Due to various considerations including increased recovery of sulfur contaminating other materials because of stricter environmental controls, the supply of elemental sulfur greatly exceeds present demand. Because of its abundance and low cost the use of sulfur in construction of buildings and roads and for roadway markers has been desired for some time. Elemental sulfur per se is, however, too brittle to use directly for these purposes and considerable effort has been put forth to find additives which, without markedly increasing the cost of the final product, would serve to modify the brittleness of sulfur increasing its impact resistance and render it commercially useful.
The commercially available liquid polysulfide polymers as well as an experimental styrene based polysulfide polymer have been reported as being among those agents which have been employed as sulfur modifiers for various purposes. U.S. Pat. No. 3,316,115 illustrates the use of a liquid polysulfide polymer and a styrene polysulfide polymer to modify sulfur in preparing a road marker composition. Dale in "Advances in Chemical Science" No. 110, Sulfur Research Trends, Chapter 15 page 201, Chemical-Mechanical Alteration of Elemental Sulfur (ACS) gives a review of the problems involved and success achieved in permanent modification of the mechanical properties of the element.
While good results are known to be obtainable using commercial polysulfide polymers and styrene polysulfide polymers, these materials apparently are oxidized by the sulfur as evidenced by H.sub.2 S evolution when the commercial polysulfide polymer is mixed with molten sulfur and its continued evolution from the cooled product. Mixing of styrene polysulfide polymer with sulfur is accompanied by the same effect obtained on mixing styrene monomer with sulfur, that is, noticeable evolution of styrene both from the molten mixture and from the cooled product.
The present invention relates to polysulfide polymers based on polyethers and polyformals which have terminals not subject to oxidative curing and which blend well with molten sulfur without evolution of noxious by-products in the molten solid state and which give a permanent increase to the fracture resistance of the elemental sulfur with which they are combined.
USPTO Backgrounds
USPTO Backgrounds