| 摘要 |
A method of forming a nonwoven web having delayed antimicrobial activity, in that the web does not exhibit antimicrobial activity upon its formation but develops such activity within from about three hours to about 30 days thereafter without any post-formation treatment, which method involves the steps of (1) melting a mixture consisting of a thermoplastic polyolefin, an additive, and a retardant coadditive; (2) forming fibers by extruding the resulting melt through under defined conditions of shear and throughput; (3) drawing the fibers; and (4) collecting the fibers on a moving foraminous surface as a web of entangled fibers. The additive is a defined siloxane quaternary ammonium salt having a weight average molecular weight of from about 800 to about 2,000 and a polydispersity of up to about 3.0. The additive is present in an amount of from about 0.5 to about 2.0 percent by weight, based on the amount of thermoplastic polyolefin. The retardant coadditive is a high surface area particulate inorganic or organic material which is insoluble in the polymer at both ambient and melt-extrusion temperatures, is present in an amount of from about one-half to about two times the amount on a weight basis of the additive, has a surface area of from about 50 to about 500 m2, and is capable of being at least partially being coated by the additive.
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