Backing film for photovoltaic module with improved pigment dispersion
A multilayered laminate film containing dispersed pigment which is suitable as a back cover for a solar module is provided. The film comprises, in the order listed: a) a layer of a moulding composition which comprises: at least 35% by weight, of polyamide; and from 1 to 65% by weight of a light-reflecting filler; b) optionally, a layer of a thermoplastic moulding composition; and c) a layer of a moulding composition which comprises at least 35% by weight, of polyamide; and from 1 to 65% by weight of a light-reflecting filler; wherein at least one of layers a) and c) further comprises from 1 to 25% by weight of the layer composition of a polyamide elastomer which is a polyetheresteramide, a polyetheramide or a combination thereof. A solar module containing the multilayered laminate film is also provided.
1. A multilayer film, comprising, in the order listed:
a) a first outermost surface layer of a moulding composition, comprising:
at least 35% by weight of polyamide; and
from 1 to 65% by weight of a light-reflecting filler, wherein the % by weight is based on the weight of the moulding composition of the first outermost surface layer;
c) the second outermost surface layer opposite to the first outermost surface layer of a moulding composition which comprises at least 35% by weight of polyamide; and
from 1 to 65% by weight of a light-reflecting filler, wherein the % by weight is based on the weight of the moulding composition of the second outermost surface layer; and
wherein
at least one of the first outermost surface layer and second outermost surface layer further comprises from 1 to 25% by weight of the layer composition of a polyamide elastomer which is a polyetheresteramide, a polyetheramide or a combination thereof,
the first outermost surface layer and the second outermost surface layer are in direct succession,
a thickness of the first outermost surface layer is from 15 to 100 μm, and
a thickness of the second outermost surface layer is from 100 to 500 μm.
2. The multilayer film according to claim 1 , wherein the polyamide elastomer present in at least one of the first and second outermost surface layers is a polyetheramide.
3. The multilayer film according to claim 1 , wherein the light-reflecting filler is titanium dioxide.
4. The multilayer film according to claim 1 , wherein the polyamide of each of the first and second outermost surface layers comprises at least one selected from the group consisting of a partly crystalline polyamide having an enthalpy of fusion of more than 25 J/g, a semicrystalline polyamide having an enthalpy of fusion of from 4 to 25 J/g and an amorphous polyamide having an enthalpy of fusion of less than 4 J/g.
5. The multilayer film according to claim 2 wherein the polyetheramide comprises from 4 to 60% by weight of a polyamine obtained from a diol selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol and 1,3-butanediol.
6. The multilayer film according to claim 1 wherein at least one of the first outermost surface layer and the second outermost surface layer further comprises an impact-modifying rubber which is optionally modified with a polyamide compatible functional group.
7. A photovoltaic module, comprising;
a solar cell embedded in a sealing layer; and
the multilayer film according to claim 1 as a back cover,
wherein the first outermost surface layer of the multilayer film is bonded to the sealing layer.
8. The photovoltaic module according to claim 7 ,
wherein the polyamide elastomer is a polyetheramide.
9. The photovoltaic module according to claim 7 ,
wherein the light-reflecting filler is titanium dioxide.
10. The photovoltaic module according to claim 7 , wherein at least one of the first outermost surface layer and the second outermost surface layer further comprise an impact-modifying rubber optionally modified with a polyamide compatible functional group.