GB1050042A - - Google Patents

Abstract

1,050,042. Spontaneously crimpable composite filaments. SOCIETE RHODIACETA. Feb. 10, 1965 [Feb. 14, 1964], No. 5841/65. Heading B5B. Spontaneously crimpable composite filaments are produced by continuously melting a thermoplastic linear polymer, dividing the resulting melt into at least two streams, subjecting each stream to a different thermal treatment, and extruding the streams contiguously as one or more composite filaments. At least one characteristic, for example viscosity, molecular weight or molecular weight distribution, which affects the shrinkage properties of the polymer, changes at elevated temperature, notably that temperature employed in the melt-spinning process. The melt is preferably divided into two streams. The thermal treatment may be of different durations, for example, by having different path lengths for each stream to traverse, and/or at different temperatures. The polymer is exemplified as polypropylene, but may be any thermoplastic linear polymer which can be melt-spun. The filaments, as such or in the form of a multifilament yarn, may subsequently be heat-treated to a temperature at which a crimp develops spontaneously, i.e. by relief of internal stress and not by mechanical deformation, for example, by means of a hot stretching operation or by a steam or boiling water treatment without applied tension. The filaments may be spun from apparatus comprising a continuously operating melting device provided with means for the supply of polymer and means for expelling molten polymer, at least two ducts which communicate at one end with the output of the melting device and at the other end with a supply chamber of a spinneret and which are adapted to cause polymer melts passing therethrough to be given different thermal treatments, and a compartmented supply chamber each compartment of which is connected to the outlet orifice of a particular heating duct and communicates separately with the orifice, or with some or all of the orifices, of the spinneret. The ducts may differ in length and/or may be provided with separately controlled heating means. Each duct is preferably provided with a metering pump at or near its input end. As illustrated in the Figure, polymer is supplied by hopper 1 to melting chamber 2 heated by elements 3 and is passed by screw 4 from the output end 12 of the melting chamber via pumps 7 and 7<SP>1</SP> to ducts 5 and 6 which are of different lengths and which are heated by elements 8 and 8<SP>1</SP>. Each duct leads to a cell 9 of a filtration unit and communicates via channel 13 with one compartment 10 of the supply chamber of spinneret 11.