Multilayer surface protective film and method for manufacturing same

Abstract

A multilayer surface protective film and methods of making and using such films are provided. The surface protective film has first and second thermoplastic polyurethane (TPU) layers and an intermediate ethylene vinyl acetate (EVA) layer located between the first and second TPU layers. The use of the first and second TPU layers as outer layers contributes to the optical transparency of the film. The TPU layers may have different thicknesses. The use of EVA as a component of the film layer provides a lower cost film compared to conventional single layer TPU films. The component characteristics of the EVA and the total proportion of EVA in the film can be used to alter the physical characteristics of multilayer structures while maintaining comparable or better performance than these films when used as surface coatings in a wide range of applications such as automobiles, wind turbine blades, appliances, electronic displays, mobile devices, and the like.

Description

[0001] Cross-reference to related applications

[0002] 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

[0003] This specification relates generally to films and, more particularly, to a multilayer film for protecting exterior surfaces. Background Art

[0004] Films and laminates having high optical clarity for visible light are desirable in many applications. For example, films having high optical clarity are used in vehicle windshields and sunroofs, food packaging, optical disc devices, residential and commercial windows, and the like.

[0005] Surface protection films provide protection for bare or painted surfaces exposed to extreme conditions, such as metal, glass, and plastic. They help prevent damage caused by abrasion, chipping, chemicals, and mechanical and environmental wear. Desirable properties for such surface protection films include optical clarity, a high-gloss finish, high and low-temperature flexibility, conformability to three-dimensional surfaces, and abrasion and impact resistance. Furthermore, they are expected to be easy to install and cost-effective.

[0006] While surface protection films with such properties are known, the optical and gloss properties of these films can be compromised during downstream coating and handling. Furthermore, temperature, pressure, wind strain, and contact with other surfaces can negatively impact these properties.

[0007] Thermoplastic polyurethane (TPU) surface protection films are commercially available. TPU surface protection films are typically a double-layer structure comprising a carrier layer (e.g., polyethylene terephthalate (PET)) and a TPU layer. In recent years, commercially available TPU has become increasingly expensive. Research has begun on cost-effective alternatives to TPU surface protection films. However, such films have one or more disadvantages, including suboptimal conformability / flexibility, poor optical clarity, gloss, and poor abrasion and impact resistance. In addition, some of these alternatives contain halogens, which can cause undesirable corrosion to metal surfaces.

[0008] Therefore, it would be advantageous to develop a cost-effective film having the above-mentioned properties. It would be further advantageous if such a cost-effective film were easy to use, environmentally friendly, and compatible with commercial adhesive systems. Summary of the Invention

[0009] The following provides a brief summary of the claimed subject matter to provide a basic understanding of certain aspects of the claimed subject matter. This summary is not an exhaustive overview of the claimed subject matter. It is not intended to identify key elements of the claimed subject matter or to delineate the scope of the claimed subject matter. It is intended solely to present some concepts of the claimed subject matter in a concise form as a prelude to the detailed description presented later.

[0010] Provided herein are surface protection films and methods of making and using the same. In a first aspect, the film includes first and second thermoplastic polyurethane (TPU) layers and an ethylene vinyl acetate (EVA) layer positioned between the first and second thermoplastic polyurethane layers.

[0011] The invention relates to a multilayer surface protection film comprising a plurality of layers of TPU films, a plurality of layers of TPU films and a plurality of layers of PVC films. The multilayer surface protection film comprises a plurality of layers of TPU films, a plurality of layers of PVC ...

[0012] In various embodiments, the first and second thermoplastic layers have different thicknesses. In another embodiment, the thickness of the first thermoplastic layer is less than the thickness of the second thermoplastic layer, and the thickness of the intermediate EVA layer is greater than the thickness of the first thermoplastic layer and greater than or equal to the thickness of the second thermoplastic layer.

[0013] In various embodiments, the EVA layer comprises from about 20% to about 70% of the total thickness of the film, or from about 20% to about 55% or less. In an exemplary embodiment, the thickness of the EVA layer 106a is from about 30% to about 35% of the total thickness of the film, or about 33% of the total thickness of the film.

[0014] In various embodiments, the EVA layer comprises a thermoplastic EVA copolymer composition based on a moderate proportion of vinyl acetate (VA) in the EVA copolymer, for example, less than about 40%. 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% of the VA proportion in the EVA copolymer.

[0015] In various embodiments, the TPU layer comprises aliphatic thermoplastic polyurethane (ATPU), and the composition of each thermoplastic layer can be the same or different.

[0016] In various embodiments, the surface protection film has a carrier layer located on the surface of one of the thermoplastic layers. In one embodiment, the carrier layer is PET.

[0017] In various embodiments, the surface protection film has a pressure-sensitive adhesive (PSA) attached 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) layer adhered to the first TPU layer. The EVA layer is located on the first TPU layer, and the second TPU layer is located on the middle EVA layer. Optionally, a carrier layer is located on the second TPU layer. Also optionally, a release layer is located on the outer surface of the PSA layer.

[0018] In another aspect, a window comprising any of the above films is provided. In another aspect, a vehicle exterior component comprising any of the above films is provided. In another aspect, a wind turbine blade comprising any of the above films is provided. In yet another aspect, an electronic display comprising any of the above films is provided.

[0019] In another aspect, a protective coating for a surface includes first and second thermoplastic polyurethane layers and an ethylene vinyl acetate layer positioned between the first and second thermoplastic polyurethane layers. The protective coating has a 5% secant modulus of less than approximately 5,000 psi, less than approximately 3,600 psi, or less than approximately 2,200 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 install.

[0020] In various embodiments, the coating has a chip rating of 8.5A as measured by a stone chip tester according to ASTM D3170. Thus, the coating has a lower cost compared to a single layer of TPU film while maintaining comparable chip resistance as measured by a stone chip tester.

[0021] In various embodiments, the coating has an MD ultimate elongation of about 450% to about 550%, or about 500%.

[0022] In various embodiments, the coating has a light transmittance of at least about 93%.

[0023] In another aspect, a method for manufacturing a surface protection film is provided. The method includes providing an extrusion assembly for coextruding a three-layer film. Also provided are a carrier layer, first and second polymer resins comprising TPU, and an EVA resin comprising a thermoplastic EVA copolymer. The first and second polymer resins and the EVA resin are coextruded onto the carrier layer via the extrusion assembly to form a surface protection film having first and second TPU layers as outer layers and an intermediate EVA layer positioned between the first and second TPU layers.

[0024] In various embodiments, the surface protection film has asymmetric layers, wherein one or more of the first and second TPU layers and the middle EVA layer have a different thickness than the other layer. 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.

[0025] The recitation herein of desirable objectives met by various embodiments of this specification is not meant to suggest or imply that any or all of these objectives are present as essential features, either individually or collectively, in the most general embodiment of this specification or in any of its more specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A is a side view of a multi-layer surface protection film;

[0027] Figure 1B is a side view of another embodiment of a multi-layer surface protection film;

[0028] Figure 1C is a side view of another embodiment of a multi-layer surface protection film;

[0029] Figure 2A is a side view of another embodiment of a multilayer surface protection film having a PSA layer and a liner;

[0030] Figure 2B is a side view of a surface coated with a multi-layer surface protection film according to another embodiment;

[0031] Figure 3A is a graph showing the 5% secant modulus of the multilayer surface protection film described herein;

[0032] Figure 3B is a schematic diagram illustrating the ultraviolet (UV) blocking properties of the multilayer surface protection film described herein;

[0033] Figure 4 is a schematic diagram illustrating the UV barrier properties of the multilayer surface protection film described herein;

[0034] Figure 5A and Figure 5B is a schematic diagram showing the accelerated aging results of the multilayer surface protection film described herein compared to a TPU film;

[0035] Figure 6A and Figure 6B are schematic diagrams showing hysteresis tests of a TPU / PVDF-PMMA (polyvinylidene fluoride (PVDF)-polymethyl methacrylate (PMMA) blend) film and a two-layer TPU film provided as comparative examples, respectively; and

[0036] Figure 7 is a schematic diagram illustrating hysteresis testing of the multilayer surface protection films described herein. DETAILED DESCRIPTION

[0037] This specification and the accompanying drawings illustrate exemplary embodiments and should not be considered restrictive, and the claims (including equivalents) limit the scope of this specification. Various mechanical, composition, structural and operational changes can be made without departing from the spirit and scope of this specification and the claims (including equivalents). In some cases, well-known structures and technologies are not shown or described in detail to avoid confusing the description. The same numbers in two or more drawings represent the same or similar elements. In addition, as long as feasible, the elements and related aspects described in detail with reference to one embodiment can be included in other embodiments that are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment but is not described with reference to a second embodiment, the element can still be included in the second embodiment. In addition, the description herein is for illustrative purposes only and does not necessarily reflect the actual shape, size or dimensions of the system or the components shown.

[0038] It should be noted that as used in this specification and the appended claims, the singular forms "a," "an," and "the," as well as any use of any word in the singular, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term "include" and its grammatical variations are intended to be non-limiting, such that the recitation of items in a list does not exclude other like items that can be substituted or added to the listed items.

[0039] Unless otherwise indicated, any numerical values are approximate, whether or not indicated by the word "about" or "approximately." The materials, methods, and examples described herein are illustrative only and not limiting.

[0040] This article provides a multilayer surface protection film and its manufacture and use method.The surface protection film has a first and a second thermoplastic polyurethane (TPU) layer and an intermediate ethylene vinyl acetate (EVA) layer between the first and the second TPU layer.Using EVA as a component of the film layer provides a lower cost film (compared with a single-layer TPU film) while maintaining considerable performance in a gravel impact tester test.For example, according to current market prices, the commercial price of EVA resin is $6.30 / pound lower than that of virgin TPU.For a 6 mil surface protection film with about 2 mil EVA layers and the remaining layers being virgin TPU, this cost saving is equivalent to saving about $0.50 per linear foot.

[0041] The physical properties (rigidity / elasticity) of the multilayer surface protection film described herein can be changed by the grade of the EVA layer to customize the finished product according to the installer's preferences, such as harder or softer stretchability. In addition, the surface protection film described herein is easy to use, compatible with commercial adhesive systems, and environmentally friendly, that is, they include non-PVC, halogen-free and lubricant-free materials. Moreover, the surface protection film has excellent wear resistance and impact resistance, thereby providing users with a durable protective layer for cars, trucks, appliances, mobile devices, computers and electronic displays, etc.

[0042] Now please refer to Figure 1A , surface protection film 100 includes a first TPU layer 102 and a second TPU layer 104. An intermediate EVA layer 106 is located between the first TPU layer 102 and the second TPU layer 104. In some embodiments, layers 102, 104, and 106 are stacked on top of each other as described herein without the use of an intermediate adhesive layer. In one embodiment, layers 102, 104, and 106 are suitable for coextrusion and are secured by coextrusion of these layers without the need for an adhesive layer. In this embodiment, layers 102, 104, and 106 have substantially the same thickness.

[0043] Please refer to Figure 1B, Another embodiment of the surface protective film 100a includes a first TPU layer 102a, a second TPU layer 104a, and an intermediate EVA layer 106a located 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 protective film 100a has a total thickness (T4), and the total thickness (T4) includes the thicknesses of the two TPU layers 102a, 104a and the EVA layer 106a, that is, T4 = T1 + T2 + T3. In this embodiment, the surface protective film 100a, the first and second TPU layers 102a, 104a are asymmetric, for example, having different thicknesses. As shown in the figure, the thickness T1 of the first TPU layer 102a is less than the thickness T2 of the second TPU layer 104a, that is, T1 < T2. In some embodiments, the thickness T3 of the EVA layer 106a is greater than one or both of the first and second TPU layers T1 and T2, respectively. In other embodiments, T2 > T3 > T1, that is, T2 > T3 > T1. In some embodiments, the thickness T3 of the intermediate EVA layer 106a is about 20% to about 70% of the total thickness T4 of the film 100a, and in some embodiments, the thickness T3 of the intermediate EVA layer 106a is about 20% to about 55% or less of the total thickness T4 of the film 100a. In some embodiments, the thickness T3 of the intermediate EVA layer 106a is 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 accounts for about one-third (33%) of the total thickness T4 of the film 100a.

[0044] In some embodiments, the surface protective 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. Although the thicknesses of the thermoplastic layers 102a, 104a and the intermediate EVA layer 106a are shown in Figure 2B and Figure 3A - FIG. 3C and are described as T2 > T3 > T1 in some embodiments, other embodiments are also within the scope of this specification.

[0045] The middle EVA layer comprises an EVA copolymer composition, which is also referred to as an EVA copolymer resin, and is formed by the copolymerization of ethylene and vinyl acetate. The copolymer of ethylene and vinyl acetate can be copolymerized with other resins such as low-density polyethylene (LDPE), and / or contain other polymers or polymer blends and additives to enhance the desired properties of the surface protection film, such as transparency, hardness, flexibility, toughness, etc. By changing the properties of the EVA components, such as changing the VA content of the EVA copolymer, the properties of the surface protection film can be changed. For example, a harder film is produced when the percentage of VA in the EVA copolymer is lower. The properties of the multilayer surface protection film can also be changed by the total thickness of the EVA layer. The properties of the EVA components and the thickness of the EVA layer can be used to customize the finished product according to the preference of the installer, such as harder or softer stretchability.

[0046] In some embodiments, the middle EVA layer comprises a thermoplastic EVA copolymer composition based on a VA content of less than about 40% and ranging from about 10% to about 40% in the EVA copolymer resin. In one embodiment, the EVA copolymer is an extrudable polymer comprising a VA content of about 28% to about 33% in the EVA copolymer resin. The EVA copolymer may contain other additives, stabilizers, such as UV stabilizers, tackifiers, copolymers, crosslinkers, and polymer blends to enhance the properties of the film.

[0047] EVA copolymer resins are commercially available. Examples of suitable EVA copolymer resins include ATEVA-2861A (EVA-28) and ATEVA-3325A (EVA-33), which are available from Celanese EVA Performance Polymers LLC, 4405-101 Northwest Avenue, Edmonton, AB T6A 0L2, Canada. Table 1 shows exemplary resin properties, thermal properties, and molded plaque properties of EVA copolymer resins suitable for use in surface protection films as described herein, as well as typical properties of EVA-28 and EVA-33.

[0048] Table 1: EVA resin properties

[0049]

[0050] The first and second thermoplastic polymer layers comprise TPU resin. TPU resin is produced by an addition polymerization reaction between a diisocyanate and one or more polyols or long-chain diols, a chain extender, or a short-chain diol and a diisocyanate. TPU is a linear block copolymer consisting of a hard segment and a soft segment. The soft segment can be a polyether, polyester, or polycaprolactone, which provides the flexibility and elasticity properties of TPU. The hard segment (aromatic or aliphatic) is composed of a chain extender and an isocyanate. In some embodiments, the hard segment is based on an aliphatic isocyanate. In one embodiment, the TPU resin comprises ATPU. The first and second TPU layers 102, 104 can be composed of the same or different TPU resins. Using different TPU resins in the first and second thermoplastic layers 102, 104 can impart different properties and provide different advantages. For example, one layer can impart high gloss and stain resistance, while the other layer can impart chip resistance. Other additives, stabilizers such as UV stabilizers, tackifiers, copolymers, cross-linkers, and polymer blends may be included in the TPU resin to enhance the properties of the film.

[0051] TPU compounds are commercially available. ATPU resins may be extrudable, UV-stabilized weathering grades, such as those commercially available for use in the manufacture of paint protection films. Examples of suitable ATPUs include PN23-200, an aliphatic polycaprolactone-based TPU commercially available from Huntsman Corporation, The Woodlands, TX, USA; A290, an aliphatic polyester-based TPU, commercially available from Miracl Chemicals Co., Ltd., Yantai, Shandong, PRC; ALR CLC93A-V, commercially available from The Lubrizol Corporation, Wickliffe, OH, USA; and L-series 785A10, a fatty ester-based TPU, is commercially available from BASF, Florham Park, NJ, USA.

[0052] Table 2 shows exemplary TPU properties that may be used in the surface protection film 100 .

[0053] Table 2: TPU resin properties

[0054]

[0055] Now please refer to Figure 1CIn some embodiments, the surface protection film 100a further comprises a carrier layer 108 in contact with the outer surface of one of the TPU layers. In one such embodiment, the carrier layer 108 is adhered to the outer surface of the second TPU layer 104a. In an exemplary embodiment, the carrier layer comprises PET.

[0056] 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 initial properties of the two pure components (ATPU and EVA) and the relative thickness of each. In some embodiments, the ATPU and EVA resins in the film 100 have compatible (or matching) viscosities at similar temperatures.

[0057] Table 3: Film properties of TPU / EVA / TPU surface protection films.

[0058]

[0059]

[0060] In one embodiment, the film 100 has an ultimate tensile strength greater than about 7000 as measured by ASTM D882. The film 100 has a 5% secant modulus - MD of less than about 5000 psi. In other embodiments, the surface protection film 100 has a 5% secant modulus - MD of about 3240 psi to less than about 3550 psi. The secant modulus is calculated by calculating the slope of stress / strain using two points on the stress-strain curve, the first point being at zero and the second point being stress / 5% strain. For example, for the secant modulus calculated at 5% tensile strain, the calculation formula is: secant modulus = (σ2-σ1) / (ε2-ε1) = (stress at 2% strain - 0) / (2% strain - 0).

[0061] The secant modulus indicates the ease of installation of the film. It is one of several methods used to calculate elastic modulus, a measure of a material's elasticity. In some embodiments, film 100 exhibits lower force at low elongations, as shown in Table 3. In exemplary embodiments, film 100 has an ultimate longitudinal elongation greater than about 450, or greater than about 500, as measured by ASTM D882.

[0062] Now please refer to Figure 2AIn some embodiments, the surface protection film 200 has a PSA attached to the surface protection film 200. In one such embodiment, the surface protection film 200 coated with PSA has a PSA layer 210 in contact with the outer surface of one of the TPU layers, preferably adhered to the outer surface of the first TPU layer 202. The intermediate EVA layer 206 is located on the first TPU layer 202, and the second TPU layer 204 is located on the intermediate EVA layer 206. In some embodiments, the carrier layer 208 is located on the second TPU layer 206. Also in some embodiments, the surface protection film 200 having the PSA layer 210 has a release layer 212 located on the outer surface of the PSA layer 210, which is also referred to as a release liner.

[0063] Now please refer to Figure 2B , which shows a surface 214 with a surface protection film 200 attached. According to some embodiments, the surface has a PSA layer 210 adhered to the surface 214, and the first TPU layer 202 is adhered to the PSA layer 210. The intermediate EVA layer 206 is located on the first TPU layer 202, and the second TPU layer 104 is located on the intermediate EVA layer 206. In some embodiments, the carrier layer 208 is located on the second TPU layer 206. In some embodiments, the carrier 208 may include a double surface film having a rough, matte surface on one side and a glossy, smooth surface on the other side, thereby combining different 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 MT44, Mitsubishi Chemical America, Inc..

[0064] Surface protection film 200 can be applied to various painted or exposed surfaces, which are also referred to as substrates, and surface protection film 200 can be cut into the size of various surfaces. Examples of surfaces suitable for application of surface protection film are car bodies, windows, and aerospace vehicles and various other consumer goods, such as electronic screens and sporting goods, to protect these articles from wear and tear. In one embodiment, the surface is a painted surface, and in some embodiments, the painted surface is an automobile.

[0065] A method for manufacturing a surface protection film according to this specification is provided. First, a carrier layer 108 is provided, such as a PETCarrier MT44, Mitsubishi. A three-layer coextrusion feedblock is used to extrude a multilayer structure consisting of two TPU outer layers and an intermediate EVA layer. These layers are positioned so that the thickest outer layer is formed adjacent to the carrier layer to place the thickest TPU layer. Then, the three coextruded layers of TPU / EVA / TPU are extruded onto the carrier layer 108 through a suitable extrusion die.

[0066] Although the method for manufacturing the layers of film 100 is described as being formed by extrusion, other methods known in the art, such as calendering and solvent casting, can be used. For example, these layers can be extruded in sequence, or two of these layers can be coextruded, and then a third layer can be extruded in sequence. The film layer can be extruded using a multi-manifold coextrusion die or a coextrusion feedblock method. The method can also include laminating the multilayer film to one or more adhesive layers so that one or more of these layers are "sandwiched" between the adhesive layers. The adhesive can include acrylic resins, polyurethanes, silicones, styrene-butadiene block copolymers, styrene-isoprene block copolymers, epoxy resins, cyanoacrylates, etc. In one embodiment, the adhesive can be a PSA. In other embodiments, one or more layers are solvent cast, which can be combined with subsequent coextrusion or sequential extrusion of other layers. For example, the carrier layer 108 can be solvent cast on the liner, and the layers of film 100 can be subsequently extruded onto the carrier layer 108.

[0067] In some embodiments, an adhesive layer 110 is attached to the upper surface of the surface protection film 100. In one embodiment, a surface protection film 100 is provided, optionally having a carrier layer 108, and an adhesive (e.g., PSA) layer 110 attached to a release liner 112 adhered to the surface protection film 100. In some embodiments, the release liner 112 is removed and the PSA 110 is attached to the surface protection film, which is then attached to a surface or substrate 114. In some embodiments, the PSA 110 and accompanying surface protection film 100 can be attached to the surface 114 without the use of heat.

[0068] Example

[0069] General procedure:

[0070] Coextrusion of multiple thermoplastic melt streams can be accomplished using a variety of techniques known in the art. Ultimately, the individual material layers are brought together at or before the point of extrusion. This can be accomplished using various commercially available "feedblock" configurations, where the layers are oriented as desired in the final structure before introduction into the extrusion die. Coextrusion can also be accomplished using a multi-manifold die, which brings the layers together at the point of extrusion. This allows for greater flexibility in using different processing temperatures for each layer compared to feedblock methods.

[0071] Example 1: Double-layer TPU / EVA surface protection film

[0072] Using Huntsman Corporation's A double-layer surface protection film was prepared using PN23-200 as the TPU layer and ATEVA-2861A (EVA-28) and ATEVA-3325A (EVA-33) from Celanese EVA Performance Polymers LLC as the second EVA layer. Single layers of TPU, EVA-28, and EVA-33 were prepared as comparative examples as shown in Table 4 below. The double-layer surface protection film was extruded onto the liner using two single-layer extrusions. 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.

[0073] Table 4: Double-layer TPU / EVA samples

[0074]

[0075] 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 As shown, and have acceptable elongation, as shown in Table 5. The two-layer EVA-28-TPU films with acceptable tensile strength were found to have a micro-EVA layer thickness of less than about 53% of EVA-28 (2.2-3.2 mil EVA layer, the remainder being TPU), as shown in Table 5. The two-layer EVA-33-TPU films with acceptable tensile strength were found to have a micro-EVA layer thickness of less than about 40% of EVA-33, as shown in Table 5. All films showed acceptable UV blocking properties when using standard UV additives, as shown in Table 5. Figure 3B However, all EVA-TPU two-layer films were found to have unacceptable optical qualities, such as haze.

[0076] Table 5: Mechanical properties of samples 1-9

[0077]

[0078] Example 2: Three-layer TPU / EVA / EVA surface protection film.

[0079] Using The Lubrizol Corporation's Three-layer TPU / EVA / EVA prototype samples (total thickness of 6 mils) were prepared using ALR CLC93A-V2 as the TPU layer (thickness of 4 mils), a layer of ATEVA-3325A (EVA-33) from Celanese EVA Performance Polymers LLC with or without Fusabond C25 as the middle layer (thickness of 0.5 mils), and a layer of ATEVA-3325A (EVA-33) (thickness of 1.5 mils) as the top layer. The TPU and EVA resin compositions were extruded onto a Mitsubishi MT44 PET carrier layer (0.002" x 68"). For the three-layer TPU / EVA / EVA examples, a 3-layer coextrusion feedblock was used to extrude the multilayer structure with TPU as the outer layers and EVA as the center layer and outer layers. The feedblock was configured so that the TPU layer was formed adjacent to the carrier layer. The three coextruded layers of TPU / EVA / EVA were then extruded through an extrusion die onto the carrier layer. Samples were prepared with the percentage compositions of EVA and TPU shown in Table 6, and the properties of the sample films were evaluated as shown in Table 6. Tests marked with an asterisk (*) were performed using the film only. Tests marked with a double asterisk (**) were performed by wet laminating the exposed EVA side to 1 / 8" clear glass. Tests marked with a triple asterisk (***) were performed using Tesa SP PSA; dry laminating to the exposed EVA side, leaving it for 24 hours; 180 degree peeling at 2" / min, and high UVT at 365nm due to the CLC-93A-V2 resin. Tensile strength, elongation, modulus, and secant modulus were tested according to ASTM D-882. Interlayer adhesion testing (TPU side / EVA side) was performed according to ASTM D3359. Dimensional stability testing was performed at 60°C for 30 minutes.

[0080] Table 6

[0081]

[0082]

[0083] As shown in Table 6, the samples exhibited a UVT greater than 3 at 365 nm, which is a desirable level. Due to the rough surface of the EVA, they also exhibited a high level of haze, as shown in Table 6. The tests did not reveal any difference in initial interlayer adhesion between samples with and without Fusabond added to the EVA.

[0084] Example 3: Three-layer TPU / EVA / TPU surface protection film.

[0085] The high initial haze found in Example 2 was addressed by changing the layer construction to an asymmetric film having a TPU outer layer and an inner core EVA middle layer. The first three-layer prototype samples were prepared following the general procedure described above. Three samples were prepared as shown in Table 7 below. PN23-200 as the bottom layer (3 mils thickness), a layer of ATEVA-3325A (EVA-33) as the middle layer (2 mils thickness), and An asymmetric three-layer TPU / EVA / TPU film (6 mil total thickness) was prepared using EVA-33 with PN23-200 as the top layer (1 mil) (49710J28836).

[0086] Table 7

[0087]

[0088]

[0089] use PN23-200 as the bottom layer (3 mils thickness), a layer of ATEVA-2861A (EVA-28) as the middle layer (2 mils thickness), and Asymmetric three-layer TPU / EVA / TPU films (6 mil total thickness) (49710J28837) were prepared using PN23-200 as the top layer (1 mil) and EVA-28. For the three-layer TPU / EVA / TPU embodiment, 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. The three coextruded asymmetric TPU / EVA / TPU resin compositions were extruded onto a PET carrier layer, MT44, Mitsubishi (0.002" x 68"), under the conditions shown in Table 8 below.

[0090] Table 8: Coextrusion conditions.

[0091] Temperature (F) Ext#1 EVA (middle) 320 Ext#2 EVA (main body) 340 Ext#3 EVA (outer skin) 350 Feed block 320-340 die head 340

[0092] A single layer TPU control film was prepared as a control (49320J2574) under the general conditions described herein. The EVA and TPU percent compositions and the optical and mechanical properties of the films are shown in Table 7. As also shown in Table 7, EVA-33 produced a similar 5% secant modulus to neat TPU, while EVA-28 was slightly higher / stiffer. The asymmetric design resolved the processing issues in the previous three layer trial (Example 2). There were no issues with sticking to the die lip and the initial haze was <1%. 3-EVA-28-1 completely resolved the flow defects and had fairly low gel levels. The material prepared with EVA-28 was acceptable for standard production. The thicker TPU layers had the opposite pattern, but the TPU outer skin was always 1 mil. As Figure 4 As shown, the UV transmittance curve of the asymmetric three-layer sample is very similar to that of the TPU control, but with slightly stronger barrier properties. Table 9 shows a summary of the hysteresis tests performed on the TPU / EVA / TPU films prepared in Example 3. Figure 5A and Figure 5B Shown are the results of accelerated aging evaluation of the film prepared in Example 3 compared to TPU control film 49320J2574.

[0093] Table 9: Summary of 10% Hysteresis Tests

[0094]

[0095]

[0096] Example 4: Comparative example - double-layer TPU / PVDF-PMMA and double-layer TPU film.

[0097] Now please refer to Figure 6A and Figure 6B , which shows the hysteresis curve of the multilayer film and is compared with Figure 7 For comparison, Figure 7 Hysteresis curves of the three-layer TPU / EVA / TPU film (EVA-33 and EVA-28) and the TPU film prepared in Example 3 are shown. Figure 6A The hysteresis curve for the bilayer TPU / PVDF-PMMA film is shown. The hysteresis curve for the bilayer TPU / PVDF-PMMA film shows that the force at 5% elongation is high (about 4 pounds).

[0098] Figure 6B The hysteresis curve for the dual-layer TPU film 49510-60DV shows the "high end" currently accepted by the industry - force at 5% elongation (about 2.2 pounds).

[0099] Figure 7Shown is the hysteresis curve of an asymmetric three-layer EVA / TPU / TPU film prepared with EVA-33 and EVA-22 compared to the hysteresis curve of a single layer of TPU in Example 3. The hysteresis curve of the three-layer EVA / TPU / TPU film prepared with EVA-33 and EVA-22 shows that the force at 5% elongation (about 1.5 pounds) is acceptable, that is, the value is equal to or lower than the force at 5% elongation of a single layer of TPU that is a recognized industry standard.

[0100] Installation tests showed that the TPU / PVDF-PMMA film was too stiff to be installed effectively. A double layer of 49510-60DV was the stiffest film acceptable in the industry. Based on these results, a target maximum value for the 5% secant modulus (a calculated value proportional to the initial force mentioned above) was determined. In addition, Figure 6A The hysteresis tests shown indicate higher residual strain on the membrane containing PVDF-PMMA.

[0101] Although the devices, systems, and methods have been described in detail herein with respect to certain preferred embodiments, numerous modifications and variations thereto will occur to those skilled in the art. Therefore, the foregoing description should not be construed as limited thereby, but rather should be construed to include the obvious variations described above, and to be limited only by the spirit and scope of the appended claims.

[0102] For example, in a first aspect, a first embodiment is a film comprising first and second thermoplastic polyurethane layers and an ethylene vinyl acetate layer positioned between the first and second thermoplastic polyurethane layers.

[0103] 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, wherein at least one of the first thickness, second thickness, and third thickness is different from the other thicknesses.

[0104] A third embodiment is any combination of the first two embodiments, wherein the film has a total thickness, and the thickness of the ethylene vinyl acetate (EVA) layer is from about 20% to about 70% of the total thickness.

[0105] A fourth embodiment is any combination of the first three embodiments, wherein the thickness of the EVA layer is from about 20% to about 55% of the total thickness.

[0106] A fifth embodiment is any combination of the first four embodiments, wherein the thickness of the EVA layer is from about 30% to about 35% of the total thickness.

[0107] A sixth embodiment is any combination of the first five embodiments, wherein the thickness of the EVA layer is about 33% of the total thickness.

[0108] A seventh embodiment is any combination of the first six embodiments, wherein the ethylene vinyl acetate layer has a thickness of about 2 mils to about 4 mils.

[0109] An eighth embodiment is any combination of the previous seven embodiments, wherein the first thermoplastic layer and the second thermoplastic layer have different thicknesses.

[0110] 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 about 1 mil to about 3 mils.

[0111] A tenth embodiment is any combination of the previous 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.

[0112] 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 mils, and the ethylene vinyl acetate layer has a thickness of about 2 mils.

[0113] A twelfth embodiment is any combination of the previous ten embodiments, wherein the ethylene vinyl acetate layer comprises a thermoplastic ethylene vinyl acetate copolymer having a vinyl acetate ratio of about 28% to about 33%.

[0114] A thirteenth embodiment is any combination of the previous twelve embodiments, wherein the first and second thermoplastic polyurethane layers comprise aliphatic thermoplastic polyurethane.

[0115] 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.

[0116] A fifteenth embodiment is any combination of the previous fourteen embodiments, further comprising a support layer.

[0117] A sixteenth embodiment is any combination of the previous fifteen embodiments, wherein the carrier layer comprises polyethylene terephthalate (PET).

[0118] The seventeenth embodiment is any combination of the previous sixteen embodiments, further comprising: a pressure sensitive adhesive layer, wherein the first thermoplastic polyurethane layer is adhered to the pressure sensitive adhesive layer; and a facing layer positioned on the second thermoplastic polyurethane layer.

[0119] An eighteenth embodiment is any combination of the previous seventeen embodiments, further comprising a release layer on an outer surface of the pressure-sensitive adhesive layer.

[0120] In another aspect, a window comprising the film of any one of the above 18 embodiments is provided.

[0121] In another aspect, there is provided a vehicle exterior part comprising the film of any one of the above 18 embodiments.

[0122] In another aspect, there is provided a turbine blade comprising the membrane of any one of the above 18 embodiments.

[0123] In another aspect, an electronic display comprising the film of any one of the above 18 embodiments is provided.

[0124] In another aspect, a protective coating for a surface includes first and second thermoplastic polyurethane layers and an ethylene vinyl acetate layer positioned between the first and second thermoplastic polyurethane layers. The protective coating has a 5% secant modulus of less than about 5000 psi.

[0125] A second embodiment is the first embodiment, wherein the 5% secant modulus is less than about 3600 psi.

[0126] A third embodiment is any combination of the first two embodiments, wherein the coating has an 8.5A chip rating as measured by a stone chip tester according to ASTM D3170.

[0127] A fourth embodiment is any combination of the first three embodiments, wherein the coating has an ultimate elongation in the longitudinal direction of about 450% to about 550%.

[0128] A fifth embodiment is any combination of the first four embodiments, wherein the ultimate elongation in the longitudinal direction is about 500%.

[0129] A sixth embodiment is any combination of the first five embodiments, wherein the coating has a light transmittance of at least about 93%.

[0130] A seventh embodiment is any combination of the first six embodiments, wherein the coating has a total thickness, and the thickness of the ethylene vinyl acetate (EVA) layer is from about 20% to about 70% of the total thickness.

[0131] An eighth embodiment is any combination of the first seven embodiments, wherein the thickness of the EVA layer is from about 20% to about 55% of the total thickness.

[0132] A ninth embodiment is any combination of the first eight embodiments, wherein the thickness of the EVA layer is from about 30% to about 35% of the total thickness.

[0133] A tenth embodiment is any combination of the previous nine embodiments, wherein the thickness of the EVA layer is about 33% of the total thickness.

[0134] An eleventh embodiment is any combination of the first ten embodiments, further comprising a pressure sensitive adhesive layer configured to adhere to a surface.

[0135] A twelfth embodiment is any combination of the previous eleven embodiments, further comprising a carrier layer on the second thermoplastic polyurethane layer.

[0136] A thirteenth embodiment is any combination of the previous twelve embodiments, wherein the surface is a painted surface.

[0137] A fourteenth embodiment is any combination of the previous thirteen embodiments, wherein the painted surface is an automobile.

[0138] In another aspect, a first embodiment is a method of manufacturing a surface protection film, the method comprising providing first and second polymer resins comprising thermoplastic polyurethane, providing an ethylene vinyl acetate resin comprising a thermoplastic ethylene vinyl acetate copolymer, and coextruding the first and second polymer resins and the ethylene vinyl acetate resin to form a surface protection film comprising first and second thermoplastic polyurethane layers and an ethylene vinyl acetate layer located between the first and second thermoplastic polyurethane layers.

[0139] A second embodiment is the first embodiment further comprising providing a carrier layer, and coextruding the first and second polymer resins and the ethylene vinyl acetate resin onto the carrier layer.

[0140] A third embodiment is any combination of the first two embodiments, wherein the first thermoplastic polyurethane layer has a first thickness, the second thermoplastic polyurethane layer has a second thickness, and the intermediate ethylene vinyl acetate layer has a third thickness, wherein at least one of the first thickness, the second thickness, and the third thickness is different from the others.

[0141] A fourth embodiment is any combination of the first three embodiments, wherein the first and second thermoplastic polyurethane layers and the intermediate ethylene vinyl acetate layer each have a thickness, and 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.

[0142] A fifth embodiment is any combination of the first four embodiments, wherein the second thermoplastic layer is coextruded adjacent to the carrier layer.

[0143] A sixth embodiment is any combination of the first five embodiments, wherein the surface protection film has a total thickness, and the thickness of the ethylene vinyl acetate (EVA) layer is from about 20% to about 70% of the total thickness.

[0144] A seventh embodiment is any combination of the first six embodiments, wherein the thickness of the EVA layer is from about 20% to about 55% of the total thickness.

[0145] An eighth embodiment is any combination of the first seven embodiments, wherein the thickness of the EVA layer is from about 30% to about 35% of the total thickness.

[0146] A ninth embodiment is any combination of the previous eight embodiments, wherein the thickness of the EVA layer is about 33% of the total thickness.

Claims

1. A membrane comprising: a first thermoplastic polyurethane (TPU) layer and a second thermoplastic polyurethane (TPU) layer; and An ethylene vinyl acetate (EVA) layer is positioned between the first thermoplastic polyurethane layer and the second thermoplastic polyurethane layer.

2. 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, wherein at least one of the first thickness, the second thickness, and the third thickness is different from the other thicknesses.

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

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

5. The film of claim 3, wherein the thickness of the EVA layer is from about 30% to about 35% of the total thickness. The film of claim 3 , wherein the thickness of the EVA layer 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. The film of claim 1, wherein the first TPU layer and the second TPU layer have different thicknesses.

9. 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 . The film of claim 1 , wherein a thickness of the first TPU layer is smaller than a thickness of the second TPU layer, and a thickness of the EVA layer is larger than a thickness of the first TPU layer.

11. 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. The film of claim 1, wherein the EVA layer comprises a thermoplastic ethylene vinyl acetate copolymer having a vinyl acetate ratio in the copolymer of about 28% to about 33%.

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

14. The film of claim 1, wherein the film has a 5% secant modulus of about 5000 psi or less.

15. The film of claim 1 further comprising a support layer.

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

17. A window comprising the film of claim 1.

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

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

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

21. The film of claim 1 , further comprising: a pressure-sensitive adhesive layer, wherein the first TPU layer is adhered to the pressure-sensitive adhesive layer; and A surface layer is located on the second TPU layer.

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

23. A protective coating for a surface, comprising: a first thermoplastic polyurethane (TPU) layer and a second thermoplastic polyurethane (TPU) layer; an ethylene vinyl acetate (EVA) layer positioned between the first TPU layer and the second TPU layer; and wherein the protective coating has a 5% secant modulus of less than about 5000 psi.

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

25. The coating of claim 23, wherein the coating has a chip rating of 8.5A as measured by a stone chip tester according to ASTM D3170.

26. The coating of claim 23, wherein the coating has an ultimate elongation in the longitudinal direction of about 450% to about 550%.

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

28. The coating of claim 23, wherein the coating has a light transmittance of at least about 93%.

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

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

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

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

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

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

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

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

37. A method for manufacturing a surface protection film, comprising: providing a first polymer resin comprising thermoplastic polyurethane (TPU) and a second polymer resin; Providing an ethylene vinyl acetate (EVA) resin comprising a thermoplastic ethylene vinyl acetate copolymer; as well as The first and second polymer resins and the ethylene vinyl acetate resin are co-extruded to form a surface protection film including a first and second TPU layers and an EVA layer located between the first and second TPU layers.

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

39. 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, wherein at least one of the first thickness, the second thickness, and the third thickness is different from the other thicknesses.

40. The method according to claim 37, wherein the first and second TPU layers and the EVA layer each have a thickness, and the thickness of the first TPU layer is less than the thickness of the second TPU layer, and the thickness of the EVA layer is greater than the thickness of the first TPU layer.

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

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

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

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

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

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