Patent GB-948073-A (GB)
Title: Improvements in or relating to spinnerets for the production of tubular filaments by melt-spinning
IPC: D01D5/24
Filed: 1960-06-03
Abstract: 948,073. Melt spinning spinnerets. W. C. HEREAUS G.m.b.H. June 3, 1960 [June 3, 1959; Dec. 23, 1959], No. 19722/60. Heading B5B. A spinneret for the production of tubular filaments by melt spinning comprises a spinneret plate provided with one or more bores parallel with the axis of the plate and terminating at the lower or outlet face thereof in an extrusion orifice of generally circular shape, the or each bore being provided with an insert member retained therein and an upper part of said insert member being relieved along its length, the lower portions of the or each bore in the spinneret plate being of smaller diameter than the remainder of the bore and being coaxial therewith, the clearance between said corresponding portion and the surrounding bore in the plate constituting an extrusion jet for the passage of the melt to the consequently annular extrusion orifice, and wherein the lower portion of the insert member has an axial bore leading from the outlet face of the plate and communicating with a generally radial bore that extends into a bored passage or duct in the spinneret plate that communicates with the atmosphere or other cooling medium into which the filaments are extruded, whereby said cooling medium is sucked into the tubular filament as it is extruded from the spinneret plate and drawn while still in a molten or plastic state and the filament is prevented from collapsing. As shown in Figs. 1 and 4, an insert member 3 is fitted into the bore of a spinneret plate 1, said bore consisting of an upper part 2a and a lower part 2b having a smaller cross section than the upper part. The insert member has the general shape of a cylinder with two flattened parallel sides. The portion of the insert member located at the inlet end for the melt tapers at 5 to facilitate the steady flow of the melt. At the other end the insert member is reduced to a cylindrical portion 6, whose diameter is less than that of the portion 2b of the spinneret plate bore. The insert member 3 is provided with a bore 7 which communicates with a duct 4 which passes through the spinneret plate 1 and the insert member to allow air to be sucked into the bore 7 to maintain the tubular form of the filament after it has been extruded from the spinneret plate and drawn while still in a molten or plastic state. During spinning the melt after passing over the tapered portion 5 of the insert member 3, through the clearance between the flats on the upper portion of the insert member and the upper part 2a of the bore in the spinneret plate and finally through the clearance of annular cross section between the cylindrical lower portion 6 of the insert member and the lower part 2b of the bore in the spinneret plate. The lower part 2b of the bore in the spinneret plate may be provided with one or more longitudinal recesses extending radially outwards from the lower part 2b of the bore and extending to the outlet of the bore. In this way a profiled shape will be imparted to the tubular filaments, which may thus be provided along their length with ribs or flutes. The upper part 2a of the insert member may be provided with more than two parallel flats or with ribs. Application 32548/48 as open to public inspection is referred to.