Patent GB-827643-A (GB)
Title: Method for producing fibrous webs and filters therefrom and apparatus for carrying out the method
IPC: B01D29/11
Filed: 1956-03-26
Abstract: 827,643. Blending and stapling fibres; forming fibre laps. AMERICAN VISCOSE CORPORATION. March 26, 1956 [April 18, 1955], No, 9291/56. Classes 120(1) and 120(3) [Also in Group VIII] A fibrous web is produced by distributing fibres from spaced apart sources into a gas stream, the fibres of these sources differing in physical properties e.g. diameter, suspending the fibres in the stream and depositing them therefrom on a common surface in such intermingled relationship that there is a gradual gradation in the relative proportions of the fibres from the different sources. As shown in Fig. 1, preformed staple fibres having a minimum diameter of 10 microns (1.5 denier) are supplied to a chamber 1 by a blower 2 and duct 3 and fibres having a diameter of 0.5-10 microns are produced by feeding a plastic composition e.g. a liquid comprising 20% of a copolymer of vinyl chloride and vinyl acetate dissolved in a mixture of tetrahydrofuran and methyl ethyl ketone, pumped from a reservoir 4, to a spraying unit 6 comprising a liquid spraying tube 7 in the centre of a nozzle 8 through which air is forced at high velocity. Both forms of fibre are deposited at random over the areas A and B, .with overlap and blending at C, on a perforated continuously moving screen 9 and held there by suction induced in a box 11. The web is removed continuously by a belt 13, passed between pressure rolls 14 and collected on a roll 15. The distance of the unit 6 and duct 3 from the screen and from each other and the height of an adjustable partition 16 may be varied (or the partition omitted) to vary the length of the areas A, Band C (or merge them in less-defined layers), Figs. 3 and 4 (not shown). Fig. 5 shows apparatus for producing a web wherein the properties vary from edge to edge in which units 23 (similar to 6) and 24 forming fine and coarse fibres are spaced transversely of the direction of travel of a collecting screen 25 within a chamber 26. The unit 24 comprises concentric tubes 27 and 28 through which primary and, optionally, secondary high velocity gas streams are forced. A tow 29 of filaments, supplied from a package 30 by rollers 32 and 33, fed into the tube 27 and carried therethrough by the air stream, is cut by rotating blades 36 to form staple fibres. Fine and coarse fibres and a mixture thereof are deposited in the areas A. B and C, between which is a graded transition of average fibre diameter, on the screen 25. The web is removed by a conveyer 40 and may be passed between heated pressure rollers 42 to render any thermoplastic fibres in the web adhesive so as to bind the fibres, before collection on a roll 41. An alternative fibreforming means, Fig. 7, comprises a hollow rotating shaft 57 through which liquid is supplied to a chamber formed by a plate 53 and a flanged disc 51 carrying spray nozzles 55 and vanes 56 for producing the air blast required to form fibres. The webs may be cut into strips which are coiled around foraminous cores to form gas or liquid filters, Figs. 9 and 10 (not shown). Specifications 794,725 and 827,641 are referred to.