Monolithic breathable film and composite manufactured therefrom
Breathable multilayer films suitable for a wide variety of uses (e.g., protective apparel, surgical gowns, surgical drapes, aprons, roofing material, house wrap, etc.) are disclosed. The breathable multilayer film may include a monolithic core layer. The monolithic core layer may comprise at least one highly breathable polymer. The breathable multilayer film may also include at least one skin layer. The skin layer or layers may comprise at least one highly breathable polymer, a filler, and a non-breathable material. An exemplary structure of the breathable multilayer film provides a monolithic core layer, a first skin layer on one side of the monolithic core layer, and a second skin layer on the other side of the monolithic core layer. An exemplary construction of one or both of the skin layers includes one or more highly breathable polymers, a filler, and a non-breathable material. The filler, for example, may comprise calcium carbonate.
1 . A process for forming a breathable multilayer film, comprising:
(a) forming a core-layer polymer melt comprising at least one core-layer highly breathable polymer that is selectively permeable to water vapor and impermeable to liquid water;
(b) forming a first-skin-layer polymer melt comprising (i) at least one first-skin-layer highly breathable polymer that is selectively permeable to water vapor and impermeable to liquid water, and (ii) a first-skin-layer filler;
(c) forming a second-skin-layer polymer melt comprising at least one second-skin-layer highly breathable polymer that is selectively permeable to water vapor and impermeable to liquid water;
(d) co-extruding the core-layer polymer melt, the first-skin-layer polymer melt, and the second-skin-layer polymer melt to form a monolithic core layer, a first skin layer, and a second skin layer; and
(e) combining the monolithic core layer, the first skin layer, and the second skin layer to form the multilayer film;
wherein the first skin layer comprises a first-skin-layer thickness and the first-skin-layer filler comprises a median particle diameter greater than the first-skin-layer thickness, and wherein the monolithic core layer is devoid of micropores.
2 . The process of claim 1 , wherein (i) the first-skin-layer polymer melt further comprises a first-skin-layer non-breathable material, (ii) the second-skin-layer polymer melt further comprises a second-skin-layer non-breathable material, or (iii) both (i) and (ii).
3 . The process of claim 2 , wherein (i) the first-skin-layer polymer melt comprises from about 0.5 wt. % to about 6 wt. % of the first-skin-layer non-breathable material, (ii) the second-skin-layer polymer melt comprises from about 0.5 wt. % to about 6 wt. % of the second-skin-layer non-breathable material, or (iii) both (i) and (ii).
4 . The process of claim 2 , wherein (i) the first-skin-layer filler comprises particles or aggregates of particles, (ii) the second-skin-layer polymer melt further comprises a second-skin-layer filler comprising particles or aggregates of particles, or (iii) both (i) and (ii).
5 . The process of claim 4 , wherein (i) the first skin layer comprises from 2 wt. % to 40 wt. % of the first-skin filler, (ii) the second skin layer comprises from 2 wt. % to 40 wt. % of the second-skin filler, or (iii) both (i) and (ii).
6 . The process of claim 1 , wherein the multilayer film has a coefficient of friction less than 1.
7 . The process of claim 1 , wherein the multilayer film has an MVTR of at least 8000 g/m 2 /day.
8 . The process of claim 1 , wherein the core-layer polymer melt comprises at least about 80 wt. % of the at least one core-layer highly breathable polymer.
9 . The process of claim 1 , wherein the at least one core-layer highly breathable polymer comprises at least one of a thermoplastic urethane, a polyether block amide copolymer, or a copolyester thermoplastic elastomer.
10 . The process of claim 1 , wherein at least one of the first skin layer and the second skin layer are less hygroscopic than the monolithic core layer.
11 . The process of claim 1 , wherein at least one of the first-skin-layer filler defines a plurality of protrusions on an outer surface of the first skin layer and a second-skin-layer filler defines a plurality of protrusions on an outer surface of the second skin layer.
12 . The process of claim 10 , wherein the first-skin-layer filler, second-skin-layer filler, or both comprise organic particles, inorganic particles, or combinations thereof.
13 . A process for forming a laminate, comprising:
(a) forming a multilayer film according to the process of claim 1 ; and
(b) bonding the multilayer film to a nonwoven layer.
14 . The process of claim 13 , wherein the nonwoven layer comprises a spunbond layer, a meltblown layer, or a combination thereof.
15 . The process of claim 13 , wherein bonding the multilayer film to the nonwoven layer comprises adhesively bonding the multilayer film to the nonwoven layer via a discontinuous adhesive layer.