Keynote paper to the Polymer Processing Society’s European Meeting, Stuttgart, Germany, 26th-28th September 1995, paper KN1-01.
S F Bush with R N Britton and J L Uarich
Introduction
Pigmented polymer fibres are usually made by distributing master batch colour concentrate from an Extruder into the hopper of an extruder which feeds a number of fibre spinning heads. At each spinning head the polymer flow is further subdivided into typically 100 filaments which are drawn down and then wound up as yarn together.
The combination of the extruder, the six or twelve spinning heads which it feeds and the windup arrangements is commonly referred to as a spinning machine.
The twin requirements for continuous running of the plant and for colour uniformity in the spun thread are critically dependent on the mixing which the colour concentrates experience in the extruder, the downstream static mixer (if fitted), in the lines from the extruder to the spinning heads and through the filter pack in the spinning head itself.
In general, achieved colour uniformity varies with the polymer, the colour, the machine (i.e. the extruder-spinning heads combination), and the throughput. To obtain the required operational flexibility in a plant running dozens of colours it is important therefore to be able to characterise the colour uniformity performance of machines with various pigment-polymer combinations.
Experiments have been performed on 32 different machines as follows. A slug of black concentrate from a compounding extruder was introduced at the throat of the spinning machine extruder in the middle of a run of natural polymer. The spun yarn was wound up as a standard package. Short lengths of yarn were subsequently removed at intervals through the package and wrapped on cards. The colour change from natural for each card was measured by a spectrophotometer.
Each card wrap corresponds to a particular time in seconds from approximately the time (tf) when colour is first visible in the spun filaments approaching the windup. Typical outputs from three different machines are shown.