| 摘要 |
<PICT:0872796/IV (a)/1> An apparatus for the continuous manufacture of a microporous plastic web by sintering a plastic powder layer comprises a heated drum rotatable about a horizontal axis, the plastic powder being applied adjacent to the apex of the drum which consists of a spokeless cylindrical shell ring guided by carrying or guide rollers, the shell ring being suspended from at least one carrying roller which engages the inside of the ring adjacent to its apex and the lower portion of the ring being free to expand downwardly when heated. As shown, the carrying roller 3 is driven by belt 5 and in turn drives the shell ring 1 by means of the gears 4 and 2 in the sense of the arrow. The feed hopper 6 for plastic powder is provided with a cooling jacket 7, and the powder applied to the ring may be smoothed by a roll 8, which is preferably water-cooled, and revolves at a lower peripheral velocity than the ring. The powder may be applied directly to the drum after the latter has been treated with a parting agent, e.g. talc, or the drum may be covered first with a base layer 9 (e.g. paper or open-mesh glass wool fabric) fed from supply spool 10 via deflecting roller 11. Cover layer 12, which may be the same material as 9, is fed from supply spool 13 via deflecting roller 14, which also prevents a swinging movement of the shell ring 1. The product comprising the sintered layer 15 plus layers 9 and 12 is withdrawn by the rolls 16, 17 which may be used, if desired, for profiling the product. The ring is surrounded by an insulated housing 18 containing heating devices, e.g. a radiant heater 19 in the first part of the sintering zone and resistors 20 for general heating. In modifications, layers 9 and/or 12 may be omitted, or 12 may be replaced by an endless belt which is detached from the layer 15 behind the roller 17 and fed back to roller 14. Sinterable plastic powders specified are polyvinyl acetate, polyvinyl carbazole, polyvinyl chloride, polystyrene, poly-compounds of acrylic acid and methacrylic acid and esters; polymer mixtures and copolymers. |
