EP2195813A1 - Electrical insulation system with improved electrical breakdown strength - Google Patents

Electrical insulation system with improved electrical breakdown strength

Info

Publication number
EP2195813A1
EP2195813A1 EP07820881A EP07820881A EP2195813A1 EP 2195813 A1 EP2195813 A1 EP 2195813A1 EP 07820881 A EP07820881 A EP 07820881A EP 07820881 A EP07820881 A EP 07820881A EP 2195813 A1 EP2195813 A1 EP 2195813A1
Authority
EP
European Patent Office
Prior art keywords
filler material
component
electrical insulation
insulation system
pretreated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07820881A
Other languages
German (de)
French (fr)
Inventor
Martin Carlen
Xavier Kornmann
Andrej Krivda
Felix Greuter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Research Ltd Switzerland
ABB Research Ltd Sweden
Original Assignee
ABB Research Ltd Switzerland
ABB Research Ltd Sweden
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ABB Research Ltd Switzerland, ABB Research Ltd Sweden filed Critical ABB Research Ltd Switzerland
Publication of EP2195813A1 publication Critical patent/EP2195813A1/en
Withdrawn legal-status Critical Current

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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
    • H01B3/40—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 epoxy resins
    • 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
    • H01B3/002—Inhomogeneous material in general
    • H01B3/006—Other inhomogeneous material
    • 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
    • H01B3/302—Polyurethanes or polythiourethanes; Polyurea or polythiourea
    • 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
    • H01B3/303—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups H01B3/38 or H01B3/302
    • H01B3/305—Polyamides or polyesteramides
    • 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
    • H01B3/42—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 polyesters; polyethers; polyacetals
    • H01B3/421—Polyesters
    • 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
    • H01B3/44—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 vinyl resins; acrylic resins
    • H01B3/441—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 vinyl resins; acrylic resins from alkenes

Definitions

  • the present invention refers to an electrical insulation system with improved electrical breakdown strength.
  • Electrical insulations for potting applications for instance in embedded poles, instrument and distribution transformers or sensors, generally consist of an epoxy resin cured with an acid anhydride in the presence of an accelerator.
  • the starting compo- nents usually are mixed together with a filler material, preferably silica flower, typically in the range of 60 to 65 % by weight of filler material, calculated to the total weight of the electrical insulator; the mixture is then cured.
  • a filler material preferably silica flower, typically in the range of 60 to 65 % by weight of filler material, calculated to the total weight of the electrical insulator; the mixture is then cured.
  • Alternative polymers can also be used such as polyesters, polyamides, poly- butylene terephthalate, polyurethanes or polydicyclopentadiene .
  • a large amount of filler generally decreases the overall price of the insulation, however, it also increases the stiffness, the fracture toughness, the thermal conductivity of the insulator and decreases its thermal expansion coefficient.
  • WO 2006/008422 proposes the production of an electrical insulator for high voltage use comprising a mineral filler material wherein the mineral filler material is a combination of a filler material with an average grain size distribution within the micron size together with a selected filler material with an average grain size distribution within the nano size, i.e. less than 1 ⁇ m.
  • a combination especially for industrial potting applications, e.g. in epoxy resins, has different disadvantages such as increased viscosity which reduces processability and possible not yet quantified impact of nanoparticles on health, safety and environment.
  • a mineral micro filler material is used having an average grain size distribution within the range of 1 ⁇ m-500 ⁇ m, preferably within the range of 5 ⁇ m-100 ⁇ m.
  • micro filler material when previously treated with an intercalating compound, for example with an alkyl ammonium compound, may be added to the untreated filler material in comparatively small quantities, thereby significantly improving the electrical properties of the insulator system, especially its electrical breakdown strength.
  • an intercalating compound for example with an alkyl ammonium compound
  • Such pretreated filler material comprises for example silica, quartz and layered silicates.
  • the present invention is defined in the claims.
  • the present invention specifically refers to an electrical insulation system with improved electrical breakdown strength, said electrical insulation system comprising a hardened polymer component having incorporated therein a conventional filler material and a selected pretreated filler material, characterized in that
  • the hardened polymer component is selected from epoxy resin systems, polyesters, polyamides, polybutylene terephthalate, polyurethanes and polydicyclopentadiene, and preferably is a hardened epoxy resin system;
  • the conventional filler material is a known filler material having an average grain size distribution within the range of 1 ⁇ m-500 ⁇ m, being present in a quantity within the range of 40 %-65 % by weight, calculated to the total weight of the insulator system; and
  • the selected pretreated filler material is selected from silica, quartz, or a silicate, preferably mica (glimmer) , kaolin or a layered silicate or talc, or is a mixture of these compounds, having an average grain size distribution within the range of 1 ⁇ m-500 ⁇ m, wherein said selected filler material has been pretreated with an intercalating compound and wherein said pretreated filler material is present in an amount of 1 %-30 % by weight, calculated to the weight of the
  • the present invention also refers to the selected pretreated filler material as defined as component (c) herein above having an average grain size distribution within the range of 1 ⁇ m-500 ⁇ m, preferably within the range of 5 ⁇ m-100 ⁇ m, having been treated with an intercalating compound.
  • the present invention also refers to the mixture of the selected pretreated filler material as defined as component (c) herein above and the conventional non-treated filler material as defined as component (b) herein above, wherein the selected pretreated filler material is present in an amount of 1 %-30 % by weight, calculated to the weight of the conventional filler material, said selected pretreated filler material and said conventional non-treated filler material having an average grain size distribution within the range of 1 ⁇ m-500 ⁇ m.
  • the present invention also refers to a method of producing said electrical insulation system with improved electrical breakdown strength .
  • the present invention further refers to electrical articles comprising said electrical insulation system with improved electrical breakdown strength.
  • An important feature of the present invention is that the selected pretreated filler material has an average grain size distribution within the range of 1 ⁇ m-500 ⁇ m.
  • Said pretreated filler material is selected from silica, quartz, or a silicate, preferably mica, kaolin or a layered silicate, or talc or is a mixture or these compounds.
  • phyllosilicates preferably selected from montmorillonite, hectorite, saponite, vermiculite, smectite, illite, sepiolite, palygorscite, muscovite, allevardite, amesite, fluorohectorite, beidellite, talcum, nontronite, stevensite, bentonite, gl
  • montmorillonite Preferred are montmorillonite, hectorite, saponite, vermiculite, smectite, illite; most preferred are montmorillonite, hectorite, vermiculite, smectite, illite.
  • Different compounds can be used to pretreat the selected filler material, thereby modifying the surface properties of the selected filler material. It is understood that the modified surface properties of the pretreated micro filler material disperse remarkably well in the epoxy, thereby surprisingly improving the dielectric strength as well as the mechanical properties of the insulator system.
  • the invention is not bound to this explanation.
  • Preferred compounds for modifying the surface properties of the selected filler material are known per se . These compounds are also named intercalating compounds. Preferred such compounds are for example protonated primary, secondary or tertiary amines, protonated basic heterocyclic compounds such as protonated imidazole compounds, or quaternary ammonium compounds, substituted by at least one alkyl residue or at least one functiona- lized alkyl residue. Preferred is the treatment with substituted ammonium compounds, or with 2-hydroxyalkyl-substituted imidazole compounds.
  • alkyl-substitu- ted or hydroxyalkyl-substituted ammonium compounds such as dimethyl-dihydrogenatedtallow-quaternaryammonium and related hydroxyalkyl-containing compounds.
  • alkyl-substitu- ted or hydroxyalkyl-substituted ammonium compounds such as dimethyl-dihydrogenatedtallow-quaternaryammonium and related hydroxyalkyl-containing compounds.
  • intercalating compounds known in the art for the treatment of layered silicates and other inorganic layered compounds, such as metallic salts of aromatic, aliphatic, araliphatic and cyclo- aliphatic carbonic acids as well as other acids. Examples are alkali salts (lithium, sodium or potassium salts) of formic acid, acetic acid, oxalic acid, gluconic acid, ethyleneglykol, and of other diols. These compounds can also be used within the scope of the present invention.
  • the conventional filler material as well as the selected pre- treated filler material, both independent of each other, preferably have an average grain size distribution within the range of 5 ⁇ m-100 ⁇ m, preferably within the range of 5 ⁇ m-50 ⁇ m, preferably within the range of 5 ⁇ m-30 ⁇ m.
  • the conventional filler material may be selected independently from the selected pretreated filler material and may also be the same inorganic filler material as listed above for the pretreated filler material selected from silica, quartz, or talc or a silicate, preferably mica, kaolin or a layered silicate.
  • the conventional filler may also be chosen from other known filler compounds such as aluminium oxide, aluminium tri- hydrate [ATH, Al 2 O 3 .3H 2 O, corresponding to Al(OH) 3 ], titanium oxide or dolomite [CaMg (CO 3 ) 2 ] , metal nitrides, such as silicon nitride, boron nitride and aluminium nitride or metal carbides, such as silicon carbide.
  • Mica (glimmer) and kaolin are aluminium silicates substantially composed of SiO 2 and Al 2 O 3 .
  • the conventional filler material may be surface treated with a coupling agent known per se .
  • the coupling agent is preferably selected from the group comprising silanes and siloxanes and preferably is a silane, for example 3-glycidoxypropyl- trimethoxysilane or 3-glycidoxypropyldimethoxymethylsilane .
  • the method of producing the selected pretreated filler material with an intercalating compound is characterized in that the selected filler material is brought in contact with the intercalating compound, optionally in the presence of a suitable solvent and under stirring, within the temperature range of 20 0 C to 150 0 C, preferably at room temperature up to 60 0 C, and for a time long enough so that the intercalating compound modifies the surface of the selected filler material. This time is generally between one hour and three days depending on the temperature used. Preferred is room temperature and a reaction time of about one to three days.
  • the suitable solvent is usually water but a low molecular alcohol may also be used.
  • the concentration of the intercalation compound in the solvent is not critical and is preferably within the range of 0.1 mol to 5.0 mol per liter of solvent.
  • the suspension is then filtered off, washed with the solvent, preferably with water, and dried for several hours, preferably for about 10 to 24 hours, at a temperature within the range of 50°C to 80°C, preferably at about 60°C.
  • the conventional filler material preferably is present within the insulator system in a quantity within the range of 50 %-60 % by weight, preferably in a quantity of about 55 % by weight, calculated to the total weight of the insulator system.
  • the selected pretreated filler material having been pretreated with an intercalating compound preferably is present in an amount of 2 %-20 % by weight, preferably in an amount of 2 %- 10 % by weight, calculated to the weight of the conventional filler material present in the insulator system.
  • the electrical insulation system with improved electrical breakdown strength according to the present invention comprises a filler containing hardened polymer component.
  • Said hardened polymer component is selected from epoxy resin systems, polyesters, polyamides, preferably nylon, polybutylene terephtha- late, polyurethanes and polydicyclopentadiene, and preferably is a hardened epoxy resin system.
  • filler containing epoxy resin systems polyesters, polyamides, polybutylene terephthalate, polyurethanes and polydicyclo- pentadiene have been described in the literature.
  • a special filler composition according to the present invention i.e. a mixture of a conventional filler material as defined herein above as component (b) and a selected pretreated filler material as defined herein above as component (c)
  • said filler components of said filler composition can be incorporated into the respective monomeric starting material of component (a) as defined herein above, in an analogous manner as described in the literature for other filler materials. This is within the knowledge of the expert.
  • the filler material is incorpo- rated into the monomeric starting materials of the respective polymer by known methods so as to be uniformly dispersed therein.
  • the non-hardened composition, resp. dispersion, thus obtained e.g. the non-hardened epoxy resin composition
  • APG automated pressure gelation
  • the dispersion is formed into the desired shape using known methods, optionally with the help of a molding tool, and then hardened out, optionally using post-curing.
  • the present invention also refers to a method of producing an electrical insulation system with improved electrical breakdown strength, characterized in that a conventional filler material [as defined herein above as component (b) ] and a selected pretreated filler material [as defined herein above as component (c) ] , are incorporated into the monomeric starting material of the respective polymer of the component (a) as defined herein above, so as to be uniformly dispersed therein, the dispersion is then formed into the desired shape, optionally with the help of a molding tool, and then hardened and optionally post-cured.
  • composition may comprise further components selected from wetting/dispersing agents, plasticizers, antioxidants, light absorbers, and from further additives generally used in electrical applications.
  • Preferred epoxy resins used within the context of the present invention are aromatic and/or cycloaliphatic compounds. These compounds are known per se. Epoxy resins are reactive glycidyl compounds containing at least two 1,2-epoxy groups per molecule. Preferably a mixture of polyglycidyl compounds is used such as a mixture of diglycidyl- and triglycidyl compounds.
  • Epoxy compounds useful for the present invention comprise unsub- stituted glycidyl groups and/or glycidyl groups substituted with methyl groups. These glycidyl compounds preferably have a molecular weight between 200 and 1200, especially between 200 und 1000 and may be solid or liquid.
  • the epoxy value (equiv./100 g) is preferably at least three, preferably at least four and especially at about five, preferably about 4.9 to 5.1.
  • Preferred are glycidyl compounds which have glycidyl ether- and/or glycidyl ester groups. Such a compound may also contain both kinds of glycidyl groups, e.g.
  • polyglycidyl esters with 1 to 4 glycidyl ester groups, especially diglycidyl ester and/or triglycidyl esters.
  • Preferred glycidyl esters may be derived from aromatic, arali- phatic, cycloaliphatic, heterocyclic, heterocyclic-aliphatic or heterocyclic-aromatic dicarbonic acids with 6 to 20, preferably 6 to 12 ring carbon atoms or from aliphatic dicarbonic acids with 2 to 10 carbon atoms.
  • Examples are glycidyl ethers derived from Bisphenol A or Bis- phenol F as well as glycidyl ethers derived from Phenol-Novolak- resins or cresol-Novolak-resins .
  • Cycloaliphatic epoxy resins are for example hexahydro-o-phthalic acid-bis-glycidyl ester, hexahydro-m-phthalic acid-bis-glycidyl ester or hexahydro-p-phthalic acid-bis-glycidyl ester.
  • ali- phatic epoxy resins for example 1, 4-butane-diol diglycidyl- ether, may be used as a component for the composition of the present invention.
  • Preferred within the present invention are also aromatic and/or cycloaliphatic epoxy resins which contain at least one, preferably at least two, aminoglycidyl group in the molecule.
  • Such epoxy resins are known and for example described in WO 99/67315.
  • Pre ferred compounds are those of formula (VI) :
  • aminoglycidyl compounds are N, N-diglycidyl- aniline, N, N-diglycidyltoluidine, N, N, N' ,N ' -tetraglycidyl-1, 3- diaminobenzene, N, N, N' , N ' -tetraglycidyl-1, 4-diaminobenzene, N, N, N' ,N ' -tetraglycidylxylylendiamine, N, N, N' ,N ' -tetraglycidyl- 4,4' -diaminodiphenylmethane, N, N, N' , N ' -tetraglycidyl-3, 3 ' -diethyl- 4, 4 ' -diaminodiphenylmethane, N, N, N ' , N ' -tetraglycidyl-3, 3 ' - diaminodiphenyl
  • Preferred aminoglycidyl compounds are also those of formula (VII) :
  • Hardeners are known to be used in epoxy resins. Hardeners are for example hydroxyl and/or carboxyl containing polymers such as carboxyl terminated polyester and/or carboxyl containing acrylate- and/or methacrylate polymers and/or carboxylic acid anhydrides. Useful hardeners are further cyclic anhydrides of aromatic, aliphatic, cycloaliphatic and heterocyclic poly- carbonic acids. Preferred anhydrides of aromatic polycarbonic acids are phthalic acid anhydride and substituted derivates thereof, benzene-1, 2, 4, 5-tetracarbonic acid dianhydride and substituted derivates thereof. Numerous further hardeners are from the literature.
  • the optional hardener can be used in concentrations within the range of 0.2 to 1.2, equivalents of hardening groups present, e.g. one anhydride group per 1 epoxide equivalent. However, often a concentration within the range of 0.2 to 0.4, equivalents of hardening groups is preferred.
  • the composition may comprise further at least a curing agent (accelerant) for enhancing the polymeri- zation of the epoxy resin with the hardener, at least one wetting/dispersing agent, plasticizers, antioxidants, light absorbers, as well as further additives used in electrical applications .
  • a curing agent for enhancing the polymeri- zation of the epoxy resin with the hardener
  • at least one wetting/dispersing agent for enhancing the polymeri- zation of the epoxy resin with the hardener
  • plasticizers plasticizers
  • antioxidants antioxidants
  • light absorbers as well as further additives used in electrical applications.
  • Curing agents for enhancing the polymerization of the epoxy resin with the hardener are for example tertiary amines, such as benzyldimethylamine or amine-complexes such as complexes of tertiary amines with boron trichloride or boron trifluoride; urea derivatives, such as N-4-chlorophenyl-N' ,N ' -dimethylurea (Monu- ron) ; optionally substituted imidazoles such as imidazole or 2- phenyl-imidazole .
  • curing catalyst such as transition metal complexes of cobalt (III), copper, manganese, (II) , zinc in acetylacetonate may also be used, e.g. cobalt acetylacetonate (III) .
  • the amount of catalyst used is a concentration of about 50-1000 ppm by weight, calculated to the composition to be cured.
  • wetting/dispersing agents are known per se for example in the form of surface activators; or reactive diluents, preferably epoxy-containing or hydroxyl-containing reactive diluents; thixotropic agents or resinous modifiers.
  • reactive diluents for example are cresylglycidylether, diepoxyethyl-1, 2- benzene, bisphenol A, bisphenol F and the diglycidylethers thereof, diepoxydes of glycols and of polyglycols, such as neo- pentylglycol-diglycidylether or trimethylolpropane-diglycidyl- ether.
  • Preferred commercially available wetting/dispersing agents are for example organic copolymers containing acidic groups, e.g. Byk® W-9010 having an acid value of 129 mg KOH/g) .
  • Such Wetting/dispersing agents are preferably used in amounts of 0.5 % to 1.0 % based on the filler weight.
  • Plasticizers, antioxidants, light absorbers, as well as further additives used in electrical applications are known in the art and are not critical.
  • the insulating composition made from epoxy resin is made simply by mixing all the components, optionally under vacuum, in any desired sequence and curing the mixture by heating.
  • the hardener and the curing agent are separately added before curing.
  • the curing temperature is preferably within the range of 50 0 C to 280 0 C, preferably within the range of 100°C to 200 0 C. Curing generally is possible also at lower temperatures, whereby at lower temperatures complete curing may last up to several days, depending also on catalyst present and its concentration.
  • the non-hardened insulating resin composition is preferably applied by using vacuum casting or automated pressure gelation (APG) manufacturing processes, optionally under the application of vacuum, to remove all moisture and air bubbles from the coil and the insulating composition.
  • the encapsulating composition may then be cured by any method known in the art by heating the composition to the desired curing temperature.
  • Preferred uses of the insulation produced according to the present invention are electrical insulations, especially in the field of impregnating electrical coils 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-rod, 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.
  • Example 1 (Preparation of the pretreated filler material) 10 parts of montmorillonite (a layered silicate) with an average grain size distribution (d 50 %) of 16 ⁇ m are mixed with an aqueous solution of 120 ml water containing 20 parts of dimethyl- dihydrogenated-tallow-quaternary ammonium. The mixture is stirred for 3 days at room temperature. The montmorillonite is filtered off, washed with 100 ml of pure water and then dried for 24 hours at 60 0 C in a closed vessel.
  • montmorillonite a layered silicate
  • the epoxy resin compositions Formulation A and Formulation B are made from the components as given in Table 1.
  • the compositions are prepared by thoroughly mixing the epoxy resin, the hardener, the accelerator and the filler material at a temperature of 80 0 C. Then the anhydride hardener and the catalyst are added under further stirring. Then the mixture is outgassed under vacuum and poured into a mold at 80 0 C. The mixture is then cured for ten hours at 140°C.
  • EPR 845 diglycidylether-bisphenol A (DGEBA) from Hexion Specialty
  • EPC 845 modified tertiary amine from Hexion Specialty Chemicals Silica W12 silica flower d 50 % 16 ⁇ m from Quarzwerke GmbH (Example 1) : montmorillonite type layered silicate modified with dimethy1-dehydrogenated-tallow-quaternaryammonium, prepared according to Example 1
  • Table 2 Weibull parameters of the dielectric breakdown strength distribution of Formulations A and Formulation B.
  • Formulation A corresponds to a standard electrical insulation formulation with 60 % by weight of microsilica. Replacing 5 % of microsilica with 5 % of a microfiller treated with alkylammonium according to Example 1 (i.e. Formulation B) increases the electrical breakdown strength of the material by 50 % from 61 kVpeak/mm to 93 kVpeak/mm.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Organic Insulating Materials (AREA)

Abstract

Electrical insulation system with improved electrical breakdown strength, said electrical insulation system comprising a hardened polymer component having incorporated therein a conventional filler material and a selected pretreated filler material, wherein (a) the hardened polymer component is selected from epoxy resin systems, polyesters, polyamides, polybutylene terephthalate, polyurethanes and polydicyclopentadiene; (b) the conventional filler material is a known filler material having an average grain size distribution within the range of 1 µm- 500 µm, being present in a quantity within the range of 40 %- 65 % by weight, calculated to the total weight of the insulator system; and (c) the selected pretreated filler material is selected from silica, quartz, or a silicate, or is a mixture of these compounds, having an average grain size distribution within the range of 1 µm-500 µm, wherein said selected filler material has been pretreated with an intercalating compound and wherein said pretreated filler material is present in an amount of 1 %-30 % by weight, calculated to the weight of the conventional filler material present in the insulator system.

Description

Electrical insulation system with improved electrical breakdown strength
The present invention refers to an electrical insulation system with improved electrical breakdown strength.
Electrical insulations for potting applications, for instance in embedded poles, instrument and distribution transformers or sensors, generally consist of an epoxy resin cured with an acid anhydride in the presence of an accelerator. The starting compo- nents usually are mixed together with a filler material, preferably silica flower, typically in the range of 60 to 65 % by weight of filler material, calculated to the total weight of the electrical insulator; the mixture is then cured. Alternative polymers can also be used such as polyesters, polyamides, poly- butylene terephthalate, polyurethanes or polydicyclopentadiene . A large amount of filler generally decreases the overall price of the insulation, however, it also increases the stiffness, the fracture toughness, the thermal conductivity of the insulator and decreases its thermal expansion coefficient.
A key property for the reliability of an electrical insulation material is that it has a high electrical breakdown strength and therewith good insulating properties also at high electrical field strengths. WO 2006/008422 proposes the production of an electrical insulator for high voltage use comprising a mineral filler material wherein the mineral filler material is a combination of a filler material with an average grain size distribution within the micron size together with a selected filler material with an average grain size distribution within the nano size, i.e. less than 1 μm. However, such a combination, especially for industrial potting applications, e.g. in epoxy resins, has different disadvantages such as increased viscosity which reduces processability and possible not yet quantified impact of nanoparticles on health, safety and environment. In the production of an electrical insulator for high voltage use generally a mineral micro filler material is used having an average grain size distribution within the range of 1 μm-500 μm, preferably within the range of 5 μm-100 μm.
It has now surprisingly been found that such micro filler material, when previously treated with an intercalating compound, for example with an alkyl ammonium compound, may be added to the untreated filler material in comparatively small quantities, thereby significantly improving the electrical properties of the insulator system, especially its electrical breakdown strength. We could show that by adding about 5 parts by weight of such micro filler material, pretreated with an alkyl ammonium compound, to about 55 parts by weight of conventional micro silica, it is possible to improve the dielectric breakdown strength of the polymeric insulation by up to 50% compared to the case where 60 parts by weight of micro silica only was used. Such pretreated filler material comprises for example silica, quartz and layered silicates.
The present invention is defined in the claims. The present invention specifically refers to an electrical insulation system with improved electrical breakdown strength, said electrical insulation system comprising a hardened polymer component having incorporated therein a conventional filler material and a selected pretreated filler material, characterized in that
(a) the hardened polymer component is selected from epoxy resin systems, polyesters, polyamides, polybutylene terephthalate, polyurethanes and polydicyclopentadiene, and preferably is a hardened epoxy resin system; (b) the conventional filler material is a known filler material having an average grain size distribution within the range of 1 μm-500 μm, being present in a quantity within the range of 40 %-65 % by weight, calculated to the total weight of the insulator system; and (c) the selected pretreated filler material is selected from silica, quartz, or a silicate, preferably mica (glimmer) , kaolin or a layered silicate or talc, or is a mixture of these compounds, having an average grain size distribution within the range of 1 μm-500 μm, wherein said selected filler material has been pretreated with an intercalating compound and wherein said pretreated filler material is present in an amount of 1 %-30 % by weight, calculated to the weight of the conventional filler material present in the insulator system.
The present invention also refers to the selected pretreated filler material as defined as component (c) herein above having an average grain size distribution within the range of 1 μm-500 μm, preferably within the range of 5 μm-100 μm, having been treated with an intercalating compound.
The present invention also refers to the mixture of the selected pretreated filler material as defined as component (c) herein above and the conventional non-treated filler material as defined as component (b) herein above, wherein the selected pretreated filler material is present in an amount of 1 %-30 % by weight, calculated to the weight of the conventional filler material, said selected pretreated filler material and said conventional non-treated filler material having an average grain size distribution within the range of 1 μm-500 μm.
The present invention also refers to a method of producing said electrical insulation system with improved electrical breakdown strength .
The present invention further refers to electrical articles comprising said electrical insulation system with improved electrical breakdown strength. An important feature of the present invention is that the selected pretreated filler material has an average grain size distribution within the range of 1 μm-500 μm. Said pretreated filler material is selected from silica, quartz, or a silicate, preferably mica, kaolin or a layered silicate, or talc or is a mixture or these compounds. Preferred are two-layered or three- layered silicates selected from phyllosilicates, preferably selected from montmorillonite, hectorite, saponite, vermiculite, smectite, illite, sepiolite, palygorscite, muscovite, allevardite, amesite, fluorohectorite, beidellite, talcum, nontronite, stevensite, bentonite, glimmer, fluorovermiculite, halloysite, hydrotalcite or mixtures of these compounds. Preferred are montmorillonite, hectorite, saponite, vermiculite, smectite, illite; most preferred are montmorillonite, hectorite, vermiculite, smectite, illite.
Different compounds can be used to pretreat the selected filler material, thereby modifying the surface properties of the selected filler material. It is understood that the modified surface properties of the pretreated micro filler material disperse remarkably well in the epoxy, thereby surprisingly improving the dielectric strength as well as the mechanical properties of the insulator system. The invention, however, is not bound to this explanation.
Preferred compounds for modifying the surface properties of the selected filler material are known per se . These compounds are also named intercalating compounds. Preferred such compounds are for example protonated primary, secondary or tertiary amines, protonated basic heterocyclic compounds such as protonated imidazole compounds, or quaternary ammonium compounds, substituted by at least one alkyl residue or at least one functiona- lized alkyl residue. Preferred is the treatment with substituted ammonium compounds, or with 2-hydroxyalkyl-substituted imidazole compounds. Most preferred is the treatment with alkyl-substitu- ted or hydroxyalkyl-substituted ammonium compounds, such as dimethyl-dihydrogenatedtallow-quaternaryammonium and related hydroxyalkyl-containing compounds. There are many more intercalating compounds known in the art for the treatment of layered silicates and other inorganic layered compounds, such as metallic salts of aromatic, aliphatic, araliphatic and cyclo- aliphatic carbonic acids as well as other acids. Examples are alkali salts (lithium, sodium or potassium salts) of formic acid, acetic acid, oxalic acid, gluconic acid, ethyleneglykol, and of other diols. These compounds can also be used within the scope of the present invention.
The conventional filler material as well as the selected pre- treated filler material, both independent of each other, preferably have an average grain size distribution within the range of 5 μm-100 μm, preferably within the range of 5 μm-50 μm, preferably within the range of 5 μm-30 μm. Preferably at least 70 % of the particles, preferably at least 80 % of the particles, have a particle size within the range indicated.
The conventional filler material may be selected independently from the selected pretreated filler material and may also be the same inorganic filler material as listed above for the pretreated filler material selected from silica, quartz, or talc or a silicate, preferably mica, kaolin or a layered silicate. In addition the conventional filler may also be chosen from other known filler compounds such as aluminium oxide, aluminium tri- hydrate [ATH, Al2O3.3H2O, corresponding to Al(OH)3], titanium oxide or dolomite [CaMg (CO3) 2] , metal nitrides, such as silicon nitride, boron nitride and aluminium nitride or metal carbides, such as silicon carbide. Mica (glimmer) and kaolin are aluminium silicates substantially composed of SiO2 and Al2O3.
The conventional filler material may be surface treated with a coupling agent known per se . The coupling agent is preferably selected from the group comprising silanes and siloxanes and preferably is a silane, for example 3-glycidoxypropyl- trimethoxysilane or 3-glycidoxypropyldimethoxymethylsilane .
The method of producing the selected pretreated filler material with an intercalating compound is characterized in that the selected filler material is brought in contact with the intercalating compound, optionally in the presence of a suitable solvent and under stirring, within the temperature range of 200C to 1500C, preferably at room temperature up to 600C, and for a time long enough so that the intercalating compound modifies the surface of the selected filler material. This time is generally between one hour and three days depending on the temperature used. Preferred is room temperature and a reaction time of about one to three days. The suitable solvent is usually water but a low molecular alcohol may also be used. The concentration of the intercalation compound in the solvent is not critical and is preferably within the range of 0.1 mol to 5.0 mol per liter of solvent. The suspension is then filtered off, washed with the solvent, preferably with water, and dried for several hours, preferably for about 10 to 24 hours, at a temperature within the range of 50°C to 80°C, preferably at about 60°C.
The conventional filler material preferably is present within the insulator system in a quantity within the range of 50 %-60 % by weight, preferably in a quantity of about 55 % by weight, calculated to the total weight of the insulator system.
The selected pretreated filler material having been pretreated with an intercalating compound preferably is present in an amount of 2 %-20 % by weight, preferably in an amount of 2 %- 10 % by weight, calculated to the weight of the conventional filler material present in the insulator system. The electrical insulation system with improved electrical breakdown strength according to the present invention comprises a filler containing hardened polymer component. Said hardened polymer component is selected from epoxy resin systems, polyesters, polyamides, preferably nylon, polybutylene terephtha- late, polyurethanes and polydicyclopentadiene, and preferably is a hardened epoxy resin system.
Filler containing epoxy resin systems, polyesters, polyamides, polybutylene terephthalate, polyurethanes and polydicyclo- pentadiene have been described in the literature. When a special filler composition according to the present invention is used, i.e. a mixture of a conventional filler material as defined herein above as component (b) and a selected pretreated filler material as defined herein above as component (c) , said filler components of said filler composition can be incorporated into the respective monomeric starting material of component (a) as defined herein above, in an analogous manner as described in the literature for other filler materials. This is within the knowledge of the expert. Regularly the filler material is incorpo- rated into the monomeric starting materials of the respective polymer by known methods so as to be uniformly dispersed therein. The non-hardened composition, resp. dispersion, thus obtained, e.g. the non-hardened epoxy resin composition, can for example be processed using conventional vacuum casting and/or automated pressure gelation (APG) manufacturing processes. The dispersion is formed into the desired shape using known methods, optionally with the help of a molding tool, and then hardened out, optionally using post-curing.
The present invention also refers to a method of producing an electrical insulation system with improved electrical breakdown strength, characterized in that a conventional filler material [as defined herein above as component (b) ] and a selected pretreated filler material [as defined herein above as component (c) ] , are incorporated into the monomeric starting material of the respective polymer of the component (a) as defined herein above, so as to be uniformly dispersed therein, the dispersion is then formed into the desired shape, optionally with the help of a molding tool, and then hardened and optionally post-cured.
As optional additives the composition may comprise further components selected from wetting/dispersing agents, plasticizers, antioxidants, light absorbers, and from further additives generally used in electrical applications.
Preferred epoxy resins used within the context of the present invention are aromatic and/or cycloaliphatic compounds. These compounds are known per se. Epoxy resins are reactive glycidyl compounds containing at least two 1,2-epoxy groups per molecule. Preferably a mixture of polyglycidyl compounds is used such as a mixture of diglycidyl- and triglycidyl compounds.
Epoxy compounds useful for the present invention comprise unsub- stituted glycidyl groups and/or glycidyl groups substituted with methyl groups. These glycidyl compounds preferably have a molecular weight between 200 and 1200, especially between 200 und 1000 and may be solid or liquid. The epoxy value (equiv./100 g) is preferably at least three, preferably at least four and especially at about five, preferably about 4.9 to 5.1. Preferred are glycidyl compounds which have glycidyl ether- and/or glycidyl ester groups. Such a compound may also contain both kinds of glycidyl groups, e.g. 4-glycidyloxy-benzoic acidglycidyl ester. Preferred are polyglycidyl esters with 1 to 4 glycidyl ester groups, especially diglycidyl ester and/or triglycidyl esters. Preferred glycidyl esters may be derived from aromatic, arali- phatic, cycloaliphatic, heterocyclic, heterocyclic-aliphatic or heterocyclic-aromatic dicarbonic acids with 6 to 20, preferably 6 to 12 ring carbon atoms or from aliphatic dicarbonic acids with 2 to 10 carbon atoms. Preferred are for example optionally substituted epoxy resins of formula (IV) :
D = -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C(CF3)2- n = zero or 1
or formula (V)
Examples are glycidyl ethers derived from Bisphenol A or Bis- phenol F as well as glycidyl ethers derived from Phenol-Novolak- resins or cresol-Novolak-resins .
Cycloaliphatic epoxy resins are for example hexahydro-o-phthalic acid-bis-glycidyl ester, hexahydro-m-phthalic acid-bis-glycidyl ester or hexahydro-p-phthalic acid-bis-glycidyl ester. Also ali- phatic epoxy resins, for example 1, 4-butane-diol diglycidyl- ether, may be used as a component for the composition of the present invention.
Preferred within the present invention are also aromatic and/or cycloaliphatic epoxy resins which contain at least one, preferably at least two, aminoglycidyl group in the molecule. Such epoxy resins are known and for example described in WO 99/67315. Pre ferred compounds are those of formula (VI) :
D = -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C(CF3)2- n = Zero or 1
Especially suitable aminoglycidyl compounds are N, N-diglycidyl- aniline, N, N-diglycidyltoluidine, N, N, N' ,N ' -tetraglycidyl-1, 3- diaminobenzene, N, N, N' , N ' -tetraglycidyl-1, 4-diaminobenzene, N, N, N' ,N ' -tetraglycidylxylylendiamine, N, N, N' ,N ' -tetraglycidyl- 4,4' -diaminodiphenylmethane, N, N, N' , N ' -tetraglycidyl-3, 3 ' -diethyl- 4, 4 ' -diaminodiphenylmethane, N, N, N ' , N ' -tetraglycidyl-3, 3 ' - diaminodiphenylsulfone, N, N ' -Dimethyl-N, N ' -diglycidyl-4 ,4 ' -diaminodiphenylmethane, N, N, N' ,N ' -tetraglycidyl-alfa, alfa ' -bis (4- aminophenyl) -p-diisopropylbenzene and N, N, N' ,N ' -tetraglycidyl- alfa, alfa ' -bis- (3, 5-dimethyl- 4 -aminophenyl ) -p-diisopropylbenzene .
Preferred aminoglycidyl compounds are also those of formula (VII) :
or of formula (VIII) :
Further aminoglycidyl compounds which can be used according to the present invention are described in e.g. Houben-Weyl, Methoden der Organischen Chemie, Band E20, Makromolekulare Stoffe, Georg Thieme Verlag Stuttgart, 1987, pages 1926-1928.
Hardeners are known to be used in epoxy resins. Hardeners are for example hydroxyl and/or carboxyl containing polymers such as carboxyl terminated polyester and/or carboxyl containing acrylate- and/or methacrylate polymers and/or carboxylic acid anhydrides. Useful hardeners are further cyclic anhydrides of aromatic, aliphatic, cycloaliphatic and heterocyclic poly- carbonic acids. Preferred anhydrides of aromatic polycarbonic acids are phthalic acid anhydride and substituted derivates thereof, benzene-1, 2, 4, 5-tetracarbonic acid dianhydride and substituted derivates thereof. Numerous further hardeners are from the literature.
The optional hardener can be used in concentrations within the range of 0.2 to 1.2, equivalents of hardening groups present, e.g. one anhydride group per 1 epoxide equivalent. However, often a concentration within the range of 0.2 to 0.4, equivalents of hardening groups is preferred.
As optional additives the composition may comprise further at least a curing agent (accelerant) for enhancing the polymeri- zation of the epoxy resin with the hardener, at least one wetting/dispersing agent, plasticizers, antioxidants, light absorbers, as well as further additives used in electrical applications .
Curing agents for enhancing the polymerization of the epoxy resin with the hardener are for example tertiary amines, such as benzyldimethylamine or amine-complexes such as complexes of tertiary amines with boron trichloride or boron trifluoride; urea derivatives, such as N-4-chlorophenyl-N' ,N ' -dimethylurea (Monu- ron) ; optionally substituted imidazoles such as imidazole or 2- phenyl-imidazole . Preferred are tertiary amines. Other curing catalyst such as transition metal complexes of cobalt (III), copper, manganese, (II) , zinc in acetylacetonate may also be used, e.g. cobalt acetylacetonate (III) . The amount of catalyst used is a concentration of about 50-1000 ppm by weight, calculated to the composition to be cured.
Wetting/dispersing agents are known per se for example in the form of surface activators; or reactive diluents, preferably epoxy-containing or hydroxyl-containing reactive diluents; thixotropic agents or resinous modifiers. Known reactive diluents for example are cresylglycidylether, diepoxyethyl-1, 2- benzene, bisphenol A, bisphenol F and the diglycidylethers thereof, diepoxydes of glycols and of polyglycols, such as neo- pentylglycol-diglycidylether or trimethylolpropane-diglycidyl- ether. Preferred commercially available wetting/dispersing agents are for example organic copolymers containing acidic groups, e.g. Byk® W-9010 having an acid value of 129 mg KOH/g) . Such Wetting/dispersing agents are preferably used in amounts of 0.5 % to 1.0 % based on the filler weight.
Plasticizers, antioxidants, light absorbers, as well as further additives used in electrical applications are known in the art and are not critical.
The insulating composition made from epoxy resin is made simply by mixing all the components, optionally under vacuum, in any desired sequence and curing the mixture by heating. Preferably the hardener and the curing agent are separately added before curing. The curing temperature is preferably within the range of 500C to 2800C, preferably within the range of 100°C to 2000C. Curing generally is possible also at lower temperatures, whereby at lower temperatures complete curing may last up to several days, depending also on catalyst present and its concentration. The non-hardened insulating resin composition is preferably applied by using vacuum casting or automated pressure gelation (APG) manufacturing processes, optionally under the application of vacuum, to remove all moisture and air bubbles from the coil and the insulating composition. The encapsulating composition may then be cured by any method known in the art by heating the composition to the desired curing temperature.
Preferred uses of the insulation produced according to the present invention are electrical insulations, especially in the field of impregnating electrical coils 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-rod, 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.
Example 1 (Preparation of the pretreated filler material) 10 parts of montmorillonite (a layered silicate) with an average grain size distribution (d50%) of 16 μm are mixed with an aqueous solution of 120 ml water containing 20 parts of dimethyl- dihydrogenated-tallow-quaternary ammonium. The mixture is stirred for 3 days at room temperature. The montmorillonite is filtered off, washed with 100 ml of pure water and then dried for 24 hours at 600C in a closed vessel.
Example 2 (Preparation of an epoxy resin composition)
The epoxy resin compositions Formulation A and Formulation B are made from the components as given in Table 1. The compositions are prepared by thoroughly mixing the epoxy resin, the hardener, the accelerator and the filler material at a temperature of 800C. Then the anhydride hardener and the catalyst are added under further stirring. Then the mixture is outgassed under vacuum and poured into a mold at 800C. The mixture is then cured for ten hours at 140°C.
Definition of raw materials:
EPR 845 diglycidylether-bisphenol A (DGEBA) from Hexion Specialty
Chemicals
EPH 845 pre-reacted mixture of methyltetrahydrophthalic anhydride and neopentylglycol from Hexion Specialty Chemicals
EPC 845 modified tertiary amine from Hexion Specialty Chemicals Silica W12 silica flower d50%=16 μm from Quarzwerke GmbH (Example 1) : montmorillonite type layered silicate modified with dimethy1-dehydrogenated-tallow-quaternaryammonium, prepared according to Example 1
Table 1:
Table 2 : Weibull parameters of the dielectric breakdown strength distribution of Formulations A and Formulation B.
Table 2 Comparison between Formulation A and Formulation B
Formulation A corresponds to a standard electrical insulation formulation with 60 % by weight of microsilica. Replacing 5 % of microsilica with 5 % of a microfiller treated with alkylammonium according to Example 1 (i.e. Formulation B) increases the electrical breakdown strength of the material by 50 % from 61 kVpeak/mm to 93 kVpeak/mm.

Claims

Claims
1. Electrical insulation system with improved electrical breakdown strength, said electrical insulation system comprising a hardened polymer component having incorporated therein a conventional filler material and a selected pretreated filler material, characterized in that
(a) the hardened polymer component is selected from epoxy resin systems, polyesters, polyamides, polybutylene terephthalate, polyurethanes and polydicyclopentadiene, and preferably is a hardened epoxy resin system;
(b) the conventional filler material is a known filler material having an average grain size distribution within the range of 1 μm-500 μm, being present in a quantity within the range of 40 %-65 % by weight, calculated to the total weight of the insulator system; and
(c) the selected pretreated filler material is selected from silica, quartz, or a silicate, preferably mica (glimmer) , kaolin or a layered silicate or talc, or is a mixture of these compounds, having an average grain size distribution within the range of 1 μm-500 μm, wherein said selected filler material has been pretreated with an intercalating compound and wherein said pretreated filler material is present in an amount of 1 %-30 % by weight, calculated to the weight of the conventional filler material present in the insulator system.
2. Electrical insulation system according to claim 1, characterized in that the conventional filler material [component (b) ] as well as the selected pretreated filler material [component (c) ] , both independent of each other, have an average grain size distribution within the range of 5 μm-100 μm, preferably within the range of 5 μm-50 μm, preferably within the range of 5 μm- 30 μm.
3. Electrical insulation system according to claim 2, characterized in that at least 70 % of the particles, preferably at least 80 % of the particles, have a particle size within the range indicated in claim 2.
4. Electrical insulation system according to any one of the claims 1-3, characterized in that the conventional filler material [component (b) ] is selected independently from the selected pretreated filler material [component (c) ] , and prefe- rably is the same inorganic filler material as the pretreated filler material.
5. Electrical insulation system according to any one of the claims 1-4, characterized in that the conventional filler material [component (b) ] and the selected pretreated filler material [component (c) ] independently of each other are selected from silica, quartz, or talc or a silicate, preferably mica, kaolin or a layered silicate.
6. Electrical insulation system according to any one of the claims 1-3, characterized in that the conventional filler [component (b) ] is selected from aluminium oxide, aluminium tri- hydrate, titanium oxide or dolomite, metal nitrides, preferably silicon nitride, boron nitride and aluminium nitride, or metal carbides, such as silicon carbide.
7. Electrical insulation system according to any one of the claims 1-3, characterized in that the conventional filler [component (b) ] has been surface treated with a coupling agent, preferably selected from the group comprising silanes and siloxanes, preferably with 3-glycidoxypropyltrimethoxysilane or 3-glycidoxypropyldimethoxymethylsilane .
8. Electrical insulation system according to any one of the claims 1-7, characterized in that the selected pretreated filler material [component (c) ] is a two-layered or three-layered silicate selected from phyllosilicates, preferably selected from montmorillonite, hectorite, saponite, vermiculite, smectite, illite, sepiolite, palygorscite, muscovite, allevardite, amesite, fluorohectorite, beidellite, talcum, nontronite, stevensite, bentonite, glimmer, fluorovermiculite, halloysite, hydrotalcite or a mixture of these compounds.
9. Electrical insulation system according to any one of the claims 1-7, characterized in that the selected pretreated filler material [component (c) ] is selected from montmorillonite, hectorite, saponite, vermiculite, smectite, illite; preferably from montmorillonite, hectorite, vermiculite, smectite, illite.
10. Electrical insulation system according to any one of the claims 1-9, characterized in that the selected pretreated filler material [component (c) ] has been pretreated with an intercalating compound, preferably selected from the group comprising protonated primary, secondary or tertiary amines; protonated basic heterocyclic compounds, preferably as protonated imidazole compounds, or quaternary ammonium compounds, substituted by at least one alkyl residue or at least one functionalized alkyl residue .
11. Electrical insulation system according to claim 10, characterized in that the intercalating compound is selected from substituted ammonium compounds, or from 2-hydroxyalkyl-substi- tuted imidazole compounds, and preferably is an alkyl-substitu- ted or hydroxyalkyl-substituted ammonium compounds, preferably dimethyl-dihydrogenatedtallow-quaternaryammonium and a related hydroxyalkyl-containing compound.
12. Electrical insulation system according to any one of the claims 1-11, characterized in that the conventional filler material [component (b) ] is present within the insulator system in a quantity within the range of 50 %-60 % by weight, preferably in a quantity of about 55 % by weight, calculated to the total weight of the insulator system.
13. Electrical insulation system according to any one of the claims 1-12, characterized in that the selected pretreated filler material [component (c) ] is present in an amount of 2 %-20 % by weight, preferably in an amount of 2 %-10 % by weight, calculated to the weight of the conventional filler material present in the insulator system.
14. Electrical insulation system according to any one of the claims 1-13, characterized in that the hardened polymer component [component (a) ] is selected from epoxy resin systems, polyesters, polyamides, preferably nylon, polybutylene terephtha- late, polyurethanes and polydicyclopentadiene, and preferably is a hardened epoxy resin system.
15. Electrical insulation system according to any one of the claims 1-14, characterized in that the polymer composition comprises further additives selected from wetting/dispersing agents, plasticizers, antioxidants, light absorbers, and from further additives generally used in electrical applications.
16. Electrical insulation system according to any one of the claims 1-15, characterized in that component (a) is an epoxy resin composition is an aromatic and/or cycloaliphatic epoxy resin composition, preferably a mixture of polyglycidyl compounds, with an epoxy value (equiv./100 g) preferably at least three, preferably at least four and especially at about five, preferably about 4.9 to 5.1.
17. Method of producing the selected pretreated filler material according to any one of the claims 1-16, characterized in that the selected filler material is brought in contact with the intercalating compound, optionally in the presence of a suitable solvent and under stirring, within the temperature range of 200C to 1500C, preferably at room temperature up to 600C, and for a time long enough so that the intercalating compound modifies the surface of the selected filler material, the suspension is then filtered off, washed with the solvent, preferably with water, and dried for several hours, preferably for about 10 to 24 hours, at a temperature within the range of 500C to 800C, preferably at about 60 °C.
18. Method of producing the selected pretreated filler material according to claim 17, characterized in that the pretreatment is carried out at room temperature, the solvent being water or a low molecular alcohol or a mixture of these compounds, the concentration of the intercalation compound in the solvent being within the range of 0.1 mol to 5.0 mol per liter of solvent.
19. The selected pretreated filler material as defined as component (c) in any one of the claims 1-16.
20. The mixture of the selected pretreated filler material as defined as component (c) and the conventional non-treated filler material as defined in any one of the claims 1-16.
21. Method of producing an electrical insulation system according to any one of the claims 1-16, characterized in that a conventional filler material [component (b) ] and a selected pre- treated filler material [component (c) ] , are incorporated into the monomeric starting material of the respective polymer of the component (a) , so as to be uniformly dispersed therein, the dispersion is then formed into the desired shape, optionally with the help of a molding tool, and then hardened and optionally post-cured.
22. Use of the electrical insulation system according to any one of the claims 1-16 in the field of impregnating electrical coils and in the production of electrical components, high- voltage insulations for indoor and outdoor use, especially for outdoor insulators associated with high-voltage lines, as long- rod, 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 im- pregnate electrical components.
23. Electrical articles comprising an electrical insulation system as defined in any one of the claims 1-16.
EP07820881A 2007-10-03 2007-10-03 Electrical insulation system with improved electrical breakdown strength Withdrawn EP2195813A1 (en)

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