Patent GB-1220213-A (GB)
Title: Improvements in or relating to the alignment of fibrous material
Inventor: AYERST RONALD PERCY
IPC: B29C48/00
Filed: 1966-10-04
Abstract: 1,220,213. Reinforced alginic acid filaments. NATIONAL RESEARCH DEVELOPMENT CORP. 4 Jan., 1968 [4 Oct., 1966], No. 44318/66. Addition to 1,128,321. Heading B5B. [Also in Divisions C3 and D1] A process for aligning fibrous material comprises dispersing the fibrous material in a liquid medium in a vessel and extruding the resulting dispersion through an orifice in a wall of the vessel, the orifice being shaped from its entry end to its exit end to have a continuously diminishing width and to present to the dispersion surfaces which are generally convex in the direction of flow of the dispersion through the orifice, the width of the entry end of the orifice being at least one and a half times the length of any fibre to be passed through the orifice. Aligned fibres suitable for embedding in a material to produce a fibre-reinforced composite material may be so made by dispersing the fibres in a viscous liquid medium; extruding the dispersion through an orifice shaped as above, whereby the fibres are aligned in passing through the orifice; treating the extruded dispersion to form the liquid medium into a solid carrier for the aligned fibres; and removing the solid carrier from the fibres whilst maintaining their alignment. As shown, the sides of the orifice preferably terminate tangentially to the thread of extruding dispersion as at 2, and the sides of the entry end of the orifice preferably commence substantially tangentially to the inner face of the walls of the vessel in which the orifice is formed, as at 1. The transverse cross-section of the orifice is preferably circular or elliptical. Asbestos or single crystal whisker fibres, polycrystalline and glass fibres, cotton or wool fibres, in a random mass, may thus be aligned. The profile of the sides of the orifice between its entry and exit ends may be substantially flat part way in longitudinal section, the necessary convexity being obtained by curves at the entry and exit ends of the orifice. On the other hand the sides may be continuously convexly curved, in any desired manner. In an example of an orifice in accordance with the invention the profile of the sides is that of a quarter circle whose radius is equal to the thickness of the plate or vessel wall in which it is situated. Suitably the nozzle is made of a plastics material as for example polymethyl methacrylate. In an example, chrysotile asbestos fibres between about 1 and 2 cms. in length are dispersed in an ammonium alginate solution in a concentration of up to 5% by volume, the solution containing 1 to 5% by weight of pure ammonium alginate. The dispersion is extruded through a circular orifice having a convex wall of quarter circle convex shape in longitudinal cross-section, as shown in the drawings. The walls of the entry end 1 of the orifice commence tangentially to the vessel wall and the wall at the exit end of 2 terminates tangentially to the thread of extruding solution 3. The diameter of the orifice at the exit is 2 mms., and the radius of curvature of the convex wall is about three quarters of an inch. The dispersion is extruded into normal (N/1) hydrochloric acid under pressure at about 3 feet per second, and the rubbery extrudate so formed is wound on a rotating drum. The extrudate is dried, heated at about 200 C. for 15 mins. and then at 400 C. to remove the carrier and leave a thread of aligned fibres.