| 摘要 |
<p>1,116,739. Laminates. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 10 Oct., 1966 [11 Oct., 1965; 15 April, 1966 (2)], No. 45188/66. Heading B5N. A laminated thermoplastic film is produced by extruding and blowing a thermoplastic film, sealing the blown tube in a non-plasticized condition, heating the flat film tube so that the facing surfaces thereof become in a plasticized condition, and fusing the opposite sections of the flat tube by the application of pressure. An apparatus for performing these operations comprises an extruder 10 having an annular die 21 from which a thin-walled tube 11 is extruded and then blown up by air, a pair of sealing rolls 13 having guide plates 11 for flattening the tube, drive rolls 16 and 19 which keep the flattened tube taut as it passes heaters 18, which may be, e.g. infra-red heaters, roll 19 also supplying the pressure to bond the facing surfaces of the tubular film. The flattened tube should preferably be kept horizontal while it is heated, and the heating is arranged so that the inner surfaces of the tube plasticize, but the lower surface does not and can stand being drawn by rolls 16 and 19. An alternative apparatus uses two extruders, each leading into a half of the same annular die. In this case, the edges are suitably cut off the final laminate, since the boundary between the film halves will not be a straight line. A further apparatus produces a four-layer laminate by extruding a laminated film using a die having two concentric annular openings each fed by a different extruder. In this case it is found that the layers of the tubular laminate produced have varying thicknesses, but it is stated that the extruders are preferably arranged coaxially, with the sealing rolls 13 normal to this axis, to produce a laminate having a uniform overall thickness and the same proportions of the two components across its width. The thermoplastic material is suitably polyethylene, and if two extruders are used, a laminate of black and white polyethylene e.g. for packaging milk, may be produced.</p> |
