Abstract:
A roofing shingle is a composite sheet which includes a roofing substrate having a front side and a back side. An asphalt material impregnates the substrate and coats at least the front side of the substrate. A polymer film is attached to the back side of the substrate and forms a back surface of the roofing shingle. The polymer film was applied to the substrate in the form of a film. The roofing shingle does not include backdust on the back surface. The composite sheet is formed into the size and shape of the roofing shingle. A method of manufacturing roofing shingles includes continuously supplying a roofing substrate having a front side and a back side. An asphalt material is applied to the substrate so that it impregnates the substrate and coats at least the front side of the substrate. A composite sheet is produced by providing a polymer film and attaching the polymer film to the back side of the substrate in a manner that avoids applying backdust to the substrate so that the polymer film forms a back surface of the composite sheet. The composite sheet is cut into roofing shingles while maintaining the back surface free of backdust.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to building construction materials and more particularly to asphalt roofing shingles. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a typical roofing shingle manufacturing process, a continuous roofing substrate, such as a glass fiber mat or an organic felt, is passed into contact with a coater where it is impregnated and coated with a molten asphalt material. Roofing granules are applied on the front surface of the coated substrate. The coated substrate is cooled and then cut into individual shingles. 
         [0003]    Typically a fine particulate material known as a “backdust” is applied on the back surface of the coated substrate. The backdust prevents the roofing shingles from sticking together when they are stacked in a bundle. Some examples of particulate materials that have been used include sand, talc and other crushed rocks or minerals. 
         [0004]    U.S. Patent Application Publication No. 2007/0218250 A1 assigned to Elk Premium Building Products, published Sep. 20, 2007, discloses roofing shingles that are made without a backdust material. The roofing shingles include a substrate, an asphalt material coating the front side of the substrate, and roofing granules disposed on the asphalt material coated on the substrate. The shingles also include a hot melt material, applied to the back side of the substrate, which replaces the backdust material. 
       SUMMARY OF THE INVENTION 
       [0005]    A roofing shingle is a composite sheet which includes a roofing substrate having a front side and a back side. An asphalt material impregnates the substrate and coats at least the front side of the substrate. A polymer film is attached to the back side of the substrate and forms a back surface of the roofing shingle. The polymer film is applied to the substrate in the form of a film. The roofing shingle does not include backdust on the back surface. The composite sheet is formed into the size and shape of the roofing shingle. 
         [0006]    A method of manufacturing roofing shingles includes continuously supplying a roofing substrate having a front side and a back side. An asphalt material is applied to the substrate so that it impregnates the substrate and coats at least the front side of the substrate. A composite sheet is produced by providing a polymer film and attaching the polymer film to the back side of the substrate in a manner that avoids applying backdust to the substrate so that the polymer film forms a back surface of the composite sheet. The composite sheet is cut into roofing shingles while maintaining the back surface free of backdust. 
         [0007]    Various additional aspects of the roofing shingles and their manufacture will become apparent to those skilled in the art from the following detailed description and the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic elevational view, partially in cross section, of a portion of an apparatus for making roofing shingles according to the invention. 
           [0009]      FIG. 2  is a schematic plan view of a portion of an asphalt-coated sheet, showing a roofing shingle made according to the invention. 
           [0010]      FIG. 3  is an enlarged schematic cross-sectional elevational view of a first embodiment of a roofing shingle according to the invention. 
           [0011]      FIG. 4  is an enlarged schematic cross-sectional elevational view of a second embodiment of a roofing shingle according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    The present invention relates to roofing shingles in which a polymer film is attached to the back side of the shingles as a replacement for the backdust typically used on shingles. The roofing shingles will be described in more detail below, after a description of an example of a method of making the shingles. 
         [0013]    Referring now to the drawings, there is shown in  FIG. 1  an apparatus  10  for manufacturing asphalt-based roofing shingles according to the invention. The illustrated manufacturing process involves passing a continuous sheet in a machine direction (indicated by an arrow  12 ) through a series of manufacturing operations. The sheet usually moves at a speed from about 300 feet/minute to about 800 feet/minute, but other speeds can be used. 
         [0014]    In a first step of the manufacturing process, a continuous sheet of shingle mat  14  is payed out from a roll (not shown). The shingle mat  14  can be any type of substrate suitable for use in reinforcing asphalt-based roofing shingles, such as a web, scrim or felt of synthetic or natural fibrous materials. The fibrous materials may include, for example, glass fibers, other mineral fibers, polymer fibers, carbon fibers, cellulose fibers, rag fibers, or mixtures of these fibers. Suitable mineral fibers may include fibers of a heat-softenable mineral material, such as glass, ceramic, rock, slag, or basalt. In one embodiment, the shingle mat is a nonwoven web of glass fibers. 
         [0015]    The shingle mat  14  is fed, in machine direction  12 , through a coater  16  where a coating of asphalt material  18  is applied to the shingle mat  14 . The asphalt material  18  can include any materials suitable for coating asphalt-based roofing shingles. The asphalt material  18  includes asphalt, by which is meant any type of bituminous material suitable for coating roofing shingles, such as asphalt, tar or pitch, or any compatible mixture of different materials. The asphalt material usually includes at least about 20% asphalt by weight, and often at least about 40%. The asphalt material can also include various additives and/or modifiers, such as inorganic fillers or mineral stabilizers. In a typical asphalt roofing shingle, the coating material includes asphalt and a filler of finely ground inorganic particulate matter, such as ground limestone, dolomite or silica, in an amount of from about 40% to about 80% by weight of the asphalt material. The asphalt material can also be modified with any suitable polymeric material, which can be virgin polymers or recycled polymers, to make a polymer modified asphalt. The asphalt material can also be treated in any suitable manner with any suitable materials, such as ferric chloride treated or phosphoric acid treated. The asphalt material can have any suitable physical properties. In one embodiment, the asphalt material has a softening point in a range from about 190° F. to about 300° F., but in other embodiments the softening point can be higher or lower. 
         [0016]    The asphalt coating  18  can be applied in any suitable manner. In the illustrated embodiment, the shingle mat  14  contacts a supply of hot, melted asphalt material  18  from a coater  16  to coat the shingle mat  14  with a tacky coating of asphalt material  18 . However, in other embodiments, the asphalt coating  18  could be sprayed on, rolled on, or applied to the shingle mat  14  by other means. For example, the asphalt coating could be formed into an emulsion or a cutback and be cold applied. The asphalt material impregnates the shingle mat and coats at least the front side of the mat. The “front side” is the side of the mat facing away from the roof when the roofing shingle is installed on a roof, and the “back side” is the side of the mat facing toward the roof. 
         [0017]    In one embodiment, the asphalt material impregnates the shingle mat and coats the front side of the mat, but it does not coat the back side of the mat. In another embodiment, the asphalt material impregnates the shingle mat and coats both the front and back sides of the mat. The coating apparatus can include any suitable equipment to control the amount of coating on the back side of the mat. For example, the equipment can include a scraper (not shown) or similar apparatus, and/or one or more rolls (not shown), to remove coating from the back side of the mat in a controlled manner. The structure of the roofing mat, including the coating, is further described below. 
         [0018]    The shingle mat  14  exits the coater  16  as an asphalt-coated sheet  20 . The asphalt coating  18  on the asphalt-coated sheet  20  remains hot. 
         [0019]    The asphalt-coated sheet  20  is shown in more detail in  FIG. 2 . As shown, the asphalt-coated sheet  20  for the three-wide apparatus  10  comprises six distinct regions or lanes including three headlap lanes h 1 , h 2 , and h 3 , and three prime lanes p 1 , p 2 , and p 3 . An exemplary roofing shingle is shown by a phantom line  22  and may be cut from asphalt-coated sheet  20  as shown. In this manner, three roofing shingles of any length desired may be cut from each such section of asphalt-coated sheet  20 . Each shingle  22  would contain one headlap lane h 1 , h 2 , or h 3 , and one respective adjacent prime lane p 1 , p 2 , or p 3 . Accordingly, the shingle  22  includes a headlap region  26  and a prime region  24 . 
         [0020]    The headlap region  26  of the shingle  22  is that portion which is covered by adjacent shingles when the shingle  22  is ultimately installed upon a roof. The prime region  24  of the shingle  22  is that portion which remains exposed when the shingle  22  is ultimately installed upon a roof. 
         [0021]    In this embodiment, the shingle  22  is cut from the asphalt-coated sheet  20  to be three feet long by one foot wide. As further shown in  FIG. 2 , the shingle  22  includes two cut-out regions  28  which define three tabs  30 . It will be apparent to one skilled in the art that the asphalt-coated sheet  20  may be manufactured having a wide variety of widths to allow different numbers of shingles to be cut therefrom. For example, some roofing shingle manufacturing plants use an asphalt-coated sheet (not shown) which is sufficiently wide to allow four, one foot wide shingles to be cut therefrom. Such a wider asphalt-coated sheet would include an additional headlap region, and an additional prime region. Other manufacturing plants use an asphalt-coated sheet (not shown) which is sufficiently wide to allow six, one foot wide shingles to be cut therefrom. One skilled in the art will also recognize that roofing shingles of different sizes, i.e. roofing shingles having different lengths and/or widths, may be cut from the asphalt-coated sheet  20 . Instead of three-tab roofing shingles as shown in  FIG. 2 , alternatively the shingle manufacturing apparatus can be set up for manufacturing laminated roofing shingles (not shown) or any other types of asphalt-based shingles. The manufacture of laminated shingles typically includes adhering the backs of one section of asphalt-coated sheet to the tops of another section. 
         [0022]    As further illustrated in  FIG. 1 , a polymer film  72  is fed from a roll  74  onto the back side  21  of the asphalt-coated sheet  20  after it exits the coater  16 . Another roll  75  presses the film against the sheet. The hot asphalt coating  18  on the sheet can help the film to adhere to the sheet. The polymer film  72  is described in more detail below. Although the embodiment shown in  FIG. 1  illustrates one example of a method of applying the polymer film to the back side of the sheet, it should be recognized that the polymer film can be applied by any suitable method. Also, the polymer film can be applied at any suitable location during the manufacturing process. For example, it could be applied after the roofing granules are applied as described below. 
         [0023]    As further illustrated in  FIG. 1 , the asphalt-coated sheet  20  is passed beneath a series of granule applicators  56  and  58  for applying prime and headlap granules onto the coated sheet. The granule applicators can be of any type of applicator, blender or dispenser suitable for applying granules onto the coated sheet, such as for example a fluted roll applicator, gravity feed applicator or an auger-type dispenser. An example of a granule applicator,  56  and  58 , is a granule applicator of the type disclosed in U.S. Pat. No. 5,599,581 to Burton et al., which is hereby incorporated by reference, in its entirety. Additionally, a granule valve such as the granule valve disclosed in U.S. Pat. No. 6,610,147 to Aschenbeck may also be used. U.S. Pat. No. 6,610,147 to Aschenbeck is also incorporated by reference in its entirety. In the embodiment shown, the prime granule applicator  56  is fed from a prime granule hopper  60  via a prime granule hose  60   a.  The headlap applicator  58  can be fed by similar apparatus (not shown). 
         [0024]    Although two granule applicators  56  and  58  are shown in the embodiment illustrated in  FIG. 1 , any suitable number and configuration of granule applicators can be used. For example, a series of two prime granule applicators can be used, wherein the granule applicator  56  can be used to apply prime granules  57  onto the prime lanes p 1 , p 2  and p 3  as shown in  FIG. 2 . Similarly, the granule applicator  58  can be used to apply headlap granules  59  on the headlap lanes h 1 , h 2  and h 3  as shown in  FIG. 2 . Applying prime granules  57  and headlap granules to the coated sheet  20  defines a granule-covered sheet  62 . In another embodiment (not shown), additional granule applicators can be used for additional granule drops, such as different colors, sharp demarcations and background granules. 
         [0025]    As shown in  FIG. 1 , after all the granules are deposited on the asphalt-coated sheet  20 , the granule-covered sheet  62  is turned around a slate drum  64  to press the prime granules  57  and headlap granules  59  into the asphalt coating  18 . The slate drum  64  temporarily inverts the granule-covered sheet  62  so that the excess and non-adhering granules fall off. The excess granules fall into a backfall container  70  and are recovered for later use. The granule covered sheet is turned around a drum  78 . The granule-covered sheet  62  is passed between a pair of press rolls  80 ,  82  that further press the prime granules  57  and headlap granules  59  into the granule-covered sheet  62 . 
         [0026]    As further shown in  FIG. 1 , downstream from the press rolls,  80  and  82 , the granule covered-sheet  62  is passed through a cooling section  84 . The cooling section  84  is configured to sufficiently cool the granule-covered sheet  62  to allow downstream manufacturing operations. In one embodiment, the cooling section  84  includes rollers allowing the granule-covered sheet  62  to be passed up and down while being sprayed with water to cool the hot asphalt coating  18 . In another embodiment, any means of cooling the granule-covered sheet  62  can be used. A laminated roofing shingle has additional process steps. 
         [0027]    Downstream from the cooling section  84 , the granule-covered sheet  62  is subsequently fed through a cutter  86  that cuts the granule-covered sheet  62  into individual shingles  22 . The cutter  86  may be any type of cutter, such as for example a rotary cutter, sufficient to cut the granule-covered sheet  62  into individual shingles  22 . 
         [0028]      FIG. 3  shows a cross-section, taken through the prime region, of a first embodiment of a roofing shingle  22  according to the invention. The roofing shingle  22  includes a roofing mat  14  or substrate. The roofing mat  14  has a front side  14   f  and a back side  14   b.  An asphalt material  18  impregnates the roofing mat  14  and coats the front side  14   f  of the mat. In the embodiment shown in  FIG. 3 , the asphalt material  18  does not coat the back side  14   b  of the mat. However,  FIG. 4  (described below) shows an embodiment in which the asphalt material coats both the front side and the back side of the mat. Prime granules  57  are embedded in the front surface of the asphalt material  18 . 
         [0029]    A polymer film  72  is attached to the back side of the roofing mat and forms a back surface of the roofing shingle  22 . The polymer film replaces the backdust typically included on roofing shingles. The polymer film can be made from any suitable material(s), and it can have any suitable structure and properties. By “film” is meant a substantially continuous sheet of polymer, in contrast to discontinuous structures such as woven or nonwoven sheets or webs. 
         [0030]    The polymer film  72  can be attached to the back side of the roofing mat by any suitable method. For example, the surface of the film can be heated (not shown) to make it soft so that it adheres to the mat during production of the shingle. Alternatively, the polymer film can be a self-adhering film similar to Scotch brand adhesive tape. Alternatively, any suitable adhesive (not shown) can be used for adhering the polymer film to the roofing mat during production of the shingle. 
         [0031]    The polymer film can be produced from any suitable polymer or any suitable blend of different polymers. Some examples of polymers that may be used to produce the polymer film include polyolefins such as polypropylene and polyethylene; or polyesters such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate. Either low density or high density polyolefins could be used. In some embodiments, a polymer such as a polyamide, for example nylon, can be blended with the polyolefin or polyester to control the melt temperature or other properties of the film. Also, in some embodiments, the polymer excludes materials such as polyvinyl chloride, polycarbonate, ionomer resin and polyvinylidene chloride. In contrast to the roofing shingles disclosed in U.S. 2007/0218250 A1, the film is not a hot melt material. 
         [0032]    The polymer film can include conventional additives such as antioxidants, delusterants, pigments, fillers such as silica, calcium carbonate, kaolin, titanium dioxide, antistatic agents and the like, or mixtures thereof. 
         [0033]    The polymer film can be produced by any suitable method, such as any of those known in the art. In one method of making a relatively high strength polymer film, the polymer is melted and extruded as an amorphous sheet onto a revolving casting drum to form a cast sheet of the polymer. The sheet is cooled and then stretch oriented in one or more directions to impart strength and toughness to the film. Where necessary, the film is heat treated after stretching to lock in the properties by further crystallizing the film. 
         [0034]    The polymer film can have any suitable thickness. Depending on the type of polymer used, and depending on whether or not the film is used to strengthen the roofing shingle, the thickness of the film can vary over a wide range. For example, in some embodiments the polymer film has a thickness within a range of from about 0.05 mil to about 35 mils, and more particularly from about 0.3 mil to about 20 mils. In some embodiments the polymer film is a relatively thin film, for example, having a thickness within a range of from about 0.05 mil to about 10 mils, and more particularly from about 0.3 mil to about 6 mils. In other embodiments the polymer film is a relatively thick film, for example, having a thickness within a range of from about 10 mils to about 35 mils. 
         [0035]    Different approaches may be taken in the selection of the polymer film. In some embodiments, the polymer film is a relatively high strength film that not only functions as a parting agent like backdust, but that also builds significant strength properties into the roofing shingle. For example, the polymer film may have a tear strength of at least about 1500 g, more particularly at least about 1700 g, and more particularly at least about 2000 g. The tear strength measurement can be the Elmendorf tear strength measured in accordance with ASTM Method D1922, although any other suitable strength measurement can be used. Some examples of relatively high strength films include oriented polyethylene or polypropylene films, or films made from a blend of polyethylene or polypropylene with a high strength polymer such as nylon. 
         [0036]    The use of a relatively high strength film could enable the production of a higher strength roofing shingle, or it could enable the production of a roofing shingle having the same strength but including a lower strength roofing mat. In one embodiment, the roofing mat is a relatively lightweight mat weighing not more than about 1.6 lb/100 ft 2 , and the polymer film has sufficient strength to maintain the strength of the roofing shingle with the lightweight mat. For example, a current roofing shingle having sufficient strength may include a roofing mat having a weight of 1.95 lb/100 ft 2 , but a roofing shingle made with a polymer film may be able to use a roofing mat having a weight of 1.3-1.5 lb/100 ft 2  while obtaining the same shingle strength. 
         [0037]    In other embodiments, the polymer film is a relatively low strength film that functions as a parting agent like backdust but that does not provide any significant strength to the roofing shingle. For example, the polymer film may have a strength of less than about 1000 g, more particularly less than about 500 g, and more particularly less than about 100 g. Some examples of relatively low strength polymer films include non-oriented polymer films, films made from recycled polymers, and/or very thin films. For example, the polyethylene films used to produce garbage bags are usually relatively thin and low strength films. 
         [0038]      FIG. 4  shows a cross-section, taken through the prime region, of a second embodiment of a roofing shingle  23  according to the invention. The roofing shingle  23  includes a roofing mat  14  or substrate. The roofing mat  14  has a front side  14   f  and a back side  14   b.  An asphalt material  18  impregnates the roofing mat  14  and coats the front side  14   f  of the mat. Prime granules  57  are embedded in the front surface of the asphalt material  18 . A layer  19  of the asphalt material  18  also coats the back side  14   b  of the mat. A polymer film  72  is attached to the back side of the layer  19  of asphalt material and forms a back surface of the roofing shingle  23 . In one embodiment, the layer  19  of asphalt material  18  is a relatively thin layer that is just thick enough to act as an adhesive, when molten during the production of the shingle, to bond the polymer film  72  to the roofing mat  14 . For example, a relatively thin layer  19  of asphalt material  18  may have a thickness within a range of from about 0.5 mils to about 5 mils. Optionally, the asphalt material  18  or the polymer film  72  can be modified in any suitable manner to facilitate the bonding and/or to increase the strength of the bond. In another embodiment, the layer  19  of asphalt material  18  may have a wider thickness range, for example, a thickness within a range of from about 1 mil to about 20 mils, and more particularly from about 3 mils to about 9 mils. 
         [0039]    The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its scope.