Three-layer UV protective film for decorative laminated sheets (HPL)

Abstract

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.

Claims

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.

Description

EXAMPLES

(1) The weathering tests used a Beta LM Xenotest from Atlas in accordance with DIN EN ISO 4892-2, Method A, Cycle 1. Optical and mechanical assessments were made after 0 h, 1000 h, 2500 h, 3333 h, 10,000 h and 15,000 h. Alternatively, an accelerated process was carried out, based on DIN EN ISO 4892-2, Method A, Cycle 1 but with a black standard temperature of 70° C.+/−5° C., sample compartment temperature of 40° C.+/−5° C., and UV irradiation at 180 W/m.sup.2 in the wavelength range from 300 to 400 nm. Optical and mechanical assessments were made after 0 h, 333 h, 833 h, 1666 h, 2500 h, 3333 h and 5000 h.

(2) The haze value was determined in accordance with ASTM D1003 at 23° C. The measurements to determine the haze value of the fluoropolymers were made on an appropriate monofilm of thickness 30 μm.

(3) The UV stabilizer package used was a mixture of 46.3% by weight of Tinuvin® 360, 18.7% by weight of Sabostab® 119FL and 35.0% by weight of Tinuvin® 1600.

(4) The HPLs were produced by simultaneous lamination of the resin-impregnated paper layers and of the superposed protective films. The core layer was composed of phenolic-resin-impregnated papers. Between these and the protective film there was a melamine-resin-impregnated decorative paper. A first HPL was used for the results according to Table 1. A similarly constructed, anthracite-coloured HPL was used from the results according Table 2.

(5) The protective films were produced by adapter coextrusion by way of the chill-roll process. Alternatively, production can be achieved by way of a multiple-manifold coextrusion process or a combination of adapter and multiple-manifold coextrusion.

(6) The adhesion promoter used was a copolymer of 75% by weight of MMA, 15% by weight of styrene and 10% by weight of maleic anhydride. The weight-average molar mass M.sub.w of this copolymer was about 100,000 g/mol (determined by means of GPC against a PMMA standard).

(7) General data relating to the PMMA in the layers B and C: Matrix materials with impact modifier were used here. The impact modifier is core-shell or core-shell-shell particles. Since the outermost shell of these particles in each case mixes completely with the matrix material, the information below relating to the compositions attributes the respective exterior shells to the matrix material, and describes only the core of a core-shell particle and, respectively, the core and the inner shell of a core-shell-shell particle as impact modifier. This fraction is termed soft phase below. This also optionally comprises “hard” cores in a core-shell-shell particle.

(8) PMMA in layer B and C: Unless otherwise stated, an impact-modified polymer comprising a PMMA matrix material made of 92.8% by weight of MMA, 7.3% by weight of butyl acrylate and 0.8% by weight of MA, and also the soft phase of a core-(shell-) shell (meth)acrylate as impact modifier, was used in layer B and C.

(9) In Comparative Example 1 the composition of the PMMA matrix material of the layer C was different from this: 92% by weight of MMA and 8% by weight of butyl acrylate. In Inventive Examples 1 and 2 the composition of the PMMA matrix material of the layer B was respectively 96% by weight of MMA, 0.9% by weight of ethyl acrylate and 3.1% by weight of methyl acrylate.

Comparative Example 1

(10) Layer A: 5 μm of Kureha KF Polymer T850 (PVDF) with a haze value of 11.8. Layer C: Layer of thickness 45 μm made of 51.1% by weight of PMMA matrix material, 20% by weight of adhesion promoter, 26% by weight of soft phase and 2.9% by weight of UV stabilizer package. The impact modifier was a core-shell particle. The HPL exhibited a significant loss of adhesion between the layers A and C (delamination) after lamination and weathering for 3333 h in a high-energy Xenotest Alpha.

Comparative Example 2

(11) Layer A: 5 μm of Solef® 9009 with a haze value of 2.98. Layer C: Layer of thickness 45 μm made of 59.2% by weight of PMMA matrix material, 15% by weight of adhesion promoter, 24% by weight of soft phase and 1.8% by weight of UV stabilizer package. The impact modifier was a core-shell particle. The HPL exhibited significant blue sheen after the lamination process.

Inventive Example 1

(12) Layer A: 5 μm of Solef® 9009 Layer B: Layer of thickness 40 μm made of 65.5% by weight of PMMA matrix material, 32.4% by weight of soft phase of a core-shell-shell particle and 2.1% by weight of UV stabilizer package. Layer C: Layer of thickness 5 μm made of 59.2% by weight of PMMA matrix material, 15% by weight of adhesion promoter, 24% by weight of soft phase and 1.8% by weight of UV stabilizer package. The impact modifier was a core-shell particle.

Inventive Example 2

(13) Layer A: 5 μm of Solef® 9009 Layer B: Layer of thickness 40 μm made of 65.5% by weight of PMMA matrix material, 32.4% by weight of soft phase of a core-shell-shell particle and 2.1% by weight of UV stabilizer package. Layer C: Layer of thickness 5 μm made of 55.5% by weight of PMMA matrix material, 20% by weight of adhesion promoter, 22.8% by weight of soft phase and 1.7% by weight of UV stabilizer package. The impact modifier was a core-shell particle.

Inventive Example 3

(14) Layer A: 5 μm of Solef® 9009 Layer B: Layer of thickness 40 μm made of 69.4% by weight of PMMA matrix material, 28.5% by weight of soft phase of a core-shell-shell particle and 2.1 by weight of UV stabilizer package. Layer C: Layer of thickness 5 μm made of 55.5% by weight of PMMA matrix material, 20% by weight of adhesion promoter, 22.8% by weight of soft phase and 1.7% by weight of UV stabilizer package. The impact modifier was a core-shell particle.

Inventive Example 4

(15) Layer A: 5 μm of Solef® 9009 Layer B: Layer of thickness 40 μm made of 69.4% by weight of PMMA matrix material, 28.5% by weight of soft phase of a core-shell-shell particle and 2.1% by weight of UV stabilizer package. Layer C: Layer of thickness 5 μm made of 59.2% by weight of PMMA matrix material, 15% by weight of adhesion promoter, 24% by weight of soft phase and 1.8% by weight of UV stabilizer package. The impact modifier was a core-shell particle.

(16) TABLE-US-00001 Results Table 1 UV-protective Inv. Inv. Comparative film Ex. 1 Ex. 2 Inv. Ex. 3 Inv. Ex. 4 Ex. 2 “Blue sheen” + + + + − H.sub.2O test.sup.1.) 2 h @ + + + + − 100° C. (haze value) H.sub.2O test 48 h @ + + + + + 65° C. .sup.1.)Adhesion test/crosscut test: passed

(17) TABLE-US-00002 Results Table 2 UV-protective Inv. Inv. Comparative film Ex. 1 Inv. Ex. 2 Inv. Ex. 3 Ex. 4 Ex. 1 Weathering in + + + 0 −− high-energy Alpha after 3333 h H.sub.2O test.sup.1.) 2 h @ + + + + −− 100° C. (loss of adhesion) H.sub.2O test 48 h @ + + + + + 65° C.