GB948171A - Method and apparatus for increasing the air-permeability of films or sheets - Google Patents

Abstract

948,171. Abrasive blasting. OLIN MATHIESON CHEMICAL CORPORATION. May 30, 1961 [June 10, 1960], No. 19545/61. Heading B3D. The air-permeability of a web of paper (particularly cigarette paper) regenerated cellulose or plastic; e.g. polyolefin, film is increased by continuously advancing the web over a cylindrical anvil and directing solid particles, dispersed in a jet or plurality of jets of fluid, substantially at right angles to the web, as it passes over the anvil, to form, as by sand blasting, microscopic rents, perforations or openings in the web. The web W, Fig. 1, is passed from a roll S, through a slot 14 into a chamber 10, then around part of the periphery of an anvil roller 16 therein. Jets of air are directed, through tubes 21, against the outer surface of the web and particles of sand, fed into the jets through tubes 20 branching into the tubes 21, impinge against the web. The particles of sand are fed into the tubes 20 in the following manner. Particles of sand pass, from the outlet 27 of a reservoir 22, into the middle of a horizontal trough 29 and are distributed along it by a screw conveyer 23 having flights 24 and 26 of opposite hand. Particles of sand fall through outlets 28 in the base of the trough on to a rotating roller 31, which distributes them into U-shaped troughs 33. The tubes 20 are connected to the lowest parts of the troughs 33. Baffles 34 and 36 are provided in the chamber 10 to deflect rebounding particles of sand to the bottom of the chamber, from which they are drawn back, through a conduit 37, into the reservoir 22. The web emerges from the chamber 10 through a slot 17 and passes over an abrading roller 11 and then between a roller 39 and knives 38 and is slit into strips, which are wound into rolls 13. Both sides of the web may be sand blasted as by jets 46 and 47, Fig. 2.