Synthetic fabric having slip resistant properties and method of making same

Abstract

A synthetic nonwoven fabric having bonded fibers forming channels surrounding unbonded fibers forming raised slip resistant spots. The fabric is made by extruding hot polymer through a spinneret die onto a moving belt to form a sheet of random fibers, which sheet undergoes a calendering process between a pair of heated rollers, one of which rollers having a plurality of cavities defined in its surface. The resulting fabric can be laminated and otherwise combined with other layers as desired to provide an end product having good slip resistant properties.

What is claimed is: 
     
         1 . A method of preparing a nonwoven fabric comprising:
 a. forcing a thermoplastic polymer resin through a spinerette die onto a moving belt to form a sheet made of randomly oriented entangled fibers;   b. calendering said sheet between a pair of heated rolls, one of said heated rolls being an engraved roll with a plurality of cavities defined therein, to produce a calendered sheet having a plurality of elevated portions comprised of random unbonded fibers, wherein adjacent ones of said plurality of elevated portions being separated from one another by channels of bonded fibers.   
     
     
         2 . The method of  claim 1  wherein the other one of said heated rolls being a smooth roll having a smooth cylindrical outer surface. 
     
     
         3 . The method of  claim 1  wherein said heated rolls are heated to a temperature and exert a pressure on said sheet sufficient to form said channels of bonded fibers and elevated portions. 
     
     
         4 . The method of  claim 2  wherein each of said engraved roll and said smooth roll being maintained at a different temperature. 
     
     
         5 . The method of  claim 4  wherein said engraved roll being maintained at a temperature between 142-146 degrees Celsius and said smooth roll being maintained at a temperature between 137-140 degrees Celsius. 
     
     
         6 . The method of  claim 1  wherein each of said cavities having a bottom surface at a depth greater than the height of a top surface of said elevated portions above a top surface of said channels such that an air pocket is formed between said top surface of said elevated portions and said bottom surface of said cavities during calendering of said sheet. 
     
     
         7 . The method of  claim 6  wherein said height being greater than 0.5 mm. 
     
     
         8 . The method of  claim 4  wherein adjacent cavities are separated by at least 0.5 mm. 
     
     
         9 . The method of  claim 1  wherein said thermoplastic polymer resin comprises polypropylene, polyethylene, polyester or nylon. 
     
     
         10 . A method of preparing a nonwoven fabric comprising:
 a. forcing a resin through a spinerette die onto a moving belt to form a sheet made of randomly oriented entangled fibers;   b. calendering said sheet between a pair of heated rolls, one of the rolls being engraved with a pattern of cavities that allow an air pocket between the surface of the cavity and the fibers of the nonwoven sheet; heating said rolls to a temperature and exerting a pressure such that the fibers within the cavities form elevated surfaces of slip resistant spots that consist of random unbonded fibers and fibers falling outside the cavities are in direct contact with the heated calender rolls and melt sufficiently to form fused channels surrounding the elevated surfaces of unbonded fibers.   
     
     
         11 . The method of  claim 1  further comprising laminating said calendered sheet with a waterproofing layer. 
     
     
         12 . The method of  claim 11  further comprising a reinforcing scrim layer being laminated between said calendered sheet and said waterproofing layer. 
     
     
         13 . A roofing membrane comprising:
 a. a nonwoven layer of randomly oriented entangled fibers, said nonwoven layer having a top surface comprising a plurality of elevated portions having unbonded fibers, adjacent ones of said plurality of elevated portions separated by channels of fused fibers, and having a bottom surface of fused fibers; and a waterproofing layer laminated to said bottom surface.   
     
     
         14 . The roofing membrane of  claim 13  further comprising a scrim reinforcement layer laminated between the nonwoven layer and waterproofing layer. 
     
     
         15 . A nonwoven fabric comprising a plurality of randomly oriented, entangled fibers forming a sheet having a smooth bottom surface wherein said fibers are bonded and having a top surface comprising a plurality of elevated portions having unbonded fibers, said elevated portions surrounded by channels of fused fibers. 
     
     
         16 . The nonwoven fabric of  claim 15  wherein said fibers are formed from thermoplastic polymer resin. 
     
     
         17 . The nonwoven fabric of  claim 16  wherein said channels have a width of at least 0.5 mm. 
     
     
         18 . The nonwoven fabric of  claim 16  wherein said elevated portions have a top surface at least 0.5 mm above said channels.