Process for curing a curable composition

Abstract

The invention relates to a method for curing a curable composition, comprising a step of curing at a temperature of 100°C or higher and in the absence of oxygen, said composition with an organic peroxide formulation comprising a drying oil. The present invention also relates to articles obtainable by said method. No figure.

Description

Title of the invention: Method for curing a curable composition Technical field

[0001] The present invention relates to a process for curing a curable composition, comprising a step of curing at a temperature of 100°C or higher and in the absence of oxygen, said composition with an organic peroxide formulation comprising a drying oil. The present invention also relates to articles obtainable by said process. Technical background

[0002] Polymers and copolymers, namely thermoplastic polymers, elastomers and their mixtures, crosslinked with organic peroxides and / or azo compounds generally exhibit better mechanical and physical properties than non-crosslinked polymers or polymers crosslinked by sulfur curing. These properties may include, for example, high resistance to thermal aging, low percentage of compression set, reduced metal coloring and easy production of colored products with increased color stability.

[0003] However, premature crosslinking, also referred to as scorching, occurring during the preparatory phase represents a major problem in the implementation of organic peroxides and azo-type compounds in crosslinking (also referred to as curing) applications of elastomeric and / or thermoplastic materials.

[0004] The preparatory phase generally consists of the mixing or compounding of the constituents and possibly the extrusion of these at often high temperatures. The operating conditions of this preparatory phase very often lead to the partial decomposition of the peroxide or azo type initiator, thus inducing the premature crosslinking reaction with the formation of gel particles in the mass of the polymer mixture. The presence of these gel particles is responsible for conferring defects, such as inhomogeneity and surface roughness, to the final product.

[0005] This results in the scorching being able to reduce the plastic properties of the target polymeric material, so that it can no longer be processed, which can lead to the loss of the entire batch. In addition, excessive scorching can in some cases lead to the complete shutdown of the extrusion operation.

[0006] Several related attempts in the art have been developed to stem the trend towards scorching. For example, the addition of a free radical initiator with a long half-life has already been put forward. However, the disadvantages arising from this implementation are low productivity due to long curing and high energy costs.

[0007] Furthermore, other tests are based on the use of various additives as scorch inhibitors during the crosslinking of polymeric compositions, such as organic hydroperoxides, vinyl monomers, nitrites, aromatic amines, phenolic compounds, mercaptothiazole compounds, sulfides, hydroquinones, nitroxides and dialkyl dithiocarbamate compounds.

[0008] Although these additives are used to extend the time to resist scorching, they have the disadvantage of being based on low molecular weight molecules which can generate volatile compounds or low molecular weight by-products during processing or after reacting.

[0009] Therefore, there remains a real need to provide compositions which are capable of extending the scorch resistance time during crosslinking of a polymeric composition, in particular a thermoplastic composition and / or an elastomeric composition, without inducing a detrimental effect on the curing time and / or the final crosslinking density, and which make it possible to reduce, or even avoid the presence of volatile compounds or low molecular weight by-products.

[0010] In other words, one of the objectives of the present invention is to provide compositions which are capable of effectively crosslinking (or curing) polymeric compositions and at the same time conferring good properties, in terms of physical and / or mechanical properties, to the targeted product.

[0011] In particular, one of the objectives of the invention is to delay scorching during crosslinking of polymeric compositions without being based on low molecular weight additives. Summary of the invention

[0012] A first object of the invention is to provide a method for curing a curable composition comprising at least one curable polymer, comprising a step of curing at a temperature of 100°C or more and in the absence of oxygen, said composition comprising an organic peroxide formulation comprising:

[0013] - at least one organic peroxide, and

[0014] - at least one drying oil,

[0015] the weight ratio of the drying oil to the organic peroxide being less than or equal to 3.

[0016] The method of the present invention makes it possible to delay the scorching of said curable composition without significantly impeding either the crosslinking density or the crosslinking rate. Furthermore, the drying oils contain unsaturations which react with the polymeric material to be crosslinked, thus preventing the generation of low molecular weight species.

[0017] In some embodiments, the at least one drying oil has an iodine value ranging from 125 to 215 g / 100 g, preferably from 140 to 205 g / 100 g, more preferably from 150 to 180 g / 100 g. The iodine value is known to be an indirect measure of the content of unsaturated C=C bonds in a molecule.

[0018] In some embodiments, the at least one drying oil has a saponification number ranging from 175 to 200 mg KOH / g, preferably from 180 to 195 mg KOH / g.

[0019] In some embodiments, the at least one drying oil is selected from the group consisting of tung oil, hemp oil, linseed oil, poppy oil, walnut oil, sunflower oil, cottonseed oil, corn oil, soybean oil, fish oils such as sardine oil and cod liver oil, herring oil, safflower oil, flax seed oil, perilla oil, oiticica oil, and combinations thereof, preferably the at least one drying oil being a tung oil.

[0020] In some embodiments, the at least one organic peroxide is selected from the group consisting of dialkyl peroxides, diperoxyketals, peroxyketals, monoperoxycarbonates, cyclic ketone peroxides, diacyl peroxides, organosulfonyl peroxides, peroxyesters, peroxydicarbonates and combinations thereof, preferably selected from the group consisting of diperoxyketals, peroxyketals, monoperoxycarbonates, peroxyesters and combinations thereof, more preferably selected from the group consisting of OO-t-butyl-O-(2-ethylhexyl)-monoperoxycarbonate, OO-t-butyl-O-2-isopropyl-monoperoxycarbonate, OO-t-amyl-O-(2-ethylhexyl)-monoperoxycarbonate, OO-t-amyl-O-2-isopropyl-monoperoxycarbonate, OO-t-hexyl-O-(2-ethylhexyl)-monoperoxycarbonate and mixtures thereof, optionally in combination with at least one other peroxide.

[0021] In some embodiments, the organic peroxide formulation further comprises at least one silane component, preferably selected from the group consisting of vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-methacryloxypropyltriethoxysilane, 3- methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and mixtures thereof, and is more preferably 3-methacryloxypropyltriethoxysilane or / and 3-methacryloxypropyltrimethoxysilane.

[0022] In some embodiments, the weight ratio of drying oil to organic peroxide is less than or equal to 3, more preferably is less than 2, preferably less than 0.60, preferably less than 0.45. More preferably, the weight ratio of drying oil to organic peroxide is from 0.025 to 3, preferably from 0.03 to 2, more preferably from 0.03 to 0.6, even more preferably from 0.05 to 0.45, even more preferably from 0.1 to 0.4.

[0023] In some embodiments, the organic peroxide formulation further comprises at least one coagent, preferably selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, N,N'-m-phenylene dimaleimide, triallyl trimellitate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trivinylcyclohexane and mixtures thereof.

[0024] In some embodiments, the at least one polymer is an ethylene polymer, particularly a poly(ethylene vinyl acetate) and / or a polyolefin elastomer.

[0025] In some embodiments, the amount of the at least one drying oil is from 0.005 to 10 parts by weight, preferably from 0.01 to 5 parts by weight, more preferably from 0.02 to 1 part by weight, per 100 parts by weight of the at least one polymer.

[0026] The invention also relates to a method as described above for manufacturing an article.

[0027] The method according to the invention can make it possible to manufacture an article having good properties, in particular good physical and / or mechanical properties, while guaranteeing satisfactory productivity.

[0028] Accordingly, another aspect of the invention relates to an article, in particular a film, obtainable by the method as described above.

[0029] The invention also relates to the use of an organic peroxide formulation as defined below, for preventing scorching of a curable composition as defined below.

[0030] The present invention makes it possible to satisfy the above-mentioned need. In particular, the invention provides a method making it possible to increase the roasting time and thus to minimize the risk of premature crosslinking.

[0031] This is achieved by the presence in the peroxide formulation of a drying oil which is present in a specific weight ratio relative to the organic peroxide. Detailed description

[0032] The invention will now be described in more detail without limitation in the following description.

[0033] Unless otherwise stated, the percentages in this text are percentages by weight.

[0034] In this text, the quantities indicated for a given species may apply to this species according to all its definitions (as mentioned in this text), including the narrower definitions. Organic peroxide formulation

[0035] The organic peroxide formulation of the invention comprises at least one organic peroxide.

[0036] Preferably, the organic peroxide has a one-hour half-life temperature ranging from 110°C to 160°C, more preferably has a one-hour half-life ranging from 115°C to 155°C.

[0037] The term "one-hour half-life temperature" represents the temperature at which half of the organic peroxide has decomposed in a given time of one hour. Conventionally, the "one-hour half-life temperature" is measured in n-decane or n-dodecane.

[0038] As examples, the organic peroxide may be selected from the group consisting of dialkyl peroxides, diperoxyketals, peroxyketals, monoperoxycarbonates, cyclic ketone peroxides, diacyl peroxides, organosulfonyl peroxides, peroxyesters, peroxydicarbonates, and combinations thereof. More particularly, the organic peroxide may be selected from the group consisting of diperoxyketals, peroxyketals, monoperoxycarbonates, peroxyesters, dialkyl peroxides, and combinations thereof.

[0039] For the purposes of the invention, “diperoxyketals” include peroxides which contain two peroxide groups (OO) on at least one carbon.

[0040] Examples of diperoxyketals suitable for the invention are 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane; 1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-amylperoxy)valerate; ethyl 3,3-di(t-butylperoxy)butyrate; 2,2-di(t-amylperoxy)propane; 3,6,6,9,9-pentamethyl-3-ethoxycarbonylmethyl-1,2,4,5-tetraoxacyclononane; n-butyl 4,4-bis(t-butylperoxy)valerate; ethyl 3,3-di(t-amylperoxy)butyrate; and mixtures thereof.

[0041] The term “peroxyketal” means a compound of the general formula (R3)(R4)C(-ORi)(-OOR2), in which:

[0042] - Ri represents a linear or branched alkyl group, preferably C1-C12, preferably C1-C4, and more preferably C1, or represents a cycloalkyl group with R2,

[0043] - R2 represents a linear or branched alkyl group, preferably C1-C12, preferably C4-Ci2, and more preferably C5, or represents a cycloalkyl group with Rp

[0044] - R3 represents a hydrogen atom or a linear or branched alkyl group, preferably C1-C12, more preferably C4-C12, or represents a cycloalkyl group with R4,

[0045] - R4 represents a hydrogen atom or a linear or branched alkyl group, preferably C1-C12, more preferably C4-C12, or represents a cycloalkyl group with R3.

[0046] Preferably, R3 forms a cycloalkyl group with R4.

[0047] Preferably, when R3 is a hydrogen atom, R4 is a linear or branched alkyl group, preferably C1-C12, more preferably C4-C12.

[0048] The peroxyketal according to the invention preferably has the general formula (I) below:

[0049] [Chem.l] CL R—CK * G)

[0050] in which formula (I):

[0051] - Ri represents a linear or branched C1-C4 alkyl group, preferably C1,

[0052] - R2 represents a branched C4-C12 alkyl group, preferably C5,

[0053] - n denotes zero or an integer from 1 to 3,

[0054] R3 represents a linear or branched CrC3 alkyl group,

[0055] - Ri preferably represents a linear alkyl group, more particularly Cr C2, more preferably in Cp

[0056] R2 preferably represents a branched C4-C5 alkyl group, more preferably C5.

[0057] Preferably n denotes zero.

[0058] R3 preferably represents a linear or branched alkyl group, CrC2, more preferably Ci.

[0059] Preferably, in formula (I), RI represents a linear or branched C1-C2 alkyl group, R2 represents a branched C4-C5 alkyl group, and n denotes zero.

[0060] Even more preferably, in formula (I), R 1 represents a C 1 -C 1 alkyl group, R 2 represents a C 5 -C 5 branched alkyl group, and n denotes zero.

[0061] The organic peroxide or peroxides is or are preferably selected from the group consisting of 1-methoxy-1-tert-amylperoxycyclohexane (TAPMC), 1-methoxy-lt-butylperoxycyclohexane (TBPMC), 1-methoxy-lt-amylperoxy-3,3,5-trimethylcyclohexane, 1-methoxy-lt-butylperoxy-3,3,5-trimethylcyclohexane, 1-ethoxy-1-t-amylperoxycyclohexane, 1-ethoxy-1-t-butylperoxycyclohexane, 1-ethoxy-lt-butyl-3,3,5-peroxycyclohexane and mixtures thereof.

[0062] Even more preferably, the organic peroxide according to the invention is 1-methoxy-1-tert-amylperoxycyclohexane (TAPMC).

[0063] As peroxyesters useful for the present invention, mention may be made of 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; t-butyl perbenzoate; t-butyl peroxyacetate; t-butyl peroxy-2-ethyl hexanoate; t-amyl perbenzoate; t-amyl peroxyacetate; t-butyl peroxyisobutyrate; 3-hydroxy-1,1-dimethyl-t-butyl peroxy-2-ethylhexanoate; OO-t-amyl-O-hydrogen-monoperoxysuccinate; OO-t-butyl-O-hydrogen-monoperoxysuccinate; di-t-butyl diperoxyphthalate; t-butyl peroxy(3,3,5-trimethylhexanoate); 1,4-bis(t-butylperoxycarbo)cyclohexane; t-butyl peroxy-3,5,5-trimethylhexanoate; t-butyl peroxy-(cis-3-carboxy)propionate; allyl 3-methyl-3-t-butylperoxybutyrate; and mixtures thereof.

[0064] The dialkyl peroxides may be selected from the group consisting of di-t-butyl peroxide; t-butyl cumyl peroxide; 2,5-di(cumylperoxy)-2,5-dimethyl hexane; 4-methyl-4-(t-butylperoxy)-2-pentanol; 4-methyl-4-(t-amylperoxy)-2-pentanol; 4-methyl-4-(cumylperoxy)-2-pentanol; 4-methyl-4-(t-butylperoxy)-2-pentanone; 4-methyl-4-(t-amylperoxy)-2-pentanone; 2,5-dimethyl-2,5-di(t-butylperoxy)hexane; 2,5-dimethyl-2,5-di(t-amylperoxy)hexane; 2,5-dimethyl-2-t-butylperoxy-5-hydroperoxyhexane; 2,5-dimethyl-2-cumylperoxy-5-hydroperoxy hexane; 2,5-dimethyl-2-t-amylperoxy-5-hydroperoxyhexane; l,3-bis(tert-butylperoxyisopropyl)-benzene, l,4-bis(tert-butylperoxyisopropyl)-benzene; l,3,5-tris(t-butylperoxyisopropyl)benzene; 1,3,5-tris(t-amylperoxyisopropyl)benzene; l,3,5-tris(cumylperoxyisopropyl)benzene; di[ 1,3-dimethyl-3-(t-butylperoxy)butyl]carbonate; di[ 1,3-dimethyl-3-(t-amylperoxy)butyl]carbonate;di[l,3-dimethyl-3-(cumylperoxy)butyl]carbonate; di-t-amyl peroxide; dicumyl peroxide; t-butylperoxy-meta-isopropenyl-cumyl-peroxide; t-amyl cumyl peroxide; t-butyl-; isopropenylcumylperoxide; 2,4,6-tri(butylperoxy)-s-triazine; 1,3,5-tri[l-(t-butylperoxy)-l-methylethyl]benzene; l,3,5-tri-[(t-butylperoxy)-isopropyl]benzene; 1,3-dimethyl-3-(t-butylperoxy)butanol; 1,3-dimethyl-3-(t-amylperoxy)butanol; and mixtures thereof.

[0065] Other dialkyl peroxides which may be used individually or in combination with the other free radical initiators according to the present disclosure are those selected from the group represented by the following formula (I):

[0066] [Chem.2]

[0067] R4 and R5 may be independently in the meta or para positions and be the same or different and be selected from hydrogen and straight or branched chain alkyls of 1 to 6 carbon atoms; Dicumyl peroxide and isopropylcumyl cumyl peroxide are illustrative.

[0068] Preferably, the dialkyl peroxides are chosen from compounds having the following formula (II):

[0069] [Chem.3] (II)

[0070] - Ri and R'b independently of each other, representing a C3-C10 alkyl radical, linear or branched, preferably branched,

[0071] - R2 and R'2, independently of each other, representing a C3-C10 alkyl radical, linear or branched, preferably branched.

[0072] More preferably, according to formula (II):

[0073] - Ri and R' 1 are the same and represent a linear or C3-C10 alkyl radical branched, especially branched, and

[0074] - R2 and R'2 are the same and represent a linear or C3-C10 alkyl radical branched, preferably branched.

[0075] Even more preferably, according to formula (II):

[0076] - Ri and R' i are the same and represent a branched C3-Ci0 alkyl radical, in particular a branched C3-C6 alkyl radical,

[0077] - R2 and R'2 are the same and represent a branched C3-Ci0 alkyl radical, in particular a branched C3-C6 alkyl radical.

[0078] Preferably, the group R'2-OO-R' i may be in the meta or para position on the benzene ring defined in formula (II).

[0079] The dialkyl peroxides corresponding to formula (II) are preferably chosen from the group consisting of 1,3-bis(tert-butylperoxyisopropyl)-benzene, 1,4-bis(tert-butylperoxyisopropyl)-benzene, and their mixture.

[0080] The dialkyl peroxides are preferably selected from the group consisting of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dialkyl peroxides represented by formula (I), dialkyl peroxides represented by formula (II) and mixtures thereof.

[0081] The dialkyl peroxides are more preferably selected from the group consisting of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, tert-butyl cumyl peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,4-bis(tert-butylperoxyisopropyl)benzene, and mixtures thereof.

[0082] The dialkyl peroxides are even more preferably selected from the group consisting of 1,3-bis(tert-butylperoxyisopropyl)-benzene, 1,4-bis(tert-butylperoxyisopropyl)-benzene, and mixtures thereof.

[0083] Imidoperoxides may also be used, such as those of the type described in PCT application publication WO 97 / 03961. Advantageously, the monoperoxydicarbonates are chosen from the group consisting of OO-t-amyl-O-2-isopropyl-monoperoxycarbonate (TAIC), OO-t-amyl-On-propyl monoperoxycarbonate (TAPC), OO-t-butyl-O-2-isopropyl-monoperoxycarbonate (TBIC), t-octyl-isopropyl-monoperoxycarbonate (TOIC), OO-t-hexyl-O-isopropyl-monoperoxycarbonate (THIC), OO-t-amyl-O-(2-ethylhexyl)-monoperoxycarbonate (TAEC), OO-t-butyl-O-(2-ethylhexyl)-monoperoxycarbonate (TBEC), OO-t-octyl-O-(2-ethylhexyl)-monoperoxycarbonate (TOEC), OO-t-hexyl-O-(2-ethylhexyl)-monoperoxycarbonate (THEC) and mixtures thereof. More preferably, the organic peroxide is selected from the group consisting of OO-t-butyl-O-(2-ethylhexyl)-monoperoxycarbonate (TBEC), OO-t-butyl-O-2-isopropyl-monoperoxycarbonate (TBIC), OO-t-amyl-O-(2-ethylhexyl)-monoperoxycarbonate (TAEC), OO-t-amyl-O-2-isopropyl-monoperoxycarbonate (TAIC), OO-t-hexyl-O- (2-ethylhexyl)-monoperoxycarbonate (THEC) and mixtures thereof. These monoperoxycarbonates may optionally be used in combination with at least one other peroxide, such as those mentioned above (e.g. t-butyl peroxy-2-ethylhexanoate).

[0085] Even more preferred monoperoxycarbonates are TBEC, TAEC, THEC, or a mixture thereof, optionally in combination with at least one other peroxide, such as those mentioned above (e.g., a dialkyl peroxide or a diperoxyketal). The most preferred organic peroxides are TBEC, TAEC, or a mixture thereof, optionally in combination with at least one other peroxide, such as those mentioned above (e.g., a dialkyl peroxide or a diperoxyketal).

[0086] The organic peroxide may be present in the formulation in an amount ranging from 40 to 99% by weight, based on the total weight of the organic peroxide formulation. Preferably, the organic peroxide is present in the formulation in an amount ranging from 50 to 98% by weight, even more preferably from 60 to 97% by weight, based on the total weight of the organic peroxide formulation.

[0087] The organic peroxide formulation of the invention also comprises at least one drying oil. The term "drying oil" means an oil having an iodine value greater than 110 g / 100 g, as measured according to GB / T5532-2008. Any drying oil known to those skilled in the art may be employed in the organic peroxide formulation of the present invention. Drying oils may comprise oils derived from plant, animal and fish sources, for example, glycerol triesters of fatty acids which are characterized by relatively high levels of polyunsaturated fatty acids, including eleostearic acid and alpha-linolenic acid. Advantageously, at least one drying oil is selected from the group consisting of tung oil, hemp oil, biofen or trans-beta-farnesene (e.g., that prepared by Amyris), linseed oil, poppy seed oil, walnut oil, sunflower oil, cottonseed oil, corn oil, soybean oil, fish oils such as sardine oil and cod liver oil, herring oil, safflower oil, linseed oil, perilla oil, oiticica oil, and combinations thereof, preferably from the group consisting of tung oil, hemp seed oil, linseed oil, poppy seed oil, walnut oil, sunflower oil, cottonseed oil, corn oil, soybean oil, fish oils such as sardine oil and cod liver oil, herring oil, safflower oil, linseed oil, perilla oil, oil of oïticica, and corresponding combinations.

[0088] More preferably, the drying oil comprises, consists essentially of, or consists of tung oil, linseed oil, fish oils, in particular cod liver oil, walnut oil, oiticica oil, poppy oil. Most preferably, the drying oil comprises, consists essentially of, or consists of tung oil, linseed oil, and in particular tung oil.

[0089] The above-mentioned oil may be modified or not. It may be virgin oil or refined oil.

[0090] The drying oil used in the formulation of the invention preferably has an iodine value ranging from 125 to 215 g / 100 g, preferably from 140 to 205 g / 100 g, more preferably from 150 to 180 g / 100 g. The iodine value can be measured according to GB / T5532-2008.

[0091] The drying oil may have a saponification index ranging from 175 to 210 mg KOH / g, preferably from 182 to 195 mg KOH / g.

[0092] The peroxide formulation advantageously contains the drying oil in an amount ranging from 1 to 35% by weight, based on the total weight of the organic peroxide formulation. More preferably, the organic peroxide formulation of the invention comprises the drying oil in an amount ranging from 2 to 25% by weight, more preferably from 3 to 20% by weight, even more preferably from 5 to 15% by weight, based on the total weight of the organic peroxide formulation.

[0093] The weight ratio of drying oil to organic peroxide in the organic peroxide formulation is less than or equal to 3, more preferably is less than 2, preferably less than 0.60, preferably less than 0.45. More preferably, the weight ratio of drying oil to organic peroxide is from 0.025 to 3, preferably from 0.03 to 2, more preferably from 0.03 to 0.6, even more preferably from 0.05 to 0.45, even more preferably from 0.1 to 0.4.

[0094] When two or more organic peroxides are present in the organic peroxide formulation, the weight ratio of drying oil to organic peroxide is based on the total weight of the organic peroxides.

[0095] When two or more drying oils are present in the organic peroxide formulation, the weight ratio of drying oils to organic peroxide is based on the total weight of the drying oils.

[0096] The organic peroxide formulation may also comprise a silane component. The silane component has a scorch-protecting effect and makes it possible to further increase the scorch time. The silane component may further act as a coupling agent, the silane component making it possible to improve the adhesion properties of the polymer composition in which the peroxide formulation is used.

[0097] In some embodiments, the silane component may be a silane component with amino functionality, a silane component with sulfur functionality, a silane component with epoxy functionality, a silane component with (meth)acryl functionality, a silane component with chloro functionality and / or a silane component with vinylyl functionality.

[0098] The amount of silane component in the organic peroxide formulation is preferably 5 to 50% by weight, more preferably 10 to 50% by weight, more preferably 20 to 40% by weight, based on the total weight of the organic peroxide formulation.

[0099] The weight ratio of the silane component to the organic peroxide is preferably 0.1 to 1, more preferably 0.3 to 0.7.

[0100] When two or more organic peroxides are present in the organic peroxide formulation, the weight ratio of the silane component to the organic peroxides is based on the total weight of the organic peroxides.

[0101] When two or more silane components are present in the organic peroxide formulation, the weight ratio of silane components to organic peroxide is based on the total weight of the silane components.

[0102] The organic peroxide formulation may consist essentially of, or consist of, the at least one organic peroxide and the at least one drying oil.

[0103] Alternatively, the organic peroxide formulation may consist essentially of, or consist of, the at least one organic peroxide, the at least one drying oil, and the at least one silane component.

[0104] Alternatively, the organic peroxide formulation may further comprise a coagent (which is not an organic peroxide). Advantageously, said coagent carries at least one carbamate, maleimide, acrylate, methacrylate, or allyl functional group. Allyl carboxylates may be used, which may be selected from the group consisting of those of the allyl, diallyl, and triallyl type.

[0105] The coagent may 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, 1,3-glycerol 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, diacrylate, hexanediol, aliphatic urethane diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, glycerol propoxylate triacrylate, aliphatic urethane triacrylate, dipentaerythritol pentaacrylate, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), triallyl trimellitate, N,N'-m-phenylene dimaleimide, butadiene, chloroprene, isoprene, trivinylcyclohexane and mixtures thereof.

[0106] More preferably, the coagent is selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, N,N'-m-phenylene dimaleimide, triallyl trimellitate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trivinylcyclohexane and mixtures thereof, even more preferably selected from the group consisting of triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA) and mixtures thereof, and most preferably is triallyl isocyanurate (TAIC).

[0107] The main objective of using a coagent is to increase the level of crosslinking of the cured polymer using the formulation of the invention. The coagent also makes it possible to reduce residual gas emissions during the decomposition of peroxides, and ultimately to reduce the number of bubbles in the encapsulating film.

[0108] The weight ratio of the coagent to the organic peroxide is preferably from 0.1 to 10, more preferably from 0.3 to 3, even more preferably from 0.4 to 1.

[0109] When two or more organic peroxides are present in the organic peroxide formulation, the weight ratio of coagent to organic peroxide is based on the total weight of the organic peroxides.

[0110] When two or more coagents are present in the organic peroxide formulation, the weight ratio of coagents to organic peroxide is based on the total weight of the coagents.

[0111] In some embodiments, the organic peroxide formulation may consist essentially of, or consisting of, T at least one organic peroxide, T at least one drying oil, the at least one silane component, and T at least one coagent.

[0112] In other embodiments, the organic peroxide formulation may comprise one or more other additives, preferably selected from the group consisting of UV stabilizers, UV absorbers, coupling agents, fillers, plasticizers, flame retardants, antioxidants, dyes and pigments, free radical scavengers and mixtures thereof. UV stabilizers may be selected from amine type light stabilizers hindered (HALS). UV absorbers may be selected, for example, from benzophenones, triazines and benzotriazoles. UV stabilizers and UV absorbers may be present in the organic peroxide formulation in a weight ratio relative to the organic peroxide ranging from 0.0005 to 0.01. As examples of coupling agents (other than the silane components described above), mention may be made of monoalkyl titanates. Inorganic fillers such as silicon dioxide, alumina, talc, calcium carbonate may be added to increase the mechanical strength of the polymeric material once crosslinked using the present peroxide formulation, although nanoscale clays are preferred for the transparency they provide. Examples of plasticizers are paraffinic or aromatic mineral oils, phthalates, azelates, adipates and the like.Antioxidants may be phenolic, phosphate-type, or sulfur-containing antioxidants. Alternatively or additionally, quinolines such as 1,2-dihydro-2,2,4-trimethylquinoline may be used as the antioxidant. Organic or inorganic pigments may also be added for coloring the polymer composition in which the formulation is intended to be used. Particular mention may be made of titanium dioxide, which makes it possible to produce a white color, which may be particularly useful when the formulation is used in a polymer composition employed for the manufacture of a film for use on the backside of photovoltaic modules. Examples of free radical scavengers suitable for the present invention are those selected from the group consisting of nitroxides (especially 4-hydroxy-TEMPO) and quinones.As used herein, the term "quinone" includes both quinones and hydroquinones. Non-limiting examples of quinones that may be used in formulations of the present invention include mono-tert-butylhydroquinone (MTBHQ), hydroquinone, hydroquinone monomethyl ether (HQMME) also known as 4-methoxyphenol, mono-t-amyl-hydroquinone, hydroquinone bis(2-hydroxyethyl) ether, 4-ethoxyphenol, 4-phenoxyphenol, 4-(benzyloxy)phenol, 2,5-bis(morpholinomethyl)hydroquinone and benzoquinone.

[0113] The organic peroxide formulation may consist essentially of, or consist of, the at least one organic peroxide, the at least one drying oil, the at least one silane component, the at least one coagent and optionally one or more additives selected from the group consisting of UV stabilizers, UV absorbers, coupling agents, fillers, plasticizers, flame retardants, antioxidants, dyes and pigments, free radical scavengers and combinations thereof.

[0114] The organic peroxide formulation may comprise free radical scavengers selected from the group consisting of nitroxides, quinones and mixtures thereof.

[0115] The organic peroxide formulation may comprise free radical scavengers in a weight ratio of free radical scavengers to organic peroxide of 0 to 0.5, more preferably 0 to 0.15, even more preferably 0 to 0.05, even more preferably 0 to 0.002.

[0116] The organic peroxide formulation may comprise a total amount of nitroxide and quinone free radical scavengers in a weight ratio relative to the organic peroxide ranging from 0 to 0.5, more preferably ranging from 0 to 0.15, more preferably ranging from 0 to 0.05, even more preferably ranging from 0 to 0.002.

[0117] When two or more organic peroxides are present in the organic peroxide formulation, the weight ratio of free radical scavengers to organic peroxide is based on the total weight of organic peroxide.

[0118] In certain advantageous embodiments, the organic peroxide formulation does not comprise (i.e., is free of) 4-hydroxy-TEMPO and / or MTBHQ, and more particularly, does not comprise nitroxide and / or quinone free radical scavengers.

[0119] The organic peroxide formulation may be free of any free radical scavenger.

[0120] The curable composition comprises at least one curable polymer, preferably selected from the group consisting of a thermoplastic polymer, an elastomeric polymer and a mixture thereof.

[0121] By "curable composition / polymer" is meant that the polymer composition can be cured (or crosslinked).

[0122] The thermoplastic and / or elastomeric polymers considered in the present invention can be defined as natural or synthetic polymers which possess a thermoplastic and / or elastomeric character and which can be crosslinked (cured) under the action of a crosslinking agent. The crosslinking action and the crosslinkable polymers are described in Rubber World, "Elastomer Crosslinking with Diperoxyketals", October 1983, pages 26-32, and in Rubber and Plastic News, "Organic Peroxides for Rubber Crosslinking", 29 Sep. 1980, pages 46-50. The polyolefins which are suitable for the present invention are described in Modern Plastics Encyclopedia 89, pages 63-67, 74-75.

[0123] The polymer may be selected from the group consisting of linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene, ethylene-propylene copolymers (EPM), polypropylene, ethylene-propylene-diene terpolymers (EPDM), ethylene- vinyl acetate (EVA), ethylene-alphaolefin copolymers (in particular, polyolefin elastomers (POE)), ethylene-butyl acrylate copolymers (EBA), ethylene-methyl acrylate copolymers (EMA), ethylene-ethyl acrylate copolymers (EBA), silicone rubber, natural rubber (NR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene copolymers (NBR), styrene-butadiene copolymers (SBR), neoprene rubber (CR), acrylonitrile-butadiene-styrene (ABS), styrene-butadiene-styrene block copolymers (SBS), chlorinated polyethylene (CPE), chlorosulfonated polyethylene, fluoroelastomers, copolymers ethylene-methyl(meth)acrylate and ethylene-glycidyl(meth)acrylate copolymers, biopolymers, and mixtures thereof.

[0124] Preferred biopolymers are selected from the group consisting of poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly-e-caprolactone (PCL), polyhydroxybutyrate (PHB), polybutylene adipate terephthalate (PBAT), and poly(3-hydroxyvalerate), corresponding copolymers and mixtures thereof.

[0125] Preferably, the polymers do not contain olefinic double bonds in the backbone or in the side chains.

[0126] Preferably, the polymer may be selected from the group consisting of linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene-propylene copolymers (EPM), polypropylene, ethylene-vinyl acetate copolymers (EVA), ethylene-alphaolefin copolymers (in particular, polyolefin elastomers (POE)), ethylene-butyl acrylate copolymers (EBA), ethylene-methyl acrylate copolymers (EMA), ethylene-ethyl acrylate copolymers (EBA), silicone rubber, chlorinated polyethylene (CPE), chlorosulfonated polyethylene, fluoroelastomers, ethylene-methyl (meth)acrylate copolymers and ethylene-glycidyl (meth)acrylate copolymers, biopolymers, and combinations thereof. corresponding.

[0127] Preferably, the polymer may be selected from the group consisting of an ethylenic copolymer, and more preferably ethylene-vinyl acetate copolymers (EVA), low density polyethylene (LDPE), polyolefin elastomers (POE), high density polyethylene (HDPE), and combinations thereof.

[0128] The EVA copolymer may comprise from 15 to 60% by weight, preferably from 25 to 45% by weight, of units derived from vinyl acetate (VA) monomers. Examples of such EVA copolymers are available under the trade name “Evatane® 18-150” and “Evatane® 40-55” from ARKEMA.

[0129] Other ethylene polymers that can be used in the invention have been disclosed, e.g., in EP 2242647. They comprise a functionalized polyolefin, such as a homopolymer of ethylene or a copolymer of ethylene with an alkyl (meth)acrylate or vinyl acetate, which can be functionalized either by grafting or by copolymerization with maleic anhydride or glycidyl methacrylate. This functionalized polyolefin can optionally be blended with an ethylene / carboxylic acid vinyl ester copolymer such as LEVA.

[0130] Alternatively, or in addition, the polymer may advantageously be a polyolefin elastomer (comprising units derived from ethylene or not).

[0131] A "polyolefin" as used herein means a polymer derived from an olefin, for example ethylene, propylene, butene, hexene, etc.

[0132] By the terms "derived from [a monomer]", it is meant that the polymer comprises in its main chain and / or in its adjacent chains (or pendant chains) units resulting from the polymerization or copolymerization of at least said monomer.

[0133] Preferably, the at least one organic peroxide is present in the curable composition in an amount ranging from 0.05 to 20 parts by weight per 100 parts by weight of polymer (preferably ethylene polymer). More preferably, the organic peroxide is present in an amount ranging from 0.1 to 3 parts by weight, even more preferably from 0.3 to 1.5 parts by weight, per 100 parts by weight of polymer.

[0134] The at least one drying oil may advantageously be present in the curable composition in an amount ranging from 0.005 to 10 parts by weight per 100 parts by weight of polymer (preferably, of ethylene polymer), preferably from 0.01 to 5 parts by weight, even more preferably from 0.02 to 1 part by weight, per 100 parts by weight of polymer.

[0135] When present, the at least one silane component may preferably be present in the curable composition in an amount ranging from 0.01 to 20 parts by weight per 100 parts by weight of polymer (preferably ethylene polymer), more preferably from 0.05 to 5 parts by weight, even more preferably from 0.1 to 1 part by weight, per 100 parts by weight of polymer.

[0136] When present, the at least one coagent may be included in the curable composition in an amount ranging from 0.005 to 10 parts by weight, preferably from 0.01 to 5 parts by weight, more preferably from 0.05 to 2 parts by weight, even more preferably from 0.1 to 1 part by weight, per 100 parts by weight of polymer (preferably ethylene polymer).

[0137] Other additives, preferably selected from UV stabilizers, UV absorbers, coupling agents, fillers, plasticizers, flame retardants, antioxidants, dyes and pigments, free radical scavengers and mixtures thereof, may be present in the polymer composition.

[0138] The curable composition of the invention may consist essentially of, or consist of, the at least one polymer (preferably an ethylene polymer), the at least one organic peroxide, the at least one drying oil, optionally the at least one silane-type component, optionally the at least one coagent, and optionally the additives (preferably selected from the group consisting of UV stabilizers, UV absorbers, coupling agents, fillers, plasticizers, flame retardants, antioxidants, dyes and pigments, free radical scavengers and mixtures thereof).

[0139] In some embodiments, the curable composition is free of 4-hydroxy-TEMPO and / or MTBHQ, and more particularly, is free of nitroxide and / or quinone free radical scavengers. The polymer composition may be free of free radical scavengers.

[0140] The curing step is advantageously carried out at a temperature ranging from 120 to 250°C, preferably from 130 to 180°C, more preferably from 130 to 165°C. The curing step can last from 4 to 50 minutes, preferably from 6 to 35 minutes.

[0141] The expression "in the absence of oxygen" means that the curable composition is at least not intentionally in contact with oxygen during the curing step. In other words, the curable composition is substantially not in the presence of oxygen during the curing step, and preferably the curable composition is not in the presence of oxygen during the curing step. Not limited to the following conditions, the absence of oxygen may for example occur when the rubber is cured by pressure molding or injection molding between metal plates, in a lamination between two other materials, when the composition is cured in an autoclave which has been purged of air and maintained under nitrogen or vacuum during the curing step, or when it is cured in a molten salt bath after extrusion of the rubber.

[0142] Accordingly, the curing step may be carried out by a method selected from the group consisting of pressure molding, injection molding, lamination, curing in an autoclave which has been purged of air and maintained under nitrogen or vacuum during the curing step and curing in a molten salt bath.

[0143] Preferably, the curing step is not carried out with a hot air oven, or a hot air tunnel or a steam autoclave which has not been purged of air. Said apparatus requires the presence of air in the system, which is not desired in the method of the invention.

[0144] Preferably, the method also comprises a step of shaping the curable composition. This step can be carried out before and / or simultaneously with the curing step. Advantageously, the step of shaping the polymer composition is chosen from a molding step, an extrusion step, and a step of injection molding the polymer composition.

[0145] Preferably, the step of shaping the polymer composition is carried out before the step of curing the polymer composition. Thus, preferably, no curing or substantially no curing takes place during the shaping step. When the shaping step is carried out before the curing step, said shaping step may be carried out at a temperature ranging from 80 to 150°C, more preferably from 90 to 120°C. Alternatively, the shaping step and the curing step may be carried out in a single step.

[0146] The process of the invention may comprise a step a') of mixing the at least one organic peroxide and the at least one drying oil and optionally other components of the formulation (such as the at least one coagent and / or the other additives).

[0147] The mixing step may be carried out in one or more steps (some of the components may thus be premixed before being mixed with the other components of the formulation). The mixing step may be carried out using any kind of apparatus suitable for mixing formulations containing mainly a liquid.

[0148] The mixing step is preferably carried out at a temperature below the decomposition temperature of the organic peroxide. It can be carried out at a temperature ranging from -10°C to 50°C, preferably from 10°C to 40°C.

[0149] The method of the invention may comprise a step a”) of mixing the at least one polymer and the organic peroxide formulation as described above. The polymer may be mixed with a previously prepared organic peroxide formulation, or may be mixed, in one or more steps, with all or each of the components of the organic peroxide formulation, and / or any premix of components of the organic peroxide formulation.

[0150] In other words, the process of the invention may comprise a step a') of preparing the organic peroxide formulation as described above followed by a step a”) of mixing the at least one polymer as described above and the organic peroxide formulation obtained in step a'). Alternatively, said steps a') and a”) may be carried out simultaneously.

[0151] The mixing step(s) may be carried out in any conventional device, such as a continuous mixer, a batch mixer, a compound extruder, a two-roll mill, or directly in the barrel of a film extrusion line. The temperature of the mixing step is preferably lower than the decomposition temperature of the peroxide. In particular, the mixing step may be carried out at a temperature in the range of -10 to 120°C, preferably 10 to 120°C.

[0152] Preferably, when the organic peroxide is a liquid or can be dissolved in other additives of the composition, the method also comprises an impregnation step after the mixing step a”). In such an impregnation step, the polymer, preferably in the form of pellets, is allowed to stand after being mixed with the organic peroxide formulation, preferably for at least 1 h, so that the organic peroxide impregnates the polymer pellets.

[0153] In the above methods, the components and their amounts may be as described in the preceding sections. Applications

[0154] Another object of the invention is the use of an organic peroxide formulation as described above for curing, in the absence of oxygen, a curable composition. Preferably, the curable composition is as defined above.

[0155] Preferably, the composition is curable at a temperature of 100°C or higher, preferably at a temperature of 120 to 250°C, preferably 130 to 180°C, more preferably 130 to 165°C.

[0156] The invention also relates to the method as described above for the manufacture of an article.

[0157] In some embodiments, the produced article is a film (or sheet). In such embodiments, the method comprises a step of shaping the polymer composition so as to form a film. Said step can be carried out using a T-die extruder or, alternatively, using a twin-screw extruder coupled to a twin-roll mill.

[0158] The film may for example have a thickness ranging from 50 to 2,000 μm, preferably from 100 to 1,000 μm.

[0159] The article manufactured by the method described above may advantageously be selected from the group consisting of encapsulant materials, particularly encapsulants for solar cells, wires and cable insulations, tubes and pipes (including those for automobile radiators, potable water, and underfloor heating, for example), roll coverings, rotational moldings, cellular articles, and shoe soles.

[0160] Most preferably, the article is an encapsulant material and more particularly an encapsulant for solar cells.

[0161] The invention also relates to an article obtainable, or obtainable, by the method as described above. The article may be as described above.

[0162] Another object of the invention is a photovoltaic module comprising an article as described above, preferably a film as described above.

[0163] Another theme of the invention relates to the use of an organic peroxide formulation as defined above, to prevent scorching of a curable composition as defined above. Examples

[0164] The following examples illustrate the invention without limiting it. Example 1

[0165] A first base composition was prepared by mixing a POE-type polymer (14 MI, ENGAGE® from DOW Chemical Company), 0.75 phr of OO-t-butyl-O-2-ethylhexyl-monoperoxycarbonate (TBEC) (Luperox® TBEC from Arkema), 0.3 phr of 3-methacryloxypropyltrimethoxysilane (KH-570 from Sigma-Aldrich) and 0.5 phr of triallyl isocyanurate (TAIC) (from Ourchem) in a 125 mL bottle. The mixture was then heated for 7.5 hours at 40 °C in an oven. During the heating step, the mixture required stirring every 2 to 3 hours.

[0166] Phr means “parts per hundred rubber,” and so, in the present example, means “parts by weight per 100 parts of POE-type polymer”.

[0167] A second base composition was prepared in the same manner as the first base composition except that 0.75 phr of OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC) (Luperox® TAEC, available from Arkema) was used instead of 0.75 phr of TBEC.

[0168] To these base compositions, a certain amount of tung oil (from Anhui Refined Oil and Fat CO., Ltd), odorless mineral spirits (synthetic isoparaffin hydrocarbon, from Idemitsu kosan Co. Ltd.) or refined tung oil (from Anhui Refined Oil and Fat CO., Ltd) was added, as shown in the table below. The tung oil used in the examples has a saponification value of 193 (determined according to GB / T5534-1995) and an iodine value of 167 g / 100 g (determined according to GB / T5532-2008).

[0169] [Tables 1] Composition n O Tung oil (phr) Refined tung oil (phr) Mineral oil (phr) Oil / organic peroxide weight ratio Peroxide = TBEC 1 - - - 2 - - 0.1125 0.15 3 0.0375 - - 0.05 4 0.075 - - 0.1 5 0.1125 - - 0.15 6 - 0.0375 - 0.05 7 - 0.075 - 0.1 Peroxide = TAEC 8 - - - 9 0.1125 - - 0.15

[0170] Compositions Nos. 3, 4, 5, 6, 7 and 9 are compositions according to the invention; compositions Nos. 1, 2 and 8 are comparative compositions. Compositions Nos. 1 to 7 comprise TBEC as organic peroxide; compositions 8 and 9 comprise T AEC as organic peroxide.

[0171] Samples of about 2 to 3 g of the compositions thus produced were deposited in a plate on a Rubber Process Analyzer (RPA), of the model type EKT-2003RPA-N of EKTRON TEK.CO., LTD, which is capable of measuring the curing properties of the samples and includes software for analyzing the results. Each of the samples was placed in a temperature-controlled cavity between two plates, the lower of which oscillates to apply cyclic stress or strain to the sample while the upper die is connected to a torque sensor to measure the torque response of the sample to deformation. Under these conditions, the surfaces of the sample are protected from the presence of air (and thus oxygen) by the metal surfaces of the plates. The stiffness is recorded continuously as a function of time. The stiffness of the sample increases with crosslinking.

[0172] The RPA is capable of providing, inter alia, calculated values ​​of ML (minimum torque), MH (maximum torque), tSi (time to reach a 1 dN.m increase in torque from minimum torque) and tc90 (time to reach 90% of the MH-ML curing state) as defined by international standards (such as the ASTM D5289 standard). Tsi represents the scorch time. From this data, the relative degree of MH-ML crosslinking (or crosslink density) can be determined.

[0173] The RPA was operated at a temperature of 145°C with an oscillation amplitude (degree of deformation) of 0.5°, an oscillation frequency of 1.667 and a stress index of 7 applied to the sample for 30 min, except for examples 10 and 11 where the test was carried out for 45 minutes.

[0174] The results are described in the table below.

[0175] [Tables2] Composition No. T S1 (s) Mh-Ml (dN.m / s) T c90 (s) Peroxide = TBEC (30 min RPA test) 1 411 2.59 1136 2 418 2.53 1163 3 433 2.56 1153 4 446 2.56 1181 5 471 2.55 1218 6 419 2.50 1150 7 436 2.51 1161 Peroxide = TAEC (45 min RPA test) 8 240 2.34 772 9 268 2.50 824

[0176] The compositions of the invention, which comprise tung oil, result in a longer scorch time compared to compositions not comprising oil or comprising mineral spirits. Thus, tung oil is effective as a scorch protection agent. In addition, the crosslink density obtained with the compositions of the invention is not altered and the tc90 remains within an acceptable range. This conclusion is true regardless of the peroxide used. Furthermore, it can be seen that refined tung oil also acts as an effective scorch protection agent. Example 2

[0177] A first base composition was prepared by mixing an EVA type polymer (V2825 from JiangSu Sailboat Petrochemical), 0.6 phr of TBEC (Luperox TBEC® from Arkema), 0.3 phr of 3-methacryloxypropyltrimethoxysilane (KH-570 from Sigma-Aldrich) and 0.5 phr of TAIC (from Ourchem) in a 125mL bottle. The mixture was was then heated for 6.5 h at 40 °C in an oven. During the heating step, the mixture required stirring every 2 to 3 hours.

[0178] In this example, phr means “parts by weight per 100 parts of EVA-type polymer”.

[0179] Another base composition was prepared in the same manner except that 0.6 phr of OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate (TAEC) (Luperox® TAEC, available from Arkema) was used instead of 0.6 phr of TBEC.

[0180] Yet another base composition was prepared in the same manner as the first base composition, except that 1.2 phr of TAEC (Luperox® TAEC) was used instead of 0.6 phr of TBEC.

[0181] Yet another base composition was prepared in the same manner as the first base composition, except that 1.2 phr of a mixture of 90% by weight TAEC (Luperox® TAEC) and 10% by weight t-butyl peroxy-2-ethylhexanoate (TBPO) (Luperox® 26 from Arkema) was used instead of 0.6 phr of TBEC.

[0182] Yet another base composition was prepared in the same manner as the first base composition, except that 0.75 phr of TBEC was used instead of 0.6 phr of TBEC.

[0183] To each of these compositions, tung oil or castor oil (ADANI castor oil) was added or not, as indicated in the following table.

[0184] Castor oil has a saponification value of 180 mg KOH / g and an iodine value of 85 g / 100 g determined as described above.

[0185] [Tables3] Composition No. Peroxide Tung oil (phr) Rie oil (phr) Oil / peroxide weight ratio 10 TBEC (0.6 phr) - 11 TBEC (0.6 phr) 0.09 0.15 12 TAEC (0.6 phr) - 13 TAEC (0.6 phr) 0.09 0.15 14 TAEC (1.2 phr) - 15 TAEC (1.2 phr) 0.1 0.08 16 90% TAEC + 10% TBPO (1.2 phr) - 17 90% TAEC + 10% TBPO (1.2 phr) 0.1 0.08 18 TBEC (0.75 phr) - 19 TBEC (0.75 phr) 0.1125 0.15 20 TBEC (0.75 phr) 0.1125 0.15

[0186] Compositions Nos. 11, 13, 15, 17 and 19 are compositions according to the invention; compositions Nos. 10, 12, 14, 16, 18 and 20 are comparative compositions.

[0187] The crosslinking properties of compositions Nos. 10 to 13 were determined as described in Example 1, with a curing time of 30 min.

[0188] The crosslinking properties of compositions Nos. 14 to 17 were determined as described in Example 1 but at three different temperatures: at 145 °C, at 130 °C and at 110 °C. The RPA measurement was carried out for 45 min. Temperatures of 145 and 130 °C simulate the conditions of a lamination process (e.g., for the manufacture of a photovoltaic module); a temperature of 110 °C simulates the conditions of an extrusion process (e.g., for the formation of a film before a lamination process).

[0189] The crosslinking properties of compositions Nos. 18 to 20 were determined as described in Example 1, with a curing time of 45 min.

[0190] The results are presented in the table below.

[0191] [Tables4] Composition n O Temperature (°C) T S1 (s) Mh-Ml (d Nm / s) T c90 (s) Curing time = 30 min 10 145 235 3.99 871 11 145 335 4.03 1172 12 145 159 3.74 589 13 145 197 3.72 592 Curing time = 45 min RPA operating temperature = 145 °C 14 145 100 4.37 412 15 145 109 4.38 430 16 145 99 4.09 383 17 145 108 4.31 447 18 145 237 4.13 896 19 145 292 4.04 1089 20 145 231 3.81 875 RPA operating temperature = 130 °C 14 130 318 3.95 1099 15 130 373 3.95 1188 16 130 290 3.75 1071 17 130 362 3.93 1158 RPA operating temperature = 110 °C 14 110 ND 0.83 Not relevant 15 110 ND 0.38 Not relevant 16 110 1726 1.1 Not relevant 17 110 ND 0.42 Not relevant

[0192] ND = not determinable. This indicates that the increase of 1 dN.m was not achieved during the 45 minutes of measurement duration.

[0193] A significant increase in roasting time is observed with the compositions of the invention at operating temperatures of 145°C and 130 °C compared to tung oil-free compositions, regardless of the peroxide used, while the crosslinking density remains good.

[0194] Furthermore, it can be seen that at the operating temperature of 110°C, very little crosslinking takes place with the compositions of the invention. This is desired because it is preferable that no crosslinking or substantially no crosslinking takes place during the extrusion step for shaping the composition. In contrast, the comparative compositions exhibit a higher crosslink density at 110°C, suggesting that the presence of tung oil makes possible a reduction in crosslinking at the temperature of 110°C.

[0195] When comparing Example 20 with Examples 18 and 19, no scorch protection was observed when using castor oil and the crosslink density was even lower than the counterexample without any oil.

Claims

Claims

1. A method for curing a curable composition comprising a curable polymer, comprising a step of curing at a temperature ranging from 120 to 250°C and in the absence of oxygen, said composition with an organic peroxide formulation comprising: - at least one organic peroxide, and - at least one drying oil, the weight ratio of the drying oil to the organic peroxide being less than or equal to 3.

2. A method according to claim 1, wherein the at least one drying oil has an iodine value ranging from 125 to 215 g / 100 g, preferably from 140 to 205 g / 100 g, more preferably from 150 to 180 g / 100 g.

3. A method according to claim 1 or 2, wherein the at least one drying oil has a saponification number ranging from 175 to 210 mg KOH / g, preferably from 182 to 195 mg KOH / g.

4. A method according to any one of claims 1 to 3, wherein the at least one drying oil is selected from the group consisting of tung oil, hemp oil, linseed oil, poppy oil, walnut oil, sunflower oil, cottonseed oil, corn oil, soybean oil, fish oils such as sardine oil and cod liver oil, herring oil, safflower oil, linseed oil, perilla oil, oiticica oil, and combinations thereof, preferably the at least one drying oil is a tung oil.

5. A method according to any one of claims 1 to 4, wherein the at least one organic peroxide is selected from the group consisting of dialkyl peroxides, diperoxyketals, peroxyketals, monoperoxycarbonates, cyclic ketone peroxides, diacyl peroxides, organosulfonyl peroxides, peroxyesters, peroxydicarbonates and combinations thereof, preferably selected from the group consisting of diperoxyketals, peroxyketals, monoperoxycarbonates, peroxyesters and combinations thereof, more preferably selected from the group consisting of OO-t-butyl-O-(2-ethylhexyl)-monoperoxycarbonate, OO-t-butyl-O-2-isopropyl-monoperoxycarbonate, OO-t-amyl-O-(2-ethylhexyl)-monoperoxycarbonate, OO-t-amyl-O-2-isopropyl-monoperoxycarbonate, OO-t-hexyl-O-(2-ethylhexyl)-monoperoxycarbonate and mixtures thereof, optionally in combination with at least one other peroxide.

6. The method of any one of claims 1 to 5, wherein the organic peroxide formulation further comprises at least one free radical scavenger selected from the group consisting of nitroxides, quinones and mixtures thereof.

7. A method according to any one of claims 1 to 6, wherein the weight ratio of drying oil to organic peroxide is less than 2, preferably less than 0.60, preferably less than 0.

45.

8. A method according to any one of claims 1 to 7, wherein the organic peroxide formulation further comprises at least one coagent, preferably selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, N,N'-m-phenylene dimaleimide, triallyl trimellitate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trivinylcyclohexane and mixtures thereof.

9. A method according to any one of claims 1 to 8, wherein the at least one polymer is an ethylene polymer, in particular a poly(ethylene vinyl acetate) and / or a polyolefin elastomer.

10. A method according to any one of claims 1 to 9, wherein the amount of the at least one drying oil in the composition is from 0.005 to 10 parts by weight, preferably from 0.01 to 5 parts by weight, more preferably from 0.02 to 1 part by weight, per 100 parts by weight of the at least one polymer.

11. A method according to any one of claims 1 to 10 for manufacturing an article.

12. Article, in particular film, obtainable by the method according to any one of claims 1 to 11.

13. Use of an organic peroxide formulation as defined in any one of claims 1 to 8, for preventing scorching of a curable composition as defined in any one of claims 1 to 10.