Patent GB-865707-A (GB)
Title: Method of manufacturing artificial fibres
IPC: D01D5/42
Filed: 1957-04-29
Abstract: Fine fibres are produced from relatively thick filaments or films of normally crystalline organic polymers by treating a relatively thick, oriented filament or film of the material containing a uniformly distributed foreign substance in such a way that the latter changes physically and/or chemically to produce an internal mechanical stress in the filament or film which at least weakens and preferably forms fissures in the filament or film, parallel with the direction of orientation, and thereafter, if the filament or film is not already completely transformed into fibres, mechanically working the filament or film to cause it to split up into separate fine fibres.  The foreign substance may be incorporated in the polymer before the polymer is shaped into a filament or film or may be absorbed into the filament or film after the latter has been formed.  The foreign substance may be a solid which undergoes a chemical reaction as a result of the treatment with liberation of a gas or may itself undergo expansion as a result of the treatment.  Alternatively, the internal mechanical stress may be produced by causing a gas which has been absorbed by the filament or film to expand, or by causing a solid substance in the filament or film to swell when it comes into contact with a liquid which penetrates into the interior of the filament or film so that osmotic pressure is produced within the filament or film.  The filament or film material may be a polyamide, regenerated cellulose, a vinyl high polymer such as polyvinyl alcohol, a polyester or a cellulose ester.  The foreign substance may be a finely divided catalyst, (preferably supported in a porous carrier) which causes a component, such as hydrogen peroxide, of a liquid penetrating into the filament or film to decompose with liberation of a gas in the interior of the filament or film.  The foreign substance may also be of a kind which can readily be decomposed with liberation of a gas if the filament or film is heated or irradiated, as by radio or supersonic waves. The foreign substance may be volatile and insoluble in the polymer and may be caused to evaporate by heating the filament or film or by suddenly decreasing the pressure of the atmosphere surrounding the filament or film, evaporation of the substance being preferably facilitated by the incorporation of porous particles in the filament or film.  The foreign substance may also be a finely divided porous carrier having a gas, such as carbon dioxide or ammonia, adsorbed therein which may be caused to expand by heating the filament or film or by reducing the pressure around it.  The carrier may initially contain a liquid in which the gas is soluble and a gas may be caused to dissolve in this liquid by forcing the gas under elevated pressure into the filament or film before the pressure of the atmosphere surrounding the filament or film is decreased to cause the gas to expand.  This treatment may be preceded by a step in which osmotic pressure is generated in the filament or film.  Specifications 479,202 and 810,001 are referred to.