Sulfur vulcanization a reaction with low levels of unsaturated organic linkers (e.g. 1,3‐diisopropenylbenzene). This process is called inverse vulcanisation and produces polymers where sulfur is the main component. It is not currently of commercial importance but had been investigated as a means of producing polymers for lithium–sulfur batterys and for creating water filters with a high affinity for mercury. The curing of rubber has been carried out since prehistoric times. The name of the first major civilization in Guatemala and Mexico, the Olmec, means 'rubber people' in the Aztec language. Ancient Mesoamericans, spanning from ancient Olmecs to Aztecs, extracted latex from "Castilla
Union Sulphur Company original patents thus expired in 1908. Competitors such as the Freeport Sulphur Company quickly emerged and began to use the Frasch Process to extract sulfur from other nearby salt dome sites. The Union Sulphur Company tried to stop the Freeport Sulphur Company by suing on the basis of later patents that improved upon the original patents. The Delaware District Court largely sided with the Union Sulphur Co. The Third Circuit Court of Appeals, however, reversed the district court, concluding that the new patents were not really new inventions, but merely extensions of the original expired patents. Union Sulphur appealed to