Elastomeric controlled release formulation and article comprising same

An article comprising an elastomeric matrix and at least one biologically or nonbiologically active agent contained in the matrix, the active agent to be released from the matrix into the environment substantially continuously over an extended period of time, the matrix material having a modulus between about 10.sup.4 Pa and about 10.sup.8 Pa at 23.degree. C. and a glass transition temperature T.sub.g less than 0.degree. C., the matrix comprising polyurethane formed by a process comprising reacting a polyol with an isocyanate,

• (a) the polyol comprising a major component selected from the group consisting of hydroxyl-terminated polybutadiene, hydroxyl-terminated polyisoprene, hydroxyl-terminated copolymers of butadiene with acrylonitrile, hydroxyl-terminated copolymers of butadiene with styrene, hydroxyl-terminated copolymers of isoprene with acrylonitrile, hydroxyl-terminated copolymers of isoprene with styrene, and mixtures of the above, the major component being at least 90% by weight of the total amount of the polyol, the polyol having an average molecular weight in the range 400-10,000;
• (b) the isocyanate is selected from the group consisting of the aromatic isocyanates, the cycloaliphatic isocyanates, the aliphatic isocyanates, the heterocyclic isocyanates, and mixtures thereof, the isocyanate having an average molecular weight in the range 80-1000 and an average functionality between about 2 and about 3, the NCO/OH ratio of polyol and isocyanate being in the range of 0.8 to 1.2.