Ropes having improved cyclic bend over sheave performance

Abstract

An improved rope is formed from a blend of fluoropolymer fibers and high tenacity polyolefin fibers. The fibers and/or the rope are coated with a composition comprising an amino functional silicone resin and a neutralized low molecular weight polyethylene. The ropes are useful in marine applications, such as in deep sea lifting, and have improved cyclic bend over sheave fatigue resistance.

1 . A rope having improved cyclic bend over sheave (CBOS) fatigue resistance, said rope comprising a blend of fluoropolymer fibers and high tenacity polyolefin fibers, said rope and/or said fibers being coated with a composition comprising an amino functional silicone resin and a neutralized low molecular weight polyethylene. 
   
   
       2 . The rope of  claim 1  wherein said high tenacity polyolefin fibers comprise extended chain polyethylene fibers. 
   
   
       3 . The rope of  claim 3  wherein said extended chain polyethylene fibers have a tenacity of at least about 15 g/d. 
   
   
       4 . The rope of  claim 3  wherein said extended chain polyethylene fibers have a tenacity of at least about 30 g/d. 
   
   
       5 . The rope of  claim 1  wherein said rope is formed from said blended fibers which are coated with said composition prior to forming said rope. 
   
   
       6 . The rope of  claim 1  wherein said rope is formed from said blended fibers and is thereafter coated with said composition. 
   
   
       7 . The rope of  claim 1  wherein said composition is present on said rope in an amount of at least about 5 weight percent based on the weight of said rope. 
   
   
       8 . The rope of  claim 1  wherein said low molecular weight polyethylene is the major component of said composition. 
   
   
       9 . The rope of  claim 1  wherein said low molecular weight polyethylene is present in an amount of from about 55 percent to about 85 percent by weight based on the total weight of said composition. 
   
   
       10 . The rope of  claim 9  wherein said low molecular weight polyethylene is fully neutralized. 
   
   
       11 . The rope of  claim 1  wherein said blended fibers are twisted together. 
   
   
       12 . The rope of  claim 1  wherein said rope comprises from about 1 to about 40 percent by weight, based on the total weight of the fibers, of said fluoropolymer fibers and correspondingly from about 60 to about 99 percent by weight, based on the total weight of the fibers, of said high tenacity polyolefin fibers. 
   
   
       13 . The rope of  claim 1  wherein said rope comprises a blend of polytetrafluoroethylene fibers and extended chain polyethylene fibers. 
   
   
       14 . The rope of  claim 13  wherein said polytetrafluoroethylene fibers comprise expanded polytetrafluoroethylene fibers. 
   
   
       15 . The rope of  claim 14  wherein said rope comprises from about 1 to about 40 percent by weight, based on the total weight of the fibers, of said expanded polytetrafluoroethylene fibers and correspondingly from about 60 to about 99 percent by weight, based on the total weight of the fibers, of said extended chain polyethylene fibers. 
   
   
       16 . The rope of  claim 15  wherein said rope is a braided rope. 
   
   
       17 . The rope of  claim 15  wherein said expanded polytetrafluoroethylene fibers are present in the form of yarns having a denier of from about 50 to about 1600, and said extended chain polyethylene fibers are present in the form of yarns having a denier of from about 50 to about 5000. 
   
   
       18 . The rope of  claim 1  wherein said blend consists essentially of a blend of polytetrafluoroethylene fibers and extended chain polyethylene fibers. 
   
   
       19 . The rope of  claim 1  wherein said fluoropolymer fibers are selected from the group consisting of polytetrafluoroethylene, polychorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymers, ethylene-chlorotrifluorethylene copolymers, fluorinated ethylene-propylene copolymers, perfluoroalkoxy polymer, and blends thereof 
   
   
       20 . A method of improving the cyclic bend over sheave (CBOS) fatigue life of a rope, said method comprising forming said rope from a blend comprising fluoropolymer fibers and high tenacity polyolefin fibers, and coating said rope and/or said fibers forming said rope with a composition comprising an amino functional silicone resin and a neutralized low molecular weight polyethylene. 
   
   
       21 . The method of  claim 20  wherein high tenacity polyolefin fibers comprises extended chain polyethylene fibers. 
   
   
       22 . The method of  claim 21  wherein said fluoropolymer fibers comprise polytetrafluoroethylene fibers. 
   
   
       23 . The method of  claim 22  wherein said rope comprises from about 1 to about 40 percent by weight, based on the total weight of the fibers, of expanded polytetrafluoroethylene fibers and correspondingly from about 60 to about 99 percent by weight, based on the total weight of the fibers, of extended chain polyethylene fibers. 
   
   
       24 . The method of  claim 23  wherein said expanded polytetrafluoroethylene fibers and said extended chain polyethylene fibers are twisted together. 
   
   
       25 . The method of  claim 20  wherein said low molecular weight polyethylene is present in said composition in an amount of from about 55 percent to about 85 percent by weight based on the total weight of said composition. 
   
   
       26 . The method of  claim 25  wherein said composition has a solids content of at least about 25% by weight. 
   
   
       27 . The method of  claim 26  wherein said amino functional silicone resin is in the form of an emulsion having a pH of from about 9 to about 11. 
   
   
       28 . The method of  claim 27  wherein said low molecular weight polyethylene in said composition has a molecular weight of from about 300 to about 3000 Dalton, and is in the form of an emulsion. 
   
   
       29 . In a method of lifting and placing heavy objects from and onto a seabed using a synthetic fiber rope, the improvement comprising utilizing as said rope a rope comprising a blend of fluoropolymer fibers and high tenacity polyolefin fibers, said rope and/or said fibers being coated with a composition comprising an amino functional silicone resin and a neutralized low molecular weight polyethylene. 
   
   
       30 . The method of  claim 29  wherein said high tenacity polyolefin fibers comprise extended chain polyethylene fibers. 
   
   
       31 . The method of  claim 30  wherein said fluoropolymer fibers comprise polytetrafluoroethylene fibers. 
   
   
       32 . The method of  claim 31  including coating said composition onto said rope and/or said fibers to provide said composition on said rope in an amount of from about 10 to about 30 weight percent based on the weight of said rope.