Separating film having a foamed structure
Separating film, comprising at least one layer(s) having a foamed structure of at least one thermoplastic polymer, at least one of the surfaces of the separating film being provided with a release layer (b) of at least one cured polysiloxane as an outer layer, the use thereof as a detachable protective and covering film, and roofing membrane provided with the separating film as a detachable protective and covering film.
1. A release film comprising at least one layer (s) with a closed-cell foam structure of at least one thermoplastic polymer,
where the closed-cell foam structure is formed of expanded, hollow thermoplastic microparticles, the expansion of which has been achieved by virtue of at least one volatile organic compound present in the cavity of the microparticles,
where the diameter of the expanded, hollow thermoplastic microparticles is from 30 μm to 300 μm, and the average diameter of the expanded hollow thermoplastic microparticles is greater than the overall thickness of the release film, thereby providing the release film with a rough and uneven surface,
where at least one of the surfaces of the release film is provided with a release layer (b) as external layer, formed of at least one crosslinked polysiloxane, and connected to said at least one layer (s) with an anchoring aid,
where the melting point of the thermoplastic polymer of the layer (s) is lower than that of the thermoplastic polymer of which the hollow thermoplastic microparticles are formed.
2. The release film as claimed in claim 1 , wherein the diameter of the expanded, hollow thermoplastic microparticles is from 70 to 200 μm.
3. The release film as claimed in claim 1 , wherein the overall density of the layer (s) is from 0.2 to 1.2 g/cm 3 .
4. The release film as claimed in claim 1 , wherein the release layer (b) comprises at least one levelling aid.
5. The release film as claimed in claim 4 , wherein the at least one levelling aid comprises at least one polysiloxane having at least one functional group having at least one carbon double bond.
6. The release film as claimed in claim 4 , wherein the release layer (b) contains from 1 to 10% by weight the at least one of a levelling aid and from 1 to 5% by weight of anchoring aid, based in each case on the total weight of the release layer (b).
7. The release film of claim 1 , wherein the anchoring aid comprises at least one polysiloxane having at least one functional group selected from the group consisting of a functional group having at least one carbon double bond, an epoxy group, an isocyanate group, a hydroxy group, alkoxysilane group and a silane group.
8. The release film as claimed in claim 1 , wherein the at least one layer (s) is formed of at least one olefin homo- or copolymer.
9. The release film as claimed in claim 8 , wherein the free surface of the at least one layer (s) is bonded to at least one layer (a) which has no foam structure and which is formed of at least one olefin homo- or copolymer.
10. The release film as claimed in claim 9 , wherein the free surface of said at least one layer (a) is bonded to an unfoamed layer (c) formed of at least one olefin homo- or copolymer and the free surface of the layer (c) can be bonded to at least one other layer (d) which has no foam structure and which is formed of at least one olefin homo- or copolymer.
11. The release film as claimed in claim 10 , further comprising at least one barrier layer (e) which is arranged between the layer (a) and the layer (c) or between the layer (c) and the layer (d), and which is optionally bonded by means of an adhesion-promoter layer (f) and/or (g) to the layer (a) or, respectively, the layer (c) or, respectively, the layer (d).
12. The release film as claimed in claim 11 , wherein barrier layer (e) which is formed of at least one homo- or copolyamide and is bonded by means of an adhesion-promoter layer (f) and/or (g) to the layer (a) or, respectively, to the layer (c) or, respectively, to the layer (d).
13. Self-adhesive labels, adhesive tapes, stickers or self-adhesive roof sheeting provided with the release film of claim 1 as a removable protective film or removable protective-covering film.
14. A rollable, self-adhesive roof-sheeting material provided with the release film of claim 1 as removable protective film or as removable protective-covering film.
15. A rolled, self-adhesive bitumen roof-sheeting material provided with the release film of claim 1 as removable protective film or as removable protective-covering film.