Multi-layer structure and method of producing the same
A multi-layer structure comprising a functional resin layer obtained by covering a core layer of a base body resin or a second functional resin with a shell layer of a first functional resin, and a base body resin layer containing the functional resin layer therein. The layers of the functional resins are formed at positions where they are allowed to exhibit their functions to a sufficient degree, a plurality of functions can be imparted, and a molten resin mass having the above multi-layer structure can be formed by the compression-forming.
1. A method of producing a multi-layer structure by press-forming a molten resin mass of a thermoplastic resin and a functional resin, wherein said molten resin mass is the one that wraps therein a functional resin mass which comprises a core layer of a base body resin or a second functional resin covered with a shell layer of a first functional resin, said functional resin is a molten resin mass comprising any one of a gas-barrier resin, an oxygen-absorbing resin, a cyclic olefin resin or a liquid crystal polymer, and said molten resin mass is formed by continuously feeding the base body resin in a molten state, flowing the first functional resin into the interior of the base body resin, flowing the second functional resin or the base body resin into the interior of the first functional resin that has been fed already, and halting the flow out of the first functional resin by flowing out the second functional resin or the base body resin; flowing the first functional resin in again by halting the flow out of the second functional resin or the base body resin; halting the flow out of the first functional resin and feeding the base body resin only; and forming, in the base body resin, a molten resin flow in which a shell layer of the first functional resin and a core layer of the second functional resin or the base body resin are formed, and cutting away a portion of said molten resin flow in which only the base body resin is present; said first or second functional resin comprising any one of a gas-barrier resin, an oxygen-absorbing resin, a cyclic olefin resin or a liquid crystal polymer.
2. A method of producing a multi-layer structure according to claim 1 , wherein said multi-layer structure is a container closure comprising a top panel and a skirt portion hanging down from the peripheral edge of the top panel, and after the container closure is formed by compression-forming said molten resin mass, a sealing member is formed on the inner surface of the top panel by feeding and compressing a molten resin mass containing therein a functional resin different from the functional resin used for said molten resin mass.