Multi-layer breathable films
The invention relates to a breathable multi-layer film with at least one layer containing a breathable resin, such as block copolymers with polyether blocks, and one layer containing a soft polymer (Tg<0° C.), such as a polyolefin. The film is selectively permeable to water vapor but not permeable to water. The film can be bonded to a woven or non-woven substrate to produce a breathable fabric.
1. A multi-layer breathable film having a total film thickness of from 10 to 150 microns, comprising:
a) at least one thin layer (A), with each layer (A) making up from 5 to 20 percent of the total multi-layer breathable film thickness, comprising a blend of;
1) one or more breathable resins
2) one or more soft polymers having a Tg of less than 0° C.; and
b) at least on one thick layer (B), the thick layer or layers (B) making up from 60 to 95 percent of the total multi-layer breathable film thickness, comprising one or more breathable resins,
wherein layer (A) comprises at least 10 weight percent less breathable resin than layer (B),
and wherein the breathable resin is selected from the group consisting of a polyether-block-amide, a polyester block amide, a copolyester thermoplastic elastomer, or a thermoplastic urethane elastomer (TPU), or mixtures thereof, and wherein said multi-layer breathable film contains less than 3 percent by weight of dyes, pigments, UV absorbers, impact modifiers, process aids and fillers in each layer.
2. The multi-layer breathable film of claim 1 , comprising:
a) at least one thin layer (A), with each layer (A) making up from 5 to 20 percent of the total multi-layer breathable film thickness, comprising a blend of;
1) from 10 to 90 weight percent of said one or more breathable resins; and
2) from 10 to 90 weight percent of said soft polymers.
b) at least one thick layer (B), the thick layer or layers (B) making up from 60 to 95 percent of the total multi-layer breathable film thickness, comprising one or more breathable resins, and one or more soft polymers having a Tg of less than 0° C., and wherein the breathable resin is selected from the group consisting of a polyether-block-amide, a polyester block amide, a copolyester thermoplastic elastomer, or a thermoplastic urethane elastomer (TPU), or mixtures thereof.
3. The multi-layer breathable film of claim 2 , wherein the soft polymers in (A) and (B) have a Tg of less than −20° C.
4. The multi-layer breathable film of claim 3 , wherein the soft polymer is one or more polyolefins.
5. The multi-layer breathable film of claim 4 , wherein the soft polymer is a copolymer of one or more olefins and one or more alkyl(meth)acrylates.
6. The multi-layer breathable film of claim 5 , wherein an olefin/alkyl(meth)acrylate copolymer is a terpolymer having maleic anhydride or glycidyl methacrylate monomer units.
7. The multi-layer breathable film of claim 2 , wherein the layer (A) comprising a blend of;
1) from 20 to 90 weight percent of said one or more breathable resins; and
2) from 10 to 80 weight percent of said soil polymers.
8. The multi-layer breathable film of claim 1 , wherein the breathable resin is one or more polyether-block-amide (PEBA).
9. The multi-layer breathable film of claim 8 , wherein the total ratio of the polyether blocks to polyamide blocks is from 20 to 60 weight percent polyether blocks to 40 to 80 weight percent of polyamide blocks.
10. The multi-layer breathable film of claim 8 , wherein the polyether-block amide consists of two or more PEBAs with different ratios of polyether blocks to polyamide blocks.
11. The multi-layer breathable film of claim 1 , comprising:
a) 5-60 weight percent of at least one thin layer (A), with each layer (A) making up from 5 to 20 percent of the total multi-layer breathable film thickness, and
b) 40-95 weight percent of at least one thick layer (B), the thick layer or layers (B) making up from 60 to 95 percent of the total multi-layer breathable film thickness, and wherein the breathable resin is selected from the group consisting of a polyether-block-amide, a polyester block amide, a copolyester thermoplastic elastomer, or a thermoplastic urethane elastomer (TPU), or mixtures thereof.
12. The multi-layer breathable film of claim 1 , wherein one or more layers (A) or (B) may optionally further comprise additives and/or fillers.
13. The multi-layer breathable film of claim 1 , having the structure AB.
14. The multi-layer breathable film of claim 1 , having the structure ABA.
15. The multi-layer breathable film of claim 1 , wherein said film has a total thickness of from 10 to 30 microns.
16. A breathable article comprising at least one woven or non-woven substrate layer and at least one layer of the multi-layer breathable film of claim 1 , wherein said Layer (A) is directly attached to a said woven or non-woven substrate layer.
17. The breathable article of claim 16 , wherein said substrate is a non-woven selected from the group consisting of polypropylene, polyamide, polyester, polyethylene, and blends thereof.
18. The breathable article of claim 16 having either the structure: substrate/(A)/(B), or the structure substrate/(A)/(B)/(A)/substrate.
19. A process for forming said breathable article of claim 16 , wherein said multi-layer film is coextrusion coated or coextrusion laminated onto one or more substrate layers.