Roof Consultants Should Know

oof consultants should know production of the underlayment. ASPHALT-SATURATED ORGANIC FELT their materials inside and out. There are many similarities among tra- The manufacture of asphalt-saturated To fully understand under- ditional, specialty, and synthetic under- felt begins with the delivery of dry organic layment, one must have a layment products. Here we compare anal- felt to the factory. This material is made basic understanding of raw ogous manufacturing processes for tradi- out of cellulose fibers obtained from post- materials and manufacturing. tional asphalt-coated felts and premium consumer and post-industrial waste such RSubtle variations at the molecular level have modified-bitumen membranes, as well as as newspapers, cardboard, and wood. The large effects on the properties of materials; synthetics. cellulose fibers are reduced to a water-based furthermore, variations on the macroscopic An underlayment company should be pulp, formed into sheets, dried, cut into scale also affect performance. Ideally, the intimately involved with the manufactur- strips, and wound onto rolls. Being made manufacturer of the roofing underlayment ing processes. Manufacturing facilities that from 100% post-consumer recycled materi- is knowledgeable of engineered polymers, are dedicated to the production of roofing al, dry organic felt mat is an eco-friendly or and its technical staff can work with poly- underlayment can be continually improved “green” material. mer producers to optimize the formulas for as more is learned from the end-users. The dry felt is delivered to the plant by polymers that are blended for use in the truck and stored on-site. Meanwhile, hot asphalt is delivered by tanker truck (Figure 1) and pumped into one of several asphalt storage tanks. The asphalt is kept hot by electric and natural gas-fired heaters located at the asphalt storage tanks. The liquid asphalt circulates in a loop through the saturator and back to the asphalt tanks. The asphalt temperature is carefully controlled at all times. Rolls of dry felt are loaded onto the unwind stand (Figure 2) and unrolled through the dry looper section (Figure 3). The dry looper consists of a series of rollers, pulled along by a chain, which is used to form loops, maintain tension on the paper, and allow product accumulation. From the dry looper, the dry felt enters the saturator (Figure 4). The saturator consists of a series of rollers, commonly referred to as “gates.” The bottom rollers of these gates are submerged in hot asphalt, maintained usually at a temperature of Figure 1 – Asphalt unloading. 350°F (177°C). The gates can be raised or 8 • I NTERFACE O CTOBER 2 0 1 6 Figure 2 – Unwind stand. Figure 3 – Dry looper. lowered to change the level of saturation of • Type of dry felt, the asphalt into the felt paper. whether soft or The saturation level is expressed as a hard percentage, ranging between no absorp- • Temperature of tion (0%) and fully saturated (100%). It the asphalt describes the extent to which the felt, upon • “Dwell time,” being immersed in hot asphalt, absorbs and or the period of adsorbs the asphalt and retains it under the time that dry felt Envirospec Ad 262-0801 1/21/08 9:03 AM Pa processing conditions. The type of asphalt resides in the used is called “saturant asphalt.” The sat- saturator uration level has a direct correlation to the • Speed of the production line finished product weight; the greater the saturation, the higher the weight. After the felt is saturated, it passes over Saturation level depends on various fac- a series of three to five scraper blades to tors, such as: remove excess asphalt. The second blade Figure 4 – Saturator. O CTOBER 2 0 1 6 I NTERFACE • 9 Figure 6 – Winder. Figure 5 – Finish looper. MODIFIED- mixing tanks have a capacity of 25,000 BITUMEN ROOFING lbs., which is approximately 3,000 gallons Modified bitu- (Figure 8). Asphalt is heated to approx- minous self-adher- imately 400°F (204°C), and the various ing underlayments polymers are added into the tank. The exact are made of bitumen quantities depend on the specific product compounds such as formulation. can be adjusted in or out to increase or asphalt that have Mix tanks are equipped with agitators decrease the amount of asphalt removed been modified with polymers to be more or blades that keep the asphalt and poly- from the surface of the paper. The saturator rubber-like and easier to handle. A tough mers in circulation at high speeds. The is totally enclosed; asphalt vapors from the fiberglass mat gives strength against rips blending process takes from two hours up process are routed to the scrubber/cooler and tears and makes it easy to handle the to six hours, depending upon the quan- (for cooling) and to the fiber-bed filter mist modified-bitumen material. The fiberglass tity and type of polymers, as well as the eliminator for control of emissions. mats used in roofing are made of chopped equipment specifications. During this pro- The asphalt-saturated felt enters the strands of fiberglass. cess, the polymers break down and bond cooling section (also known as “the black The manufacture of polymer-modified with asphalt, resulting in a homogeneous rack” or the “striking section”), where it bituminous specialty underlayment prod- asphalt-polymer network or matrix. Other is drawn over several rollers and allowed ucts consists of several distinct steps: ingredients such as oil and tackifying resins to cool in ambient conditions. The cooling • Mixing and filler addition are added as needed. Filler materials such section is also enclosed, and the vapors are • Saturating and coating the rein- as limestone or talc are added into the mix routed to the scrubber/cooler and then to forcement the mist eliminator for emissions control. • Surfacing From the cooling section, the saturated • Cooling felt rolls onto the finish looper, which is • Cutting and another series of rollers that forms the winding (into saturated felt into hanging loops (Figure 5). roll form) The asphalt-saturated felt is pulled into the winder, where the rolls are formed and cut Mixing and Filler into varying lengths (Figure 6). Addition At this stage, “ply marks” or “laying Asphalt is blended lines” can be printed on the surface of the with polymeric addi- felts. They are typically marked at 2, 8½, tives such as atactic 11¼, 17, 19, 24¾, 27½, and 34 in. polypropylene (APP), The roll is pushed along a conveyor, styrene butadiene where it is wrapped with a paper label and styrene (SBS), poly- stacked vertically on pallets. When a pallet ethylene (PE), and is full, it is automatically banded and stored other chemicals in in the warehouse, ready for shipment. mixing tanks or ves- sels (Figure 7). Typical Figure 7 – Polymer additives. 1 0 • I NTERFACE O CTOBER 2 0 1 6 tank and allowed to blend, usually for one hour or so. In some cases, the polymer- modified asphalt blend is transferred to a holding tank before being transferred to the production line. Saturating and Coating the Reinforcement From the mix tank or holding tank, the modified-asphalt blend is transferred to the coater in the production line. From the unwind stand located at one end of the production line, the reinforcement (also known as carrier or mat)—such as dry felt, glass mat, or polyester—is unwound from master rolls. The coater section typically consists of a rectangular tank and a series of rollers. When the reinforcement enters the coater, it is saturated with the modified-asphalt blend. Simultaneously, the modified-asphalt coating is applied to the upper and lower surfaces of the saturated reinforcement. Figure 8 – Mix tanks. The level of saturation again is greatly dependent upon several factors. In this • Run speed • Temperature of the modified-asphalt case, the factors include the following: • Type of modified-bitumen compound blend • Dwell time of the reinforcement in • Viscosity of the modified-bitumen • Type of reinforcement the coater compound 7.50W X 5H.indd 1 1/12/16 5:06 PM O CTOBER 2 0 1 6 I NTERFACE • 1 1 Also present at the coater section are Cooling metering rollers, which are employed to The sheet is achieve the desired product thickness by con- then fed through trolling the amount of modified-asphalt blend water-cooled drums applied on either side of the reinforcement. to allow it to cool rapidly (Figure 10). Surfacing In some cases, Once the saturated and coated rein- the sheet trav- forcement exits the coater section, the els through a necessary surfacing material is applied. chilled water bath. Surfacing materials are added for various Alternatively, water reasons. For example, sand, talc, or liquid spray may be used parting agent (LPA) is applied to the upper to cool the sheet. surface of the product to keep the material Some manufac- from sticking within itself when wound into turing lines are roll form. Silicone-coated release film is equipped with applied to the self-adhesive compound on dryers to air-dry the bottom side to prevent roll sticking and the sheets. After Figure 9 – Release film application. to maintain the adhesive characteristics of cooling, the sheet the finished product Figure( 9). enters the accumulator section, which con- THE MANUFACTURE OF SYNTHETICS Alternatively, polymeric film or fab- sists of a series of rollers that allow the Producing synthetic underlayment from ric materials are applied to the topside, material to form into loops. polypropylene (PP) pellets is a marvel of depending on the product configuration and modern manufacturing. The process can end use. In the case of mineral-surfaced Cutting and Winding be subdivided into several distinct stages membranes or underlayments, mineral or From the finished product looper at the as follows: ceramic granules are applied to the topside accumulator section, the sheet travels to • Spinning the fibers or filaments of the finished product.

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