Patent GB-1132575-A (GB)
Title: Improvements relating to the production of non-woven fabrics
IPC: D01D5/04
Filed: 1965-10-22
Abstract: 1,132,575. Filamentary structures. CARL FREUDENBERG. 22 Oct., 1965 [24 Oct., 1964], No. 44844/65. Addition to 1,055,187. Heading B5B. [Also in Division D1] A non-woven fibre structure is made by extruding molten or dissolved fibre forming polymeric material through non-circular apertures arranged in one or more rows to form a sheet or sheets of parallel continuous filaments, stretching and setting the filaments while keeping them parallel to but separate from one another, and forming the sheet or sheets into a fleece, suitably by collecting the sheet or sheets of filaments on a carrier. Stretching and setting may be effected by gas or vapour suitably air, flowing in the same direction as the filaments but at a higher velocity. Preferably all the apertures through which each sheet is formed are in a single spinerette and all the filaments in the sheet pass from the spinnerette into an openended duct down which a current of gas or vapour flows without turbulence, which duct may be oscillated while the filaments are passing therethrough. The gas or vapour stream passing along one side of the filaments may have a temperature different from that of the stream passing along the other side of the filaments, whereby crimped filaments are produced, these then being formed into a fleece. A binder may be subsequently applied to the fleece. In the apparatus of Fig. 2, a spinerette 1 has in its base a row of Y-shaped apertures 2 (Fig. 1, not reproduced) close together, e.g. two millimetres apart, through which filaments 5 are extruded and along the sides of this row there are slots 3 and 4 through which streams of gas or vapour, e.g. air, are forced alongside the sheet of filaments. Filaments 5 pass between sides 6 of guide duct 7 having air passageways 8 and 9 at the top of each of its sides. Continuously moving beneath the guide duct is a mesh screen 10 on which filaments 5 are collected into a fleece. Vacuum is applied from beneath the screen. To improve fleece formation, the screen moves at a speed considerably less than that of the filaments reaching it, e.g. at 20 metres as opposed to 2000 metres per minute. A number of spinnerettes 1, each associated with a guide duct 7, may be arranged together above the screen. Each guide duct 7 is oscillated in the sense shown by the arrows, above a pivot, not shown, to improve fleece formation. By varying the velocities of the gas or vapour streams passing through slits 3, 4, 8 and 9 with respect to one another properties of the resultant filaments, and thus of the resultant fleece, may be varied. Where only a short screening is desired, the air streams through slots 3 and 4 may be throttled or altogether closed down. Alternatively, additional air slots may be provided if additional air stretching is required. The properties of the filaments may also be varied by alteration of the temperatures of the stream. Thus if the temperatures of the streams 8 and 9 are increased then the filaments are maintained in the plastic state longer, while if stream 3 is at a different temperature from stream 4, or if stream 8 is at a different temperature from stream 9, crimping will result. Filaments so produced have improved adhesion for binders and a binder may be applied to a fleece forming on the screen 10 by spraying from a duct 11 extending across screen 10. Examples relate to the processing of polycaprolactam.