Patent Publication Number: US-8968502-B1

Title: Method for coating a tufted athletic turf backing

Description:
This application is a continuation-in-part that claims the benefit of nonprovisional application Ser. No. 12/614,287 a filed Nov. 6, 2009, now U.S. Pat. No. 8,647,452. Furthermore, application Ser. No. 12/614,287 is hereby incorporated by reference. 
    
    
     BACKGROUND 
     Artificial turf has long been used as a playing surface for sports that are traditionally played on grass fields, such as football, baseball and soccer to name a few. In parts of the country that experience exceedingly cold, rainy or dry weather during times of year that such sports are customarily played, an artificial turf playing surface can be virtually essential to conducting those sports outdoors. For example, an artificial turf may be preferable to natural grass for an outdoor football field in the Great Lakes region of the United States because of the tendency of a natural surface to harden and become more difficult to maintain as a consequence of the cold weather that that the region experiences during the autumn football season. At the same time, in the Pacific Northwest region of the country, a highly permeable synthetic surface may be desirable because of the water puddling and overall deterioration that a natural surface would exhibit due to the area&#39;s considerable rainfall. Conversely, because the arid conditions of the desert Southwest region require that extensive irrigation efforts be made in order to maintain natural grass fields, synthetic turf is often preferred as a playing surface there too. Furthermore, because artificial turf does not require the exposure to sunlight needed to sustain natural grass, it enables sports traditionally performed on grass to be played inside climate controlled indoor facilities. 
     Artificial athletic turf is generally comprised of at least one textile fabric backing through which grass-resembling filament yarn is inserted via a tufting process, as well as a resilient base mat which provides underlying support to the tufted backing. A variety of different types of yarn may be used, and slit-film yarn, with its flat profile, is a popular such yarn used in synthetic turfs. 
     A tufting machine of some construct is used to insert loops of selected yarn into a backing sheet. Typically, the tufting machine features a series of yarn-carrying, reciprocating needles which punch downward through the backing so that the delivered yarn may be caught by looper devices to form elongate yarn loops along the top side of the backing (i.e., the side of the backing which faces upward upon the turf&#39;s installation as a playing surface) as the needles returns upward and out of the backing. After the needles reciprocate, the backing or needles shift so that the needles may repeat their stroke and form backloops along the bottom of the backing. In this tufting process, yarn is selectively protruded through the backing to a depth that corresponds with the desired length of the simulated grass blades being formed, and the ends of the top side loops are severed to render cut piles that simulate grass. 
     After tufting, a coating material is applied to the backloops, by some means, in order to bond the tufted yarn to the backing with lock strength (i.e., the force required to pull a strand yarn out of the backing) sufficient to withstand the stresses of the athletic performance to take place on the created turf. Traditionally, coating has been applied, in liquid form, by pouring it onto the tufted backing and then allowing it to cool and harden, or it is applied as a film that is liquefied by heating and then cooled. Alternatively, the backloops of thermoplastic yarns may, themselves, be heated in order that they fuse to the backing. 
     For field installation, the tuft-locked backing is usually placed atop a resilient base mat which helps to help cushion athletes&#39; joints and give the synthetic turf surface a more natural feel. Additionally, a granular mix of small particles (typically, rubber and sand particles) may be poured atop the tufted backing to infill the space between synthetic grass blades. Aside from further improving resiliency, this infill material also imposes a protective barrier between the athletes&#39; cleats and the backing fabric. 
     Again, it is generally necessary to coat the bottom of the tufted backing in order to prevent yarn from dislodging during athletic use, but doing so can pose challenges that the prior art has evolved in effort to overcome. Historically, a continuous solid film or viscous liquid layer of thermoplastic or thermosetting coating material has been applied to the bottom side of a backing sheet, and then heat is applied thereto in order to either solidify the liquid or to liquefy the solid film so that it envelops the yarn backloops, seals the yarn insertion holes and then forms a solid layer upon being cured by cooling. In either case, the cured coating layer locks the tufts to the backing. Furthermore, since the spacing of their individual woven fibers may cause some woven fabrics to exhibit poor dimensional stability under the stress of athletic activity, putting the backing fibers in a common matrix with a coating layer should improve the stableness of the turf and render it less prone to stretch or otherwise deform during use. 
     Applying a continuous coating film to an athletic turf backing can present potential drawbacks, though. First of all, while it is generally desired that a tufted pile structure made for home or office carpet use be water sealed, the opposite is true for that made for athletic use. As mentioned earlier, it is essential that water and other fluids be able to drain through an athletic turf. Therefore, assuming that the continuous coating layer adhered to an athletic turf backing is water impermeable, as tends to be the case when coating material is deposited onto the backing in a liquid or solid phase, the coated backing must undergo further processing to give it porosity. Specifically, water drainage holes must be introduced into it. For artificial turfs that are infilled, as most contemporary sports turfs are, these drainage holes can present challenges. To wit, although the infill layer is a porous element, its individual particles can flow into and clog drainage holes within the backing, and can further matriculate down into pores residing within a base layer of material underlying the backing. Consequently, in addition to diminishing the porosity of the turf, enough infill particles may eventually sift through the backing&#39;s drainage holes to necessitate a replenishing of infill material in order to prevent the playing condition of the turf from appreciably degrading. Finally, punching these needed drainage holes into a fabric backing may, to some extent, offset the increase in dimensional stability that was achieved by coating it in the first place. So, over time, the cumulative effects of climate exposure and stress applied by athletic use may cause the drainage holes to stretch and exacerbate the aforementioned problems of their existence. This simply accelerates the turf maintenance demands and shortens the useful life of the turf. 
     Another negative implication of continuously coating the backing (as opposed to coating it in some selective, discontinuous manner) is the volume of coating material consumed in doing so. Not only is the material cost obviously greater, a continuous coating layer substantially increases the weight of the turf product and, thus, makes it more expensive to transport. As fuel prices skyrocket, this becomes a significant cost factor in the turf product distribution and sales chain. 
     A well-known alternative method of achieving tuft lock in an artificial athletic turf applications involves thermally bonding to the backing a tufted, grass-simulating thermoplastic yarn in lieu of applying coating material. For example, U.S. Pat. No. 4,705,706 to Avery discloses a process of tufting yarn fabricated of thermoplastic material, such as polyethylene, into a backing fabricated of a material, such as nylon, which has a higher fusion point than the yarn. After the tufting process, the bottom side of the backing is heated to a temperature not quite high enough to degrade the backing, but sufficient to melt the yarn tufts so that their inner surfaces can adhere to the adjacent backing surface, obviating the further need to apply a coating in order to achieve satisfactory tuft lock. However, because the pile yarn atop the tufted backing must be shielded from the heat being applied to the yarn backloops disposed below the backing layer, as a practical matter, it may be necessary to tuft the yarn into multiple layers of backing fabric that can, together, form an adequate heat sink. Therefore, the total cost of producing the turf product may be increased by the inclusion of a secondary backing sheet(s) that might not be needed if the yarn was bonded to the primary backing by way a separate coating material. 
     To overcome these disadvantages, methods for discretely applying coating onto the linear the rows of yarn tufts disposed along the bottom surface of a backing, while leaving space between tuft rows uncoated, have been developed in the prior art as well. For example, U.S. Pat. No. 6,726,976 to Dimitri discloses a method of producing a tufted pile which involves applying linear strips of binding material to a backing and, subsequently, tufting yarn through both the backing and binding material so that areas of the backing surface between the tufted yarn rows remain uncoated. Alternatively, Dimitri teaches the pre-tufting application of a continuous sheet of highly shrinkable thermoplastic binder material to a backing that, upon being heated post-tufting, will shrink so that binder material concentrates around the yarn backloops and leaves uncoated spaces along the backing surface. 
     Similarly, U.S. Pat. No. 6,338,885 to Prévost discloses the proposition of depositing strips of coating material only onto rows of yarn backloops so that interstitial spaces between rows remain uncoated. Alternatively, Prévost teaches the placement of a comb-like device, which has fingers that fit within the channels between backstitch rows, over the bottom of a backing prior to applying coating material and then removing the device and the coating that is deposited onto it thereafter. The comb-like device shields the backing fabric between yarn rows from the applied coating so that it retains its permeability characteristics, and, depending on the backing fiber, the need to puncture drainage holes may be averted. Prévost also discloses the proposition of using a series of nozzles to apply thin lines of coating exclusively onto the yarn backstitch rows. 
     There are a couple of obvious benefits of depositing coating material exclusively onto the yarn rows in order to achieve tuft lock, as such a practice minimizes production costs by reducing the amount of coating material consumed therein, and it eliminates the need to mechanically perforate the coated backing for drainage purposes—thereby avoiding the above mentioned perils of doing so. However, in order to be practiced in a remotely efficient, automated manner, previously disclosed methods for coating a backing sheet in such discontinuous fashion generally required the use of a coating machine possessing a series of several nozzles or solid strip applicators which are appropriately spaced to enable coating material to be deposited precisely onto the discrete longitudinal rows of yarn (or row paths yet to be tufted) formed along a backing sheet that is advanced below them. In fact, if a particular such machine features a series of fewer coating applicators than are the total number of yarn rows to be coated, then the backing necessarily must be run through the machine multiple times so that its applicators can be laterally shifted into positions for coating individual rows left uncoated during a previous run(s). 
     Further complicating the issue are matters of tufted yarn rows being spaced differently, from one article of artificial turf to another, or of them being non-linear, as may be dictated by the particular athletic activities to be performed upon them or by graphic design considerations. Consequently, the coating applicators along a machine for applying a discontinuous coat must be spaced and/or shifted in accordance with the precise layout of yarn rows along a particular backing piece or pieces to be seamed together. Similarly, multiple different coat shielding devices may need to be substituted, from coating task to task, to accommodate the need for variations in finger spacing. This can demand tedious work in adjusting coating delivery and shielding mechanisms between coating tasks. Moreover, the proposition of applying coating material in alignment with non-linear tuft patterns can be even more daunting. 
     Therefore, it can be appreciated that there exists a need for an improved method for applying coating material to artificial turf—a method in which the backloops of yarn tufted into the turf backing are coated to achieve tuft lock sufficient to render the turf adequate for athletic use, and a method that can be repeated with equal effectiveness on virtually all turf backings which bear linear rows of tufted yarn, regardless of the relative spacing of their respective yarn rows or of the characteristics of their yarns employed. The present method for coating a tufted athletic turf backing substantially fulfills this need. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to methods for applying adhesive to the stitches, or backloops, of yarn that are tufted into a backing material in order to produce synthetic grass that exhibits water permeability and dimensional stability qualities sufficient to make it usable as athletic turf. The invention specifically relates to such a method that is particularly effective in producing those qualities, in a time efficient manner, when the yarn being coated is a slit-film or other flat profile yarn. 
     It is an object of the present invention to achieve tuft lock by coating a tufted backing in a way that may be precisely replicated on virtually all backings that are linearly tufted, irrespective of the actual spacing of their respective parallel rows of tufts. Consequently, the present invention eliminates the need to adjust coating machinery or modify coating technique in accordance with variations in the tuft placement specifications of different articles of linearly tufted backing. 
     It is another object of the invention to create a synthetic turf product without implementing any of the traditional practices for achieving both the tuft lock and drainage properties that render the product sufficient for use as an outdoor athletic turf. Specifically, by introducing a coating application technique that represents an unconventional step in the process of producing artificial athletic turf, the present method obviates the need to, for example, heat yarn tufts in order to tackify and thermoplastically bond them to the bottom face of a primary backing. Consequently, the material cost associated with including a secondary backing that functions as a heat sink and protects the yarn pile which extends from the top face of the backing may be avoided. 
     The present method also renders unnecessary a precision driven coating dispenser capable of discretely placing thin lines of liquefied coating material precisely onto the spaced tuft rows formed within a particular backing. At the same time, the instant method eliminates the need to perform the additional turf-making step of perforating a continuously coated backing in order to give it porosity. 
     Finally, it is yet another object of the invention to provide a spray coating method that is more effective in simultaneously creating tuft lock and leaving porosity in a backing tufted with slit-film or other flat profile yarn than are any prior art spray coating methods. 
     In one aspect of the invention, a new turf product is produced that comprises: (1) a water permeable backing member, (2) yarn—preferably of the slit-film type—that is tufted into the backing in separate linear rows and (3) a substantially continuous, but porous, layer of coating material that is disposed along the bottom face of the backing. More specifically, coating material is applied to the bottom face of the backing such that it (i) impermeably covers the top and a side (right or left) of the composite tube-shaped yarn backloops within each row and (ii) fills the interstitial space between individual yarns that form each of those tubular backloops, but (iii) leaves uncoated a small area around the opposing side of the backloops and (iv) forms a continuous, but porous, layer across the rest of the backing surface area. 
     The backing may be of any type commonly used in athletic turf applications, and the yarn may be of any type that simulates natural grass. However, it should be noted that the present method yields especially superior results compared to previously disclosed coating methods when flattened profile yarn is used, as yarn of this shape is difficult to penetrate, intrabundle, using some prior art coating methods. In any case, the yarn is tufted into the backing so as to form a pile along the top face of the backing and rows of backloops along the bottom face. 
     The coating material has the dual purposes of: (a) bonding together individual fibers that exist within the backloop portion of each tuft; and (b) bonding the tufts to the backing so that the tufts are not dislodged under the strains of athletic use. It is believed that a wide variety of sprayable adhesive materials could be used as coatings in the present turf construction. However, it must be a composition that, when sprayed at high pressure, expels from a spray nozzle in small, discrete droplets which rapidly solidify upon being exposed to the spray environment and depositing onto the backing. 
     In another aspect of the invention, these discrete coating droplets are sprayed toward the backing such that their trajectory, immediately prior to contacting the backing or yarn or other, previously landed coating droplets is along an inclination angle of less than 45 degrees to the plane of the backing and is 90 degrees relative to the axes of the parallel tuft rows. This inclination angle is important for two distinct reasons: (1) it enables the tufts along the bottom face of the backing, simply by virtue of their disposition, to block airborne coating particles from landing along extremely surface areas of backing adjacent each tuft; and (2) it enables the sprayed coating material to penetrate into small voids that exist within the looped bundle of yarn that is each tuft. 
     In another aspect of the invention, the coating material droplets are to be sprayed in successive passes over the backing so that discretely deposited droplets are able to form a visually continuous, but porous layer due to newly deposited, rapidly congealing droplets either landing upon previously uncoated surface areas of backing fabric or landing upon other previously landed, already solidified droplets and creating a bridging effect with them. 
     To that end, the coating composition should be selected and the spray environment controlled such that multiple factors, including the number of spray passes, spray pressure, spray flight distance, ambient temperature and reactivity of the coating composition, cooperate to ensure that sprayed coating droplets begin congealing in flight or immediately upon landing onto the backing, tufts or previously landed droplets. Resulting changes in phase and surface tension of sprayed coating droplets, therefore, occurs rapidly enough to prevent extensive puddle formation or flow of coating material into a liquid sheet along the backing surface or along the yarn surface. This, again, has the effect of creating a coating layer, formed of congealed droplets that have bridged with one another, that is highly porous. It has the further effect of causing sprayed coating material that has penetrated and filled much of the interstitial space between the individual loops of yarn which define each tuft to, effectively, form an impenetrable wall, along the spray-side of the tuft, that shields the narrow area of backing surface adjacent the opposite side of the tuft. This phenomenon may also allow extremely small side portions of the fiber openings created by yarn protrusion through the backing to function as drainage apertures without appreciably sacrificing tuft lock. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded plan view of a small section of woven backing fabric; 
         FIG. 2  is a bottom perspective view of a section of tufted backing that is uncoated, the view showing cut pile yarn extending from the backing&#39;s top face and rows of yarn backloops along its bottom face; 
         FIG. 3  is a bottom plan view showing uncoated yarn backloops along a backing; 
         FIG. 4  is a bottom plan view showing yarn backloops along a backing coating using the present angled spray method, the view showing uncoated areas adjacent the non-spray side of each backloop; 
         FIG. 5  is a side perspective view showing the non-spray side of a yarn backloop; 
         FIG. 6  is an opposite side perspective view showing the spray side of that yarn backloop; and 
         FIG. 7  is a partial diagrammatic view of a coating formulation and delivery system, the view showing coating particles being sprayed toward the backing along a trajectory angle to the backing plane according to the present method. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It should be understood that the present disclosure has particular applicability to the making of artificial turf that is intended for use as a sports playing surface, but can be applied to the manufacture of synthetic grass generally. This disclosure, as illustrated in the accompanying Figure drawings, relates to a spray coating process to be performed on an artificial athletic turf comprising a backing  20  to which at least one yarn is mechanically adhered via a tufting process. Due to the particular way in which a porous layer  30  of coating material is formed along its backing element  20  as shown in  FIGS. 4 &amp; 7 , the turf remains adequately water permeable without having to be perforated after being coated. 
     The backing  20  may be constructed of polypropylene fabric or any other fabric commonly used for athletic turf, and it should be woven (or perforated, in the case of a nonwoven fabric) so that, even prior to being tufted and coated, it exhibits the porosity characteristics required of an installation-ready outdoor athletic turf—most notably a water drain rate of at least 40 inches per hour. However, it is preferred that the untufted, uncoated backing  20  has a significantly greater drain rate due to the existence of fabric pores  46  throughout it, as can be seen in the section of backing fabric  20  shown in  FIG. 1 . As will be discussed, the present method is for a coating application, depicted in  FIG. 7 , which is designed to ensure that uncoated spots  48  remain throughout the backing fabric  20 , as can be best seen in the exploded view of  FIG. 4 , so that fluids may seep through fabric pores  46  existent within the exposed areas  48  of the backing  20 . It is also designed to ensure that the interstitial spaces that typically exist between the individual, quasi-concentric loops  40  of often flat-profiled yarn that, together, form each tuft backloop  50  become occupied with coating material as shown in  FIG. 5 . This creates superior tuft lock. 
     It is anticipated that a variety of sprayable materials, such as polyurethane, polyurea, a polyurethane/polyurea hybrid or even a hot melt adhesive, conceivably can be used to bind the yarn to the backing  20  within the concept of the present invention. 
     The yarn may be inserted into the backing  20  via any of a variety of conventional tufting processes. For example, the backing  20  may be intermittently conveyed underneath a series of vertically reciprocating, yarn-carrying needles (not shown) that are aligned transverse to the direction of conveyance. Alternatively, the backing  20  may be statically held while being operated upon by the advancing tufting head of a computer-operated, gantry-type tufting apparatus such as that described by the present inventor in U.S. Published Application No. 2008/0134949 published Jun. 12, 2008 and incorporated herein by reference. In either case, the relative positions of the backing  20  and needles shift between successive downward plunges of the needles through the backing  20  so as to create yarn backloops  50  that closely overlie the backing&#39;s bottom face  24 . Parallel rows  12  of these backloops  50  are illustrated in  FIG. 2 . Simultaneously, with the aid of catch and cutting mechanisms (not shown), the reciprocating needles form elongate yarn loops along the top face  22  of the backing  20 , which are then severed to form a cut pile  14  as is also shown in  FIG. 2 . 
     Generally, the spacing of parallel, tufted yarn rows  12  depends upon the anticipated use for the turf. For example, tuft rows  12  tend to be spaced further apart in football turfs, as football turfs are typically covered with an infill material mixture (not shown), such as a blend of sand and cryogenically ground rubber, which provides greater cushioning and abrasion resistance for athletes performing on them. Wider tuft spacing accommodates the infill mixture and helps to minimize the risk of athletes&#39; cleats getting wedged and snagged between tufts of yarn—a phenomenon that often causes serious leg injury. On the other hand, yarn rows  12  may be tufted more narrowly in synthetic turf made for activities in which cleats are typically not used and for which a less forgiving playing surface is desired. 
     In order to bind tufted yarn to the backing  20  so that tufts are not dislodged from the turf during its use, an adhesive coating layer  30  is applied to the bottom face  24  of the backing  20 . The present invention requires that tiny, generally spherical droplets  32  of coating material be deposited onto the backing face  24  via a series of multiple, high pressure, wide-area droplet spray showers  34 . The invention further requires that the trajectory “T” of each such spray shower  34  be at an inclination angle “A” of less than 45 degrees, and preferably within a range of 10 to 30 degrees, to the plane of the backing  20  and be perpendicular to the axes of the parallel tuft rows  12 . The invention even further requires that multiple such spray passes (preferably, four to six) be made over the entire backing  20  and that they be made from a spray nozzle-to-backing face distance (preferably, four to six feet) that, given spray volume, causes coating droplets to land discretely along a wide area of the backing face  24  and rows of backloops  50 . 
     The angled spray orientation, illustrated in  FIG. 7 , will cause coating material to deposit far disproportionately more along the proximate, “spray sides”  52  of backloops  50  than on their distal, “non-spray” sides  54 , as can be seen by comparing  FIGS. 5 &amp; 6 . For purposes of this discussion, the proximate side  52  of a backloop  50  shall be considered its side that faces the spray emitter  62  when the backloop  50  is within the path of spray  34 . More importantly, the positioning of backloops  50  relative to the spray path causes the backloops  50  to block spray droplets  32  from depositing on small spots  48  of backing surface  24  that are immediately adjacent the distal sides  54  of the backloops  50 . These uncoated areas  48  provide additional porosity to the already porous finished turf. Of course, the rough dimensions of such spots  48  will depend upon both the spray trajectory angle A and height “H” of the backloops  50 . 
     In addition to leaving a porous coat  30  over the backing  20 , the angled orientation of the spray trajectory T enhances penetration of coating material into the fiber bundled backloops  50  and gets in spaces between bands of yarn  40  (see  FIG. 5 ). This, in turn, locks their yarn filaments together and greatly inhibits the unraveling of individual tufts. The natural grass-simulating yarn may be fabricated of, for example, monofilament polyethylene or polypropylene fibers that are twisted and bundled into strands. However, the present inventors have observed that the present spray method is especially effective when applied to slit-film fibers. That is because of the overlapping arrangement of their flattened yarn strands  40 , as can be seen in  FIG. 5 , inhibits coating penetration within each yarn backloop  50  when coating is applied normal to the plane of the backing  20  (or at least not at a considerable angle to that plane). More specifically, the outer bands of yarn would effectively shield inner bands as well as the interstitial spaces between them from receiving coating. 
     The present angled spray technique also puts each yarn filament  40  within a backloop  50  in direct adhesion with backing fibers  26 , as coating material  30  is accumulated against and adhered to the proximate side  52  of the entire backloop  50  as well as to the backing fibers  26 —effectively increasing the tuft bond strength of the turf. To those ends, it is desirable to produce an artificial turf that exhibits a water drain rate of at least 5 inches per minute and tuft bond strength of at least 12 pounds according to ANSI/ASTM D 1335-67. 
     A polyurethane composition is used as coating material in a preferred embodiment of the present coating application method, although, as previously mentioned, other rapidly curing compositions may be used instead. As partially schematically shown in  FIG. 7 , reaction monomers are separately held in fluid reservoirs  68  before being pumped into a mixing head  66  within which they are blended to react and form the polyurethane coating. While in a liquid state, the coating then advances to a spray head  62  that emits a high velocity shower  34  of coating droplets  32  onto the backing face  24  as the spray head  62  traverses over the backing  20 . It has been observed that superior turf bond and porosity results are achieved when the backing face  24  is spray-coated in multiple successive passes of the spray head  62 . 
     The spray head  62 , in fact, may comprise one or more nozzles that are moveably mounted along a computer-operated, gantry-type coating apparatus (not shown) configured very similarly to the tufting machine referenced above and previously described by the present inventor in U.S. Published Patent App. No. 20080134949, except that, most notably, (1) a spray head  62  replaces the tufting head of said machine and (2) the orientation of the spray head  62  is such that it expels a shower  34  of coating droplets along a 4 to 6 foot flight path that forms a less than 45-degree angle A with the plane of the backing  20 . However, alternative means for controlling the spray head  62 , including manual control, may be employed so long as they allow for careful control of the parameters of spray trajectory, spray flight distance and relative movement of the spray head  62  and backing  20 . 
     Finally, to enable formation of a porous coating layer  30  along the backing face  24 , a number of spray and environmental parameters must be precisely set in consideration of the chemical reaction of the particular coating composition selected for use. Such parameters are intended to ensure that landed composition particles  32  solidify too quickly to reconstitute liquid masses that can flow along the backing  20  and concentrate in, for example, fabric pores  46  within the narrow areas  48  that were shielded from spray  34  by the backloops  50 . In fact, the coating droplets  32  should begin to cure immediately upon exiting the spray head  62  and become too viscous to flow along the fibrous backing  20  by the time they contact it. 
     To this end, the present inventors have observed that, in addition to maintaining a spray inclination angle A of 10 to 30 degrees with the plane of the backing  20 , coating objectives are best met by maintaining the following combination of spray parameters: (a) a spray head pressure within a range of 1,800 to 2,000 psi; (b) a spray distance within a range of 48 to 72 inches; (c) the coating material at a temperature of at least 130 degrees Fahrenheit within the mixing head  66 ; and (d) an ambient temperature within a range of 68 to 77 degrees Fahrenheit. 
     It is further preferred that a suction device (not shown) be placed underneath the backing  20  (facing the backing&#39;s top face  22 ) so that spray particles  32  neither escape into the ambient air nor accumulate on any other equipment used (e.g., hood enclosure, spray head, etc.). 
     It is understood that substitutions and equivalents for various elements set forth above may be obvious to those skilled in the art and may not represent a departure from the spirit of the invention. Therefore, the full scope and definition of the present invention is to be set forth by the claims that follow.