GB868497A - Improvements in or relating to staple fibres of linear co-polyesters - Google Patents

Abstract

High-tenacity staple fibres are made from a polymer of ethylene terephthalate in which at least 90% of the recurring structural units are -OC(p)C6H4,CO,OCH2,CH2,O- and which has a "relative viscosity" of 14,0 to 17,0 unless part or all of the remaining structural units contain sulphonate groups, in which case the relative viscosity of the polymer is (14,0+0,75x) to (17,0+0,75x), where x is the mole percentage (preferably not exceeding about 3,5 mole per cent) of sulphonate groups in the copolymer. The fibres are formed by melt-spinning the polymer, drawing the filaments so obtained, and cutting the drawn filaments into staple lengths. "Relative viscosity" is defined as the ratio of the viscosity of a 10% solution of the polymer in a mixture of 10 parts of phenol and 7 parts of 2, 4, 6-trichlorophenol (by weight) to the viscosity of the phenol-trichlorophenol mixture per se at 25 DEG C., the viscosities being determined in an Ostwald-Fenske viscometer which has been standardized by means of aqueous solutions of glycerol of known absolute viscosities. The term "polymers of ethylene terephthalate" is defined as including ethylene terephthalate copolymers containing residues of other dicarboxylic acids and/or other glycols, e.g. glycols of the series HO(CH2)xOH, where x is an integer from 2 to 10, dibasic acids of the series HOOC(CH2)yCOOH, where y is 0 or an integer from 1 to 8, hydroxy acids of the series HO(CH2)zCOOH, where z is an integer from 1 to 9, and analogous compounds in which the radicals (CH2)x, (CH2)y and (CH2)z are replaced by radicals of the type (CnH2nO)a, where n is an integer from 2 to 4 and a is an integer from 1 to 300. Other polyester linking units may be derived from isophthalic acid, phthalic acid, naphthalic acids and bibenzoic acids. The above polymers may be modified to include sulphonate groups to increase their affiinity for dyes as described in Specification 868,496. In an example, polyethylene terephthalate (homopolyester) having a relative viscosity of 16 is melt-spun to give a yarn which is combined into a tow, drawn in a water bath maintained at 90 DEG C. at a draw ratio of 3,16, crimped in a stuffing-box crimper, relaxed in air at 140 DEG C. and cut into 2 1/2 -inch lengths. In the other example, staple fibres are similarly prepared from a copolymer of polyethylene terephthalate containing 2 mole per cent of sodium 3, 5-di (carbomethoxy) benzene sulphonate and having a relative viscosity of 17. Yarns and fabrics prepared from the fibres have improved resistance to "pilling" and "frosting." Specification 578,079 also is referred to.