Patent Publication Number: US-2019193369-A1

Title: Alveolar multilayer structure having a metal coating

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/018,614, filed Feb. 8, 2016; which is a continuation of U.S. patent application Ser. No. 13/700,333, filed Mar. 26, 2013; which is a 371 national phase application of International Application No. PCT/FR2011/051223, filed May 27, 2011; which claims priority to French Application No. 1054073, filed May 27, 2010. The disclosures of each of these applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a multilayer structure comprising: at least one first layer comprising a first polymer film that carries, on a first face, a metal deposit, the first face ( 15 ) being a free face of said first layer ( 10 ); and a second layer comprising a second polymer film. 
     Structures are known that are constituted by a plurality of layers such as a polymer film, possibly with a metal deposit, a metal film, polymer foam, fiberglass, rock wool. Stacking such layers seeks to multiply the thermal barriers, so as to thermally insulate the air situated on one side of the structure from the air situated on the other side. 
     However, such multilayer structures provide little insulation since air is free to flow between the layers and thus to pass via the sides of the structure from a space between two layers to another space between two layers, and this contributes to transferring heat through the multilayer structure. 
     It is possible to contain the structure in a frame that holds the edges of the layers of the structure captive so as to prevent the air from flowing. However, the material of the frame then acts as a thermal bridge that greatly reduces the thermal insulating properties of the structure. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to remedy those drawbacks. 
     The invention seeks to propose a multilayer structure having improved thermal insulation properties. 
     This object is achieved as a result of the second layer being joined, in a plurality of junction zones, to the first layer on the first face carrying said metal deposit, the junction zones defining a region of contact between the first layer and the second layer, the first layer and the second layer forming at least one cell outside the contact region. 
     By means of such provisions, the metallized face of the first film carrying the metal deposit is in contact with the volume of air (or of gas) present in the space between the first film and the second layer. This presents several advantages compared to the prior-art solution in which the space is filled by another material such as foam or by fibers such as wool. Since such materials are opaque to infrared radiation, infrared radiation is absorbed and then re-emitted by such materials. However, such re-emission is weak since the temperature gradient between the fibers or between the walls of the pores in the foam is very low. The dissipation of heat by radiation by such material is thus very small. Even if the first layer is metal, the barrier of the metal to radiant heat transfer is minimized by its contact with the above material, and the metal contributes solely to limiting the transmission of infrared and far-infrared radiation. 
     In contrast, in the solution of the invention, since the metal deposit is directly in contact with the volume of air (or of gas) which is more transparent to thermal radiation than foam or fibers, the thermal radiation re-emitted by the metal deposit does not contribute to heating the space between the first layer and the second layer. 
     In addition, given that the metallized face has lower emissivity than the other face of the first film (e.g. made of polymer) of the first layer, it re-emits less radiation towards the other face (and thus through the first layer), and given that the metallized face is opaque, no radiation can pass through the first layer. 
     This results in better thermal insulation for a structure comprising an assembly of the invention formed of the first layer and of the second layer. 
     Advantageously, the region of contact between the first layer and the second layer comprises a set of crossed continuous lines that form a grid, such that the portions of the first layer and of the second layer that are separated by the lines form a set of closed disjoint cells. 
     For example, all of the space between the first layer and the second layer comprises a set of closed disjoint cells. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be well understood and its advantages appear better on reading the following detailed description of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings, in which: 
         FIG. 1  is a perspective and section view of a multilayer structure of the invention; 
         FIG. 2  is a perspective and section view of another configuration of a multilayer structure of the invention; 
         FIG. 3  is a perspective and section view of another configuration of a multilayer structure of the invention; 
         FIG. 4  is a perspective and section view of another configuration of a multilayer structure of the invention; and 
         FIG. 5  is a section view of another configuration of a multilayer structure of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, the terms “inner” and “outer” respectively indicate, with reference to any two adjacent layers, the space between the two layers and the region outside the two layers. 
       FIG. 1  shows an example of a two-layer structure of the invention. The first layer  10  is constituted by a first polymer film  13  that carries a metal deposit  50  on one of its faces, referred to as its “first” face  15 . 
     The polymer film  13  of the first layer  10  may itself be constituted by a plurality of polymer films. For example, the polymer film  13  may be constituted by a film made of polyethylene (PE) sandwiched between two films made of Surlyn® (manufactured by Dupont de Nemours). 
     A second layer  20 , constituted by a second polymer film  23 , is fastened on the first face  15  that carries the metal deposit  50 . 
     Said fastening is performed in known manner, e.g. using a second film  23  comprising Nucrel® (manufactured by Dupont de Nemours). 
     The second film  23  is fastened on the first film  13  in certain selected junction zones of the surface of the first film  13 . These junction zones taken together are referred to as the contact region  30 . 
     Outside the contact region  30 , the first layer  10  and the second layer  20  co-operate to define a space  40  that has a shape that varies depending on the arrangement of the junction zones forming the contact region  30 . Whatever the configuration, at least a portion of the space  40  is in the shape of a cell  42 , i.e. in this portion, and at rest, the first layer  10  and the second layer  20  form a cell  42  occupying a certain volume, as shown in  FIG. 1 . A layer is at rest when it is not stressed. 
     For example, the contact region  30  is configured in such a manner that the second layer  20  is quilted when the first layer  10  is plane. 
     In  FIG. 1 , the region  30  of contact between the first layer  10  and the second layer  20  comprises a set of crossed continuous lines  38  that form a grid, such that some or all of the first layer  10  and of the second layer  20  form(s) a set of closed disjoint cells  42  that are separated by the lines, the cells  42  thus forming a checkerboard. 
     The continuous lines  38  may be curved or rectilinear. 
     For example, the first half of the lines  38  are parallel to one another, the other half of the lines  38  being parallel to one another and perpendicular to the lines  38  of the first half, such that the cells  42  that are separated by the lines  38  form a rectangular checkerboard, as shown in  FIG. 1 . 
     Given that the first face  15  of the first film  10  carrying the metal deposit  50  is in contact with the volume of air present in the cells  42  between the first layer  10  and the second layer  20 , or, in equivalent manner, between the first film  10  and the second film  20 , and that the metallized face  15  constitutes the face of the first film  10  having the lowest emissivity, heat flow through the cells  42  is minimized. This results in better thermal insulation for a multilayer structure  1  comprising an assembly formed of the first layer  10  and of the second layer  20 , compared to a multilayer structure in which it is the face remote from the metallized face  15  of the first film  10  that is in contact with the volume of air present in the cells  42  between the first layer  10  and the second layer  20 , since said remote face, being made of polymer, has higher emissivity. 
     Furthermore, given that the cells  42  are closed, all of the volume of air between the first layer  10  and the second layer  20  is held captive in the cells  42 , and consequently heat transfers by convection between the two layers are minimized. This results in better thermal insulation than if the cells  42  were open. 
     Advantageously, the cells  42  contain a gas that is more thermally insulating than ambient air. For example, the gas may be dry air or argon. 
     In another configuration, each of the above-described cells  42  presents a hole  425 . 
     The hole may pass through the first layer  10  or through the second layer  20 . 
     Advantageously, the cell shape maximizes the springy properties of the second layer  20 . For example, the cells may be cylindrical in shape, having a base that is circular or hexagonal. 
     Thus, when it is constituted by deformable layers, the multilayer structure  1  may be flattened so as to form a thin sheet, since the air can thus leave the cells  42  via the holes  425 . Such a structure is shown in  FIG. 2 . The total volume of a multilayer structure  1  containing one or more assemblies formed of such first and second layers  10  and  20  may thus be considerably reduced while it is being transported. For example, the multilayer structure  1 , once flattened, may be rolled up so as to form a roll. 
     Once on site, the multilayer structure  1  may be relieved of stresses and placed at rest, so as to return to its initial deployed configuration. This initial configuration is achieved by means of the springiness of the deformable films that form the structure, which springiness tends to cause the cells  42  to return to their initial convex shape. Once deployed, the multilayer structure  1  thus offers good thermal insulation. 
     For example, such a structure may be cut to the appropriate size, then placed in the spaces between the rafters below the roof of a dwelling so as to improve the thermal insulation of the dwelling. 
     If the structure  1  is suspended by its top face, the weight of the layers situated below the top face contributes, under the effect of gravity, to causing the structure  1  to return to its initial deployed configuration. Gravity thus acts in addition to the springiness of the layers of the structure  1 . 
     The holes  425  may be situated at the tops of the cells  42 , passing through the second layer  20 . 
     Each cell  42  may present a plurality of holes  425  that are distributed over the first layer  10  and/or over the second layer  20 . 
     In another configuration, the contact region  30  comprises a set of disjoint continuous lines  38 , such that the portions of the first layer  10  and of the second layer  20  that are separated by the lines  38  form a set of disjoint cells  42  that are open to the outside. For example, all of the contact region  30  may be formed of such lines  38 , as shown in  FIG. 3 . The cells  42  are open to the outside via the side edges of the second layer  20 . 
     A multilayer structure  1  containing one or more assemblies formed of such first and second layers  10  and  20 , may be flattened for being transported, then deployed as explained above. In this configuration, the air leaves the cells  42  naturally, since said cells are open to the outside. 
     In another configuration, the contact region  30  comprises a set of disjoint zones  38 , such that the portions of the first layer  10  and of the second layer  20  that surround the zones  38  form a set of cells  42  that communicate with one another. For example, all of the contact region  30  may be formed of such zones  38 , as shown in  FIG. 4 . 
     The cells  42  may also communicate with the outside, e.g. via holes in the side edges of the second layer  20 , or via holes  425  in the cells  42 , as explained above. 
     A multilayer structure  1  containing one or more assemblies formed of such first and second layers  10  and  20 , may be flattened for being transported, then deployed as explained above. In this configuration, the air leaves the cells  42  naturally, since said cells are open to the outside. 
     In all of the above-mentioned embodiments, it is advantageous for the contact region  30  formed by the set of junction zones joining together the first and second layers  10  and  20  to be of an area that is very small compared to the total area of the surface of the first film  10  facing the second film  20 . The junction zones act as thermal bridges through the multilayer structure since they absorb thermal radiation and are thus emissive. A structure in which thermal bridges are minimized is thus more thermally insulating. 
     The multilayer structure  1  of the invention may also be built up by superposing any number of assemblies, each formed of a first layer  10  and/or of a second layer  20 , as described above. The second layer  20  is thus in contact with the first layer  10  of the adjacent assembly via an inter-assembly contact region  60 , as shown in  FIG. 5 . 
     In this configuration, it is advantageous for the contact region  30  of one assembly and the region  60  of inter-assembly contact with the adjacent assembly not to be superposed, so as to minimize thermal bridges. 
     When each of the cells  42  presents one or more holes  425  passing through the second layers  20 , and when the multilayer structure  1  must be capable of being flattened, the first layers  10  are also provided with holes so as to enable the air to escape from the space between the second layer  20  of one assembly and the first layer  10  of the adjacent assembly. 
     Advantageously, the holes are offset between two adjacent assemblies, so as to optimize the thermal insulation provided by the multilayer structure  1 . 
     Alternatively, the space between the second layer  20  of one assembly and the first layer  10  of the adjacent assembly may open to the outside via the side edges of the structure. 
     In an assembly made up of a first layer  10  and of a second layer  20  as described above, the contact region  30  may be formed of a combination of contact lines  38  and/or of contact zones  38 , as described above. 
     Alternatively, the contact region  30  may be formed of contact lines  38  or of contact zones  38  of a single type, as described above. 
     In the invention, some or all of a multilayer structure  1  may be formed of any combination of such assemblies. 
     For example, the multilayer structure  1  may be constituted by a plurality of superposed assemblies, each made up of a first layer  10  and of a second layer  20  forming disjoint cells  42 . In each assembly, some of the cells  42  present holes  425 , the cells  42  having holes  425  being distributed differently from one assembly to another, such that a straight line perpendicular to the assemblies and passing through the cells always passes through the same number of cells  42  having holes  425 . Thus, the multilayer structure  1  can be compacted in part only (since the air-filled cells  42  without holes cannot be flattened), but in its compacted state, it has a thickness that is substantially constant. 
     In the above description, a first layer  10  is a polymer film that carries, on one face, a metal deposit, and a second layer  20  is a polymer film. 
     In the invention, a first layer  10  may also comprise a plurality of films, and/or the second layer may also comprise a plurality of films. 
     The multilayer structure  1  of the invention may also include superposing any number of assemblies, with each assembly being formed of a first layer  10  and/or of a second layer  20 , as described above, and of third layers that are interposed between one or more of said assemblies. By way of example, a third layer comprises a third polymer film. 
     Advantageously, the third layer is joined, in a plurality of junction zones, to the second layer  20  of a first assembly, the junction zones defining a contact region having a surface area that is smaller than the surface area of the second layer  20 , and the third layer is also joined, in a plurality of junction zones, to the first layer  10  of another assembly, the junction zones defining a contact region having a surface area that is smaller than the surface area of the first layer  10 . The third layer thus makes it easier to assemble together two adjacent assemblies. By way of example, the contact regions are a combination of lines  38  and/or of zones  38 , as described above. 
     The first, second, and/or third layers may optionally be provided with holes  425 .