Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1993-07-13
1997-01-07
Buffalow, Edith
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
4283044, 4289033, 264DIG10, 264 456, 15624411, B29D 2200
Patent
active
055914969
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing composite sheet materials, in particular laminated sheet materials formed of layers of plastic foam such as expanded polystyrene (EPS). The invention also relates to a sheet material formed by such a method.
2. Related Art
Plastics, and in particular foamed plastics, are employed in great quantities for packaging purposes. Taking the environmental question into consideration, increasing efforts are being made to reuse these materials; that is, to recycle them. Plastics are particularly well suited for reuse in general, but the use of recycled plastics or plastic foam in packaging is inhibited by a number of problems.
On the one hand, the color of recycled plastics material is normally very difficult to alter, and in many cases will not meet requirements. Then there are the obvious psychological and hygienic considerations which apply in particular to the packaging of foodstuffs, especially where the foodstuffs might come into contact with the recycled plastic material.
To preclude any possibility of such contact and yet employ recycled material, it has long been suggested in the packaging arts that a laminate be formed in which a layer or stratum of recycled material is completely covered on at least one side by a layer of previously unused or "virgin" material. More often, to obviate any possibility of contamination or the appearance of contamination, the recycled material is encapsulated in virgin material, or in the case of sheet, foil or film a "sandwich" is formed of an inner layer of recycled material enclosed between two layers of virgin material.
EPS sheet is conventionally formed by extrusion, as by continuously extruding a cylinder or tube of EPS film, expanding the tube under internal air pressure, and slitting the expanded tube or "balloon" at one side and rolling it out to form a single sheet, or slitting it at opposite sides to form two sheets.
It is also known to form a laminate of EPS by simply introducing the extruded tube between a pair of rollers to press it flat, and then continuously trimming the lateral edges from the flattened tube. Just such a technique is disclosed in German Patent Specification No. 2,946,867, published Oct. 27, 1983 in the names of T. Komori et al.
With these considerations as a starting point, the invention addresses the problem of creating by means of a simple method sheet materials which will meet packaging requirements, yet make use of recycled plastic.
SUMMARY OF THE INVENTION
In its broader aspects, the invention provides a method of making a composite sheet material by extruding a first lamina of previously unused expanded polystyrene from a first extruder, simultaneously extruding a second lamina of recycled polystyrene from a second extruder; that is, a separate extruder, and promptly bonding the freshly extruded laminae to each other.
The laminate composition of the sheet material so formed makes it possible for the recycled layer or lamina to be shielded on at least one side with a cover lamina of fresh or virgin material, and the sheet material on that side will have the appearance and properties of sheet material formed entirely of virgin plastic.
Improved bonding may be facilitated by applying heat to at one or both of the laminae across the full width thereof immediately before the bonding step is carried out.
In a preferred method according to the invention, not one but a pair of cover laminae is extruded of previously unused expanded polystyrene from the first extruder, and the freshly extruded recycled lamina is promptly enclosed between the freshly extruded cover laminae. Both cover laminae are then immediately bonded to the recycled lamina. Here again, bonding may be facilitated by applying heat immediately before the bonding is carried out.
When sheet material formed according to the invention includes a recycled lamina covered on both-sides in this manner, it is embedded in virgin material. It will be apparent that such a sheet materi
REFERENCES:
patent: 3616020 (1971-10-01), Whelan
patent: 3669794 (1972-06-01), Mazur
patent: 4410602 (1983-10-01), Komoda
patent: 4474715 (1987-12-01), Mosier
patent: 4943489 (1990-07-01), Nedzy
patent: 5118561 (1992-06-01), Gusavage et al.
patent: 5128196 (1992-07-01), Luetkens, Jr. et al.
Anderson Michael C.
Grone Horst-Ditmar
Heap Anthony J.
Buffalow Edith
Linpac Plastics International Limited
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