Multilayer film containing propylene copolymer

Abstract

According to one or more embodiments described herein, a multilayer film may comprise a first layer which may comprise a first polyethylene polymer, a core which may comprise a first core layer which may comprise a first polyolefin, and a second layer which may comprise a second polyethylene polymer. The core may be positioned between the first layer and the second layer. The thickness of the first core layer may be less than 10% of the total thickness of the multilayer film. The first polyolefin may comprise 4% to 12% by weight of ethylene and 75% to 96% by weight of propylene, based on the total weight of the first polyolefin. The first polyethylene polymer and the second polyethylene polymer may have the same composition or different compositions. The multilayer film may be oriented in the mechanical direction with a stretch ratio of at least 4:1.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of European Patent Application No. 23382665.0, filed on June 28, 2023, the entire content of which is incorporated herein by reference.

[0002] Embodiments of the present disclosure generally relate to polymer materials, and more particularly, to multilayer films comprising polymer materials.

Background Art

[0003] Multilayer films incorporating various materials including polypropylene, polyamide, and polyethylene terephthalate are widely used in industrial and consumer products.

Summary of the Invention

[0004] Multilayer films are often strengthened by having desirable properties such as sufficient puncture resistance, for example, during the film packaging process on a pallet or during food packaging, handling, and transportation to avoid film breakage. Combinations of layers with different materials can enable good film performance, but such multilayer films can be difficult to recycle together, if not impossible, due to different types of materials that are not recyclable compatible with each other. Due to the continuing increase in the demand for sustainable and recyclable materials, there remains a need for multilayer films that can be recycled more easily, exhibit desirable puncture resistance, and / or have other properties improved or maintained.

[0005]

[0006] ​According to some embodiments, a machine direction oriented polyethylene film having relatively good puncture resistance is described herein. By adding a relatively thin core layer disposed between two polyethylene-based layers and containing a polypropylene-based copolymer containing ethylene to a multilayer film, it has been discovered that good tear resistance can be imparted while maintaining an acceptable recyclability of the machine direction oriented polyethylene film.

[0007] According to one or more embodiments of the present disclosure, a multilayer film may include a first layer that may include a first polyethylene-based polymer. The multilayer film may also include a core that may include a first core layer that may include a first polyolefin. The thickness of the first core layer may be less than 10% of the total thickness of the multilayer film. The first polyolefin may include 4 wt% to 12 wt% ethylene based on the total weight of the first polyolefin and 75 wt% to 96 wt% propylene based on the total weight of the first polyolefin. The multilayer film may also include a second layer that may include a second polyethylene-based polymer. The core may be positioned between the first layer and the second layer. The first polyethylene-based polymer and the second polyethylene-based polymer may have the same composition or different compositions. The multilayer film may be oriented in the machine direction at a draw ratio of at least 4:1.

[0008] Additional features and advantages of the present disclosure are described in the following detailed description, and some will be readily apparent to those skilled in the art from that description or may be recognized by practicing the embodiments described herein, including the detailed description and the claims.

Mode for Carrying Out the Invention

[0009] Here, specific embodiments of the present application will be described. However, the present disclosure may be embodied in different forms and should not be construed as limited to the embodiments described in the present disclosure. Rather, these embodiments are provided so that the present disclosure will be thorough and complete and will fully convey the scope of the subject matter to those skilled in the art.

[0010] In general, this disclosure describes various embodiments of multilayer films. Such multilayer films may be used, for example, in packaging applications. A multilayer film may include a first layer comprising a first polyethylene polymer, a core comprising a first core layer comprising a first polyolefin, and a second layer comprising a second polyethylene polymer. The core may be positioned between the first and second layers.

[0011] definition The term "polymer" refers to polymer compounds prepared by polymerizing monomers, whether of the same or different types. Therefore, the general term polymer includes homopolymers, which are polymers prepared by polymerizing only one monomer, and copolymers, which are polymers prepared by polymerizing two or more different monomers.

[0012] The term "interpolymer" refers to a polymer prepared by polymerizing at least two different types of monomers. Therefore, the general term interpolymer includes copolymers and other polymers prepared by polymerizing more than two different monomers, such as terpolymers.

[0013] The terms "polyolefin," "polyolefin polymer," and "polyolefin resin" refer to simple olefins (also called alkenes, with general formula C11). n H 2n This refers to polymers prepared by polymerizing monomers (containing one or more comonomers). Therefore, the general term polyolefin includes polymers prepared by polymerizing ethylene monomers with or without one or more comonomers, such as polyethylene, and polymers prepared by polymerizing propylene monomers with or without one or more comonomers, such as polypropylene.

[0014] The terms "polyethylene" and "ethylene polymer" refer to polyolefins containing units derived from more than 50 mole percent (%) of ethylene monomer, including polyethylene homopolymers and copolymers. Common forms of polyethylene known in the art include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0015] The term "LDPE" may also be referred to as "high-pressure ethylene polymer" or "highly branched polyethylene," but is defined to mean that the polymer is partially or completely homopolymerized or copolymerized in an autoclave or tubular reactor at a pressure exceeding 14,500 psi (100 MPa) using a free radical initiator such as a peroxide (see, for example, U.S. Patent No. 4,599,392, incorporated herein by reference). LDPE resins typically have a viscosity of 0.916–0.935 g / cm³. 3 It has a density within the range.

[0016] The term "LLDPE" includes both resins produced using single-site catalysts, including but not limited to traditional Ziegler-Natta catalyst systems and chromium-based catalysts, as well as mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), geometrically constrained catalysts, phosphineimine catalysts, and polyvalent aryloxyether catalysts (typically referred to as bisphenylphenoxy), and includes linear, substantially linear, or heterogeneous polyethylene copolymers or homopolymers. LLDPEs include substantially linear ethylene polymers, as further defined in U.S. Patents 5,272,236, 5,278,272, 5,582,923, and 5,733,155, which contain fewer long-chain branches than LDPEs; homogeneously branched linear ethylene polymer compositions, such as those in U.S. Patent 3,645,992; heterogeneously branched ethylene polymers, such as those prepared according to the process disclosed in U.S. Patent 4,076,698; and / or blends thereof (such as those disclosed in U.S. Patents 3,914,342 or 5,854,045). LLDPEs can be produced via gas-phase, solution-phase, or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0017] The term "MDPE" refers to 0.926-0.935 g / cm³ 3 This refers to polyethylene having a density of 2.5. "MDPE" is typically produced using chromium or Ziegler-Natta catalysts, or single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), geometrically constrained catalysts, phosphineimine catalysts, and polyvalent aryloxyether catalysts (typically referred to as bisphenylphenoxy), and typically has a molecular weight distribution greater than 2.5 ("MWD").

[0018] The term "HDPE" refers to polyethylene having a density of about 0.935 g / cm 3 to a maximum of about 0.980 g / cm 3 prepared using single-site catalysts including, but not limited to, Ziegler-Natta catalysts, chromium catalysts, or substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), geometrically constrained catalysts, phosphine imine catalysts, and polyvalent aryloxy ether catalysts (typically referred to as bisphenol phenoxy).

[0019] The term "ULDPE" refers to polyethylene having a density of 0.855 to 0.912 g / cm 3 prepared using single-site catalysts including, but not limited to, Ziegler-Natta catalysts, chromium catalysts, or substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), geometrically constrained catalysts, phosphine imine catalysts, and polyvalent aryloxy ether catalysts (typically referred to as bisphenol phenoxy). ULDPE includes, but is not limited to, polyethylene (ethylene-based) plastomers and polyethylene (ethylene-based) elastomers.[[ID=I1]]

[0020] As used herein, the term "polypropylene" or "propylene-based polymer" refers to a polymer that, in its polymerized form, contains units derived from more than 50 mol% propylene monomer. This includes propylene homopolymers, random copolymer polypropylene, impact copolymer polypropylene, propylene / α-olefin copolymers, and propylene / ethylene / α-olefin terpolymers.

[0021] The term "melt flow ratio" refers to the ratio of the melt indices of a polymer. Thus, the general term "melt flow ratio" includes the ratio of the high load melt index (I 21 ) of a polymer to the melt index (I2) of the polymer, and may also be referred to as "MFR 21 ".

[0022] The term "composition" refers to a mixture of materials containing the composition, as well as reaction and decomposition products formed from the materials of the composition.

[0023] The terms “comprising,” “including,” and “having,” and their derivatives, are not intended to exclude the existence of any additional components, processes, or procedures, whether or not they are specifically disclosed. To avoid any doubt, all compositions claimed through the use of the term “comprising” may include any additional additives, adjuvants, or compounds, whether polymeric or otherwise, unless otherwise stated. In contrast, the term “essentially consisting of” excludes any other components, processes, or procedures from any subsequently enumerated scope, except those not essential to operability. The term “consisting of” excludes any components, steps, or procedures not specifically described or enumerated.

[0024] A "multilayer structure" or "multilayer film" means any structure having more than one layer. For example, a multilayer structure (e.g., a film) may have two, three, four, five, or more layers. A multilayer structure may be described as having layers specified by letters. For example, a three-layer structure designated as A / B / C may have a core layer B, and two outer layers A and C. Similarly, a structure having two core layers B and C, and two outer layers A and D would be designated A / B / C / D.

[0025] Multilayer film Here, we refer to embodiments of multilayer films described herein. Embodiments of multilayer films described herein may include at least three layers.

[0026] The multilayer films of this disclosure may comprise at least three layers, and more than eleven layers. The number of layers in a multilayer film may depend on a number of factors, including, for example, the composition of each layer of the multilayer film, the desired properties of the multilayer film, the desired end use of the multilayer film, and the manufacturing process of the multilayer film. In one or more embodiments, the multilayer film may have 3 to 11 layers, for example, 3 to 4 layers, 4 to 5 layers, 5 to 6 layers, 6 to 7 layers, 7 to 8 layers, 8 to 9 layers, 9 to 10 layers, 10 to 11 layers, or any combination of one or more of these endpoints.

[0027] In one or more embodiments, the multilayer films of the Disclosure may be oriented in the machine direction. The multilayer films of the Disclosure may be oriented in the machine direction with a stretch ratio of at least 4:1, at least 5:1, or even more than at least 6:1.

[0028] A multilayer film may have a three-layer structure designated A / B / C, where the first layer may be designated A, the first core layer may be designated B, and the second layer may be designated C. In some embodiments, the first layer, and / or the second layer may be designated “skin layer” or “outer layer”. In embodiments, the first core layer may be positioned between the first and second layers. In further embodiments, the first and second layers may be the outermost layers of the multilayer film. As used herein, the outermost layer of a multilayer film may mean that there may be no other layer deposited on top of the outermost layer so that the outermost layer is in direct contact with the surrounding air.

[0029] In one or more embodiments, the first core layer and the first layer, the first core layer and the second layer, or both, may be in direct contact with each other. As used herein, “direct contact” means that there may be no other layers positioned between the two layers that are in direct contact with each other. In other embodiments, the multilayer film may include one or more additional layers, for example, one or more additional core layers, which may be positioned between the first core layer and the first layer, between the first core layer and the second layer, or both.

[0030] As will be described in more detail later in this disclosure, a multilayer film may comprise a first layer comprising a first polyethylene polymer, a first core layer comprising a first polyolefin, and a second layer comprising a second polyethylene polymer. The first polyethylene polymer and the second polyethylene polymer may have the same or different compositions. It should be understood that each of the aforementioned layers may further comprise one or more additives known to those skilled in the art, such as plasticizers, stabilizers including viscosity stabilizers, hydrolysis stabilizers, primary and secondary antioxidants, ultraviolet absorbers, antistatic agents, dyes, pigments, or other colorants, inorganic fillers, flame retardants, lubricants, reinforcing agents such as glass fibers and flakes, synthetic (e.g., aramid) fibers or pulp, forming agents or foaming agents, processing aids, slip additives, anti-tack agents such as silica or talc, release agents, tackifying resins, or two or more combinations thereof. Inorganic fillers such as calcium carbonate and analogues may also be incorporated into one or more of the first layer, second layer, third layer, and combinations thereof. In some embodiments, each of the first layer, second layer, third layer, and combinations may contain up to 5 weight percent of such additional additives based on the total weight of each layer. All individual values ​​and subranges from 0% by weight to 5% by weight are included and disclosed herein, for example, the total amount of additives in the first, second, or third layer may be 0.5% to 5% by weight, 0.5% to 4% by weight, 0.5% to 3% by weight, 0.5% to 2% by weight, 0.5% to 1% by weight, 1% to 5% by weight, 1% to 4% by weight, 1% to 3% by weight, 1% to 2% by weight, 2% to 5% by weight, 2% to 4% by weight, 2% to 3% by weight, 3% to 5% by weight, 3% to 4% by weight, or 4% to 5% by weight, based on the total weight of each layer. The incorporation of additives may be carried out by any known process, such as by dry blending, by extruding a mixture of various components, or by conventional masterbatch techniques.

[0031] In one or more embodiments, the multilayer film of the present disclosure comprises 85% by weight or more of a polyethylene polymer based on the total weight of the multilayer film, for example, 86% by weight or more, 87% by weight or more, 88% by weight or more, 89% by weight or more, or even 90% by weight or more of a polyethylene polymer based on the total weight of the multilayer film.

[0032] The multilayer films of this disclosure may have a variety of thicknesses. The thickness of the multilayer film may depend on a number of factors, including, for example, the number of layers of the multilayer film, the composition of the layers of the multilayer film, the desired properties of the multilayer film, the desired end use of the film, and the manufacturing process of the multilayer film. In one or more embodiments, the multilayer film is 10 microns to 250 microns, for example, 10 microns to 20 microns, 20 microns to 30 microns, 30 microns to 40 microns, 40 microns to 50 microns, 50 microns to 60 microns, 60 microns to 70 microns, 70 microns to 80 microns, 80 microns to 90 microns, 90 microns to 100 microns, 100 microns to 110 microns, 110 microns to 120 microns, 120 microns to 130 microns, 130 microns The thickness may be between 140 microns, 140-150 microns, 150-160 microns, 160-170 microns, 170-180 microns, 180-190 microns, 190-200 microns, 200-210 microns, 210-220 microns, 220-230 microns, 230-240 microns, 240-250 microns, or any combination of one or more of these ranges.

[0033] In one or more embodiments, the multilayer film may have a puncture force of 10 Newtons or more, for example, 15 Newtons or more, 20 Newtons or more, or even 25 Newtons or more, as measured according to the test methods described later in this disclosure. In one or more embodiments, the multilayer film may have a puncture force of 10 to 50 Newtons, for example, 10 to 15 Newtons, 15 to 20 Newtons, 20 to 25 Newtons, 25 to 30 Newtons, 30 to 35 Newtons, 35 to 40 Newtons, 40 to 45 Newtons, 45 to 50 Newtons, or any combination of one or more of these ranges.

[0034] In one or more embodiments, the multilayer film may have a mechanical tear resistance of 0.1 Newtons or more, for example, 0.2 Newtons or more, 0.3 Newtons or more, 0.4 Newtons or more, 0.5 Newtons or more, 0.6 Newtons or more, 0.7 Newtons or more, 0.8 Newtons or more, 0.9 Newtons or more, or even 1.0 Newton or more. In one or more embodiments, the multilayer film may have a transverse tear resistance of 0.5 Newtons or more, for example, 1 Newton or more, 1.5 Newtons or more, 2 Newtons or more, 2.5 Newtons or more, 3 Newtons or more, or 3.5 Newtons or more.

[0035] core As described above, the multilayer films of this disclosure may include a core layer. In a multilayer film with a three-layer structure, referred to as A / B / C, the core layer may be referred to as B. In one or more embodiments, the core may include a first core layer. In further embodiments, the core layer may include additional core layers, such as a second core layer and a third core layer.

[0036] In one or more embodiments, the core includes a first core layer. The first core layer may include a first polyolefin. The first polyolefin may contain 4% to 12% by weight of ethylene, based on the total weight of the first polyolefin, and 75% to 96% by weight of propylene, based on the total weight of the first polyolefin. In one or more embodiments, the first polyolefin may contain ethylene in amounts of 4% to 5% by weight, 5% to 6% by weight, 6% to 7% by weight, 7% to 8% by weight, 8% to 9% by weight, 9% to 10% by weight, 10% to 11% by weight, 11% to 12% by weight, or any combination of one or more of these ranges. In one or more embodiments, the first polyolefin may contain propylene in amounts of 75% to 76% by weight, 76% to 78% by weight, 78% to 80% by weight, 80% to 82% by weight, 82% to 84% by weight, 84% to 86% by weight, 86% to 88% by weight, 88% to 90% by weight, 90% to 92% by weight, 92% to 94% by weight, 94% to 96% by weight, or any combination of one or more of these ranges. In some embodiments, the first polyolefin may contain 8% to 12% by weight of ethylene and 75% to 85% by weight of propylene, based on the total weight of the first polyolefin.

[0037] While not bound by theory, it is believed that when pure polyethylene and pure polypropylene are co-extruded into a multilayer film and come into adhesive contact with each other, they may delaminate when force is applied due to incompatibility in the crystallization conditions of polyethylene and polypropylene. The different crystallization rates and temperatures of polyethylene and polypropylene can prevent polymer adhesion during co-extrusion by making polypropylene and polyethylene immiscible during melting or cooling. While adding polyethylene to a polypropylene polymer to form a propylene-ethylene copolymer cannot eliminate these incompatibility issues, it can reduce them, thereby lowering the risk of delamination and reducing the degree of polymer immisability. However, the incompatibility between propylene-ethylene copolymers and polyethylene-based polymers can be beneficially improved when the properties of oriented multilayer films containing polyethylene-based polymers and propylene-ethylene copolymers, such as the multilayer films described herein, are compared to multilayer films without such polymers. Interlayer mismatches can cause micro-delamination when force is applied, and this micro-delamination can absorb energy, which is thought to improve the physical resistance of multilayer films compared to multilayer films that do not contain such layers.

[0038] In one or more embodiments, the first polyolefin is 0.850 g / cm³ 3 ~0.885g / cm 3 For example, 0.850 g / cm³ 3 ~0.855 g / cm³ 3 , 0.855 g / cm³ 3 ~0.860g / cm 3 , 0.860 g / cm³ 3 ~0.865 g / cm³ 3 , 0.865 g / cm³ 3 ~0.870g / cm 3 , 0.870 g / cm³ 3 ~0.875g / cm 3 , 0.875 g / cm³ 3~0.880g / cm 3 , 0.880 g / cm³ 3 ~0.885g / cm 3 It may have densities of one or any combination of these ranges.

[0039] In one or more embodiments, the first polyolefin is used in doses of 1.5g / 10min to 25g / 10min, for example, 2g / 10min to 3g / 10min, 3g / 10min to 4g / 10min, 4g / 10min to 5g / 10min, 5g / 10min to 6g / 10min, 6g / 10min to 7g / 10min, 7g / 10min to 8g / 10min, 8g / 10min to 9g / 10min, 9g / 10min to 10g / 10min, 10g / 10min to 11g / 10min, 11g / 10min to 12g / 10min, 12g / 10min to 13g / 10min, 13g / 10min to 14g / 10min The melt index (I2) may be one of the following ranges: 14g / 10 min to 15g / 10 min, 15g / 10 min to 16g / 10 min, 16g / 10 min to 17g / 10 min, 17g / 10 min to 18g / 10 min, 18g / 10 min to 19g / 10 min, 19g / 10 min to 20g / 10 min, 20g / 10 min to 21g / 10 min, 21g / 10 min to 22g / 10 min, 22g / 10 min to 23g / 10 min, 23g / 10 min to 24g / 10 min, 24g / 10 min to 25g / 10 min, or any combination of one or more of these ranges.

[0040] Examples of commercially available propylene-ethylene copolymers that may be used in the embodiments of the subject matter described herein include the VERSIFY® polymer, commercially available from Dow, Inc., and the VISTAMAXX® polymer, from ExxonMobil Chemical Company.

[0041] In some embodiments, the first polyolefin comprises a first core layer in an amount of 80% to 100% by weight, based on the total weight of the first core layer. All individual values ​​and partial ranges of 80% to 100% by weight are disclosed herein. In some embodiments, the first polyolefin comprises a first core layer in an amount of 85% to 100% by weight, 90% to 100% by weight, 95% to 100% by weight, or 99% to 100% by weight, based on the total weight of the first core layer.

[0042] In one or more embodiments, the thickness of the first core layer may be less than 10% of the total thickness of the multilayer film. In one or more embodiments, the thickness of the first core layer may be less than 9%, less than 8%, less than 7%, less than 6%, or even less than 5% of the total thickness of the multilayer film.

[0043] In one or more embodiments, the core may include a second core layer and a third core layer. In one or more embodiments, the first core layer may be positioned between the second core layer and the third core layer. In other embodiments, the second core layer may be positioned between the first core layer and the third core layer. In one or more embodiments, the second core layer may include a third polyethylene polymer. In one or more embodiments, the third core layer may include a fourth polyethylene polymer. In some embodiments, the second core layer may include a fifth polyethylene polymer. In some embodiments, the third polyethylene polymer and the fourth polyethylene polymer may have the same composition. In other embodiments, the third polyethylene polymer and the fourth polyethylene polymer may have different compositions.

[0044] As described above, in one or more embodiments, the second core layer may be positioned between the first core layer and the third core layer. In such embodiments, both the first core layer and the third core layer may contain the first polyolefin. The second core layer may contain a fifth polyethylene polymer. In embodiments in which the first and third core layers contain the first polyolefin, the sum of the thickness of the first core layer and the thickness of the third core layer may be less than 20% of the total thickness of the multilayer film, for example, less than 18%, less than 16%, less than 14%, less than 12%, or even less than 10% of the total thickness of the multilayer film. In one or more embodiments, the sum of the thickness of the first core layer and the thickness of the third core layer may be 5% to 20% of the total thickness of the multilayer film, for example, 5% to 6%, 6% to 7%, 7% to 8%, 8% to 9%, 9% to 10%, 10% to 11%, 11% to 12%, 12% to 13%, 13% to 14%, 14% to 15%, 15% to 16%, 16% to 17%, 17% to 18%, 18% to 19%, 19% to 20%, or any combination of one or more of these ranges.

[0045] In one or more embodiments, the third polyethylene polymer, the fourth polyethylene polymer, and the fifth polyethylene polymer may comprise one or more of LLDPE, HDPE, MDPE, and LDPE. In some embodiments, the third polyethylene polymer, the fourth polyethylene polymer, and the fifth polyethylene polymer may be a blend of polyethylene polymers.

[0046] In one or more embodiments, the third polyethylene polymer, the fourth polyethylene polymer, and the fifth polyethylene polymer are 0.952 g / cm³ 3 The following densities may be present. For example, the third polyethylene polymer and the fourth polyethylene polymer have a density of 0.920 g / cm³. 3 ~0.952 g / cm³ 3 For example, 0.920 g / cm³ 3 ~0.925g / cm 3 , 0.925 g / cm³ 3 ~0.930g / cm 3 , 0.930 g / cm³3 ~0.935g / cm 3 , 0.935 g / cm³ 3 ~0.940g / cm 3 , 0.940 g / cm³ 3 ~0.945g / cm 3 , 0.945 g / cm³ 3 ~0.950g / cm 3 , 0.950 g / cm³ 3 ~0.952 g / cm³ 3 , or any combination of one or more of these endpoints, may have a density.

[0047] In one or more embodiments, the third polyethylene polymer, the fourth polyethylene polymer, and the fifth polyethylene polymer may have a melt index (I2) of 7.5 g / 10 min or less. The fourth polyethylene polymer and the fifth polyethylene polymer may have a melt index of 0.3 g / 10 min to 7.5 g / 10 min, for example, 0.3 g / 10 min to 0.5 g / 10 min, 0.5 g / 10 min to 1.0 g / 10 min, 1.0 g / 10 min to 1.5 g / 10 min, 1.5 g / 10 min to 2.0 g / 10 min, 2.0 g / 10 min to 2.5 g / 10 min, 2.5 g / 10 min to 3.0 g / 10 min, 3.0 g / 10 min to 3.5 g / 10 min, 3 The melt index may be in the following ranges: 0.5g / 10 min to 4.0g / 10 min, 4.0g / 10 min to 4.5g / 10 min, 4.5g / 10 min to 5.0g / 10 min, 5.0g / 10 min to 5.5g / 10 min, 5.5g / 10 min to 6.0g / 10 min, 6.0g / 10 min to 6.5g / 10 min, 6.5g / 10 min to 7.0g / 10 min, 7.0g / 10 min to 7.5g / 10 min, or any combination of one or more of these ranges.

[0048] Examples of commercially available polyethylene polymers that can be used as the third, fourth, and fifth polyethylene polymers include, for example, those marketed by Dow, Inc. under the names ELITE® and INNATE, including ELITE® 5538G, INNATE® ST70, and INNATE® TH60, and those marketed by ExxonMobil Chemical Company under the names EXCEED® and ENABLE®, including, for example, EXCEED® 1018 MA, ENABLE® 3505 MC, EXCEED® XP 8318 MJ, and EXCEED® S 9272 ML.

[0049] As described above, in one or more embodiments, the second core layer may be positioned between the first core layer and the third core layer. In such embodiments, both the first core layer and the third core layer may contain the first polyolefin, and the second core layer may contain the fifth polyethylene polymer.

[0050] The first and second layers of the multilayer film The first and second layers of the multilayer film are not particularly limited. In one or more embodiments, the first and second layers may have the same polymer composition or different polymer compositions. In one or more embodiments, the first layer may contain a first polyethylene-based polymer, and the second layer may contain a second polyethylene-based polymer.

[0051] In one or more embodiments, the first polyethylene polymer and the second polyethylene polymer may include one or more of LLDPE, HDPE, MDPE, and LDPE.

[0052] In one or more embodiments, one or both of the first polyethylene polymer and the second polyethylene polymer are 0.925 g / cm³. 3 ~0.970g / cm 3 For example, 0.925 g / cm³ 3 ~0.930g / cm3 , 0.930 g / cm³ 3 ~0.935g / cm 3 , 0.935 g / cm³ 3 ~0.940g / cm 3 , 0.940 g / cm³ 3 ~0.945g / cm 3 , 0.945 g / cm³ 3 ~0.950g / cm 3 , 0.950 g / cm³ 3 ~0.955 g / cm³ 3 , 0.955 g / cm³ 3 ~0.960g / cm 3 , 0.960 g / cm³ 3 ~0.965g / cm 3 , 0.965 g / cm³ 3 ~0.970g / cm 3 , 0.970 g / cm³ 3 ~0.975g / cm 3 It may have densities of one or any combination of these ranges.

[0053] In one or more embodiments, one or both of the first polyethylene polymer and the second polyethylene polymer are present in concentrations of 0.3 g / 10 min to 7.0 g / 10 min, for example, 0.3 g / 10 min to 0.5 g / 10 min, 0.5 g / 10 min to 1.0 g / 10 min, 1.0 g / 10 min to 1.5 g / 10 min, 1.5 g / 10 min to 2.0 g / 10 min, 2.0 g / 10 min to 2.5 g / 10 min, 2.5 g / 10 min to 3.0 g / 10 min, 3 The melt index (I2) may be in the range of 0.0g / 10 min to 3.5g / 10 min, 3.5g / 10 min to 4.0g / 10 min, 4.0g / 10 min to 4.5g / 10 min, 4.5g / 10 min to 5.0g / 10 min, 5.0g / 10 min to 5.5g / 10 min, 5.5g / 10 min to 6.0g / 10 min, 6.0g / 10 min to 6.5g / 10 min, 6.5g / 10 min to 7.0g / 10 min, or any combination of one or more of these ranges.

[0054] Examples of commercially available polyethylene polymers that can be used as the first or third polyethylene polymer include, for example, those marketed under the name ELITE® by Dow, Inc., including ELITE® 5960G1, and, for example, those marketed by ExxonMobil Chemical Company, including ExxonMobil® High Density Polyethylene HTA 108.

[0055] Test method density Density was measured according to ASTM D792, in grams / cm³. 3 (g / cm 3 It is expressed as g / cc.

[0056] Melt Index (I2) The melt index (I2) was measured at 190°C and 2.16 kg according to ASTM D-1238. The value is reported as g / 10 min, corresponding to the number of grams dissolved per 10 minutes.

[0057] Tensile strength Tensile strength is measured according to ASTM D-882 and expressed in megapascals (MPa).

[0058] Tensile modulus The tensile modulus is measured according to ASTM D-882 and expressed in megapascals (MPa).

[0059] Elmendorf tear resistance Elmendorf tear resistance is measured according to ASTM D-1922 and expressed in Newtons (N).

[0060] puncture resistant Puncture resistance was measured using a ZWICK Model Z010 with TestXpertII software. The specimen size was 6''×6'', and at least 5 measurements were taken to determine the average puncture value. A 1000 Newton load cell was used with a round specimen holder. The specimen was a circular specimen with a diameter of 4 inches. The puncture resistance procedure followed the ASTM D5748-95 standard, with modifications to the probe described herein. The puncture probe was a 1 / 2 inch diameter ball-shaped polished stainless steel probe. There was no gauge length, and the probe was as close to the specimen as possible, but not in contact. The probe was set by raising it until it touched the specimen. Then the probe was gradually lowered until it no longer touched the specimen. The crosshead was then set to zero. Considering the maximum travel distance, this distance would be approximately 0.10 inches. The crosshead speed used was 250 mm / min. The thickness was measured at the center of the specimen. The software determines the puncture using the film thickness, crosshead travel distance, and peak load. The puncture probe is cleaned after each specimen. Puncture energy is the area under the load / elongation curve (in joules).

[0061] Turbidity Turbidity is measured according to ASTM D1003 and expressed as a percentage (%).

[0062] transparency Transparency is measured according to ASTM D1003 and expressed as a percentage (%). [Examples]

[0063] The following embodiments illustrate the features of the present disclosure, but are not intended to limit the scope of the present disclosure.

[0064] The raw materials shown in Table 1 were used to prepare the films of the present invention and comparative examples discussed below. Unless otherwise noted, each of the resins is commercially available from The Dow Chemical Company.

[0065] [Table 1]

[0066] Multilayer films were formed using the materials listed in the table above. The multilayer films were produced using the Dr. Collin 5-layer co-extrusion inflation film line. The extruder size was 25 mm for extruders A, B, and D, and 30 mm for extruder C. The extruder order was A:B:C:B:D. The die gap was 1.8 mm. The maximum line speed was 30 m / min. A gravimetric feeder was used. The maximum yield for LLDPE was 25 kg / hour. The 5-layer co-extruded films were cast with thicknesses of 120 microns, 100 microns, and 20 microns. Table 2 shows the composition of the comparative films, and Tables 3, 4, and 5 show the compositions of films 1, 2, and 3 of the present invention, respectively.

[0067] Films with thicknesses of 120 microns and 100 microns were subsequently subjected to a mechanical orientation process to reach a thickness of 20 microns. Tables 6 and 7 show the extruder temperature profiles and details of the mechanical orientation process for the comparative films in Table 2, respectively. For the comparative films, the 120-micron thick film had an extrusion rate of 3.0 m / min, the 100-micron thick film had an extrusion rate of 3.4 m / min, and the 20-micron thick film had an extrusion rate of 15.3 m / min. Tables 8 and 9 show the extruder temperature profiles and details of the mechanical orientation process for Film 1 of the present invention, respectively. For Film 1 of the present invention, the 120-micron thick film had an extrusion rate of 2.8 m / min, the 100-micron thick film had an extrusion rate of 3.5 m / min, and the 20-micron thick film had an extrusion rate of 17.4 m / min. Tables 10 and 11 show the extruder temperature profile and details of the mechanical orientation process for film 2 of the present invention, respectively. For film 2 of the present invention, the 120-micron thick film had an extrusion rate of 3.1 m / min, the 100-micron thick film had an extrusion rate of 3.8 m / min, and the 20-micron thick film had an extrusion rate of 19 m / min. Tables 12 and 93 show the extruder temperature profile and details of the mechanical orientation process for film 3 of the present invention, respectively. For film 3 of the present invention, the 120-micron thick film had an extrusion rate of 3.1 m / min, the 100-micron thick film had an extrusion rate of 3.8 m / min, and the 20-micron thick film had an extrusion rate of 19 m / min.

[0068] [Table 2]

[0069] [Table 3]

[0070] [Table 4]

[0071] [Table 5]

[0072] [Table 6]

[0073] [Table 7]

[0074] [Table 8]

[0075] [Table 9]

[0076] [Table 10]

[0077] [Table 11]

[0078] [Table 12]

[0079] Referring to Tables 13, 14, and 15, various physical properties of the inflation film (20 microns), 5X oriented film (100 microns), and 6X oriented film (120 microns) were tested and recorded in Tables 13, 14, and 15, respectively.

[0080] [Table 13]

[0081] [Table 14]

[0082] [Table 15]

[0083] As shown in Tables 13, 14, and 15, increasing the stretch of both the comparative film and the film of the present invention had the expected effects on the tensile strength in both directions and the 2% secant modulus in both directions. Increasing the orientation was expected to increase the stiffness of the film and therefore increase the 2% secant modulus. Furthermore, increasing the molecular alignment of the film by orientation was expected to increase the tensile strength in the medium-density (MD) and decrease the tensile strength in the temporal (TD) direction.

[0084] As the orientation increases, the rigidity of the oriented film increases, and as a result, it was expected that the force required to puncture the film would increase. At the same time, due to the decrease in the film's ability to stretch further when force is applied, the corresponding puncture energy decreases (with increasing orientation). This phenomenon could be clearly observed in the comparative film, where an increase in puncture force for penetrating the film and, simultaneously, a decrease in puncture energy were experienced. However, when a thin functional core, or multiple thin functional cores, were introduced into the co-extruded film, as in films 1, 2, and 3 of the present invention, a more significant increase in puncture force was observed with increasing film orientation compared to the control film. Furthermore, film 1 of the present invention showed an increase in puncture energy when further oriented to 5 to 6 times. Films 2 and 3 of the present invention did not show an increase in puncture energy with further orientation, but they had significantly higher puncture energy compared to similarly oriented comparative films.

[0085] Furthermore, Tables 13, 14, and 15 show that the presence of one or more thin functional layers resulted in a significant improvement in the Elmendorf tear resistance of films 1, 2, and 3 of the present invention in both the MD and TD directions, compared to the comparative film at 6x orientation. As can be observed in the comparative film, the MD tear resistance was expected to decrease significantly with increasing orientation. However, the results for the films of the present invention demonstrate that the presence of one or more thin functional layers can improve the Elmendorf tear resistance of oriented films.

[0086] Referring to Table 16, the turbidity and transparency of the film were tested, and the results were recorded in Table 16 below.

[0087] [Table 16]

[0088] As shown in Table 16, increasing the orientation resulted in the film of the present invention exhibiting similar turbidity and transparency compared to the comparative film. This indicates that the presence of one or more thin functional layers does not adversely affect the optical properties of the film.

[0089] According to a first aspect of this disclosure, a multilayer film may include a first layer which may contain a first polyethylene-based polymer. The multilayer film may also include a core which may include a first core layer which may contain a first polyolefin. The thickness of the first core layer may be less than 10% of the total thickness of the multilayer film. The first polyolefin may contain 4% to 12% by weight of ethylene and 75% to 96% by weight of propylene, based on the total weight of the first polyolefin. The multilayer film may also include a second layer which may contain a second polyethylene-based polymer. The core may be positioned between the first layer and the second layer. The first polyethylene-based polymer and the second polyethylene-based polymer may have the same composition or different compositions. The multilayer film may be oriented in the mechanical direction with a stretch ratio of at least 4:1.

[0090] A second aspect of this disclosure may include the first aspect, wherein the first polyolefin comprises the first core layer in an amount of 80% to 100% by weight, based on the total weight of the first core layer.

[0091] A third aspect of the present disclosure may include any of the above-described aspects or combinations thereof, wherein the first polyolefin comprises 8% to 12% by weight of ethylene and 75% to 85% by weight of propylene, based on the total weight of the first polyolefin.

[0092] A fourth aspect of the present disclosure may include any of the aforementioned aspects or combinations thereof, wherein the elongation ratio is at least 5:1.

[0093] A fifth aspect of this disclosure may include any of the aforementioned aspects or combinations thereof, wherein the multilayer film comprises 3 to 11 layers.

[0094] A sixth aspect of the present disclosure may include any of the above-described aspects or combinations thereof, wherein the core further comprises a second core layer comprising a third polyethylene polymer and a third core layer comprising a fourth polyethylene polymer, and the first core layer is positioned between the second core layer and the third core layer.

[0095] A seventh aspect of this disclosure may include a sixth aspect, wherein the third polyethylene polymer and the fourth polyethylene polymer each contain 0.952 g / cm³ of each. 3 It has the following densities and a melt index (I2) of 7.5 g / 10 min or less.

[0096] An eighth aspect of the present disclosure may include any of the first to fourth aspects, wherein the core layer further comprises a second core layer comprising a fifth polyethylene polymer and a third core layer comprising a first polyolefin, the second core layer being positioned between the first core layer and the third core layer.

[0097] The ninth aspect of this disclosure may include the eighth aspect, and the fifth polyethylene polymer is 0.952 g / cm³. 3 It has the following densities and a melt index (I2) of 7.5 g / 10 min or less.

[0098] A tenth aspect of this disclosure may include a seventh or eighth aspect, wherein the sum of the thickness of the first core layer and the thickness of the third core layer is less than 20% of the total thickness of the multilayer film.

[0099] An eleventh aspect of this disclosure may include any of the aforementioned aspects or combinations thereof, wherein the first polyethylene polymer and the second polyethylene polymer each contain 0.925 g / cm³ of each. 3 ~0.970g / cm 3 It has a density and a melt index (I2) of 0.3g / 10min to 7.0g / 10min.

[0100] A twelfth aspect of the present disclosure may include any of the aforementioned aspects or combinations thereof, wherein the multilayer film contains 85% by weight or more of a polyethylene polymer based on the total weight of the multilayer film.

[0101] A thirteenth aspect of this disclosure may include any of the aforementioned aspects or combinations thereof, wherein the first polyolefin is 0.850 g / cm³. 3 ~0.885g / cm 3 It has a density and a melt flow rate (I2) of 1.5 g / 10 min to 25 g / 10 min.

[0102] A fourteenth aspect of the present disclosure may include any of the aforementioned aspects or combinations thereof, wherein the multilayer film has a mechanical direction tear resistance of 0.5 Newtons or more.

[0103] A fifteenth aspect of the present disclosure may include any of the above-described aspects or combinations thereof, wherein the multilayer film has a puncture force of 25 Newtons or more.

[0104] It will be apparent to those skilled in the art that various modifications and alterations can be made to the technology disclosed herein without departing from the spirit and scope of the technology. Since combinations, partial combinations, and variations of the disclosed embodiments incorporating the spirit and substance of the technology disclosed are conceivable to those skilled in the art, the technology should be construed as encompassing all of the appended claims and their equivalents. Furthermore, while certain aspects of the disclosure may be specified herein as preferred or particularly advantageous, the disclosure is intended to be in no way limited to these aspects.

[0105] It should be noted that the various details described herein should not be construed to imply that these details relate to elements that are essential components of the various embodiments described herein, even if certain elements are illustrated in each of the drawings accompanying this specification. Unless specifically identified in this way, features disclosed and described herein should not be construed as “essential.” The embodiments intended for the art include those that include some or all of the features of the appended claims.

[0106] For the purposes of describing and defining this disclosure, the term “approximately” is used in this disclosure to express the degree of inherent uncertainty that may arise from any quantitative comparison, value, measurement, or other representation. The term “approximately” is also used in this disclosure to indicate the degree to which a quantitative representation may vary from the standard of description without altering the fundamental function of the subject matter in question.

[0107] Note that one or more of the following claims and detailed descriptions utilize the terms “where” or “wherein” as a transitional clause. Note that for the purpose of defining the art, this term is introduced into the claims as an unrestricted transitional clause used to introduce an enumeration of a set of structural features and should be interpreted similarly to the more commonly used unrestricted preamble term “comprising.”

[0108] Any two quantitative values ​​assigned to a characteristic may constitute a range for that characteristic, and it should be understood that all combinations of ranges formed from all described quantitative values ​​of a given characteristic are contemplated in this disclosure. If multiple ranges are given for a quantitative value, these ranges may be combined to form a broader range, which is contemplated in the embodiments described herein.

Claims

1. It is a multilayer film, A first layer containing a first polyethylene polymer, A core comprising a first core layer containing a first polyolefin, wherein the thickness of the first core layer is less than 10% of the total thickness of the multilayer film, and the first polyolefin is Based on the total weight of the first polyolefin, 4% to 12% by weight of ethylene and Based on the total weight of the first polyolefin, a core comprising 75% to 96% by weight of propylene, A second layer comprising a second polyethylene polymer, wherein the core is positioned between the first layer and the second layer, and the first polyethylene polymer and the second polyethylene polymer have the same or different compositions. A multilayer film wherein the multilayer film is oriented in the machine direction with a stretch ratio of at least 4:

1.

2. The multilayer film according to claim 1, wherein the first polyolefin comprises 80 to 100% by weight of the first core layer, based on the total weight of the first core layer.

3. The first polyolefin described above is Based on the total weight of the first polyolefin, 8% to 12% by weight of ethylene and A multilayer film according to claim 1 or 2, comprising 75% to 85% by weight of propylene, based on the total weight of the first polyolefin.

4. The multilayer film according to any one of claims 1 to 3, wherein the stretch ratio is at least 5:

1.

5. The multilayer film according to any one of claims 1 to 4, wherein the multilayer film has a total of 3 to 11 layers.

6. The aforementioned core, A second core layer containing a third polyethylene polymer, A multilayer film according to any one of claims 1 to 5, further comprising a third core layer containing a fourth polyethylene polymer, wherein the first core layer is positioned between the second core layer and the third core layer.

7. The third polyethylene polymer and the fourth polyethylene polymer are each present in a concentration of 0.952 g / cm³. ３ The following densities and melt index (I) of 7.5 g / 10 min or less ２ A multilayer film according to claim 6, having the following characteristics:

8. The aforementioned core layer, A second core layer containing a fifth polyethylene polymer, A multilayer film according to any one of claims 1 to 4, further comprising a third core layer comprising the first polyolefin, wherein the second core layer is positioned between the first core layer and the third core layer.

9. The fifth polyethylene polymer is 0.952 g / cm³ ３ The following densities and melt index (I) of 7.5 g / 10 min or less ２ A multilayer film according to claim 8, having the following characteristics:

10. The multilayer film according to claim 7 or 8, wherein the sum of the thickness of the first core layer and the thickness of the third core layer is less than 20% of the total thickness of the multilayer film.

11. The first polyethylene polymer and the second polyethylene polymer are each present in a concentration of 0.925 g / cm³. ３ ~0.970g / cm ３ The density, and the melt index (I) of 0.3 g / 10 min to 7.0 g / 10 min. ２ A multilayer film according to any one of claims 1 to 10, having the following characteristics:

12. The multilayer film according to any one of claims 1 to 11, wherein the multilayer film contains 85% by weight or more of a polyethylene polymer based on the total weight of the multilayer film.

13. The first polyolefin has a density of 0.850 g / cm ｍ３ to 0.885 g / cm ３ and a melt flow rate (I ２ ) of 1.5 g / 10 min to 25 g / 10 min. The multilayer film according to any one of claims 1 to 12.

14. The multilayer film according to any one of claims 1 to 13, wherein the multilayer film has a mechanical tear resistance of 0.5 Newtons or more.

15. The multilayer film according to any one of claims 1 to 14, wherein the multilayer film has a puncture force of 25 Newtons or more.

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