Patent Publication Number: US-2017362831-A1

Title: Cool roof systems and methods

Description:
FIELD OF THE INVENTION 
     The disclosure generally relates to roofing systems. 
     BACKGROUND OF THE INVENTION 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Commercial and industrial buildings typically have roofing systems with a metal deck, lightweight concrete, structural concrete, or wood deck (e.g., low-slope roof deck). These roofing systems usually have one or more layers of insulation on top of the roof deck and one or more waterproof layers that protect the insulation from moisture. However, without protection from the sun&#39;s ultraviolet light the waterproof layers may decompose or breakdown. For example, the ultraviolet light may break polymer chains in the water proofing material. As the polymer chains break the water proofing material becomes brittle and susceptible to cracking and/or breaking. To protect the waterproof layers, some roofing systems place granules on top of the waterproof layers. The granules protect the underlying waterproof layers by absorbing and/or reflecting ultraviolet light. However, granules are typically colored (e.g., have a low reflectivity) and therefore absorb significant amounts of energy during the day, which may increase cooling costs. 
     SUMMARY OF THE INVENTION 
     The present disclosure is directed to a membrane roofing system. The membrane roofing system includes a waterproof layer that protects an insulation layer and a granule having a 65% or greater reflectivity coupled to the waterproof layer. The granule protects the waterproof layer by reducing transmission of ultraviolet light to the waterproof layer. The granule is coated in a fluorinated (meth)acrylic copolymer that resists adsorption and absorption of asphaltic chemicals by the granule from the waterproof layer. 
     An aspect of the disclosure includes a built-up roofing system. The built-up roofing system includes a first waterproof layer that protects an insulation layer. A first fiberglass, polyester or combination fiberglass/polyester reinforced layer coupled to the first waterproof layer, and a granule having a 65% or greater reflectivity coupled to the first waterproof layer. The granule protects the first waterproof layer by reducing transmission of ultraviolet light to the first waterproof layer. The granule is coated in a cationic fluorinated (meth) acrylic copolymer that resists adsorption and absorption of asphaltic chemicals by the granule from the waterproof layer. 
     Another aspect of the disclosure includes a method of manufacturing a roofing system. The method begins by coating a granule. The coating includes a cationic fluorinated (meth) acrylic copolymer that resists adsorption and absorption of asphaltic chemicals by the granule from a waterproof layer. After coating the granule, the granule is dried and coupled to the waterproof layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, aspects, and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a cross-sectional view of an embodiment of a membrane roofing system with granules; 
         FIG. 2  is a cross-sectional view of an embodiment of a built-up roofing (BUR) system with granules; 
         FIG. 3  is a side view of an embodiment of a granule coated with a cationic fluorinated (meth) acrylic copolymer; 
         FIG. 4  is a cross-sectional detail view of an embodiment of a pore in a granule coated with a cationic fluorinated (meth) acrylic copolymer; 
         FIG. 5  is a process for preparing and attaching granules to a waterproof layer; and 
         FIG. 6  is a process for preparing and attaching granules to a waterproof layer. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present invention will be described below. These embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The embodiments discussed below include a roofing system with granules coated with cationic fluorinated (meth) acrylic copolymer. The cationic fluorinated (meth) acrylic copolymer enables the granules to resist and/or block absorption/adsorption of asphaltic chemicals that may leach out of the waterproof layer. Absorption and/or adsorption of asphaltic chemicals may change the color of the granules and thus their reflectivity. By resisting absorption/adsorption of color changing substances from the waterproof layer, the cationic fluorinated (meth) acrylic copolymer enables highly reflective granules to maintain their reflectivity. The greater the granule&#39;s reflectivity the less energy absorbed by the roof, which reduces power consumption by building climate control systems. 
       FIG. 1  is a cross-sectional view of an embodiment of a membrane roofing system  10  with granules  12 . The membrane roofing system  10  includes one or more insulation layers  14  that resist heat transfer through the roof of a building. To protect the insulation layer(s)  14  from the environment (e.g., rain, snow), the membrane roofing system  10  includes one or more waterproof layers or membranes  16 . In some embodiments, the waterproof layer  16  may be reinforced with a matrix  18  (e.g., fiberglass, polyester, or fiberglass/polyester combination reinforcement) that increases the tensile strength and tear resistance of the waterproof layer  16 . 
     The waterproof layers  16  may be an asphalt-based material (e.g., Styrene-Butadiene-Styrene (SBS) Modified Asphalt, Atactic Polypropylene (APP) Modified Asphalt, or Oxidized Asphalt Coating). Asphaltic chemicals are highly complex chemicals containing saturated and unsaturated aliphatic and aromatic compounds with up to 150 carbon atoms. Their composition varies depending on the source of crude oil. Many of the compounds contain oxygen, nitrogen, sulfur, and other heteroatoms. Asphalt typically contains about 80% by weight of carbon; around 10% hydrogen; up to 6% sulfur; small amounts of oxygen and nitrogen; and trace amounts of metals such as iron, nickel, and vanadium. The molecular weights of the constituent compounds range from several hundred to many thousands. 
     As explained above, ultraviolet light can break down the waterproof layer  16  by breaking polymer chains. As polymer chains break, the waterproof material may become brittle and susceptible to cracking and/or breaking. To protect the waterproof layer  16 , the membrane roofing system  10  includes a layer  20  of granules  12  that block and/or reduce the amount of ultraviolet light that reaches the waterproof layer  16 . The granules  12  may be made out of stone, aluminum silicate, Barium Sulfate, sintered glass, ceramic, etc. and have a small particle size (e.g., 0.2 mm to 2.4 mm). The granules  12  have a greater surface area than regular masonry slab material, such as granite or limestone tile, which makes stain resistance a challenge, especially when the granules  12  are partially embedded in asphaltic material (e.g., asphaltic chemicals). 
     In addition to protecting the waterproof layer  16 , the granules  12  reduce energy absorption by the membrane roofing system  10 . For example, the granules  12  have a reflectivity of 65% or greater (e.g., 65%, 70%, 80%, 90%, 95% or greater). By reflecting light away from the membrane roofing system  10  the granules  12  decrease power consumption by climate control systems that cool the building. In addition, the highly reflective cool roof may also reduce the urban heat island effect. Because the granules  12  are embedded or otherwise in contact with the waterproof layer  16 , the granules  12  may absorb and/or adsorb asphaltic chemicals from the waterproof layer  16 . For example, high temperatures may cause asphaltic chemicals to leach out of the waterproof layer  16 . If these substances are absorbed and/or adsorbed by the granules  12  they may change the color of the granules  12 . A change in granule  12  color changes the reflectivity of the granule  12 , which increases the energy absorbed by the membrane roofing system  10 . To maintain the reflectivity of the granules  12 , the granules  12  are coated with a cationic fluorinated (meth) acrylic copolymer (e.g., DuPont® ST-100, DuPont® ST-110, or a combination thereof). The cationic fluorinated (meth) acrylic copolymer coating may be about 0.001% to about 3.0% by weight of an uncoated granule  12 . The cationic fluorinated (meth) acrylic copolymer blocks and/or reduces adsorption and/or absorption by the granule  12  of asphaltic chemicals in the waterproof layer  16 . Accordingly, the granules  12  are able to protect the waterproof layer  16  as well as maintain their reflectivity. 
     The cationic fluorinated (meth)acrylic copolymer can be either acrylate or methylate copolymer that includes at least fluorinated alkyl containing acrylate/methacrylate monomer, such as 1H, 1H, 2H, 2H-perfluorooctyl acrylate/methacrylate, and amine containing acrylate or methacrylate monomer, such as 2-(dimethylamino) ethyl methacrylate. The amine functionality, in particular tertiary and quaternary, may provide cationic sites along the polymer chain, which enables the polymer to be dispersed in aqueous solution. In addition, the cationic characteristic of the polymer enables it to wet and adsorb to a cementatious substrate, such as an aluminum silicate based granule  12 . The fluorinated alkyl chain of the cationic fluorinated (meth) acrylic copolymer may provide both hydrophobic and lipophobic protection to the granule  12 . In some embodiments, the polymer may include a silane containing monomer, such as methacryloxypropyltrimethoxysilane, which may form a covalent bond with the granule  12  increasing adhesion and durability of the coating. In contrast, anionic copolymers made with the same fluorinated alkyl acrylate/methylate co-monomer wet and coat the surface of the granule  12  poorly and do not provide the same hydrophobic and lipophobic protection. 
       FIG. 2  is a cross-sectional view of an embodiment of a built-up roof (BUR) system  40  with granules  12 . The BUR system  40  includes one or more insulation layers  14  that resist heat transfer through the roof of a building. To protect the insulation layer(s)  14  from the environment (e.g., rain, snow), the BUR system  40  includes one or more waterproof layers or membranes  42 . The waterproof layers  42  may be a polymer material such as an asphalt-based material (e.g., Styrene-Butadiene-Styrene (SBS) Modified Asphalt, Atactic Polypropylene (APP) Modified Asphalt, or Oxidized Asphalt Coating) The BUR system  40  structurally reinforces the waterproof layers  42  with fiberglass, polyester, or fiberglass/polyester combination reinforcement layers  44  (e.g., fiberglass, polyester, or fiberglass/polyester combination reinforcement) that increase the tensile strength and tear resistance of the waterproof layers  42 . As illustrated, the fiberglass layers  44  are placed between the waterproof layers  42  in an alternating manner to strengthen the overall BUR system  40 . 
     As explained above, ultraviolet light may negatively affect the waterproof layer material. To protect the waterproof layers  42 , the membrane roofing system  10  includes a layer  20  of granules  12  that block and/or reduce the amount of ultraviolet light that reaches the exterior or outermost waterproof layer  42 . The granules  12  may be made out of stone, aluminum silicate, Barium Sulfate, sintered glass, ceramic, etc. In addition to protecting the waterproof layers  42 , the granules  12  reduce energy absorption by the BUR system  40 . For example, the granules  12  have a reflectivity of 65% or greater (e.g., 65%, 70%, 80%, 90%, 95% or greater). By reflecting light away from the BUR system  40 , the granules  12  decrease the amount of energy needed to cool the building. In other words, the granules  12  reduce power consumption by climate control units (e.g., air conditioning units). 
     Because the granules  12  are embedded or otherwise in contact with the waterproof layers  42  the granules  12  may absorb and/or adsorb color-changing chemicals, oils, etc. from the waterproof layers  42 . For example, the high temperatures may cause asphaltic chemicals to leach out of the waterproof layers  42 . If these substances are absorbed and/or adsorbed by the granules  12  they can change the color of the granules  12 . A change in the granule  12  color changes the granule&#39;s reflectivity. To maintain the reflectivity of the granules  12 , the granules  12  are coated with a fluorinated (meth)acrylic copolymer (e.g., DuPont® ST-100, DuPont® ST-110, or a combination thereof). The cationic fluorinated (meth)acrylic copolymer blocks and/or reduces adsorption and/or absorption by the granule  12  of the chemicals, oils, etc. in the waterproof layers  42 . Accordingly, the granules  12  are able to protect the waterproof layers  42  as well as maintain their reflectivity. 
       FIG. 3  is a side view of an embodiment of a granule  12  coated with a fluorinated (meth)acrylic copolymer. The cationic fluorinated (meth)acrylic copolymer blocks and/or reduces absorption/adsorption of asphaltic chemicals in the waterproof layers  16 ,  42 . In some embodiments, the granules  12  may be made out of a porous material. By coating the granules  12  with the cationic fluorinated (meth)acrylic copolymer, the granules  12  resist absorbing asphaltic chemicals through the pores  60  and/or adsorbing the asphaltic chemicals In other words, the cationic fluorinated (meth)acrylic copolymer coating enables the granules  12  to maintain their reflectance by resisting absorption/adsorption of asphaltic chemicals that leach out of the waterproof layers  16 ,  42 . The cationic fluorinated (meth)acrylic copolymer coating may be about 0.001% to about 3.0% by weight of an uncoated granule  12 . 
     Table 1 below illustrates the absorption/adsorption resistance of the granules  12  coated with cationic fluorinated (meth)acrylic copolymer versus granules coated with silicone. In the example below, the reflectance of the granule  12  remains unchanged when the cationic fluorinated (meth)acrylic copolymer coating amount is greater than 0.50% by weight of an uncoated granule  12 , while a granule  12  with a fluorinated acrylic copolymer coating of 0.25% by weight changes only slightly. In contrast, the reflectance of a silicone coated granule changes significantly in the same testing procedures. The ability of the coating to provide stain resistance at low coating weight may be due to monolayer formation on the granule surface. As explained above, a reduction in reflectance increases energy absorption by the roof and thus energy consumption by climate control units. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Change in 
                   
                   
               
               
                 Coating Amount 
                 Granule Reflectance with 
                 Cationic fluorinated 
               
               
                 (coating amount is 
                 Cationic fluorinated 
                 (meth)acrylic copolymer 
                 Granule Reflectance 
                 Change in Silicone 
               
               
                 shown in percent by 
                 (meth)acrylic copolymer 
                 Coated Granule 
                 with Silicone 
                 Coated Granule 
               
               
                 weight of an 
                 Coating (28 Days of Dark 
                 Reflectance (original 
                 Coating (28 Days of Dark 
                 Reflectance (original 
               
               
                 uncoated granule) 
                 Oven Exposure at 80° C.) 
                 reflectance 73.9%) 
                 Oven Exposure at 80° C.) 
                 reflectance 73.9%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 0.25% 
                 72.4% 
                 −1.5%       
                 53.1% 
                 −19.3% 
               
               
                 0.50% 
                 73.9% 
                 0% 
                 60.1% 
                 −14.2% 
               
               
                 0.75% 
                 73.9% 
                 0% 
                 57.7% 
                 −16.1% 
               
               
                  1.0% 
                 73.9% 
                 0% 
                 58.7% 
                 −14.9% 
               
               
                  2.0% 
                 73.9% 
                 0% 
                 62.9% 
                 −11.0% 
               
               
                   
               
            
           
         
       
     
       FIG. 4  is a cross-sectional detail view of an embodiment of a pore  60  in a granule  12  coated with a cationic fluorinated (meth)acrylic copolymer. As illustrated, the cationic fluorinated (meth)acrylic copolymer does not fill the pore  60 ; but instead, coats the interior surface  64  of the pore  60 . In some instance, the fluorinated (meth)acrylic copolymer can form a monolayer on the substrate that protects at very low concentrations. This unique characteristic of fluorinated (meth)acrylic copolymer provides granule protection over a wide range of applied concentrations. Even though the interior surface  64  is covered, the lipophobicity of the cationic fluorinated (meth)acrylic copolymer blocks or reduces absorption of oils into the granule  12  through the aperture  66 . In some embodiments, the cationic fluorinated (meth)acrylic copolymer may completely fill the pore  60  blocking oil absorption by the granule  12 . 
       FIG. 5  illustrates a process  80  for preparing and attaching the granules  12  to the waterproof layers  16 ,  42 . The process  80  begins by coating the granules  12  in cationic fluorinated (meth) acrylic copolymer dispersion, block  82 . In some embodiments, the cationic fluorinated (meth)acrylic copolymer dispersion may be applied to the granules  12  via direct spray (e.g., quick spray) using a dispersion solution containing between about 10% to about 80% fluorinated acrylic copolymer. The concentration of the fluorinated acrylic copolymer in the solution may be determined by the liquid pickup of the granule  12 , so that the desired amount of cationic fluorinated (meth)acrylic copolymer coats the granule  12  (e.g., coating amount between about 0.001% to about 0.5% by weight of an uncoated granule  12 ). In another embodiment, the cationic fluorinated (meth)acrylic copolymer coating may be applied via dip coating. 
     The granules  12  are then dried, block  84 . In some embodiments, the granules  12  may be air-dried. In another embodiment, the granules  12  may be dried in an oven (e.g., dried in an oven at about 100° C.). In still other embodiments, the granules  12  may be dried using a combination of air-drying and an oven. In some embodiments, the granules  12  may be recoated with cationic fluorinated (meth)acrylic copolymer and then dried again. This may be repeated multiple times (e.g., 1, 2, 3, 4, 5, or more times) to ensure adequate coating of the granules  12 . Once the granules  12  are dried, the granules  12  are attached to a waterproof layer  16 ,  42 , block  86 . For example, the waterproof layer  16 ,  42  may be in a molten state when the granules  12  are placed on the waterproof layer  16 ,  42 , block  86 . As the waterproof layer  16 ,  42  cools and hardens the granules  12  couple to the waterproof layer  16 ,  42 . In some embodiments, the granules  12  may couple to the waterproof layer  16 ,  42  with an adhesive. 
       FIG. 6  illustrates a process  90  for preparing and attaching the granules  12  to the waterproof layer  16 ,  42 . However, instead of coating the granules  12  and then attaching the granules  12  to the waterproof layer  16 ,  42 , the granules  12  are first attached to the waterproof layer  16 ,  42 , block  92 . In some embodiments, the waterproof layer  16 ,  42  is in a molten state when the granules  12  are placed on the waterproof layer  16 ,  42 . As the waterproof layer  16 ,  42  cools and hardens the granules  12  couple to the waterproof layer  16 ,  42 . In some embodiments, the granules  12  may couple to the waterproof layer  16 ,  42  with an adhesive. 
     Once the granules  12  are coupled to the waterproof layer  16 ,  42 , the granules  12  are coated with a cationic fluorinated (meth)acrylic copolymer, block  94 . For example, the granules  12  may be coated via direct spray with a dispersion solution containing between about 10% to about 80% cationic fluorinated (meth)acrylic copolymer. The concentration of the cationic fluorinated (meth)acrylic copolymer in the solution may be determined by the liquid pickup of the granule  12 , so that the desired amount of fluorinated acrylic copolymer coats the granule  12  (e.g., coating amount between about 0.001% to about 0.5% by weight of an uncoated granule  12 ). In another embodiment, the fluorinated acrylic copolymer coating may be applied via dip coating. For example, the granules  12  and waterproof layer  16 ,  42  may be dipped together in a cationic fluorinated (meth) acrylic copolymer dispersion. In some embodiments, only a portion of the granules  12  may be dipped in a cationic fluorinated (meth)acrylic copolymer dispersion. The liquid pickup of the granules  12  may then facilitate coating and absorption of the cationic fluorinated (meth)acrylic copolymer. 
     After coating the granules  12 , the granules  12  are dried, block  96 . In some embodiments, the granules  12  may be air-dried. In another embodiment, the granules  12  may be dried in an oven (e.g., dried in oven at temperatures around 100° C.). In still other embodiments, the granules  12  may be dried using a combination of air-drying and an oven. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.