Abstract: A copolymer having carbonate linkages is produced by copolymerizing an epoxy compound with carbon dioxide in the presence of an isoprene-magnesium complex compound or a reaction mixture of said complex compound with an active hydrogen compound as a catalyst. The catalyst has a much improved polymerization activity when treated with carbon dioxide in advance.

Abstract: A mechanical seal assembly for installation about a shaft includes at least one floating seat having intersecting axial and radial seat sections defining an L-shaped seat, the opening of the L-shape receiving a packing therein. The packing is of a rubbery, elastic material and includes a cylindrical inner circumferential surface; a front surface extending generally radially outwardly from one end of said inner circumferential surface and generally aslant toward the other end of said inner circumferential surface; a back surface extending generally radially outwardly from said other end of said inner circumferential surface and generally aslant in generally the same direction as said front surface, said back surface including at least one annular groove slit therein; and a cylindrical outer circumferential surface connecting said back surface with said front surface.