Crosslinkable polyolefin composition

Abstract

This invention relates to crosslinkable polyolefin compositions and methods for preparing such polyolefin compositions. The polyolefin composition comprises, by weight of the total polyolefin composition: a) ≥60.0 wt% and ≤99.0 wt% of an ethylene-α-olefin copolymer; b) ≥1.0 wt% and ≤35.0 wt% of an ethylene-α-olefin-diene terpolymer; and c) ≥0.1 wt% and ≤5.0 wt% of a crosslinking agent. The invention also relates to a film comprising the polyolefin composition and an encapsulated solar cell encapsulated by at least two sealing layers, each comprising the film. Furthermore, the invention relates to a cured solar cell obtained by subjecting the encapsulated solar cell to conditions that cure the sealing layers, and a photovoltaic module comprising the cured solar cell.

Description

[0001] This invention relates to crosslinkable polyethylene compositions, methods for preparing such polyethylene compositions, and uses of such polyethylene compositions in the manufacture of encapsulations suitable for photovoltaic modules. The invention also relates to films comprising polyethylene compositions and encapsulated solar cells encapsulated by at least two sealing layers, each containing the film. Furthermore, the invention relates to cured solar cells obtained by subjecting the encapsulated solar cells to conditions sufficient to cure the sealing layers, and photovoltaic modules comprising the cured solar cells.

[0002] Polymer materials such as ethylene-vinyl acetate copolymer (EVA) and polyolefin elastomers (POE) are commonly used as encapsulants in photovoltaic modules and other similar electronic devices such as liquid crystal panels, electroluminescent devices, and plasma display units. Some desired properties of these polymer materials intended for use in photovoltaic modules include: (i) protection of the module from external environmental factors such as moisture and air; (ii) protection of the module from mechanical shock; (iii) ease of processing; (iv) short curing time and protection of the module from mechanical stresses caused by polymer shrinkage during curing; (v) high electrical resistance (volume resistivity); and (vi) high resistance to thermal creep.

[0003] One possible way to improve resistance to thermal creep is to subject the polymeric material to crosslinking conditions in the presence of an organic peroxide initiator. Furthermore, for the photovoltaic manufacturing industry, the use of crosslinkable polymeric encapsulant materials results in shorter curing times and improved manufacturing efficiency. While crosslinking of polymeric materials partially solves the problem of thermal creep, it can cause other problems, such as: 1) material corrosion due to the presence of residual peroxides after crosslinking treatment, or 2) adverse processability due to premature crosslinking of the polymeric material.

[0004] Polymer materials such as ethylene-vinyl acetate copolymer (EVA) and polyolefin elastomers (POE) have been used to prepare polymeric encapsulants suitable for photovoltaic and other similar applications. However, compared to polyolefin elastomers, EVA copolymers suffer from low volume resistivity and poor moisture resistance due to their polarity. Furthermore, EVA-based films have been observed to gradually darken upon exposure to sunlight due to chemical degradation, which can lead to power output losses. Additionally, EVA resin tends to absorb moisture when exposed to the atmosphere and is therefore prone to degradation.

[0005] On the other hand, polyolefin elastomers (POEs) have low crosslinking rates, which limits their commercial application as encapsulants. In the past, several encapsulant manufacturers and processors have attempted to address the low crosslinking rate of POEs by developing materials based on EVA-POE polymer co-extrusion, aiming to obtain materials that combine the best properties of both EVA copolymers and POEs. However, while promising, these materials do not completely resolve all the combined drawbacks of EVA and POE, as industry practitioners have observed that the desired balance of properties for encapsulant materials, such as volume resistivity and crosslinking rate, has not been achieved.

[0006] Therefore, the object of the present invention is to provide a polyolefin composition suitable for use in the manufacture of photovoltaic module encapsulations, having one or more of the following advantages: (i) short curing time, (ii) high volume resistivity, and (iii) improved processability.

[0007] Therefore, one or more objects of the present invention are achieved by comprising a polyolefin composition containing the following:

[0008] a) ≥60.0% by weight and ≤99.0% by weight of an ethylene α-olefin copolymer relative to the total weight of the polyolefin composition, wherein the ethylene α-olefin copolymer has at least one of the following:

[0009] i. Melting peak temperature ≥60℃ and ≤90℃, preferably ≥65℃ and ≤75℃, according to ASTM D3418-15, using differential scanning calorimetry (DSC), for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23℃ to 200℃ and a heating and cooling rate of 10℃ / min, with nitrogen purge gas at a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle;

[0010] ii. ≥20.0% by weight and ≤45.0% by weight, preferably ≥28.0% by weight and ≤40.0% by weight, preferably ≥30.0% by weight and ≤40.0% by weight, relative to the total weight of the ethylene α-olefin copolymer, of polymeric units derived from one or more α-olefins having 3-12 carbon atoms;

[0011] iii. When measured according to ASTM D6248-98 (2012), ≥6.0 per 10 5 10 carbon atoms, preferably ≥7.0 per 10 5 10 carbon atoms, preferably ≥12.0 per 10 5 Vinyl unsaturation of 1 carbon atom;

[0012] b) ≥1.0% by weight and ≤35.0% by weight of an ethylene-α-olefin-diene terpolymer relative to the total weight of the polyolefin composition, wherein, when measured according to ASTM D6248-98 (2012), the ethylene-α-olefin-diene terpolymer contains ≥20.0% and ≤100.0% per 10 5 10 carbon atoms, preferably ≥30.0 ​​and ≤80.0 per 10 5 The total vinyl and vinylidene unsaturation of carbon atoms; and

[0013] c) Crosslinking agent of ≥0.1% by weight and ≤5.0% by weight relative to the total weight of the polyolefin composition.

[0014] Preferably, the present invention relates to a polyolefin composition comprising:

[0015] a) ≥60.0% by weight and ≤99.0% by weight of an ethylene α-olefin copolymer relative to the total weight of the polyolefin composition, preferably wherein the ethylene α-olefin copolymer comprises polymeric units derived from ethylene and one or more α-olefins, wherein the α-olefin is selected from 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, or combinations thereof, preferably selected from 1-butene or 1-octene.

[0016] The ethylene α-olefin copolymer also has at least one of the following:

[0017] i. Melting peak temperature ≥60℃ and ≤90℃, preferably ≥65℃ and ≤75℃, according to ASTM D3418-15, using differential scanning calorimetry (DSC), for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23℃ to 200℃ and a heating and cooling rate of 10℃ / min, with nitrogen purge gas at a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle;

[0018] ii. ≥20.0% by weight and ≤45.0% by weight, preferably ≥28.0% by weight and ≤40.0% by weight, preferably ≥30.0% by weight and ≤40.0% by weight, relative to the total weight of the ethylene α-olefin copolymer, of polymeric units derived from one or more α-olefins having 3-12 carbon atoms;

[0019] iii. When measured according to ASTM D6248-98 (2012), ≥6.0 per 10 5 10 carbon atoms, preferably ≥7.0 per 10 5 10 carbon atoms, preferably ≥12.0 per 10 5 Vinyl unsaturation of 1 carbon atom;

[0020] b) ≥1.0% by weight and ≤35.0% by weight of an ethylene-α-olefin-diene terpolymer relative to the total weight of the polyolefin composition, wherein, when measured according to ASTM D6248-98 (2012), the ethylene-α-olefin-diene terpolymer contains ≥20.0% and ≤100.0% per 10 5 10 carbon atoms, preferably ≥30.0 ​​and ≤80.0 per 10 5 The total vinyl and vinylidene unsaturation of carbon atoms; and

[0021] c) Crosslinking agent of ≥0.1% by weight and ≤5.0% by weight relative to the total weight of the polyolefin composition.

[0022] The ethylene α-olefin copolymer can be selected to have a suitable melt flow rate and density. Preferably, the ethylene α-olefin copolymer may have at least one of the following:

[0023] a) Melt flow rate (MFR) ≥5.0 g / 10 min and ≤25.0 g / 10 min, preferably ≥10.0 g / 10 min and ≤20.0 g / 10 min, preferably ≥11.0 g / 10 min and ≤15.0 g / 10 min, when measured according to ASTM D1238 (2013) at 190 °C with a 2.16 kg load; and / or

[0024] b) ≥850 kg / m² when measured according to ASTM D792 (2008) 3 And ≤900kg / m 3 Preferred weight: ≥870kg / m 3 And ≤880kg / m 3 The density.

[0025] Ethylene α-olefin copolymers may, for example, contain a suitable amount of end-chain unsaturation, at a ratio of 10 5 The amount of vinyl unsaturation per carbon atom is expressed. Without being bound by any specific theory, it is considered that for ethylene α-olefin copolymers, the vinyl unsaturation content affects the crosslinking rate, and therefore the amount of vinyl unsaturation should desirably exceed a certain limit to promote crosslinking. On the other hand, it is considered that for ethylene α-olefin copolymers, the vinylidene unsaturation content has a limited effect on promoting crosslinking. Therefore, the type of unsaturation content (e.g., vinyl or vinylidene) will play a role in selecting a suitable ethylene α-olefin copolymer to improve crosslinking.

[0026] Preferably, when measured according to ASTM D6248-98 (2012), the ethylene α-olefin copolymer has ≥6.0 per 10 5 10 carbon atoms, preferably ≥7.0 per 10 510 carbon atoms, preferably ≥12.0 per 10 5 Vinyl unsaturation per carbon atom. Preferably, when measured according to ASTM D6248-98 (2012), the ethylene α-olefin copolymer has a vinyl unsaturation of ≥6.0 and ≤25.0 per 10 carbon atoms. 5 10 carbon atoms, preferably ≥10.0 and ≤20.0 per 10 5 Vinyl unsaturation of 1 carbon atom.

[0027] Preferably, the ethylene α-olefin copolymer has:

[0028] a) A melting peak temperature ≥60°C and ≤90°C, preferably ≥65°C and ≤75°C, determined using differential scanning calorimetry (DSC) according to ASTM D3418-15, for a 10 mg membrane sample, with a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, purged with nitrogen at a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle; and / or

[0029] b) ≥20.0% by weight and ≤45.0% by weight, preferably ≥28.0% by weight and ≤40.0% by weight, preferably ≥30.0% by weight and ≤40.0% by weight, relative to the total weight of the ethylene α-olefin copolymer, of polymeric units derived from one or more α-olefins having 3-12 carbon atoms; and / or

[0030] c) When measured according to ASTM D6248-98 (2012), ≥6.0 per 10 5 10 carbon atoms, preferably ≥7.0 per 10 5 10 carbon atoms, preferably ≥12.0 per 10 5 Vinyl unsaturation of 1 carbon atom;

[0031] d) Melt flow rate (MFR) ≥5.0 g / 10 min and ≤25.0 g / 10 min, preferably ≥10.0 g / 10 min and ≤20.0 g / 10 min, preferably ≥11.0 g / 10 min and ≤15.0 g / 10 min, when measured according to ASTM D1238 (2013) at 190 °C with a 2.16 kg load; and / or

[0032] e) ≥850 kg / m² when measured according to ASTM D792 (2008) 3 And ≤900kg / m 3 Preferred weight: ≥870kg / m 3 And ≤880kg / m 3 The density.

[0033] Preferably, the melting peak temperature of the ethylene α-olefin copolymer can be ≥70°C and ≤75°C. According to ASTM D3418-15, differential scanning calorimetry (DSC) is used for a 10 mg film sample, with a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, using nitrogen purge gas at a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle. At this melting temperature, the resulting polyolefin composition can be effectively processed while maintaining its thermal and creep stability.

[0034] Ethylene α-olefin copolymers may, for example, comprise polymeric units derived from ethylene and one or more α-olefins selected from 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, or combinations thereof. Preferably, the α-olefin is selected from 1-butene or 1-octene. In some embodiments of the invention, polymeric units derived from one or more α-olefins having 3-12 carbon atoms may be present in suitable amounts in the ethylene α-olefin copolymer to impart a desired balance between crystalline and amorphous phases in the copolymer.

[0035] Preferably, the ethylene α-olefin copolymer has ≥20.0% by weight and ≤45.0% by weight, preferably ≥28.0% by weight and ≤40.0% by weight, preferably ≥30.0% by weight and ≤40.0% by weight, and preferably ≥35.0% by weight and ≤40.0% by weight, relative to the total weight of the ethylene α-olefin copolymer, polymeric units derived from one or more α-olefins having 3-12 carbon atoms. The polymeric units derived from ethylene and α-olefins can be produced, for example, by the method presented in JAPS, Vol. 42, pp. 399-408, 1991. 13 The determination was performed using C NMR spectroscopy.

[0036] The polyolefin composition comprises an ethylene-α-olefin-diene terpolymer having a certain degree of end-chain unsaturation, at a concentration of 10% per 10000 ppm. 5 The total amount of vinyl and vinylidene unsaturation per carbon atom is expressed. Without being bound by any specific theory, it is considered that the total amount of vinyl and vinylidene unsaturation should exceed a certain limit, as both vinyl and vinylidene unsaturation contribute to promoting crosslinking reactions in the terpolymer. Preferably, when measured according to ASTM D6248-98 (2012), the ethylene-α-olefin-diene terpolymer contains ≥20.0 and ≤100.0, preferably ≥30.0 ​​and ≤80.0, preferably ≥35.0 and ≤50.0 per 10 5 Total vinyl and vinylidene unsaturation of carbon atoms.

[0037] Preferably, when measured according to ASTM D6248-98, the ethylene-α-olefin-diene terpolymer contains ≥5.0 and ≤50.0, preferably ≥25.0 and ≤50.0, and preferably ≥27.0 and ≤40.0 per 10 5 The degree of vinylidene unsaturation of each carbon atom. In some preferred embodiments of the invention, the degree of unsaturation can be determined by... 13 C NMR was measured on a Bruker Avance 500 spectrometer equipped with a cryogenically cooled probe operating at 125 °C, wherein the sample was dissolved in C2D2Cl4 containing DBPC as a stabilizer at 130 °C according to ASTM D6248-98 (2012).

[0038] The ethylene-α-olefin-diene terpolymer comprises: 1) polymeric units derived from ethylene, 2) polymeric units derived from α-olefins, and 3) polymeric units derived from dienes. For example, the ethylene-α-olefin-diene copolymer may comprise polymeric units derived from: (i) ethylene; (ii) one or more α-olefins comprising 3-12 carbon atoms, preferably one or more α-olefins selected from the group consisting of propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene; and (iii) a diene selected from the group consisting of: 5-ethylidene-2-norbornene (ENB), 5-propylidene-5-norbornene, dicyclopentadiene (DCPD), and 5-vinylene. -2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, norbornediene, 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 5-methyl-1,5-heptadiene, 6-methyl-1,5-heptadiene, 6-methyl-1,7-octadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 2,5-norbornediene, and 7-methyl-1,6-octadiene. Preferably, the ethylene-α-olefin-diene terpolymer is an ethylene-propylene-diene terpolymer. Preferably, the ethylene-α-olefin-diene terpolymer is an ethylene / propylene / 5-ethylene-2-norbornene terpolymer.

[0039] The ethylene-α-olefin-diene terpolymer has a suitable proportion of polymeric units derived from ethylene, α-olefin monomers, and diene monomers. The ethylene-α-olefin-diene terpolymer may, for example, comprise, by weight relative to the total weight of the ethylene-α-olefin-diene terpolymer:

[0040] a) ≥40.0 and ≤80.0% by weight of ethylene-derived polymeric units, as determined according to ASTM D3900 (2015);

[0041] b) ≥20.0 and ≤50.0% by weight of polymeric units derived from α-olefins, preferably propylene, as determined according to ASTM D3900 (2015); and

[0042] c) ≥0.1 and ≤15.0% by weight of polymeric units derived from diene monomers, preferably 5-ethylidene-2-norbornene (ENB), as determined according to ASTM D6047(99).

[0043] The ethylene, α-olefin, and diene monomer content of the terpolymer can be determined, for example, by the method presented in JAPS, Vol. 42, pp. 399-408, 1991. 13 The determination is performed using C10 NMR spectroscopy. When measured according to ASTM D1646, the ethylene-α-olefin-diene terpolymer may, for example, have a Mooney viscosity ML(1+4) of ≥10.0 and ≤100.0 MU, preferably ≥20.0 and ≤80.0 MU. When measured according to ASTM D297-15 (2019), the ethylene-α-olefin-diene terpolymer may, for example, have a Mooney viscosity ML(1+4) of ≥850.0 kg / m³. 3 And ≤910.0kg / m 3 Preferred weight ≥870.0 kg / m³ 3 And ≤900.0kg / m 3 The density.

[0044] In some embodiments of the invention, the polyolefin composition comprises a crosslinking agent. Preferably, the crosslinking agent is an organic peroxide selected from the group consisting of: 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 3-di-tert-butylperoxide, tert-dicumylene peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne, dicumyl peroxide, α,α'-bis(tert-butylperoxide isopropyl)benzene, 2,2-di(tert-butylperoxide)butane, n-butyl-4,4-bis(tert-butylperoxide)butane, 1,1-bis(tert-butylperoxide)cyclohexane, tert-butylperoxide-2-ethylhexyl carbonate, tert-butylperoxide benzoate, 1,6-di(tert-butylperoxide carbonyloxy)hexane, and combinations thereof. Preferably, the crosslinking agent is dicumyl peroxide (DCP).

[0045] Crosslinking agents can be selected to have a suitable half-life intended for use in encapsulations. For example, if the half-life of an organic peroxide is too short at a given temperature, the composition may crosslink prematurely, adversely affecting its processability during lamination or molding. On the other hand, if the half-life of the organic peroxide is long, the overall processing efficiency will be reduced during lamination or during photovoltaic module production.

[0046] For example, the crosslinking agent can be used in equation t0.5 =ln(2) / k Organic peroxides having a half-life of ≥3.0 minutes and ≤85.0 minutes, preferably ≥10.0 minutes and ≤70.0 minutes, or preferably ≥12.0 minutes and ≤25.0 minutes when measured, where t 0.5 'k' represents the half-life, and 'k' is the reaction rate constant determined using the Arrhenius equation at 140 °C.

[0047] Preferably, the polyolefin composition may further comprise ≥0.05% by weight and ≤5.0% by weight of a coupling agent, preferably a silane coupling agent. The amount of silane coupling agent used in the practice of this invention can vary considerably depending on the nature of the ethylene-α-olefin copolymer, the type of silane used, processing conditions, grafting efficiency, intended application area, and similar factors, but is generally used at least 0.05% by weight, preferably at least 0.5% by weight, based on the total weight of the polyolefin composition.

[0048] Preferably, the coupling agent can be grafted onto the ethylene α-olefin copolymer. Suitable coupling agents include silane coupling agents. For example, any suitable silane coupling agent that effectively grafts and crosslinks the ethylene α-olefin copolymer can be used in the practice of this invention. Suitable silane coupling agents include unsaturated silanes containing an olefinically unsaturated hydrocarbon group, such as vinyl, allyl, isopropenyl, butenyl, cyclohexenyl, or γ-(meth)acryloyloxyallyl, and a hydrolyzable group, such as hydrocarbyloxy, hydrocarbonyloxy, or hydroamino. Non-limiting examples of hydrolyzable or polar groups include methoxy, acrylate, ethoxy, formyloxy, acetoxy, propionyloxy, and alkylamino or aromatic amino groups. Preferred silane coupling agents are unsaturated alkoxysilanes that can be grafted onto the ethylene α-olefin copolymer.

[0049] These silanes and their preparation methods are described in patent US 5,266,627, which is incorporated herein by reference. Vinyltrimethoxysilane, vinyltriethoxysilane, γ-(meth)acryloyloxypropyltrimethoxysilane, and mixtures of these silanes are some preferred silane coupling agents suitable for use according to the present invention.

[0050] More preferably, the polyolefin composition comprises ≥0.05% by weight and ≤5.0% by weight of a silane coupling agent, wherein the silane coupling agent is selected from vinyltrimethoxysilane, vinyltriethoxysilane, γ-(meth)acryloyloxypropyltrimethoxysilane, and combinations thereof. Alternatively, the silane coupling agent may be blended with the polyolefin composition and subsequently compounded using an extruder.

[0051] Preferably, the polyolefin composition may further comprise one or more additives in an amount of ≥0.05% by weight and ≤5.0% by weight relative to the total weight of the polyolefin composition. These additives may be selected from: antioxidants, heat stabilizers, acid removers, mold release agents, plasticizers, hindered amine light stabilizers, antistatic additives, non-phenolic processing stabilizers, lubricants, and anti-scratch agents.

[0052] Recycling additives, clarifying agents, processing stabilizers, antimicrobial agents, antifogging additives, slip additives, anti-blocking additives, non-phenolic processing stabilizers, or combinations thereof.

[0053] The polyolefin composition may also contain a non-phenolic processing stabilizer. This non-phenolic processing stabilizer may be present, for example, in an amount ≥0.05% by weight and ≤5.0% by weight relative to the total weight of the polyolefin composition. For example, the non-phenolic processing stabilizer comprises a mixture of hydroxylamine and a phosphite compound, preferably a 1:1 mixture of hydroxylamine and a phosphite compound. Preferably, the non-phenolic processing stabilizer is N,N-di(octadecyl)hydroxylamine. FS042) and tris(2,4-di-tert-butylphenyl) phosphite ( A 1:1 mixture of 168).

[0054] The polyolefin composition may also contain a hindered amine light stabilizer. Preferably, the hindered amine light stabilizer is poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexamethylenediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]] (Chimasorb 944FD or SabostabUV94 / =HALS). The hindered amine light stabilizer may be present, for example, in an amount of ≥0.05% by weight and ≤5.0% by weight relative to the total weight of the polyolefin composition.

[0055] The coupling agent and one or more additives may be present in suitable amounts such that each of the coupling agent and one or more additives is present in an amount of ≥0.05% by weight and ≤5.0% by weight relative to the total weight of the polyolefin composition.

[0056] Preferably, the polyolefin composition comprises, by weight relative to the total weight of the polyolefin composition:

[0057] a) ≥0.05% by weight and ≤5.0% by weight of coupling agent; and

[0058] b) One or more additives, ≥0.05% by weight and ≤5.0% by weight;

[0059] One or more of the additives are selected from: antioxidants, heat stabilizers, deacidifiers, mold release agents, plasticizers, hindered amine light stabilizers, antistatic additives, non-phenolic processing stabilizers, lubricants, antistatic agents, antiscratch agents, recycling additives, clarifying agents, processing stabilizers, antimicrobial agents, antifogging additives, slip additives, anti-blocking additives, non-phenolic processing stabilizers, or combinations thereof.

[0060] In some preferred embodiments of the invention, the composition comprises, by weight relative to the total weight of the polyolefin composition:

[0061] a) ≥60.0% by weight and ≤99.0% by weight of ethylene-α-olefin copolymers;

[0062] b) ≥1.0% by weight and ≤35.0% by weight of ethylene-α-olefin-diene terpolymer;

[0063] c) Crosslinking agent ≥0.1% by weight and ≤5.0% by weight;

[0064] d) Coupling agents ≥0.05% by weight and ≤5.0% by weight; and

[0065] e) One or more additives, ≥0.05% by weight and ≤5.0% by weight.

[0066] Therefore, polyolefin compositions possess a unique set of properties that make them suitable for use as encapsulations for solar cells and other electronic modules. For example, a polyolefin composition may have at least one of the following:

[0067] a)>1.0×10 15 The volume resistivity (VR) in Ω·cm is preferred for the polyolefin composition, and is preferably >1.0 × 10⁻⁶ Ω·cm. 15 Ω.cm and <2.0×10 18 Ω.cm, preferably >1.0×10 16 Ω.cm and <1.0×10 17 Volume resistivity (VR) in Ω·cm, measured according to ASTM D257-14 (2021) for a period of 600 seconds under an applied voltage of 1000V and at a temperature of 25°C;

[0068] b) A melting peak temperature ≥60°C and ≤75°C, preferably ≥65°C and ≤72°C, is determined using differential scanning calorimetry (DSC) according to ASTM D3418-15, for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, with nitrogen purge gas at a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle;

[0069] c) ≥850 kg / m² when measured according to ASTM D792 (2008). 3 And ≤880kg / m 3 The density;

[0070] d) The β-conversion rate (β) of crosslinking ≥0.4 and ≤0.7 over a time period of 1000 seconds, wherein the β-conversion rate of crosslinking is determined using the following formula:

[0071] β conversion rate (β) = (G'(1000) - G'(0)) / (G'(5000) - G'(0)), where G'(1000) is the storage modulus of the polyolefin composition at 1000 seconds, G'(0) is the storage modulus of the polyolefin composition at 0 seconds, and G'(5000) is the storage modulus of the polyolefin composition at 5000 seconds. The storage modulus is determined according to ISO 6721-10, at 150°C, under nitrogen atmosphere, using a parallel plate with a frequency of 6.28 radians / second and a vibration strain of 0.1%.

[0072] e) Tensile modulus ≥11.0 MPa and ≤25.0 MPa when measured according to ASTM D882 (2018);

[0073] f) Tensile strength at break ≥10.5 MPa and ≤25.0 MPa, as determined according to ASTM D882 (2018);

[0074] g) Hardness (Shore D) ≥19.0 when measured according to ASTM D2240-15(2021) using a durometer.

[0075] Preferably, the polyolefin composition has at least one of the following:

[0076] a)>1.0×10 15 The volume resistivity (VR) in Ω·cm is preferred for the polyolefin composition, and is preferably >1.0 × 10⁻⁶ Ω·cm. 15 Ω.cm and <2.0×10 18 Ω.cm, preferably >1.0×10 16 Ω.cm and <1.0×10 17 Volume resistivity (VR) in Ω·cm, measured according to ASTM D257-14 (2021) for a period of 600 seconds under an applied voltage of 1000V and at a temperature of 25°C;

[0077] b) A melting peak temperature ≥60°C and ≤75°C, preferably ≥65°C and ≤72°C, is determined using differential scanning calorimetry (DSC) according to ASTM D3418-15, for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, with nitrogen purge gas at a flow rate of 50±5 mL / min, followed by a second heating cycle identical to the first heating cycle;

[0078] c) ≥850 kg / m² when measured according to ASTM D792 (2008). 3 And ≤880kg / m 3 The density;

[0079] d) The β-conversion rate (β) of crosslinking ≥0.4 and ≤0.7 over a time period of 1000 seconds, wherein the β-conversion rate of crosslinking is determined using the following formula:

[0080] β conversion rate (β) = (G'(1000) - G'(0)) / (G'(5000) - G'(0)), where G'(1000) is the storage modulus of the polyolefin composition at 1000 seconds, G'(0) is the storage modulus of the polyolefin composition at 0 seconds, and G'(5000) is the storage modulus of the polyolefin composition at 5000 seconds. The storage modulus is determined according to ISO 6721-10, at 150°C, under nitrogen atmosphere, using a parallel plate with a frequency of 6.28 radians / second and a vibration strain of 0.1%.

[0081] e) Tensile modulus ≥11.0 MPa and ≤25.0 MPa when measured according to ASTM D882 (2018);

[0082] f) Tensile strength at break ≥10.5 MPa and ≤25.0 MPa, as determined according to ASTM D882 (2018);

[0083] g) Hardness of ≥19.0 (Shore hardness D) as measured according to ASTM D2240-15(2021).

[0084] Specifically, the polyolefin composition has a suitable curing time, allowing the composition to crosslink over a relatively short period. A convenient alternative method for determining the ease of crosslinking is to measure the β-conversion rate. In other words, the β-conversion rate represents the degree of crosslinking at a specific time interval, such as 1000 seconds, after the start of the crosslinking reaction. For calculation purposes, a time interval of 5000 seconds is considered to represent a sufficiently long time interval (an infinite time interval from the start of the process) at which a certain degree of crosslinking reaction has been achieved, such as >60%, preferably >80%, more preferably >85%. Preferably, the polyolefin composition has a curing time of >1.0 × 10⁻⁶.15 Ω.cm and <2.0×10 18 Ω.cm, preferably >1.0×10 16 Ω.cm and <1.0×10 17 Volume resistivity (VR) in Ω·cm and crosslinking β conversion (β) of ≥0.4 and ≤0.7 over a 1000-second time period at 150°C indicate that the polyolefin composition can maintain high volume resistivity and even simultaneously exhibit rapid crosslinking properties.

[0085] In some preferred embodiments of the present invention, the present invention relates to a method for preparing a polyolefin composition, wherein the method comprises the following steps:

[0086] a) To supply the extruder with a group of components comprising an ethylene α-olefin copolymer, an ethylene-α-olefin-diene terpolymer, a crosslinking agent, an optional coupling agent, and optional one or more additives; and

[0087] b) Extruding the component at a melting temperature of ≤100°C to form a composition.

[0088] Preferably, in some embodiments of the invention, the component comprises an ethylene-α-olefin copolymer, an ethylene-α-olefin-diene terpolymer, a crosslinking agent, a silane coupling agent, and one or more additives. Preferably, the component is extruded at a melt temperature of ≥55°C and ≤100°C, more preferably at a melt temperature of ≥60°C and ≤80°C, to form a composition. The component may be dry-blended to form a blended mixture outside the extruder, and the blended mixture may subsequently be introduced into the extruder via the extruder hopper. Alternatively, the component may be introduced separately into the extruder via the hopper, such that the component is blended within the extruder and then extruded.

[0089] In some preferred embodiments of the invention, the invention relates to a membrane comprising or composed of the polyolefin composition of the invention. The membrane can be prepared by a method comprising the following steps:

[0090] a) Provide the extruder with a group of components comprising an ethylene α-olefin copolymer, an ethylene-α-olefin-diene terpolymer, a crosslinking agent, an optional coupling agent, and an optional one or more additives;

[0091] b) Extruding the component at a melting temperature ≤100℃ to form an extrudate;

[0092] c) Cast the extrudate at a temperature ≤100°C to form a film.

[0093] In some embodiments of the invention, the component comprises an ethylene-α-olefin copolymer, an ethylene-α-olefin-diene terpolymer, a crosslinking agent, a silane coupling agent, and one or more additives. Preferably, during membrane production, the component is extruded at a melt temperature of ≥55°C and ≤100°C, more preferably at a melt temperature of ≥60°C and ≤80°C, and an extrudate is formed. The extrudate can be further cast to form a membrane. The casting of the membrane can be carried out at any suitable temperature of ≥70°C and ≤100°C. In some embodiments of the invention, the membrane thus obtained can be further heated and subsequently stretched to form an oriented membrane, such as a biaxially oriented membrane.

[0094] Once formed, the film can be used to prepare a sealing layer suitable for use in photovoltaic modules or other electronic modules. For example, in some embodiments of the invention, the invention relates to an encapsulated solar cell comprising a solar cell located between a first sealing layer and a second sealing layer, wherein the first and second sealing layers each comprise or consist of the film of the invention, wherein the solar cell can be placed such that the first and second sealing layers are connected to completely encapsulate the solar cell. The film may have a suitable thickness. For example, the film has a cross-sectional thickness of ≥200 μm and ≤800 μm, preferably ≥300 μm and ≤500 μm.

[0095] The solar cells used in the context of this 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 understand what type of electrical connection is used; for example, the electrical conductor may be a metal strip, such as a strip containing copper, aluminum and / or silver, or, alternatively, a metal wire.

[0096] Encapsulated solar cells can undergo further processing, such as curing, to make them suitable for use in photovoltaic modules. For example, in some embodiments of the invention, the invention relates to cured solar cells obtained by subjecting the encapsulated solar cells to conditions sufficient to cure a first sealing layer and a second sealing layer.

[0097] Cured solar cells can be prepared by a method including the following steps:

[0098] (a) Providing a first sealing layer, a second sealing layer, and a solar cell;

[0099] (b) Assemble the first sealing layer, the solar cell, and the second sealing layer to form an encapsulated solar cell;

[0100] (c) Curing the encapsulated solar cell under conditions sufficient to cure the first and second sealing layers to form a cured solar cell.

[0101] As used herein, the term "curing" means crosslinking the various components of a polyolefin composition under heat or radiation or chemically. Preferably, crosslinking can be achieved by any of a variety of different methods known to those skilled in the art, for example by using: thermally activated initiators, such as peroxides and azo compounds; photoinitiators, such as benzophenone; radiation techniques, including sunlight, UV light, electron beams, and X-rays; silanes, such as vinyltriethoxysilane or vinyltrimethoxysilane; and moisture curing. Preferably, organic peroxides are used for crosslinking. As used herein, the term "cured solar cell" means a solar cell encapsulated in a sealing layer, wherein the sealing layer has been cured under conditions sufficient to induce crosslinking within the sealing layer.

[0102] Preferably, the curing process is carried out by heating. The heat curing step can be carried out, for example, at any temperature ≥135°C and ≤150°C, preferably ≥140°C and ≤145°C. The curing step can be carried out, for example, for a period of ≤1 hour, preferably ≤30 minutes, preferably ≤20 minutes and ≥3 minutes. Advantageously, the sealing layer consists of a film having a polyethylene composition, which allows for curing in a relatively short time while maintaining a sufficiently high volume resistivity.

[0103] Therefore, in some embodiments of the present invention, the present invention relates to the use of polyolefin compositions or films for shortening crosslinking time during the production of photovoltaic modules.

[0104] For example, once formed, the cured solar cell can be integrated with various components of a photovoltaic module. Preferably, in some embodiments of the invention, the invention relates to a photovoltaic module incorporating the cured solar cell of the invention. Preferably, the photovoltaic module may include:

[0105] a) Front protective component;

[0106] b) Rear protective components;

[0107] c) A solidified solar cell, wherein the solidified solar cell is located between the front protective member and the rear protective member.

[0108] Preferably, the present invention relates to a photovoltaic module comprising the cured solar cell of the present invention, and more preferably, the photovoltaic module comprises:

[0109] a) Front protective component;

[0110] b) Rear protective components;

[0111] c) A solidified solar cell, wherein the solidified solar cell is located between the front protective member and the rear protective member.

[0112] The front and rear protective components can be made of suitable materials, such as polypropylene. The photovoltaic module can be manufactured, for example, by placing a cured solar cell between the front and rear protective components and then laminating the cured solar cell between the front and rear protective components through heat treatment.

[0113] Alternatively, the solidified solar cells can be manufactured in situ during the production of the photovoltaic module itself. For example, in some embodiments of the invention, the photovoltaic module is prepared by a method comprising:

[0114] (a) Assemble a front protective member, a first sealing layer, a second sealing layer, a solar cell, and a rear protective member to form a photovoltaic module having: i) encapsulated solar cells comprising a solar cell located between the first sealing layer and the second sealing layer; ii) a first sealing layer in contact with the front protective member; and iii) a second sealing layer in contact with the rear protective layer;

[0115] (b) subjecting the photovoltaic module to pressure and heat conditions, such that at least a portion of the sealing layer melts to form a laminated photovoltaic module;

[0116] (c) subjecting the laminated photovoltaic module to curing conditions to form a photovoltaic module containing cured solar cells.

[0117] In some embodiments of the present invention, the assembly step involves assembling various components of the photovoltaic module in a specific sequence to form the photovoltaic module. The steps for preparing the photovoltaic module may include:

[0118] a) Provide rear protective components;

[0119] b) Place the second sealing layer on the rear protective member so that the second sealing layer contacts the rear protective member;

[0120] c) Place the solar cell on the second sealing layer, such that the second sealing layer is located between the solar cell and the rear protective member;

[0121] d) Place the first sealing layer on the solar cell, such that the solar cell is located between the first sealing layer and the second sealing layer;

[0122] e) Place the front protective member on the first sealing layer, such that the first sealing layer is located between the front protective member and the solar cell;

[0123] f) subject the above components to another set of processing steps, including curing, to form a photovoltaic module.

[0124] Optionally, the cured laminated assembly can be cooled to form a photovoltaic module. Preferably, the assembly is heated to a temperature during the heating step such that the front and rear protective components do not melt. For example, the temperature of this heating step can be selected such that the front protective component reaches a temperature at least 5°C below the melting temperature of the preceding layer. In practice, the temperature of the heating step is selected to be as high as possible to achieve maximum adhesion between the sealing layer and the protective layer, but at the same time, the temperature cannot be too high so that the front and rear layers remain solid.

[0125] The following includes specific embodiments illustrating some implementations of the invention. These embodiments are for illustrative purposes only and are not intended to limit the invention. It should be understood that the embodiments and aspects disclosed herein are not mutually exclusive, and these aspects and embodiments can be combined in any manner. Those skilled in the art will readily recognize that parameters can be changed or modified to produce substantially the same results. Example

[0126] Objective: For the purpose of illustrating the present invention, four inventive formulations (IE1-IE3) were prepared, and their properties were compared with those of a comparative formulation (CE1). Details of the formulations are provided below:

[0127] Table 1

[0128]

[0129] Preparation method: Approximately 50 g by weight of the above formulation was prepared by dry blending C13075DP, EPDM 3720, and DCP peroxide in a twin-screw extruder. The blend was then extruded at a rate of 15 kg / h below 100°C to obtain a sample. The resulting sample was further cast in a single-screw extruder at 90°C to form a 400 μm thick encapsulation sheet. The resulting sample was further subjected to crosslinking or curing conditions at 150°C.

[0130] Testing: For the measurement of β-conversion, the storage modulus was determined according to ISO 6721-10. Rheological measurements were performed at 150°C using an ARES-G2 rheometer with 25 mm parallel plates. Frequency sweeps were performed at a frequency of 6.28 radians / second and a vibrational strain of 0.1%. For the determination of β-conversion, the storage modulus was measured over a period of time from 0 seconds to 5000 seconds after the onset of crosslinking.

[0131] Volume resistivity can be measured according to ASTM D257-14 (2021) for a period of 600 seconds under an applied voltage of 1000V and at a temperature of 25°C.

[0132] The results of the test analysis are provided below.

[0133] Table 2

[0134]

[0135] It is evident from the data provided in Table 2 that as the concentration of EPDM present in the inventive polyolefin compositions (IE1-IE3) increases, the crosslinking time shortens, as indicated by the higher β conversion values ​​(e.g., IE3 vs. CE3). Advantageously, the inventive polyolefin compositions are able to maintain sufficiently high volume resistivity, making them suitable for use in the manufacture of photovoltaic modules.

Claims

1. A polyolefin composition comprising: a) ≥ 60.0% by weight and ≤ 99.0% by weight of ethylene α-olefin copolymer relative to the total weight of the polyolefin composition; The ethylene α-olefin copolymer further comprises at least one of the following: i. Melting peak temperature ≥ 60°C and ≤ 90°C, determined by differential scanning calorimetry according to ASTM D3418-15, for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, with nitrogen purge gas at a flow rate of 50 ± 5 mL / min, followed by a second heating cycle identical to the first heating cycle; ii. ≥ 20.0% by weight and ≤ 45.0% by weight of polymeric units derived from one or more α-olefins having 3-12 carbon atoms, relative to the total weight of the ethylene α-olefin copolymer; iii. When measured according to ASTM D6248-98 (2012), ≥ 6.0 per 10 5 Vinyl unsaturation of 1 carbon atom; b) ≥ 1.0% by weight and ≤ 35.0% by weight of an ethylene-α-olefin-diene terpolymer relative to the total weight of the polyolefin composition, wherein, when measured according to ASTM D6248-98 (2012), the ethylene-α-olefin-diene terpolymer contains ≥ 20.0% and ≤ 100.0% per 10 5 The total vinyl and vinylidene unsaturation of carbon atoms; and c) Crosslinking agent of ≥ 0.1% by weight and ≤ 5.0% by weight relative to the total weight of the polyolefin composition.

2. The polyolefin composition of claim 1, wherein the ethylene α-olefin copolymer comprises a polymerization unit derived from ethylene and one or more α-olefins selected from 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, or combinations thereof.

3. The polyolefin composition according to claim 2, wherein the α-olefin is selected from 1-butene or 1-octene.

4. The polyolefin composition according to claim 1, wherein the ethylene α-olefin copolymer has a melting peak temperature of ≥ 65°C and ≤ 75°C, and is measured using differential scanning calorimetry according to ASTM D3418-15, for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, with nitrogen purge gas at a flow rate of 50 ± 5 mL / min, followed by a second heating cycle identical to the first heating cycle.

5. The polyolefin composition according to claim 1, wherein the ethylene α-olefin copolymer has ≥ 28.0% by weight and ≤ 40.0% by weight of polymeric units derived from one or more α-olefins having 3-12 carbon atoms relative to the total weight of the ethylene α-olefin copolymer.

6. The polyolefin composition according to claim 1, wherein the ethylene α-olefin copolymer has ≥ 30.0% by weight and ≤ 40.0% by weight of polymeric units derived from one or more α-olefins having 3-12 carbon atoms relative to the total weight of the ethylene α-olefin copolymer.

7. The polyolefin composition of claim 1, wherein the ethylene α-olefin copolymer has a content of ≥ 7.0 per 10 when measured according to ASTM D6248-98 (2012). 5 Vinyl unsaturation of 1 carbon atom.

8. The polyolefin composition of claim 1, wherein the ethylene α-olefin copolymer has a content of ≥ 12.0 per 10 when measured according to ASTM D6248-98 (2012). 5 Vinyl unsaturation of 1 carbon atom.

9. The polyolefin composition of claim 1, wherein, when measured according to ASTM D6248-98 (2012), the ethylene-α-olefin-diene terpolymer contains ≥ 30.0 and ≤ 80.0 per 10 5 Total vinyl and vinylidene unsaturation of carbon atoms.

10. The polyolefin composition according to any one of claims 1-9, wherein the ethylene α-olefin copolymer has at least one of the following: a) Melt flow rate ≥ 5.0 g / 10 min and ≤ 25.0 g / 10 min, measured at 190°C with a 2.16 kg load according to ASTM D1238 (2013); and / or b) ≥ 850 kg / m³ when measured according to ASTM D792 (2008) 3 And ≤ 900 kg / m 3 The density.

11. The polyolefin composition of claim 10, wherein the ethylene α-olefin copolymer has a melt flow rate ≥ 10.0 g / 10 min and ≤ 20.0 g / 10 min when measured at 190°C with a 2.16 kg load according to ASTM D1238 (2013).

12. The polyolefin composition of claim 10, wherein the ethylene α-olefin copolymer has a melt flow rate ≥ 11.0 g / 10 min and ≤ 15.0 g / 10 min when measured at 190°C with a 2.16 kg load according to ASTM D1238 (2013).

13. The polyolefin composition of claim 10, wherein the ethylene α-olefin copolymer has a strength of ≥ 870 kg / m³ as determined according to ASTM D792 (2008). 3 And ≤ 880 kg / m 3 The density.

14. The polyolefin composition according to any one of claims 1-9, wherein the ethylene-α-olefin-diene terpolymer comprises a polymeric unit derived from: (i) ethylene; (ii) one or more α-olefins comprising 3-12 carbon atoms; and (iii) a diene selected from the group consisting of: 5-ethylidene-2-norbornene, 5-propylidene-5-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, 5-Methylene-2-norbornene, 5-isopropylidene-2-norbornene, norbornadiene, 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 5-methyl-1,5-heptadiene, 6-methyl-1,5-heptadiene, 6-methyl-1,7-octadiene, 1,6-octadiene, 3,7-dimethyl-1,6-octadiene, 2,5-norbornadiene, and 7-methyl-1,6-octadiene.

15. The polyolefin composition according to claim 14, wherein the one or more α-olefins comprising 3-12 carbon atoms are selected from the group consisting of propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene.

16. The polyolefin composition according to claim 14, wherein the ethylene-α-olefin-diene terpolymer is an ethylene / propylene / 5-ethylidene-2-norbornene copolymer.

17. The polyolefin composition according to any one of claims 1-9, wherein the crosslinking agent is an organic peroxide selected from the group consisting of: 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 3-di-tert-butylperoxide, tert-diisopropylbenzene peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne, diisopropylbenzene peroxide, α,α'-bis(tert-butylperoxide isopropyl)benzene, n-butyl-4,4-bis(tert-butylperoxide)butane, 2,2-di(tert-butylperoxide)butane, 1,1-bis(tert-butylperoxide)cyclohexane, tert-butylperoxide-2-ethylhexyl carbonate, tert-butylperoxide benzoate, 1,6-di(tert-butylperoxide carbonyloxy)hexane, and combinations thereof.

18. The polyolefin composition according to claim 17, wherein the crosslinking agent is dicumyl peroxide.

19. The polyolefin composition according to any one of claims 1-9, wherein the polyolefin composition further comprises, by weight relative to the total weight of the polyolefin composition: a) Coupling agents ≥ 0.05% by weight and ≤ 5.0% by weight; and b) One or more additives, ≥ 0.05% by weight and ≤ 5.0% by weight; The one or more additives mentioned therein are selected from: antioxidants, heat stabilizers, deacidifiers, mold release agents, plasticizers, hindered amine light stabilizers, antistatic additives, non-phenolic processing stabilizers, lubricants, antistatic agents, antiscratch agents, recycling additives, clarifying agents, processing stabilizers, antimicrobial agents, antifogging additives, slip additives, anti-blocking additives, non-phenolic processing stabilizers, or combinations thereof.

20. The polyolefin composition according to any one of claims 1-9, wherein the composition comprises, by weight relative to the total weight of the polyolefin composition: a) ≥ 60.0% by weight and ≤ 99.0% by weight of the ethylene α-olefin copolymer; b) ≥ 1.0% by weight and ≤ 35.0% by weight of the ethylene-α-olefin-diene terpolymer; c) ≥ 0.1% by weight and ≤ 5.0% by weight of the crosslinking agent; d) Coupling agent ≥ 0.05% by weight and ≤ 5.0% by weight; and e) One or more additives, ≥ 0.05% by weight and ≤ 5.0% by weight.

21. The polyolefin composition according to any one of claims 1-9, wherein the polyolefin composition has at least one of the following: a)> 1.0×10 15 Volume resistivity in Ω·cm, measured according to ASTM D257-14 (2021) for a period of 600 seconds under an applied voltage of 1000 V and at a temperature of 25°C; b) Melting peak temperature ≥ 60℃ and ≤ 75℃, determined by differential scanning calorimetry according to ASTM D3418-15, for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23℃ to 200℃ and a heating and cooling rate of 10℃ / min, with nitrogen purge gas at a flow rate of 50 ± 5 mL / min, followed by a second heating cycle identical to the first heating cycle; c) ≥ 850 kg / m³ when measured according to ASTM D792 (2008) 3 And ≤ 880 kg / m 3 The density; d) The β-conversion rate of crosslinking at 150°C for a time period of 1000 seconds ≥ 0.4 and ≤ 0.7, wherein the β-conversion rate of crosslinking is determined by using the following formula: β conversion rate = (G'(1000) - G'(0)) / (G'(5000) - G'(0)), where G'(1000) is the storage modulus of the polyolefin composition at 1000 seconds, G'(0) is the storage modulus of the polyolefin composition at 0 seconds, and G'(5000) is the storage modulus of the polyolefin composition at 5000 seconds, wherein the storage modulus is determined according to ISO 6721-10, at 150°C, under nitrogen atmosphere, using a parallel plate setup with a frequency of 6.28 radians / second and vibration strain of 0.1%; e) Tensile modulus ≥ 11.0 MPa and ≤ 25.0 MPa when measured according to ASTM D882 (2018); f) Tensile strength at break ≥ 10.5 MPa and ≤ 25.0 MPa, as determined according to ASTM D882 (2018); and g) Hardness of ≥ 19.0, i.e. Shore hardness D, as determined according to ASTM D2240-15 (2021).

22. The polyolefin composition according to claim 21, wherein the polyolefin composition has a particle size of > 1.0 × 10⁻⁶. 15 Ω.cm and < 2.0×10 18 Volume resistivity in Ω·cm, measured according to ASTM D257-14 (2021) for a period of 600 seconds under an applied voltage of 1000 V and at a temperature of 25°C.

23. The polyolefin composition according to claim 21, wherein the polyolefin composition has a particle size of > 1.0 × 10⁻⁶. 16 Ω.cm and < 1.0×10 17 Volume resistivity in Ω·cm, measured according to ASTM D257-14 (2021) for a period of 600 seconds under an applied voltage of 1000 V and at a temperature of 25°C.

24. The polyolefin composition of claim 21, wherein the polyolefin composition has a melting peak temperature of ≥ 65°C and ≤ 72°C, and is determined by differential scanning calorimetry according to ASTM D3418-15, for a 10 mg membrane sample, using a first heating and cooling cycle at a temperature of 23°C to 200°C and a heating and cooling rate of 10°C / min, with nitrogen purge gas at a flow rate of 50 ± 5 mL / min, followed by a second heating cycle identical to the first heating cycle.

25. A method for preparing a polyolefin composition according to any one of claims 1-24, wherein the method comprises the following steps: a) To supply the extruder with a group of components comprising an ethylene α-olefin copolymer, an ethylene-α-olefin-diene terpolymer, a crosslinking agent, an optional coupling agent, and optional one or more additives; and b) Extruding the components at a melting temperature ≤ 100°C to form the composition.

26. A membrane comprising or consisting of a polyolefin composition according to any one of claims 1-24.

27. A method for preparing the membrane of claim 26, wherein the method comprises the following steps: a) Provide the extruder with a group of components comprising an ethylene α-olefin copolymer, an ethylene-α-olefin-diene terpolymer, a crosslinking agent, an optional coupling agent, and an optional one or more additives; b) Extruding the components at a melting temperature ≤ 100°C to form an extrudate; c) Cast the extrudate at a temperature ≤ 100°C to form the film.

28. An encapsulated solar cell comprising a solar cell located between a first sealing layer and a second sealing layer, wherein the first sealing layer and the second sealing layer each comprise or consist of the film of claim 26, wherein the solar cell is positioned such that the first sealing layer and the second sealing layer are connected to completely encapsulate the solar cell.

29. A cured solar cell, obtained by subjecting the encapsulated solar cell of claim 28 to conditions sufficient to cure the first sealing layer and the second sealing layer.

30. A method comprising the following steps: (a) Providing the first sealing layer, the second sealing layer, and the solar cell as claimed in claim 28; (b) Assemble the first sealing layer, the solar cell, and the second sealing layer to form an encapsulated solar cell; (c) The encapsulated solar cell is cured under conditions sufficient to cure the first sealing layer and the second sealing layer to form a cured solar cell.

31. A photovoltaic module comprising a solidified solar cell according to claim 29.

32. The photovoltaic module according to claim 31, wherein the photovoltaic module comprises: a) Front protective component; b) Rear protective components; c) The cured solar cell, wherein the cured solar cell is located between the front protective member and the rear protective member.

33. Use of the polyolefin composition according to any one of claims 1-24 or the film according to claim 26 for shortening the crosslinking time during the production of photovoltaic modules.

Images