GB1088240A - Melt spinning of fibre-forming polymers - Google Patents

Abstract

1,088,240. Melt-spinning apparatus. IMPERIAL CHEMICAL INDUSTRIES Ltd. Aug. 2, 1966 [Aug. 20, 1965], No. 35785/65. Heading B5B. An apparatus for controlling the flow of ambient fluid in the vicinity of filaments while being melt-spun consists of deflecting means disposed at intervals along the lengths of the path of the stream or streams of polymer whereby the flow of the ambient fluid towards the stream or each stream of polymer and thereafter following a path of the, or of each, stream of polymer is a stable laminar flow, the said conditions of stable laminar flow persisting until the temperature of the, or of each, stream of polymer falls to the solidification point. Suitably, at least two control surfaces are arranged about the stream or streams of polymer in the form of a collar or forming in effect a collar, the inner edge of each of said control surfaces being distant by not less than about 4 mm. and not more than about 30 mm. from the stream of polymer or the outermost streams of polymer and the said control surface extending outwards to at least about 10 mm. from its inner edge, said control surfaces being distant from adjacent control surfaces by at least about 5 mm. and at most about 100 mm. and a point moving radially along a surface from the inner to the outer edge of each of said control surfaces having at no time any downward component of motion, adjacent control surfaces being optionally bridged by substantially vertically disposed laminae. Such collars may advantageously be in the form of the surface of a conical frustum with the wider part uppermost, or of the surface generated by the rotation of a portion of an exponential curve about the abscissa. Alternatively, the plurality of control surfaces may comprise a single member, e.g. a suitably offset Archimedean screw with at least two complete turns. As in Fig. 1, a series of six identical members 5, each consisting of a portion 6 in the form of the curved surface of a right conical frustum of conical angle 140 degrees, base 7 cm. diameter and top 1À75 cm. diameter, integral with an annular disc 11 of outside diameter 10 cm. and internal diameter 7 cm., are held in fixed juxtaposition, with the annular discs 11 being in parallel planes and the bases of the conical frustral portions 6 facing all in the same direction, by means of rods 7, 8 and 9 which are threaded and passed through holes of which there are three equid.stant bores through each annular disc 11 with centres 0.5 cm. from the outer edge of the disc 11. The members are held in their relative positions by means of nuts 10 screwed on the threaded rods 7, 8 and 9. The apparatus may be used not only with an array of spinneret holes with radial symmetry but also with other configurations, e.g. a rectangular configuration. In a modification, the top of the conical frustum was of 5-8 cm. diameter for the uppermost member reducing by uniform stages to 5.2 cm. for the lowermost member, this variation being in conformity with the convergence of the filaments to a guide 1-5 m. below the spinneret. A cylinder of gauze may be fitted around the assembly of members if desired, so that the induced flow of ambient air has to flow through the meshes of the gauze. A further improvement in the stability of the air can be effected by incorporating vertical fins in the space between adjacent control surfaces. The effect of the apparatus in inducing a laminar flow of ambient fluid towards the polymer streams and thereafter along with the polymer streams is such that the rate of heat transfer from the polymer streams to the ambient fluid is minimized. Thus for a given size of polymer stream, the use of the inventive process results in the minimum degree of orientation of the spun fibre as shown by its possessing a relatively low birefringence. Examples relate to the spinning of polyethylene terephthalate and isotactic polypropylene filaments.