GB986619A - Process for the manufacture of fibres and filaments of linear polyesters - Google Patents

Abstract

Fibres and filaments of a linear polyester, especially polyethylene terephthalate are made by adding 0.01-5% by weight of the polyester, of terephthalic acid, isophthalic acid, dimethyl terephthalate, diglycol terphthalate, dimethyl isophthalate, diglycol isophthalate or a mixture of these substances as a decomposing agent to the polyester, and melt extruding the product to form filaments in known manner, the filaments thus made having a specific viscosity lower than that of the original polyester by 0.2 to 0.5 units. The specific viscosities are measured at 25 DEG C. in 1% solution in a 60:40 by weight mixture of phenol and tetrachlorethane. The decomposing agent may be stirred into the molten polycondensate at the end of the polycondensation, and the polycondensate then fed to the spinning head, or the melt can be extruded through a slot die, cooled in air or water, the ribbon obtained cut into granules, the granules dried to less than 0.04% water and then melted and fed to the spinning head. Alternatively the decomposing agent, preferably in the form of granules or powder, can be mixed with polyester granules, e.g. in an offset tumbling mixer, and the mixture dried to a water content of less than 0.04% and then melted and fed to the spinning head. Alternatively the decomposing agent may be dissolved in a solvent, the solution applied to the polyester chips, the solvent evaporated and the impregnated chips dried and spun. Specified solvents include methylene chloride, dioxane, ethyl acetate and ethanol. The chips are then dried to less than 0.04% water, melted and fed to the spinning head. In examples, polyesters of specific viscosity 0.85 are treated with the specified decomposing agents to yield products of specific viscosities of 0.55-0.6. Filaments spun from the treated melts, when made into yarns, show less tendency to pilling than conventional polyester filaments.