GB1088386A - High bulk yarn and process for its preparation - Google Patents

Abstract

A non-elastic filamentary composite structure, comprised of at least two continuous polymeric components adhered in a continuous side-by-side relationship to one another, has the property of permanently retaining 25%-75% of the composite side-by-side structure on being treated under tensionless conditions in a hot medium. The structure may be in the form of continuous filament, staple fibre or fabric. The composite filaments are made by extruding and coagulating a laminar liquid structure having at least three alternating layers of two different synthetic polymers, one being elastomeric, the other being hard, essentially inelastic, wherein every layer of polymer has at least one continuous common interface with a different polymer layer, and then washing the filaments, drawing the washed filaments at least two times and drying. Drying may be effected in two stages at e.g. 75-105 DEG C. The dried non-elastic composite filaments are then treated in an untensioned state with a hot p medium, e.g. boiling water to partially separate the components and produce a filamentary structure in which the elastomeric and hard polymer components are permanently fused in side-by-side relationship in at least two recurring segments of the overall structure, said fused segments being separated by recurring segments in which the components are separated, there being at least one separated segment and at least two fused segments per staple fibre length and the cumulative length of the recurring fused segments comprising 25-75% of the overall length of the filament. The heat-treatment, by which the elasticity of the structure is developed, may be carried out on the filament, or on the fabric made therefrom. Separation of the components may be aided by flexing the structure. The elastomeric component may be a spandex polymer, and the hard, inelastic component may be a polyamide, polyester, polyolefin, polyether or polyacrylonitrile. The laminar liquid structure may be obtained by use of the plate mixing device disclosed in Specification 980403. Examples describe the wet-spinning of spandex-acrylic systems, and the development of elastic properties and crimp by exposure of the composite filaments to boiling water. In example 1, undeveloped composite filaments are mechanically crimped, cut into staple fibre, blended with conventional acrylonitrile/vinyl acetate staple, processed into worsted yarn, and knitted into a non-elastic twill fabric. The latent stretch of the fabric is then developed by treatment with boiling water.