Adhesive film

Abstract

This disclosure provides a film. In one embodiment, the film includes a core structure having a first side and a second side on the opposite side. The core structure includes a release layer. The release layer is composed of an ethylene-based polymer on the first side. An adhesion layer is located on the second side of the core structure. The adhesion layer contains an acrylic polymer. The film has an adhesion force of 300 g to 1100 g when stretched to 100%.

Description

[Technical Field]

[0001] Polymer films have a wide range of applications in packaging because their properties can be tailored to the desired end use. Overlap films, for example, are used to package goods, food products, feed crops, and bales. In such applications, it is important that overlap films have good barrier properties, good mechanical properties, adhesion, and elasticity, good toughness, and strong resistance to puncture, impact, and tearing.

[0002] Silage film is used on farms to store pasture and other animal feed crops during the non-growing season. A typical silage bale wrap film contains a core layer that provides mechanical properties to the film, an adhesive layer that provides sufficient tackiness and adhesion, and a release layer that prevents clogging, reduces the unwinding force of the roll, and controls noise during unwinding. The adhesive layer typically contains polyisobutylene (PIB) to provide tackiness and adhesion. PIB is problematic for the following reasons: (i) it is a sticky liquid and difficult to handle, (ii) it causes plate-out and contaminates equipment, (iii) it is migratory and therefore needs to be incorporated into the core layer to reduce bloom-out, and (iv) it can give the film a stretch effect.

[0003] Therefore, there is a need for adhesive films with improved adhesion performance for silage applications that avoid PIB (Primary Impact Bonding). [Overview of the project]

[0004] This disclosure provides a film. In one embodiment, the film includes a core structure having a first side and a second side on the opposite side. The core structure includes a release layer. The release layer is composed of an ethylene-based polymer on the first side. An adhesion layer is located on the second side of the core structure. The adhesion layer contains an acrylic polymer. The film has an adhesion force of 300 g to 1100 g when stretched to 100%. [Brief explanation of the drawing]

[0005] [Figure 1] This graph shows the adhesion force of the embodiment according to the present disclosure.

[0006] All references to the periodic table refer to the version published by CRC Press, Inc., 1990–1991. References to element groups in this table refer to a new notation used to number the groups.

[0007] For the purposes of U.S. patent practice, any referenced patent, patent application, or publication is incorporated by reference in its entirety, particularly with respect to definitional disclosures (to the extent that they do not conflict with any definitions specifically provided in this disclosure) and general knowledge in the art (or equivalent U.S. editions are incorporated by reference in this way).

[0008] Numerical ranges disclosed herein include all values ​​from the lower limit to the upper limit (including the lower and upper limits). In the case of ranges that include explicit values ​​(e.g., 1 or 2, or 3 to 5, or 6 or 7), any subrange between any two explicit values ​​(e.g., 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc.) is included.

[0009] Unless otherwise stated, implied by the context, or customary in the art, all parts and percentages are based on weight, and all test methods are current as of the filing date of this disclosure.

[0010] As used herein, "acrylic monomer" refers to the following structure (I): Structure (I)

[0011] [ka] (In the formula, R1 is H or C1~C 18A monomer having an alkyl group, or a C1-C4 alkyl group, where R2 is H or CH3. Non-limiting examples of acrylic comonomers include acrylic acid, methacrylic acid, acrylates, and methacrylates.

[0012] The term "composition" refers to a mixture of materials that constitute a composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0013] As used herein, the terms “blend” or “polymer blend” refer to a blend of two or more polymers. Such a blend may or may not be miscible (i.e., not phase-separated at the molecular level). Such a blend may or may not be phase-separated. Such a blend may or may not contain one or more domain configurations as determined by transmission electron spectroscopy, light scattering, X-ray scattering, and other methods well known in the art.

[0014] The terms “comprising,” “including,” and “having,” and their derivatives, are not intended to exclude the presence 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, unless otherwise stated, include any additional additives, adjuvants, or compounds, whether or not they are polymers. In contrast, the term “consisting essentially of” excludes any other components, processes, or procedures from the scope of any prior description, except those not essential for operability. The term “consisting of” excludes any components, processes, or procedures that are not specifically described or enumerated. The term “or” refers to the enumerated members individually and in any combination, unless otherwise stated. The use of the singular includes the use of the plural, and vice versa.

[0015] An "ethylene-based polymer" is a polymer containing more than 50 weight percent (wt%) of polymerizable ethylene monomers (based on the total amount of polymerizable monomers) and optionally containing at least one comonomer. Ethylene-based polymers include ethylene homopolymers and ethylene copolymers (meaning units derived from ethylene and one or more comonomers). The terms "ethylene-based polymer" and "polyethylene" may be used interchangeably. Non-limiting examples of ethylene-based polymers (polyethylene) include low-density polyethylene (LDPE) and linear polyethylene. Non-limiting examples of linear polyethylene include linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), multi-component ethylene-based copolymers (EPE), ethylene / α-olefin multiblock copolymers (also known as olefin block copolymers (OBCs)), substantially linear or linear plastomers / elastomers, and high-density polyethylene (HDPE). Generally, polyethylene can be produced in gas-phase fluidized bed reactors, liquid-phase slurry process reactors, or liquid-phase solution process reactors using heterogeneous catalytic systems such as Ziegler-Natta catalysts, and homogeneous catalytic systems containing group 4 transition metals and ligand structures such as metallocenes, non-metallocene metal centers, heteroaryls, heterovalent aryloxyethers, and phosphine imines. Combinations of heterogeneous and / or homogeneous catalysts can also be used in either single-reactor or double-reactor configurations.

[0016] "High-density polyethylene" (or "HDPE") is an ethylene homopolymer, or at least one C4-C 10The HDPE is an ethylene / α-olefin copolymer containing α-olefin comonomers or C4-C8 α-olefin comonomers, having a density of 0.940 g / cc, 0.945 g / cc, 0.950 g / cc, 0.953 g / cc to 0.955 g / cc, 0.960 g / cc, 0.965 g / cc, 0.970 g / cc, 0.975 g / cc, or 0.980 g / cc. The HDPE may be a unimodal copolymer or a multimodal copolymer. A "unimodal ethylene copolymer" is an ethylene / C4-C8 copolymer that has one distinct peak in gel permeation chromatography (GPC) showing the molecular weight distribution. 10 It is an α-olefin copolymer. A "multimodal ethylene copolymer" is an ethylene / C4-C copolymer that has at least two distinct peaks in the GPC showing the molecular weight distribution. 10 These are α-olefin copolymers. Multimodal copolymers include those with two peaks (bimodal) and those with three or more peaks. Non-limiting examples of HDPE include DOW® high-density polyethylene (HDPE) resin (commercially available from The Dow Chemical Company), CONTINUUM® bimodal polyethylene resin (commercially available from The Dow Chemical Company), LUPOLEN® (commercially available from LyondellBasell), and HDPE products from Borealis, Ineos, and ExxonMobil.

[0017] "Low-density polyethylene" (or "LDPE") is an ethylene homopolymer, or at least one C3-C 10It consists of an ethylene / α-olefin copolymer containing α-olefin, has a density of from 0.915 g / cc to less than 0.940 g / cc, and contains long-chain branches with a broad MWD. LDPE is typically produced by high-pressure free-radical polymerization (tubular reactor or autoclave using a free-radical initiator). Non-limiting examples of LDPE include MarFlex (trademark) (Chevron Phillips), LUPOLEN (trademark) (LyondellBasell), and LDPE products from Borealis, Ineos, ExxonMobil, etc.

[0018] "Linear low-density polyethylene" (or "LLDPE") is a linear ethylene / α-olefin copolymer containing units derived from ethylene and units derived from at least one C3 - C 10 α-olefin comonomer, having a heterogeneous short-chain branch distribution. In contrast to conventional LDPE, LLDPE is characterized by having little to no long-chain branches, and LLDPE has a density of from 0.910 g / cc to less than 0.940 g / cc. Non-limiting examples of LLDPE include TUFLIN (trademark) linear low-density polyethylene resin (available from The Dow Chemical Company), DOWLEX (trademark) polyethylene resin (available from the Dow Chemical Company), FINGERPRINT (trademark) polyethylene resin (available from the Dow Chemical Company), and MARLEX (trademark) polyethylene (available from Chevron Phillips).

[0019] "Olefin polymer" or "polyolefin" is a polymer containing more than 50 weight percent of polymerized olefin monomers (based on the total amount of polymerizable monomers), and optionally may contain at least one comonomer. Non-limiting examples of olefin polymers include ethylene polymers and propylene polymers.

[0020] A “polymer” is a compound prepared by polymerizing monomers that provide multiple and / or repeating “units” or “mer units” that constitute a polymer, whether of the same or different types, in a polymeric form. Therefore, the general term polymer encompasses both the term homopolymer, commonly used to refer to polymers prepared from only one type of monomer, and the term copolymer, commonly used to refer to polymers prepared from at least two types of monomers. It also encompasses all forms of copolymers, such as random, block, etc. The terms “ethylene / α-olefin polymer” and “propylene / α-olefin polymer” refer to the aforementioned copolymers prepared by polymerizing ethylene or propylene with one or more additional polymerizable α-olefin monomers, respectively. Polymers are often referred to as "made of" one or more specified monomers, "based on" a specified monomer or type of monomer, or "containing" a specified monomer content. However, it should be noted that in this context, the term "monomer" is understood to refer to the specified monomer of the polymerization residue, and not to the non-polymerized species. Generally, polymers as used herein are based on "units," which are the polymerization forms of the corresponding monomers.

[0021] A "propylene polymer" is a polymer containing more than 50 weight percent of polymerizable propylene monomer (based on the total amount of polymerizable monomers) and may optionally contain at least one comonomer. Propylene polymers include propylene homopolymers and propylene copolymers (meaning units derived from propylene and one or more comonomers). The terms "propylene polymer" and "polypropylene" may be used interchangeably. Non-limiting examples of propylene polymers (polypropylene) include at least one C2 or C4-C2 polymer. 10It is a propylene / α-olefin copolymer containing an α-olefin comonomer or a C2 α-olefin comonomer.

[0022] "Ultra-low density polyethylene (or "ULDPE")" and "Very-low density polyethylene (or "VLDPE")" are each heterogeneous short-chain branched distributions containing units derived from ethylene and at least one C3-C 10 It is a linear ethylene / α-olefin copolymer containing units derived from an α-olefin comonomer with a heterogeneous short-chain branched distribution. ULDPE and VLDPE each have a density of 0.885 g / cc to 0.915 g / cc. Non-limiting examples of ULDPE and VLDPE include ATTANE (trademark) ultra-low density polyethylene resin (available from The Dow Chemical Company) and FLEXOMER (trademark) very-low density polyethylene resin (available from The Dow Chemical Company).

[0023] Test methods Adhesion. Adhesion is the degree of adhesion of the adhesive layer to the release layer. Adhesion is measured according to ASTM D-5458-95, which is a peel adhesion procedure. A 25.4 mm × 140 mm sample is adhered to a flat film attached to a surface inclined at a tensile angle of 20°. Then, the stripe is fixed with a clip attached to the movable frame and load cell. When the clip is pulled, the adhesive force is measured as the force required to remove the film strip from the flat film. The main sheet is attached to the inclined surface, a thin stripe is placed on it, and pressed against the inclined surface. The adhesion obtained from the test is reported in grams.

[0024] Density is measured according to ASTM D792, Method B. The results are recorded in g / cc.

[0025] Differential Scanning Calorimetry (DSC). Differential scanning calorimetry (DSC) can be used to measure the melting, crystallization, and glass transition behavior of polymers over a wide range of temperatures. For example, this analysis is performed using a TA Instruments Q1000 DSC equipped with an RCS (refrigerated cooling system) and an autosampler. A nitrogen purge gas flow rate of 50 mL / min is used during the test. Each sample is melted and compressed at 190°C to form a thin film, and then the molten sample is air-cooled to room temperature (approximately 25°C). Test specimens of 3–10 mg, 6 mm in diameter are extracted from the cooled polymer, weighed, placed in a light aluminum pan (approximately 50 mg), and sealed by pressing. The analysis is then performed to determine its thermal properties.

[0026] The thermal behavior of the sample is determined by raising and lowering the sample temperature to create a heat flow-to-temperature profile. First, to remove its thermal history, the sample is rapidly heated to 180°C and held isothermally for 3 minutes. Next, the sample is cooled to -80°C at a cooling rate of 10°C / min and held isothermally at -80°C for 3 minutes. Then, the sample is heated to 180°C at a heating rate of 10°C / min (this is the "second heating" gradient). The cooling curve and the second heating curve are recorded. The values ​​to be determined are the extrapolated melting onset point Tm and the extrapolated crystallization onset point Tc. Heat of fusion (Hf) (in joules per gram), crystallinity % of polyethylene sample calculated using the following formula: crystallinity % = ((Hf) / 292J / g) × 100, and crystallinity % of polypropylene sample calculated using the following formula: crystallinity % = ((Hf) / 165J / g) × 100.

[0027] The heat of fusion (Hf) and peak melting temperature are reported from the second thermal curve. The peak crystallization temperature is determined from the cooling curve.

[0028] The melting point Tm is first determined from the DSC heating curve by drawing a baseline between the start and end of the melting transition. Next, a tangent line is drawn to the lower temperature data of the melting peak. The point where this line intersects the baseline is the extrapolated melting start point (Tm). This is as described in Bernhard Wunderlich, The Basis of Thermal Analysis, in Thermal Characterization of Polymeric Materials 92, 277-278 (Edith A. Turi ed., 2d ed. 1997).

[0029] The melt index (MI)(I2) of ethylene polymers in g / 10 mins is measured using ASTM D-1238-04 (190°C / 2.16 kg).

[0030] Melt (Brookfield) viscosity. Melt viscosity is measured using a Brookfield Laboratories DVII+ viscometer with a disposable aluminum sample chamber, according to ASTM D3236, incorporated herein by reference. Generally, an SC-31 spindle is used, which is suitable for measuring viscosities in the range of 30–100,000 centipoise (cP). If the viscosity is outside this range, an alternative spindle suitable for the viscosity of the polymer should be used. Using a cutting blade, the sample is cut into sections small enough to fit into a sample chamber measuring 1 inch wide and 5 inches long. A disposable tube is loaded with 8–9 grams of polymer. This sample is placed in the chamber and inserted into a Brookfield Thermosel, and secured with bent needle-tip pliers. The sample chamber has a notch at the bottom that fits into the bottom of the Brookfield Thermosel, ensuring that the chamber does not rotate when the spindle is inserted and rotating. The sample is heated to the desired temperature (177°C / 350°F). Lower the viscometer and immerse the spindle in the sample chamber. Continue lowering until the viscometer bracket aligns with the Thermosel. Turn on the viscometer and set it to shear rate, and read the torque in the range of 40-70%. Reads are taken every minute for approximately 15 minutes, or until the value stabilizes, and then the last read is recorded.

[0031] Stretching (or film stretching) is measured according to ASTM D4649-03, and the results are reported as a percentage (%). For example, a 100% stretched film is a film that has been stretched or otherwise oriented to 100% of its original length. To achieve 100% stretching (mechanical orientation) during testing, the film was stretched to 200% using a tensile testing machine, elastically recovered, and then the adhesion force was measured at approximately 100% stretching in the region of the film showing neck-in. [Modes for carrying out the invention]

[0032] This disclosure provides a film. In one embodiment, the film includes a core structure having a first side and a second side opposite to the first side. The core structure includes a release layer made of an ethylene polymer. The release layer is located on the first side of the core structure. The film includes an adhesion layer on the second side of the core structure. The adhesion layer is made of an olefin polymer. The film has an adhesion value of 300 g to 1100 g when stretched to 100%.

[0033] 1. Core Structure The film includes a core structure having sides on opposite sides. The release layer is located on one side of the core structure. The core structure may be a single-layer film structure (where the release layer constitutes the entire core structure). Alternatively, the core structure may be a multi-layer film structure.

[0034] The release layer is composed of one or more ethylene-based polymers. Non-limiting examples of suitable ethylene-based polymers include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, and any combination thereof.

[0035] In one embodiment, the core structure is a single-layer structure, and the release layer forms the core structure. That is, when the core structure is a single-layer structure, the core structure consists only of the release layer. The release layer is composed of one or more ethylene-based polymers.

[0036] In one embodiment, the core layer has a multilayer structure. The core layer may have two, three, four, five, six, seven, eight, nine, or more layers. The composition of each layer may be the same or different.

[0037] In one embodiment, the core structure is a three-layer structure consisting of (i) a release layer, (ii) a core layer, and (iii) an intermediate layer disposed between the release layer and the core layer. The core layer is in direct contact with the adhesion layer. In a further embodiment, each of the release layer, core layer, and intermediate layer is composed of one or more ethylene-based polymers.

[0038] In one embodiment, the core layer has a thickness of 6.0 μm, or 7.0 μm, or 8.0 μm, or 9.0 μm, or 10.0 μm, or 11.0 μm, or 12.0 μm, or 13.0 μm, or 14.0 μm, or 15.0 μm, or 16.0 μm, or 17.0 μm, or 18.0 μm, or 19.0 μm, or 19.8 μm, or 22.2 μm, or 23.0 μm, or 25 μm, or 30 μm, or 35 μm, or 40 μm, or 45 μm, or 50 μm, or 65 μm, or 70 μm, or 75 μm, or 80 μm, or 85 μm, or 90 μm.

[0039] 2. Adhesion layer The film of the present invention includes an adhesion layer. The adhesion layer is located on the second side surface of the core structure and is the outermost layer. The adhesion layer is on the opposite side of the core structure from the release layer. The adhesion layer is in direct contact with the core structure. The terms "direct contact with" and "in direct contact" refer to a layer configuration in which the first layer is located directly adjacent to the second layer, and there is no intervening layer or intervening structure between the first layer and the second layer.

[0040] The adhesion layer is composed of an acrylic polymer. The acrylic polymer is applied to the second side of the core structure by an aqueous acrylic dispersion. The term "aqueous acrylic dispersion" refers to a composition in which water is the continuous phase, i.e., a composition having an aqueous medium. The aqueous acrylic dispersion contains water, one or more acrylic monomers, an initiator, a surfactant, and an optional neutralizer, but does not contain an ethylene polymer (interchangeably referred to as "acrylic emulsion"). The surfactant acts as an emulsifier, allowing droplets of hydrophobic acrylic monomers to form throughout the aqueous medium. A neutralizer is then introduced into the emulsified mixture. The neutralizer reacts with the acrylic monomer(s) dispersed throughout the aqueous medium until all or substantially all of the acrylic monomer(s) are polymerized. The final result is an acrylic dispersion consisting of a dispersion of acrylic polymer particles in an aqueous medium, where the acrylic polymer particles consist of one or more acrylic monomer subunits, excluding the ethylene polymer.

[0041] The acrylic polymer has a Tg of less than -20 °C, or -80 °C to -20 °C, or -70 °C to -30 °C, or -60 °C to -40 °C, and an Mw of greater than 100,000 Daltons to 10,000,000 Daltons. Non-limiting examples of suitable acrylic monomers include acrylic acid (AA), butyl acrylate (BA), ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), butyl methacrylate (BMA), octyl acrylate, isooctyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate (MMA), isobutyl methacrylate, octyl methacrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, pentadecyl methacrylate, stearyl methacrylate, n-butyl methacrylate, C 12 ~C 18 alkyl methacrylates, cyclohexyl methacrylate, methacrylic acid, and combinations thereof. In addition to the acrylic monomers, the acrylic polymer may also include monomers such as 2-hydroxyethyl acrylate (2-HEA), styrene (STY), vinyl esters, vinyl acetate, and combinations thereof.

[0042] In one embodiment, the acrylic polymer is composed of or consists of acrylic monomers such as butyl acrylate, methyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, ethyl acrylate, styrene, acrylic acid, and any combination thereof, and the acrylic polymer has a Tg of -50°C to -20°C. In a further embodiment, the acrylic polymer is a butyl acrylate / methyl methacrylate / ethyl acrylate / ethylhexyl acrylate polymer (>95%) and does not contain or excludes ethylene (or a polymerization unit of ethylene) and / or butene (or a polymerization unit of butene).

[0043] In one embodiment, the acrylic polymer is either styrene-free or otherwise does not contain styrene.

[0044] The aqueous acrylic dispersion contains a surfactant. Suitable surfactants, though not limited to specific examples, include cationic surfactants, anionic surfactants, bipolar surfactants, nonionic surfactants, and combinations thereof.

[0045] The aqueous acrylic dispersion contains a neutralizing agent to stabilize the acrylic dispersion.

[0046] The adhesion layer is formed by applying an aqueous acrylic dispersion onto the second side surface of the core structure, followed by drying or curing. Coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, curtain coaters, slot die coaters, comma coaters, and knife coaters can be used to apply the aqueous acrylic dispersion.

[0047] In one embodiment, the surface of the second side of the core structure is subjected to a surface treatment. Non-limiting examples of preferred surface treatments include primer coating, plasma treatment, and / or corona discharge treatment before applying an aqueous acrylic dispersion to the second side of the core structure. The second surface is corona-treated or plasma-treated to increase the surface energy of the film. After such corona-treated or plasma-treated surfaces, the second surface has a surface energy of at least 38 dynes / cm² as measured according to ASTM D 2578-04. 2 , or at least 39 dynes / cm 2 , or at least 40 dynes / cm 2 , or at least 41 dynes / cm 2 , or at least 42 dynes / cm 2 , or 38 dynes / cm 2 ~42 dynes / cm 2 The surface energy is shown. In a further embodiment, the surface of the second side of the core structure is 38 dynes / cm² 60 days after corona treatment. 2 ~42 dynes / cm 2 This shows the surface energy. The surface energy is measured using a US ACC dyne pen according to ASTM D2578-04.

[0048] Upon drying, the particles of the aqueous acrylic dispersion coalesce on the second side surface of the core structure to form a uniform or substantially uniform adhesion layer on the core structure. The adhesion layer has the same or substantially the same extent as the second side surface, thereby forming the adhesion layer. The adhesion layer is in direct contact with the second side surface of the core structure. In one embodiment, the thickness of the adhesion layer is 1 to 100 microns, or 10 to 75 microns, or 15 to 30 microns.

[0049] The core structure and / or adhesion layer may contain optional additives. If additives are present, non-limiting examples of suitable additives include anti-blocking additives, antioxidants, antistatic agents, stabilizers, nucleating agents, colorants, pigments (TiO2 particles), ultraviolet (UV) absorbers or stabilizers, flame retardants, compatibilizers, plasticizers, fillers, processing aids, slip agents, and combinations thereof.

[0050] The film of the present invention is an adhesive film and also a stretchable film. As used herein, “adhesive film” refers to a film that adheres to itself when superimposed on itself, or a film that adheres to itself when the adhesive layer comes into contact with a release layer. The adhesive film of the present invention can be stretched to 100% or 400% of its original unstretched length, or to between 100% and 200%. The film exhibits an adhesive force of 300g to 1100g when stretched to 100%.

[0051] In one embodiment, the film is (i) A core structure having a single-layer structure in which the core structure consists only of a release layer, wherein the release layer consists only of one or more ethylene-based polymers (and optionally selected additives), (ii) An adhesive layer in direct contact with the core structure, comprising or consisting of an acrylic polymer having monomers selected from butyl acrylate, methyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, ethyl acrylate, styrene, acrylic acid, and any combination thereof, The film has a thickness of 20 μm to 90 μm, or 25 μm to 80 μm, and has an adhesion strength of 300 g to 1100 g, or 450 g to 1100 g, when stretched to 100%.

[0052] In one embodiment, the film is (i) A core structure having a multilayer structure having three layers, namely (i) a release layer, (ii) a core layer, and (iii) an intermediate layer disposed between the release layer and the core layer, wherein each of the release layer, core layer, and intermediate layer is composed of only one or more ethylene-based polymers (and optionally additives), (ii) An adhesion layer in direct contact with the core structure, wherein the adhesion layer comprises or consists of an acrylic polymer containing monomers, i.e., butyl acrylate, methyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, ethyl acrylate, styrene, acrylic acid, and any combination thereof. The film has a thickness of 20 μm to 90 μm, or 25 μm to 80 μm, and has an adhesion strength of 300 g to 1100 g, or 450 g to 1100 g, when stretched to 100%.

[0053] The film may include two or more embodiments disclosed herein.

[0054] 3. Process This disclosure provides a process. In one embodiment, the process includes stretching a film to at least 100%. The film is the film of the present invention and includes a core structure having a first side and a second side on the opposite side. The core structure includes a release layer made of an ethylene polymer on the first side. The film includes an adhesion layer on the second side of the core structure. The adhesion layer is made of an acrylic polymer. The process includes wrapping the film around a bale of forage crops, bringing the adhesion layer into contact with the release layer, and adhering the adhesion layer to the release layer with an adhesion force of 300 g to 1100 g when stretched to 100%.

[0055] The film used in the process is the film of the present invention having a core structure and an adhesion layer. The core structure can be a single-layer structure (release layer only) or a multi-layer structure, as already disclosed herein.

[0056] The process involves stretching the film to at least 100% and wrapping the film around a bale of forage crops. The stretching and wrapping steps can be performed continuously, or simultaneously or substantially simultaneously. "Forage crops" are any plants that are cultivated and given to livestock. Non-limiting examples of forage crops include legumes, clover, maize, maize stalks, grasses, grains (barley, oats, rice, wheat, rye, millet), hay, legumes (alfalfa, red clover, white clover, alschoenoprasum, lotus, vetch, sweet clover), sorghum, soybeans, vegetables, and any combination of the aforementioned.

[0057] In one embodiment, a portion of the film adhesion layer comes into contact with a portion of the bale and / or a portion of the forage crop.

[0058] In one embodiment, the process involves forming a barrier around a bale of forage crop using a film. A bale packaging device forms the barrier by wrapping the film around the bale. The bale packaging device typically includes a loading arm that lifts the bale and places it on a packaging table. The packaging table includes rollers and belts that rotate the bale while the table itself rotates. A dispensing device provides one or more rolls of the packaging film (i.e., the film). As the bale rotates, the packaging film is typically stretched as it is pulled through the dispensing device, wrapping tightly around the bale and removing oxygen from the bale. After the table has rotated a predetermined number of times, a lifting device tilts the packaging table, tilting the packaged bale off the packaging table. The dispensing device cuts the packaging film before the packaged bale falls from the packaging table. The operation of the bale packaging device can be controlled automatically (by computer or similar logic) or manually. Conventional bale packaging procedures typically involve packaging a bale with 4 to 6 layers of packaging film (i.e., the film).

[0059] The process includes stretching the film to at least 100%, wrapping the film around a bale of forage crops, and forming a barrier around the bale with the stretched and wrapped film to form bale silage. The adhesive layer adheres to the release layer with an adhesive force of 300g to 1100g or 450g to 1100g when stretched to 100%, forming and maintaining the barrier. The barrier is held together by the adhesive force applied by the stretched adhesive film of the present invention. "Bale silage" is one or more forage crops formed in a bale and covered with packaging material (i.e., covered with the stretched film) to remove oxygen. Once packaged, the bale of forage crops undergoes a silo storage process, in which anaerobic microorganisms ferment the carbohydrates present in the forage crops into lactic acid, forming silage. This fermentation process inhibits the growth of other harmful microorganisms. Bale silage typically has a water content of 40% to 60% by weight.

[0060] Damage to the barrier covering, surrounding, or encasing the bale silage is undesirable. For example, holes or tears in the barrier allow oxygen to enter the bale silage. Oxygen in the bale silage leads to aerobic deterioration of the silage and subsequent spoilage. This film, stretched to at least 100%, or up to 100%, having a core structure and an adhesive layer, and with an adhesive strength of 300g to 1100g, provides suitable adhesion to maintain an airtight or substantially airtight barrier over long periods, and advantageously prevents aerobic deterioration of the bale silage.

[0061] Rather than being limiting, some embodiments of this disclosure are described in detail in the following examples. [Examples]

[0062] The materials used in the embodiment ("IE") and comparative sample ("CS") of the present invention are shown in Table 1 below.

[0063] [Table 1]

[0064] 1. Preparation of multilayer film A multilayer film having a thickness of 50 microns is provided with a core structure having layer configurations A / B / C in a volume ratio of 15 / 70 / 15, where A and B are Dowlex 2045G, and C is 85 wt% Dowlex 2045G and 15 wt% LDPE150E, based on the total weight of layer C. Layer A is applied by directly coating an aqueous dispersion of acrylic polymer onto a horizontal lamination table using a stainless steel Meyer bar set to a dry coating weight of 5.0 gsm. The coated multilayer film sample is dried in an oven at 120°C for 3 minutes to form a uniform adhesion layer on the core structure, the adhesion layer A having a thickness of 5 to 12.5 microns and a coating weight of 5 to 8 gsm (grams / square meter). The sample is then protected with a silicone-treated release liner and conditioned in a controlled temperature chamber (CTR) at 23.0 ± 0.5°C and 50 ± 5% RH for 30 minutes.

[0065] 2. Stretch and adhesion evaluation The adhesion strength of the film samples was measured at 0% and 100% stretch. The results are shown in Table 2 below.

[0066] [Table 2] * Weight % based on the total weight of the adhesion layer composition

[0067] The applicant discovered that the level of adhesion is unexpectedly maintained when the film is 100% stretched. The film of the present invention thereby provides adhesion to the outer film surface when 100% stretched.

[0068] This disclosure is not limited to the embodiments and examples contained herein, but is specifically intended to include some embodiments and modified forms of those embodiments, including combinations of elements of different embodiments, to the extent that they fall within the scope of the following claims.

Claims

1. A core structure having a first side and a second side on the opposite side, wherein the first side is provided with a release layer made of an ethylene-based polymer, A film comprising an adhesion layer on the second side surface of the core structure, wherein the adhesion layer contains an acrylic polymer, The aforementioned film has an adhesion strength of 300g to 1100g when stretched to 100%.

2. The film according to claim 1, wherein the core structure comprises the release layer and one or more other layers.

3. The film according to claim 2, wherein the core structure comprises one or more ethylene-based polymers.

4. The film according to any one of claims 1 to 3, wherein the adhesion layer comprises an acrylic polymer having a butyl acrylate monomer.

5. The aforementioned adhesion layer (i) Having a thickness of 4 GSM to 10 GSM, (ii) The film has an adhesion force of 450 g to 1100 g when stretched to 100%, The film according to claim 4.

6. The second side surface of the core structure has at least 38 dynes / cm² ２ A film according to any one of claims 1 to 5, comprising a surface treatment layer having a surface energy.

7. The film is stretched to at least 100%, and the film is A core structure having a first side and a second side on the opposite side, wherein the core structure comprises a release layer made of an ethylene-based polymer on the first side and an adhesion layer on the second side of the core structure, wherein the adhesion layer contains an acrylic polymer, and is stretchable. Wrapping the aforementioned film around the bale of the forage crop, The adhesion layer is brought into contact with the release layer, A process comprising bonding the adhesion layer to the release layer with an adhesion force of 300 g to 1000 g when stretched to 100%.

8. The process according to claim 7, comprising forming a barrier around the veil using the film.

9. The process according to claim 7 or 8, comprising bringing a portion of the veil into contact with a portion of the adhesion layer.

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