GB1162617A - Method for Heating a Thermoplastic Yarn - Google Patents

Abstract

1,162,617. Yarn heating apparatus. BEMBERG S.p.A. 21 Feb., 1968 [4 March, 1967], No. 8530/68. Heading B5B. [Also in Division H5] A thermoplastic yarn wound on a supporting tube in the form of a spool, is heated by positioning the wound yarn mass as a dielectric between two electrodes energized by an R.F. voltage having an R.M.S. value of from 1000 to 2000 volts, a frequency between 10 and 200 megacycles and a generator power input between 2 and 6 kilowatts, for a time of from 1 to 10 minutes. Either field electrode of the R.F. field may be formed by the metal tube which supports the yarn spool, which tube is preferably made of aluminium, but may also be made of other metals, e.g. steel. The second electrode is preferably made of copper. Specified thermoplastic materials include polyamides, including polyhexamethylene adipamide, polycaprolactam and polyurethanes, polyesters, especially polyethylene terephthalate, polyolefins and polyvinyl materials. Thus, in Fig. 1, 1 indicates either field electrode, having a cylindrical configuration, the yarn spool 2 being placed in the interior of said electrode. The metal tube 3, on which the yarn is wound, acts as the second field electrode. Electrodes 1 and 3 are inserted in the supporting plate 4, in the interior of which they are connected to the coaxial leads 5 and 6 through which the R.F. voltage is fed. In Figs. 2 and 3, electrodes 1 and 2 are so shaped as to exhibit annular projections 3 and 4. The yarn spool 5, having a cylindrical supporting member 6 made of a non-metallic material, is positioned between electrodes 1 and 2 so that its sides directly contact the annular projections 3 and 4 of the electrodes. In addition, to the electrodes 1 is affixed a cylindrical block 7, of a non-metallic material, intended to support the spool 5. Electrodes 1 and 2 have, on their bottom portion, two coaxial plugs 10 and 11 which permit insertion into, and withdraw from, the coaxial sockets 8 and 9 formed in the supporting plate 12, the electrodes and spool assembly. The coaxial plugs 8 and 9 are connected, in the interior of bedplate 12, to coaxial leads 13 and 14 through which the R.F. voltage is supplied. Continuous treatment processes may also be effected. Thus, for example, the yarn spools may be arranged in a horizontal row on a conveyer belt or another like member which, being moved in a continuous run, causes the yarn spools sequentially to be passed between two confronting plate electrodes, energized by an R.F. voltage, the spatial velocity of the spool being calculated so that each individual portion thereof is subjected to the heat treatment for a time whose duration is roughly that required in the stationary treatment for producing an acceptable reduction of residual shrinkage. Examples are given, relating to the use of the apparatus for the reduction of residual shrinkage in yarns of polyamide and polyester materials.