GB1244753A - Non woven fabrics - Google Patents

Abstract

1,244,753. Non woven fabric, testing textiles. E. I. DU PONT DE NEMOURS & CO. 8 July, 1968 [7 July, 1967 (3)], No. 32524/68. Headings D1F, D1N and D1R. [Also in Division F2] A non-woven web is made by forming a plurality of primary gas streams each forwarding a plurality of electrostatically charged continuous filaments 1, collecting the separated filaments on a continuously moving surface 3 and pneumatically oscillating at least one of the gas streams so that its filaments traverse the moving surface 3 at a substantially constant deflection amplitude and at a substantially consant deflection velocity which is at least one third of the velocity of the filaments along their length as measured immediately before oscillation. The oscillation can be effected by impinging on the primary gas stream at least one secondary gas stream, e.g. via slots 5, 6, at an angle of 60-90‹ thereto to deflect the filaments by up to 45‹. A plurality of parallel streams of filaments, as shown, can be deposited on a foraminous surface subjected to suction so that they touch each other either at the points of reversal or at adjacent edges. The gas supply to the secondary stream jets can be via a single source and a rotary valve providing a gas flow at sonic velocity through the outlet and a less sonic velocity in the conduits to the gas jets 5, 6. The secondary stream jets may produce 6-100 pulses/sec. The filaments can be segmentally drawn isotactic polypropylene. The webs formed can be bonded with saturated stream, lubricated with a polysiloxane containing surface active agent and tufted. The web produced may have the properties described in Specification 1244754. Determination of filament orientation in the web produced can be achieved by directing a beam of parallel light rays on the web at an incidence angle of less than 90‹. The light reflected in a plane perpendicular to the filament axis (which will come from only those filaments in the plane of the web having an axial orientation perpendicular to the incedent rays) collected, magnified and focussed onto a photomultiplier tube to be electrically estimated. An estimation for varying directions of incedent light rays is performed to measure the proportions of filaments in the varying directions in the web. See Fig. 6 (not shown).