FI49783B

1,101,472. Package seams. TETRA PAK A.B. 28 March, 1966 [15 April, 1965], No. 13604/66. Heading B8C. [Also in Divisions B4 and B5] A web suitable for forming into tubular packaging material is made by permanently bonding a coating layer, e.g. of plastics, to a carrier web, e.g. of paper, along two spaced longitudinal zones whilst leaving an unbonded continuous longitudinal zone therebetween and cutting through each of the layers along different continuous longitudinal lines laterally spaced apart in the intermediate unbonded zone, thus splitting the web into two and producing a strip of coating material overlapping the edge of the carrier web. The projecting strip so produced may be lapped over in various ways to produce a sealed seam when the web is formed into a tube (Figs. 5, 8a or 8b, not shown). The material may be produced by extruding a layer, e.g. of polyethylene or polypropylene on to the paper layer and passing them around a chilled roll and co-operating pressure roll, adhesion in a longitudinal zone being avoided either by prior application of a strip of parting agent, or by providing an annular groove in one of the rolls so that they do not press the two layers together in this zone. Preferably vacuum is applied to the grooved roller to ensure non- adhesion. The laminated web is then cut through in the unbonded zone by a double cutting wheel 10, one cutter 11 of which cuts through both layers 1 and 2 whilst the other 12 cuts only through the carrier 1, thus producing a projecting strip of the coating layer. Both. sides of the paper web may be coated, a separate cutter being used to cut through each coating layer at transversely spaced position, the unbonded strip of coating thus freed then being laid back, and a double cutting wheel used to remove the intervening zone of carrier web thus producing two webs coated on both sides and on single projecting strip of coating material along one edge (Figs. 6 and 7, not shown).