Injection-molded refrigerator liners

Details Injection-molded refrigerator liners Injection-molded refrigerator liners

1998-10-14

2001-02-20

Loney, Donald (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including variation in thickness

C428S120000, C428S167000

Reexamination Certificate

active

06190755

ABSTRACT:

The present invention concerns injection moulded refrigerator liners characterized by the possibility of mechanical bonding of the insulating foam. In particular the invention concerns refrigerator inner liners having appropriately shaped and distributed protruding parts, obtained by injection moulding of a thermoplastic polymer, in particular a propylene polymer, in order to make possible the subsequent coupling of the insulating foam to the back surface of the liner without the use of any particular pretreatment of said surface.
The present technology for the production of the refrigerator inner liners is essentially based on thermoforming a thermoplastic sheet, primarily of polystyrene. Such a technology, however, presents quite a few drawbacks, e.g. low productivity in the sheet extrusion process, difficulties in the dimensional control of the sheets, difficulties or even impossibility to integrate the creation of complex constructive features, like tubing for air streaming in the “no frost” refrigeration system, in the main production process.
Moreover, the thermoforming technology can hardly be used with a propylene polymer, which should actually be preferred on the basis of just the physical-mechanical properties of the polymer, owing to a few additional difficulties, like low melt strength, excessive sag of the polymer, narrow working temperature range. Furthermore a polypropylene refrigerator liner prepared with the thermoforming technology would require some special treatment in order to modify its surface and make possible the necessary bonding with a polyurethane foam.
We have found that all these drawbacks can be overcome by shifting from the thermoforming technology to the injection moulding technology, introducing some innovative features in the shape of the liner, such features being easily obtainable by way of the injection moulding technology using opportunely shaped moulds, in order to make possible a mechanical bonding between the liner itself and the insulating foam. The invention can be applied to any thermoplastic polymer, but it is particularly suitable for polyolefins and further in particular for propylene polymers.


REFERENCES:
patent: 3970324 (1976-07-01), Howat
patent: 4136220 (1979-01-01), Olabisi
patent: 4156045 (1979-05-01), Burger
patent: 1609424 (1970-04-01), None
patent: 2510930 (1976-09-01), None
patent: 2143465 (1984-07-01), None
patent: 2171189 (1986-02-01), None
European Patent Office, Patent Abstract of Japan, Abstract of Japanese Patent Application Publication No. JP58081134 (1983).
Derwent English Language Abstract of DE 2510930.

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