Patent GB-970285-A (GB)
Title: Improvements in or relating to the melt spinning of threads,ribbons and films from thermoplastic thread forming materials
IPC: B29C48/08
Filed: 1962-09-06
Abstract: 970,285. Melt-spinning apparatus. ONDERZOEKINGSINSTITUUT RESEARCH N.V. Sept. 6, 1962 [March 7, 1962], No. 34165/62. Heading B5B. Melt-spinning apparatus comprises a filter for the melt, a die, at least one pump, a device for collecting the extruded product, and, located in the conduit system after the first pump and before the filter, a mixer having no moving parts and comprising a combination of dividing and guiding means located between a feed end and a discharge end, and forming a channel system in which, when viewed in section, the outlets of the channels are in a different position relative to the inlets. In apparatus comprising a melting grid, a pressure pump and a metering pump for the molten material, the mixer may be located between the two pumps. Preferably the combination of dividing and guiding means forms a tubular unit square or rectangular in crosssection which is inserted in a straight section of the melt conduit. The mixer may comprise a plurality of mixing sections, each consisting of two sets of four sub-channels, being positioned in continuous series in the conduit, wherein at the feed end of each mixing section, there is located guiding means which serve to divide the cross-section of the conduit into four quadrants, each constituting a sub-channel, each of the sub-channels being located adjacent to each of the other three and arranged to converge in pairs in a direction which is in one and the same axial plane to a point where the cross-sections of each of the sub-channels cover two diagonally opposite quadrants of the conduit crosssection, each pair of sub-channels debouching cross-wise into a subsequent set of four subchannels by diverging in pairs in a direction along an axial plane which is perpendicular to the aforementioned plane until the cross-sections of the resulting sub-channels cover the four quadrants of the conduit. The combination of dividing and guiding means may comprise a longitudinal member square in cross-section, which member fits into a channel having a similar cross-section and which member shows in each of its side faces similarly shaped wavelike channels having constant width and depth of preferably 0.4 to 0.45 times the width of the member, which channels run in longitudinal direction between two adjoining side faces such that in each following side face the wave of the channel is alternately about 0.7 and about 0.3 wavelengths ahead of its preceding wave and that the grooves begin as well as end in different quadrants of the longitudinal member. The stationary dividing and guiding means divide the melt stream into a plurality of sub-streams a, b, c, d, Fig. 4, and the sub-streams are then partially united to form at least two sub-streams (a + b) and c + d) which are subsequently successively divided and united as shown to form a single stream before the melt is filtered. In apparatus shown, melt collecting in pool 4 flows through channel 6 and (pressure) gear pump 7 to channels 9, 10, thence through a second (metering) gear pump 13 and channel 15 to the melt filter and spinnerets (not shown). Inserted in channel 9 is a cylindrical filling piece 17 (Fig. 3b) having a square internal cross-section, and containing the stationary mixer 20, shown in cross-section in Fig. 2a, consisting principally of a longitudinal member of cruciform crosssection having recesses in its side walls. Figs. 2b, 2c, 2d and 2e are side elevations of the mixer viewed from the directions of the arrows b, c, d, e in Fig. 2a, the arrow lines in Figs. 2b-2e indicating the flow path of the melt. Specification 883,989 is referred to.