GB1050983A - - Google Patents

Abstract

1,050,983. Making high load bearing filaments. E. I. DU PONT DE NEMOURS & CO. Jan. 30, 1964 [Jan. 30, 1963], No. 4070/64. Heading B5B. Synthetic polymer filaments which have been drawn and preferably crimped are drawn at their maximum operable draw ratio at a temperature of from 30‹ to 80‹ C. below their melting point and are then cooled or are allowed to be cooled by loss of heat to the atmosphere while at or near drawing tension to a temperature at least 150‹ C. below their melting point. In one preferred process the filaments are drawn while being heated to from 170‹ to 230‹ C. and subsequently cooled to below 100‹ C. while at or near the drawing tension. The process is particularly applicable to filaments of linear condensation polymers such as nylon 66 (polyhexamethylene adipamide), nylon 6 (polycaproamide) and linear terephthalate polyesters. In the examples the filaments are in the form of a band of tow and are heated in the drawing zone by passing them between pairs of heated plates. The plates are preferably heated to about 50‹ C. below the melting point of the tow and may be heated electrically or by means of oil or steam. Instead of hot plates the tow may be heated by direct contact with high pressure steam or hot air. The band of tow may be cooled by passage between a pair of hollow plates cooled by circulating a fluid heattransfer medium through them. The band of tow may thereafter be further cooled by passing it over a drum on to which a stream of cold air is directed by a blower. If the tow speed is sufficiently low, the artificial cooling means may be omitted and the tow allowed to cool to the required temperature by losing its heat to the atmosphere before the tension on it is released, the path of travel of the tow from the draw rolls to the tension holding rolls being long enough to effect this. When higher tow speeds are to be employed, the tow may be hot stretched in a number of controlled steps instead of only one or two in order to improve uniformity and reduce slippage. The hot-stretching and cooling may be combined in one zone, the tension holding rolls then becoming in effect draw rolls.