GB915353A - Fibrous batt - Google Patents

Abstract

<PICT:0915353/IV(a)/1> A fibrous batt is made by extruding a liquid comprising an organic filament-forming material through a plurality of orifices into a gaseous atmosphere to effect solidification of the material in the form of a multiplicity of continuous filaments and rendering turbulent the gaseous atmosphere in a zone in which the forming filaments are in a mutually adhesive condition, whereby the filaments come into contact and coalesce at randomly spaced points along their lengths and form a three-dimensional lace-like fibrous structure, and collecting the structure at a linear rate substantially below the linear rate of extrusion of the filament-forming material as a batt of a denier of at least 40,000, preferably 55,000-100,000. Desirably, the filament-forming material is extruded at a linear speed more than 400 times the linear speed of collection. Specified materials include cellulose ethers and esters, e.g. ethyl cellulose, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-butyrate, ripened cellulose esters and unripened cellulose esters, e.g. cellulose triacetate, polyamides, e.g. nylon 6 or 66, polyesters, e.g. polyethylene terephthalate, acrylonitrile polymers and copolymers, olefinic polymers, e.g. polyethylene and polypropylene, polyvinyl chloride, polyvinylidene chloride, and vinyl chloride-vinyl acetate copolymers. In a preferred method, a solution of cellulose acetate in a volatile solvent is extruded under a pressure of 600 psig. into an evaporative atmosphere. This may be effected by using spinneret orifices of 0,04 mm. or less diameter, with linear rates of extrusion of 700 m./min. or more. Continuously with its production the batt is condensed into a cylindrical rope of the approximate cross-sectional area of a cigarette and the rope is converted to cigarette filter tips. In apparatus as shown, spinning solution is extruded from spinneret 18 into the cabinet 11, which is supplied with hot air entering at 15 and leaving at 16. Jets of air from pipes 20 and 21 draw and entangle the filaments, which coalesce at the points of contact to form a fibrous batt, which falls between baffles 22 and 23, serving to prevent lateral spread of the batt, on to the endless porous support 12 (e.g. a wire screen), from which the batt is conveyed to the trumpet 27, where it assumes the dimensions of a cigarette. The batt is then wrapped with paper in a cigarette-wrapping machine 29 and the resulting cylindrical structure 32 cut by blade 33 to form filter tips 34. In place of the elongated spinneret 18 shown, a conventional circular spinneret, or several such spinnerets, may be used. The porous support 12 may be omitted if the entangled mass of filaments is sufficiently coherent.