EP4728005A1

EP4728005A1 - Blend of uv stabilizers and hindered amine light stabilizers for achieving excellent long term uv and thermal stability

Info

Publication number: EP4728005A1
Application number: EP24732908.9A
Authority: EP
Inventors: Minna Kaarina AARNIO-WINTERHOF; Francis Reny COSTA; Dietrich Gloger; Jeroen Oderkerk; Jessica HESSELGREN; Yuliia ROMANENKO
Original assignee: Borealis GmbH
Current assignee: Borealis GmbH
Priority date: 2023-06-13
Filing date: 2024-06-12
Publication date: 2026-04-22
Also published as: WO2024256443A1

Abstract

The present invention relates to a photovoltaic module having a protective back layer element that comprises a polypropylene composition comprising a certain combination of hindered amine light stabilizers and UV stabilizers, as well as to the use of the certain blend of hindered amine light stabilizers and UV stabilizers for maintaining elongation at break after UV or oven treatment.

Description

Blend of UV stabilizers and hindered amine light stabilizers for achieving excellent long term UV and thermal stability

Field of the Invention

Background to the Invention

In certain end use applications, e.g. outdoor end use, the mechanical properties of polymeric articles have particular requirements. The polymeric material must, for example, withstand UV light that can be severe in some geographical regions. Moreover, at outdoor end use the temperature can vary within wide range. Therefore, long-term thermal stability, especially at high temperatures, is also often required.

Usually articles produced using polymer material, such as polypropylene (PP), require additives to provide the UV stability and long-term temperature stability.

Whilst a wide range of additives are known for improving the UV stability of polypropylenes, it is far from straightforward to predict which combination of additives may be the most effective at providing the UV protection, as well as also providing long term thermal protection.

For polypropylenes used as external elements in photovoltaic modules, in particular in bifacial photovoltaic modules, it is important to combine good UV and thermal stability with excellent optical properties to ensure that the polypropylene external elements do not reduce the amount of light arriving at the photovoltaic elements of the photovoltaic module.

Accordingly, there is a continuous need for polymer compositions for demanding end applications wherein UV light stability and long-term thermal stability are required, without sacrificing the transmittance of the material. Summary of the Invention

The present invention is based on the finding that a combination of certain polymeric hindered amine light stabilizers, certain triazine -based UV stabilizers and certain further UV stabilizers combine to give excellent UV protection for polypropylenes, making polypropylene compositions comprising such a combination of additives an excellent choice for use as an external layer of a photovoltaic module.

Therefore, in a first aspect, the present invention is directed to a photovoltaic (PV) module, comprising, in the given order, a protective front layer element (1), a front encapsulation layer element (2), a photovoltaic element (3), a rear encapsulation layer element (4) and a protective back layer element (5), wherein the protective back layer element (5) comprises a polypropylene composition (PC) that comprises: a) 90.00 to 99.90 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); and b) 0.10 to 4.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers, said blend (B) comprising, more preferably consisting of: i) one or more polymeric hindered amine light stabilizers (HAUS) having a structure according to formula (I) wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R^A is selected from the group consisting of hydrogen and Ci to Cw alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl;

R^B is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

A¹ and B¹ are each independently selected from the group consisting of direct single bond, Ci to Ce alkylene, and phenylene; and

A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to Cw alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, and , wherein R^D is selected from the group consisting of hydrogen,

Ci to Ce alkyl and Ci to C5 alkoxy, wherein if A¹ and A² are both direct single bond then A¹ and A² together form a single bond linking the nitrogen atom to the 6-membered ring, and wherein if B¹ and B² are both direct single bond then B¹ and B² together form a single bond linking the nitrogen atom to the 6-membered ring; ii) one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II) wherein R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to C10 alkyl and Ci to C 12 alkoxy, and

R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to C10 alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to C10 alkyl and Ci to C12 alkoxy; and iii) one or more further UV stabilizers (UV2) having a structure according to formula (III) wherein X is selected from the group consisting of O and direct single bond; R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to C10 alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to C10 alkyl and Ci to C12 alkoxy; and R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to C10 alkyl being optionally substituted by acrylate substitution and Ci to C12 alkoxy being optionally substituted by acrylate substitution, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy.

In a second aspect, the present invention is directed to a polypropylene composition (PC) that comprises: a) 90.00 to 99.90 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); and b) 0.10 to 4.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers, said blend (B) comprising, more preferably consisting of: i) one or more polymeric hindered amine light stabilizers (HALS) having a structure according to formula (I) wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R^A is selected from the group consisting of hydrogen and Ci to Cio alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl;

R^B is selected from the group consisting of Ci to Cio alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to Cio alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to Cio alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, and , wherein R^D is selected from the group consisting of hydrogen,

In a third aspect, the present invention is directed to a use of a blend (B) of UV stabilizers and hindered amine light stabilizers for maintaining elongation at break, determined according to ISO 527-3 on monolayer fdm specimens having a thickness of 400 pm, of a polypropylene composition comprising said blend (B) after UV aging for 3000 h as described in the determination methods, wherein the blend (B) comprises, more preferably consists of: i) one or more polymeric hindered amine light stabilizers (HALS) having a structure according to formula wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R^A is selected from the group consisting of hydrogen and Ci to C alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl;

R^B is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to C alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to C alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, wherein R^D is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, wherein if A¹ and A² are both direct single bond then A¹ and A² together form a single bond linking the nitrogen atom to the 6-membered ring, and wherein if B¹ and B² are both direct single bond then B¹ and B² together form a single bond linking the nitrogen atom to the 6-membered ring; ii) one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II) wherein R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cio alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cio alkyl and Ci to C12 alkoxy, and R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cio alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cio alkyl and Ci to Ci 2 alkoxy; and iii) one or more further UV stabilizers (UV2) having a structure according to formula (HI) wherein X is selected from the group consisting of O and direct single bond;

R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cio alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cio alkyl and Ci to C12 alkoxy; and

R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cio alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution and Ci to C12 alkoxy being optionally substituted by acrylate substitution, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy, wherein maintaining the elongation at break is achieved when the value of the elongation at break after UV aging for 3000 h as described in the determination methods is at least 40% of the value determined before the UV aging.

In a final aspect, the present invention is directed to a use of a blend (B) of UV stabilizers and hindered amine light stabilizers for maintaining elongation at break, determined according to ISO 527-3 on monolayer film specimens having a thickness of 400 pm, of a polypropylene composition comprising said blend (B) after oven aging at 120 °C for 2000 h, wherein the blend (B) comprises, more preferably consists of: i) one or more polymeric hindered amine light stabilizers (HALS) having a structure according to formula wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy; R^A is selected from the group consisting of hydrogen and Ci to Cw alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to C alkyl and unsubstituted phenyl;

R^B is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to Cw alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl, wherein R^D is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, wherein if A¹ and A² are both direct single bond then A¹ and A² together form a single bond linking the nitrogen atom to the 6-membered ring, and wherein if B¹ and B² are both direct single bond then B¹ and B² together form a single bond linking the nitrogen atom to the 6-membered ring; ii) one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II) wherein R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to C alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, and R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to Ci 2 alkoxy; and iii) one or more further UV stabilizers (UV2) having a structure according to formula (HI) wherein X is selected from the group consisting of O and direct single bond;

R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to C10 alkyl and Ci to C12 alkoxy; and

R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution and Ci to C12 alkoxy being optionally substituted by acrylate substitution, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy, wherein maintaining the elongation at break is achieved when the value of the elongation at break after oven aging at 120 °C for 2000 h is at least 50% of the value determined before the oven aging.

Definitions

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although, any methods and materials similar or equivalent to those described herein can be used in practice for testing of the present invention, the preferred materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below.

Unless clearly indicated otherwise, use of the terms “a,” “an,” and the like refers to one or more.

In the following, amounts are given in % by weight (wt.-%) unless it is stated otherwise.

A propylene homopolymer is a polymer that essentially consists of propylene monomer units. Due to impurities especially during commercial polymerization processes, a propylene homopolymer can comprise up to 0.1 mol% comonomer units, preferably up to 0.05 mol% comonomer units and most preferably up to 0.01 mol% comonomer units.

A propylene copolymer is a copolymer of propylene monomer units and comonomer units, preferably selected from ethylene and C4-C8 alpha-olefins. A propylene random copolymer is a propylene copolymer wherein the comonomer units are randomly distributed along the polymer chain, whilst a propylene block copolymer comprises blocks of propylene monomer units and blocks of comonomer units. Propylene random copolymers can comprise comonomer units from one or more comonomers different in their amounts of carbon atoms.

Heterophasic propylene copolymers typically comprise: a) a crystalline propylene homopolymer or copolymer matrix (M); and b) an elastomeric rubber, preferably a propylene -ethylene copolymer (E).

In case of a random heterophasic propylene copolymer, said crystalline matrix phase is a random copolymer of propylene and at least one alpha-olefin comonomer.

A plastomer is a polymer that combines the qualities of elastomers and plastics, such as rubber-like properties with the processing abilities of plastic.

An ethylene-based plastomer is a plastomer with a molar majority of ethylene monomer units.

A bifacial photovoltaic module is a photovoltaic module that produces solar power from the front and the rear side of the solar cells of the photovoltaic element.

Different in the context of the present invention means that two polymers differ in at least one property or structural element.

The present invention will now be described in more detail.

Detailed Description

Photovoltaic (PV) module

In a first aspect, the present invention is directed to a photovoltaic (PV) module, comprising, in the given order, a protective front layer element (1), a front encapsulation layer element (2), a photovoltaic element (3), a rear encapsulation layer element (4) and a protective back layer element (5). The protective back layer element (5) comprises, more preferably consists of, the polypropylene composition (PC) as defined below.

The “photovoltaic element” means that the element has photovoltaic activity. The photovoltaic element can be e.g. an element of photovoltaic cell(s), which has a well-known meaning in the art. Silicon based material, e.g. crystalline silicon, is a non-limiting example of materials used in photovoltaic cell(s). Crystalline silicon material can vary with respect to crystallinity and crystal size, as well known to a skilled person. Alternatively, the photovoltaic element can be a substrate layer on one surface of which a further layer or deposit with photovoltaic activity is subjected, for example a glass layer, wherein on one side thereof an ink material with photovoltaic activity is printed, or a substrate layer on one side thereof a material with photovoltaic activity is deposited. For instance, in well-known thin film solutions of photovoltaic elements e.g. an ink with photovoltaic activity is printed on one side of a substrate, which is typically a glass substrate.

The photovoltaic element is most preferably an element of photovoltaic cell(s).

“Photovoltaic cell(s)” means herein a layer element(s) of photovoltaic cells, as explained above, together with connectors.

The materials of the above elements other than the protective back layer element (5) are well known in the prior art and can be chosen by a skilled person depending on the desired PV module.

The front and rear encapsulation layers (2 and 4) may be selected from any known encapsulation layers known in the art. Suitable materials for encapsulation layers include ethylene vinyl acetate (EVA) and silane-functionalized polyethylenes, such as those disclosed in WO 2017/076629 Al.

The photovoltaic (PV) module of the present invention is a bifacial photovoltaic module, meaning that light may enter from either the front side or the rear (back) side. As such, it is preferred that the protective back layer element (5) has a total luminous transmittance, determined according to ASTM DI 003- 13, in the range from 70 to 100%, more preferably in the range from 75 to 100%, most preferably in the range from 78 to 100%.

The protective front layer element (1) and the protective back layer element (5) may be rigid or flexible. Preferably, the protective front layer element (1) and the protective back layer element (5) are flexible.

The protective back layer element is preferably a fdm having a thickness in the range from 100 to 1000 pm, more preferably in the range from 200 to 800 pm, most preferably in the range from 300 to 600 pm.

The fdm may be either a monolayer fdm or a multilayer fdm. If the fdm is a multilayer fdm, then it is preferred that each layer contains the blend (B) of UV stabilisers, although only one layer is required to comprise the polypropylene composition (PC).

If the fdm is a multilayer fdm, it is also preferred that the fdm is a three-layered fdm, having, in the given order, an adhesive layer, a core layer and a skin layer, wherein at least the core layer, more preferably each of the core layer and the skin layer, comprises the polypropylene composition (PC). Preferably, each of the adhesive layer, the core layer and the skin layer contains the blend (B) of UV stabilisers.

Due to the presence of the blend (B) of UV stabilizers and hindered amine light stabilizers in the polypropylene composition (PC) of the protective back layer element, the back layer element has exceptionally good UV protection. This may be evaluated by comparing the elongation at break before and after aging treatments, such as UV aging and thermal (i.e. oven) aging.

As such, it is preferred that the protective back layer element (5) has an elongation at break, determined according to ISO 527-3, after UV aging for 3000 h as described in the determination methods is at least 40%, more preferably at least 50%, most preferably at least 70% of the elongation at break, determined according to ISO 527-3, before the UV aging.

It is also preferred that the protective back layer element (5) has an elongation at break, determined according to ISO 527-3, after oven aging at 120 °C for 2000 h is at least 50%, more preferably at least 65%, most preferably at least 80% of the elongation at break, determined according to ISO 527-3, before the oven aging.

It is especially preferred that the protective back layer element (5) has an elongation at break, determined according to ISO 527-3, in the range from 300 to 1000%, more preferably in the range from 400 to 900%, most preferably in the range from 500 to 800%.

Polypropylene composition (PC)

In the first aspect, the protective back layer element (5) of the photovoltaic (PV) module comprises a polypropylene composition (PC).

In the second aspect, the polypropylene composition (PC) is disclosed independently of the other photovoltaic module components.

The polypropylene composition (PC) of the first and second aspects comprises: a) 90.00 to 99.90 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); and b) 0.10 to 4.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers.

It is preferred that the polypropylene composition (PC) of the first and second aspects comprises: a) 95.00 to 99.70 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); and b) 0.30 to 3.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers. It is particularly preferred that the polypropylene composition (PC) of the first and second aspects comprises: a) 97.00 to 99.50 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); and b) 0.50 to 2.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers.

In one embodiment, the remaining amount of the polypropylene composition (PC) that is not the polypropylene or mixture of polypropylenes (PP), or the blend (B) is made up of one or more further additives (A) other than hindered amine light stabilizers and UV stabilizers.

In this embodiment, it is therefore preferred that the polypropylene composition (PC) of the first and second aspects consists of: a) 90.00 to 99.90 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); b) 0.10 to 4.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers; and c) 0.00 to 6.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of one or more further additives (A) other than hindered amine light stabilizers and UV stabilizers.

It is further preferred that the polypropylene composition (PC) of the first and second aspects consists of: a) 95.00 to 99.70 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); b) 0.30 to 3.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers; and c) 0.00 to 4.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of one or more further additives (A) other than hindered amine light stabilizers and UV stabilizers. It is ever further preferred that the polypropylene composition (PC) of the first and second aspects consists of: a) 97.00 to 99.50 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); b) 0.50 to 2.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers; and c) 0.00 to 2.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of one or more further additives (A) other than hindered amine light stabilizers and UV stabilizers.

It is furthermore preferred that the polypropylene composition (PC) of the first and second aspects is free from benzotriazole -based UV stabilizers.

The individual components of the polypropylene composition (PC) of the first and second aspects will now be described in more detail.

Polypropylene or mixture of polypropylenes (PP)

One of the essential components of the polypropylene composition (PC) is a polypropylene or mixture of polypropylenes (PP).

In the broadest sense, this component may be any polypropylene or mixture of polypropylenes. Suitable polypropylenes for use in back layer elements of photovoltaic (PV) modules are well known in the art.

In the context of the present disclosure, it is preferred that the polypropylene or mixture of polypropylenes (PP) is a heterophasic propylene -ethylene copolymer (HECO), comprising: a) a crystalline matrix (M) being a propylene homopolymer; and b) an amorphous propylene -ethylene elastomer (E) that is dispersed in said crystalline matrix (M). It is preferred that the crystalline matrix (M) has a melt flow rate (MFR2), determined according to ISO 1133 at 230 °C and 2.16 kg, in the range from 0.5 to 15.0 g/10 min, more preferably in the range from 1.0 to 10.0 g/10 min, most preferably in the range from 1.5 to 5.0 g/10 min.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has a melt flow rate (MFR2), determined according to ISO 1133 at 230 °C and 2.16 kg, in the range from 0.5 to 20.0 g/10 min, more preferably in the range from 1.0 to 10.0 g/10 min, most preferably in the range from 2.0 to 5.0 g/10 min.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has a xylene cold soluble (XCS) content, determined according to ISO 16152, in the range from 2.0 to 30.0 wt.-%, more preferably in the range from 5.0 to 25.0 wt.-%, most preferably in the range from 10.0 to 20.0 wt.-%.

It is preferred that the xylene cold soluble content of the polypropylene or mixture of polypropylenes (PP), more preferably of the heterophasic propylene-ethylene copolymer (HECO), has an ethylene content (C2(XCS)), determined by FT-IR spectroscopy, calibrated using quantitative ¹³C-NMR spectroscopy, in the range from 20.0 to 60.0 wt.-%, more preferably in the range from 25.0 to 50.0 wt.-%, most preferably in the range from 30.0 to 45.0 wt.-%.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has a melting temperature (Tm), determined by differential scanning calorimetry (DSC), in the range from 155 to 171 °C, more preferably in the range from 160 to 170 °C, most preferably in the range from 165 to 169 °C.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has an ethylene content (C2(total)), determined by FT-IR spectroscopy, calibrated using quantitative ¹³C-NMR spectroscopy, in the range from 0.5 to 20.0 wt.-%, more preferably in the range from 1.0 to 10.0 wt.-%, most preferably in the range from 2.0 to 6.0 wt.-%.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has a Vicat softening temperature, determined according to ASTM D 1525 method A, in the range from 125 to 170 °C, more preferably in the range from 135 to 165 °C, most preferably in the range from 145 to 160 °C.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has a flexural modulus, determined according to ISO 178 using 80x 10x4 mm³ test bars injection-moulded in line with ISO 19069-2, in the range from 1000 to 2500 MPa, more preferably in the range from 1100 to 2000 MPa, most preferably in the range from 1200 to 1600 MPa.

It is preferred that the polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has a Charpy Notched Impact Strength (NIS), determined according to ISO 178 using 80x 10x4 mm³ test bars injection-moulded in line with ISO 19069-2, in the range from 20 to 100 kJ/m², more preferably in the range from 30 to 80 kJ/m², most preferably in the range from 40 to 60 kJ/m².

Blend (B) of UV stabilizers and hindered amine light stabilizers

One of the essential components of the polypropylene composition is the blend (B) of UV stabilizers and hindered amine light stabilizers.

The blend (B) comprises, more preferably consists of, one or more polymeric hindered amine light stabilizers (HALS), one or more triazine -based UV stabilizers (UV1), and one or more further UV stabilizers (UV2).

The blend (B) may further comprise further hindered amine light stabilizers other than the one or more polymeric hindered amine light stabilizers (HALS) and UV stabilizers other than the one or more triazine -based UV stabilizers (UV1) and one or more further UV stabilizers (UV2).

Preferably, the blend (B) consists of: i) an amount in the range from 20 to 80 wt.-%, more preferably in the range from 25 to 75 wt.-%, most preferably in the range from 30 to 70 wt.-%, relative to the total weight of the blend (B), of the one or more polymeric hindered amine light stabilizers (HALS); ii) an amount in the range from 10 to 40 wt.-%, more preferably in the range from 13 to 35 wt.-%, most preferably in the range from 15 to 30 wt.-%, relative to the total weight of the blend (B), of the one or more triazine-based UV stabilizers (UV1); iii) an amount in the range from 10 to 40 wt.-%, more preferably in the range from 13 to 35 wt.-%, most preferably in the range from 15 to 30 wt.-%, relative to the total weight of the blend (B), of the one or more further UV stabilizers (UV2); and iv) optionally an amount in the range from 0 to 50 wt.-%, more preferably in the range from 0 to 40 wt.-%, most preferably in the range from 0 to 35 wt.-%, relative to the total weight of the blend (B), of further hindered amine light stabilizers other than the one or more polymeric hindered amine light stabilizers (HALS) and UV stabilizers other than the one or more triazine-based UV stabilizers (UV1, and one or more further UV stabilizers (UV2).

Thus in one embodiment, the blend (B) consists of: i) an amount in the range from 20 to 80 wt.-%, relative to the total weight of the blend (B), of the one or more polymeric hindered amine light stabilizers (HALS); ii) an amount in the range from 10 to 40 wt.-%, relative to the total weight of the blend (B), of the one or more triazine-based UV stabilizers (UV1); iii) an amount in the range from 10 to 40 wt.-%, relative to the total weight of the blend (B), of the one or more further UV stabilizers (UV2); and iv) optionally an amount in the range from 0 to 50 wt.-%, relative to the total weight of the blend (B), of further hindered amine light stabilizers other than the one or more polymeric hindered amine light stabilizers (HALS) and UV stabilizers other than the one or more triazine-based UV stabilizers (UV1) and one or more further UV stabilizers (UV2).

In a preferred embodiment, the blend (B) consists of: i) an amount in the range from 25 to 75 wt.-%, relative to the total weight of the blend (B), of the one or more polymeric hindered amine light stabilizers (HAUS); ii) an amount in the range from 13 to 35 wt.-%, relative to the total weight of the blend (B), of the one or more triazine-based UV stabilizers (UV1); iii) an amount in the range from 13 to 35 wt.-%, relative to the total weight of the blend (B), of the one or more further UV stabilizers (UV2); and iv) optionally an amount in the range from 0 to 40 wt.-%, relative to the total weight of the blend (B), of further hindered amine light stabilizers other than the one or more polymeric hindered amine light stabilizers (HAUS) and UV stabilizers other than the one or more triazine-based UV stabilizers (UV1) and one or more further UV stabilizers (UV2).

In a further preferred embodiment, the blend (B) consists of: i) an amount in the range from 30 to 70 wt.-%, relative to the total weight of the blend (B), of the one or more polymeric hindered amine light stabilizers (HAUS); ii) an amount in the range from 15 to 30 wt.-%, relative to the total weight of the blend (B), of the one or more triazine-based UV stabilizers (UV1); iii) an amount in the range from 15 to 30 wt.-%, relative to the total weight of the blend (B), of the one or more further UV stabilizers (UV2); and iv) optionally an amount in the range from 0 to 35 wt.-%, relative to the total weight of the blend (B), of further hindered amine light stabilizers other than the one or more polymeric hindered amine light stabilizers (HAUS) and UV stabilizers other than the one or more triazine-based UV stabilizers (UV1) and one or more further UV stabilizers (UV2).

It is furthermore preferred that the blend (B) is free from benzotriazole-based UV stabilizers. The individual components of the blend (B) of UV stabilizers and hindered amine light stabilizers will now be described in more detail.

One or more polymeric hindered amine light stabilizers (HALS)

One of the essential components of the blend (B) of UV stabilizers and hindered amine light stabilizers is one or more polymeric hindered amine light stabilizers (HALS).

The one or more polymeric hindered amine light stabilizers (HALS) have a structure according to formula (I) m is an integer in the range from 2 to 8, more preferably in the range from 4 to 8, yet more preferably in the range from 4 to 6, most preferably is 6. n is an integer in the range from 2 to 10.

Each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, more preferably from the group consisting of hydrogen and Ci to C4 alkyl, yet more preferably from the group consisting of hydrogen, methyl, ethyl, n-propyl and n- butyl, even more preferably from the group consisting of hydrogen and methyl, most preferably R is hydrogen. R^A is selected from the group consisting of hydrogen and Ci to Cw alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, more preferably R^A is selected from the group consisting of hydrogen and Ci to Cs alkyl, yet more preferably from the group consisting of hydrogen and C2 to Ce alkyl, even more preferably from the group selected from C3 to Ce alkyl, most preferably R^A is n-butyl.

R^B is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, more preferably wherein R^B is selected from the group consisting wherein R^c is selected from the group consisting of hydrogen, and Ci to Ce alkyl, yet more preferably R^B is selected from the group selected from the group consisting wherein R^c is selected from the group consisting of H and Me, most preferably

A¹ and B¹ are each independently selected from the group consisting of direct single bond, Ci to Ce alkylene, and phenylene. A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to Cio alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to Cio alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from

Ci to Cio alkyl and unsubstituted phenyl, wherein R^D is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy.

In one preferred embodiment, A¹ and B¹ are each independently selected from the group consisting of Ci to Ce alkylene, and A² and B² are each independently selected from the group consisting wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to Cio alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to C 10 alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, wherein R^D is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy. In this embodiment, it is further preferred that A¹ and B¹ are each independently selected from the group consisting of C2 to Ce alkylene, and A² and B² are each independently selected from the group consisting wherein each of R^A1, R^A2 and

R^A3 are each independently selected from the group consisting of Ci to Cw alkyl, and R^B1 is , wherein R^D is selected from the group consisting of hydrogen and Ci to Ce alkyl.

In this embodiment, it is yet further preferred that A¹ and B¹ are each independently selected from the group consisting of C3 to C5 alkylene, and A² and B² are each independently selected from the group consisting wherein each of R^A1, R^A2 and

R^A3 are each independently selected from the group consisting of C2 to Ce alkyl, and R^B1 is In one particular embodiment, A¹ and B¹ are both n-butylene (i.e. linear C4 alkylene), whilst In all of the above embodiments having the following substructure , the NR^A2 group is bonded to the 6-membered ring, whilst the NR^A3 group is bonded to A¹ or B¹.

In an alternative particularly preferred embodiment, A¹, B¹, A² and B² are each direct single bond, meaning that A¹ and A² together form a single bond linking the nitrogen atom to the 6- membered ring and that B¹ and B² together form a single bond linking the nitrogen atom to the 6-membered ring.

It is particularly preferred that the one or more polymeric hindered amine light stabilizers (HALS) has a structure according to formula (la) m is an integer in the range from 2 to 8, more preferably in the range from 4 to 8, yet more preferably in the range from 4 to 6, most preferably is 6. n is an integer in the range from 2 to 10.

R^A is selected from the group consisting of hydrogen and Ci to Cw alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, more preferably R^A is selected from the group consisting of hydrogen and Ci to Cs alkyl, yet more preferably from the group consisting of hydrogen and C2 to Ce alkyl, even more preferably from the group selected from C3 to Ce alkyl, most preferably R^A is n-butyl.

R^B is selected from the group consisting of Ci to Cio alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, more preferably wherein R^B is selected from the group consisting wherein R^c is selected from the group consisting of hydrogen, and Ci to Ce alkyl, yet more preferably R¹ is selected from the group selected from the group consisting wherein R^c is selected from the group consisting of H and Me, most preferably It is particularly preferred that the one or more polymeric hindered amine light stabilizers (HALS) are selected from the group consisting of

mixtures thereof.

More preferably, the one or more polymeric hindered amine light stabilizers (HALS) are selected from the group consisting of thereof. Most preferably, the one or more polymeric hindered amine light stabilizer(s) is a single polymeric hinder amine light stabilizer (HALS) being

One or more triazine-based UV stabilizers (UV1)

Another essential component of the blend (B) of UV stabilizers and hindered amine light stabilizers is one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II)

R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to C10 alkyl and Ci to C12 alkoxy, more preferably R¹ represents from 0 to 2 substitutions, each independently selected from the group consisting of hydroxy, Ci to C10 alkyl, and C3 to C12 alkoxy, yet more preferably R¹ represents no substitution or a single substitution selected from hydroxy and C3 to C12 alkoxy, most preferably R1 is a single substitution located para to the triazine ring, being selected from C to C alkoxy. R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to C alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, more preferably each independently represent from 0 to 2 substitutions, each independently selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of Ci to Cw alkyl.

It is preferred that R² and R³ are the same.

In one particularly preferred embodiment, R² and R³ both represent no substitution.

In an alternative preferred embodiment, R² and R³ both represent 2,4-dimethyl substitution.

In an alternative preferred embodiment, R² and R³ both represent 4-phenyl substitution.

It is particularly preferred that the one or more triazine-based UV stabilizers (UV 1) are selected from the group consisting of One or more further UV stabilizers (UV2)

Another essential component of the blend (B) of UV stabilizers and hindered amine light stabilizers is one or more further UV stabilizers (UV2) having a structure according to formula (III)

X is selected from the group consisting of O and direct single bond.

R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy.

R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution and Ci to C12 alkoxy being optionally substituted by acrylate substitution.

The structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R” is phenyl substituted by at least a hydroxy.

In one preferred embodiment, X is O, R’ represents form 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, wherein at least one instance of R’ is hydroxy, and R” is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy.

In this embodiment, it is further preferred that R’ represents 3, 5 -ditert-butyl, 4-hydroxy- substitution, wherein R” is preferably selected from Ce to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from Ci to C10 alkyl.

In an alternative preferred embodiment, X is direct single bond R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, and R” is a phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution and Ci to C12 alkoxy being optionally substituted by acrylate substitution, wherein at least one substitution is hydroxy, preferably 2-hydroxy substitution.

In this embodiment, it is preferred that R’ represents no substitution, whilst R” represents 2- hydroxy and 4-Ci-Cw alkoxy being optionally substituted by acrylate substitution.

It is particularly preferred that the one or more further UV stabilizers (UV2) are selected from the group consisting of mixtures thereof.

It is especially preferred that the one or more further UV stabilizers (UV2) are selected from the group consisting mixtures thereof.

One or more further additives (A)

In addition to the polypropylene or mixture of polypropylenes (PP) and the blend (B), the polypropylene composition (PC) may contain one or more further additives (A) other than hindered amine light stabilizers and UV stabilizers.

The skilled practitioner would be able to select suitable additives that are well known in the art.

Preferably, the one or more further additives (A) are selected from the group consisting of antioxidants, nucleating agents, pigments, fdlers, clarifiers, brighteners, acid scavengers, slip agents, processing aids, release agents and mixtures thereof.

It is understood that the content of additives includes any carrier polymers used to introduce the additives to the polypropylene composition (PC), i.e. masterbatch carrier polymers. An example of such a carrier polymer would be a polypropylene homopolymer in the form of powder. Use

In a second aspect, the present invention is directed to a use of a blend (B) of UV stabilizers and hindered amine light stabilizers for maintaining elongation at break, determined according to ISO 527-3 on monolayer fdm specimens having a thickness of 400 pm, of a polypropylene composition comprising said blend (B) after UV aging for 3000 h as described in the determination methods, wherein the blend (B) comprises, more preferably consists of: i) one or more polymeric hindered amine light stabilizers (HALS) having a structure according to formula wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R^A is selected from the group consisting of hydrogen and Ci to C10 alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl;

R^B is selected from the group consisting of Ci to C10 alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to C10 alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to C alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl, wherein R^D is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, wherein if A¹ and A² are both direct single bond then A¹ and A² together form a single bond linking the nitrogen atom to the 6-membered ring, and wherein if B¹ and B² are both direct single bond then B¹ and B² together form a single bond linking the nitrogen atom to the 6-membered ring; ii) one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II) wherein R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to C alkyl and Ci to C12 alkoxy, and R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to Ci 2 alkoxy; and iii) one or more further UV stabilizers (UV2) having a structure according to formula (III) wherein X is selected from the group consisting of O and direct single bond;

R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution and Ci to C12 alkoxy being optionally substituted by acrylate substitution, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy, wherein maintaining the elongation at break is achieved when the value of the elongation at break after UV aging for 3000 h as described in the determination methods is at least 40% of the value determined before the UV aging.

In a final aspect, the present invention is directed to a use of a blend (B) of UV stabilizers and hindered amine light stabilizers for maintaining elongation at break, determined according to ISO 527-3 on monolayer film specimens having a thickness of 400 pm, of a polypropylene composition comprising said blend (B) after oven aging at 120 °C for 2000 h, wherein the blend (B) comprises, more preferably consists of: i) one or more polymeric hindered amine light stabilizers (HALS) having a structure according to formula wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

All fallback positions for the blend (B) of UV stabilizers and hindered amine light stabilizers, the one or more polymeric hindered amine light stabilizers (HALS), the one or more triazine -based UV stabilizers (UV1), and the one or more further UV stabilizers (UV2), given above for the first and second aspect apply mutatis mutandis for the uses of the third and final aspects.

E X A M P L E S

1. Measurement methods

The following definitions of terms and determination methods apply for the above general description of the invention including the claims as well as to the below examples unless otherwise defined.

Comonomer content

The comonomer content was determined by quantitative Fourier transform infrared spectroscopy (FTIR) after basic assignment calibrated via quantitative ¹³C nuclear magnetic resonance (NMR) spectroscopy in a manner well known in the art. Thin films are pressed to a thickness of between 100-500 micrometer and spectra recorded in transmission mode. Specifically, the ethylene content of a polypropylene-co-ethylene copolymer is determined using the baseline corrected peak area of the quantitative bands found at 720-722 and 730-733 cm ¹. Specifically, the butene or hexene content of a polypropylene copolymer is determined using the baseline corrected peak area of the quantitative bands found at 1377-1379 cm ¹. Quantitative results are obtained based upon reference to the film thickness.

The comonomer content is herein assumed to follow the mixing rule (equation 2):

Where C is the content of comonomer in weight-%, w is the weight fraction of the component in the mixture and subscripts b, 1 and 2 refer to the overall mixture, component 1 and component 2, respectively.

As it is well known to the person skilled in the art the comonomer content in weight basis in a binary copolymer can be converted to the comonomer content in mole basis by using the following equation where c_m is the mole fraction of comonomer units in the copolymer, c_w is the weight fraction of comonomer units in the copolymer, MW_C is the molecular weight of the comonomer (such as ethylene) and MW_m is the molecular weight of the main monomer (i.e., propylene).

CRYSTEX QC analysis

Crystalline and soluble fractions method

The crystalline (CF) and soluble fractions (SF) of the polypropylene (PP) compositions as well as the comonomer content and intrinsic viscosities of the respective fractions were analyzed by use of the CRYSTEX instrument, Polymer Char (Valencia, Spain). Details of the technique and the method can be found in literature (Ljiljana Jeremie, Andreas Albrecht, Martina Sandholzer & Markus Gahleitner (2020) Rapid characterization of high-impact ethylenepropylene copolymer composition by crystallization extraction separation: comparability to standard separation methods, International Journal of Polymer Analysis and Characterization, 25:8, 581-596)

The crystalline and amorphous fractions are separated through temperature cycles of dissolution at 160 °C, crystallization at 40 °C and re-dissolution in 1 ,2,4-trichlorobenzene at 160 °C. Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an integrated infrared detector (IR4) and for the determination of the intrinsic viscosity (IV) an online 2-capillary viscometer is used.

The IR4 detector is a multiple wavelength detector measuring IR absorbance at two different bands (CPF stretching vibration (centred at app. 2960 cm ¹) and the CH stretching vibration (2700-3000 cm ¹) that are serving for the determination of the concentration and the Ethylene content in Ethylene-Propylene copolymers. The IR4 detector is calibrated with series of 8 EP copolymers with known Ethylene content in the range of 2 wt.-% to 69 wt.-% (determined by ¹³C-NMR) and each at various concentrations, in the range of 2 and 13mg/ml. To encounter for both features, concentration and ethylene content at the same time for various polymer concentrations expected during Crystex analyses the following calibration equations were applied:

Cone = a + b*Abs(CH) + c*(Abs(CH))² + d*Abs(CH₃) + e*(Abs(CH₃)² + f*Abs(CH)*Abs(CH₃) (Equation 1)

CH₃/1000C = a + b*Abs(CH) + c* Abs(CH₃) + d * (Abs(CH₃)/Abs(CH)) + e * (Abs(CH₃)/Abs(CH))² (Equation 2) The constants a to e for equation 1 and a to f for equation 2 were determined by using least square regression analysis.

The CH3/IOOOC is converted to the ethylene content in wt.-% using following relationship:

Wt.-% (Ethylene in EP Copolymers) = 100 - CH3/IOOOTC * 0.3 (Equation 3)

Amounts of Soluble Fraction (SF) and Crystalline Fraction (CF) are correlated through the XS calibration to the “Xylene Cold Soluble” (XCS) quantity and respectively Xylene Cold Insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration is achieved by testing various EP copolymers with XS content in the range 2-31 wt.-%. The determined XS calibration is linear:

Wt.-% XS = 1 ,01 * Wt.-% SF (Equation 4)

Intrinsic viscosity (IV) of the parent EP copolymer and its soluble and crystalline fractions are determined with a use of an online 2-capillary viscometer and are correlated to corresponding IV’s determined by standard method in decalin according to ISO 1628-3. Calibration is achieved with various EP PP copolymers with IV = 2-4 dL/g. The determined calibration curve is linear:

IV (dL/g) = a* Vsp/c (equation 5)

The samples to be analyzed are weighed out in concentrations of lOmg/ml to 20mg/ml.

After automated filling of the vial with 1,2,4-TCB containing 250 mg/1 2,6-tert-butyl-4- methylphenol (BHT) as antioxidant, the sample is dissolved at 160 °C until complete dissolution is achieved, usually for 60 min, with constant stirring of 400rpm. To avoid sample degradation, the polymer solution is blanketed with the N2 atmosphere during dissolution.

A defined volume of the sample solution is injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline part is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the IV[dl/g] and the C2[wt.%] of the PP composition. During the second injection the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt.-% SF, wt.-% C2, IV).

Intrinsic viscosity

The intrinsic viscosity (iV) is measured according to DIN ISO 1628/1, October 1999, in Decalin at 135 °C.

Melt Flow Rate

The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g/10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR2 of polypropylene is determined at a temperature of 230 °C and a load of 2.16 kg.

Density:

The density is measured according to ISO 1183-187. Sample preparation is done by compression moulding in accordance with ISO 1872-2:2007.

The xylene soluble fraction at room temperature (XCS, wt.-%): The amount of the polymer soluble in xylene is determined at 25 °C according to ISO 16152; 5^th edition; 2005- 07-01.

Vicat softening temperature

The Vicat softerin temperature was measured according to ASTM D 1525 method A (50°C/h, 10N).

DSC analysis, melting temperature (T_m) and heat of fusion (Hf), crystallization temperature (T_c) and heat of crystallization (H_c): measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357 / part 3 /method C2 in a heat / cool / heat cycle with a scan rate of 10 °C/min in the temperature range of -30 to +225 °C. Crystallization temperature (T_c) and crystallization enthalpy (H_c) are determined from the cooling step, while melting temperature (T_m) and melting enthalpy (H_m) are determined from the second heating step.

Flexural Modulus

Flexural Modulus is determined according to ISO 178 method A (3-point bending test) on 80 mm x 10 mm x 4 mm specimens. Following the standard, a test speed of 2 mm/min and a span length of 16 times the thickness was used. The testing temperature was 23±2 ° C. Injection moulding was carried out according to ISO 19069-2 using a melt temperature of 230 °C for all materials irrespective of material melt flow rate.

Impact Strength

The Charpy notched impact strength (NIS) is measured according to ISO 179 leA at +23 °C or -20 °C, using injection moulded bar test specimens of 80x 10x4 mm³ prepared in accordance with ISO 19069-2 using a melt temperature of 230 °C for all materials irrespective of material melt flow rate.

Tensile properties of films

Tensile properties (i.e. Elongation at Break) in machine and transverse direction were determined according to ISO 527-3 at 23 °C on the monolayer films produced in the experimental section. Testing was performed at a cross-head speed of 1 mm/min.

Total luminous transmittance

Total luminous transmittance was determined according to ASTM D1003-13 directly on the monolayer films produced in the experimental section.

Oven aging

The monolayer films produced in the experimental section were heated at 120°C for the specified amount of time. No protective atmosphere was employed, the samples simply being exposed to the air present in the oven during the test.

UV aging

UV aging was carried out according to IEC 62788-2-2, conditions A5. Specimens are mounted in aluminium frames such that the surface faces a xenon arc and are rotated around the irradiation source. The rotation and the air-flow is put such that the defined reference black standard (defined black surface without enhanced heat dissipation) or black panel (defined black surface with enhanced heat dissipation by metal back surface) is at a defined temperature.

A5 conditions:

Irradiation energy :

82 W/m² (300-400nm)

0.8 W/m³ (340 nm)

Temperature: 110 °C

Humidity: 20 %

Filter: Quarz

The irradiation of the xenon arc is filtered by a suprax filter as to accurately reflect spectral power distribution of sunlight especially in the ultraviolet region of radiation. The humidity of the environment is defined. Conditioning is performed for a defined time interval without any testing.

2. Examples

2.1 Compounding of polypropylene compositions

The inventive, comparative, and reference compositions were prepared in a co-rotating twin- screw extruder (Coperion ZSK 57 for RE1 to RE3 and Coperion ZSK 18 for all other examples) at 220 °C according to the recipes in Table 1. Table 1 Recipes of Reference, Comparative and Inventive Examples

The following components were employed in Table 1 :

PP Ziegler-Natta catalysed heterophasic propylene copolymer composition with a propylene homopolymer matrix phase having a MFR2 of 2.5 g/10 min and an ethylene-propylene elastomeric phase in an amount of 14 wt.-% (measured as XCS content), and an ethylene content in the elastomeric phase of 37 wt.-%. The heterophasic propylene copolymer composition has a MFR2 of 3.6 g/10 min, a total ethylene content of 4.2 wt.-%, a melting temperature of 168 °C, a Vicat A softening temperature of 153°C, a flexural modulus of 1400 MPa and a Charpy notched impact strength at 23 °C of 45 kJ/m² and has been produced using the process as described for the heterophasic propylene copolymer Inv. 2 in the example section of WO 2015/173175. Contains 0.60 wt.-% of an additive blend, commercially available from BASF AG (Germany) under the trade name Irganox CB OP 124.

HALS1 Hindered amine light stabilizer (CAS No. 65446-77-0, commercially available from BASF AG (Germany) under the trade name Tinuvin 622) having a structure:

HALS2 Hindered amine light stabilizer (CAS No. 71878-19-8, commercially available from BASF AG (Germany) under the trade name Chimassorb 944) having a structure: HALS3 Hindered amine light stabilizer (CAS No. 192268-64-7, commercially available from BASF AG (Germany) under the trade name Chimassorb 2020) having a structure:

HALS4 Hindered amine light stabilizer (CAS No. 52829-07-9, commercially available from BASF AG (Germany) under the trade name Tinuvin 770) having a structure:

UV1 Triazine-based UV stabilizer (CAS No. 204583-39-1, commercially available from BASF AG (Germany) under the trade name Tinuvin 1600) having a structure: UV2a UV stabilizer (CAS No. 1843-05-6, commercially available from

BASF AG (Germany) under the trade name Chimassorb 81) having a structure:

UV2b UV stabilizer (CAS No. 4221-80-1, commercially available from

BASF AG (Germany) under the trade name Tinuvin 120) having a structure:

UV3 Benzotriazole-based UV stabilizer (CAS No. 70321-86-7, commercially available from BASF AG (Germany) under the trade name Tinuvin 234) having a structure:

Monolayer fdms having a thickness of 400 pm were produced on a Collin line (single screw) with calendaring on both sides, chill roll temperature 25 °C. The total luminous transmittance was in the range from 85 to 91% for each of the films. A4 samples were cut from the resulting films, for use in the UV and oven aging experiments. 2.2 Evaluation of HALS additive

The performance of the HALS additives were evaluated by comparing the elongation at break in the machine direction before UV aging and after 1000 or 2000 hours of UV aging as described in the determination methods section.

Table 2 Relative performance of HALS additives

As can be seen from the data in Table 2, the best HALS additive is HALS3, although HALS2 also results in reasonable UV protection. RE4 and RE5, which have higher amounts of HALS3 are less effective than RE3, thus it can be seen that a simple correlation between amount of HALS and UV protection cannot be assumed. A comparative fdm containing only the base PP was completely degraded after 1000 hours of UV aging, thus no tensile properties could be measured.

2.3 Combinations of HALS and various UV stabilizers

The films containing the inventive and comparative examples were subjected to UV aging and to oven aging as described in the determination methods section, with the elongation at break in the machine direction again measured at to determine the UV and thermal stability of the polypropylene compositions. Table 3 UV aging behavior of inventive and comparative examples n.m. - not measured, n/a - not applicable (due to sample decomposition) Table 4 oven aging behavior of inventive and comparative examples

Table 5 average % retention of UV and oven aging tests

As can be seen from the data presented in Tables 3 and 4, IE1 and IE2 have an improved balance of protection from UV and oven aging (see Table 5 for the average values, reflecting the improved balance), with IE1 having superior long term (i.e. 2000 h) oven aging and IE2 having superior long term (i.e. 2000 h) UV aging relative to CE1 to CE3, with CE4 being worse. Similar tests on fdms prepared from compositions without UV1 and UV2 (i.e. only containing various hindered amine light stabilizers) showed that these fdms completely degraded after 2000 h of UV aging and the % retention after 2000 h of oven aging was less than 5%.

Claims

C L A I M S

1. A photovoltaic (PV) module, comprising, in the given order, a protective front layer element (1), a front encapsulation layer element (2), a photovoltaic element (3), a rear encapsulation layer element (4) and a protective back layer element (5), wherein the protective back layer element (5) comprises a polypropylene composition (PC) that comprises: a) 90.00 to 99.90 wt.-%, relative to the total weight of the polypropylene composition (PC), of a polypropylene or mixture of polypropylenes (PP); b) 0. 10 to 4.00 wt.-%, relative to the total weight of the polypropylene composition (PC), of a blend (B) of UV stabilizers and hindered amine light stabilizers, said blend (B) comprising, more preferably consisting of: i) one or more polymeric hindered amine light stabilizers (HALS) having a structure according to formula (I) wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R^A is selected from the group consisting of hydrogen and Ci to C10 alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl; R^B is selected from the group consisting of Ci to C10 alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cw alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

A² and B² are each independently selected from the group consisting of direct single bond, wherein each of R^A1, R^A2 and R^A3 are each independently selected from the group consisting of hydrogen and Ci to C10 alkyl, unsubstituted phenyl and phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl, and R^B1 is selected from the group consisting of Ci to C10 alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C10 alkyl and unsubstituted phenyl, wherein R^D is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy, wherein if A¹ and A² are both direct single bond then A¹ and A² together form a single bond linking the nitrogen atom to the 6- membered ring, and wherein if B¹ and B² are both direct single bond then B¹ and B² together form a single bond linking the nitrogen atom to the 6- membered ring; ii) one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II) wherein R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, and

R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to C10 alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy; and iii) one or more further UV stabilizers (UV2) having a structure according to formula (III) wherein X is selected from the group consisting of O and direct single bond;

R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy; and R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy.

2. The photovoltaic (PV) module according to claim 1, wherein the one or more polymeric hindered amine light stabilizers (HALS) has a structure according to formula (la) wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10,

R^B is selected from the group consisting of Ci to Cw alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to C alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy.

3. The photovoltaic (PV) module according to claim 1 or claim 2, wherein R^B is

4. The photovoltaic (PV) module according to any one of the preceding claims, wherein the one or more polymeric hindered amine light stabilizers (HALS) are selected from the group consisting of mixtures thereof.

5. The photovoltaic (PV) module according to any one of the preceding claims, wherein the one or more triazine-based UV stabilizers (UV1) are selected from the group consisting of

and mixtures thereof.

6. The photovoltaic (PV) module according to any one of the preceding claims, wherein the one or more further UV stabilizers (UV2) are selected from the group

7. The photovoltaic (PV) modules according to any one of the preceding claims, wherein the polypropylene composition (PC) is free from benzotriazole -based UV stabilizers.

8. The photovoltaic (PV) module according to any one of the preceding claims, wherein the protective back layer element (5) has a total luminous transmittance, determined according to determined according to ASTM DI 003- 13, in the range from 70 to 100%, more preferably in the range from 75 to 100%, most preferably in the range from 78 to 100%.

9. The photovoltaic (PV) module according to any one of the preceding claims, wherein the blend (B) consists of: i) an amount in the range from 20 to 80 wt.-%, more preferably in the range from 25 to 75 wt.-%, most preferably in the range from 30 to 70 wt.-%, relative to the total weight of the blend (B), of the one or more polymeric hindered amine light stabilizers (HALS); ii) an amount in the range from 10 to 40 wt.-%, more preferably in the range from 13 to 35 wt.-%, most preferably in the range from 15 to 30 wt.-%, relative to the total weight of the blend (B), of the one or more triazinebased UV stabilizers (UV1); iii) an amount in the range from 10 to 40 wt.-%, more preferably in the range from 13 to 35 wt.-%, most preferably in the range from 15 to 30 wt.-%, relative to the total weight of the blend (B), of the one or more further UV stabilizers (UV2); and iv) optionally an amount in the range from 0 to 50 wt.-%, more preferably in the range from 0 to 40 wt.-%, most preferably in the range from 0 to 35 wt.-%, relative to the total weight of the blend (B), of further hindered amine light stabilizers other than the one or more polymeric hindered amine light stabilizers (HALS) and/or further UV stabilizers other than the one or more triazine-based UV stabilizers (UV1) and one or more further UV stabilizers (UV2).

10. The photovoltaic (PV) module according to any one of the preceding claims wherein, the remaining amount of the polypropylene composition (PC) that is not the polypropylene or mixture of polypropylenes (PP), or the blend (B) is made up of one or more further additives (A) other than other than hindered amine light stabilizers and UV stabilizers, preferably selected from the group consisting of antioxidants, nucleating agents, pigments, fillers, clarifiers, brighteners, acid scavengers, slip agents, processing aids, release agents and mixtures thereof.

11 . The photovoltaic (PV) module according to any one of the preceding claims, wherein the polypropylene or mixture of polypropylenes (PP) is a heterophasic propylene -ethylene copolymer (HECO), comprising: a) a crystalline matrix (M) being a propylene homopolymer; and b) an amorphous propylene -ethylene elastomer (E) that is dispersed in said crystalline matrix (M).

12. The photovoltaic (PV) module according to any one of the preceding claims, wherein polypropylene or mixture of polypropylenes (PP), more preferably the heterophasic propylene-ethylene copolymer (HECO), has one or more, preferably all, of the following properties: a) a melt flow rate (MFR2), determined according to ISO 1133 at 230 °C and 2.16 kg, in the range from 0.5 to 20.0 g/10 min; b) a xylene cold soluble (XCS) content, determined according to ISO 16152, in the range from 2.0 to 30.0 wt.-%; c) a melting temperature (Tm), determined by differential scanning calorimetry (DSC), in the range from 155 to 171 °C; d) an ethylene content (C2(total)), determined by FT-IR spectroscopy, calibrated using quantitative ¹³C-NMR spectroscopy, in the range from 0.5 to 20.0 wt.-%; e) a Vicat softening temperature, determined according to ASTM D 1525 method A, in the range from 125 to 170 °C; and f) a flexural modulus, determined according to ISO 178 using 80x 10x4 mm³ test bars injection-moulded in line with ISO 19069-2, in the range from 1000 to 2500 MPa.

13. The photovoltaic (PV) module according to any one of the preceding claims, wherein the protective back layer element (5) has an elongation at break, determined according to ISO 527-3, after UV aging for 3000 h as described in the determination methods is at least 40% of the elongation at break, determined according to ISO 527- 3, before the UV aging; and/or wherein the protective back layer element (5) has an elongation at break, determined according to ISO 527-3, after oven aging at 120 °C for 2000 h is at least 50% of the elongation at break, determined according to ISO 527-3, before the oven aging.

14. Use of a blend (B) of UV stabilizers and hindered amine light stabilizers for maintaining elongation at break, determined according to ISO 527-3 on monolayer film specimens having a thickness of 400 pm, of a polypropylene composition comprising said blend (B) after UV aging for 3000 h as described in the determination methods, wherein the blend (B) comprises, more preferably consists of: i) one or more polymeric hindered amine light stabilizers (HAUS) having a structure according to formula (I) wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R^B is selected from the group consisting of Ci to C10 alkyl, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from Ci to Cio alkyl and unsubstituted phenyl, wherein R^c is selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

Ci to Ce alkyl and Ci to C5 alkoxy, wherein if A¹ and A² are both direct single bond then A¹ and A² together form a single bond linking the nitrogen atom to the 6-membered ring, and wherein if B¹ and B² are both direct single bond then B¹ and B² together form a single bond linking the nitrogen atom to the 6-membered ring; ii) one or more triazine-based UV stabilizers (UV1) having a structure according to formula (II) wherein R¹ represents from 0 to 4 substitutions, each independently selected from the group consisting of hydroxy, Ci to C alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to Cw alkyl and Ci to C 12 alkoxy, and

R² and R³ each independently represent from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, and phenyl substituted by one or more groups independently selected from the group consisting of hydroxy, Ci to C alkyl and Ci to C12 alkoxy; and iii) one or more further UV stabilizers (UV2) having a structure according to formula (III) wherein X is selected from the group consisting of O and direct single bond; R’ represents from 0 to 5 substitutions, each independently selected from the group consisting of hydroxy, Ci to Cw alkyl, Ci to C12 alkoxy, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy; and

R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy, wherein maintaining the elongation at break is achieved when the value of the elongation at break after UV aging for 3000 h as described in the determination methods is at least 40% of the value determined before the UV aging.

15. Use of a blend (B) of UV stabilizers and hindered amine light stabilizers for maintaining elongation at break, determined according to ISO 527-3 on monolayer film specimens having a thickness of 400 pm, of a polypropylene composition comprising said blend (B) after oven aging at 120 °C for 2000 h, wherein the blend (B) comprises, more preferably consists of: i) one or more polymeric hindered amine light stabilizers (HAUS) having a structure according to formula (I) wherein m is an integer in the range from 2 to 8 and n is an integer in the range from 2 to 10, each R is independently selected from the group consisting of hydrogen, Ci to Ce alkyl and Ci to C5 alkoxy;

R’ ’ is selected from the group consisting of Ci to C20 alkyl, unsubstituted phenyl and phenyl with from 1 to 5 substitutions, each of which are independently selected from the group consisting of hydroxy, Ci to Cw alkyl being optionally substituted by acrylate substitution, Ci to C12 alkoxy being optionally substituted by acrylate substitution, unsubstituted phenyl, phenyl substituted by one or more groups independently selected from hydroxy, Ci to Cw alkyl and Ci to C12 alkoxy, wherein the structure according to formula (III) contains a phenol moiety, wherein either at least one instance of R’ is hydroxy or R’ ’ is phenyl substituted by at least a hydroxy, wherein maintaining the elongation at break is achieved when the value of the elongation at break after oven aging at 120 °C for 2000 h is at least 50% of the value determined before the oven aging.