Process for producing a mixed-shrinkage heat-bulkable polyester yarn

Abstract

The disclosure relates to cospinning and drawing polyester filaments to produce a composite yarn which develops bulk due to differential shrinkage of the filaments when heated. Filaments of ethylene terephthalate synthetic linear condensation polymer are melt spun to form two separate filament bundles, a water-based spring finish is applied to the filaments of one bundle and a substantially non-volatile spin finish is applied to filaments of the other filament bundle, the filament bundles are drawn under identical treatment conditions during passage along separate paths and the filaments are then combined and intermingled during passage around draw rolls. The product is a mixed-shrinkage yarn wherein the filaments treated with aqueous-based finish have a higher heat-shrinkage than the filaments treated with non-volatile finish, even though both are otherwise processed in the same manner.

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