Polyurethane prepared by reaction of an organic polyisocyanate, a chain extender and an isocyanate-reactive material of m.w. 500-20,000 characterized by the use of only 2-25 percent by weight of the latter material

Granted: Mar 15, 1983 Filed: Oct 14, 1981

This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.