Multi-Layer Structure and Method of Producing the Same

Abstract

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.

Description

TECHNICAL FIELD [0001] The present invention relates to a multi-layer structure having a base body resin layer of a thermoplastic resin and a functional resin layer of a functional resin. More specifically, the invention relates to a multi-layer structure having a layer structure in which functional resins such as a barrier resin and an oxygen-absorbing resin are allowed to efficiently exhibit their functions, and to a method of producing the same. BACKGROUND ART [0002] In the field of packaging containers, there have been used a variety of resins and resin compositions capable of exhibiting such functions as heat resistance, barrier property, oxygen-absorbing property and the like properties. These functional resins are used in combination with a base body resin which chiefly works to maintain the formability of the structure. [0003] As the functional resins, there have been known gas-barrier resins such as ethylene / vinyl alcohol copolymers, and oxygen-absorbing resin compositions ...

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Benefits of technology

[0022] As described above, the functional resin layer comprises the shell layer of the first functional resin and the core layer of the base body resin or the second functional resin, the shell layer covering the core layer, and the base body resin layer wrapping the functional resin layer therein. Therefore, the functional resin layer is allowed to exist near the surface of the structure, and the multi-layer structure permits the functional resin to effectively exhibit its function.

[0023] According to the present invention, further, the core layer which is the functional resin layer is formed by using a second functional resin different from the first functional resin that constitutes the shell layer to impart a multiplicity of functions to the multi-layer structure. As will be described later, for example, an oxygen-absorbing resin is used as the first functional resin, and a gas-barrier resin is used as the second functional resin thereby to efficiently absorb oxygen remaining in the container, to shut off the permeation of oxygen from the exterior of the container through the container closure and, hence, to minimize the effect of oxygen upon the content.

[0024] According to the present invention, further, the base body resin can be used as the core layer which is the functional resin layer. In this case, a small amount of the functional resin can be permitted to exist efficiently near the surface of the multi-layer structure.

[0025] According to the method of producing a multi-layer structure of the invention, further, there can be efficiently formed by compression-forming a multi-layer structure permitting the layers of the functional resins to be formed at positions where they exhibit their functions to a sufficient degree, and having a multiplicity of functions.

Problems solved by technology

In the multi-layer structure bodies such as container closures and containers having a multi-layer structure of functional resins and other resin such as a base body resin, however, it is difficult to place the layers of the functional resins at positions where excellent functions possessed by the functional resins can be exhibited to a sufficient degree.

When the functional resin which is an oxygen-absorbing resin is covered for its surfaces with a thick base body resin, however, oxygen that is to be absorbed is prevented from efficiently arriving at the layer of the oxygen-absorbing resin, making it difficult to efficiently exhibit oxygen-absorbing property.

On the other hand, if the amount of the functional resin is increased so as to exist up to near the surface of the structure, a problem arouses concerning the cost and, besides, deteriorating the mechanical strength and the formability.

It has also been attempted to combine a plurality of layers of the functional resins to enhance the effect encountering, however, the difficulty in efficiently forming the layers by the compression-forming.

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