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Application filed by Grace W R & CofiledCriticalGrace W R & Co
Publication of PT72792ApublicationCriticalpatent/PT72792A/en
Publication of PT72792BpublicationCriticalpatent/PT72792B/en
Prodn. comprises keeping the neck of the pack dilated while the thermoplastic material is heated by infra red radiation sufficiently to weld when subsequently pressed together. Pref. appts. claimed for this process comprises a chamber which can be evacuated to dilate one or more packs of which the mouths are restricted by elastic clamps to maintain a sufficient residual internal pressure differential to keep the neck distended until fully softened and collapsed. Process is esp. for producing packages enclosed in heat shrunk wrappers pref. based on laminates (I) having a layer of polyvinylidene chloride between a layer of ethylene-vinyl acetate copolymer (EVA) film and an irradiated layer of EVA film. Separates the heating and consolidation phases of the weld cycle. Allows the heaters to get close to the matl, without contact, then shift them from the path of the consolidation bars. Minimises loss of moisture from damp contents, e.g. fresh meat.
PT7279281A1980-06-251981-04-02Packaging process and apparatus
PT72792B
(en)