Patent GB-873648-A (GB)
Title: Improvements in method of making polyurethane filamentray material
IPC: C08G18/10
Filed: 1960-01-18
Abstract: Polyurethane filamentary material is made by extruding a stream of a liquid polyurethane prepolymer, which is a reaction product of a polyester or polyether having terminal hydroxy groups with an excess of an aromatic diisocyanate, into an aqueous solution of a saturated diprimary diamine to effect initial setting, washing the extruded material with acid to remove the diamine, and curing the extruded material with water.  Specified diamines include ethylene diamine, propylene diamine, hexamethylene diamine, 1,3-diaminopropane, 1,4-diamino-cyclohexane, 1, 6-hexane diamine, 3,31-diaminodipropyl ether and diaminodibutyl sulphide.  The aqueous solution may contain 0,5%-20% by weight of the diamine, and a wetting agent, preferably of the anionic or non-ionic type, and may be used at room temperature or up to 200 DEG F., preferably at 110 DEG -160 DEG F., higher temperatures being used for thicker filaments.  The acid is preferably a 1%-15% by weight aqueous solution of a volatile organic acid, especially 4% by weight acetic acid, but other acids may be used including formic, benzoic, succinic, oxalic and phthalic acids, and inorganic acids, e.g. hydrochloric acid.  If hydrochloric acid is used, the thread should subsequently be water-washed.  Water-curing may be effected under pressure and at elevated temperatures, e.g. at 50-150 p.s.i. and 100 DEG -160 DEG F., especially at 80-100 p.s.i. and 130 DEG -145 DEG F.  As shown, liquid prepolymer 10 is stored in tank 11 and degassed via the vacuum line.  It is then extruded through spinneret 13 or 13a into bath 14 or 14a containing the diamine.  Acid washing of the initially set filament, which now consists of a solid sheath surrounding a liquid core, is effected either in bath 16, or by dripping acid from a tank 26 on to the threadline.  The reels of thread are now immersed in water 18 in a tank 19 which can be heated and pressurized by pumping in air.  The treatment solidifies the fluid core of the thread, so that the finished thread 21 consists of an inner water-cured zone 22 and an outer diamine-cured zone 23.  The liquid polyurethane prepolymer may be made from a polyester of molecular weight 500-5000 made from a glycol containing 4-20 carbon atoms, <PICT:0873648/IV (a)/1> <PICT:0873648/IV (a)/2> <PICT:0873648/IV (a)/3> <PICT:0873648/IV (a)/4> preferably a mixture of ethylene and propylen glycols, and a saturated organic dicarboxylic acid containing 4-20 carbon atoms, e.g. adipic acid.  An excess of glycol is used so that the resulting polyester has terminal hydroxyl groups.  Specified polyesters include polyethylene adipiate, poly (ethylene propylene) adipate, polyethylene adipate-phthalate and polyneopentyl sebacate. Alternatively, a polyether may be used in place of the polyester, especially a polyether of formula H(OR)nOH, where R is a 2-6 carbon atom alkylene group and n is an integer such that the molecular weight is from 500-5000. Specified polyethers are polyethylene glycol, polypropylene glycol, polypropylene-ethylene glycol and polytetramethylene glycol.  Poly-ether-esters may also be used, e.g. polydiethylene glycol adipate and poly-triethylene glycol adipate. The polyester or polyether is reacted with an excess, preferably a 20%-250% molar excess, of the aromatic diisocyanate, suitably by mixing the reactants under anhydrous conditions at room temperature or at 70 DEG -150 DEG C. to form an uncured liquid polyurethane prepolymer having terminal isocyanate groups which is soluble in methyl ethyl ketone.  Specified aromatic diisocyanates include m- and p-phenylene diisocyanate, toluene diisocyanate, p-p1-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and aromatic-aliphatic diisocyanates, e.g. p-p1-diphenylmethane diisocyanate.