Abstract:
A composite headliner material allows sound waves originating within a vehicle to penetrate deeply into the headliner where all of a significant portion of their energy is absorbed rather than reflected back into the vehicle. The coverstock sheet is backed by a multilayer material with a foam core coated above and below by a fibrous glass mat impregnated with an adhesive with scrim layers above and below glass mat layers.

Description:
CLAIM OF BENEFIT OF FILING DATE 
     The present application claims the benefit of the filing date of PCT Application Serial No. PCT/US2008/071359 (filed Jul. 28, 2008) (Published as WO 2009/018218) and 60/952,360 (filed Jul. 27, 2007), the contents of which are hereby incorporated by reference in their entirety. 
     CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/952,360 filed Jul. 27, 2007, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a vehicle panel such as a composite headliner that provides improved acoustic performance. 
     BACKGROUND 
       FIG. 1  shows a conventional vehicle panel  90  that includes a decorative coverstock material  112 , a coverstock foam layer  114 , an air-impermeable adhesive barrier layer  116 , a lower glass mat layer  120 , a core foam layer  130 , an upper glass mat layer  160 , and a scrim layer  140 . The upper glass mat layer  160 , the core foam layer  130 , and the lower glass mat layer  120  are adhered together using a thermosetting adhesive, such as, for example methylene diphenyl diisocyanate (“MDI”), along with a catalyst, which can be sprayed on or rolled on to the core foam layer  130 , between the upper glass mat layer  160  and the core foam layer  130  and between the lower glass mat layer  120  and the core foam layer  130  to form a rigid composite reinforcing layer. Because the process uses a thermosetting adhesive, such as MDI, as opposed to using an adhesive film or a hot melt adhesive to bind the upper glass mat layer  160  and lower glass mat layer  120  to the core foam layer, the adhesive flows through the upper glass mat layer  160  and lower glass mat layer  120 . This is advantageous, as the upper adhesive layer can also be used to adhere a coverstock laminate  105 , comprising the decorative coverstock material  112 , the coverstock foam layer  114 , and the adhesive barrier  116 , to the lower surface of the upper glass mat layer  160 . In many cases, the adhesive barrier  116  is the same as the scrim layer  140 . 
     The composite headliner is formed by placing the various layers, including the coverstock laminate, between two plates of a press and applying heat and pressure to the stack of layers. The pressure forces the MDI adhesive through the upper glass mat layer  160  and lower glass mat layer  120  to adhere the various layers together, while the heat and the catalyst causes the MDI adhesive to cure or set and forms the composite matrix. 
     However, at the same time, if not prevented, the MDI adhesive can flow to areas where it is not desired. Specifically, such areas include the tool surfaces used to heat and compress the various layers and the decorative coverstock composite material. In particular, the MDI adhesive can mar or otherwise negatively affect the appearance of the surface of the decorative coverstock material if it were allowed to reach the decorative coverstock material  112  or the coverstock foam  114 , such as, for example, by causing pits, bumps, adhesive bleed through, and ripples in the surface. Accordingly, the scrim layer  140  and the adhesive barrier layer  116  protect the tool surfaces and the decorative coverstock material  112  and coverstock foam layer  114 , respectively, by preventing the MDI adhesive from flowing past the scrim layer  140  and adhesive barrier layer  116 . 
     SUMMARY 
     The present disclosure relates to a thermosetting composite headliner, comprising a porous open-cell, semi-rigid foam core; a porous fibrous reinforcement layer adjacent the porous open-cell, semi-rigid foam core; a coverstock sheet adjacent the porous fibrous reinforcement layer; and adhesive material that binds together the porous open-cell, semi-rigid foam core, the porous fibrous reinforcement layer and the coverstock sheet, the adhesive material comprising a cured liquid adhesive, wherein the coverstock sheet comprises a coverstock material layer, a coverstock foam layer, and an adhesive barrier comprising a non-woven polyethylene terephthalate (“PET”) material that allows sound waves or energy to pass from the coverstock material layer into the porous fibrous reinforcement layer and that reduces an ability of the liquid adhesive to pass through the adhesive barrier and into at least the coverstock foam layer. 
     The present disclosure also relates to a method for producing a composite headliner, comprising applying adhesive to the top surface and bottom surface of the foam core; placing a fibrous layer to the adhesive coated surface of the foam core; placing a scrim layer next to the lower porous fiber layers; preparing a coverstock sheet comprising a coverstock material layer and an adhesive barrier; and applying heat and pressure to the layered materials with a hot press. 
     These and other features and advantages of various exemplary embodiments of systems and methods according to this invention are described in, or are apparent from, the following detailed descriptions of various exemplary embodiments of various devices, structures and/or methods according to this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary embodiments of the systems and methods according to this invention will be described in detail, with reference to the following figures, wherein: 
         FIG. 1  is a schematic view of a conventional composite headliner; 
         FIG. 2  is a schematic view of a composite headliner according to this invention; and 
         FIG. 3  is a schematic representation of a process for forming the composite headliners shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     This invention relates to a composite headliner that has improved acoustic properties, comprising a decorative coverstock material, a coverstock foam layer, an adhesive barrier layer that allows sound energy to pass through while reducing the ability of adhesive from passing through, an upper porous fibrous layer, a foam core layer, an upper adhesive material adhering the adhesive barrier layer and the upper fibrous layer to the foam core layer, a lower porous fibrous layer, a scrim layer, and an lower adhesive material adhering the scrim layer and the lower fibrous layer to the foam core layer. 
     This invention also relates to a thermosetting composite headliner, comprising a porous open-cell, semi-rigid foam core, a porous fibrous reinforcement layer adjacent the porous open-cell, semi-rigid foam core, a coverstock sheet adjacent the porous fibrous reinforcement layer and adhesive material that adhesively connects together the porous open-core, semi-rigid foam core, the porous fibrous reinforcement layer and the coverstock sheet, the adhesive material comprising a cured polyurethane (e.g., MDI and a polyol) adhesive, wherein the coverstock sheet comprises a coverstock material layer, a coverstock foam layer and an adhesive barrier comprising a non-woven polyethylene terephthalate (“PET”) material that allows sound waves or energy to pass from the coverstock material layer into the porous fibrous reinforcement layer and that reduces an ability of the liquid adhesive to pass through the adhesive barrier and into at least the coverstock foam layer. 
     As utilized herein, the terms “approximately,” “about,” “substantially,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims. 
     It should be noted that references to relative positions (e.g., “top” and “bottom”) in this description are merely used to identify various elements as are oriented in the FIGURES. It should be recognized that the orientation of particular components may vary greatly depending on the application in which they are used. 
     As shown in  FIG. 1 , the inventors have determined that the conventional adhesive barrier layer  116  acts as a barrier to sound waves and other types of acoustic energy. While this is advantageous when the sound energy arises outside of the passenger compartment (external sound  210 ), this is not advantageous for sound energy that travels from the passenger compartment into the composite headliner. In such situations, the conventional adhesive barrier layer  116  reflects the internal sound energy  200  back through the coverstock foam  114  and decorative coverstock material  112  and into the passenger compartment. Because the coverstock foam  114  is typically relatively thin and the decorative coverstock material  112  is not designed to attenuate sound energy, the composite headliner  105  does not absorb or dissipate substantial amounts of sound energy. 
     Both U.S. Pat. Nos. 6,204,209 and 6,368,702, each of which is incorporated herein by reference in its entirety, disclose a composite headliner having a foam core and adjacent fibrous layers. The &#39;209 Patent outlines how this composite headliner has improved acoustic properties due to the sound absorbing characteristics of the foam core and fibrous layers. 
     The inventors have discovered that the acoustic properties of a composite headliner such as that shown in  FIG. 1  can be improved if the adhesive barrier can be modified to allow sound energy to pass through it to the underlying fibrous layers and foam core, while maintaining the competing adhesive barring characteristics of the adhesive barrier. The inventors have developed a composite headliner that includes a barrier that allows for improved acoustic performance while having the ability to slow the movement of the adhesive into the coverstock composite. 
       FIG. 2  schematically illustrates one exemplary embodiment of a composite headliner  100  having improved acoustic performance according to this invention. As shown in  FIG. 2 , the composite headliner  100  includes a three-layer laminated, or trilaminate, coverstock sheet  110 , a lower porous fibrous layer  120 , a lower adhesive layer  122 , an at least semi-rigid foam core  130 , an upper adhesive layer  122 , an upper porous fibrous layer  160 , a scrim layer  140 , and a release sheet  150 . It should be appreciated that the release sheet can be omitted if it is not necessary. The trilaminate coverstock sheet  110  includes a coverstock material layer  112 , a coverstock foam layer  114 , and a sound-permeable adhesive barrier  118 . The upper and lower adhesive layers  122  may include a liquid adhesive and a catalyst that causes the liquid adhesive to cure when heated. 
     As shown in  FIG. 2 , sound waves or energy  200  from the passenger compartment impinge on the passenger surface (also called the “show surface” or “A surface”) of the composite headliner  100 . Likewise, external sound waves or energy  210  impinge on the exterior side of the composite headliner  100 . As shown in  FIG. 1 , in conventional composite headliner  90 , the sound waves or energy from the passenger compartment pass through the coverstock material and coverstock foam, but reflect off of the adhesive barrier back into the passenger compartment. Thus, the other layers of the composite headliner are not able to contribute to the sound absorbing quality of the conventional headliner. As shown in  FIG. 1 , the conventional scrim layer  14  is able to reduce the ability of the sound waves or energy from the exterior side of the composite headliner from entering the passenger compartment through the composite headliner. Furthermore, any external sound  210  that did penetrate scrim layer  140  would be effectively blocked by at least conventional adhesive barrier  116 . 
     As shown in  FIG. 2 , a composite headliner  100  according to this invention includes an adhesive barrier  118  that more readily allows the sound waves or energy  200  impinging on the composite headliner  100  from the passenger compartment to pass through the adhesive barrier  118 , the lower porous fibrous layer  120 , the foam core  130 , and the upper porous fibrous layer  160 . It should be appreciated that the sound waves or energy  200  are at least partially absorbed in these layers that underlie the adhesive barrier, attenuating the sound waves or energy  200 . Furthermore, as shown in  FIG. 2 , should the sound waves or energy  200  reach the scrim layer  140  and be reflected back towards the passenger compartment, the upper porous fibrous layer  160 , the foam core  130 , and the lower porous fibrous layer  120  absorb more of the reflected sound waves or energy, further attenuating the sound waves or energy  200 . Thus, even if some portion of the sound waves or energy  200  re-enters the passenger compartment from the composite headliner  100 , the sound waves or energy  200  are significantly attenuated. 
     It should further be appreciated that, in some exemplary embodiments of the composite headliner  100 , the adhesive barrier  118  also tends to reflect sound waves or energy  210  that impinge on the composite headliner  100  from the vehicle side of the composite headliner. 
     In the exemplary embodiment shown in  FIG. 2 , the coverstock material layer  112  is a sheet of Rhonby fabric and is about 0.5 mm thick. However, it should be appreciated that any known or later-developed material can be used as desired as the coverstock material layer  112 , and the thickness of the coverstock material layer  112  will vary depending on the selected material. In the exemplary embodiment shown in  FIG. 2 , the coverstock foam layer  114  is shown as a layer of polyurethane foam having a finished foam thickness of at least 2.25 mm. Typically, the coverstock foam layer  114  will have a pre-mold thickness of about 2 mm to about 4 mm, while the finished foam thickness of the coverstock foam layer  114  after molding will be about 1 mm to about 3 mm. It should be appreciated that any desired known or later-developed foam material can be used as the coverstock foam layer  114 . It should be appreciated that the coverstock material can be technical or non-technical. 
     As shown in  FIG. 2 , in the illustrated exemplary embodiment, the sound-permeable adhesive barrier  118  is a non-woven layer or mat of PET fibers. In an exemplary embodiment, the adhesive barrier  118  is about 0.8 mm to about 1.3 mm thick before molding, and about 0.6 mm to about 1.1 mm thick after molding. The adhesive barrier  118  does not allow the upper adhesive layer  122  to bleed through into the coverstock foam layer  114  or the coverstock material layer  112  but allows sound waves or energy  200  to pass through into the underlying upper porous fibrous layer  160  and/or lower porous fibrous layer  120 . If the upper adhesive layer  122  bleeds into, and possibly through, the coverstock foam layer  114 , the liquid adhesive of the upper adhesive layer  122  will cause surface defects in the composite headliner  100 , which means that that particular composite headliner  100  would have to be scrapped. 
     In one exemplary embodiment, the sound-permeable adhesive barrier is a layer of Dutexim (e.g., Dutexim 41-12C), which is manufactured by Tharreau Industries, of Chemille, France. However, it should be appreciated that any material which is able to sufficiently reduce the ability of the liquid components of the upper adhesive layer  122  to flow into the coverstock sheet  110  so that the appearance and function of the coverstock sheet  110  is not degraded, while at the same time allowing sound waves or energy  200  to pass through the adhesive barrier  118  and into at least the upper porous fibrous layer  120 , can be used as the sound-permeable adhesive barrier  118 . Thus, for example, various non-woven PET layers or mats may be used. For example, the sound-permeable adhesive barrier  118  may comprise PGI GS-35 (manufactured by Polymer Group, Inc. of Charlotte, N.C.) with a hydro-resistive fluorocarbon treatment. 
     In general, the inventors have determined that the characteristics of the PET non-woven mat affect the acoustic and adhesive blocking performance of the adhesive barrier  118 . The fiber material used to form the adhesive barrier  118 , the diameter of the fibers of the selected material, and the coating, if any, on the mat or layer of the selected fibers should be appropriately selected, as each contributes to the ability of the adhesive barrier  118  to block the adhesive while allowing sound to travel through to the underlying upper porous fibrous layer  160  and/or lower porous fibrous layer  120 . 
     It should be appreciated that, in other exemplary embodiments of the composite headliner  100 , a two-layer laminate, or bilaminate, coverstock sheet can be used in place of the trilaminate coverstock sheet  110  shown in  FIGS. 1 and 2 . In such exemplary embodiments, the bilaminate coverstock sheet includes the coverstock material layer  112  and the adhesive barrier  118 , while omitting the coverstock foam layer  114 . It should be appreciated that the adhesive barrier  118  in the bilaminate coversheet  110  will also allow sound waves or energy  200  to pass through to at least the lower porous fibrous layer  120  while not allowing the liquid adhesive of the lower adhesive layer  122  to bleed through into the coverstock material layer  112 . 
     In addition to the sound-permeable adhesive barrier  118 , the composite headliner  100  also desirably uses a less dense, more open cell core polyurethane (PU) foam as the foam core  130 . Using a less dense, more open core polyurethane foam as the foam core  130  also allows needle punching of the foam core  130  to be reduced, and ideally eliminated. Needle punching is sometimes done on polyurethane foam layers to improve their acoustic characteristics or performance. Of course, it should be appreciated that needling or capping the foam core  130  allows for a non open celled foam material to be used. However, needling is an additional process which adds cost. It should be appreciated that using an open cell foam in the foam core  130  also increases the acoustic performance of the composite. 
     As shown in  FIG. 2 , in the illustrated exemplary embodiment, the foam core  130  is a layer polyurethane foam. For example, the foam core  130  may be Woodbridge Stratas 1615 polyurethane foam (manufactured by Woodbridge Sales &amp; Engineering, Inc., of Troy, Mich.). Another suitable material is Woodbridge Stratas 1220 polyurethane foam. It should be appreciated that any semi-rigid foam having suitable acoustic characteristics can be used in the foam core  130 . In the exemplary embodiments shown in  FIGS. 1 and 2 , the foam core  130  has a pre-mold thickness of about 8 mm and a post-mold thickness of about 7 mm. It should be appreciated that the thickness of the foam core  130  can range from about 5 mm, or even less, to about 14 mm, or even more. In general, the thicker the foam core  130  is, the better the acoustic performance of the composite headliner  100  will be. 
     The upper porous fibrous layer  160  and lower porous fibrous layer  120  can also be desirably selected to further improve the acoustic characteristics of the composite headliner  100 . In the exemplary embodiment shown in  FIG. 2 , the upper porous fibrous layer  160  and lower porous fibrous layer  120  are formed using fiberglass mats. Typically, each of the upper porous fibrous layer  160  and lower porous fibrous layer  120  will have pre-mold and post-mold thicknesses of about 0.5 min to about 0.7 mm. It should be appreciated that any appropriate known or later developed material can be used in the upper porous fibrous layer  160  and lower porous fibrous layer  120 , so long as the upper porous fibrous layer  160  and lower porous fibrous layer  120  provide a desired amount of reinforcement and a desired level of acoustic performance. In various embodiments, the foam core may have a thickness from about 3 to 15 mm. 
     It should be appreciated that the thicknesses of the above-outlined layers will typically vary throughout the manufacturing process. It should also be appreciated that it may be desirable to reduce the thickness and/or weight of the composite headliner  100 . This can be accomplished by reducing the thickness or weight, as desired, of one or more of the foam core  130 , the upper glass mat layer  160  and/or lower porous fibrous layers  120 , the scrim layer  140  and/or the coverstock sheet  110 . For example, a foam core having a 5 mm pre-mold thickness and/or a thinner and/or less-dense fibrous layer could be used in place of those layers discussed above. 
       FIG. 3  illustrates one exemplary embodiment of a manufacturing process usable to manufacture the composite headliner  100 . As shown in  FIG. 3 , the foam core  130  passes through a first station, where a liquid adhesive and then the catalyst  124  is sprayed onto each surface of the foam core  130  to form the upper and lower adhesive layers  122 . Then, the upper porous fibrous layer  160  and lower porous fibrous layer  120  are placed next to the foam core  130 , and the scrim layer  140  is placed next to the upper porous fibrous layer  160 . The release sheet  150 , if used, is then placed next to the scrim layer  140 , although this is not shown in  FIG. 3 . 
     The coverstock sheet  110 , comprising the coverstock material layer  112 , the (optional) coverstock foam layer  114 , and the adhesive barrier  118 , is then placed next to the lower porous fibrous layer  120 . 
     The resulting stack of layers is then placed in a hot press, which applies heat and pressure to the resulting stack to form the composite headliner  100 . The pressure and heat cause the liquid adhesive to flow into the foam core  130  and to flow through the upper porous fibrous layer  160  and lower porous fibrous layer  120  and against the scrim layer  140  and the adhesive barrier  118 . At the same time, the heat and pressure cause the catalyst to cure the liquid adhesive, bonding together the adhesive barrier  118 , and thus the coverstock sheet  110 , the upper porous fibrous layer  160  and lower porous fibrous layer  120 , the foam core  130  and the scrim layer  140  to form the composite headliner  100 . At the same time, the heat and pressure form the composite and set the adhesive in the composite headliner  100  to match the shape of the molds used in the hot press. 
     In various embodiments, the hot press is operated at a temperature of about 100 to about 160 degrees centigrade. More particularly, the hot press is operated at temperatures from about 120 to about 160 degrees centigrade. The headliner will be in the press for about 30 to about 60 seconds. As illustrated in  FIG. 3 , the hot press may be designed to impart a desired shape to the headliner. 
       FIG. 3  further shows an exploded view of the resulting composite headliner  100 , with the adhesive barrier  118  identified as a scrim layer between the coverstock material layer  112  and the optional coverstock foam layer  114  (which is referred to as a face good layer in  FIG. 3 ) and the upper adhesive-saturated porous fibrous layer  120  (which is referred to as a saturated glass mat in  FIG. 3 ). 
     It should be understood that the drawings are not necessarily to scale (e.g., the relative thickness of various layers as shown does not necessarily reflect the relative thickness of the actual layers). In certain instances, details that are not necessary to the understanding of the invention or render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
     It is also important to note that the above-outlined construction and arrangement of the elements of the composite headliner  100  is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, elements shown as integrally formed may be constructed of multiple parts or elements show as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, the length or width of the structures and/or members or connector or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied (e.g. by variations in the number of engagement slots or size of the engagement slots or type of engagement). It should be noted that the elements and/or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient acoustic performance, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the following claims. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement without departing from the spirit of the present inventions. Also, although the disclosed composite material has been illustrated in the form of a headliner, it should be understood that the material may be used on any interior surface of a vehicle or wherever acoustic energy absorption is desired.