EP1168372A1 - Resin for electrical insulation - Google Patents

Abstract

Liquid or semi-solid casting composition for producing self-healing electrical insulation comprises an encapsulated hydrophobizing compound (I) dispersed in a polymeric resin matrix.

Description

scope

The present invention relates to casting compounds based on polymeric matrix resins for the production of self-healing electrical insulation, in particular in the form of molded parts and coatings in the field of high-voltage insulation for outdoor use, and to the electrical insulation produced in accordance with the invention.

Technical field

High-voltage insulation based on polymer matrix resins for outdoor use are known per se. Isolators based on the materials glass and ceramic are traditionally used for outdoor applications. In recent years, polymer insulation materials have also been able to gain a steadily increasing market share. Outdoor insulators are used in large numbers both for high-voltage lines and in the medium-voltage range, especially as post insulators. Further areas of application are outdoor circuit breakers, instrument transformers, bushings, arresters and in switchgear construction.

In recent years, polymeric materials such as silicones (RTV, HTV) or ethylene-propylene rubber (EPR, EPDM) have been used increasingly, but also casting resin systems based on epoxy resins and polyurethanes. Of the polymeric materials, however, only silicones have achieved general technical acceptance, since silicones are superior to the other polymeric materials due to their inherent pronounced hydrophobicity, and in particular due to the inherent hydrophobicity recurrence. The high price for silicones, however, significantly slows down their technical use.

The polymeric materials mentioned, such as ethylene-propylene rubber or cast resin systems based on epoxy resins and polyurethanes, have no intrinsic hydrophobicity recurrence and also have a significantly lower hydrophobicity. Furthermore, these materials are relatively strongly degraded by thermal and oxidative influences, in particular by UV radiation. There is therefore a need for improved polymeric materials which are better than silicones in terms of their mechanical properties and are suitable for the production of electrical insulations which have increased hydrophobicity and at the same time also the property of hydrophobicity return without their mechanical properties noticeably changing or are weakened. With such improved polymeric materials, for example, inexpensive epoxy resins could be produced and used for the production of electrical insulation.

If polymeric materials, such as ethylene-propylene rubber or cast resin systems based on epoxy resins and polyurethanes, are used as high-voltage insulation in outdoor use and if the surface is thawed, the insulating effect is largely dependent on the water-repellent effect (hydrophobicity) of this surface. In the case of strongly hydrophobic surfaces, as usually occur with silicones, dew deposits form in the form of individual, separate droplets. If there is a loss of hydrophobicity, coherent film deposits form on the insulator surface in a humid climate. Clearly increased currents flow through these film coverings, which currents can possibly lead to flashovers of the insulator, but in any case cause accelerated thermal and / or oxidative damage to the polymer matrix. Due to the polar nature of the epoxy resin matrix, epoxy resin surfaces and a large number of other thermosetting resin surfaces do not have sufficient water-repellent properties. Therefore, the use of epoxy resins and related materials is essentially limited to indoor use.

State of the art

No references to the intrinsic modification of cast resin systems are found in the literature, in which the cast resin systems are given additional hydrophobicity and the property of hydrophobicity return and at the same time the mechanical properties are changed only slightly or not at all.

US Pat. No. 4,537,803 proposes the addition of a polymerizable silicone oil to the epoxy resin mixture. US 5,306,747 relates to the addition of a modified silicone oil which can react chemically with the resin system. The addition of silicones to the epoxy resin mixture or to other thermosetting systems has the fundamental disadvantage that the physical properties, the reaction behavior, the flow and processing properties of the matrix are changed such that, for example, separation phenomena or electrical discharges occur in cavities. In US 5,306,747 the silicone oil is provided with hydroxyphenyl groups at the end and chemically incorporated into the matrix. The main disadvantage of this method, as described in the patent, lies in the poorer mechanical properties, with a longer chain length of the silicone oil introduced. Due to the direct integration of the hydrophobic components into the resin matrix, there is no return of hydrophobicity with this method either, since the return of hydrophobicity is linked to the diffusion of freely mobile, low-molecular-weight silicone oligomers.

Presentation of the invention

It has now been found that casting compounds based on polymeric matrix resins for the production of self-healing electrical insulation are obtained if encapsulated selected water-repellent compounds are added to the polymeric matrix resins before they are cured. Hardened casting compounds based on polymeric matrix resins, which contain encapsulated water-repellent compounds according to the invention, show good hydrophobicity and pronounced hydrophobicity recurrence without the mechanical properties being noticeably changed. It occurs no phase separation. In particular, it can be seen that when the capsule material is broken, which is accompanied by the thermal and / or oxidative degradation of the hardened matrix surface, the encapsulated water-repellent compound (s) are released, so that they diffuse to the immediate surface. These compounds penetrate the surface and can also penetrate any degraded and / or superimposed foreign layers that form, so that the oxidative and / or thermal degradation of the surface is accompanied by restoration of the hydrophobicity or self-healing. This process of self-healing continues as long as the surface exposed to erosion consists of the casting compound according to the invention. The life expectancy of products which are produced from the casting compounds according to the invention is consequently significantly extended. With the potting compounds according to the invention, the good mechanical properties of inexpensive thermoset materials can be combined in an excellent manner with the properties of hydrophobicity and hydrophobicity return.

The present invention is defined in the claims. In particular, the present invention relates to a liquid or pasty potting compound based on a polymeric matrix resin or a mixture of such resins, for the production of self-healing electrical insulation, and this potting compound is characterized in that it distributes a selected hydrophobic compound or a mixture in a uniform distribution contains such compounds in encapsulated form.

The potting compounds according to the invention are particularly suitable for the production of molded parts and coatings in the field of electrical insulation, in particular high-voltage insulation, in particular for outdoor use. It is also possible to use this insulation in indoor systems.

In this sense, the present invention relates to the use of the casting compounds according to the invention for the production of molded parts and coatings in the field of electrical insulation, in particular high-voltage insulation, in particular high-voltage insulation for outdoor use.

The invention further relates to the electrical insulation produced from the casting compounds according to the invention.

The invention further relates to a method for producing the casting compounds according to the invention.

Potting compounds in liquid or pasty form according to the invention are polymeric materials, such as thermosetting casting compounds. Examples of such casting compounds are casting resin systems, in particular thermosetting curable polycondensates, thermosetting curable polyadducts and their mixed forms. According to the invention, the thermosetting molding compounds known per se can be used as thermosetting curable casting resins. A large number of thermosetting plastics are known from the literature. Thermosetting curable polycondensates and polyadducts are, for example, curable phenol / formaldehyde plastics, curable urea / formaldehyde plastics, melamine / formaldehyde plastics, curable melamine / phenol / formaldehyde molding compositions, unsaturated polyester resins, DAP resins (polydiallyl phthalates), polyimides, polyimides, polyimides, polyimides or cross-linked polyurethane (PUR). Preferred are those with good electrical properties, preferably aromatic and / or cycloaliphatic epoxy resins and / or PUR casting compounds.

Such epoxy resins and PUR resins used in the electrical industry are known per se from the literature and can be used according to the invention. Epoxy resins and PUR resins used in the electrical industry are known per se and are described, for example, in I. Quint, Investigations on the Influence of Weakly Conductive Foreign Layers on the Surface Aging Behavior of AC-Loaded Cylindrical Test Objects Made of Epoxy Resin Molding Material, Dissertation TH Darmstadt, Darmstadt (1993) or O. Claus, characterization of the surface condition of cylindrical test specimens made of molded epoxy resin before and after exposure to aqueous saline foreign layers and 50 Hz AC voltage, dissertation TH Darmstadt, Darmstadt (1995). Numerous publications also exist on the electrical Araldit® casting resin systems from Ciba-Geigy AG.

Epoxy resins for electrical applications generally contain at least one carboxyl-containing polymer, in particular a carboxyl-terminated polyester and / or a carboxyl-containing acrylate and / or methacrylate polymer and / or a hydroxyl-containing compound or a mixture of such compounds, and also a glycidyl compound or a mixture of glycidyl compounds and optionally (also works without) an accelerator for the crosslinking reaction of the glycidyl compound or glycidyl compounds with the carboxyl-containing polymer and / or the hydroxyl-containing compound and other additives which are customary per se.

Crosslinking glycidyl compounds which have at least two 1,2-epoxy groups in the molecule are preferred. A mixture of polyglycidyl compounds, for example a mixture of diglycidyl and triglycidyl compounds, is preferably used. Such compounds are known per se and are described in detail in the literature. As a rule, a selection suitable for the intended electrical application can be made from the known glycidyl compounds, which represents an optimization problem for the person skilled in the art.

Suitable glycidyl compounds are described, for example, in EP-A-0 297 030, EP-A-0 356 391, EP-A-0 462 053, EP-A-0 506 617, EP-A-0 536 085 or in US Pat. A-3,859,314 or in DE-A-31 26 411. These include compounds which have unsubstituted glycidyl groups and / or glycidyl groups substituted with methyl groups. The glycidyl compounds preferably have a molecular weight between 200 and 1200, in particular between 200 and 1000, and can be solid or liquid. Their epoxy content is preferably at least three equivalents per kilogram of the compound, preferably at least four equivalents per kilogram and in particular at least five equivalents per kilogram. Glycidyl compounds which have glycidyl ether and / or glycidyl ester groups are preferred. A glycidyl compound can also contain both types of glycidyl groups, such as glycidyl 4-glycidyloxybenzoate. Polyglycidyl esters with 1-4 glycidyl ester groups, in particular diglycidyl esters and / or triglycidyl esters, are preferred. The preferred diglycidyl esters are preferably derived from aromatic, araliphatic, cycloaliphatic, heterocyclic, heterocyclic-aliphatic or heterocyclic-aromatic dicarboxylic acids with 6 to 20, in particular 6 to 12 ring carbon atoms or from aliphatic dicarboxylic acids with 2 to 10 carbon atoms. Such compounds are commercially available, for example, under the trade name Araldit® (Ciba SC Ltd). For example, the epoxy resins known per se based on polyvalent aromatic or cycloaliphatic hydroxyl compounds are preferred. Based on aromatic hydroxyl compounds, for example, the glycidyl ethers of bisphenol A or bisphenol F and the glycidyl ethers of phenol novolak resins or cresol novolak resins are known. Cycloaliphatic epoxy resins are, for example, bis-epoxidized 1,2,3,6-tetrahydrobenzoic acid beta-1 ', 2', 3 ', 6'-tetrahydrophenylethyl ester, hexahydro-o-phthalic acid bis-glycidyl ester. Aliphatic epoxy resins, such as 1,4-butanediol diglycidyl ether, are also suitable for the use according to the invention.

Potting compounds which contain at least one filler are preferably used. Such fillers are preferably quartz powder, aluminum oxide and / or dolomite in various known grindings. The fillers are preferably provided with a silanization in order to ensure optimal chemical bonding of the particles in the resin matrix.

Compounds which have a hydrophobic action are preferably flowable fluorinated and / or chlorinated hydrocarbons which are —CH ₂ units and / or —CHF units, —CF ₂ units, —CF ₃ units, -CHCl units, -C (Cl) ₂ units and / or -C (Cl) ₃ units or cyclic, linear or branched flowable organopolysiloxanes. These preferably have a viscosity in the range from about 50 cSt to 10,000 cSt, preferably in the range from 100 cSt to 10,000 cSt and preferably in the range from 500 cSt to 3,000 cSt, measured according to DIN 53 019 at 20 ° C. ,

worin

R

unabhängig voneinander einen gegebenenfalls chlorierten und/oder fluorierten Alkylrest mit 1 bis 8 Kohlenstoffatomen, (C₁-C₄)-Alkylaryl oder Aryl; vorzugsweise einen gegebenenfalls fluorierten Alkylrest mit 1 bis 4 Kohlenstoffatomen oder Phenyl; vorzugsweise 3,3,3-Trifluoropropyl, Monofluoromethyl, Difluoromethyl oder Alkyl mit 1-4 Kohlenstoffatomen; vorzugsweise Methyl;

R₁

unabhängig voneinander eine der Bedeutungen von R oder R₂, wobei gegebenenfalls zwei an verschiedene Si-Atome gebundene endständige Substituenten R₁ zusammen genommen für ein Sauerstoffatom stehen (= cyclische Verbindung);

R₂

eine der Bedeutungen von R, oder Wasserstoff, oder einen Rest -(A)_r-CH=CH₂;

A

einen Rest -C_sH_2s- , vorzugsweise -(CH₂)_s- , worin

s

eine ganze Zahl von 1 bis 6, vorzugsweise 1;

r

Null oder eins;

m

durchschnittlich von Null bis 5000, vorzugsweise von 20 bis 5000, vorzugsweise 50 bis 1500;

n

durchschnittlich von Null bis 100, vorzugsweise 2 bis 100, vorzugsweise 2 bis 20;

bedeuten, wobei die Summe von [m+n] für nicht-cyclische Verbindungen mindestens 20, vorzugsweise mindestens 50 beträgt und die Gruppen -[Si(R)(R)O]- und -[Si(R₁)(R₂)O]- in beliebiger Reihenfolge im Molekül angeordnet sind. Die Summe von [m+n] für nicht-cyclische Verbindungen liegt vorzugsweise durchschnittlich im Bereich von 20 bis 5000, vorzugsweise im Bereich von 50 bis 1500.The organopolysiloxane is preferably a compound or a mixture of compounds of the general formula (I):

wherein

R

independently of one another an optionally chlorinated and / or fluorinated alkyl radical having 1 to 8 carbon atoms, (C ₁ -C ₄ ) -alkylaryl or aryl; preferably an optionally fluorinated alkyl radical having 1 to 4 carbon atoms or phenyl; preferably 3,3,3-trifluoropropyl, monofluoromethyl, difluoromethyl or alkyl with 1-4 carbon atoms; preferably methyl;

R ₁

independently of one another one of the meanings of R or R ₂ , where optionally two terminal substituents R ₁ bonded to different Si atoms taken together represent an oxygen atom (= cyclic compound);

R ₂

one of the meanings of R, or hydrogen, or a radical - (A) _r -CH = CH ₂ ;

A

a radical -C _s H _2s -, preferably - (CH ₂ ) _s -, wherein

s

an integer from 1 to 6, preferably 1;

r

Zero or one;

m

on average from zero to 5000, preferably from 20 to 5000, preferably 50 to 1500;

n

on average from zero to 100, preferably 2 to 100, preferably 2 to 20;

mean, the sum of [m + n] for non-cyclic compounds being at least 20, preferably at least 50 and the groups - [Si (R) (R) O] - and - [Si (R ₁ ) (R ₂ ) O] - are arranged in any order in the molecule. The sum of [m + n] for non-cyclic compounds is preferably on average in the range from 20 to 5000, preferably in the range from 50 to 1500.

R ₂ preferably has one of the meanings of R, and R preferably denotes methyl or phenyl, it being possible for both methyl and phenyl to be present in the molecule. The ratio of methyl to phenyl is determined by the fluidity of the compound or the mixture of compounds. R is preferably methyl. The compound of the formula (I) is generally a mixture of compounds of the formula (I), which is known to the person skilled in the art.

If the compound of formula (I) is a cyclic compound, it is composed of - [Si (R) (R) O] - and / or - [SiR ₁ (R ₂ ) O] units, which have a ring with preferably form 4 to 12 such units. Of the ring-shaped siloxanes, however, the ring-shaped oligomeric polysiloxanes with 4 to 8 siloxy units are preferred, in particular polydimethylsiloxanes with 4 to 8 siloxy units. However, these cyclic compounds can also be, for example, organohydrogenpolysiloxanes which contain, for example, only [SiH (R ₂ ) O] units, or correspondingly organovinylpolysiloxanes.

In a special embodiment of the present invention, R _{2 means} both hydrogen and -A-CH = CH ₂ , where R _{2 means} only either hydrogen or -A-CH = CH ₂ per molecule. In this case, one compound is encapsulated separately, in which R2 is hydrogen and the other compound, in which R _{2 is} -A-CH = CH ₂ , and these two encapsulated compounds are added at least in equimolar amounts to the casting compound according to the invention. However, those containing Si-H groups are preferably used Compound in a molar excess of 20 to 50% based on the component containing the rest -A-CH = CH ₂ . If the capsule shells break open as a result of thermal and / or oxidative degradation, the two components flow into one another and together undergo an addition reaction which increases the hydrophobicity and hydrophobicity recurrence by forming a more stable layer. To enable the addition-crosslinking reaction, at least one of the two encapsulated components contains a complex compound or a mixture of such complex compounds from the group of rhodium, nickel, palladium and / or platinum metals, such as those as catalytically active compounds for addition reactions between SiH bonds and alkenyl residues are known. Pt (0) complexes with alkenylsiloxanes as ligands or Rh catalysts in catalytic amounts of preferably 1 to 100 ppm of platinum are preferred. Such compounds are described in detail in the literature and are known to the person skilled in the art. For this embodiment, the two terminal silyloxy groups of the component containing the radical -A-CH = CH ₂ , independently of one another, preferably mean dimethylvinylsiloxy, where n is preferably zero. The individual components have a viscosity preferably in the range from about 10 cSt to 10,000 cSt, preferably in the range from 100 cSt to 10,000 cSt and preferably in the range from 500 cSt to 3,000 cSt, measured according to DIN 53 019 at 20 ° C. Depending on the preparation, the compounds of the formula (I) can contain up to 10 mol percent, calculated on the Si atoms present, both alkoxy and OH groups. Such compounds are within the present invention.

For the encapsulation of the hydrophobicizing compound or compounds, the same polymeric compound or compositions which are used as the polymeric matrix resin are preferably used. This has the advantage that the encapsulation, ie the wall material, is broken down at the same rate by thermal and / or oxidative influences as the surface of the insulation itself. Thus, the encapsulation breaks open in time and sets the encapsulated one Connection free at the ideal time. The encapsulation material is preferably selected such that it is broken down thermally and / or oxidatively at the same rate or faster than the matrix material. In any case, the encapsulation material does not have to be the same as the matrix material.

The same compound, which are listed above as matrix materials, are suitable as encapsulation material. Synthetic rubbers and the above-mentioned thermosetting curable compositions are suitable, and these can generally be introduced into all matrix systems independently of one another. The encapsulation material used is preferably ethylene-propylene rubber (EPR), ethylene-propylene-diene terpolymers (EPDM) or styrene-butadiene copolymers (PBR) and related compounds if the encapsulated compounds are to be introduced into synthetic rubbers. Thermosetting polycondensates, thermosetting polyadducts and their mixed forms are advantageously used as the encapsulation material if the encapsulated compounds are to be introduced into a thermosetting casting resin system. Preferred encapsulation materials are melamine / formaldehyde resins, curable melamine / phenol / formaldehyde molding compositions, epoxy resins and crosslinked polyurethanes.

Preferably, an encapsulation material is used which behaves in the same way as the matrix material. If you use e.g. a melamine / formaldehyde resin as the encapsulation material in an epoxy resin matrix, so this is built into the matrix when the matrix is hardened and fixed, which ensures a uniform distribution of the hydrophobizing compound over a long period of time and has a positive effect on the mechanical properties of the insulation produced ,

Methods for encapsulating liquid and pasty compounds are known and are described, for example, in Advances in Polymer Science, Part 136, Microencapsulation, Microgels, Iniferters, Springer Verlag, 1998 or in ACS Symposium Series, Part 590, Encapsulation and controlled release of food ingredients. As a rule, the procedure is such that the compound to be encapsulated (core material), for example a silicone oil, is finely dispersed in the encapsulation material (wall material), for example a melamine / formaldehyde resin, for example in a ratio of wall material to core material of 10: 1 to 2: 1, preferably 6: 1 to 3: 1, in particular about 4: 1, and then the dispersion obtained at least partially cures at high temperature, for example by spraying. Suitable process methods are known per se to the person skilled in the art.

The encapsulated material or the particles which contain the liquid or pasty compound (s) or encapsulated compound (s) preferably have a particle diameter of preferably 2 μm to 1000 μm, preferably 5 μm. 500 µm, and preferably 5 µm - 100 µm. The potting compound according to the invention preferably contains about 0.1% by weight - 10% by weight of a compound having a hydrophobic action, preferably 0.25% by weight - 5% by weight of a compound having a hydrophobic action, preferably about 0.25% by weight - 3% by weight .-%, based on the total weight of the casting compound.

The casting compounds according to the invention are produced by stirring the encapsulated liquid or pasty compound or an encapsulated mixture of such compounds, that is to say the encapsulated material, into the matrix material, optionally using a surface-active compound or an emulsifier. To avoid floating, it is advantageous to add highly disperse (pyrogenic) silica (Aerosil) or an analogue compound to the matrix.

In this sense, the present invention relates to a process for the production of liquid or pasty potting compounds based on polymeric matrix resins for the production of self-healing electrical insulation, which is characterized in that (a) a selected hydrophobizing compound or a mixture of such compounds in encapsulated in a suitable encapsulation material and at least partially cures, and (b) the encapsulated material is dispersed in a suitable liquid or pasty polymeric matrix resin in a uniform distribution.

The "selected hydrophobizing compound or a mixture of such compounds", the "encapsulation material", the "suitable liquid or pasty polymeric matrix resin", the other auxiliaries which are used in this production process and the preferred meanings have already been described above.

The casting compounds according to the invention are used in particular for the production of high-voltage insulation for outdoor use, in particular for the production of outdoor insulators in high-voltage lines as long-rod, composite and cap insulators and for post insulators in the medium-voltage range. The casting compounds according to the invention can also be used in the manufacture of insulations for outdoor circuit breakers, measuring transformers, bushings and arresters, in switchgear construction, in circuit breakers, dry-type transformers and electrical machines. In addition, the casting compounds according to the invention can also be used as coating materials for transistors and other semiconductor elements and very generally for impregnating electrical components. Likewise, the potting compound according to the invention can be used as corrosion protection for metallic components, e.g. for bridges and industrial plants, whereby, for example, the gloss of the layer is not lost even with aging.

The molded part is produced or cast in one step or in two or more steps. So you can first cast a core, the material of which does not contain an encapsulated aggregate. The finished mold is then produced in a second casting step by coating the core with the potting material according to the invention. The core can consist of any suitable material, for example also made of a fiber-reinforced plastic. A material is preferably used as the core which is compatible with the potting material according to the invention and in particular can form a chemical bond with it. This is the case, for example, when the core consists of an unmodified casting resin and the coating consists of a casting resin modified according to the invention. Furthermore, it is possible that the potting material according to the invention is cast onto a core, and the core with the polymer matrix of the potting material does not form a chemical bond, but that a sufficiently strong mechanical connection is created between the core and the cast part due to the shrinkage pressure of the potting material. The following examples illustrate the invention.

example 1 a) Encapsulation of a silicone oil:

15 grams of a mixture of a linear dimethylsiloxane (Baysilone M-1000, from GE-Bayer Silicones, D-Leverkusen) with a viscosity of 1000 cSt at 20 ° C. are dispersed in 90 grams of a liquid, non-hardened melamine-formaldehyde resin starting mixture, until the silicone oil has reached an average droplet size in the range of 10 µm - 50 µm. The dispersion is then sprayed finely through a nozzle and partially cured at a temperature of 150 ° C., so that a free-flowing powder with an average particle size in the range from 5 μm to 100 μm is obtained.

b) Production of the potting compound:

10.0 grams of the powdery encapsulated silicone oil obtained according to a) are mixed into 100 parts of the liquid epoxy resin formulation EP 1020-6 QMEST (CIBA SC AG, Basel) until uniform distribution. The epoxy resin formulation contains 62% by weight of silanized quartz powder. The casting resin is evacuated in a recipient and poured into a casting mold at 80 ° C under vacuum. After a gelling time of 4 hours at 80 ° C, the test specimens are removed from the mold and at 140 ° C post-cured for 10 hours. This gives a 4 mm thick plate, which is processed into test specimens.

c) Test method for the measurement of the hydrophobicity, the hydrophobicity preservation and the hydrophobicity return as well as comparison results between the (i) hardened casting resin with the addition of the encapsulated silicone oil and (ii) hardened casting resin without the addition of the encapsulated silicone oil.

To test the electrical behavior of the (i) test specimens produced from the potting compound according to the invention with the (ii) test specimens made from the conventional potting compound, the two test specimens are subjected to an electrical corona discharge for a period of at least 20 minutes. The surface hydrophobicity is temporarily reduced or completely destroyed, whereupon a recovery of hydrophobicity begins. The hydrophobicity is measured in a manner known per se using the dynamic advance angle with water in degrees (°). The larger the advance angle, the higher the hydrophobicity. The measured dynamic advancing angles for hardened casting compounds or test specimens according to the invention and the comparative values for the comparable conventional test specimens are listed in Table 1 . The measured mechanical properties of the two test specimens are essentially of a comparable order of magnitude and are in any case significantly above the required use values. Table 1 Dynamic advance angle (water, in °) test specimen according to example 1 (b) Dynamic advance angle (water, in °) test specimen without the addition of encapsulated silicone oil Basic hydrophobicity (without corona discharge) 95 115 Hydrophobia immediately after the corona discharge zero 50 Hydrophobicity after 20 h 40 80 Hydrophobicity after 100 h 50 90 Hydrophobicity after 200 h 50 100 Hydrophobicity after 300 h 50 100 Hydrophobicity after 400 h 50 110 Hydrophobicity after 500 h 50 110

Replacing the silicone oil in the example with a fluorinated linear dimethylsiloxane gives comparable results.

Claims (21)

Liquid or pasty potting compound based on a polymeric matrix resin or a mixture of such resins, for the production of self-healing electrical insulation, characterized in that this potting compound contains a selected hydrophobic compound or a mixture of such compounds in encapsulated form in a uniform distribution. Potting compound according to claim 1, characterized in that it is a thermosetting curable casting resin system, preferably based on a thermosetting curable polycondensate, a thermosetting curable polyadduct and / or a mixed form thereof. Potting compound according to claim 1 or 2, characterized in that the matrix resin is selected from the group of curable phenol / formaldehyde plastics, urea / formaldehyde plastics, melamine / formaldehyde plastics, melamine / phenol / formaldehyde molding compositions, unsaturated polyester resins, DAP- Resins, polyimides, polybenzimidazoles, epoxy resins or crosslinked polyurethanes (PUR), and preferably an aromatic and / or cycloaliphatic epoxy resin and / or a PUR casting compound. Potting compound according to one of claims 1-3, characterized in that it is an aromatic and / or cycloaliphatic epoxy resin and contains at least one crosslinking glycidyl compound which has at least two 1,2-epoxy groups in the molecule, preferably a mixture of such polyglycidyl compounds, preferably a mixture of diglycidyl and triglycidyl compounds. Potting compound according to claim 4, characterized in that the glycidyl compound has a molecular weight between 200 and 1200, in particular between 200 and 1000 and its epoxy content is at least three equivalents per kilogram of the compound, preferably at least four equivalents per kilogram and in particular at least five equivalents per kilogram. Potting compound according to one of claims 1-5, characterized in that it contains at least one filler, preferably quartz powder, aluminum oxide and / or dolomite, preferably a filler provided with a silanization. Potting compound according to one of claims 1-6, characterized in that the hydrophobizing compound has a flowable fluorinated and / or chlorinated hydrocarbon which -CH ₂ units and / or -CHF units, -CF ₂ units, - CF ₃ - Units, -CHCl units, -C (Cl) ₂ units and / or - C (Cl) ₃ units or represents a cyclic, linear or branched flowable organopolysiloxane. Potting compound according to one of claims 1-7, characterized in that the hydrophobizing compound has a viscosity in the range from 50 cSt to 10,000 cSt, preferably in the range from 100 cSt to 10,000 cSt and preferably in the range from 500 cSt to 3 '000 cSt, measured according to DIN 53 019 at 20 ° C. Potting compound according to one of claims 1-8, characterized in that the compound having a hydrophobic effect has a compound, or a compound mixture, of the general formula (I):

represents what R independently of one another is an optionally chlorinated and / or fluorinated alkyl radical having 1 to 8 carbon atoms, (C ₁ -C ₄ ) -alkylaryl or aryl; R ₁ independently of one another has one of the meanings of R or R ₂ , where optionally two terminal substituents R ₁ bonded to different Si atoms taken together represent an oxygen atom (= cyclic compound); R _{2 has} one of the meanings of R, or hydrogen, or a radical - (A) _r -CH = CH ₂ ; A is a radical -C _s H _2s -, preferably - (CH ₂ ) _s -, wherein s is an integer from 1 to 6, preferably 1; r zero or one; m on average from zero to 5000; n on average from zero to 100; mean, the sum of [m + n] for non-cyclic compounds being at least 20, preferably at least 50, and the groups - [Si (R) (R) O] - and - [Si (R ₁ ) (R ₂ ) O] - are arranged in the molecule in any order. Potting compound according to claim 9, characterized in that in the compound of formula (I) R independently of one another is an optionally fluorinated alkyl radical having 1 to 4 carbon atoms or phenyl; preferably 3,3,3-trifluoropropyl, monofluoromethyl, difluoromethyl or alkyl with 1-4 carbon atoms; preferably methyl or phenyl, preferably methyl; m on average 20 to 5000, preferably 50 to 1500; n an average of 2 to 100, preferably 2 to 20; mean, the sum of [m + n] for non-cyclic compounds on average in the range from 20 to 5000, preferably in the range from 50 to 1500, and the groups - [Si (R) (R) O] - and - [Si (R ₁ ) (R ₂ ) O] - are arranged in the molecule in any order. Potting compound according to claim 9, characterized in that the compound of formula (I) is a cyclic compound which consists of - [Si (R) (R) O] - and / or - [SiR ₁ (R ₂ ) O] units is composed, and which forms a ring with 4 to 12 such units, preferably with 4 to 8 such siloxy units. Potting compound according to claim 11, characterized in that the compound of formula (I) is a cyclic polydimethylsiloxane with 4 to 8 siloxy units or a cyclic organohydrogenpolysiloxane or a cyclic organovinylpolysiloxane. Potting compound according to claim 12, characterized in that in the compound of formula (I) R _{2 means} both hydrogen and - A-CH = CH ₂ , where R ₂ means only either hydrogen or -A-CH = CH ₂ per molecule, and these two separately encapsulated compounds are present at least in equimolar amounts in the casting compound together with at least one complex compound or a mixture of complex compounds from the group of the rhodium, nickel, palladium and / or platinum metals. Potting compound according to one of claims 1-13, characterized in that for the encapsulation of the hydrophobicizing compound or compounds, a thermosetting curable casting resin system according to one of claims 2-4, preferably based on a thermosetting curable polycondensate, a thermosetting curable polyadduct and / or a mixed form of the same. Potting compound according to claim 14, characterized in that a melamine / formaldehyde resin, a curable melamine / phenol / formaldehyde molding compound, an epoxy resin and / or a crosslinked polyurethane is used for the encapsulation of the hydrophobizing compound or compounds. Potting compound according to one of claims 1-15, characterized in that the ratio of wall material to the compound to be encapsulated is in the range from 10: 1 to 2: 1, preferably in the range from 6: 1 to 3: 1 and in particular approximately 4: 1 is. Potting compound according to one of claims 1-16, characterized in that the encapsulated material or the particles which contain encapsulated compound (s) have a particle diameter of 2 µm - 1000 µm, preferably 5 µm - 500 µm, and preferably 5 µm - 100 µm , exhibit. Potting compound according to one of claims 1-17, characterized in that it contains 0.1% by weight to 10% by weight, preferably 0.25% by weight to 5% by weight, and preferably 0.25% by weight - 3% by weight. -%, contains a hydrophobing compound. A process for the production of liquid or pasty potting compounds based on polymeric matrix resins for the production of self-healing electrical insulation, characterized in that (a) a selected hydrophobic compound or a mixture of such compounds according to any one of claims 1-13 in a suitable encapsulation material according to encapsulated and at least partially cured, and (b) the encapsulated material is dispersed in a suitable liquid or pasty polymeric matrix resin according to claim 17 in a uniform distribution. Use of a casting compound according to one of claims 1-18 for the production of high-voltage insulation for outdoor use, in particular for the production of outdoor insulators for high-voltage lines as long-rod, composite and cap insulators as well as for post insulators in the medium-voltage range, in the manufacture of insulations for outdoor circuit breakers, measuring transformers, bushings and arresters, in switchgear construction, in circuit breakers, floor transformers and electrical machines, as coating materials for transistors and other semiconductor elements , for impregnating electrical components and / or as corrosion protection for metallic components. The components treated according to claim 20.