Three-layer UV protective film for decorative laminated sheets (HPL)
The present invention relates to novel films for application on materials as protective film in respect of weathering effects. In particular, the present invention relates to a novel film composite which has at least three layers and which features particularly good adhesion on the substrate and particularly good optical properties. The outermost layer here is a layer comprising a fluoropolymer, the middle layer is a PMMA layer comprising at least one UV absorber and/or UV stabilizer, and the innermost layer is a PMMA layer comprising at least one adhesion promoter which improves adhesion on the substrate.
1. A UV-protective film suitable for lamination on high-pressure laminates (HIPLs), comprising, from the outside to the inside, the following layers bonded to one another:
a layer A comprising a fluoropolymer,
a PMMA layer B comprising a matrix material B comprising at least one impact modifier and at least one UV stabilizer and/or UV absorber, and
a layer C comprising 5 to 35% by weight of at least one adhesion promoter and a matrix material C comprising at least one poly(meth)acrylate, at least one impact modifier and optionally, at least one UV stabilizer and/or UV absorber,
wherein
the PMMA matrix material in layer B and the poly(meth)acrylate in layer C are respectively a polymer obtained through polymerization of a composition composed of from 80 to 100% by weight of methyl methacrylate and from 0 to 20% by weight of one or more other ethylenically unsaturated monomers capable of free radical polymerization,
a molar mass of the PMMA in layer B is from 100,000 to 200,000 g/mol,
the at least one impact modifier in the layers B and C are core-shell or core-shell-shell particles having an outermost shell wherein the outermost shell of said particles completely mixes with the PMMA matrix material in layer B and the poly(meth)actylate in layer C, respectively, and
the at least one adhesion promoter is a copolymer comprising at least one (meth)acrylate and one anhydride and/or diacid, and
the layer C is suitable for lamination with a resin-impregnated paper to obtain an HPL.
2. The protective film according to claim 1 , wherein a thickness of layer A is from 1 to 25 μm, a thickness of layer B is from 15 to 125 μm and a thickness of layer C is from 1 to 25 μm.
3. The protective film according to claim 1 , wherein the layer B comprises HALS compounds and triazines and/or benzotriazoles; and layer C optionally comprises HALS compounds and triazines and/or benzotriazoles.
4. The protective film according to claim 1 , wherein the fluoropolymer in layer A is polyvinylidene fluoride (PVDF), polyvinylfluoride (PVF), polyethylene-tetrafluoroethylene (PETFE) or polyfluorinated ethylene vinyl ether (PFEVE).
5. The protective film according to claim 4 , wherein the fluoropolymer is a predominantly amorphous PVDF with a haze value smaller than 5 or a microcrystalline PVDF with a haze value smaller than 5.
6. The protective film according to claim 1 , wherein layer A consists of PVDF and optional additives.
7. The protective film according to claim 1 , wherein the adhesion promoter in layer C is a copolymer of MMA, styrene and maleic anhydride.
8. The protective film according to claim 1 , wherein, after a press procedure, the layer A has a structure on the external side.
9. A process for the production of a protective film according to claim 1 , wherein the protective film is produced by adapter coextrusion or multiple-manifold coextrusion or a combination of the two processes.
10. A method for the production of HPLs, MPLs or CPLs comprising lamination of the protective film according to claim 1 onto a resin-impregnated paper layer.
11. The method according to claim 10 , wherein the protective film is pressed directly onto a melamine-resin-impregnated paper layer.
12. The method according to claim 10 , wherein the protective film is pressed onto a melamine-resin-impregnated paper in a press by a pressure ≥5 Mpas at a temperature ≥120° C. with a cycle time of from 30 to 100 min.
13. The method according to claim 12 , wherein in the press on the side counterposed to the layer A there is a structured surface.