Patent GB-1006136-A (GB)
Title: Improvements relating to polyethylene terephthalate textile filaments
Inventor: CHANTRY WILLIAM AMDOR
IPC: B60C9/00
Filed: 1962-12-31
Abstract: 1,006,136. Polyethylene terephthalate filaments. E. I. DU PONT DE NEMOURS & CO. Dec. 31, 1962 [Jan. 2, 1962], No. 49136/62. Drawings to Specification. Heading B5B. High molecular weight polyethylene terephthalate is melt spun to form filaments having a relative viscosity between 47 and 100, a sufficiently low tension being maintained in the spinning threadline in the zone of solidification to produce solidified filaments having an optical birefringence of 0-0À0030, and the filaments are then drawn at least 5À7 times their undrawn length at 80-225‹ C., at least the final part of the drawing being effected at above 140‹ C. High molecular weight polyethylene terephthalate is defined as comprising at least 95%, preferably at least 97%, ethylene terephthalate units, other ester-forming units which may be present including diethylene glycol, other polymethylene glycols having 1-10 carbon atoms, hexahydro-p-xylylene glycol, other aromatic dicarboxylic acids, e.g. isophthalic acid, bibenzoic acid, p-terphenyl-4,4<SP>11</SP>'-dicarboxylic acid, hexahydroterephthalic acid, adipic acid and hydroxyacetic acid. Relative viscosities are determined in 10% solution in a mixture of 10 parts by weight of phenol and 7 parts by weight of 2,4,6-trichlorophenol. Preferably, the relative viscosity of the polyethylene terephthalate is at least 49, and the tension maintained in the spinning threadline in the zone of solidification is less than 0À028 g.p.d., especially less than 0À012 g.p.d. The low tension in the threadline in the zone of solidification may be achieved by providing adjacent to the spinneret face an atmosphere at a temperature above the melting point of the polymer, said atmosphere being preferably free from uncombined oxygen (e.g. nitrogen, carbon dioxide, or an inert organic vapour) so as to delay quenching of the filaments. A cylinder surrounding the spinneret, through which the gas passes, may be employed. The delayed quenching zone may be followed by a rapid quenching zone where cold air or other gas is blown across the filaments. Suitable apparatus comprises (i) an insulated cylindrical foraminous collar 12À7 cms. in length surrounding the spinneret, through which inert hot gas may be passed, (ii) a 48 cms. long insulated cylindrical skirt attached to the collar, (iii) a second cylindrical foraminous tube 40À5 cms. long, placed 15 cms. below the skirt, through which cooling air is passed radially inwards to cool the threads, (iv) an open-ended tube 2À13 m. long, 76 cms. below the second cylinder, serving to quench the filaments by the passage of air therethrough. Desirably, the temperature of the atmosphere in the zone of solidfication is adjusted to maintain at a distance L from the spinneret face a gas temperature Tg such that is between 0À001 and 0À008, Tg o  being the temperature of the atmosphere adjacent to the spinneret face, T s  the temperature of the spinneret face, mpm. the threadline speed in metres per minute and dpf. the filament denier. Drawing is preferably effected in a steam jet, using steam temperatures of 175-450‹ C., using cold feed and draw rolls, or cold feed rolls and hot draw rolls. Alternatively hot rolls may be used instead of steam, e.g. the threads may be heated to 80-120‹ C. on heated feed rolls, passed to and around first stage draw rolls heated to about 150‹ C. and having a peripheral speed 3À75-5 times that of the feed rolls, and then passed to a second set of draw rolls heated to 180-225‹ C. having a peripheral speed 1À5-2 times that of the first stage draw rolls to give a total draw ratio of 5À7-10À0. Filaments so made have a filament tensity of at least 10 gpd. at break, a break elongation of at least 10%, and a flex life of at least 50,000 cycles when repeatedly bent 180 degrees about a wire of diameter 0À076 mm., and may have a molecular orientation along the filament axis sufficient to give a sonic velocity of 4-6 kms./ second, a density of 1À37-1À42 g./c.c., and have an average distance between crystallites or between regions of high crystallinity, sufficient to give a long period spacing value of at least 125A degrees. Such filaments are useful as reinforcement in elastomeric articles, especially as tyre cord. Specifications 533,304, 773,778, 753,526, 924,089 and U.S.A. Specifications 2,534,028 and 2,916,474 are referred to.