Multilayer surface protection film and method for producing the same

Abstract

Multilayer surface protection films and methods for making and using such films are provided. The surface protection films have first and second thermoplastic polyurethane (TPU) layers and an intermediate ethylene vinyl acetate (EVA) layer disposed between the first and second TPU layers. The use of the first and second TPU layers as outer layers contributes to the optical clarity of the film. These TPU layers may have different thicknesses. The use of EVA as a component of the film layers provides a film with lower cost compared to traditional single-layer TPU films. When used as a surface coating for a wide range of applications, such as automobiles, wind turbine blades, home appliances, electronic displays, and mobile devices, the EVA component properties and the total EVA ratio of the film can be used to improve the physical properties of the multilayer structure while maintaining comparable or superior performance to these films.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 482,859, filed February 2, 2023, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field FIELD OF THE INVENTION This specification relates generally to films, and more particularly to multilayer films for use in protecting exterior surfaces. [Background technology]

[0002] Films and laminates with high optical clarity to visible light are desirable in many applications, for example, films with high optical clarity are used in vehicle windshields and sunroofs, food packaging, optical disk drives, residential and commercial windows, etc. Surface protection films provide a shield for bare or painted surfaces, such as metal, glass, and plastic, that are exposed to harsh conditions, helping to prevent damage from abrasion, chipping, chemicals, and mechanical and environmental abrasion. Desirable properties of such surface protection films include optical clarity, a high-gloss surface, flexibility at high and low temperatures, conformability to three-dimensional surfaces, abrasion resistance, and impact resistance. Additionally, it is desirable for the films to be easy and cost-effective to apply.

[0003] While surface protection films with such properties are known, the optical and gloss characteristics of these films can be compromised during downstream coating and handling processes. Additionally, temperature, pressure, wind pressure, and contact with other surfaces can adversely affect these properties. Thermoplastic polyurethane (TPU) surface protection films are commercially available. TPU surface protection films generally have a two-layer structure, consisting of a carrier layer (e.g., polyethylene terephthalate (PET)) and a TPU layer. In recent years, commercially available TPU has become increasingly expensive. Research has been conducted into cost-effective alternatives to TPU surface protection films. However, such films suffer from one or more drawbacks, including undesirable levels of conformability / flexibility, poor optical clarity, gloss, and poor abrasion and impact resistance. Furthermore, many of these alternatives contain halogens, which can potentially cause unwanted corrosion of metal surfaces. Summary of the Invention

[0004] It would therefore be advantageous to develop a cost-effective film for surface protection that possesses the above properties. It would be even more advantageous if the cost-effective film was easy to use, environmentally friendly, and compatible with commercially available adhesive systems.

[0005] The following presents a simplified summary of the claimed subject matter in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is not intended to identify essential elements of the claimed subject matter or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts of the claimed subject matter in a simplified form as a prelude to the more detailed description that is presented later.

[0006] Surface protection films and methods of making and using such films are provided. In a first embodiment, the film includes first and second thermoplastic polyurethane (TPU) layers and an ethylene vinyl acetate (EVA) layer disposed between the first and second thermoplastic polyurethane layers. These films are less expensive to manufacture than conventional monolayer TPU films, yet maintain comparable or superior performance when used as surface coatings for a wide range of applications, including automobiles, wind turbine blades, home appliances, electronic displays, and mobile devices. The surface protection films described herein are easy to use, compatible with commercially available adhesive systems, and environmentally friendly, i.e., PVC-free, halogen-free, and lubricant-free materials. Furthermore, the physical properties (stiffness / resilience) of the multilayer surface protection films described herein can be modified by the grade of the EVA layer, allowing the installer to tailor the finished product to their preferences, such as stiffer or softer elongation. Furthermore, the surface protection films have excellent abrasion and impact resistance, providing users with a durable protective layer for automobiles, trucks, home appliances, mobile devices, computers, electronic display screens, and more.

[0007] In various embodiments, the first and second thermoplastic layers have different thicknesses. In other embodiments, the first thermoplastic layer has a thickness less than the thickness of the second thermoplastic layer, and the intermediate EVA layer has a thickness greater than the first thermoplastic layer and greater than or equal to the thickness of the second thermoplastic layer. In various embodiments, the EVA layer is about 20% to about 70%, or about 20% to about 55% of the total thickness of the film, or less. In one exemplary embodiment, the thickness of EVA layer 106a is about 30% to about 35% of the total thickness of the film, or about 33% of the total thickness of the film. In various embodiments, the EVA layer comprises a thermoplastic EVA copolymer composition based on a moderate proportion of vinyl acetate (VA), e.g., less than about 40% VA, in the EVA copolymer. In one embodiment, the EVA copolymer comprises from about 10% to about 40%, and in another embodiment, the EVA copolymer comprises from about 28% to about 33% VA in the EVA copolymer.

[0008] In various embodiments, the TPU layers comprise an aliphatic thermoplastic polyurethane (ATPU), and the composition of each thermoplastic layer may be the same or different. In various embodiments, the surface protection film has a carrier layer disposed on one surface of the thermoplastic layer. In one embodiment, the carrier layer is PET. In various embodiments, the surface protection film has a pressure-sensitive adhesive (PSA) layer affixed to the outer surface of the surface protection film. According to one embodiment, the PSA-coated surface protection film has a pressure-sensitive adhesive (PSA) adhered to a first TPU layer. An EVA layer is disposed on the first TPU layer, and a second TPU layer is disposed on the intermediate EVA layer. Optionally, a carrier layer is disposed on the second TPU layer. Also, optionally, a release layer is disposed on the outer surface of the PSA layer.

[0009] In another aspect, a window is provided comprising any of the above films. In another aspect, an exterior vehicle component is provided comprising any of the above films. In another aspect, a wind turbine blade is provided comprising any of the above films. In yet another aspect, an electronic display is provided comprising any of the above films. In another embodiment, a protective coating for a surface includes a first thermoplastic polyurethane layer, a second thermoplastic polyurethane layer, and an ethylene vinyl acetate layer disposed between the first and second thermoplastic polyurethane layers. The protective coating has a 5% secant modulus of less than about 5000 psi, or less than about 3600 psi, or less than about 2200 psi. The secant modulus is a measure of the initial stiffness of a material. Thus, the EVA layer provides a more resilient coating that is easier to apply. In various embodiments, the coating has a chip rating of 8.5 A as measured by a gravelometer according to ASTM D3170. Thus, the coating is less expensive than a monolayer TPU film while maintaining comparable performance in chip resistance as measured by the gravelometer test. In various embodiments, the coating has an ultimate elongation MD of about 450% to about 550% or about 500%. In various embodiments, the coating has a light transmittance of at least about 93%.

[0010] In another aspect, a method for producing a surface protection film is provided. The method includes providing an extrusion assembly for coextrusion of a three-layer film. Also provided is a carrier layer, a first polymer resin and a second polymer resin including a TPU, and an EVA resin including a thermoplastic EVA copolymer. The first polymer resin, the second polymer resin, and the EVA resin are coextruded onto the carrier layer via the extrusion assembly to form a surface protection film having a first TPU layer and a second TPU layer as outer layers and an intermediate EVA layer disposed between the first TPU layer and the second TPU layer. In various embodiments, the surface protection film has asymmetric layers, where one or more of the first TPU layer, the second TPU layer, and the intermediate EVA layer have a different thickness than the other layers. In one embodiment, the thickest TPU layer is coextruded adjacent to the carrier layer. In one embodiment, the thickest thermoplastic layer is coextruded adjacent to the carrier layer. The enumeration herein of desirable objects met by various embodiments herein is not meant to imply or suggest that any of these objects, individually or collectively, are present as essential features of the most general embodiment herein or its more specific embodiments. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 2 is a side view of the multilayer surface protection film. [Figure 1B] FIG. 2 is a side view of another embodiment of a multi-layer surface protection film. [Figure 1C] FIG. 2 is a side view of another embodiment of a multi-layer surface protection film. [Figure 2A] FIG. 2 is a side view of another embodiment of a multilayer surface protection film having a PSA layer and a liner. [Figure 2B] FIG. 2 is a side view of a surface coated with a multi-layer surface protection film according to another embodiment. [Figure 3A] 1 is a graph showing the 5% secant modulus of the multilayer surface protection films described herein. [Figure 3B]1 is a graph showing ultraviolet (UV) blocking of multilayer surface protection films described herein. [Figure 4] 1 is a graph showing the UV blocking of multilayer surface protection films described herein. [Figure 5A] 1 is a graph showing accelerated aging results for a multilayer surface protection film described herein compared to a TPU film. [Figure 5B] 1 is a graph showing accelerated aging results for a multilayer surface protection film described herein compared to a TPU film. [Figure 6A] 1 is a graph showing hysteresis tests of a TPU / PVDF-PMMA (polyvinylidene fluoride (PVDF)-polymethyl methacrylate (PMMA) blend) film shown as a comparative example, and a two-layer TPU film. [Figure 6B] 1 is a graph showing hysteresis tests of a TPU / PVDF-PMMA (polyvinylidene fluoride (PVDF)-polymethyl methacrylate (PMMA) blend) film shown as a comparative example, and a two-layer TPU film. [Figure 7] 1 is a graph showing hysteresis testing of a multilayer surface protection film described herein. DETAILED DESCRIPTION OF THE INVENTION

[0012] This specification and the accompanying drawings depict exemplary embodiments and should not be construed as limiting, with the claims defining the scope of this specification, including equivalents. Various mechanical, compositional, structural, and operational changes can be made without departing from the scope of this specification and claims, including equivalents. In some instances, well-known structures and techniques have not been shown or described in detail to avoid obscuring the description. Like numbers in two or more figures represent the same or similar elements. Furthermore, elements and their related aspects described in detail with respect to one embodiment may, whenever possible, be included in other embodiments where they are not specifically shown or described. For example, if an element is described in detail with respect to one embodiment but not with respect to a second embodiment, the element can still be claimed to be included in the second embodiment. Furthermore, the depictions herein are for illustrative purposes and do not necessarily reflect the actual shape, size, or dimensions of the system or illustrated components.

[0013] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," as well as the use of the singular form of any word, include plural referents unless expressly and unambiguously limited to one referent. As used herein, the term "include" and its grammatical variations are intended to be open-ended, and the enumeration of items in a list does not exclude other similar items that may be substituted for or added to the listed items. Unless otherwise indicated, all quantitative values ​​are approximations, whether preceded by words such as "about" or "approximately." The materials, methods, and examples described herein are illustrative only and are not intended to be limiting.

[0014] Provided herein are multilayer surface protection films and methods for making and using such films. The surface protection film has first and second thermoplastic polyurethane (TPU) layers and an intermediate ethylene vinyl acetate (EVA) layer disposed between the first and second TPU layers. Using EVA as a component of the film layers results in a lower-cost film (compared to a single-layer TPU film) while maintaining comparable performance in Gravometer testing. For example, at current market prices, the commercial price of EVA resin is approximately $6.30 / lb less than virgin TPU. This cost savings translates to a savings of approximately $0.50 / linear foot for a 6-mil surface protection film with approximately a 2-mil EVA layer, with the remaining layers being virgin TPU. The physical properties (stiffness / resilience) of the multilayer surface protection films described herein can be modified by the grade of the EVA layer to tailor the finished product to the installer's preferences, such as stiffer or softer elongation. Furthermore, the surface protection films described herein are easy to use, compatible with commercially available adhesive systems, and environmentally friendly, i.e., contain non-PVC, halogen-free, and lubricant-free materials. Furthermore, the surface protection films have excellent abrasion and impact resistance, providing users with a durable protective layer for, for example, automobiles, trucks, home appliances, mobile devices, computers, and electronic display screens.

[0015] Referring now to FIG. 1A , a surface protection film 100 includes a first TPU layer 102 and a second TPU layer 104. An intermediate EVA layer 106 is disposed between the first and second TPU layers 102, 104. In some embodiments, the layers 102, 104, and 106 are disposed on top of one another as described herein without the use of an intermediate adhesive layer. In one embodiment, the layers 102, 104, and 106 are compatible with coextrusion and are secured together by coextrusion without an adhesive layer. In this embodiment, the thicknesses of the layers 102, 104, and 106 are substantially the same. Referring to FIG. 1B, another embodiment of the surface protection film 100a includes a first TPU layer 102a, a second TPU layer 104a, and an intermediate EVA layer 106a disposed therebetween. The first TPU layer 102a has a thickness (T1), the second TPU layer 104a has a thickness (T2), the intermediate EVA layer 106a has a thickness (T3), and the surface protection film 100a has a total thickness (T4) that includes the thicknesses of the two TPU layers 102a, 104a and the EVA layer 106a, thus T4 = T1 + T2 + T3. In this embodiment, the surface protection film 100a, the first TPU layer, and the second TPU layers 102a, 104a are asymmetric and, for example, have different thicknesses. As shown, the thickness T1 of the first TPU layer 102a is thinner than the thickness T2 of the second TPU layer 104a, thus T1 < T2. In some embodiments, the thickness T3 of the EVA layer 106a is, individually, thicker than one or both of the first TPU layer and the second TPU layers T1 and T2. In other embodiments, T2 is thicker than T3, which is thicker than T1, thus T2 > T3 > T1. In some embodiments, the thickness T3 of the intermediate EVA layer 106a is in the range of about 20% to about 70% of the total thickness T4 of the film 100a, and in some embodiments, about 20% to about 55% or thinner. In some embodiments, the thickness T3 of the intermediate EVA layer 106a is in the range of about 30% to about 35% of the total thickness T4 of the film 100a. In one embodiment, the thickness T3 of the intermediate EVA layer 106a includes about one-third (33%) of the total thickness T4 of the film 100a.

[0016] In some embodiments, the surface protection film 100s has a total thickness T4 of about 6 mils. In one embodiment, the intermediate EVA layer 106a has a thickness T3 of about 2 mils to 4 mils, and in another embodiment, the intermediate EVA layer 106a has a thickness T3 of about 2 mils. In another embodiment, the first thermoplastic layer 102a has a thickness T1 of about 1 mil, and the second thermoplastic layer 104a has a thickness T2 of about 1 mil to about 3 mils. In another embodiment, the first thermoplastic layer 102a has a thickness T1 of about 1 mil, the second thermoplastic layer 104a has a thickness T2 of about 3 mils, and the intermediate EVA layer 106a has a thickness of about 2 mils. The thicknesses of the thermoplastic layers 102a, 104a, and the intermediate EVA layer 106a are shown in FIGS. 2B and 3A-C and are described in some embodiments as T2 > T3 > T1, although other embodiments are within the scope of this specification. The intermediate EVA layer comprises an EVA copolymer composition, also known as an EVA copolymer resin, formed from the copolymerization of ethylene and vinyl acetate. The ethylene vinyl acetate copolymer may be copolymerized with other resins, such as low-density polyethylene (LDPE), and / or may contain other polymers or polymer blends and additives to enhance the desired characteristics of the surface protection film, such as clarity, hardness, flexibility, and toughness. The properties of the surface protection film can be varied by modifying the EVA component properties, such as the VA content of the EVA copolymer. For example, a lower VA percentage in the EVA copolymer results in a harder film. The properties of the multilayer surface protection film can also be varied by the total thickness of the EVA layers. The EVA component properties and EVA layer thickness can be used to tailor the finished product to the user's preferences, such as stiffer or softer elongation.

[0017] In some embodiments, the intermediate EVA layer comprises a thermoplastic EVA copolymer composition based on a moderate percentage of VA, such as less than about 40% and from about 10% to about 40% in the EVA copolymer resin. In one embodiment, the EVA copolymer is an extrudable polymer containing about 28% to about 33% VA in the EVA copolymer resin. The EVA copolymer may contain other additives, stabilizers such as UV stabilizers, adhesion promoters, copolymers, crosslinkers, and polymer blends to enhance film performance. EVA copolymer resins are commercially available. Examples of suitable EVA copolymer resins include ATEVA-2861A (EVA-28) and ATEVA-3325A (EVA-33), available from Celanese EVA Performance Polymers LLC, 4405-101 Ave. NW, Edmonton, AB 6A 0L2, Canada. Table 1 shows exemplary resin, thermal, and molded plaque properties of EVA copolymer resins suitable for use in the surface protection films described herein, as well as typical properties of EVA-28 and EVA-33. [Table 1]

[0018] The first and second thermoplastic polymer layers comprise a TPU resin. TPU resins are produced by the polyaddition reaction between a diisocyanate and one or more polyols or long-chain diols, chain extenders or short-chain diols, and a diisocyanate. TPUs are linear, segmented block copolymers consisting of hard and soft segments. The soft segments can be polyether, polyester, or polycaprolactone and provide the flexibility and elastomeric properties of TPUs. The hard segments (aromatic or aliphatic) are composed of a chain extender and an isocyanate. In some embodiments, the hard segments are based on aliphatic isocyanates. In one embodiment, the TPU resin comprises an ATPU. The first and second TPU layers 102, 104 can be composed of the same or different TPU resins. Using different TPU resins for the first and second thermoplastic layers 102, 104 can impart different properties and provide different benefits. For example, one layer can impart high gloss and stain resistance, while another layer can impart chip resistance. The TPU resin may also contain other additives, stabilizers such as UV stabilizers, adhesion promoters, copolymers, crosslinkers, and polymer blends to enhance the performance of the film. TPU compounds are commercially available. ATPU resins may be extrudable, UV-stabilized, and weather-resistant grades, such as those commercially available for use in the manufacture of paint protection films. Examples of suitable ATPUs include KRYSTALGRAN® PN23-200, an aliphatic polycaprolactone-based TPU available from Huntsman Corporation, The Woodlands, Texas, USA; MIRATHANE® A290, an aliphatic polyester-based TPU, available from Miracl Chemicals Co., Ltd., Yantai, Shandong Province, China; ELASTANE® ALR CLC93A-V, available from The Lubrizol Corporation, Wickliffe, Ohio, USA; and ELASTOLLANE® L Series 785 A10, an aliphatic ester-based TPU, available from Florham Park, New Jersey, USA.

[0019] Table 2 shows the properties of exemplary TPUs that can be used in the surface protection film 100. [Table 2]

[0020] 1C, in some embodiments, the surface protection film 100a further includes a carrier layer 108 in contact with one outer surface of the TPU layer. In one such embodiment, the carrier layer 108 is adhered to the outer surface of the second TPU layer 104a. In one exemplary embodiment, the carrier layer includes PET. In some embodiments, the surface protection film 100, 100a according to the present specification has the properties shown in Table 3. The adjustment parameters are the starting properties of the two pure components (ATPU and EVA) and their relative thicknesses. In some embodiments, the ATPU resin and EVA resin in the film 100 have compatible viscosities at similar temperatures. [Table 3]

[0021] In one embodiment, the film 100 has an ultimate tensile strength greater than about 7000 as measured by ASTM D882. The 5% secant modulus - MD of the film 100 is less than about 5000 psi, and in other embodiments, the 5% secant modulus - MD of the surface protection film 100 is less than about 3240 psi to about 3550 psi. The secant modulus was calculated using two points on the stress-strain curve, and the slope of the stress / strain was calculated using zero as the first point and 5% as the second stress / strain. For example, for the secant modulus calculated at 5% tensile strain, the formula is: Secant modulus = (σ2 - σ1) / (ε2 - ε1) = (stress @ 2% strain - 0) / (2% strain - 0). Secant modulus describes how easily a film can be attached. Secant modulus is one of several methods used to calculate modulus, which is a measure of a material's elasticity. In some embodiments, film 100 exhibits lower force at lower elongation, as shown in Table 3. In exemplary embodiments, film 100 has an ultimate elongation greater than about 450, or greater than about 500 MD, as measured by ASTM D882.

[0022] 2A , in some embodiments, surface protection film 200 has a PSA affixed thereto. In one such embodiment, PSA-coated surface protection film 200 has PSA layer 210 in contact with one outer surface of a TPU layer, preferably adhered to the outer surface of first TPU layer 202. An intermediate EVA layer 206 is disposed on first TPU layer 202, and second TPU layer 204 is disposed on intermediate EVA layer 206. In some embodiments, carrier layer 208 is disposed on second TPU layer 206. Also, in some embodiments, surface protection film 200 having PSA layer 210 has release layer 212, also known as a release liner, disposed on the outer surface of PSA layer 210. Referring now to FIG. 2B, a surface 214 is shown having a surface protection film 200 attached thereto. According to some embodiments, the surface has a PSA layer 210 adhered to the surface 214, with a first TPU layer 202 adhered to the PSA layer 210. An intermediate EVA layer 206 is disposed on the first TPU layer 202, and a second TPU layer 104 is disposed on the intermediate EVA layer 206. In some embodiments, a carrier layer 208 is disposed on the second TPU layer 206. In some embodiments, the carrier 208 may comprise a dual-surface film having a rough, matte surface on one side and a glossy, smooth surface on the other side, combining varying surface roughness with high strength and durability, good dimensional stability, and chemical resistance. An example of a suitable carrier layer film 208 is a PET carrier. An example of a commercially available carrier film is Hostaphan® MT44, available from Mitsubishi Chemical America, Inc.

[0023] The surface protection film 200 can be applied to a variety of painted or bare surfaces, also referred to as substrates, and can be cut to fit various surface dimensions. Examples of surfaces suitable for application of the surface protection film include vehicle bodies, windows, and aerospace vehicles, as well as various other consumer goods, such as electronic screens and sporting goods, to protect the item from wear. In one embodiment, the surface is a painted surface, and in some embodiments, the painted surface is an automobile. A method for manufacturing a surface protection film according to the present disclosure is provided. First, a carrier layer 108, e.g., PET carrier MT44 (Mitsubishi), is provided. A three-layer coextrusion feedblock was used to extrude a multilayer structure including two outer layers of TPU and a center layer of EVA. The layers were positioned so that the thickest TPU layer was adjacent to the carrier layer, with the thickest outer layer being formed adjacent to the carrier layer. Next, the three coextruded layers of TPU / EVA / TPU were applied onto the carrier layer 108 through an appropriate extrusion die.

[0024] While the method for manufacturing the layers of film 100 has been described as being formed by extrusion, other methods known in the art, such as calendaring and solvent casting, can also be used. For example, the layers can be extruded sequentially, or two of the layers can be coextruded, followed by the third layer. Film layers can be extruded using a multi-manifold coextrusion die or a coextrusion feedblock approach. The method can also include laminating the multilayer film to one or more adhesive layers such that one or more layers are "sandwiched" between the adhesive layers. Adhesives can include acrylics, polyurethanes, silicones, styrene-butadiene block copolymers, styrene-isoprene block copolymers, epoxies, cyanoacrylates, and the like. In one embodiment, the adhesive can be a PSA. In other embodiments, one or more layers can be solvent-cast, which can be combined with subsequent coextrusion or sequential extrusion of additional layers. For example, a carrier layer 108 can be solvent-cast onto a liner, followed by extrusion of film 100 layers onto the carrier layer 108. In some embodiments, adhesive layer 110 is affixed to the top surface of surface protection film 100. In one embodiment, surface protection film 100 is provided, optionally with carrier layer 108, and an adhesive, such as PSA layer 110 affixed to release liner 112, is adhered to surface protection film 100. In some embodiments, release liner 112 is removed and PSA 110 is affixed to the surface protection film, which is in turn affixed to a surface or substrate 114. In some embodiments, PSA 110 and associated surface protection film 100 are affixed to surface 114 without the use of heat. [Example]

[0025] General steps: Coextrusion of multiple thermoplastic melt streams can be accomplished using several techniques known in the art. Ultimately, the separate layers of material are brought together at or before the point of extrusion. This can be accomplished using a variety of commercially available "feedblock" configurations, which orient the layers as desired in the final structure before entering the extrusion die. Coextrusion can also be achieved using a multi-manifold die, which brings the layers together at the point of extrusion, allowing for more flexibility for layers with different processing temperatures compared to the feedblock approach.

[0026] Example 1: Two-layer TPU / EVA surface protection film Two-layer surface protection films were made using KRYSTALGRAN® PN23-200, Huntsman Corporation, as the TPU layer and ATEVA-2861A (EVA-28) and ATEVA-3325A (EVA-33), Celanese EVA Performance Polymers LLC, as the second EVA layer. As comparative examples, single-layer TPUs, EVA-28 and EVA-33, were also made, as shown in Table 4 below. Two single-layer extruders were used to extrude the two-layer surface protection films onto the liner. The first layer of TPU was applied to the carrier layer, and the EVA layer was extruded as a separate layer onto the TPU surface of the carrier layer / TPU structure. [Table 4]

[0027] Samples 1-9 were evaluated as shown in Table 5 below. All films were found to have acceptable 5% secant, as shown in Table 5 and Figure 3A, and acceptable elongation, as shown in Table 5. Two-layer EVA-28-TPU films with acceptable tensile strength were found to have a microscopic EVA layer thickness of less than about 53% of that of EVA-28 (2.2-3.2 mil EVA layer with remaining TPU), as shown in Table 5. Two-layer EVA-33-TPU films with acceptable tensile strength were found to have a microscopic EVA layer thickness of less than about 40% of that of EVA-33, as shown in Table 5. All films were found to have acceptable UV blocking with standard UV additives, as shown in Figure 3B. However, all EVA-TPU two-layer films were found to have unacceptable optical quality, such as haze. [Table 5]

[0028] Example 2: Three-layer TPU / EVA / EVA surface protection film Three-layer TPU / EVA / EVA prototype samples (6 mil total thickness) were fabricated using ELASTANE® ALR CLC93A-V2 (The Lubrizol Corporation) as the TPU layer (4 mil thick), ATEVA-3325A (EVA-33) with or without Fusabond C25 as the middle layer (0.5 mil thick), and ATEVA-3325A (EVA-33) Celanese EVA Performance Polymers LLC (1.5 mil thick) as the top layer. The TPU and EVA resin compositions were extruded onto a PET carrier layer, MT44 (Mitsubishi) (0.0508 millimeters (0.002 inches) x 172.72 centimeters (68 inches)). For the three-layer TPU / EVA / EVA example, a three-layer coextrusion feedblock was used to extrude a multilayer structure with TPU as the outer layers and EVA as the center and outer layers. The feedblock was configured so that the TPU layer was formed adjacent to the carrier layer. Three coextruded layers of TPU / EVA / EVA were then applied to the carrier layer through an extrusion die. Samples were made with the EVA and TPU percentage compositions shown in Table 6, and the sample film properties were evaluated as shown in Table 6. * ) tests were performed on film only. ** Tests marked with a triple asterisk ( ) were performed with the exposed / EVA side wet laminated to 1 / 8" clear glass. *** Tests marked with an asterisk (*) were performed using Tesa SP PSA dry laminated to the bare / EVA side, with a 24-hour dwell, 180-degree peel at 2 inches per minute, and high UVT of 365 nm with CLC-93A-V2 resin. Tensile, elongation, modulus, and secant modulus tests were performed according to ASTM D-882. Interlayer adhesion tests were performed according to ASTM D3359 (TPU side / EVA side). Dimensional stability tests were performed at 60°C / 30 minutes. [Table 6]

[0029] The sample exhibited a UVT@365nm greater than 3, which is the desired level, as shown in Table 6. There was also a high level of haze due to the roughness of the EVA surface, as shown in Table 6. In this test, no difference in initial interlayer adhesion was observed between samples made with and without Fusabond added to the EVA.

[0030] Example 3: Three-layer TPU / EVA / TPU surface protection film The high initial haze observed in Example 2 was addressed by changing the layer configuration to an asymmetric film with outer TPU layers and an EVA core middle layer. An initial three-layer prototype sample was prepared as described above in the general procedure. Three samples were prepared, as shown in Table 7 below. An asymmetric three-layer TPU / EVA / TPU film was prepared with EVA-33 (total thickness 6 mils) using KRYSTALGRAN® PN23-200 as the bottom layer (3 mils thick), an ATEVA-3325A (EVA-33) layer as the middle layer (2 mils thick), and KRYSTALGRAN® PN23-200 as the top layer (1 mil) (product number 49710 J28836). [Table 7]

[0031] Asymmetric three-layer TPU / EVA / TPU films were fabricated using KRYSTALGRAN® PN23-200 as the bottom layer (3 mil thick), ATEVA-2861A (EVA-28) as the middle layer (2 mil thick), and KRYSTALGRAN® PN23-200 as the top layer (1 mil thick) with EVA-28 (total thickness 6 mil) (Product No. 49710 J28837). For the three-layer TPU / EVA / TPU example, a three-layer coextrusion feedblock was used to extrude a multilayer structure with TPU as the two outer layers and EVA as the center layer. The feedblock was configured so that the thickest (6 mil) TPU layer was formed adjacent to the carrier layer. Three coextruded asymmetric TPU / EVA / TPU resin compositions were extruded onto a PET carrier layer, MT44, Mitsubishi (0.0508 millimeters (0.002 inches) x 172.72 centimeters (68 inches)), under the conditions shown in Table 8 below. [Table 8]

[0032] A single-layer TPU control film was fabricated under the general conditions described herein as a control (product number 49320 J2574). The EVA and TPU percent compositions, as well as the optical and mechanical properties of the film, are shown in Table 7. Also shown in Table 7, EVA-33 produced a 5% secant modulus similar to that of pure TPU, while EVA-28 was slightly higher / stiffer. The asymmetric design addressed processing concerns from the previous three-layer study (Example 2). There were no lip adhesion issues, and the initial haze was less than 1%. 3-EVA-28-1 completely resolved the flow defect, and the gel level was significantly lower. Materials made with EVA-28 would be acceptable for standard manufacturing. Thicker TPU layers showed the opposite pattern, but the TPU skin layer was consistently 1 mil thick. As shown in Figure 4, the UV transmittance profile of the asymmetric three-layer sample was very similar to that of the TPU control, with slightly more blocking. Table 9 shows a summary of the hysteresis tests performed on the TPU / EVA / TPU films made in Example 3. Figures 5A and 5B show the results of the accelerated aging evaluation of the films made in Example 3 compared to the TPU control film 49320 J2574. [Table 9]

[0033] Example 4 Comparative Example - Two-Layer TPU / PVDF-PMMA Film and Two-Layer TPU Film Referring now to Figures 6A and 6B, the hysteresis curves of the multilayer films are shown in comparison to Figure 7, which shows the hysteresis curves of the three-layer TPU / EVA / TPU films (EVA-33 and EVA-28) and the TPU film produced in Example 3. Figure 6A shows the hysteresis curve of the two-layer TPU / PVDF-PMMA film. The hysteresis curve for the two-layer TPU / PVDF-PMMA film shows a high force at 5% elongation (~4 lbs). Figure 6B shows the hysteresis curve for the two-layer TPU film. The hysteresis curve for the two-layer TPU film 49510-60DV exhibits a force at 5% elongation (~2.2 lbs) at the currently industry-accepted "high end." Figure 7 shows the hysteresis curves of the asymmetric three-layer EVA / TPU / TPU films made with EVA-33 and EVA-22 compared to the hysteresis curve of the monolayer TPU film produced in Example 3. The hysteresis curves of the three-layer EVA / TPU / TPU films made with EVA-33 and EVA-22 exhibit acceptable force at 5% elongation (~1.5 bs), which is below the accepted industry standard force at 5% elongation for monolayer TPUs. Attachment testing showed that the TPU / PVDF-PMMA film was too stiff for effective attachment. Two-ply 49510-60DV was the stiffest acceptable by the industry. Based on these results, a target maximum of 5% secant modulus (a calculated value proportional to the raw force shown above) was set. Furthermore, hysteresis testing, shown in Figure 6A, indicates higher residual strain for PVDF-PMMA-containing films.

[0034] While the devices, systems, and methods have been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and variations therein may be made by those skilled in the art. Accordingly, the foregoing description should not be construed as limited thereby, but should be construed as including such obvious variations as may be set forth above, and should be construed as limited only by the spirit and scope of the following claims.

[0035] For example, in a first aspect, a first embodiment is a film including first and second thermoplastic polyurethane layers and an ethylene vinyl acetate layer disposed between the first and second thermoplastic polyurethane layers. A second embodiment is the first embodiment, wherein the first thermoplastic polyurethane layer has a first thickness, the second thermoplastic polyurethane layer has a second thickness, and the ethylene vinyl acetate layer has a third thickness, and at least one of the first, second, and third thicknesses is different from the other thicknesses. A third embodiment is any combination of the first two embodiments, where the film has a total thickness and the ethylene vinyl acetate (EVA) layer has a thickness of about 20% to about 70% of the total thickness. A fourth embodiment is any combination of the first three embodiments, where the EVA layer thickness is from about 20% to about 55% of the total thickness. A fifth embodiment is any combination of the first four embodiments, where the EVA layer thickness is about 30% to about 35% of the total thickness.

[0036] A sixth embodiment is any combination of the first five embodiments, where the EVA layer thickness is about 33% of the total thickness. A seventh embodiment is any combination of the first six embodiments, wherein the ethylene vinyl acetate layer has a thickness of from about 2 mils to about 4 mils. An eighth embodiment is any combination of the first seven embodiments, wherein the first thermoplastic layer and the second thermoplastic layer have different thicknesses. A ninth embodiment is any combination of the first eight embodiments, wherein the first thermoplastic layer has a thickness of about 1 mil and the second thermoplastic layer has a thickness of from about 1 mil to about 3 mils. A tenth embodiment is any combination of the first nine embodiments, wherein the thickness of the first thermoplastic layer is less than the thickness of the second thermoplastic layer, and the thickness of the intermediate ethylene vinyl acetate layer is greater than the thickness of the first thermoplastic layer.

[0037] An eleventh embodiment is any combination of the first ten embodiments, wherein the first thermoplastic layer has a thickness of about 1 mil, the second thermoplastic layer has a thickness of about 3 mil, and the ethylene vinyl acetate layer has a thickness of about 2 mil. A twelfth embodiment is any combination of the first ten embodiments, wherein the ethylene vinyl acetate layer comprises a thermoplastic ethylene vinyl acetate copolymer, and the percentage of vinyl acetate in the copolymer is from about 28% to about 33%. A thirteenth embodiment is any combination of the first twelve embodiments, wherein the first thermoplastic polyurethane layer and the second thermoplastic polyurethane layer comprise an aliphatic thermoplastic polyurethane. A fourteenth embodiment is any combination of the first thirteen embodiments, wherein the film has a 5% secant modulus of less than about 5000 psi. A fifteenth embodiment is any combination of the first fourteenth embodiment, further comprising a carrier layer.

[0038] A sixteenth embodiment is any combination of the first fifteen embodiments, wherein the carrier layer comprises polyethylene terephthalate (PET). A seventeenth embodiment is any combination of the first sixteen embodiments, further comprising a pressure sensitive adhesive layer to which the first thermoplastic polyurethane layer is adhered and a topcoat disposed on the second thermoplastic polyurethane layer. An eighteenth embodiment is any combination of the first seventeen embodiments, further including a release layer disposed on the outer surface of the pressure-sensitive adhesive layer.

[0039] In another aspect, there is provided a window comprising a film of any of the above 18 embodiments. In another aspect, there is provided an exterior vehicle part comprising a film of any of the above 18 embodiments. In another aspect, there is provided a turbine blade comprising a film of any of the above 18 embodiments. In another aspect, there is provided an electronic display comprising a film of any of the above 18 embodiments.

[0040] In another aspect, a protective coating for a surface is provided, the protective coating comprising first and second thermoplastic polyurethane layers and an ethylene vinyl acetate layer disposed between the first and second thermoplastic polyurethane layers, the protective coating having a 5% secant modulus of less than about 5000 psi. The second embodiment is the first embodiment, wherein the 5% secant modulus is less than about 3600 psi. A third embodiment is any combination of the first two embodiments, wherein the coating has a chipping rating of 8.5A as measured with a gravelometer according to ASTM D3170. A fourth embodiment is any combination of the first three embodiments, where the coating has an ultimate elongation MD of about 450% to about 550%. A fifth embodiment is any combination of the first four embodiments with an ultimate elongation MD of about 500%.

[0041] A sixth embodiment is any combination of the first five embodiments, wherein the coating has a light transmittance of at least about 93%. A seventh embodiment is any combination of the first six embodiments, wherein the coating has a total thickness and the ethylene vinyl acetate (EVA) layer has a thickness of about 20% to about 70% of the total thickness. An eighth embodiment is any combination of the first seven embodiments, where the EVA layer thickness is from about 20% to about 55% of the total thickness. A ninth embodiment is any combination of the first eight embodiments, where the EVA layer thickness is about 30% to about 35% of the total thickness. A tenth embodiment is any combination of the first nine embodiments, where the EVA layer thickness is about 33% of the total thickness.

[0042] An eleventh embodiment is any combination of the first ten embodiments, further comprising a pressure sensitive adhesive layer configured to adhere to a surface. A twelfth embodiment is any combination of the first eleven embodiments, further comprising a carrier layer disposed on the second thermoplastic polyurethane layer. A thirteenth embodiment is any combination of the first twelve embodiments, wherein the surface is a painted surface. A fourteenth embodiment is any combination of the first thirteen embodiments, wherein the painted surface is an automobile.

[0043] In another aspect, a first embodiment is a method for making a surface protection film, comprising: providing a first polymer resin and a second polymer resin comprising a thermoplastic polyurethane; providing an ethylene vinyl acetate resin comprising a thermoplastic ethylene vinyl acetate copolymer; and co-extruding the first polymer resin, the second polymer resin, and the ethylene vinyl acetate resin to form a surface protection film comprising a first thermoplastic polyurethane layer, a second thermoplastic polyurethane layer, and an ethylene vinyl acetate layer disposed between the first thermoplastic polyurethane layer and the second thermoplastic polyurethane layer.

[0044] A second embodiment is the first embodiment, further comprising providing a carrier layer and co-extruding the first polymer resin, the second polymer resin, and the ethylene vinyl acetate resin onto the carrier layer. A third embodiment is any combination of the first two embodiments, where the first thermoplastic polyurethane layer has a first thickness, the second thermoplastic polyurethane layer has a second thickness, and the middle ethylene vinyl acetate layer has a third thickness, and at least one of the first, second, and third thicknesses is different from the other thicknesses.

[0045] A fourth embodiment is any combination of the first three embodiments, wherein the first thermoplastic polyurethane layer, the second thermoplastic polyurethane layer, and the intermediate ethylene vinyl acetate layer each have a thickness, the thickness of the first thermoplastic layer being less than the thickness of the second thermoplastic layer, and the thickness of the intermediate ethylene vinyl acetate layer being greater than the thickness of the first thermoplastic layer. A fifth embodiment is a combination of any of the first four embodiments, where a second thermoplastic layer is coextruded adjacent to the carrier layer. A sixth embodiment is any combination of the first five embodiments, wherein the surface protection film has a total thickness and the ethylene vinyl acetate (EVA) layer has a thickness of about 20% to about 70% of the total thickness.

[0046] A seventh embodiment is any combination of the first six embodiments, where the EVA layer thickness is from about 20% to about 55% of the total thickness. An eighth embodiment is any combination of the first seven embodiments, where the EVA layer thickness is about 30% to about 35% of the total thickness. A ninth embodiment is any combination of the first eight embodiments, where the EVA layer thickness is about 33% of the total thickness.

Claims

1. a first thermoplastic polyurethane (TPU) layer and a second thermoplastic polyurethane layer; and an ethylene vinyl acetate (EVA) layer disposed between the first thermoplastic polyurethane layer and the second thermoplastic polyurethane layer; Including, the film.

2. 10. The film of claim 1, wherein the first TPU layer has a first thickness, the second TPU layer has a second thickness, and the EVA layer has a third thickness, and at least one of the first, second, and third thicknesses is different from the other thicknesses.

3. The film of claim 1, wherein the film has a total thickness and the EVA layer has a thickness of about 20% to about 70% of the total thickness.

4. The film of claim 3, wherein the EVA layer thickness is from about 20% to about 55% of the total thickness.

5. The film of claim 3, wherein the EVA layer thickness is about 30% to about 35% of the total thickness.

6. 4. The film of claim 3, wherein the EVA layer thickness is about 33% of the total thickness.

7. The film of claim 1, wherein the EVA layer has a thickness of about 2 mils to about 4 mils.

8. 10. The film of claim 1, wherein the first TPU layer and the second TPU layer have different thicknesses.

9. 10. The film of claim 1, wherein the first TPU layer has a thickness of about 1 mil and the second TPU layer has a thickness of about 1 mil to about 3 mils.

10. 10. The film of claim 1, wherein the first TPU layer has a thickness less than the thickness of the second TPU layer and the EVA layer has a thickness greater than the thickness of the first TPU layer.

11. 10. The film of claim 1, wherein the first TPU layer has a thickness of about 1 mil, the second TPU layer has a thickness of about 3 mils, and the EVA layer has a thickness of about 2 mils.

12. 10. The film of claim 1, wherein the EVA layer comprises a thermoplastic ethylene vinyl acetate copolymer, the percentage of vinyl acetate in the copolymer being from about 28% to about 33%.

13. 10. The film of claim 1, wherein the first TPU layer and the second TPU layer comprise an aliphatic thermoplastic polyurethane.

14. 10. The film of claim 1 having a 5% secant modulus of less than about 5000 psi.

15. The film of claim 1 further comprising the carrier layer.

16. 16. The film of claim 15, wherein the carrier layer comprises polyethylene terephthalate (PET).

17. A window comprising the film of claim 1.

18. An exterior vehicle part comprising the film of claim 1.

19. A wind turbine blade comprising the film of claim 1.

20. An electronic display comprising the film of claim 1.

21. a pressure-sensitive adhesive layer to which the first TPU layer is adhered; and a top coat disposed on the second TPU layer; The film of claim 1 further comprising:

22. 22. The film of claim 21, further comprising a release layer disposed on the outer surface of the pressure-sensitive adhesive layer.

23. a first thermoplastic polyurethane (TPU) layer and a second thermoplastic polyurethane layer; an ethylene vinyl acetate (EVA) layer disposed between the first TPU layer and the second TPU layer; Including, a 5% secant modulus of less than about 5000 psi; Protective coating for surfaces.

24. 24. The coating of claim 23, wherein the 5% secant modulus is less than about 3600 psi.

25. 24. The coating of claim 23, having a chipping rating of 8.5A as measured with a gravelometer according to ASTM D3170.

26. 24. The coating of claim 23, wherein the ultimate elongation MD is from about 450% to about 550%.

27. 27. The coating of claim 26, wherein the ultimate elongation MD is about 500%.

28. 24. The coating of claim 23, having a light transmittance of at least about 93%.

29. 24. The coating of claim 23, wherein the coating has a total thickness and the EVA layer has a thickness of about 20% to about 70% of the total thickness.

30. 30. The coating of claim 29, wherein the EVA layer thickness is about 20% to about 55% of the total thickness.

31. 30. The coating of claim 29, wherein the EVA layer thickness is about 30% to about 35% of the total thickness.

32. 30. The coating of claim 29, wherein the EVA layer thickness is about 33% of the total thickness.

33. 24. The coating of claim 23, further comprising a pressure sensitive adhesive layer configured to adhere to the surface.

34. 24. The coating of claim 23, further comprising a carrier layer disposed on the second thermoplastic polyurethane layer.

35. 24. The coating of claim 23, wherein the surface is a painted surface.

36. 36. The coating of claim 35, wherein the painted surface is an automobile.

37. A method for producing a surface protection film, comprising: providing a first polymeric resin and a second polymeric resin comprising thermoplastic polyurethane (TPU); Providing an ethylene vinyl acetate (EVA) resin comprising a thermoplastic ethylene vinyl acetate copolymer; and co-extruding the first polymer resin, the second polymer resin, and the ethylene vinyl acetate resin to form a surface protection film including a first TPU layer, a second TPU layer, and an EVA layer disposed between the first TPU layer and the second TPU layer; A method comprising:

38. 38. The method of claim 37, further comprising providing a carrier layer and co-extruding the first polymer resin, the second polymer resin, and the ethylene vinyl acetate resin onto the carrier layer.

39. 38. The method of claim 37, wherein the first TPU layer has a first thickness, the second TPU layer has a second thickness, and the EVA layer has a third thickness, and at least one of the first, second, and third thicknesses is different from the other thicknesses.

40. 38. The method of claim 37, wherein the first TPU layer, the second TPU layer, and the EVA layer each have a thickness, the thickness of the first TPU layer being less than the thickness of the second TPU layer, and the thickness of the EVA layer being greater than the thickness of the first TPU layer.

41. 38. The method of claim 37, wherein the second TPU layer is coextruded adjacent to the carrier layer.

42. 38. The method of claim 37, wherein the surface protection film has a total thickness, and the EVA layer has a thickness of about 20% to about 70% of the total thickness.

43. 43. The method of claim 42, wherein the EVA layer thickness is about 20% to about 55% of the total thickness.

44. 43. The method of claim 42, wherein the EVA layer thickness is about 30% to about 35% of the total thickness.

45. 43. The method of claim 42, wherein the EVA layer thickness is about 33% of the total thickness.

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