Patent GB-1137822-A (GB)
Title: Method of lining receptacles
IPC: B29C51/06
Filed: 1965-12-06
Abstract: 1,137,822. Laminated receptacles. LILY CUPS OVERSEAS Ltd. 6 Dec., 1965 [4 Dec.. 1964; 6 April, 1965], No. 19507/68. Divided out of 1,137,821. Heading B5N. A method of simultaneously forming and adhesively securing an unseamed liner 22 of heat-stretchable plastics film material to the interior surfaces of an open-topped receptacle 21, Fig. 1, comprises positioning a flat sheet of plastics film across the top of the receptacle; disposing thermoplastic adhesive having a softening point below that of the plastics film between the sheet and the receptacle; applying fluid pressure and/or vacuum to the sheet and adhesive to press them against the interior surfaces of the receptacle while heating the sheet and adhesive to soften the adhesive; stretching the sheet during the pressing step; and, after the pressing step, cooling the sheet and adhesive so that the adhesive secures the sheet to the interior surfaces of the receptacle. As described the liner 22 comprises a cast polypropylene film which has been treated by corona discharge, and a polyethylene layer applied and bonded in extruded form to the treated polypropylene film. The polyethylene layer acts as the thermoplastic adhesive in bonding the liner to a twoply paper receptacle 21. The composite film 23, Fig. 6, is fed by rollers 42 to a position above a receptacle 21, and a disc is cut from the film 23 by die 35 and positioned on and tacked to the rim 26 of the receptacle by a heated plunger 34. The base of the receptacle may be preheated by an element 32. The liner and receptacle are then placed in the apparatus shown in Fig. 7, which is heated electrically or by hot oil or steam, to render the polyethylene tacky and the polypropylene stretchable. The liner is first drawn upwardly to the position 22a by vacuum and then gradually into contact with an upper die socket 68 so that a thickness gradient is imparted to the liner. The vacuum is then cut off and further vacuum applied which draws the liner downwardly into the receptacle and stretches it to a uniform thickness. Air pressure is then applied above the liner to bond it to the receptacle. The air pressure is then removed, the apparatus opened, and the receptacle and liner cooled by part filling them with cold water. The lined receptacle is then ejected from the apparatus by raising an ejector plate 56. In an alternative embodiment the receptacle is open-bottomed. In a further embodiment the receptacle is in the form of a plate moulded from pulp slurry and the liner is of transparent grease- and liquidresistant polypropylene which is fed from a roll or extruded, is printed with a design and has a layer or coating of polyethylene applied thereto, e.g. by extrusion. The liner and/or plate may be preheated before placing them in the apparatus of Fig. 15, in which the liner 121 is cut to size by a knife and applied to the plate 126 by vacuum and air pressure. The lined plate is cooled by air or water. The apparatus of Fig. 15 may be one of a set of four such units operated simultaneously. In alternative embodiments the thermoplastic adhesive may be a sheet separate from the liner sheet, and the adhesive and liner may be of polyethylene of different densities.