Patent GB-964459-A (GB)
Title: Artificial textile filaments and spinnerets for their production
IPC: D01D5/253
Filed: 1962-10-05
Abstract: 964,459. Spinnerets for melt-spinning. MONSANTO CHEMICAL CO. Oct. 5, 1962 [Oct. 26, 1961], No. 37796/62. Heading B5B. Melt-spun filaments having a cross-sectional shape which is substantially a polygon, e.g. a regular polygon having three, five, six or nine sides, the filaments having relatively flat surfaces resembling a prism, may be melt spun by use of a spinneret having an extrusion face comprising a solid plate having a melt side and an extrusion side and having at least one orifice extending between said faces to provide a passageway for molten polymer, said orifice being defined by a bounding wall having a form at the extrusion face determined by at least three inward extending lines connected at their outer extremities and assuming at their closest approach to the centre of said orifice the curve of catenary arcs extended by lines enclosing three or more radially elongated slots. The cross-sections of the filaments deviate from a circular cross-section by an amount represented by a deviation coefficient (D.C.) in certain ranges, depending on the number of sides of the filament cross-section. The coefficient is defined as the quotient of the perimeter of a given filament cross-section or orifice and the perimeter of a circle having the same crosssectional area of the given filament or orifice, i.e. the coefficient = P/2#A = P/3.54#A, wherein P = the actual perimeter of a given filament or orifice cross section and A is the actual area of such cross-section. For filaments of trigonal cross-section the coefficient is 1.10 to 1.26, for filaments of pentagonal cross-section the coefficient is 1.05 to 1.19, for filaments of heptagonal cross-section 1.03 to 1.17, for filaments of nonagonal cross-section 1.02 to 1.16. For an orifice adapted to produce filaments of trigonal cross-section the D.C. of the orifice is 1.73 to 3.51 and for pentagonal cross-section filaments 2.23 to 4.42. As shown in Fig. 1, a spinneret orifice suitable for spinning trigonal cross-section filaments comprises three catenary arcs 2, 3 and 4, each of which is extended by lines radiating away from the centre of the orifice. Adjacent lines from which adjacent catenary arcs are extended are joined at their outer ends and enclose three radially elongated slots. For example, lines 5 and 6 from which arcs 2 and 4, respectively, are extended define a slot. As shown, lines 5 and 6 are joined at their ends remote from the centre of the orifice by outwardly rounded line 7. Alternatively, line 7 may extend perpendicularly between the ends of lines 5 and 6, or the outer ends of lines 5 and 6 may be joined in various other ways. Lines 5 and 6 may diverge slightly, preferably at an angle less than 20 degrees (as shown in Fig. 2) or may converge. Cross-sections of filaments according to the invention are shown in Figs. 6 and 8 to 11. Mathematical formulµ are furnished for calculating the design of spinneret orifice configurations according to the invention. Spinning variables such as melt viscosity, jet velocity, spinning speed and rate of solidification must be properly co-ordinated as determined in an empirical manner in order to produce filaments according to the invention. A list is furnished of synthetic thermoplastic polymers which may be melt spun to produce filaments according to the invention.