MXPA99006165A - USE OF MIXTURES WITH BASE OF Pt AND OF TRANSITION METAL COMPOUNDS OTHER THAN Pt FOR IMPROVING THE RESISTANCE TO ARC TRACKING AND TO ARC EROSION OF SILICON ELASTOMERS - Google Patents

Abstract

The invention concerns the use as additive for improving properties of resistance to arc tracking and arc erosion:of a mixture A, B or C formed by:concerning mixture A:A1:platinum;and A2:at least an inorganic compoundA2.1 of a metal with several degrees of oxidation selected from the group formed by V, Cr, Mn, Fe, Co, Ni, and Cu, in which the metal atom is at a degree of oxidation higher than zero, the least possible (abbreviation:DOX mini);or A3:a combination of at least an inorganic compound A2.1 with at least an inorganic compound A2.2 in which the atom of V, Cr, Mn, Fe, Co, Ni or Cu is at a degree of oxidation higher than DOX mini;concerning mixture B:B1 platinum;and B2:at least an inorganic compound B2.1 of cerium-IV or of lanthanum-III;or B3:a combination of at least an inorganic compound B2.1 with at least an inorganic compound B2.2 of titanium-IV;concerning mixture C3:C1 platinum;and C2 a combination of constituent A2 or A3 with the constituent B2 or B3;in a polyorganosiloxane composition D for obtaining a silicon elastomer, either cross-linkable at room temperature or by heat by reactions of polyaddition in the presence of a metal catalyst, or cross-linkable at high temperature by the action of organic peroxide(s).

Description

USE OF MIXTURES BASED ON Pt AND COMPOSED OF METALS OF DIFFERENT TRANSITION OF THE Pt, TO IMPROVE THE RESISTANCE PROPERTIES TO THE ARC, OF THE SILI-C ELASTOMEROS NA DESCRIPTION OF THE INVENTION The object of the present invention is the use as additives that improve the properties of resistance to sliding or arc sliding and erosion under arc: • mixtures based on platinum and compound (s) of a metal (or metals) of transition other than platinum, and judiciously chosen, in the compositions of polyorganosiloxanes for obtaining silicone elastomers, either by crosslinking at room temperature or with heat with polyaddition reactions in the presence of a metallic catalyst (compositions called RTV, LSR or EVA of polyaddition), or by crosslinking at high temperature under the action of organic peroxides (compositions known as EVC). The term "properties of resistance to sliding or arch sliding and erosion under arc" means the properties of this type of silicone elastomers obtained by crosslinking polyorganosiloxane compositions called RTV, LSR, polyaddition EVC or EVC. The expressions RTV, LSR, EVC are well known to the person skilled in the art: RTV is the abbreviation of "Vulcanization at Ambient Temperature" ("Room Temperature Vulcanizing" for its meaning in English); LSR is the abbreviation of "Liquid Silicone Rubber" ("Liquid -SilÍGone Rubber", for its meaning in English) and EVC is the abbreviation of "Hot Vulcanizable Elastomer". It is known, from Japanese Patent JP-A-6/035, 501 to use a mixture of platinum and a mixed oxide of iron of the formula (FeO) x, (Fe203) and where the ratio x7y e-stá Compressed between 0.05 / 1 and 1/1, to improve the flame resistance properties of iast-eaters = illcontained obtained from the EVC compositions. It is known-, from the French Patent FR-A-2, 166, 313 and European Patent EP-A-0, 347, 349, using a mixture of platinum with at least one rare metal oxide, in particular a mixture of platinum with cerium oxide IV- Ce02-, to improve the flame resistance properties of the silicone elastomers obtained from the EVC compositions (French Patent FR-A-2, 166, 313) or from the RTV compositions (European Patent EP-A -0, 347, 349). The Applicant has now found that the compositions of polyorganosiloxanes RTV, LSR, EVA polyaddition or EVC containing this type of additive based on a mixture of platinum with a mixed oxide of iron or a cerium IV oxide also present of the good properties of resistance to bow slippage and erosion under the arch; the Applicant has also found other additives than the aforementioned mixtures, which can be used for obtaining silicone elastomers having good sliding or sliding properties. arc and erosion under arc, which always have good properties of flame resistance and good mechanical properties, these elastomers having been obtained from compositions of polyorganosiloxanes of the RTV, LSR, EVA type of polyaddition or EVC. The present invention thus relates to the use, as an additive for improving the properties of resistance to sliding or arch sliding and erosion under arc: a mixture A, B or C formed of: * in the case of a mixture A: Al: platinum; and A2: at least one inorganic compound A2.1 of a metal with various oxidation degrees taken from the group consisting of V, Cr, Mn, Fe, Co. Ni and Cu, in which the metal atom is at an oxidation level greater than zero, the lowest possible (in short DOX mini); or A3: a combination of at least one inorganic compound A2.1 with at least one inorganic compound A2.2 in which the atom of V, Cr, Mn, Fe, Co, Ni or Cu is found at a degree of oxidation higher than DOX min; * in the case of mixture B: Bl: platinum; and B2: at least one inorganic compound B2.1 cerium IV or lanthanum II; or B3: a combination of at least one inorganic compound B2.1 with at least one inorganic compound B2.2 of titanium IV; * when dealing with the mixture C: Cl: platinum; and C2: a combination of the constituent A2 or A3 with the constituent B2 or B3; • in a polyorganosiloxane D composition for obtaining a silicone elastomer, either by crosslinking at room temperature or with heat by reacting polyaddition in the presence of a metal catalyst, or by crosslinking at elevated temperature under the action of organic peroxide (s) (s) The platinum, which constitutes Al, Bl and Cl of the mixtures A, B and C, can be mainly: - under the form: of metallic platinum (elemental) or - under the form: • of chloroplatinic acid H2PtCl6 • 6H20; as described in U.S. Patent No. 2,823,218. • of anhydrous chloroplatinic acid, • of PtCl2 [P (CH2-CH2-CH3) 3] 2 • of complexes such as those of the formula (PtCl2, olefin) 2 and H (PtCl3, olefin) described in US Pat. No. 3,159,601, the olefin of the complex representing mainly ethylene, propylene, butylene, cyclohexane, styrene, • of (PtCl2, C3H6) 2, complex of platinum and cyclopropane chloride, described in US Patent No. 3,159,662, • the following products, compounds or complexes: Pt (CH3CN) 2CI2 [Pt (CH3CN) 2 (NH3) 4] C1C Pt (NH3) 2C12, K [PtCl3 (CH2CH2CH2OH)] PtBr2 (C2H4) 2, K [PtBr3 (C2H4)], PtCl2C2C2H4 (CH3) 2C = CH2 »PtCl2, H2Pt (CN) 4, 5H20 H [PtCl3 (CH3CN)], Pt (NH3) 2 (CNS) 2 [Pt (NH3) 4]« [PtCl4] / PtCl2 [P (CH2CH3) 3] 2, PtCl2 »PCl3 PtCl2, P (OH) 3, PtCl2» P (OCH2CH3) 3 PtCl2, [P (OCH2CH3) 3] 2, Pt (OOCCH2SCH2CH3) 2 Pt (CN) 3, (CH3) 4Pt, (CH3) 3Pt- Pt (CH3) 3 (CH3) 3Pt (CH3COCH = CCH3) PtCl2CO and PtBr2CO The amount of platinum, expressed in parts by weight of elemental platinum, is in the range generally ranging from 1 to 250 ppm and, preferably, from 3 to 100 ppm , relative to the total weight of the polyorganosiloxane constituent (s) of the hardenable compositions D ^ In the case of compositions D of type RTV, LSR and EVC of polyaddition, the platinum constituent advantageously corresponds to the catalytic platinum that is normally put into operation to perform the polyaddition reactions responsible for the crosslinking of these compositions.

Concerning the constituents A2 or A3, B2 or B3 and C2 of the mixtures A, B and C, by the expression "inorganic compound", it is meant to define more particularly the oxides and the hydroxides; these compounds are in general solid, anhydrous or not, which are used in the form of particles having an average diameter not exceeding 20 μm and, preferably ranging from 0 ^ 02 5 μm, and a specific upper BET numeral or equal to 0.2 m / g and, preferably, ranging from 0.5 to 100 m2 / g. When speaking of a group of particles having an average diameter located in a given range, it should be understood that more than 50% by weight of the particles have a diameter located in the range in question. The BET surface area is determined according to the BRUNAUER, EMMET, TELLER method described in "The Journal of the American Chemical Society, Vol. 80, page 309 (1338)" corresponding to the AFNOR NFT 45007 standard of November 1987. The quantities of the constituents A2 or A3, B2 or B3 and C2 of the mixtures A, B and C expressed in parts by weight of the constituent, are in the range generally ranging from 0.5 to 30 and, preferably, from 1 to 15 parts by weight for 100 parts of the polyorganosiloxane constituent (s) of the hardenable compositions D. In the constituent A3 (combination), the ratio between the weight amount of the compound (s) A2 .1 and that of the compound (s) A2.2 is in the range generally ranging from 0.1 / 1 to 9/1 and preferably from 0.25 / 1 to 4/1. In the constituent B3 (combination), the ratio between the weight amount of the compound (s) B2.1 and that of the compound (s) B2.2 is in the range that goes in overall from 0.6 / 1 to 6/1 and preferably from 0.8 / 1 to 4/1. In the constituent C2 (combination) the ratio between the weight amount of the constituent A2 or A3 and that of constituent B2 or B3 is in the range of generally 0.02 / 1 to 1/1 and preferably 0.05 / 1 to 0.5 / 1. According to an embodiment of the present invention which is convenient, recourse is made, as additive: to a mixture A of the type Al + A3 where: the constituent Al is of platinum, in the form of a complex or a compound of platinum; and the constituent A3 consists of a combination of FeO with Fe203; to a mixture B of type Bl + B2 where: the constituent Bl has the meaning of the constituent Al of f; and the constituent B2 consists of the oxide and / or the cerium VI hydroxide; to a mixture B of type Bl + B3 where: the constituent Bl has the meaning of the constituent Al of; and the constituent B3 consists of a combination of oxide and / or cerium IV hydroxide with titanium oxide Ti02; or ® to a mixture C where: the constituent Cl has the meaning of the constituent Al of; and constituent C2 consists of a combination of constituent B3. cited below with the constituent A3 cited under F the quantities of the various constituents Al, A3, Bl, B2, B3, Cl and C2 and the relationships that may exist between the quantities of some of them, in the case of combinations, are situated in large intervals called "ranging in general from (...) to (...) "mentioned above. According to an embodiment of the present invention, which is more particularly convenient, one of the mixtures mentioned under the subparagraphs is used as an additive, and for which the quantities of the various constituents and the relations that may exist between the quantities of some of them in the case of the combinations, they are situated in the narrow intervals denominated "which go preferably from (..) to (...)" mentioned above. The compositions of hardenable polyorganosiloxanes D considered within the framework of the present invention, presented in one or several containers (single or multiple components) include a main constituent formed of one or several polyorganosiloxane constituents, a suitable catalyst and optionally one or several compounds, taken from the group consisting mainly of: reinforcing or semi-reinforcing fillers or fillers or used to adapt the rheology of hardenable compositions, crosslinking agents, adhesion agents, plasticizing agents, inhibitors of the catalyst and the coloring agents. The polyorganosiloxanes, main constituents of the compositions D considered within the framework of the present invention, can be linear, branched or crosslinked, and include hydrocarbon radicals and / or reactive groups consisting of the alkenyl groups and hydrogen atoms. It should be noted that the polyorganosiloxane compositions are widely described in the literature and mainly in the work of Walter NOLL: "Chemistry and Technology of Silicones", Academic Press. 1968, 2nd edition, pages 386 to 409. More precisely, the polyorganosiloxanes, main constituents of the compositions D considered within the framework of the invention, consist of siloxyl portions of the general formula: RnSi04- (i: and / or siloxyl portions of the formula: ZxRyS l? 4-x-y (II) 2 formulas in which the various symbols have the following meaning: - the R symbols, identical or different, each represent a group of hydrocarbon nature not hydrolysable, this radical being: * an alkyl radical, halogenoalkyl having 1 to 5 atoms carbon and including from 1 to 6 chlorine and / or fluorine atoms, * cycloalkyl radicals and halogenocycloalkyls having from 3 to 8 carbon atoms and containing from 1 to 4 chlorine and / or fluorine atoms, * aryl, alkylaryl and halogenaryl radicals having 6 to 8 carbon atoms and containing 1 to 4 chlorine and / or fluorine atoms, * cyanoalkyl radicals having 3 to 4 carbon atoms; - the symbols Z each represent a hydrogen atom or an alkenyl group of 2 to 6 carbon atoms; n = an integer to 0, 1, 2 or 3; x = an integer equal to 0, 1, 2 or 3; y = an integer equal to 0, 1 or 2; - the sum x + y is in the range from 1 to 3. Illustratively, organic radicals R, directly linked to the silicon atoms, may be mentioned: the methyl groups; ethyl; propyl; isopropyl; butyl, isobutyl; n-pentyl; t-butyl; chloromethyl; dichloromethyl; a-chloroethyl; a, β-dichloroethyl; fluoromethyl; difluoromethyl; α-difluoroethyl; 3, 3, 3-trifluoropropyl; trifluorocyclopropyl; 4, 4, 4-trifluorobutyl; 3, 3, 4, 4, 5, 5-hexafluoropentyl; β-cyanoethyl; ? -cyanopropyl; phenyl; p-chlorophenyl; m-chlorophenyl; 3, 5-dichlorophenyl; trichlorophenyl; tetrachlorophenyl; o-, p- or m-tolyl; a, a, α-trifluorotolyl; xylyls such as 2,3-dimethylphenyl, 3,4-dimethylphenyl. Preferably, the organic radicals R bonded to the silicon atoms are methyl radicals, phenyl, these radicals possibly being halogenated or even also the cyanoalkyl radicals. The symbols Z are hydrogen atoms or alkenyl groups which are preferably vinyl groups. The nature of the polyorganosiloxane and thus the relations between the siloxyl portions (I) and (II) and the distribution of these is as chosen depending on the crosslinking treatment that will be carried out on the hardenable composition, with a view to its transformation into an elastomer . Compositions of polyorganosiloxanes D, two-component or single-component, which crosslink at room temperature or with heat by polyaddition reactions, essentially by reaction of hydrogenosilylated groups on the alkenyl-silyl groups, in the presence of a metal catalyst. platinum-based general, is disclosed, for example, in U.S. Patent Nos. 3,220,972; 3,284,406; 3,436,366; 3,697,473 and 4,340,709. The polyorganosiloxanes which enter into these compositions are in general constituted by pairs based on one hand on a linear, branched or crosslinked polysiloxane consisting of portions (II) in which the residue Z represents an alkenyl group of 2 to 6 carbon atoms and where x is at least equal to 1, optionally associated with portions (I), and on the other hand a linear, branched or crosslinked hydrogen-polysiloxane consisting of portions (II) in which the residue Z then represents a hydrogen atom and where x is at least equal to 1, possibly associated with the portions (I). In the case of the compositions D crosslinking by means of polyaddition reactions called RTV, the polyorganosiloxane constituent (s) = carriers of the alkenylsilyl groups advantageously have a viscosity at 25 ° C at most equal to 100,000 mPa.s, preferably , between 400 and 100,000 mPa.s. In the case of the compositions D crosslinking by means of polyaddition reactions called LSR, the polyorganosiloxane constituent (s) carrying the alkenyl-silyl groups have a viscosity at 25 ° C higher than 100,000 mPa.s, preferably in the range that goes from a value greater than 100,000 mPa.s up to 500,000 mPa.s. In the case of compositions D which crosslink by the polyaddition reactions known as polyaddition EVC, the polyorganosiloxane constituents or carriers of alkenylsilyl groups have a viscosity at 25 ° C higher than 500,000 mPa.s and preferably between 1 million. of mPa.s and 30 million mPa.se even higher. In the case of polyorganosiloxane D compositions termed RTV, LSR or polyaddition EVC, the polyorganosiloxane constituent (s) carrying the hydrogen-silyl groups generally have a viscosity at 25 ° C at most equal to 10,000 mPa.s and preference, comprised between 5 and 1,000 mPa.s.

It is also possible to treat compositions D which are curable at high temperature under the action of organic peroxides. The polyorganosiloxane or gum entering such compositions called EVC is then optionally composed of siloxyl portions (I), optionally associated with the portions (II) in which the residue Z represents an alkenyl group of 2 to 6 carbon atoms and where x is equal to 1. Such EVCs are for example described in US Pat. No. 3,142,655; 3,821,140; 3,836,489 and 3, 839,266. The polyorganosiloxane constituent of these compositions EVC advantageously has a viscosity at 25 ° C at most equal to 1 million mPa.s and, preferably, between 2 million and 30 million mPa.s and even higher. The hardenable compositions D considered within the scope of the invention may also include - beside the polyorganosiloxane constituent (s), the catalyst and optionally the crosslinking agent and / or the adhesion promoter and / or the coloring agent - reinforcing fillers or fillers. semi-reinforcing or filling or that serve to adapt the rheology, which are preferably chosen among siliceous loads. The reinforcing fillers are chosen between the combustion silicas and the precipitated silicas. These have a specific surface area, measured according to BET methods, of at least 50 m2 / g, preferably greater than 100 m2 / g, and an average particle size of less than 0.1 micrometer (μm). These silicas can be preferably incorporated as such or after they have been treated with organosilicon compositions usually used for this use. Among these compounds include methylpolysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, hexamethyldisilazane methylpolysilazanes such as hexamethylcyclotrisilazane, chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, metiIviniIdiclorosilano, dimethylvinylchlorosilane, alkoxysilanes such as dimethyldimethoxysilane, dimethylvinylethoxysilane, trimethylmethoxysilane. After that treatment, silicas can increase their starting weights up to a rate of 20%, preferably approximately 10%. 1! Semi-reinforcing or filler fillers or which serve to adapt the rheology, have a specific BET surface area of less than 100 m2 / g and a particular average diameter greater than 0.1 μm, and are preferably chosen from crushed quartz, calcined clays or the diatomaceous earth. It can be used, when there is a need, for 0. 5 to 120% by weight, preferably 1 to 100% by weight, of fillers, based on the weight of the organopolysiloxane constituent (s) of the compositions D. The preferred polyorganosiloxane D compositions within the framework of the present invention are those , of a single component or bicomponents, which crosslink at room temperature or with heat, by means of polyaddition reactions, called RTV, comprising: a) 100 parts by weight of at least one polydiorganosiloxane chosen from the homopolymers and linear copolymers present by molecule at least 2 vinyl groups linked to the different silicon atoms, located in the chain and / or at the ends of the chain, where the other organic radicals linked to the silicon atoms are chosen from the methyl, ethyl and phenyl radicals, less 60 mol% of these other radicals (and preferably all of these other radicals) are the methyl radicals, and have a viscosity ranging from 400 to 100. , 000 mPa.s at 25 ° C; b) at least one polyorganohydrogenosiloxane chosen from linear or cyclic homopolymers and copolymers having at least 2 hydrogen atoms bonded to the different silicon atoms per molecule, and where the organic radicals bonded to the silicon atoms are chosen from the methyl radicals , ethyl and phenyl, at least 60 mole% of these radicals (and preferably all of these radicals) are the methyl radicals, and having a viscosity ranging from 5 to 1,000 mPa.s at 25 ° C, the reactant (b) in an amount such that the molar ratio of the hydride functional groups of (b) to the vinyl groups of (a) is between 1.1 and 4; c) a catalytically effective amount of a platinum catalyst; d) 0 to 120 parts by weight, preferably 0 to 100 parts by weight, of siliceous fillers for 100 parts by weight of the group of polyorganosiloxanes (a) + (b). According to a variant embodiment, up to 100% by weight of the reagent (a) is replaced by a polyorganosiloxane resin that includes in its structure from 0.1 to 20% by weight of vinyl groups, said structure having at least two different portions chosen between the M (triorganosiloxyl), D (diorganosiloxyl), T (monoorganosiloxyl) and Q (Si04 / 2) portions, with at least one of these portions being a T or Q portion, the vinyl group (s) can be carried by the M-portions. , D and / or T. Reagent (a) can advantageously be a linear polydiorganosiloxane where the chain consists essentially of portions (I) where n = 2, this chain being blocked at each end by a portion (II) where Z = vinyl and where x = 1 and y = 2. Reagent (b) can be advantageously: a linear polyorganohydrogensiloxane, which includes in its structure at least 3 hydrogen atoms bonded to silicon, where the chain consists essentially of portions (II ) or Z = H and where x = y = 1, possibly associated with the portions (I) where n = 2, this chain being blocked at each end by a portion (II) where Z = H and where x = 1 and Y = 2 or for a portion (I) on = 3; or a mixture of said polyorganohydrogenosiloxane with another linear polyorganohydrogensiloxane where the chain consists essentially of portions (I) where n = 2, this chain being blocked at each end by a portion (II) where Z = hydrogen and where x = 1 and y = 2. The amount by weight of the catalyst (c), calculated in parts by weight of platinum metal, is generally between 1 and 250 ppm, preferably between 3 and 100 ppm, based on the weight of the organosiloxane group (a) + (b). Other preferred polyorganosiloxane D compositions are those, monocomponentes or bicomponentes, that reticulate with heat by means of reactions of polyaddition, denominated compositions LSR. These compositions correspond to the definitions given above with respect to the preferred compositions known as RTV, except as regards the viscosity of the vinylated polydiorganosiloxane reagent (a) which is in this case in the range of a value greater than 100,000 mPa. sa 500,000 mPa. s.

Other preferred polyorganosiloxane D compositions are those, monocomponent or bicomponent, which crosslink with heat by polyaddition reactions, so-called EVA polyaddition compositions comprising: (a ') 100 parts by weight of a polydiorganosiloxane gum which is a linear homopolymer or copolymer which has per molecule at least 2 vinyl groups linked to the different silicon atoms, located in the chain and / or at the ends of the chain, where the other organic radicals bonded to the silicon atoms are chosen from the methyl, ethyl radicals , phenyl, at least 60 mole% of these other radicals (and preferably all of these other radicals) are methyl radicals, and said form has a viscosity greater than 500,000 mPa.s at 25 ° C, and preferably at minus 1 million mPa.s; b ') at least one polyorganohydrogenosiloxane chosen from homopolymers and linear, cyclic and network copolymers, which have per molecule at least 3 hydrogen atoms bonded to the different silicon atoms, and where the organic radicals bonded to the silicon atoms are chosen from the methyl, ethyl, phenyl radicals, at least 60 mol% of these radicals (and preferably all of these radicals) are methyl radicals, and have a viscosity ranging from 5 to 1,000 mPa.s at 25 ° C, the reactant (b ') is used in an amount such that the molar ratio of the hydride functional groups of (b') on the vinyl groups of (a ') is between 0.4 and 10 and preferably between 1.1 and 4; c ') a catalytically effective amount of a platinum catalyst; d ') 0.5 to 120 parts by weight, preferably 1 to 100 parts by weight, of siliceous fillers for 100 parts by weight of the whole, of the polyorganosiloxanes (a') + (b '). The rubber (a ') is constituted, for the entire length of its chain, of portions (I) where n = 2, possibly associated with the portions (II) where Z = vinyl and where x = y = 1, and is blocked at each end of its chain by a portion (II) where Z = vinyl and where x = law = 2 or by a portion (I) where n = 3. Advantageously, it is put into operation as a constituent (b ') ), at least one linear polyorganohydrogensiloxane where the chain consists essentially of portions (II) where Z = H and where x = y = 1, possibly associated with the portions (I) where n = 2, this chain being blocked at each end pox a portion (JLLJL) where -Z = H and where x = law = 2 or by a portion (I) where n - 3. The amount by weight of the catalyst (c '), expressed in parts in that of metal pl ai no in relation to the weight of the gum (a ') and the hydrogen-silylated compound (b') is between 1 and 250 ppm, and preferably between 3 and 100 ppm. and The silicone compositions D may further include, on one side of the constituents (a '), (b'), (cf) and (df), from 1 to 10 parts by weight of oil or oils of polydimethylsiloxanes (ef) with silanol ends of viscosity at 25 ° C comprised between 10 and 1,000 mPa.s, for 100 parts of rubber (a '). If there is a need to retard cross-linking, it can be added to the polyorganosiloxane D composition which cross-links by polyaddition reactions termed RTV, LSR or polyaddition EVC, a platinum catalyst inhibitor. These inhibitors are known. In particular, organic amines, silazanes, organic oximes, diesters of dicarboxylic acids, acetylenic ketones and especially, and in the case of the preferred inhibitors, acetylenic alcohols can be used (see, for example, French Patent 1,528,464; 2,372,874 and 2,704,553) and the cyclic polydiorganosiloxanes consisting essentially of portions (II) where Z = vinyl and where x = y = 1, possibly associated with the portions (I) where n = 2. The inhibitor, when one is used, is used at a ratio of 0.005 to 5 parts by weight, preferably 0.01 to 3 parts by weight, to 100 parts of polyorganosiloxane (a) or rubber (to' ) . Other preferred polyorganosiloxane D compositions are even those, monocoquers, referred to as EVC, which include: (a ") 100 parts by weight of a polydiorganosiloxane gum which is a homopolymer or a linear copolymer having per molecule at least 2 vinyl groups linked to the different silicon atoms, located in the chain and / or at the ends of the chain, where the other organic radicals bonded to the silicon atoms are chosen from the methyl, ethyl, phenyl radicals, at least 60 mol% of these other radicals (and preferably all of these other radicals) are the methyl radicals, and said gum has a viscosity of at least 1 million mPa.s at 25 ° C, and preferably at least 2 million mPa.s; bf ') 0.1 to 7 parts by weight of an organic peroxide; c ") 0.5 to 120 parts by weight, preferably 1 to 100 parts by weight, of siliceous fillers for 100 parts by weight of gum (a"). The rubber (a'f) is constituted, for the whole length of its chain, of portions (I) where n = 2, possibly associated to the portions (II) where Z = vinyl and where x = y = 1, and is blocked at each end of its chain by a portion (II) where Z = vinyl and where x = law = 2 or by a portion (I) where n = 3; notwithstanding the presence in mixture with these conformal portions, of portions of different structure, for example of the formula (I) with n = 1 and / or SÍO4 / 2 and / or of formula (II) where Z = vinyl and where x = 1 and y = 0, it is not excluded in the proportion of at most 2% in relation to the total number of the conforming portions. The organic peroxides (b ") are used at a ratio of 0.1 to 7 parts, preferably 0.2 to 5 parts, per 100 parts of the gums (a"). These are well known to those skilled in the art and include, more especially, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, 2,5-bis (t-butylperoxy) -2,5-dimethylhexane, perbenzoate. of t-butyl, peroxy-t-butyl and isopropyl carbonate, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyanohexane. Compositions D of the EVC type may further include 1 to 10 parts by weight of oil or oils of polydimethylsiloxanes (df ') with silanol ends of viscosity, at 25 ° C, comprised between 10 and 5,000 mPa.s for 100 parts of gum (a'f) The preparation of the polyorganosiloxane compositions D called RTV, LSR, EVA of polyaddition and EVC, which also contain the additive for improving the properties of resistance to arc displacement and arc erosion, which have been defined above in the present description it is carried out with the help of known mechanical means, for example devices equipped with a turbine agitator, mixers, screw mixers, cylinder mixers. The various constituents are incorporated in these apparatuses in an order that can be any or that will take into account the monocomponent or bicomponent form desired for the compositions. Thus, the polyorganosiloxane D compositions, which also contain the additive, can be monocomponent compositions, ie distributed in a single package or container; if the composition is to be stored before use, it may be desirable to add, in the case of the polyaddition RTV, LSR and EVC compositions, an effective amount of an inhibitor (of what has been discussed above) of the catalytic action of the platinum, which disappears by heating at the time of crosslinking the composition. These compositions D that also contain the additive can also be the bicomponent compositions, ie distributed in two different packagings or containers, where only one of them includes the crosslinking catalyst; to obtain the elastomer, the content of the two packagings is mixed and the crosslinking takes place thanks to the catalyst. Similar monocomponent and bicomponent compositions are well known to the person skilled in the art. The crosslinking of curable compositions D, which also contain the additive for obtaining the elastomers, can be carried out in a manner known per se at room temperature (23 ° C) or at temperatures ranging, for example, from 40 ° C to 250 ° C according to the type of the composition (RTV, SLR, EVA of polyaddition or EVC) put into operation. The compositions D which additionally contain the additive harden to lead to the elastomers having good strength properties, arc shifting and under arc erosion, as well as good flame resistance properties and good mechanical properties. These elastomers can be used in any of the applications in which the polyorganosiloxane elastomers that are difficult to burn and / or resistant to fire and electric arc currents are put into operation; These can be used for example to make electrical insulation materials, medium voltage and high voltage insulators, cable end fittings, cable splices, anode caps for television tubes, and molded objects or extruded articles for the aeronautical industry. . The following examples are given by way of illustration and these can not be considered as a limitation of the scope of the invention.

EXAMPLES 1 and 2 A) Preparation of the elastomers: The elastomers of the RTV type have been obtained from monocomponent compositions defined immediately: 1) Control composition No. 1: With a turbine laboratory stirrer, 93.3 parts by weight of a suspension containing: 67.3 parts by weight of a blocked polydimethylsiloxane oil at each of the ends of the chains is mixed at room temperature (23 ° C). portion (CH3) 2ViSiOo.5 (Vi - vinyl group), which has a viscosity of 600 mPa.s and which contains 0.014 Si-Vi functional groups per 100 g of oil; 26 parts by weight of pyrogenation silica, which develops a BET specific surface of 300 m2 / g treated with hexamethyldisilazane so that the weight of the starting silica is greater than 8%; • 4-7 parts, by weight of a polydimethylsiloxane oil blocked at each end of the chains by a portion (CH3) 2HSÍO0.5, which has a viscosity of 8 mPa.s and which contains 0.19 SiH functional groups for 100 g of oil; • 2 parts by weight of a poly (dimethyl) (hydrogengenyl) siloxane oil blocked at each end of the chains by a portion (CH3) 2HSÍO0.5, having a viscosity of 300 mPa.s and containing a total of 0.16 Si-H functional groups per 100 g of oil; • 0.011 parts by weight of a solution in divinyltetramethyldisiloxane of a platinum complex at 12% by weight of platinum bound by divinyltetramethyldisiloxane (sodium catalyst) Karstedt), or 0.0013 parts by weight of metallic platinum; and • "0.04 part by weight cyclic tetramer of methyl vinyl polysiloxane containing 1.15 Si-Vi functional groups per 100 g of compound. 2) Composition of Example 1: This is obtained by adding, by means of a turbine-type agitator, to 100 parts by weight of the control composition No. 1, 10 parts by weight of a combination of FeO (21% by weight in the combination) with Fe203 (79%). in weight in the combination), these oxides having an average diameter of 0.1 μm and a BET specific surface area of 10 m2 / g. 3) Control composition No. 2: This is obtained by adding, by means of a turbine-type agitator, to 100 parts by weight of the control composition No. 1, 30 parts by weight of crushed natural silica (quartz), having an average diameter of 3 μm and a surface specifies BET of 2 pr / g. 4) Composition of Example 2: This is obtained by adding, by means of a turbine-type agitator, to 100 parts by weight of the control composition No. 1: • 25 parts by weight of the crushed natural silica, used in the control composition No. 2; and • 5 parts by weight of the combination of iron oxides used in the composition of Example 1. To obtain the elastomers, the compositions are crosslinked in adapted molds (having a thickness of 6 mm for the test pieces used to measure the hardness , and a thickness of 2 mm for the test pieces used to measure the resistance to tearing and the putting into operation of the tests of flame resistance and erosion under arc), during 60 minutes operating at 150 ° C in a ventilated oven marketed by the company HERAEUS.

B) Evaluation of the properties of the elastomers: The results obtained are shown in .la Table I below: Table I (1) DSA: Shore A hardness; the measurements are made according to the indications of DIN 53505; (2) R / D: tear resistance; the measurements are made according to the indications of ASTM D 624-A; (3) The flame resistance tests of the obtained elastomers are carried out according to the protocol defined by "The Underwriters Laboratories" (UL 94V), fourth edition of June 18, 1991, which consists of exposing a test piece (where the length is 127 mm, the width is 12.7 mm and the thickness is 2 mm), at an exposure of 10 seconds to a flame of 980 ° C, and the duration of the extinction is measured after this exposure (each duration corresponds to the average of 9 tests of flame resistance); (4) The tests of resistance to erosion under arc are made according to the protocol defined below: The principle of this test is to apply locally to the surface of the material comprising the silicone elastomer, a tension of the type "arc of dry band "and in measuring the erosion of the material induced by the tension. One of the specificities of this test lies in the fact that the applied electrical power is limited and regulated around an average value of 9 ± 1 watts. The assembly scheme is described in the attached figure 1; in this scheme, references (1) to (9) designate respectively: (1) the material comprising the silicone elastomer to be tested, (2) an electric arc generating tip, (3) a cell that supports the material ( 1) and containing water, (4) water (5) a bypass resistance, measuring resistance, (6) a limiting resistor, (7) a high voltage or voltage generator operating under 50 Hertz, 3 (8) a voltage divider; and (9) a computer whose role is to precisely control the electrical parameters that make it possible to start and maintain an electric arc on the surface of the material (1). 4. 1) Conducting the test: 4. 1.1 Mechanical placement of the sample: The samples of dimensions of 1.5 x 2 x 0.2 cm are glued on plates of epoxy resin of 1 cm of base of these. The plate is then placed on a support in a glass vessel so as to form an angle of 50.6 ° with the horizontal, as indicated in the accompanying Figure 2, where the reference (10) designates a sample of silicone elastomer and the reference (11) designates an epoxy resin plate. The assembly formed by the plate (11) on which the sample (10) is glued, constitutes the material (1) comprising the silicone elastomer of which it was previously mentioned, with reference to Figure 1.

A mass electrode is then made by winding the tin wire on the base of the plate; the assembly is then put in place in the cell and the water level is regulated at a given distance from the bottom. The tip is then placed with the help of verniers or verniers. The position of the tip for the type test is 7 mm above the surface of the water and 1.3 mm from the sample in the horizontal, as indicated in the attached Figure 3, where the distance di = 7 mm and the distance d2 = 1.3 mm. 4. 1.2 - Regulation of the parameters and launch of the test: The vacuum voltage of the generator is regulated at 7 kV. The intermittent sample washing system is launched. The surface of the sample treated with the arch is rinsed in an intent manner in order to remove the ashes that are formed under the impact of the arch. This wash consists of a very fine water jet that is directed for 10 seconds for 10 minutes. The water level in the cell is kept constant by aspiration. Once all the test parameters are regulated, the ground electrode and the tip are attached to the assembly. The generator can then be hooked. 4. 1.3 - End of the trial The electrical circuit is open since the applied energy reaches 500 watts / minute. 4. 2 Measurement of eroded volumes: The samples are removed from the epoxy resin plates. The eroded areas are removed from all traces of ash by rinsing with water, the samples are rinsed with alcohol and then dried. A mixture of epoxy resin sufficiently fluid is then prepared to be applied and fill the eroded areas (see Figure 4 attached). After mixing the resin must be degassed under a vacuum hood for at least ten minutes. Once degassed, the resin is used to fill the erosion marks (holes) on the surface of the samples, and return them to their initial volumes. The visual control is then very important - A cut with cutting blade serves to remove most of the resin on the samples. After complete polymerization (one night), the impressions or traces of the erosions carried out are demoulded and weighed on a precision balance. The masses found (in mg) are representative of the eroded volumes. In the left part of Figure 4 appended, it is recognized: the material (1) comprising the silicone elastomer, the tip (2) that generates the electric arc (12), the container (3) containing the water (4) ) and the high voltage generator (7); on the right side of Figure 4 appended, a sample of silicone elastomer (10) which has been decoupled from its epoxy resin backing plate, and which includes an erosion mark under arc (or hole) (13) has been depicted. ). The benefit provided by iron oxides is evident. It is even observed that the results of the flame resistance tests and the tests of resistance to erosion under arc are well correlated.

EXAMPLE 3 A) Preparation of elastomers: The RTV elastomers have been obtained from other monocomponent compositions defined below: Control composition No. 3 With a turbine laboratory stirrer, it is mixed at room temperature (23 ° C): • 65 parts by weight of resin of structure MMVlDDVlQ containing 0.55% by weight of vinyl groups and constituted of 17.5% by weight portions (CH) 3YO0.5, 0.3% by weight of portions (CH3) 2ViSiOo.5, 74.5% by weight of portions (CH3) 2SiO, 1.5% by weight of portions (CH3) ViSiO and 6.2% by weight of portions Si02; • 33 parts by weight of crushed natural silica (quartz), which has an average diameter of 3 μm and a BET specific surface area of 2 m2 / g; • 2.9 parts by weight of a poly (dimethyl) (hydrogengenyl) siloxane oil blocked at each end of the chains by a portion (CH3) 2HSiO0.5, which has a viscosity of mPa.s and containing in total 0.7 Si-H functional groups per 100 g of oil; 0.0063 parts by weight of a solution in divinyltetramethyldisiloxane of a platinum complex at 12% by weight of platinum bound by divinyltetramethyldisiloxane ( Karstedt), or 0.00075 parts by weight of metallic platinum; and 0.03 parts by weight of inhibitor consisting of 1- ethynyl-1-cyclohexanol. 2) Composition of Example 3: This is obtained by adding, by means of a turbine-type agitator, to 100 parts by weight of the control composition No. 3, 5 parts by weight of the combination of iron oxides used, in the composition of Example 1. To obtain the elastomers, the compositions are crosslinked for 60 minutes operating at 150 ° C in a ventilated oven, marketed by the company HERAEUS.

B) Evaluation of the properties of the elastomers: The results obtained are shown in the following Table II: Table II Rubrics (1) through (4): see Table I EXAMPLES 4 to 6: A) Preparation of elastomers Elastomers of the RTV L type have been obtained from other monocomponent compositions defined below: 1) Control composition No. 4 With a turbine laboratory stirrer, it is mixed at room temperature (23 ° C): • 93.4 parts by weight of a suspension containing: 70.4 parts by weight of polydimethylsiloxane oil blocked at each end of the chains by a portion (CH3) 2ViSiOo.5 used in control composition No. 1; '23 parts by weight of the pyrogenation silica treated with hexamethyldisilazane used in the control composition No. 1; • 1.7 parts by weight of crushed natural silica (quartz), which has an average diameter of 2 μm and a BET specific surface of 3 μ2 / g; • 3.0 parts by weight of polydimethylsiloxane oil blocked at each end of the chains by a portion (CH3) 2HSiO0.5 used in the control composition No. 1; • 1.9 parts by weight of a poly (dimethyl) (hydrogengenyl) siloxane oil blocked at each end of the chains by a portion (CH3) 3SÍO0.5, having a viscosity of 10 mPa.s and containing in total 0.36 Si-H functional groups per 100 g of oil; • 0.025 parts by weight of a solution in divinyltetramethyldisiloxane of a platinum complex at 12% by weight of platinum bound by divinyltetramethyldisiloxane (Karstedt catalyst), or 0.003 parts by weight of metal platinum; and • 0.08 parts by weight of cyclic tetramer of methyl vinyl polysiloxane and containing 1.15 Si-Vi functional groups per 100 g of the compound. 2) Composition of Example 4: This is obtained by adding, by means of a turbine-type stirrer, to 100 parts by weight of the control composition No. 4, 3 parts by weight of anhydrous cerium hydroxide IV, this hydroxide having a diameter average of 2 μm and a BET specific surface area of 1 m2 / g. 3) Composition of Example 5: This is obtained by adding, by means of a turbine-type stirrer, to 100 parts by weight of control composition No. 4: • 3 parts by weight of cerium hydroxide IV used in the composition of Example 4; and • 3 parts by weight of titanium oxide Ti02, which has an average diameter of 0.03 μm and a BET specific surface area of 50 m2 / g. 4) Composition of Example 6: This is obtained by adding, by means of a turbine-type agitator, to 100 parts by weight of the control composition No. 4: • 3 parts by weight of cerium hydroxide IV used in the composition of Example 4; • 1 part by weight of TIO2 used in the composition of Example 5; and • 0.25 parts by weight of the combination of iron oxides used in the composition of Example 1. To obtain the elastomers, the compositions are crosslinked for 60 minutes operating at 150 ° C in a ventilated oven, marketed by the company HERAEUS.

B) Evaluation of the properties of the elastomers: The results obtained are shown in the following Table III: Table III Rubrics (1), (2) and (3): see Table I It should be noted that within the framework of the UL 94 test, the classification is completed by indicating the number of test pieces (out of a total of 9) that correspond to the classification obtained.

Claims (10)

1. The use as additive of improvement of the properties of resistance to sliding or arch sliding and erosion under arc: • of a mixture A, B or C formed of: in the case of the unit A, the constituents Al + A3 where: constituent Al is platinum in the form of a complex or a platinum compound; and the constituent A3 consists of a combination of FeO with Fe203; in the case of the mixture Br constituents Bl + B2 where: the constituent Bl has the meaning of the constituent Al of?; and the constituent B2 consists of cerium oxide and / or hydroxide VI; in the case of mixture B, the constituents Bl + B3 where: the constituent Bl has the meaning of constituent Al of '; and the constituent B3 consists of a combination of oxide and / or cerium IV hydroxide with titanium oxide Ti02; or for the mixture C, the constituents Cl + C2 where: the constituent Cl has the meaning of the constituent Al of; and the constituent C2 consists of a combination of the constituent B3 mentioned under with the constituent A3 mentioned under ©. the quantities of the various constituents Al, A3, Bl, B2, B3, Cl and C2 and the relationships that may exist between the quantities of some of them, in the case of the combinations, are in the intervals mentioned below; the amount of platinum, expressed in parts by weight of elemental platinum, is in the range from 1 to 250 ppm relative to the total weight of the polyorganosiloxane constituent (s) of the hardenable compositions D; and the amounts of constituents A3, B2, B3 and C2 of mixtures A, B and C, expressed in parts by weight of the constituent, are in the range of 0.5 to 30 parts by weight per 100 parts of the the polyorganosiloxane constituents of the curable compositions D; in the constituent A3 (combination) the ratio between the weight of FeO and that of Fe203 is in the range from 0.1 / 1 to 9/1; in the constituent B3 (combination), the ratio between the weight by weight of the oxide and / or cerium IV hydroxide and that of Ti0 is in the range from 0.6 / 1 to 6/1; in the constituent C2 (combination), the ratio between the weight amount of the constituent A3 and that of the constituent B3 is in the range from 0.02 / 1 to 1/1; • in a polyorganosiloxane D composition for obtaining a silicone elastomer, either by crosslinking at room temperature or with heat by means of polyaddition reactions in the presence of a platinum catalyst, or by cross-linking at elevated temperature under the action of peroxide ( s) organic (s); • the constituent Al, Bl or Cl of the additive which may be present in the form of catalytic platinum, which is contained in a polyorganosiloxane D composition, crosslinked at room temperature or with heat by polyaddition reactions.

2. The use according to claim 1, characterized in that the compositions of hardenable polyorganosiloxanes D, presented in a single or in several containers (mono- or multicomponent), include a main constituent formed of one or more polyorganosiloxane constituents, an appropriate catalyst and .incidentally one or more compounds taken from the group consisting mainly of: reinforcing or semi-reinforcing or filler fillers or which serve to adapt the rheology of curable compositions, cross-linking agents, adhesion agents, plasticizing agents, catalyst inhibiting agents and coloring agents.

3. The use according to claim 27, characterized in that the polyorganosiloxanes, main constituents of the compositions D, consist of siloxyl portions of the general formula: RnSi04- (I) and / or siloxyl portions of the formula: ZjRySÍ04- Z X (II) formulas in which the various symbols have the following meaning: -The R symbols, identical or different, each represent a group of a non-hydrolysable hydrocarbon nature, this radical being: * an alkyl, haloalkyl radical having from 1 to 5 carbon atoms and including from 1 to 6 chlorine and / or fluorine atoms, * cycloalkyl radicals and halogenocycloalkyls having from 3 to 8 carbon atoms and containing from 1 to 4 chlorine and / or fluorine atoms, * the aryl, alkylaryl and halogenaryl radicals having 6 to 8 carbon atoms and containing 1 to 4 chlorine and / or fluorine atoms, * the cyanoalkyl radicals having from 3 to 4 carbon atoms; the symbols Z each represent a hydrogen atom or an alkenyl group of 2 to 6 carbon atoms; n = an integer to 0, 1, 2 or 3; x = an integer equal to 0, 1, 2 or 3; y = an integer equal to 0, 1 or 2; the sum x + y is in the range from 1 to 34.

The use according to claim 2 or 3, characterized in that the polyorganosiloxane D compositions are those, monocomponent or bicomponent, which crosslink at room temperature or with heat by polyaddition reactions, called RTV, which comprise: a) 100 parts in weight of at least one polydiorganosiloxane selected from homopolymers and linear copolymers having per molecule at least 2 vinyl groups linked to the different silicon atoms, located in the chain and / or at the ends of the chain, where the other organic radicals linked to the silicon atoms are chosen from the methyl, ethyl and phenyl radicals, at least 60 mol% of these other radicals are the methyl radicals, and have a viscosity ranging from 400 to 100,000 mPa.s at 25 ° C; b) at least one polyorganohydrogenosiloxane chosen from linear or cyclic homopolymers and copolymers having at least 2 hydrogen atoms bonded to the different silicon atoms per molecule, and where the organic radicals bonded to the silicon atoms are chosen from the methyl radicals , ethyl and phenyl, at least 60 mol% of these radicals are the methyl radicals, and having a viscosity ranging from 5 to 1,000 mPa.s at 25 ° C, the reagent (b) being used in such quantity that the molar ratio of the hydride functional groups of (b) on the vinyl groups of (a) is between 1.1 and 4; c) a catalytically effective amount of a platinum catalyst; d) 0 to 120 parts by weight, preferably 0 to 100 parts by weight, of siliceous fillers per 100 parts by weight of the polyorganosiloxane group (a) + (b).

5. The use according to claim 4, characterized in that up to 100% by weight of the reactant (a) is replaced by a polyorganosiloxane resin that includes in its structure from 0.1 to 20% by weight of vinyl groups, said structure having at least two different portions chosen between the portions M (triorganosiloxilo), D (diorganosiloxilo), T (monoorganosiloxilo) and Q (Si0 / 2), being at least one of these portions a portion T or Q, the or vinyls groups can be ported by the portions M, D and / or T.

6. The use according to claims 2 to 5, characterized in that the polyorganosiloxane D compositions are those, monocomponent or bicomponent, which crosslink with heat by means of polyaddition reactions, called LSR, these compositions responding to the definitions given above in claims 4 or 5, with regard to compositions known as RTV, except for the viscosity of the vinylated polydiorganosiloxane reagent (a) which is in the range of more than 100,000 mPa.s to 500,000 mPa.s .

7. The use according to claim 2 or 3, characterized in that the polyorganosiloxane D compositions are those, monocomponent or bicomponent, which are heat crosslinked by polyaddition reactions, so-called EVA polyaddition compositions, comprising: (a ') 1.00 parts by weight of a polydiorganosiloxane gum which is a linear homopolymer or copolymer having per molecule at least 2 vinyl groups linked to the different silicon atoms, located in the chain and / or at the ends of the chain, where the other organic radicals bonded to the silicon atoms are chosen from the methyl, ethyl, phenyl radicals, at least 60 mol% of these other radicals are methyl radicals, and said form has a viscosity greater than 500,000 mPa.sa 25 ° C; b ') at least one polyorganohydrogenosiloxane chosen from homopolymers and linear, cyclic and network copolymers, which have per molecule at least 3 hydrogen atoms bonded to the different silicon atoms, and where the organic radicals bonded to the silicon atoms are chosen from methyl, ethyl, phenyl radicals, at least 60 mol% of these radicals are methyl radicals, and have a viscosity ranging from 5 to 1,000 mPa.s at 25 ° C, reagent (b ') is used in quantity such that the molar ratio of the hydride functional groups of (b ') on the vinyl groups of (af) is between 0.4 and 10; c ') a catalytically effective amount of a platinum catalyst; d ') 0.5 to 120 parts by weight of siliceous fillers for 100 parts by weight of the polyorganosiloxane group (a') + (b ').

8. The use according to claims 2 6 3, characterized in that the polyorganosiloxane D compositions are those, monocomponents, called EVC, which comprise: (a ") 100 parts by weight of a polydiorganosiloxane gum which is a homopolymer or a copolymer linear that presents per molecule at least 2 vinyl groups linked to the different silicon atoms, located in the chain and / or at the ends of the chain, where the other organic radicals bonded to the silicon atoms are chosen from the methyl radicals, ethyl, phenyl, at least 60 mole% of these other radicals are the methyl radicals, and said gum has a viscosity of at least 1 million mPa.s at 25 ° C; b ") 0.1 to 7 parts by weight of an organic peroxide; ) 0.5 to 120 parts by weight of siliceous fillers for 100 parts by weight of rubber (a ").

9. Silicone elastomeric articles having good properties of arc shifting and arc erosion, as well as good flame resistance properties and good mechanical properties, characterized in that they are obtained by cross-linking: • of the polyorganosiloxane D compositions as defined in accordance with claims 2 to 8, • containing the breeding additive as defined in its nature and its proportions of use in claim 1.

10. The articles according to claim 9, characterized in that they consist of electrical insulation materials, medium voltage and high voltage insulators, cable end fittings, cable splicing, anode caps for television tubes, and molded objects. or extruded articles for the aeronautical industry. SUMMARY OF THE INVENTION The invention relates to the use as an additive for improving the properties of resistance to arc shifting and erosion under arc: of a mixture A, B or C formed of: in the case of the mixture A: Al: platinum; and A2: at least one inorganic compound A2.1 of a metal with various degrees of oxidation, taken from the group consisting of V, Cr, Mn, Fe, Co, Ni and Cu, in which the metal atom is in a degree of oxidation greater than zero, the lowest possible (in abbreviation: DOX mini); or A3: a combination of at least one inorganic compound A2.1 with at least one inorganic compound A2.2 in which the V, Cr. Mn, Fe, Co, Ni or Cu atom is at a higher oxidation degree to DOX mini; in the case of mixture B: Bl: platinum; and B2: at least one inorganic compound B2.1 of cerium IV or of lanthanum III; or B3: a combination of at least one inorganic compound B2.1 with at least one inorganic compound B2.2 of titanium IV; in the case of the mixture C: Cl: platinum; and C2 a combination of the constituent A2 or A3 with the constituent B2 or B3; in a polyorganosiloxane D composition for obtaining a silicone elastomer, either by crosslinking at room temperature or with heat by means of polyaddition reactions in the presence of a metal catalyst, or cross-linked at elevated temperature under the action of organic peroxide (s) (s)