Photovoltaic cells with improved multilayer backsheet

1. A multilayer structure comprising

an outer skin layer comprising a polyamide-ionomer blend composition;

an interior core layer comprising polyamide or a blend of ionomer and polyamide, optionally filled with about 10 to about 30 weight % of an inorganic filler;

an inner skin layer comprising the polyamide-ionomer blend composition, an ionomer, a polyethylene, an ionomer-polyethylene blend or an ethylene vinyl acetate copolymer optionally comprising about 10 to about 20 weight % of an inorganic pigment; and optionally

one or more tie layers positioned between the core layer and the outer skin layer, between the core layer and the inner skin layer, or between the core layer and each of the skin layers;

wherein the polyamide-ionomer blend composition comprises

(i) a polymer component comprising

1) 53 to 64 weight %, based on the combination of (1) and (2), of a polyamide;

2) 36 to 47 weight %, based on the combination of (1) and (2), of an ionomer comprising a copolymer of copolymerized units of

(a) ethylene;

(b) from 2 weight % to 30 weight % of an alpha, beta-unsaturated C 3 -C 8 monocarboxylic acid;

(c) from 0 weight % to 12 weight % of at least one comonomer that is an ethylenically unsaturated dicarboxylic acid or derivative thereof selected from maleic acid, fumaric acid, itaconic acid, maleic anhydride, or a C 1 -C 4 alkyl half ester of maleic acid; and

(d) from 0 weight % to 30 weight % of monomers selected from alkyl acrylate or alkyl methacrylate, wherein the alkyl groups have from one to twelve carbon atoms; wherein the carboxylic acid functionalities present are at least partially neutralized to carboxylate salts comprising one or more alkali metal, transition metal, or alkaline earth metal cations; and

wherein when the polyamide comprises nylon-6 the ionomer comprises from 5 weight % to 15 weight % of an alpha, beta-unsaturated C 3 -C 8 carboxylic acid and from 0.5 weight % to 12 weight % of at least one comonomer that is an ethylenically unsaturated dicarboxylic acid or derivative thereof selected from maleic acid, fumaric acid, itaconic acid, maleic anhydride, or a C 1 -C 4 alkyl half ester of maleic acid; and

(ii) 0 to 20 weight % of pigment;

(iii) 0 to 40 weight % of filler; wherein the combination of (ii) and (iii) comprises 8 to 50 weight % of the combination of (i), (ii), (iii) and (iv); and

(iv) 0 to 5 weight % of additives selected from oxidation inhibitors, UV stabilizers and hindered amine light stabilizers.

2. The multilayer structure of claim 1 wherein the polyethylene or the ionomer-polyethylene blend independently comprises low density polyethylene, linear low density polyethylene, or high density polyethylene.

3. The multilayer structure of claim 1 wherein the polyethylene or the ionomer-polyethylene blend independently comprises high density polyethylene.

4. The multilayer structure of claim 1 wherein the inner skin layer comprises about 10 to about 20 weight % of inorganic pigment.

5. The multilayer structure of claim 1 wherein the polyamide in each of the layers is independently selected from nylon-6, nylon-11, nylon-12, nylon-66, nylon-6,10, nylon-6,12, nylon-610/6T, nylon-612/6T, nylon-6/66, nylon-6/610, nylon-6/66/610, nylon-6/6T, nylon-1010, nylon-11 and nylon-12, nylon-66/6T, nylon-6T/DT, nylon-61/6T, nylon-61/6T/66, or combinations thereof.

6. The multilayer structure of claim 1 wherein the polyamide in each of the layers is independently selected from nylon-6, nylon-66, nylon-610, nylon-612, nylon-6/66, nylon-6/610, nylon-6/66/610, nylon-6/6T, nylon-610/6T, nylon-12/6T, nylon-1010, nylon-11, nylon-12 or combinations thereof.

7. The multilayer structure of claim 1 wherein the polyamide in each of the layers is nylon-6 and the ionomer comprises an acid copolymer comprising from 5 weight % to 15 weight % of an alpha, beta-unsaturated C 3 -C 8 carboxylic acid and from 0.5 weight % to 12 weight % of at least one comonomer that is an ethylenically unsaturated dicarboxylic acid or derivative thereof selected from maleic acid, fumaric acid, itaconic acid, maleic anhydride, or a C 1 -C 4 alkyl half ester of maleic acid; wherein the carboxylic acid functionalities present are at least partially neutralized to carboxylate salts comprising one or more alkali metal cations.

8. The multilayer structure of claim 7 wherein the polyamide-ionomer blend composition comprises 10 to 40 weight % of filler and 8 to 15 weight % of pigment.

9. The multilayer structure of claim 7 wherein the polyamide-ionomer blend composition comprises 8 to 12 weight % of pigment and 12 to 18 weight % of filler.

10. The multilayer structure of claim 1 wherein the pigment comprises titanium dioxide, zinc oxide, or antimony oxide.

11. The multilayer structure of claim 1 wherein the filler comprises an inorganic oxide, carbonate, sulfate, silica, alkali and alkaline earth metal silicate, or baryte of a metal of Groups IA, IIA, IIIA, IIB, VIB or VIII of the periodic table of the elements.

12. The multilayer structure of claim 1 wherein one or more tie layer is present and each tie layer independently comprises a maleic anhydride-grafted polymer selected from maleated linear low density polyethylene, maleated polypropylene, maleated styrene-ethylene-butene-styrene triblock copolymer, maleated ethylene vinyl acetate copolymers or maleated polybutadiene; or

a copolymer comprising ethylene copolymerized with a functional comonomer comprising an ethylenically unsaturated dicarboxylic acid or derivative thereof.

13. The multilayer structure of claim 1 wherein the inner skin layer comprises a polyamide-ionomer blend composition or an ionomer-high density polyethylene blend comprising about 10 to about 20 weight % of inorganic pigment; and comprising at least one tie layer.

14. The multilayer structure of claim 12 wherein each tie layer comprises a maleic anhydride-grafted polymer selected from maleated linear low density polyethylene or maleated polypropylene.

15. The multilayer structure of claim 1 wherein the inner skin layer comprises an ionomer-high density polyethylene blend comprising about 10 to about 20 weight % of inorganic pigment; and comprising at least one tie layer.

16. The multilayer structure of claim 8 wherein the outer skin layer comprises the polyamide-ionomer blend composition of claim 1 ; the interior core layer comprises polyamide filled with about 10 to about 30 weight % of inorganic filler or the polyamide-ionomer blend; the inner skin layer comprises the polyamide-ionomer blend; and tie layers positioned between the core layer and the outer skin layer and between the core layer and the inner skin layer.

17. The multilayer structure of claim 16 wherein each tie layer comprises a maleic anhydride-grafted polymer selected from maleated linear low density polyethylene or maleated polypropylene.

18. The multilayer structure of claim 1 wherein the structure comprises from 8 to 12 mils in total of the polyamide-ionomer blend composition in one or more layers and from 3 to 5 mils in total of polyethylene, a polyethylene-based composition or a combination thereof in one or more layers.

19. The multilayer structure of claim 17 wherein the polyamide in each of the layers is nylon-6 and the ionomer comprises an acid copolymer comprising from 5 weight % to 15 weight % of an alpha, beta-unsaturated C 3 -C 8 carboxylic acid and from 0.5 weight % to 12 weight % of at least one comonomer that is an ethylenically unsaturated dicarboxylic acid or derivative thereof selected from maleic acid, fumaric acid, itaconic acid, maleic anhydride, or a C 1 -C 4 alkyl half ester of maleic acid; wherein the carboxylic acid functionalities present are at least partially neutralized to carboxylate salts comprising one or more alkali metal cations.

20. The multilayer structure of claim 19 wherein the polyamide-ionomer blend composition comprises 10 to 40 weight % of filler and 8 to 15 weight % of pigment.