a closure unit for a container for storing and handling flowable products is made from at least two different thermoplastic materials , the different materials fulfilling different functions . a basic thermoplastic material is used for sealing against the container , and an area made of another different thermoplastic material is provided to fulfill additional sealing functions , to increase mechanical stability , to have a reduced permeability , and to provide increased elasticity for additional opening and closing and / or absorption characteristics . the closure unit is produced by a multimaterial injection molding process , so that contact surfaces between the different thermoplastic materials can be interconnected by reversible or irreversible positive engagement and / or by more or less pronounced melting into one another . the closure unit is in two parts and comprises a pouring part and a closure part , or is in one part . the two - part closure unit is produced in a single operation in a closed state .