Method of preparing a nonwoven web having delayed antimicrobial activity

Claim 1

A method of forming a nonwoven web having delayed antimicrobial activity, in that said 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 comprises the steps of: (A) melting a mixture which comprises a thermoplastic polyolefin, an additive, and a retardant coadditive; (B) forming fibers by extruding the resulting melt through a die at a shear rate of from about 50 to about 30,000 sec -1 and a throughput of no more than about 5.4 kg/cm/hour; (C) drawing said fibers; and (D) collecting said fibers on a moving foraminous surface as a web of entangled fibers; in which: (1) said additive has the general formula, ##STR4## in which: (a) R 2 -R 8 and R 10 are independently selected monovalent C 1 -C 3 alkyl groups; (b) R 1 and R 9 are independently selected monovalent C 6 -C 25 alkyl groups; (c) A represents a monovalent anion; (d) n represents an integer of from 1 to about 20; (e) said additive has a weight average molecular weight of from about 800 to about 2,000; (f) said additive has a polydispersity of up to about 3.0; and (g) said additive is present in an amount of from about 0.5 to about 2 percent by weight, based on the amount of thermoplastic polyolefin; and (2) said retardant coadditive is a high surface area particulate inorganic or organic material, which retardant coadditive: (a) is insoluble in the polymer at both ambient and melt-extrusion temperatures; (b) is present in an amount of from about one-half to about two times the amount on a weight basis of said additive; (c) has a surface area of from about 50 to about 1,000 m 2 ; and (d) is capable of being at least partially coated by said additive.

Claim 2

A method of forming a nonwoven web having delayed antimicrobial activity, in that said 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 comprises the steps of: (A) melting a mixture which comprises a thermoplastic polyolefin, an additive, and a retardant coadditive; (B) forming fibers by extruding the resulting melt through a die at a shear rate of from about 50 to about 30,000 sec -1 and a throughput of no more than about 5.4 kg/cm/hour; (C) drawing said fibers; and (D) collecting said fibers on a moving foraminous surface as a web of entangled fibers; in which: (1) said additive has the general formula, ##STR4## in which: (a) R 2 -R 8 and R 10 are independently selected monovalent C 1 -C 3 alkyl groups; (b) R 1 and R 9 are independently selected monovalent C 6 -C 25 alkyl groups; (c) A represents a monovalent anion; (d) n represents an integer of from 1 to about 20; (e) said additive has a weight average molecular weight of from about 800 to about 2,000; (f) said additive has a polydispersity of up to about 3.0; and (g) said additive is present in an amount of from about 0.5 to about 2 percent by weight, based on the amount of thermoplastic polyolefin; and (2) said retardant coadditive is a high surface area particulate inorganic or organic material, which retardant coadditive: (a) is insoluble in the polymer at both ambient and melt-extrusion temperatures; (b) is present in an amount of from about one-half to about two times the amount on a weight basis of said additive; (c) has a surface area of from about 50 to about 1,000 m 2 ; and (d) is capable of being at least partially coated by said additive.