Patent GB-950797-A (GB)
Title: Methods of making polyurethane filamentary material
IPC: C08G18/10
Filed: 1962-05-31
Abstract: Polyurethane filaments are made by wet spinning a liquid polyurethane prepolymer having terminal isocyanate groups into an aqueous aliphatic diprimary diamine bath containing from 5-95%, preferably 20-70%, by weight of an organic solvent which is a monoalcohol or a glycol having 2 to 10 carbon atoms in the molecule, or a mixture thereof, to effect an initial setting or coagulation of the freshly extruded filaments, and thereafter curing the filaments by the action of water. Preferred alkanols are those having 1-4 carbon atoms, especially 3-4 carbon atom alkanols.  The alkanols may be primary, secondary, or tertiary, tertiary butyl alcohol being the most preferred.  Other monoalcohols which may be used include methyl, ethyl and butyl "carbitol" and methyl, ethyl and butyl "cellosolve", tetrahydrofuryl alcohol, tetra-hydropyran - 2 - methanol, 4 - methoxy - 4 - methyl pentanol-2, and methoxy triglycol. Suitable glycols which may be used include alkylene glycols, and alkylene ether glycols, having 2 to 8 carbon atoms, e.g. ethylene and propylene glycol, di- and triethylene glycol, and 2-methyl-2,4-pentanediol. The glycols are preferably used together with one or more of the monoalcohols referred to above. Unsaturated monoalcohols and unsaturated glycols may be used.  The setting bath may contain 0.5 to 20% by weight of the diamine and is preferably operated at 110 DEG to 160 DEG F.  In the preferred diprimary diamines the two amino groups are linked by a divalent aliphatic hydrocarbon radical, as in ethylene diamine, hexamethylene diamine, and 1,4-diamino-cyclohexane. The radical connecting the two amino groups may contain other atoms in addition to carbon and hydrogen, as in 3,31-diaminodipropyl ether and diamino-dibutyl sulphide. The setting bath preferably contains a small proportion of a wetting agent, e.g. 1/2 % of sodium oleyl sulphate.  An important preferred feature of the invention is the rapid removal by washing the filaments with water of all traces of the setting bath after the emergence of the filaments from the bath in order to prevent the subsequent cure of the threads being interfered with by any organic solvent remaining on the filaments. The filaments may be cured by taking them up on reels which are subsequently subjected to the action of water or steam, preferably under pressure to prevent the formation of voids in the filaments by the carbon dioxide generated during the water cure of the polyurethane. Alternatively the filaments may be cured continuously by conveying them continuously through a water bath or a humid atmosphere by means of a conveyer belt or thread advancing reels partially or completely immersed in water and/or surrounded by steam or water vapour and/or sprayed with water.  The water washed filaments before being cured, may be washed with a dilute aqueous solution of a water-soluble fatty acid to neutralize any diamine remaining in the thread to prevent the remaining isocyanate groups of the polyurethane from reacting with the diamine instead of with water. The batchwise curing may be carried out a 80 DEG F. to 250 DEG F. for 1/4 to 24 hours at pressures of 10 to 250 p.s.i.g.  The continuous curing may be carried out at atmospheric pressure, a temperature of 100 to 212 DEG F. and a period of residence of one to 20 minutes.  The cure water may contain a small proportion, e.g. about 0.1 to 10% by weight of a water-soluble organic carboxylic acid such as acetic or benzoic acid to catalyse the cure. Alternatively other catalysts may be used in the cure water, such as 1 to 4% of 1,2-dimethylimidazole, tetramethyl-1,3-butane-diamine, tetramethylethylene-diamine, pentamethyldiethylene-diamine or 4-methylpyridine. In an example, the polyurethane prepolymer is produced by reacting 1 mol. of a polyester, prepared by condensing a slight excess of 70/30 mixture of ethylene glycol and 1,2-propylene glycol with adipic acid, with 2 moles of p, p1-diphenylmethane diisocyanate. In another example, the prepolymer is prepared by reacting 1 mol. of polypropylene glycol with 2 mols of p,p1-diphenylmethane diisocyanate.  U.S.A. Specifications 2,953,839, 3,009,762 and 3,009,765 are referred to.