Abstract:
The composite material comprises (i) a polyurethane elastomer produced on site by reacting a polyurethane prepolymer finished in isocyanate and a polyol, and (ii) rubber. The material can be obtained by means of a method that involves mixing, molding and pressing the raw materials. The material, which is provided with good mechanical properties and, optionally, fireproofing, insulating, waterproofing and aesthetic, can be used in construction, decoration and engineering works.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a compacted material comprising a polyurethane elastomer and rubber, to a method for obtaining it that involves mixing, molding and pressing the raw materials, and to the use of this material.  
           [0003]    2. Description of the Related Art  
           [0004]    There are numerous products currently used in construction and engineering work, as well as in various fields of the art such as the automobile industry, the aeronautics industry, the naval industry, etc. for their insulating properties (thermal, acoustic, electrical), as well as their properties for fire-protection, water proofing, aesthetics and other attributes. Despite this, the need remains to find new materials that can be easily processed and handled to give them the desired properties.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention provides a solution to the current need of developing a compacted material comprising a polyurethane elastomer and rubber that can also incorporate suitable additives to give the material the desired properties.  
           [0006]    Polyurethane is a polymer of urethane resulting from the reaction of a polyisocyanate with a polyol, which can be obtained in the form of elastomers or flexible or stiff foams. Polyurethane elastomers are made of flexible macromolecule chains that form a three-dimensional lattice. They are generally amorphous, have a very low vitreous transition temperature and are elastic. Polyurethanes in general have good mechanical properties, particularly stability, elasticity and fatigue strength, and adhere very well to many materials.  
           [0007]    Rubber is a natural or synthetic polymer with a high molecular mass, which shows elasticity at room temperature and which is normally used vulcanized, so that a certain degree of cross-linkage is obtained in its structure. Certain properties of rubber, such as its tensile strength and wear resistance can be increased by using suitable additives.  
           [0008]    An object of this invention is to provide a compacted material comprised of a polyurethane elastomer and rubber, as an option having one or more additives that give the material desired properties. Also, an object of this invention is to provide finished products made from this material.  
           [0009]    A further object of the invention is to provide a method for obtaining this material that comprises the mixture of the raw materials, its molding and pressing.  
           [0010]    An additional object of this invention is the use of this compacted material to manufacture finished products with applications in construction and any other type of industry.  
         DETAILED DESCRIPTION OF THE INVENTION  
         [0011]    The invention provides a compacted material that comprises a polyurethane elastomer and rubber, hereinafter referred to as the “material of the invention”. The polyurethane elastomer can be present in the material of the invention in amounts between 5% and 40% by weight with respect to the total weight, while rubber can be present in the material of the invention in amounts between 95% and 60% by weight with respect to the total weight.  
           [0012]    The polyurethane elastomer is obtained in situ by the reaction of an isocyanate terminated polyurethane prepolymer with a polyol. Polyurethane can act as a monocomponent adhesive without solvents for the rubber and the additives that can, as an option, be present in the material of the invention.  
           [0013]    The isocyanate terminated polyurethane prepolymer, hereinafter “polyurethane prepolymer”, is a commercially available product or can be easily obtained from reacting a hydroxy-finished polymer with excess diisocyanate. The polyurethane prepolymer can be any polymer finished at each of its ends with an isocyanate group. The invention considers, in general, the full or generalized use of polyurethane prepolymers that contain aromatic groups. In a particular example, the polyurethane prepolymer is a product obtained by reacting a polyol with excess aromatic isocyanates, such as the one commercialized by CROMOGENIA-UNITS, S.A., under the name FORZAL AGL, an aromatic polyurethane prepolymer finished in isocyanate.  
           [0014]    A polyol is an alcohol containing 2 or more hydroxyl groups, such as butanediol, hexanediol, trimethylol propane, etc. In a specific example, the polyol is 1,4-butanodiol. By extension, the term polyol includes polyesters and polyethers, as is general in the field of the production of polyurethanes.  
           [0015]    The rubber that can be present in the material of the invention can be of any type (natural or synthetic) and origin, both recycled or not recycled. In a specific example, the rubber used is recycled rubber of any type, both vulcanized and not, such as recycled rubber from used tires; manufacturing surpluses, cutouts, defective parts, etc. from vulcanized rubber factories; waste from vehicle scrapping such as seats, workshops, mats, parts of tires, etc. containing rubber. The various materials that contain rubber and can be used as raw material for producing the material of the invention can be classified in groups with respect to their quality, quantity, etc.  
           [0016]    The grain size of the rubber is an important factor, as the homogeneity of the mixture depends on it. Thus, regardless of the substrate which can be conveniently added to obtain a greater volume, less weight, better soundproofing, etc., the use of a suitable grain size in each case will allow one to even out the losses or excess spaces in the mass.  
           [0017]    In a specific example, the invention considers the use of a rubber powder, normally in a proportion of 5 to 80%, with the following grain size distribution:  
                                       Sieve   ASTM mesh   Retention                   1.40 mm   14   —       1.00 mm   18   10% (maximum)       0.60 mm   30   60-80%       0.30 mm   50   15-30%       &lt;0.30 mm     remainder   10% (maximum)                  
 
           [0018]    In another specific example, the invention considers the use of a special rubber powder, normally in a proportion of 5 to 75%, with the following grain size distribution:  
                                                     Sieve   ASTM mesh   Retention                                1.00 mm   18   —       0.60 mm   30   0.5% (maximum)       0.30 mm   50   60-80%       0.15 mm   100   15-25%       &lt;0.15 mm     remainder   0.5-20%                   
 
           [0019]    In another specific example, the invention considers the use of rubber chippings, normally in a proportion of 5 to 80%, with the following grain size distribution:  
                                       Sieve   ASTM mesh   Retention                   4.00 mm   05   0.3% (maximum)       3.00 mm   07   15-25%       2.00 mm   10   55-65%       1.00 mm   18   15-25%       &lt;1.00 mm     remainder   0.3% (maximum)                  
 
           [0020]    In another specific example, the invention considers the use of a rubber fiber, usually in a proportion of 5 to 80%, with the following grain size distribution:  
                                       Sieve   ASTM mesh   Retention                   4.00 mm   05   0.3% (maximum)       2.00 mm   10   0.5-15%        1.40 mm   14   25-45%       1.00 mm   18   30-50%       &lt;1.00 mm     remainder   10-20%                  
 
           [0021]    The invention also considers the possibility of using mixtures of rubber powder, chippings and fibers with different grain sizes.  
           [0022]    The material of the invention may contain one or more additives specifically meant to provide the material of the invention with properties that make it better suited for its intended function. The great versatility of the material of the invention allows making advantageous transformations to it in order to provide it, for example, with fireproofing properties, such as antimony trioxide, hydrated alum; sound insulating properties, such as by adding sound insulators or using a balanced composition of materials with adequate grain sizes and certain thickness; chromatic properties, by adding pigments which can color the material of the invention, such as iron oxide (red, rust, ochre, green), titanium oxide (white), chromium yellow (red), etc.; waterproofing, by incorporating waterproofing materials or by pressure compacting of the material of the invention, preferably obtained from raw materials with a small grain size; thermal insulation, by using additives which provide heat insulation characteristics; weather resistance; etc.  
           [0023]    The material of the invention may also include a core to eliminate or reduce its flexibility, such as when the material of the invention adopts the configuration of a board with a significant thickness in order to prevent its deformation. The core may be of any material and must be capable of adding strength and stiffness to the material of the invention. In a specific example, the core is a plastic material such as a recycled plastic, for example, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyester (PET), etc. ground and extruded.  
           [0024]    The characteristics of the material of the invention allow it to adopt any configuration.  
           [0025]    Because of the agglomeration capacity of polyurethane and rubber, the material of the invention can take the form of a single composite layer including all the components, or as a material made from several clearly differentiated layers.  
           [0026]    In this latter case, the material of the invention can be obtained:  
           [0027]    1) by placing the various layers in the desired order in a mold and then applying the pressure required to compact the material in a single press, or;  
           [0028]    2) by preparing and pressing each layer separately and then mixing them and pressing them together, or;  
           [0029]    3) in an alternative example, the components of a first layer are deposited in the mold and pressed, then on top of this first layer that is still in the mold the components of a second layer are deposited and pressed again, and so on until the total number of layers have been deposited and the desired product has been obtained.  
           [0030]    This last alternative is particularly suitable when different pressures are required to compact the different layers. As an option, if desired the material can be allowed to dry between successive presses.  
           [0031]    Given the characteristics of the material of the invention, it is possible to obtain any product that can be obtained by molding, pressing and agglomeration. The material of the invention, because of its properties, can be used in any industry, such as in construction as part of ceilings, roofs, floors and wall coatings, etc.; in engineering work, such as in construction of roads, bridges, etc.; in urban development, such as in pavements, etc.; and in general in any industry that requires the use of elastic materials with good mechanical properties, such as stability, elasticity and fatigue strength as well as other interesting properties such as fire-proofing, insulating, water-proofing, adhering, etc.  
           [0032]    By way of example, the material of the invention can be given the form of roof tiles (with and without insulation); floor tiles (with and without insulation); wall panels; false ceilings; composited materials for roads; road safety barriers; surfacing for rural roads; pavements for squares and streets; protective panels for garages; baseboards; noise, vibration and deformation force absorbers (silent blocks); staircases; attics without beams; very strong and adaptable waistboards; tabletops; etc.  
           [0033]    In its simplest example the material of the invention consists of only polyurethane elastomer and rubber, compacted, molded into the form of a board, plate, panel or tile, and pressed to obtain a product with a given thickness. An illustrative example of this specific example consists of a material configured by molding and pressing into the form of a tile, with the following formulation:  
           [0034]    Polyurethane elastomer 20%  
           [0035]    Rubber 80%  
           [0036]    where percentages are by weight with respect to the total weight.  
           [0037]    In another specific example, the material of the invention comprises a polyurethane elastomer and rubber, molded and pressed into the form of a silent block, with the following formulation:  
                                                       Polyurethane elastomer   40%           Rubber chippings (1-3 mm)   30%           Rubber powder (0.6 mm)   30%                      
 
           [0038]    where percentages are by weight with respect to the total weight and the figures in parenthesis are the grain size of the component.  
           [0039]    In another specific example, the material of the invention comprises a polyurethane elastomer, rubber and cloth, molder into the form of a board, plate, panel or tile, and is pressed until obtaining a product with a given thickness. An illustrative example of this specific example consists of a material configured by molding and pressing into the form of a hard compact panel, with the following formulation:  
                                                       Polyurethane elastomer   30%           Rubber chippings (1-3 mm)   40%           Rubber fiber and substrates   20%           Cloth   10%                      
 
           [0040]    where percentages are by weight with respect to the total weight and the figures in parentheses are the grain size of the component.  
           [0041]    In another specific example, the material of the invention comprises a polyurethane elastomer, rubber and additives which provide insulating characteristics, molded into the form of a board, plate, panel or tile and pressed until obtaining a product with a given thickness. An illustrative example of this specific example consists of a material configured by molding and pressing into the form of an insulating tile, with the following formulation:  
                                                       Rubber fiber (1-3 mm)   31%           Rubber powder (0.6-1 mm)   24%           Recycled substrates (1-4 mm)   19%           Recycled cloths (0.5 × 1 cm)   7%           Polyurethane elastomer   19%                      
 
           [0042]    where percentages are by weight with respect to the total weight and the figures in parentheses are the grain size of the component. The term “recycled substrates” includes all previously used materials (such as foam, fiber, plastic and their mixtures).  
           [0043]    In another specific example, the material of the invention comprises a polyurethane elastomer, rubber and additives which provide insulating characteristics, molded into the form of a board, plate, panel or tile and pressed until obtaining a product with a given thickness. An illustrative example of this specific example consists of a material configured by molding and pressing into the form of an insulating floor tile with a lower insulating later and a top layer or tile, with the layers having the following formulations:  
                                                       Insulating layer:               Rubber fiber (2-5 mm)   30%           Rubber chippings (1-3 mm)   20%           Recycled substrates (1-4 mm)   12%           Recycled cloth (0.5 × 1 cm)   10%           Polyurethane elastomer   28%           Tile:           Rubber (impurity-free powder, 0.6 microns)   60%           Rubber (impurity-free powder, 1 micron)   20%           Polyurethane elastomer   20%                      
 
           [0044]    where percentages are by weight of total weight of each layer and the figures in parenthesis show the grain size of the component.  
           [0045]    In another specific example, the material of the invention is an agglomerate for industrial roofing with tile, insulating layer and without a core with the composition [A] or [B] of Example 4 (below).  
           [0046]    The material of the invention provides similar properties to a conventional vulcanized rubber, with the property that it is not necessary to use high temperatures to obtain it, nor vulcanization reagents as sulfur and accelerators. Thus it is possible to speak of a cold vulcanization without using solvents, with the resulting energy saving and environmental advantages, as in accordance with this invention it suffices to add the polyurethane prepolymer to the rubber with the required humidity in order to form an agglomerate. The required degree of curing can be obtained by adding polyol to the polyurethane prepolymer.  
           [0047]    The possibility of using rubber from recycling any material containing rubber as a raw material also provides a solution to the environmental problem posed by the management and processing of these residues.  
           [0048]    The material of the invention shows an ideal adaptation capability and can adapt to any space or shape desired, and further allowing perforations, mutilations, etc. as well as allowing foreign elements such as metals (iron, steel, aluminum, etc.), concrete, wood, etc. to come in contact with it, with the addition of the corresponding adhesive.  
           [0049]    The invention also provides a method for obtaining the material of the invention, hereinafter referred to as the “method of the invention”, which comprises:  
           [0050]    a) mixing a polyurethane prepolymer finished in isocyanate with a polyol until obtaining a homogenous mixture;  
           [0051]    b) adding rubber to this homogenous mixture of polyurethane prepolymer and polyol;  
           [0052]    c) adding the mixture resulting from stage b) to a mold in order to form it by pressing;  
           [0053]    d) closing the mold and applying the required pressure for a suitable time in order to compact the mixture introduced in the mold;  
           [0054]    e) drying the compacted material resulting from the press at a suitable temperature and for a suitable time, without removing the mold lid; and  
           [0055]    f) demolding the compacted material made of polyurethane and rubber.  
           [0056]    The polyurethane prepolymer finished in isocyanate can be any polymer finished at each of its ends with an isocyanate group. In a specific example, this polymer contains aromatic groups.  
           [0057]    A polyol is an alcohol with 2 or more hydroxyl groups, such as butanediol, hexanediol, trimethylol propane, etc. In a specific example the polyol is 1,4-butanediol.  
           [0058]    The rubber can be of any type and origin, both recycled and not, and may be in any form, such as powder, chippings or fiber. The rubber grain size distribution plays an important role in obtaining a material of the invention with suitable properties. Each application requires using a specific type of rubber, a specific grain size, as its hardness, configuration, elongation etc. plays a crucial role in its final finish. Likewise, depending on the rubber grain size both the weight and the thickness of the material of the invention can be controlled.  
           [0059]    Rubber powder can be produced mechanically from any material containing rubber, whether recycled or not. In a specific example, the rubber powder is obtained from tire strips or full tires, passing the material through a sieve with a mesh opening of 1 mm or less. The rubber powder may or may not be free of impurities and metal particles.  
           [0060]    Rubber chippings can be produced mechanically from any material containing rubber, whether recycled or not. In a specific example, the rubber chippings are obtained from tire strips or full tires, and have particle sizes of between 1 and 5 mm. The rubber may or may not be free of impurities and metal particles.  
           [0061]    Rubber fiber can be produced mechanically from any material containing rubber, whether recycled or not. In a specific example, the rubber fiber is obtained from scraping or grinding tires, tire residues, or from vehicle scrapping, has a particle size between 1 and 50 mm, and may or may not be free of impurities and metal particles.  
           [0062]    Any mold may be used that allows obtaining the material of the invention in the desired configuration.  
           [0063]    The pressure applied is important to compact the mixture of raw materials and obtain the material of the invention. The pressure is applied by conventional methods, such as with a press. The pressure to apply is generally less than 500 kg/cm2 (approximately 49 MPa) [1 kg/cm2=0.098 Pa approximately], and preferably between 1 and 100 kg/cm2 (approximately 0.098 and 9.8 MPa).  
           [0064]    The method of the invention can be performed at a temperature between 15° C. and 85° C. A suitable temperature is room temperature, approximately 20° C., although it may be of interest to use higher temperatures that will aid drying of the material of the invention, and therefore a faster management of the handling and demolding. A much faster drying may be forced by using a drying oven.  
           [0065]    The handling time (pressing) is normally less than 36 hours, while the drying time is normally less than 3 days after finishing the pressing.  
           [0066]    Suitable additives can be used to provide the material of the invention with desired properties. By way of example, additives that may be added include fireproofing agents, such as antimony trioxide or hydrated alum in amounts ranging between 15% and 25% by weight with respect to the total weight. In a specific example, by adding to the mixture from the start the amounts of fireproofing agent as per specifications and degree desired and as set by ordinances, it is possible to obtain the certification of the material of the invention as a fireproof product.  
           [0067]    In the event that the material of the invention includes pigments, these may be added as incorporated to the mass or superficially, in one or several layers of the material of the invention. The amounts range between 0.5 and 5 g/cm2 [grams of pigment per cm2 of surface of the material of the invention] for the case of surface pigmentation, and 1 to 5% by weight for mass pigmentation.  
           [0068]    In a specific example, when the material of the invention comprises a polyurethane elastomer and rubber and is configured as a compacted plate, the method of the invention can be performed as follows:  
           [0069]    in a vessel are mixed the polyurethane prepolymer finished in isocyanate and the polyol, shaking until a full homogenization is achieved; then the rubber is added to obtain a product with a gum-like appearance, continuing to shake until the gum is completely wetted;  
           [0070]    the resulting mixture is introduced in a mold and the corresponding pressure is applied, ensuring that the mixture is even and identically dosed throughout all the spaces of the mold; and  
           [0071]    when the mold is sufficiently compacted, and without removing the lid, it is allowed to dry for the required time and the product is removed from the mold, then manipulating or processing the product if desired.  
           [0072]    In another specific example, when the material of the invention comprises a polyurethane elastomer, rubber and additives, and it is configured in the form of a compacted plate, the method of the invention can be performed as follows:  
           [0073]    the polyurethane prepolymer finished in isocyanate is mixed in a vessel with the polyol, shaking until a homogenous paste is obtained;  
           [0074]    in another vessel are mixed, dry, the suitable amounts of rubber fibers (o chippings), with the suitable grain size, and in another vessel is mixed the rubber powder with the suitable grain size;  
           [0075]    after this, a mixer is used to mix the different components, for which the homogenous mixture of polyurethane prepolymer and polyol is added first, then the mixture of rubber fiber and finally the mixture of rubber powder; these components are added in the stated order and by parts, normally 25% of the required amount of each component at each time until the first cast is finished;  
           [0076]    the first cast is poured into the mold, ensuring that it is correctly leveled and dosed;  
           [0077]    aside from this, the tile is fabricated, which must be placed on the surface of the first cast; for this, the necessary amounts of polyurethane prepolymer and the polyol are prepared, then they are mixed evenly and the suitable amounts of rubber powder are added until obtaining a homogenous mixture;  
           [0078]    the homogenous mixture corresponding to the tile is poured on the first cast, ensuring that it is correctly leveled and dosed;  
           [0079]    after this, the mold is closed and pressing is performed at the suitable temperature and for the time required to obtain the desired thickness; and  
           [0080]    finally it is allowed to dry for the required time to then remove it from the mold.  
           [0081]    In another specific example, when the material of the invention comprises a polyurethane elastomer, rubber, additives (fireproofing agents, pigments) and a core, and it is configured in the form of a compacted plate, the method of the invention can be performed as follows:  
           [0082]    the full amount of polyurethane elastomer needed to obtain the material of the invention (including the polyurethane elastomer present in the tile) is prepared in a vessel by mixing the polyurethane prepolymer finished in isocyanate with the polyol, shaking until a homogenous paste is formed; then one or more fireproofing agents are added, such as antimony trioxide, hydrated alum or their mixtures, in the suitable proportions, to form a paste;  
           [0083]    from the previously obtained paste is separated the amount of paste required to fabricate the tile;  
           [0084]    to the resulting paste is added slowly the mixture of rubber fibers, and later the mixture of rubber powder, prepared previously;  
           [0085]    in the corresponding mold is placed a thin layer, approximately 1 mm thick, of the previously obtained paste and it is extended evenly throughout the entire mold, in the form of a carpet, above which are placed the cores vertically and with the separation corresponding to the intended use and its linking and stability elements. Afterwards the rest of the cast is added;  
           [0086]    then the tile is fabricated, which must be well spread and leveled above the previous cast; for this, the part of homogenous paste containing the polyurethane prepolymer and the polyol prepared and separated previously is taken, and the rubber powder is added to it until the desired mixture is obtained;  
           [0087]    the resulting mixture is poured on the previous cast, properly leveling and dosing it;  
           [0088]    afterwards, before closing the mold and in a dry state, the pigment powder to be added is scattered with a sieve; the mold is then closed and the suitable pressure is applied for the suitable time, allowing it to dry, and the mold is removed.  
           [0089]    The following examples are meant to illustrate preferred embodiments of the invention and should not be considered as a limitation of its scope.  
           [0090]    The polyurethane prepolymer used in all examples is an aromatic polyurethane prepolymer finished in isocyanate, commercialized by CROMOGENIA-UNITS, S.A. under the name FORZAL AGL. 
       
    
    
     EXAMPLE 1  
     Compacted Material Made from a Polyurethane Elastomer and Rubber  
       [0091]    A material is prepared with the following composition:  
                                                   Component   % weight of total weight                           Polyurethane elastomer   20           Rubber   80                      
 
         [0092]    The adequate amounts of polyurethane prepolymer finished with isocyanate groups and 1,4-butanediol are mixed to obtain the desired amount of polyurethane elastomer, shaking until a homogenous mixture is obtained. Rubber powder free of impurities is then added and mixed, obtaining a product similar in appearance to a gum, and shaking is continued until the mixture is well humidified.  
         [0093]    The resulting mixture is placed in a mold at room temperature; the mold is then closed and a pressure is applied of 10 kg/cm2 (0.98 MPa approximately) for 6 hours, ensuring that the mixture is leveled and dosed identically throughout all the spaces of the mold. The product is then sufficiently compacted and it is allowed to dry at 80° C. for 48 hours, without removing the mold lid. After this time, the mold is removed, obtaining a compacted material that contains a polyurethane elastomer and rubber and which can be subsequently processed.  
       EXAMPLE 2  
     Compacted Material Made from a Polyurethane Elastomer, Rubber and Glass Fiber  
       [0094]    The procedure described in Example 1 was repeated, with the required changes, which involved adding glass fiber and drying at 35° C. for 18 hours, to obtain a compacted material made of a polyurethane elastomer, rubber and glass fiber, with the following composition:  
                                                   Component   % weight of total weight                           Polyurethane elastomer   20           Rubber   40           Glass fiber   40                      
 
       EXAMPLE 3  
     Compacted Material Made from a Polyurethane Elastomer, Rubber, Substrates and Glass Fiber  
       [0095]    The procedure described in Example 2 was repeated, with the required changes, which involved adding substrates, to obtain a compacted material made from a polyurethane elastomer, rubber, substrates and glass fiber, with the following composition:  
                                                   Component   % weight of total weight                           Polyurethane elastomer   25           Rubber   30           Substrates   15           Glass fiber   30                      
 
       EXAMPLE 4  
     Agglomerate for an Industrial Roof with Tile, Insulating Layer and without a Core  
       [0096]    The agglomerates for industrial roofs with tile, insulating layer and without a core were prepared according to the above described procedures, with the compositions as shown below:  
                                                       Agglomerate   [A]   [B]                           Insulating layer                   Rubber fiber (2-5 mm)   20%   10%           Rubber chippings (1-3 mm)   15%   20%           Rubber powder (0.3-1 mm)   15%   20%           Recycled substrate (1-4)   12%   12%           Recycled cloths (0.5-1 cm)   10%   10%           Polyurethane elastomer   28%   28%           Tile           Rubber (powder without impurities, 0.6 μm)   60%   65%           Rubber (powder without impurities, 1 μm)   20%   15%           Polyurethane elastomer   20%   20%                      
 
         [0097]    where percentages are by weight with respect to the total weight of each layer and the figures in parentheses represent the grain size of the component.  
         [0098]    The agglomerate [A] showed good acoustic properties, was spongy and easy to handle, particularly well suited for difficult installations. On its part, the agglomerate [B] had worse acoustic properties than the agglomerate [A], but was harder and well suited to be used as a support for foreign bodies.  
         [0099]    For the purposes of promoting an understanding of the principles of the invention, reference has been made to the preferred embodiments, and specific language has been used to describe these embodiments. However, no limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art.  
         [0100]    The particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way. It should be noted that many alternatives may be present in a practical application of the invention. Moreover, no item or component is essential to the practice of the invention unless the element is specifically described as “essential” or “critical”. Numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention.