Bitumen/rubber compositions crosslinked with polythiomorpholines, polysulfides and/or mercaptobenzimidazole

Abstract

Asphalt and elastomeric polymer compositions crosslinked with mixed polythiomorpholines or at least one alkyl polysulfide can give polymer modified asphalts (PMAs) with improved properties and/or reduced H 2 S evolution. When at least one alkyl polysulfide is used to completely or partially replace conventional crosslinkers such as S or MBT, mercaptobenzimidazole (MBI) may be optionally used as a co-crosslinker. The use of mixed polythiomorpholines as crosslinkers provide PMAs with better low temperature profiles (BBR m-values). The use of at least one alkyl polysulfide crosslinker gives PMAs with improved PAV-aged DSR results, and reduced H 2 S evolution. The use of at least one alkyl polysulfide crosslinker together with MBI may give PMAs with improved PAV DSR Fail Temperatures.

1 . A method for preparing asphalt and polymer compositions comprising: heating a mixture comprising asphalt, an elastomeric polymer; and a crosslinker, where the crosslinker comprises at least one crosslinker that is selected from the group consisting of mixed polythiomorpholines and at least one alkyl polysulfide, and curing the mixture to give a polymer modified asphalt (PMA).  
   
   
       2 . The method of  claim 1  where the crosslinker comprises mixed polythiomorpholines and sulfur.  
   
   
       3 . The method of  claim 1  where the crosslinker consists essentially of mixed polythiomorpholines.  
   
   
       4 . The method of  claim 3  where the PMA has an improved low temperature property (BBR m-value) when mixed polythiomorpholines are employed instead of equivalent amounts of sulfur and/or mercaptobenzothiazole (MBT).  
   
   
       5 . The method of  claim 1  where the crosslinker comprises at least one polythiomorpholine having the structure:  
     
       
         
         
             
             
         
       
     
     where x is greater than 2.  
   
   
       6 . The method of  claim 1  where the crosslinker has an absence of elemental sulfur.  
   
   
       7 . The method of  claim 1  where the crosslinker has an absence of MBT.  
   
   
       8 . The method of  claim 1  where the crosslinker is at least one alkyl polysulfide, and the crosslinker further comprises mercaptobenzimidazole (MBI).  
   
   
       9 . The method of  claim 1  where the crosslinker consists essentially of at least one alkyl polysulfide.  
   
   
       10 . The method of  claim 9  where the evolution of H 2 S from the asphalt polymer mixture is reduced compared with an equivalent mixture in the absence of the alkyl polysulfide, but using the same amount of sulfur.  
   
   
       11 . The method of  claim 9  where the PMA has an improved PAV-aged DSR result as compared with an identical PMA absent the alkyl polysulfide.  
   
   
       12 . The method of  claim 9  where the alkyl polysulfide has the structure  
       R1 3 —S—S—R2 3    
     where R1 and R2 are independently straight, branched or cyclic alkyl groups or aromatic groups, where R1 and R2 may be substituted with N, S and/or O, and the total number of carbon atoms in all R1 groups is 9 or greater and the total number of carbon atoms in all R2 groups is 9 or greater.  
   
   
       13 . The method of  claim 1  where the crosslinker consists essentially of at least one polysulfide and MBI and the PMA has a PAV DSR Fail Temperature better than an identical PMA where the crosslinker is sulfur and/or MBT.  
   
   
       14 . The method of  claim 1  where the elastomeric polymer comprises from about 1 to 20 wt % of the asphalt/polymer mixture.  
   
   
       15 . The method of  claim 1  where the crosslinker is present in an amount ranging from about 0.01 to about 1 wt %, based on the weight of the asphalt/polymer mixture.  
   
   
       16 . A method for preparing asphalt and polymer compositions comprising: heating a mixture comprising asphalt, an styrene-butadiene copolymer, and a crosslinker within a temperature range from about 300° F. (149° C.) to about 500° F. (260° C.), where the crosslinker comprises at least one selected from the group consisting of mixed polythiomorpholines and at least one alkyl polysulfide, where the crosslinker is present in an amount ranging from about 0.01 to about 1 wt %, based on the weight of the asphalt/polymer mixture; and curing the mixture to give a PMA.  
   
   
       17 . The method of  claim 16  where the crosslinker comprises mixed polythiomorpholines and sulfur.  
   
   
       18 . The method of  claim 16  where the crosslinker consists essentially of mixed polythiomorpholines.  
   
   
       19 . The method of  claim 18  where the PMA has an improved low temperature property (BBR m-value) when mixed polythiomorpholines are employed instead of equivalent amounts of sulfur and/or mercaptobenzothiazole (MBT).  
   
   
       20 . The method of  claim 16  where the crosslinker has an absence of elemental sulfur.  
   
   
       21 . The method of  claim 16  where the crosslinker has an absence of mercaptobenzothiazole (MBT).  
   
   
       22 . The method of  claim 16  where the crosslinker is at least one alkyl polysulfide, and the crosslinker further comprises mercaptobenzimidazole (MBI).  
   
   
       23 . The method of  claim 16  where the crosslinker consists essentially of at least one alkyl polysulfide.  
   
   
       24 . The method of  claim 23  where the evolution of H 2 S from the asphalt polymer mixture is reduced compared with an identical mixture in the absence of the alkyl polysulfide, but using the same amount of sulfur.  
   
   
       25 . The method of  claim 23  where the PMA has an improved PAV-aged DSR result as compared with an identical PMA absent the alkyl polysulfide.  
   
   
       26 . The method of  claim 16  where the crosslinker consists essentially of at least one polysulfide and MBI and the PMA has a PAV DSR Fail Temperature better than an identical PMA where the crosslinker is sulfur and/or MBT.  
   
   
       27 . The method of  claim 16  where the elastomeric polymer comprises from about 1 to 20 wt % of the asphalt/polymer mixture.  
   
   
       28 . A polymer modified asphalt (PMA) composition prepared by the method comprising: heating a mixture of asphalt, an elastomeric polymer, and a crosslinker, where the crosslinker comprises at least one crosslinker selected from the group consisting of mixed polythiomorpholines and at least one alkyl polysulfide; and curing the mixture to give the PMA.  
   
   
       29 . The PMA of  claim 28  where the crosslinker comprises mixed polythiomorpholines and sulfur.  
   
   
       30 . The PMA of  claim 28  where the crosslinker consists essentially of mixed polythiomorpholines.  
   
   
       31 . The PMA of  claim 28  where the PMA has an improved low temperature property (BBR m-value) when mixed polythiomorpholines are employed instead of equivalent amounts of sulfur and/or mercaptobenzothiazole (MBT).  
   
   
       32 . The PMA of  claim 28  where the crosslinker comprises at least one polythiomorpholine having the structure:  
     
       
         
         
             
             
         
       
     
     where x is greater than 2.  
   
   
       33 . The PMA of  claim 28  where the crosslinker has an absence of elemental sulfur.  
   
   
       34 . The PMA of  claim 28  where the crosslinker has an absence of mercaptobenzothiazole (MBT).  
   
   
       35 . The PMA of  claim 28  where the crosslinker is at least one alkyl polysulfide, and the crosslinker further comprises mercaptobenzimidazole (MBI).  
   
   
       36 . The PMA of  claim 28  where the crosslinker consists essentially of at least one alkyl polysulfide.  
   
   
       37 . The PMA of  claim 36  where the evolution of H 2 S from the asphalt polymer mixture is reduced compared with an identical mixture in the absence of the alkyl polysulfide, but using the same amount of sulfur.  
   
   
       38 . The PMA of  claim 36  where the PMA has an improved PAV-aged DSR result as compared with an identical PMA absent the alkyl polysulfide.  
   
   
       39 . The PMA of  claim 36  where the alkyl polysulfide has the structure  
       R1 3 —S—S—R2 3    
     where R1 and R2 are independently straight, branched or cyclic alkyl groups or aromatic groups, where R1 and R2 may be substituted with N, S and/or O, and the total number of carbon atoms in all R1 groups is 9 or greater and the total number of carbon atoms in all R2 groups is 9 or greater.  
   
   
       40 . The PMA of  claim 28  where the crosslinker consists essentially of at least one polysulfide and MBI and the PMA has a PAV DSR Fail Temperature better than an identical PMA where the crosslinker is sulfur and/or MBT.  
   
   
       41 . The PMA of  claim 28  where the elastomeric polymer comprises from about 1 to 20 wt % of the asphalt/polymer mixture.  
   
   
       42 . The PMA of  claim 28  where the crosslinker is present in an amount ranging from about 0.01 to about 1 wt %, based on the weight of the asphalt/polymer mixture.  
   
   
       43 . A road comprising the PMA of  claim 28 .  
   
   
       44 . A roof sealed with the PMA of  claim 28 .  
   
   
       45 . A method of sealing a roof with PMA comprising heating the PMA of  claim 28  and distributing it over at least a portion of roof surface.  
   
   
       46 . A method of road building comprising combining the PMA of  claim 28  with aggregate to form a road paving material, and forming road pavement with the material.  
   
   
       47 . A method of reducing H 2 S evolution from a polymer modified asphalt (PMA) comprising: heating a mixture of asphalt, an elastomeric polymer; and a crosslinker, where the crosslinker comprises at least one alkyl polysulfide crosslinker; and curing the mixture to give the PMA, where the evolution of H 2 S from the PMA is reduced compared with an identical mixture in the absence of the alkyl polysulfide, but using an equivalent amount of sulfur.  
   
   
       48 . The method of  claim 47  where the crosslinker further comprises MBI.  
   
   
       49 . A method of recycling asphalt comprising physically removing asphalt from a location and in any order reducing the size of the removed asphalt, heating the removed asphalt, adding a crosslinker to the mixture, where the crosslinker comprises at least one selected from the group consisting of mixed polythiomorpholines and at least one alkyl polysulfide.  
   
   
       50 . The method of  claim 49  where the crosslinker further comprises MBI.  
   
   
       51 . Recycled asphalt made by the process of  claim 49 .  
   
   
       52 . Aggregate comprising a PMA at least partially coating the aggregate, where the PMA comprises asphalt, an elastomeric polymer, and a crosslinker comprising at least one crosslinker selected from the group consisting of mixed polythiomorpholines and at least one alkyl polysulfide.  
   
   
       53 . The aggregate of  claim 52  where the crosslinker further comprises MBI.