Improvements in or relating to setting fabric of synthetic linear polyamide fibre yarns

摘要

Fabric comprising fibres of a synthetic linear polyamide is set by bringing it into contact with a hot chemically inert gaseous medium which remains in the gaseous state at atmospheric temperatures and pressures and is substantially devoid of free oxygen and water vapour, while the dimensions of the fabric are mechanically controlled. This control is defined as the holding of the fabric extended by mechanical means under suitable tensions with regard to its length and width respectively, so as to allow it to shrink or even to stretch it, lengthwise and widthwise, to the extent desired, the tensions in any case being at least sufficient to cause the fabric to be taut at the end of the setting process and before cooling. The fabric may be allowed during its setting to shrink 10 per cent of its width and 5 per cent of its length. The fabric may be woven or knitted and may consist of polyhexamethylene adipamide or sebacamide, polypentamethylene sebacamide or polyethylene octadecandioic diamide. The gaseous medium may be nitrogen, carbon dioxide or methane. The temperature of the gaseous medium during the process may be between 160 DEG and 25 DEG C. below the melting point of the polyamide, which may, for example be 207-248 DEG C. In the example a warp-knitted polyhexamethylene adipamide cloth is passed continuously on a stenter through a chamber filled with nitrogen at 216 DEG C., taking 30-120 seconds to traverse the chamber. The fabric enters and leaves the chamber through slots provided with gas seals. Data are furnished showing that the degree of yellowing, loss of strength and chemical degradation of the fabric are less when its setting is carried out in nitrogen or carbon dioxide than when carried out in air at the same temperatures and for the same heating periods. Specification 524,953 is referred to.