Oriented film comprising polyethylene

Abstract

An oriented film and a method for making an oriented film are provided. The method for making an oriented film according to an embodiment disclosed herein comprises: providing a low density polyethylene and an ethylene-based copolymer; extruding the low density polyethylene in the first outer layer and the ethylene copolymer in the inner layer to form a multilayer film; and orienting the film to obtain a specific thickness of the first outer layer. The resulting oriented films may provide desirable characteristics, such as heat seal initiation temperature and recoverability, etc.

Description

Technical Field

[0001] The implementation scheme disclosed herein generally relates to oriented films and their manufacturing methods. Background Technology

[0002] Oriented films are emerging as a leading technological solution for packaging. Orientation of the film along its longitudinal direction (MDO), transverse direction, or both (i.e., biaxially oriented film) improves properties such as optical characteristics, tensile strength, stiffness, low elongation, and heat resistance. Oriented films are commonly used as printing substrates to form laminates, but the demand for single-film solutions continues to rise, as does the need for lower-gauge, sustainable, and recyclable films made from a single material. A particular challenge with oriented and single-film packaging solutions is the difficulty in achieving a low heat seal onset temperature (HSIT) while maintaining other desired properties. To orient the film, the extruded film is typically heated at high temperatures, for example, by rapidly passing it through chromium-heated rollers to achieve optimal heat transfer, resulting in the polymer in the film reaching a semi-molten state suitable for stretching. When a low-HSIT sealant resin is extruded as the outer layer of an oriented film, a lower temperature and slower manufacturing process is required because the film tends to stick to the rollers. Therefore, there remains a great demand for oriented films that can maintain other properties while providing the desired heat-sealing initiation temperature, enable single-material solutions, and can be rapidly processed at high temperatures for stretching. Summary of the Invention

[0003] The embodiments disclosed herein meet the aforementioned needs by providing an oriented membrane that enables low-heat sealing initiation, is recyclable, and can be used as a single solution.

[0004] This article discloses a method for fabricating an oriented film. The method includes: providing a density of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 Low-density polyethylene and highest peak melt temperature (T m The low-density polyethylene is a copolymer based on ethylene with a temperature of 105°C or lower; a first outer layer is extruded to have a thickness of “X” and includes the low-density polyethylene; an inner layer adjacent to the first outer layer is extruded to include the ethylene-based copolymer; and a second outer layer is extruded to form a film comprising at least three layers; and the film is oriented in at least one direction, wherein the film is oriented with a stretch ratio “Y”, wherein the thickness “X” divided by Y is less than 0.45.

[0005] This document also discloses a method for fabricating a laminate. The method includes fabricating an orientation film according to an embodiment disclosed herein and adhering the orientation film to a base film via an adhesive.

[0006] This article also discloses an oriented film. This oriented film can be manufactured by the method described above. The oriented film includes a first outer layer having a density of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 Low-density polyethylene; an inner layer adjacent to the first outer layer, the inner layer containing the highest peak melt temperature (T). m The first outer layer is an ethylene-based copolymer with a temperature of 105°C or lower; and a second outer layer; wherein the first outer layer has a thickness of less than 0.45 micrometers.

[0007] These and other implementation schemes are described in more detail in the specific embodiments. Detailed Implementation

[0008] The aspects of the disclosed film are described in more detail below. The oriented film of this disclosure can be used in a wide variety of packaging applications, including, for example, bags, stand-up pouches, pillow bags, bulk bags, pre-packaged products, pouches, sealing films, etc.

[0009] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers of the same or different types. Therefore, the general term polymer encompasses the term homopolymer (used to refer to a polymer prepared from only one type of monomer) and the term copolymer or interpolymer. Trace amounts of impurities (e.g., catalyst residues) may be incorporated into and / or within a polymer. A polymer can be a single polymer, a polymer blend, or a mixture of polymers comprising a mixture of polymers formed in situ during polymerization.

[0010] As used herein, the term "polyethylene" or "ethylene-based polymer" should mean a polymer comprising a majority amount (>50 mol%) of units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). 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); single-point catalytic linear low-density polyethylene, including both linear and substantially linear low-density resins (m-LLDPE); ethylene-based plastomers (POP) and ethylene-based elastomers (POE); medium-density polyethylene (MDPE); and high-density polyethylene (HDPE). These polyethylene materials are generally known in the art; however, the following description may help to understand the differences between some of these different polyethylene resins.

[0011] The term "LDPE" can also be referred to as "high-pressure ethylene polymer" or "highly branched polyethylene," and it is defined as meaning that the polymer is partially or wholly homopolymerized or copolymerized in an autoclave or tubular reactor at pressures above 14,500 psi (100 MPa) using a free radical initiator (such as peroxide) (see, for example, US 4,599,392, which is hereby incorporated herein by reference). LDPE resin typically has a viscosity of 0.916 g / cm³. 3 Up to 0.935 g / cm 3 The density within the range.

[0012] The term "LLDPE" encompasses two resins prepared using conventional Ziegler-Natta catalyst systems and chromium-based catalyst systems, as well as single-site catalysts (including, but not limited to, substituted mono- or dicyclopentadienyl catalysts (commonly referred to as metallocenes), confined geometry catalysts, phosphine imine catalysts, and polyvalent aryloxy ether catalysts (commonly referred to as diphenylphenoxys), and comprising linear, substantially linear, or heterogeneous polyethylene copolymers or homopolymers. LLDPE comprises less long-chain branching than LDPE and includes substantially linear ethylene polymers, further defined in U.S. Patents 5,272,236, 5,278,272, 5,582,923, and 5,733,155; homogeneously branched linear ethylene polymer compositions, such as those in U.S. Patent 3,645,992; non-homogeneously branched ethylene polymers, such as those prepared according to the method disclosed in U.S. Patent No. 4,076,698; and / or blends thereof (such as those in US 3,914,342 or US 4,076,698). (Those disclosed in 5,854,045). LLDPE can be prepared by gas-phase, solution-phase, or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0013] As used herein, the term "polyethylene elastomer / plasticizer" should mean units derived from ethylene and units derived from at least one C3-C. 10 A substantially linear or linear ethylene / α-olefin copolymer containing homogeneous short-chain branched units of α-olefin comonomers, or at least one C4-C8 α-olefin comonomer, or at least one C6-C8 α-olefin comonomer. The density of the polyethylene elastomer / plastic is 0.865 g / cm³. 3 or 0.870 g / cm 3 or 0.880 g / cm 3 or 0.890 g / cm 3 Up to 0.900 g / cm 3 or 0.902 g / cm3 or 0.904 g / cm 3 or 0.909 g / cm 3 or 0.910 g / cm 3 Non-limiting examples of polyethylene elastomers / plastics include AFFINITY. ™ Plastics and elastomers (available from The Dow Chemical Company), EXACT ™ plasmid (available from ExxonMobil Chemical), Tafmer (available from Mitsui), Nexlene ™ (Available from SK Chemicals Co.) and Lucene ™ (Available from LG Chem Ltd.)

[0014] The terms “comprising,” “including,” “having,” and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not such components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless otherwise stated, all compositions claimed using the term “comprising” may include any additional additives, auxiliaries, or compounds, whether in polymeric or other forms. In contrast, the term “consistently comprising” excludes any other components, steps, or procedures from any subsequently listed scope, except those that are not essential for operability. The term “consisting of” excludes any components, steps, or procedures not specifically described or listed.

[0015] Methods for producing oriented films and oriented films

[0016] This article discloses a method for fabricating oriented films. The method includes providing a density of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 Low-density polyethylene and highest peak melt temperature (T mThe film is an ethylene-based copolymer with a temperature of 105°C or lower; a first outer layer is extruded to have a thickness of "X" and comprising the low-density polyethylene; an inner layer adjacent to the first outer layer is extruded to comprise the ethylene-based copolymer; and a second outer layer is extruded to form a film comprising at least three layers; and the film is oriented in at least one direction, wherein the film is oriented with a stretch ratio "Y", and the thickness "X" divided by Y is less than 0.45. In some embodiments, the film is oriented longitudinally. In some embodiments, the film is oriented transversely. In some embodiments, the film is oriented longitudinally with a stretch ratio of 4:1 to 12:1 and transversely with a stretch ratio of 4:1 to 12:1. In some embodiments, the first outer layer is less than 2% of the total thickness of the film, wherein the thickness of the first outer layer is calculated using the formula X divided by Y.

[0017] The methods described above and below can be used to form the oriented membrane disclosed herein. The oriented membrane comprises at least three layers—a first outer layer, an inner layer adjacent to the first outer layer, and a second outer layer. The term "adjacent to" means that there is no intermediary layer between the inner layer and the first outer layer. The oriented membrane may include 4, 5, 6, 7, 8, 9, 10, or more layers, and includes additional layers, such as bonding layers or barrier layers. The oriented membrane may have an A / B / C structure, wherein the first outer layer is "A", the inner layer is "B", and the second outer layer is "C". An oriented membrane according to an embodiment disclosed herein may have an A / B / C / D / E structure, wherein A is the first outer layer, B is the inner layer, C is the filler layer, D is the bonding layer, and E is the second outer layer and the barrier layer.

[0018] The oriented film includes a first outer layer. The thickness of the first outer layer at extrusion and before orientation and stretching is “X”. In some embodiments, the thickness of the first outer layer at extrusion and before orientation and stretching is less than 10.00 micrometers, or less than 8.00 micrometers, or less than 5.00 micrometers, or less than 3.00 micrometers, or less than 2.60 micrometers. In some embodiments, the thickness of the first outer layer (after orientation) is less than 0.45 micrometers, or less than 0.43 micrometers, or less than 0.40 micrometers, or less than 0.38 micrometers, or less than 0.35 micrometers, or less than 0.33 micrometers, or less than 0.31 micrometers, or less than 0.29 micrometers, or less than 0.27 micrometers, or less than 0.25 micrometers.

[0019] The thickness of the first outer layer after orientation depends on the degree of film orientation or stretching. In some embodiments, the film is oriented in at least one direction with a stretching ratio to achieve a "calculated" thickness of less than 0.45 micrometers. For example, an extruded outer layer with a thickness of 2.00 micrometers before orientation and stretching will have a calculated thickness of 0.40 micrometers after stretching at a 5:1 ratio. This relationship between thickness and orientation or stretching ratio is expressed herein as thickness "X" and stretching ratio "Y", where the stretching ratio Y is the product of the stretching ratios along the longitudinal and transverse directions. For example, if the thickness "X" of the extruded first outer layer before orientation and stretching is 2.00 micrometers, and the film is then stretched longitudinally at a 2:1 ratio and transversely at a 4:1 ratio, then the value of "Y" is 8 (2 × 4), and the calculated thickness X / Y is 2.00 micrometers / 8 = 0.25 micrometers. Since the film is an oriented film, the stretching ratio is greater than 1. In some implementations, the calculated thickness of the first outer layer is less than 0.45 micrometers, or less than 0.43 micrometers, or less than 0.40 micrometers, or less than 0.38 micrometers, or less than 0.35 micrometers, or less than 0.33 micrometers, or less than 0.31 micrometers, or less than 0.29 micrometers, or less than 0.27 micrometers, or less than 0.25 micrometers.

[0020] In some embodiments, the first outer layer has a specific weight percentage to stretch ratio relationship. For example, in some embodiments, the ratio of the product of the weight percentage of the first outer layer and the stretch ratio based on the total weight of the membrane is less than 0.35, or less than 0.30, or less than 0.25, or less than 0.20.

[0021] In some embodiments, based on the total weight of the membrane, the first outer layer accounts for less than 10.0 wt.%, or less than 5.0 wt.%, or less than 3.0 wt.%, or less than 2.5 wt.%, or less than 2.0 wt.%, or less than 1.5 wt.% of the total membrane weight. In some embodiments, after orientation, the first outer layer is less than 3.0%, or less than 2.0%, or less than 1.5%, or less than 1.0%, or less than 0.5% of the total membrane thickness.

[0022] The first outer layer comprises a density of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 Low-density polyethylene. Low-density polyethylene can have a lower limit of 0.910 g / cm³. 3 0.913 g / cm 3 0.915g / cm 3 0.918 g / cm 3 0.924 g / cm 3 0.930g / cm 3 0.933g / cm3 0.935g / cm 3 Or 0.937g / cm 3 The upper limit is 0.915 g / cm³. 3 0.920g / cm 3 0.925g / cm 3 0.930g / cm 3 0.935g / cm 3 Or 0.940 g / cm 3 The density. In some embodiments, low-density polyethylene is LDPE. In some embodiments, low-density polyethylene is a low-density polyethylene homopolymer polymerized under high pressure. In other embodiments, low-density polyethylene is LLDPE.

[0023] In some implementations, the peak melting temperature (T) of low-density polyethylene is... m (105℃, 110℃, 115℃ or 120℃)

[0024] In some embodiments, the melt index (I2) of low-density polyethylene is 0.2 g / 10 min to 50.0 g / 10 min, or 0.3 g / 10 min to 40.0 g / 10 min, or 0.4 g / 10 min to 30.0 g / 10 min, or 0.5 g / 10 min to 20.0 g / 10 min, or 0.5 g / 10 min to 10 g / 10 min, or 0.5 g / 10 min to 5.0 g / 10 min.

[0025] In some embodiments, the first outer layer is substantially composed of low-density polyethylene, or alternatively, of only low-density polyethylene. In other embodiments, the first outer layer may contain additional polymers besides low-density polyethylene. For example, in some embodiments, the first outer layer may comprise a blend of low-density polyethylene with another polymer, such as ULDPE, VLDPE, LLDPE, LDPE, MDPE, or HDPE. In some embodiments, the first outer layer comprises at least 90 wt.% low-density polyethylene. All individual values ​​and subranges of at least 90 wt.% are disclosed and included herein. For example, in some embodiments, based on the total weight of the polymers in the first outer layer, the first outer layer may comprise at least 90 wt.%, at least 95 wt.%, at least 99 wt.%, at least 99.5 wt.%, or 90 wt.% to 100 wt.%, or 95 wt.% to 99 wt.%, or 90 wt.% to 99.9 wt.% low-density polyethylene. In some embodiments, based on the total weight of the polymer in the first outer layer, the first outer layer comprises at least 90 wt.%, at least 95 wt.%, at least 99 wt.%, at least 99.5 wt.%, or 90 wt.% to 100 wt.%, or 95 wt.% to 99 wt.%, or 90 wt.% to 99.9 wt.% of an ethylene-based polymer.

[0026] Commercially available examples of low-density polyethylene that can be used for the first outer layer include those available from Dow Chemical, such as ELITE. ™ 5400GS, ELITE ™ 5401 GT, DOWLEX ™ 2045G, DOW ™ LDPE 410E and AGILITY ™ EC7000, and those available from ExxonMobil Company, such as Exceed ™ 1018, Exceed ™ XP 8318 and LDPE LD158BW.

[0027] The oriented film includes an inner layer adjacent to the first outer layer. This inner layer contains the highest peak melting temperature (T0). m The ethylene-based copolymer is 105°C or lower. In some embodiments, the highest peak melt temperature (T0) of the ethylene-based copolymer is... mThe temperature is 100°C or lower, or 95°C or lower, or 90°C or lower, or 85°C or lower. In some embodiments, the density of the ethylene-based copolymer is less than 0.905 g / cc, or less than 0.900 g / cc, or less than 0.895 g / cc, or less than 0.890 g / cc, or less than 0.888 g / cc, or in the range of 0.855 g / cc to 0.905 g / cc, 0.860 g / cc to 0.905 g / cc, 0.865 g / cc to 0.905 g / cc, or 0.880 g / cc to 0.900 g / cc, or 0.880 g / cc to 0.895 g / cc. In some embodiments, the ethylene-based copolymer is a polyethylene elastomer / plasticizer. In other embodiments, the ethylene-based copolymer is a polyethylene elastomer / plasticizer with a density of less than 0.900 g / cc or less than 0.895 g / cc. In some implementations, the highest peak melting temperature (T) of the inner layer m () is 100°C or lower, or 95°C or lower, or 90°C or lower, or 85°C or lower.

[0028] In some embodiments, the melt index (I2) of the ethylene-based copolymer may be less than 10.0 g / 10 min, less than 5.0 g / 10 min, or less than 4.0 g / 10 min, or less than 3.0 g / 10 min, or less than 2.0 g / 10 min.

[0029] In some embodiments, based on the total weight of the polymer in the inner layer, the inner layer contains at least 70 wt.% of the highest peak melt temperature T(T). m The inner layer is an ethylene-based copolymer with a temperature of 105°C or lower. This document discloses and includes all individual values ​​and sub-ranges of at least 70 wt.%. For example, in some embodiments, based on the total weight of the polymer in the inner layer, the inner layer may contain at least 70 wt.%, at least 80 wt.%, at least 90 wt.%, at least 95 wt.%, at least 99 wt.%, at least 99.5 wt.%, or 70 wt.% to 100 wt.%, 75 wt.% to 99 wt.%, 80 wt.% to 95 wt.%, or 90 wt.% to 95 wt.%. In some embodiments, based on the total weight of the polymer in the inner layer, the inner layer is substantially composed of or consists of an ethylene-based polymer. In some embodiments, the inner layer does not contain polyolefins other than ethylene-based copolymers.

[0030] In some embodiments, the inner ethylene copolymer is selected from the group consisting of: polyethylene plastomer / elastomer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, or ethylene-ethyl acrylate copolymer.

[0031] In some implementations, the inner layer contains at least 70 wt.% of the highest peak melt temperature (T0). m The inner polyethylene elastomer / plastic is heated to 100°C or lower. In such embodiments, the density of the inner polyethylene elastomer / plastic can be 0.855 g / cm³. 3 Up to 0.910 g / cm 3 Within the scope. This document discloses and includes 0.855 g / cm³. 3 Up to 0.910 g / cm 3 All individual values ​​and sub-ranges of density; for example, the density of polyethylene elastomer / plastic can be as low as 0.865 g / cm³. 3 Up to 0.910 g / cm 3 0.865g / cm 3 Up to 0.900 g / cm 3 0.865g / cm 3 Up to 0.890 g / cm 3 0.865g / cm 3 Up to 0.880 g / cm 3 0.865g / cm 3 Up to 0.870 g / cm 3 0.870 g / cm 3 Up to 0.910 g / cm 3 0.870 g / cm 3 Up to 0.900 g / cm 3 0.870 g / cm 3 Up to 0.890 g / cm 3 0.870 g / cm 3 Up to 0.880 g / cm 3 0.880 g / cm 3 Up to 0.910 g / cm 3 0.880 g / cm 3 Up to 0.900 g / cm 3 0.880 g / cm 3 Up to 0.890 g / cm 3 0.890 g / cm 3 Up to 0.910 g / cm 3 0.890 g / cm 3 Up to 0.900 g / cm 3 Or 0.900g / cm 3 Up to 0.910 g / cm 3 Within the range.

[0032] In embodiments where the inner layer comprises a polyethylene elastomer / plastic, the melt index (I2) of the polyethylene elastomer / plastic can be in the range of 0.50 g / 10 min to 20 g / 10 min. This document discloses and includes all individual values ​​and sub-ranges of the melt index (I2) from 0.50 g / 10 min to 20 g / 10 min; for example, the melt index (I2) of the polyethylene elastomer / plastic can be from an upper limit of 0.50 g / 10 min, 1.0 g / 10 min, 2.0 g / 10 min, 5.0 g / 10 min, 10.0 g / 10 min, 15 g / 10 min, or 18 g / 10 min to a lower limit of 1.0 g / 10 min, 2.0 g / 10 min, 5.0 g / 10 min, 10.0 g / 10 min, 15 g / 10 min, 18 g / 10 min, 19 g / 10 min, or 20 g / 10 min.

[0033] Commercially available examples of polyethylene elastomers / plasticizers that can be used for inner layers include those from Dow Chemical Company (Midland, Michigan) under the name AFFINITY. ™ Those acquired through commercial purchases include, for example, AFFINITY ™ VP 8770G1, AFFINITY ™ PF7266, AFFINITY ™ PL 1881G and AFFINITY ™ PF1140G.

[0034] In some embodiments, in addition to the ethylene-based copolymer, the inner layer may also contain at least one other polymer and / or at least one additive. For example, the at least one other polymer may be selected from the group consisting of LDPE, LLDPE, or combinations thereof, in an amount less than 30 wt.% of the inner layer. And, for example, the at least one additive may be selected from the group consisting of antioxidants, UV stabilizers, heat stabilizers, slip agents, anti-blocking agents, antistatic agents, pigments or colorants, processing aids, crosslinking catalysts, flame retardants, fillers, foaming agents, or combinations thereof, in an amount less than 30 wt.% of the inner layer. In some embodiments, the inner layer contains 0.1 wt.% to 10 wt.%, 0.5 wt.% to 8 wt.%, 1.0 wt.% to 7.5 wt.%, or 2.5 wt.% to 7.5 wt.% of additives, such as slip agents and anti-blocking masterbatch additives. In embodiments where the inner layer contains a polymer other than the ethylene-based copolymer, the highest peak melt temperature of the inner layer is 105°C or lower.

[0035] In some embodiments, the inner layer is at least 10 micrometers thick after orientation, or alternatively at least 15 micrometers thick, or alternatively at least 20 micrometers thick. In other embodiments, the inner layer is 25% to 60% of the total thickness of the orientation film.

[0036] The oriented film includes a second outer layer. The second outer layer is not particularly limited herein. The second outer layer may comprise low-density polyethylene having the same characteristics or properties as the low-density polyethylene of the first outer layer. The second outer layer has a similar or the same thickness and elongation ratio as the first outer layer. The second outer layer may comprise LDPE, LLDPE, MDPE, HDPE, or a combination thereof. In some embodiments, the second outer layer may comprise polyamide or polypropylene.

[0037] In some embodiments, the multilayer film includes a bonding layer, and the second outer layer is a barrier layer. In such embodiments, the orientation film includes a bonding layer located between the inner layer and the second outer layer.

[0038] In an embodiment where the bonding layer is located between the inner layer and the second outer layer, the second outer layer, which serves as a barrier layer, may comprise an ethylene-vinyl alcohol copolymer (EVOH).

[0039] Various overall thicknesses are envisioned for the oriented film. In one embodiment, the second layer, serving as a barrier layer, can be 5% to 25% of the overall thickness of the multilayer film.

[0040] In embodiments where a bonding layer exists between the inner layer and the second outer layer, the bonding layer may comprise an adhesive resin selected from the group consisting of: anhydride-grafted ethylene-based polymers, ethylene-acid copolymers, and ethylene-vinyl acetate. Examples of anhydride grafts may include, but are not limited to, maleic anhydride, citrate anhydride, 2-methylmaleic anhydride, 2-chloromaleic anhydride, 2,3-dimethylmaleic anhydride, bicyclo[2,2,1]-5-heptene-2,3-dicarboxylic anhydride and 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride, bicyclo(2.2.2)oct-5-ene-2,3-dicarboxylic anhydride, o-octahydronaphthalene-2,3-dicarboxylic anhydride, 2-oxa-1,3-diketospiro(4.4)non-7-ene, bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride, tetrahydrophthalic anhydride, norbornene-5-ene-2,3-dicarboxylic anhydride, and nadic anhydride. (anhydride), methylnadic anhydride, hisicanhydride, methylhimicanhydride, and x-methyl-bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride. In one embodiment, the anhydride grafting portion comprises maleic anhydride.

[0041] In some embodiments, the bonding layer comprises anhydride-modified linear low-density polyethylene. In some embodiments, the density of the anhydride-modified linear low-density polyethylene is 0.860 g / cm³.3 Up to 0.935 g / cm 3 Within the scope. This document discloses and includes 0.860 g / cm. 3 Up to 0.935 g / cm 3 All individual values ​​and sub-ranges; for example, the density of anhydride-modified linear low-density polyethylene can be as low as 0.875 g / cm³. 3 Up to 0.935 g / cm 3 0.900g / cm 3 Up to 0.925 g / cm 3 0.910 g / cm 3 Up to 0.935 g / cm 3 0.910 g / cm 3 Up to 0.925 g / cm 3 0.915g / cm 3 Up to 0.935 g / cm 3 Or 0.920 g / cm 3 Up to 0.930 g / cm 3 Within the range. In some embodiments, the melt index (I2) of the anhydride-modified linear low-density polyethylene is 0.1 g / 10 min to 50 g / 10 min, or 0.5 g / 10 min to 20 g / 10 min, or 1.0 g / 10 min to 10 g / 10 min.

[0042] In some embodiments, an orientation film may be adhered to a substrate (such as another film) to form a laminate. The laminate includes an orientation film according to embodiments disclosed herein, an adhesive, and a substrate. An adhesive may be applied to the outermost layer of the orientation film (e.g., a barrier layer in one embodiment or a second outer layer in another) to act as an adhesive layer and adhere the orientation film to the substrate, such as a polyethylene film. A method for producing a laminate is also disclosed herein. This method includes producing an orientation film according to embodiments disclosed herein and adhering the orientation film to a substrate film via an adhesive.

[0043] In some embodiments, the adhesive is a solvent-based adhesive, a solvent-free adhesive, or a water-based adhesive. Examples of commercially available adhesives that can be used in these embodiments include those with the name ADCOTE. ™ MOR-FREE ™ and ROBOND ™ Those were purchased from Dow Chemical Company (Midland, Michigan).

[0044] In some embodiments, the oriented film is a longitudinally oriented film. In such embodiments, the oriented film may be a longitudinally oriented (MDO) polyethylene film. In some embodiments, the oriented film is longitudinally oriented at a stretch ratio of 4:1 to 12:1 or 5:1 to 10:1. MDO film is a uniaxially oriented film. The stretching or orientation of the film is performed by longitudinally oriented rollers, via stretching, or via meshing gears, thereby circumferentially rolling the film or otherwise progressively stretching it longitudinally.

[0045] In other embodiments, the oriented film is biaxially oriented. In such embodiments, the oriented film may be a biaxially oriented polyethylene (BOPE) film. In embodiments where the oriented film is BOPE, the BOPE can be bidirectionally oriented using a tenter frame sequential biaxial orientation process and may be referred to as tenter frame biaxially oriented polyethylene (TF-BOPE). Such techniques are generally known to those skilled in the art. In other embodiments, based on the teachings herein, other techniques known to those skilled in the art (such as a double-bubble orientation process) can be used to make the oriented film biaxially oriented. Typically, in a tenter frame sequential biaxial orientation process, the tenter frame is incorporated as part of a multilayer co-extrusion production line. After extrusion from a flat die, the film is cooled on cooling rollers and immersed in a water bath filled with room temperature water. The cast film is then conveyed to a series of rollers with different rotational speeds to achieve longitudinal stretching. There are several pairs of rollers in the MD stretching section of the production line, and these pairs of rollers are all oil-heated. The pairs of rollers are used sequentially as preheating rollers, stretching rollers, and rollers for relaxation and annealing. The temperature of each pair of rollers is controlled individually. After longitudinal stretching, the film web is conveyed to a tenter frame hot air furnace with heating zones for transverse stretching. The first few zones are used for preheating, the following zones are used for stretching, and then the final zone is used for annealing.

[0046] In some embodiments, the transverse stretch ratio of the oriented film is greater than its longitudinal stretch ratio, and the ratio of the longitudinal elongation at break percentage to the transverse elongation at break percentage of the oriented film is at least 2:1.

[0047] In some embodiments, the oriented film can be longitudinally oriented at a stretch ratio of 2:1 to 6:1, or alternatively at a stretch ratio of 3:1 to 5:1. In some embodiments, the oriented film can be transversely stretched at a stretch ratio of 2:1 to 9:1, or alternatively at a stretch ratio of 3:1 to 8:1. In some embodiments, the oriented film is longitudinally stretched at a stretch ratio of 2:1 to 6:1 and transversely stretched at a stretch ratio of 2:1 to 9:1. In some embodiments, the film is oriented in the longitudinal, transverse, or both directions at a combined stretch ratio of at least 2:1 or greater to achieve a calculated thickness of less than 0.45 micrometers for the first outer layer.

[0048] In some implementations, depending on the end-use application, the orientation film may be corona treated or printed using techniques known to those skilled in the art.

[0049] Oriented films can have various thicknesses, depending on, for example, the number of layers. For example, in some embodiments, the thickness of the oriented film can be from 10 micrometers to 200 micrometers or alternatively from 15 micrometers to 150 micrometers.

[0050] This oriented film can exhibit superior heat-sealing performance compared to films in the prior art, while also being able to be produced at higher speeds and with better stretching temperatures. In some embodiments, the oriented film has a heat-sealing initiation temperature below 105°C (defined as the sealing temperature required to achieve a 5N / 15mm seal strength according to ASTM F88) or a heat-sealing initiation temperature below 104°C and below 105°C at 5N / 15mm.

[0051] In some embodiments, based on the total weight of the polymers in the oriented film, the oriented film comprises at least 90 wt.% of an ethylene-based polymer, or at least 95 wt.% of an ethylene-based polymer, or at least 97 wt.% of an ethylene-based polymer, or at least 99 wt.% of an ethylene-based polymer, or at least 99.9 wt.% of an ethylene-based polymer. In some embodiments, based on the total weight of the polymers in the oriented film, the oriented film comprises less than 5 wt.%, or less than 3 wt.%, or less than 1 wt.%, or less than 0.1 wt.% of polypropylene or other polyolefins other than ethylene-based polymers, or contains no polypropylene or other polyolefins other than ethylene-based polymers.

[0052] additive

[0053] It should be understood that any of the aforementioned layers in a multilayer system may also include one or more additives known to those skilled in the art, such as antioxidants, UV stabilizers, heat stabilizers, slip agents, antiblocking agents, antistatic agents, pigments or colorants, processing aids, crosslinking catalysts, flame retardants, fillers, and foaming agents. For example, in an embodiment, the inner layer comprises at least one of a slip agent or an antiblocking agent.

[0054] Products

[0055] Embodiments of the present invention also provide articles formed from the oriented films and laminates described herein. Examples of such articles may include packaging, flexible packaging, and bags. In some embodiments, the packaging of the present invention may include liquids, powders, food, or other articles. In view of the teachings herein, the articles and packaging of the present invention can be formed from the laminates disclosed herein using techniques known to those skilled in the art.

[0056] Test methods

[0057] density

[0058] Density was measured according to ASTM D792 and expressed in grams per cubic centimeter. 3 (g / cm) 3 )express.

[0059] Melt index (I2)

[0060] Melt index (I2) is measured at 2.16 kg at 190°C according to ASTM D-1238. The value is reported in g / 10 min, corresponding to the number of grams eluted per 10 minutes.

[0061] Heat sealing starting temperature and sealing strength

[0062] Heat Seal Onset Temperature (HSIT): To determine the heat seal onset temperature (HSIT) and seal strength, the sample was sealed using a heat-sealing device with opposing sealing jaws. The sample width was 15 mm, the dwell time for a thickness less than 100 micrometers was 0.5 seconds, and the sealing pressure was 2.5 kg / cm². The heat-sealed sample was conditioned for 24 hours and then measured using a tensile tester equipped with a 100 N load cell at a pulling speed of 500 mm / min. HSIT is reported as the minimum temperature in degrees Celsius required to obtain a seal strength of 5 Newtons (50 kg). Heat Seal Strength: Heat seal strength, or seal strength, is measured according to ASTM F88. Values ​​are reported in N / 15 mm.

[0063] Peak melting temperature (Tm)

[0064] Differential scanning calorimetry (DSC) was used to measure the melting and crystallization behavior of polymers over a wide temperature range. For example, this analysis was performed using a TA Q1000 DSC instrument equipped with a refrigerated cooling system (RCS) and an autosampler. The instrument was first calibrated using the software calibration wizard. A baseline was first obtained by heating the individual cells from -80°C to 280°C with no sample in the DSC aluminum disk. Then, sapphire standards were used as instructed by the calibration wizard. Next, fresh indium samples ranging from 1 mg to 2 mg were analyzed by heating the standard sample to 180°C, cooling it to 120°C at a cooling rate of 10°C / min, and then holding the standard sample isothermally at 120°C for 1 minute. The standard sample was then heated from 120°C to 180°C at a heating rate of 10°C / min. The heat of fusion (H2) of the indium standard sample was then determined. fThe initial melting temperature was 28.71 joules / gram (J / g) ± 0.50 joules / gram (J / g) and the initial melting temperature was 156.6℃ ± 0.5℃. The test sample was then analyzed on a DSC instrument.

[0065] During testing, a nitrogen purge flow of 50 ml / min was used. Each sample was melt-pressed into a film at approximately 175 °C; the molten sample was then cooled to room temperature (approximately 25 °C). Film samples were formed by pressing 0.1 g to 0.2 g of sample at 1,500 psi for 30 seconds to create a film of 0.1 mil to 0.2 mil thickness. Samples of 3 mg to 10 mg in diameter with a diameter of 6 mm were extracted from the cooled polymer, weighed, placed in a light aluminum dish (approximately 50 mg), and capped. Analysis was then performed to determine its thermal properties.

[0066] The thermal behavior of a sample was determined by generating a heat flow versus temperature curve through steep inclines and declines in sample temperature. First, the sample was rapidly heated to 180°C and held isothermally for five minutes to remove its thermal history. Next, the sample was cooled to -40°C at a cooling rate of 10°C / min and held isothermally at -40°C for five minutes. Then, the sample was heated to 150°C at a heating rate of 10°C / min (this is the "second heating" ramp). The cooling and heating curves were recorded. The cooling curve was analyzed by setting a baseline endpoint from the start of crystallization to -20°C. The heating curve was analyzed by setting a baseline endpoint from -20°C to the end of melting. The measured value is the peak melting temperature (T0). m ), peak crystallization temperature (T) c ), initial crystallization temperature (Tc initial), heat of fusion (H) f (in joules per gram), and the calculated crystallinity % of the polyethylene sample is calculated using the following formula: Furthermore, the crystallinity % of the polypropylene sample was calculated using the following formula: The heat of fusion (H) is reported from the second thermal curve. f The maximum peak melting temperature and the initial crystallization temperature are determined based on the cooling curve.

[0067] Example

[0068] The following embodiments illustrate the features of this disclosure, but are not intended to limit the scope of this disclosure.

[0069] Materials used

[0070] The following materials are included in the exemplary membranes discussed below.

[0071] AGILITY ™EC7000 is a low-density polyethylene resin and LDPE with a density of 0.919 g / cm³. 3 The melt index (I2) is 3.9 g / 10 min, and the highest peak melting temperature (T) is [missing value]. m The temperature is 110°C and it is commercially available from Dow Chemical Company (Midland, Michigan).

[0072] ELITE ™ 5410GT is a linear low-density polyethylene resin with a density of 0.917 g / cm³. 3 The melt index (I2) is 1.0 g / 10 min, and the highest peak melting temperature (T) is [missing value]. m The temperature is 123°C and it is commercially available from Dow Chemical Company (Midland, Michigan).

[0073] XZ89810.00 (“XZ”) is a low-density polyethylene resin with a density of 0.902 g / cm³. 3 The melt index (I2) is 0.85 g / 10 min, and it is commercially available from Dow Chemical Company (Midland, Michigan).

[0074] ELITE ™ 5960G1 is a reinforced polyethylene resin with a density of 0.962 g / cm³. 3 It has a melt index (I2) of 0.85 g / 10 min and is commercially available from Dow Chemical Company (Midland, Michigan).

[0075] ELITE ™ 5940ST is a reinforced polyethylene resin with a density of 0.941 g / cm³. 3 It has a melt index (I2) of 0.8 g / 10 min and is commercially available from Dow Chemical Company (Midland, Michigan).

[0076] AFFINITY ™ VP 8770G1 is an ethylene copolymer and polyethylene elastomer / plasticizer with a maximum peak melting temperature (T0). m The temperature is 82℃, and the density is 0.885 g / cm³. 3 It has a melt index (I2) of 1.0 g / 10 min and is commercially available from Dow Chemical Company (Midland, Michigan).

[0077] Polybatch FSU 105 E (“FSU”) is a slip agent / anti-blocking masterbatch commercially available from LyondellBasell.

[0078] Oriented films designated as Examples 1 to 2 and Comparative Examples 1 to 3 of the present invention were formed on a Windmoller and Holscher blow molding co-extrusion apparatus, wherein the layer configuration and composition are indicated in Table 1 below. Comparative Examples 1 and 2 have the following layer wt.%: 10 / 10 / 15 / 10 / 10 / 10 / 15 / 10 / 10. Comparative Example 3 has the following layer wt.%: 2 / 18 / 15 / 10 / 10 / 10 / 15 / 10 / 10. Examples 1 and 2 of the present invention have the following layer wt%. 1 / 19 / 15 / 10 / 10 / 10 / 15 / 10 / 10. All films were extruded to have a thickness of 127 micrometers prior to orientation. Examples 1 and 2 of the present invention have a first outer layer thickness of less than 2 micrometers or 1.27 micrometers prior to orientation. Comparative Example 3 has a first outer layer thickness of greater than 2 micrometers or 2.54 micrometers prior to orientation.

[0079]

[0080] All samples were stretched longitudinally at a ratio of 5.5:1 (3.5 m / min MDO inlet to 19.2 m / min MDO outlet). The speed was not reduced during annealing. To produce oriented films, each film was stretched in an MDO unit roll with a preheating temperature of 90°C-100°C-105°C-110°C, a stretching temperature of 110°C, and an annealing temperature of 95°C. The thickness X of the first outer layer before extrusion at a 5.5 stretch ratio resulted in a calculated thickness of less than 0.45 micrometers for the film of this invention and a calculated thickness greater than 0.45 micrometers for the comparison film.

[0081] The thermal sealing strength of the membrane was measured at a series of sealing temperatures and recorded in Table 2 below.

[0082]

[0083] Compared to Comparative Examples 1 to 3, Examples 1 and 2 of the present invention have improved HSIT. For the embodiments of the present invention, the HSIT is below 105°C.

[0084] Unless expressly excluded or otherwise limited, every document cited herein (if any), including any cross-referenced or related patent or application and any patent application or patent claiming priority or benefit thereof, is incorporated herein by reference in its entirety. No reference to any document acknowledges it as prior art to any invention disclosed or claimed herein, or as teaching, indicating, or disclosing any such invention, alone or in combination with any other referenced document. Furthermore, in the event of any conflict between the meaning or definition of any term in this document and the meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to the term in this document shall prevail.

[0085] While specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be covered in the appended claims.

Claims

1. A method for making a oriented film, the method comprising: A low density polyethylene having a density of 0.910 g / cm 3 to 0.940 g / cm 3 and an ethylene-based copolymer having a peak melting temperature (T m ) of 105°C or less; extruding a first outer layer to have a thickness of "X" and comprising the low density polyethylene, extruding an inner layer adjacent to the first outer layer to comprise the ethylene-based copolymer, and extruding a second outer layer to form a film comprising at least three layers; and orienting the film in at least one direction, wherein the film is oriented at a stretch ratio of "Y", wherein the thickness "X" divided by Y is less than 0.

45.

2. The method of claim 1, wherein the film is oriented in the machine direction.

3. The method of claim 1, wherein the film is oriented in the transverse direction.

4. The method of claim 1, wherein the film is oriented in the machine direction at a stretch ratio of 4: 1 to 12: 1 and in the transverse direction at a stretch ratio of 4: 1 to 12:

1.

5. The method of any preceding claim, wherein the first outer layer is less than 2% of the total thickness of the film, wherein the thickness of the first outer layer is calculated using the formula X divided by Y.

6. The method of any preceding claim, wherein the first outer layer is less than 2 wt.% of the film based on the total weight of the film.

7. The method of any preceding claim, wherein the ethylene-based copolymer is a polyethylene elastomer / plastomer having a density less than 0.900 g / cc.

8. The method of any preceding claim, wherein the oriented film comprises at least 95 wt.% based on the total weight of polymers in the oriented film.

9. The method of any preceding claim, wherein the film has a heat seal initiation temperature (defined as the seal temperature required to achieve a 5 N / 15 mm seal strength according to ASTM F88 method) of less than 105°C.

10. A method for making a laminate, the method comprising: making an oriented film according to claims 1 to 9, and adhering the oriented film to a base film via an adhesive.

11. An oriented film, the oriented film comprising: a first outer layer comprising a low density polyethylene having a density of 0.910 g / cm 3 to 0.940 g / cm 3 ; an inner layer adjacent to the first outer layer, the inner layer comprising an ethylene-based copolymer having a highest peak melting temperature (T m ) of 105 °C or less; and a second outer layer; and wherein the first outer layer has a thickness of less than 0.45 microns.

12. The oriented film of claim 11, wherein the film is oriented in the machine direction, transverse direction, or both directions at a combined stretch ratio of at least 2: 1 or greater to achieve a calculated thickness of the first outer layer of less than 0.45 microns.

13. The oriented film of claims 11-12, wherein the low density polyethylene has a maximum peak melting temperature (Tm) of 105°C or greater. m ).

14. The oriented film of claims 11 to 13, wherein the low density polyethylene is a linear low density polyethylene.

15. The oriented film according to claims 11 to 14, wherein the ethylene-based copolymer is a polyethylene elastomer / plastomer having a highest peak melting temperature (T m ) of 100 °C or less.

Images