Patent Description:
Patent application <CIT> discloses panels comprising first and second layers and a core disposed there between, wherein the core has a plurality of walls providing a series of connected cells, wherein some of the cell walls have openings providing fluid communication between a series of at least <NUM> cells, and wherein the opening in a cell wall has an area that is at least <NUM> percent of the area of a side of that cell wall. The panels may be shaped via thermoforming, via insert molding or via compression molding to provide an article. The panels may be used for absorbing sound in a designed frequency range.

Patent application <CIT> discloses a laminate of PVC or polyurethane foam with a leather-type surface, together with a film and a non-woven layer that is placed in a stretching frame to be drawn into a mould by vacuum.

Patent application <CIT> discloses an enclosure for isolating noise sources composed of four walls and a ceiling, in which some or all of the sides and top consist of a muffler barrier including one or more air paths transverse to the principal direction of sound transmission through the structure. Various types of component muffler barriers are disclosed which include double leaf structures lined with sound absorbing material where the two leaves are disposed in spaced apart relation and include oppositely disposed air intakes and air exhausts to provide the intervening air paths. The components may comprise corrugated panels of sound absorbing material disposed in face-to-face relation to provide multiple air channels.

In a first aspect, a method of making an article is provided. The method includes placing at least a portion of a panel in an injection molding die; and overmolding at least one molded structure on a surface of the panel in the injection molding die, thereby forming a material-to-material connection between the surface of the panel and the molded structure. The molded structure includes a foam composition. The panel includes first and second layers each having first and second opposed major surfaces and a core disposed there between, the second layer being free of any openings between the first and second major surfaces of the second layer. The core has a plurality of walls extending from the second surface of the first layer to the first surface of the second layer providing a series of connected cells, wherein some of the cell walls have openings providing fluid communication between a series of at least <NUM> cells. Each cell wall has a plurality of sides, each side of a cell wall has an area, and the opening in a cell wall has an area that is at least <NUM> percent of the area of a side of that cell wall. The first layer has at least a first opening extending between the first and second major surfaces of the first layer into at least one cell in the series.

In a second aspect, an article is provided made by the method according to the first aspect.

In a third aspect, an article is provided. The article includes at least one molded structure disposed on a surface of a panel, having a material-to-material connection between the surface of the panel and the molded structure. The molded structure includes a foam composition. The panel includes first and second layers each having first and second opposed major surfaces and a core disposed there between, the second layer being free of any openings between the first and second major surfaces of the second layer. The core has a plurality of walls extending from the second surface of the first layer to the first surface of the second layer providing a series of connected cells, wherein some of the cell walls have openings providing fluid communication between a series of at least <NUM> cells. Each cell wall has a plurality of sides, each side of a cell wall has an area, and the opening in a cell wall has an area that is at least <NUM> percent of the area of a side of that cell wall. The first layer has at least a first opening extending between the first and second major surfaces of the first layer into at least one cell in the series.

Exemplary embodiments of articles described herein can be formed into articles such as panels, walls, or other parts with curved surfaces. In one exemplary method, panels are shaped via thermoforming. In another exemplary method, panels are shaped via insert molding to provide the article.

It has been discovered that it is possible to injection overmold a foam composition into an acoustically absorbing honeycomb panel. Advantageously, the panel can also be formed to have a shape (other than flat) prior to overmolding the foam onto a surface of the panel. Injection overmolding the foam composition in the injection mold decreases the complexity of handling the materials, as opposed to casting the foam composition on a flat panel followed by shaping the panel. The final article can have variations in thickness and shape to meet requirements of a particular application in both size and acoustic absorption.

Suitable acoustically absorbing honeycomb panels are described in detail in co-owned application publication <CIT>). Briefly, referring to <FIG>, <FIG>, a panel <NUM> has first and second layers <NUM>, <NUM> each having first and second opposed major surfaces, <NUM>, <NUM>, <NUM>, <NUM> and a core <NUM> disposed there between. The second layer <NUM> is free of any openings between the first and second major surfaces <NUM>, <NUM> of the second layer <NUM>. The core <NUM> has plurality of walls <NUM> extending from second surface <NUM> of first layer <NUM> to first surface <NUM> of second layer <NUM> providing first series <NUM>, <NUM>' of connected cells <NUM>, <NUM>'. Also shown are second and third series of cells <NUM>, <NUM>', and <NUM>, <NUM>'. Some of the cell walls 141a, 141b, 141c have openings <NUM> providing fluid communication between the first series <NUM> of five cells <NUM>. Each cell wall <NUM> has a plurality of sides <NUM>, <NUM>. Each side <NUM>, <NUM> of the cell wall <NUM> has an area A. The opening <NUM> in the cell wall 141a has area A' that is at least <NUM> percent of area A. The first layer <NUM> has at least a first opening 190a, 190b extending between the first and second major surfaces <NUM>, <NUM> of the first layer <NUM> into at least one cell in series <NUM>, <NUM>'. Note that openings 190a, 190b, 190c, etc., displayed as circles, but can be any of a variety of shapes including squares, triangles, rectangles, hexagons, or other polygons. Multiple openings could also be used, including openings having at least two holes, or openings which include a woven or non-woven permeable material. In some embodiments, at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even at least <NUM>) percent of the openings <NUM> in a cell wall <NUM> emanate from either the first layer <NUM> or the second layer <NUM>. Referring to <FIG>, the opening <NUM> can have contours having curved and straight portions, and any straight portions can be either perpendicular to or tilted at another angle to the layers <NUM> and <NUM>. Optionally, the center cell <NUM> could have an opening in the first layer <NUM>. In some embodiments, each cell has at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even at least <NUM>) walls.

In a first aspect, a method of making an article is provided. The method comprises:.

In a second aspect, an article is provided made by the method according to the first aspect. In a third aspect, another article is provided. The article comprises at least one molded structure disposed on a surface of a panel, having a material-to-material connection between the surface of the panel and the molded structure, wherein the molded structure comprises a foam composition,
wherein the panel comprises first and second layers each having first and second opposed major surfaces and a core disposed there between, the second layer being free of any openings between the first and second major surfaces of the second layer, wherein the core has a plurality of walls extending from the second surface of the first layer to the first surface of the second layer providing a series of connected cells, wherein some of the cell walls have openings providing fluid communication between a series of at least <NUM> cells, wherein each cell wall has a plurality of sides, wherein each side of a cell wall has an area, and wherein the opening in a cell wall has an area that is at least <NUM> percent of the area of a side of that cell wall, and wherein the first layer has at least a first opening extending between the first and second major surfaces of the first layer into at least one cell in the series.

The disclosure below relates to each of the first, second, and third aspects.

It was unexpectedly discovered that it is possible to injection mold a curable composition onto an acoustic honeycomb panel with a sufficiently low force to maintain the structure of the panel, e.g., avoid collapsing the panel due to the pressure of injecting and curing the composition when forming an overmolding structure comprising a foam on the panel. Molded structures can be applied to any portion of a panel, such as on at least one major surface of the panel, an edge of the panel, or a shaped part of the panel. Additionally, at least one profile element may be molded directly onto the mold structure, on an edge side of the panel, or both.

Suitable curable compositions include at least one blowing agent and at least one of a polyethylene, a polypropylene, a polyolefin, a polyvinylchloride, a polyurethane, a polyester, a polyamide, a polystyrene, a polyisocyanurate, a silicone, or a copolymer thereof. In some embodiments, the composition can further comprise at least one filler, such as beads, bubbles, fibers, carbon black, a mineral, a fire retardant (described in detail below), or other particles (e.g., macroparticles, microparticles, nanoparticles, nonporous particles, and/or porous particles (such as the porous carbon particles described in co-owned application <CIT>)).

In some embodiments, a suitable curable composition comprises Tufcote Acoustical Foam (commercially available from Aearo Technologies, LLC, Indianapolis, IN), which is reported to be based on a toluene diisocyanate (TDI) pre-polymer formed from TDI and a polyether polyol having a molecular weight of <NUM>,<NUM> grams per mole. Additives in the composition include silicone surfactant as a cell stabilizer, amine catalyst, a black pigment dispersion, and a chlorinated phosphate flame retardant. Foam cells are provided by water reacting with the TDI to form carbon dioxide, which foams the composition as it cures.

The blowing agent can be at least one of a chemical blowing agent, a physical blowing agent, or expandable microspheres. Physical blowing agents (PBAs), such as volatile liquid and gas blowing agents, expand when heated and then tend to escape from the mixture, leaving voids behind, to form the foam composition. Suitable physical blowing agents include for instance and without limitation, water, nitrogen, or carbon dioxide. Chemical blowing agents (CBAs) decompose and at least a portion of the decomposition product(s) expand and then escape from the mixture, leaving voids behind. Suitable chemical compound blowing agents include for instance and without limitation, a diazocompound, a sulfonyl hydrazide, a tetrazole, a nitrosocompound, an acyl sulfonyl hydrazide, hydrazones, thiatriazoles, azides, sulfonyl azides, oxalates, thiatrizine dioxides, isotaoic anhydride, or any combination thereof. Expandable microspheres are composed of gas or liquid hydrocarbon PBAs inside a polymer shell. When heated past the glass transition temperature (Tg) of the shell, the shell becomes malleable and expands due to the internal pressure of the heated PBA inside. The thickness of the shell and the quantity of PBA encapsulated is tuned to enable isotropic expansion rather than shell rupture, leading to an increase in volume. This process leads to a syntactic foam filled with polymer shells, generally with very uniform foam cell sizes.

Referring to <FIG>, at least a portion of a panel <NUM> is clamped in a clamp frame <NUM> and placed in an injection molding die <NUM>, e.g., between a first injection mold half 220a and a second injection mold half 220b. In the embodiment shown in <FIG>, the entire panel <NUM> is inserted into the injection molding die <NUM>. The two halves 220a and 220b of the injection molding die <NUM> are then closed, and the panel <NUM> conforms to the shape between the first half 220a and the second half 220b of the injection molding die <NUM>. Hence, the panel <NUM> may comprise a shape (e.g., flat) and the shape of the panel <NUM> is altered inside the injection molding die <NUM>.

As shown in <FIG>, a portion <NUM> of the panel <NUM> is consolidated by the compression of the injection molding die <NUM>. Optionally, at least one cell of the panel is consolidated and folded over to form a reinforcement bead. In some embodiments, the injection molding die is configured to reduce a thickness of at least a portion of the panel or of the entire panel by <NUM>% to <NUM>% or increase a thickness of at least a portion of the panel or of the entire panel by <NUM>% to <NUM>%. For example, the injection molding die may be shaped to reduce the thickness of a portion or all of a panel by <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more; and <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or <NUM>% or less. Typically, the decrease in thickness is a decrease in the thickness of the core of the panel. Likewise, the injection molding die may be shaped to increase the thickness of a portion or all of a panel by <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more; and <NUM>% or less, <NUM>% or less, <NUM>% or less, or <NUM>% or less. Increasing the thickness of a panel may involve pulling a vacuum in the injection molding die to draw out the panel material.

Moreover, the two halves 220a and 220b of the injection molding die <NUM> are configured to leave vacant cavity space <NUM> between at least a portion of the panel <NUM> and the second half 220b of the injection molding die <NUM>. In some embodiments, the panel is supported in the injection molding die on at least a portion of a first layer of the panel. In other embodiments, the panel is supported in the injection molding die on each of the first layer and the second layer of the panel. In certain embodiments, the panel is unsupported in the injection molding die on each of the first layer and the second layer. The locations of support (if any) will be determined by the design of the final product, in particular where overmolding structure is to be formed on the panel.

The method further comprises overmolding at least one molded structure <NUM> on a surface <NUM> of the panel <NUM> in the injection molding die <NUM>, thereby forming a material-to-material connection <NUM> between the surface <NUM> of the panel <NUM> and the molded structure <NUM>. As used herein, "material-to-material" connection refers to the material of a surface of a panel directly contacting the material of a molded structure, with the exception of at most two intermediate layers, preferably one intermediate layer (or no intermediate layer), such as a primer layer and/or a tie layer that assists to adhere the two materials together optionally being present on at least a portion of the material of the surface of the panel. In the injection molding die <NUM> of <FIG>, an overmolding material <NUM> is injected through an injection port <NUM> into the vacant cavity <NUM>. Typically, the molded structure <NUM> is applied to at least one major surface <NUM> of the panel <NUM>. To obtain a molded structure that comprises a foam, the molded structure may be formed by providing a curable composition comprising a blowing agent into a vacant cavity in the injection molding die and curing the curable composition to form the foam composition.

In some embodiments, the injection molding die is configured to increase a thickness of at least a portion of the panel or of the entire panel by <NUM>% to <NUM>,<NUM>% due to the overmolding in a vacant cavity of the injection molding die. For example, the injection molding die may be shaped to increase the thickness of a portion or all of a panel, due to the presence of an overmolded structure adding to the overall thickness, by <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more; and <NUM>,<NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or <NUM>% or less.

Advantageously, formation of an overmolded structure that comprises a foam provides a wide range of thicknesses of the structure. The flexibility in design of the overmolded structure allows for the article to fit a variety of desired shapes and thicknesses for a particular purpose, e.g., including filling up space in need of acoustic absorption that might otherwise require three, four, five, or more stacked acoustic panels to fill. In some embodiments, the molded structure comprises a thickness of <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater; and a thickness of <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less. Stated another way, the molded structure may comprise a thickness of <NUM> millimeters (mm) to <NUM>.

The molded structure optionally comprises a closed cell foam, an open cell foam, or a combination of both closed cell foam and open cell foam. As used herein, an open cell foam means that the foam contains connected cell pathways that extend from one outer surface through the material to another outer surface. In contrast, as used herein, a closed cell foam means that the foam contains substantially no connected cell pathways that extend from one outer surface through the material to another outer surface. A closed cell foam can include up to about <NUM>% open cells, within the meaning of "substantially" no connected cell pathways. Stated another way, the foam composition comprises <NUM>% or greater closed cells, <NUM>% or greater closed cells, <NUM>% or greater closed cells, or <NUM>% or greater closed cells. Achieving a particular cell type (i.e., open and/or closed) depends on the specific blowing agent and curing conditions of the curable composition.

In some embodiments, the molded structure comprises a material exhibiting a hardness of <NUM> Shore OO or greater, <NUM> Shore OO or greater, <NUM> Shore OO or greater, <NUM> Shore OO or greater, <NUM> Shore OO or greater, <NUM> Shore OO or greater, <NUM> Shore OO or greater, <NUM> Shore OO or greater, or <NUM> Shore OO or greater; and a hardness of <NUM> Shore D or less, <NUM> Shore D or less, <NUM> Shore D or less, <NUM> Shore D or less, <NUM> Shore D or less, <NUM> Shore D or less, <NUM> Shore D or less, <NUM> Shore D or less, or <NUM> Shore D or less. Stated another way, the molded structure may comprise a material exhibiting a hardness of <NUM> Shore OO to <NUM> Shore D, <NUM> Shore OO to <NUM> Shore OO, <NUM> Shore OO to <NUM> Shore D, or <NUM> Shore D to <NUM> Shore D.

A porous layer such as the molded structure can be generally characterized by its specific acoustic impedance, which is the ratio in frequency space of acoustic pressure to the associated particle speed in an acoustic medium. In the theoretical model based on a rigid film with perforations, for example, the velocity derives from air moving into and out of the holes. If the film is flexible, motion of the wall can contribute to the acoustic impedance calculation. Specific acoustic impedance varies as a function of frequency and is generally a real quantity in progressive plane wave condition, however, the specific acoustic impedance becomes a complex number under the standing plane wave or diverging wave conditions. Therefore, the specific impedance of an acoustic medium reflects the fact that pressure and velocity waves can create phase mismatch between the two properties and this phase mismatch behavior reflects the acoustic absorption performance. When the two components are in phase to each other the maximum acoustic absorption is possible and vice versa when the two components are out of phase to each other. The flow resistance is the low frequency limit of the transfer impedance. Experimentally, this can be estimated by blowing a known, small velocity of air at the molded structure and measuring the pressure drop associated therewith. The flow resistance can be determined as the measured pressure drop divided by the velocity. As used herein, specific acoustic impedance is measured in units of Pa·s/m<NUM>, which is equivalent to MKS Rayl/m. In some embodiments, the molded structure exhibits an airflow resistance of <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, <NUM>,<NUM> Pa·s/m<NUM> or greater, or <NUM>,<NUM> Pa·s/m<NUM> or greater; and an airflow resistance of <NUM>,<NUM> Pa·s/m<NUM> or less, <NUM>,<NUM> Pa·s/m<NUM> or less, <NUM>,<NUM> Pa·s/m<NUM> or less, <NUM>,<NUM> Pa·s/m<NUM> or less, <NUM>,<NUM> Pa·s/m<NUM> or less, <NUM>,<NUM> Pa·s/m<NUM> or less. Stated another way, the molded structure exhibits an airflow resistance of <NUM>,<NUM> to <NUM>,<NUM> Pa·s/m<NUM>.

Referring to <FIG>, an acoustical panel <NUM> is optionally preheated outside of the injection mold, e.g., using an infrared heater <NUM>. Closing of the injection mold die <NUM> shapes the preheated panel <NUM> as described below in Example <NUM>, such that the overmolding of a foam composition on the shaped panel occurs in a single machine. In some embodiments, the method further comprises cooling the shaped panel prior to overmolding the molded structure on a surface of the panel, such as by exposure to ambient air or circulating a cooling fluid through the injection mold die.

Alternatively, the panel may be thermoformed as described below in Example <NUM>, then inserted into an injection mold for the foam composition to be overmolded on the panel. In some embodiments, thermoforming includes heating the panel and applying force to shape the panel against at least one tool. Typically, the panel is heated to a processing temperature where it becomes compliant. For instance, the panel can be heated to a softening temperature of the first layer, the second layer, or both, of the panel. The panel is then positioned within a mold, between <NUM> platens prior to the platens closing. The panel is shaped by mechanical force from the tool, or by vacuum or pneumatic pressure followed by a cooling period to return the panel to a rigid structure. Polypropylene (PP) panels can be thermoformed, for example, with the panel pre-heat temperature of <NUM>-<NUM>°F (<NUM>-<NUM>), mold temperature of <NUM>°F (<NUM>), clamping force of <NUM>,<NUM> lbs. (<NUM>,<NUM> kgf) and cooling time of <NUM> seconds.

Referring to <FIG>, at least a portion of a panel <NUM> is clamped in a clamp frame <NUM> and placed in a thermoforming machine <NUM>, e.g., between a first thermoforming tool half 370a and a second thermoforming tool half 370b. The panel <NUM> is optionally preheated outside of the thermoforming machine, e.g., using an infrared heater <NUM>, as shown in <FIG>. In the embodiment of <FIG>, the entire panel <NUM> is inserted into the thermoforming machine <NUM>. The two tool halves 370a and 370b of the thermoforming machine <NUM> are then closed, and the panel <NUM> conforms to the shape between the first half 370a and the second half 370b of the thermoforming machine <NUM>. As shown in <FIG>, a portion <NUM> of the panel <NUM> is consolidated by the compression of the thermoforming machine <NUM>.

Referring to <FIG>, in a separate step, the pre-formed panel <NUM> is removed from the thermoforming machine. Next, the pre-formed panel <NUM> is inserted between two halves 320a and 320b of an injection molding die <NUM>, which are configured to provide a vacant cavity space <NUM> between at least a portion of the panel <NUM> and the second half 320b. The method further comprises overmolding at least one molded structure <NUM> on a surface <NUM> of the panel <NUM> in the injection molding die <NUM>, thereby forming a material-to-material connection <NUM> between the surface <NUM> of the panel <NUM> and the molded structure <NUM>. In the injection molding die <NUM> of <FIG>, an overmolding material <NUM> is injected through an injection port <NUM> into the vacant cavity <NUM>, thereby forming the article. Typically, the molded structure <NUM> is applied to at least one major surface <NUM> of the panel <NUM>.

Accordingly, methods for making articles from panels can comprise shaping a panel described herein via insert molding to provide the article. In some embodiments, putting a pre-heated panel inside of an injection mold tool, closing the tool, and injection molding a foam composition on the panel to provide the article. The mold closing action forms the panel into a three-dimensional shape while the overmolded structure comprising foam provides additional acoustic absorption of the final article. The mold closing force may be enough to shape the panel, or thermoforming/compression molding performed prior to insert molding may be required; in either case, pre-heating the formed panel may not be necessary. In certain embodiments, the panel is perforated by the injection mold. A panel undergoing overmolding may be flat or alternatively comprise a (e.g., three-dimensional) shape. For a panel that has already been shaped, the method may further comprise altering the shape of the panel (e.g., "reshaping" the panel) in the injection molding die. In certain embodiments, at least one cell is consolidated and folded over to form a reinforcement bead. When a number of adjacent cells are consolidated and folded over they can form a "hem" having a thickness approximately equal to twice the thickness of the first and second layers of the panel.

Suitable methods optionally further comprise at least partially shaping a (flat) panel using thermoforming or compression molding prior to placing at least a portion of the panel within the injection molding die, e.g., using vacuum, pressure, or matched mold forming to shape the panel. Materials used in matched mold forming are not particularly limited, and include for instance and without limitation, metal, plywood, or epoxy board (e.g., available under the trade designation "RENSHAPE", from OBO-Werke GmbH, Stadthagen, Germany). In some embodiments, putting a panel inside of a mold between <NUM> platens, heating the mold, closing the platens to shape the panel while maintaining pressure during a mold cooling stage provides the article. In some embodiments, the panel must be pre-heated prior to closing the mold to ensure material compliance. Exemplary polypropylene (PP) panels can be compression molded, for example, without panel pre-heating, thermal cycling mold temperatures of <NUM>°F (<NUM>) and <NUM>°F (<NUM>), clamping force of <NUM>,<NUM> lbs. (<NUM>,<NUM> kgf) and cooling/pressure holding time of <NUM> seconds.

In some embodiments, the first layer of the panel comprises at least one opening between the first and second major surfaces of the first layer, and the method further comprises plugging the at least one opening prior to overmolding the at least one molded structure on a surface of the panel in the injection molding die. An opening may be plugged by a pin selected to have a diameter large enough to fit in the opening but minimize entry of curable composition into the opening during the overmolding process.

In some embodiments, panels have a thickness of <NUM> millimeters (mm) or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater; and a thickness of <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less. Stated another way, panels may have a thickness in a range from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>.

In some embodiments, each cell of a panel has a largest distance between two opposed walls of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even at least <NUM>; in some embodiments, in a range from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or even <NUM> to <NUM>). In some embodiments of panels, each cell has a largest distance between two opposed vertices of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even at least <NUM>; in some embodiments, in a range from <NUM> to <NUM>, <NUM> to <NUM>, or even <NUM> to <NUM>).

In some embodiments, each cell of a panel has a distance from the second surface of the first layer to the first surface of the second layer of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even at least <NUM>; in some embodiments, in a range from <NUM> to <NUM>, <NUM> to <NUM>, or even <NUM> to <NUM>).

In some embodiments of panels, each cell has a volume of at least <NUM><NUM> (in some embodiments, at least <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, or even at least <NUM><NUM>; in some embodiments, in a range from <NUM><NUM> to <NUM><NUM>, <NUM><NUM> to <NUM><NUM>, <NUM><NUM> to <NUM><NUM>, <NUM><NUM> to <NUM><NUM>, or even <NUM><NUM> to <NUM><NUM>). In some embodiments of panels, a series of cells has a cumulative volume of at least <NUM><NUM> (in some embodiments, at least <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, or even at least <NUM><NUM>; in some embodiments, in a range from <NUM><NUM> to <NUM><NUM>, <NUM><NUM> to <NUM><NUM>, or even <NUM><NUM> to <NUM><NUM>).

In some embodiments of panels, a first series of cells comprises at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more) cells. In some embodiments, panels further comprise a second series of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more) cells. In some embodiments, panels further comprise a third series of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more) cells. In some embodiments of panels, a series of cells has a cumulative length of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even at least <NUM>; in some embodiments, in a range from <NUM> to <NUM>, <NUM> to <NUM>, or even <NUM> to <NUM>).

In some embodiments of panels, the first layer comprises at least one of polymeric, metallic, ceramic, or composite materials (e.g., fiber reinforced, woven or non-woven in a resin matrix). In some embodiments of panels described herein, the second layer comprises at least one of polymeric, metallic, ceramic, or composite materials (e.g., fiber reinforced, woven or non-woven in a resin matrix). In some embodiments of panels described herein, the core comprises at least one of polymeric, metallic, ceramic, or composite materials (e.g., fiber reinforced, woven or non-woven in a resin matrix).

Exemplary polymeric materials include polyethylenes, polypropylenes, polyolefins, polyvinylchlorides, polyurethanes, polyesters, polyamides, polystyrene, copolymers thereof, and combinations thereof (including blends). The polymeric materials may be thermosetting by, for example, heat or ultraviolet (UV) radiation, or thermoplastic. In some embodiments, the molded structure and the panel comprise the same type(s) of polymer.

Exemplary metallic materials include aluminum, steel, nickel, copper, brass, bronze, and alloys thereof. Exemplary ceramic (including glass, glass-ceramic, and crystalline ceramic) materials include oxides, nitrides, and carbides. Exemplary fiber containing materials include fibers such as cellulose, carbon, thermoplastic fibers (polyamide, polyester, and aramid, polyolefin), steel, and glass, as may be applicable to the particular type of material. In some embodiments, materials for panels may be in the form of multilayers.

Optionally, materials for panels may also include fillers, colorants, plasticizers, dyes, etc., as may be applicable to the particular type of material.

In some embodiments, panels further comprise a tie layer on at least a portion of the second of the major surface of the first layer. In some embodiments, panels described herein further comprising a tie layer on at least a portion of the first of the major surface of the second layer. Although not wanting to be bound by theory, the tie layer is believed to facilitate adhesion between first or second layer <NUM>, <NUM> and core layer <NUM>.

In some embodiments, a panel may be surface treated, such as by treating a surface of the panel to increase adhesion of the molded structure to the panel. The surface on which a curable composition is to be molded can be treated to improve adhesion between the panel surface and the molded structure using typical treatment methods, e.g., chemical treatment (e.g., primer layer), corona treatment such as air or nitrogen corona, plasma, flame, or actinic radiation.

In some embodiments, methods further comprise disposing a substrate facing into an injection molding die at a distance from the panel and attaching the substrate to the molded structure when the foam composition forms, such that the molded structure is disposed between the panel and the substrate in the final article. Suitable substrates include for instance, a polymeric film, a woven material, a nonwoven material (e.g., a microperforated film), or a combination thereof. In select embodiments, the substrate can provide acoustic properties to the final article. In some embodiments, the substrate may provide a function such as in-mold labelling or further tuning acoustic properties of the foam composition.

In some embodiments, articles described herein exhibit at least one absorption band less than <NUM> (in some embodiments, less than <NUM>, or even less than <NUM>). In some embodiments, articles described herein exhibit at least one absorption band in a range from at least <NUM> to <NUM> (in some embodiments, in a range from at least <NUM> to <NUM>, at least <NUM> to <NUM>, at least <NUM> to <NUM>, or even at least <NUM> to <NUM>). The molded structure itself may exhibit at least one absorption band in a range from <NUM> to <NUM>, such as <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. In some embodiments, articles described herein exhibit an acoustical absorption of at least <NUM> (in some embodiments, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>) percent. The absorption bands of articles and the acoustical absorption of panels are measured as described in the Examples using the "Normal Incidence Acoustical Absorption Test" and the "Reverberation Chamber Test.

Both modeling and physical experimental measurements have shown that the acoustic absorption behavior of a honeycomb panel is a function of each of the panel thickness, cell sizes, passageway percentage, skin hole sizes, and number of connected cells. This is demonstrated in <NPL>, incorporated herein by reference. For instance, <NUM>) as the number of connected cells is increased, the frequency of the peak absorption decreases; <NUM>) as the skin hole size (whether provided by one hole or multiple holes) increases, the frequency of the peak absorption increases; <NUM>) as the width of the cell decreases, more cells need to be connected to exhibit absorption at the same frequency; <NUM>) as the cell height decreases, the frequency of the peak absorption increases; <NUM>) as the passageway size decreases, the frequency of the peak absorption decreases (plus with less total absorption and narrower absorption peaks); and <NUM>) as the skin thickness increases, the frequency of peak absorption decreases. Hence, multiple variables can be adjusted to optimize (e.g., tune) the acoustic absorption of a panel or article for a particular end use application.

Exemplary embodiments can be formed articles such as automotive parts, such as engine covers, wheel well liners, underbody shields, headliners, trunk covers, floor mats, carpet backings, hood liners, and tonneau covers, housings for generators, motors, appliances, tools, etc., and in general, any item emitting sound; architectural walls, panels, floors, doors, enclosures, ducts, sound barriers, etc., aircraft, watercraft, trucks, trains, agricultural equipment, fork lifts, and trailers.

The panels can find utility as an engine cover. In such cases, it will likely be useful to use polymers with high temperature resistance and flame retardant properties. Suitable polymers include for instance and without limitation, polyamides including PA6, PA66, polybutylene terephthalate (PBT), poly ethylene terephthalate (PET), poly ethylene naphthalate (PEN), polyphenylene sulfide (PPS), Polyether imide (PEI), Polyether sulfone (PES), Polyether ketone (PEK) and Polyether ether ketone (PEEK) and fluoropolymers.

Moreover, additives such as flame retardants are typically added to heat resistant polymeric materials to provide further protection during high temperature applications. Useful flame retardants include for instance and without limitation, inorganics such as alumina trihydrate (ATH), huntite and hydromagnesite, various hydrates, phosphorus, boron compounds, antimony trioxide and pentoxide and sodium antimonate; halogenated compounds such as organochlorines including chlorendic acid derivatives and chlorinated paraffins; organobromines such as decabromodiphenyl ether (decaBDE), decabromodiphenyl ethane, polymeric brominated compounds, brominated carbonate oligomers (BCOs), brominated epoxy oligomers (BEOs), tetrabromophthalic anyhydride, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD); organophosphates such as triphenyl phosphate (TPP), resorcinol bis(diphenylphosphate) (RDP), bisphenol A diphenyl phosphate (BADP), and tricresyl phosphate (TCP); phosphonates such as dimethyl methylphosphonate (DMMP); and phosphinates such as aluminium diethyl phosphinate; compounds containing both phosphorus and a halogen such as tris(<NUM>,<NUM>-dibromopropyl) phosphate(brominated tris) and chlorinated organophosphates such as tris(<NUM>,<NUM>-dichloro-<NUM>-propyl)phosphate (chlorinated tris or TDCPP) and tetrakis(<NUM>-chlorethyl)dichloroisopentyldiphosphate.

The acoustical spectrum of an engine depends on many factors including engine design, load and rotations per minute (rpm). The articles of the present disclosure may thus need to be tuned to several prominent frequencies.

Advantages and embodiments of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. All parts and percentages are by weight unless otherwise indicated.

An approximately <NUM>-millimeter (mm) thick polypropylene acoustically absorbing honeycomb panel made according to the Honeycomb Panel Preparation method described in <CIT>) is loaded into the clamp frame of an industrial robot (e.g., Fanuc Mi10/<NUM>, Fanuc, Echternach, Luxembourg). The robot positions the panel within an IR heating oven and holds the panel until a critical softening temperature of the panel skin is reached (e.g., approximately <NUM>-<NUM>). The panel is quickly transferred between the injection mold halves of an injection molding machine (e.g., Engel 100TL, ENGEL AUSTRIA GmbH, Schwertberg, Austria) and the mold closing sequence is initiated, subsequently forming the panel until the mold is fully clamped. In the fully clamped position, the acoustic panel may be fully supported on both sides, it may be only supported on one side, it is possible to be unsupported on both sides or it is able to be consolidated to a thickness below <NUM> and potentially perforated by the injection mold steel. Next, the injection molding machine's injection unit actuates, providing an open or closed cell foam overmolding material into the vacant cavity regions or space where the acoustic panel is unsupported.

An approximately <NUM>-mm thick polypropylene acoustically absorbing honeycomb panel made according to the Honeycomb Panel Preparation method described in <CIT>) is loaded into the clamp frame of a thermoforming machine (e.g., MAAC C5535SPT, MAAC MACHINERY, Carol Stream, IL). The thermoforming machine positions the panel within an IR heating oven and holds the panel until a critical softening temperature of the panel skin is reached (e.g., approximately <NUM>-<NUM>). The panel is quickly transferred between the thermoforming tool halves and the tool closing sequence is initiated, subsequently forming the panel until the mold is fully clamped at which point air pressure or vacuum may be applied to further shape the panel. After a cooling duration, the tool is opened and the formed panel is removed from clamp frame.

In the next step of the process, the pre-formed panel is loaded within the injection mold of an injection molding machine (e.g., Engel 100TL) and the mold is closed fully. The injection molding machine's injection unit actuates, providing an open or closed cell foam overmolding material into the vacant cavity regions or space where the acoustic panel is unsupported.

Claim 1:
A method of making an article, the method comprising:
placing at least a portion of a panel in an injection molding die; and
overmolding at least one molded structure on a surface of the panel in the injection molding die, thereby forming a material-to-material connection between the surface of the panel and the molded structure, wherein the molded structure comprises a foam composition,
wherein the panel comprises first and second layers each having first and second opposed major surfaces and a core disposed there between, the second layer being free of any openings between the first and second major surfaces of the second layer, wherein the core has a plurality of walls extending from the second surface of the first layer to the first surface of the second layer providing a series of connected cells, wherein some of the cell walls have openings providing fluid communication between a series of at least <NUM> cells, wherein each cell wall has a plurality of sides, wherein each side of a cell wall has an area, and wherein the opening in a cell wall has an area that is at least <NUM> percent of the area of a side of that cell wall, and wherein the first layer has at least a first opening extending between the first and second major surfaces of the first layer into at least one cell in the series.