Polyurethanes cured with mixtures of aromatic primary and secondary diamines

Claim 1

IN A CURED POLYETHER POLYURETHANE ELASTOMER WHICH IS THE REACTION PRODUCT OF (I) AN AROMATIC DIAMINE, WITH (II) A LIQUID POLYISOCYANATE COMPOSITION BEING THE REACTION PRODUCT OF (A) A MOLAR EXCESS OF AT LEAST ONE MONOMERIC ORGANIC POLYISOCYANATE FREE OF ISOCYANATE-REACTIVE GROUPS, AND (B) AT LEAST ONE POLYETHER HAVING ON THE AVERAGE ABOUT 2 TO 3 HO-GROUPS PER MOLECULE AND A MOLECULAR WEIGHT OF ABOUT 700 TO 6000, SAID POLYETHER SELECTED FROM THE GROUP CONSISTING OF POLYALKYLENEETHER GLYCOLS, POLYALKYLENE-ARYLENEETHER GLYCOLS, POLYALKYLENEETHER-THIOETHER GLYCOLS, POLYALKYLENE-ARYLENEETHER-THIOETHER GLYCOLS, AND POLYALKYLENE ETHER TRIOLS; THE IMPROVEMENT WHEREIN SAID AROMATIC DIAMINE (I) IS A MIXTURE OF (1) AT LEAST ONE AROMATIC PRIMARY DIAMINE, AND (2) AT LEAST ONE AROMATIC SECONDARY DIAMINE WHOSE SECONDARY AMINO GROUPS HAVE ONE VALENCE OF EACH NITROGEN ATOM ATTACHED TO AN AROMATIC RING AND ANOTHER VALENCE ATTACHED TO AN ALIPHATIC CARBON ATOM, THE MOLAR RATIO OF (1) TO (2) RANGING FROM ABOUT 0.33:1 TO 5.7:1.