Acrylic multilayer foil with improved mechanical properties and a high weathering resistance

1. A multilayer foil comprising a layer A and a layer D adjacent to the layer A, wherein the layer A consists of a moulding composition comprising, based on the total weight of the layer A:

from 0.0 to 78.0 wt. % of a polyalkyl (meth)acrylate;

from 20.0 to 98.0 wt. % of an impact modifier;

from 2.0 to 40.0 wt. % of particulate silica;

from 0.0 to 20.0 wt. % of an adhesion-promoting copolymer, comprising, based on the weight of the adhesion-promoting copolymer:

from 70.0 to 99.5 wt. % of methyl methacrylate;

from 0.5 to 15.0 wt. % of an adhesion-promoting monomer; and

from 0.0 to 25.0 wt. % of another vinyl-copolymerizable monomer having no functional group other than a vinyl functional group;

from 0.0 to 38.0 wt. % of a fluoropolymer;

from 0.0 to 5.0 wt. % of a UV absorber; and

from 0.0 to 5.0 wt. % of a UV stabilizer,

wherein

a cumulative content of the polyalkyl (meth)acrylate and the impact modifier in the moulding composition of the layer A is at least 50 wt. %, based on the weight of the layer A,

the particulate silica is a hydrophilic precipitated silica or a hydrophilic pyrogenic silica,

the particulate silica has a silanol group density of not lower than 0.5 SiOH/nm 2 ; and

the layer D comprises at least a partially cross-linked material selected from the group consisting of a cross-linked polyurethane, a cross-linked polyurethane-(meth)acrylate, a cross-linked poly(meth)acrylate, and a mixture thereof.

2. The foil according to claim 1 , further comprising a layer B adjacent to the layer A, wherein the layer B consists of a moulding composition comprising, based on the total weight of the layer B:

from 0.0 to 100.0 wt. % of a polyalkyl (meth)acrylate;

from 0.0 to 95.0 wt. % of an impact modifier;

from 0.0 to 40.0 wt. % of a fluoropolymer;

from 0.0 to 5.0 wt. % of a UV absorber;

from 0.0 to 5.0 wt. % of a UV stabilizer; and

from 0.0 to 20.0 wt. % of an adhesion-promoting copolymer, comprising, based on the weight of the adhesion-promoting copolymer:

from 70.0 to 99.5 wt. % of methyl methacrylate;

from 0.5 to 15.0 wt. % of an adhesion-promoting monomer; and

from 0.0 to 25.0 wt. % of another vinyl-copolymerizable monomer having no functional group other than a vinyl functional group,

wherein the cumulative content of the polyalkyl (meth)acrylate and the impact modifier in the moulding composition of the layer B is at least 50 wt. %, based on the weight of the layer B.

3. The foil according to claim 1 , wherein the content, in wt. %, based on the total weight of the layer A, the impact modifier n im in the polyalkyl (meth)acrylate foil satisfies the following relationship:

0.01* n im <n si <0.4* n im

n si being the content, in wt. %, of the particulate silica in the foil.

4. The foil according to claim 1 , wherein the particulate silica has a specific surface area, measured by BET method according to ISO 9277, of more than 200 m 2 /g.

5. The foil according to claim 1 , wherein the particulate silica is a hydrophilic precipitated silica.

6. The foil according to claim 1 , wherein the particulate silica is a precipitated silica which has a weight average particle size d 50 of from 1.0 μm to 20.0 μm determined by laser diffraction according to ISO 13320.

7. The foil according to claim 1 , wherein the particulate silica is a precipitated silica having a specific surface area, measured by BET method according to ISO 9277, of more than 500 m 2 /g.

8. The foil according to claim 1 , wherein the particulate silica has DBP absorption of 100 to 500 g/100 g determined in accordance with ASTM D6854-12a.

9. The foil according to claim 1 , wherein the particulate silica has a tamped density from 10 g/l to 800 g/l determined in accordance with DIN EN ISO 787-11.

10. The foil according to claim 1 , wherein the polyalkyl (meth)acrylate is a polymethyl methacrylate having a mass average molar weight Mw of from 50 000 g/mol to 180 000 g/mol, and is obtained by polymerization of a composition whose polymerizable constituents comprise, based on the weight of the polymerizable composition:

(a) from 50.0 to 99.9 wt. % of methyl methacrylate;

(b) from 0.1 to 50.0 wt. % of an acrylic acid ester of a C1-C4 alcohol; and

(c) from 0.0 to 10.0 wt. % of a monomer copolymerizable with the monomers (a) and (b).

11. The foil according to claim 1 , wherein the impact modifier is at least one particulate impact modifier selected from the group consisting of core, core-shell, core-shell-shell, and core-shell-shell-shell impact modifiers.

12. The foil according to claim 2 , wherein the layer B comprises, based on the total weight of the layer B:

from 0.5 to 4.0 wt. % of a benzotriazole compound as a first UV absorber;

from 0.5 to 3.0 wt. % of a triazine compound as a second UV absorber; and

from 0.2 to 2.0 wt. % of a Hindered Amine Light Stabilizer (HALS) compound as a UV stabilizer.

13. The foil according to claim 2 , wherein the foil further comprises a layer C, wherein the layer B is located between the layer A and the layer C, and wherein the layer B consists of a moulding composition comprising, based on the total weight of the layer B:

from 0.0 to 100.0 wt. % of a polyalkyl (meth)acrylate;

from 0.0 to 95.0 wt. % of an impact modifier;

from 0.0 to 40.0 wt. % of a fluoropolymer;

from 0.0 to 5.0 wt. % of a UV absorber; and

from 0.0 to 5.0 wt. % of a UV stabilizer, and

wherein the layer C consists of a moulding composition comprising, based on the total weight of the layer C:

from 0.0 to 78.0 wt. % of a polyalkyl (meth)acrylate;

from 20.0 to 98.0 wt. % of an impact modifier;

from 0.0 to 40.0 wt. % of particulate silica;

from 0.0 to 40.0 wt. % of an adhesion-promoting copolymer, comprising, based on the weight of the adhesion-promoting copolymer:

from 70.0 to 99.5 wt. % of methyl methacrylate;

from 0.5 to 15.0 wt. % of an adhesion-promoting monomer; and

from 0.0 to 25.0 wt. % of another vinyl-copolymerizable monomer having no functional group other than a vinyl functional group

from 0.0 to 5.0 wt. % of a UV absorber; and

from 0.0 to 5.0 wt. % of a UV stabilizer,

wherein a cumulative content of the polyalkyl (meth)acrylate and the impact modifier in the moulding composition of the layer C is at least 50 wt. %, based on the weight of the layer C; and

a cumulative content of the particulate silica and the adhesion-promoting copolymer is at least 2.0 wt %, based on the weight of the layer C.

14. The foil according to claim 13 , wherein

the layer A has a thickness from 1.0 μm to 150.0 μm;

the layer B has a thickness from 15.0 μm to 150.0 μm;

the layer C has a thickness from 1.0 μm to 30.0 μm; and

the layer D has a thickness from 10.0 μm to 50.0 μm.

15. A multi-layer article, having an outer surface, comprising a substrate which is at least partially covered by the foil according to claim 13 , comprising the layers A, B, C, and D in the following order, starting from the outer surface of the multi-layer article:

layer D forming the outer surface of the multi-layer article;

layer A;

layer B; and

layer C.

16. A process for manufacturing the multi-layer article according to claim 15 , the process comprising i) to iii):

i) preparing a foil comprising the layers A, B and C by co-extrusion;

ii) coating the layer A of the foil obtained in the preparing i) with the layer D; and

iii) applying the coated foil obtained in the coating ii) onto a substrate by lamination or extrusion lamination, wherein the multi-layer article is obtained,

wherein the coating layer D comprises a material which undergoes a partial cross-linking in the coating ii) and a further cross-linking in the applying iii).

17. The process according to claim 16 , wherein the multi-layer article is a high-pressure laminate, and wherein the applying of iii) is carried out at a pressure of from 1 MPa to 20 MPa and a temperature of from 120° C. to 220° C.