US RE35,991 EGranted

Method of welding thermoplastic film

AssigneeDF Albums Ltd.

InventorsClaude Desmarais, Richard Desmarais

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Abstract

A method of welding at least two layers of a thermoplastic film which comprises a copolymer or copolymer-polymer mixture selected from the group consisting of ethylenevinylacetate (EVA) copolymer, an EVA copolymer and polyethylene, an EVA copolymer and polypropylene, and an EVA copolymer and polyethylene and polypropylene, with the proviso that the concentration of vinylacetate in said film is from about 12 to about 28% by weight, said method comprising the steps of: pressing said at least two layers of said thermoplastic film; applying a high frequency current to said pressed layers in order to weld said layers together; and recovering said welded layers.

Claims9

Dependent claims

A method of high frequency welding together layers of a thermoplastic film comprising vinylacetate in a concentration of about 12 to 28% by weight of said thermoplastic film and a ..copolymer or.!. copolymer-polymer mixture selected from the group consisting of:

..an ethylenevinylacetate EVA copolymer,.!.
an ethylenevinylacetate EVA copolymer and polypropylene,
an EVA copolymer and polyethylene, and
an EVA copolymer and polypropylene and polyethylene, the method comprising the steps of:
a) pressing together layers of said thermoplastic film between solid surfaces;
b) applying a high frequency electromagnetic wave energy to said pressed layers so as to effect high frequency welding together of said layers, said film being capable of being welded by high frequency wave-energy without requiring the application of heat to said layers of said film prior to high frequency welding said layers;
and
c) releasing said pressure on said layers, cooling said layers and recovering said welded layers.

5 more elements

Dependencies are inferred from the claim text.