Crosslinkable silicone elastomer composition containing heat-resistant additive

Abstract

To provide a crosslinkable silicone elastomer composition that makes it possible to obtain a thermally stable silicone elastomer.SOLUTION: Provided is a crosslinkable silicone elastomer composition X comprising at least one heat-resistant additive D, which is cerium(IV) neodecanoate, the silicone composition X having a content of cerium(IV) from 50 ppmw to 3000 ppmw.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a crosslinkable silicone elastomer composition containing a heat-resistant additive, in particular, a crosslinkable silicone elastomer composition containing a heat-resistant additive that is cerium (IV) neodecanoate. [Background technology]

[0002] Silicone elastomers are well known to exhibit considerable inertness to heating and cooling in continuous use from −50° C. to 200° C. Nearly all of the chemical, mechanical, and dielectric properties are maintained over this temperature range.

[0003] However, when silicone elastomers are used for a long time, for example for several days, at temperatures above 200°C, their properties tend to deteriorate.Therefore, it may be necessary to include suitable heat-resistant additives in their composition.This is all the more true when silicone elastomers are intended to be used for the manufacture of coverings or primary insulations that are included in the composition of fire protection for electric wires or cables, which must withstand high temperatures.This also applies when silicone elastomers are intended to be used for the manufacture of automotive cables.

[0004] For example, it is known to use antioxidant compounds to stop this thermal degradation. These antioxidants are mainly of two types: non-metallic (sulfur, phosphorus, amine-based, etc.) or inorganic or organometallic.

[0005] US Patent No. 8,084,529 discloses a silicone composition containing 0.001 to 10% by weight of cerium oxide powder. The addition of cerium oxide makes it possible to improve the thermal stability of the elastomer obtained after crosslinking.

[0006] GB 1251305 proposes incorporating at least 3% by weight of fumed titanium dioxide into an elastomeric composition and reports an improvement in the behavior (resistance to compression and recovery) of the elastomers held at temperatures of 232°C and 315°C for 16 and 24 hours, respectively. Summary of the Invention [Problem to be solved by the invention]

[0007] However, the antioxidant used does not always allow to obtain a transparent silicone elastomer that can be easily colored.In addition, it may be necessary to formulate the antioxidant in a solvent so that it can be added to the crosslinked silicone elastomer composition, which makes the formulation of the silicone composition complicated.The presence of antioxidant in silicone composition may also slow down the crosslinking rate.

[0008] In this regard, the present invention is intended to meet at least one of the following objectives:

[0009] One essential object of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain thermally stable silicone elastomers.

[0010] One essential object of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain a silicone elastomer having excellent mechanical properties and heat resistance, e.g. capable of withstanding temperatures of 250°C or higher for several days.

[0011] One essential object of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain silicone elastomers which retain their elastomeric properties even after repeated and / or prolonged exposure to heat.

[0012] One of the essential objects of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain silicone elastomers which maintain good elongation properties after heat treatment, for example maintaining an elongation at break of more than 150% or 200% after heat treatment.

[0013] One of the essential objects of the present invention is to provide a heat-resistant additive which does not have a solubility problem in a silicone composition and can be directly dispersed in the silicone composition without the use of a solvent.

[0014] Another essential objective of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain silicone elastomers which are transparent and therefore can be easily colored by adding pigments.

[0015] Another essential object of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain a transparent silicone elastomer even when the silicone composition contains a large amount of filler, for example more than 15% by weight of filler.

[0016] Another essential object of the present invention is to provide a crosslinkable silicone elastomer composition which makes it possible to obtain a silicone elastomer having excellent mechanical properties and heat resistance, and which does not suffer from a slow crosslinking rate.

[0017] Another essential object of the present invention is to provide a crosslinkable silicone elastomer composition which can be used to prepare a coating or primary insulation included in the construction of electrical wire or cable.

[0018] Another essential object of the present invention is to provide a crosslinkable silicone elastomer composition which can be used in the manufacture of automotive cables.

[0019] One essential object of the present invention is to provide a crosslinkable silicone elastomer composition that is easy to formulate. [Means for solving the problem]

[0020] These objects are achieved, inter alia, by the present invention, which relates to a crosslinkable silicone elastomer composition X which comprises: At least one heat resistant additive D which is cerium(IV) neodecanoate.

[0021] The use of heat resistant additive D, which is cerium (IV) neodecanoate, can improve the thermal stability of the silicone elastomer while maintaining the transparency of the silicone elastomer, even when silicone composition X contains more than 15 wt. % of filler E or when the cerium content is high.

[0022] Indeed, and quite surprisingly, the resulting elastomer is thermally stable: it has acceptable elastomeric properties and does not become brittle when treated at 300° C. for 3 days, at 275° C. for 7 days, or at 250° C. for 21 days. The hardness, elasticity, strength at break, elongation at break, and modulus at 100% remain entirely within acceptable limits, i.e., within ranges that allow the intended use of the elastomer.

[0023] Moreover, the elastomers obtained are thermally stable even after long heat treatments, for example 3000 hours at 200° C. This long-term heat treatment corresponds to the tests carried out on automotive cables (see standard ISO 6722). It is therefore possible to use the crosslinkable silicone elastomer composition X for producing automotive cables, in particular automotive cables for electric or hybrid vehicles.

[0024] Furthermore, cerium neodecanoate (IV) is liquid at room temperature, making it easy to handle and mix. It can be added directly to the silicone composition without the use of a solvent, making it easy to incorporate into the silicone composition.

[0025] Furthermore, silicone composition X makes it possible to obtain silicone elastomers with good mechanical properties, and the use of cerium(IV) neodecanoate does not affect the crosslinking kinetics.

[0026] The present invention also relates to silicone elastomers obtainable by crosslinking composition X, preferably by heating to a temperature between 80°C and 250°C.

[0027] The present invention also relates to an electric wire or cable comprising at least one conductive element 1 surrounded by at least one layer of primary insulation 2, characterized in that said layer of primary insulation 2 comprises a silicone elastomer obtained by crosslinking of composition X.

[0028] The present invention also relates to the use of silicone composition X for producing the covering or primary insulation of a single conductor included in a wire or cable construction.

[0029] The invention also relates to the use of silicone composition X for producing automotive cables, in particular automotive cables for electric or hybrid vehicles.

[0030] The present invention also relates to a method for producing an electric wire or cable, comprising the steps of: i. forming around the conductor 1 at least one layer of primary insulation 2 made of a material obtained by crosslinking a silicone composition X (preferably by heating to a temperature between 80°C and 250°C); ii. optionally assembling at least two insulated conductors obtained in step i; iii. Optionally, extruding an outer sheath as defined above around the insulated conductor or conductors from step i or ii. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] definition By "thermally stable silicone elastomer" is meant in particular, within the meaning of the present invention, a silicone elastomer which retains its elastomeric properties and does not become hard or brittle when exposed to temperatures above 200° C., in particular between 250° C. and 300° C., and maintained for several days, in particular for 3 days. Highly preferred are therefore elastomers which are maintained at temperatures above 250° C., in particular between 275° C. and 300° C., for 3 days or more.

[0032] "Electric wire" means an electrotechnical component that serves as a conductor of electricity to transmit energy or information and that consists of an electrically conductive material (single or multi-stranded wire surrounded by an insulating sheath). The inside of the wire is called the "conductor" of the wire.

[0033] "Core" or "single core" means an element consisting of a conductor and its insulating sheath.

[0034] "Electrical cable" means an electrotechnical component serving to transmit electricity and consisting of a number of electrically separate and mechanically solid conductors, optionally with an external screening, for the transmission of energy or information.

[0035] An electric cable consists of one or more single conductors, generally of copper or aluminium type. Each of these single conductors is protected by a covering or primary insulation, consisting of one or more concentric layers based on insulation. Around this covering or these coverings (in the case of a cable with several single conductors), one or more filling elements are provided and / or one or more reinforcing elements, in particular based on glass fibres and / or mineral fibres, and there is generally an outer sheath, which may include one or more sheaths. In the case of an electric cable with several single conductors, the filling elements and / or reinforcing elements arranged around the single conductors (each with a primary insulation) constitute the common covering of all the single conductors.

[0036] In this application, all parts, percentages and ppm are by weight unless otherwise stated.

[0037] The crosslinkable silicone elastomer composition X according to the present invention comprises: At least one heat resistant additive D which is cerium(IV) neodecanoate.

[0038] Heat resistance additive D

[0039] Heat-resistant additive D is cerium(IV) neodecanoate. The oxidation degree of cerium is IV. The chemical formula of cerium(IV) neodecanoate is CeC 40 H 76 It is O8.

[0040] One possible structural formula for cerium(IV) neodecanoate is:

[0041] [ka]

[0042] Neodecanoate has the formula (C 10 H 19 O2) - Preferably, the neodecanoate is a mixture of structural isomers containing trialkyl acetate (i.e., the carbon alpha to the carbonyl is a quaternary carbon). Among the neodecanoate isomers, mention may be made of 2,2,3,5-tetramethylhexanoate, 2,4-dimethyl-2-isopropylpentanoate, 2,5-dimethyl-2-ethylhexanoate, and 2,2-dimethyloctanoate.

[0043] Cerium (IV) neodecanoate is liquid at room temperature and dispersible in silicone. Therefore, it can be used alone or in a blend. When used alone, it is added directly to silicone composition X. When blended, it may be added to silicone oil or silicone rubber before being added to silicone composition X.

[0044] Cerium(IV) neodecanoate disperses well in silicones. It is directly compatible with silicones. Therefore, it is not necessary to use a solvent to incorporate it into a silicone composition.

[0045] According to one embodiment, the silicone composition X has a cerium(IV) content of 50 to 3000 ppmw, preferably 50 to 1000 ppm, preferably 50 to 500 ppm.

[0046] Preferably, silicone composition X has a cerium (IV) content of 50 to 350 ppm, preferably 60 to 300 ppm, preferably 70 to 250 ppm, more preferably 90 to 200 ppm.

[0047] A cerium content of 50 to 350 ppm makes it possible to obtain an elastomer that maintains an elongation at break of more than 200% especially after heat treatment at 275° C. for 7 days.

[0048] Cerium(IV) neodecanoate makes it possible to obtain thermally stable elastomers which retain their elastomeric properties and do not become hard or brittle even when kept at temperatures above 200° C., especially at temperatures between 250° C. and 300° C., for several days, especially for 3 days. In particular, cerium(IV) neodecanoate makes it possible to obtain thermally stable elastomers after heat treatment at 300° C. for 3 days, at 275° C. for 7 days, at 250° C. for 21 days or at 200° C. for 3000 hours.

[0049] Furthermore, the resulting elastomer is transparent even when the silicone composition X contains a large amount of filler and / or a high cerium content. Therefore, it can be easily colored by adding a pigment to the silicone composition X. In addition, since there is no discoloration or change in transparency, it is possible to make the color vivid.

[0050] Advantageously, the cerium(IV) neodecanoate has a level of free acid of less than 5%, preferably less than 2.5%, preferably less than 1.5%, which level of free acid corresponds to the level of free, uncomplexed neodecanoic acid.

[0051] Crosslinkable silicone elastomer composition X

[0052] The crosslinkable silicone elastomer composition X may be provided in a single package or in multiple packages (single component or multicomponent) which, in addition to the heat-resistant additive D, comprises a main component formed from one or more polyorganosiloxane components, a suitable catalyst, and optionally one or more compounds, preferably selected from fillers, crosslinking inhibitors, and pigments.

[0053] The silicone composition X can be crosslinked in the presence of metal catalysts, under the action of organic peroxides (EVC or HCR) at elevated temperature or at room temperature, optionally in the presence of moisture (polyaddition or polycondensation RTV) or thermally (EVC or polyaddition LSR).

[0054] The expressions RTV, LSR, EVC or HCR are well known to those skilled in the art. RTV is an abbreviation for "Room Temperature Vulcanized". LSR is an abbreviation for "Liquid Silicone Rubber". HCR is an abbreviation for "Heat Cured Rubber" and EVC is an abbreviation for "Elastomere Vulcanisable a Chaud" (Heat Vulcanizable Elastomer).

[0055] To prepare silicone composition X according to the invention, the various ingredients can be intimately mixed using equipment well known in the silicone elastomer art. They can be combined in any order.

[0056] According to the first embodiment, the crosslinkable silicone elastomer composition X comprises: Under the action of organic peroxides; or Polyaddition reaction at room temperature or under heating in the presence of a polyaddition catalyst It is a crosslinking composition.

[0057] In this case, the crosslinkable silicone elastomer composition X further comprises: at least one polyorganosiloxane A containing at least two alkenyl groups having 2 to 6 carbon atoms per molecule; optionally at least one polyorganosiloxane B containing at least two hydrogenosilyl functional groups Si-H per molecule; at least one crosslinking catalyst C; and At least one filler E.

[0058] According to one embodiment, the crosslinkable silicone elastomer composition X is at least one polyorganosiloxane A containing at least two alkenyl groups having 2 to 6 carbon atoms per molecule; optionally at least one polyorganosiloxane B containing at least two hydrogenosilyl functional groups Si-H per molecule; at least one crosslinking catalyst C; at least one heat-resistant additive D which is cerium(IV) neodecanoate; At least one filler E wherein the silicone composition X has a cerium (IV) content of 50 to 3000 ppmw.

[0059] Polyorganosiloxane A

[0060] Advantageously, the polyorganosiloxane A is chosen from polyorganosiloxane compounds containing units of formula (I) and optionally other units of formula (II): Z a U b SiO (4-(a+b)) / 2 (I) During the ceremony, the radicals Z, which may be identical or different, are linear or branched alkenyl groups having 2 to 6 carbon atoms, the radicals U, which may be identical or different, represent monovalent radicals having 1 to 12 carbon atoms, a=1, 2, or 3, b=0, 1, or 2, a+b=1, 2, or 3; U c SiO(4-c) / 2 (II) wherein U has the same meaning as above and c=0, 1, 2, or 3.

[0061] Preferably, the radical Z represents a vinyl group.

[0062] In the above formula (I) and formula (II), it is understood that when several groups U are present, they may be identical or different from each other. In formula (I), the symbol "a" is preferably equal to 1. According to one embodiment, in formula (I), a=1 or 2, b=1 or 2, a+b=2 or 3. According to one embodiment, in formula (II), c=2 or 3.

[0063] In formula (I) and formula (II), U may represent a monovalent radical selected from the group consisting of an alkyl group having 1 to 8 carbon atoms (optionally substituted with at least one halogen atom such as chlorine or fluorine), a cycloalkyl group having 3 to 8 carbon atoms, and an aryl group having 6 to 12 carbon atoms. U may advantageously be selected from the group consisting of methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl.

[0064] The polyorganosiloxane A may be an oil having a dynamic viscosity of the order of 10 to 1,000,000 mPa·s at 25° C., typically of the order of 10 to 70,000 mPa·s at 25° C., or may be a rubber having a dynamic viscosity of more than 1,000,000 mPa·s at 25° C. Silicone oils and silicone rubbers are polymers with a linear structure.

[0065] All viscosities referred to in this document correspond to the dynamic viscosity at 25° C., termed “Newtonian”, i.e. the dynamic viscosity measured in a manner known per se with a Brookfield viscometer at a shear rate gradient sufficiently low so that the viscosity measured is independent of the shear rate gradient.

[0066] These polyorganosiloxanes A may have a linear, branched or cyclic structure. Their degree of polymerization is preferably between 2 and 5,000.

[0067] The polyorganosiloxanes A preferably have a linear structure. In the case of linear polymers, they essentially consist of siloxy units ZSiO 2 / 2 , ZUSiO 2 / 2 and U2SiO 2 / 2 siloxy units "D" selected from the group consisting of siloxy units ZUSiO 1 / 2 , Z2USiO 1 / 2 and Z3SiO 1 / 2 The siloxy units "M" are selected from the group consisting of: The symbols Z and U are as defined above.

[0068] Examples of terminal units "M" include trimethylsiloxy, dimethylphenylsiloxy, dimethylvinylsiloxy, or dimethylhexenylsiloxy groups.

[0069] Examples of units "D" include dimethylsiloxy, methylphenylsiloxy, methylvinylsiloxy, methylbutenylsiloxy, methylhexenylsiloxy, methyldecenylsiloxy, diphenylsiloxy, or methyldecadienylsiloxy groups.

[0070] Examples of linear polyorganosiloxanes which may be the unsaturated compound A according to the invention are: · Dimethylvinylsilyl terminated poly(dimethylsiloxane); · Dimethylvinylsilyl terminated poly(dimethylsiloxane-co-methylphenylsiloxane); · Dimethylvinylsilyl terminated poly(dimethylsiloxane-co-diphenylsiloxane); · Dimethylvinylsilyl terminated poly(dimethylsiloxane-co-methylvinylsiloxane); · trimethylsilyl-terminated poly(dimethylsiloxane-co-methylvinylsiloxane); and ·Cyclic poly(methylvinylsiloxane).

[0071] Cyclic polyorganosiloxanes which may be the unsaturated compound A according to the invention are, for example, those consisting of siloxy units "D" of the following formula: ZSiO 2 / 2 , U2SiO 2 / 2 Or ZUSiO 2 / 2 These can be of the dialkylsiloxy, alkylarylsiloxy, alkylvinylsiloxy, or alkylsiloxy type. The cyclic polyorganosiloxane has a viscosity of about 10 to 5000 mPa·s at 25°C.

[0072] Preferably, the polyorganosiloxane compound A has a weight content of Si-vinyl units of 0.001 to 30%, preferably 0.01 to 10%.

[0073] Other examples of unsaturated compounds A include silicone resins containing at least one vinyl group. For example, they may be selected from the group consisting of the following silicone resins: MD containing vinyl group in unit D Vi Q, MD containing vinyl group in unit D Vi TQ, - MM containing vinyl groups in some of the M units Vi Q, - MM containing vinyl groups in some of the M units Vi TQ, - MM containing vinyl groups in some of the units M and D Vi DD Vi Q, and mixtures thereof, Where: M Vi = Formula (R) 2 (vinyl) SiO 1 / 2 Siloxy units D Vi = Formula (R) (vinyl)SiO 2 / 2 Siloxy units ·T=Formula(R)SiO 3 / 2 Siloxy units Q = SiO 4 / 2 Siloxy units ·M=Formula (R)3SiO 1 / 2 Siloxy units ·D=formula(R)2SiO 2 / 2 Siloxy units The groups R may be the same or different and are monovalent hydrocarbon groups selected from alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, and 3,3,3-trifluoropropyl, and aryl groups, such as xylyl, tolyl, and phenyl. Preferably, the group R is methyl.

[0074] Of course, according to a variant, polyorganosiloxane A may be a mixture of several oils or resins corresponding to the definition of polyorganosiloxane A. Advantageously, polyorganosiloxane A is resin-free.

[0075] According to one embodiment, the crosslinkable silicone elastomer composition X comprises 55 to 85% by weight of polyorganosiloxane A, based on the total weight of the silicone composition X, preferably 60 to 80%.

[0076] In the case where the silicone composition X is crosslinked by a polyaddition reaction at room temperature (polyaddition RTV), the polyorganosiloxane A having alkenyl groups advantageously has a viscosity of up to 50000 mPa·s, preferably from 200 to 10000 mPa·s, at 25° C. In the case of a silicone composition X crosslinked by a reaction of thermal polyaddition (polyaddition LSR), the polyorganosiloxane A having alkenyl groups advantageously has a viscosity of more than 1000 mPa·s, preferably in the range of more than 5000 Pa·s to 300000 Pa·s, at 25° C. In the case of a composition X crosslinked by a reaction of thermal polyaddition (polyaddition EVC), the polyorganosiloxane A having alkenyl groups advantageously has a viscosity of more than 300000 mPa·s, preferably from 1 million mPa·s to 30 million mPa·s or more, at 25° C.

[0077] Polyorganosiloxane B

[0078] In a particular case, the crosslinkable silicone elastomer composition X comprises at least one polyorganosiloxane B comprising at least two hydrogenosilyl functional groups Si-H per molecule. According to one embodiment, the crosslinkable silicone elastomer composition X comprises a polyorganosiloxane B comprising at least two hydrogenosilyl functional groups Si-H per molecule and a crosslinking catalyst C selected from polyaddition catalysts.

[0079] Compound B is an organohydrogenopolysiloxane compound containing at least two, preferably at least three hydrogenosilyl functional groups (Si-H) per molecule.

[0080] The organohydrogenopolysiloxane B may advantageously be a polyorganosiloxane comprising at least one unit of formula (III) and optionally other units of formula (IV): H d U e SiO (4-(d+e)) / 2 (III) During the ceremony, the radicals U, which may be identical or different, represent a hydrocarbon group having 1 to 12 carbon atoms, d=1 or 2, e=0, 1 or 2, d+e=1, 2 or 3; U f SiO (4-f) / 2 (IV) where U has the same meaning as above and f=0, 1, 2, or 3.

[0081] In the above formulas (III) and (IV), it is understood that when several groups U are present, they may be identical or different from each other. In formula (III), the symbol d is preferably equal to 1. Furthermore, in formulas (III) and (IV), U can represent a monovalent radical selected from the group consisting of an alkyl group having 1 to 8 carbon atoms (optionally substituted with at least one halogen atom such as chlorine or fluorine), a cycloalkyl group having 3 to 8 carbon atoms, and an aryl group having 6 to 12 carbon atoms. U can advantageously be selected from the group consisting of methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl.

[0082] These polyorganosiloxanes B may have a linear, branched or cyclic structure. The degree of polymerization is preferably greater than or equal to 2. Generally, it is less than 5000.

[0083] For linear polymers, these consist essentially of: The formula: USiO 2 / 2 or UHSiO 2 / 2 a siloxy unit "D" selected from the units The formula below is: USiO 1 / 2 or U2HSiO 1 / 2 A siloxy unit "M" selected from the units:

[0084] The linear polyorganosiloxane may be an oil having a dynamic viscosity of about 1 to 100,000 mPa·s at 25°C, more typically about 10 to 5,000 mPa·s at 25°C.

[0085] Examples of polyorganosiloxanes which may be compound B according to the invention and which contain at least one hydrogen atom bonded to a silicon atom are: · Hydrogenodimethylsilyl terminated poly(dimethylsiloxane); · Trimethylsilyl terminated poly(dimethylsiloxane-co-methylhydrogenosiloxane); · Hydrogenodimethylsilyl terminated poly(dimethylsiloxane-co-methylhydrogenosiloxane); · trimethylsilyl-terminated poly(methylhydrogenosiloxane); and ·Cyclic poly(methylhydrogenosiloxane).

[0086] In the case of cyclic polyorganosiloxanes, these have the formula: USiO 2 / 2 and UHSiO 2 / 2 The siloxy unit "D" is of the dialkylsiloxy or alkarylsiloxy type or unit UHSiO 2 / 2 They have a viscosity of about 1 to 5000 mPa·s.

[0087] The following compounds are particularly suitable according to the invention as organohydrogenopolysiloxane compound B:

[0088] [ka]

[0089] wherein a, b, c, d, and e are defined as follows: In the polymer of formula S1: 0≦a≦150, preferably 0≦a≦100, more specifically 0≦a≦20; 1≦b≦90, preferably 10≦b≦80, more particularly 30≦b≦70; In the polymer of formula S2: 0≦c≦15 In the polymers of formula S3: 5≦d≦200, preferably 20≦d≦100, 2≦e≦90, preferably 10≦e≦70.

[0090] Preferably, the organohydrogenopolysiloxane compound B has a content of hydrogenosilyl functional groups Si-H of 0.2 to 91% by weight. The organohydrogenopolysiloxane compound B can have a content of hydrogenosilyl functional groups Si-H of 5% or more by weight, preferably 10% or more by weight. For example, the weight content of hydrogenosilyl functional groups Si-H is 5 to 40%, or 10 to 30%.

[0091] According to one embodiment, organohydrogenopolysiloxane B is a resin having a branched structure. It may be selected from the group consisting of the following silicone resins: The hydrogen atom bonded to the silicon atom is held in the group M, M'Q, The hydrogen atom bonded to the silicon atom is retained as part of the unit M, MM'Q, The hydrogen atom bonded to the silicon atom is held in the group D, MD'Q, The hydrogen atom bonded to the silicon atom is held by part of the group D, MDD'Q, Hydrogen atoms are included in the unit M, MM'TQ, - The units M and D contain hydrogen atoms, MM'DD'Q, · and mixtures thereof; Where: M, D, T, and Q are as defined above ·M'=formula R2HSiO 1 / 2 Siloxy units ·D'=formulaRHSiO 2 / 2 Siloxy units, The groups R may be the same or different and are monovalent hydrocarbon groups selected from alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, 3,3,3-trifluoropropyl, etc. Preferably, the group R is methyl.

[0092] Preferably, organohydrogenopolysiloxane resin B is resin M'Q or MD'Q as defined above. Even more preferably, organohydrogenopolysiloxane resin B is resin M'Q.

[0093] Of course, according to a variant, organohydrogenopolysiloxane B may be a mixture of several oils or resins which correspond to the definition of organohydrogenopolysiloxane B. Advantageously, organohydrogenopolysiloxane B is resin-free.

[0094] The crosslinkable silicone elastomer composition X may contain 0 to 10% by weight, and preferably 0.5 to 10% by weight, of organohydrogenopolysiloxane B relative to the total weight of the silicone composition X.

[0095] Advantageously, the molar ratio of the hydrogenosilyl functions Si—H of compound B to the alkene functions of compound A ranges from 0.02 to 5, preferably from 0.1 to 4 and more preferably from 0.5 to 3.

[0096] Crosslinking catalyst C

[0097] The crosslinkable silicone elastomer composition X contains a crosslinking catalyst C.

[0098] The crosslinkable silicone elastomer composition X may contain 0.1 to 2% by weight of the crosslinking catalyst C, based on the total weight of the silicone composition X.

[0099] According to a first embodiment, the crosslinking catalyst C is an organic peroxide.

[0100] The organic peroxide can be any one of those that act as vulcanizing agents for the composition that forms silicone elastomers.Thus, it can be any of the peroxides or peresters known for use with silicone elastomers, such as di-t-butyl peroxide, benzoyl peroxide, t-butyl peracetate, dicumyl peroxide, 2,5-dimethylhexane 2,5-diperbenzoate and bis(t-butylperoxy)-2,5dimethyl-2,5hexane, monochlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, bis(2,4-dichlorobenzoyl)peroxide, t-butyl peracetate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,2-bis(t-butylperoxy)-p-diisopropylbenzene, t-butyl perbenzoate, t-butyl peroxy and isopropyl carbonate, and bis(t-butylperoxy)-1,1-trimethyl-3,3,5cyclohexane.

[0101] According to one embodiment, the organic peroxide is selected from benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butyl peracetate, dicumyl peroxide, and mixtures thereof.

[0102] Preferably, the organic peroxide is selected from the group consisting of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, bis(2,4-dichlorobenzoyl) peroxide, and mixtures thereof.

[0103] Generally, when an organic peroxide is present in silicone composition X, the amount of the organic peroxide is 0.05 to 10 parts by weight, preferably 0.5 to 2 parts by weight, per 100 parts by weight of silicone composition X.

[0104] In the manufacture of electric cables or wires by extrusion, the choice of peroxide actually depends on the method used for curing the elastomer (vulcanization method). If the vulcanization method works without pressure (for example hot air and / or (infrared) radiation ovens), the peroxide used is preferably monochlorobenzoyl peroxide and / or 2,4-dichlorobenzoyl peroxide. If the vulcanization method works in the presence of pressure (for example steam tubes), the peroxide used is preferably bis(t-butylperoxy)-2,5-dimethyl-2,5-hexane.

[0105] According to a second embodiment, the catalyst C is a hydrosilylation reaction catalyst, in which case the crosslinkable silicone elastomer composition X comprises at least one polyorganosiloxane B containing at least two hydrogenosilyl functional groups Si-H, preferably at least three hydrogenosilyl functional groups Si-H per molecule.

[0106] Hydrosilylation catalysts are well known. Compounds of platinum and rhodium are preferably used. In particular, it is possible to use platinum complexes with organic products (described in US Pat. Nos. 3,159,601, 3,159,602, 3,220,972, and EP-A-0057459, 0188978, 0190530), platinum complexes with vinylorganosiloxanes (described in US Pat. Nos. 3,419,593, 3,715,334, 3,377,432, and 3,814,730). The generally preferred catalyst is platinum. In this case, the amount by weight of catalyst C, calculated as the weight of platinum metal, is generally 2 to 400 ppm, preferably 5 to 200 ppm, based on the total weight of polyorganosiloxane A. C may be a platinum catalyst, such as a Karstedt catalyst.

[0107] Filler E

[0108] The crosslinkable silicone composition X comprises a filler E. The filler E makes it possible to improve the mechanical properties of the silicone elastomer article obtained at the end of crosslinking, while maintaining good elastomeric properties. In particular, the filler E makes it possible to improve the modulus of rupture of the silicone elastomer article obtained, while maintaining a high elongation at rupture.

[0109] According to one embodiment, the silicone composition X comprises between 15 and 35% by weight of filler E. Advantageously, the silicone composition X comprises between 20 and 30% by weight of filler E.

[0110] The optional filler E is preferably a mineral. It may be a very fine product with an average particle size of less than 0.1 μm. It may in particular be siliceous. In the case of siliceous materials, they may play the role of reinforcing or semi-reinforcing fillers. Reinforcing siliceous fillers are selected from powders of colloidal silica, fumed and precipitated silica, or mixtures thereof. These powders generally have an average particle size of less than 0.1 μm (micrometer) and a fineness of less than 30 μm. 2 / g, preferably 30 to 350 m 2 / g. Semi-reinforcing siliceous fillers such as diatomaceous earth or crushed quartz can also be used. These silicas can be incorporated as is or after treatment with organosilicon compounds usually used for this purpose. These compounds are methylpolysiloxanes (hexamethyldisiloxane, octamethylcyclotetrasiloxane, etc.), methylpolysilazanes (hexamethyldisilazane, hexamethylcyclotrisilazane, tetramethyldivinyldisilazane, etc.), chlorosilanes (dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, etc.), alkoxysilanes (dimethyldimethoxysilane, dimethylvinylethoxysilane, trimethylmethoxysilane, etc.), and mixtures thereof. As for non-siliceous mineral materials, they can be used as semi-reinforcing or filling mineral fillers. Examples of these non-siliceous fillers, which can be used alone or in admixture, are calcium carbonate (optionally surface-treated with an organic acid or an ester of an organic acid), calcined clay, titanium dioxide in the rutile form, oxides of iron, zinc, chromium, zirconium or magnesium, various forms of alumina (hydrated or non-hydrated), boron nitride, lithopone, barium metaborate, barium sulfate, glass microbeads. These fillers are coarser, generally with an average particle size greater than 0.1 μm and a specific surface area generally greater than 30 m. 2 / g. These fillers can be surface modified by treatment with various organosilicon compounds commonly used for this purpose.

[0111] Preferably, the filler E is silica, even more preferably fumed silica. Advantageously, the silica has a viscosity of 75 to 410 μm. 2 / g BET specific surface area.

[0112] According to one embodiment, the crosslinkable silicone elastomer composition X is · 55-85% by weight, preferably 60-80% by weight, of at least one polyorganosiloxane A containing at least two alkenyl groups having 2-6 carbon atoms per molecule; · 0-10% by weight, preferably 0.5-10% by weight, of at least one polyorganosiloxane B containing at least two hydrogenosilyl functional groups Si-H per molecule; 0.1-2 wt.-% of at least one crosslinking catalyst C; at least one heat-resistant additive D, which is cerium(IV) neodecanoate; and 15-35% by weight of at least one filler E, wherein the silicone composition X has a cerium (IV) content of 50 to 3000 ppmw.

[0113] Other Additives

[0114] The crosslinkable silicone elastomer composition X may also contain crosslinking inhibitors F. The latter are generally used to give the ready-to-use composition a certain pot life. These crosslinking inhibitors are present in particular when the precursor silicone composition X of the silicone coating is a polyorganosiloxane crosslinkable by polyaddition or dehydrogenation and the catalyst C used is platinum-based. The crosslinking inhibitors F are preferably selected from acetylenic alcohols (ethynylcyclohexanol: ECH), diallyl maleate, triallyl isocyanurate, dialkyl maleates (diethyl maleate or dialkylalkynyl dicarboxylates) (diethyl acetylenedicarboxylate), or polyorganosiloxanes (advantageously cyclic and substituted with at least one alkenyl, tetramethylvinylcyclotetrasiloxane being particularly preferred), or alkylated maleates. Acetylenic alcohols are useful retarders according to the invention. Examples include: 1-ethynyl-1-cyclohexanol; Methyl-3-dodecyn-1-ol-3; Trimethyl-3,7,11-dodecyn-1-ol-3; Diphenyl-1,1-propyn-2-ol-1 Ethyl-3-ethyl-6-nonyn-1-ol-3; Methyl-3-pentadecyn-1-ol-3.

[0115] The crosslinkable silicone elastomer composition X may also contain a pigment G. The pigment G may be an organic pigment or an inorganic pigment (mineral pigment).

[0116] The crosslinkable silicone elastomer composition X may also contain a plasticizer H. The plasticizers H are generally of organosilicic nature and are added to the silicone composition in a proportion of 0 to 20 parts per 100 parts of polyorganosiloxane A. They make it possible to prevent hardening of the composition during storage. Among the plasticizers, mention may be made of silanes bearing hydrolyzable groups or low molecular weight hydroxylated or alkoxylated diorganopolysiloxane oils. Such compositions are described, for example, in French Patent No. 1 111 969.

[0117] According to a particular embodiment, the crosslinkable silicone elastomer composition X consists of: at least one polyorganosiloxane A containing at least two alkenyl groups having 2 to 6 carbon atoms per molecule; optionally at least one polyorganosiloxane B containing at least two hydrogenosilyl functional groups Si-H per molecule; at least one crosslinking catalyst C; at least one heat-resistant additive D which is cerium(IV) neodecanoate; at least one filler E; optionally at least one cross-linking inhibitor F, optionally at least one pigment G; and Optionally, at least one plasticizer H.

[0118] According to a particular embodiment, the crosslinkable silicone elastomer composition X does not comprise an adhesion promoter.

[0119] According to a particular embodiment, the crosslinkable silicone elastomer composition X does not comprise a silicone resin, in particular does not comprise a silicone resin comprising at least one alkenyl radical.

[0120] According to a second embodiment, the crosslinkable silicone elastomer composition X is crosslinkable in the presence of moisture and at room temperature in the presence of a metal catalyst (polycondensation RTV).

[0121] In this second embodiment, the crosslinkable silicone elastomer composition X further comprises: at least one polyorganosiloxane A' capable of crosslinking by polycondensation; at least one crosslinkable organosilicon compound B'; at least one catalyst C'; at least one filler E; and Optionally, pigment G.

[0122] The polyorganosiloxane A' may be linear or branched, contains hydroxyl groups or hydrolyzable groups selected from the group consisting of alkoxy, alkoxy-alkylene-oxy, amino, amido, acylamino, aminoxy, iminoxy, ketiminoxy, acyloxy and enoxy, preferably alkoxy, and crosslinks at room temperature under the action of moisture by a polycondensation reaction.

[0123] Examples of alkoxy-type hydrolyzable, condensable groups Z include groups having 1 to 8 carbon atoms (such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, s-butoxy, t-butoxy, 2-methoxyethoxy, hexyloxy, and octyloxy groups).

[0124] As an example of a hydrolyzable, condensable group Z of the alkoxy-alkylene-oxy type, mention may be made of the methoxy-ethylene-oxy group.

[0125] As examples of hydrolyzable, condensable groups Z of the amino type, mention may be made of the methylamino, dimethylamino, ethylamino, diethylamino, n-butylamino, s-butylamino or cyclohexylamino groups.

[0126] An example of an amide type hydrolyzable, condensable group Z is the N-methyl-acetamide group.

[0127] An example of an acylamino-type hydrolyzable, condensable group Z is a benzoylamino group.

[0128] As examples of hydrolyzable, condensable groups Z of the aminoxy type, mention may be made of the dimethylaminooxy, diethylaminooxy, dioctylaminooxy or diphenylaminooxy groups.

[0129] As examples of hydrolysable, condensable groups Z of the iminoxy, and in particular ketiminoxy, type, mention may be made of the groups derived from the following oximes: acetophenone oxime, acetone oxime, benzophenone oxime, methylethylketoxime, diisopropyl-ketoxime or methylisobutyl-ketoxime.

[0130] An example of an acyloxy-type hydrolyzable, condensable group Z is an acetoxy group.

[0131] An example of an enoxy-type hydrolyzable, condensable group Z is 2-propeneoxy.

[0132] Polyorganosiloxane A' has at least two hydroxyl or alkoxy groups per molecule and has a dynamic viscosity at 25°C of 50 mPa s to 50 × 10 6 mPa·s, and for silicone oil, 50mPa·s to 10 6 mPa·s, preferably 10 for silicone rubber 6 The polydiorganosiloxane may be a linear polydiorganosiloxane having a viscosity of greater than mPa·s.

[0133] The same or different organic groups generally present in the structure of polyorganosiloxane A' are methyl, ethyl, phenyl or trifluoropropyl groups.Preferably, at least 80% by number of said organic groups are methyl groups directly bonded to silicon atoms.In the context of the present invention, α,ω-bis(dimethylhydroxysilyl)polydimethylsiloxane and α,ω-bis(dimethylalkoxysilyl)polydimethylsiloxane are more particularly preferred.

[0134] According to one embodiment, the crosslinkable silicone elastomer composition X comprises 40 to 90% by weight, preferably 50 to 80% by weight, of polyorganosiloxane A', relative to the total weight of the silicone composition X.

[0135] Catalyst C' is a catalyst for polycondensation reaction. Polycondensation catalysts are well known to those skilled in the art. Without intending to be limited, catalyst C' can be selected from compounds based on tin or titanium, as well known to those skilled in the art, or from organic catalysts such as guanidines, as described in EP 2268743 and EP 2367867, or from metal complexes based on, for example, Zn, Mo, Mg, etc., as described in EP 2222626, EP 2222756, EP 2222773, EP 2935489, EP 2935490 and WO 2015 / 082837.

[0136] The crosslinkable silicone elastomer composition X may contain 0.1 to 2 wt % of the catalyst C' based on the total weight of the silicone composition X.

[0137] The crosslinking agent B' is preferably an organosilicon compound having more than two hydrolyzable groups attached to the silicon atom per molecule. Crosslinking agents of this type are well known to those skilled in the art and are commercially available.

[0138] The crosslinker B' is preferably a silicon compound, each molecule of which contains at least three hydrolyzable, condensable groups selected from the group consisting of alkoxy, alkoxy-alkylene-oxy, amino, amido, acylamino, aminoxy, iminoxy, ketiminoxy, acyloxy and enoxy, preferably alkoxy, these groups being as defined above.

[0139] The crosslinkable silicone elastomer composition X may contain, based on the total weight of the silicone composition X, 1 to 20% by weight, and preferably 2 to 15% of the crosslinkable organosilicon compound B'.

[0140] Filler E and pigment G are as defined above.

[0141] According to one embodiment, the crosslinkable silicone elastomer composition X comprises 10 to 40% by weight, preferably 15 to 35% by weight, of the filler E relative to the total weight of the silicone composition X.

[0142] According to one embodiment, the crosslinkable silicone elastomer composition X is 40 to 90% by weight, preferably 50 to 80% by weight, of at least one polyorganosiloxane A' crosslinkable by polycondensation, 1 to 20% by weight, preferably 2 to 15% by weight, of at least one crosslinkable organosilicon compound B', · 0.1-2 wt. % of at least one catalyst C'; at least one heat-resistant additive D, which is cerium(IV) neodecanoate; and 10 to 40% by weight, preferably 15 to 35% by weight, of at least one filler E, wherein the silicone composition X has a cerium (IV) content of 50 to 3000 ppmw.

[0143] Silicone Elastomer

[0144] The invention also relates to silicone elastomers obtained by crosslinking composition X at room temperature, optionally in the presence of moisture, or by heating. Heating is preferably carried out at temperatures between 80° C. and 250° C. The heating time varies depending on the temperature, but also on the pressure optionally applied. According to one embodiment, heating is carried out as follows: 100-120℃ for a few seconds to a few minutes 180~200℃ for a few seconds.

[0145] Silicone composition X makes it possible to obtain thermally stable elastomers after heat treatment for 3 days at 300° C., for 7 days at 275° C. or for 21 days at 250° C. The elastomers obtained therefore have very good thermal stability and can be used to make the covering or primary insulation of single conductors included in the construction of wires or cables.

[0146] The present invention therefore also relates to an electric wire or cable comprising at least one conductive element 1 surrounded by at least one layer of primary insulation 2, characterized in that said layer of primary insulation 2 comprises a silicone elastomer obtained by crosslinking a silicone composition X.

[0147] The invention also relates to the use of silicone composition X for producing automotive cables, in particular automotive cables for electric or hybrid vehicles.

[0148] The present invention also relates to the use of silicone composition X for producing the covering or primary insulation of a single conductor included in a wire or cable construction.

[0149] The present invention also relates to a method for producing an electric wire or cable, comprising the steps of: i. forming around the conductor 1 at least one layer of primary insulation 2 made of a material obtained by crosslinking a silicone composition X by heating it to a temperature preferably between 80°C and 250°C; ii. optionally assembling at least two insulated conductors obtained in step i; iii. Optionally, extruding an outer sheath as defined above around the insulated conductor or conductors from step i or ii.

[0150] In connection with this method, the formation of at least one layer of the primary insulation 2 around the conductor 1 can be carried out by depositing the silicone composition X around the conductor 1 by conventional methods, in particular by extrusion. The deposit thus obtained is crosslinked, preferably by heating, to form a silicone elastomer primary insulation. The heating time depends, of course, on the temperature of the material and the optional working pressure. It is usually on the order of a few seconds to a few minutes at 100-120 ° C and on the order of a few seconds at 180-200 ° C. It is possible to deposit several layers together, for example using a tandem extrusion with a crosshead or by coextrusion.

[0151] The wire or cable according to the invention may further comprise an outer sheath surrounding the insulated conductor or conductors. This outer sheath is well known to those skilled in the art. It may burn completely locally and turn into residual ash under the effect of the high temperature of the fire, but the fire will not spread. The material constituting the outer sheath may be, for example, a polymer matrix based on polyolefins and at least one hydrated refractory mineral filler, in particular chosen from metal hydroxides, such as magnesium dihydroxide or aluminum trihydroxide. The outer sheath is conventionally obtained by extrusion.

[0152] According to a preferred embodiment, the electric wire or cable according to the invention is characterized in that the layer of primary insulation 2 is formed by depositing said silicone composition X around an electrically conductive element 1, by extrusion techniques and heating means, so as to obtain a material temperature ranging from 80°C to 250°C, until said silicone composition X has hardened.

[0153] The following examples are given for illustrative purposes and should not be construed as limiting the scope of the present invention. EXAMPLES

[0154] Heat Resistant Additives

[0155] Cerium Neodecanoate

[0156] Cerium(IV) neodecanoate was synthesized according to the procedure described in EP 0575189. Cerium(IV) neodecanoate is a liquid. It can be used alone (Additive 1) or in combination (Additives 2 and 3).

[0157] Additive 1: The proportion of cerium in Additive 1 is 16.6% by weight.

[0158] Additive 2: Cerium(IV) neodecanoate compounded in a kneader In the kneader, 56.6% by weight of poly(dimethyl)(methylvinyl)siloxane rubber having 720 ppm of vinyl groups and a viscosity of 20 million mPa·s at 25°C was added to 235 m 2 5.6 wt. % of fumed silica treated with octamethylcyclotetrasiloxane having a BET specific surface area of ​​1.0 g / g was mixed with 37.8 wt. % of cerium (IV) neodecanoate. The mixture was mixed at room temperature for 10 minutes.

[0159] Additive 3: Roll-blended cerium(IV) neodecanoate A two-roll machine was used to roll 56.6% poly(dimethyl)(methylvinyl)siloxane rubber with 720 ppm vinyl group and a viscosity of 20 million mPa·s at 25°C onto 235 m 2 5.6 wt. % of fumed silica treated with octamethylcyclotetrasiloxane having a BET specific surface area of ​​1.0 g / g was mixed with 37.8 wt. % of cerium (IV) neodecanoate. The mixture was mixed at room temperature for 10 minutes.

[0160] Additives 2 and 3 have a proportion of cerium of 0.063% by weight relative to the total weight of the additive.

[0161] Additive 4

[0162] Additive 4 is an additive based on TiO2 and Fe2O3 in silicone rubber. The iron content is 0.7-2.1 wt.%. The TiO2 content is more than 94 wt.%.

[0163] Additive 5

[0164] Additive 5 is cerium oxide purchased from Sigma Aldrich.

[0165] Additive 6

[0166] Additive 6 is cerium(III) octoate purchased from Sigma Aldrich.

[0167] Additive 7

[0168] Additive 7 is an antioxidant based on iron(III) ethyl-2-hexanoate in silicone rubber. The iron content is 0.78% by weight.

[0169] Composition HCR1:

[0170] Base A: 67.8% by weight of a mixture of vinylated polyorganosiloxanes having a viscosity of 20 million mPa·s at 25°C and a vinyl content of 100-800 ppm, 1.8% by weight of a polydimethylsiloxane oil having two hydroxyl units, and 235m 2 30.4 wt. % fumed silica treated with octamethylcyclotetrasiloxane having a BET specific surface area of ​​1.0 g / g. 1.25% of 2,4-dichlorobenzoyl peroxide sold under the reference PERKADOX PD-50S-PS from Akzo Nobel and a heat resistant additive were then added to 100 parts of this base A.

[0171] Composition HCR2: Base A: 68.0% by weight of a mixture of vinylated polyorganosiloxanes having a viscosity of 20 million mPa·s at 25°C and a vinyl content of 100-800 ppm, 1.70% by weight of a polydimethylsiloxane oil having two hydroxyl units, and 235m 2 30.30 wt. % of fumed silica treated with octamethylcyclotetrasiloxane having a BET specific surface area of ​​1.0 g / g. 1.25% by weight of 2,4-dichlorobenzoyl peroxide sold under the reference PERKADOX PD-50S-PS from Akzo Nobel and a heat resistance additive were then added to 100 parts of this base A. Composition LSR: The following was added to the mixer: Each end is Me2ViSiO 1 / 2 29 parts of dimethylpolysiloxane oil with a viscosity of 60,000 mPa·s, blocked in units; Each end is Me2ViSiO 1 / 2 29 parts of dimethylpolysiloxane oil with a viscosity of 100000 mPa·s, blocked in units; 300m 2 / g BET specific surface area and 26 parts hexamethyldisilazane. The mixture was heated with stirring at 70° C. for 1 hour, stripped of volatiles, cooled, and stored as Base 1. Next, in a high speed mixer, to 45 parts of this Base 1 was added: Platinum is introduced in the form of a 10% by weight organometallic complex of platinum metal (known as Karstedt's catalyst) diluted in vinylating oil; 3 parts of dimethylpolysiloxane oil having vinyl groups in the chain and at the chain ends and a viscosity of 1000 mPa·s, · 2 parts of a dimethylpolysiloxane oil containing vinyl groups in the chain and at the chain ends and having a viscosity of 400 mPa·s. Part A of this composition LSR was mixed in a high speed mixer at 1000 revolutions per minute for 1 minute. The proportion of Pt is 10 ppm. Next, in a high speed mixer, to 45 parts of this Base 1 was added: 1.3 parts of organohydrogenopolysiloxane resin M'Q containing Si-H groups, 0.5 parts of a linear organohydrogenopolysiloxane containing Si-H groups in the chain and at the chain ends, containing about 20% by weight of Si-H groups, 1.5 parts of a dimethylpolysiloxane oil containing vinyl groups in the chain and at the chain ends and having a viscosity of 400 mPa s, 1.6 parts of dimethylpolysiloxane oil having vinyl groups in the chain and at the chain ends and a viscosity of 1000 mPa s, · 0.08 parts of ethynyl-1-cyclohexanol-1 as a reaction inhibitor. Part B of this composition LSR was mixed in a high speed mixer at 1000 revolutions per minute for 1 minute. Then, using a high speed mixer, equal amounts of heat resistant additive were added to parts A and B. Parts A and B were then mixed in a 1:1 ratio.

[0172] Mechanical properties of elastomers obtained after crosslinking of silicone compositions

[0173] Test plates (150 mm x 150 mm x 2 mm) were prepared in a four-cavity mold under pressure at 115°C for 8 minutes.

[0174] After a post-curing step of 4 hours at 200°C in a ventilated stove, the plates were subjected to thermo-oxidative ageing in a ventilated stove under different conditions of time and temperature, as detailed in the examples presented below.

[0175] The mechanical properties, in this case hardness Shore A (ISO 868, DIN 53505), breaking strength (ISO 37, DIN 53504-51), elongation at break (ISO 37, DIN 53504-51) and tear resistance (ASTM D624A), were measured for all plates aged in this way and compared with the mechanical properties measured for the initial plates after 4 hours curing at 200°C.

[0176] A variety of heat resistant additives were tested and the results are shown in Table 1.

[0177] [Table 1]

[0178] These results show that cerium (IV) neodecanoate (example 1) makes it possible to obtain better mechanical properties and better thermal stability than cerium oxide (additive 5), cerium (III) octanoate (additive 6) and iron (III) ethyl-2-hexanoate (additive 7) (comparative examples 2 to 4). Moreover, the mechanical properties obtained with cerium (IV) neodecanoate are comparable to those obtained with TiO2 (additive 4, comparative example 1). However, the plates obtained with cerium (IV) neodecanoate are transparent, in contrast to the plates obtained with TiO2 (additive 4, comparative example 1).

[0179] The composition according to the invention therefore makes it possible to obtain transparent silicone elastomers having good mechanical properties and good thermal stability.

[0180] Various concentrations of cerium(IV) neodecanoate were tested, and the results are shown in Table 2.

[0181] [Table 2]

[0182] These results indicate that good mechanical properties and good thermal stability are obtained over a wide range of cerium (IV) neodecanoate concentrations.

[0183] Both free and compounded cerium(IV) neodecanoate were tested, and the results are shown in Table 3.

[0184] [Table 3]

[0185] The results show that it is possible to use cerium(IV) neodecanoate, either alone or in a blend, since the results obtained are comparable.

[0186] The results also show that the elastomer obtained retains its good mechanical properties, especially the elastomeric properties, even after heat aging at 250° C. for 21 days.

[0187] Cerium (IV) neodecanoate was also tested in composition LSR, and the results are shown in Table 4.

[0188] [Table 4]

[0189] These results show that it is also possible to use cerium (IV) neodecanoate to increase the thermal stability of the composition LSR, crosslinkable by polyaddition. Moreover, the mechanical properties obtained with cerium (IV) neodecanoate are good. In fact, after aging at 250°C or 275°C for 3 days, the elongation at break for cerium (IV) neodecanoate (Examples 10-12) is greater than without heat-resistant additive or with iron (III) ethyl-2-hexanoate (Additive 7) (Comparative Examples 5-6). The tests also showed that above 300 ppm, the crosslinking kinetics of the composition LSR is affected, decreasing the crosslinking rate.

[0190] Cerium (IV) neodecanoate was also tested under the conditions that automotive cables are tested under. The results are shown in Table 5.

[0191] [Table 5]

[0192] These results show that the elastomers obtained retain their good mechanical and especially elastomeric properties, even after 3000 hours of thermal aging at 200 °C, which corresponds to the standard for testing automotive cables (see ISO 6722-1).

Claims

1. A crosslinkable silicone elastomer composition X, Said silicone composition X contains at least one heat resistant additive D which is cerium (IV) neodecanoate and has a cerium (IV) content of 50 to 3000 ppmw.

2. The composition of claim 1 further comprising: at least one polyorganosiloxane A containing at least two alkenyl groups having 2 to 6 carbon atoms per molecule; optionally at least one polyorganosiloxane B containing at least two hydrogenosilyl functions Si—H per molecule; at least one crosslinking catalyst C; and at least one filler E;

3. 3. Composition according to claim 1 or 2, characterized in that it has a content of cerium (IV) of 50 to 350 ppm, preferably of 60 to 300 ppm, preferably of 70 to 250 ppm, even more preferably of 90 to 200 ppm.

4. Composition according to any one of claims 1 to 3, characterized in that it contains from 15 to 35% by weight of a filler E, preferably silica.

5. The composition according to any one of claims 1 to 4, characterized in that the crosslinking catalyst C is an organic peroxide.

6. 5. Composition according to any one of claims 1 to 4, characterized in that it comprises at least one polyorganosiloxane B containing at least two hydrogenosilyl functional groups Si-H per molecule, and the crosslinking catalyst C is selected from polyaddition catalysts.

7. A silicone elastomer obtainable by crosslinking the crosslinkable silicone elastomer composition X according to any one of claims 1 to 6, preferably by heating at a temperature of 80°C to 250°C.

8. 8. An electric wire or cable comprising at least one conductive element 1 surrounded by at least one layer of primary insulation 2, characterized in that said layer of primary insulation 2 comprises a silicone elastomer according to claim 7.

9. Use of the crosslinkable silicone elastomer composition X according to any one of claims 1 to 6 for producing a coating or primary insulation for a single conductor included in a wire or cable construction.

10. Use of the crosslinkable silicone elastomer composition X according to any one of claims 1 to 6 for producing automotive cables, in particular automotive cables for electric or hybrid vehicles.

11. 9. A method for producing an electric wire or cable according to claim 8, characterized in that it comprises the following steps: i. forming around the conductor 1 at least one layer of primary insulation 2 made of a material obtained by crosslinking the silicone composition X according to any one of claims 1 to 6 by heating it at a temperature preferably between 80°C and 250°C; ii. Optionally, assembling at least two insulated conductors obtained in step i; iii. Optionally, extruding an outer sheath as defined above around the insulated conductor(s) from step i or ii.

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