Patent GB-1168510-A (GB)
Title: Process for Melt-Spinning Polyamides
Inventor: CENZATO LORENZO
IPC: F24F11/08
Filed: 1967-12-29
Abstract: 1,168,510. Making artificial fibres, films &c. E. I. DU PONT DE NEMOURS & CO. 29 Dec., 1967, No. 59255/67. Heading B5B. A polyamide having a spun melt viscosity (# melt) of at least 12,000 poises and prepared from bis (4-aminocyclohexyl) methane containing 70 to 100% trans-trans stereoisomer and one or more aliphatic diacids of 10 to 16 carbon atoms (such as dodecandioic acid) is spun through a spinneret orifice in such a manner that the temperature (T s ) of the spun filament immediately after it leaves the orifice is at least 10 C. above the melting point (T m ) of the polyamide into a gaseous medium heated to provide gas temperatures Tg adjacent to the spun filament which are less than and greater than wherein # melt is the viscosity in poises of the polyamide when measured on the solidified filament before it is drawn and at a temperature of T m  + 30 C. and at a shear rate of 10 seconds<SP>-1</SP>, and which is at least 12,000 poises, dpf is the denier per filament of the solidified filament before it is drawn and t is 100 times the time in seconds, obtained by dividing the distance from where Tg was measured to the spinneret by the spinning speed, the filament being retained in this gaseous medium until the gas temperature (Tg) is 150 C. or more below (T s ), and subsequently drawing the solidified filament. The temperature of the extruded polymer (T s ) may be at least 20 C. above the melting point (T m ) of the polyamide and the gas temperatures (Tg) may be less than and greater than wherein #T min  is equal to T s  minus the highest gas temperature (Tg) in the gaseous medium and # melt, dpf and t are as defined in Claim 1. The polyamide may have an # melt between 20,000 and 100,000 poises. The polyamide may be melt-spun into an atmosphere of a gas such as nitrogen, steam or carbon dioxide, the gas containing substantially no oxygen. The spun filaments may be drawn at a draw ratio of at least 3À5. The spinning speed may be 150 to 500 metres per minute. T s  is preferably less than T s  is estimated in the examples by correcting the temperature of the polymer in the melt pool in the spinning block by 2À76 C. for each 70À3 Kg/cm.<SP>2</SP> pressure drop between the melt pool and the outside atmosphere. T s  can be determined directly by means of a thermocouple in the extruded polymer stream very close to but not touching the spinneret face. In the example, the relative viscosity (RV) of the polymer is determined at 25 C. using a solution of 5À5 grams of the polymer in 50 ml. of a mixture of equal parts by weight of 98% formic acid and phenol. Tg is measured with an aspirating thermocouple placed as close as possible to the filaments. In an example, a polyamide prepared from bis (para-amino cyclohexyl) methane (containing 90% of transtrans configurations) and dodecanedioic acid, having a (RV) of 176 and a crystalline melting point of 300 C. is extruded from a melt at 330 C. through a spinneret into a zone heated by steam, the filaments thereby formed are then passed through a quenching zone provided by ambient air to a feed roll and from the feed roll to a two-stage drawing process. In the first stage the yarn is drawn at a draw ratio of 3 using a metal pin at 155 C. over a metal plate at 165 C. to a first stage draw roll, thence round a tube (2 wraps) heated at 205 to 235 C. to the second stage draw roll and then to a windup. The total draw ratio is 5À5 to 5À9. The temperature in the zone heated by superheated steam ranges from 383 C. at the threadline 20 cm. from the spinneret face to 204 C. 51 cm. from the spinneret face. T s  is estimated to be about 347 C. The arrangement of the steam heating zone is described.