GB892901A - Improvements in method of making a continuous network of individual filaments of thermoplastic material and extrusion dies for use in the same - Google Patents

Abstract

892,901. Extruding nets. REEVES BROS. Inc. Jan. 4, 1960 [Jan. 9, 1959], No. 225/60. Class 87(2). A continuous network of thermoplastic filaments is made by extruding at least two sets of fluid thermoplastic material and thereafter bringing individual filaments from one set into contact with filaments from the other set or sets while in a non-supported condition at the points of contact of said filaments until the contacting filaments have fused together. An extrusion die for use with the above method is illustrated in Fig. 1 and comprises two concentrically mounted, relatively rotatable die heads 17, 31, the former being the base of an inner cylinder 12 of a stationary die-holder 10 whilst the latter is affixed by bolts 32 to the body portion 26 of an outer die-holder 11. The die heads 17, 31 have oblique annular faces 19a, 41 in which are series of ports 19, 42 to which the thermoplastic material 14 is fed by passages 18, 40 with the result that the filaments extruded from ports 19 are directed towards those extruded from ports 42. Rotation is imparted to the outer die-holder 11 by means of a pinion 46 driven by an electric motor (not shown) and engaging a flat spur gear 47 affixed by means of bolts 28, 48 and a disc 27 to the body portion 26. The outer die-holder 11 is supported on thrust bearings 43, 44. Cylinder 12 is connected to a source (not shown) of fluid thermoplastic material 14 which passes directly to the passages 18 in die head 17 and indirectly to the passages 40 in die head 31 via a series of radial passages 33 in the wall of cylinder 12, a common annular chamber 34 formed within the adjacent walls of cylinder 12 and the surrounding cylindrical member 20, a series of radial passages 35 in member 20, an annular chamber 36 of triangular cross-section in body portion 26, a series of vertical passages 38 and an annular chamber 39 of oblong cross-section. The upper and lower ends of chamber 36 are sealed by annular sealing rings 37 retained in grooves in the outer wall of member 20. When the apparatus is mounted vertically as shown, the resulting tubular net is removed over a mandrel 50 under the action of gravity which is assisted by the use of pull-out rollers (not shown) causing a stretching of the net and orientation of the molecular chains in the filaments. In a modification, an inner cylinder for the stationary die holder 10 not having radial passages 33 is used and thermoplastic material from another source (not shown), e.g. of different colour, is fed to the die head 31 through passage P which, in the first embodiment, is blocked by a plug T. A helical heating coil is provided within this modified inner cylinder and the mandrel contains a coil for receiving a fluid heating or cooling medium in order to control the temperature of the mandrel.