GB1270758A - Improved manufacture of laminates - Google Patents

Abstract

1,270,758. Laminates. A. L. JAMES. 15 June, 1970, No. 28965/70. Heading B5N. A laminate is produced from a film of thermoplastic material having one surface treated to render it polar, e.g. by gas flame oxidation or corona discharge, and having the other surface left non-polar and a substrate sheet formed of a material different from the thermoplastic film but capable of forming a permanent chemical band therewith, by passing the film and substrate sheet through a pressure zone defined by a first pressure applying medium and a revolving convex heating drum the surface of which has release characteristics with respect to the non- polar surface of the film, the film being interposed between the substrate sheet and heating drum so that the non-polar surface of the film is positioned against the heating drum, the film being maintained against the heating drum through a predetermined arc of travel rapidly to cause the film to be heated from ambient temperature to a condition in which at least the polar surface is at least at its heat sealing temperature, the pressure applying zone causing the polar surface of the heated film intimately to contact the surface of the substrate sheet to effect heat sealing of the interfacial surfaces thereof and the production of a permanent chemical bond thereat, the adhesive force between the film and substrate sheet being substantially greater than that between the non- polar surface of the film and the surface of the heating drum, the film being stripped from the heating drum subsequent to the bonding of the film to the substrate sheet. The film may be of polyethylene, polyvinyl acetate, polyvinylidene chloride, cellulose acetate or triacetate, polyvinyl chloride, vinylchloride-acetate copolymer, ethylcellulose, rubber hydrochloride, polystyrene, polyvinyl alcohol or polyvinyl butyral. The substrate sheet may be of Kraft paper which may be printed, paperboard, regenerated cellulose, glassine paper, "Saran" (Registered Trade Mark) coated regenerated cellulose, sulphite paper, ground wood sheet or metal. In Fig. 1 substrate S is unwound from roll 10 on stand 11 and passed over spreader roll 12, preheating roll 13 and spreader roll 14 to the nip between film heating roll 23 and laminating roll 24 where it is contacted with film F unwound from roll 15 revolvably mounted on one of a pair of shafts 16 carried by swingable arm 17 pivotally mounted by pivot 18 on turret-type unwind stand 19 carrying second roll 15a of thermoplastic film which permits a flying splice to be made, between splicing nip rolls 20, over spreader roll 20a, over metal roll 21 covered with silicone rubber and in contacting relation with cooling roll 22 and round heating roll 23 which may be covered with polytetrafluoroethylene or silicone varnish or having a hard chrome plated surface which is polished or etched or sand blasted to a matte finish, the non-polar surface of the film being in contact with the surface of roll 23. The laminate L is passed over cooling drums or cylinders 25, spreader roll 26 and taken upon stand 28. A second pressurapplying medium may be provided so that the film and substrate when moved between the first and second pressure applying zone and against the surface of the heating drum are moved through an arcuate path of travel through an arc of between 10 degrees and nearly 360 degrees.