Patent Application
20080050559
The novel features of the present invention will be more readily apparent upon reading the following description in conjunction with the accompanying drawings, in which:
The roofing material 10 in accordance with the present invention therefore utilizes at least one UV-curable coating, i.e., on the individual granules 18 and/or applied as the coating layer 22. While the present invention has been explained with reference to granule-faced roofing material, the UV-curable coating may be applied to roofing material that does not have granules.
A bottom coating 24 is embedded or otherwise adhered to the asphalt layer 14. The bottom coating 24 may be conventional, such as a coating of sand or talc. Before describing the composition and preparation of the UV-curable material used in forming the UV-curable coating layer 22, the method and apparatus for making the roofing material 10 will be described below with reference to
The granule-faced roofing material 62 is then fed through water cooling trays 64 to lower the temperature of the asphalt for further processing and to lock the applied granules 50/56 onto the surface of the mat 48. After leaving the water cooling tray 64, the cool roofing material 66 has a backing material 68 applied at a backing applicator station 70. The backing is typically sand or talc. The backed roof material 72 is then cooled and dried by air knives and/or cooling fans 74, and passed to the top coater 78. The top coater 78 receives the top coating composition 76 and applies it to the roofing material 72 producing top coated roofing material 80. In the event that the top coating 76 is UV-curable in accordance with the present invention, it is cured by UV light 82 after leaving the top coater 78. The top coater 78 may apply a top coating using any of the well known methods for applying coatings, such as by roller, brush, spray, dip and knife coating methods. The cured, top coated roofing material 80 is accumulated on a finish looper (accumulator) 84 and then fed to a roll winder/cutter 86 to produce the finished roofing material 88, either in the form of roll roofing or cut shingles which are then placed in storage 90.
An exemplary UV-curable coating in accordance with the present invention includes resin, pigment and photoinitiator component packages as follows, in the weight percentages indicated. The operable weight percentage range is stated first, followed by a preferred weight percentage applicable to the specific example given.
Between 10.00%-40.00%, preferably 30.00% BE-111 low viscosity, non-yellowing, polyester acrylate (primary oligomer);
Between 6.00%-25.00%, preferably 17.5% PONPGDA propoxylated neopentylglycol diacrylate (primary monomer due to its good pigment/filler compatibility, its good diluent properties and low cost);
Between 2.00%-15.00%, preferably 7.7% DPGDA dipropyleneglycol diacrylate (a secondary monomer, being an economical high cross-linker with good physical properties);
Between 0.50%-7.00%, preferably 3.0% PETA pentaerythritol triacrylate (another high cross-linking secondary monomer). The foregoing resins are obtainable from San Esters (www.sanesters.com).
Between 0.30%-5.50%, preferably 2.5% Disperbyk 168 (disperse aid for limestone);
Between 0.02%-1.50%, preferably 0.3% Disperbyk 111 (disperse aid or TiO2);
Between 0.10%-1.50%, preferably 0.5% BYK 1790 (non-silicone de-foamer, for UV applications); Each of the foregoing may be obtained from BYK Chemie (www.byk-chemie.com).
Between 5.00%-45.00%, preferably 23.5% Omycarb #10 (limestone)available from Omya AG (omya.com);
Between 5.00%-40.00%, preferably 6.0% Titanium Kronos 2160;
Between 5.00%-40.00%, preferably 5.0% Titanium Ukraine 2160; The foregoing pigments may be obtained from Kronos, Inc. (kronostio2.com).
Between 0.50%-5.50%, preferably 3.0% Omnirad 481;
Between 0.10%-5.50%, preferably 1.0% Omnirad TPO; The foregoing can be obtained from IGM Resins (igmresins.com).
Adding the weight percents of all of the foregoing compounds in the resin, pigment and photoinitiator packages gives a total weight percent of 100%. To combine these components into the UV-curable coating, the BE-111 and the PONGDA may be utilized as the grind media for the pigment/extender package to form an intermediate resin/pigment dispersion. The DPGDA and the PETA may be utilized together as a solvent for the photoinitiator package to form a resin/photoinitiator solution. The resin/pigment dispersion and the resin/photoinitiator solution are then mixed together using low to medium shear mixing. It is preferable to degas the resin/pigment dispersion before combining it with the resin/photoinitiator solution. While mixing the resin/pigment dispersion with the resin/photoinitiator solution to form the UV-curable coating of the present invention, it is preferable to minimize the introduction of air.
An iron-doped or, more preferably, a gallium-doped UV bulb producing at or above 300 watts per inch of power would be suitable to cure the UV-curable coating of the present invention. The lower the viscosity of the coating, the quicker the cure time. Since non-aqueous acrylated systems rarely support the growth of microbes, fungus, moss or other unwanted flora or fauna, a biocide is not required for most applications. For tropical or other bio-promoting enviroments/applications, a biocide, such as Nuosept from International Specialty Products Corporation (ispcorp.com)may be added.
The foregoing UV-curable coating composition can be applied using conventional apparatus and methods for applying coatings, such as roller coating, spray coating, etc. The coating starts to cure immediately upon exposure to UV light and when using a 300 W/in bulb can cure in two to four seconds, thus allowing movement of the roofing material through the production line at a normal speed, i.e., the curing of the top coating composition is accomplished at a quicker rate than other processes used during manufacture of the roofing material, e.g., application of the granules, cooling of the hot roofing material, etc., which are conducted at a slower rate than curing.
While the present invention has been described in reference to a specific embodiment thereof, those with normal skill in the art may see the potential to change certain aspects of the disclosed embodiment without departing from the scope of the present invention. It is therefore intended that such variations fall within the scope of the appended claims. For example, various pigments may be used as alternatives to those listed above to obtain different colors for the UV-cured top-coating composition. In the event that the color of the granular layer is the desired finish color, the U-V curable composition can be made without adding a pigment resulting in a clear coating. A clear coating may be desired to lock in, unify and protect the granular layer, while still permitting the color of the granular layer to show through the coating. Similarly, the granules may be coated with a clear coating prior to being embedded in the asphalt. If granules are not utilized on the roofing material, the UV-curable coating may be applied to the upper surface of the roofing material.
