Composite fiberboard

Abstract

The present invention relates to a composite fiberboard, which is specifically adapted for use as a coverboard in roofing systems. The formulation and physical characteristics of the composite fiberboard of the invention have increased the flexural strength of the board relative the flexural strength of current commercial fiberboards of similar type. In turn, the composite fiberboard is able to meet the Class 90 wind uplift requirements as measured by Factory Mutual FM 4450 Approval Standard for Class I Insulated Steel Deck Roofs.

1 . A composite fiberboard for use as a roof coverboard, the fiberboard comprising: 
 cellulose fibers in the range from about 30% to about 60% by dry weight;    expanded perlite particles in the range from about 20% to about 50% by dry weight;    the composite fiberboard having a thickness in the range from about 0.475 inches to about 0.70 inches and a basis weight of from about 0.70 pounds per square foot to about 0.95 pounds per square foot; and    wherein the composite fiberboard achieves a Class I-90 rating using the FM 4450 test as measured against the mode of failure of fastener fracturing.    
   
   
       2 . The composite fiberboard for use as a roof coverboard of  claim 1 , comprising from about 40% to about 44% cellulosic fibers and from about 29% to about 33% expanded perlite.  
   
   
       3 . The composite fiberboard for use as a roof coverboard of  claim 1 , comprising from 0% to about 35% mineral wool fibers by dry weight, from about 5% to about 15% starch binder by dry weight, from 0% to about 6% latex binder by dry weight, from 0% to about 1% alum by dry weight, from about 0.2% to about 0.6% silicone by dry weight and from about 0.1% to about 0.3% polymer retention aid by dry weight.  
   
   
       4 . The composite fiberboard for use as a roof coverboard of  claim 3 , comprising from 14% to about 20% mineral wool fibers, from about 8% to about 9% starch binder, from 2% to about 3% latex binder, from 0.4% to about 0.5% alum, from about 0.4% to about 0.45% silicone and from about 0.2% to about 0.25% polymer retention aid.