Abstract:
A composite panel made of hybrid structural resins containing fillers and reinforcing members for use in, but not limited to, the construction and automotive industries. The panel provides superior weatherability and excellent mechanical properties while achieving various aesthetic appearances. The panel employs a multi-layer composite construction. The panel is made of a weatherable outer layer of hybrid resin, with a pigmented or graphic second layer that may or may not contain reinforcing fillers suspended in hybrid resin. The pigments in this second layer give the panel the outward appearance desired, such as wood, granite, stone, metal, or other appropriate cladding. The second layer is followed by at least one structural layer of hybrid resin that may or may not contain fillers and/or reinforcing agents. The panel may or may not have an insulating core of foam, fiberglass, or similar insulating material in order to achieve added R value.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to self-supporting structures that can be used as curtain walls, fascia panels, and for other structural purposes. The structures are either flat, textured or three dimensional, and may be opaque or translucent. The panel is a self-supporting, weather resistant, flame retardant panel containing, or completely made up of, at least one layer of hybrid resin that is sufficiently strong to act as an outer, weather resistant, sunlight resistant, and mechanical-impact resistant structure. Such a panel is particularly useful for exterior building coverings, fascia, cladding, wall panels and the like.  
           [0002]    Historically the architect has been left out of the loop in favor of a designer who designed the building cladding to be functional and aesthetically pleasing, then added signs onto a building as requested by a client. The results in many cases were less than pleasing. This “add-on” practice is one of the reasons that most cities have passed sign codes and are making it harder to just hang signs on a business. In many cases an architect is now being asked to include signs and logos as part of the initial presentation to the client and to consult with local code officials to approve the project before it starts. Traditional signs are being forced off these projects in favor of backlit canopies and non-illuminated signs that are mounted flat on the walls of a building. Clearly a new approach to this problem was needed. The present invention allows a sign, logo, numbers, and names to be built into a wall system. The panel can be molded to the same shape and appearance as the building cladding, and can now be part of the building element.  
           [0003]    Panels currently being produced for wall systems range from exterior insulating and finishing system (EIFS) Dryvit™ type systems, metal panels, FRP, fiberglass reinforced cement, pre-cast cement, thermo-formed plastic, roll formed metal, aluminum composite material (ACM) and stone. These products are being installed on buildings routinely. Most of the building panels used today are two-dimensional, flat panels, with 90° returns. Many of these systems are heavy and require substantial framing systems to support them. For the most part, these heavy panels require a crane to lift into place. The most recognized systems that can be three-dimensional are FRP and pre-cast concrete. FRP is a short-lived material and, while pre-cast-concrete will last for 20 years or more, it is heavy and can be very costly.  
           [0004]    Spranderal glass is also very popular as in-fill paneling. Most of today&#39;s glass buildings are “curtain wall” with viewing glass in the top and spanderal glass in the knee wall. Such a wall system is flat and very common. Spranderal glass is an insulated, thermo-pane, glass.  
           [0005]    The present invention also allows a logo panel to be installed as part of a fascia system used on a canopy, such as found over the gas islands in a filling station, or on the front of a cladding. The present invention can be made to match or contrast with the building cladding or structure to achieve the desired look.  
           [0006]    Today, most plastic or polymer panels are thermoformed from large sheets of acrylic or polycarbonate, or made of standard FRP materials. For the most part these products reply on thickness to provide the needed mechanical strength to withstand wind loads. These products are heavy and expensive. Most of these products have a poor coefficient of expansion and become brittle in very cold weather. These products yellow with age and exposure to the Sun&#39;s UV radiation. These products have served well, however, because they are used in systems that hold and control their movement and rely on UV inhibitors to make them weatherable.  
           [0007]    Designers and engineers have wanted an alternate reinforced product for years. The problem is that up to now there was no way to provide a three-dimensional product (other than FRP and Cement) that had the needed structure to withstand wind loads. Other reinforced products on the market are laminated or coated fabric. These products are strong for their weight but require a framing system to provide tension on the material so it will withstand wind loads and weather.  
           [0008]    For many years FRP panels have been used in the building and automotive industries. These panels are lightweight and have very high mechanical strength, as well as being dimensionally stable through a wide temperature range. The problem is that FRP panels are short lived. The UV radiation from the sun tends to break down the resin and expose the glass fibers to the elements. The present invention solves this problem by employing an improved weatherable surface of resin and hybrid resin in multi-layers. The subsequent layers provide good mechanical strength and superior dimensional stability through a wide range of temperatures and weather conditions.  
           [0009]    The present invention overcomes many problems related to panels of the prior art and is sufficiently versatile to use for signage, building and automotive panels, and for a variety of other purposes.  
                                                 REFERENCES CITED            U.S. Pat. No.   Date   To Whom Granted   Class               4,642,959   Feb. 17, 1987   Swiech, Jr., et.al.   52/311       5,070,668   Dec. 10, 1991   Lieberman.   52/309.9       5,266,234   Nov. 30, 1993   Ho, et.al.   252/182.27       4,201,003   May 6, 1980   With   40/545       5,020,252   June 4, 1991   DeBoef   40/564       5,070,668   Dec. 10, 1991   Leiberman   52/309.9       5,073,424   Dec. 17, 1991   Dressler   428/42       5,087,508   Feb. 11, 1992   Beck   428/195       5,215,699   June 1, 1993   Leiberman   264/225       5,225,260   June 6, 1993   McNaul, et.al.   428/40       5,345,705   Sept. 13, 1994   Lawrence   40/616       5,398,435   Mar. 21, 1995   Kanzelberger   40/1.5       5,423,142   June 13, 1995   Douglass, et.al.   40/605       5,443,869   Aug. 22, 1995   Harris   428/13       5,466,317   Nov. 14, 1995   Lause, et.al.   156/79       5,524,373   June 11, 1996   Plumly   40/600       5,655,324   Aug. 12, 1997   Siener, Jr., et.al.   40/615       5,633,063   May 27, 1997   King   428/71       5,794,402   Aug. 18, 1998   Dunlau, et.al.   52/783.17       6,023,806   Feb. 15, 2000   Dunlau, et.al.   14/73                  
 
         SUMMARY OF THE INVENTION  
         [0010]    One objective of the present invention is to provide a structural, self-supporting panel, comprised of at least one layer of high-density hybrid resin containing an ultraviolet (UV) blocker; one that is sufficiently thick to provide an outer weather-resistant and mechanically strong layer for the panel.  
           [0011]    A further objective of the present invention is to incorporate superior weathering and flame retardant characteristics into additional hybrid resin layers, thus giving the panel a sufficient flame and smoke rating for use as a curtain wall, panels, cladding, or other building components. Class I or Class II fire ratings are incorporated, depending on the end-use for the panel.  
           [0012]    Another objective of the present invention is to provide a method for manufacturing the self-supporting hybrid resin panel, which includes a high pressure spray, injection mold, a high pressure open tool molding technique, a low pressure open tool pouring technique, hand or machine mixing and casting technique, a low pressure continuous machine casting process, and reaction injection molding (RIM) technique.  
           [0013]    The present invention can be practiced in a wide variety of ways while taking advantage of the basic concept. Specifically the outer surface is resistant to mechanical shock, resistant to ultraviolet radiation from the Sun and weather, and is also sufficiently flexible to be easily transported without damage and sufficiently versatile so that any outward appearance, whether flat, textured, or three-dimensional, can be provided to the panel.  
           [0014]    This can be achieved in many ways. Among these is a technique of layering or spraying the hybrid resin material onto a mold that may be flat or three-dimensional. Building up layer after layer of the hybrid resin material, fillers, and other intermediate materials as needed to impart characteristics of strength, flatness, dimensionality mechanical, graphic, translucency or opaqueness is then incorporated into the process, depending on the end use of the panel. In this way the same invention can be utilized to produce a wide variety of structures. The panels can be used for sign fascias, or even for applying graphics in curtain walls on buildings that are made from the panels. With appropriate fire-resistance where necessary, strength and flexibility as needed, and extremely long life as appropriate, they can be used for building exteriors in particular.  
           [0015]    One key to the present invention is that the first layer has a weatherable surface. Products for exterior applications must withstand heat, cold, precipitation and sun. Prolonged exposure to the Sun&#39;s UV radiation is harmful to color and surface characteristics such as gloss and texture. The UV blocker is a part of the panel that further improves the weatherability of the first layer of the composite.  
           [0016]    The composite panels of the invention can be used for, but are not limited to, the following for both interior and exterior applications: architectural panels, exterior building elements, in-fill panels in a curtain wall system, fascia panels, decorative panels, equipment screens, rooftop structures, address or other information signs, non back-lighted sign panels, logo panels, or raised letters which are referred to as “channel letters” in the sign art.  
           [0017]    All panels made for these applications must have superior weathering characteristics and can be flame retardant to Class I or Class II, based on application.  
           [0018]    The panel is thin and lightweight yet maintains structural integrity so that it transfers wind loads to the structure or curtain wall system to which it is attached.  
           [0019]    The inventive panel is extremely versatile based on need, and the flexibility of the molds. Tooling can be made of many materials, wood, metal, silicon rubber, high temperature epoxy and other filled compounds. Molds can be made in many parts to produce a product that is three-dimensional, and with negative draft angles and may have framing or attachment points held in place to become part of the panel.  
           [0020]    The mold can be made as a one-piece open pan, or as two parts to produce a panel to a desired thickness or shape on the back side as well as on the face of the panel. This includes changes for multi-colors in the first and second layers. Tooling may be of multi-pieces to allow negative draft angles and for attachment points and hardware to be incorporated into the finished product.  
           [0021]    One technique for achieving the invention is to first spray an initial layer of weatherable resin into the mold with a sweeping back-and-forth motion to maintain uniform thickness. This layer has no filler, but is sprayed to a thickness to achieve optimum UV protection. One attribute of the present invention is that the hybrid resin is formulated to cure very quickly—initially in a few seconds—so that subsequent layers can be applied immediately behind the first layer. This allows the entire composite to cure, achieving a homogenous bond between layers.  
           [0022]    A sweeping back-and-forth movement that is perpendicular to the movement that was used to spray on the first layer applies to the second layer. This has been found to drastically increase the strength and flatness of the panel by crossing the orientation direction of the resin and the fillers from one layer to the next. The first and/or the second layer may also include pigment or solid additives, such as fibers, flakes or particles, to achieve the desired texture and color in the outer layers.  
           [0023]    Advantageously, the first layer may be without these additives so as to produce a clear, hard UV resistant finish of a flame-resistant shell. If need be the second layer may include the additives for decoration. Chopped fibers and fillers may be included in the second and subsequent layers for drastically increasing strength in a manner analogous to fiberglass reinforced structures of the prior art (FRP technology). Fillers may include, but are not limited to, micro-spheres, ceramic material, flyash, glass fibers, glass scrim, Kevlar™ wire mesh, core materials, and foam core.  
           [0024]    For additional resistance to flexing or bending a structural element or other reinforcing material can be included, such as an egg crate or grid structure, wood, metal, or framing around the perimeter. The reinforcing material may be installed behind the first or second layer. Then a further layer of resin is sprayed over the reinforcing element to encase and mechanically bond the structural element to the remainder of the composite. Because of the nature of the sprayed hybrid resin, each layer is intimately adhered to the next without any possibility of de-lamination or separation.  
           [0025]    The mechanical strength, shock-resistance, fire-resistance and UV-resistance for various panels constructed according to the present invention have been demonstrated by a number of industry-accepted tests.  
           [0026]    In accordance with another embodiment of the invention, a corrugated sheet of hybrid resin can be made using the same spray, pouring, or molding technique of the invention, this sheet being used as the structural strength-adding component incorporated into the panel. This has the further advantage of being economical to make and completely compatible with the rest of the hybrid resin layers. The use of a corrugated layer also produces air pockets in the panel that improve its thermal insulating characteristics.  
           [0027]    In the remainder of this disclosure the term “hybrid resin” is used interchangeably with urethane and polyurea, even though the two are considered chemically separate from each other. Both urethane and polyurea can be used, depending upon the application of the invention, and in particular, the thickness of the single or multiple layers needed in a particular panel structure. Both are thermoset polymers and are acceptable for the present invention. Thermoplastic panels are not appropriate although some characteristics of thermoplastics, such as their good orientation when extruded, are also characteristics of the present invention where the orientation of the hybrid resin is utilized to improve strength.  
           [0028]    Among the attributes that can be incorporated into the present invention is the use of a flame and/or smoke retardant within the hybrid resin layer or layers. This gives the panel a Class I or Class II, also known as Class A or Class B, fire rating and a 15-year or longer life. Both the fire resistance and life span of the invention have been confirmed by industrially accepted tests.  
           [0029]    Using appropriate inserts, such as a structural panel in the form of an egg crate, a corrugated sheet, a honeycomb, a fiber mat or other reinforcing sheets, appropriate bend-resistance can be achieved. The panels can even be made bulletproof against small arms fire by incorporating a layer of KEVLAR (a trademark of Dupont). For some architectural requirements, such as buildings for sensitive telecommunication equipment, bulletproofing is actually specified as a requirement for an exterior wall of these equipment buildings.  
           [0030]    The present invention can also have comparable expansion characteristics to that of FRP and, in fact, the expansion characteristics can be tailored to a particular need.  
           [0031]    The use of a UV blocker, is particularly advantageous. The sufficient thickness of the hybrid resin layer containing the UV blocker and pigments permits blocking of virtually all sunlight. The thinner the layer, the less the blocking effect. UV blocking is superior to UV inhibitors which, over the course of years, prevent UV damage by undergoing chemical changes within the first layer of the panel structure that produce an outward chalky substance on the panel and normally increase its brittleness. No such deterioration occurs in the present invention.  
           [0032]    According to the present invention, the panel includes at least one layer of hybrid resin and filler which is at least thirty thousandths of an inch thick and preferably 30 to 60 thousandths of an inch thick (30-60 mils). This gives the layer individually, and the panel as a whole, self-supporting structural strength and distinguishes it from hybrid resin and hybrid resin coatings used, for example, on automobiles or other structures meant for outdoor use. Generally, these coatings are no more than two to five mils thick and, further, do not have the other attributes of the present invention, such as fire-resistance, hardness and structural strength.  
           [0033]    The panel as a whole can be 0.060 to 0.250 inches thick for skin or cladding and 0.250 to 4.0 inches thick for structural uses. A letter panel or channel letter of the invention may have a depth of 0.250 to 6.0 inches at its return (side wall). For this disclosure the term channel letter includes not only three-dimensional letters but also characters or symbols of any kind such as numbers, logos, designs or any other shape to be displayed.  
           [0034]    The use of the spraying technique to manufacture a panel of the present invention involves the mixing together of two components to reactively form the high-density hybrid resin in a spray head just before it is sprayed onto the mold. The mold itself can be flat, have a surrounding ridge that forms a set back and flange for the panel, and may include three-dimensional structures onto which the hybrid resin is sprayed, such as lettering, logos and any other three-dimensional shapes. Multiple layers can then be built up behind the initial layer and, subsequently, the negative impression of the letters, logos and other three-dimensional structures can be filled in with coloring or decorative elements as desired for the final product look. The spray technique can even be utilized to produce simulated granite, marble or other graphic effect.  
           [0035]    Another technique is to paint the logo or lettering onto the mold before the initial layer of hybrid resin is laid onto the mold. This can be done using automotive grade hybrid resin, paint, UVX, or other clear topcoat. The subsequent sprayed-on layer of hybrid resin permanently encases the artwork into the outer layer and then back layers can be applied as needed to provide desired thickness, strength or other characteristics.  
           [0036]    The spray head can be used with a third inlet, which mixes structural fillers with the two parts that make up the hybrid resin. The fillers can be fibers, particles of granite or acrylic, flakes of granite, and/or other colored or non-colored fragments that impart the desired appearance to the layer. A marble effect can be achieved by swirling a combination of black and white pigments in the actual spraying process for the first layer.  
           [0037]    The fast curing of the invention makes it practical for continuous use in a continuous or semi-continuous process. This permits the application of layer-after-layer on a practical basis. Where time is needed to lay up a second layer after an initial layer has been applied, the curing time for the hybrid resin can be tailored to decrease its curing time so that there is enough time to apply subsequent layers before the previous layer has completely cured. As noted above, cure times from two to twelve seconds are possible, and this time can be increased if more time is needed to apply back layers, fillers, or structural elements behind the initial layers.  
           [0038]    A typical fire retardant component to be added to the hybrid resin is bromine. Bromine tends to reduce the structural strength of the layer, however. It is generally desirable for curtain walls of buildings to have a strength of about 3,000 to 3,500 PSI (following ASTM standards). By adding bromine to achieve a Class I or Class A fire rating, strength is reduced to about 2,800 PSI. Strength can be increased again, however, by the addition of subsequent back layers that incorporate glass or other reinforcing agents behind the initial layer, thus achieving the overall strength requirements for building purposes.  
           [0039]    Graphic elements can also be laid into subsequent layers where the initial layer is clear hybrid resin. For example, a sheet of DAYCRON or TYVEK material (trademarks of Dupont) which adds a wood grain or other desired appearance, can be laid behind an initial layer and then a subsequent hybrid resin layer sprayed onto the insert, permanently encasing it. This produces a panel with a wood grain appearance in an-extremely economical and fast manner.  
           [0040]    In addition to spraying, casting or pouring of thicker layers of hybrid resin into a mold can produce thicker, single layer hybrid resin structures with or without graphic components of any desired color. In accordance with another method and apparatus of the present invention, the biased multi-layer spray application can be used to produce long panels. As long as the cure times are selected to give sufficient time to apply a second layer in an edge-to-edge relationship to the previous layer, sheets of 60 feet or longer maybe produced in this manner. This semi-continuous technique can also be used with a filler sheet that is applied between the sprayed-on layers. The filler sheet can also be used to pull the panel as it is being manufactured. Alternatively, the spraying-in of filler that is structural, graphic or both, can also be utilized with this process.  
           [0041]    As noted, reinforcing elements can be added to the panel. Fiberglass can be inducted into the stream of resin that is sprayed into the mold. Or, fiberglass matt can be precut and placed into the mold as part of a layer or between layers. Other reinforcing may-be added to achieve desired results. Graphic layers may be added as a layer behind the first in mold coating and encapsulated between first and second layers for both decoration and reinforcing.  
           [0042]    Many substances may be used as reinforcing agents such as, but not limited to, corrugated paper, metal, wood, plastic reinforcing, foam core, foam, microspheres, ceramic particles, flyash, drywall, fire resistant board, metal sheets or plates, honey comb or geometric shapes for strength or flatness. Wire mesh for grounding or EM shielding, or electrical components as part of an alarm system, and other items may be incorporated as needed for specific applications.  
           [0043]    Color may be added to the panels as well. Structural hybrid resin may be pigmented in the polyol side of the system. This allows the structural layers to be colored clear through. An in-mold coating can be used to pigment the first surface. Pigments, color chips, acrylic chips, photographic elements, graphic elements, decals or color sheets can be encapsulated into the first layer or between layers to be viewed from the front. Pigmenting is based on hybrid resin paints and dyes that can be mixed into the polyol.  
           [0044]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which the preferred embodiments of the invention are illustrated.  
       
    
    
     IN THE DRAWINGS  
       [0045]    [0045]FIG. 1 is a perspective view of an open pan mold that can be used in accordance with the present invention;  
         [0046]    [0046]FIG. 2 is a perspective view of another pan mold of the present invention;  
         [0047]    [0047]FIG. 3 is a perspective view or a structural panel constructed with the mold of FIG. 1;  
         [0048]    [0048]FIG. 4 is a rear perspective view of a sign that can be constructed with the mold of FIG. 2;  
         [0049]    [0049]FIG. 5 is a view similar to FIG. 1 of another embodiment of the mold;  
         [0050]    [0050]FIG. 6 is a view similar to FIG. 5 of another embodiment of the mold;  
         [0051]    [0051]FIG. 7 is a perspective view of another embodiment of a mold that can incorporate surface features on the finished panel;  
         [0052]    [0052]FIG. 8 is a perspective view of a structural element that can be used in combination with the panel of the present invention;  
         [0053]    [0053]FIG. 9 is a rear perspective view of a finished panel constructed with the mold of FIG. 7;  
         [0054]    [0054]FIG. 10 is a perspective view of a finished panel constructed with the mold of FIG. 7;  
         [0055]    [0055]FIG. 11 is a perspective view of another structural element that can be used in accordance with the present invention;  
         [0056]    [0056]FIG. 12 is a perspective view of a planar element that can be used with the panel of the present invention;  
         [0057]    [0057]FIG. 13 is a perspective view of a flexible non-woven and printed fabric sheet that can be incorporated into the panel of the present invention;  
         [0058]    [0058]FIG. 14 is a schematic representation of an apparatus that can be used to manufacture the structural panel of the present invention;  
         [0059]    [0059]FIG. 15 is a schematic view of a technique for laying down initial and subsequent layers of the panel of the present invention;  
         [0060]    [0060]FIG. 16 is a schematic view similar to FIG. 15 showing the manner of laying down a second and subsequent alternating layer of the panel of the present invention;  
         [0061]    [0061]FIG. 17 is a partial sectional view of one embodiment of the panel of the present invention;  
         [0062]    [0062]FIG. 18 is a sectional view of an open pan mold with a panel of the invention therein;  
         [0063]    [0063]FIG. 19 is a sectional view of another embodiment of the panel of the present invention;  
         [0064]    [0064]FIG. 20 is a sectional view of a still further embodiment of the panel of the present invention;  
         [0065]    [0065]FIG. 21 is a sectional view of a closed mold that can be used in accordance with the present invention;  
         [0066]    [0066]FIG. 22 is a schematic perspective view of an apparatus for mass-producing a panel of the present invention;  
         [0067]    [0067]FIG. 23 is a schematic sectional view of the panels of the present invention used with a mounting system and as curtain walls or exterior building elements for a building wall;  
         [0068]    [0068]FIG. 24 is a schematic perspective view of the invention used as a canopy sign;  
         [0069]    [0069]FIG. 25 is a sectional view of a mold in an early step of casting a panel or member according to the invention;  
         [0070]    [0070]FIG. 26 is a top plan view of the mold of FIG. 25;  
         [0071]    [0071]FIG. 27 is a view similar to FIG. 26 of the mold during a subsequent step in the process;  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0072]    Referring to the drawings in particular, various embodiments of the invention will now be disclosed.  
         [0073]    General Panel and Mold Structure  
         [0074]    [0074]FIGS. 3 and 4 illustrate two examples of the structural panel of the present invention.  
         [0075]    In FIG. 3, the panel generally designated  10  has a front or visible surface  12  which is rectangular and has a 90° setback or return perimeter wall  14  and a peripheral flange  16  which can either be cut away in the finished panel or used to help mount the finished panel. In FIG. 3, an optional reinforcing element  18  is shown adhered to one of flanges  16 . Reinforcing element  18 , e.g. of aluminum square tubing, may extend around the entire perimeter of flange  16 , or be provided on any one of the setback sides or, as in the embodiment of FIG. 4, the panel generally designated  20  can have no reinforcing element, but due to its shape, thickness and construction is self-supporting. FIG. 4 illustrates the back surface of panel  20 . Throughout the figures, the same reference numerals will be utilized to designate the same or functionally similar parts.  
         [0076]    In the embodiment of FIG. 3, a recessed or negative indicia  22  is provided on the broad surface of panel  10  in the form of words, logos or any other desired indicia. The space in the negative indicia can be left free of material or may be filled with other material, such as light-enhancing acrylic of contrasting color to the panel  10 .  
         [0077]    A positive indicia  24  is provided in panel  20  as shown in FIG. 4. This produces raised letters on the front side of the panel (not shown in FIG. 4).  
         [0078]    [0078]FIG. 1 illustrates an open pan mold generally designated  30 , which was used to manufacture the panel of FIG. 3 and FIG. 2 illustrates the pan mold  40  used to manufacture the panel of FIG. 4. Both pan molds are made up of a flat base  32 , having a planar upper surface that forms the broad front or visible surface of the panel or sign. A border ridge  34  produces the perimeter of the sign with the inner surface of ridge  34  forming the setback or return surfaces  14  and a top surface of ridge  34  forming the flange  16 . Raised letters, channel letters or indicia  36  are fixed on base  32  in the selected position for making the negative indicia  22  in the panel of FIG. 3. As shown in FIG. 2, negative or indented indicia  46  can be provided in base  42  to produce the raised or positive indicia  24  of FIG. 4.  
         [0079]    For ease of disassembling the panel from the mold after the panel has been made, ridge  34  may be made of multiple, for example, four separate parts which can be detached from mold base  32 , to ease the separation process.  
         [0080]    [0080]FIGS. 5 and 6 show similar pan molds for producing positive or negative indicia on a panel that is used with forwardly extending setbacks, rather than rearwardly extending setbacks. FIG. 6, the positive indicia or plug elements  36  produce a forward, rather than a reverse image, to produce a corresponding forward positive image. In FIG. 5, the recessed  46  produces a forward negative image in the finished panel.  
         [0081]    [0081]FIG. 7 illustrates an open mold  30  where the exposed surface of base  32  is provided with various features, such as a painted on indicia  33 ; applied textural material  35 , such as particles of granite or colored acrylic; and a painted on pattern, such as a marble pattern  37 . With these different patterns applied to the upper surface of base  32 , and supplied in a manner to be released from the upper surface of base  32 , these textures and patterns are imbedded in the upper surface of a resulting panel shown at  50  in FIG. 10. Due to the nature of the present invention and the manner in which the panels are created, the painted on indicia  33 , texture  35  and pattern  37  are incorporated into the outer resin surface of the panel  50 . The entire surface of base  32  and the ridges of the mold may also be coated with resin that is released from the mold to coat the entire outer surface of the panel.  
         [0082]    [0082]FIG. 8 illustrates a rectangular structural element  38  in the form of a plastic grid or “egg crate”, such as those used in fluorescent ceiling fixtures. In accordance with the present invention, after one or more initial layers of hybrid resin are sprayed into the pan mold and before the resin cures, element  38  is placed into the mold and then additional layers sprayed, poured, or injected above or around it. This will greatly reinforce the strength of the finished panel and completely incorporate the structural element  38  into the panel as shown in FIG. 9 which is a rear perspective view of the panel  50  which has been provided with the structural element  38 .  
         [0083]    Other structural elements, such as a corrugated sheet or resin, FRP, or metal  52  shown in FIG. 11, can be incorporated into the layers of the panel. Sheet  52  can be made using the same spray method of the invention, by spraying the hybrid resin system onto a corrugated mold. FIG. 12 illustrates another element that can be incorporated into the panel of the present invention, namely a flexible non-woven printed fabric sheet  56  that in FIG. 12 has been imprinted with a wood grain pattern. Since the first layer of the panel is preferably clear, it sheet  56  is laid into the panel after the first layer is installed and then embedded by installing subsequent layers, the wood grain would be clearly visible on the front surface of the panel. Since fabric sheet  56  is porous, liquid hybrid resin impregnates the sheet and positively fixes it into the layers of the panel.  
         [0084]    Spray Technique  
         [0085]    [0085]FIG. 13 illustrates a spray apparatus generally designated  60  which can be used to spray layers of the panel into the pan molds of FIGS. 1, 2,  5 ,  6  and  7 . Apparatus  60  includes a spray head  62  that contains a mixing chamber for receiving various components of the thermosetting, high-density hybrid resin that forms the structural panel of the present invention. The apparatus sprays this mixture through a nozzle  64  which can be accurately directed toward the mold either manually or with automatic equipment.  
         [0086]    Apparatus  60  includes a first pressurized container  66 , for example, a 55-gallon drum containing a component “A”, and a second pressurized container  68  containing a component “B”. Both containers carry pressure pumps  70  and  72  that simultaneously pressurize the containers and produce a metered supply of components A and B along supply lines  71  and  73 , respectively. The components are actively mixed within the mixing chamber in the head  62 . A propellant, such as compressed air, is supplied from a compressor  74 . This propellant that is labeled “D” may also be a gas, such as CO 2 , or N 2.  A combination of air and CO 2  can also be used to insure that the mixed together components A and B, after being thoroughly mixed, are applied with sufficient force, e.g., 1500 PSI, in an atomized stream  76  which can be accurately aimed and directed.  
         [0087]    Additives “C”, such as chopped fibers, pigment acrylic, colored granules, flakes, or particles, flyash, ceramic microspheres, or other additives, can also be supplied from an additive container  78 , under pressure of a pressurizing unit  80  and along a line  81 , to the mixing chamber in the mix head  62 . Alternatively, these additives can be evenly sprinkled into the open mold after an initial layer has been applied to the mold and before it cures. One particularly useful additive which lightens and strengthens the dense hybrid resin of the second layer in a panel, or other member of the invention, are microspheres, e.g., solid or hollow glass extender beads known by the name HGS-14 and available from Larand Chemical Corp., of Hawley, Pa. This particulate material is powder-like and flows freely. Average particle size is 60 microns at 0.16 specific gravity. Another reinforcing and/or filling material is a ceramic particle called Dynamic Matrix. This filler is also flowable but rather than spherical in shape the particles look like jacks on the order of tens of microns in size. Flyash is yet another filler having many of the properties of microspheres and ceramic particles.  
         [0088]    As will be explained in greater detail later under a separate section of this disclosure involving the chemistry of the invention, components A and B may be supplied in approximately equal parts by volume; and, in the shorthand notation of hybrid resin chemistry, component A is known as the “iso” part, and component B is known as the “polyol” part.  
         [0089]    Various additives can be included in one or the other component or part, such as curing catalysts, UV blocker, fire retardant, e.g., bromine, and plasticizers. Additional catalysts may be added to complete the cross-linking of the resin over any carbon or oxides present in the flyash.  
         [0090]    [0090]FIG. 15 illustrates an initial step for forming a single or multi-layer panel of the present invention. In FIG. 15, spray head  62 , which is embodied as a manual spray head with a handle and trigger, is moved in a zigzag pattern  63  over the surface of mold  30  to lay down an initial layer  15 , having hybrid resin chain orientations that roughly mimic pattern  63 . This produces an orientation in the layer across the upper surface of mold  30 .  
         [0091]    Before layer  15  cures a subsequent layer  17  is applied as shown in FIG. 16, but using a zigzag pattern  65  that is substantially orthogonal to pattern  63 . Subsequent layer  17 , thus, has an orthogonal orientation. Although the spraying pattern from layer-to-layer need not be orthogonal, they should be at some non-zero angle to each other to increase the strength of the overall panel as the layers build up.  
         [0092]    If the same composition is used for all layers, a monolithic one-layer panel will result. If the composition is changed, for example, by including a reinforcing additive in a subsequent layer, a multi-layer panel is formed.  
         [0093]    [0093]FIG. 23 illustrates an automatic apparatus  90  for automatically applying the various layers of a panel of this present invention onto a mold  30 . In an initial zone  92 , a first automatic-spray head  62  can apply the first layer of clear hybrid resin in pattern  63  of FIG. 15. In a second zone  93 , a second automated head  62  is used to apply hybrid resin, perhaps with pigment in pattern  65  of FIG. 16.  
         [0094]    In zone  94 , an additional spray head  62  is used in conjunction with an additive spray head  67  which is used to deposit an even layer of additive, such as chopped glass fibers, colored acrylic flakes or particles, or other reinforcing or decorative additive to the layer applied in zone  94 .  
         [0095]    In zone  95 , a further spray head  62  is used to apply a final, rearmost layer to the panel that is now completed in mold  30  and allowed to fully cure. Mold  30  is moved from station to station on a conveyer  82 , which moves the mold in steps in the direction of arrow  83 .  
         [0096]    Other Forming Methods  
         [0097]    [0097]FIG. 21 shows an alternate mechanism for forming the panel of the present invention, specifically a high or low-pressure mold (RIM) having a male part  44 , a female part  48 , and raised or recessed feature  45  in the panel  10  molded between the mold parts. The hybrid resin components and additives are poured or injected into the mold.  
         [0098]    A mixing process and multistage mold can also be used according to the present invention as illustrated in FIGS.  28  to  31 . The Iso and Polyol components of the hybrid resin are modified so that they can be used in a low-pressure machine mixer. This type of system is known for use with low-density hybrid resin and pour foams for both open and closed multi part cavity molds. Examples of these machines that can be used with the present invention are the Decker mixing machines available from Decker Industries of Port Solarno, Fla., and a mixing machine available from Edge Sweets, Grand Rapids, Mich. These devices can deliver a required amount of hybrid resin into a mold to produce a multi layer product according to the invention.  
         [0099]    Some Uses for the Panel of the Invention  
         [0100]    [0100]FIGS. 3, 4,  9  and  10  illustrate rectangular, substantially flat panels which can be constructed according to the present invention and which can be used for back-lit signs, curtain walls, other exterior walls, free-standing signs and the like. The apparatus of FIG. 24 can also be used to produce a continuous web of the panel material.  
         [0101]    One example for use of the present invention, especially where part of the panel or all of the panel is transparent or translucent, is as a backlit light box of a light box sign schematically illustrated in FIG. 22. Panel  10  is attached over the open front of light box  19  that contains a light source, such as fluorescent tubes  21 . The indicia carrying parts of sign  10  shown, for example, at  22  may receive acrylic inserts or be painted with shiny acrylic material and left transparent to light up the indicia. The surrounding surface of the sign shown at  23  which can be opaque is produced by flakes or grains of colored acrylic to simulate granite or the like, and supplied in a subsequent layer in the panel.  
         [0102]    [0102]FIG. 25 illustrates use of a panel  10  as a curtain wall on a structural building wall  25 , for example, made of masonry. The outer surface of panel  10  may simulate granite or other stone, or may be decorative in another fashion. Indicia, such as logos or words can be provided in one of the panels, for example panel  11 . In this way, the outer surface of the wall is uninterrupted but still carries a lit decorative element to produce a highly unusual and attractive appearance.  
         [0103]    Using rectangular panels  10  and  11  having returns  14 , the panels can be attached to the wall using elongated unshaped rails  28 , having inner facing teeth  41  which are biased toward the building wall  25  to firmly retain the panels by biting into the inner surfaces of the setbacks or returns  14 . This is a very simple mounting technique that is permitted by the low expansion co-efficient of the panels of the present invention as well as their weatherability, fire-resistance and UV resistance. Rails  28  are easily mounted to wall  25 , e.g., by studs  43  fired by a stud gun into the base of the rail.  
         [0104]    Examples of the Panel Layers  
         [0105]    [0105]FIG. 17 illustrates one embodiment of the structural panel of the present invention. In this embodiment the outer, or visible layer  1 , is a clear thermosetting hybrid resin made in accordance with the present invention that was sprayed using the technique of spraying into an open mold. Behind this layer, a second clear resin layer  2  was laid, on which acrylic flakes were encapsulated to produce a granite appearance. The flakes were supplied from container  78  in FIG. 14 in the form of colored acrylic flakes having a color distribution to simulate stone such as granite, marble, sandstone, limestone, stucco, ceramic tiles, brick, slate and the like.  
         [0106]    A subsequent layer  3  resin was applied to the still uncured layer  2  to form a permanent seal and attachment to that layer. Black or silver pigment may be used to produce an opaque layer. As a further alternative, layer  2 , rather than including granules, can include chopped fiberglass and/or other fiber lengths or other components to conduct heat energy away from the front surface and increase the structural strength of the panel. FIG. 18 illustrates a panel  10  made of a single built-up layer of resin containing coloring to produce a panel with a single layer construction. Despite the single layer construction, the thickness of resin can be built up using the spray head  62 , operating in orthogonal directions as shown in FIG. 15 and  16  to maintain the flatness of the panel and avoid warping or other deformation in the cured panel.  
         [0107]    [0107]FIG. 19 illustrates another embodiment of the invention that includes the clear visible layer  1 , a reinforced layer  2  and an opaque layer  3 . In the embodiment of FIG. 19, recesses  29  have either been formed by plugs in the base of the mold or are machined out of the surface of the panel after it has cured. These spaces are filled with pigmented resin  31 . Recesses  29  can be in the form of logos, alpha/numeric characters or other indicia, and the panel can be backlit. Light is amplified and dispersed by a light dispersion panel  54 , but the light is directed only to the elements  31  which light up on the surface of the panel. The remainder of the panel can be provided with any desired color or texture by the graphic and/or reinforcing features of layer  2 .  
         [0108]    [0108]FIG. 20 illustrates another panel of the present invention which includes the outer clear layer  1 , a pigmented layer  2 , a graphic particle-containing layer  3 , reinforcing fabric  56 , and a rear insulating layer of low density urethane foam  39 , with or without fillers, which increases the R value of the overall panel without reducing its strength, weatherability, fire-resistance or other advantageous characteristics.  
         [0109]    Two types of microspheres can be used with the invention. One is hollow (e.g. HGS-14) and is also called micro balloons, and is added to increase strength and reduce weight and thus cost, since resins are sold by the pound. The second are solid microspheres. Flyash or other extenders can also be used to make the panel denser.  
         [0110]    With these additional factors in mind, another panel of the invention has a first layer about {fraction (3/16)} inches thick and made of hybrid resin (explained in greater detail later in the disclosure), on which a second layer of hybrid resin containing about one third part by volume HGS-14 micro balloons. The result is light yet very flat and strong. Dynamic Matrix ceramic particles can replace the micro balloons. In another embodiment of the invention flyash particles can replace these fillers.  
         [0111]    A further example of the invention has a first 1/8 inch thick layer of hybrid resin and a second layer about ⅜ inches thick of closed cell, eight-pounds-per-cubic-foot density foam. The conventional foam, for example a three-pounds-per-cubic-foot hybrid resin foam sold by Burton under the name BUC 152, is open celled and does not add appreciable strength or insulation as does the foam used with the present invention.  
         [0112]    A still further example of the invention is a three layer hybrid resin structure having a first white layer, about 0.030 inches thick of UV blocked automotive grade urethane, a second layer, about 0.060 inches thick of hybrid resin and filler, and a third layer, also about {fraction (3/16)} inches thick of 8 pound structural closed cell, hybrid resin foam, which also may contain filler.  
       CHEMISTRY OF THE STRUCTURAL PANELS  
       [0113]    As noted above, the high density thermosetting hybrid resin of tile present invention which may also be referred to as high density polyurethane and polyurea or hybrid resin, is prepared by combining components A and B with various additives to enhance the properties of the resulting panel in accordance with the present invention.  
         [0114]    Components A and B that can be used for the present invention are available from Burtin Corporation of Santa Ana, Calif. One composition that is particularly useful for the present invention is known by the trademark SUPERFLEX, a plural component thermoset polyhybrid resin system. SUPERFLEX is a trademark of Burtin Corporation. Another composition useful is a hybrid resin made by Hehr International Polymers called TR90.  
         [0115]    When using components A and B of the SUPERFLEX system, both components must be preheated to a temperature of approximately 120° to 140° F. Appropriate heaters must be provided in the containers and along the feed lines of  71  and  73  of the apparatus of FIG. 14.  
         [0116]    For SUPERFLEX, hybrid resin component A is a pre-polymerized, monomeric diisocyanate (MDI). Component B is a blend of polyols and catalysts (amine). Neither A nor B contains volatile organic compounds (VOCs). They are supplied under pressure in equal amounts to the spray head.  
         [0117]    Reaction takes place immediately, with gel times of 3-10 seconds and tack-free times of 30-60 seconds. The reacted product can be handled within minutes, although care must be taken to prevent product deformation in the first few minutes. As with most polyhybrid resins, complete polymerization does not occur for 24 hours although the product can be trimmed and finished sooner.  
         [0118]    The hybrid resin product has good thermal stability up to 180° F. It is paintable and machinable with most conventional processes.  
         [0119]    Although different catalysts can be used, the amount of catalysts is selected to be between 0.1 and to 1.0 percent by weight of the combined hybrid resin (components A plus B) and is preferably reduced so that the curing rate, rather than being on the order of seconds, can be increased to a minute or more to allow for application of subsequent layers behind the first layer.  
         [0120]    The other components, such as the sun blocker, pigment and plasticizer are all blended with component A to avoid upsetting the delicate catalytic action in component B. The fire retardant, preferably bromine, in the proportion of 1.5 to 3 percent by weight, is also present in component A. The sun blocker Tinvnin (pronounced tin a vin) can also be used and can be in component B (the polyol side) in the rage of 0.05% to 10% of component B, depending on the life cycle needed for the panel. For a panel life of 10 to 15 years, 2.5 to 7% by weight Tinvnin on thicker panels is used to block UV passage into the panel body.  
         [0121]    The resins used with the present invention are selected to have a grade that produces either a “water clear” resin for the outer, preferably thin coating, since the water clear hybrid resin is more expensive than a more yellowish or tan lower grade hybrid resin which is a distinctive color, but is far less expensive. The lower grade resin is used for the rearward invisible layers where the outer visible surface must be either clear or reveal the underlying graphics, pigments, embedded indicia, or the like lower layer. Structural elements that were present are also encased in the lower grade hybrid resin. Another way to understand the difference between the water clear, versus natural color hybrid resin, is to appreciate the MDI and the Clear Polyol are highly refined and very pure. They are very expensive and are the highest priced MDI and Polyol on the market. The natural colored MDI and Polyol are pure, but they are not refined as much to the same extent and are, thus, much cheaper. For example, clear Iso and clear Polyol cost approximately $5.00 to $6.00 per pound. The natural color Iso and Polyol cost approximately $1.00 to $2.85 per pound. Both can be used in the present invention, depending upon the desired result. If a translucent color is required, this can be based on clear resin containing pigments. For building panels, the less expensive natural resin can be used with a stronger pigment than used in the resin to produce the desired color.  
         [0122]    The UVX™ product is an example of the water clear grade hybrid resin. An example of the yellowish, less expensive, hybrid resin is the SE-270™ polyurea resin product which uses the same iso component A and polyol component B supplied in spray equipment at a pressure of at least 1,500 PSI and maintained at a temperature of 120-140° F.  
         [0123]    The flame retarder (bromine) is typically 1% by weight; usually in the A side as the iso seems to carry it well. For the invention this amount has been adjusted to 2% and 3% based on application. For most panels 2% is used. The plasticizer in the polyol 13 side can also range from a low of 2% to a high of 20% based on the desired hardness of the finished panel. Examples of usable plasticizers are phthalate, adipate and sebacate esters, ethylene glycol, tricresyl phosphate and castor oil.  
         [0124]    The following is a typical composition for layers of the resin of the present invention:  
       EXAMPLE 1 (A RIGID URETHANE TWO-PART SYSTEM)  
       [0125]    [0125]                                                                     Amount   Range       Ingredient   Chemical   (Weight %)   (Weight %)                                Polyisocyanate   Polymeric   44   20-65           Diaphenylmethane           Diisocyanate (MDI)       Plastisizer   Ethylene Glycol   2.0   0.10-25         UV blocker   Tinvnin   1.0    0.1-10.0       Flame retardant   Bromine   1.0    0.1-10.0       Pigment   Urethane   1.0   0.1-5.0       Polyol   Polyester and   47   20-65           Polyether blend       Catalyst   Amine   4   0.10-20                      
       EXAMPLE 2 (A FLEXIBLE URETHANE TWO-PART SYSTEM)  
       [0126]    [0126]                                                                     Amount   Range       Ingredient   Chemical   (Weight %)   (Weight %)                                Polyisocyanate   MDI   41   20-65       Plastisizer   Ethylene Glycol   5.0   0.10-25         UV Blocker   Tinvnin   2.0   0.10-10.0       Flame Retardant   Bromine   1.5   0.10-10.0       Pigment   Urethane   0.5   0.10-5.0        Polyol   Polyester and   48   20-65           Polyether blend       Catalyst   Amine   2.0   0.10-20                      
         [0127]    Chemistry of Available Products  
         [0128]    The above table shows the basic chemical makeup of the present invention. For years architects and specification writers have looked at plastic and polymer panel products with caution. They wanted a lightweight product with superior weatherability, with the same fire and mechanical properties as a stone or cement product. The present invention addresses many of the concerns and desires of the building and automotive industries. The present invention is based on multiple layers of resins, clear or pigmented, on the outside or first surface. These resins are commercially available from a variety of sources. Burtin Corporation of Santa Ana, Calif. markets one product, a clear topcoat, under the trade name UVX. Another product is called DUC 2021, produced by PPG Industries. Still another coating called Chromacoat, by Dupont is available. These products can be used successfully in the present invention based on the end use of the product. The second layer chemistry is also very versatile. Pigmented resin is available from many sources. The UVX clear from Burtin can be pigmented and applied behind the first layer. Other Products that can be used are Ultrachrome by Futura Coating of St. Louis, Mo. Centari by Dupont and Duranar by PPG Industries may also be used. The Duranar is very useful in the present invention as it contains polyvinylidene fluoride (PVDF) resin. PVDF has been used successfully for over 25 years and is a proven UV blocker.  
         [0129]    The third and subsequent layers are also based on urethane and polymer chemistry. Hybrid resin has been referred to throughout the description of the present invention. Products such as Burtin&#39;s SE271 are based on structural urethane and their SE270 is based on polyurea chemistry. The hybrid resin is made by combining urethane and polyurea resins in a combination that achieves the desired mechanical and thermal chemistry. One such hybrid resin is available from Hehr of Decatur, Ga., called HPTR90. The hybrid resin has proven to be very useful in the present invention. Hybrid resins can be blended to cross-link and polymerize and encapsulate oxides found in ceramic fillers, metal traces found in and on glass fibers, roving and matting, as well as carbon found in flyash.  
         [0130]    Conventional thermoplastics and polymers cannot deal with residual heat energy. Approximately 90% of the sun&#39;s heat energy is reflected from the surface of most buildings and automotive claddings and panels. The remaining 10% or residual energy must be removed from the surface. The hybrid resins with oxides and carbon containing fillers allow this residual heat energy to move into the inner layers and into the insulating core of the product during daylight hours and allow this same heat energy to move back to the surface and into the air at night.  
         [0131]    There are two primary factors that make the present invention possible. They are 1) the ability to move residual heat energy to achieve the desired coefficient of thermal expansion; and, 2) improvements in the properties of plastic and polymer products that were not previously available.  
         [0132]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.