Film with adjustable water vapor-permeability
Hydrophobic breathable film based on a polymer mixture of A) at least one hydrophilic elastomer block copolymer made of at least one polyamide block and at least one polyalkylene oxide block and B) at least one thermoplastic polymer, which regulates the steam-permeability of the breathable film.
1. A single-layer or multilayer, breathable film which repels aqueous liquids, and of which the water vapor transmission rate is from 20 to 3000 g/m 2 24 h (at 23° C., 100% relative humidity and film thickness: 75 μm) measured in accordance with ASTM F1249, comprising at least one layer based on a polymer mixture of
A) from 40 to 90% by weight of at least one hydrophilic, elastomeric block copolymer with a water vapor transmission rate of at least 1200 g/m 2 24 h, determined as mentioned before, built of at least one polyamide block and of at least one polyalkylene oxide block having a molar mass from 200 to 3000 g/mol,
B) for regulating the water vapor transmission rate of the breathable film from 10 to 60% by weight of at least one thermoplastic ethylene/vinyl ester copolymer, wherein the gravimetrically measured water absorption of the ethylene vinyl ester copolymer is ≤2% by weight, and
C) optionally conventional auxiliaries, selected from the group consisting of UV stabilizers, antiblocking agents, pigments, antistatic agents, antimicrobial substances, primers to improve adhesive anchoring, processing aids, lubricants, antifogging additives, and dyes, whereby all the components A) to C) must add up always to 100% by weight.
2. The breathable film as claimed in claim 1 , wherein the gravimetrically measured water absorption of the hydrophilic block copolymer A) with film of thickness of 75 μm at 23° C. after 72 h in water at 23° C. is at least 10% by weight.
3. The breathable film as claimed in claim 1 , wherein the polyamide content of the hydrophilic block copolymer A) is at least 50% by weight, based on the total weight of the hydrophilic block copolymer A).
4. The breathable film as claimed in claim 1 , wherein the hydrophilic block copolymer A) is composed of at least one polyamide block made of an at least aliphatic, partial aromatic, or aromatic polyamide.
5. The breathable film as claimed in claim 3 , wherein the hydrophilic block copolymer A) has a plurality of polyamide blocks, of which all of the polyamide blocks are composed of the same polyamide or copolyamide.
6. The breathable film as claimed in claim 1 , wherein the hydrophilic block copolymer A) has at least one polyalkylene oxide block made of C 2 - to C 4 -alkylene oxides.
7. The breathable film as claimed in claim 6 , wherein the hydrophilic block copolymer A) comprises a plurality of polyalkylene oxide blocks.
8. The breathable film as claimed in claim 1 , wherein the film has at least two layers, of which each layer has a different water vapor transmission rate.
9. The breathable film as claimed in claim 1 , wherein the water vapor transmission rate of the film is from 20 to 2000 g/m 2 24 h (at 23° C. and 100% relative humidity and a film thickness: 75 μm).
10. A substrate film of an adhesive tape applicable in the construction sector comprising the breathable film of claim 1 .
11. An adhesive tape composed of a breathable film as claimed in claim 9 as substrate layer, of an adhesive layer, of optionally a lattice scrim arranged there between, and of optionally a releasable protective film on top of the adhesive layer.
12. The adhesive tape as claimed in claim 11 , wherein the adhesive layer is based on at least one adhesive selected from the group consisting of adhesives based on polyacrylates or on acrylate copolymers, adhesives based on synthetic rubber, adhesives based on polysilicones, and adhesives based on polyurethanes.
13. The adhesive tape as claimed in claim 11 , wherein the total thickness of the adhesive tape is from 50 to 500 μm and its water vapor transmission rate is at least 20 g/m 2 24 h.
14. A large-surface-area sheeting material in the construction sector, comprising the breathable film of claim 1 .
15. A roof-lining membrane comprising at least one breathable film as claimed in claim 1 and optionally at least one nonwoven layer.
16. A roof lining composed of a roof-lining membrane bonded by the adhesive tape as claimed in claim 11 .
17. A protective film of a hygiene product, comprising the breathable film of claim 1 .
18. A protective film of a hygiene product such as a sanitary napkin, or of an incontinence product, comprising a breathable film as claimed in claim 1 , with water vapor transmission rate at least 1000 g/m 2 24 h, up to 2500 g/m 2 ·24 h (at 23° C. and 100% relative humidity, film thickness: 75 μm), measured in accordance with ASTM F1249.