초록 ▼

A multilayer plastics sheet destined to be formed into foodstuff containers by thermoforming has a barrier layer for low oxygen permeability, and incorporates reclaim material for providing desired mechanical properties to the sheet. The reclaim material represents 40-60% of the sheet by volume, and

A multilayer plastics sheet destined to be formed into foodstuff containers by thermoforming has a barrier layer for low oxygen permeability, and incorporates reclaim material for providing desired mechanical properties to the sheet. The reclaim material represents 40-60% of the sheet by volume, and in order to incorporate these high reclaim levels without concomitant organoleptic problems the reclaim material is formed as a single layer adjacent what is to be the outside surface of the container. The sheet is accordingly highly asymmetric, but any substantial polymer melt instability during coextrusion tending to cause layer thickness variation and lack of visual appeal of the sheet is prevented by forming the sheet as two substantially symmetrical components which are individually and separately coextruded, and subsequently extrusion laminated together. Of the components one includes, and is symmetrical in relation to, the barrier layer, and the other likewise incorporates the reclaim layer.

대표청구항 ▼

An asymetric multi-layer plastics sheet structure which comprises: (a) a barrier layer of a polymer material; (b) first and second skin layers of a skin polymer, disposed one on either side of said barrier layer and bonded thereto said barrier layer and said first and second skin layers having been

An asymetric multi-layer plastics sheet structure which comprises: (a) a barrier layer of a polymer material; (b) first and second skin layers of a skin polymer, disposed one on either side of said barrier layer and bonded thereto said barrier layer and said first and second skin layers having been coextruded and forming a first multi-layer sheet component; (c) a reconstituted reclaim layer; (d) third and fourth skin layers of said skin polymer, disposed one on either side of said reclaim layer and bonded thereto; said third and fourth skin layers and said reclaim layer having been extruded and forming a second multi-layer sheet component; (e) an interface at which said first and third skin layers are bonded together by extrusion lamination of the said first and second multi-layer sheet components; said sheet structure thereby comprising at least six layers; (f) said reconstituted reclaim layer comprising waste material of said sheet structure; (g) the reclaim layer having a volume which is generally in excess of 30% of the total volume of the sheet structure up to generally 60% of the total volume of the sheet structure; and (h) said sheet structure thereby comprising at least six discrete layers and having said first skin layer spaced from a medial line of said sheet structure.