Use of a mixture of organic peroxides for the crosslinking of polyolefin elastomers

Abstract

The present invention relates to the use of a mixture of organic peroxides for crosslinking polyolefin elastomers (POE), in particular intended for use in photovoltaic applications. The present invention also relates to a crosslinkable composition comprising at least one polyolefin elastomer (POE) and a mixture of at least one organic peroxide. The present invention also relates to a method for preparing a material, preferably an encapsulant or sealant, made of polyolefin elastomer (POE), in particular for photovoltaic cells, comprising the step of crosslinking such a crosslinkable composition.

Description

Disclosure of the Invention

[0001] The present invention relates to the use of a mixture of organic peroxides, defined below, for crosslinking a polyolefin elastomer (POE), preferably a copolymer of ethylene and at least one alpha-olefin, which is particularly intended for use in photovoltaic applications.

[0002] The present invention also relates to a crosslinkable composition comprising at least one polyolefin elastomer (POE), preferably a copolymer of ethylene and at least one alpha-olefin, and at least one mixture of organic peroxides defined below.

[0003] The present invention also relates to a method for producing a material based on a polyolefin elastomer (POE), preferably an encapsulating material particularly for photovoltaic cells, comprising the step of crosslinking the crosslinkable composition defined above.

[0004] The present invention likewise relates to polyolefin elastomers, preferably materials based on copolymers of ethylene and at least one alpha-olefin, obtainable by the above method, and to photovoltaic modules comprising such materials.

[0005] The role of a photovoltaic module (also called a solar panel or solar collector) is generally to convert incident solar energy into electrical energy so as to generate electricity in the form of a continuous current.

[0006] A photovoltaic module mainly consists of semiconductors and corresponds in particular to an assembly of photovoltaic cells (also called solar cells) arranged side by side between a first transparent layer forming the front face of the module and a second layer forming the rear face of the module.

[0007] The first layer forming the front face of the module is generally made using a transparent solid glass sheet so that the photovoltaic cells can receive a light beam.

[0008] The second layer forming the rear face (or backing) of the module can be made of a flexible material, such as plastic, or a glass or metal material. In particular, both the front and rear faces of the module can be made of glass sheets (the manufacturing method of which is called the double-glass process). Furthermore, this film is generally colored with a titanium oxide type pigment, optionally in combination with other fillers (such as those of the type calcium carbonate, talc, silica, etc.), so as to reflect light towards the top of the module and to transmit part of the radiation that is usually lost with a single glass panel to the cells.

[0009] In the case of a single glass panel, the second layer forming the rear face of the module preferably consists of a multilayer assembly made of a thin film of an electrically insulating polymer, such as polyethylene terephthalate (PET) or polyamide (PA) for example, on top of which there is one or more thin films based on polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF), and on top of that layer there is a layer of metal, such as aluminum, to protect the module from possible mechanical shocks. In that case, the rear face of the module can be made of this type of multilayer assembly, while the front face of the module is made of a glass sheet.

[0010] The photovoltaic cells are electrically connected to each other (in series or in parallel) and are encapsulated in order to provide electrical insulation to them and protection from adverse weather conditions such as moisture, rain or snow, and external environmental factors such as ultraviolet light.

[0011] The material used for encapsulating the photovoltaic cells, preferably in the form of a film, is currently designed based on homopolymers or copolymers of ethylene. More specifically, copolymers of ethylene and vinyl acetate (EVA) are particularly advantageous for such encapsulation implementations, because they can produce transparent materials that can easily adhere to the substrate of the photovoltaic module while having a high electrical resistivity. For these reasons, EVA-based resins currently occupy most of the market.

[0012] Particularly with regard to good adhesion properties, creep resistance, and weathering resistance to adverse weather conditions for the module substrate, in order to obtain satisfactory thermomechanical properties from the perspective of the present application, it is important to crosslink the ethylene-vinyl acetate copolymer and obtain a good crosslink density. In fact, if the crosslink density is too low, the resulting material may be troubled by, among other things, insufficient tear and fracture resistance and may flow over time in the presence of the high temperatures that the upper surface of the photovoltaic panel can reach. Typically used crosslinking agents are peroxides such as dicumyl peroxide (DCP), peroxy esters, peroxy ketals, peroxy carbonates, dialkyl peroxides, and mixtures thereof. As an example of a monoperoxy carbonate, for crosslinking an ethylene-vinyl acetate (EVA) copolymer, it is a well-known practice to use OO-tert-amyl O-2-ethylhexyl monoperoxy carbonate (TAEC), OO-tert-butyl O-2-ethylhexyl monoperoxy carbonate (TBEC), OO-tert-isobutyl O-isopropyl monoperoxy carbonate (TBIC), or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0013] Therefore, in a method for manufacturing a photovoltaic module, the solar cells and their conductors are arranged between two layers (or films) obtained from a composition based on an ethylene-vinyl acetate copolymer and one or more crosslinking agents. This type of manufacturing method includes a single step of laminating the various layers that form the photovoltaic module at a specific temperature over a given period during which the EVA-based composition is crosslinked. Thus, the various layers of the module are pressed against each other, and the solar cells will be covered with a transparent EVA-based material.

[0014] Nevertheless, under the influence of ultraviolet rays and moisture, EVA tends to undergo chemical decomposition and release acetic acid, which has been observed to accelerate the corrosion of solar cells and even cause yellowing or browning of the material encapsulating the cells. Such phenomena can also induce changes in the transmittance of the incident light beam in the solar cells, thereby reducing their power over the long term.

[0015] Furthermore, this yellowing defect may be accompanied by a decrease in the adhesion between the encapsulation material and the various layers of the module, resulting in, on the one hand, water penetration into the interior of the module and, on the other hand, the formation of air bubbles trapped between the encapsulation material and the front and / or rear faces of the module. The formation of these air bubbles causes swelling between the encapsulation material and the face of the module, particularly the rear face, thereby causing an unattractive visible surface trace appearance (referred to as a snail trail). The presence of these air bubbles also makes it more difficult to dissipate heat from the solar cell, thereby increasing the overheating of the solar cell and affecting their lifespan. Alternatively, materials based on EVA have the disadvantage of being permeable under humid specific heat conditions.

[0016] Furthermore, photovoltaic modules manufactured with EVA also have the drawback of being particularly sensitive to the gradual deterioration of the electrical characteristics of the cells due to the presence of parasitic leakage current. This phenomenon is known as potential-induced degradation (PID).

[0017] In order to overcome the various drawbacks mentioned above, proposals have already been made in the prior art to manufacture materials used for encapsulating solar cells using compounds other than EVA. Examples include polyvinyl butyrate (PVB), silicone rubber, or polyolefin elastomer (POE), which aim to obtain materials with lower permeability than those prepared with EVA under humid specific heat conditions.

[0018] More specifically, the use of polyolefin elastomers has proven to be advantageous for manufacturing materials intended for encapsulating solar cells, because these materials have a high electrical resistivity along with low permeability under humid specific heat conditions. Polyolefin elastomers have particularly good performance characteristics in photovoltaic modules whose front and rear faces are manufactured using glass sheets.

[0019] However, it has been demonstrated that polyolefin elastomers are more difficult to crosslink than ethylene-vinyl acetate copolymers in the presence of the same crosslinking agent and under the same operating conditions. More specifically, the method of crosslinking polyolefin elastomers may require, in particular, a higher crosslinking temperature, a higher concentration of peroxide, and / or a longer crosslinking time than those used for ethylene-vinyl acetate copolymers. This result represents a substantial decrease in productivity in industries that utilize polyolefin elastomers as a substitute for ethylene-vinyl acetate copolymers.

[0020] To overcome this difficulty, Patent Publication No. 2017-085032 describes the use of copolymers of ethylene and alpha-olefins crosslinked in the presence of tert-amyl peroxy isopropyl monocarbonate (TAIC) in photovoltaic applications. By using this type of crosslinking agent, satisfactory crosslinking rates and densities are made possible compared to those obtained for copolymers of ethylene and alpha-olefins under similar operating conditions.

[0021] However, tert-amyl peroxy isopropyl monocarbonate (TAIC) is associated with the risk of premature crosslinking of polyolefin elastomers, especially in the barrel or at the head of the extruder, before the process of laminating the various layers useful for the manufacture of photovoltaic modules is carried out. This phenomenon of premature crosslinking (also called scorching) results in the formation of gel particles in the mass of the mixture, which causes a certain number of irregularities (non-uniformities, surface roughness) in the encapsulating material and can ultimately affect the appearance and characteristics of the photovoltaic module. Furthermore, excessive scorching can lead to a complete stoppage of the extrusion process and reduce the productivity of the material.

[0022] Alternatively, a reduction in scorching is likely to affect both the final properties of the photovoltaic module and their productivity.

[0023] Accordingly, one of the objectives of the present invention is to obtain a material with thermomechanical properties suitable for the desired applications, while minimizing the risk of premature crosslinking (or scorch) that can easily affect the productivity and final properties of the material. In particular, it is to use a compound having good properties for crosslinking polyolefin elastomers, which can bring about satisfactory crosslinking speed and density.

[0024] In other words, there is a real need to provide a compound that can effectively crosslink polyolefin elastomers under operating conditions similar to those used for ethylene-vinyl acetate copolymers, while minimizing the risk of scorch or premature crosslinking.

[0025] From the above perspective, the objective of the present invention is, more specifically, to provide a material, preferably intended for encapsulating solar cells in a photovoltaic module, which has not only a higher electrical resistivity but also a lower permeability than that of a material obtained from an ethylene-vinyl acetate copolymer under wet specific heat conditions.

[0026] Accordingly, the present invention particularly relates to - at least one monoperoxycarbonate corresponding to formula (I): TIFF0007685836000001.tif19170[In formula (I), R 1 represents an alkyl group containing 6 or fewer carbon atoms, and R 2 represents an alkyl group] - at least one monoperoxycarbonate corresponding to the following formula (II): TIFF0007685836000002.tif19170[In formula (II), R 1 represents an alkyl group containing 7 or more carbon atoms, and R 2 represents an alkyl group] and provides the use of a composition containing the same for crosslinking polyolefin elastomers.

[0027] The composition preferably contains less than exactly 0.4% by weight of tert-alkyl hydroperoxide, calculated on 100 parts by weight of the mixture of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II). The term "less than exactly 0.4%" means from 0 to 0.4% by weight, meaning that the endpoint 0% is included and the endpoint 0.4% is excluded.

[0028] The composition preferably lacks tert-alkyl hydroperoxide, present in an amount of from 0.4 to less than 4% by weight, calculated on 100 parts by weight of the mixture of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II).

[0029] The composition preferably lacks tert-alkyl hydroperoxide, present in an amount of from 0.4 to less than 4% by weight, calculated on the total content of monoperoxycarbonate of the composition. More preferably, the composition lacks tert-alkyl hydroperoxide.

[0030] Alternatively, the present invention relates to the use of a mixture of at least two different monoperoxycarbonates corresponding to formulas (I) and (II) respectively, for crosslinking a polyolefin elastomer, preferably a copolymer of ethylene and at least one alpha-olefin, wherein the mixture contains less than exactly 0.4% by weight of dialkyl hydroperoxide, calculated on 100 parts by weight of the mixture.

[0031] Thus, the composition of the present invention has the advantage of providing a satisfactory crosslinking rate and crosslinking density while minimizing the risk of scorch or premature crosslinking that could impair productivity and the final properties of the resulting material.

[0032] In other words, the composition of the present invention allows an increase in scorch resistance time without impairing the overall crosslinking rate and crosslinking density of the polyolefin elastomer.

[0033] More specifically, the composition of the present invention enables the preservation of good cross-linking properties obtained with tert-amyl peroxy isopropyl monocarbonate, while particularly reducing the risk of premature cross-linking.

[0034] Furthermore, the composition of the present invention enables effective cross-linking of polyolefin elastomers, preferably copolymers of ethylene and at least one alpha-olefin, under operating conditions similar to those used for copolymers of ethylene and vinyl acetate.

[0035] The present invention also relates to a crosslinkable composition comprising at least one polyolefin elastomer (preferably a copolymer of ethylene and at least one alpha-olefin), at least one monoperoxycarbonate corresponding to formula (I) as described above, and at least one monoperoxycarbonate different from the monoperoxycarbonate of formula (I) and corresponding to formula (II) as described above.

[0036] The composition preferably contains less than exactly 0.4% by weight of tert-alkyl hydroperoxide, calculated relative to the mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II). "Less than exactly 0.4%" means from 0 to 0.4% by weight, with the 0% endpoint included and the 0.4% endpoint excluded.

[0037] The composition preferably lacks tert-alkyl hydroperoxide in an amount of from 0.4 to less than 4% by weight, calculated relative to the mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II). The composition preferably lacks tert-alkyl hydroperoxide in an amount of from 0.4 to less than 4% by weight, calculated relative to the total content of monoperoxycarbonate in the composition. More preferably, the composition lacks tert-alkyl hydroperoxide.

[0038] The crosslinkable composition of the present invention has high productivity and provides access to materials, particularly preferably encapsulation or sealing materials for solar cells, having thermomechanical properties suitable for the desired applications.

[0039] Thus, the crosslinkable composition of the present invention shows the advantage of undergoing crosslinking during the method for manufacturing a photovoltaic module.

[0040] Furthermore, the present invention also relates to a method for manufacturing a material, which includes a step of crosslinking a crosslinkable composition as described above.

[0041] The method of the present invention has the advantage of providing a material having good thermomechanical properties and minimizing the possible coarsening of its structure.

[0042] Similarly, another subject of the present invention relates to a material containing at least one polyolefin elastomer (preferably a copolymer of ethylene and at least one alpha olefin) obtainable by the above method.

[0043] The material has the advantage of having good electrical resistivity and low permeability under wet specific heat conditions compared to a material obtained from an ethylene-vinyl acetate copolymer.

[0044] Furthermore, this material shows no (or almost no) significant surface defects due to its scorch resistance.

[0045] The obtained material is preferably a material for encapsulating a solar cell.

[0046] The present invention also relates to a photovoltaic module containing such a material for encapsulating a solar cell.

[0047] The photovoltaic module shows enhanced properties due to the presence of the encapsulation material.

[0048] Other features and advantages of the present invention will become clearer upon reading the following description and examples.

[0049] Unless otherwise indicated, the endpoints of a range of values are included in this range.

[0050] The expression "at least one" is equivalent to the expression "one or more".

[0051] Use According to the present invention, the above composition enables crosslinking of a polyolefin elastomer, preferably a copolymer of ethylene and at least one alpha-olefin.

[0052] "Polyolefin" in the meaning of the present invention means a polymer derived from olefins such as ethylene, propylene, butene, hexene, etc.

[0053] "Derived from" in the meaning of the present invention means that the units of the polymer main chain and / or the adjacent chains (or pendant chains) of the polymer are due to the polymerization or copolymerization of the monomers from which the polymer is made.

[0054] "Polyolefin elastomer" in the meaning of the present invention means an elastomeric polymer derived from olefins such as ethylene, propylene, butene, hexene, etc.

[0055] "Elastomer" in the meaning of the present invention means a polymer that can recover its initial shape with a residual deformation of less than 5% compared to the initial shape when, at ambient temperature for 15 minutes, preferably, it undergoes at least 20% uniaxial deformation and preferably the stress has disappeared.

[0056] The polyolefin elastomer according to the present invention is advantageously derived from ethylene. In other words, the polyolefin elastomer preferably contains at least one unit obtained from ethylene.

[0057] The polyolefin elastomer according to the present invention preferably further contains at least one alpha olefin.

[0058] The polyolefin elastomer preferably contains an alpha olefin in an amount of at least 15% by weight, preferably at least 20% by weight, more preferably at least 25% by weight, calculated based on the total weight of the polymer.

[0059] The polyolefin elastomer preferably contains an alpha olefin content of less than 50% by weight, preferably less than 45% by weight, more preferably less than 35% by weight, calculated based on the total weight of the polymer.

[0060] Therefore, the polyolefin elastomer may contain an alpha olefin content of 15% to 50% by weight, preferably 15% to 45% by weight, more preferably 15% to 35% by weight, even more preferably 20% to 35% by weight, calculated based on the total weight of the polymer.

[0061] The alpha olefin content in the polymer can be measured by carbon-13 nuclear magnetic resonance (NMR) spectroscopy according to the protocol described by Randall (Rev. Macromol Chem. Phys., C29(2 and 3)).

[0062] The alpha olefin is preferably a linear, branched or cyclic C 3 -C 20 alpha olefin.

[0063] Preferably, the alpha olefin is a linear or branched C 3 -C 20 alpha olefin.

[0064] C 3 -C 20The alpha olefin is preferably selected from the group consisting of propene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and 1-octadecene.

[0065] The alpha olefin may also contain a cyclic structure that gives rise to alpha olefins such as 3-cyclohexyl-1-propene (allylcyclohexane) and vinylcyclohexane, for example cyclohexane or cyclopentane.

[0066] Certain cyclic olefins, such as norbornene and the corresponding olefins, may be considered alpha olefins in the context of the present invention and may be used in place of the above alpha olefins.

[0067] The polyolefin elastomer is preferably a copolymer of ethylene and an alpha olefin, particularly a linear or branched C 3 -C 20 alpha olefin.

[0068] The polyolefin elastomer is preferably a copolymer of ethylene and at least one alpha olefin, particularly a linear or branched C 3 -C 20 alpha olefin.

[0069] The polyolefin elastomer is preferably a copolymer consisting only of ethylene and at least one alpha-olefin, excluding other monomers. The polyolefin elastomer is preferably selected from the group consisting of ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, particularly very low density polyethylene (VLDPE) (e.g., ethylene / 1-hexene polyethylene sold under the name Flexomer® by Dow Chemical Company), ethylene / 1-octene copolymers, ethylene / styrene copolymers, ethylene / propylene / 1-octene copolymers, ethylene / propylene / 1-butene copolymers, ethylene / 1-butene / 1-octene copolymers, and ethylene / 1-butene / styrene copolymers.

[0070] Preferred polyolefin copolymers are selected from the group consisting of linear or uniformly branched copolymers of ethylene and alpha-olefins. Substantially linear ethylene copolymers are particularly preferred and are described in particular in U.S. Patent Nos. 5,272,236, 5,278,272, and 5,986,028.

[0071] Examples of linear and uniformly branched copolymers of ethylene and alpha-olefins include copolymers sold under the name TAFMER® by Mitsui Petrochemicals Company Limited, copolymers sold under the name EXACT® by Exxon Chemical Company, and copolymers sold under the name AFFINITY® by Dow Chemical Company.

[0072] Polyolefin elastomers may also contain copolymers including propylene, 1-butene, and other alkylene-based copolymers, such as copolymers containing a majority of units derived from propylene and a minority of units derived from another alpha olefin (including ethylene). Examples of polypropylenes belonging to the present invention include, in particular, polymers sold under the name VERSIFY® by Dow Chemical Company, and polymers sold under the name VISTAMAXX® by Exxon Mobil Chemical Company.

[0073] The polyolefin elastomer of the present invention preferably has a glass transition temperature (Tg) of less than -35°C, preferably less than -40°C, more preferably -45°C, and even more preferably -50°C, as measured by differential scanning calorimetry (DSC) according to ASTM D-3418-03 procedure.

[0074] The polyolefin elastomer preferably has a melt flow index (MFI) of less than 100 g / 10 min, preferably less than 75 g / 10 min, more preferably less than 50 g / 10 min, and even more preferably less than 35 g / 10 min.

[0075] Advantageously, the polyolefin elastomer has a melt flow index (MFI) of less than 1 g / 10 min, and even more preferably less than 5 g / 10 min.

[0076] The melt flow index (MFI) of the polyolefin elastomer is measured according to methods generally used for characterizing thermoplastic materials, such as the methods described in ASTM standard D1238, NF standard T51-016, or ISO standard 1133, which provide access to information on the extrudability and moldability of the material.

[0077] The referenced MFI value is determined according to ASTM standard D1238 at a temperature of 190°C under a load of 2.16 kg (expressed in g / 10 min).

[0078] The polyolefin elastomer preferably has a density of less than 0.9 g / cc, particularly less than 0.89 g / cc, preferably less than 0.885 g / cc, even more preferably less than 0.88 g / cc, and even more preferably less than 0.875 g / cc.

[0079] The polyolefin elastomer advantageously has a density of more than 0.85 g / cc, even more preferably more than 0.86 g / cc.

[0080] The density of the polyolefin elastomer is measured according to the procedure described in ASTM standard D - 792.

[0081] According to the present invention, the composition used to crosslink the polyolefin elastomer contains at least one monoperoxycarbonate of formula (I) as described above.

[0082] Preferably, in formula (I), R 1 represents a branched alkyl group containing 6 or fewer carbon atoms, and R 2 represents a branched alkyl group.

[0083] Preferably, in formula (I), R 1 and R 2 are different.

[0084] According to formula (I), R 1 is preferably a C 2 -C 5 group. R 1 is preferably a C 3 alkyl group, particularly a branched C 3 alkyl group (isopropyl).

[0085] According to formula (I), R 2 is preferably a C 1 -C 10 preferably a C 4 -C 8 alkyl group. R 2 is preferably a C 5 or C 6An alkyl group, especially a branched C 5 (tert-amyl) or C 6 (tert-hexyl) alkyl group.

[0086] Preferably, R 1 is a C 2 -C 5 alkyl group, and R 2 is a C 1 -C 10 alkyl group, especially a C 4 -C 8 alkyl group.

[0087] Even more preferably, R 1 is a C 3 alkyl group, and R 2 is a C 5 or C 6 alkyl group.

[0088] The monoperoxycarbonate of formula (I) is preferably selected from the group consisting of tert-amyl peroxy isopropyl monocarbonate (TAIC), tert-amyl peroxy n-propyl monocarbonate (TAPC), tert-butyl peroxy isopropyl monocarbonate (TBIC), tert-octyl peroxy isopropyl monocarbonate (TOIC), and tert-hexyl peroxy isopropyl monocarbonate (THIC).

[0089] The monoperoxycarbonate of formula (I) is preferably selected from the group consisting of tert-amyl peroxy isopropyl monocarbonate (TAIC) and tert-hexyl peroxy isopropyl monocarbonate (THIC).

[0090] The monoperoxycarbonate of formula (I) is preferably the following formula: Corresponding to tert-amyl peroxy isopropyl monocarbonate (TAIC) of TIFF0007685836000003.tif27170.

[0091] Preferably, in formula (II), R 1 represents a branched alkyl group containing 7 or more carbon atoms, and R 2 represents a branched alkyl group.

[0092] Preferably, in formula (II), R 1 and R 2 are different.

[0093] According to formula (II), R 1 is an alkyl group containing 7 or more carbon atoms, preferably a C 7 -C 10 alkyl group, more preferably a C 7 -C 9 alkyl group. R 1 is preferably a C 8 alkyl group, particularly a branched C 8 alkyl group.

[0094] According to formula (II), R 2 is preferably a C 1 -C 10 alkyl group, preferably a C 2 -C 9 alkyl group, particularly a C 4 -C 8 alkyl group. Preferably, R 2 is a C 4 or C 5 alkyl group, particularly a branched C 4 or C 5 alkyl group. More preferably, R 2 is a C 4 alkyl group, particularly a branched C 4 alkyl group.

[0095] Advantageously, R 1 is a C 7 -C 10 alkyl group, particularly a C 7 -C 9 alkyl group, and R 2 is a C 1 -C 10 alkyl group, particularly a C 2 -C 9 alkyl group, particularly a C4 -C 8 is an alkyl group.

[0096] The monoperoxycarbonate of formula (II) is preferably selected from the group consisting of OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC), OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC), OO-tert-octyl O-(2-ethylhexyl) monoperoxycarbonate (TOEC), and OO-tert-hexyl O-(2-ethylhexyl) monoperoxycarbonate (THEC).

[0097] The above and the monoperoxycarbonates according to the present invention are commercially available under the trade names Luperox® or Lupersol® sold by Arkema.

[0098] Preferably, the monoperoxycarbonate of formula (II) corresponds to OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC) or OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC), more specifically OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC).

[0099] The mass ratio between the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II) preferably varies in the range of 0.1:99.9 to 80:20, preferably 1:99 to 70:30, more preferably 10:90 to 60:40.

[0100] More preferably, the mass ratio between the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II) is 60:40.

[0101] Preferably, in formula (I), R 1 represents a branched alkyl group containing 6 or fewer carbon atoms, and R 2represents a branched alkyl group, and in formula (II), R 1 represents a branched alkyl group containing 7 or more carbon atoms, and R 2 represents a branched alkyl group.

[0102] The present invention advantageously relates to the use of a monoperoxycarbonate of formula (II) selected from the group consisting of tert-amyl peroxy isopropyl monocarbonate (TAIC), and OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC), OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC), OO-tert-octyl O-(2-ethylhexyl) monoperoxycarbonate (TOEC), and OO-tert-hexyl O-(2-ethylhexyl) monoperoxycarbonate (THEC) for crosslinking polyolefin elastomers.

[0103] Preferably, the present invention relates to the use of tert-amyl peroxy isopropyl monocarbonate (TAIC) and OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC) or OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC) for crosslinking polyolefin elastomers, preferably copolymers of ethylene and at least one alpha olefin.

[0104] Preferably, the present invention relates to the use of tert-amyl peroxy isopropyl monocarbonate (TAIC) and OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC) for crosslinking polyolefin elastomers.

[0105] According to these embodiments, the polyolefin elastomer preferably contains at least one unit derived from ethylene.

[0106] According to these embodiments, the polyolefin elastomer is preferably ethylene and an alpha olefin, particularly a linear or branched C 3 -C 20 selected from the group consisting of copolymers of alpha olefins.

[0107] The composition preferably contains strictly less than 0.4% by weight of tert-alkyl hydroperoxide, calculated with respect to a mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II).

[0108] The composition of the present invention preferably does not contain tert-alkyl hydroperoxide in an amount of from 0.4 to less than 4% by weight, calculated with respect to a mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II). Advantageously, the composition is lacking in tert-alkyl hydroperoxide in an amount of from 0.4 to less than 4% by weight, calculated with respect to the total content of monoperoxycarbonate of the composition. More preferably, In particular, the composition of the present invention does not contain tert-alkyl hydroperoxide in an amount of less than 4% by weight, calculated with respect to a mixture consisting of 100 parts by weight of tert-amyl peroxy isopropyl monocarbonate (TAIC) and OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC).

[0109] Tert-alkyl hydroperoxide is preferably selected from the group consisting of t-butyl hydroperoxide (TBHP), t-amyl hydroperoxide (TAHP), t-hexyl hydroperoxide (THHP), 1,1,3,3-tetramethylbutyl hydroperoxide (TOHP), paramethane hydroperoxide (PMHP), 2,5-dimethyl-2,5-dihydroperoxide (2,5-2,5), and mixtures thereof.

[0110] More specifically, the composition lacks tert-alkyl hydroperoxide.

[0111] Crosslinkable composition As shown above, the crosslinkable composition is: - At least one polyolefin elastomer as described above (preferably a copolymer of ethylene and at least one alpha-olefin), - At least one monoperoxycarbonate conforming to formula (I) as described above, and - At least one monoperoxycarbonate conforming to formula (II) as described above and contains.

[0112] The composition preferably contains strictly less than 0.4% by weight of tert-alkyl hydroperoxide, calculated relative to a mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II).

[0113] Preferably, the composition lacks tert-alkyl hydroperoxide present in an amount of from 0.4 to less than 4% by weight, calculated relative to a mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II).

[0114] Preferably, the composition lacks tert-alkyl hydroperoxide present in an amount of from 0.4 to less than 4% by weight, calculated relative to the total content of monoperoxycarbonate of the composition.

[0115] The monoperoxycarbonates of formula (I) and (II) are preferably present in the composition in an amount of 3 parts by weight or less per 100 parts by weight of polyolefin elastomer.

[0116] Accordingly, the amount of the monoperoxycarbonates of formula (I) and (II) is preferably 3 parts by weight or less per 100 parts by weight of polyolefin elastomer.

[0117] Preferably, the amount of the monoperoxycarbonates of formula (I) and (II) varies within the range of from 0.1 to less than 3 parts by weight, preferably from 0.2 to 1.5 parts by weight, more preferably from 0.3 to 1 part by weight, more preferably from 0.4 to 1 part by weight, more preferably from 0.4 to 0.7 part by weight, even more preferably about 0.5 part by weight, per 100 parts by weight of the polyolefin elastomer.

[0118] The crosslinkable composition advantageously comprises a polyolefin elastomer, tert-amyl peroxy isopropyl monocarbonate (TAIC), and a monoperoxycarbonate of formula (II) selected from the group consisting of OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC), OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC), OO-tert-octyl O-(2-ethylhexyl) monoperoxycarbonate (TOEC), and OO-tert-hexyl O-(2-ethylhexyl) monoperoxycarbonate (THEC).

[0119] The crosslinkable composition preferably comprises a polyolefin elastomer, tert-amyl peroxy isopropyl monocarbonate (TAIC), and OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC).

[0120] Alternatively, the crosslinkable composition preferably comprises a polyolefin elastomer, tert-amyl peroxy isopropyl monocarbonate (TAIC), and OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC).

[0121] Even more preferably, the polyolefin elastomer is preferably a copolymer of ethylene and an alpha-olefin, particularly a copolymer of ethylene and a linear or branched C 3 -C 20 selected from the group consisting of alpha-olefins.

[0122] The mass ratio between the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II) is preferably 60:40.

[0123] The crosslinkable composition of the present invention may further contain at least one auxiliary agent that is not an organic peroxide.

[0124] The auxiliary agent preferably contains at least one carbamate, maleimide, acrylate, methacrylate, or allyl functional group. An allyl carboxylate may be used, which may be selected from the group consisting of allyl, diallyl, and triallyl types.

[0125] The auxiliary agent can be selected from the group consisting of divinylbenzene, diisopropenylbenzene, alpha-methylstyrene, alpha-methylstyrene dimer, ethylene glycol dimethacrylate, phenylene dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol 200 dimethacrylate, polyethylene glycol 400 dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,12-dodecanediol dimethacrylate, glycerol 1,3-dimethacrylate, diurethane dimethacrylate, trimethylolpropane trimethacrylate, bisphenol A epoxy diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol 600 diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol ethoxylate diacrylate, butanediol diacrylate, hexanediol diacrylate, aliphatic urethane diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, glycerol propoxylate triacrylate, aliphatic urethane triacrylate, trimethylolpropane triacrylate and dipentaerythritol pentaacrylate, triallyl cyanurate (TAC), triallyl isocyanurate, N,N'-m-phenylenedimaleimide, butadiene, chloroprene, and isoprene.

[0126] More preferably, the coagent is selected from the group consisting of: triallyl cyanurate, triallyl isocyanurate, N,N'-m-phenylenedimaleimide, triallyl trimellitate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate, preferably selected from the group consisting of: triallyl cyanurate (TAC), triallyl isocyanurate, trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TMPTMA), and even more preferably triallyl isocyanurate.

[0127] The coagent may be present in an amount of 0.05% to 30% by weight, preferably 0.1% to 10% by weight, based on the total weight of the composition.

[0128] The main purpose of using the coagent in the crosslinkable composition of the present invention is to increase the crosslinking rate. This coagent also enables the reduction of residual gas emissions during the decomposition of the peroxide and ultimately the reduction of the number of bubbles in the encapsulating material.

[0129] The mass ratio of the monoperoxycarbonate to the coagent is preferably in the range of 1:10 to 10:1, most preferably 1:3 to 3:1.

[0130] The crosslinkable composition of the present invention may further comprise one or more additives such as coupling agents, UV stabilizers, UV absorbers, fillers, plasticizers, flame retardants, antioxidants, dyes, organic or inorganic pigments, and mixtures thereof. Examples of coupling agents are monoalkyl titanates, (vinyl)trichlorosilane, and (vinyl)trialkoxysilane. They may be present in an amount of 0.01 to 5% by weight based on the weight of the ethylene polymer.

[0131] The UV stabilizer may be selected from hindered amine light stabilizers (HALS), while the UV absorber may be selected from, for example, benzophenone, triazine, and benzotriazole. These compounds may be present in an amount of 0.01 to 3% by weight based on the weight of the ethylene polymer.

[0132] Inorganic fillers such as silicon dioxide, alumina, talc, and calcium carbonate can be added to enhance mechanical strength, but nanometer clays are preferred for the transparency they provide.

[0133] Organic or inorganic pigments can also be added to color the crosslinkable composition. Titanium dioxide, which enables the production of white, is particularly mentioned, and this is especially useful when the composition is used to produce a film for use on the back side of a photovoltaic panel.

[0134] Examples of plasticizers are paraffinic or aromatic mineral oils, phthalates, azelates, adipates, and the like.

[0135] The antioxidant can be a phenol, phosphate, or sulfur antioxidant. As one variant, quinoline such as 1,2-dihydro-2,2,4-trimethylquinoline can be used as an antioxidant.

[0136] According to a preferred embodiment, the total amount of peroxide in the crosslinkable composition is less than 3 parts by weight per 100 parts by weight of the polyolefin elastomer, more preferably less than 1.5 parts by weight per 100 parts by weight of the polyolefin elastomer.

[0137] More preferably, the crosslinkable composition consists of a polyolefin elastomer as described above, a monoperoxycarbonate of formula (I) as described above, and a monoperoxycarbonate of formula (II), and optionally at least one of the following additives: coupling agent, UV stabilizer, UV absorber, filler, plasticizer, flame retardant, antioxidant, dye, auxiliary agent, and mixtures thereof.

[0138] The crosslinkable composition of the present invention preferably contains a polyolefin elastomer as described above, a monoperoxycarbonate of formula (I), a monoperoxycarbonate of formula (II) as described above, a coupling agent, and an auxiliary agent.

[0139] Use of the monoperoxycarbonate of formula (II) The present invention also relates to the use of a monoperoxycarbonate of formula (II) as described above for reducing the risk of premature crosslinking of a composition comprising at least one polyolefin elastomer (preferably a copolymer of ethylene and at least one alpha olefin) and at least one monoperoxycarbonate of formula (I) as described above.

[0140] Alternatively, the monoperoxycarbonate of formula (II) enables an increase in the scorch time of a composition comprising at least one polyolefin elastomer (preferably a copolymer of ethylene and at least one alpha olefin) and at least one monoperoxycarbonate of formula (I).

[0141] Method for producing a crosslinkable composition The present invention also relates to a method for producing a crosslinkable composition comprising a step of mixing at least one polyolefin elastomer (preferably a copolymer of ethylene and at least one alpha olefin) as described above, at least one monoperoxycarbonate of formula (I) as described above, and at least one monoperoxycarbonate different from the monoperoxycarbonate of formula (I) corresponding to formula (II) as described above.

[0142] The mixing step can advantageously be carried out at a temperature preferably lower than the decomposition temperature of the monoperoxycarbonate of the present invention using conventional devices such as continuous mixers and mixer-extruders.

[0143] Method for producing a material from a crosslinkable composition The present invention also relates to a method for producing a material comprising a step of crosslinking (or curing) a crosslinkable composition as described above.

[0144] The material preferably comprises a polyolefin elastomer containing at least one unit obtained from ethylene.

[0145] The material is particularly selected from the group consisting of encapsulating materials, in particular for solar cells, wire and cable insulation, pipes and hoses (including those for automotive radiators, drinking water, and floor heating), roller coatings, rotational molding, mobile phone articles, and materials for encapsulating shoe soles.

[0146] The material is advantageously a material for encapsulating solar cells.

[0147] The crosslinking (or curing) step preferably consists of a lamination step.

[0148] The crosslinking step (a) is preferably carried out at a temperature of 130 to 250 °C, preferably 130 to 180 °C, more preferably 140 to 165 °C.

[0149] The crosslinking step (a) is preferably carried out for a time of 8 to 30 minutes, more preferably 12 to 25 minutes.

[0150] The method preferably includes a step (a') selected from forming, extrusion molding, and injection molding of the composition as described above before and / or simultaneously with the crosslinking step (a). When the material is a material for encapsulating solar cells, the step is preferably an extrusion molding step.

[0151] The step (a') can be carried out, for example, to produce a sheet having a thickness of 50 to 2000 μm, preferably 100 to 1000 μm.

[0152] The step (a') can be carried out using a T-die extruder or, as a variant, a twin-screw extruder coupled to a two-roll machine.

[0153] The step (a') is carried out at a temperature of 80 to 150 °C, more preferably 90 to 120 °C.

[0154] Preferably, no crosslinking is obtained during step (a’).

[0155] In a particular embodiment, steps (a’) and (a) are carried out in a single step.

[0156] Method for manufacturing a photovoltaic module According to one embodiment, the present invention provides:[[]] (i) the following:[[]] · a first transparent layer forming the front face of the photovoltaic module,[[]] · a layer obtained from the crosslinkable composition of the present invention,[[]] · a plurality of solar cells electrically connected to each other and arranged side by side,[[]] · a layer obtained from the crosslinkable composition of the present invention,[[]] · a second layer or multilayer assembly forming the rear face (or backing) of the module,[[]] and at least one step of laminating an assembly continuously comprising these,[[]] (ii) at least one step of pressing the layers laminated together during step (i)[[]] and relates to a method for manufacturing a photovoltaic module.

[0157] The first layer forming the front face of the photovoltaic module can be a glass sheet or a sheet of poly(methyl methacrylate) (PMMA).

[0158] The second layer forming the rear face of the module can be a thin glass sheet or a sheet of poly(methyl methacrylate) (PMMA).

[0159] Alternatively, the multilayer assembly forming the rear face of the module consists of a film of an electrically insulating polymer such as polyethylene terephthalate (PET) or polyamide (PA) (at the top of which there is one or more films based on a fluoropolymer such as polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF), and at the top of that layer there may be a film of a metal, such as aluminum).

[0160] In a variant, the multilayer assembly forming the rear face of the module is made of a glass sheet on the top of which there is a material containing a polyolefin elastomer obtainable by the above method.

[0161] The solar cell preferably consists of crystalline silicon or an organic photovoltaic material.

[0162] The layer obtained from the crosslinkable composition of the present invention is preferably a sheet.

[0163] The pressing step can be carried out by conventional techniques over a curing time that can vary, for example, from 8 to 30 minutes, preferably from 8 to 25 minutes, under reduced pressure at a temperature of, for example, from 130 to 250 °C, preferably from 130 to 180 °C, more preferably from 140 to 165 °C, while heating and / or under reduced pressure. The composition of the present invention can be crosslinked during or subsequent to this pressing step.

[0164] The method preferably includes a single simultaneous step of pressing and curing (or crosslinking).

[0165] Material based on polyolefin elastomer Similarly, another subject of the present invention relates to a material comprising at least one polyolefin elastomer (preferably a copolymer of ethylene and at least one alpha olefin) obtainable by the above method.

[0166] The resulting material is preferably selected from the group consisting of encapsulating materials, in particular for solar cells, wire and cable insulation, pipes and hoses (including those for automotive radiators, drinking water, and floor heating), roller coatings, rotational molding, and materials for encapsulating mobile phone articles, and shoe soles.

[0167] The material is advantageously an encapsulating material, even more preferably a material for encapsulating solar cells.

[0168] More preferably, the encapsulation material is a transparent film disposed between the solar cell and a glass panel (upper glass panel) forming the front surface of the photovoltaic module, or, in the case of a double glass process, a transparent or colored film disposed between the glass panel (lower glass panel) forming the rear portion of the module and the solar cell.

[0169] Thus, the material is preferably used in a method for manufacturing a photovoltaic module, particularly in a double glass process.

[0170] More preferably, the material containing a polyolefin elastomer is a film, particularly a film of an ethylene polymer, particularly a copolymer of linear and uniformly branched ethylene and an alpha olefin.

[0171] The material of the present invention improves the crosslink density and significantly reduces or even eliminates the scorch problem. Thereby, a film without surface defects and having a high resistivity can be obtained.

[0172] Photovoltaic module The present invention also relates to a photovoltaic module comprising at least one material for encapsulating a solar cell as described above.

[0173] In particular, the photovoltaic module of the present invention comprises at least the following: · A first transparent layer forming the front surface of the photovoltaic module and intended to receive a light beam, · A material for encapsulating a plurality of solar cells electrically coupled to each other and arranged side by side as described above, · A second layer or multilayer assembly forming the rear surface (or backing) of the photovoltaic module and includes; The material for encapsulating a plurality of solar cells is disposed between the first layer and the second layer of the multilayer assembly.

[0174] The following examples serve to illustrate the present invention but are not intended to be limiting in nature.

Examples

[0175] Example 1: The following compositions were prepared by mixing the following: - A polyolefin elastomer (KST340T from Nippon Polyethylene Co., Ltd., MFI 12 - 16 g / 10 min, 5 kg load; melting point 55 - 70 °C, measured by DSC), tert-amyl peroxy isopropyl monocarbonate (Luperox® TAIC sold by Arkema) - The same polyolefin elastomer, but containing OO-tert-butyl O-isopropyl monoperoxycarbonate (Luperox® TBIC sold by Arkema), - The same polyolefin elastomer, but containing tert-amyl peroxy isopropyl monocarbonate (TAIC) and OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC) in a mass ratio of 60:40, - The same polyolefin elastomer, but containing tert-amyl peroxy isopropyl monocarbonate (TAIC) and OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC) in a mass ratio of 60:40, - The same polyolefin elastomer, but containing OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC), - The same polyolefin elastomer, but containing OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC).

[0176] Thus, they were prepared in a Haake closed mixer at a temperature of 35 °C for 12 minutes using a rotational speed of 50 revolutions per minute. The polymer mixture was then passed through an open roll mill adjusted to a temperature of 50 °C, and a sheet with a thickness of approximately 2 mm was produced.

[0177] A sample of approximately 2 to 3 grams of the above composition is applied to the plate of a movable rheometer (MDR) supplied by GOTECH, which can measure the curing characteristics of the sample and includes software for analyzing the results. Each sample is placed in a temperature-controlled cavity between two dies (the lower die vibrates to apply a periodic stress or deformation to the sample, and the upper die is connected to a torque sensor for measuring the torque response to the deformation of the sample).

[0178] The stiffness is continuously recorded as a function of time. The stiffness of the sample increases with the vulcanization that occurs.

[0179] This instrument can provide calculated values of ML (minimum torque), MH (maximum torque, which also defines the time required to reach the curing state when reached), tc10 (time to 10% of the curing state), and tc90 (time to 90% of the curing state), as defined by international standards (ASTM D5289 and ISO 6502), among other data.

[0180] The MDR is activated by applying a vibration amplitude (degree of deformation) of 0.5° to the sample for 30 minutes at temperatures of 115°C and 145°C. The scorch time is defined as the time required to reach 10% of full cure, i.e., tc10.

[0181] This test is carried out on the following samples, and the amount of monoperoxycarbonate is shown as parts per hundred parts of POE (phr): TIFF0007685836000004.tif74170

[0182] The use of TBIC results in a POE crosslinking rate that is too slow, industrially insufficient, if the crosslinking time (tc90) is 20 minutes.

[0183] The use of TAIC enables an increase in the POE crosslinking rate and a slight improvement in crosslink density (MH-ML) with respect to TBIC. However, the scorch time (tc10) causes problems and can pose risks from an industrial perspective, for example by creating roughness on the surface of encapsulating materials.

[0184] The use of TBEC results in an overly long polymer crosslinking time (tc90). Furthermore, the use of TAEC and TBEC results in insufficient crosslink density (MH-ML).

[0185] The use of a mixture of TAIC and TAEC enables both promoting the crosslinking of POE (tc90) compared to formulations containing only TBIC or only TBEC, and protecting against the risk of premature crosslinking by extending the scorch time (tc10) compared to formulations containing only TAIC, while maintaining a better crosslink density than TAEC or TBEC.

[0186] Similarly, the use of a mixture of TAIC and TBEC enables both promoting the crosslinking of POE (tc90) compared to formulations containing only TBIC or only TBEC, and protecting against the risk of premature crosslinking by extending the scorch time (tc10) compared to formulations containing only TAIC, while maintaining a good crosslink density.

Claims

1. Use of a composition for crosslinking a polyolefin elastomer, - at least one monoperoxycarbonate corresponding to formula (I): [In formula (I), R １ represents an alkyl group containing a number of carbon atoms of 6 or less, and R ２ represents an alkyl group], and - at least one monoperoxycarbonate corresponding to formula (II), [In formula (II), R １ represents an alkyl group containing 7 or more carbon atoms, and R ２ represents an alkyl group] characterized in that the polyolefin elastomer is a copolymer of ethylene and at least one alpha-olefin.

2. Use according to claim 1, characterized in that the composition contains strictly less than 0.4% by weight of tert-alkyl hydroperoxide, calculated with respect to the mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II).

3.

4. The polyolefin elastomer is a copolymer of ethylene and at least one linear, branched or cyclic C ３ -C ２０ alpha-olefin, characterized in that it is used according to claim 1 or 2. Use according to any one of claims 1 to 3, characterized in that the polyolefin elastomer is selected from the group consisting of ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 1-octene copolymer, ethylene / styrene copolymer, ethylene / propylene / 1-octene copolymer, ethylene / propylene / 1-butene copolymer, ethylene / 1-butene / 1-octene copolymer, and ethylene / 1-butene / styrene copolymer.

5. Use according to any one of claims 1 to 4, characterized in that the polyolefin elastomer is selected from the group consisting of linear and uniformly branched copolymers of ethylene and alpha-olefins.

6.

7. In formula (I), R １ is a C ２ -C ５ alkyl group, and the use according to any one of claims 1 to 5 is characterized thereby.

8. In formula (I), R ２ is a C １ -C10 alkyl group, and the use according to any one of claims 1 to 6 is characterized thereby. Use according to any one of claims 1 to 7, characterized in that the monoperoxycarbonate of formula (I) is selected from the group consisting of tert-amyl peroxy isopropyl monocarbonate (TAIC), tert-butyl peroxy isopropyl monocarbonate (TBIC), tert-octyl peroxy isopropyl monocarbonate (TOIC), and tert-hexyl peroxy isopropyl monocarbonate (THIC).

9.

10. In formula (II), R １ is a C ７ -C10 alkyl group, and the use according to any one of claims 1 to 8 is characterized thereby.

11. In formula (II), R ２ is a C １ -C10 alkyl group, and the use according to any one of claims 1 to 9 ​ The use according to any one of claims 1 to 10, wherein the monoperoxycarbonate of formula (II) is selected from the group consisting of OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC), OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate (TBEC), OO-tert-octyl O-(2-ethylhexyl) monoperoxycarbonate (TOEC), and OO-tert-hexyl O-(2-ethylhexyl) monoperoxycarbonate (THEC).

12. The use according to any one of claims 1 to 11, wherein the mass ratio between the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II) varies in the range of 0.1:99.9 to 80:

20.

13. - A polyolefin elastomer which is at least one polyolefin elastomer according to any one of claims 1 to 5 and is a copolymer of ethylene and at least one alpha-olefin, - At least one monoperoxycarbonate of formula (I) according to any one of claims 1 and 6 to 8, - At least one monoperoxycarbonate of formula (II) according to any one of claims 1 and 9 to 11, A crosslinkable composition comprising.

14. The crosslinkable composition according to claim 13, wherein the amount of the monoperoxycarbonates of formulas (I) and (II) is 3 parts by weight or less per 100 parts by weight of the polyolefin elastomer.

15. The crosslinkable composition according to claim 13 or 14, further comprising at least one auxiliary agent other than the organic peroxide.

16. The use according to any one of claims 1 and 3 to 12, wherein the composition is free of tert-alkyl hydroperoxide present in an amount of less than 0.4 to 4% by weight, calculated relative to the mixture of the monoperoxycarbonates of formula (I) and formula (II). **Claim 17**: The composition according to any one of claims 13 to 15, characterized in that it lacks tert-alkyl hydroperoxide present in an amount of from 0.4 to less than 4% by weight, calculated with respect to a mixture of 100 parts by weight of the monoperoxycarbonate of formula (I) and the monoperoxycarbonate of formula (II). **Claim 18** Use according to any one of claims 1 and 3 to 12, characterized in that the composition lacks tert-alkyl hydroperoxide. **Claim 19**: The composition according to any one of claims 13 to 15, characterized in that it lacks tert-alkyl hydroperoxide. **Claim 20** A method for manufacturing a material, comprising at least one step (a) of crosslinking a crosslinkable composition according to any one of claims 13 to 15, 17 and 19. **Claim 21** The method according to claim 20, characterized in that the material is selected from the group consisting of encapsulating materials, in particular for solar cells, wire and cable insulation, pipes and hoses, roller coatings, rotational molding, mobile phone articles, and materials for encapsulating shoe soles. **Claim 22** The method according to claim 20 or 21, characterized in that the crosslinking step (a) is carried out at a temperature of from 130 to 250 °C. **Claim 23** The method according to any one of claims 20 to 22, characterized in that it comprises a step (a') selected from the group consisting of forming, extrusion molding, and injection molding the crosslinkable composition according to any one of claims 13 to 15, 17 and 19, before and / or simultaneously with the crosslinking step (a). **Claim 24** (i) Continuously: - A first transparent layer forming the front face of the photovoltaic module, - A layer obtained from the crosslinkable composition according to any one of claims 13 to 15, 17 and 19, - A plurality of solar cells electrically connected to each other and arranged side by side, - A layer obtained from the crosslinkable composition according to any one of claims 13 to 15, 17 and 19, - A second layer or multilayer assembly forming the rear face (or backing) of the module; comprising at least one step of laminating an assembly comprising: (ii) At least one step of pressing the layers laminated together during step (i): A method for manufacturing a photovoltaic module. **Claim 25**: - A first transparent layer forming the front face of the photovoltaic module, ・A layer obtained from the crosslinkable composition according to any one of claims 13 to 15, 17, and 19, ・A plurality of solar cells electrically coupled to each other and arranged side by side, ・A layer obtained from the crosslinkable composition according to any one of claims 13 to 15, 17, and 19, and ・A second layer or multilayer assembly forming the rear (or backing) of the module A photovoltaic module comprising.

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