Encapsulating films based on functionalized polyolefins

Abstract

The present invention relates to films comprising functionalized polyolefin polymers and to the use of such films as encapsulating films for photovoltaic modules. The functionalized polyolefin polymer is a polymer selected from the group consisting of (a) a propylene copolymer, (b) a propylene terpolymer, (c) an ethylene terpolymer, and (d) a polymer mixture comprising any combination of polymers (a) to (c). In addition, the functionalized polyolefin polymer comprises < = 0.8% by weight of an inorganic metal oxide, such as alumina, based on the total weight of the functionalized polyolefin polymer. The invention further relates to an encapsulated solar cell comprising an encapsulation layer comprising the film. The invention further relates to a photovoltaic module comprising the encapsulated solar cells and to a method for producing a photovoltaic module.

Description

Technical Field

[0001] The present invention relates to a film comprising a polyolefin polymer functionalized with polar groups and to the use of the film as an encapsulation film for a photovoltaic module. The present invention further relates to an encapsulated solar cell comprising one or more encapsulation layers comprising the film. The present invention further relates to a photovoltaic module comprising the encapsulated solar cell and to a method for preparing such a photovoltaic module. Background Art

[0002] Polymer materials such as ethylene-vinyl acetate copolymers (EVA) and polyolefin elastomers (POE) are commonly used as encapsulants in photovoltaic modules. Some desirable properties and functions of such polymer materials include (i) high electrical resistance (or volume resistivity), (ii) excellent moisture and gas barrier properties, (iii) ease of processing, (iv) excellent optical transmittance, and (v) suitable mechanical properties such as tensile modulus.

[0003] Polymer materials such as ethylene-vinyl acetate copolymer (EVA) and polyolefins such as polyolefin elastomers (POE) have been used to prepare polymer encapsulants suitable for photovoltaic modules and other related applications. However, EVA copolymers have low volume resistivity and low moisture barrier properties due to their polarity compared to conventional polyolefin elastomers. It has been observed in addition that due to chemical degradation, EVA base films gradually darken when exposed to sunlight for a long time, which adversely affects the practicality of the film. In addition, EVA resins tend to degrade due to long-term exposure to atmospheric moisture caused by hydrolysis. In addition, the hydrolysis of EVA forms acetic acid as an undesirable by-product, which is harmful to the electronic components of photovoltaic modules.

[0004] To circumvent these disadvantages of EVA copolymers, polyolefin polymers have been investigated as possible alternatives.While polyolefin encapsulation films may offer benefits, such as possessing high volume resistivity, low gas and moisture permeability, polyolefins have their own set of disadvantages.

[0005] Therefore, an object of the present invention is to provide a film that can be used as an encapsulation film in a photovoltaic module, which film has one or more of the following advantages: (i) desirably high electrical resistance (or volume resistivity), (ii) excellent adhesion properties, (iii) excellent moisture and gas barrier properties, (iv) ease of processing, (v) excellent optical transmittance, (vi) recyclability and (vii) suitable mechanical properties, such as tensile modulus. Summary of the invention

[0006] Therefore, one or more objects of the present invention are achieved by a film comprising a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer is a polymer selected from the group consisting of:

[0007] a. A propylene copolymer comprising, based on the total number of moles of all polymer units constituting the propylene copolymer:

[0008] i. ≥95.0 mol% and ≤99.95 mol%, preferably ≥98.0 mol% and ≤99.95 mol%, preferably ≥99.0 mol% and ≤99.9 mol%, preferably ≥99.5 mol% and ≤99.9 mol% of polymer units derived from propylene, and

[0009] ii. ≥0.05 mol% and ≤5.0 mol%, preferably ≥0.05 mol% and ≤2.0 mol%, preferably ≥0.1 mol% and ≤1.0 mol%, preferably ≥0.1 mol% and ≤0.5 mol% of polymer units derived from functionalized olefin monomers;

[0010] b. A propylene terpolymer comprising, based on the total number of moles of all polymer units constituting the propylene terpolymer:

[0011] i. ≥80.0 mol% and ≤98.95 mol%, preferably ≥88.0 mol% and ≤98.0 mol%, preferably ≥90.0 mol% and ≤96.0 mol% of polymer units derived from propylene;

[0012] ii. ≥0.1 mol% and ≤19.95 mol%, preferably ≥1.0 mol% and ≤10.0 mol%, preferably ≥3.5 mol% and ≤9.9 mol% of polymer units derived from a first olefin monomer, the first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprising 2 or 6 carbon atoms; and

[0013] iii. ≥0.05 mol% and ≤5.0 mol%, preferably ≥0.1 mol% and ≤2.0 mol%, preferably ≥0.1 mol% and ≤0.5 mol% of polymer units derived from functionalized olefin monomers;

[0014] c. an ethylene terpolymer comprising, based on the total number of moles of all polymer units constituting the ethylene terpolymer:

[0015] i. ≥80.0 mol % and ≤98.95 mol %, preferably ≥90.0 mol % and ≤97.0 mol % of polymer units derived from ethylene,

[0016] ii. ≥0.1 mol% and ≤19.95 mol%, preferably ≥2.5 mol% and ≤9.9 mol% of polymer units derived from a second olefin monomer, the second olefin monomer comprising 3 to 8 carbon atoms, preferably the second olefin monomer comprising 8 carbon atoms; and

[0017] iii. ≥0.05 mol% and ≤5.0 mol%, preferably ≥0.1 mol% and ≤0.5 mol% of polymer units derived from functionalized olefin monomers; and

[0018] d. a polymer mixture comprising any combination of polymers (a) to (c);

[0019] Wherein the functionalized olefin monomer is a monomer selected from the following:

[0020] i. an olefin monomer having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms, containing a hydroxyl group;

[0021] ii. a carboxylic acid-containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms; and

[0022] iii. an esterified olefin monomer represented by the formula:

[0023]

[0024] ●R 1 is selected from hydrocarbon groups having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, more preferably 4 or 6 carbon atoms;

[0025] ●R 2 is selected from hydrocarbon groups having 2 to 10 carbon atoms, and

[0026] ● wherein 'n' is an integer from 1 to 3, and 'm' is an integer from 0 to 4, preferably 1 to 4.

[0027] Wherein the functionalized polyolefin polymer comprises ≤0.8 wt%, preferably ≤0.5 wt%, preferably ≤0.2 wt% of an inorganic metal oxide, based on the total weight of the functionalized polyolefin polymer and determined using inductively coupled plasma mass spectrometry, preferably the inorganic metal oxide comprises a metal selected from Group 13 (Group III) of the Periodic Table, preferably the inorganic metal oxide is aluminum oxide.

[0028] Preferably, the present invention is achieved by a film comprising a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer is a propylene terpolymer comprising, based on the total number of moles of all polymer units constituting the propylene terpolymer:

[0029] i. ≥80.0 mol% and ≤98.95 mol%, preferably ≥88.0 mol% and ≤98.0 mol%, preferably ≥90.0 mol% and ≤96.0 mol% of polymer units derived from propylene;

[0030] ii. ≥0.1 mol% and ≤19.95 mol%, preferably ≥1.0 mol% and ≤10.0 mol%, preferably ≥3.5 mol% and ≤9.9 mol% of polymer units derived from a first olefin monomer, the first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprising 2 or 6 carbon atoms; and

[0031] iii. ≥0.05 mol % and ≤5.0 mol %, preferably ≥0.1 mol % and ≤2.0 mol %, preferably ≥0.1 mol % and ≤0.5 mol % of polymer units derived from functionalized olefin monomers,

[0032] Wherein the functionalized olefin monomer is a monomer selected from the following:

[0033] a. an olefin monomer having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms, containing a hydroxyl group;

[0034] b. a carboxylic acid-containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms; and

[0035] c. An esterified olefin monomer represented by the formula:

[0036]

[0037] ●R 1 is selected from hydrocarbon groups having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, more preferably 4 or 6 carbon atoms;

[0038] ●R 2 is selected from hydrocarbon groups having 2 to 10 carbon atoms, and

[0039] ● wherein 'n' is an integer from 1 to 3 and 'm' is an integer from 0 to 4.

[0040] Wherein the functionalized polyolefin polymer comprises ≤0.8 wt %, preferably ≤0.5 wt %, preferably ≤0.2 wt % of an inorganic metal oxide, based on the total weight of the functionalized polyolefin polymer and determined using inductively coupled plasma mass spectrometry, preferably, the inorganic metal oxide comprises a metal selected from Group 13 (Group III) of the Periodic Table, preferably, the inorganic metal oxide is aluminum oxide.

[0041] The term "hydrocarbyl" as used throughout this disclosure means a hydrocarbon group formed by removing one or more hydrogen atoms from a hydrocarbon compound, and such groups include straight chain or branched hydrocarbons, saturated or unsaturated hydrocarbons, aliphatic and aromatic hydrocarbon groups. The term "terpolymer" as used throughout this disclosure means a polymer molecule having polymer units derived from three different monomers. The term "copolymer" as used throughout this disclosure means a polymer molecule having polymer units derived from three different monomers.

[0042] The symbol "≥" used throughout this disclosure means any of "greater than or equal to" or "at least". For example, the term "≥95.0" means "greater than or equal to 95.0" or "at least 95.0". The symbol "≤" used throughout this disclosure means "less than or equal to" or "not greater than". For example, the term "≤95.0" means "less than or equal to 95.0" or "not greater than 95.0".

[0043] The film of the present invention may, for example, comprise a functionalized polyolefin polymer present in an amount of ≥95.0 wt % and ≤100.0 wt %, preferably ≥96.0 wt % and ≤100.0 wt %, preferably ≥97.0 wt % and ≤100.0 wt %, preferably ≥98.0 wt % and ≤100.0 wt %, preferably ≥99.95 wt % and ≤100.0 wt %, preferably 100.0 wt %, based on the total weight of the film. In some embodiments of the present invention, the film may comprise a combination of a functionalized polyolefin polymer and a polyolefin elastomer.

[0044] Thus, in some embodiments of the present invention, the films of the present invention may, for example, comprise a combination of a polyolefin elastomer and a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer is present in an amount of ≥25.0 wt. % and ≤95.0 wt. %, preferably ≥30.0 ​​wt. % and ≤80.0 wt. %, preferably ≥35.0 wt. % and ≤75.0 wt. %, preferably ≥40.0 wt. % and ≤70.0 wt. %, based on the total weight of the film.

[0045] Therefore, in some embodiments of the present invention, the film of the present invention may comprise a blend of a functionalized polyolefin polymer and a non-functionalized polyolefin polymer, preferably the non-functionalized polyolefin polymer is selected from polyethylene, poly(ethylene-co-propylene), poly(ethylene-co-1-butene), poly(ethylene-co-1-hexene), poly(ethylene-co-1-octene), polypropylene, poly(propylene-co-ethylene), poly(propylene-co-1-butene), poly(propylene-co-1-octene), poly(propylene-co-1-octene).

[0046] Advantageously, the films of the present invention exhibit a suitable combination of one or more of the following: (i) desirably high electrical resistance (or volume resistivity), (ii) excellent adhesion properties, (iii) excellent moisture and gas barrier properties, (iv) ease of processing, (v) excellent optical transmittance, and (vi) suitable mechanical properties, such as tensile modulus. The combination of one or more of such advantageous properties makes the films of the present invention particularly suitable for being encapsulation films. As a further advantage, the use of the films of the present invention imparts excellent adhesion and mechanical properties without the need for chemical crosslinking, thereby resulting in reduced processing time compared to conventional films using crosslinked polymers and making such films easily recyclable.

[0047] Thus, in some aspects of the invention, the invention relates to the use of a film according to one or more embodiments of the invention as an encapsulation film for a photovoltaic module.

[0048] Functionalized polyolefin polymers

[0049] Propylene copolymer

[0050] In some embodiments of the invention, the film may, for example, comprise a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer may, for example, be a propylene copolymer. The propylene copolymer may, for example, comprise polymer units derived from propylene and polymer units derived from functionalized olefin monomers, and polymer units derived from propylene ...

[0051] The propylene copolymer can, for example, comprise 96.0 mol%, 97.0 mol%, 98.0 mol%, 99.0 mol%, 99.5 mol%, 99.6 mol%, 99.7 mol%, 99.8 mol%, 99.9 mol% or 99.95 mol% of polymer units derived from propylene, based on the total moles of all polymer units constituting the propylene copolymer. The propylene copolymer can, for example, comprise 4.0 mol%, 3.0 mol%, 2.0 mol%, 1.0 mol%, 0.5 mol%, 0.4 mol%, 0.3 mol%, 0.2 mol%, 0.1 mol% or 0.05 mol% of polymer units derived from functionalized olefin monomers, based on the total moles of all polymer units constituting the propylene copolymer.

[0052] Preferably, in some embodiments of the invention, the propylene copolymer may comprise ≥98.0 mol% and ≤99.95 mol% of polymer units derived from propylene and ≥0.05 mol% and ≤2.0 mol% of polymer units derived from a functionalized olefin monomer, based on the total moles of all polymer units constituting the propylene copolymer.

[0053] Preferably, in some embodiments of the present invention, the propylene copolymer may comprise ≥99.0 mol% and ≤99.90 mol% of polymer units derived from propylene and ≥0.1 mol% and ≤1.0 mol% of polymer units derived from functionalized olefin monomers, based on the total moles of all polymer units constituting the propylene copolymer. Preferably, in some embodiments of the present invention, the propylene copolymer may comprise ≥99.5 mol% and ≤99.90 mol% of polymer units derived from propylene and ≥0.1 mol% and ≤0.5 mol% of polymer units derived from functionalized olefin monomers, based on the total moles of all polymer units constituting the propylene copolymer.

[0054] Propylene terpolymer

[0055] In some embodiments of the invention, the film may, for example, comprise a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer may, for example, be a propylene terpolymer. The propylene terpolymer may, for example, comprise (i) ≥80.0 mol% and ≤98.95 mol% of polymer units derived from propylene, (ii) ≥0.1 mol% and ≤19.95 mol% of polymer units derived from a first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprising 2 or 6 carbon atoms, and (iii) ≥0.05 mol% and ≤5.0 mol% of polymer units derived from a functionalized olefin monomer, based on the total moles of all polymer units constituting the propylene terpolymer.

[0056] The polymer units derived from propylene can be present in an amount of, for example, 85.0 mol%, 86.0 mol%, 88.0 mol%, 91.0 mol%, 91.2 mol%, 92.0 mol%, 94.0 mol%, 98.0 mol% or 98.95 mol%. The polymer units derived from the first olefin monomer can be present in an amount of, for example, 0.1 mol%, 1.0 mol%, 4.5 mol%, 6.0 mol%, 8.5 mol%, 11.0 mol%, 15.0 mol% or 19.5 mol%. The polymer units derived from the functionalized olefin monomers can be present in an amount of, for example, 0.05 mol%, 0.1 mol%, 0.5 mol%, 1.0 mol%, 2.0 mol%, 3.0 mol%, 4.0 mol% or 5.0 mol%.

[0057] Preferably, the propylene terpolymer may comprise (i) ≥88.0 mol% and ≤98.0 mol% of polymer units derived from propylene, (ii) ≥1.0 mol% and ≤10.0 mol% of polymer units derived from a first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprises 2 or 6 carbon atoms, preferably the first olefin monomer comprises 6 carbon atoms, and (iii) ≥0.1 mol% and ≤2.0 mol% of polymer units derived from a functionalized olefin monomer, based on the total moles of all polymer units constituting the propylene terpolymer.

[0058] More preferably, the propylene terpolymer may comprise (i) ≥90.0 mol% and ≤96.0 mol% of polymer units derived from propylene, (ii) ≥3.5 mol% and ≤9.9 mol% of polymer units derived from a first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprises 2 or 6 carbon atoms, preferably the first olefin monomer comprises 6 carbon atoms, and (iii) ≥0.1 mol% and ≤0.5 mol% of polymer units derived from a functionalized olefin monomer, based on the total moles of all polymer units constituting the propylene terpolymer.

[0059] Ethylene terpolymer

[0060] In some embodiments of the invention, the film may, for example, comprise a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer may, for example, be an ethylene terpolymer. The ethylene terpolymer may, for example, comprise (i) ≥80.0 mol % and ≤98.95 mol % of polymer units derived from ethylene, (ii) ≥0.1 mol % and ≤19.95 mol % of polymer units derived from a second olefin monomer comprising 3 to 8 carbon atoms, preferably the second olefin monomer comprising 8 carbon atoms, and (iii) ≥0.05 mol % and ≤5.0 mol % of polymer units derived from the functionalized olefin monomer, based on the total moles of all polymer units constituting the ethylene terpolymer.

[0061] The polymer units derived from ethylene can be present in an amount of, for example, 85.0 mol%, 86.0 mol%, 88.0 mol%, 91.0 mol%, 91.2 mol%, 92.0 mol%, 94.0 mol%, 98.0 mol% or 98.95 mol%. The polymer units derived from the second olefin monomer can be present in an amount of, for example, 0.1 mol%, 1.0 mol%, 4.5 mol%, 6.0 mol%, 8.5 mol%, 11.0 mol.%, 15.0 mol% or 19.5 mol%. The polymer units derived from the functionalized olefin monomer can be present in an amount of, for example, 0.05 mol%, 0.1 mol%, 0.5 mol%, 1.0 mol%, 2.0 mol%, 3.0 mol%, 4.0 mol% or 5.0 mol%.

[0062] Preferably, the ethylene terpolymer may comprise (i) ≥90.0 mol% and ≤97.0 mol% of polymer units derived from ethylene, (ii) ≥2.5 mol% and ≤9.9 mol% of polymer units derived from a second olefin monomer comprising 3 to 8 carbon atoms, preferably the second olefin monomer comprises 8 carbon atoms, and (iii) ≥0.1 mol% and ≤0.5 mol% of polymer units derived from a functionalized olefin monomer, based on the total moles of all polymer units constituting the ethylene terpolymer.

[0063] Preferably, in some embodiments of the present invention, the first olefin monomer containing 2 or 4 to 8 carbon atoms is a monomer selected from the following: ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, vinyl cyclohexane and 1-octene, preferably the first olefin monomer is selected from ethylene or 1-hexene. Preferably, in some embodiments of the present invention, the second olefin monomer containing 3 to 8 carbon atoms is a monomer selected from the following: propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, vinyl cyclohexane and 1-octene, preferably the second olefin monomer is 1-octene.

[0064] Preferably, in some embodiments of the present invention, (i) the first olefin monomer containing 2 or 4 to 8 carbon atoms is a monomer selected from the following: ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, vinyl cyclohexane and 1-octene, preferably the first olefin monomer is selected from ethylene or 1-hexene; and / or (ii) the second olefin monomer containing 3 to 8 carbon atoms is a monomer selected from the following: propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, vinyl cyclohexane and 1-octene, preferably the second olefin monomer is 1-octene.

[0065] Functionalized olefin monomers:

[0066] Olefin monomers containing hydroxyl groups

[0067] In some embodiments of the present invention, the functionalized olefin monomer is an olefin monomer containing a hydroxyl group having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms. Preferably, the olefin monomer containing a hydroxyl group is selected from 3-butene-1-ol, 5-hexene-1-ol, 7-octen-1-ol and 10-undecene-1-ol, and preferably the olefin monomer containing a hydroxyl group is 5-hexene-1-ol.

[0068] Therefore, in some embodiments of the present invention, the propylene copolymer may, for example, comprise polymer units derived from propylene and polymer units derived from olefin monomers containing hydroxyl groups having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms. Preferably, the propylene copolymer comprises polymer units derived from propylene and polymer units derived from 5-hexene-1-ol.

[0069] The propylene terpolymer may for example comprise (i) polymer units derived from propylene, (ii) polymer units derived from a first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprises 2 or 6 carbon atoms, preferably the first olefin monomer comprises 6 carbon atoms, and (iii) polymer units derived from a hydroxyl group-containing olefin monomer having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

[0070] Preferably, in some embodiments of the present invention, the propylene terpolymer may comprise (i) polymer units derived from propylene, (ii) polymer units derived from a first olefin monomer comprising 6 carbon atoms, and (iii) polymer units derived from 5-hexene-1-ol. Preferably, in some embodiments of the present invention, the propylene terpolymer may comprise (i) polymer units derived from propylene, (ii) polymer units derived from 1-hexene, and (iii) polymer units derived from 5-hexene-1-ol.

[0071] Preferably, in some embodiments of the present invention, the propylene terpolymer may comprise (i) polymer units derived from propylene, (ii) polymer units derived from ethylene, and (iii) polymer units derived from 5-hexen-1-ol.

[0072] The ethylene terpolymer may, for example, comprise (i) polymer units derived from ethylene, (ii) polymer units derived from a second olefin monomer comprising 3 to 8 carbon atoms, preferably the second olefin monomer comprising 8 carbon atoms, and (iii) polymer units derived from a hydroxyl group-containing olefin monomer having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

[0073] Olefin monomers containing carboxylic acid

[0074] In some embodiments of the present invention, the functionalized olefin monomer is a carboxylic acid-containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms. Preferably, in some embodiments of the present invention, the carboxylic acid-containing olefin monomer is selected from acrylic acid, 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid, 10-undecenoic acid, 5-norbornene-2-carboxylic acid and 5-norbornene-2-acetic acid, preferably the carboxylic acid-containing olefin monomer is acrylic acid, 3-butenoic acid, 4-pentenoic acid and 5-norbornene-2-carboxylic acid.

[0075] Thus, in some embodiments of the invention, the propylene copolymer may for example comprise (i) polymer units derived from propylene and (ii) polymer units derived from a carboxylic acid containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

[0076] In some embodiments of the invention, the propylene terpolymer may comprise (i) polymer units derived from propylene, (ii) polymer units derived from a first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprises 2 or 6 carbon atoms, preferably the first olefin monomer comprises 6 carbon atoms, and (iii) polymer units derived from a carboxylic acid-containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

[0077] In some embodiments of the present invention, the ethylene terpolymer may comprise (i) polymer units derived from ethylene, (ii) polymer units derived from a second olefin monomer comprising 3 to 8 carbon atoms, preferably the second olefin monomer comprises 8 carbon atoms, and (iii) polymer units derived from a carboxylic acid-containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

[0078] Preferably, in some embodiments of the present invention, (i) the carboxylic acid-containing olefin monomer is selected from acrylic acid, 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid, 10-undecenoic acid, 5-norbornene-2-carboxylic acid and 5-norbornene-2-acetic acid, preferably the carboxylic acid-containing olefin monomer is acrylic acid, 3-butenoic acid, 4-pentenoic acid and 5-norbornene-2-carboxylic acid; and / or wherein (ii) the hydroxyl group-containing olefin monomer is selected from 3-butene-1-ol, 5-hexene-1-ol, 7-octen-1-ol and 10-undecene-1-ol, preferably the hydroxyl group-containing olefin monomer is 5-hexen-1-ol.

[0079] Functionalized polyolefin polymers with carboxylic acid-containing olefin monomers or hydroxyl-containing olefin monomers can be prepared, for example, by a solution process using protected carboxylic acid-containing olefin monomers or protected hydroxyl-containing olefin monomers. Non-limiting examples of protecting groups include silyl halides, trialkylaluminum complexes, dialkylaluminum alkoxide complexes, dialkylmagnesium complexes, dialkylzinc complexes and trialkylboron complexes, alumina-based compounds and complexes.

[0080] For functionalized polyolefin polymers, particularly for encapsulation film applications for photovoltaic modules, it is particularly preferred to involve a purification step or deashing step that removes the protective agent that remains in the resin as an impurity after the production process. By performing the purification (deashing) step, the film exhibits improved adhesion strength and a desired increased volume resistivity. The inventors believe that by removing the protecting group from the resin, the film has more hydroxyl functional groups that can be used to enhance both the adhesion properties and the volume resistivity of the film.

[0081] Esterified olefin monomers

[0082] In some embodiments of the present invention, the functionalized olefin monomer is an esterified olefin monomer represented by the formula:

[0083]

[0084] ●R 1 is selected from hydrocarbon groups having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, more preferably 4 or 6 carbon atoms;

[0085] ●R 2 is selected from hydrocarbon groups having 2 to 10 carbon atoms, and

[0086] ● wherein 'n' is an integer from 1 to 3, and 'm' is an integer from 0 to 4, preferably 1 to 4.

[0087] Thus, in some embodiments of the invention, the propylene copolymer may, for example, comprise polymer units derived from propylene and polymer units derived from esterified olefin monomers.

[0088] In some embodiments of the invention, the propylene terpolymer may, for example, comprise (i) polymer units derived from propylene, (ii) polymer units derived from a first olefin monomer comprising 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprises 2 or 6 carbon atoms, preferably the first olefin monomer comprises 6 carbon atoms, and (iii) polymer units derived from an esterified olefin monomer.

[0089] In some embodiments of the invention, the ethylene terpolymer may, for example, comprise (i) polymer units derived from ethylene, (ii) polymer units derived from a second olefin monomer comprising 3 to 8 carbon atoms, preferably the second olefin monomer comprises 8 carbon atoms, and (iii) polymer units derived from an esterified olefin monomer.

[0090] The functionalized polyolefin polymer comprising polymer units derived from esterified olefin monomers can be prepared, for example, by first obtaining an intermediate functionalized polyolefin polymer using a solution process. The intermediate functionalized polyolefin polymer can, for example, comprise polymer units derived from propylene, optionally polymer units derived from a first monomer, and polymer units derived from carboxylic acid-containing olefin monomers or hydroxyl group-containing olefin monomers.

[0091] Alternatively, the intermediate functionalized polyolefin polymer may, for example, comprise polymer units derived from ethylene, a second monomer, and polymer units derived from a carboxylic acid-containing olefin monomer or a hydroxyl group-containing olefin monomer.

[0092] Subsequently, the intermediate functionalized polyolefin polymer can be esterified with a polyacid or corresponding anhydride, preferably a diprotic or triprotic acid moiety, to obtain a functionalized polyolefin polymer comprising polymer units derived from the esterified olefin monomer. The polyacid can, for example, have one or more hydroxyl group functionalities. The step of esterification by a polyacid or polyanhydride can be performed using a solution process or during a reactive extrusion melt process.

[0093] The polyacid and its corresponding anhydride can be selected from, for example, citric acid, citric anhydride, gluconic acid, saccharic acid, isocitric acid, tartaric acid, succinic acid, succinic anhydride, fumaric acid, malic acid, maleic anhydride, itaconic acid, itaconic anhydride, oxalic acid, trimesic acid, 1,2,4-benzenetricarboxylic acid-1,2-anhydride, propane-1,2,3-tricarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), preferably the polyacid is citric acid.

[0094] For illustration purposes, a propylene terpolymer as an intermediate functionalized polyolefin polymer, such as (poly(propylene-co-1-hexene-co-5-hexene-1-ol)) represented by the formula (poly(C3-co-C6-co-C6OH)) can be obtained by polymerizing propylene, 1-hexene, and 5-hexene-1-ol in solution. The propylene terpolymer can then be esterified with citric acid to obtain a propylene terpolymer comprising polymer units derived from propylene, 1-hexene, and the esterified olefin monomer.

[0095] Preferred functionalized polyolefin polymers

[0096] In some embodiments of the present invention, the functionalized polyolefin polymer is selected from poly(C3-co-C2-co-C6OH), poly(C3-co-C4-co-C6OH), poly(C3-co-C6-co-C6OH), poly(C3-co-C8-co-C6OH), poly(C3-co-C6OH), poly(C3-co-C2-co-C6OX), poly(C3-co-C6-co-C6OX), or a combination thereof, preferably the functionalized polyolefin polymer is selected from poly(C3-co-C2-co-C6OH), poly(C3-co-C4-co-C6OH), poly(C3-co-C6-co-C6OH), poly(C3-co-C6-co-C6OX), more preferably the functionalized polyolefin polymer is selected from poly(C3-co-C2-co-C6OH), poly(C3-co-C4-co-C6OH), poly(C3-co-C6-co-C6OH), poly(C3-co-C6-co-C6OX), The polymer is poly(C3-co-C6-co-C6OH), wherein C2 represents an ethylene monomer, C3 represents a propylene monomer, C4 represents a 1-butene monomer, C6 represents a 1-hexene monomer, C8 represents a 1-octene monomer and C6OH represents a 5-hexene-1-ol monomer, and 'X' represents a structural portion derived from citric acid, citric anhydride, gluconic acid, saccharic acid, isocitric acid, tartaric acid, succinic acid, succinic anhydride, fumaric acid, malic acid, maleic anhydride, itaconic acid, itaconic anhydride, oxalic acid, trimesic acid, 1,2,4-benzenetricarboxylic acid-1,2-anhydride, propane-1,2,3-tricarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), preferably 'X' is a structural portion derived from citric acid.

[0097] Preferably, the membrane comprises a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer is poly(C3-co-C6-co-C6OH), wherein C3 represents propylene monomer, C6 represents 1-hexene monomer and C6OH represents 5-hexene-1-ol monomer, and wherein the functionalized polyolefin polymer comprises ≤0.8 wt%, preferably ≤0.5 wt%, preferably ≤0.2 wt% of an inorganic metal oxide, based on the total weight of the functionalized polyolefin polymer and determined using inductively coupled plasma mass spectrometry, preferably the inorganic metal oxide comprises a metal selected from Group 13 (Group III) of the Periodic Table, preferably the inorganic metal oxide is aluminum oxide.

[0098] Preferably, the functionalized polyolefin polymer is (poly(propylene-co-1-hexene-co-5-hexene-1-ol)) represented by the formula (poly(C3-co-C6-co-C6OH)), wherein the content of polymer units derived from propylene is 91.2 mol%, the content of polymer units derived from 1-hexene is 8.5 mol%, and the content of polymer units derived from 5-hexene-1-ol is 0.3 mol%, wherein the functionalized polyolefin polymer contains ≤0.8 wt%, preferably ≤0.5 wt%, preferably ≤0.2 wt% of aluminum oxide as determined using inductively coupled plasma mass spectrometry.

[0099] Alternatively, in some embodiments of the present invention, the functionalized polyolefin polymer is (poly(propylene-co-1-hexene-co-5-hexene-1-ol)) represented by the formula (poly(C3-co-C6-co-C6OH)), wherein the polymer units derived from propylene are 88.0 mol%, the polymer units derived from 1-hexene are 11.5 mol%, and the polymer units derived from 5-hexene-1-ol are 0.5 mol%, wherein the functionalized polyolefin polymer contains ≤0.8 wt%, preferably ≤0.5 wt%, and preferably ≤0.2 wt% of aluminum oxide as determined using inductively coupled plasma mass spectrometry.

[0100] Preferably, the functionalized polyolefin polymer is (poly(propylene-co-1-hexene-co-5-hexene-1-ol)) represented by the formula (poly(C3-co-C6-co-C6OH)), wherein the content of polymer units derived from propylene is 95.0 mol%, the content of polymer units derived from 1-hexene is 4.5 mol%, and the content of polymer units derived from 5-hexene-1-ol is 0.5 mol%, wherein the functionalized polyolefin polymer contains ≤0.8 wt%, preferably ≤0.5 wt%, preferably ≤0.2 wt% of aluminum oxide as determined using inductively coupled plasma mass spectrometry.

[0101] Ash content and polar functionalization

[0102] Advantageously, the film comprising the functionalized polyolefin polymer has a sufficiently low ash content, or in other words sufficiently low inorganic metal oxide content. Inorganic metal oxides such as aluminum oxide can be regarded as impurities derived from the residual traces of the catalyst composition (comprising cocatalysts or catalyst activators) generally used to prepare functionalized polyolefin polymers. Or, inorganic metal oxides can also be derived from scavengers / protective agents that can be used to protect the hydroxyl or carboxylic acid functional groups present in the functionalized polyolefin polymer.

[0103] It is suspected that the presence of inorganic metal oxides above a certain threshold limit (or concentration) may negatively affect the performance of the film as an encapsulant for photovoltaic modules. For example, if the film has a high metal oxide content (e.g., greater than 0.8 wt %), the film may become hard, affecting its processability. In addition, at such high inorganic metal oxide content, the thermal and volume resistivity properties of the film may also be affected, thereby reducing its practicality as an encapsulation film for photovoltaic modules requiring high resistivity.

[0104] Preferably, in some embodiments of the present invention, the functionalized polyolefin polymer comprises ≤0.8 wt%, preferably ≤0.5 wt%, preferably ≤0.2 wt% of an inorganic metal oxide, based on the total weight of the functionalized polyolefin polymer and determined using inductively coupled plasma mass spectrometry, preferably the inorganic metal oxide comprises a metal selected from Group 13 (Group III) of the Periodic Table, preferably the inorganic metal oxide is aluminum oxide.

[0105] More preferably, in some embodiments of the present invention, the functionalized polyolefin polymer comprises ≥0.0 wt% and ≤0.8 wt%, preferably ≥0.0 wt% and ≤0.5 wt%, preferably ≥0.0 wt% and ≤0.2 wt%, preferably ≥0.0 wt% and ≤0.1 wt% of an inorganic metal oxide, preferably the inorganic metal oxide comprises a metal selected from Group 13 (Group III) of the Periodic Table, preferably the inorganic metal oxide is aluminum oxide or a hydrated analog thereof, aluminum hydroxide oxide or aluminum hydroxide, based on the total weight of the functionalized polyolefin polymer and determined using inductively coupled plasma mass spectrometry.

[0106] Inductively coupled plasma mass spectrometry (ICP-MS) can be carried out, for example, by contacting the film sample with an inorganic acid such as nitric acid under heat in a closed pressure vessel. The pressure vessel can be heated, for example, using microwave technology. The analysis is controlled by a temperature and pressure sensor. The closed pressure vessel can be manufactured, for example, using a fluoropolymer (PTFE-TFM) or quartz. The polymer portion of the film sample can be decomposed by an acid oxidation reaction to form carbon dioxide, water, and nitrogen oxides, while the remaining metal oxides are converted into corresponding nitrates, and their content can be measured using ICP-MS to measure the amount of metal oxides present in the film sample. In other words, the ICP-MS analysis process involves a microwave-assisted acid digestion process of a polymer sample using nitric acid, followed by inductively coupled plasma mass spectrometry analysis. In some aspects of the present invention, inductively coupled plasma mass spectrometry (ICP-MS) can be carried out according to ISO24047:2021.

[0107] Advantageously, the functionalized polyolefin polymer has a suitable content of polar functional groups such as hydroxyl functional groups, which impart desired adhesion properties to the film. It is believed that the adjustable functionality of these functionalized polyolefin polymers makes these classes of polymers particularly suitable for polymer adhesives to various substrates such as metals, glass, wood and polar polymers. The general non-polar properties of functionalized polyolefin polymers additionally provide excellent adhesion to low surface energy substrates such as polyolefins (i.e., HDPE, LDPE, LLDPE, PP), particularly to the front and back layers of photovoltaic modules.

[0108] Polar groups such as hydroxyl groups can be used, for example, 1 H NMR spectroscopy. Such analysis can be performed, for example, at 130° C. using deuterated tetrachloroethane (TCE-D2) as solvent and recorded on a Varian Mercury spectrometer operating at a frequency of 400 MHz in a 5.0 mm tube. Chemical shifts can be reported in ppm relative to tetramethylsilane and determined by reference to solvent protons.

[0109] Preferably, the functionalized polyolefin polymer has:

[0110] i) an inorganic metal oxide content of ≥ 0.0 wt % and ≤ 0.8 wt %, preferably ≥ 0.0 wt % and ≤ 0.3 wt %, preferably ≥ 0.0 wt % and ≤ 0.2 wt %, preferably ≥ 0.01 wt % and ≤ 0.1 wt %, preferably ≥ 0.1 wt % and ≤ 0.2 wt %, based on the total weight of the functionalized polyolefin copolymer and determined using inductively coupled plasma mass spectrometry; and

[0111] ii) a content of hydroxyl functions of ≥0.1 and ≤1.0 mol %, preferably ≥0.2 and ≤0.8 mol %, preferably ≥0.2 and ≤0.6 mol %, when determined using NMR spectroscopy.

[0112] Stabilizers and additives in membranes

[0113] Preferably, the film comprising the functionalized polyolefin polymer may further comprise ≥0.05 wt % and ≤5.0 wt % of one or more additives relative to the total weight of the film. The one or more additives may be selected from antioxidants, heat stabilizers, acid scavengers, plasticizers, hindered amine light stabilizers, antistatic additives, non-phenolic processing stabilizers, lubricants, anti-scratch agents, recycling additives, clarifiers, processing stabilizers, microbials, anti-fog additives, anti-blocking additives, non-phenolic processing stabilizers, and combinations thereof.

[0114] Properties of Functionalized Polyolefin Polymers

[0115] The functionalized polyolefin polymer has a suitable balance of properties required for a functionalized polyolefin polymer to be used as an encapsulation film.

[0116] Preferably, the functionalized polyolefin polymer has:

[0117] i) an inorganic metal oxide content of ≥ 0.0 wt. % and ≤ 0.8 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.3 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.2 wt. %, preferably ≥ 0.01 wt. % and ≤ 0.1 wt. %, preferably ≥ 0.1 wt. % and ≤ 0.2 wt. %, based on the total weight of the functionalized polyolefin copolymer and determined using inductively coupled plasma mass spectrometry; and / or

[0118] ii) a peak melting temperature (T ) of ≥ 50.0°C and ≤ 120.0°C, preferably ≥ 70.0°C and ≤ 100.0°C, preferably ≥ 75.0°C and ≤ 95.0°C, preferably ≥ 75.0°C and ≤ 90.0°C, as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008). m ).

[0119] Preferably, the functionalized polyolefin polymer has:

[0120] i) a hydroxyl functional group content of ≥0.1 and ≤1.0 mol %, preferably ≥0.2 and ≤0.8 mol %, preferably ≥0.2 and ≤0.6 mol % when determined using NMR spectroscopy; and / or

[0121] ii) a polydispersity index (PDI) of ≥1.5 and ≤6.0, preferably ≥2.0 and ≤6.0, preferably ≥4.0 and ≤6.0, wherein the weight average molecular weight (M w ) divided by the number average molecular weight (M n ) PDI is calculated according to ASTM D6474-12, and M is determined according to ASTM D6474-12 w and M n Each one of them.

[0122] Preferably, the functionalized polyolefin polymer has:

[0123] i) a weight average molecular weight (M) of ≥75.0 kg / mol and ≤150.0 kg / mol, preferably ≥100.0 kg / mol and ≤150.0 kg / mol and measured according to ASTM D6474-12 w ); and / or

[0124] ii) a crystallization temperature (T ) of ≥ 20°C and ≤ 80°C, preferably ≥ 40°C and ≤ 60°C, preferably ≥ 35°C and ≤ 55°C, preferably ≥ 35°C and ≤ 50°C as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008); c ); and / or

[0125] iii) a glass transition temperature (T ) of ≥ -50.0°C and ≤5.0°C, preferably -10.0°C and ≤2.0°C, preferably ≥ -5.0°C and ≤2.0°C, preferably ≥ -2.0°C and ≤ -1.0°C as determined using dynamic mechanical thermal analysis (DMTA) according to ISO 6721-10:2015 g ).

[0126] More preferably, the functionalized polyolefin polymer has:

[0127] i) an inorganic metal oxide content of ≥ 0.0 wt. % and ≤ 0.8 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.3 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.2 wt. %, preferably ≥ 0.01 wt. % and ≤ 0.1 wt. %, preferably ≥ 0.1 wt. % and ≤ 0.2 wt. %, based on the total weight of the functionalized polyolefin copolymer and determined using inductively coupled plasma mass spectrometry; and / or

[0128] ii) a peak melting temperature (T ) of ≥ 50.0°C and ≤ 120.0°C, preferably ≥ 70.0°C and ≤ 100.0°C, preferably ≥ 75.0°C and ≤ 95.0°C, preferably ≥ 75.0°C and ≤ 90.0°C, as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008). m ); and / or

[0129] iii) a hydroxyl functional group content of ≥0.1 and ≤1.0 mol %, preferably ≥0.2 and ≤0.8 mol %, preferably ≥0.2 and ≤0.6 mol % when determined using NMR spectroscopy; and / or

[0130] iv) a polydispersity index (PDI) of ≥1.5 and ≤6.0, preferably ≥2.0 and ≤6.0, preferably ≥4.0 and ≤6.0, wherein the weight average molecular weight (M w ) divided by the number average molecular weight (M n ) PDI is calculated according to ASTM D6474-12, and M is determined according to ASTM D6474-12 w and M n each of; and / or

[0131] v) a weight average molecular weight (M) of ≥75.0 kg / mol and ≤150.0 kg / mol, preferably ≥100.0 kg / mol and ≤150.0 kg / mol and measured according to ASTM D6474-12 w ); and / or

[0132] vi) a crystallization temperature (T ) of ≥ 20° C. and ≤ 80° C., preferably ≥ 40° C. and ≤ 60° C., preferably ≥ 35° C. and ≤ 55° C., preferably ≥ 35° C. and ≤ 50° C., as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008); c ); and / or

[0133] vii) a glass transition temperature (T ) of ≥ -50.0°C and ≤5.0°C, preferably ≥ -10.0°C and ≤2.0°C, preferably ≥ -5.0°C and ≤2.0°C, preferably ≥ -2.0°C and ≤ -1.0°C as determined using dynamic mechanical thermal analysis (DMTA) according to ISO 6721-10:2015 g ).

[0134] More preferably, the functionalized polyolefin polymer has:

[0135] i) an inorganic metal oxide content of ≥ 0.0 wt. % and ≤ 0.8 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.3 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.2 wt. %, preferably ≥ 0.01 wt. % and ≤ 0.1 wt. %, preferably ≥ 0.1 wt. % and ≤ 0.2 wt. %, based on the total weight of the functionalized polyolefin copolymer and determined using inductively coupled plasma mass spectrometry;

[0136] ii) a peak melting temperature (T ) of ≥ 50.0°C and ≤ 100.0°C, preferably ≥ 70.0°C and ≤ 100.0°C, preferably ≥ 75.0°C and ≤ 95.0°C, preferably ≥ 75.0°C and ≤ 90.0°C, as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008). m );

[0137] iii) a hydroxyl functional group content of ≥0.1 and ≤1.0 mol %, preferably ≥0.2 and ≤0.8 mol %, preferably ≥0.2 and ≤0.6 mol %, when determined using NMR spectroscopy;

[0138] iv) a polydispersity index (PDI) of ≥1.5 and ≤6.0, preferably ≥2.0 and ≤6.0, preferably ≥4.0 and ≤6.0, wherein the weight average molecular weight (M w ) divided by the number average molecular weight (M n) PDI is calculated according to ASTM D6474-12, and M is determined according to ASTM D6474-12 w and M n Each of the;

[0139] v) a weight average molecular weight (M) of ≥75.0 kg / mol and ≤150.0 kg / mol, preferably ≥100.0 kg / mol and ≤150.0 kg / mol and measured according to ASTM D6474-12 w );

[0140] vi) a crystallization temperature (T ) of ≥ 20° C. and ≤ 80° C., preferably ≥ 40° C. and ≤ 60° C., preferably ≥ 35° C. and ≤ 55° C., preferably ≥ 35° C. and ≤ 50° C., as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008); c );and

[0141] vii) a glass transition temperature (T ) of ≥ -50.0°C and ≤5.0°C, preferably -10.0°C and ≤2.0°C, preferably ≥ -5.0°C and ≤2.0°C, preferably ≥ -2.0°C and ≤ -1.0°C as determined using dynamic mechanical thermal analysis (DMTA) according to ISO 6721-10:2015 g ).

[0142] Properties of membranes comprising functionalized polyolefin polymers

[0143] The films of the present invention comprising the functionalized polyolefin polymers exhibit suitable properties of resistivity, optical and mechanical properties required for films to be used as encapsulation films for photovoltaic modules.

[0144] Preferably, the film exhibits a thermal conductivity of ≥ 1.0×10 13 and ≤3.0×10 16 , preferably ≥1.0×10 14 and ≤2.5×10 15 , preferably ≥1.0×10 14 and ≤2.0×10 14 At such a volume resistivity, the film has a desired resistivity required for a photovoltaic module.

[0145] Preferably, the film exhibits:

[0146] a. ≥1.0×10 when measured according to ASTM D257-14 (2021) at an applied voltage of 1000 V for a period of 600 seconds and at a temperature of 25°C 13and ≤3.0×10 16 , preferably ≥1.0×10 14 and ≤2.5×10 15 , preferably ≥1.0×10 14 and ≤2.0×10 14 Volume resistivity; and / or

[0147] b. An optical transmittance of ≥30.0% and ≤95.0%, preferably ≥40.0% and ≤95.0%, preferably ≥44.0% and ≤85.0%, preferably ≥45.0% and ≤60.0%, preferably ≥45.0% and ≤50.0% when measured according to ASTM D1003 (2021).

[0148] Preferably, the film exhibits:

[0149] a. a tensile strength at break of ≥15.0 MPa and ≤60.0 MPa, preferably ≥15.0 MPa and ≤60.0 MPa, preferably ≥20.0 MPa and ≤40.0 MPa, preferably ≥22.0 MPa and ≤30.0 MPa, when measured according to ASTM D882 (2018); and / or

[0150] b. A tensile modulus of ≥30.0 ​​MPa and ≤130.0 MPa, preferably ≥30.0 ​​MPa and ≤100.0 MPa, preferably ≥30.0 ​​MPa and ≤80.0 MPa, preferably ≥30.0 ​​MPa and ≤60.0 MPa, preferably ≥35.0 MPa and ≤55.0 MPa, preferably ≥40.0 MPa and ≤50.0 MPa, when measured according to ASTM D882 (2018).

[0151] More preferably, the film exhibits:

[0152] a. ≥1.0×10 when measured according to ASTM D257-14 (2021) at an applied voltage of 1000 V for a period of 600 seconds and at a temperature of 25°C 13 and ≤3.0×10 16 , preferably ≥1.0×10 14 and ≤2.5×10 15 , preferably ≥1.0×10 14 and ≤2.0×10 14 Volume resistivity;

[0153] b. An optical transmittance of ≥30.0% and ≤95.0%, preferably ≥40.0% and ≤95.0%, preferably ≥44.0% and ≤85.0%, preferably ≥45.0% and ≤60.0%, preferably ≥45.0% and ≤50.0% when measured according to ASTM D1003 (2021);

[0154] c. a tensile strength at break of ≥15.0 MPa and ≤60.0 MPa, preferably ≥15.0 MPa and ≤60.0 MPa, preferably ≥20.0 MPa and ≤40.0 MPa, preferably ≥22.0 MPa and ≤30.0 MPa, when measured according to ASTM D882 (2018); and

[0155] d. A tensile modulus of ≥30.0 ​​MPa and ≤130.0 MPa, preferably ≥30.0 ​​MPa and ≤100.0 MPa, preferably ≥30.0 ​​MPa and ≤80.0 MPa, preferably ≥30.0 ​​MPa and ≤60.0 MPa, preferably ≥35.0 MPa and ≤55.0 MPa, preferably ≥40.0 MPa and ≤50.0 MPa, when measured according to ASTM D882 (2018).

[0156] The film may, for example, have suitable moisture barrier properties. For example, the film of the present invention has a relative humidity of 85% (R 23° C.) according to ASTM F1249. H )≥0.5g / (m 2 ·day) and ≤8.0g / (m 2 ·day) water vapor transmission rate (WVTR).

[0157] Preparation of membranes comprising functionalized polyolefin polymers

[0158] Films comprising functionalized polyolefin polymers can be prepared by using suitable methods such as film extrusion / casting, or by compression molding. Therefore, in some aspects of the present invention, the present invention relates to a method for preparing a film according to any one or more embodiments of the present invention, wherein the method comprises at least one step, the step involving either (i) film extrusion and casting, or (ii) compression molding. Preferably, the method for preparing the film comprises the steps of film extrusion and casting, the steps of film extrusion and casting comprising the following steps:

[0159] a. providing a functionalized polyolefin polymer according to one or more embodiments of the present invention;

[0160] b. extruding the functionalized polyolefin polymer at a melt temperature of ≤225°C and forming an extrudate; and

[0161] c. The extrudate is cooled and formed into a film.

[0162] In some embodiments of the invention, extrusion is performed at a melt temperature of ≤225° C., preferably ≤210° C., preferably ≤210° C. Preferably, extrusion is performed at a melt temperature of ≥140° C. and ≤225° C., preferably ≥150° C. and ≤210° C., preferably ≥160° C. and ≤200° C. and an extrudate is formed.

[0163] The cooling of the extrudate may include the step of casting the film. For example, the method for preparing the film includes the step of casting the extrudate at a temperature of ≤100°C and forming the film. The casting of the film can be carried out, for example, at any suitable temperature of ≥70°C and ≤100°C. In some embodiments of the invention, the film thus obtained can be further heated and subsequently stretched to form an oriented film, such as a biaxially oriented film.

[0164] Alternatively, in some aspects of the present invention, the present invention relates to a method for preparing a film according to one or more embodiments of the present invention, wherein the method comprises a step of compression molding, the step of compression molding comprising the following steps:

[0165] a. providing a functionalized polyolefin polymer according to one or more embodiments of the present invention;

[0166] b. heating the functionalized polyolefin polymer at any temperature of ≥150°C and ≤225°C, preferably ≥160°C and ≤200°C, and forming a precursor melt film;

[0167] c. applying a compressive force of ≥50 kN and ≤150 kN, preferably ≥80 kN and ≤120 kN, to the precursor film for a period of ≥1.0 min and ≤15.0 min, preferably ≥2.0 min and ≤8.0 min; and

[0168] d. cooling the precursor molten film to a temperature of ≥35°C and ≤50°C at a cooling rate of 10°C / min and at a compressive force of ≥50 kN and ≤150 kN, preferably ≥80 kN and ≤120 kN and forming a precursor film; and

[0169] e. Remove the compressive force and cool the precursor film to ambient room temperature to obtain a film.

[0170] Optionally, the precursor melt film can be stabilized for a period of ≥1.0 minute and ≤15.0 minutes, preferably ≥2.0 minutes and ≤8.0 minutes in the absence of any compressive force before applying the compressive force. Once formed, the film can be used to form an encapsulation layer or sealing layer suitable for use in photovoltaic modules or other electronic modules. The film can have a suitable thickness as may be required for a particular application. For example, the film has a cross-sectional thickness of ≥200 μm and ≤3000 μm, preferably ≥200 μm and ≤800 μm, preferably ≥300 μm and ≤500 μm.

[0171] Solar cell applications:

[0172] Therefore, in some embodiments of the present invention, the present invention relates to an encapsulated solar cell, which includes a solar cell located between a first encapsulation layer and a second encapsulation layer, wherein at least one of the first encapsulation layer or the second encapsulation layer, preferably each of the first encapsulation layer and the second encapsulation layer comprises a film according to one or more embodiments of the present invention or is composed of a film according to one or more embodiments of the present invention, and further wherein the solar cell is positioned so that the first encapsulation layer and the second encapsulation layer are bonded so as to at least partially encapsulate the solar cell.

[0173] Solar cells for use in the context of the present invention are known to those skilled in the art. For example, the solar cell may be any standard commercially available crystalline or amorphous silicon solar cell or a CIGS (copper indium gallium selenide) thin film. Those skilled in the art will know what type of electrical connection to use, for example the electrical conductor may be a metal ribbon, for example a ribbon comprising copper, aluminum and / or silver, or alternatively may be a metal wire.

[0174] In some aspects of the invention, the invention relates to a photovoltaic module comprising an encapsulated solar cell according to the invention, preferably wherein the photovoltaic module comprises:

[0175] a.front layer;

[0176] b. backing layer; and

[0177] c. An encapsulated solar cell, wherein the encapsulated solar cell is located between a front layer and a back layer, preferably such that the front layer is in direct contact with the first encapsulation layer and the second encapsulation layer is in direct contact with the back layer.

[0178] In some embodiments of the present invention, the present invention relates to a photovoltaic module comprising an encapsulated solar cell according to the present invention, preferably wherein the photovoltaic module comprises in the following order:

[0179] a.front layer;

[0180] b. The first encapsulation layer;

[0181] c. Solar cells;

[0182] d. a second encapsulation layer; and

[0183] e. Back layer;

[0184] The solar cell is located between the first encapsulation layer and the second encapsulation layer, and preferably the front layer is in direct contact with the first encapsulation layer and the second encapsulation layer is in direct contact with the back layer.

[0185] In some embodiments of the invention, the front layer and / or the back layer comprises a material selected from the group consisting of a polypropylene composition, glass, a polycarbonate composition, and any combination thereof, preferably the front layer and / or the back layer comprises a polypropylene composition. The polypropylene composition may, for example, comprise a polypropylene homopolymer, particularly isotactic polypropylene (iPP). Alternatively, the polypropylene composition may, for example, be a propylene-ethylene random copolymer (random PP), which optionally comprises an inorganic filler such as glass or talc.

[0186] In some embodiments of the present invention, the front layer and / or the back layer comprises a polypropylene composition. The front layer suitable for the present invention may be, for example, the same as described on pages 3-9 of the published patent application WO2021053180A1, and the back layer suitable for the present invention may be, for example, the same as described on pages 12-17 of the published patent application WO2021053180A1.

[0187] In addition to the front layer, the sealing layer and the back layer, the photovoltaic module may further comprise further layers such as protective (UV and / or fire) coatings on the sun-facing side of the front layer. Preferably, the photovoltaic module of the invention does not comprise a metal layer, making the process of recycling the photovoltaic module of the invention easier.

[0188] Photovoltaic modules can be manufactured, for example, by a suitable method. For example, in some aspects of the invention, the invention relates to a method for preparing a photovoltaic module according to one or more embodiments of the invention, wherein the method comprises the following steps:

[0189] a) assembling the front layer, the first encapsulation layer, the solar cell, the second encapsulation layer and the back layer to form a photovoltaic module, so that the solar cell is located between the first encapsulation layer and the second encapsulation layer, preferably so that the front layer is in direct contact with the first encapsulation layer; and the second encapsulation layer is in direct contact with the back layer;

[0190] b) heating the photovoltaic module at a certain temperature so that at least a portion of the first encapsulation layer and the second encapsulation layer melt to form a melted photovoltaic module containing solar cells;

[0191] c) pressing the melted photovoltaic components under heating and forming a laminated photovoltaic module; and

[0192] d) Cooling the laminated photovoltaic module to ambient temperature and obtaining a photovoltaic module.

[0193] Preferably, the ambient temperature suitable for the method for producing a photovoltaic module may be ≥ 15.0°C and ≤ 35.0°C, preferably ≥ 20.0°C and ≤ 35.0°C.

[0194] Preferably, the photovoltaic module is heated at any temperature ≥110.0° C. and ≤180.0° C., preferably ≥120.0° C. and ≤170.0° C., preferably ≥125.0° C. and ≤165.0° C., preferably ≥130.0° C. and ≤160.0° C. Preferably, in the heating step, the module is heated to a temperature such that the front layer and the back layer do not melt, for example the temperature of the heating step is selected such that the front layer obtains a temperature of at least 5° C. below the melting temperature of the front layer.

[0195] In practice, the temperature of the heating step is chosen to be as high as possible allowing maximum adhesion between the first encapsulation layer and the front layer and between the second encapsulation layer and the back layer while ensuring that the polymer front and back layers do not melt.

[0196] During such a lamination method, the structural integrity of the assembly and the back layer is maintained, and the photovoltaic module of the present invention with consistent size can be prepared. In addition, lamination is a simple method with a short cycle time because it can be carried out at a high speed. It should be clear to those skilled in the art that the layers can also be partially laminated. For example, the front layer and the first encapsulation layer can first be laminated to each other, after which the laminated front layer and the sealing layer can be laminated to the back layer.

[0197] Included below are specific examples that demonstrate some embodiments of the present invention. Described embodiment is for illustrative purposes only and is not intended to limit the present invention. It should be understood that the embodiments and aspects disclosed herein are not mutually exclusive, and such aspects and embodiments can be combined in any manner. Those of ordinary skill in the art will readily recognize that parameters that can be changed or modified to produce substantially the same results. Example

[0198] Purpose: For the purpose of illustrating the present invention, three film samples were prepared. Film sample "IE" represents a film according to the present invention (formulation of the present invention), and films CE1 and CE2 are comparative formulations, and their performance is compared. Details of the film samples are provided below:

[0199] Table 1

[0200]

[0201] Method for preparing functionalized polyolefin polymer poly(C3-co-C6-co-C6OH): A stainless steel tube filled with pentamethylheptane (PMH) solvent (1 L) was used. Reactor (2 L), using a stirring speed of 600 rpm for polymerization experiments. Catalyst and comonomer solutions were prepared in a glove box under an inert dry nitrogen atmosphere.

[0202] The reactor was first heated to 40°C, and then TiBA (1.0 M solution in toluene, 2 mL), 1-hexene (pure 10 mL) and triethylaluminum (TEA)-pacified 5-hexen-1-ol (1.0 M solution in toluene, TEA:5-hexen-1-ol (molar ratio) = 1, 10 mL) were added. Gaseous propylene (100 g) was charged to the reactor at 40°C, and the reactor was heated to the desired polymerization temperature of 130°C, resulting in a propylene partial pressure of about 15 bar. Once the set temperature was reached, polymerization was initiated by injecting the preactivated catalyst precursor bis((2-oxo-3-(dibenzo-1H-pyrrol-1-yl)-5-(methyl)phenyl)-2-phenoxy)-2,4-pentanediylhafnium(IV) dimethyl [CAS 958665-18-4]; alias [[2',2"'-[(1,3-dimethyl-1,3-propanediyl)bis(oxy-κO)]bis[3-(9H-carbazol-9-yl)-5-methyl[1,1'-biphenyl]-2-phenol-κO]](2-)]dimethyl]hafnium (Hf-O4, 2 μmol) in MAO (30 wt% in toluene, 11.2 mmol). The polymer solution was poured into a mixture containing demineralized water / iPrOH (50 wt%, 1 L) and Irganox. The reaction was stopped by adding 1010 (1.0 M, 2 mmol) into a container flask. The resulting suspension was filtered and dried in a vacuum oven at 80°C, and then Irganox 1010 was added as an antioxidant. White powdery poly(propylene-co-1-hexene-co-5-hexene-1-ol) (25.6 g) was obtained.

[0203] Deashing method: The copolymer obtained from the solution process may be deashed to remove traces of protective compounds used during the polymer synthesis or to remove traces of aluminum oxide originating from catalyst residues. To this end, the polymer (10 g) was dispersed in a mixture of dry toluene (400 ml) and concentrated (37%) HCl (10 ml, 0.13 mol, 4.74 g) and heated under reflux until the terpolymer was dissolved. Once the polymer was properly dissolved, methanol (250 ml) was added to the hot mixture and the mixture was heated at 90-100° C. for another hour under stirring. The polymer was then precipitated in cold methanol, filtered and washed twice with methanol and dried at 60° C. under reduced pressure.

[0204] Method for preparing membrane:Film samples were prepared via compression molding on a LabEcon 600 high temperature press (Fontijne Presses, The Netherlands) using a PP ISO setting. A compression molding cycle was applied: heating to 180°C, stabilization for 5 min without applied force, stabilization for 5 min under 100 kN normal force, and cooling to 40°C at 10°C / min and 100 kN normal force, and films were obtained.

[0205] Test parameters and methodology: The evaluation parameters were determined according to the methodology provided below:

[0206] Procedure for determining the content of aluminum oxide (ICP-MS test method) : Deashed poly (C3-co-C6-co-C6OH) (0.3 mol% OH; PDI = 4.6; 150 mg (5.6·10 -6 mol)) was digested in 6 mL of concentrated nitric acid (trace metal grade) by microwave assisted acid digestion using an Anton Paar Multiwave PRO equipped with a closed high pressure quartz digestion vessel. After the microwave digestion run, the acid was analytically transferred to a pre-cleaned plastic centrifuge tube containing 1 mL of internal standard solution and diluted to the 50 mL mark with MilliQ water. The elements in the samples were quantified using an Agilent 8900 ICP-MS system using a multi-element calibration set from Inorganic Ventures.

[0207] Volume resistivity: The determination was conducted according to ASTM D257-14 (2021) at an applied voltage of 1000 V for a period of 600 seconds and at a temperature of 25°C.

[0208] Amount of hydroxyl functionality: pass 1 H NMR spectroscopy determines the level of functionality by comparing the integration of the CH2 signal next to the hydroxyl group (OH) to the integration of the resonance of the polymer backbone. The analysis was performed at 130°C using deuterated tetrachloroethane (TCE-D2) as solvent and recorded in 5 mm tubes on a Varian Mercury spectrometer operating at a frequency of 400 MHz. Chemical shifts are reported in ppm relative to tetramethylsilane and are determined by reference to residual solvent protons.

[0209] Peak melting temperature (T m ): The peak melting temperature was determined using differential scanning calorimetry (DSC) according to ASTM D3418-15, wherein for 3-6 mg film samples, a first heating and cooling cycle was performed at a temperature between -40°C and 230°C and a heating and cooling rate of 10°C / min, using a nitrogen purge gas with a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle.

[0210] Crystallization temperature (T c ): The determination was made using differential scanning calorimetry (DSC) according to ASTM D3418-15, wherein for 3-6 mg film samples, a first heating and cooling cycle was performed at a temperature between -40°C and 230°C and a heating and cooling rate of 10°C / min, using a nitrogen purge gas with a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle.

[0211] Weight average molecular weight (M w ) and number average molecular weight (M n ): Measured according to ASTM D6474-12.

[0212] Polydispersity Index (PDI): The weight average molecular weight (M w ) divided by the number average molecular weight (M n ) calculates PDI, and where M w and M n Each of is measured according to ASTM D6474-12.

[0213] Tensile modulus and tensile strength at break: Measured according to ASTM D882(2018).

[0214] Glass transition temperature (T g ): Determined by DMTA according to ISO 6721-10:2015.

[0215] result: The results from the test analysis are provided in the following table:

[0216] Table 3

[0217]

[0218] By polydispersity index (PDI), the functionalized polyolefin polymer of the present invention has a higher polydispersity index and a lower glass transition temperature Tg than the comparative polymer CE2, indicating the improved processability of the polymer. In addition, the polymer of the present invention has a higher molecular weight that contributes to the improved structural integrity of the film. The following table provides the properties of the film samples:

[0219] Table 3

[0220]

[0221] As is apparent from the data provided in Table 3, the inventive film "IE" exhibits a higher volume resistivity than CE1 and CE2, making the film particularly suitable for use in photovoltaic modules. For example, the inventive film "IE" having the functionalized polyolefin polymer has a volume resistivity nearly 60 times higher than CE1, while the film "IE" has a volume resistivity nearly 1.6 times higher than CE2. Comparison of the volume resistivity function of the inventive film "IE" with "CE1" indicates that the deashed polymer is particularly suitable for use in an encapsulation film having a high electrical resistance.

[0222] Compared to film CE1, the film "IE" of the present invention has a significantly lower (nearly 66% lower) tensile modulus or stiffness, thereby allowing improved film processing. In addition, the higher tensile strength at break of the film of the present invention compared to film CE2 makes the film have excellent mechanical properties, which is required for films to be used as packaging films.

[0223] Thus, the film "IE" of the present invention comprising a functionalized polyolefin polymer such as a propylene terpolymer of the formula poly(C3-co-C6-co-C6OH) and having an alumina content of approximately 0.168 wt% imparts desirable properties of resistivity and mechanical properties suitable for use as an encapsulation film for photovoltaic modules.

Claims

1. A film comprising a functionalized polyolefin polymer, wherein the functionalized polyolefin polymer is a polymer selected from the group consisting of: a. A propylene copolymer comprising, based on the total number of moles of all polymer units constituting the propylene copolymer: i. ≥95.0 mol% and ≤99.95 mol%, preferably ≥98.0 mol% and ≤99.95 mol%, preferably ≥99.0 mol% and ≤99.9 mol%, preferably ≥99.5 mol% and ≤99.9 mol% of polymer units derived from propylene, and ii. ≥0.05 mol% and ≤5.0 mol%, preferably ≥0.05 mol% and ≤2.0 mol%, preferably ≥0.1 mol% and ≤1.0 mol%, preferably ≥0.1 mol% and ≤0.5 mol% of polymer units derived from functionalized olefin monomers; b. A propylene terpolymer comprising, based on the total number of moles of all polymer units constituting the propylene terpolymer: i. ≥80.0 mol% and ≤98.95 mol%, preferably ≥88.0 mol% and ≤98.0 mol%, preferably ≥90.0 mol% and ≤96.0 mol% of polymer units derived from propylene; ii. ≥0.1 mol% and ≤19.95 mol%, preferably ≥1.0 mol% and ≤10.0 mol%, preferably ≥3.5 mol% and ≤9.9 mol% of polymer units derived from a first olefin monomer, wherein the first olefin monomer comprises 2 or 4 to 8 carbon atoms, preferably the first olefin monomer comprises 2 or 6 carbon atoms; and iii. ≥0.05 mol% and ≤5.0 mol%, preferably ≥0.1 mol% and ≤2.0 mol%, preferably ≥0.1 mol% and ≤0.5 mol% of polymer units derived from functionalized olefin monomers; c. an ethylene terpolymer comprising, based on the total number of moles of all polymer units constituting the ethylene terpolymer: i. ≥80.0 mol % and ≤98.95 mol %, preferably ≥90.0 mol % and ≤97.0 mol % of polymer units derived from ethylene, ii. ≥0.1 mol% and ≤19.95 mol%, preferably ≥2.5 mol% and ≤9.9 mol% of polymer units derived from a second olefin monomer, wherein the second olefin monomer comprises 3 to 8 carbon atoms, preferably the second olefin monomer comprises 8 carbon atoms; and iii. ≥0.05 mol % and ≤5.0 mol %, preferably ≥0.1 mol % and ≤0.5 mol % of polymer units derived from functionalized olefin monomers; and d. a polymer mixture comprising any combination of polymers (a) to (c); The functionalized olefin monomer is selected from the following monomers: i. an olefin monomer having 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms, containing a hydroxyl group; ii. a carboxylic acid-containing olefin monomer having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms; and iii. an esterified olefin monomer represented by the formula: ●R 1 is selected from hydrocarbon groups having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, more preferably 4 or 6 carbon atoms; ●R 2 is selected from hydrocarbon groups having 2 to 10 carbon atoms, and ● wherein 'n' is an integer from 1 to 3, and 'm' is an integer from 0 to 4, preferably from 1 to 4, Wherein, the functionalized polyolefin polymer contains ≤0.8 wt %, preferably ≤0.5 wt %, preferably ≤0.2 wt % of inorganic metal oxide based on the total weight of the functionalized polyolefin polymer and determined using inductively coupled plasma mass spectrometry, preferably the inorganic metal oxide contains a metal selected from Group 13 (Group III) of the periodic table, and preferably the inorganic metal oxide is aluminum oxide.

2. The film according to claim 1, wherein (i) the carboxylic acid-containing olefin monomer is selected from the group consisting of acrylic acid, 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid, 10-undecenoic acid, 5-norbornene-2-carboxylic acid and 5-norbornene-2-acetic acid, preferably the carboxylic acid-containing olefin monomer is acrylic acid, 3-butenoic acid, 4-pentenoic acid and 5-norbornene-2-carboxylic acid; and / or wherein (ii) the hydroxyl group-containing olefin monomer is selected from the group consisting of 3-butene-1-ol, 5-hexene-1-ol, 7-octen-1-ol and 10-undecene-1-ol, preferably the hydroxyl group-containing olefin monomer is 5-hexen-1-ol.

3. The film according to claims 1-2, wherein (i) the first olefin monomer containing 2 or 4 to 8 carbon atoms is a monomer selected from the group consisting of ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, vinyl cyclohexane and 1-octene, preferably the first olefin monomer is selected from ethylene or 1-hexene; and / or wherein (ii) the second olefin monomer containing 3 to 8 carbon atoms is a monomer selected from the group consisting of propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, vinyl cyclohexane and 1-octene, preferably the second olefin monomer is 1-octene.

4. The film according to any one of claims 1 to 3, wherein the functionalized polyolefin polymer is selected from the group consisting of poly(C3-co-C2-co-C6OH), poly(C3-co-C4-co-C6OH), poly(C3-co-C6-co-C6OH), poly(C3-co-C8-co-C6OH), poly(C3-co-C6OH), poly(C3-co-C2-co-C6OX), poly(C3-co-C6-co-C6OX) and combinations thereof, preferably the functionalized polyolefin polymer is selected from the group consisting of poly(C3-co-C2-co-C6OH), poly(C3-co-C4-co-C6OH), poly(C3-co-C6-co-C6OH), poly(C3-co-C6-co-C6OX) and combinations thereof, more preferably the functionalized polyolefin polymer is poly(C3-co-C6-co-C6OH), Wherein C2 represents ethylene monomer, C3 represents propylene monomer, C4 represents 1-butene monomer, C6 represents 1-hexene monomer, C8 represents 1-octene monomer and C6OH represents 5-hexene-1-ol monomer, and 'X' represents a structural part derived from citric acid, citric anhydride, gluconic acid, saccharic acid, isocitric acid, tartaric acid, succinic acid, succinic anhydride, fumaric acid, malic acid, maleic anhydride, itaconic acid, itaconic anhydride, oxalic acid, trimesic acid, 1,2,4-benzenetricarboxylic acid-1,2-anhydride, propane-1,2,3-tricarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), preferably 'X' is a structural part derived from citric acid.

5. The film of any one of claims 1-4, wherein the functionalized polyolefin polymer has: i) an inorganic metal oxide content of ≥ 0.0 wt. % and ≤ 0.8 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.3 wt. %, preferably ≥ 0.0 wt. % and ≤ 0.2 wt. %, preferably ≥ 0.01 wt. % and ≤ 0.2 wt. %, preferably ≥ 0.1 wt. % and ≤ 0.2 wt. %, based on the total weight of the functionalized polyolefin copolymer and determined using inductively coupled plasma mass spectrometry; and / or ii) a peak melting temperature (T ) of ≥ 50.0°C and ≤ 120.0°C, preferably ≥ 70.0°C and ≤ 100.0°C, preferably ≥ 75.0°C and ≤ 95.0°C, preferably ≥ 75.0°C and ≤ 90.0°C, as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008); m ).

6. The film of any one of claims 1-5, wherein the functionalized polyolefin polymer has: i) a hydroxyl functional group content of ≥0.1 and ≤1.0 mol %, preferably ≥0.2 and ≤0.8 mol %, preferably ≥0.2 and ≤0.6 mol % when determined using NMR spectroscopy; and / or ii) a polydispersity index (PDI) of ≥1.5 and ≤6.0, preferably ≥2.0 and ≤6.0, preferably ≥4.0 and ≤6.0, wherein the weight average molecular weight (M w ) divided by the number average molecular weight (M n ) PDI is calculated according to ASTM D6474-12, and M is determined according to ASTM D6474-12 w and M n Each one of them.

7. The film of any one of claims 1-6, wherein the functionalized polyolefin polymer has: i) a weight average molecular weight (M) of ≥75.0 kg / mol and ≤150.0 kg / mol, preferably ≥100.0 kg / mol and ≤150.0 kg / mol and measured according to ASTM D6474-12 w ); and / or ii) a crystallization temperature (T ) of ≥ 20°C and ≤ 80°C, preferably ≥ 40°C and ≤ 60°C, preferably ≥ 35°C and ≤ 55°C, preferably ≥ 35°C and ≤ 50°C, as determined using differential scanning calorimetry (DSC) according to ASTM D3418 (2008); c ); and / or iii) a glass transition temperature (T ) of ≥ -50.0°C and ≤5.0°C, preferably ≥ -10.0°C and ≤2.0°C, preferably ≥ -5.0°C and ≤2.0°C, preferably ≥ -2.0°C and ≤ -1.0°C, as determined using dynamic mechanical thermal analysis (DMTA) according to ISO 6721-10:2015 g ).

8. The film according to any one of claims 1 to 7, wherein the film exhibits: a. ≥1.0×10-1 when measured at 1000 V for 600 seconds and at 25°C according to ASTM D257-14 (2021) 13 and ≤3.0×10 16 , preferably ≥1.0×10 14 and ≤2.5×10 15 , preferably ≥1.0×10 14 and ≤2.0×10 14 Volume resistivity; and / or b. An optical transmittance of ≥30.0% and ≤95.0%, preferably ≥40.0% and ≤95.0%, preferably ≥44.0% and ≤85.0%, preferably ≥45.0% and ≤60.0%, preferably ≥45.0% and ≤50.0% when measured according to ASTM D1003 (2021).

9. The film according to any one of claims 1 to 8, wherein the film exhibits: a. a tensile strength at break of ≥15.0 MPa and ≤60.0 MPa, preferably ≥15.0 MPa and ≤60.0 MPa, preferably ≥20.0 MPa and ≤40.0 MPa, preferably ≥22.0 MPa and ≤30.0 MPa, when measured according to ASTM D882 (2018); and / or b. A tensile modulus of ≥30.0 ​​MPa and ≤130.0 MPa, preferably ≥30.0 ​​MPa and ≤100.0 MPa, preferably ≥30.0 ​​MPa and ≤80.0 MPa, preferably ≥30.0 ​​MPa and ≤60.0 MPa, preferably ≥35.0 MPa and ≤55.0 MPa, preferably ≥40.0 MPa and ≤50.0 MPa, when measured according to ASTM D882 (2018).

10. The film according to any one of claims 1 to 9, wherein the functionalized polyolefin polymer is blended with a non-functionalized polyolefin polymer or a polyolefin elastomer, preferably the non-functionalized polyolefin polymer is selected from polyethylene, poly(ethylene-co-propylene), poly(ethylene-co-1-butene), poly(ethylene-co-1-hexene), poly(ethylene-co-1-octene), polypropylene, poly(propylene-co-ethylene), poly(propylene-co-1-butene), poly(propylene-co-1-octene), poly(propylene-co-1-octene).

11. A method for preparing a film according to any one of claims 1 to 10, wherein the method comprises at least one step involving film extrusion and casting, or compression molding, preferably the method for preparing the film comprises the steps of film extrusion and casting, the steps of film extrusion and casting comprising the following steps: a. providing a functionalized polyolefin polymer according to any one of claims 1-7; b. extruding the functionalized polyolefin polymer at a melt temperature of ≤225°C and forming an extrudate; and c. Cooling the extrudate and forming the film.

12. An encapsulated solar cell, comprising a solar cell located between a first encapsulation layer and a second encapsulation layer, wherein at least one of the first encapsulation layer or the second encapsulation layer, preferably each of the first encapsulation layer and the second encapsulation layer comprises a film according to any one of claims 1 to 10 or consists of a film according to any one of claims 1 to 10, and further wherein the solar cell is positioned so that the first encapsulation layer and the second encapsulation layer are bonded so as to at least partially encapsulate the solar cell.

13. A photovoltaic module comprising the encapsulated solar cell according to claim 12, preferably wherein the photovoltaic module comprises: a.front layer; b. Back layer; and c. An encapsulated solar cell, wherein the encapsulated solar cell is located between the front layer and the back layer, preferably such that the front layer is in direct contact with the first encapsulation layer and the second encapsulation layer is in direct contact with the back layer.

14. The photovoltaic module according to claim 13, wherein the front layer and / or the back layer comprises a material selected from the group consisting of a polypropylene composition, glass, a polycarbonate composition and any combination thereof, preferably the front layer and / or the back layer comprises a polypropylene composition.

15. A method for preparing a photovoltaic module according to claims 13-14, wherein the method comprises the following steps: e) assembling the front layer, the first encapsulation layer, the solar cell, the second encapsulation layer and the back layer to form a photovoltaic module, such that the solar cell is located between the first encapsulation layer and the second encapsulation layer, preferably such that the front layer is in direct contact with the first encapsulation layer; and the second encapsulation layer is in direct contact with the backing layer; f) heating the photovoltaic module at a certain temperature so that at least a portion of the first encapsulation layer and the second encapsulation layer melts to form a melted photovoltaic module including the solar cell; g) pressing the melted photovoltaic components under heating and forming a laminated photovoltaic module; and h) cooling the laminated photovoltaic module to ambient temperature and obtaining the photovoltaic module.

16. Use of the film according to claims 1 to 10 as encapsulation film for photovoltaic modules.

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