WO2000001523A1

WO2000001523A1 - Structural urethane panel

Info

Publication number: WO2000001523A1
Application number: PCT/US1999/015067
Authority: WO
Inventors: Michael G. Robinson; Thomas W. Brignall
Original assignee: Signstrut Composite Materials, Llc
Priority date: 1998-07-07
Filing date: 1999-07-02
Publication date: 2000-01-13
Also published as: AU4856899A

Abstract

A self-supporting structural panel (10), method of making the panel and uses for the panel, apply multiple layers of high density thermosetting urethane, one behind the other. The panel is sufficiently thick and strong to be self-supporting. The panel has an outer surface, adapted to be visible (22), and an inner surface. An ultraviolet stabilizer is in the at least one layer for blocking UV radiation to make the panel weather and age resistant. At least one additional high density thermosetting urethane layer adhered to the outer layer contains a pigment, a graphic component and/or a reinforcing component (18).

Description

STRUCTURAL URETHANE PANEL

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates in general to self- supporting structures which can be used as curtain walls, fascia panels, and other structural and display purposes which are either flat, textured or three dimensional, and which may be opaque, translucent or even transparent, in part of entirety, with or without backlighting, and in particular to a new and useful, self-supporting, weather resistant and, in some instances, flame resistant panel containing, or completely made up of, at least one layer of urethane or polyurethane which is sufficiently thick and strong to act as an outer, or only, weather resistant, sunlight resistant, mechanical-impact resistant structure which may also have fire retardant characteristics. Such a panel is particularly useful for exterior signs, building coverings and the like. The invention also includes a method and apparatus for making the panel as well as structural combinations incorporating the panel, such as light boxes, canopy signs, curtain walls and other appropriate uses.

U.S. Patent 2,095,269 to Schuler discloses a decorative transparent sheet composed of stacked layers of mastic, metal foil, an adhesive, paint and glass. The decorative sheet of Schuler '269 is particularly suited to protecting decorated glass tiles from water damage.

U.S. Patent 1,688,196 to Masson teaches a display made from layered plastic sheets in which the first sheet is pressed into a shape for a sign. Coloring is then added to the back of the first sheet followed by a protective plastic sheet layer. A white layer may be added to provide a background for the pressed portion of the sign.

A fiberglass sign panel is disclosed by U.S. Patent 2,782,544 to Tobin in which a raised face portion containing the sign indicia is formed from matted fiberglass, while the sides of the raised face are formed from chopped fiberglass. The face portion may be colored or not.

A road sign having reflective surfaces is taught by U.S. Patent 3,176,420 to Alverson. The sign is a durable panel made from a fiberglass backing layer supporting a reflective layer of mastic containing glass beads. The mastic is pigmented in a background color for the sign while a differently colored coating is applied to the back of the reflective layer. The indicia the sign is intended to display are pressed into the mastic to the colored coating. The backing layer and reflective layer are each coated by an acrylic layer and a layer of lacquer coats the front and back of the sign structure. The lacquer and acrylic are both preferably methyl methacrylate. U.S. Patent 3,751,319 to Green et al . teaches a method of making signs having a facing layer of a clear polyester resin over a graphic pattern layer supported by a polyester resin layer and a stiff fiberglass backing layer. The preferred polyester resin is an unsaturated thermosetting polymerizable polyester resin with some minor amounts of additives. U.S. Patent 3,827,169 to Chase et al . discloses a billboard display panel composed of a fiberglass panel and polyester resin panel surrounding a display sheet between them. The Chase '169 billboard is semi-rigid. A multilayer vending machine panel is taught by U.S.

Patent 4,642,959 to Swiech, Jr. et al . The panel is composed of a steel panel coated with a polymeric seal layer having a printed polymeric ink graphic further coated with a hard, cross-linked polyester material. A textured building material composed of a fiberglass mat bonded to a PVC foam material, and a second fiberglass mat between the foam material and a textured polymeric gel is disclosed by U.S. Patent 5,070,668 to Lieberman. U.S. Patent 5,266,234 teaches a non-structural polyurethane skin and how to make it.

Other multi-layer display and sign panels at teach in U.S. Patents 1,592,400 to Bloem; 2,674,558 to Neugass; 3,076,294 to Schiessl; 3,244,579 to Chiesa; 3,542,630 Pfiffner; 3,768,186 to Chase et al.; 3,802,944 to Tung; 4,201,003 to With; 5,020,252 to DeBoef; 5,073,424 to Dressier; 5,087,508 to Beck; 5,225,260 to McNaul et al.; 5,345,705 to Lawrence; 5,398,435 to Kanzelberger, 5,423,142 to Douglas et al.; 5,443,869 to Harris; 5,524,373 to Plumly; and 5,655,324 to Siener, Jr. et al.

In the past decade large plastic, back lighted signs have given way to smaller signage that is being limited as to where it can be installed. In the past the architect has been left out of the loop in favor of a designer who added signs on to a building as requested by a client. The results in many cases was less than pleasing. This "add-on" practice is one of the reasons that most cities have passes 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 local code officials to approve the project before it starts. Traditional signs and light boxes are being forced off these projects in favor of back lighted canopies and non-illumated signs, that are mounted flat on the walls of a building. The problem with that is a sign is much more effective when it is lighted. Clearly a new approach to this problem was needed. The present invention allows a light source to be built into a wall system, the panel can be molded to the same shape and appearance as the building cladding, and a lighted logo or sign can now be part of the building element.

Panels currently being produced for wall systems range from EIFS divit type systems, metal panels, FRP, fiberglass reinforced cement, precast cement, thermoformed plastic, roll formed metal, 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 precast concrete. FRP is a short lived material and, while precast concrete will last for 20 years or more, it is heavy and can be very costly.

Spranderal glass is also very popular as in fill panel. Most of today's glass buildings are curtain wall with viewing glass and spranderal glass in the knee wall. Such a wall system is flat and very common. Almost all building panels (except the glass) are opaque and can not be made to be illuminated from behind.

Other composite products are disclosed in U.S. Patents 4,077,830; 4,268,574; 4,587,754; 4,743,485; and 5,102,710. The present invention also allows a logo panel to be installed as part of light band or fascia system used on a canopy, such as found over the gas islands in a filling station, or on the front of a business.

As of this time, most plastic signs are thermoformed from large sheets of acrylic or polycarbinate and then painted or decaled. For the most part these products reply on thickness to provide the needed mechanical strength to withstand wind loads and weather. These products are heavy and expensive. Most of these products have a poor coefficient of expansion and become brittle in very cold weather. As is the case with most plastics, these products yellow with age and exposure to the Sun's UV radiation. These products have served well, however, because they are used in systems that hold and control their movement. Designers and engineers have wanted an alternate reinforced product for years . The problem is that up to now there was no way to back light any product that had structure in the sheet material. Once any other material was introduced into a sign product the light passage properties were reduced so dramatically that it was not suitable for use as a sign face product. 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.

For many years FRP (fiber reinforced polyester) panels have been used in the building industry. These panels are light weight and have very high mechanical strength, as well as being dimensionally stable through a wide temperature range. The problem is that FRP panels do not pass light and are not useable for back lighted signs or fascia systems. The present invention lends it self to back lighted fascia systems as it is light weight yet has good mechanical strength and superior dimensional stability through a wide range of temperatures and weather conditions . Low density structural polyurethane foams have been used in the past as panel structures. An example is a panel product known by the trademark DURAFORM and supplied by Vacuform Industries, Inc. of Columbus, Ohio. High density urethane systems have been used as thin coatings of films but not as self-supporting layers of panels.

The present invention solves many problems for panels of the prior art and is sufficiently versatile form use as signage, building panels and other varied uses.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a structural, self-supporting panel, which comprises at least one layer of high density urethane containing an ultraviolet (UV) stabilizer, preferably a UV blocker, and which is sufficiently thick to provide an outer sun resistant, weather resistant and mechanically strong layer for the panel, or form the panel as a one layer structure.

A further object of the present invention is to provide a method for manufacturing the self-supporting urethane panel which includes a high pressure spray or injection mold (RIM), a high pressure open tool molding technique, a low pressure open tool or RIM pouring, or hand or machine casting technique, or a low pressure continuous machine casting process.

A still further object of the present invention is to incorporate superior weathering and flame retardant characteristics into the urethane layer or panel, which gives the panel a sufficient flame and smoke rating for use as a curtain wall or other building component. Class II or Class I ratings can be achieved depending on the end use for the panel .

The present invention can be practiced in a wide variety of ways while taking advantage of the basic concept, specifically to provide an outer surface which is resistant to mechanical shock, which is resistant to ultraviolet radiation from the Sun and from weather, and which 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.

This can be achieved in many ways. Among these is a technique of layering or spraying the urethane material onto a mold which may be flat or three dimensional, for building up layer after layer of the urethane material and other intermediate materials as needed to impart characteristics of strength, flatness, graphic transparency, translucency or opaqueness, depending on the purpose to which the panel will be put.

In this way, the same invention can be utilized to produce a wide variety of structures which can be backlit or not backlit as desired, which can be used for sign fascias, or even for applying graphics in curtain walls on buildings which are made from the panels, or with appropriate fire-resistance where necessary, strength and flexibility as needed and extremely long life as appropriate for buildings in particular.

One key to the present invention is that the first layer has a weatherable surface. Any product used outdoors, or for exterior applications must withstand heat, cold, precipitation and sun. Prolonged effect of Sun's UV radiation are harmful to color and surface characteristics such as gloss and textural . The UV blocker and stabilizer are part of the panel to further improve the weatherability of first layer of the composite.

The composite panels of the invention can be used for, but 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; and lighted and non-lighted sign panels; lighted panels; logo panels; or raised letters which are referred to as "channel letters" in the sign art.

All panels made for these applications must have superior weathering characteristics and should be flame retardant to Class II or Class I based on application.

The panel can be thin and lightweight yet maintain structural integrity so that panel will transfer wind loads to the structure or curtain wall system. The inventive panel is extremely versatile based on need, and the flexibility of the molds. The tooling can be made of many materials, wood, metal, silicon rubber or plastic. 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.

The mold can be made as a one piece open pan, or as two parts to produce a part to a desired thickness or shape on the back side as well as the face of the panel. This includes changes for multi-colors and for lighting.

Tooling may be of multi-pieces to allow negative draft angles and for attachment points in the finished product.

One technique for achieving the invention is to first spray an initial urethane layer into the mold with a sweeping back-and-forth movement. Preferably, this layer has no filler, but is sprayed to an appropriate self-supporting depth. One attribute of the present invention is that the urethane is formulated to cure very quickly, in a manner of two to twelve seconds so that subsequent layer can be applied behind the first layer. Advantageously, the second layer is applied by a sweeping back-and-forth movement which is substantially perpendicular to the movement which was used to spray on the first layer which, in any case, is at some angle to the direction of application of the first layer. This has been found to drastically increase the strength and flatness of the resulting panel by crossing the "grain" or predominate orientation 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 impart desired texture and color to the layers. Advantageously, the first layer is without these additives and produces a clear, hard UV resistant and, where desired, flame- resistant shell. The inner layer may include the additives for decoration. Chopped fibers, for example, glass fibers, can also be included in the second layer for drastically increasing strength in a manner analogous to fiberglass reinforced structures of the prior art (FRP technology) .

If resistance against flexing or bending of the panel is required, a structural element can be included, such as an egg crate or grid structure behind the first or second layer, and then a further layer sprayed over the structural element to encase and mechanically marry the structural element to the remainder of the panel. Because of the nature of the sprayed urethane, each layer is intimately adhered to the next without any possibility of de-lamination or separation even after long periods of time.

The mechanical strength, mechanical 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 .

In accordance with another embodiment of the invention, a corrugated sheet of urethane can be made using the same spray technique or pouring/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 urethane layers, The use of a corrugated layer also produces air pockets in the panel which improve its thermal insulating characteristics.

Throughout this disclosure the term "urethane" is used interchangeably with polyurethane, even though the two are considered chemically separate from each other. Both 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, and both are thermoset plastics which are essential for the present invention. Thermoplastic panels are not appropriate although some characteristics of thermal thermoplastics, such as their good orientation when extruded, are also characteristics of the present invention where the orientation of the urethane is utilized to improve strength.

Among the attributes that can be incorporated into one or more layers of the panel of the present invention, is the use of a flame and/or smoke retardant within the urethane layer or layers which gives the panel a Class I or Class A fire rating and a 15 year life. Both the fire resistance and life span of the invention have been confirmed by industrially accepted tests.

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). For some architectural requirements, such as buildings for sensitive telecommunication equipment, bullet proofing is actually specified as a requirement for an exterior wall of a building.

The present invention can also have comparable expansion characteristics to that of aluminum, and, in fact, the expansion characteristics can be tailored to a particular need.

The use of UV stabilizer, in particular a UV blocker, is particularly advantageous. The sufficient thickness of the urethane layer containing the UV blocker permits blocking of virtually 100 percent of sunlight. The thinner the layer, the less the blocking effect. UV blocking is superior to the use of UV inhibitors which, over the course of years, prevent UV damage by undergoing chemical changes within the panel structure that produce an outward chalky substance on the panel and increase its brittleness. No such deterioration occurs in the present invention.

According to the present invention, the panel includes at least one layer of urethane which is at least three thousandths of an inch thick and preferably 3 to 6 thousandths of an inch thick (3-6 mils). This gives the layer individually, and the panel as a whole, self- supporting structural strength and distinguishes it from urethane and polyurethane coatings used, for example, on automobiles or other structures meant for outdoor use. Generally, these coatings are no more than two mils thick and, further, do not have the other attributes of the present invention, such as fire-resistance, hardness and structural strength.

The panel as a whole should be 0.060 to 0.250 inches thick for signage 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. 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 urethane in a spray head just before it is sprayed onto the mold. The mold itself can be flat, have a surrounding ridge which forms a set back and flange for the panel, and may include three dimensional structures onto which the urethane 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 or 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. Another technique is to paint the logo or lettering onto the mold before the initial layer of urethane is laid onto the mold. This can be done using automotive grade urethane paint or UVX topcoat. The subsequent sprayed on layer of urethane 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 . The spray head can be used with a third inlet which mixes structural or graphic fillers with the two parts that make up the urethane. The fillers can be fibers, particles or granite or acrylic or flakes of granite or other colored or non-colored fragments which impart the desired appearance to the layer. A marble effect can be used by swirling a combination of black and white pigments in the actual spraying process for the first layer.

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 urethane can be tailored to increase 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 of 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.

A typical fire retardant component to be added to the urethane is bromine. Bromine tends to reduce the structural strength of the layer, however. It is generally desired 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 1 or class A fire rating, this can reduce the urethane strength to about 2,800 psi. The strength can be increased again, however, by the addition of subsequent back layers with glass or other reinforcing, behind the initial layer to achieve the overall strength requirements for building.

Graphic elements can also be laid into subsequent layers where the initial layer is clear urethane. For example, a sheet of DAYCRON or TYVEK material (DAYCRON and TYVEK are trademarks) which has a wood grain or other desired appearance, can be laid behind an initial layer and then a subsequent urethane layer sprayed on to the insert for permanently encasing it. This produces a panel with a wood grain appearance in an extremely economical and fast manner.

In addition to spraying, casting or pouring of thicker layers of urethane into a mold can produce thicker, single layer urethane structures with or without graphic components and clear, translucent or opaque panels of any desired color. In accordance with another method and apparatus of the present invention, the biased multi-layer spray application of a panel can be achieved on a conveying surface to produce a desired length of panel and then the surface stepped forward to make the next length in a continuous sheet of the material . As long as the cured times are selected to give sufficient time to apply a second layer in an edge-to-edge relationship to the previous layer, a continuous sheet of material can be formed. A separation sheet of inexpensive material (such as waxed paper, or the like) can be applied to the bottom of the sheet and then the sheet rolled up into a large roll. The flexibility of the invention permits this storage technique and, thus, the production of an endless roll of material. 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 which is structural, graphic or both, can also be utilized with this process.

As noted reinforcing elements can be added to the panel. Fiberglass can be sprayed into the stream of resin that is sprayed into the mold. 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. Many substances may be used as reinforcing such as but not limited to; corrugated paper, or metal, wood, plastic reinforcing, foam core, foam, microspheres, ceramic particles, 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 others as needed for specific applications.

Color may be added to the panels as well.

Structural urethane 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. Panels may also be made of translucent resin and may be back lighted, allowing light to pass through to graphic elements. Pigmenting is based on urethane paints and dyes that can be mixed into the polyol .

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

In the drawings:

Fig. 1 is a perspective view of an open pan mold which can be used in accordance with the present invention;

Fig. 2 is a perspective view of another pan mold of the present invention;

Fig. 3 is a perspective view of structural panel constructed with the mold of Fig. 1;

Fig. 4 is a rear perspective view of a sign which can be constructed with the mold of Fig. 2;

Fig. 5 is a view similar to Fig. 1 of another embodiment of the mold;

Fig. 6 is a view similar to Fig. 5 of another embodiment of the mold;

Fig. 7 is a perspective view of another embodiment of a mold which can incorporate surface features on the finished panel;

Fig. 8 is a perspective view of a structural element which can be used in combination with the panel of the present invention; Fig. 9 is a rear perspective view of a panel of the present invention incorporating the structural element of Fig. 8;

Fig. 10 is a perspective view of a finished panel constructed with the mold of Fig. 7; Fig. 11 is a perspective view of another structural element which can be used in accordance with the present invention;

Fig. 12 is a perspective view of a planar element which can be used with the panel of the present invention;

Fig. 13 is a perspective view of a flexible non- woven and printed fabric sheet which can be incorporated into the panel of the present invention;

Fig. 14 is a schematic representation of an apparatus which can be used to manufacture the structural panel of the present invention;

Fig. 15 is a schematic view of a technique for laying down initial and subsequent layers of the panel of the present invention; Fig. 16 is a schematic view similar to Fig. 15 showing the manner of laying down a second and subsequent alternating layers of the panel of the present invention;

Fig. 17 is a partial sectional view of one embodiment of the panel of the present invention; Fig. 18 is a sectional view of an open pan mold with a panel of the invention therein; Fig. 19 is a sectional view of another embodiment of the panel of the present invention;

Fig. 20 is a sectional view of a still further embodiment of the panel of the present invention; Fig. 21 is a sectional view of a closed mold which can be used in accordance with the present invention;

Fig. 22 is a front elevational view, with part of a panel removed, showing a light box sign which can be constructed in accordance with the present invention; Fig. 23 is a schematic perspective view of an apparatus for mass producing a panel of the present invention;

Fig. 24 is a perspective view of another apparatus for producing a continuous web panel of the present invention;

Fig. 25 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; Fig. 26 is a schematic perspective view of the invention used as a canopy sign;

Fig. 27 is a schematic perspective view of a channel letter of the invention with and panel of the invention, illuminated by LEDs; Fig. 28 is a sectional view of a mold in an early step of casting a panel or member according to the invention;

Fig. 29 is a top plan view of the mold of Fig. 28; Fig. 30 is a view similar to Fig. 28 of the mold during a subsequent step in the process;

Fig. 31 is a view similar to Fig. 28 of the mold during a still further step in the process; and

Fig. 32 is a schematic view of a CRRM device for use according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, various embodiments of the invention will now be disclosed.

General Panel and Mold Structures

Figs. 3 and 4 illustrate two examples of the structural panel of the present invention.

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 the setback walls 14. Reinforcing element 18, e.g. of aluminum square tubing, may extend around the entire perimeter of setback 14, 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.

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. This is particularly advantageous when the panel is to be backlit.

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).

Fig. 1 illustrates an open pan mold generally designated 30, which was used to manufacture the sign or 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 which 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. Fig. 1 also illustrates placement of the elongated reinforcing element 18 inside the pan mold. 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.

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 .

Figs. 5 and 6 show similar pan molds for producing positive or negative indicia on a panel which is used with forwardly extending setbacks, rather than rearwardly extending setbacks. In 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.

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 upper urethane surface of the panel 50. The entire surface of base 32 and the ridges of the mold may also be painted with paint that is released from the mold to "paint" the entire outer surface of the panel.

Fig. 8 illustrates a rectangular, structural element 38 in the form of a plastic grid or "egg crate", such as those used in flourescent ceiling fixtures. In accordance with the present invention after one or more initial layers of urethane are sprayed into the pan mold and before the urethane cures, element 38 is placed into the mold and then additional layers sprayed above 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. Other structural elements, such as a urethane corrugated sheet 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 urethane system onto a corrugated mold. For backlit panels, a white acrylic sheet 54 can be used as a rearmost layer in the panel structure to diffuse light throughout the backlit panel. Fig. 13 illustrates another element which can be incorporated into the panel of the present invention, namely a flexible, non-woven printed fabric sheet 56 which in Fig. 13 has been imprinted with a wood grain pattern. Since the first layer of the panel is preferably clear, if 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 urethane impregnates the sheet and positively fixes it into the layers of the panel.

Spray Technique

Fig. 14 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 which contains a mixing chamber for receiving various components of the thermosetting, high-density urethane forming the structural panel of the present invention, and sprays this mixture through a nozzle 64 which can be accurately directed toward the mold either manually or with automatic equipment.

Apparatus 60 includes a first pressurized container 66, for example, a 55 gallon drum containing a component "A". A second pressurized container 68 contains a component "B" . Both containers carry pressure heads 70 and 72 which 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 spray head 72. A propellent, such as compressed air, is supplied from a compressor 74. This propellent which is labeled "D" may also be other gas, such as C0₂. A combination of air and C0₂ can also be used to insure that the mixed together components A and B, after being thoroughly mixed, are supplied with sufficient force, e.g. 1500 psi, in an atomized stream 76 which can be accurately aimed and directed.

Additives "C", such as chopped fibers, pigment acrylic, colored granules, flakes or particles, or other additives, can also be supplied from an additive container 78, under pressure of a pressurizing head 80 and along a line 81, to the mixing chamber in spray head 62. Alternatively, these additives can be evenly sprinkled into the pan 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 urethane of the second layer in a panel, channel letter of 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 that spherical in shape the particles look like jacks on the order of tens of microns in size.

As will be explained in greater detail later under a separate section of this disclosure involving the chemistry of the invention, component A and B are supplied in approximately equal parts by volume, and in the shorthand notation of urethane chemistry component A is known as the "iso" part, and component B is known as the "polyol" part. 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 .

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 urethane chain orientations that roughly mimic pattern 63. This produces an orientation in the layer across the upper surface of mold 30.

Before layer 15 cures a subsequent layer 17 is applied as shown in Fig. 16, but using a zig-zag pattern 65 which 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.

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.

Fig. 23 illustrates an automatic apparatus 90 for automatically applying the various layers of a panel of the present invention onto a mold 30. In an initial zone 92, a first automatic spray head 62 can apply the first layer of clear urethane in pattern 63 of Fig. 15. In a second zone 93, a second automated head 62 is used to apply urethane, perhaps with pigment in pattern 65 of Fig. 16. 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.

In zone 95, a further spray head 62 is used to apply a final, rearmost layer to the panel which is now complete on 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.

The automated spray apparatus, generally designated 96 in Fig. 24, also uses a conveyer 82, but is adapted to produce a continuous sheet or web of panel material that can be accumulated in a storage roll 97. As with the embodiment of Fig. 23 in one of the stations 93, 94 or 95, a structural element can be laid into the mold before spraying takes place. In the embodiment of Fig. 24, an additional structural fabric can be laid onto the structure from a fabric roll 84 shown, for example, in zone 93. Since the product is not fully cured when it leaves conveyer 82, a release or separation sheet, for example, of wax paper or similar inexpensive material can be supplied from a separation sheet roll 86, to the lower surface of the panel web of the present invention which is designated 88. By not allowing the urethane of the present invention to be fully cured from zone to zone, an almost continuous and fully integrated edge-to-edge relationship is established from zone to zone to produce a substantially continuous web of panel material 88 accumulated in storage roll 97. From each station to the next, the thickness of web 88 increases incrementally until the final thickness is achieved at the storage roll 97; preferably 0.03 to 4.0 inches at the low and high extremes .

Other Forming Methods

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 urethane components and additives are poured or injected into the mold.

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 urethane 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 urethane and pour foams for both open and closed multi part cavity molds . Examples of these machines which can be used with the present invention are the Decker mixing machines available from Decker Industries of Port Solarno, FL and a mixing machine available from Admiral Industries. These devices can deliver a required amount of urethane into a mold to produce a multi layer product according to the invention.

Fig. 28 shows a low pressure RIM mold with upper mold part 44 and lower mold part 48 defining a cavity 46 there between. The upper volume of the cavity contains a plug 57 bounded at the edges by stops 55. As shown in Fig. 2 , gates 51, 53 and 61 provide passages for the two component urethane in its liquid state to fill cavity 46 and form a first layer 10 in the empty part of the volume. While the first layer is still only partly cured, the mold is opened and plug 57 is removed.

A second plug 77 is now placed in the mold cavity as shown in Fig. 30, the mold is again closed and a second layer 13 is poured or injected through the gates. In Fig. 31, a third plug 87 has been used to change the shape and size of the cavity again to form a third layer 9.

Fig. 32 illustrates the use of an CRRM or continuous resin reaction method for practicing the present invention. A mixing motors 73 in spray heads 75 and 85, mix urethane components A and B supplied at their respective inlet conduits in each spray head. The mixed urethanes flow along main headers 98 and 99 or the two heads and are sprayed at 90° to each other in accordance with inventive use of crossing spray patterns. This is all done onto the conveyor belt which carries the panel as it is being formed.

Some Uses for the Panel of the Invention

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 backlit 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. 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 which 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.

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 which is backlit by a light fixture 26 mounted within an opening 27 through the wall 25. 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. Using rectangular panels 10 and 11 having returns 14, the panels can be attached to the wall using elongated u-shaped 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 which 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.

Fig. 26 illustrates a use of the panel web 88 of the present invention in the canopy of a gasoline stationed island which is entirely backlit around its perimeter and can be provided with any desired indicia. The rigidity of the structural panel web of the present invention eliminates the need for elaborate mounting systems that are required when the canopy sign is made of flexible fabric-type material. The panel web 88 is sufficiently resistant to wind load, sunlight, fire and weathering to permit this use. Discreet panels 10 can also be utilized, but it is desirable to utilize the continuous web produced by the apparatus Fig. 24, in the environment of a canopy sign.

Fig. 27 illustrates additional possibilities according to the present invention. The invention can be used to produce a channel letter, generally designated 58, which in the Fig. 27 is a letter "E" visible from the rear hollow side, the opposite side being visible to the public. This is placed adjacent a panel 58, also made according to the invention. It is noted that the channel letter is not limited to a flat panel shape, but can take the shape of the letter and can be incorporated into other signs which are either backlit or not lit. An example of how the invention can be lit is by LED (light emitting diode) . Because the urethane panels of the present invention can be made to have light-transmitting capacity, LED 47 can be provided at the edge of the panel and, thereby, illuminate the entire panel. Alternatively, an LED 49 can be placed behind a broad surface of the panel to illuminate that surface. LED 69 is positioned to illuminate the edge of channel letter 58 and LED 71 is positioned to illuminate the broad interior surfaces of the channel letter, the light passing through the body of the urethane material and illuminating the visible surfaces of the sign. It is also noted that the panels of the present invention can be made in any shape and are not limited to flat shapes. They can, for example, be convex, concave, cylindrical, parabolic, or any other required shape. Also, light sources are not limited to fluorescent tubes and LEDs but may include neon tubes, incandescent lights, quartz lights or any other illumination source, depending upon the desired lighting effect.

Examples of the Panel Layers

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 urethane made in accordance with the present invention which was sprayed using the technique of spraying into an open mold. Behind this layer, a second urethane layer 2 was laid, on which acrylic flakes were spread to produce a granite appearance. Gray pigment was also included. The pigment was included in component A, and the flakes were supplied from container 78 in Figs. 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 .

A subsequent layer 3 of clear urethane was deposited, and a rear white, light-diffusing acrylic panel 54 was applied to the still uncured layer 3 to form a permanent seal and attachment to that layer. The final structure can be backlit. As an alternative, panel 54. is replaced by a urethane layer containing black or silver pigment to produce an opaque layer. As a further alternative layer 2, rather than including granules, can include chopped fiberglass or other fiber lengths to increase the structural strength of the panel.

Fig. 18 illustrates a panel 10 made of a single built up layer of clear urethane containing coloring to produce a transparent clear panel with a single layer construction. Despite the single layer construction, the thickness of urethane can be built up using the spray head 62, operating in orthogonal directions as shown in Figs. 15 and 16 to maintain the flatness of the panel and avoid warping or other deformation in the cured panel. Fig. 19 illustrates another embodiment of the invention which 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 urethane 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 sign. The remainder of the panel can be provided with any desired color or texture by the graphic and/or reinforcing features of layer 2. 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 foam urethane 39 which increases the R value of the overall panel without reducing its strength, weatherability, fire-resistance or other advantageous characteristics .

Two type of icrospheres 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. Solid microspheres can also be used to make the panel, channel letter of member of the invention denser.

With these additional factors in mind, another panel of the invention has a first layer about 3/16 inches thick and made of Burton SE-271 dense urethane (explained in greater detail later in the disclosure), on which a second layer of SE-271 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.

A further example of the invention has a first 1/8 inch thick layer of SE-271 and a second layer about 3/8 inches thick and of closed cell, 8 pounds per cubic foot, structural urethane foam. The conventional foam, for example a 3 pounds per cubic foot urethane foam sold by Burton under the name BUC 152, is open celled and does not add appreciable strength as well as insulation as the foam used with the present invention.

A still further example of the invention is a three layer urethane structure having a first white layer, about 0.030 inches thick of UV blocked structural urethane, a second layer, about 0.060 inches thick of SE- 271 and a third layer, also about 3/16 inches thick of 8 pound structural closed cell, urethane foam. Chemistry of the Structural Panels

As noted above, the high density thermosetting urethane of the present invention which may also be referred to as high density polyurethane, 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.

Components A and B that can be used for the present invention are available from Burtin Corporation of Santa Ana, California. One composition which is particularly useful for the present invention is known by the trademark SUPERFLEX, a plural component thermoset polyurethane system. SUPERFLEX is a trademark of Burtin Corporation. Other Burtin products suitable for use in the present invention are referred to as SE-270 and SE- 271 which, like SUPERFLEX material, are sprayable. Castable CU-200, CU-201, CU-202, CU-203, CU-205, CU-206, CU-WH204, BK-204, and CU-BK 305 are also useful to the present invention when cast, rather than sprayed. These are all available from Burtin.

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.

For SUPERFLEX, urethane component A is a prepolymerized, 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.

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 polyurethanes , complete polymerization does not occur for 24 hours although the product can be trimmed and finished sooner.

The urethane product has good thermal stability up to 180° F. It is paintable and machinable with most conventional processes .

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 urethane (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.

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 range 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.

The urethanes used with the present invention are selected to have a grade which produces either a "water clear" urethane for the outer, preferably thin coating, since the water clear urethane is more expensive, or a more yellowish or tan lower grade urethane which has a distinctive color, but is far less expensive. The lower grade urethane 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 which were present are also encased in the lower grade urethane .

Another way to understand the difference between the water clear, versus natural color urethane, is to appreciate that 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 $0.85 to $1.85 per pound. Both can be used in the present invention, depending upon the desired result. If a sign face in 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 the resin to produce the desired color.

The UVX product is an example of the water clear grade urethane. An example of the yellowish, less expensive, urethane is the SE-270 urethane 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.

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.

The following is a typical composition for layers of the urethane of the present invention: Example 1 (a rigid urethane two part system):

Example 2 (a flexible urethane two part system) :

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 .

Claims

WHAT IS CLAIMED IS;

1. A self-supporting structural panel comprising: at least one layer of high density thermosetting urethane which is sufficiently thick and strong to be self- supporting, said at least one layer having an outer surface adapted to be visible and an inner surface, the at least one layer having a ultraviolet stabilizer for blocking UV radiation to make the at least one layer weather resistant.

2. A panel according to claim 1, including at least one additional high density thermosetting urethane layer adhered to the at least one layer, the at least one additional layer containing at least one additive of: a pigment; a graphic additive; and a reinforcing additive.

3. A panel according to claim 2, including a reinforcing additive in the at least one further layer, the reinforcing additive comprising at least one of: fibers; microspheres and ceramic particles.

4. A panel according to claim 2, including a graphic additive in the at least one further layer, the graphic additive comprising flakes with color for simulating stone.

5. A panel according to claim 4 wherein the flakes are made of acrylic.

6. A panel according to claim 1, including a structural element on the inner surface of the at least one layer and at least one additional layer of high density thermosetting urethane over the structural element for encasing the structural element and attaching the structural element and the at least one further layer to the at least one layer.

7. A panel according to claim 6 wherein the structural element comprises a grid element.

8. A panel according to claim 6 when the element comprises a corrugated sheet.^"

9. A panel according to claim 6 when the structural element comprises a sheet of fabric.

10. A panel according to claim 9 wherein the sheet of fabric is a non-woven fibrous fabric having a pattern thereon.

11. A panel according to claim 1, including an outer layer element embedded in the outer surface of the at least one layer, the outer layer element being selected from the group consisting of two-dimensional indicia, a two-dimensional pattern and a three-dimensional surface texture material .

12. A panel according to claim 1, including a further layer of high density, thermosetting urethane connected to the inner surface of the at least one layer, the further layer containing at least one of pigment, a graphic component and a reinforcing component, and a third layer applied to the further layer, the third layer containing light-blocking pigment.

13. A panel according to claim 12 when the light- blocking pigment comprises silver or black particles.

14. A panel according to claim 1, including at least one recess in the outer surface of the at least one layer for producing indicia on the panel .

15. A panel according to claim 1, including at least one projection on the outer surface of the least one layer for producing indicia on the panel.

16. A panel according to claim 14, including pigmented urethane in the recess for producing a contrasting color in the recess from a remainder of at least one layer.

17. A panel according to claim 1 wherein the at least one layer is clear.

18. A panel according to claim 17, including at least one additional layer attached to the inner surface of the at least one layer, the additional layer being made of high density thermosetting urethane and containing at least one of a pigment, a graphic component, and a reinforcing component, the additional layer being visible through the one layer.

19. A panel according to claim 1 made by the process comprising combining two components which form a high density thermosetting urethane in a chamber, one of the components containing a catalyst for curing the urethane and the other component containing a UV stabilizer and spraying the components under pressure from the chamber onto an open mold to form the at least one layer.

20. A panel according to claim 19, including making the panel by spraying at least one further layer on the inner surface of the at least one layer with additional high density thermosetting urethane, the at least one additional layer containing at least one of pigment, graphite component and reinforcing component.

21. A panel according to claim 20, including making the panel by the process of inserting a reinforcing structural element between the at least one layer and before the at least one further layer is sprayed on.

22. A panel according to claim 19 made by the process comprising spraying the at least one layer in one pattern and spraying at least one additional layer of high density thermosetting urethane on to the inner surface of the at least one layer using a different pattern which is at a non-zero angle to the first mentioned pattern.

23. A panel according to claim 22, including making the panel by the process of distributing, reinforcing component onto the inner surface of the at least one layer before spraying on the at least one further layer for encasing the reinforcing component between the at least one layer and the at least one further layer.

24. A panel according to claim 1 including, in combination with the panel, a light enclosure containing a light source, the enclosure having an open front, and the panel covering the open front.

25. A panel according to claim 1 including, in combination, means for attaching the panel to the outer surface of a building to cover the outer surface of the building with the panel .

26. A panel according to claim 1 wherein the panel is elongated and is in combination with means for supporting the panel as a canopy sign.

27. A panel according to claim 1 wherein the at least one layer includes a plurality of edges, the panel including at least one elongated reinforcing element attached along at least one of the edges.

28. A panel according to claim 1, including a fire retardant in the at least one layer.

29. A panel according to claim 28 wherein the fire retardant comprises bromine.

30. A panel according to claim 1, including an additional layer of urethane foam attached to the inner surface of the at least one layer.

31. A panel according to claim 1, including in the at least one layer, an additive comprising at least one of: a pigment; a graphic additive; and a reinforcing additive.

32. An apparatus for forming a self-supporting structural panel comprising: a base; a ridge on the base defining an open pan mold; and a means for spraying a two-component, high density thermosetting urethane onto the pan mold to form at least one layer of high density, thermosetting urethane which is sufficiently thick to be self-supporting.

33. A method of making a self-supporting structural panel comprising: spraying two components of a high density, thermosetting urethane system into an open pan mold having the shape of the panel to be formed, to build up at least one layer of urethane which is sufficiently thick and strong to be self-supporting; and including in the system a UV blocker for blocking UV radiation from entering into the at least one layer.

34. A self-supporting structural member comprising: at least one layer of high density thermosetting urethane which is sufficiently thick and strong to be self- supporting, said at least one layer having an outer surface adapted to be visible and an inner surface, the at least one layer having a ultraviolet stabilizer for blocking UV radiation to make the at least one layer weather resistant.

35. A member according to claim 34, including in the at least one layer, an additive comprising at least one of: a pigment; a graphic additive; and a reinforcing additive.

36. A member according to claim 34, including at least one additional high density thermosetting urethane layer adhered to the at least one layer, the at least one additional layer containing at least one additive of: a pigment; a graphic additive; and a reinforcing additive.

37. A member according to claim 34, the member being in the form of a channel letter with a hollow interior.

38. A member according to claim 34, including in combination a light source for illuminating the member.

39. A member according to claim 38 wherein the light source is adjacent an edge of the member for illuminating the member.

40. A member according to claim 38 wherein the light source is adjacent the inner surface of the member.

41. A member according to claim 38 wherein the light source comprises at least one of an LED, a fluorescent tube and an incandescent light.