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 breathable multilayer film comprising:
(a) a monolithic core layer comprising at least one core-layer highly breathable polymer that is selectively permeable to water vapor and impermeable to liquid water, the monolithic core layer defining a first film layer of the breathable multilayer film, wherein the monolithic core layer has a top surface and a bottom surface;
(b) a first skin layer located directly adjacent the top surface of the monolithic core layer, the first skin layer comprising at least one first-skin-layer highly breathable polymer that is selectively permeable to water vapor and impermeable to liquid water, a first-skin-layer filler comprising particles or aggregates of particles, and a first-skin-layer non-breathable material that comprises from about 0.5 wt. % to about 6 wt. % of the first skin layer, the first skin layer defining a second film layer of the breathable multilayer film; and
(c) a second skin layer located directly adjacent the bottom surface of the monolithic core layer, the second skin layer comprising at least one second-skin-layer highly breathable polymer that is selectively permeable to water vapor and impermeable to liquid water, and a second-skin-layer non-breathable material that comprises from about 0.5 wt. % to about 6 wt. % of the second skin layer, the second skin layer defining a third film layer of the breathable multilayer film;
wherein the monolithic core layer, the first skin layer, and the second skin layer have been co-extruded to define the breathable 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 first skin layer comprises from 2 wt. % to 40 wt. % of the first-skin filler.
2. The breathable multilayer film according to claim 1 , wherein the second skin layer further comprises a second-skin-layer filler.
3. The breathable multilayer film according to claim 2 , wherein the multilayer film has a coefficient of friction less than 1.
4. The breathable multilayer film according to claim 2 , wherein the multilayer film has an MVTR of at least 8000 g/m 2 /day.
5. The breathable multilayer film according to claim 2 , wherein the core layer has a core-layer thickness, the first skin layer has a first-skin-layer thickness, the second skin layer has a second-skin-layer thickness, and the core-layer thickness is greater than each of the first-skin-layer thickness and the second-skin-layer thickness.
6. The breathable multilayer film according to claim 2 , wherein the core layer comprises at least about 80 wt. % of a highly breathable polymer.
7. The breathable multilayer film according to claim 6 , wherein the core-layer highly breathable polymer comprises at least one of a thermoplastic urethane, a polyether block amide copolymer, or a copolyester thermoplastic elastomer.
8. The breathable multilayer film according to claim 7 , wherein the core-layer highly breathable polymer comprises a copolyester thermoplastic elastomer.
9. The breathable multilayer film according to claim 2 , wherein at least one of the first skin layer and the second skin layer are less hygroscopic than the core layer.
10. The breathable multilayer film according to claim 2 , wherein at least one of a 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.
11. The breathable film according to claim 10 , wherein the first-skin-layer filler, second-skin-layer filler, or both comprise organic particles, inorganic particles, or combinations thereof.
12. A breathable multilayer film comprising:
(a) a monolithic core layer including a top surface and a bottom surface, the monolithic core layer comprising from about 50 wt. % to about 100 wt. % of a core-layer highly breathable polymer, wherein the core-layer highly breathable polymer is (i) selectively permeable to water vapor, (ii) impermeable to liquid water, and (iii) hygroscopic, wherein the monolithic core layer defines a first film layer of the multilayer film;
(b) a first skin layer positioned above and directly adjacent to the top surface of the monolithic core layer and having a first-skin-layer thickness, the first skin layer being formed from a first-skin-layer polymer melt comprising:
i. about 50 wt. % to about 95 wt. % of a first-skin-layer highly breathable polymer,
ii. about 2 wt. % to 40 wt. % of a first-skin-layer filler, and
iii. about 0.5 wt. % to about 8 wt. % of at least one first-skin-layer non-breathable material,
wherein the first skin layer defines a second film layer of the breathable multilayer film;
wherein the first-skin-layer filler comprises particles or aggregates of particles having a first-skin-layer filler median particle diameter greater than the first-skin-layer thickness, and
the first-skin-layer filler particles or aggregates of particles define a plurality of protrusions on an outer surface of the first skin layer; and
(c) a second skin layer positioned below and directly adjacent to the bottom surface of the monolithic core layer and having a second-skin-layer thickness, the second skin layer being formed from a second-skin-layer polymer melt comprising:
i. about 50 wt. % to about 95 wt. % of one or more second-skin-layer highly breathable polymers,
ii. about 2 wt. % to 40 wt. % of a second-skin-layer filler, and
iii. about 0.5 wt. % to about 8 wt. % of at least one first-skin-layer non-breathable material,
wherein the second-skin-layer comprises particles or aggregates of particles having a second-skin-layer filler median particle diameter greater than the second-skin-layer thickness, and
wherein the second skin layer defines a third film layer of the breathable multilayer film;
the second-skin-layer filler particles or aggregates of particles define a plurality of protrusions on an outer surface of the second skin layer;
wherein the core-layer highly breathable polymer is more hygroscopic than the first-skin-layer highly breathable polymer; and
wherein the monolithic core layer, the first skin layer, and the second skin layer are each devoid of micropores.
13. A laminate, comprising a breathable multilayer film of claim 2 and at least one of a nonwoven layer and a woven layer.
14. The laminate according to claim 13 , wherein the nonwoven material comprises a sub-micron nonwoven layer.
15. The breathable multilayer film according to claim 1 , wherein the first-skin-layer non-breathable material comprises from about 0.5 to about 5 wt. % of the first skin layer.
16. The breathable multilayer film according to claim 1 , wherein the first-skin-layer non-breathable material comprises from about 0.5 to about 3 wt. % of the first skin layer.
17. The breathable multilayer film according to claim 1 , wherein the first-skin-layer non-breathable material comprises from about 0.5 to about 2 wt. % of the first skin layer.
18. The breathable multilayer film according to claim 1 , wherein the first skin layer comprises from 15 wt. % to 40 wt. % of the first-skin filler.
19. The breathable multilayer film according to claim 1 , wherein the first skin layer comprises from 25 wt. % to 40 wt. % of the first-skin filler.
20. The breathable multilayer film according to claim 1 , wherein the breathable multilayer film is a co-extruded multi-layer film including the first film layer, the second film layer, and the third film layer.