GB1247223A - Drawing and heat treating polyester filaments - Google Patents

Abstract

1,247,223. Drawing and heat-treating polyester filaments. TEIJIN Ltd. 14 Feb., 1969 [15 Feb., 1968; 20 April, 1968], No. 8292/69. Heading B5B. Polyester undrawn polyester filaments containing at least 85 mol. per cent of ethylene terephthalate units are treated in the following steps:-(1) The filaments are drawn at a draw ratio of 1À1-4À0 at a temperature within the range of 40-100‹ C. (2) The filaments are further drawn at a temperature within the range 10-85‹ C. and lower than that employed in step (1) at a draw ratio within a range of 1À2-7À0 and which is at least 80% of the "maximum draw ratio." (3) The filaments are heat-treated at a temperature within range of 55-120‹ C. and higher than that employed in step (2), while being subjected to such a tension as will maintain the filament length during the treatment at 95-130% of that immediately before the treatment, i.e., at the end of step (2). (4) The filaments are then subjected to a second heat treatment wherein they are heated in one or more stages to a temperature or temperatures higher than that employed in step (3), at least one stage of this heat treatment being performed at a temperature not lower than 110‹ C., the filaments being subjected (in each stage when there is more than one) to such tension as will maintain the filament length at 95-130% of that at the end of the immediately preceding step or stage and also as will produce a filament length after the final stage which is at least 90% of that immediately before step (3). The drawing temperature in step (2) may be at least 10‹ C., preferably at least 15‹ C., below that employed in step (1). The heat treating temperature of step (3) may be at least 10‹ C. above the drawing temperature of step (2), and the heat-treating temperature or temperatures in step (4) may be at least 10‹ C. above that employed in step (3). The drawing operations in steps (1) and (2) may be performed in a liquid, which is a non-solvent for the ester, water or ethylene glycol. The units in the polyester which may be copolymerized with the ethylene terephthalate units may be units formed from diethylene glycol, or other polymethylene glycols, said other glycol containing 1 to 10 carbon atoms in the molecule, such as hexahydro-pxylylene glycol, and from isophthalic, dibenzoic, p-terphenyl-4,4<SP>1</SP>-dicarboxylic and hexahydrotene phthalic acids, adipic acid, and hydroxyacetic acid. Filaments having a birefringence within the range 0À0005-0À0120 and an intrinsic viscosity (determined in orthochlorophenol at 35‹ C.) are preferred. The term "maximum draw ratio" is defined as the maximum draw ratio (under the drawing conditions obtaining in step 2) at which no filament breakage occurs.