Coextruded polymer films with continuous release

Abstract

The present disclosure describes a multilayer polymer film configured such that a continuous constituent layer grouping can be delaminated from the remaining film in a continuous sheet form. The present disclosure further describes compositions, materials, and methods for minimizing the possibility of removing the multilayer groupings together, including by increasing the peel force between the layer groupings. In some embodiments, the peel force gradually increases from the interface between the first layer grouping and the second layer grouping to the interface between the second to last ((n-1)th layer grouping) and the last (nth layer grouping).

Description

Summary of the invention

[0001] The present disclosure describes a multilayer polymer film that is constructed so that the continuous constituent layer groups can be delaminated from the remaining film in a continuous sheet. Due to the continuous peeling force between the layer groups, the possibility of removing the multilayer groups together, rather than removing the single layer groups at a time, can be minimized.

[0002] In one aspect, the present disclosure describes a film comprising a coextruded stack of polymer layers. The polymer layers are organized into layer groups, each layer comprising a first layer A, a second layer B, and a third layer C. Layer B is disposed between layer A and layer C. The film also includes a group interface between layers A and C of adjacent layer groups, the group interface exhibiting a first peel force of 1 gram per inch or greater; a layer interface between adjacent layers A and B, the layer interface exhibiting a second peel force greater than the first peel force; and a layer interface between adjacent layers B and C, the layer interface exhibiting a third peel force greater than the first peel force. The layer groupings are capable of being irreversibly peeled off individually from the rest of the stack. The coextruded stack of polymer layers comprises at least a first layer grouping and a second layer grouping.

[0003] In some embodiments, each layer grouping includes a conformable layer including layer B and layer C, and the thickness of the conformable layer of the second layer grouping is greater than the thickness of the conformable layer of the first layer grouping.

[0004] In some embodiments, the thickness of layer A of the second layer grouping is less than the thickness of layer A of the first layer grouping.

[0005] In another aspect, the present disclosure describes a film comprising a coextruded stack of polymer layers. The polymer layers are organized into layer groups, each layer comprising a first layer A, a second layer B, and a third layer C. Layer B is disposed between layer A and layer C. Layer A of the film comprises a first polymer composition A, layer B of the film comprises a second polymer composition B, and layer C of the film comprises a third polymer composition C.

[0006] Polymer composition A comprises polyester, copolyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, polyurethane, aliphatic polyester, polyhydroxybutyrate, polyhydroxysuccinate, styrene copolymer, silicone, silicone thermoplastic, acrylic resin or copolymer or blend thereof. Polymer composition B comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymer or blend thereof. Polymer composition C comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymer or blend thereof.

[0007] The layer groupings are individually irreversibly peelable from the remainder of the stack.The coextruded stack of polymer layers comprises at least a first layer grouping and a second layer grouping.

[0008] In some embodiments, each layer grouping includes a conformable layer including layer B and layer C, and the thickness of the conformable layer of the second layer grouping is greater than the thickness of the conformable layer of the first layer grouping.

[0009] In some embodiments, the thickness of layer A of the second layer grouping is less than the thickness of layer A of the first layer grouping.

[0010] In another aspect, the present disclosure describes a face mask comprising the multilayer polymer film as described herein.

[0011] The words "preferred" and "preferably" refer to embodiments of the present invention that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, and is not intended to exclude other embodiments from the scope of the present invention.

[0012] The term "comprise" and variations thereof do not have a limiting meaning where these terms appear in the specification and claims. Such terms will be understood to imply the inclusion of the stated steps or elements or groups of steps or elements but not the exclusion of any other steps or elements or groups of steps or elements.

[0013] By "consisting of is meant including and limited to what follows the phrase "consisting of." Thus, the phrase "consisting of" indicates that the listed elements are required or mandatory, and that no other elements may be present. By "consisting essentially of" is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified for the listed elements in this disclosure. Thus, the phrase "consisting essentially of" indicates that the listed elements are required or mandatory, but other elements are optional and may or may not be present, depending on whether they substantially affect the activity or action of the listed elements.

[0014] Unless specifically stated otherwise, "a," "an," "the," and "at least one" are used interchangeably and mean one or more than one.

[0015] As used herein, the term "or" is generally used in its ordinary sense including "and / or" unless the context clearly dictates otherwise.

[0016] The term "and / or" means one or all of the listed elements, or a combination of any two or more of the listed elements.

[0017] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0018] As used herein, "up to" a number (eg, up to 50) includes the number (eg, 50).

[0019] The terms "in the range" or "within a range" (and similar expressions) include the endpoints of the range.

[0020] For any method disclosed herein including discrete steps, the steps may be performed in any feasible order. In addition, any combination of two or more steps may be performed simultaneously, where appropriate.

[0021] All headings are for the convenience of the reader and should not be used to limit the meaning of the text that follows the heading unless so specified.

[0022] References throughout this specification to "one embodiment," "an embodiment," "certain embodiments," or "some embodiments," etc., mean that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearance of such phrases in various places throughout this specification are not necessarily referring to the same embodiment in the present disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

[0023] Unless otherwise indicated, all numbers used in the specification and claims indicating components, molecular weights, etc., are to be understood as being modified by the term "about" in all cases. As used herein, with respect to a measured amount, the term "about" refers to a deviation in the measured amount that would be expected by a skilled person who would take a certain degree of care in making the measurements, commensurate with the objective of the measurements and the precision of the measuring equipment used. Therefore, unless otherwise indicated, the numerical parameters set forth in the specification and claims are approximate values ​​that may vary with the desired properties sought to be obtained by the present invention. At a minimum, without intending to limit the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of significant figures reported and using customary rounding techniques.

[0024] Although the numerical ranges and parameters set forth within the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Nevertheless, all numerical values ​​inherently encompass a range inevitably resulting from the standard deviation found in their respective testing procedures.

[0025] The above summary of the invention of the present invention is not intended to describe each disclosed embodiment or each implementation mode of the present invention. The following description more specifically illustrates exemplary embodiments. In several places throughout this application, guidance is provided by example lists, which can be used in various combinations. In each case, the cited list is only used as a representative group and should not be interpreted as an exclusive list. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A Schematic side or cross-sectional views of a grouping of layers of a polymer film. Figure 1B-Figure 1E is a schematic side view or cross-sectional view of an exemplary polymer film comprising layer groupings and configured for continuous irreversible delamination.

[0027] Figure 2A is a schematic side view or cross-sectional view of a polymer film configured for continuous irreversible delamination. Figure 2B-Figure 2D When the successive layers are grouped and separated from the film, Figure 2A Schematic side view or cross-sectional view of a polymer film.

[0028] Figure 3A is a schematic side view or cross-sectional view of a polymer film including a substrate layer and configured for continuous irreversible delamination. Figure 3B-Figure 3E When the successive layers are grouped and separated from the film, Figure 3A Schematic side view or cross-sectional view of a polymer film.

[0029] Figure 4Schematic diagram of a manufacturing system for coextruding three polymer materials to form a multilayer polymer film.

[0030] Figure 5 Schematic diagram of a film processing apparatus that can be used to stretch cast multilayer polymer films.

[0031] Figure 6 is a schematic front view of a face mask comprising a polymer film including groupings of layers configured for continuous irreversible delamination.

[0032] Figure 7 is a graph of the peel force in grams per inch (g / inch) of a layer of polymer film that underwent continuous irreversible delamination in grams per inch (g / inch) prepared and measured as described in Example 1.

[0033] Figure 8 is a graph of the peel force in grams per inch (g / inch) of a layer of polymer film that underwent continuous irreversible delamination in grams per inch (g / inch) prepared and measured as described in Comparative Example 1. DETAILED DESCRIPTION

[0034] The present disclosure describes a polymer material combination that, when incorporated into a coextruded stack of polymer layers, can be used to produce a multilayer polymer film comprising many layer groups that can be layered or peeled off from the remaining film one layer group at a time. The stack of polymer layers is arranged or organized to form layer groups, each layer group having at least two layers of these polymer layers. In contrast to the films of U.S. Applications 2015 / 0183178A1, 2019 / 0248117A1, and 2019 / 0248118A1, the films disclosed herein exhibit a gradient peeling force between layer groups throughout the stack of polymer layers. The gradient can be increased so that the peeling force gradually increases from the interface between the first layer grouping and the second layer grouping to the interface between the penultimate ((n-1)th layer grouping) and the last (nth layer grouping). The gradient peeling force reduces the possibility of removing multiple layer groups together rather than removing a single layer grouping from the stack of polymer layers.

[0035] These films can be made by coextruding all of the polymer layers in the stack, without the need to laminate separately manufactured films or layers to construct the stack. This construction allows individual layer groupings (which can be peeled off in sequence) to be made much thinner than otherwise formed layer groupings, so that more individually peelable sheets can be included in a film of a given overall thickness. In addition, coextruded layers are less susceptible to contamination during manufacturing than layers that are prepared separately and then laminated together.

[0036] Films can also be made without requiring any pressure sensitive adhesive or other type of adhesive in the stack of polymer layers. The absence of adhesive can simplify manufacturing and also produce a film surface that is located inside the film in the initial finished product but becomes the exterior surface when the layer groups are peeled off during use, which is purer than the film surface that can be achieved in a film made using a separate lamination step.

[0037] Some features of the peelable polymer films described in commonly assigned U.S. publications 2015 / 0183178A1, 2019 / 0248117A1, and 2019 / 0248118A1 and International publication WO 2019 / 032635 (including, for example, the composition of the polymers of the polymer layers in the layer groupings or the method of making the polymer stack) may be applicable to the films disclosed herein that exhibit gradient peel forces between layer groupings in the entire stack of polymer layers.

[0038] Specific embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described in the accompanying drawings. In the accompanying drawings, like numbers represent like elements.

[0039] Figure 1A Exemplary polymer layers of layer groupings are shown in FIG. Figure 1A As shown in FIG, each layer grouping includes a first layer A, a second layer B, and a third layer C, labeled 142, 144, and 146, respectively. Layer B 144 is disposed between layer A 142 and layer C 146. Layer B 144 and layer C 146 may together form conformable layer 132. In some embodiments, layer B 144 and layer C 146 may have the same composition, and in those embodiments, the layer grouping may be considered to include two layers, layer A 142 and a conformable layer.

[0040] In some embodiments, such as Figure 1A , the conformable layer 132 may include layer B 144 and layer C 146 having the same thickness. However, in some embodiments, when the coextruded stack of polymeric layers exhibits a thickness gradient for the conformable layer, as further described below, layer B may increase in thickness while the thickness of layer C remains constant, or layer C may increase in thickness while the thickness of layer B remains constant, or both layer B and layer C may increase in thickness such that the ratio of the thickness of layer B to the thickness of layer C remains constant throughout the depth of the stack of polymeric layers.

[0041] Layer A, layer B, and layer C can each be formed from any suitable polymer composition. In some embodiments, layer A can include a first polymer composition A, layer B can include a second polymer composition B, and layer C can include a third polymer composition C. In some embodiments, polymer composition B can be different from polymer composition A, and polymer composition C can be different from polymer composition A. In other embodiments, polymer composition C can be different from polymer composition A and polymer composition B. In some embodiments, polymer composition B can be different from polymer composition A, and polymer composition C can be different from polymer composition A, but polymer composition B can be the same as polymer composition C.

[0042] In some embodiments, polymer compositions A, B, and C are preferably melt processable at a temperature of at least 204°C (400°F).

[0043] In some embodiments, polymer composition A, B and C or their combination can be polyester-based materials, but other suitable materials can also be used. For example, polymer composition A can be or can include polyester, copolyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, polyurethane, aliphatic polyester such as polylactic acid, polyhydroxybutyrate, polyhydroxysuccinate, styrene copolymer, silicone, silicone thermoplastic, acrylic resin or their copolymer and / or blend. In an exemplary embodiment, polymer composition A can be or can include polyethylene terephthalate (PET). In some embodiments, polymer composition B or polymer composition C or both can be or can include polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester such as polyhydroxybutyrate, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or their copolymer and / or blend. Exemplary polyolefins include polypropylene and polyethylene. In an exemplary embodiment, polymer composition B or polymer composition C or both can be or can include a copolymer based on styrene and ethylene / butylene. For example, polymer composition B or polymer composition C or both can be or can include KRATON G1645 (Kraton Corporation, Houston, TX), a linear triblock copolymer based on styrene and ethylene / butylene. The copolymer can be a block copolymer, a random copolymer, or a combination of the two copolymers.

[0044] In some embodiments, polymer composition B and polymer composition A or polymer composition C are preferably polyester-based materials. As further described in U.S. Publication No. 2019 / 0248117, the combination of polyester and non-polyester-based materials is appropriately incorporated into layer B, layer A, or layer C of the layer grouping, so that the layer grouping can be preferentially delaminated along the interface between adjacent layer groups (e.g., between layer C and layer A) rather than delaminated within the layer grouping (e.g., between layer A and layer B or layer B and layer C).

[0045] about Figure 1A In the three-layer embodiment of the present invention, delamination between layer C and layer A can be achieved by making the attachment of layer C to layer A weaker than the attachment of layer C to layer B, and weaker than the attachment of layer B to layer A. In some embodiments, preferential delamination between layer groupings (e.g., between adjacent layers C and layer A) can be achieved by using a blend of a polypropylene copolymer with an appropriate amount of another resin for polymer composition C. For example, polymer composition C can be a miscible blend of a propylene copolymer and a styrene block copolymer, or a miscible blend of a propylene copolymer and an ethylene alpha olefin copolymer, or a miscible blend of a propylene copolymer and an olefin block copolymer. In the case where polymer composition C is a miscible blend of a propylene copolymer and a styrene block copolymer, polymer composition B can be an immiscible blend of a copolyester and an olefin, and polymer composition A can be a semi-crystalline polyester optionally blended with an amorphous copolyester, or polymer composition B can be an amorphous copolyester and polymer composition A can be a semi-crystalline polyester. When polymer composition A is a blend of a semicrystalline polyester and an amorphous copolyester, the composition may contain up to 50% amorphous copolyester, but in some embodiments, including when cost is a factor, up to 20% amorphous copolyester may be preferred.

[0046] In some cases, although polymer composition C is at least partially miscible with polymer composition B, and polymer composition B is at least partially miscible with polymer composition A, polymer composition C is not miscible with polymer composition A. As used herein, if at least one component of an immiscible blend is miscible with another polymer composition (or if another polymer composition is also an immiscible blend or block copolymer, wherein "component" refers to a single block region of a block copolymer, then at least one component of another polymer composition) is miscible, then a given polymer composition as an immiscible blend of polymers, such as any one of polymer compositions A, B or C, may be referred to as being at least partially miscible with another polymer composition. As described above, even if the attachment between the polymer A layer and the polymer C layer may be the weakest, such attachment may still be greater than zero. For example, the peel force at the packet interface (between adjacent layers A and C) may be at least 1 gram / inch, or at least 2 grams / inch. The peel force unit grams / inch (or grams / inch width) abbreviated as g / in is sometimes referred to as grams / line inch (abbreviated as gli). One (1) g / in is equal to 0.3860886 N / m.

[0047] For purposes of the present invention, the terms "miscible," "miscibility," and the like do not imply a requirement in an absolute sense that the two or more polymers under consideration form a constant spatial composition of a homogeneous phase, but rather in a relative sense that there is sufficient interdiffusion of the two or more polymers to provide significant entanglement interactions across the interface between the phases, and / or what is sometimes referred to in the literature as an "interphase" between layers. This relative sense of miscibility is also sometimes referred to in the polymer science literature as "compatibility" or "partial miscibility." Additionally, for example, a homopolymer or random copolymer may be said to exhibit miscibility with a block copolymer in this sense, wherein it has such an ability to interact with regions of only one block of the block copolymer, even though the homopolymer or copolymer is completely immiscible with regions of the other blocks of the block copolymer.

[0048] In addition to miscibility differences, the presence of macromolecular orientation or crystallinity, or both, in at least one component of an adjacent layer (e.g., in adjacent layer A or layer B, or both) can affect the peel force of the adjacent layer due to a reduction in intermolecular entanglement across the interface between the two layers. Intermolecular entanglement may be caused by reduced mobility of polymer molecules in molecular orientation (rather than random coil configuration), involving structured crystallites (rather than an amorphous state), or both. In other words, morphology (e.g., crystallinity) and composition can be used to influence the relative peel force among a layer pair.

[0049] For example, the peel force between adjacent layers can be increased by increasing molecular orientation or crystallinity, or both. In some embodiments, at least one of layer A, layer B, or layer C comprises a crystalline or semi-crystalline polymer. In one embodiment, layer A comprises a crystalline or semi-crystalline polymer.

[0050] In some embodiments, polymer composition A, polymer composition B and polymer composition C may independently include one or more polymers selected from the following: polyesters, polyolefins, poly-α-olefins, polymethacrylates, polycarbonates, polycarbonate alloys, polyurethanes, polylactic acid, polyhydroxybutyrates, polyhydroxysuccinates, styrene copolymers, silicones, or copolymers or blends thereof.

[0051] In some embodiments, polymer composition A comprises polyester, copolyester, acrylic resin or silicone thermoplastic, or a combination thereof (including, for example, a blend). In some embodiments, polymer composition A can be selected from polyester, copolyester, acrylic resin and silicone thermoplastic. In some embodiments, polymer composition A comprises semi-crystalline polyester. In an exemplary embodiment, polymer composition A comprises polyethylene terephthalate (PET).

[0052] In some embodiments, polymer composition B comprises copolyester, PMMA, co-PMMA, styrene block copolymer, polypropylene or silicone polyoxamide, or a combination thereof (including, for example, a blend). In some embodiments, polymer composition B can be selected from a variety of polymers and polymer blends, including, but not limited to, copolyester, PMMA, co-PMMA, styrene block copolymer, polypropylene and silicone polyoxamide, and in some embodiments, polymer composition B comprises copolyester or styrene block copolymer, or a combination thereof (including, for example, a blend). In an exemplary embodiment, polymer composition B comprises a copolymer based on styrene and ethylene / butylene, including, for example, KRATON G1645 (Kraton Corporation, Houston, Texas), a linear triblock copolymer based on styrene and ethylene / butylene.

[0053] In some embodiments, polymer composition C can be selected from blends of olefins, such as blends of polypropylene or polyethylene with a suitable amount of styrene block copolymers or ethylene alpha olefin copolymers or olefin block copolymers. In some embodiments, polymer composition C comprises olefins or styrene block copolymers, or combinations thereof (including, for example, blends). In exemplary embodiments, polymer composition C comprises copolymers based on styrene and ethylene / butylene, including, for example, KRATON G1645 (Kraton, Houston, Texas), linear triblock copolymers based on styrene and ethylene / butylene.

[0054] It should be noted that not all combinations of the aforementioned compositions applicable to different polymer compositions will produce the desired results, and judgment must be used to identify the appropriate combination of polymer materials for use in different types of layers to achieve the desired functions and layered characteristics. For example, polymer composition A can be or include a semi-crystalline polyester, polymer composition C can be or include a blend of polypropylene and a styrene block copolymer, an ethylene alpha olefin copolymer, or an olefin block copolymer, and polymer composition B can be or include a copolyester. For another example, polymer composition A can be or include polymethyl methacrylate (PMMA) or co-PMMA, polymer composition C can be or include a blend of polypropylene and a styrene block copolymer, and polymer composition B can be a blend of PMMA or co-PMMA and a styrene block copolymer or polypropylene. For another example, polymer composition A can be or include silicone polyoxamide, polymer composition C can be or include polypropylene and a styrene block copolymer, and polymer composition B can be a styrene block copolymer.

[0055] In some embodiments, polymer composition C is at least partially miscible with polymer composition B. In some embodiments, polymer composition B is at least partially miscible with polymer composition A. In some embodiments, polymer composition C is immiscible with polymer composition A. In some embodiments, polymer composition C is at least partially miscible with polymer composition B, and polymer composition B is at least partially miscible with polymer composition A, and polymer composition C is immiscible with polymer composition A.

[0056] One or more optional additives may also be included in some or all of the compositions. Optional additives include, for example, UV light stabilizers, antimicrobial agents, beads or other particles of suitable size and / or other required additives. In some embodiments, additives may be dispersed in the layer A of each layer grouping, but may not be present in any layer in the other polymer layers. In some embodiments, additives may exist as continuous or co-continuous phase materials. In some embodiments, additives may also be dissolved in one, some or all layers of the layers of the stack.

[0057] In some embodiments, layer A, layer B, or layer C, or a combination thereof, comprises one or more ultraviolet (UV) light stabilizers. In some embodiments, layer A, layer B, or layer C, or a combination thereof, does not comprise a UV light stabilizer.

[0058] In some embodiments, layer A, layer B, or layer C, or a combination thereof, comprises one or more organic antimicrobial agents. In some embodiments, layer A, layer B, or layer C, or a combination thereof, does not comprise an antimicrobial agent.

[0059] In some embodiments, layer A and layer B, or layer A and layer C, or layer B and layer C, or some combination thereof, can be oriented. Such oriented layers can have a minimum level of birefringence, including, for example, birefringence of 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.07 or greater, or 0.10 or greater. In this regard, a given material or layer of material is considered to be birefringent when its refractive index for light polarized in one direction is different from its refractive index for light polarized in a different direction. The "birefringence" of the material or layer of material is the maximum difference between such refractive indices. In some cases, this maximum difference may occur at two orthogonal axes (e.g., Figure 1B-Figure 1E 2 and 3), while in other cases, such a maximum difference may occur between two orthogonal axes (e.g., Figure 1B-Figure 1E , between the x-axis and the z-axis shown in Figures 2 and 3).

[0060] Figure 1A Three layers (ABC) of layer grouping are illustrated. The layers may be organized differently, or other layer types (e.g., polymer layers D, E, etc.) may be added to the stack so that the layer grouping includes more than three separate polymer layers. For example, A, B, C layers may be arranged into A, B, A, B, C, A, B, A, B, C, etc., so that each layer grouping is a 5-layer group (ABABC) of polymer layers. In this case, the attachment of the C layer to the A layer will be made significantly weaker than the attachment of the C layer to the B layer and weaker than the attachment of the B layer to the A layer, so that a delamination surface will be formed at the grouping interface between the C layer and the A layer. However, to ensure that the film is not just broken, the attachment of the C layer to the A layer is characterized by a peeling force greater than zero. For example, the peeling force between adjacent C layers and the A layer may be 0.8 g / inch or more, 1 g / inch or more, 1.5 g / inch or more, or 2 g / inch or more.

[0061] In one example, a polymer layer D made of a polymer composition D different from compositions A, B, and C can be added to the stack of layers. According to one embodiment, the polymer compositions are co-extruded with each other so that the entire stack of layers can be co-extruded in a single operation. In some embodiments, the polymer composition D is preferably melt-processable at a temperature of at least 204° C. (400° F.). In some cases, none of the compositions A, B, C, D is a pressure sensitive adhesive (PSA) or other type of adhesive.

[0062] Preferably, any additional polymer layers are added in such a way that the modified stack can be prepared by a single coextrusion process and the sheets or layer groupings can be sequentially irreversibly delaminated from the rest of the layer stack of the multilayer polymer film. The modified stack including the additional polymer layers can remain free of adhesive or PSA.

[0063] In some embodiments, any or all of the polymer layers A, B, C, D, etc. can be oriented. Such oriented layers can have a minimum level of birefringence, including, for example, birefringence of 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.07 or greater, or 0.10 or greater.

[0064] like Figure 1B-Figure 1E As shown in FIG. 1 , layer groupings 122b, 122c, 122d, 122e, 124b, 124c, 124d, 124e, 126b, 126c, 128b, 128c may be organized into a coextruded stack of polymer layers. The coextruded stack of polymer layers may include as few as two layer groupings, but as shown in FIG. Figure 1B-Figure 1E In some embodiments, the stack may include any suitable number (n) of layer groups. The number of layer groups may be selected by those skilled in the art for ease of manufacture or intended use of the coextruded stack of polymer layers. In some embodiments, the coextruded stack of polymer layers includes n layer groups. In some embodiments, the nth layer grouping is the second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth, twentieth or twenty-first layer grouping. One benefit of preparing a polymer layer in a single coextrusion operation is that up to twenty or more very thin layer groups (which can be sequentially removed in a continuous sheet form) can be incorporated into the polymer film.

[0065] In some embodiments, the peel force between adjacent layer groups (i.e., at the group interface) increases from one group interface to the next group interface. This increased peel force can help prevent more than one layer group from being peeled at the same time. However, even at the last group interface, the peel force is less than the peel force within a given group (i.e., at the layer interface within the group).

[0066] In some embodiments, the coextruded stack of polymer layers may exhibit a peel force gradient from the first layer grouping to the nth layer grouping. For example, the peel force at the grouping interface between layer A of the second layer grouping and layer C of the first layer grouping may be less than the peel force between layer A of the third layer grouping and layer C of the second layer grouping. The peel force at the grouping interface between layer A of the second layer grouping and layer C of the first layer grouping may be less than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping. The peel force at each successive grouping interface may be greater than the peel force at the previous grouping interface.

[0067] In some embodiments, the peel force at the packet interface between layer A of the second layer grouping and layer C of the first layer grouping is at least 5 times, at least 10 times, at least 100 times, or at least 250 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping. In some embodiments, the peel force at the packet interface between layer A of the second layer grouping and layer C of the first layer grouping is at most 500 times, at most 250 times, at most 100 times, or at most 10 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping. For example, in an exemplary embodiment, the peel force at the packet interface between layer A of the second layer grouping and layer C of the first layer grouping is 500 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0068] In some embodiments, the peel force at each continuous group interface increases by at least 0.5%, at least 1%, at least 5%, at least 10%, at least 20%, at least 50%, or at least 100% relative to the previous group interface. In some embodiments, the peel force at each continuous group interface can increase by at most 1%, at most 5%, at most 10%, at most 20%, at most 50%, at most 100%, at most 1000%, at most 10,000%, or at most 50,000% relative to the previous group interface.

[0069] In some embodiments, the coextruded stack of polymer layers may exhibit a thickness gradient of layer A, B, or C, or a combination thereof, from the first layer grouping to the nth layer grouping. In one embodiment, the coextruded stack of polymer layers exhibits a thickness gradient of layer A. The gradient may be a decrease in the thickness of layer A in the stack from the first layer grouping to the nth layer grouping. In one embodiment, the coextruded stack of polymer layers exhibits a thickness gradient of layer B or layer C, or a combined thickness of layer B and layer C. The gradient may be an increase in the thickness of layer B or layer C, or a combined thickness of layer B and layer C in the stack from the first layer grouping to the nth layer grouping.

[0070] In an exemplary embodiment, Figure 1BAs shown in FIG. 1 , the coextruded stack of polymer layers exhibits a thickness gradient from the first layer grouping to the conformable layer (including layer B and layer C) of the nth layer grouping. In some embodiments, as Figure 1B As shown, the thickness of the conformable layer of the first layer grouping 122b is less than the thickness of the conformable layer of the nth layer grouping 128b. The thickness of the conformable layer (e.g., combined layers B and C) can increase continuously from the first layer grouping to the nth layer grouping throughout the stack.

[0071] In some embodiments, the thickness of the conformable layer of the first layer grouping can be at least 1.1 times, at least 1.2 times, at least 1.5 times, or at least 2 times smaller than the thickness of the conformable layer of the nth layer grouping. In some embodiments, the thickness of the conformable layer of the first layer grouping can be at most 2 times, at most 5 times, or at most 10 times smaller than the thickness of the conformable layer of the nth layer grouping. According to one embodiment and as described in Example 1, as the thickness of each conformable layer increases (compared to the previous conformable layer), the peel force from one grouping interface to the next grouping interface increases. In an exemplary embodiment, the thickness of the conformable layer of the first layer grouping can be 3 times smaller than the thickness of the conformable layer of the nth layer grouping.

[0072] In some embodiments, the thickness of the conformable layer of each successive layer grouping increases by at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, or at least 30%. In some embodiments, the thickness of the conformable layer of each layer grouping increases by up to 50%, up to 100%, up to 200%, up to 500%, or up to 1000%. In some embodiments, the thickness of the conformable layer of each successive layer grouping increases by 5% to 500%, 10% to 200%, or 15% to 100%. As described in Example 1, in some embodiments, a 20% change in the thickness of the conformable layer from one layer to the next can provide a peel force difference of about 0.5 g / in.

[0073] In some embodiments, the sum of the thicknesses of all conformable layers in a stack of polymeric layers can be at least 10 microns, at least 15 microns, at least 20 microns, at least 25 microns (about 1.0 mil), at least 30 microns, at least 35 microns, at least 40 microns (about 1.6 mils), at least 45 microns, at least 50 microns (about 2.0 mils), at least 55 microns, at least 60 microns, at least 65 microns (about 2.5 mils), at least 70 microns, at least 80 microns, at least 90 microns, or at least 100 microns. In some embodiments, the sum of the thicknesses of all conformable layers in a stack of polymeric layers may be at most 300 microns, at most 200 microns, at most 100 microns, at most 90 microns, at most 80 microns, at most 70 microns, at most 65 microns (about 2.5 mils), at most 60 microns, at most 55 microns, at most 50 microns (about 2.0 mils), at most 45 microns, at most 40 microns (about 1.6 mils), at most 35 microns, at most 30 microns, at most 25 microns (about 1.0 mil). In some embodiments, the sum of the thicknesses of all conformable layers in a stack of polymeric layers may be from 20 microns to 200 microns, or from 25 microns to 100 microns.

[0074] As described in Example 1, the thickness of each conformable layer in the stack of polymeric layers can be added together to form the "sum of the thickness of the conformable layers". As the sum of the thickness of the conformable layers increases, the difference in peel force from layer grouping to layer grouping increases. In some embodiments, the upper end of the sum of the thickness of the conformable layers can be determined by the extrusion and / or film orientation capabilities.

[0075] In some embodiments, a coextruded stack of polymeric layers may exhibit both a peel force gradient and a thickness gradient. In some embodiments, a peel force gradient between layer groupings in a stack of polymeric layers is achieved by varying the ratio of the thickness of the conformable layer to the thickness of layer A throughout the stack. In some embodiments, the thickness of layer A, the thickness of layer B, the thickness of layer C, or a combination thereof varies.

[0076] In an exemplary embodiment, Figure 1C As shown in , the coextruded stack of polymer layers exhibits a thickness gradient from the first layer grouping to the layer A of the nth layer grouping. In some embodiments, as Figure 1C As shown in FIG. 1 , the thickness of layer A of the first layer grouping 122 c is less than the thickness of layer A of the n-th layer grouping 128 c. The thickness of layer A decreases continuously in adjacent layer groups.

[0077] In some embodiments, the thickness of layer A of the first layer grouping may be at least 1.1 times, at least 1.2 times, at least 1.5 times, or at least 2 times greater than the thickness of layer A of the nth layer grouping. In some embodiments, the thickness of layer A of the first layer grouping may be at most 2 times, at most 5 times, or at most 10 times greater than the thickness of layer A of the nth layer grouping. In an exemplary embodiment, the thickness of layer A of the first layer grouping may be 3 times greater than the thickness of layer A of the nth layer grouping.

[0078] In some embodiments, the thickness of layer A of each layer grouping decreases from one layer grouping to the next by at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, or at least 30%. In some embodiments, the thickness of layer A of each layer grouping decreases from one layer grouping to the next by at most 50%, at most 100%, at most 200%, at most 500%, or at most 1000%.

[0079] In some embodiments, both the thickness of the conformable layer and the thickness of layer A may vary throughout the stack. Figure 1D As shown in , as the thickness of the conformable layer increases from the first layer to the nth layer, the thickness of layer A decreases from the first layer to the nth layer. Figure 1E As shown in , the thickness of the conformable layer and the thickness of layer A can increase from the first layer to the nth layer. Therefore, the ratio of the thickness of layer A to the thickness of the conformable layer remains constant throughout the depth of the stack. Without wishing to be bound by theory, it is believed that the thicker A layer that is semi-crystalline or mostly semi-crystalline is harder and easier to initiate peeling.

[0080] The front main surface and the rear main surface of the adjacent layer groupings are in close contact with each other, thereby forming a grouping interface. Each layer grouping in the layer grouping has at least two polymer layers arranged between the front main surface and the rear main surface: a polymer layer A and a conformable layer (which may include a monolayer or layer B and layer C). As shown in the figure, the layer A of a given grouping is the front polymer layer in the grouping, and layer B is the last polymer layer in the grouping. The stack of layer groups can be configured so that the front polymer layer is intended to be peeled off first. The last polymer layer can be formed or attached to the workpiece. For example, the last polymer layer can be attached to a mask, such as a face mask, a set of safety glasses, a pair of sunglasses, safety goggles, ski goggles or another application in which removing contaminants on the surface may be beneficial. In one embodiment, the stack of layer groups is co-extruded with the workpiece or a part of the workpiece, such as a mask, a safety glasses, sunglasses, a safety goggles, a ski goggles, etc. The shield or lens.

[0081] In some embodiments, the thickness of the individual layer groupings in the coextruded stack of polymer layers is at most 10 microns, at most 25 microns, at most 50 microns, at most 75 microns, at most 100 microns, at most 125 microns, or at most 150 microns. In some embodiments, the thickness of the individual layer groupings in the coextruded stack of polymer layers is at least 1 micron, at least 5 microns, at least 10 microns, at least 25 microns, at least 50 microns, at least 75 microns, at least 100 microns, or at least 125 microns.

[0082] Figure 2A Schematically illustrate exemplary multilayer polymer film.In this exemplary embodiment, film 210a is made of the stack 220a of polymer layer.Film 210a is relatively thin and flexible usually, so that it can be applied to wavy profile rather than flat workpiece and conform to it.For example, film 210a can have at most 510 microns (about 20 mils), at most 380 microns (about 15 mils), at most 300 microns, at most 200 microns, at most 100 microns or at most 50 microns overall thickness.In some embodiments, film 210a can have at least 25 microns, at least 50 microns, at least 100 microns, at least 200 microns, at least 300 microns or at least 380 microns overall thickness.

[0083] Alternatively, in some cases, it is desirable that the film 210a is relatively thick and inflexible or rigid. For example, when the film is used in an application such as a face mask, where at least a portion of the film is unsupported, a more rigid film may be preferred. In some embodiments, the Young's modulus of the film may be at least 1 GPa, at least 2 GPa, or at least 3 GPa. In some embodiments, the Young's modulus of the film may be at most 3 GPa, at most 4 GPa, at most 5 GPa, or at most 10 GPa. (For reference, the Young's modulus of steel is about 200 GPa).

[0084] Figure 2A The polymer film 210a includes layer groups 222, 224, 226, and 228. Four layer groups are shown. However, the polymer film 210a may include more than four layer groups, such as at most 10, at most 15, at most 20, at most 25, or at most 30 layer groups. The layer groups can be irreversibly peeled off individually from the rest of the stack.

[0085] Each layer grouping (222, 224, 226 and 228) includes layer A (layers 242a, 242b, 242c and 242d of layer groupings 222, 224, 226 and 228, respectively) and a conformable layer (conformable layers 232a, 232b, 232c, 232d of layer groupings 222, 224, 226 and 228, respectively). Each layer grouping is characterized by a front major surface and a rear major surface. Layer grouping 222 has a front major surface 222a and a rear major surface 222b. Layer grouping 224 has a front major surface 224a (which is in close contact with the rear major surface 222b) and a rear major surface 224b. Layer grouping 226 has a front major surface 226a (which is in close contact with the rear major surface 224b) and a rear major surface 226b. The layer grouping 228 has a front major surface 228a (which is in close contact with the rear major surface 226b) and a rear major surface 228b.

[0086] As used in the context of this discussion, the terms "front," "rear," and the like (e.g., frontmost, backmost) are used for convenience to designate the ordering of the layers relative to the outer major surfaces of the film or stack, and should not be interpreted in a limiting manner. Thus, even for a film or grouping that is intended to have one outer major surface facing outward (front) and another outer major surface facing inward (rear), either of the outer major surfaces may be considered "front" and the other outer major surface would be considered "rear." In some embodiments, the first layer grouping may be the frontmost layer grouping of a coextruded stack of polymeric layers.

[0087] The polymer composition of each layer of the layer grouping is tailored so that the last polymer layer (e.g., layer C) is less attached to the frontmost polymer layer (e.g., layer A) than to the inner polymer layers (e.g., layer B). Thus, the first layer grouping tends to irreversibly delaminate from the second layer grouping along a delamination surface corresponding to the interface between the layer groupings.

[0088] For example, in some embodiments, the group interface between layer A and layer C of adjacent layer groupings exhibits a first peel force; the layer interface between adjacent layer A and layer B exhibits a second peel force greater than the first peel force; and the layer interface between adjacent layer B and layer C exhibits a third peel force greater than the first peel force. In some embodiments, the third peel force is greater than the second peel force.

[0089] In some embodiments, the first peel force is 0.8 g / in or greater, 1 g / in or greater, 1.5 g / in or greater, 2 g / in or greater, or 5 g / in or greater. In some embodiments, the first peel force is up to 500 g / in.

[0090] In some embodiments, the second peel force is at least 1.02 times, at least 1.04 times, at least 1.07 times, at least 1.1 times, at least 2 times, or at least 3 times the first peel force. In some embodiments, the second peel force is up to 500 times the second peel force.

[0091] In some embodiments, the third peel force is at least 1.02 times, at least 1.04 times, at least 1.07 times, at least 1.1 times, at least 2 times, or at least 3 times the first peel force. In some embodiments, the third peel force is up to 500 times the first peel force.

[0092] Figure 2A The film is constructed so that successive layer groups can be delaminated from the remaining film in a continuous sheet. Figure 2A The film is configured such that the first peel force increases from the first grouping interface (between the first layer grouping 222 and the second layer grouping 224) to the last grouping interface (between the third layer grouping 226 and the fourth layer grouping 228). However, even if the first peel force is increased at the grouping interface, the second peel force and the third peel force are greater than the first peel force to promote delamination at the grouping interface.

[0093] The stratification is based on FIG. 2B to FIG. 2D The sequence is shown. Figure 2B By removing the top or frontmost group 222, Figure 2A The film 210a of the present invention is changed into the modified film 210b. The delamination of each layer grouping can be initiated by pulling at the top layer grouping. As discussed further below, delamination can be assisted by applying a knife or other sharp tool on the edge of the film 210a, by applying an adhesive tape (including, for example, Scotch brand tape (3M Company, St. Paul, MN)) on the top layer grouping, or by using a tab or tab-like feature.

[0094] Layer grouping 222 is delaminated from the remainder of stack 220a in a continuous sheet such that reduced layer stack 220b remains in place as part of modified film 210b, as shown in FIG. Figure 2B . Delamination preferably occurs along a delamination surface corresponding to the grouping interface between layer grouping 222 and layer grouping 224. After removing layer grouping 222, layer grouping 224 becomes the outermost grouping of film 210b, and the front major surface 224a of layer grouping 224 becomes the front major surface of film 210b. Surface 224a is then typically exposed to air or other surrounding environments. Removing layer grouping 222 can expose an uncontaminated (or sterile in some cases) surface.

[0095] Subsequently, the outermost packet 224 may be removed from the film 210b to form a new modified film 210c, such as Figure 2C 210c. Layer grouping 224 is delaminated from the remainder of stack 220b in a continuous sheet form so that the reduced layer stack 220c is kept in place as a part of modified film 210c. Delamination preferably occurs along the delamination surface corresponding to the grouping interface between layer grouping 224 and layer grouping 226. After removing layer grouping 224, layer grouping 226 becomes the outermost grouping of film 210c, and the front main surface 226a of layer grouping 226 becomes the front main surface of film 210c. Then, surface 226a is usually exposed to air or other surrounding environments. Removing layer grouping 224 can expose uncontaminated (or sterile in some cases) surface.

[0096] After removing layer grouping 224, the now outermost layer grouping 226 may be removed from film 210c to form a new modified film 210d, such as Figure 2D 210d. The layer grouping 226 is layered from the remainder of the stack 220c in a continuous sheet form so that the reduced layer stack 220d is kept in place as a part of the modified film 210d. The layering preferably occurs along the layering surface corresponding to the grouping interface between the layer grouping 226 and the layer grouping 228. After removing the layer grouping 226, the layer grouping 228 becomes the outermost grouping of the film 210d, and the front main surface 228a of the layer grouping 228 becomes the front main surface of the film 210d. The surface 228a is then usually exposed to air. Removing the layer grouping 226 can expose an uncontaminated (or sterile in some cases) surface.

[0097] Although Figure 2A The initial film 210a is shown as having four layer groupings, but in other cases, the initial film may include more than four layer groupings, or may include less than four (but at least two) layer groupings if desired.

[0098] Figure 3A The membrane, such as Figure 2A The film is constructed so that successive layer groups can be delaminated from the remaining film in a continuous sheet. FIG. 3B to FIG. 3E 3, wherein the same reference numerals in FIG. 3 represent the same elements in FIG. 2. For example, Figure 2A3 includes layer groupings 322, 324, 326, and 328. Each layer grouping (322, 324, 326, and 328) includes layer A (layers 342a, 342b, 342c, and 342d of layer groupings 322, 324, 326, and 328, respectively) and conformable layers (conformable layers 332a, 332b, 332c, and 332d of layer groupings 322, 324, 326, and 328, respectively). Each layer grouping includes a front major surface (front major surfaces 322a, 324a, 326a, 328a of layer groupings 322, 324, 326 and 328, respectively) and a rear major surface (rear major surfaces 322b, 324b, 326b, 328b of layer groupings 322, 324, 326 and 328, respectively).

[0099] like Figure 3A As shown in , in some embodiments, a membrane (such as Figure 3A The initial film 310a) can be in close contact with the base layer 312. For example, the rear major surface 328b of the layer grouping 328 can be in contact with the base layer 312.

[0100] exist Figure 3B By removing the top or frontmost group 322, Figure 3A The film 310a is changed into the modified film 310b. Figure 3C By removing layer group 324, Figure 3B The film 310b is changed into the modified film 310c. Figure 3D By removing layer group 326, Figure 3C The film 310c becomes the modified film 310d.

[0101] exist Figure 3E , the film 310e shown is identical to the film 310d after completely removing the third layer packet 326. Thus, the layer stack 320d includes only the fourth layer packet 328 that remains attached to the base layer 312. The base layer 312 may optionally be attached to the workpiece via an adhesive backing layer.

[0102] Fourth layer grouping 328 may also be removed, and the front major surface of base layer 312 becomes the front major surface of film 310d.

[0103] In some embodiments, the base layer may comprise the same polymer composition as layer A. In some embodiments, the base layer may additionally comprise an amorphous polymer composition that is miscible with the polymer composition of layer A. In an exemplary embodiment, the base layer may be or may comprise polyethylene terephthalate (PET). In some embodiments, the base layer may further comprise an amorphous polyester (e.g., PETg) at a level sufficient to eliminate any haze that may result from crystallization of PET. For example, in an exemplary embodiment, the base layer may further comprise at least 5% amorphous polyester (PETg).

[0104] Because the polymer composition of each layer of the layer grouping is tailored so that the attachment of the rearmost polymer layer (e.g., layer C) to the frontmost polymer layer (e.g., layer A) is weaker than the attachment to the inner polymer layers (e.g., layer b), forming the base layer from the same polymer composition as layer A means that the final layer grouping can be irreversibly delaminated from the base layer along a delamination surface corresponding to the interface between the rear surface of the final layer grouping and the base layer.

[0105] In some embodiments, the substrate layer can be thicker than individual layers A, B, or C. In some embodiments, the substrate layer can have a thickness of at least 100 microns, at least 150 microns, at least 200 microns, at least 250 microns (about 10 mils), or at least 300 microns. In some embodiments, the substrate layer can have a thickness of at most 150 microns, at most 200 microns, at most 250 microns (about 10 mils), at most 300 microns, at most 500 microns, or up to 1000 microns.

[0106] In some embodiments, the base layer may be coextruded with the layer packets in a film construction.

[0107] To facilitate the sequential removal of only one layer group at a time, the film 210a or the film 310a and other multilayer polymer films described herein can be made to have a protrusion at the edge of the film. For example, the polymer film can have a kiss-cut protrusion-shaped feature with different depths at the edge of the film. In this regard, the published international application WO 2012 / 092478 (Wu et al.) illustrates that laser radiation can be used to cut and subdivide the polymer multilayer film body without any significant delamination at the laser cutting edge line, which can be used to form the desired tongue-shaped feature. The laser radiation can be selected to have a wavelength at which at least some of the material of the film has significant absorption, so that the absorbed electromagnetic radiation can effectively evaporate or ablate the film body along the cutting line. The laser radiation can also be shaped with a suitable focusing optical system and controlled to a suitable power level to achieve evaporation along a narrow cutting line. The laser radiation can also be quickly scanned across the workpiece according to pre-programmed instructions and quickly switched on and off so that a cutting line of any shape can be followed.

[0108] In some cases, it may be desirable that the layer stack is sterilization compatible, for example by ethylene oxide or by radiation.In some embodiments, the coextruded polymer film is sterilized, for example by ethylene oxide or by radiation.

[0109] Ethylene oxide has the ability to penetrate paper, many plastics, and rubber. It is currently used to sterilize disposable syringes, hypodermic needles, pre-packaged materials, culture dishes, pipettes, etc. Advantages of ethylene oxide sterilization may include its applicability to heat-labile materials because it can be performed at or just above room temperature; it will not damage moisture-sensitive materials and equipment because only low humidity is required; due to its high penetration ability, it can be used for pre-packaged products; and although ethylene oxide is a highly reactive compound, the process damages relatively few materials.

[0110] In certain embodiments, it may be desirable to sterilize the film by ionizing radiation such as gamma rays or electron beams. In such cases, the material composition of the film is selected to tolerate the treatment. One or more antioxidants such as hindered phenols, phosphites and hindered amines can be added to the polymer composition used in the film to increase polymer stability during sterilization. In some embodiments, the coextruded polymer film comprises one or more antioxidants and is sterilized by ionizing radiation.

[0111] In addition to the gradient of peeling force between layer groups in the entire polymer layer stack, the stack can be further constructed to promote irreversible delamination at the group interface. Examples of physical structures that promote such delamination are described in U.S. Publication 2019 / 0248118A1 and include a set of nested kiss-cut holes formed by a mechanical blade, laser radiation, or any other suitable means.

[0112] The coextruded polymer film may include a label, logo or other visual or texturized marking or feature. For example, a label, logo or other marking or feature may be provided on or in one or more layers of the stack.

[0113] Additionally or alternatively, the markings may include holes of varying depths through the stack. These holes may all open at the exposed surface of the frontmost layer and terminate at different layer groupings: the shallowest hole may terminate in the frontmost layer grouping, the next deepest hole may terminate in the next layer grouping, the next deepest hole may terminate in the next layer grouping, and so on.

[0114] In some embodiments, the various layers can be made to have different colors by incorporating dyes, pigments, or other coloring or staining agents so that, for example, each other layer grouping (or one or more layers thereof) is a different color, or the last layer grouping or the last small number of layer groupings in the stack can be colored with such dyes, pigments, etc. to provide a visual indication to the user that no more layer groupings (or only one or a small number of layer groupings) are available for layering.

[0115] Preparation method

[0116] like Figure 1A As shown in FIG, individual layers A, B, and C form layer grouping 122; and as Figure 2A and Figure 3A As shown in , the layers may be grouped and coextruded together to form a stack 220a or 320a, which may form all or part of a multilayer polymer film 210a or 310a. Figure 1A In the embodiment depicted in , layer grouping 122 is composed of three types of layers: layer A 142, layer B 144, and layer C 146, which can be composed of different polymer compositions A, B, and C, respectively. These three different layer types are organized into repeating groups of layers A, B, C, A, B, C, etc., with the minimum repeating unit (A, B, C) defining a single layer grouping. In some cases, a layer grouping may include only two types of layers.

[0117] In some embodiments, it is preferred that none of polymer compositions A, B or C is a pressure sensitive adhesive (PSA) or other types of adhesives. In this regard, "adhesive" refers to a material or layer that, when applied to surfaces with different components, bonds these surfaces together, resists separation and is tacky at room temperature. In addition, polymer compositions A, B and C are preferably coextruded with each other so that the entire stack 220a or 320a (comprising repeating layers of polymer compositions A, B and C) can be coextruded in a single operation, rather than being made in different operations and then later laminated together with adhesive.

[0118] In some cases, the multilayer polymer film can be made by coextrusion. Coextrusion can include melt processing at a temperature of at least 190°C, at least 195°C, at least 200°C, at least 200°C, at least 204°C, at least 206°C, at least 208°C, or at least 210°C.

[0119] In some cases, the preparation of the multilayer polymer film may also include one or more stretching or orientation steps. In some embodiments, layer A and layer B, or layer A and layer C, or layer B and layer C, or some combination thereof may be oriented. Such oriented layers may have a minimum level of birefringence, including, for example, a birefringence of at least 0.05. As described above, macromolecular orientation or crystallinity or both in at least one component of layer A or layer B or both may affect the peeling force of AB pairs. One or more uniaxial stretching steps or one or more biaxial stretching steps in the film preparation process may be used to promote macromolecular orientation, crystallization, or both.

[0120] Stretching (sometimes referred to as drawing) can be uniaxial or biaxial, and if biaxial, the stretching can be simultaneous or sequential. The action or method of stretching a multilayer film can result in all, or only some, or in some cases none of the constituent polymer layers being oriented, depending on the materials used and the process conditions, such as the temperature of the film during stretching. References in U.S. Pat. No. 6,179,948 (Merrill et al.) also discuss known stretching or drawing techniques. For example, a two-step drawing process can be performed in which one set of layers (e.g., layer A) is substantially oriented during two drawing steps, while another set of layers (e.g., layer B) is substantially oriented only during one drawing step. This results in a multilayer film having a set of material layers that are substantially biaxially oriented after drawing, and having another set of material layers that are substantially uniaxially oriented after drawing.

[0121] Figure 4 and Figure 5 is a schematic diagram of a manufacturing system that can be used to make the disclosed multilayer polymer films. Figure 4Schematically depicting the coextrusion of polymer compositions A, B, C to form a multilayer polymer film 410. Here, the polymer composition can be fed to a feed block 430 via a twin screw extruder or other suitable tool, which staggers the molten polymer flow path so that it forms a multilayer extrudate 409, in which the polymer layers A, B, and C are arranged in a repeating pattern desired in the finished film. In some cases, the extrudate 409 can be fed to one or more layer multiplier units to form an output extrudate having multiples (e.g., 2×, 3×, or 4×) of the number of layers in the initial extrudate 409. Whether or not a layer multiplier is used, the multilayer extrudate can then be fed into a film die 432, the output of which can be quenched on a casting wheel to form a cast multilayer polymer film. In some cases, the cast film can become a finished multilayer polymer film 410 without other components. In other cases, additional layers and coatings can be applied to the cast film to obtain additional functionality. For example, a release liner can be applied to one or two exposed main surfaces of the cast film. Additionally, an adhesive backing layer may be coated onto one of the exposed major surfaces of the cast film so that it can be easily applied to a workpiece. Regardless of how many additional layers and coatings are applied, the finished multilayer polymer film 410 comprises a stack of polymer layers formed by coextrusion using a feed block 430, an optional layer multiplier, and a die 432, the layers in the stack being organized into layer groupings that are regulated to irreversibly delaminate from each other as discussed elsewhere herein.

[0122] In some cases, it may be desirable to stretch or orient the multilayer cast film, whether to impart birefringence to some or all of the individual layers in the film, or to alter other material properties of some or all of the individual polymer layers. Figure 5 Such stretching or orientation is schematically shown in FIG. The multilayer cast film 508 can be fed sequentially, simultaneously, or a combination thereof, into one or more known film processing devices that stretch the film in the downweb direction and / or in the crossweb direction to provide an oriented multilayer polymer film 510 having the layered characteristics described herein, which can be connected to the multilayer cast film. Figure 4 The cast film 410 is the same or similar to the cast film 410 and includes at least three different polymer layer types arranged in a repeating pattern desired in the finished film. Figure 5In the figure, the multilayer cast film 508 is shown to be first fed into a length orientation machine (LO) 534, which stretches the film in the downweb direction to provide a preliminary oriented film 509, followed by a tenter 536, which stretches the film in the crossweb direction to produce a finished oriented multilayer polymer film 510. In alternative embodiments, the length orientation machine 534 can be omitted, or the tenter 536 can be omitted, or additional length orientation machines and / or tenters can be added. A tenter (not shown) designed to be able to stretch the film in the downweb direction and the crossweb direction at the same time can also be used alone or in combination with the aforementioned stretching device. A specially designed tenter, such as a so-called parabolic tenter, can be used alone or in combination with other stretching units. In other embodiments (not shown), the cast film can be formed into a tubular rather than a flat film configuration, and the tubular cast film can then be stretched using a blown film process, etc. The method that can be used to stretch / orient the cast film into a stretched film is not limited.

[0123] Similar to the above combination Figure 4 The finished oriented film 510 may be, without other components, a finished multilayer polymer film whose delamination properties are discussed herein. In other cases, additional layers and coatings such as release liners and adhesive backing layers may be applied to the oriented film to provide additional functionality. Regardless of how many additional layers and coatings are applied, the finished multilayer polymer film comprises a stack of polymer layers initially formed by coextrusion and then optionally oriented by stretching, the layers in the stack being organized into groupings of layers that are regulated to irreversibly delaminate with each other as discussed elsewhere herein.

[0124] Since the polymer layers in the layer stack are preferably compatible with simultaneous formation by coextrusion, e.g. Figure 4 As shown, the individually peelable layer groups can be made thinner than the layer groups that are made separately and then laminated to each other. Preferably, each layer grouping in the layer groupings in the stack can have a thickness of no more than about 2 mils (about 50 microns). In addition, the layer stack can contain a total of n layer groups, and n can be at least 5 or at least 10, and the film can have an overall thickness of no more than about 15 mils or 20 mils (about 380 microns or 510 microns, respectively). At least n-1 of the layer groups can have the same number m of polymer layers, and m can be at least 3. The m polymer layers can be arranged in the same order as the n-1 layer groups or all n layer groups.

[0125] In a method of regulating the attachment strength of one polymer layer to other polymer layers in a layer grouping, a polymer composition consisting of a blend of polypropylene and one of several copolymer resins exhibits an attachment strength to other polypropylene layers that is a function of the proportions of the blended components. This method is discussed in more detail in U.S. Publication No. 2019 / 0248817.

[0126] How to use

[0127] The multilayer polymer films described herein can be customized for a variety of purposes and a variety of end-use applications. In some cases, the film can be an anti-graffiti film. In some cases, the film can be used as a covering for a mask, such as a face mask, a set of safety glasses, a pair of sunglasses, safety goggles, ski goggles, and other applications where removing contaminants on the surface of the mask, glasses, or goggles by removing the film may be beneficial. In some embodiments, the film can be used as a covering for high-touch surfaces in hospitals, laboratories, schools, hotels, restaurants, or other environments, where the ability to remove contaminated surfaces and expose sterile surfaces would be beneficial.

[0128] In some embodiments, the film and (if included) substrate layer can be substantially transparent so that the workpiece to which it is applied does not change its appearance or its functionality at any given time, no matter how many initial films are present on the workpiece. In some embodiments, the film and (if included) substrate layer can have a haze of at most 2%, at most 3%, at most 4%, or at most 5%. In some embodiments, the film and (if included) substrate layer can have a transmission of at least 70%, at least 75%, at least 80%, at least 85%, or at least 90%. In some embodiments, the film and (if included) substrate layer can have a clarity of at least 80%, at least 85%, at least 90%, at least 95%, or at least 99%. In some embodiments, haze and transmission are measured using ASTM D1003-13. In some embodiments, clarity is measured using ASTM D3430-95 (2016).

[0129] In other embodiments, for example, when transparency is not important, the transmission can be as low as 0%, the haze as high as 100% and the clarity as low as 0%.

[0130] In some embodiments, the multilayer polymer films as described herein can be used to provide a sterile, substantially sterile environment. In this regard, the benefit of manufacturing the individual polymer layers and layer groupings in a single coextrusion operation rather than in separate manufacturing operations involving the handling, alignment, and lamination of separately manufactured films is that the front major surface of the layer grouping can be more easily maintained in an uncontaminated (e.g., sterile) state until it is exposed by peeling off the layer grouping in front of a given layer grouping.

[0131] In some embodiments, the multilayer polymer film as described herein can be used to provide a controlled surface topography at a workpiece. For example, it may be desirable to efficiently provide a workpiece with a high quality smooth (low roughness) surface finish. Rather than polishing the surface of the workpiece itself, the film can be applied to the workpiece to provide the desired smooth surface. In use, when the outer surface of the film becomes abrasive or otherwise not smooth, the layer groups can be delaminated to restore the desired smooth surface.

[0132] In other embodiments, the workpiece may require a controlled roughness. In such cases, a controlled amount of appropriately sized beads or other particles may be provided in the frontmost polymer layer of each layer grouping so that the frontmost (exposed) surface of the film has the desired amount of surface roughness. If the exposed surface were to become damaged, abraded, contaminated with other materials, etc., the desired surface roughness can be easily restored by simply delaminating the outermost layer grouping to expose the pure surface of the immediately adjacent layer grouping, and the exposed surface once again has the desired surface roughness.

[0133] Mask

[0134] Figure 6 790. An exemplary embodiment of a film used as a cover for a face mask 790 is shown in FIG. The base layer 712 can be coextruded with layer groups 722 and 724 in one film construction. Alternatively, the film can include layer groups 722 and 724 attached to the workpiece via an adhesive backing layer. Figure 6 A face mask 790 is shown that includes two layer groupings, but the face mask may include a polymer layer stack including any suitable number of layer groupings.

[0135] In some embodiments, such as Figure 6 As shown in , layer groupings 722 and 724 include protrusions 782 and 784 to facilitate sequential removal of only one layer grouping at a time. Protrusions 782, 784 can have different depths at the edge of each layer grouping. Protrusions 782, 784 can be formed by any suitable method, such as a kiss-cut process. In this regard, published international application WO 2012 / 092478 (Wu et al.) illustrates that laser radiation can be used to cut and subdivide a polymer multilayer film body without any significant delamination at the laser cut edge line, which can be used to form the desired protrusions.

[0136] In some embodiments, the mask 790 is sterilizable, for example, by ethylene oxide or by radiation. In some embodiments, the mask 790 is sterilizable, for example, by ethylene oxide or by radiation.

[0137] In some embodiments, such as Figure 6As shown in FIG, the base layer 712 includes a pattern of strips, protrusions, or pins 772, 774 to allow the mask to be connected to a mounting component, such as a crown.

[0138] In some embodiments, the base layer 712 comprises the same polymer composition as layer A. In some embodiments, the base layer may additionally comprise an amorphous polymer composition that is miscible with the polymer composition of layer A. In an exemplary embodiment, the base layer 712 may be or may comprise polyethylene terephthalate (PET). In some embodiments, the base layer 712 may also comprise an amorphous polyester (PETg) at a level sufficient to eliminate any haze that may result from crystallization of the PET. For example, in an exemplary embodiment, the base layer 712 may also comprise at least 5% amorphous polyester (PETg).

[0139] In an exemplary embodiment, the thickness of at least some of the layers in the layer groupings in the mask 790 varies continuously from the frontmost layer grouping to the rearmost layer grouping. For example, the thickness of the conformable layer (e.g., combined layer B and layer C) can increase continuously from the first layer grouping (e.g., layer grouping 722) to the second layer grouping (e.g., layer grouping 724) and in subsequent layer groupings. The thickness of layer A can decrease continuously from the first layer grouping (e.g., layer grouping 722) to the second layer grouping (e.g., layer grouping 724) and in subsequent layer groupings.

[0140] In an exemplary embodiment, layer A comprises polymer composition A, which comprises polyester, copolyester, acrylic resin or silicone thermoplastic or a combination thereof; layer B comprises polymer composition B, which comprises copolyester, PMMA, coPMMA, styrene block copolymer, polypropylene or silicone polyoxamide or a combination thereof; and layer C comprises polymer composition C, which comprises olefin or styrene block copolymer or a combination thereof. For example, polymer composition A may comprise polyethylene terephthalate (PET), and polymer composition B and polymer composition C may comprise copolymers based on styrene and ethylene / butylene, including, for example, KRATONG 1645 (Kraton Corporation, Houston, Texas), a linear triblock copolymer based on styrene and ethylene / butylene.

[0141] In an exemplary embodiment, the face mask including the base layer exhibits a haze of at most 5%, a transmission of at least 85%, and a clarity of at least 95% as measured using ASTM D1003-13 (for transmission and haze) and ASTM D3430-95 (2016) (for clarity).

[0142] Exemplary Film Aspects Including a Conformable Layer of Variable Thickness

[0143] 1. A film comprising:

[0144] A coextruded stack of polymer layers, the polymer layers being organized into layer groups, each layer group comprising a first layer A, a second layer B, and a third layer C, layer B being disposed between layer A and layer C;

[0145] a grouping interface between layer A and layer C of adjacent layer groupings, the grouping interface exhibiting a first peel force of 1 g / inch or greater;

[0146] a layer interface between adjacent layers A and B, the layer interface exhibiting a second peel force greater than the first peel force; and

[0147] a layer interface between adjacent layers B and C, wherein the layer interface exhibits a third peel force greater than the first peel force;

[0148] wherein the layer groupings are individually capable of being irreversibly peeled from the remainder of the stack; and

[0149] The coextruded stack of polymer layers comprises at least a first layer grouping and a second layer grouping, each layer grouping comprises a conformable layer, the conformable layer comprises layer B and layer C, and the thickness of the conformable layer of the second layer grouping is greater than the thickness of the conformable layer of the first layer grouping.

[0150] 2. A film as described in aspect 1, wherein the coextruded stack of polymer layers includes n layer groups, and wherein the coextruded stack of polymer layers exhibits a peel force gradient from the first layer grouping to the nth layer grouping, or a thickness gradient of the conformable layer from the first layer grouping to the nth layer grouping, or both a peel force gradient and a thickness gradient.

[0151] 3. The film of aspect 2, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is less than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0152] 4. A film as described in aspect 3, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is at least 5 times, at least 10 times, at least 100 times or at least 250 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0153] 5. A film as described in aspect 3 or 4, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is at most 500 times, at most 250 times, at most 100 times or at most 10 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0154] 6. The film of any of aspects 3 to 5, wherein the peel force at each successive packet interface increases by at least 0.5%, at least 1%, at least 5%, at least 10%, at least 20%, at least 50%, or at least 100%.

[0155] 7. A film as described in any of Aspects 3 to 6, wherein the peel force at each consecutive grouping interface increases by at most 1%, at most 5%, at most 10%, at most 20%, at most 50%, at most 100%, at most 1000%, at most 10,000% or at most 50,000%.

[0156] 8. The film of any one of aspects 2 to 7, wherein the thickness of the conformable layer of the first layer grouping is at least 1.1 times, at least 1.2 times, at least 1.5 times, or at least 2 times less than the thickness of the conformable layer of the nth layer grouping.

[0157] 9. The film of any of aspects 2 to 8, wherein the thickness of the conformable layer of the first layer grouping is at most 2 times, at most 5 times, or at most 10 times less than the thickness of the conformable layer of the nth layer grouping.

[0158] 10. The film of any of aspects 2 to 9, wherein the thickness of the conformable layer increases by at least 15%, at least 20%, at least 25%, or at least 30% with each successive layer grouping.

[0159] 11. The film of any of aspects 2 to 10, wherein the thickness of the conformable layer increases by at most 50%, at most 100%, at most 200%, at most 500%, or at most 1000% with each successive layer grouping.

[0160] 12. The film of any of the preceding aspects, wherein the peel force at the packet interface between layer C of the first layer grouping and layer A of the second layer grouping is less than the peel force between layer C of the nth layer grouping and the substrate layer.

[0161] 13. The film of any of aspects 2 to 12, wherein the nth layer grouping is the second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth, twentieth, or twenty-first layer grouping.

[0162] 14. The film of any of the preceding aspects, wherein layer A comprises a first polymer composition A, layer B comprises a second polymer composition B, and layer C comprises a third polymer composition C.

[0163] 15. The film of aspect 14, wherein polymer composition B is different from polymer composition A, and polymer composition C is different from polymer composition A.

[0164] 16. The film of aspect 15, wherein polymer composition C is different from polymer composition B.

[0165] 17. A film as described in any of Aspects 14 to 16, wherein the polymer composition A, polymer composition B and polymer composition C independently contain one or more polymers selected from the following: polyesters, polyolefins, poly-α-olefins, polymethacrylates, polycarbonates, polycarbonate alloys, polyurethanes, polylactic acid, polyhydroxybutyrates, polyhydroxysuccinates, styrene copolymers, silicones, or copolymers or blends thereof.

[0166] 18. The film of any one of aspects 14 to 17, wherein polymer composition A comprises a semi-crystalline polyester.

[0167] 19. The film of any one of aspects 14 to 18, wherein polymer composition B comprises a copolyester or a styrene block copolymer or a combination thereof.

[0168] 20. The film of any one of aspects 14 to 19, wherein polymer composition C comprises an olefin or styrene block copolymer or a combination thereof.

[0169] 21. The film of any of aspects 14 to 20, wherein polymer composition C is at least partially miscible with polymer composition B, and polymer composition B is at least partially miscible with polymer composition A, and polymer composition C is immiscible with the first polymer composition.

[0170] 22. The film of any of aspects 14 to 21, wherein the film further comprises a substrate layer comprising the same polymer composition as layer A.

[0171] 23. The film of aspect 22, wherein the base layer further comprises an amorphous polymer composition that is miscible with the polymer composition of layer A.

[0172] 24. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more additives.

[0173] 25. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more ultraviolet (UV) light stabilizers.

[0174] 26. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more organic antimicrobial agents.

[0175] 27. The film of any of the preceding aspects, wherein layer A and layer B, or layer A and layer C, or layer B and layer C, or a combination thereof, are oriented and have a birefringence of at least 0.5.

[0176] 28. The film of any of the preceding aspects, wherein each of the groupings of layers in the coextruded stack of polymer layers has a thickness of at most 10 microns, at most 25 microns, at most 50 microns.

[0177] 29. The film of any of the preceding aspects, wherein each of the groupings of layers in the coextruded stack of polymeric layers has a thickness of at least 1 micron, at least 5 microns, or at least 10 microns.

[0178] 30. The film of any of the preceding aspects, wherein the second peel force is at least 1.04 times the first peel force.

[0179] 31. The film of any of the preceding aspects, wherein the second peel force is at most 500 times greater than the first peel force.

[0180] 32. The film of any of the preceding aspects, wherein the third peel force is at least 1.1 times the first peel force.

[0181] 33. The film of any of the preceding aspects, wherein the third peel force is at most 500 times greater than the first peel force.

[0182] 34. The film of any of the preceding aspects, wherein the third peel force is at least 1.04 times the second peel force.

[0183] 35. The film of any of the preceding aspects, wherein the third peel force is at most 500 times greater than the second peel force.

[0184] 36. The film of any of the preceding aspects, wherein the first peel force is at most 500 grams / inch.

[0185] 37. The film of any of the preceding aspects, wherein the total thickness of the film is at most 510 microns, at most 380 microns, at most 300 microns, at most 200 microns, at most 100 microns, or at most 50 microns.

[0186] 38. The film of any of the preceding aspects, wherein the total thickness of the film is at least 25 microns, at least 50 microns, at least 100 microns, at least 200 microns, at least 300 microns, or at least 380 microns.

[0187] 39. The film of any of aspects 2 to 38, wherein the thickness of layer A remains constant from the first layer grouping to the nth layer grouping.

[0188] 40. The film of any of aspects 2 to 38, wherein the coextruded stack of polymeric layers comprises a thickness gradient from the first layer grouping to the layer A of the nth layer grouping.

[0189] 41. The film of aspect 40, wherein the thickness of layer A of the first layer grouping is greater than the thickness of layer A of the nth layer grouping.

[0190] 42. The film of aspect 40, wherein the thickness of layer A of the first layer grouping is less than the thickness of layer A of the nth layer grouping.

[0191] 43. The film of aspect 42, wherein the ratio of the thickness of layer A to the thickness of the conformable layer remains constant throughout the depth of the stack.

[0192] Exemplary Film Aspects Including Layer A of Variable Thickness

[0193] 1. A film comprising:

[0194] A coextruded stack of polymer layers, the polymer layers being organized into layer groups, each layer group comprising a first layer A, a second layer B, and a third layer C, layer B being disposed between layer A and layer C;

[0195] a grouping interface between layer A and layer C of adjacent layer groupings, the grouping interface exhibiting a first peel force of 1 g / inch or greater; and

[0196] a layer interface between adjacent layers A and B, wherein the layer interface exhibits a second peel force greater than the first peel force;

[0197] a layer interface between adjacent layers B and C, wherein the layer interface exhibits a third peel force greater than the first peel force;

[0198] wherein the layer groupings are individually capable of being irreversibly peeled from the remainder of the stack; and

[0199] The coextruded stack of polymer layers comprises at least a first layer grouping and a second layer grouping, and wherein the thickness of layer A of the second layer grouping is less than the thickness of layer A of the first layer grouping.

[0200] 2. A film as described in aspect 1, wherein the coextruded stack of polymer layers includes n layer groups, and wherein the coextruded stack of polymer layers exhibits a peel force gradient from the first layer grouping to the nth layer grouping, or a thickness gradient of the layer A from the first layer grouping to the nth layer grouping, or both a peel force gradient and a thickness gradient.

[0201] 3. The film of aspect 2, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is less than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0202] 4. A film as described in aspect 3, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is at least 5 times, at least 10 times, at least 100 times or at least 250 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0203] 5. A film as described in aspect 3 or 4, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is at most 500 times, at most 250 times, at most 100 times or at most 10 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0204] 6. The film of any of aspects 3 to 5, wherein the peel force at each successive packet interface increases by at least 0.5%, at least 1%, at least 5%, at least 10%, at least 20%, at least 50%, or at least 100%.

[0205] 7. A film as described in any of Aspects 3 to 6, wherein the peel force at each consecutive grouping interface increases by at most 1%, at most 5%, at most 10%, at most 20%, at most 50%, at most 100%, at most 1000%, at most 10,000% or at most 50,000%.

[0206] 8. The film of any of aspects 2 to 7, wherein the thickness of the layer A of the first layer grouping is at least 1.1 times, at least 1.2 times, at least 1.5 times, or at least 2 times greater than the thickness of the layer A of the nth layer grouping.

[0207] 9. The film of any of aspects 2 to 8, wherein the thickness of the layer A of the first layer grouping is at most 2 times, at most 5 times, or at most 10 times greater than the thickness of the layer A of the nth layer grouping.

[0208] 10. The film of any of aspects 2 to 9, wherein the thickness of layer A in each successive layer grouping decreases by at least 15%, at least 20%, at least 25%, or at least 30%.

[0209] 11. The film of any of aspects 2 to 10, wherein the thickness of Layer A of each successive layer grouping decreases by at most 50%, at most 100%, at most 200%, at most 500%, or at most 1000%.

[0210] 12. The film of any of the preceding aspects, wherein the peel force at the packet interface between layer C of the first layer grouping and layer A of the second layer grouping is less than the peel force between layer C of the nth layer grouping and the substrate layer.

[0211] 13. The film of any of aspects 2 to 12, wherein the nth layer grouping is the second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth, twentieth, or twenty-first layer grouping.

[0212] 14. The film of any of the preceding aspects, wherein layer A comprises a first polymer composition A, layer B comprises a second polymer composition B, and layer C comprises a third polymer composition C.

[0213] 15. The film of aspect 14, wherein polymer composition B is different from polymer composition A, and polymer composition C is different from polymer composition A.

[0214] 16. The film of aspect 15, wherein polymer composition C is different from polymer composition B.

[0215] 17. A film as described in any of Aspects 14 to 16, wherein the polymer composition A, polymer composition B and polymer composition C independently contain one or more polymers selected from the following: polyesters, polyolefins, poly-α-olefins, polymethacrylates, polycarbonates, polycarbonate alloys, polyurethanes, polylactic acid, polyhydroxybutyrates, polyhydroxysuccinates, styrene copolymers, silicones, or copolymers or blends thereof.

[0216] 18. The film of any one of aspects 14 to 17, wherein polymer composition A comprises a semi-crystalline polyester.

[0217] 19. The film of any one of aspects 14 to 18, wherein polymer composition B comprises a copolyester or a styrene block copolymer or a combination thereof.

[0218] 20. The film of any one of aspects 14 to 19, wherein polymer composition C comprises an olefin or styrene block copolymer or a combination thereof.

[0219] 21. The film of any of aspects 14 to 20, wherein polymer composition C is at least partially miscible with polymer composition B, and polymer composition B is at least partially miscible with polymer composition A, and polymer composition C is immiscible with the first polymer composition.

[0220] 22. The film of any of aspects 14 to 21, wherein the film further comprises a substrate layer comprising the same polymer composition as layer A.

[0221] 23. The film of aspect 22, wherein the base layer further comprises an amorphous polymer composition that is miscible with the polymer composition of layer A.

[0222] 24. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more additives.

[0223] 25. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more ultraviolet (UV) light stabilizers.

[0224] 26. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more organic antimicrobial agents.

[0225] 27. The film of any of the preceding aspects, wherein layer A and layer B, or layer A and layer C, or layer B and layer C, or a combination thereof, are oriented and have a birefringence of at least 0.5.

[0226] 28. The film of any of the preceding aspects, wherein each of the groupings of layers in the coextruded stack of polymer layers has a thickness of at most 10 microns, at most 25 microns, at most 50 microns.

[0227] 29. The film of any of the preceding aspects, wherein each of the groupings of layers in the coextruded stack of polymeric layers has a thickness of at least 1 micron, at least 5 microns, or at least 10 microns.

[0228] 30. The film of any of the preceding aspects, wherein the second peel force is at least 1.04 times the first peel force.

[0229] 31. The film of any of the preceding aspects, wherein the second peel force is at most 500 times greater than the first peel force.

[0230] 32. The film of any of the preceding aspects, wherein the third peel force is at least 1.1 times the first peel force.

[0231] 33. The film of any of the preceding aspects, wherein the third peel force is at most 500 times greater than the first peel force.

[0232] 34. The film of any of the preceding aspects, wherein the third peel force is at least 1.04 times the second peel force.

[0233] 35. The film of any of the preceding aspects, wherein the third peel force is at most 500 times greater than the second peel force.

[0234] 36. The film of any of the preceding aspects, wherein the first peel force is at most 500 grams / inch.

[0235] 37. The film of any of the preceding aspects, wherein the total thickness of the film is at most 510 microns, at most 380 microns, at most 300 microns, at most 200 microns, at most 100 microns, or at most 50 microns.

[0236] 38. The film of any of the preceding aspects, wherein the total thickness of the film is at least 25 microns, at least 50 microns, at least 100 microns, at least 200 microns, at least 300 microns, or at least 380 microns.

[0237] 39. The film of any of aspects 2 to 38, wherein each layer grouping comprises a conformable layer comprising layer B and layer C, and wherein a thickness of the conformable layer remains constant from the first layer grouping to the nth layer grouping.

[0238] 40. A film as described in any of Aspects 2 to 38, wherein each layer grouping includes a conformable layer, the conformable layer includes layer B and layer C, and wherein the coextruded stack of polymer layers includes a thickness gradient of the conformable layer from the first layer grouping to the nth layer grouping.

[0239] 41. The film of aspect 40, wherein the conformable layer of the first layer grouping has a thickness less than the thickness of layer A of the nth layer grouping.

[0240] 42. The film of aspect 41, wherein the ratio of the thickness of layer A to the thickness of the conformable layer remains constant throughout the depth of the stack.

[0241] Exemplary Film Aspects Including Polymer Compositions

[0242] 1. A film comprising:

[0243] A coextruded stack of polymer layers, the polymer layers being organized into layer groups, each layer group comprising a first layer A, a second layer B, and a third layer C, layer B being disposed between layer A and layer C;

[0244] wherein layer A of the film comprises a first polymer composition A, layer B of the film comprises a second polymer composition B, and layer C of the film comprises a third polymer composition C;

[0245] wherein the polymer composition A comprises polyester, copolyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, polyurethane, aliphatic polyester, polyhydroxybutyrate, polyhydroxysuccinate, styrene copolymer, silicone, silicone thermoplastic, acrylic resin or copolymers or blends thereof;

[0246] wherein the polymer composition B comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof;

[0247] wherein the polymer composition C comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof;

[0248] wherein the layer groupings are individually capable of being irreversibly peeled from the remainder of the stack; and

[0249] The coextruded stack of polymer layers comprises at least a first layer grouping and a second layer grouping, each layer grouping comprises a conformable layer, the conformable layer comprises layer B and layer C, and the thickness of the conformable layer of the second layer grouping is greater than the thickness of the conformable layer of the first layer grouping.

[0250] 2. A film comprising:

[0251] a coextruded stack of polymer layers, the polymer layers being organized into layer groups, each layer group comprising a first layer A, a second layer B, and a third layer C, layer B being disposed between layer A and layer C;

[0252] wherein layer A of the film comprises a first polymer composition A, layer B of the film comprises a second polymer composition B, and layer C of the film comprises a third polymer composition C;

[0253] wherein the polymer composition A comprises polyester, copolyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, polyurethane, aliphatic polyester, polyhydroxybutyrate, polyhydroxysuccinate, styrene copolymer, silicone, silicone thermoplastic, acrylic resin or copolymers or blends thereof;

[0254] wherein the polymer composition B comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof;

[0255] wherein the polymer composition C comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof;

[0256] wherein the layer groupings are individually capable of being irreversibly peeled from the remainder of the stack; and

[0257] The coextruded stack of polymer layers comprises at least a first layer grouping and a second layer grouping, wherein the thickness of layer A of the second layer grouping is less than the thickness of layer A of the first layer grouping.

[0258] 3. The film of aspect 1 or 2, wherein polymer composition A comprises polyester, copolyester, acrylic resin or silicone thermoplastic or a combination thereof;

[0259] wherein polymer composition B comprises copolyester, PMMA, co-PMMA, styrene block copolymer, polypropylene or silicone polyoxamide or a combination thereof;

[0260] The polymer composition C comprises an olefin or styrene block copolymer or a combination thereof.

[0261] 4. The film according to any one of the preceding aspects, wherein the film further comprises

[0262] a grouping interface between layer A and layer C of adjacent layer groupings, the grouping interface exhibiting a first peel force of 1 g / inch or greater;

[0263] a layer interface between adjacent layers A and B, the layer interface exhibiting a second peel force greater than the first peel force; and

[0264] The layer interface between the adjacent layers B and C exhibits a third peeling force greater than the first peeling force.

[0265] 5. The film of any one of the preceding aspects, wherein polymer composition A comprises a semi-crystalline polyester.

[0266] 6. The film of any one of the preceding aspects, wherein polymer composition A comprises polyethylene terephthalate (PET).

[0267] 7. The film of any one of the preceding aspects, wherein polymer composition B comprises a copolyester or a styrene block copolymer or a combination thereof.

[0268] 8. The film of any one of the preceding aspects, wherein polymer composition B comprises a copolymer based on styrene and ethylene / butylene.

[0269] 9. The film of any one of the preceding aspects, wherein polymer composition C comprises a copolymer based on styrene and ethylene / butylene.

[0270] 10. A film as described in any of the preceding aspects, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is less than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0271] 11. A film as described in aspect 10, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is at least 5 times, at least 10 times, at least 100 times or at least 250 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0272] 12. A film as described in aspect 10 or 11, wherein the peel force at the group interface between layer A of the second layer grouping and layer C of the first layer grouping is at most 500 times, at most 250 times, at most 100 times or at most 10 times smaller than the peel force between layer A of the nth layer grouping and layer C of the (n-1)th layer grouping.

[0273] 13. The film of any of the preceding aspects, wherein the peel force at each successive packet interface increases by at least 0.5%, at least 1%, at least 5%, at least 10%, at least 20%, at least 50%, or at least 100%.

[0274] 14. A film as described in any of the preceding aspects, wherein the peel force at each successive packet interface increases by at most 1%, at most 5%, at most 10%, at most 20%, at most 50%, at most 100%, at most 1000%, at most 10,000% or at most 50,000%.

[0275] 15. The film of any of the preceding aspects, wherein the peel force at the packet interface between layer C of the first layer packet and layer A of the second layer packet is less than the peel force between layer C of the nth layer packet and a substrate layer.

[0276] 16. The film of any of aspects 10 to 15, wherein the nth layer grouping is the second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth, twentieth, or twenty-first layer grouping.

[0277] 17. The film of any of the preceding aspects, wherein polymer composition C is at least partially miscible with polymer composition B, and polymer composition B is at least partially miscible with polymer composition A, and polymer composition C is immiscible with the first polymer composition.

[0278] 18. The film of any of the preceding aspects, wherein the film further comprises a substrate layer comprising the same polymer composition as layer A.

[0279] 19. The film of aspect 18, wherein the base layer further comprises an amorphous polymer composition that is miscible with the polymer composition of layer A.

[0280] 20. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more additives.

[0281] 21. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more ultraviolet (UV) light stabilizers.

[0282] 22. The film of any of the preceding aspects, wherein layer A, layer B, or layer C, or a combination thereof, comprises one or more organic antimicrobial agents.

[0283] 23. The film of any of the preceding aspects, wherein layer A and layer B, or layer A and layer C, or layer B and layer C, or a combination thereof, are oriented and have a birefringence of at least 0.5.

[0284] 24. The film of any of the preceding aspects, wherein each of the groupings of layers in the coextruded stack of polymer layers has a thickness of at most 10 microns, at most 25 microns, at most 50 microns.

[0285] 25. The film of any of the preceding aspects, wherein each of the groupings of layers in the coextruded stack of polymeric layers has a thickness of at least 1 micron, at least 5 microns, or at least 10 microns.

[0286] 26. The film of any of the preceding aspects, wherein the second peel force is at least 1.04 times the first peel force.

[0287] 27. The film of any of the preceding aspects, wherein the second peel force is at most 500 times greater than the first peel force.

[0288] 28. The film of any of the preceding aspects, wherein the third peel force is at least 1.1 times the first peel force.

[0289] 29. The film of any of the preceding aspects, wherein the third peel force is at most 500 times greater than the first peel force.

[0290] 30. The film of any of the preceding aspects, wherein the third peel force is at least 1.04 times the second peel force.

[0291] 31. The film of any of the preceding aspects, wherein the third peel force is at most 500 times greater than the second peel force.

[0292] 32. The film of any of the preceding aspects, wherein the first peel force is at most 500 grams / inch.

[0293] 33. The film of any of the preceding aspects, wherein the total thickness of the film is at most 510 microns, at most 380 microns, at most 300 microns, at most 200 microns, at most 100 microns, or at most 50 microns.

[0294] 34. The film of any of the preceding aspects, wherein the total thickness of the film is at least 25 microns, at least 50 microns, at least 100 microns, at least 200 microns, at least 300 microns, or at least 380 microns.

[0295] 35. The film of any of aspects 1 or 3 to 34, wherein the thickness of layer A remains constant from the first layer grouping to the nth layer grouping.

[0296] 36. The film of any of aspects 1 or 3 to 34, wherein the coextruded stack of polymeric layers comprises a thickness gradient from the first layer grouping to the layer A of the nth layer grouping.

[0297] 37. The film of aspect 36, wherein the thickness of layer A of the first layer grouping is greater than the thickness of layer A of the nth layer grouping.

[0298] 38. The film of aspect 36, wherein the thickness of layer A of the first layer grouping is less than the thickness of layer A of the nth layer grouping.

[0299] 39. The film of aspect 38, wherein the ratio of the thickness of layer A to the thickness of the conformable layer remains constant throughout the depth of the stack.

[0300] 40. The film of any of aspects 2 to 34, wherein each layer grouping comprises a conformable layer comprising layer B and layer C, and wherein a thickness of the conformable layer remains constant from the first layer grouping to the nth layer grouping.

[0301] Mask

[0302] 1. A face mask comprising the membrane according to any one of the membrane claims.

[0303] 2. The mask according to aspect 1 further comprises a mask base.

[0304] 3. The mask of aspect 2, wherein the mask base and the film are co-extruded.

[0305] 4. A mask as described in any of the preceding aspects, wherein layer A of the film comprises a first polymer composition A, layer B of the film comprises a second polymer composition B, and layer C of the film comprises a third polymer composition C, and further wherein the mask base comprises the polymer composition A.

[0306] 5. The face mask of aspect 4, wherein the face mask comprises a mask base, the mask base further comprising an amorphous polymer composition miscible with the polymer composition of layer A.

[0307] 6. The face mask of aspect 4 or aspect 5, wherein polymer composition B and polymer composition C are the same.

[0308] 7. The face mask of any one of aspects 4 to 6, wherein polymer composition A comprises polyethylene terephthalate (PET).

[0309] 8. The mask of aspect 7, wherein the mask base further comprises amorphous polyethylene terephthalate (PET).

[0310] 9. The mask of any of aspects 2 to 8, wherein the mask base has a thickness of at least 100 microns, at least 150 microns, at least 200 microns, at least 250 microns, or at least 300 microns.

[0311] 10. The mask of any of aspects 2 to 9, wherein the mask base has a thickness of at most 150 microns, at most 200 microns, at most 250 microns, at most 300 microns, at most 500 microns, or at most 1000 microns.

[0312] 11. The mask of any of the preceding aspects, wherein the layer groupings include protrusions.

[0313] 12. The mask of any of the preceding aspects, wherein the mask further comprises an overhead protector.

[0314] 13. The face mask of any of aspects 2 to 12, wherein the face mask and the face mask base exhibit a haze of at most 5%, a transmission of at least 85%, and a clarity of at least 95%.

[0315] 14. The mask of any one of aspects 2 to 12, wherein the layer groupings of the mask include kiss-cut protrusions.

[0316] 15. The face mask of any of the preceding aspects, wherein layer A of the film comprises a first polymer composition A, layer B of the film comprises a second polymer composition B, and layer C of the film comprises a third polymer composition C;

[0317] wherein the polymer composition A comprises polyester, copolyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, polyurethane, aliphatic polyester, polyhydroxybutyrate, polyhydroxysuccinate, styrene copolymer, silicone, silicone thermoplastic, acrylic resin or copolymers or blends thereof;

[0318] wherein the polymer composition B comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof;

[0319] The polymer composition C comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof.

[0320] 16. The mask of any of the preceding aspects, wherein polymer composition A comprises a polyester, a copolyester, an acrylic resin, or a silicone thermoplastic, or a combination thereof;

[0321] wherein polymer composition B comprises copolyester, PMMA, co-PMMA, styrene block copolymer, polypropylene or silicone polyoxamide or a combination thereof;

[0322] The polymer composition C comprises an olefin or styrene block copolymer or a combination thereof.

[0323] 17. The face mask of any one of the preceding aspects, wherein composition A comprises polyethylene terephthalate (PET).

[0324] 18. The face mask of any one of the preceding aspects, wherein polymer composition B comprises a copolyester or a styrene block copolymer or a combination thereof.

[0325] 19. The face mask according to any one of the preceding aspects, wherein polymer composition B comprises a copolymer based on styrene and ethylene / butylene.

[0326] 20. The face mask according to any one of the preceding aspects, wherein polymer composition C comprises a copolymer based on styrene and ethylene / butylene.

[0327] The present invention is illustrated by the following examples. It is to be understood that the specific examples, materials, amounts and procedures are to be interpreted broadly in accordance with the scope and spirit of the present invention as set forth herein.

[0328] Example

[0329] All reagents, starting materials, and solvents used in the following examples were purchased from commercial suppliers (such as Sigma Aldrich, St. Louis, MO) and used without further purification unless otherwise noted.

[0330] Example 1

[0331] The film stack was prepared using 3 extruders feeding into a single 16-layer feedblock attached to a 13" wide die. One extruder was fed polyester (PET) resin to feed 6 PET layers (A layers). Another extruder was fed 5 layers of "tie layer" (layer B) material (Kraton G1645 (Kraton Corporation, Houston, TX), a linear triblock copolymer based on styrene and ethylene / butylene). Another extruder was fed 5 layers of "peel layer" (layer C) material (a blend of polypropylene (PP) and KRATON G1645 (Kraton Corporation, Houston, TX), a linear triblock copolymer based on styrene and ethylene / butylene, used in a ratio of 9:1 (PP:KRATON)).

[0332] The feedblock was designed to feed 6 PET layers at uniform thickness. However, the feedblock was designed to increase the thickness of the combined "bond" and "peel" layers (i.e., Layer B and Layer C or "conformable layers") throughout the stack so that the thickest conformable layer was three times thicker than the thinnest conformable layer.

[0333] The results are as follows Figure 7The predicted layer thickness of each conformable layer of the sample is shown in Table 1. The measured layer thickness of each conformable layer of the sample is shown in Table 2. Layer A was designed to maintain a thickness of 9.5 microns throughout the depth of the stack.

[0334] Different peel force increases or decreases were observed depending on the direction of the gradient. Lower peel forces were associated with the thinner end of the gradient, and higher peel forces were associated with the thicker end of the gradient.

[0335] like Figure 7 As shown in , with increasing thickness of the conformable layer, an increase in peel force from group to group was observed as the thickness of each conformable layer increased. In addition, as the total thickness of the conformable layer (i.e., the sum of all conformable layers in each film sample) increased, the difference in peel force from group to group became more pronounced.

[0336] Using the data in the table, the combination of layer thickness and peel force indicates that a 20% change in conformable layer thickness is sufficient to provide a peel force difference of about 0.5 g / in (ie, about 0.5%).

[0337] A gradient where the thickness of the thickest compliant layer is more than three times the thickness of the thinnest compliant layer can provide an even greater peel force differential from "ABC" layer grouping to "ABC" layer grouping.

[0338] Table 1. Predicted layer thickness

[0339]

[0340] Table 2. Measured layer thickness

[0341]

[0342] Comparative Example 1

[0343] Film stacks were prepared as described in Example 1, except that a different feedblock was used. As in Example 1, the feedblock was designed to feed 6 PET layers at a uniform thickness. In contrast to Example 1, the feedblock was designed to extrude 5 tie layers at a uniform thickness throughout the stack, and 5 release layers at a uniform thickness throughout the stack.

[0344] The nominal thickness of each PET layer was about 10 um thick. The nominal thickness of each adhesive + release layer (ie, layer B and layer C or "conformable layer") was about 11 um.

[0345] The results are as follows Figure 8 shown.

[0346] The entire disclosure of all patents, patent applications and publications cited herein and the available electronic materials are incorporated by reference. In the event of a conflict between the disclosure of this patent application and any document incorporated by reference into this application, the disclosure of the present invention shall prevail. The foregoing detailed description and examples are given only for a clear understanding of the present invention. However, they should not be construed as unnecessary limitations. The present invention is not limited to the specific details shown and described, and variations obvious to those skilled in the art will be included in the present invention defined by the claims.

Claims

1. A film comprising: a coextruded stack of polymer layers, the coextruded stack of polymer layers comprising n layer groupings, each layer grouping comprising a first layer A, a second layer B, and a third layer C, layer B being disposed between layer A and layer C, wherein each layer grouping comprises a conformable layer, the conformable layer comprising layer B and layer C; a grouping interface between layer A and layer C of adjacent layer groupings, the grouping interface exhibiting a first peel force of 1 g / inch or greater; a layer interface between adjacent layers A and B, wherein the layer interface exhibits a second peel force greater than the first peel force; as well as a layer interface between adjacent layers B and C, wherein the layer interface exhibits a third peel force greater than the first peel force; wherein the layer groupings are capable of being individually and irreversibly peeled from the remainder of the stack; and wherein the coextruded stack of polymer layers exhibits a peel force gradient and a thickness gradient of the conformable layer from the first layer grouping to the nth layer grouping, and The peel force at the interface of each successive packet increases by at least 0.5%, and the thickness of the conformable layer of each successive layer packet increases by at least 20%.

2. The film of claim 1, wherein the thickness of layer A remains constant from the first layer grouping to the nth layer grouping, or the coextruded stack of polymer layers comprises a thickness gradient of layer A from the first layer grouping to the nth layer grouping.

3. A membrane comprising: a coextruded stack of polymer layers, the coextruded stack of polymer layers comprising n layer groupings, each layer grouping comprising a first layer A, a second layer B, and a third layer C, layer B being disposed between layer A and layer C, wherein each layer grouping comprises a conformable layer, the conformable layer comprising layer B and layer C; wherein layer A of the film comprises a first polymer composition A, layer B of the film comprises a second polymer composition B, and layer C of the film comprises a third polymer composition C; wherein the polymer composition A comprises polyester, copolyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, polyurethane, aliphatic polyester, polyhydroxybutyrate, polyhydroxysuccinate, styrene copolymer, silicone, silicone thermoplastic, acrylic resin or copolymers or blends thereof; wherein the polymer composition B comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof; wherein the polymer composition C comprises polyester, polyolefin, poly-α-olefin, polymethacrylate, polycarbonate, polycarbonate alloy, aliphatic polyester, polyethylene succinate, polylactic acid, styrene block copolymer, silicone or copolymers or blends thereof; wherein the layer groupings are individually capable of being irreversibly peeled from the remainder of the stack; and wherein the coextruded stack of polymer layers exhibits a peel force gradient and a thickness gradient of the conformable layer from the first layer grouping to the nth layer grouping, and The peel force at the interface of each successive packet increases by at least 0.5%, and the thickness of the conformable layer of each successive layer packet increases by at least 20%.

4. The film of claim 3, wherein the thickness of layer A remains constant from the first layer grouping to the nth layer grouping, or the coextruded stack of polymer layers comprises a thickness gradient of layer A from the first layer grouping to the nth layer grouping.

5. A face mask comprising the membrane according to any one of claims 1 to 4.

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