Patent GB-1111113-A (GB)
Title: Improvements in or relating to the manufacture of non-woven fabrics
Inventor: MERCER FRANK BRIAN
IPC: D04H1/4391
Filed: 1964-04-22
Abstract: A non-woven fabric is produced by forming a web of randomly disposed synthetic staple fibres which have an inherent or induced capacity to coil into unidirectional spiral or helical form only, and subjecting the web to heat or chemical treatment to cause the fibres to coil and thus interlock with adjacent fibres.  Fine natural or synthetic staple fibres may be introduced into a partially treated web, as by vibration, and the treatment of the web subsequently continued.  The web may be laid in a water based liquid in which the individual fibres are suspended or tend to float to the surface of the liquid; the liquid is then heated to effect coiling of the fibres.  The web may be condensed between heated flat surfaces during the final coiling stage. Alternatively, the fibres may be introduced between two converging surfaces which may or may not be moving, vibration may be applied and the surfaces are heated to effect coiling of the fibres.  The surfaces are preferably co-axial conical surfaces to form a tubular fabric.  Shaped articles may be formed by depositing the staple fibres on a former or matrix, the deposition being by air or liquid suction through holes in the surface of the former or matrix or by an electrostatic field.  The former or matrix is preferably submerged in a liquid and is contracted as the coiling of the fibres causes contaction of the fabric.  If the web is laid in air a conventional random web forming machine may be used.  After the fibres of the web have been at least partially coiled, the web may be sprayed with or immersed in adhesive or a solvent to effect further bonding of the fibres, the web thereafter being heat treated to further coil the fibres.  Thick webs may be split in or parallel to the median plane or continuous sheets may be shaved off in a manner analogous to wood veneer production.  A backing material may be applied to both surfaces of a thick web prior to splitting, to produce a fabric having a simulated pile surface.  The surface of the fabric may be embossed, smoothed between heated platers or rolls, raised or brushed.  The fibres used preferably comprise at least two components, eccentrically arranged, and one being co-extensive with but of shorter mean length than the other, Fig. 1 (not shown). Examples of cross-sections of fibres which coil into spiral or helical forms only are illustrated in Fig. 3 (not shown).  Binary fibres having components of nylon 6 and nylon 66 and binary fibres having components of low density polypropylene and high density polypropylene are particularly suitable for use in making webs according to the invention.  Separation of the fibre components at points along the fibre length may occur during the final coiling stages for example in fibres having components of polyethylene and polypropylene.  In the case of a web composed of identical fibres it is essential that coiling of the fibres takes place simultaneously at the same rate and to the same degree; in the case of a web composed of proportions of different fibres it is essential that the last proportion of fibres to start coiling does so before the first proportion of fibres to coil has reached an advanced stage, this occurs when different fibres react to heat treatment at different temperatures.  A condensed web such as that described may be covered on each surface by an adhesively secured backing fabric e.g. woven jute, and the composite structure split in the median plane to produce two identical backed layers each having a simulated cut pile surface.