Abstract:
A prefabricated asphalt-based waterproof roofing membrane for use in a multi-ply asphalt-based commercial roofing system, e.g. a cap sheet that forms the exposed layer of a multi-ply built-up roofing system, is manufactured at a factory to have a highly reflective non-asphalt based elastomeric top coating layer with an upper surface that meets current EPA Energy Star requirements. Preferably, a polymer primer layer is interposed between the highly reflective coating layer and an asphalt saturated and coated reinforcing substrate to keep oils and other colored components in the asphalt from exuding into the highly reflective coating layer.

Description:
BACKGROUND OF THE INVENTION 
   The subject invention relates to asphalt-based waterproof roofing membranes used in multi-ply asphalt-based commercial roofing systems and, in particular, to a prefabricated asphalt-based waterproof roofing membrane for use in a multi-ply asphalt-based commercial roofing system, e.g. a cap sheet that forms the exposed layer of a multi-ply built-up roofing system, that is manufactured at a factory to have a highly reflective upper surface that meets EPA Energy Star requirements. 
   Asphalt-based waterproof roofing membranes, such as cap sheets, are currently manufactured in a process that includes several major process steps. The process steps for producing these black asphalt-based waterproof roofing membranes include: saturating a reinforcing substrate with asphalt (bitumen), typically an oxidized or modified asphalt (bitumen); building up layers of asphalt on both major surfaces of the reinforcing substrate until the asphalt saturated and coated reinforcing substrate formed attains a desired thickness; applying granules, release agents or release films, or a combination of granules and release agents or release films to at least one major surface of the asphalt-based waterproof roofing membrane; winding the finished asphalt-based waterproof roofing membrane into a roll; and packaging the roll of asphalt-based waterproof roofing membrane for storage and shipment to a job site. The process steps of saturating the reinforcing substrate with black asphalt, e.g. an oxidized or modified asphalt, and building up layers of asphalt on both major surfaces of the reinforcing substrate may occur simultaneously. Typically, the reinforcing substrate used in the asphalt-based waterproof roofing membrane is a non-woven fiberglass mat, a reinforced fiberglass mat, a non-woven polyester mat, a reinforced polyester mat, a veiled scrim of various fiber combinations, or a laminated composite of two or more of the preceding reinforcing substrates that provide the asphalt-based waterproof roofing membrane with the necessary strength and flexibility. 
   In a typical manufacturing process, the reinforcing substrate is passed through a saturator/coater where the reinforcing substrate is saturated and coated with asphalt at temperatures from 300 to 425° F. The asphalt typically contains asphalt and mineral fillers and may contain modifiers, such as thermoplastics [Amorphous Polypropylene (APP)], rubbers [Styrene-Butadiene-Styrene (SBS)], and other polymers, antioxidants, resins, oils, etc. Where the saturator and coater units are separate, the asphalts used in the saturator unit to saturate the reinforcing substrate and in the coater unit to coat the reinforcing substrate and build up the thickness of the asphalt saturated and coated reinforcing substrate may have the same composition or different compositions. 
   The reinforcing substrate is typically saturated and coated with asphalt by dipping the reinforcing substrate into a tank of the asphalt or by spreading asphalt over the top surface of the substrate as it passes through a coater. Squeeze rollers and other rollers in the saturator/coater apply the asphalt to the bottom surface of the sheet and distribute the asphalt evenly over the top and bottom surfaces of the reinforcing substrate to form built up layers of asphalt on the top and bottom surfaces of the reinforcing substrate. 
   After passing through the saturator/coater unit or the separate saturator and coater units, surfacing materials are typically adhered to both the top and bottom surfaces of the asphalt saturated and coated reinforcing substrate. In some processes, the asphalt saturated and coated reinforcing substrate may pass through a cooling unit where the asphalt saturated and coated reinforcing substrate is cooled prior to applying surfacing materials to the asphalt saturated and coated reinforcing substrate. Typically, the surfacing materials are applied to the asphalt saturated and coated reinforcing substrate by first passing the asphalt saturated and coated reinforcing substrate through a top surfacing unit. In the top surfacing unit, granules or other surfacing material(s) are applied to the top surface of the asphalt saturated and coated reinforcing substrate. With the desired surfacing material(s) applied to the top surface of the asphalt saturated and coated reinforcing substrate, the asphalt saturated and coated reinforcing substrate passes over a first press drum where the surfacing materials applied to the top surface of the asphalt saturated and coated reinforcing substrate are pressed into the asphalt layer on the top surface of the asphalt saturated and coated reinforcing substrate to assure good adhesion between the surfacing materials and the asphalt layer. As the asphalt saturated and coated reinforcing substrate passes over the first press drum, the asphalt saturated and coated reinforcing substrate is normally flipped simultaneously with the pressing operation so that the bottom surface of the asphalt saturated and coated reinforcing substrate is facing upward. This permits the application of surfacing materials (such as sand, other minerals (e.g. mica, talc, etc.), chemical release agents, and/or polymeric films) to the bottom surface of the asphalt saturated and coated reinforcing substrate by a bottom-surfacing unit. The asphalt saturated and coated reinforcing substrate then passes over a second press drum where the surfacing materials applied to the bottom surface of the asphalt saturated and coated reinforcing substrate are pressed into the asphalt layer on the bottom surface of the asphalt saturated and coated reinforcing substrate to assure good adhesion between the surfacing materials and the asphalt layer. The second turnover press drum returns the asphalt saturated and coated reinforcing substrate to its normal orientation. 
   After the application of the surfacing materials to the top and bottom surfaces of the asphalt saturated and coated reinforcing substrate, the surfaced asphalt saturated and coated reinforcing substrate is cooled rapidly by water-cooled rolls and/or water sprays. The surfaced asphalt saturated and coated reinforcing substrate is then passed through a drying section where the surfaced asphalt saturated and coated reinforcing substrate is typically air dried to finish the manufacture of the asphalt-based waterproof roofing membrane. The finished asphalt-based waterproof roofing membrane is then fed through a looper or accumulator section to permit the continuous movement of the finished asphalt-based waterproof roofing membrane during the cutting and winding operation where the finished asphalt-based waterproof roofing membrane is cut into selected lengths and wound into rolls for packaging, storage, and shipment to a job site. 
   The ever increasing consumption of energy to cool buildings, coupled with global and regional environmental warming issues, has caused a conversion in contemporary roofing technologies to roofing with more reflective top surfaces so that the roofing better reflects solar radiation to thereby reduce the amount of solar radiation absorbed by the roofing and the amount of energy required to cool buildings. Contemporary roofing technologies typically increase the reflectivity of the top surface of the roofing by making the top surface (the exposed surface) of the roofing system white. 
   Due to their irregular granular top surfaces and the intergranule spaces that reveal the black light-absorbing asphalt surfaces to which the granules are adhered, asphalt-based waterproof roofing membranes, such as cap sheets, currently on the market do not meet current EPA Energy Star reflective requirements as measured by ASTM standard E 903—Standard Test Method for Solar Absorptance, Reflectance, and Transmission of Materials Using Integrating Spheres. The current technology used at the job site to upgrade asphalt-based waterproof roofing membranes and provide these roofing membranes with more reflective top surfaces involves covering the exposed surfaces of the roofing membranes with a reflective white coating at the job site. This procedure leads to several problems: a waiting period of up to 30 days before the coating can be applied to the top surface of the membrane; the cost of and time required to clean the top surface of the membrane before applying the coating to the top surface of the membrane; the cost of and time involved in the labor intensive application of the coating to the top surface of the membrane; the quality and/or consistency of the application of the coating to the top surface of the membrane which is dependent on the skill and conscientiousness of the laborer; the limited service life of such coatings on the top surface of the membrane; and the requirement for the periodic maintenance and reapplication of the coating to the top surface of the membrane. The problems associated with applying white coatings at the job site to the top surfaces of asphalt-based waterproof roofing membranes, plus the ease with which single-ply roofing membranes, such as polyvinyl chloride and thermoplastic olefin single-ply roofing membranes, can be made from white compounds, have contributed to market shifts away from multi-ply asphalt-based commercial roofing systems to single-ply membrane roofing systems. 
   SUMMARY OF THE INVENTION 
   The method of prefabricating the asphalt-based waterproof roofing membrane and the prefabricated asphalt-based waterproof roofing membrane of the subject invention solve the problems associated with asphalt-based waterproof roofing membranes discussed in the background of the invention by providing an asphalt-based waterproof roofing membrane that is manufactured in a factory with a standardized reflective top surface that meets current EPA Energy Star reflective requirements as measured by ASTM standard E 903—Standard Test Method for Solar Absorptance, Reflectance, and Transmission of Materials Using Integrating Spheres. The standardized, prefabricated asphalt-based waterproof roofing membrane of the subject invention can be easily applied at a job site with no need to coat the asphalt-based roofing membrane at the job site to improve the reflectivity of the top surface of the membrane to meet EPA Energy Star requirements as measured by ASTM standard E 903. In the method of manufacturing the prefabricated asphalt-based waterproof roofing membrane of the subject invention, a highly reflective non-asphalt based elastomeric coating, in liquid or powder form, is applied to the top surface of a black asphalt saturated and coated reinforcing substrate of the membrane during the manufacture of the asphalt-based waterproof roofing membrane at the factory to provide the asphalt-based waterproof roofing membrane with a highly reflective top surface that meets current EPA Energy Star requirements as measured by ASTM standard E 903. Preferably, the highly reflective top surface of the asphalt-based waterproof roofing membrane is white. The highly reflective top surface of the asphalt-based waterproof roofing membrane may be smooth or may be embossed to enhance the appearance of the top surface and to provide a slip-resistant roofing surface on which the workers can walk. 
   The highly reflective elastomeric coating used in the prefabricated asphalt-based waterproof roofing membrane of the subject invention is opaque to protect the underlying asphalt layer of the asphalt saturated and coated reinforcing substrate of the membrane from the deleterious effects of ultraviolet radiation and may have various additives to improve the performance of the composite, e.g. fungi growth-inhibiting agents, fire retardants, etc. 
   The highly reflective coating of the subject invention is a polymer material binder that is preferably colored with a white pigment, such as titanium dioxide, zinc oxide, aluminum oxide. The polymer material binder used in the highly reflective coating to carry and bind the highly reflective pigments of the coating to the top surface of the asphalt layer of the asphalt saturated and coated reinforcing substrate of the membrane includes several families of binders. Preferably, the polymer binders are made up of amine-terminated polymer resins and/or amine-terminated chain extenders. Acrylic and isocyanate-based elastomers are particularly well suited for use as the coatings with the isocyanate elastomers being preferred. Preferably, a polymer primer, which is impermeable to the oils and other components of the asphalt, is applied between the highly reflective coating layer and the top surface of the top asphalt layer of the asphalt saturated and coated reinforcing substrate to prevent the exuding of oils and other components from the asphalt into the highly reflective coating and to thereby prevent the oils and other components of the asphalt from staining and otherwise discoloring or adversely affecting the highly reflective coating layer. 
   The highly reflective coating may be applied to the top surface of the asphalt saturated and coated reinforcing substrate, typically after the temperature of the asphalt saturated and coated reinforcing substrate has fallen to about 300° F. or less, by a number of techniques including: dip coating, spread coating, roll coating, spray coating and powder coating. The coatings are dried to maintain the cleanliness of the reflective surfaces of the asphalt-based waterproof roofing membranes thus formed and release films or agents are applied to the highly reflective top surfaces of the asphalt-based waterproof roofing membranes prior to winding the membranes into rolls. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic perspective view of a first embodiment of the asphalt-based waterproof roofing membrane of the subject invention. 
       FIG. 2  is a partial schematic cross section taken substantially along lines  2 — 2  of  FIG. 1 , on a larger scale than  FIG. 1 , to illustrate the layers of the asphalt-based waterproof roofing membrane of  FIG. 1  plus the release sheets. 
       FIG. 3  is a schematic perspective view of a second embodiment of the asphalt-based waterproof roofing membrane of the subject invention. 
       FIG. 4  is a partial schematic cross section taken substantially along lines  4 — 4  of  FIG. 3 , on a larger scale than  FIG. 3 , to illustrate the layers of the asphalt-based waterproof roofing membrane of  FIG. 3  plus the release sheets. 
       FIG. 5  is a schematic side view of a production line that may be used to practice the method of the subject invention for prefabricating the asphalt-based waterproof roofing membrane of the subject invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The prefabricated asphalt-based waterproof roofing membrane  10  of the subject invention, shown in  FIGS. 1 and 2 , has a top major surface  12  and a bottom major surface  14  that are each defined by the length and width of the membrane  10 . The prefabricated asphalt-based waterproof roofing membrane  10  has a lateral edge portion  16 , typically called the selvage edge portion of the roofing membrane, that extends for the length of the prefabricated asphalt-based waterproof roofing membrane. The lateral edge portion  16  of prefabricated asphalt-based waterproof roofing membrane  10  is typically about four inches in width and when the prefabricated asphalt-based waterproof roofing membrane  10  is installed on a roof, the top surface of this lateral edge portion  16  is overlapped and sealed to the underside of a lateral edge portion  18  of an adjacent prefabricated asphalt-based waterproof roofing membrane to form a watertight seam. The edge portion  18  has substantially the same width as the lateral edge portion  16  and also extends for the length of the prefabricated asphalt-based waterproof roofing membrane  10 . Thus, when the prefabricated asphalt-based waterproof roofing membrane  10  is installed on a roof, the top surface of the lateral edge portion  16  is covered by the lateral edge portion  18  of the adjacent prefabricated asphalt-based waterproof roofing membrane while the remainder of the top major surface  12  of the prefabricated asphalt-based waterproof roofing membrane  10  is exposed to the weather. The prefabricated asphalt-based waterproof roofing membrane  10  is typically between 36 and 40 inches in width and comes in 1 square (108 square foot) rolls. 
   The prefabricated asphalt-based waterproof roofing membrane  10  includes: a reinforcing substrate  20 ; asphalt with which the reinforcing substrate  20  is saturated and which forms top and bottom layers  22  and  24  encapsulating the reinforcing substrate; and a top coating layer  26  with a highly reflective top surface  28  that is coextensive with or substantially coextensive with the top major surface  12  of the prefabricated asphalt-based waterproof roofing membrane  10 . Preferably, the prefabricated asphalt-based waterproof roofing membrane  10  has a polymer primer layer  30 , which is impermeable to the oils and other components of the asphalt. The impermeable polymer primer layer  30  is located between the highly reflective coating layer  26  and the top surface of the top asphalt layer  22  to prevent the exuding of oils and other components from the asphalt into the highly reflective coating layer  26  and to thereby prevent the oils and other components of the asphalt from staining and otherwise discoloring or adversely affecting the highly reflective top surface  28  of the coating layer  26 . In addition, the prefabricated asphalt-based waterproof roofing membrane  10  normally includes a bottom surface layer  32  formed of conventional mineral surfacing materials, such as but not limited to such as mica, talc, sand, etc., chemical release agents, and/or polymeric film. 
   A release film or sheet  34  may overlie the bottom surface layer  32  of the membrane to keep the bottom major surface  14  of the prefabricated asphalt-based waterproof roofing membrane  10  from adhering to or discoloring the highly reflective coating layer  26  of top major surface  12  of the prefabricated asphalt-based waterproof roofing membrane  10  when the prefabricated asphalt-based waterproof roofing membrane is wound into a roll for packaging, storage, shipment and handling prior to installation. A release film or sheet  36  may overlie the top surface  28  of the highly reflective coating layer  26  and thus the top major surface  12  of the prefabricated asphalt-based waterproof roofing membrane  10  to maintain the cleanliness of the top surface  28  of the highly reflective coating layer  26 . Where a release film or sheet  34  is not used on the bottom major surface of the prefabricated asphalt-based waterproof roofing membrane  10 , the release film or sheet  36  also functions to keep the bottom major surface  14  of the prefabricated asphalt-based waterproof roofing membrane  10  from adhering to or discoloring the top major surface  12  of the prefabricated asphalt-based waterproof roofing membrane  10  when the prefabricated asphalt-based waterproof roofing membrane is wound into a roll for packaging, storage, shipment and handling prior to installation. The surfaces of the release sheets  34  and  36  in contact with the bottom and top major surfaces of the prefabricated asphalt-based waterproof roofing membrane  10  are treated with conventional release agents, e.g. silicone or some other conventional release agent, so that the sheets  34  and  36  may be easily peeled off of the major surfaces of the prefabricated asphalt-based waterproof roofing membrane  10  during installation. 
   The prefabricated asphalt-based waterproof roofing membrane  110  of the subject invention, shown in  FIGS. 3 and 4 , has a top major surface  112  and a bottom major surface  114  that are each defined by the length and width of the membrane  110 . The prefabricated asphalt-based waterproof roofing membrane  110  has a lateral edge portion  116 , typically called the selvage edge portion of the roofing membrane, which extends for the length of the prefabricated asphalt-based waterproof roofing membrane. The lateral edge portion  116  of prefabricated asphalt-based waterproof roofing membrane  110  is typically about four inches in width and when the prefabricated asphalt-based waterproof roofing membrane  110  is installed on a roof, the top surface of this lateral edge portion  116  is overlapped and sealed to the underside of a lateral edge portion  118  of an adjacent prefabricated asphalt-based waterproof roofing membrane to form a watertight seam. The edge portion  118  has substantially the same width as the lateral edge portion  116  and also extends for the length of the prefabricated asphalt-based waterproof roofing membrane  110 . Thus, when the prefabricated asphalt-based waterproof roofing membrane  110  is installed on a roof, the top surface of the lateral edge portion  116  is covered by and sealed to the bottom surface of the lateral edge portion  118  of the adjacent prefabricated asphalt-based waterproof roofing membrane while the remainder of the top major surface  112  of the prefabricated asphalt-based waterproof roofing membrane  110  is exposed to the weather. The prefabricated asphalt-based waterproof roofing membrane  110  is typically between 36 and 40 inches in width and comes in 1 square (108 square foot) rolls. 
   The prefabricated asphalt-based waterproof roofing membrane  110  includes: a reinforcing substrate  120 ; asphalt with which the reinforcing substrate  120  is saturated and which forms top and bottom layers  122  and  124  encapsulating the reinforcing substrate; and a top coating layer  126  with a highly reflective top surface  128  that, except for the lateral edge portion  116  which remains uncoated by the top coating layer  126 , is coextensive with or substantially coextensive with the remainder of top major surface  112  of the prefabricated asphalt-based waterproof roofing membrane  110 . Preferably, the prefabricated asphalt-based waterproof roofing membrane  110  has a polymer primer layer  130 , which is impermeable to the oils and other components of the asphalt. The impermeable polymer primer layer  130  is located between the highly reflective coating layer  126  and the top surface of the top asphalt layer  122  to prevent the exuding of oils and other components from the asphalt into the highly reflective coating layer  126  and to thereby prevent the oils and other components of the asphalt from staining and otherwise discoloring or adversely affecting the highly reflective top surface  128  of the coating layer  126 . In addition, the prefabricated asphalt-based waterproof roofing membrane  110  includes a bottom surface layer  132  formed of conventional mineral surfacing materials, such as but not limited to such as mica, talc, sand, etc., chemical release agents, and/or polymeric film. 
   Preferably, the bottom surface layer  132 , except for the lateral edge portion  118 , which remains uncoated by the bottom surface layer  132 , is coextensive with or substantially coextensive with the remainder of bottom major surface  114  of the prefabricated asphalt-based waterproof roofing membrane  110 . This structure is especially well suited for prefabricated asphalt-based waterproof roofing membranes  110  that are to be used in cold-applied roof installations. With this structure, a SBS (Styrene-Butadiene-Styrene) rubber modified bitumen that is a pressure sensitive adhesive may be used to form the top and bottom asphalt layers  122  and  124  to thereby enable the overlapping lateral edge portions  116  and  118  of adjacent prefabricated asphalt-based waterproof membranes  110  to be bonded together with a watertight weather secure seal. Preferably, a release film or sheet  134  overlies the bottom surface layer  132  and lateral edge portion  118  of the bottom major surface of the membrane to keep the bottom major surface  114  of the prefabricated asphalt-based waterproof roofing membrane  110  from adhering to or discoloring the highly reflective coating layer  126  of top major surface  112  of the prefabricated asphalt-based waterproof roofing membrane  110  when the prefabricated asphalt-based waterproof roofing membrane is wound into a roll for packaging, storage, shipment and handling prior to installation. Preferably, a release film or sheet  136  overlies the top surface  128  of the highly reflective coating layer  126  and the lateral edge portion  116  of the top major surface  112  of the prefabricated asphalt-based waterproof roofing membrane  110  to maintain the cleanliness of the top surface  128  of the highly reflective coating layer  126  and keep the lateral edge portion  116  from adhering to the bottom major surface  114  of the membrane when the prefabricated asphalt-based waterproof roofing membrane is wound into a roll for packaging, storage, shipment and handling prior to installation. Where a release film or sheet  134  is not used on the bottom major surface of the prefabricated asphalt-based waterproof roofing membrane  110 , the release film or sheet  136  functions to keep the bottom major surface  114  of the prefabricated asphalt-based waterproof roofing membrane  110  from adhering to or discoloring the top major surface  112  of the prefabricated asphalt-based waterproof roofing membrane  110  when the prefabricated asphalt-based waterproof roofing membrane is wound into a roll for packaging, storage, shipment and handling prior to installation. The surfaces of the release sheets  134  and  136  in contact with the bottom and top major surfaces of the prefabricated asphalt-based waterproof roofing membrane  110  are treated with conventional release agents, e.g. silicone or some other conventional release agent, so that the sheets  134  and  136  may be easily peeled off of the major surfaces of the prefabricated asphalt-based waterproof roofing membrane  110  for installation on a roof. 
   While the prefabricated asphalt-based waterproof roofing membranes  10  and  110  may include a layer of top surfacing materials, such as granules, mica, talc, etc. intermediate the top surfaces of the top asphalt layers  22  and  122  and the highly reflective coating layers  26  and  126  or on the highly reflective coating layers  26  and  126 , the preferred embodiments of the prefabricated asphalt-based waterproof roofing membranes  10  and  110  do not include any such layer of traditional top surfacing materials. The presence of such a layer of traditional top surfacing materials could adversely affect the adhesion between the highly reflective coating layers  26  and  126  and the top asphalt layers  22  and  122  and/or could reduce the reflectivity of the top surfaces  28  and  128  of the highly reflective coatings  26  and  126 . 
   The reinforcing substrates  20  and  120  of the prefabricated asphalt-based waterproof roofing membranes  10  and  110  may be any of the conventional reinforcing substrates commonly used in asphalt-based waterproof roofing membranes to provide the membranes with the necessary strength and flexibility, such as, but not limited to: a non-woven fiberglass mat, a reinforced fiberglass mat, a non-woven polyester mat, a reinforced polyester mat, a veiled scrim of various fiber combinations, or a laminated composite of two or more of the preceding reinforcing substrates. 
   The compositions of the asphalt saturating the reinforcing substrates  20  and  120  and forming the top and bottom layers  22 ,  24  and  122 ,  124  on the reinforcing substrates  20  and  120  may be any of the asphalt compositions discussed above and/or commonly used in asphalt-based waterproof roofing membranes. These asphalt compositions may include fire retardant chemicals, and typically, range from mineral filled oxidized asphalts to polymer-modified asphalts that are modified with modifiers, such as thermoplastics [Amorphous Polypropylene (APP)], rubbers [Styrene-Butadiene-Styrene (SBS)], and other polymers, antioxidants, resins, oils, etc. The polymer-modified asphalts may also include mineral fillers. 
   The highly reflective coating layers  26  and  126  are composed of a polymer binder material or materials and a reflective pigment or pigments, preferably a white pigment, such as but not limited to titanium dioxide, zinc oxide, aluminum oxide, other mineral pigments, or a combination of these pigments in quantities sufficient to make the coating layers  26  and  126  both opaque to solar radiation and highly reflective. The pigments in the highly reflective coating layers  26  and  126  protect: the impermeable polymer primer layers  30  and  130  (when used); the polymer binder materials of the coating layers  26  and  126 ; and the underlying asphalt layers  22  and  122  of the asphalt saturated and coated reinforcing substrate  20  and  120  from the deleterious effects of ultraviolet radiation. The highly reflective coating layer  26  and  126  may also include additional additives that: aid in limiting the growth of fungi during service; improve fire resistance; enhance heat, light and impact stability; improve the application and flow characteristics of the coating (slip agents, surfactants, thickeners, viscosity depressants, etc.); and reduce the aging rate, discoloration, and dirt adherence of the coating during service. While the highest reflectance values require the highly reflective coating layers  26  and  126  to have smooth top surfaces  28  and  128 , it may be feasible to emboss the top surfaces  28  and  128  of the highly reflective coating layers  26  and  126  to enhance the appearance of the top major surfaces  12  and  112  of the prefabricated asphalt-based waterproof roofing membranes  10  and  110  and make the top major surfaces  12  and  112  of the prefabricated asphalt-based waterproof roofing membranes  10  and  110  more slip resistant. 
   There are several families of polymer binders that are well suited for use as the polymer binder materials in the highly reflective coating layers  26  and  126  to carry the highly reflective pigments of the highly reflective coating layers  26  and  126  and bind the highly reflective pigments of the highly reflective coating layers  26  and  126  to the top asphalt layers  22  and  122  or the impermeable polymer primer layers  30  and  130  (when used). Acrylic and isocyanate-based elastomers are particularly well suited for use as the polymer binder materials in the highly reflective coating layers  26  and  126 . Due to their fast curing times; their durability when subjected to weathering forces, chemical contaminants, and solar radiation while in service on rooftops; their low glass transition temperatures (the property of remaining flexible at low temperatures); their low or nonexistent volatile organic compound emissions (voc emissions) during application; and their ability to be reapplied at the job site should the highly reflective top surfaces  28  and  128  of the membrane be damaged; isocyanate elastomers are currently preferred. 
   The currently preferred isocyanate elastomers are formed by reacting polyisocyantes with polyester or polyester resins (urethanes) or with polyamines (polyurea). Due to their extremely fast reaction kinetics and cure and their durability, polyurea elastomers are most preferred. Polyurea elastomers may be derived from condensing an isocyanate component and a resin blend component. The isocyanate component may be aromatic or aliphatic in nature and may be a monomer, polymer, or any variant reaction of isocyanates, quasi-prepolymer, or a prepolymer. The prepolymer, quasi-prepolymer may be made of an amine-terminated polymer resin, or a hydroxyl-terminated polymer resin. However, the aliphatic variant is most preferred because the aliphatic variant exhibits the best resistance to yellowing (it does not yellow) with exposure to ultraviolet radiation. Preferably, the resin blend is made up of amine-terminated polymer resins and/or amine-terminated chain extenders. The amine-terminated polymer resins in the preferred blend will not have any intentional hydroxyl moieties. Any hydroxyls are a result of an incomplete conversion to the amine-terminated polymer resins. The preferred resin blend may also contain additives or non-primary components. These additives may contain hydroxyls, such as pre-dispersed pigments in a polyol carrier. Normally, the resin blend will not contain a catalyst. Polyurea coatings may also be comprised of aspartic esters, which provide amine functionality. 
   In the application of the highly reflective coating layers  26  and  126  to the top asphalt layers  22  and  122  of the membranes  10  and  110 , incompatibility between the acrylic or isocyanate elastomers of the coating layers  26  and  126  and the asphalt (e.g. oxidized or polymer modified asphalt) of the asphalt layers  22  and  122  is a primary concern. This interaction can result in the exudation of oils and other colored components out of the asphalt into the pores or structure of the highly reflective coating layers  26  and  126 . The exudation of such oils and other colored components into the highly reflective coating layers  26  and  126  can cause permanent staining and discoloration of the highly reflective top surfaces  28  and  128  of the coating layers  26  and  126 . In addition, the exudation of such oils into the elastomers of the coating layers  26  and  126  may also exacerbate the aging rate of or otherwise adversely affect the coating layers. To prevent any significant exudation of oils and other colored components from the asphalt layers  22  and  122  into the coating layers  26  and  126 , the polymer primer layers  30  and  130  that are impermeable or substantially impermeable to the oils and other colored components of the asphalt in the asphalt layers  22  and  122  may be located intermediate the top surface of the asphalt layers  22  and  122  and the bottom surfaces of the highly reflective coating layers  26  and  126 . Suitable polymer primers for the layers  30  and  130  include those containing polyvinyl acetate, polyvinylidene chloride, cured polyacrylonitrile, cellulose polymers, and others such as disclosed in U.S. Pat. No. 4,442,148, issued Apr. 10, 1984. The disclosure of U.S. Pat. No. 4,442,148, is hereby incorporated herein in its entirety by reference. Other polymer primers than those set forth above that will block or substantially block the exudation of oils and other colored components from the asphalt may also be used. 
   The reflectance of the top major surfaces  12  and  112  of the prefabricated asphalt-based waterproof roofing membranes  10  and  110  formed by the top highly reflective surfaces  28  and  128  of the top coating layers  26  and  126 , as measured by ASTM standard E 903—Standard Test Method for Solar Absorptance, Reflectance, and Transmission of Materials Using Integrating Spheres, will meet current EPA Energy Star reflective requirements for low-slope roof products. The current EPA Energy Star reflectance requirements are an Initial Solar Reflectance greater than or equal to 0.65 and a Maintenance of Solar Reflectance greater or equal to 0.50 three years after installation under normal conditions. The current test criteria for determining the Initial Solar Reflectance requires the testing of a 3 inch by 3 inch sample of the product in accordance with ASTM E 903 (values for solar absorptance and transmission need not be obtained) using a black background. The current test criteria for determining the Maintenance of Solar Reflectance three years after installation under normal conditions may use any of three test methods set forth in the current EPA Energy Star guidelines including the following test method. A minimum of three (3) samples from three existing roofs on which the product has been installed for a minimum of three years with one of the existing roofs being located within a major metropolitan area such as Atlanta, Boston, Chicago, Dallas, Houston, Los Angles, Miami, Minneapolis, New York, Philadelphia, San Francisco, St. Louis, Washington D. C., etc. At least three (3) measurements of solar reflectance are to be taken from different areas on each sample in accordance with ASTM E 903. The average of all solar reflectance values obtained from the samples will be used to determine the solar reflectance of the weathered roof product. ASTM standard E 903 test method measures solar reflectance by using spectrophotometers that are equipped with integrating spheres. The test method is set forth in the ASTM test Designation E 903-96, approved Apr. 10, 1996 and published May 1996. ASTM test Designation E 903-96 is hereby incorporated herein by reference in its entirety. 
     FIG. 5  schematically illustrates a typical manufacturing line  220  that could be used for making the prefabricated asphalt-based waterproof roofing membranes  10  and  110 . As shown in  FIG. 5 , in the manufacturing process of the subject invention, the reinforcing substrate  20  or  120  may be passed through a standard saturator/coater unit  222  or a standard saturator unit and a standard coater unit (not shown) where the reinforcing substrate  20  or  120  is saturated and coated with asphalt  224  at temperatures typically between 300 to 425° F. The saturator/coater unit  222  of  FIG. 5  includes a tank  226  that contains the asphalt  224  and squeeze rollers  228 . The asphalt  224  may be any of the asphalt compositions discussed above and/or commonly used in the industry to make asphalt-based waterproof roofing membranes and typically contains asphalt and mineral fillers and may contain modifiers, such as thermoplastics [Amorphous Polypropylene (APP)], rubbers [Styrene-Butadiene-Styrene (SBS)], and other polymers, antioxidants, resins, oils, etc. Where the saturator and coater units are separate, the asphalts used in the saturator unit to saturate the reinforcing substrate  20  or  120  and in the coater unit to coat the reinforcing substrate  20  or  120  and build up the thickness of the saturated and coated reinforcing substrate  20  or  120  may have the same composition or different compositions. 
   As shown in  FIG. 5 , the reinforcing substrate  20  or  120  is saturated and coated with the asphalt  224  by passing the reinforcing substrate  20  or  120  through a pool of asphalt  224  in the tank  226 . The thicknesses of the top and bottom asphalt layers  22 ,  24  or  122 , 124  of the asphalt saturated and coated reinforcing substrate  20  or  120  and the overall thickness of the asphalt saturated and coated reinforcing substrate  20  or  120  are then set by passing the saturated and coated reinforcing substrate between the spaced apart squeeze rollers  228 . The spaced apart squeeze rollers  228  distribute the asphalt  224  evenly throughout the reinforcing substrate and over the top and bottom surfaces of the reinforcing substrate to form the built up layers of asphalt  22 ,  24  or  122 ,  124  on the top and bottom surfaces of the reinforcing substrate  20  or  120 . 
   In the preferred method of the subject invention, a polymer primer layer  30  or  130  that is impermeable or substantially impermeable to the oils and other colored components of the asphalt  224  is then applied to the top surface of the top asphalt layer  22  or  122 . The polymer primer material  230  that forms the polymer primer layer  30  or  130  would typically be applied to the top surface of the top asphalt layer  22  or  122  after the top asphalt layer  22  or  122  has been cooled to a temperature below 300° F. To form the polymer primer layer  30  of the roofing membrane  10 , the polymer primer material  230  would be applied (e.g. poured or sprayed) across the entire width of the top surface of the top asphalt layer  22  by an applicator  232 . To form the polymer primer layer  130  of the roofing membrane  110 , the polymer primer material  230  would not be applied to the lateral edge portion  116 , but would be applied (e.g. poured or sprayed) across the remaining width of the top surface of the top asphalt layer  122  by an applicator  232  with a barrier preventing the primer material from flowing onto the lateral edge portion  116 . The pool of polymer primer material  230  thus formed then passes beneath a doctor blade  234  that smoothes the top surface of the polymer primer material and forms the pool of polymer primer material into the polymer primer layer  30  or  130 . The polymer primer layer  30 , 130  is then typically air dried or cured prior to applying the pigment filled polymer binder material  236  that is formed into the highly reflective coating layer  26 ,  126 . While the technique shown for applying the polymer primer material  230  to the top surface of the top asphalt layer  22  or  122  is a spread coating technique, it is contemplated that the polymer primer material  230  could be applied to the top surface of the top asphalt layer  22  or  122  by other techniques commonly used in the industry, such as but not limited to, dip coating, roll coating, spray coating, and powder coating techniques. 
   Where the polymer primer material  230  is utilized to provide the membrane  10 ,  110  with the polymer primer layer  30  or  130 , after the polymer primer layer  30  or  130  is dried, the pigment filled polymer binder material  236  that is formed into the highly reflective coating layer  26  or  126  may be poured or sprayed in liquid form onto the top surface the polymer primer layer  30  or  130  by an applicator  238 . Where the polymer primer material  230  is not utilized to form the polymer primer layer  30  between the asphalt layer  22  and the highly reflective coating layer  26  of the roofing membrane  10 , the pigment filled polymer binder material  236  that is formed into the highly reflective coating layer  26  could be poured or sprayed in liquid form across the entire width of and directly onto the top surface of the top asphalt layer  22  by the applicator  238 . Where the polymer primer material  230  is not utilized to form the polymer primer layer  130  between the asphalt layer  122  and the highly reflective coating layer  126  of the roofing membrane  110 , the pigment filled polymer binder material  236  that is formed into the highly reflective coating layer  126  would not be poured or sprayed onto the lateral edge portion  116 , but would be poured or sprayed in liquid form across the remaining width of and directly onto the top surface of the top asphalt layer  122  by the applicator  238  with a barrier preventing the pigment filled polymer binder material from flowing onto the lateral edge portion  116 . The pool of pigment filled polymer binder material  236  thus formed then passes beneath a doctor blade  240  that smoothes the top surface of the pigment filled polymer binder material  236  and forms the pool of pigment filled polymer binder material  236  into the highly reflective coating layer  26  or  126 . The highly reflective coating layer  26  or  126  is formed by the doctor blade  240  to a desired thickness and smoothness that is sufficient to provide the highly reflective coating layer  26 or  126  and the prefabricated asphalt-based waterproof roofing membrane  10  or  110  with the necessary reflectance. 
   While the technique shown for applying the pigment filled polymer binder material  236  to the top surface of the polymer primer layer  30  or  130  or the top surface of the top asphalt layer  22  or  122  is a spread coating technique, it is contemplated that the pigment filled polymer binder material  236  could be applied to the top surface of the polymer primer layer  30 ,  130  or the top surface of the top asphalt layer  22 ,  122  by other techniques commonly used in the industry, such as but not limited to, dip coating, roll coating, spray coating, and powder coating techniques. Where the pigment filled polymer binder material  236  is in powder form, preferably, the pigment filled polymer binder material  236  is heated by a heater (not shown) to melt the powder or the surface temperature of the polymer primer layer  30 ,  130  or the top asphalt layer  22 ,  122  is hot enough to melt the pigment filled polymer binder material  236  to form a pool of the pigment filled polymer binder material  236 . 
   With the highly reflective coating layer  26  or  126  applied to the top surface of the asphalt layer  22  or  122  or the top surface of the polymer primer layer  30  or  130 , the laminate  242  thus formed by the asphalt saturated and coated reinforcing substrate  20  or  120  with the highly reflective coating layer  26  or  126  or the polymer primer layer  30  or  130  and the highly reflective coating layer  26  or  126  may be passed around a first press drum  244 . As the laminate  242  passes around the first turnover press drum  244 , the layers  22 ,  26  or  22 ,  30 ,  26  of the roofing membrane  10  or the layers  122 ,  126  or  122 ,  130 ,  126  of the roofing membrane  110  are pressed together to assure good adhesion between the layers. As or after the laminate  242  passes over the first press drum  244 , the laminate is flipped (represented schematically by  245  in  FIG. 5 ) so that the bottom surface of the bottom asphalt layer  24  or  124  of the laminate is facing upward. This permits the application of surfacing materials (such as sand, other minerals (e.g. mica, talc, etc.), chemical release agents, and/or polymeric films) to the bottom surface of the laminate  242 . 
   In  FIG. 5 , bottom surfacing material(s)  246  that form the bottom surface layer  32  or  132  of the roofing membrane  10  or  110  are shown being poured or sprayed onto the bottom surface of the bottom asphalt layer  24  or  124  by an applicator  248 . To form the bottom surface layer  32  of the roofing membrane  10 , the surfacing materials  246  would be poured, sprayed or otherwise applied across the entire width of the bottom surface of the bottom asphalt layer  24  by an applicator  248 . To form the bottom surface layer  132  of the roofing membrane  110 , the surfacing materials  246  would not be poured, sprayed or applied onto the lateral edge portion  118 , but would be poured, sprayed or otherwise applied across the remaining width of the bottom surface of the bottom asphalt layer  124  by an applicator  248  with a barrier preventing the surfacing materials from flowing onto the lateral edge portion  118 . The layer of surfacing material(s) thus formed then passes beneath a doctor blade  250  that smoothes the normally bottom surface of the surfacing material(s) and forms the layer of surfacing material(s) into a bottom surface layer  32  or  132  having a desired thickness and smoothness. 
   The laminate  252  thus formed is then passed around a second press drum  254  where the surfacing materials  246  applied to the normally bottom surface of the asphalt layer  24  or  124  of the laminate  252  are pressed into the bottom surface of the asphalt layer  24  or  124  to assure good adhesion between the surfacing material(s)  246  and the asphalt layer  24  or  124 . After the laminate  252  passes over the second turnover press drum  254 , the laminate  252  is then flipped (represented schematically by  255  in  FIG. 5 ) and returned to its normal orientation. 
   After the application of the top layers  22 ,  26  and the bottom layers  24 ,  32  or the top layers  22 ,  30 ,  26  and bottom layers  24 ,  32  to the top and bottom surfaces of the asphalt saturated and coated reinforcing substrate  20  or the application of the top layers  122 ,  126  and the bottom layers  124 ,  132  or the top layers  122 ,  130 ,  126  and bottom layers  124 ,  132  to the top and bottom surfaces of the asphalt saturated and coated reinforcing substrate  120 , the laminate  252  formed is rapidly cooled by water-cooled rolls and/or water sprays. The laminate  252  is then passed through a drying section where the composite is air dried/cured to solidify the highly reflective top coating layer  26  or  126  and the bottom layer  32  or  132  and complete the manufacture of the prefabricated asphalt-based waterproof roofing membrane  10  or  110 . A bottom release sheet  34  or  134  is applied to the bottom surface layer  32  or  132  and a top release sheet  36  or  136  is applied to the top surface of the highly reflective coating layer  26  or  126  of the prefabricated asphalt-based waterproof roofing membrane  10  or  110  from rolls  256  and  258 . 
   The prefabricated asphalt-based waterproof roofing membrane  10  or  110  is then fed through a looper or accumulator section  260  to permit the continuous movement of the prefabricated asphalt-based waterproof roofing membrane  10  or  110  during the cutting and winding operation. In the cutting and winding operation, the prefabricated asphalt-based waterproof roofing membrane  10  or  110  is periodically cut to a desired length or lengths by a cutting unit  262  and wound into rolls  264  for packaging, storage, and shipment to a job site. 
   Preferably, additional surfacing materials are not applied to the top surface of the highly reflective coating layer  26  or  126 . However, after the highly reflective top layer  26  or  126  is applied to the top asphalt layer  22  or  122  or the polymer primer layer  30  or  130  and prior to passing the asphalt saturated and coated reinforcing substrate  20  or  120  over the first press drum  244 , surfacing materials (such as roofing granules, sand, other minerals (e.g. mica, talc, etc.), chemical release agents, and/or release films) may be applied to the top surface  28  or  128  of the highly reflective coating layer  26  or  126 . While it is preferred to prefabricate the prefabricated asphalt-based waterproof roofing membrane  10  or  110  in line, as described above, it is contemplated that the application of the highly reflective coating layer  26  or  126  could be effected on a separate process line. However, this would appear to be relatively impractical in that it would add to the number of process steps and the costs of manufacture. 
   In describing the invention, certain embodiments have been used to illustrate the invention and the practices thereof. However, the invention is not limited to these specific embodiments as other embodiments and modifications within the spirit of the invention will readily occur to those skilled in the art on reading this specification. Thus, the invention is not intended to be limited to the specific embodiments disclosed, but is to be limited only by the claims appended hereto.