Abstract:
A method of applying a waterproof coating comprises providing a resin solution and an accelerator solution, and further utilizing a spray system for applying the coating, the spray system including a spray gun having first and second nozzles, a first pump fluidly connected between the first nozzle and a resin solution reservoir for delivering the resin solution to the first nozzle at a first fluid pressure, and a second pump fluidly connected between the second nozzle and an accelerator solution reservoir for delivering the accelerator solution to the second nozzle at a second fluid pressure different from the first pressure. The accelerator solution may be aerated by a source of compressed air prior to discharge from the second nozzle.

Description:
DOMESTIC PRIORITY INFORMATION 
       [0001]    This Application is a Continuation Application of U.S. patent application Ser. No. 11/307,551 filed Feb. 13, 2006, of U.S. patent application Ser. No. 12/728,881 filed Mar. 22, 2010 and of U.S. patent application Ser. No. 14/605,896, filed Jan. 26, 2015. The disclosures of these applications are incorporated herein by reference. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    This invention relates generally to waterproof coating systems, and more particularly to a two-part water-based coating and method for applying the coating to a surface so that the coating is substantially immediately cured upon application to the surface. 
         [0003]    Exterior coatings are exposed to the vicissitudes of weather from the very moment they are applied to protect an exterior surface. Water-based coatings are favored over solvent borne coatings for a number of well-known reasons. They offer ease of application, reduced toxic solvent emission, lower raw material and application costs, and easy cleanup of site and equipment. However, water-based coatings are particularly vulnerable to water damage during and immediately after application. A sudden summer shower can wash away or otherwise damage the result of many hours of labor and waste valuable materials. 
         [0004]    Exterior water-based coatings may be formulated using aqueous dispersions of water-insoluble polymer latex as binders. After application, the aqueous carrier evaporates, and the individual latex particles coalesce to form an integral film. Some applications require relatively thick coating films, conventionally on the order of 20-40 mils (0.05-0.10 cm) or more. These coatings are often applied by spraying techniques with mixed results. Because they are applied as a thick coating, they lose water by evaporation relatively slowly in comparison with other polymer latex coating products such as house paints, which are typically applied at 5-8 mils (0.013-0.02 cm). Thus, roof coatings are particularly vulnerable to being washed off by unanticipated precipitation. In order to avoid roof coating washout or damage due to water, it is typically necessary to apply the full thickness in two or more separate applications, which effectively increases labor costs. 
         [0005]    The application of such coatings also requires the laborer to haul heavy equipment and materials to the surface to be coated. This is especially inconvenient and time consuming when the coating is to be applied to a rooftop. Since some coating systems require components with high viscosity and large particle sizes, it would be very difficult to pump such liquids and particles to the rooftop from a lower level or over long lengths of tubing or hose. 
         [0006]    Many roof membranes also require joint details or laps and mechanical or chemical fastening techniques that can eventually lead to membrane failure. In addition, commercial, industrial and home roof structures typically include many penetrations for vent stacks, mounting hardware for antennas or other equipment, and structures, with each penetration being a potential leak sight. 
         [0007]    It would therefore be desirable to provide a coating system and method of application that overcomes at least some of the disadvantages of the prior art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    According to one aspect of the invention, a coating comprises a resin solution including a solution of neoprene latex and liquid asphalt emulsion and an accelerator solution including an aqueous solution of zinc sulfate powder and water. 
         [0009]    According to a further aspect of the invention, a spraying system for applying a coating to a surface includes a spray gun having first and second nozzles, a first pump fluidly connected between the first nozzle and a resin solution reservoir for delivering the resin solution to the first nozzle at a first fluid pressure, and a second pump fluidly connected between the second nozzle and an accelerator solution reservoir for delivering the accelerator solution to the second nozzle at a second fluid pressure different from the first pressure. 
         [0010]    According to yet a further aspect of the invention, a method for applying a coating includes providing a spray gun with first and second nozzles; discharging a resin solution from the first nozzle at a first fluid pressure; discharging an accelerator solution from the second nozzle at a second fluid pressure; combining the discharged resin solution with the discharged accelerator solution before application to the surface; and substantially curing the combined resin and accelerator solutions before application to the surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing summary as well as the following detailed description of the preferred embodiments of the present invention will be best understood when considered in conjunction with the accompanying drawings, wherein like designations denote like elements throughout the drawings, and wherein: 
           [0012]      FIG. 1  is a perspective view of a coating system according to the present invention; 
           [0013]      FIG. 2  is a side perspective view of a hand-held applicator spray gun that forms part of the coating system of  FIG. 1 ; 
           [0014]      FIG. 3  is a left side elevational view of the spray gun of  FIG. 2 ; 
           [0015]      FIG. 4  is a right side elevational view of the spray gun; 
           [0016]      FIG. 5  is a top plan view of the spray gun; 
           [0017]      FIG. 6  is a front elevational view of the spray gun; and 
           [0018]      FIG. 7  is a rear elevational view of the spray gun. 
       
    
    
       [0019]    It is noted that the drawings are intended to depict typical embodiments of the invention and therefore should not be considered as limiting the scope thereof. It is further noted that the drawings are not necessarily to scale. The invention will now be described in greater detail with reference to the accompanying drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring to the drawings, and to  FIG. 1  in particular, a coating system  10  in accordance with the present invention is illustrated. The coating system  10  preferably includes a coating comprising a resin solution  12  contained within a barrel  14  and an accelerator solution  16  (shown in hidden line) contained within a bucket  18 , and a coating delivery system  20  for combining the resin and accelerator solutions and applying them to a surface to be coated, as will be described in greater detail below. It will be understood that the particular containers shown are exemplary only and that the resin solution  12  and accelerator solution  16  may be stored in any type of container. 
         [0021]    The resin solution  12  preferably includes water-based liquid neoprene latex, such as polychloroprene, combined with a water-based liquid asphalt emulsion. Preferably, the neoprene latex contains approximately 59% solids and has a high pH value of about 12.0. It has been found that an asphalt grade of SS 1 h works particularly well since it is tackier and dries faster than other grades of asphalt. The optimal weight ratio of liquid latex to asphalt emulsion is approximately 1:1 (50% of each product), which results in optimal adhesive strength and elongation of the cured coating than other ratios. However, the particular latex to asphalt ratio may vary over a broad range depending on the particular properties desired. For example, an increase in the amount of latex would result in a higher cost coating with higher tensile strength and less adhesive strength. In some instances, it may be desirable to eliminate either the liquid neoprene latex or the asphalt emulsion. Accordingly, the liquid latex and asphalt emulsion of the resin solution  12  may proportionately range from 0% to 100%. At the optimal weight ratio of 1:1, a low viscosity resin solution of about 30 to 50 centipoises is obtained, which greatly facilitates delivery of the resin solution over long lengths of supply tubing. 
         [0022]    The accelerator solution  16  preferably includes an aqueous solution of zinc sulfate powder dissolved in water. For optimum performance and coagulation of the resin solution  12 , eight pounds of zinc sulfate is preferably added to five gallons of water to produce a low pH level of about 4.5. Since a gallon of water weighs about 8.35 pounds, an optimum weight ratio of zinc sulfate to water is about 1:5. However, it will be understood that the particular zinc sulfate to water ratio may vary over a broad range depending on the particular properties and performance desired. The zinc sulfate powder is preferred not only because of its ability to quickly coagulate the resin solution  12 , but also because it has been found to be less irritating to persons applying the coating to a surface than other coagulating materials. However, it will be understood that other materials may be used in place of zinc sulfate, such as citric acid or any other material that will cause coagulation of the resin solution  12 . As with the resin solution  12 , the accelerator solution  16  is also preferably of low viscosity. 
         [0023]    During application of the coating to a surface, the delivery system  20  preferably combines the resin solution  12  and the accelerator solution  16  during spraying such that the resin to accelerator spray ratio is in the range of about 15:1 to 1:0, and more preferably in the range of 15:1 to 10:1. A greater amount of accelerator results in a shorter curing time, while a lesser amount results in a longer curing time. In the case of a 1:0 ratio, no accelerator is used. On some nonporous surfaces, or in high humidity and/or low temperature ambient conditions, it may be desirable to apply a tacky primer coating of resin solution only (1:0 ratio) before a coating of the combined resin and accelerator solutions to ensure superior adhesion to such surfaces and/or in such ambient conditions. Accordingly, the coating delivery system  20  of the present invention permits adjustment of the spray ratio of resin to accelerator over a wide range of values. 
         [0024]    As shown in  FIG. 1 , the coating delivery system  20  includes a cart  22  with an air-operated resin pump  24  and an air-operated accelerator pump  26 , a compressed air supply as represented by arrow  28 , and an airless spray gun  30  fluidly connected to the pumps  24 ,  26  and air supply  28 . Although the resin and accelerator pumps are preferably air-operated, it will be understood that the pumps may alternatively be electrically powered. The compressed air supply may be in the form of an air compressor, pressurized air tank, or a combination thereof. Preferably, to meet optimal coating requirements, a suitable compressed air supply delivers approximately 20 cubic feet per minute at 100 psi. 
         [0025]    The cart  22  preferably has a first U-shaped frame  32  that extends generally upwardly and rearwardly from a forward end  36  of a horizontal platform  34  to form a handle  38 , a second U-shaped frame  40  that extends generally vertically between a rear end  42  of the platform  34  and the first U-shaped frame  32 , a support panel  44  that is mounted to the second frame  40 , and a pair of wheels  46 ,  48  rotatably connected to the platform  34  for transporting the cart  22 . A tool tray  59  is mounted to the cart  22  above the support panel  44 . 
         [0026]    The resin pump  24  is preferably securely supported on the platform  34  and includes a first fluid input port  50  for receiving the resin solution  12  from the container  14 , a second fluid input port  52  for receiving air under pressure from the compressed air source  28 , and a fluid output port  54  for delivering the resin solution  12  under pressure to the spray gun  30 . A relatively stiff suction conduit  56  is adapted for insertion into the resin solution  12  located in the container  14 . A filter element  58  is connected to a lower end of the suction conduit  56  to filter out foreign matter that may be present in the resin solution during resin pump operation. A flexible suction tube  60  extends between the suction conduit  56  and the first fluid input port  50  for drawing the resin solution  12  under vacuum from the container  14  to the resin pump  24 . A flexible resin delivery tube  62  extends between the fluid output port  54  and the spray gun  30  for delivering the pressurized resin solution to the spray gun  30 . Preferably, the resin pump is a stainless steel diaphragm pump that operates when compressed air is applied to the second fluid port  52  to suction resin solution from the container  14  and deliver the resin solution under pressure to the spray gun  30 . However, it will be understood that other types of pumps can be used. Preferably, the ratio of applied compressed air pressure to the supplied resin solution pressure is 1:3, such that an applied air pressure of approximately 100 psi to the second fluid port  52  results in a supplied resin solution pressure of about 300 psi to the spray gun  30 . 
         [0027]    The accelerator pump  26  is preferably securely supported on the support panel  44  above the resin pump  24 . A relatively stiff suction conduit  70  is adapted for insertion into the accelerator solution  16  located in the container  18 . A filter element  72  is connected to a lower end of the suction conduit  70  to filter out foreign matter that may be present in the accelerator solution during accelerator pump operation. A flexible suction tube  74  extends between the suction conduit  70  and a first fluid input port  76  for drawing the accelerator solution  16  under vacuum from the container  18  to the accelerator pump  26 . A flexible accelerator delivery tube  78  extends between a fluid output port  80  of the accelerator pump  26  and the spray gun  30  for delivering the pressurized accelerator solution to the spray gun  30 . Preferably, the accelerator pump operates when compressed air is applied to an air inlet port  82  to suction accelerator solution from the container  18  and deliver the accelerator solution under pressure to the spray gun  30 . Preferably, the accelerator solution is pressurized at about 60 psi to the spray gun  30 . 
         [0028]    An air delivery tube  79  is fluidly connected between the spray gun  30  and the compressed air supply  28  to provide pressurized air to the spray gun  30  for both controlling operation of the spray gun and controlling the amount of atomization of the accelerator solution  16 , as will be described in greater detail below. The delivery tubes  62 ,  78  and  79  may be contained within a flexible sleeve  81  for protection during storage, transportation and use. 
         [0029]    The support panel  44  also includes gauges  84 ,  86  and  88  and adjustable pressure regulators  90 ,  92  and  94  for selectively monitoring and adjusting the delivery air pressure to the resin pump  24 , accelerator pump  26 , and the spray gun  30 , respectively. Accordingly, the precise delivery pressure of the resin solution  12 , the accelerator solution  16 , and the atomizing and operating air to the spray gun  30  can be controlled with a high degree of accuracy. An oil and water filter  96  is mounted to the support panel  44  and includes an input port  98  for receiving air under pressure from the compressed air source  28 . An output (not shown) of the filter  96  is in turn fluidly connected to the resin pump  24 , accelerator pump  26  and spray gun  30  through the pressure regulators  90 ,  92  and  94 , respectively. 
         [0030]    Holsters in the form of hollow storage cylinders  100  and  102  are connected to opposite sides of the first U-shaped frame  32  for receiving the suction conduits  56  and  70 , respectively, during transportation and storage. Cleaning fluid may be located in each holster for soaking the conduits and their respective filters during non-use. 
         [0031]    With additional reference to  FIGS. 2-7 , the airless spray gun  30  includes a body  110  with a handle  112  extending downwardly from the body, an air-actuated trigger  114  positioned forwardly of the handle, and nozzles  116 ,  118  for delivering the resin solution  12  and accelerator solution  16 , respectively, to a surface to be coated. A resin hose coupling  120  is arranged for connection to the flexible resin delivery tube  62  ( FIG. 1 ). A valve  122  is in turn connected to the coupling  120 . The valve  122  includes a handle  124  for adjusting the flow of resin solution  12  between a fully closed and fully open position. The valve  122  is in turn connected to a resin inlet  126  of the spray gun  30 , which is in fluid communication with the nozzle  116 . 
         [0032]    An accelerator hose coupling  128  is arranged for connection to the flexible accelerator delivery tube  78  ( FIG. 1 ). An adjustable valve  130  is connected to the coupling  128  and an integrator valve assembly  132  is in turn connected to the valve  130 . The valve  130  can be adjusted for altering the volume of accelerator solution  16  delivered to the integrator valve assembly  130 . By controlling delivery of the resin solution, accelerator solution and air pressure, the amount of atomization and pressure can be precisely controlled to achieve the desired coating effects. 
         [0033]    An air hose coupling  134  is arranged for connection to the air delivery tube  79  ( FIG. 1 ). A one-way check valve  136  is in turn connected between the coupling  134  and integrator valve assembly  132 . The integrator valve assembly  132  mixes the air under pressure with the accelerator solution at a predetermined ratio so that the accelerator solution is properly atomized as it exits the valve  118  via the accelerator inlet  138  that is connected to the valve assembly  132 . 
         [0034]    When the trigger  114  is depressed, a double-acting valve  144  ( FIG. 3 ) is actuated to release the resin solution and the accelerator lair solution under pressure through the nozzles  116  and  118 , respectively. In order to prevent user fatigue during coating operations, the trigger  114  is preferably air-actuated. To that effect, an air line  140  ( FIG. 4 ) extends between the air hose coupling  134  and a trigger inlet port  142 . When the trigger  114  is depressed, air under pressure is applied against the double-acting valve  144  to hold the valve open. In this manner, only light finger pressure is required to pull the trigger  114  and hold it in the open (spraying) position. A trigger guard  146  is attached to the handle  112  and extends around the trigger  114 . A safety latch  148  is positioned on the handle  112  in proximity to the trigger guard  146  and is movable to a position to lock the trigger in the closed (inactive) position. 
         [0035]    The relatively low pressure supply of the resin solution  12  and accelerator solution  16  to the airless spray gun  30  offers great advantages over prior art systems where pressures can easily range from about 1800 psi to about 2500 psi, requiring special safety equipment to avoid accidental injection of fluid into the operator. With the low pressure system of the present invention, the chance of injury through fluid injection from the spray nozzles is substantially reduced or eliminated. 
         [0036]    With particular reference to  FIGS. 5 and 6 , each nozzle  116 ,  118  is oriented at an angle ex with respect to a line  150  perpendicular to a front face  152  of the spray gun  30 . Preferably, the angle ex is approximately 4.4 degrees so that the atomized resin solution  12  and atomized accelerator solution  16  are combined at approximately four inches from the nozzles  116 ,  118 . It will be understood that one or both of the nozzles may have other angular orientations so that the solutions  12 ,  16  are combined at other distances from the nozzles. The nozzle  116  preferably has an aperture  160  with a predefined diameter and fan angle. Likewise, the nozzle  118  preferably has an aperture  162  with a predefined diameter and fan angle. The following chart illustrates preferred aperture sizes, fan angles and pressure settings for optimal performance during a standard coating application: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Resin Nozzle Size 
                 0.072 inch diameter × 40 degree spray angle 
               
               
                 Resin Air Pressure/Liquid 
                 100 PSI/300 PSI 
               
               
                 Pressure 
               
               
                 Air Atomization Pressure 
                 30 PSI 
               
               
                 Accelerator Nozzle Size 
                 0.061 inch diameter × 60 degree spray angle 
               
               
                 Accelerator Pressure 
                 60 PSI 
               
               
                   
               
             
          
         
       
     
         [0037]    The following chart illustrates preferred aperture sizes, fan angles and pressure settings for optimal performance during a high production coating application: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Resin Nozzle Size 
                 0.078 inch diameter × 50 degree spray angle 
               
               
                 Resin Air Pressure/Liquid 
                 100 PSI/300 PSI 
               
               
                 Pressure 
               
               
                 Air Atomization Pressure 
                 50 PSI 
               
               
                 Accelerator Nozzle Size 
                 0.075 inch diameter × 65 degree spray angle 
               
               
                 Accelerator Pressure 
                 70 PSI 
               
               
                   
               
             
          
         
       
     
         [0038]    As will be noted, the spray angle for the accelerator nozzle is greater than the spray angle for the resin nozzle so that optimal convergence can occur between the two spray streams at the different delivery pressures. It will be understood that the particular pressures, aperture sizes and spray angles are given by way of example only and can greatly vary. 
         [0039]    During the coating operation, the resin solution and accelerator solution are atomized at the airless spray nozzles  116 ,  118  under relatively low pressure when compared to prior art systems and, as before described, combine a predetermined distance from the spray nozzles. Preferably, both solutions are atomized through the airless spray nozzles at a flow rate of about 2 to 5 gallons per minute (gpm). As the atomized solutions combine, a rapid cure of the resin solution is created by the intimate mixture of the high pH resin solution and low pH accelerator solution. With the preferred settings, configurations and combinations of materials as described above, it has been found that approximately 80% of the coating is cured in about a three-second time period. The chemical reaction commenced during spraying continues at the surface where shrinkage of the coating thickness occurs. Consequently, the accelerator is squeezed out of the membrane and accumulates on the sprayed surface in the form of water droplets that can be either rinsed off with water, force dried, or left to evaporate. As the accelerator is squeezed out of the membrane, the coating will have increasingly greater adhesion strength to the undersurface until it is completely adhered at full cure. With the present invention, a coating thickness in the range of 60 mils or less to one-fourth inch or more is possible with a single pass. If greater thickness is desired, multiple passes may be used after the previous pass has cured. This is a great advantage over prior art systems and coatings since multiple passes and long cure times are typically required to achieve less than 60 mils thickness. It will be understood that the amount of coating that is substantially immediately cured can greatly vary from 80% depending on the particular formulation of the resin and acceleration solutions as well as the system settings. 
         [0040]    The low viscosity liquid resin solution and low viscosity liquid accelerator solution enable the delivery system  20  to have a longer delivery tube or hose length, typically on the order of 250 feet or more depending on pressure settings and so on, so that equipment and materials can be located on a lower level or at a remote location from the surfaces to be coated to thereby avoid the difficulty and labor of transporting materials and moving them around at the coating sight. 
         [0041]    The coating of the present invention is especially advantageous since it is forms a seamless, monolithic membrane that is immediately waterproof when applied to the surface, even before full cure. Accordingly, the coating is invulnerable to washout or damage by unanticipated precipitation as it protects the surface underneath from moisture. The time to full cure may vary depending on humidity, temperature, wind condition, film thickness, and substrate type, but is typically within 4 to 48 hours after application for the preferred formulations and settings as described above. The coating may also be applied to damp surfaces without adverse results, thereby saving considerable time and labor costs over prior art systems that require a completely dry surface. 
         [0042]    The coating of the present invention is particularly well suited to application over existing or new residential and commercial roof structures and materials. The lightweight nature of the coating, which is typically about 4 ounces per square foot for a 60 mils cured coating, permits its application over existing roof structures without expensive tear-out of previous or damaged roof materials. In one application, the coating of the present invention may be used to directly replace the typical tar paper underlayment on many roof structures. It can be used to create an impenetrable membrane and flashing system that eliminates the problems associated with paper buckling as well as improperly applied ice and water shields at approximately the same installation costs. In addition, application of the coating around vent stacks and other roof protrusions or openings to provide a water proof seal is greatly facilitated by the system and coating of the present invention. 
         [0043]    The system of the present invention may also be used to coat vertical and overhead surfaces since the coating will not run or sag. One especially suited application includes foundation waterproofing. With the ability to stretch up to 1500%, the coating will keep foundation cracks sealed. It can also be extended above grade to thereby seal the foundation against both below grade and above grade water intrusion. 
         [0044]    It will be understood that the term “preferably” as used throughout the specification refers to one or more exemplary embodiments of the invention and therefore is not to be interpreted in any limiting sense. In addition, terms of orientation and/or position as may be used throughout the specification, such as upwardly, rearwardly, horizontal, vertically, as well as their respective derivatives and equivalent terms denote relative, rather than absolute orientations and/or positions. 
         [0045]    It will be appreciated by those skilled in the art that other coating applications and advantages are made possible by the coating system and method of the present invention. It will be understood that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. Accordingly, this invention is not limited to the particular embodiments disclosed, but also covers modifications within the spirit and scope of the present invention as defined by the appended claims.