Patent GB-662880-A (GB)
Title: Improved apparatus and process for the production of artificial or synthetic filaments by spinning solutions of high polymers
IPC: D01D4/00
Filed: 1949-04-22
Abstract: <PICT:0662880/IV (a)/1> Artificial or synthetic filaments are obtained from solutions of high polymers by means of extrusion apparatus comprising a rigid spinning-plate, preferably of metal, containing extrusion orifices having a cross-section at the point of entry at least 50 times greater than that at the point of emergence of the filaments, and immediately above this plate a filter comprising at least one fabric or gauze formed by threads of a substantially cylindrical cross-section in which the average area of the apertures between the threads of the fabric formed by their crossing is less than the cross-section of the apertures of emergence of the extrusion orifices, this filter being in contact with the plate and covering the surface so as to cover all the orifices in such manner that the solution cannot pass round the filter but is compelled to pass through it, there being also provided a pre-filter arrangement which contains at least one fabric similar to the one already described and separated from it by a space so that liquid can pass freely from any point of emergence in the pre-filter to any part of the final filter and can pass from thence to any one of the extrusion orifices.  The spinning-orifice plate may be of stainless steel.  The fabric used in the final filter may be formed of threads of bronze, nickel, polyamide, or polyvinyl compound.  The tightness of the threads required to give the desired fine openings may be obtained directly or by subjecting the fabric to shrinking.  Several thicknesses of the filter-fabric may be assembled together and secured by sticking, clamping, or soldering the edges.  The pre-filtering device may also consist of several thicknesses of fabric having very fine openings, if desired together with coarser fabric, sheets of unwoven fibres, or gratings for retention of coarser particles. The filter fabric which is to be in contact with the spinning-plate is preferably flattened by rolling, calendering or ironing, or, in the case of synthetic fibres, by mounting the fabric and then submitting it to a shrinking treatment.  To prevent spinning solution from passing round the edges of the filter instead of through it, the periphery of the fabric may be soldered to the front face of the spinning-plate or the periphery may be compressed against this plate by joint-rings.  As shown, the spinning-plate 3 is screwed into member 1 which is screwed on to the flared end 11 of the solution-supply pipe 2.  The spinning-plate may be of 2 mm. thickness and the orifices 4 may have an inlet cross-section of 12.5 sq. mm. and an outlet cross-section of 0.005 sq. mm.  Above plate 3 is a ring 5 which carries two calendered bronze cloths, in which the mean area of the interstices between the threads is 0.003 sq. mm., and two thicknesses of a polyamide satin fabric having interstices of 0.001 sq. mm.  The peripheries of these fabrics are secured together by means of a polyamide varnish.  A resilient metal gasket 6 ensures the lateral fluid-tightness of the assemblage.  A rigid perforated steel plate 7 is placed over gasket 6, and over plate 7 there is an annular ring 9 carrying a bronze cloth and a fabric of polyamide fibres.  A perforated plate 10 of plastic material is placed over ring 9, and a further layer of filtering material 12 may be placed over plate 10. If desired, the spinning plate 3 may be constructed with a shoulder in replacement of the screw-thread, so that it may be secured in the jet assembly.  A filleted member with a large central aperture may be provided between the flared end 11 of the conduit 2 and the plate 10.