PHOTOVOLTAIC MODULE BACKSHEET COMPRISING POLYOLEFIN LAYERS

Abstract

The present invention relates to a photovoltaic module backsheet, comprising photovoltaic module backsheet comprising, in order: a functional layer; a connecting layer; and a weather-resistant layer, wherein each layer of the backsheet comprises at least 50 wt. % polyolefin and the backsheet is free of fluorinated polymers, characterized in that: i) the functional layer comprises a blend of polyethylene and a polyethylene copolymer; and ii) the weather-resistant layer comprises polypropylene; a UV stabilizer; a primary antioxidant, which primary antioxidant is a phenolic antioxidant or an aromatic amine antioxidant; and secondary antioxidant, which secondary antioxidant is a trivalent phosphorus containing antioxidant or a thioether containing antioxidant. The present invention also relates to a process for producing the backsheet and a photovoltaic module comprising the backsheet according to the present invention.

Claims

1. A photovoltaic module backsheet comprising, in order: a functional layer; a connecting layer; and a weather-resistant layer, wherein each layer of the backsheet comprises at least 50 wt. % polyolefin and the backsheet is free of fluorinated polymers, characterized in that: i) the functional layer comprises a blend of polyethylene and a polyethylene copolymer; and ii) the weather-resistant layer comprises polypropylene; a UV stabilizer; a primary antioxidant, which primary antioxidant is a phenolic antioxidant or an aromatic amine antioxidant; and secondary antioxidant, which secondary antioxidant is a trivalent phosphorus containing antioxidant or a thioether containing antioxidant.

2. A photovoltaic module backsheet according to claim 1, which photovoltaic module backsheet consists of a functional layer; a connecting layer; and a weather-resistant layer.

3. A photovoltaic module backsheet according to claim 1, wherein the weather-resistant layer comprises a polypropylene-polyethylenecopolymer.

4. A photovoltaic module backsheet according to claim 3, wherein the weather-resistant layer comprises from 75 to 90 wt. % polypropylene-polyethylene copolymer.

5. A photovoltaic module backsheet according to claim 1, wherein the weather-resistant layer comprises an outer sub-layer comprising an inorganic filler and an inner sub-layer comprising an inorganic filler, wherein the outer sub-layer comprises a lower wt. % of inorganic filler than the inner sub-layer.

6. A photovoltaic module backsheet according to claim 5, wherein the outer sub-layer and inner sub-layer each comprise titanium dioxide, and the outer sub-layer comprises a higher wt. % titanium dioxide than the inner sub-layer.

7. A photovoltaic module backsheet according to claim 1, wherein the primary antioxidant is a phenolic antioxidant and is selected from benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-octadecyl ester; 2,5,7,8-Tetra-methyl-2-(4′,8′,12′-tri-methyl-tri-decyl)-chroman-6-ol; N,N′-Hexamethylene bis (3,5-di-t-butyl-4-hydroxyhydrocinnamamide); ethylenebis (oxyethylene) bis (3-t-butyl-4-hydroxy-5-methylhydrocinnamate); hexamethylenebis (3,5-di-t-butyl-4-hydroxycinnamate); phenol, 4,4′4′″-[(2,4,6-trimethyl-1,3,5-benzenetriyl)-tris-(methylene)]-tris-2,6-bis(1,1-dimethylethyl)-; bis-[3,3-bis-(4′-hydroxy-3′-t-butylphenyl butanoic acid]-glycol ester; tris(3,5-di-t-butyl-4-hydroxy benzyl) isocyanurate; 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane; 1,3,5-Tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione; and tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane 3-(3,5-di-t-butyl-4-hydroxy-phenyl) propion acid ester with 1,3,5-tris (2-hydroxy-ethyl)-iso-cyanurate.

8. A photovoltaic module backsheet according to claim 1, wherein the secondary antioxidant is a thioether antioxidant, and is selected from dilauryl thiodipropionate; distearyl thiodipropionate; pentaerythrityl tetrakis (β-laurylthiopropionate); and propanoic acid, 3,3′-thiobis-, 1,1′-dimethyl ester, polymer with 1,4-cyclohexanedimethanol, octadecyl ester.

9. A photovoltaic module backsheet according to claim 1, wherein the ratio of wt. % primary antioxidant stabilizer to wt. % secondary antioxidant is from 0.1 to 1.0.

10. A photovoltaic module backsheet according to claim 1, wherein functional layer comprises a ternary blend of polypropylene, polyethylene and a polyethylene copolymer.

11. A photovoltaic module backsheet according to claim 10, wherein the polyethylene copolymer is ethylene methacrylate.

12. A photovoltaic module backsheet according to claim 1, wherein the functional layer has a thickness of from 10 to 50 μm.

13. A photovoltaic module backsheet according to claim 1, wherein the connecting layer has a thickness of from 10 to 50 μm.

14. A photovoltaic module backsheet according to claim 1, wherein the weather-resistant layer has a thickness of from 100 to 400 μm.

15. A photovoltaic module comprising a solar module backsheet as defined in claim 1.

16. A process for producing a photovoltaic module backsheet as defined in claim 1 comprising: i) feeding a functional layer composition; a connecting layer composition; and a weather-resistant layer composition independently to a multi-layer film coextrusion apparatus; and ii) melting and coextruding the compositions, in the multi-layer film coextrusion apparatus, into a photovoltaic module backsheet in the order: functional layer, connecting layer, weather-resistant layer.

17. A process according to claim 16 comprising: i) feeding a functional layer composition; a connecting layer composition; an inner weather-resistant layer composition and an outer weather-resistant layer composition independently to a multi-layer film coextrusion apparatus; and ii) melting and coextruding the compositions, in the multi-layer film coextrusion apparatus, into a photovoltaic module backsheet in the order: functional layer, connecting layer, inner weather-resistant layer and outer weather-resistant layer.

Description

EXAMPLES

Method for Manufacturing a Photovoltaic Backsheet Comprises the Following Steps:

[0067] Material of a weathering-resistant layer, an adhesive layer, a structure reinforcing layer and a functional layer are respectively pelletized by an extruder to obtain plastic pellets of respective layers.

[0068] A back sheet is prepared by a multilayer co-extrusion process whereby the pellets of the respective layers are added to multiple extruders, melt-extruded at a high temperature, flow through an adapter and a die, cooled by a cooling roller and shaped to manufacture the multi-layer back sheet. Composition of the different layers in the multilayer backsheets are given in Table 1.

Measurements

[0069] Damp heat ageing was carried out at 85° C. and 85% relative humidity for a period of 200 hours. Elongation of a sample was measured after damp heat ageing and compared to a sample which was not subjected to damp heat ageing. The elongation retention % was calculated. Calculations were made both for the machine direction and for the transverse direction.

[0070] Thermal stability was determined by heating samples to 200° C. for 5 hours. Appearance of the sample after heating is described.

[0071] Thermal ageing was carried out at 150° C. for a period of 300 hours. Elongation of a sample was measured after thermal ageing and compared to a sample which was not subjected to thermal ageing. The elongation retention % was calculated. Calculations were made both for the machine direction and for the transverse direction.

[0072] Results of these measurements are given in Table 2.

TABLE-US-00001 TABLE 1 Example Connecting layer Functional layer no. Weather-resistant layer (thickness) (thickness) (thickness) Ex. 1 71 parts of polypropylene, 5 parts of 50 parts of 50 parts of polyolefin elastomer, 12 parts of polypropylene, 49 polyethylene, 16 titanium dioxide, 10 parts of talcum parts of polyolefin parts of powder, ultraviolet absorbent is 1.0 elastomer, ultraviolet polypropylene, 20 part of Chimassorb 2020, primary absorbent is 1.0 part parts of ethyl antioxidant is 0.25 part of AO-80, the of Chimassorb 2020, copolymer, 12 parts assistant antioxidant is 0.75 part of primary antioxidant is of titanium dioxide, 412S (240 um) 0.25 part of AO-80, the the ultraviolet assistant antioxidant is absorbent is 1.0 part 0.75 part of of Chimassorb 2020, 412S (30 um) primary antioxidant is 0.25 part of AO-80, the assistant antioxidant is 0.75 part of 412S (30 um) Comp 71 parts of polypropylene, 5 parts of 50 parts of 50 parts of Ex. 1 polyolefin elastomer, 12 parts of polypropylene, 49 polyethylene, 16 titanium dioxide, 10 parts of talcum parts of polyolefin parts of powder, ultraviolet absorbent is 1.0 elastomer, ultraviolet polypropylene, 20 part of Chimassorb 2020, antioxidant absorbent is 1.0 part parts of ethyl is 1 part of Irganox ® 1010 (240 um) of Chimassorb 2020, copolymer, 12 parts antioxidant is 1 part of of titanium dioxide, Irganox ® the ultraviolet 1010 (30 um) absorbent is 1.0 part of Chimassorb 2020, antioxidant is 1 part of Irganox ® 1010 (30 um) Ex. 2 Inner sub-layer: 71 parts of 50 parts of 50 parts of polypropylene, 5 parts of polyolefin polypropylene, 49 polyethylene, 16 elastomer, 12 parts of titanium dioxide, parts of polyolefin parts of 10 parts of talcum powder, ultraviolet elastomer, ultraviolet polypropylene, 20 absorbent is 1.0 part of Chimassorb absorbent is 1.0 part parts of ethyl 2020, primary antioxidant is 0.25 part of Chimassorb 2020, copolymer, 12 parts of AO-80, the assistant antioxidant is primary antioxidant is of titanium dioxide, 0.75 part of 412S (200 um); 0.25 part of AO-80, the the ultraviolet Outer sub-layer: assistant antioxidant is absorbent is 1.0 part 71 parts of polypropylene, 5 parts of 0.75 part of of Chimassorb 2020, polyolefin elastomer, 17 parts of 412S (30 um) primary antioxidant is titanium dioxide, 5 parts of talcum 0.25 part of AO-80, powder, ultraviolet absorbent is 2.0 the assistant parts of Chimassorb 2020, antioxidant antioxidant is 0.75 is primary antioxidant is 0.5 part of part of 412S (30 um) AO-80, the assistant antioxidant is 1.5 part of 412S (40 um) Comp Commercially available polyolefin backsheet Ex. 2

TABLE-US-00002 TABLE 2 Method/ Comp Comp. Test standard Ex. 1 Ex. 1 Ex. 2 Ex. 2 Elongation MD  85° C., 73 67 69 39 retention TD 85% RH 71 65 76 76 (%) after damp-heat aging 2000 h Thermal 200° C., Not Cracked Not Cracked stability test  5 h cracked cracked Elongation MD 150° C., 25 20 36 10 retention TD 300 h 29 21 37 13 (%) after thermal aging