Polymer film and method for producing same

Abstract

A polymeric film has an orthogonal length and width. The polymeric film includes a substrate and a plurality of fins extending away from the substrate and substantially coextensive with the substrate along the length. The fins are arranged across the width. Each fin of at least a majority of the fins includes a first portion extending from the substrate to a tip of the fin opposite the substrate and a second portion extending from the tip of the fin toward or to the substrate. The second portion is attached to the first portion proximate the tip and is separated along at least a portion of the length from the first portion proximate the substrate. The first and second portions have different first and second compositions, respectively.

Description

Summary of the Invention

[0001] In some aspects, the present disclosure provides a polymeric film having orthogonal lengths and widths. The polymeric film includes a substrate and a plurality of fins extending away from the substrate and substantially coextensive with the substrate along the length. The fins are arranged across the width. Each fin of at least a majority of the fins includes a first portion extending from the substrate to a tip of the fin opposite the substrate and a second portion extending from the tip of the fin toward or to the substrate. The second portion is attached to the first portion proximate the tip and is separated from the first portion proximate the substrate along at least a portion of the length. The first and second portions may have different first and second compositions, respectively.

[0002] In some aspects, the present disclosure provides a polymeric film having an orthogonal length and width. The polymeric film includes a substrate and a plurality of fins extending along the length and arranged across the width. The plurality of fins are substantially coextensive with the substrate along the length. The substrate has an average thickness T in a direction orthogonal to the length and width. The fins extend from the substrate along a height direction to an average height H and have an average width W at a tip of the fin along a direction orthogonal to the height direction. In some embodiments, H / W≧40 and H / T≧40.

[0003] In some aspects, the present disclosure provides a polymer film including a first substrate and a plurality of fins extending along a length of the polymer film and substantially coextensive with the first substrate along the length. The fins extend along a height direction from an attachment of the fins to the first substrate to an average height H. The attachments are spaced apart at an average spacing S along a width direction of the polymer film, which is substantially perpendicular to the length and thickness directions of the polymer film. H can be greater than S. The height direction can be sufficiently inclined relative to the thickness direction such that adjacent fins contact each other.

[0004] In some aspects, the present disclosure provides a thermal management system that includes a polymer film that includes a substrate and a plurality of fins extending away from the substrate.

[0005] In some aspects, the present disclosure provides a method for making at least a first polymer film. The first polymer extends along the length of the first polymer film and has a width along the width of the first polymer film perpendicular to the length. The method includes extruding a first resin and a second resin through a first plurality of slots and a second plurality of slots, respectively, in a slot plate to form a melt laminate composed of alternating first and second elongated elements, respectively. Each of the first and second plurality of slots has a flow direction at an angle to a first plane defined by the length and width directions. The first and second elongated elements extending along the length direction are inclined in a second plane perpendicular to the length direction. The method includes extruding a first skin layer and a second skin layer on each of the first and second sides of the melt laminate to form a melt film, compressing the melt film in a thickness direction perpendicular to the length and width directions, and cooling the melt film to form a first polymer film.

[0006] These and other aspects will become apparent from the following detailed description, but in no way should this brief summary be construed as limiting the claimed subject matter. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a polymer film according to some embodiments. [Diagram 2] 1 is a schematic top view of a polymer film according to some embodiments. [Diagram 3] FIG. 2 is a schematic plan view of a die for extruding a polymer film, according to some embodiments. [Figure 4A]1 is a schematic cross-sectional view of a slot plate according to some embodiments. [Figure 4B] 1 is a schematic cross-sectional view of a slot plate according to some embodiments. [Figure 4C] 1 is a schematic cross-sectional view of a slot plate according to some embodiments. [Figure 5A] 1 is a schematic cross-sectional view of a molten film according to some embodiments. [Figure 5B] 5B is a schematic cross-sectional view of a film according to some embodiments, which may correspond to the molten film of FIG. 5A after it has been compressed. [Figure 5C] FIG. 5C is a schematic cross-sectional view of a film according to some embodiments that may correspond to the film of FIG. 5B after removal of the skin layer. [Figure 6] 1 is a schematic diagram of a method for making a film, according to some embodiments. [Figure 7A] 1 is a top perspective image of an exemplary polymer film. [Figure 7B] 1 is a perspective image of an exemplary polymer film. [Figure 7C] FIG. 7C is a perspective view of a portion of the polymer film of FIG. 7B. [Figure 8] 1 is a schematic end view of a slot plate according to some embodiments. [Figure 9] FIG. 13 is a schematic diagram of a polymer flow path through a slot plate according to some embodiments. [Figure 10] FIG. 2 is a schematic end view of a skin plate according to some embodiments. [Figure 11] 1 is a schematic cross-sectional view of a thermal management system according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0009] According to some embodiments herein, a polymer film is provided that provides a plurality of fins extending along the length of the film. The film may be an extruded and / or integrally formed film. A film is integrally formed when various portions of the film are manufactured together, rather than manufactured separately and then joined. According to some embodiments, it has been found that fins having a high aspect ratio (e.g., height at least 40 times the width) can be provided in an integrally formed film by co-extruding a web that includes a plurality of angled extension elements disposed between two skin layers, then removing one of the skin layers and rotating the extension elements. The fins can include substantially coextensive first and second portions having different compositions. The films according to some embodiments have been found to be useful, for example, for transporting material and / or energy through the film along its length. For example, fins can be used to direct a fluid along the surface of the film, where the fluid can be heated or cooled, for example, to use the film as a heat exchanger. Such films can be useful, for example, for battery cooling. Battery systems cooled using polymeric heat exchanger films are described, for example, in International Patent Publication No. WO 2021 / 044345 (Bartling et al.). According to some embodiments, the films may alternatively or additionally be utilized as packaging films.

[0010] FIG. 1 is a schematic cross-sectional view of a polymer film 100 according to some embodiments. FIG. 2 is a schematic top view of a polymer film 100 according to some embodiments. The polymer film 100 has orthogonal length and width, i.e., the length and width are along orthogonal length (z-direction) and width (x-direction) directions, respectively. The polymer film 100 includes a substrate 120 and a plurality of fins 110 that are substantially coextensive with the substrate 120 along the length (along the length (z-direction) of the polymer film 100). The substrate may also be referred to as a substrate portion, and may be a portion of the film that has a substantially constant thickness. The substrate may be integrally formed with the fins. The fins 110 extend away from the substrate 120 and along the length, and are aligned along the width (along the width (x-direction) of the polymer film). The fins 110 may extend along a height direction 147 away from the substrate 120 to an average height H. Each fin 110 can have a minimum width, which is the minimum distance between opposing major surfaces of the extension element along a direction substantially perpendicular to those major surfaces (e.g., within 30, 20, 10, or 5 degrees of perpendicular). The minimum thickness can occur at the top (e.g., tip 113) of the extension element. For example, in some embodiments, the extension element 110 includes a first portion 111 and a second portion 112 attached to each other proximate the tip 113 of the extension element, and the minimum width can be substantially equal to the combined thickness of the first portion 111 and the second portion 112. The average of the minimum widths is W, which may be referred to as the average width of the tip of the fin. In some embodiments, H / W is at least 40 or within another range described elsewhere herein. In some embodiments, the extension elements are spaced apart along the width direction and arranged with an average spacing S, which can be greater than 10W and / or greater than 10 times the average thickness T of the substrate and / or less than the average height H, or within another range described elsewhere herein. The spacing S may be described as the center-to-center distance between the fins. The fins may be regularly arranged along their width with a pitch equal to the average spacing S.

[0011] Layers or elements may be described as substantially coextensive with one another when at least about 60% of the area of ​​each layer or element (e.g., in a plan view facing a major surface of that layer or element) is coextensive with at least about 60% of the area of ​​each other layer or element. In some embodiments, for layers or elements described as substantially coextensive with one another, at least about 70% or at least about 80% or at least about 90% of the area of ​​each layer or element is coextensive with at least about 70% or at least about 80% or at least about 90% of the area of ​​each other layer or element. Layers or elements may be described as substantially coextensive with one another in length and width when at least about 60% of the length and width of each layer or element is coextensive with at least about 60% of the length and width of each other layer or element. In some embodiments, for layers or elements described as being substantially coextensive with one another in length and width, at least about 80% or at least about 90% of each layer or element is coextensive in length and / or width with at least about 80% or at least about 90% of the length and / or width of each other layer or element.

[0012] The extension elements 110 may be referred to as fins. In some embodiments, each extension element (or fin) of at least a majority (greater than 50%) of the extension elements (or fins) includes a first portion 111 extending from the substrate 120 to a tip 113 of the extension element (or fin) opposite the substrate 120, and a second portion 112 extending from the tip 113 of the extension element (or fin) toward or to the substrate 120. The second portion 112 may be attached to the first portion 111 proximate the tip and may be separated lengthwise from the first portion 111 proximate the substrate 120 along at least a portion of the length L of the extension element (or fin). In some embodiments, the first portion 111 and the second portion 112 have different first and second compositions, respectively, as further described elsewhere herein. The first portion 111 and the second portion 112 of the fin or extension element may independently be an extension element and may be referred to as a first extension element and a second extension element.

[0013] In some embodiments, the polymer film 100 has orthogonal lengths and widths and includes a substrate 120 and a plurality of fins 110 extending along the length (along the length direction (z-direction) of the polymer film 100) and arranged across the width (across the width direction (x-direction) of the polymer film). In some embodiments, the plurality of fins are substantially coextensive with the substrate 120 along the length. In some embodiments, each of the fins, or each fin of at least a majority of the fins, or each fin of at least 60, 70, 80, or 90 percent of the fins, are substantially coextensive with the substrate 120 along the length. The substrate 120 has an average thickness T in a thickness direction (y-direction) orthogonal to the length and width. In some embodiments, the fins 110 extend along a height direction 147 from the substrate 120 to an average height H and have an average width W at the tip of the fin that is an average of the smallest widths of the fins 110 along a direction orthogonal to the height direction 147. Height direction 147 may be within 30 degrees, 20 degrees, or 10 degrees of parallel to the thickness direction (y direction) for each fin of at least a majority of fins 110. In some embodiments, W is in the range of 0.05 to 2 mm. In some embodiments, H / W≧40, 80, 100, 120, 150, or 200. In some such embodiments, or in other embodiments, H / T≧40, 80, 100, 120, 150, or 200. For example, in some embodiments, H / W≧80 and H / T≧80. H / W and / or H / T may be, for example, up to 10,000, 5000, 1000, 500, or 250.

[0014] In some embodiments, the fins 110 are spaced apart along the width and arranged with an average spacing S (or pitch), which may be, for example, greater than 10T, or greater than 20T, or greater than 30T. The spacing S may be, for example, up to 1000 or 10,000 times T. In some embodiments, the fins 110 are arranged regularly along the width. In some such embodiments or other embodiments, the fins are arranged with an average spacing S in the range of 0.1-3 cm. In some embodiments, H>S. For example, H may be at least 1.5, 2, 2.5, or 3 times S. H may be, for example, up to 100, 50, 20, or 10 times S. In some embodiments, the spacing S may be, for example, greater than 10W, or greater than 20W, or greater than 30W. The spacing S may be, for example, up to 1000 or 10,000 W.

[0015] In some embodiments, each fin has a maximum height H1 along a height direction 147 and a minimum width W1 along a direction perpendicular to the height direction. The fins 110 may have an average H1 / W1 of at least 40, or H1 / W1 may be within any of the ranges described elsewhere herein for H / W.

[0016] In some embodiments, the polymer film 100 has a length L along its length (z-direction) that is greater than 1, 10, 30, or 100 meters.

[0017] In some embodiments, the first portion 111 and the second portion 112 have different first and second compositions, respectively. In some embodiments, the substrate 120 comprises the first composition. In some embodiments, the first composition is a first polyester composition and the substrate comprises a second polyester composition. In some embodiments, the first polyester composition and the second polyester composition are different. In some embodiments, the first polyester composition and the second polyester composition are the same composition. The polyester composition may comprise more than 50% polyester by weight.

[0018] In some embodiments, the first portion 111 is directly bonded to the substrate 120, but not the second portion 112. For example, the first portion 111 and the substrate 120 may be formed from the same composition or may be formed from similar polymers (e.g., polymers including at least one of the same monomeric unit) that bond well to each other, while the second portion 112 is formed from a different composition that bonds more weakly to the substrate 120, such that the second portion 112 may be pulled away from the substrate 120 when the fin (or extension element) is formed and rotated, as further described elsewhere herein. In some embodiments, the first composition is a polyester composition. In some such embodiments, or in other embodiments, the second composition includes at least one of an olefin composition and a styrenic composition. In some such embodiments, or in other embodiments, the second composition is an olefin composition. The olefin composition may include more than 50% by weight of an olefin. Similarly, the styrenic composition may include more than 50% by weight of a styrene-containing polymer(s). Compositions that contain significant amounts (e.g., greater than 10 or 20 weight percent) of olefin and styrene-containing compounds may be referred to as either or both olefin and styrene compositions, or as olefin / styrene compositions.

[0019] In some embodiments, the composition is selected such that the first portion 111 and the second portion 112, and / or the second portion 112 and the substrate 120 have surface tensions that differ from each other by at least 10%. The surface tensions may differ from each other by at least 15%, or at least 20%, for example. The surface tensions may differ from each other by up to about 130%, about 100%, or about 80%, for example. The surface tension of the polymer used in the film can often be found in standard tables of surface tensions, as will be appreciated by those skilled in the art. Surface tensions may be measured using contact angle measurements, for example, as described in ASTM D7490-13 "Standard Test Method for Measurement of the Surface Tension of Solid Coatings, Substrates and Pigments using Contact Angle Measurements".

[0020] In some embodiments, the plurality of fins 110 (or extension elements) and the substrate 120 are integrally formed. In some embodiments, the plurality of fins 110 (or extension elements) and the substrate 120 are co-extruded.

[0021] In some embodiments, the compositions used for the fins (or extension elements) and substrates include thermoplastic polymers that can be selected to be easily extrudable and processable. For example, the thermoplastic polymers can be selected to have a molecular weight and / or intrinsic viscosity and / or melt flow index (MFI) within a range suitable for extrudability. In some embodiments, the thermoplastic polymer has a weight average molecular weight Mw of more than 20,000 Daltons, or more than 35,000 Daltons, or more than 50,000 Daltons. The weight average molecular weight Mw can be, for example, up to 1,000,000 Daltons, up to 600,000 Daltons, up to 400,000 Daltons, up to 200,000 Daltons, or up to 150,000 Daltons. In some such embodiments, or in other embodiments, the thermoplastic polymer has an intrinsic viscosity in the range of 0.3 dl / g to 1.2 dl / g or 0.4 dl / g to 1.0 dl / g, as measured in a solvent blend containing 60 weight percent o-chlorobenzene and 40 weight percent phenol. In some such embodiments, or in other embodiments, the thermoplastic polymer has a melt flow index greater than 5 g / 10 min, or greater than 10 g / 10 min, or greater than 20 g / 10 min. The melt flow index may be, for example, up to 300 g / 10 min, or up to 200 g / 10 min, or up to 100 g / 10 min. The weight average molecular weight Mw may be measured, for example, using gel permeation chromatography. The intrinsic viscosity may be measured, for example, using a capillary viscometer. The melt flow index may also be referred to as melt flow rate, and may be measured, for example, using an extrusion plastometer according to ASTM D1238-20.

[0022] Suitable materials for the various portions of the films herein include, for example, polyethylene naphthalate (PEN), coPEN (copolyethylene naphthalate terephthalate copolymer), polyethylene terephthalate (PET), polyhexylethylene naphthalate copolymer (PHEN), glycol modified PET (PETG), glycol modified PEN (PENG), syndiotactic polystyrene (sPS), THV (terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride), polymethyl methacrylate (PMMA), coPMMA (copolymer of methyl methacrylate and ethyl acrylate), styrene block copolymers (block copolymers containing styrene blocks), and the like. Examples of suitable block copolymers include linear triblock copolymers based on styrene and ethylene / butylene (e.g., styrene-ethylene-butylene-styrene (SEBS) copolymers), acrylic block copolymers (block copolymers comprising an acrylate or methacrylate block), linear triblock copolymers based on methyl methacrylate and n-butyl acrylate, anhydride modified ethylene vinyl acetate polymers, ketone ethylene ester terpolymers, polyolefin-based thermoplastic elastomers, polypropylene (PP), copolypropylene (coPP), such as copolymers of polypropylene and ethylene, urethanes, such as thermoplastic polyurethanes (TPU), or blends thereof.

[0023] Atactic polystyrene (aPS) can optionally be blended with sPS (e.g., about 5 to about 30 weight percent aPS) to adjust the refractive index of the resulting layer and / or reduce the haze of the layer (e.g., by reducing the crystallinity of the layer). Suitable THV polymers include those described, for example, in U.S. Patent Application Publication No. 2019 / 0369314 (Hebrink et al.) and available under the tradename DYNEON THV from 3M Company (St. Paul, MN). In some embodiments, the THV can contain about 35 to about 75 mole percent tetrafluoroethylene, about 5 to about 20 mole percent hexafluoropropylene, and about 15 to about 55 mole percent vinylidene fluoride. Suitable styrenic block copolymers include KRATON G1645 and KRATON G1657 available from KRATON Polymers (Houston, TX). Suitable acrylic block copolymers include those available under the trade name KURARITY from Kuraray Co., Ltd. (Tokyo, JP). PETG can be described as PET in which some of the glycol units of the polymer have been replaced with different monomer units, typically monomer units derived from cyclohexanedimethanol. PETG can be produced, for example, by replacing a portion of the ethylene glycol used in the transesterification reaction to produce the polyester with cyclohexanedimethanol. Suitable PETG copolyesters include GN071 available from Eastman Chemical Company (Kingsport, TN). PEN and coPEN can be produced, for example, as described in U.S. Pat. No. 10,001,587 (Liu). A low melting PEN is a coPEN containing about 90 mole percent naphthalene dicarboxylate groups based on the total carboxylate groups, also known as coPEN 90 / 10. Another useful coPEN is coPEN 70 / 30, which contains about 70 mole percent naphthalene dicarboxylate groups and about 30 mole percent terephthalate dicarboxylate groups, based on total carboxylate groups.More generally, coPEN Z / 100-Z may be used where it contains Z mole percent naphthalene dicarboxylate groups (typically greater than 50 mole percent and up to about 90 mole percent) and 100-Z mole percent terephthalate dicarboxylate groups based on the total carboxylate groups. Glycol-modified polyethylene naphthalate (PENG) can be described as PEN in which a portion of the glycol units of the polymer have been replaced with different monomer units, for example, by replacing a portion of the ethylene glycol used in the transesterification reaction to produce the polyester with cyclohexanedimethanol. PHEN can be produced, for example, as described for PEN in U.S. Pat. No. 10,001,587 (Liu), except that a portion (e.g., about 40 mole percent) of the ethylene glycol used in the transesterification reaction is replaced with hexanediol. Suitable PET can be obtained, for example, from Nan Ya Plastics Corporation, America (Lake City, SC). Suitable sPS can be obtained, for example, from Idemitsu Kosan Co., Ltd. (Tokyo, Japan). Suitable PMMA can be obtained, for example, from Arkema Inc. (Philadelphia, PA). Suitable anhydride modified ethylene vinyl acetate polymers include, for example, those available under the trade name BYNEL from Dow Chemical (Midland, MI). Suitable ketone ethylene ester terpolymers include, for example, those available under the trade name BYNEL from Dow Chemical (Midland, MI). Suitable polyolefin-based thermoplastic elastomers include those available under the trade name ADMER from Mitsui Chemicals (Tokyo, Japan). Suitable coPPs include PP8650 (random copolymer of propylene and ethylene) available from Total Petrochemicals, Inc. (Houston, TX).

[0024] 3 is a schematic plan view of a die 444 for extruding a polymer film, according to some embodiments. The die 444 includes a slot plate 431, a skin block 432, and a compression section 433. The compression section 433 compresses the extruded web in the thickness direction (y-direction) and may optionally compress the web in the width direction (x-direction). The die 444 may include other elements not shown but commonly used in extrusion dies, as will be appreciated by those skilled in the art.

[0025] 4A-4C are schematic cross-sectional views of a slot plate 431 according to some embodiments. FIG. 4A is a cross-sectional view adjacent an input side of the slot plate 431, FIG. 4C is a cross-sectional view adjacent an output side of the slot plate 431, and FIG. 4B is a cross-sectional view between FIG. 4A and FIG. 4C. The slots are shown in FIG. 4A-4C as generally rectangular slots, but may have other shapes (e.g., to promote flow to certain areas). For example, the slots may have rounded edges or may have a generally trapezoidal shape. The slot plate 431 may include other features, such as holes on either side of the plurality of slots 410, 420 to promote flow and provide channels for filling material in the side corner areas of the plurality of slots 410, 420. There may also be additional slots on either or both sides of the plurality of slots 410 and additional slots on either or both sides of the plurality of slots 420, without interlacing with each other. Additional hole(s) and / or non-intersecting slot(s) may, for example, serve to stabilize the extruded web. As further described in the Examples, FIG. 8 is a schematic end view of a slot plate showing holes 772, 772' and non-intersecting slots 771, 771', according to some embodiments. FIG. 9 is a schematic illustration of the polymer flow produced by the slot plate of FIG. 8, and FIG. 10 shows the slot plate of FIG. 8 adjacent to a skin plate. The slot plate 431 and other die elements may be fabricated using conventional machining techniques, such as wire electrical discharge machining (EDM).

[0026] 5A is a schematic cross-sectional view of a melt film 250 according to some embodiments. The melt film 250 may correspond to the melt film formed by the slot plate 431 and the skin block 432 before being compressed in the compression section 433. The melt film 250 includes a melt laminate 240 composed of alternating first extension elements 245 and second extension elements 246 disposed between a first skin layer 325 and a second skin layer 320. The first extension elements 245 and second extension elements 246 have different first compositions 545 and second compositions 546, and the first skin layer 325 and second skin layer 320 have third compositions 525 and fourth compositions 520, which may be the same or different. For example, the third composition 525 and the fourth composition 520 may be the same composition, which may be the same as one of the first composition 545 and the second composition 546.

[0027] 5B is a schematic cross-sectional view of the first film 260 according to some embodiments. The polymer film 260 may correspond to the molten film 250 after it has been compressed and cooled in the compression section 433. The polymer film 260 may be described as including a plurality of alternating first and second extension elements 111 and 112 disposed between the first and second skin layers 125 and 120. The first and second extension elements 111 and 112 may be the first and second extension elements 245 and 246 after the molten film 250 has been compressed and cooled to form the polymer film 260. Similarly, the first and second skin layers 125 and 120 may be the first and second skin layers 325 and 320 after the molten film 250 has been compressed and cooled to form the polymer film 260.

[0028] 5C is a schematic cross-sectional view of a polymer film 262, according to some embodiments. The polymer film 262 may correspond to the polymer film 260 after the skin layer 125 has been removed.

[0029] In some embodiments, the polymer film 260, 262 includes a first substrate 120 and a plurality of fins 110 extending along the length of the polymer film (z-direction) and substantially coextensive with the first substrate 120 along the length. The fins 110 extend along a height direction 147 from an attachment portion 117 of the fin attached to the first substrate 120 to an average height H. The attachment portions 117 are spaced apart at an average spacing S along a width direction (x-direction) of the polymer film that is substantially perpendicular to the length and thickness directions (y-directions) of the polymer film. H is greater than S, and the height direction 147 is sufficiently inclined relative to the thickness direction such that adjacent fins contact each other. In some embodiments, the polymer film 260 further includes a second substrate 125, and the plurality of fins 110 are disposed between the first substrate 120 and the second substrate 125.

[0030] In some embodiments, each fin of at least a majority of the fins (or extension elements) includes a first portion 111 and a second portion 112 attached to one another and substantially coextensive with the fin. The first portion 111 and the second portion 112 may have different first and second compositions, respectively, as further described elsewhere herein. In some embodiments, the first substrate 120 includes the first composition. In some such embodiments, or in other embodiments, the polymer film 260 includes a second substrate 125, and the second substrate 125 includes the second composition.

[0031] 6 is a schematic diagram of a method for making a polymer film, according to some embodiments. Resins P1 and P2, and optionally one or both of P3 and P4, are extruded through an extrusion die 344 (e.g., equivalent to die 444) to form an extruded web 350, which is cooled by casting on a casting wheel 346 (also referred to as a chill roll) to form a cast web 351, which may correspond to polymer 260. As will be appreciated by those skilled in the art, an optional roller 347 may be included, and optionally additional rollers (not shown) may be included. The first portion 111 and the second portion 112 may be formed from a first resin P1 and a second resin P2. The first substrate 120 and the second substrate 125 (sometimes referred to as skin layers) may be formed from P1 and P2, or from any of P1-P4. In some embodiments, the first resin P1 comprises a polyester, and the second resin P2 comprises an olefin. In some such or other embodiments, the first substrate 120 and the second substrate 125 are formed from resins P3 and P4, which may include polyester and may be the same as or different from the first resin P1. In some embodiments, the first extension elements 111 and the second extension elements 112 in the first polymer film 260 have surface tensions that differ from one another by at least 10% or another range described elsewhere herein.

[0032] In some embodiments, a method is provided for making at least a first polymer film. The first polymer extends along the length of the first polymer film and has a width along the width of the first polymer film, perpendicular to the length. The method includes extruding a first resin and a second resin (e.g., P1 and P2) through a first plurality of slots (410) and a second plurality of slots (420) in a slot plate 431, respectively, to form a melt laminate 240 composed of alternating first and second elongated elements 245 and 246, respectively. Each of the first and second plurality of slots has a flow direction (e.g., 158, 159 shown diagrammatically in FIG. 3) that is angled with respect to a first plane (plane 455 or xz-plane) defined by the length and width directions. The first and second elongated elements 245 and 246 extend along the length and are inclined in a second plane (xy-plane) perpendicular to the length. The method includes extruding a first skin layer (325) and a second skin layer (320) onto respective first and second sides 242 and 241 of a molten laminate (e.g., via a skin block 432) to form a molten film 250, compressing the molten film in a thickness direction (y-direction), perpendicular to the length and width directions (e.g., in a compression section 433), and cooling the molten film to form a first polymer film 260.

[0033] In some embodiments, the flow direction 158, 159 of each of the first and second plurality of slots forms an angle θ1, θ2 with respect to the first plane in a range between 5 degrees and 85 degrees, or between 10 degrees and 90 degrees, or between 20 degrees and 80 degrees, or between 30 degrees and 60 degrees, or between 40 degrees and 50 degrees. Each of the angles θ1, θ2 may be, for example, about 45 degrees.

[0034] In some embodiments, the method further includes removing the first skin layer (125) rather than the second skin layer (120) from the first polymer film 260 to form a second polymer film 262 having a plurality of angled fins 110 formed from the first extension element 245 (or 111) and the second extension element 246 (or 112). In some embodiments, the method further includes rotating the angled fins so that the fins generally extend away from the second skin layer (e.g., rotating the fin of FIG. 5C so that the fins generally extend away from the skin or substrate 20 as shown generally in FIG. 1). In some embodiments, each angled fin of at least a majority of the angled fins comprises adjacent first and second portions 111, 112 that extend generally parallel to one another and are joined to one another along at least a portion of the angled fin. In some embodiments, rotating the angled fin causes the first portion 111 and second portion 112 to separate from one another along at least a portion of the fin adjacent the second skin layer 120. It has been found that when the fin is rotated, the first portion 111 and second portion 112 may remain connected to one another near the tips of those portions, but adjacent fins 110 may separate from one another.

[0035] FIG. 7A is a top perspective image of an exemplary polymer film that may correspond to polymer film 260. The fins of the exemplary polymer film included a dye in one of the first and second portions of the fin. In FIG. 7A, the edges of the portions with the dye are visible as dark stripes. FIG. 7B is a perspective image of an exemplary polymer film in which the top skin (e.g., of the polymer film of FIG. 7A) has been removed and the fins of a portion of the film have been rotated so that they extend generally away from the bottom skin or substrate of the film. FIG. 7C is a perspective image of a portion of the polymer film of FIG. 7B at an enlarged scale compared to FIG. 7B.

[0036] In some embodiments, the first polymer film 260 or the second polymer film 262 includes a first substrate 120 and a plurality of fins 110 extending along the length (z-direction) of the polymer film. The fins 110 extend along a height direction 147 from an attachment portion 117 of the fin attached to the first substrate 120 to an average height H. The attachment portions 117 can be spaced apart an average spacing S along a width direction (x-direction) of the polymer film 260, 262, which is substantially perpendicular to the length (z-direction) and thickness (y-direction) of the polymer film 260, 262. H can be greater than S. H, S, and / or H / S can be within any of the ranges described elsewhere herein. The height direction 147 of the polymer film 260, 262 can be sufficiently inclined with respect to the thickness direction such that adjacent fins contact each other.

[0037] FIG. 11 is a schematic cross-sectional view of a thermal management system 1000 according to some embodiments. The thermal management system 1000 includes a pump 973 for circulating a fluid 900 between the fins of a film 800, which may correspond to, for example, a polymer film 100. The film 800 may be placed on an object or device 830 that is desired to be cooled or heated. An adhesive may be placed between the film 800 and the object or device 830 to bond the film to the object or device. Alternatively, the film 800 may include an adhesive for bonding to the object or device 830. The adhesive may be a thermally conductive adhesive (e.g., the adhesive may include a thermally conductive filler). The fluid 900 may be a cooling fluid (e.g., maintained at a temperature lower than a predetermined operating temperature of the device) or a heating fluid (e.g., maintained at a temperature higher than a predetermined temperature of the object). In some embodiments, a film 800 is provided that includes a polymer film 100 (see, for example, FIG. 1) and a liquid 900 that at least partially fills the space between adjacent fins 110 of the polymer film 100. The film 100, 800 may optionally include an additional layer disposed on top of the fin 110 to define a channel between the substrate 120 of the polymer film 100 and the additional layer. The additional layer may be bonded to the tip of the fin 110, for example, via an adhesive layer. EXAMPLES

[0038] Films having extension elements (fins or louvers) were prepared and manipulated, and physical properties were evaluated and are shown in the examples below.

[0039] These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. All parts, percentages, ratios, etc. in the examples and elsewhere herein are by weight unless otherwise indicated. The following abbreviations are used herein: mil = thousandths of an inch, mm = millimeters, cm = centimeters, °C = degrees Celsius, sec = seconds, % = percent, in = inches, IV = inherent viscosity, MFI = melt flow index. [Table 1]

[0040] Examples E1 to E5 The hardware for forming the substrate and the film with multiple fins included a dual manifold die with each manifold feeding a series of slots cut into a slot plate. The slots were 0.687 inches (17.45 mm) long and 0.033 inches (0.84 mm) wide at the wide end and 0.022 inches (0.56 mm) wide at the narrow end (trapezoidal shape). The slots were spaced 0.066 inches (1.68 mm) apart, centered on the exit side. The slots were angled in the yz plane from the manifold to the centerline of the die, intersecting to form an ABAB... pattern, as shown in Figure 3. The slots were also angled 45 degrees in the xy plane (see, e.g., Figures 4A-4C), as shown in Figure 8. There were several slots 771, 771' on each edge of the slot plate, which did not intersect because the inlet end of the opposite slot was beyond the feed manifold. Holes 772, 772' angled in the yz plane were drilled into each end of the slot plate to promote flow in the manifold and to "fill" the corners of the louver stack. The output film has a solid band of A resin on one edge and a solid band of B resin on the other edge.

[0041] 9 shows the resulting polymer flow paths through the slot plate, showing the AB interlacing pattern and polymer flows 871 and 872 corresponding to slots 771 and holes 772, respectively.

[0042] After the louver laminate was formed, the resin was poured into a skin plate as shown in Figure 10. The skin plate applied a skin layer to the top and bottom of the laminate through channels 781 and 782, respectively. The skin layer could be the same resin as one or both of the louvers, or it could be one resin or two different resins. Of particular interest was when the top skin layer matched louver resin A and the bottom skin layer matched louver resin B.

[0043] The combined louver laminate and skin was run through the die exit and compressed in the y-direction from a height of 0.50 in. (1.3 cm) to approximately 0.050 in. (0.13 cm). The width in the x-direction remained constant from the slot plate to the die exit.

[0044] Preparation of Examples Using the above configuration, a series of films was produced using the following equipment settings: The chill roll (wheel) side skin layers were fed using a 18 mm Leistritz TSE (twin screw extruder) operated under vacuum and a progressive temperature profile with 8 / 0 temperatures from 260-271°C. The associated gear pump and neck tubes were also heated to 260-271°C. The air side skin layers were fed using a 27 mm Leistritz (Leistritz Extrusion Technologies, Nurnberg, Germany) TSE operated under vacuum and again a progressive temperature profile with 8 / 0 temperatures from 260-271°C. The associated gear pump and neck tubes were also heated to 260-271°C. Each set of discontinuous graded layers was fed using a 27 mm Leistritz TSE operated under vacuum and again a progressive temperature profile with 8 / 0 temperatures from 260-271°C. The associated gear pump and neck tube were also heated to 260-271° C. The die detailed above was positioned directly above a rotating chill roll at 27° C. with associated electrostatic pinning for rapid cooling of the web. This apparatus produced the above substrates in cast web thicknesses ranging from 12 to 30 mils thick.

[0045] Table 2 details the material composition of the cast webs (films) produced. [Table 2]

[0046] The cast web film was then manipulated as follows. 1) One of the skins was removed from the web. In most cases, due to poor adhesion between one of the louvers and the skin, one of the skins pulled away easily. 2) Using various sample styli, probes, or fingertips, the louvers (fins) were manipulated and moved "against the grain" of the louvers as extruded. The louvers were essentially parallel to the substrate base layer after extrusion, but formed discontinuous channels about 1 / 4 inch (0.64 cm) wide, with one end of the channel attached to the base layer and the other end free-floating like fish scales. The louvers could be easily rotated by probing against the grain. 3) The louvers, when rotated past a certain point of no return, tended to stick out nearly perpendicular to the cast web film. These louvers were approximately 3 / 16" to 5 / 16" (0.35 to 0.79 cm) in height.

[0047] Typical dimensions of the films were as follows: Prior to fin manipulation, the base film was typically about 24 mils thick. The peeled top substrate was approximately 6-7 mils thick, the bottom substrate was approximately 6-7 mils thick, and the louvers were each 5.5-6 mils thick. The louvers were spaced at approximately 6-7 lines per inch (approximately 2.4-2.8 lines per cm).

[0048] Figures 7A-7C are images of Example E5. Figure 7A shows the film before manipulation, and Figure 7B shows the same film subsequently dissociated and manipulated as described above to produce a base film having fins longer than 1 / 4 inch (0.64 cm) protruding at about 90 degrees from the film surface. The middle portion of the film in Figure 7B has been manipulated to produce essentially vertical fins about 1 / 4 inch (0.64 cm) high. Figure 7C is a close-up of the middle portion. In Figure 7B, the unmanipulated fins can be seen to assume a discontinuous flat position adjacent either side of the vertical channels.

[0049] Terms such as "about" will be understood by those of skill in the art in the context in which they are used and described herein. Where the use of "about" as applied to quantities describing feature sizes, quantities, and physical properties is not otherwise clear to those of skill in the art in the context in which it is used and described herein, "about" will be understood to mean within 10 percent of the particular value. A quantity given as about a particular value may be exactly that particular value. For example, where the use of "about" as applied to quantities describing feature sizes, quantities, and physical properties is not otherwise clear to those of skill in the art in the context in which it is used and described herein, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and may even be 1.

[0050] All references, patents, or patent applications referenced above are hereby incorporated by reference in their entirety. In the event of any inconsistency or contradiction between any of the incorporated references and this application, the information in the foregoing description shall prevail.

[0051] Descriptions of elements in the drawings should be understood to apply equally to corresponding elements in other drawings unless otherwise indicated. Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent implementations without departing from the scope of the present disclosure. The present application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and the equivalents thereof.

Claims

1. A polymeric film having orthogonal length and width, the polymeric film comprising a substrate and a plurality of fins extending away from the substrate and substantially coextensive with the substrate along the length, the fins arranged across the width, and each fin of at least a majority of the fins comprising: a first portion extending from the substrate to a tip of the fin on an opposite side of the substrate; a second portion extending from the tip of the fin toward or to the substrate, the second portion being attached to the first portion proximate the tip and separated from the first portion proximate the substrate along at least a portion of the length, wherein the first and second portions have different first and second compositions, respectively.

2. The polymeric film of claim 1 , wherein the substrate comprises the first composition.

3. The polymeric film of claim 1 , wherein the first composition is a first polyester composition and the substrate comprises a second polyester composition.

4. The polymeric film of claim 1 , wherein the second composition is an olefin composition.

5. 5. The polymer film according to claim 1, wherein the fin extends from the substrate along a height direction to an average height H, and has an average width W at a tip of the fin along a direction perpendicular to the height direction, and H / W≧40.

6. A polymeric film having orthogonal length and width, A substrate; a plurality of fins extending along the length and arranged across the width, the plurality of fins being substantially coextensive with the substrate along the length, the substrate having an average thickness T in a direction perpendicular to the length and the width, the fins extending from the substrate along a height direction to an average height H and having an average width W at a tip of the fin along a direction perpendicular to the height direction, wherein H / W≧40 and H / T≧40.

7. The polymer film of claim 6 , wherein the fins are arranged at an average spacing S along the width that is greater than 20T.

8. The polymer film of claim 7, wherein H>S.

9. 9. The polymer film of claim 6, wherein each fin among at least a majority of the fins comprises a first portion and a second portion bonded to each other and extending from a tip of the fin on opposite sides of the substrate toward or to the substrate, the first portion and the second portion having different first and second compositions, respectively.

10. 10. The polymer film of claim 9, wherein for each fin among at least a majority of the fins, the second portion is attached to the first portion proximate the tip and separated from the first portion proximate the substrate along at least a portion of the length of the fin.

11. A polymer film, a first substrate; a plurality of fins extending along a length direction of the polymer film and substantially coextensive with the first substrate along the length direction, the fins extending along a height direction from an attachment portion of the fin attached to the first substrate to an average height H, the attachment portions being spaced apart at an average spacing S along a width direction of the polymer film that is substantially perpendicular to the length direction and the thickness direction of the polymer film, H being greater than S, and the height direction being sufficiently inclined with respect to the thickness direction such that adjacent fins contact each other.

12. The polymer film of claim 11 , further comprising a second substrate, the plurality of fins being disposed between the first substrate and the second substrate.

13. 1. A method for making at least a first polymer film, the first polymer film extending along a length direction of the first polymer film and having a width along a width direction of the first polymer film that is perpendicular to the length direction, the method comprising: extruding a first resin and a second resin through a first plurality of slots and a second plurality of slots, respectively, in a slot plate to form a melt laminate comprised of alternating first and second elongated elements, respectively, wherein each of the first and second plurality of slots has a flow direction that is angled with respect to a first plane defined by the length direction and the width direction, and the first and second elongated elements extend along the length direction and are angled in a second plane perpendicular to the length direction; extruding a first skin layer and a second skin layer onto opposite first and second sides of the melt laminate to form a melt film; compressing the molten film in a thickness direction perpendicular to the length direction and the width direction; and cooling the molten film to form the first polymer film.

14. 14. The method of claim 13, further comprising removing the first skin layer but not the second skin layer from the first polymer film to form a second polymer film having a plurality of angled fins formed from the first extension elements and the second extension elements.

15. The method of claim 14 , further comprising rotating the angled fins so that the fins extend generally away from the second skin layer.

Images