Three-layer nonwoven laminiferous structure

A method of preparing an improved nonwoven laminiferous structure having three melt-extruded nonwoven layers adjacent to each other in which each melt-extruded nonwoven layer comprises at least a portion of a nonwoven web and the boundary between any two adjacent melt-extruded nonwoven layers is distinct in that fibers at or near the surfaces of such adjacent layers are not significantly intermingled, which method comprises the steps of:

• (A) separately forming a first nonwoven web by melt extruding continuous filaments which are randomly deposited on a moving foraminous support, said continuous filaments having an average filament diameter in excess of about 7 micrometers and being prepared from a first thermoplastic polymer which is selected from the group consisting of polyolefins, polyesters, polyetheresters, and polyamides;
• (B) separately forming a second nonwoven web by melt extruding substantially continuous microfibers which are randomly deposited on a moving foraminous support, said substantially continuous microfibers having an average diameter of from about 0.1 to about 10 micrometers and said second nonwoven web having a first surface and a second surface;
• (C) separately forming a third nonwoven web by melt extruding continuous filaments which are randomly deposited on a moving foraminous support, said continuous filaments having an average filament diameter in excess of about 7 micrometers and being prepared from a third thermoplastic polymer which is selected from the group consisting of polyolefins, polyesters, polyetheresters, and polyamides;
• (D) bringing said first nonwoven web adjacent to the first surface of said second nonwoven web and said third nonwoven web adjacent to the second surface of said second nonwoven web;
• (D) pattern bonding the resulting structure by the application of heat and pressure;
• and
• (E) treating at least one of said first and third nonwoven webs of the resulting pattern bonded structure by topical application of at least one agent in an amount which is sufficient to impart to the filaments of said web at least one characteristic which is different from the surface characteristics of filaments in a web not so treated, said topical treatment being carried out in a manner such that each topically applied agent is substantially restricted to the web to which it was applied;
• in which:
• (1) the microfibers of said second nonwoven web are prepared by melt extrusion through a die at a shear rate of from about 50 to about 30,000 sec.sup.-1 and a throughput of no more than about 6.4 kg/cm/hour of a mixture of an additive and a second thermoplastic polymer, which additive imparts alcohol repellency to the surfaces of said microfibers as a consequence of the preferential migration of said additive to the surfaces of said microfibers as they are formed, said preferential migration taking place spontaneously upon the formation of said microfibers without the need for a post-formation treatment of any kind;
• (2) the additive is present in said second nonwoven web in an amount which is sufficient to both impart alcohol repellency to the microfibers thereof and to substantially prevent entry into said second nonwoven web of topically applied treatment liquid;
• and
• (3) said second thermoplastic polymer is selected from the group consisting of polyolefins, polyesters, polyetheresters, and polyamides.

A method of preparing an improved nonwoven laminiferous structure having three melt-extruded nonwoven layers adjacent to each other in which each melt-extruded nonwoven layer includes at least a portion of a nonwoven web and the boundary between any two adjacent melt-extruded nonwoven layers is distinct in that fibers or filaments at or near the surfaces of such adjacent layers are not significantly intermingled, which method includes the steps of:

• (A) separately forming a first nonwoven web by melt extruding continuous filaments which are randomly deposited on a moving foraminous support, such continuous filaments having an average filament diameter in excess of about 7 micrometers and being prepared from a first thermoplastic polymer which is selected from the group consisting of polyolefins, polyesters, polyetheresters, and polyamides;
• (B) separately forming a second nonwoven web by melt extruding substantially continuous microfibers which are randomly deposited on a moving foraminous support, such substantially continuous microfibers having an average diameter of from about 0.1 to about 10 micrometers and such second nonwoven web having a first surface and a second surface;
• (C) separately forming a third nonwoven web by melt extruding continuous filaments which are randomly deposited on a moving foraminous support, such continuous filaments having an average filament diameter in excess of about 7 micrometers and being prepared from a first thermoplastic polymer which is selected from the group consisting of polyolefins, polyesters, polyetheresters, and polyamides;
• (D) treating at least one of the first and third nonwoven webs formed in steps A and C by topical application of at least one agent in an amount which is sufficient to impart to the filaments of such web at least one characteristic which is different from the surface characteristics of filaments in a web not so treated, such topical treatment being carried out in a manner such that each topically applied agent is substantially restricted to the web to which it was applied;
• (E) bringing the first nonwoven web adjacent to the first surface of the second nonwoven web and the third nonwoven web adjacent to the second surface of the second nonwoven web;
• and
• (D) pattern bonding the resulting structure by the application of heat and pressure;
• in which:
• (1) the microfibers of the second nonwoven web are prepared by melt extrusion through a die at a shear rate of from about 50 to about 30,000 sec.sup.-1 and a throughput of no more than about 6.4 kg/cm/hour of a mixture of an additive and a second thermoplastic polymer, which additive imparts alcohol repellency to the surfaces of the microfibers as a consequence of the preferential migration of the additive to the surfaces of the microfibers as they are formed, such preferential migration taking place spontaneously upon the formation of the microfibers without the need for a post-formation treatment of any kind;
• (2) the additive is present in the second nonwoven web in an amount which is sufficient to both impart alcohol repellency to the microfibers thereof and to substantially prevent entry into the second nonwoven web of topically applied treatment liquid;
• and
• (3) the second thermoplastic polymer is selected from the group consisting of polyolefins, polyesters, polyetheresters, and polyamides.