WO2010112081A1 - Silicone rubber composition - Google Patents

Silicone rubber composition Download PDF

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Publication number
WO2010112081A1
WO2010112081A1 PCT/EP2009/054014 EP2009054014W WO2010112081A1 WO 2010112081 A1 WO2010112081 A1 WO 2010112081A1 EP 2009054014 W EP2009054014 W EP 2009054014W WO 2010112081 A1 WO2010112081 A1 WO 2010112081A1
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WIPO (PCT)
Prior art keywords
silicone rubber
filler
rubber composition
range
weight
Prior art date
Application number
PCT/EP2009/054014
Other languages
French (fr)
Inventor
Bandeep Singh
Spiros Tzavalas
Xavier Kornmann
Original Assignee
Abb Research Ltd
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Priority to PCT/EP2009/054014 priority Critical patent/WO2010112081A1/en
Publication of WO2010112081A1 publication Critical patent/WO2010112081A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/46—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes silicones
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
    • C04B26/30—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Other silicon-containing organic compounds; Boron-organic compounds
    • C04B26/32—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Other silicon-containing organic compounds; Boron-organic compounds containing silicon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
    • C08L83/04—Polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00482—Coating or impregnation materials
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/14—Peroxides

Definitions

  • the present invention refers to a silicone rubber composition with improved tracking and erosion resistance.
  • the present invention specifi- cally refers to a low temperature vulcanized silicone rubber (LTV-SR) composition and a high temperature vulcanized silicone rubber (HTV-SR) composition with improved tracking and erosion resistance.
  • LTV-SR low temperature vulcanized silicone rubber
  • HTV-SR high temperature vulcanized silicone rubber
  • LTV-SR Low temperature vulcanized silicone rubber
  • HTV-SR high temperature vulcanizing silicone rubber
  • Tracks reduce the insulation strength and may lead to flashover or dielectric breakdown.
  • a preferred example is high temperature vulcanized polydimethylsiloxane filled with alumina trihydrate [(ATH), (Al 2 O 3 .3H 2 O) ] containing generally about 30 to 70% by weight of ATH, calculated to the total weight of the insulation material [corresponding to 43 parts (phr) to 230 parts (phr) of ATH per 100 part of silicone rubber] .
  • alumina trihydrate ((ATH), (Al 2 O 3 .3H 2 O)
  • LTV-SR and HTV-SR compositions show an improved tracking and erosion resistance without loss of mechanical properties when said low temperature or high temperature vulcanized silicone rubber compositions contain a defined combination of filler materials comprising a hardenable cement filler and an inorganic oxide filler such as silica or aluminum oxide, whereby said composition may optionally contain further additives .
  • the hardenable cement filler and the inorganic oxide filler are considerably cheaper than ATH and may be added in much smaller quantities .
  • the present invention refers to a vulcanized resp. hardened silicone rubber composition with improved tracking and erosion resistance, wherein said vulcanized silicone rubber comprises a low temperature vulcanized silicone rubber (LTV-SR) or a high temperature vulcanized silicone rubber (HTV-SR) as a silicone base, a defined combination of filler materials, and optionally further additives, characterized in that: (i) the combination of filler materials comprises a hardenable cement filler in combination with at least one mineral oxide filler which is different from said cement filler; wherein
  • LTV-SR low temperature vulcanized silicone rubber
  • HTV-SR high temperature vulcanized silicone rubber
  • the total amount of said hardenable cement filler and said at least one mineral oxide filler is within the range of 10 parts by weight to 230 parts by weight per 100 parts by weight of silicone base; and (iii) the weight ratio of the hardenable cement filler to the at least one mineral inorganic oxide filler is within the range of 3:1 to 1:4.
  • the present invention further refers to a method of making said vulca- nized (resp. hardened) low temperature or high temperature vulcanized (resp. hardened) silicone rubber with improved tracking and erosion resistance .
  • the present invention further refers to a low temperature as well as to a high temperature vulcanisable (resp. hardenable) silicone rubber composition
  • a low temperature vulcanisable silicone rubber LTV-SR
  • a high temperature vulcanisable silicone rubber HTV-SR
  • the present invention also refers to the use of said low temperature and said high temperature vulcanisable (resp. hardenable) silicone rubber composition, as defined above, for the production of shaped articles in the field of electrical insulators, specifically in the field of low, medium and high voltage insulators for indoor and outdoor use.
  • the present invention further refers to the use of said low temperature and said high temperature vulcanisable (resp. hardenable) silicone rubber composition, as defined herein, for the production of a surface modified electrical insulator, specifically in the field of low, medium and high voltage electrical insulators for indoor and outdoor use, characterized in that the surface of an electrical insulator, which is not made from a composition according to the present invention, is covered with a layer of the low temperature or high temperature vulcanisable silicone rubber composition as defined according to the present invention.
  • the present invention further refers to a method of making said surface modified electrical insulator, characterized in that the surface of an electrical insulator, which is not made from a composition according to the present invention, is covered with a layer of the composition according to the present invention.
  • the present invention also refers to the shaped articles in the field of electrical insulators, specifically in the field of low, medium and high voltage insulators for indoor and outdoor use, as made according to the present invention.
  • the "hardenable cement filler” is a hardenable powdery cement material as generally used in the construction industry. Such hardenable cement filler is known per se.
  • the hardenable cement filler within the sili- cone rubber matrix hardens after reaction with atmospheric moisture and/or moisture which may be released during cross-linking reaction of the silicone rubber and thus forms a heat resistant network within the hardened silicone rubber matrix.
  • the hardenable cement filler is generally made from limestone and natural mineral silicates, whereby the natural mineral silicate preferably is clay, especially an aluminum silicate or a mixture of such silicates, such as for example Montmorillonite, Kaolinite, Andalusite, Zeolithe, Muskovite, Orthoklas or Glimmer.
  • the limestone and a mineral silicate are generally mixed together within a weight ratio of ⁇ CaO ⁇ to the sum of ⁇ SiO 2 +Al 2 O 3 ⁇ being about 2 to 1 and heated to a temperature of about 1400 0 C, preferably within a rotating tubular oven.
  • the obtained sintered mass is cooled down and milled to a powder.
  • the obtained powder can be used according to the present invention as the hardenable cement filler which hardens out in the presence of moisture.
  • Such cement material is commercially available.
  • the hardenable cement filler is used in combination with the at least one mineral oxide filler which is different from said cement filler as defined above. This combination is obtained by intensively mixing the hardenable cement filler with the at least one mineral oxide filler as defined above using any mixing method known per se.
  • the at least one mineral oxide filler which is different from said cement filler is preferably selected from the group comprising silica (silicon oxide), aluminum oxide, magnesium oxide, ATH, and titanium oxide, and is preferably selected from silica and aluminum oxide or is a mixture of these filler materials .
  • the hardenable cement filler as well as the inorganic oxide filler, both, have preferably an average grain size distribution within the range of l ⁇ m-500 ⁇ m, preferably within the range of 5 ⁇ m-100 ⁇ m.
  • a part of the filler material may also have a grain size distribution within the nano-range.
  • the total content of said hardenable cement filler and of the at least one inorganic oxide filler is preferably within the range of 10 parts by weight to 230 parts by weight per 100 parts by weight of silicone base, preferably 15 parts by weight to 150 parts by weight, preferably within the range of 15 parts by weight to 100 parts by weight, preferably within the range of 15 parts by weight to 50 parts by weight and preferably within the range of 15 parts by weight to 25 parts by weight, per 100 parts by weight of silicone base.
  • the weight ratio of the hardenable cement filler to the at least one inorganic oxide filler is within the range of 3:1 to 1:4, preferably 2:1 to 1:3, preferably 1:1 to 1:2, and preferably about 2:3.
  • the special filler composition made from the hardenable cement filler and the inorganic oxide filler according to the present invention may be the only filler material present within the vulcanized silicone rubber base.
  • the vulcanized silicone composition may optionally further contain one or more fillers as generally used in electrical insulators.
  • Such an additional filler preferably is an inorganic oxide filler selected from the group comprising silica (silicon oxide), aluminium oxide preferably alumina trihydrate (ATH), magnesium oxide and/or titanium oxide, whereby said optional additional filler is not being premixed with the hardenable cement filler.
  • an optional additional filler are silica and alumina trihydrate (ATH) , preferably alumina trihydrate (ATH) .
  • the total content of said hardenable cement filler and of the at least one inorganic oxide filler [as defined in point (ii) above], including any optional additional filler present, is preferably within the range of 15 parts by weight to 230 parts by weight per 100 parts by weight of silicone base (i.e. about 13% to 70% by weight, calculated to the total weight of the filler and the silicone rubber base material) , preferably 20 parts by weight to 150 parts by weight per 100 parts by weight of silicone base; preferably within the range of 30 parts by weight to 100 parts by weight, per 100 parts by weight of silicone base .
  • the optional additional inorganic filler has preferably an average grain size distribution within the range of l ⁇ m-500 ⁇ m, preferably within the range of 5 ⁇ m-100 ⁇ m.
  • a part of the optional additional inorganic filler material may also have a grain size distribution within the nano-range.
  • Further optional additives are known per se and are for example stabilizers, flame retardants, colors and pigments.
  • the present invention further refers to the vulcanisable silicone rubber composition
  • a vulcanisable silicone rubber composition comprising a low temperature vulcanisable silicone rubber or a high temperature vulcanisable silicone rubber as a silicone base, a defined combination of filler materials, and optionally further additives as defined above.
  • said vulcanisable silicone rubber composition may also contain an organic inert solvent which evaporates during vulcanization.
  • Such solvent is preferably selected from aliphatic or aromatic hydrocarbons with a boiling point below 100 0 C, preferably below 8O 0 C, such as white spirit or petroleum based compounds, or hexane, cyclohexane, toluene, and related compounds.
  • the vulcanized silicone rubber base material is made from a low temperature or high temperature vulcanizable polydimethylsiloxane .
  • Such vulcanized silicone rubbers are generally composed of cross- linked groups of the formula [-(Ri) (R 2 )Si-O-] and [- (Ri) Si (-0-) 2 ] with terminating groups [(Ri) (R 2 ) (Ra)Si-O-], wherein R 1 , R 2 and R 3 are optionally substituted methyl or phenyl, preferably methyl or phenyl, preferably methyl.
  • the bridging [ ⁇ Si-O-Si ⁇ ] -group may be replaced by a group of the formula [ ⁇ Si-CH 2 -CH 2 -Si ⁇ ] or [ ⁇ Si-CH 2 -CH 2 -CH 2 -Si ⁇ ] , depending on the cross-linking mechanism and/or the starting materials chosen.
  • Such silicone rubbers, preferably vulcanized polydimethyl- siloxanes as used in the production of electrical insulation systems are known to the expert in the art.
  • the vulcanized silicone rubber according to the present invention is made from a hardenable liquid or pasteous silicone resin composition.
  • said hardenable liquid or pasteous silicone resin composition is a mixture of organopolysiloxanes, preferably a mixture of compounds of the general formula (I) :
  • R independent of each other is (C 1 - ⁇ ) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl;
  • Ri independent of each other has one of the meanings of R or R 2 , or is -O-Alkyl (C 1 -C 4 ) or hydroxyl; preferably one of the meanings of R or R 2 ;
  • A is a residue -C 3 H 2s - , preferably - (CH 2 ) s - , wherein s is a whole number from 1 to 3, preferably 1; r is zero or one; m is a number within the range of 500 to 20'000, preferably within the range of 1000 to 15 '000, preferably within the range of
  • n is a number within the range of zero to 500, preferably zero or within the range of 2 to 100, preferably zero or a number within the range of 2 to 20; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R 2 )O]- are ordered in an arbitrary sequence.
  • R 3 has one of the meanings given for R, wherein R preferably is methyl or phenyl, wherein the molecule contains methyl as well as phenyl residues.
  • the ratio of methyl to phenyl is given by the required flowability of the mixture and the properties required in the hardened product.
  • R is methyl.
  • the compound of formula (I) generally is a mixture of homologous compounds of formula (I) which is known to the expert .
  • Low temperature vulcanized silicone rubbers are preferably made from a compound of formula (IA) :
  • R, m, n have the meanings as given above;
  • R'i independent of each other has one of the meanings of R;
  • R' 2 independent of each other has one of the meaning of R, or is
  • Vulcanization resp. cross-linking/curing of compounds of formula (IA) may be carried out in the presence of cross-linking compounds, especially if RZ 2 is hydroxyl, such as compounds of formula [R 4 _ q -SiX q ] , wherein R is (Ci- 4 )alkyl or phenyl, preferably methyl, and X is a hydrolysable group, such as halogen, acetoxy, alkoxy, oxime or amine, preferably chlorine or (Ci_ 4 ) alkoxy, preferably chlorine or methoxy, and q is 1 to 3, preferably 2 or 3, preferably 3.
  • Formula (IA) may be hardened for example by adding an alkoxysilane of the formula [ (Ci_ 4 ) Alkyl] 4 _ q - Si [O-Alkyl (Ci- 4 ) q ] , wherein q is 1 to 3, preferably 2 or 3, preferably 3; for example methyltrimethoxysilane, methyltriethoxysilane and similar compounds or ⁇ (phenyl) 4 _ q Si [0-alkyl (Ci-C 4 ) ] q ⁇ .
  • LTV-SR low temperature vulcanized silicone rubber
  • High temperature vulcanized silicone rubbers are preferably made from a compound of formula (IB) :
  • R independent of each other is (Ci_ 4 ) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl; R"i, R" 2 , R" 3 , independent of each other have one of the meanings of R; m and n have the meaning as given above; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R 2 )O]- are ordered in an arbitrary sequence.
  • Vulcanization cross-linking/curing of compounds of formula (IB) may be carried out in the presence of peroxide compounds, such as diacylper- oxide, dialkylperoxide and other peroxides known per se to harden the siloxane mixture.
  • peroxide compounds such as diacylper- oxide, dialkylperoxide and other peroxides known per se to harden the siloxane mixture.
  • elevated temperatures are used for vulca- nization, which yields a high temperature vulcanized silicone rubber (HTV-SR) . This is known to the expert in the art.
  • R independent of each other is (C 1 -. 4 ) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl;
  • Ri independent of each other has one of the meanings of R;
  • m and m have the meaning as given above, wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R 2 )O]- are ordered in an arbitrary sequence .
  • the compounds are mixed shortly before hardening the mixture. Both compounds are mixed in equimolar amounts and are then hardened resp. vulcanized.
  • a catalyst is preferably used, preferably a complex made from a metal selected from rhodium, nickel, palladium and/or platin, in an amount of preferably 1 ppm to 100 ppm calculated to the metal bound in the complex.
  • Such catalytically active compounds and the silicon compounds of formula (I) to be used are known per se and have been described in the literature.
  • the present invention also refers to a method of making the vulcanized silicone rubber composition with improved tracking and erosion resistance according to the present invention, characterized in that the components of the hardenable mixture, i.e. the low temperature vulcanisable silicone rubber and/or a high temperature vulcanized silicone rubber as the silicone base, a defined combination of filler materials, and optionally further additives, comprising the components (i) , (ii) and (iii) as defined above, are mixed prior to the application in any desired sequence and subsequently are vulcanized, optionally under heating to an elevated temperature, preferably to a temperature within the range of 5O 0 C to 15O 0 C, preferably within the range of 100 0 C to 14O 0 C, for a time long enough to cause complete vulcanization of the composition, which generally is between about 5 minutes to about 24 hours, preferably between about 10 minutes to about 60 minutes.
  • the components of the hardenable mixture i.e. the low temperature vulcanisable silicone rubber and/or a
  • the present invention further refers to a method of making a surface modified electrical insulator, including the steps of (i) applying to the surface of an electrical insulator, which is not made from a composition according to the present invention, a layer of the vulcanizable silicone rubber composition according to the present invention and (ii) curing said layer of vulcanizable silicone rubber composition to yield a cured modified surface with improved tracking and erosion resistance.
  • An electrical insulator which is not made from a composition according to the present invention, can be made from a ceramic, or a thermoplastic polymer or a duroplastic polymer such as an epoxy resin composition or a polyurethane composition, preferably an epoxy resin composition.
  • the vulcanizable silicone rubber composition can be applied by any known method such as dipping, spaying or painting.
  • Curing of the layer of vulcanizable silicone rubber composition is carried out either at room temperature or at an elevated temperature, preferably at a temperature within the range of 6O 0 C to 15O 0 C, preferably within the range of 12O 0 C to 14O 0 C, for a time long enough to cause complete vulcanization of the composition, which generally is between about 5 minutes and about 24 hours, preferably from about 10 minutes to about 60 minutes.
  • the thickness of the layer is preferably within the range of 500 nm to 5 mm, preferably from 1 mm to 3 mm, and preferably at about 0.7 mm.
  • the present invention also refers to the shaped articles in the field of electrical insulators, specifically in the field of low, medium and high voltage insulators for indoor and outdoor use, as made according to the present invention.
  • Preferred uses of the insulation produced according to the present invention are electrical insulations, espe- cially in the field of impregnating electrical coils and core-coils assemblies and in the production of electrical components such as transformers, bushings, insulators, switches, sensors, converters and cable end seals.
  • Preferred uses of the insulation system produced according to the present invention are also high-voltage insulations for indoor and outdoor use, especially for outdoor insulators associated with high-voltage lines, as long-rods, composite and cap-type insulators, and also for base insulators in the medium-voltage sector, in the production of insulators associated with outdoor power switches, measuring transducers, lead-throughs, and overvoltage protectors, in switchgear construction, in power switches, dry-type transformers, and electrical machines, as coating materials for transistors and other semiconductor elements and/or to impregnate electrical components .
  • the components as given in Table 1 are dispersed in the silicone base by either using a blender, a duplex kneader, a two-roll mill or their combination.
  • the homogeneous formulation is then molded and cured at room temperature or at elevated temperature, chosen on the basis of the vulcanisable silicone starting material and the used peroxide or platinum compound or oxime or silanes . After remolding, a post-curing step is possible, but not necessary.
  • Table 1 shows a Formulation A prepared according to the present invention and compares this Formulation A with two commercial References 1 and 2.
  • Composition of the formulations i.e. filler, additive and curing agent content, is given in phr (parts per hundred) with respect to the silicone base.
  • Table 2 lists their properties.
  • Silicone base (1) is a room temperature curing silicone rubber, HVIC+, from Dow Corning Corp. , containing 40% by weight of ATH, calculated to the total weight of Silicone base (1) .
  • Silicone base (2) (a peroxide cured silicone rubber, Elastosil R 401/70 OH, Wacker Chemie GmbH, DE)
  • ATH aluminumt ⁇ hydrate, Martinal OL-104/S, Martinswerk GmbH, DE
  • Peroxide DCLBP-50-PSI : Di (2, 4-dichlorobenzoyl) peroxide, 50%, in silicone oil, Degussa Initiators GmbH & Co. KG, DE)
  • Table 2 Properties of the formulations according to Table 1

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Abstract

Vulcanized silicone rubber composition with improved tracking and erosion resistance, wherein said vulcanized silicone rubber comprises a low temperature vulcanized silicone rubber (LTV-SR) or a high temperature vulcanized silicone rubber (HTV-SR) as a silicone base, a defined combination of filler materials, and optionally further additives, wherein (i) the combination of filler materials comprises a hardenable cement filler in combination with at least one mineral oxide filler which is different from said cement filler; wherein (ii) the total amount of said hardenable cement filler and said at least one mineral oxide filler is within the range of 10 parts by weight to 230 parts by weight per 100 parts by weight of silicone base; and (iii) the weight ratio of the hardenable cement filler to the at least one mineral inorganic oxide filler is within the range of 3:1 to 1:4; and shaped articles in the field of low, medium and high voltage insulators for indoor and outdoor use, comprising such a vulcanized silicone rubber composition.

Description

Silicone rubber composition
The present invention refers to a silicone rubber composition with improved tracking and erosion resistance. The present invention specifi- cally refers to a low temperature vulcanized silicone rubber (LTV-SR) composition and a high temperature vulcanized silicone rubber (HTV-SR) composition with improved tracking and erosion resistance.
Low temperature vulcanized silicone rubber (LTV-SR) compositions such as room temperature vulcanized polydimethylsiloxane compositions, and high temperature vulcanizing silicone rubber (HTV-SR) compositions such as high temperature vulcanized polydimethylsiloxanes compositions are widely used in the electrical engineering industry, especially for electrical outdoor insulations, due to their good surface properties and the capability to recover hydrophobicity .
However, particularly in outdoor and wet environment often erosion patterns are observed on the rubber surface, whereby the electrical conductivity within said pattern is considerably increased due to surface discharges, leading to degradation. Said electrically conductive path is called track. Tracks reduce the insulation strength and may lead to flashover or dielectric breakdown.
As a result tracking-resistant polymer systems have been developed for the use as outdoor high-voltage insulations . A preferred example is high temperature vulcanized polydimethylsiloxane filled with alumina trihydrate [(ATH), (Al2O3.3H2O) ] containing generally about 30 to 70% by weight of ATH, calculated to the total weight of the insulation material [corresponding to 43 parts (phr) to 230 parts (phr) of ATH per 100 part of silicone rubber] . Such a material is often used to produce outdoor high-voltage insulation systems .
Testing the tracking resistance of various commercial low temperature and high temperature vulcanized rubber compositions according to IEC (International Electrotechnical Commission) standard 60587 at 3.5 kV revealed that these materials often failed during testing, showing deep erosion and a layer-wise degradation, resulting in a dielectric breakdown in the IEC 60587 tracking test. The degradation mechanism was found to be complicated, as temperatures of above 12000C (>1200°C) and even higher than 16000C (>1600°C) may arise during surface dis- charge. Therefore, there is a need to improve the tracking and erosion resistance of filler containing high temperature and low temperature vulcanized rubber compositions.
It has now been found that LTV-SR and HTV-SR compositions, and especially LTV-PMDS as well as HTV-PMDS show an improved tracking and erosion resistance without loss of mechanical properties when said low temperature or high temperature vulcanized silicone rubber compositions contain a defined combination of filler materials comprising a hardenable cement filler and an inorganic oxide filler such as silica or aluminum oxide, whereby said composition may optionally contain further additives . Further advantages are that the hardenable cement filler and the inorganic oxide filler are considerably cheaper than ATH and may be added in much smaller quantities .
The present invention is defined in the claims. The present invention refers to a vulcanized resp. hardened silicone rubber composition with improved tracking and erosion resistance, wherein said vulcanized silicone rubber comprises a low temperature vulcanized silicone rubber (LTV-SR) or a high temperature vulcanized silicone rubber (HTV-SR) as a silicone base, a defined combination of filler materials, and optionally further additives, characterized in that: (i) the combination of filler materials comprises a hardenable cement filler in combination with at least one mineral oxide filler which is different from said cement filler; wherein
(ii) the total amount of said hardenable cement filler and said at least one mineral oxide filler is within the range of 10 parts by weight to 230 parts by weight per 100 parts by weight of silicone base; and (iii) the weight ratio of the hardenable cement filler to the at least one mineral inorganic oxide filler is within the range of 3:1 to 1:4.
The present invention further refers to a method of making said vulca- nized (resp. hardened) low temperature or high temperature vulcanized (resp. hardened) silicone rubber with improved tracking and erosion resistance .
The present invention further refers to a low temperature as well as to a high temperature vulcanisable (resp. hardenable) silicone rubber composition comprising a low temperature vulcanisable silicone rubber (LTV-SR) or a high temperature vulcanisable silicone rubber (HTV-SR) as a silicone base, a defined combination of filler materials, and optionally further additives, comprising the components (i) , (ii) and (iii) as defined above, which on vulcanization (resp. hardening) yield said vulcanized silicone rubber composition with improved tracking and erosion resistance.
The present invention also refers to the use of said low temperature and said high temperature vulcanisable (resp. hardenable) silicone rubber composition, as defined above, for the production of shaped articles in the field of electrical insulators, specifically in the field of low, medium and high voltage insulators for indoor and outdoor use.
The present invention further refers to the use of said low temperature and said high temperature vulcanisable (resp. hardenable) silicone rubber composition, as defined herein, for the production of a surface modified electrical insulator, specifically in the field of low, medium and high voltage electrical insulators for indoor and outdoor use, characterized in that the surface of an electrical insulator, which is not made from a composition according to the present invention, is covered with a layer of the low temperature or high temperature vulcanisable silicone rubber composition as defined according to the present invention.
The present invention further refers to a method of making said surface modified electrical insulator, characterized in that the surface of an electrical insulator, which is not made from a composition according to the present invention, is covered with a layer of the composition according to the present invention.
The present invention also refers to the shaped articles in the field of electrical insulators, specifically in the field of low, medium and high voltage insulators for indoor and outdoor use, as made according to the present invention.
The "hardenable cement filler" is a hardenable powdery cement material as generally used in the construction industry. Such hardenable cement filler is known per se. The hardenable cement filler within the sili- cone rubber matrix hardens after reaction with atmospheric moisture and/or moisture which may be released during cross-linking reaction of the silicone rubber and thus forms a heat resistant network within the hardened silicone rubber matrix.
The hardenable cement filler is generally made from limestone and natural mineral silicates, whereby the natural mineral silicate preferably is clay, especially an aluminum silicate or a mixture of such silicates, such as for example Montmorillonite, Kaolinite, Andalusite, Zeolithe, Muskovite, Orthoklas or Glimmer. For producing the harden- able cement filler the limestone and a mineral silicate are generally mixed together within a weight ratio of {CaO} to the sum of {SiO2+Al2O3} being about 2 to 1 and heated to a temperature of about 14000C, preferably within a rotating tubular oven. The obtained sintered mass is cooled down and milled to a powder. The obtained powder can be used according to the present invention as the hardenable cement filler which hardens out in the presence of moisture. Such cement material is commercially available.
The hardenable cement filler is used in combination with the at least one mineral oxide filler which is different from said cement filler as defined above. This combination is obtained by intensively mixing the hardenable cement filler with the at least one mineral oxide filler as defined above using any mixing method known per se.
The at least one mineral oxide filler which is different from said cement filler is preferably selected from the group comprising silica (silicon oxide), aluminum oxide, magnesium oxide, ATH, and titanium oxide, and is preferably selected from silica and aluminum oxide or is a mixture of these filler materials .
The hardenable cement filler as well as the inorganic oxide filler, both, have preferably an average grain size distribution within the range of lμm-500μm, preferably within the range of 5μm-100μm. A part of the filler material may also have a grain size distribution within the nano-range.
The total content of said hardenable cement filler and of the at least one inorganic oxide filler [as defined in point (ii) above] is preferably within the range of 10 parts by weight to 230 parts by weight per 100 parts by weight of silicone base, preferably 15 parts by weight to 150 parts by weight, preferably within the range of 15 parts by weight to 100 parts by weight, preferably within the range of 15 parts by weight to 50 parts by weight and preferably within the range of 15 parts by weight to 25 parts by weight, per 100 parts by weight of silicone base.
The weight ratio of the hardenable cement filler to the at least one inorganic oxide filler is within the range of 3:1 to 1:4, preferably 2:1 to 1:3, preferably 1:1 to 1:2, and preferably about 2:3.
The special filler composition made from the hardenable cement filler and the inorganic oxide filler according to the present invention may be the only filler material present within the vulcanized silicone rubber base. However, the vulcanized silicone composition may optionally further contain one or more fillers as generally used in electrical insulators. Such an additional filler preferably is an inorganic oxide filler selected from the group comprising silica (silicon oxide), aluminium oxide preferably alumina trihydrate (ATH), magnesium oxide and/or titanium oxide, whereby said optional additional filler is not being premixed with the hardenable cement filler. Preferably such an optional additional filler are silica and alumina trihydrate (ATH) , preferably alumina trihydrate (ATH) .
The total content of said hardenable cement filler and of the at least one inorganic oxide filler [as defined in point (ii) above], including any optional additional filler present, is preferably within the range of 15 parts by weight to 230 parts by weight per 100 parts by weight of silicone base (i.e. about 13% to 70% by weight, calculated to the total weight of the filler and the silicone rubber base material) , preferably 20 parts by weight to 150 parts by weight per 100 parts by weight of silicone base; preferably within the range of 30 parts by weight to 100 parts by weight, per 100 parts by weight of silicone base .
The optional additional inorganic filler, has preferably an average grain size distribution within the range of lμm-500μm, preferably within the range of 5μm-100μm. A part of the optional additional inorganic filler material may also have a grain size distribution within the nano-range. Further optional additives are known per se and are for example stabilizers, flame retardants, colors and pigments.
The present invention further refers to the vulcanisable silicone rubber composition comprising a low temperature vulcanisable silicone rubber or a high temperature vulcanisable silicone rubber as a silicone base, a defined combination of filler materials, and optionally further additives as defined above. In order to improve, resp. to lower, the viscosity of the vulcanisable silicone rubber composition according to the present invention, said vulcanisable silicone rubber composition may also contain an organic inert solvent which evaporates during vulcanization. Such solvent is preferably selected from aliphatic or aromatic hydrocarbons with a boiling point below 1000C, preferably below 8O0C, such as white spirit or petroleum based compounds, or hexane, cyclohexane, toluene, and related compounds.
The vulcanized silicone rubber base material is made from a low temperature or high temperature vulcanizable polydimethylsiloxane . Such vulcanized silicone rubbers are generally composed of cross- linked groups of the formula [-(Ri) (R2)Si-O-] and [- (Ri) Si (-0-) 2] with terminating groups [(Ri) (R2) (Ra)Si-O-], wherein R1, R2 and R3 are optionally substituted methyl or phenyl, preferably methyl or phenyl, preferably methyl. The bridging [≡Si-O-Si≡] -group may be replaced by a group of the formula [≡Si-CH2-CH2-Si≡] or [≡Si-CH2-CH2-CH2-Si≡] , depending on the cross-linking mechanism and/or the starting materials chosen. Such silicone rubbers, preferably vulcanized polydimethyl- siloxanes as used in the production of electrical insulation systems are known to the expert in the art.
The vulcanized silicone rubber according to the present invention is made from a hardenable liquid or pasteous silicone resin composition. Preferably said hardenable liquid or pasteous silicone resin composition is a mixture of organopolysiloxanes, preferably a mixture of compounds of the general formula (I) :
Figure imgf000007_0001
wherein
R independent of each other is (C1-^) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl; Ri independent of each other has one of the meanings of R or R2, or is -O-Alkyl (C1-C4) or hydroxyl; preferably one of the meanings of R or R2;
R2 independent of each other has one of the meaning of R, or is hydrogen, or a residue of the formula: -(A)1-CH=CH2; R3 independent of each has one of the meanings of R or is hydrogen, or a residue of the formula: -(A)1-CH=CH2; or -O-Alkyl (Ci-C4) or hydroxyl;
A is a residue -C3H2s- , preferably - (CH2) s- , wherein s is a whole number from 1 to 3, preferably 1; r is zero or one; m is a number within the range of 500 to 20'000, preferably within the range of 1000 to 15 '000, preferably within the range of
4'0OO to 10 '000; and n is a number within the range of zero to 500, preferably zero or within the range of 2 to 100, preferably zero or a number within the range of 2 to 20; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence.
If R2 or R3 are independent of each other hydrogen, or a residue of the formula: -(A)1-CH=CH2, then R2 or R3 is preferably either hydrogen or a residue of the formula: -(A)1-CH=CH2; but not both residues at the same time per molecule.
If R3 has one of the meanings: hydrogen, or a residue of the formula: -(A)1-CH=CH2; or -O-Alkyl (Ci-C4) or hydroxyl; then R3 is preferably either hydrogen or a residue of the formula: -(A)1-CH=CH2, but not both residues at the same time per molecule; or is -O-Alkyl (Ci-C4) or hydroxyl .
Preferably R3 has one of the meanings given for R, wherein R preferably is methyl or phenyl, wherein the molecule contains methyl as well as phenyl residues. The ratio of methyl to phenyl is given by the required flowability of the mixture and the properties required in the hardened product. Preferably R is methyl. The compound of formula (I) generally is a mixture of homologous compounds of formula (I) which is known to the expert . Low temperature vulcanized silicone rubbers are preferably made from a compound of formula (IA) :
R R'i R'i
R'3— Si-O- -Si-O- t fi-R's (IA)
R'i R R2 R'i wherein
R, m, n, have the meanings as given above;
R'i independent of each other has one of the meanings of R;
R' 2 independent of each other has one of the meaning of R, or is
-O-Alkyl (Ci-C4) or hydroxyl; R'3 independent of each is -O-Alkyl (Ci-C4) or hydroxyl; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence.
Vulcanization resp. cross-linking/curing of compounds of formula (IA) may be carried out in the presence of cross-linking compounds, especially if RZ2 is hydroxyl, such as compounds of formula [R4_q-SiXq] , wherein R is (Ci-4)alkyl or phenyl, preferably methyl, and X is a hydrolysable group, such as halogen, acetoxy, alkoxy, oxime or amine, preferably chlorine or (Ci_4) alkoxy, preferably chlorine or methoxy, and q is 1 to 3, preferably 2 or 3, preferably 3. The mixture of the silicone compounds of formula (I), resp. Formula (IA) may be hardened for example by adding an alkoxysilane of the formula [ (Ci_4) Alkyl] 4_q - Si [O-Alkyl (Ci-4) q] , wherein q is 1 to 3, preferably 2 or 3, preferably 3; for example methyltrimethoxysilane, methyltriethoxysilane and similar compounds or { (phenyl) 4_qSi [0-alkyl (Ci-C4) ] q} . With this method a low temperature vulcanized silicone rubber (LTV-SR) may be obtained, as is known to the expert in the art.
High temperature vulcanized silicone rubbers are preferably made from a compound of formula (IB) :
Figure imgf000009_0001
wherein
R independent of each other is (Ci_4) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl; R"i, R"2, R"3, independent of each other have one of the meanings of R; m and n have the meaning as given above; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence.
Vulcanization cross-linking/curing of compounds of formula (IB) may be carried out in the presence of peroxide compounds, such as diacylper- oxide, dialkylperoxide and other peroxides known per se to harden the siloxane mixture. Generally elevated temperatures are used for vulca- nization, which yields a high temperature vulcanized silicone rubber (HTV-SR) . This is known to the expert in the art.
A further embodiment of the present invention is that the substituents of the compound of formula (I) have the following meaning: R independent of each other is (C1-.4) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl;
Ri independent of each other has one of the meanings of R; R2 independent of each other has one of the meanings of R, or is either hydrogen, or a residue of the formula: -(A)1-CH=CH2; R3 independent of each is either hydrogen, or a residue of the formula: -(A)1-CH=CH2; m and m have the meaning as given above, wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence .
In this embodiment R2 or R3 are independent of each other hydrogen, or a residue of the formula: -(A)1-CH=CH2, wherein R2 or R3 is either hydrogen or a residue of the formula: -(A)1-CH=CH2; but not both residues at the same time in the same molecule. The compound wherein R2 and/or R3 are hydrogen and the compound wherein R2 and/or R3 are -(A)1-CH=CH2, are stored separately to avoid any interaction. The compounds are mixed shortly before hardening the mixture. Both compounds are mixed in equimolar amounts and are then hardened resp. vulcanized. Preferably a molar excess of about 2 to 5% of the Si-H-groups is used with respect to the component containing the -(A)1-CH=CH2 substituent. Further a catalyst is preferably used, preferably a complex made from a metal selected from rhodium, nickel, palladium and/or platin, in an amount of preferably 1 ppm to 100 ppm calculated to the metal bound in the complex. Such catalytically active compounds and the silicon compounds of formula (I) to be used are known per se and have been described in the literature.
The present invention also refers to a method of making the vulcanized silicone rubber composition with improved tracking and erosion resistance according to the present invention, characterized in that the components of the hardenable mixture, i.e. the low temperature vulcanisable silicone rubber and/or a high temperature vulcanized silicone rubber as the silicone base, a defined combination of filler materials, and optionally further additives, comprising the components (i) , (ii) and (iii) as defined above, are mixed prior to the application in any desired sequence and subsequently are vulcanized, optionally under heating to an elevated temperature, preferably to a temperature within the range of 5O0C to 15O0C, preferably within the range of 1000C to 14O0C, for a time long enough to cause complete vulcanization of the composition, which generally is between about 5 minutes to about 24 hours, preferably between about 10 minutes to about 60 minutes.
The present invention further refers to a method of making a surface modified electrical insulator, including the steps of (i) applying to the surface of an electrical insulator, which is not made from a composition according to the present invention, a layer of the vulcanizable silicone rubber composition according to the present invention and (ii) curing said layer of vulcanizable silicone rubber composition to yield a cured modified surface with improved tracking and erosion resistance.
An electrical insulator, which is not made from a composition according to the present invention, can be made from a ceramic, or a thermoplastic polymer or a duroplastic polymer such as an epoxy resin composition or a polyurethane composition, preferably an epoxy resin composition. The vulcanizable silicone rubber composition can be applied by any known method such as dipping, spaying or painting. Curing of the layer of vulcanizable silicone rubber composition is carried out either at room temperature or at an elevated temperature, preferably at a temperature within the range of 6O0C to 15O0C, preferably within the range of 12O0C to 14O0C, for a time long enough to cause complete vulcanization of the composition, which generally is between about 5 minutes and about 24 hours, preferably from about 10 minutes to about 60 minutes. The thickness of the layer is preferably within the range of 500 nm to 5 mm, preferably from 1 mm to 3 mm, and preferably at about 0.7 mm.
The present invention also refers to the shaped articles in the field of electrical insulators, specifically in the field of low, medium and high voltage insulators for indoor and outdoor use, as made according to the present invention. Preferred uses of the insulation produced according to the present invention are electrical insulations, espe- cially in the field of impregnating electrical coils and core-coils assemblies and in the production of electrical components such as transformers, bushings, insulators, switches, sensors, converters and cable end seals.
Preferred uses of the insulation system produced according to the present invention are also high-voltage insulations for indoor and outdoor use, especially for outdoor insulators associated with high-voltage lines, as long-rods, composite and cap-type insulators, and also for base insulators in the medium-voltage sector, in the production of insulators associated with outdoor power switches, measuring transducers, lead-throughs, and overvoltage protectors, in switchgear construction, in power switches, dry-type transformers, and electrical machines, as coating materials for transistors and other semiconductor elements and/or to impregnate electrical components .
The following examples illustrate the invention without restricting the scope of the description and claims.
Examples The components as given in Table 1 are dispersed in the silicone base by either using a blender, a duplex kneader, a two-roll mill or their combination. The homogeneous formulation is then molded and cured at room temperature or at elevated temperature, chosen on the basis of the vulcanisable silicone starting material and the used peroxide or platinum compound or oxime or silanes . After remolding, a post-curing step is possible, but not necessary.
Table 1 shows a Formulation A prepared according to the present invention and compares this Formulation A with two commercial References 1 and 2. Composition of the formulations, i.e. filler, additive and curing agent content, is given in phr (parts per hundred) with respect to the silicone base. Table 2 lists their properties.
Table 1
Figure imgf000013_0001
- Silicone base (1) is a room temperature curing silicone rubber, HVIC+, from Dow Corning Corp. , containing 40% by weight of ATH, calculated to the total weight of Silicone base (1) .
Silicone base (2) (a peroxide cured silicone rubber, Elastosil R 401/70 OH, Wacker Chemie GmbH, DE)
Cement from Holcim Portland Cement Silica (e.g. quarz flour W12MST, Quarzwerke, DE)
ATH (aluminiumtπhydrate, Martinal OL-104/S, Martinswerk GmbH, DE) Peroxide (DCLBP-50-PSI : Di (2, 4-dichlorobenzoyl) peroxide, 50%, in silicone oil, Degussa Initiators GmbH & Co. KG, DE)
Table 2 : Properties of the formulations according to Table 1
Standard Formulation A Reference 1 Reference 2
Tracking pass 3.5 and fail 3.5 and fail 3.5 and
IEC 60587 Resistance 6 kV 6 kV 6 kV
Comparison between Formulation A and the Reference 1 and Reference 2 : The introduction of cement/silica filler leads to an improvement of the tracking resistance without deteriorating mechanical properties. Furthermore the material costs are reduced.

Claims

Claims
1. Vulcanized silicone rubber composition with improved tracking and erosion resistance, wherein said vulcanized silicone rubber comprises a low temperature vulcanized silicone rubber (LTV-SR) or a high temperature vulcanized silicone rubber (HTV-SR) as a silicone base, a defined combination of filler materials, and optionally further additives, characterized in that:
(i) the combination of filler materials comprises a hardenable cement filler in combination with at least one mineral oxide filler which is different from said cement filler; wherein (ii) the total amount of said hardenable cement filler and said at least one mineral oxide filler is within the range of 10 parts by weight to 230 parts by weight per 100 parts by weight of silicone base; and
(iii) the weight ratio of the hardenable cement filler to the at least one mineral inorganic oxide filler is within the range of 3 : 1 to
1:4.
2. Vulcanized silicone rubber composition according to claim 1, characterized in that the hardenable cement filler is a hardenable powdery cement material as generally used in the construction industry.
3. Vulcanized silicone rubber composition according to claim 2, characterized in that the hardenable cement filler is made from limestone and natural mineral silicates, whereby the natural mineral silicate preferably is clay, and preferably an natural aluminum silicate or a mixture of such silicates.
4. Vulcanized silicone rubber composition according to any one of claims 1-3, characterized in that the at least one mineral oxide filler which is different from said cement filler is preferably selected from the group comprising silica (silicon oxide), aluminum oxide, magnesium oxide, ATH, and titanium oxide, and is preferably selected from silica and aluminum oxide or is a mixture of these filler materials .
5. Vulcanized silicone rubber composition according to any one of claims 1-4, characterized in that the hardenable cement filler as well as the inorganic oxide filler, both, have an average grain size distribution within the range of l(Xm-500(Xm, preferably within the range of 5μm-100μm and wherein a part of the filler material optionally has a grain size distribution within the nano-range.
6. Vulcanized silicone rubber composition according to any one of claims 1-5, characterized in that the total content of said hardenable cement filler and of the at least one inorganic oxide filler is 15 parts by weight to 150 parts by weight, preferably within the range of 15 parts by weight to 100 parts by weight, preferably within the range of 15 parts by weight to 50 parts by weight and preferably within the range of 15 parts by weight to 25 parts by weight, per 100 parts by weight of silicone base.
7. Vulcanized silicone rubber composition according to any one of claims 1-6, characterized in that the weight ratio of the hardenable cement filler to the at least one inorganic oxide filler is within the range of 2:1 to 1:3, preferably 1:1 to 1:2, and preferably about 2:3.
8. Vulcanized silicone rubber composition according to any one of claims 1-7, characterized in that said vulcanized silicone rubber composition further contains one or more fillers as generally used in electrical insulators, said additional filler preferably being an inorganic oxide filler selected from the group comprising silica (silicon oxide), aluminium oxide preferably alumina trihydrate (ATH), magnesium oxide and/or titanium oxide, whereby said optional additional filler is not being premixed with the hardenable cement filler.
9. Vulcanized silicone rubber composition according to claim 8, characterized in that the optional additional filler is silica and/or alumina trihydrate (ATH) , preferably alumina trihydrate (ATH) .
10. Vulcanized silicone rubber composition according to any one of claims 1-9, characterized in that the total content of said hardenable cement filler and of the at least one inorganic oxide filler and any optional additional filler present, is within the range of 15 parts by weight to 230 parts by weight per 100 parts by weight of silicone base, preferably 20 parts by weight to 150 parts by weight per 100 parts by weight of silicone base; preferably within the range of 30 parts by weight to 100 parts by weight, per 100 parts by weight of silicone base.
11. Vulcanized silicone rubber composition according to any one of claims 1-10, characterized in that the optional additional inorganic filler, has an average grain size distribution within the range of lμm-500μm, preferably within the range of 5μm-100μm and wherein a part of the optional additional inorganic filler material optionally has a grain size distribution within the nano-range.
12. Vulcanized silicone rubber composition according to any one of claims 1-11, characterized in that said vulcanized silicone rubber composition further contains known additives, preferably stabilizers, flame retardants, colors and pigments.
13. Vulcanized silicone rubber composition according to any one of claims 1-12, characterized in that said vulcanized silicone rubber composition is made from a hardenable liquid or pasteous silicone resin composition comprising a mixture of compounds of the general formula (I) :
Figure imgf000016_0001
wherein
R independent of each other is (C1-4) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl; Ri independent of each other has one of the meanings of R or R2, or is -O-Alkyl (C1-C4) or hydroxyl; preferably one of the meanings of R or R2;
R2 independent of each other has one of the meaning of R, or is hydrogen, or a residue of the formula: -(A)1-CH=CH2; R3 independent of each has one of the meanings of R or is hydrogen, or a residue of the formula: -(A)1-CH=CH2; or -O-Alkyl (Ci-C4) or hydroxyl;
A is a residue -C3H2s- , preferably - (CH2) s- , wherein s is a whole number from 1 to 3, preferably 1; r is zero or one; m is a number within the range of 500 to 20'000, preferably within the range of 1000 to 15 '000, preferably within the range of 4'0OO to 10 '000; and n is a number within the range of zero to 500, preferably zero or within the range of 2 to 100, preferably zero or a number within the range of 2 to 20; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence.
14. Vulcanized silicone rubber composition according to claim 13, characterized in that in case that R2 or R3 are either hydrogen or a residue of the formula: -(A)1-CH=CH2; then not both residues are present at the same time in the same molecule .
15. Vulcanized silicone rubber composition according to claim 13, characterized in that said vulcanized silicone rubber composition is made from a hardenable liquid or pasteous silicone resin composition comprising a mixture of compounds of the general formula (IA) :
R R'i R'i
R'3— Si-O- -Si-O- t fi-R's (IA)
D' D D' D'
R'i R R2 R'i wherein
R, m, n, have the meanings as given above;
R' i independent of each other has one of the meanings of R; R' 2 independent of each other has one of the meaning of R, or is -O-Alkyl (Ci-C4) or hydroxyl;
R' 3 independent of each is -0-AIlCyI(Ci-C4) or hydroxyl; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence.
16. Vulcanized silicone rubber composition according to claim 13, characterized in that said vulcanized silicone rubber composition is made from a hardenable liquid or pasteous silicone resin composition comprising a mixture of compounds of formula (IB) :
Figure imgf000017_0001
wherein R independent of each other is (Ci_4) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl; R"i, R"2, P-"3, independent of each other have one of the meanings of R; m and n have the meaning as given above; and wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence.
17. Vulcanized silicone rubber composition according to claim 13, characterized in that said vulcanized silicone rubber composition is made from a hardenable liquid or pasteous silicone resin composition comprising a mixture of compounds of formula (I), wherein the substituents have the following meaning: R independent of each other is (C1-.4) -alkyl which optionally is substituted by chlorine and/or bromine or is phenyl; preferably methyl, ethyl, propyl, 3, 3, 3-trifluoropropyl, monofluoromethyl, oder difluoromethyl; preferably methyl;
Ri independent of each other has one of the meanings of R; R2 independent of each other has one of the meanings of R, or is either hydrogen, or a residue of the formula: -(A)1-CH=CH2; R3 independent of each is either hydrogen, or a residue of the formula: -(A)1-CH=CH2; m and m have the meaning as given above, wherein the groups -[Si(R) (R)O]- und -[Si(Ri) (R2)O]- are ordered in an arbitrary sequence .
18. Vulcanized silicone rubber composition according to claim 17, characterized in that when R2 or R3 are independent of each other hydrogen or a residue of the formula: -(A)1-CH=CH2, wherein R2 or R3 is either hydrogen or a residue of the formula: -(A)1-CH=CH2, not both residues are present at the same time in the same molecule and the compounds wherein R2 and/or R3 are hydrogen and the compound wherein R2 and/or R3 are -(A)1-CH=CH2, are stored separately and are mixed shortly before applying and hardening the mixture.
19. Method of making the vulcanized silicone rubber composition according to any one of the claims 1-18, characterized in that the components of the hardenable mixture are mixed in any desired sequence prior to the application and subsequently are vulcanized, optionally under heating to an elevated temperature, preferably to a temperature within the range of 6O0C to 15O0C, preferably within the range of 12O0C to 14O0C, for a time long enough to cause complete vulcanization of the composition.
20. Vulcanisable silicone rubber composition for making a vulcanized silicone rubber composition according to any one of the claims 1-18, characterized in that said vulcanisable silicone rubber composition comprises a low temperature vulcanisable silicone rubber (LTV- SR) or a high temperature vulcanisable silicone rubber (HTV-SR) as a silicone base, a combination of filler materials as defined as components (i) , (ii) and (iii) , and optionally further additives, as defined in any one of the claims 1-18.
21. Vulcanisable silicone rubber composition according to claim 20, characterized that said composition comprises an organic inert solvent which evaporates during vulcanization, said solvent being selected from aliphatic or aromatic hydrocarbons, preferably with a boiling point below 1000C, preferably below 8O0C, preferably white spirit or petroleum based compounds, or hexane, cyclohexane, toluene, and related compounds .
22. The use of the vulcanisable silicone rubber resin according to claims 20 or 21 for the production of shaped articles in the field of low, medium and high voltage insulators for indoor and outdoor use.
23. Method of making a surface modified electrical insulator, including the steps of (i) applying to the surface of an electrical insulator, which is not made from a composition as defined in any one of the claims 1-18, a layer of a vulcanizable silicone rubber composition according to claim 20 or 21 and (ii) curing said layer of vulcanizable silicone rubber composition.
24. Method according to claim 23, characterized in that said electrical insulator, which is not made from a composition as defined in any one of the claims 1-18, is made from a ceramic, or a thermoplastic polymer or a duroplastic polymer, preferably is made from an epoxy resin composition or a polyurethane composition, preferably from a polyurethane composition.
25. Method according to claim 23 or 24, characterized in that said layer of vulcanizable silicone rubber composition is cured at an elevated temperature, preferably at a temperature within the range of 6O0C to 15O0C, preferably within the range of 12O0C to 14O0C, for a time long enough to cause complete vulcanization of the composition.
26. Method according to any one of the claims 23 to 25, characterized in that said layer of vulcanizable silicone rubber composition has a thickness within the range of 500 nm to 5 mm, preferably from 1 mm to 3 mm, and preferably at about 0.7 mm.
27. Shaped articles in the field of low, medium and high voltage insulators for indoor and outdoor use, comprising a Vulcanized silicone rubber composition according to any one of the claims 1 to 18.
PCT/EP2009/054014 2009-04-03 2009-04-03 Silicone rubber composition WO2010112081A1 (en)

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WO2013096442A1 (en) * 2011-12-23 2013-06-27 Abb Technology Ag Corrosion-resistant coating system for a dry-type transformer core
CN103354141A (en) * 2013-07-04 2013-10-16 清华大学深圳研究生院 Method and system for improving surface hydrophobicity of contaminated silicon sulfide rubber product
CN107142007A (en) * 2017-06-07 2017-09-08 合肥汇之新机械科技有限公司 A kind of impact-resistant coating and its preparation technology for diel
US9920841B2 (en) 2012-12-17 2018-03-20 Emd Millipore Corporation Interface and fluid-transfer system
CN108298909A (en) * 2018-03-06 2018-07-20 广东电网有限责任公司电力科学研究院 A kind of sound insulation composite material and preparation method thereof
CN109135289A (en) * 2018-07-16 2019-01-04 江苏省苏安能节能建材科技有限公司 A kind of water base graphene oxide/aluminium silicon rubber can porcelain flexible clay facing tile and its preparation and application
CN110283462A (en) * 2019-07-02 2019-09-27 西安交通大学 A kind of mesolow flame resistant cable is with can Ceramic silicon rubber insulating materials and preparation method thereof

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Cited By (17)

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WO2011087073A1 (en) * 2010-01-18 2011-07-21 日本ジッコウ株式会社 Silicone resin composition and protective coating method using silicone resin composition
JP5710503B2 (en) * 2010-01-18 2015-04-30 日本ジッコウ株式会社 Silicone resin composition and protective coating method using silicone resin composition
WO2012103574A1 (en) * 2011-02-03 2012-08-09 Axolotl International (Asia) Pty Ltd Substrate coating with a cementitious formulation
WO2013096442A1 (en) * 2011-12-23 2013-06-27 Abb Technology Ag Corrosion-resistant coating system for a dry-type transformer core
US8610532B2 (en) 2011-12-23 2013-12-17 Abb Technology Ag Corrosion-resistant coating system for a dry-type transformer core
KR20140116104A (en) * 2011-12-23 2014-10-01 에이비비 테크놀로지 아게 Corrosion-resistant coating system for a dry-type transformer core
KR102022228B1 (en) * 2011-12-23 2019-09-19 에이비비 슈바이쯔 아게 Corrosion-resistant coating system for a dry-type transformer core
CN102911414A (en) * 2012-10-17 2013-02-06 青岛佳之源轮胎维修有限公司 Low-temperature vulcanized masterbatch and preparation method thereof
CN102911414B (en) * 2012-10-17 2015-01-14 青岛佳之源轮胎维修有限公司 Low-temperature vulcanized masterbatch and preparation method thereof
US9920841B2 (en) 2012-12-17 2018-03-20 Emd Millipore Corporation Interface and fluid-transfer system
CN103354141A (en) * 2013-07-04 2013-10-16 清华大学深圳研究生院 Method and system for improving surface hydrophobicity of contaminated silicon sulfide rubber product
CN103354141B (en) * 2013-07-04 2015-11-04 清华大学深圳研究生院 Improve the method and system of the sulphurated siliastic product surface hydrophobicity of staining
CN107142007A (en) * 2017-06-07 2017-09-08 合肥汇之新机械科技有限公司 A kind of impact-resistant coating and its preparation technology for diel
CN107142007B (en) * 2017-06-07 2019-06-07 合肥汇之新机械科技有限公司 A kind of impact-resistant coating and its preparation process for stamping die
CN108298909A (en) * 2018-03-06 2018-07-20 广东电网有限责任公司电力科学研究院 A kind of sound insulation composite material and preparation method thereof
CN109135289A (en) * 2018-07-16 2019-01-04 江苏省苏安能节能建材科技有限公司 A kind of water base graphene oxide/aluminium silicon rubber can porcelain flexible clay facing tile and its preparation and application
CN110283462A (en) * 2019-07-02 2019-09-27 西安交通大学 A kind of mesolow flame resistant cable is with can Ceramic silicon rubber insulating materials and preparation method thereof

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