| 摘要 |
A blend of a urethane prepolymer and a slow-reacting urethane curing agent is extruded in filamentary form into an aqueous bath containing a fast-reacting urethane curing agent to produce filaments having a cured surface layer and an incompletely cured core. The filaments are then removed from the bath and heated to cause the slow-reacting curing agent to complete the curing of the interior of the filament. The prepolymer may be an isocyanate-terminated polyester, polythioester, polyether, polythioether or hydrocarbon chain. Many diisocyanates and polyesters are specified. Exemplified prepolymers are isocyanate-terminated adipic acid esters of ethylene glycol/propylene glycol and 1,4-butane diol/1,2-butane diol of mol. wt. 4000-5000. The slow-reacting curing agent is defined as a polyol, a polyol-substituted amine or an aromatic amine. Among many specified, are recinoleyl alcohol, castor oil, trimethylolpropane triisopropanolamine, and N,N,N1,N1 - tetrakis - (2 - hydroxypropyl) ethylene diamine. The ratio of isocyanate to the active hydrogen of the curing agent in the blend is desirably 0.8: 1 to 2.0: 1. The blend may be a liquid or a solid, in which case it is extruded as a solution. The fast-reacting curing agent is defined as an amine having at least two primary amino groups and soluble to at least 5% by weight in water. The preferred fast-reacting curing agents, among the many specified, are ethylene diamine, propylene diamine, and hexamethylene diamine. After removal from the aqueous bath, the filaments are cured on the outside and may be plastic or fluid in the core. Curing may be completed by heating at e.g. 250-350 DEG F. for 0.5-3 hours.
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