Composition comprising a mixture of organic peroxides for crosslinking crosslinkable polymers

Abstract

The present invention relates to a composition comprising at least one mixture of organic peroxides containing a first organic peroxide of formula (I) and a second organic peroxide, n-butyl-4,4-di(tert-butylperoxy)-valerate. The invention also relates to the use of said composition for crosslinking at least one crosslinkable polymer.

Description

[0001] DESCRIPTION

[0002] Title: Composition comprising a mixture of organic peroxides for crosslinking crosslinkable polymers

[0003] The present invention relates to a composition comprising a mixture of organic peroxides, as defined below, which is intended to be used in particular for the crosslinking, in particular the improvement of the crosslinking speed, of crosslinkable polymers, such as thermoplastic and / or elastomeric polymers.

[0004] The invention also relates to the use of a composition comprising a mixture of organic peroxides, as defined below, and at least one crosslinkable polymer for the manufacture of all or part of an article.

[0005] The invention also relates to an article, in particular a molded article or an extruded article, all or part of which can be obtained by crosslinking the composition as defined above.

[0006] Crosslinking of crosslinkable polymers, in particular thermoplastic polymers and / or elastomeric polymers, generally gives a very wide variety of products, for example seals, pipes, articles belonging to the carpet industry, in particular for carpet padding / filling, articles belonging to the footwear industry, in particular soles, cables or insulators, advantageous thermomechanical properties, such as better elasticity and / or improved creep resistance.

[0007] Thus, the processes for preparing these products mainly use thermoplastic polymers and / or elastomers, such as ethylene and vinyl acetate copolymers (EVA), different grades of polyethylene, polypropylene, natural or silicone rubber, which are crosslinked (or hardened) under the action of crosslinking agents.

[0008] The crosslinking agents typically used are organic peroxides, in particular dicumyl peroxide (DCP). For example, dicumyl peroxide, sold under the trade name Luperox® DCP, is conventionally used in the manufacture of articles belonging to the floor mat industry and also to the footwear industry, in particular soles, manufactured from compositions likely to be in the form of foam containing crosslinked ethylene and vinyl acetate (EVA) copolymers or crosslinked polyethylene as the main component.

[0009] However, the thermal decomposition of dicumyl peroxide during crosslinking most often generates the formation of acetophenone, as a by-product, which produces a strong, unpleasant and irritating odor for the respiratory tract and repeated exposure to which can be dangerous for operators.

[0010] More specifically, the compositions containing the polymers thus crosslinked have this characteristic odor of acetophenone, which requires additional treatment in order to mask it or even eliminate it.

[0011] In order to overcome the disadvantages caused by acetophenone, it has been proposed in the prior art to replace dicumyl peroxide with other crosslinking agents, in particular 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene which is an organic peroxide sold under the trade name Luperox ®F or Luperox Vul-Cup®R.

[0012] Indeed, 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene has the advantage of effectively crosslinking thermoplastic polymers and / or elastomers, in particular by leading to a good crosslinking density which makes it possible to ensure satisfactory thermomechanical properties for the articles obtained. More specifically, if the crosslinking density is too low, the article or product obtained is likely to have, among other things, insufficient breaking and tearing strength. Given these advantages, 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene is increasingly used in the manufacture of articles obtained from the crosslinking of rubber or polyolefin.

[0013] However, 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene has a number of disadvantages compared to dicumyl peroxide. Indeed, the crosslinking of polymers in the presence of 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene during molding processes must be carried out at higher temperatures than those used for dicumyl peroxide, in order to obtain similar productivity and production time which would be particularly satisfactory from an industrial point of view.

[0014] Thus, one of the objectives of the present invention is to provide a composition having good crosslinking properties, in particular by providing a satisfactory crosslinking speed and density, in order to obtain an article with thermomechanical properties adapted to the desired applications while retaining the final properties of said article.

[0015] In other words, there is a real need to propose a composition capable of effectively crosslinking crosslinkable polymers, in particular thermoplastic and / or elastomeric polymers, under operating conditions similar to those used for 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene without extending the time required for this crosslinking.

[0016] In view of the above, the invention more particularly aims to propose a composition intended to improve the crosslinking speed and / or the crosslinking density of crosslinkable polymers, in particular thermoplastic polymers and / or elastomeric polymers, such as ethylene and vinyl acetate copolymers.

[0017] The present invention therefore has as its subject in particular a composition comprising at least one mixture of organic peroxides comprising:

[0018] - a first organic peroxide of the following formula (I):

[0019] [Chem 1]

[0020] For ule (I) in which:

[0021] • Ri is a linear or branched alkyl group comprising from 1 to 6 carbon atoms,

[0022] • R2 is a linear or branched alkyl group comprising from 1 to 6 carbon atoms, and

[0023] • R 3 is a linear alkyl group, comprising 1 to 3 carbon atoms, preferably 2 carbon atoms, or a phenyl group, and

[0024] - a second organic peroxide, n-butyl-4,4-di(tert-butylperoxy)-valerate.

[0025] The composition according to the invention thus has the advantage of effectively crosslinking crosslinkable polymers, in particular by leading to a satisfactory crosslinking speed and density, while retaining good final properties of the article obtained.

[0026] In other words, the composition according to the invention makes it possible to increase the speed and / or density of crosslinking of crosslinkable polymers, in particular thermoplastic polymers and / or elastomeric polymers, in particular polyolefins.

[0027] More particularly, the composition according to the invention makes it possible in particular to improve the crosslinking speed of crosslinkable polymers, in particular thermoplastic polymers and / or elastomeric polymers, compared to the use of 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene alone.

[0028] The composition according to the invention has the advantage of specifically increasing the crosslinking speed of the crosslinkable polymers while inducing a good crosslinking density. The invention also relates to the use of the composition according to the invention as defined above for the crosslinking of one or more crosslinkable polymers, preferably one or more thermoplastic polymers and / or one or more elastomeric polymers.

[0029] In particular, the composition makes it possible to improve the speed and / or density of crosslinking of one or more crosslinkable polymers as defined above.

[0030] Similarly, the invention relates to a composition comprising at least the mixture of organic peroxides, as described above, and at least one crosslinkable polymer, preferably at least one thermoplastic polymer and / or at least one elastomeric polymer.

[0031] In this case, the composition further comprising at least one crosslinkable polymer is a crosslinkable composition, i.e. the mixture of organic peroxides is capable of crosslinking the crosslinkable polymer(s) at a given temperature by generating in situ free radicals capable of causing the crosslinking of said polymers.

[0032] Thus the crosslinkable composition makes it possible to produce crosslinked compositions resulting in good properties of the desired article with significant productivity.

[0033] Furthermore, the present invention also relates to a method for manufacturing all or part of an article, comprising a step of crosslinking the crosslinkable composition according to the invention, i.e. further comprising at least one crosslinkable polymer.

[0034] Likewise, another subject of the invention relates to the article all or part of which is obtained by the method described above, i.e. by the crosslinking of the composition according to the invention further comprising one or more crosslinkable polymers.

[0035] Other characteristics and advantages of the invention will appear more clearly on reading the description and examples which follow.

[0036] In what follows, and unless otherwise indicated, the bounds of a domain of values ​​are included in this domain. The expression "at least one" is equivalent to the expression "one or more".

[0037] Composition for crosslinking

[0038] As indicated previously, the composition according to the invention comprises:

[0039] - a first organic peroxide of the following formula (I):

[0040] [Chem 1] formula (I) in which:

[0041] • Ri is a linear or branched alkyl group comprising from 1 to 6 carbon atoms, and

[0042] • R2 is a linear or branched alkyl group comprising from 1 to 6 carbon atoms,

[0043] • R 3 is a linear alkyl group, comprising 1 to 3 carbons, preferably 2 carbons, or a phenyl group, and a second organic peroxide, n-butyl-4,4-di(tert-butylperoxy)-valerate.

[0044] Ri and R2 may be the same or different. Preferably, they are the same.

[0045] Preferably, Ri is a linear alkyl group comprising from 1 to 2 carbon atoms, more preferably one carbon atom.

[0046] Preferably, R2 is a linear alkyl group comprising from 1 to 2 carbon atoms, more preferably one carbon atom. Preferably, R3 is a linear alkyl group, comprising 2 carbon atoms, or a phenyl group, preferably is a phenyl group.

[0047] Thus, preferably, the composition according to the invention comprises at least one mixture of organic peroxide comprising:

[0048] - a first organic peroxide of the following formula (I): [Chem 1] in which:

[0049] • Ri is a linear or branched alkyl group comprising from 1 to 6 carbon atoms,

[0050] • R2 is a linear or branched alkyl group comprising from 1 to 6 carbon atoms,

[0051] • R 3 is a phenyl group, and a second organic peroxide, n-butyl-4,4-di(tert-butylperoxy)-valerate.

[0052] Preferably, the peroxide of formula (I) is selected from the group consisting of 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,3-1,4-bis(tert-amylperoxyisopropyl)benzene and mixtures thereof, more preferably from the group consisting of 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, more preferably is 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene.

[0053] 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene is an organic peroxide sold under the trade name Luperox ®F or Luperox Vul-Cup®R by Arkema. 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane is an organic peroxide sold under the trade name Luperox ® 101 by Arkema.

[0054] Preferably, the organic peroxide of formula (I) is present in the composition in a content ranging from 1 to 80% by weight, preferably in a content ranging from 10 to 50% by weight, more preferably in a content ranging from 20% to 40% by weight, relative to the total weight of the composition.

[0055] Preferably, n-butyl-4,4-di(tert-butylperoxy)-valerate is present in the composition in a content ranging from 20 to 99% by weight, preferably in a content ranging from 50 to 90% by weight, preferably in a content ranging from 60 to 80% by weight, relative to the total weight of the composition.

[0056] Preferably, the organic peroxide of formula (I) represents from 1 to 80% by weight, preferably from 10 to 50% by weight, more preferably from 20% to 40% by weight, relative to the total weight of organic peroxides.

[0057] Preferably, n-butyl-4,4-di(tert-butylperoxy)-valerate represents from 20 to 99% by weight, preferably from 50 to 90% by weight, preferably from 60 to 80% by weight, relative to the total weight of organic peroxides.

[0058] Advantageously, the weight ratio between n-butyl-4,4-di(tert-butylperoxy)-valerate and the organic peroxide of formula (I) is greater than or equal to 0.5, preferably greater than 1, even more preferably greater than 2.

[0059] Advantageously, the weight ratio between n-butyl-4,4-di(tert-butylperoxy)-valerate and the organic peroxide of formula (I) is less than or equal to 5, preferably less than or equal to 4, even more preferably less than 3.

[0060] Preferably, the weight ratio between n-butyl-4,4-di(tert-butylperoxy)-valerate and the organic peroxide of formula (I) varies in the range from 0.5 to 5, preferably in the range from 1 to 4, more preferably in the range from 2 to 3. Controlling the weight ratio in the ranges indicated above makes it possible to obtain an increase in the crosslinking speed of the polymers while ensuring good crosslinking density.

[0061] Preferably, the composition according to the invention further comprises at least one nitroxide.

[0062] The nitroxide is preferably selected from the group consisting of 2,2,6,6-tetramethyl- l -piperidinyloxy (generally marketed under the trade name TEMPO), 4-hydroxy 2, 2, 6, 6-tetramethyl- 1 -piperidinyloxy (generally marketed under the trade name 4-hydroxy-TEMPO), 4-methoxy 2,2,6,6-tetramethyl- l piperidinyloxy (generally marketed under the trade name 4-methoxy-TEMPO), 4-oxo-2, 2, 6, 6-tetramethyl- l -piperidinyloxy (commonly called 4- oxo-TEMPO), 2, 2, 5, 5 tetramethyl- 1 -pyrrolidinyloxy, bis ( 1 -oxyl- 2, 2, 6, 6 tetramethylpiperidin-4-yl) sebacate (marketed under the trade name 4-hydroxy-TEMPO), 4-methoxy ... the CXA 5415 brand by Ciba Specialty Chemical), 1 - piperidinyloxy-4,4'-( l , l Odioxo l , 10-decanediyl)bis(oxy))bis(2, 2,6,6- tetramethyl-) (commonly known as di-TEMPO sebacate), 2, 2,6,6- tetramethyl-4- hydroxypiperidine- 1 -oxyl monophosphonate and 3- carboxy-2,2,5 ,5- tetramethylpirrolidinyloxy (commonly known as 3- carboxyproxyl).,

[0063] Preferably, the nitroxide is 4-hydroxy 2,2,6,6-tetramethyl- 1 -piperidinyloxy (4-hydroxy-TEMPO) or 1 -piperidinyloxy-4,4'- ( 1 , 10-dioxo 1 , 10-decanediyl)bis(oxy))bis(2,2,6,6-tetramethyl-) (di-TEMPO sebacate).

[0064] More preferably still, the nitroxide is 4-hydroxy 2,2,6,6-tetramethyl- l -piperidinyloxy (4-hydroxy-TEMPO).

[0065] Advantageously, the weight ratio between the first peroxide of formula (I) and the nitroxide is greater than or equal to 1, preferably varies in the range from 1 to 50, more preferably varies in the range from 2 to 20 and more preferably in the range from 5 to 20, and even more preferably in a range from 8 to 20.

[0066] According to a preferred embodiment, the composition according to the invention comprises the organic peroxide of formula (I), n-butyl-4,4-di(tert-butylperoxy)-valerate and at least one nitroxide corresponding to 4-hydroxy 2,2,6,6-tetramethyl-l-piperidinyloxy (4-hydroxy-TEMPO).

[0067] According to this embodiment, the peroxide of formula (I) is preferably chosen from the group consisting of 1,3-1,4-bis

[0068] (tert-butylperoxy isopropyl) benzene, 2,5-dimethyl-2,5 -di(tert-butylperoxy)hexane and 1,3-1,4-bis (tert-amylperoxy isopropyl) benzene and mixtures thereof, still preferentially from the group consisting of 1,3-1,4-bis (tert-butylperoxy isopropyl) benzene and 2,5-dimethyl-2,5 -di(tert-butylperoxy)hexane, still preferentially is 1,3-1,4-bis (tert-butylperoxy isopropyl) benzene.

[0069] The composition thus defined corresponds to a composition intended for the crosslinking of one or more crosslinkable polymers.

[0070] Thus the mixture takes on all the characteristics of the composition intended for crosslinking.

[0071] Preferably, the mixture further comprises at least one nitroxide.

[0072] Crosslinkable composition

[0073] The present invention also relates to a composition according to the invention comprising a composition as defined above and in addition one or more crosslinkable polymers.

[0074] The composition thus defined corresponds to a crosslinkable composition.

[0075] In particular, the composition thus defined comprises the mixture previously defined and in addition one or more crosslinkable polymers.

[0076] More preferably, the crosslinkable polymer(s) is(are) chosen from the group consisting of thermoplastic polymers, elastomeric polymers and their mixtures.

[0077] Preferably, the crosslinkable polymer(s) is / are polyolefins.

[0078] For the purposes of the present invention, the term "polyolefin" means a polymer derived from an olefin, for example ethylene, propylene, butene, hexene, etc.

[0079] For the purposes of the present invention, the term "derived from" means that the units of the main chain of the polymer and / or of the adjacent chains (or pendant chains) of the polymer result from the polymerization or copolymerization of the monomers from which the polymer is manufactured.

[0080] For the purposes of the present invention, the term "elastomeric polyolefin" (EPO) means an elastomeric polymer derived from an olefin, for example ethylene, propylene, butene, hexene, etc.

[0081] For the purposes of the present invention, the term "elastomer" means a polymer capable of undergoing uniaxial deformation at room temperature, preferably of at least 20% for a period of fifteen minutes, and of returning to its initial shape, preferably with a residual deformation of less than 5% compared to its initial shape, when this stress is no longer exerted.

[0082] The thermoplastic and / or elastomeric polymers used in the composition according to the invention can be defined as natural or synthetic polymers which have a thermoplastic and / or elastomeric character and which can be crosslinked (cured) under the action of a crosslinking agent. In Rubber World, "Elastomer Crosslinking with Diperoxyketals", October 1983, pages 26-32, and in Rubber and Plastic News, "Organic Peroxides for Rubber Crosslinking", September 29, 1980, pages 46-50, the crosslinking action and crosslinkable polymers are described. Polyolefins suitable for the present invention are described in Modern Plastics Encyclopedia 89, pages 63-67, 74-75.

[0083] Examples of polymers and / or elastomers include linear low density polyethylene, low density polyethylene (LDPE), high density polyethylene (HDPE), chlorinated polyethylene, ethylene-propylene-diene terpolymers (EPDM), ethylene-vinyl acetate copolymers (EVA), elastomeric polyolefins, for example ethylene-propylene copolymers, ethylene-butene copolymers, silicone rubber, natural rubber (NR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene copolymers (NBR), styrene-butadiene copolymers (SBR), chlorosulfonated polyethylene or fluoroelastomers, ethylene-methyl (meth)acrylate copolymers, ethylene-glycidyl methacrylate copolymers and mixtures thereof.

[0084] According to one embodiment, the crosslinkable polymers are free of chlorine functional groups and carboxylic acid functional groups, preferably free of halogen functional groups and carboxylic acid functional groups.

[0085] Polyethylene may include homopolymers and copolymers such as linear low density polyethylene, low density polyethylene (LDPE), high density polyethylene (HDPE), chlorinated polyethylene, ethylene-propylene-diene terpolymers (EPDM).

[0086] Preferably, the crosslinkable polymers are chosen from the group consisting of polyethylene, ethylene and vinyl acetate copolymers (EVA), ethylene and butene copolymers, polyethylene, rubber, ethylene-propylene-diene terpolymers (EPDM) and their mixtures, more preferably chosen from the group consisting of ethylene-propylene-diene terpolymers (EPDM) and ethylene and vinyl acetate copolymers (EVA), still preferentially chosen from the group consisting of ethylene-propylene-diene terpolymers (EPDM).

[0087] The mixture of organic peroxides as defined above preferably represents between 0.1 and 10 parts, preferably 0.5 to 10 parts, advantageously between 2 and 8 parts, more preferably between 3 and 8 parts, more preferably between 5.5 and 7 parts per 100 parts by weight of polymer.

[0088] Preferably, when the crosslinkable polymer is a copolymer of ethylene and vinyl acetate, the mixture of organic peroxides as defined above preferably represents between 0.1 and 2 parts, preferably between 0.2 and 1.5 parts per 100 parts by weight of polymer.

[0089] Preferably, when the crosslinkable polymer is an ethylene-propylene-diene terpolymer (EPDM), the mixture of organic peroxides as defined above preferably represents between 3 and 8 parts, preferably between 3.5 and 6 parts per 100 parts by weight of polymer.

[0090] The composition according to the invention may further comprise one or more reinforcing fillers chosen from the group consisting of silica, calcium carbonate, kaolin, carbon black and their mixtures, preferably kaolin or a mixture of calcium carbonate and silica, even more preferably kaolin.

[0091] The reinforcing filler(s) may be present in the composition in a content ranging from 1 to 60%, in particular from 10 to 50% by weight, relative to the total weight of the composition.

[0092] The composition according to the invention may further comprise at least one organic peroxide different from the mixture of organic peroxides defined previously.

[0093] The composition may further comprise at least one co-agent preferably selected from the group consisting of allyl methacrylate, triallyl cyanurate, triallyl isocyanurate, trimethyloylpropane trimethacrylate (SR-350), trimethyloylpropane triacrylate (SR-35 1 ), zinc diacrylate and zinc dimethacrylate, bis-, tri- or higher poly-maleimides, or bis-, tri- or higher poly-citraconimides, preferably such as HVA-2 (N, N'-m-phenylene dimaleimide).

[0094] The composition according to the invention may further comprise additives, preferably chosen from the group consisting of antioxidants (such as 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ)), plasticizers (such as white oils), processing aids, such as polyethylene glycol) and mixtures thereof.

[0095] Preferably, the composition is free of an organic peroxide other than the mixture of organic peroxides defined above.

[0096] Use

[0097] In accordance with the present invention, the composition as described above is used for the crosslinking of at least one crosslinkable polymer as defined above, preferably chosen from the group consisting of polyethylene, ethylene and vinyl acetate copolymers (EVA), ethylene and butene copolymers, polyethylene, rubber, ethylene-propylene-diene terpolymers (EPDM) and mixtures thereof, more preferably chosen from the group consisting of ethylene-propylene-diene terpolymers (EPDM) and ethylene and vinyl acetate copolymers (EVA), still preferably chosen from the group consisting of ethylene-propylene-diene terpolymers (EPDM).

[0098] Thus, the present invention relates to the use of a composition as defined above for the crosslinking of one or more crosslinkable polymers as defined above.

[0099] In other words, the present invention relates in particular to the use of the mixture as defined above for the crosslinking of one or more crosslinkable polymers as defined above.

[0100] By "crosslinking" is meant the formation of a three-dimensional network by the creation of bonds between crosslinkable polymer molecules. The use according to the invention is therefore preferably carried out in the context of a crosslinking process, during which crosslinking takes place.

[0101] In particular, the composition according to the invention is used to increase the crosslinking speed of at least one crosslinkable polymer as defined previously.

[0102] Furthermore, the composition according to the invention makes it possible to achieve good crosslinking density.

[0103] The crosslinking density is related to the number of bridge bonds per constitutive unit of the polymer. It can be determined by rheometric measurement, for example using a rheometer. For example, it can be determined according to ASTM D 5289A using a rheometer type RPA 2000 or MDR, at a temperature of 160°C, with an oscillation amplitude of 0.5°, an oscillation frequency of 1.667 Hz, from discs of the sample to be tested with a diameter of 3.5 cm and a diameter of 4.8 cm. 3 of volume.

[0104] Depending on the crosslinking systems, adjusting the temperature to a different value may be appropriate.

[0105] The measurement is carried out during the crosslinking of the sample to be tested, which is initiated at the same time as the measurement, by placing the sample in a preheated test cavity. It allows a rheometric curve to be obtained representing the evolution of the viscoelastic torque resulting from the deformation imposed on the composition to be tested as a function of time. In the context of the present application, the crosslinking density is defined directly by the difference between the maximum torque MH and the minimum torque ML, and is expressed in dN m.

[0106] The minimum torque ML corresponds to the minimum torque value measured during curing (at the start of the test).

[0107] The maximum torque MH corresponds to the torque value at the end of the measurement. Preferably, the test duration is adjusted so that crosslinking is essentially complete at the end of this duration, with the torque then reaching a plateau. A suitable duration for the test is, for example, 60 minutes. However, this duration can be adapted according to the actual time expected for the manufacture of a given part, from the crosslinkable polymer composition, and at a given temperature.

[0108] The crosslinking speed is evaluated by the T90 value corresponding to the time required to reach 90% of the maximum torque, which is obtained using the rheometric measurement described above. The lower the T90, the higher the crosslinking speed.

[0109] According to a particular embodiment, the crosslinking speed obtained with the composition according to the invention comprising the mixture of organic peroxides as described previously is greater than the crosslinking speed which is obtained under the same conditions with a composition comprising 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene as crosslinking agent.

[0110] By "same conditions with a composition comprising 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene as crosslinking agent" is meant crosslinking carried out with the same parameters (same duration, same temperature, etc.) and from the same composition, except that it comprises 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene as crosslinking agent instead of the mixture of organic peroxides as defined above.

[0111] Thus, the composition according to the invention makes it possible in particular to increase the crosslinking speed compared to a composition comprising 1,3-1,4-bis(tert-butylperoxyisopropyl)benzene as organic peroxide used as crosslinking agent.

[0112] In particular, the invention relates to the use of a composition as defined above for the manufacture of all or part of an article.

[0113] Crosslinking process

[0114] The present invention also relates to a method for crosslinking at least one crosslinkable polymer comprising a step of crosslinking at least one crosslinkable polymer as defined above, in the presence of the composition for crosslinking as defined above. In other words, the step of crosslinking at least one crosslinkable polymer is carried out by bringing said crosslinkable polymer into contact with the composition for crosslinking as defined above.

[0115] Preferably, the crosslinking temperature is between 140°C and 250°C, preferably from 140°C to 210°C, preferably between 150°C and 190°C, and preferably between 165°C and 190°C.

[0116] Preferably, the crosslinking step takes place for a period of time ranging from 2 to 10 minutes, preferably for a period of time ranging from 3 to 8 minutes.

[0117] Thus, the composition according to the invention makes it possible to implement a process for crosslinking crosslinkable polymers at temperatures of up to 250°C.

[0118] Process for manufacturing all or part of an article

[0119] The present invention also relates to a method for manufacturing all or part of an article, comprising a step a) of crosslinking the composition as defined above.

[0120] Preferably, the manufacturing method according to the invention is a molding method, in particular injection molding.

[0121] Preferably, the manufacturing method according to the invention comprises a step b) of injection molding of the composition obtained following crosslinking.

[0122] Article

[0123] The invention also relates to an article all or part of which is obtained by the method described above. Examples:

[0124] The following examples serve to illustrate the invention without, however, being limiting in nature.

[0125] 1. Tested compositions - EPDM

[0126] The following compositions were prepared from the ingredients listed in Tables 1 and 2 below. Amounts are given as parts of pure organic peroxides per hundred parts (phr) of EPDM copolymer. Amounts of pure organic peroxide are given in parentheses.

[0127] [Table 1]

[0128] Luperox® E = 1,3-1,4-bis (tert-butylperoxy isopropyl)benzene

[0129] (Luperox® E40 contains 40% by weight of pure Luperox® E)

[0130] Luperox® 101 = 2,5 -dimethyl-2,5-di(tert-butylperoxy)hexane

[0131] (Luperox® 101 XL45 contains 45% by weight of pure Luperox® 101)

[0132] Luperox® 230 = n-butyl-4,4-di(tert-butylperoxy)-valerate

[0133] (Luperox®230XL40 contains 40% by weight of pure Luperox® 230).

[0134] The composition of EPDM used is as follows: [Table 2]

[0135] The compositions were thus prepared in a Haake internal mixer at a temperature of 35°C for a period of 15 minutes, using a stirring speed of 50 rpm.

[0136] The polymer mixture is then passed through an open mill set at a temperature of 25°C to produce sheets approximately 2 mm thick.

[0137] Samples of approximately 2 to 3 grams of the above compositions are placed in a plate on a moving die rheometer (MDR) provided by ALPHA-TECHNOLOGIES, which is capable of measuring the cure properties of the samples and includes software to analyze the results. Each of the samples is placed in a temperature-controlled cavity between two dies, 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 sample's torque response to strain.

[0138] The stiffness is recorded continuously as a function of time. The stiffness of the sample increases as vulcanization occurs.

[0139] This device is capable of providing, among others, calculated values ​​of ML (minimum torque), MH (maximum torque), and T90 (time to obtain 90% of the total crosslink density) as defined by international standards (ASTM D5289 and ISO 6502).

[0140] The crosslinking density is defined directly by the difference between the maximum torque MH and the minimum torque ML and is expressed in dN.m.

[0141] The MDR is operated at a temperature of 175 °C with an oscillation amplitude (degree of deformation) of 0.5° applied to the sample for 30 min. 2. Results

[0142] The crosslinking density and crosslinking speed of the different compositions were thus evaluated at a temperature of 175°C. The results are shown in Table 3 below:

[0143] [Table 3]

[0144] Compositions B and D according to the invention make it possible to reduce the crosslinking time (T90) compared to comparative compositions A and C containing respectively the product Luperox ® F and Luperox® 101 alone while leading to a similar crosslinking density.

[0145] In other words, the mixture of organic peroxides according to the invention makes it possible to induce faster crosslinking during crosslinking (T90) while maintaining a similar crosslinking density (MH-ML) compared to a composition containing Luperox ® F as the sole crosslinking agent.

[0146] 3. EVA compositions

[0147] Example 1 was reproduced using the organic peroxide compositions of Table 4. Amounts are given as parts of pure organic peroxide per hundred parts (phr) of EVA copolymer.

[0148] [Table 4]

[0149] Luperox® 231 = l , l -di(tert-butylperoxy)-3 ,3 ,5-trimethylcyclohexane (Luperox®231XL40 contains 40% by weight of pure Luperox® 230).

[0150] And the following polymer composition:

[0151] [Table 5]

[0152] 4. Results

[0153] The crosslinking density and crosslinking speed of the different compositions were thus evaluated at a temperature of 175°C. The results are shown in Table 6 below:

[0154] [Table 6]

[0155] Composition E according to the invention makes it possible to reduce the crosslinking time (T90) compared to the comparative composition E containing the product Luperox® E alone while leading to a similar crosslinking density. In addition, composition E is also better than composition G in terms of both crosslinking time (T90) and crosslinking density. In other words, the mixture of organic peroxides according to the invention makes it possible to induce faster crosslinking during crosslinking (T90) while maintaining a similar crosslinking density (MH-ML) compared to a composition containing Luperox® F as the sole crosslinking agent, or a mixture of Luperox®

[0156] F and Luperox® 231.

Claims

CLAIMS 1. Composition comprising at least one mixture of organic peroxide comprising: - a first organic peroxide of the following formula (I): [Chem 1] in which: • Ri is a linear or branched alkyl group comprising from 1 to 6 carbon atoms, • R2 is a linear or branched alkyl group comprising from 1 to 6 carbon atoms, • R 3 is a phenyl group, and a second organic peroxide, n-butyl-4,4-di(tert-butylperoxy)-valerate.

2. Composition according to claim 1, in which R1 and R2 are identical.

3. Composition according to any one of the preceding claims, in which Ri is a linear alkyl group comprising from 1 to 2 carbon atoms, more preferably one carbon atom.

4. Composition according to any one of the preceding claims, in which R2 is a linear alkyl group comprising from 1 to 2 carbon atoms, more preferably one carbon atom.

5. Composition according to any one of the preceding claims, characterized in that the weight ratio between n-butyl-4,4-di(tert-butylperoxy)-valerate and the organic peroxide of formula (I) is greater than or equal to 0.5, preferably greater than 1, even more preferably greater than 2.

6. Composition according to any one of the preceding claims, characterized in that the weight ratio between n-butyl-4,4-di(tert-butylperoxy)-valerate and the organic peroxide of formula (I) is less than or equal to 5, preferably less than or equal to 4, even more preferably less than 3.

7. Composition according to any one of the preceding claims, characterized in that it further comprises at least one nitroxide, preferably chosen from the group consisting of 2,2,6,6-tetramethyl-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate, l-piperidinyloxy-4,4'-(1,10-dioxo-1,10- decanediyl)bis(oxy))bis(2,2,6,6-tetramethyl-), 2,2,6,6-tetramethyl-4-hydroxypiperidine- 1 -oxyl monophosphonate and 3 -carboxy-2, 2,5,5- tetramethylpirrolidinyloxy, more preferably is 4-hydroxy 2, 2, 6, 6-tetramethyl- l -piperidinyloxy (OH-Tempo) or 1 - piperidinyloxy-4,4'-( l , 10-dioxo l , 10-decanediy l)bis(oxy))bis(2, 2,6,6 - tetramethyl-), more preferably is 4-hydroxy 2, 2, 6,6-tetramethyl- l - piperidinyloxy (OH-Tempo)., 8. Composition according to claim 7, characterized in that the weight ratio between the second organic peroxide and the nitroxide is greater than or equal to 1, preferably varies in the range from 1 to 50, preferably in the range from 2 to 20, and more preferably in the range from 5 to 20, and even more preferably in a range from 8 to 20.

9. Composition according to any one of the preceding claims, characterized in that it further comprises one or more crosslinkable polymers.

10. Composition according to claim 9, characterized in that the crosslinkable polymer(s) is(are) chosen from the group consisting of thermoplastic polymers, elastomeric polymers and their mixtures. 1 1. Composition according to claim 9 or 10, characterized in that the crosslinkable polymer(s) is(are) chosen from the group consisting of linear low density polyethylene, low density polyethylene (LDPE), high density polyethylene (HDPE), chlorinated polyethylene, ethylene-propylene-diene terpolymers (EPDM), ethylene-vinyl acetate copolymers (EVA), elastomeric polyolefins, for example ethylene-propylene copolymers, ethylene-butene copolymers, silicone rubber, natural rubber (NR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene copolymers (NBR), styrene-butadiene copolymers (SBR), chlorosulfonated polyethylene or fluoroelastomers, ethylene-methyl (meth)acrylate copolymers, copolymers of ethylene and glycidyl methacrylate and mixtures thereof.

12. Composition according to any one of claims 9 to 11, characterized in that the crosslinkable polymer(s) is(are) chosen from the group consisting of polyethylene, ethylene and vinyl acetate copolymers (EVA), ethylene and butene copolymers, polyethylene, rubber, ethylene-propylene-diene terpolymers (EPDM) and their mixtures, more preferably chosen from the group consisting of ethylene-propylene-diene terpolymers (EPDM) and ethylene and vinyl acetate copolymers (EVA), still preferably chosen from the group consisting of ethylene-propylene-diene terpolymers (EPDM).

13. Use of a composition as defined according to any one of claims 1 to 8 for the crosslinking of one or more crosslinkable polymers as defined according to any one of claims 9 to 12.

14. Use according to claim 13, for increasing the crosslinking speed of one or more crosslinkable polymers as defined according to any one of claims 9 to 12.

15. Method of manufacturing all or part of an article comprising a step of crosslinking a composition as defined according to any one of claims 9 to 12.

16. Use of a composition as defined according to any one of claims 9 to 12 for the manufacture of all or part of an article.

17. Article of which all or part is obtained by the process as defined according to claim 15.

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