / 10min].

[0206] MFR(A2) is the calculated melt flow rate MFR2 (230℃) of polymer component TERPO-2 [in g / 10min].

[0207] The microstructure (comonomer content and regional defects) of the ethylene-propylene-1-butene terpolymer base resin was quantitatively analyzed by NMR spectroscopy.

[0208] The comonomer content of the polymer was quantitatively analyzed using quantitative nuclear magnetic resonance (NMR) spectroscopy.

[0209] Quantitative measurements were recorded in the molten state using a Bruker Avance III 500 NMR spectrometer. 13 C{ 1 H NMR spectrum, 1 H and 13 C-spectroscopy was performed at 500.13 MHz and 125.76 MHz, respectively. All spectra were obtained using [missing information - likely a specific method or technique]. 13A C-optimized 7mm magic angle rotation (MAS) probe was used for recording at 180°C, with nitrogen used for all pneumatic components. Approximately 200 mg of material was loaded into a 7mm outer diameter zirconia MAS rotor and rotated at a frequency of 4 kHz. This setup was chosen primarily for its high sensitivity required for rapid identification and accurate quantification. Standard single-pulse excitation was employed, utilizing NOE with a short 3-second cyclic delay and an RS-HEPT decoupling scheme. A total of 1024 (1k) transient signals were acquired for each spectrum.

[0210] Quantitative 13 C{ 1 The ¹H NMR spectra were processed and integrated, and the relevant quantitative characteristics were determined based on the integration results. All chemical shifts were used with the methyl isotactic pentatonic group (mmmm) at 21.85 ppm as an internal reference.

[0211] The characteristic signal {brandolini01} corresponding to the incorporation of 1-butene was observed, and the content of the comonomer was quantified.

[0212] The amount of isolated 1-butene incorporated into the PBP segment was quantified by integrating the αB2 site at 43.6 ppm, where the number of reporter sites for each comonomer was:

[0213] B = I αB2 / 2

[0214] The amount of 1-butene continuously incorporated into the PBBP segment was quantified by integrating the ααB2B2 site at 40.5 ppm, where the number of reporter sites for each comonomer was:

[0215] BB = 2 * I ααB2B2

[0216] In the presence of BB, the value of B must be corrected based on the effect of the αB2 site generated by BB:

[0217] B = (I αB2 / 2)–BB / 2

[0218] The total 1-butene content is calculated based on the sum of isolated 1-butene and continuously incorporated 1-butene:

[0219] B total =B+BB

[0220] The characteristic signal {brandolini01} corresponding to ethylene incorporation was observed, and the content of comonomers was quantified.

[0221] The amount of isolated ethylene incorporated into the PEP segment was quantified by integrating the Sββ site at 24.3 ppm, with the number of reporter sites for each comonomer as follows:

[0222] E = I Sββ

[0223] If a characteristic signal corresponding to the continuous incorporation of ethylene into the PEE chain is observed, quantification is performed using the Sβδ site at 27.0 ppm:

[0224] EE = I Sβδ

[0225] Characteristic signals {resconi00} corresponding to regional defects were observed. The presence of two methyl sites at 17.7 and 17.2 ppm, a methylene site at 42.4 ppm, and other characteristic sites indicates the existence of isolated 2,1-erythromorphic regional defects. Two inequivalent Sαβ signals at 34.8 ppm and 34.4 ppm and a Tγγ signal at 33.7 ppm indicate the presence of 2,1-erythromorphic regional defects in adjacent ethylene units.

[0226] Using 42.4ppm (I e9 The integral of the methylene site at ) is used to quantitatively isolate defects in the 2,1-erythroid region (P) 21e孤立 ) quantity:

[0227] P 21e孤立 =I e9

[0228] If present, use the methine site at 33.7 ppm (I Tγγ To quantify the relationship with ethylene (P) E21 The amount of defects in adjacent 2,1 regions:

[0229] P E21 =I Tγγ

[0230] The total ethylene content is then calculated based on the sum of ethylene from isolated, continuously incorporated, and adjacent 2,1 region defects:

[0231] E 总 =E + EE + P E21

[0232] The amount of propylene was quantified based on the Sαα methylene site at 46.7 ppm, which includes all other propylene units not covered by Sαα, e.g., coefficient 3*P. 21e孤立 Used to complete the three missing propylene units in isolated 2,1-red region defects:

[0233] P 总 =ISαα +3*P 21e孤立 +B+0.5*BB+E+0.5*EE+2*P E21

[0234] Then calculate the total mole fraction of 1-butene and ethylene in the polymer:

[0235] fB = B 总 / (E 总 +P 总 +B 总 )

[0236] fE=E 总 / (E 总 +P 总 +B 总 )

[0237] The molar percentage of comonomers is calculated using the following mole fractions:

[0238] B[mol%]=100*fB

[0239] E[mol%]=100*fE

[0240] The weight percentage of incorporated comonomers is calculated using the following mole fractions:

[0241] B[weight%] = 100*(fB*56.11) / ((fE*28.05)+(fB*56.11)+((1-(fE+fB))*42.08))

[0242] E[weight%] = 100 * (fE * 28.05) / ((fE * 28.05) + (fB * 56.11) + ((1 - (fE + fB)) * 42.08))

[0243] Based on all propylene units, the molar percentage of isolated 2,1-erythromorphic defects was quantified:

[0244] [21e]mol% = 100*P 21e孤立 / P 总

[0245] Based on all propylene units, the molar percentage of defects in the 2,1 region adjacent to ethylene was quantified:

[0246] [E21]mol% = 100*P E21 / P 总

[0247] 2.1 The total number of defects is quantified as follows:

[0248]

[21] mol% = [21e] + [E21]

[0249] No characteristic signal {resconi00} was observed corresponding to other types of regional defects (2,1-Soviet type, 3,1 insertion).

[0250] References (as stated above):

[0251] klimke06 Klimke,K.,Parkinson,M.,Piel,C.,Kaminsky,W.,Spiess,HW,

[0252] Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382.

[0253] parkinson07 Parkinson,M.,Klimke,K.,Spiess,HW,Wilhelm,M.,

[0254] Macromol. Chem. Phys. 2007;208:2128.

[0255] pollard04 Pollard,M.,Klimke,K.,Graf,R.,Spiess,HW,Wilhelm,M.,

[0256] Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004; 37:813.

[0257] filip05 Filip,X.,Tripon,C.,Filip,C.,J.Mag.Resn.2005,176,239

[0258] griffin07 Griffin,JM,Tripon,C.,Samoson,A.,Filip,C.,and Brown,SP,

[0259] Mag.Res.in Chem.2007 45,S1,S198.

[0260] castignolles09 Castignolles,P.,Graf,R.,Parkinson,M.,Wilhelm,M.,Gaborieau,M.,Polymer 50(2009)2373.

[0261] resconi00 Resconi,L.,Cavallo,L.,Fait,A.,Piemontesi,F.,Chem.Rev.2000,100,1253.

[0262] brandolini01 AJBrandolini,DDHills, “NMR spectra of polymers and

[0263] polymer additives”, Marcel Deker Inc., 2000

[0264] Xylene-soluble matter (XCS, wt%)

[0265] The xylene-soluble fraction (XCS) defined and described in this invention was determined according to ISO 16152 as follows: 2.0 g of polymer was dissolved in 250 ml of p-xylene by stirring at 135 °C. After 30 minutes, the solution was cooled to room temperature for 15 minutes, and then allowed to stand at 25 ± 0.5 °C for 30 minutes. The solution was filtered through filter paper into two 100 ml flasks. The solution in the first 100 ml flask was evaporated under a nitrogen stream, and the residue was dried under vacuum at 90 °C to constant weight. The xylene-soluble fraction (percentage) was then determined as follows:

[0266] XCS%=(100*m*V0) / (m0*v)

[0267] m0 = initial amount of polymer (g);

[0268] m = weight of residue (g);

[0269] V0 = Initial volume (ml);

[0270] v = Volume of the sample being analyzed (ml).

[0271] DSC analysis, melting temperature (T) m ) and crystallization temperature (T) c )

[0272] Data were measured using a TA Instrument Q2000 differential scanning calorimeter (DSC) on samples ranging from 5 to 7 mg. DSC was performed according to ISO 11357 / Part 3 / Method C2, with a scan rate of 10 °C / min and heating / cooling / heating cycles over a temperature range of -30 to +225 °C.

[0273] Crystallization temperature (T) c ) and crystallization enthalpy (H c The melting temperature (T) is determined by the cooling step, while the melting temperature (T) is determined by the cooling step.m ) and enthalpy of fusion (H m The result is determined by the second heating step.

[0274] Sealing performance

[0275] Sealing initiation temperature (SIT) under different sealing strengths:

[0276] Measurements were performed according to a slightly modified version of AST MF1921-12, with modifications to the sealing pressure, cooling time, and test speed. The force / temperature profile was measured until thermal failure (burn-through) of the film occurred. The sealing range was determined using a J&B4000 general-purpose sealing machine, employing a 25 μm thick three-layer biaxially oriented cast film, cut into 25 mm wide strips, and the following other parameters were measured:

[0277] Pre-processing time: >96 hours

[0278] Sample width: 25mm

[0279] Sealing pressure: 25 N / cm 2

[0280] Sealing time: 0.5 seconds

[0281] Delay time: 30 seconds

[0282] Sealing claw size: 50×5mm

[0283] Sealing claw shape: flat

[0284] Sealing claw coating: Niptef

[0285] Sealing temperature: room temperature to 240℃

[0286] Sealing temperature interval: 5℃

[0287] Starting temperature: 50℃

[0288] Fixture separation speed: 42mm / second

[0289] Sealing strength is a crucial component of the test, determined as follows: the sealing strip is subjected to tensile loading at a test speed of 200 mm / min, and the temperature values ​​at which a strength of 100, 200, and 300 g per 25 mm width are recorded. The most relevant value corresponds to the temperature at 300 g / 25 mm.

[0290] Haze

[0291] According to ASTM D1003-00, the haze of the biaxially oriented multilayer film prepared as follows was measured.

[0292] 2. Example

[0293] Preparation of propylene-ethylene random copolymers

[0294] Catalysts: Synthesis of Metallocenes

[0295] As described in WO2019 / 179959 regarding MC-2, prepare metallocene complexes (metallocene MC-2).

[0296]

[0297] Preparation of MAO-silica carrier

[0298] The steel reactor, equipped with a mechanical stirrer and filter, was flushed with nitrogen, and the reactor temperature was set to 20°C. Next, 5.0 kg of DM-L-303 grade silica (pre-calcined at 600°C) from AGC Si-Tech was added to the feed tank, and then carefully pressurized and depressurized with nitrogen using a manual valve. Toluene (22 kg) was then added. The mixture was stirred for 15 minutes. Next, a 30% by weight MAO toluene solution (9.0 kg) from Lanxess was added through the feed line at the top of the reactor over 70 minutes. The reaction mixture was then heated to 90°C and stirred for another two hours at 90°C. The slurry was allowed to settle, and the mother liquor was filtered off. The catalyst was washed twice with toluene (22 kg) at 90°C, then settled and filtered. The reactor was cooled to 60°C, and the solids were washed with heptane (22.2 kg). Finally, the MAO-treated SiO2 was dried at 60°C with a nitrogen stream for 2 hours, and then dried under vacuum (-0.5 barg) with stirring for 5 hours. The MAO-treated support was collected as a free-flowing white powder, and its aluminum content was determined to be 12.2% by weight.

[0299] Preparation of catalyst system 1 (ICS1) of the present invention

[0300] A 30% by weight MAO toluene solution (0.7 kg) was added via burette into a steel reactor under nitrogen protection at 20°C. Then, toluene (5.4 kg) was added with stirring. Metallocene MC-2 (93 g) was added using a metal cylinder and then washed with 1 kg of toluene. The mixture was stirred at 20°C for 60 minutes. Next, triphenylmethyltetra(pentafluorophenyl)borate (91 g) was added using a metal cylinder and washed with 1 kg of toluene. The mixture was stirred at room temperature for 1 hour. The resulting solution was added to a stirred filter cake of MAO-silica support prepared as described above and allowed to stand for 1 hour. The filter cake was allowed to stand for 12 hours, then dried under a nitrogen stream at 60°C for 2 hours, and then stirred and dried under vacuum (-0.5 barg) for 5 hours.

[0301] The dried catalyst was sampled as a pink, free-flowing powder containing 13.9% Al and 0.11% Zr.

[0302] The polymerization reaction for preparing the ethylene-propylene-1-butene terpolymer base resin was carried out in the Borstar pilot plant, which has two reactor units (loop-gas phase reactor (GPR)) and a prepolymerizer, using the catalyst system described above.

[0303] Table 1 shows the polymerization conditions and final properties of the ethylene-propylene-1-butene terpolymer base resins of the invention examples and comparative examples.

[0304] Table 1: Polymerization conditions and final properties of the ethylene-propylene-1-butene terpolymer base resin (IE1) of the Invention Example and the ethylene-propylene-1-butene terpolymer base resin of the Comparative Example:

[0305]

[0306]

[0307] The polymer powder was mixed in a Coperion ZSK 70 co-rotating twin-screw extruder at 220°C with 0.1 wt% of an anti-sticking agent (synthetic silica; CAS No. 7631-86-9); 0.05 wt% of an antioxidant (tris(2,4-di-tert-butylphenyl) phosphite, CAS No. 31570-04-4, available as Irgafos 168FF from BASF SE); 0.05 wt% of a sterically hindered phenol (pentaerythritol tetra(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate, CAS No. 6683-19-8, available as Irganox 1010FF from BASF SE); and 0.05 wt% (all based on the total weight of the polymer) of synthetic hydrotalcite (CAS No. 11097-59-9) as an acid scavenger.

[0308] Tafmer XM-7070 was used as the propylene-1-butene random copolymer. The butene-derived units in Tafmer XM700 were 32.5% by weight, the melt flow rate (MFR2) (ASTM D1238, 230℃, 2.16kg) was 7 g / 10 min, and the melting temperature T... m At 75℃, the Young's modulus (ASTM D638) is 290 MPa, the tensile strength at break (ASTM D638) is 34 MPa, and the elongation at break is 750%. The Shore D hardness (ASTM D2240) is 52.

[0309] Multilayer BOPP film

[0310] Invention Example: Biaxially oriented multilayer film (IE1)

[0311] The core layer (CL) uses Borealis AG's commercially available product HC101BF, which is a homopolymer with an MFR2 (230°C) of 3.2 g / 10 min.

[0312] The outer layers (OL1) and (OL2) are blends of the above-prepared inventive C2C3C4 terpolymer and 20% by weight of TafmerXM-7070.

[0313] Multilayer BOPP film is produced on a BOPP pilot production line.

[0314] To produce the BOPP film described above, three extruders were first operated to extrude a total of three layers of film. The extrusion conditions are shown in Table 2. The casting roll temperature was 35°C, and the water tank temperature was 30°C.

[0315] The thickness of the original cast film is selected / adjusted based on the final thickness of the final BOPP film and the stretch ratio in the MD / TM direction.

[0316] Table 2: Production conditions for IE1 membranes (temperature and output are the same for all examples):

[0317]

[0318]

[0319] Then bidirectional stretching was performed:

[0320] Longitudinal stretching (MDO)

[0321] MD stretch ratio = 4.7 (in one step - the first fast roller contacts the water bath side surface)

[0322] MDO roll temperature: Preheat 120℃ / Stretching 118℃ / Annealing 120℃

[0323] Lateral stretching (TDO)

[0324] TD stretch ratio = 8.8

[0325] TDO furnace temperature: Preheat 183-180-175℃ / Stretching 158-158℃ / Annealing 162-162℃

[0326] TDO guide rail widths: 195-195-195-195 / 850-1500 / 1450-1400-1395mm

[0327] deal with

[0328] Corona treatment on the top of the cast surface: 2.4kW, equivalent to 25.0Wmin / m 2

[0329] Table 3: The membrane structure after biaxial stretching of IE1 is as follows:

[0330] layer resin Final thickness A total of 1 (OL1) was extruded. blends 1μm Main (CL) HC101BF 23.0μm Co-extruded 2 (OL2) blends 1μm

[0331] Comparative biaxially stretched multilayer films CE1 and CE2

[0332] For CE1 and CE2, the outer layer uses the comparative C2C3C4 copolymer prepared above (CE1: 100 wt%, CE2: 80 wt% copolymer and 20 wt% Tafmer XM-7070 blend).

[0333] For CE3, the outer layer is made of 100% by weight of the inventive C2C3C4 terpolymer.

[0334] For CE4 and CE5, the outer layer uses TD310BF, which is a C2C3C4 terpolymer (commercially available from Borealis) prepared by Ziegler-Natta catalyst (CE1: 100% by weight, CE2: 80% by weight copolymer and 20% by weight Tafmer XM-7070 blend).

[0335] The preparation of the biaxially oriented multilayer film is carried out according to the description of the film structure of the above-described inventive example.

[0336] Table 4 shows the membrane structure of the invention example and the membrane properties of the comparative example membrane.

[0337] Table 4: Membrane performance:

[0338]

[0339] SIT@100g / 25mm is the initial sealing temperature measured when a sealing strength of 100g / 25mm is achieved.

[0340] SIT@200g / 25mm is the initial sealing temperature measured when a sealing strength of 200g / 25mm is achieved.

[0341] SIT@300g / 25mm is the initial sealing temperature measured when a sealing strength of 300g / 25mm is achieved.

[0342] It can be seen that, compared with CE1 and CE3, IE1 has a significantly lower SIT value and a processing window that is about 30°C larger. Compared with CE2, at the same elastomer concentration, the seal start temperature is reduced by more than 10°C.

Claims

1. A biaxially oriented polypropylene-based multilayer film, comprising at least: Core layer CL, first outer layer OL1, and second outer layer OL2, wherein, The first outer layer OL1 and the second outer layer OL2 are blends of the following components: i) Based on the total weight of the blend, 60.0 to 95.0% by weight of the metallocene-catalyzed ethylene-propylene-1-butene terpolymer base resin, •Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene-propylene-1-butene terpolymer base resin is processed as described in the experimental section. 13 The C2 content of ethylene, as determined by C-NMR analysis, ranged from 0.8% to 2.5% by weight. •Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene-propylene-1-butene terpolymer base resin is processed as described in the experimental section. 13 The 1-butene C4 content, as determined by C-NMR analysis, ranged from 3.0 to 10.0% by weight. •Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the ethylene-propylene-1-butene terpolymer base resin is processed as described in the experimental section. 13 The C3 content of propylene, as determined by C-NMR analysis, ranged from 89.2% to 93.0% by weight. The units derived from ethylene, propylene, and butene total 100% by weight, and • The melt flow rate (MFR2) of the ethylene-propylene-1-butene terpolymer base resin, measured at 230°C / 2.16 kg according to ISO 1133, is in the range of 3.0 to 35.0 g / 10 min. • The xylene cold soluble content (XCS) of the ethylene-propylene-1-butene terpolymer base resin, as measured at 25°C according to ISO 16152, is in the range of 1.0 to 4.5% by weight. • The melting temperature T of the ethylene-propylene-1-butene terpolymer base resin, as measured by DSC according to ISO 11357, is... m Within the range of 120 to 140°C; • The crystallization temperature T of the ethylene-propylene-1-butene terpolymer base resin, as measured by DSC according to ISO 11357, is... c Within the range of 80 to 115°C; and • The ethylene-propylene-1-butene terpolymer base resin is obtained as described in the experimental section. 13 The number of defects in region 2,1 as determined by C-NMR analysis ranged from 0.10 to 1.0 mol%. ii) Based on the total weight of the blend, 40.0 to 5.0% by weight of propylene-1-butene random copolymer, • The melting temperature T of the propylene-1-butene random copolymer was measured by differential scanning calorimetry (DSC). m The temperature is between 70 and 90 degrees Celsius. •Based on the total weight of the propylene-1-butene random copolymer, the propylene-1-butene random copolymer is produced as described in the experimental section. 13 The 1-butene content, as determined by C-NMR analysis, ranged from 20.0% to 35.0% by weight. The sum of units derived from propylene and 1-butene is 100% by weight. • The melt flow rate (MFR2) of the propylene-1-butene random copolymer, measured at 230°C / 2.16 kg according to ISO 1133, is 1.0 to 18.0 g / 10 min; and • Optionally, the propylene-1-butene random copolymer has an elongation at break of 100% to 900% as measured according to ASTM D638. The core layer CL is a polypropylene-based layer, and Among them, the biaxially oriented polypropylene-based multilayer film has the following characteristics: According to the experimental section, the seal initiation temperature (SIT) @100g / 25mm at a seal strength of 100 g / 25 mm, measured on a 25µm biaxially stretched cast film, was in the range of 50 to 90°C. According to ASTM D1003-00, the haze on a 25µm thick BOPP film is in the range of 0.5% to 1.5%.

2. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, Based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the total content of ethylene and 1-butene comonomers in the ethylene-propylene-1-butene terpolymer base resin is in the range of 7.0 to 10.8% by weight.

3. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The propylene-ethylene random copolymer comprises two polymer components, TERPO-1 and TERPO-2, wherein, based on the total weight of the ethylene-propylene-1-butene terpolymer base resin, the amount of component TERPO-1 is 50.0 to 80.0% by weight, and the amount of component TERPO-2 is 20.0 to 50.0% by weight based on the total weight of the ethylene-propylene-1-butene terpolymer base resin.

4. The biaxially oriented polypropylene-based multilayer film according to claim 3, wherein, Based on the total weight of component TERPO-1, the ethylene content of component TERPO-1 in the ethylene-propylene-1-butene terpolymer base resin is 0.2 to 2.0% by weight, and based on the total weight of component TERPO-2, the ethylene content of component TERPO-2 is 1.0 to 4.0% by weight. Based on the total weight of component TERPO-1, the 1-butene content of component TERPO-1 in the ethylene-propylene-1-butene terpolymer base resin is 2.5 to 10.0% by weight, and based on the total weight of component TERPO-2, the 1-butene content of component TERPO-2 is 5.0 to 15.0% by weight.

5. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The propylene-1-butene random copolymer also has one or more of the following properties: a) The tensile strength at break, as measured by ASTM D638, is at least 15 MPa; b) The tensile modulus, as measured by ASTM D638, is at least 200 MPa; c) The Shore D hardness, as measured by ASTM D2240, is at least 45.

6. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The core layer CL contains propylene homopolymer H-PP.

7. The biaxially oriented polypropylene-based multilayer film according to claim 6, wherein, The propylene homopolymer H-PP is characterized in that its xylene-soluble content XCS, as measured according to ISO 16152, is less than 5.0% by weight, and / or its melting temperature T, as measured by DSC, is... m The temperature must be at least 145°C.

8. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The membrane may also include one or two connecting layers TL1 and TL2, wherein the optional connecting layer is located between the core layer CL and one of the outer layers OL1 and / or OL2 or between the two outer layers.

9. The biaxially oriented polypropylene-based multilayer film according to claim 8, wherein, The connecting layers TL1 and TL2 are made of polypropylene-based polymer.

10. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The thickness of each layer after biaxial stretching is: Each outer layer: 0.3µm to 3.0µm; Core layer: 5µm to 40µm; If present, each connection layer: 1.0µm to 5µm, and The total thickness of the BOPP membrane ranges from 8µm to 80µm.

11. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The membrane is characterized in that, as described in the experimental section, the seal initiation temperature SIT@100g / 25mm at a seal strength of 100g / 25mm, measured on a 25μm biaxially stretched cast film, is in the range of 65 to 88°C.

12. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The membrane is characterized in that its haze, measured according to ASTM D1003-00 on a 25µm thick BOPP membrane, is in the range of 0.55 to 1.0%.

13. The biaxially oriented polypropylene-based multilayer film according to claim 1, wherein, The membrane has an enlarged processing window, which is determined by the melting temperature T of the ethylene-propylene-1-butene terpolymer base resin by DSC analysis. m The difference between the membrane's sealing initiation temperature (SIT) and the membrane's sealing initiation temperature (SIT) is defined, and the difference is in the range of 30 to 70°C.

14. Use of the biaxially oriented polypropylene-based multilayer film of claim 1 as a packaging material.

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