Coating composition for electrical conductors and method of producing such a composition

Abstract

The aim of the invention is to create a composition for coating electric conductors which is significantly more resistant to partial discharges than prior art compositions while the produced insulating layer is highly extensible. Said aim is achieved by a composition comprising 1 to 50 percent by weight of microparticles that have a specifically adjusted electronic defect structure in the crystal lattice, resulting in greater polarizability of the valence electrons, and an organic and/or organic-inorganic matrix. The microparticles that have a specifically adjusted electronic defect structure are composed of oxides, sulfides, selenides, tellurides of the elements which are part of the series encompassing silicon, zinc, aluminum, tin, boron, germanium, gallium, lead, the transition metals, lanthanides, and actinides, particularly from the series encompassing silicon, titanium, zinc, yttrium, cerium, vanadium, hafnium, zirconium, nickel, and/or tantalum, in such a way that the basic lattice is provided with vacant lattice positions by doping 4 the basic lattice with adequate low-valent or higher-valent elements, said vacant lattice positions increasing the electronic polarizability of the microparticles by means of defect chemistry (the defect structure).

Claims

1. A coating composition for electrical conductors, consisting of 1-50 wt. % of microparticles with a selectively adjusted electronic defect structure in the crystal lattice, said defect structure making the valence electrons more easily polarizable, and an organic and/or organic-inorganic electrically-isolating polymeric matrix, the microparticles with the selectively adjusted electronic defect structure being made up of zirconium dioxide in such manner that via doping with yttrium the basic crystal lattice is provided with vacancies which, by way of defect chemistry (defect structure), make it easier for the microparticles to be electronically polarized, wherein the yttrium doping is present in an amount of at least 0.5 mol. % and less than 8 mol. %; and wherein the organic and/or organic-inorganic matrix includes one or more polymerizable and/or hybrid binders; wherein the microparticles contain reactive surface groups adapted to the polymer-based and/or hybrid binders; and wherein said composition contains organically modified inorganic condensates.

2. The composition according to claim 1, wherein the reactive surface groups are selected from the group comprising metal acid esters, cyanate groups, urethane groups, epoxide groups, epoxy, carboxylic acid anhydride, CC double bond systems, hydroxyl groups, alcohols bound by way of oxygen, esters, ethers, chelating agents, carboxyl groups, amino groups, ammonium and/or reactive resin components, the polymer-based binders containing acrylate groups, phenol groups, melamine groups, polyester-polyester imide groups, polysulfide groups, epoxide or polyamide groups, polyvinyl formal resins, aromatic compounds, aliphatic compounds, esters, ethers, alcoholates, fats or chelating agents.

3. The composition according to claim 1, wherein said composition contains one or more of the substances from the group consisting of additives, polymerization initiators, solvents, pigments and/or fillers.

4. The composition according to claim 1, wherein the average particle diameter of the microparticles with an electronic defect structure is 1-1,000 nm.

5. The composition according to claim 1, wherein said composition is transparent.

6. The composition according to claim 1, wherein said composition contains a fluorine compound.

7. The composition according to claim 1, wherein said composition contains a fluorinated silane, its pre-condensate or condensate.

8. A combination comprising an electrical conductor with the coating composition according to claim 1 applied to said electrical conductor.

9. A method for coating an electrical conductor comprising the steps of providing an electrical conductor, and applying to said electrical conductor the coating composition according to claim 1.

Description

EXAMPLE 1

Reference Insulation Enamel

(1) Commercially available polyurethane resin was used as reference insulation enamel. PU resin contains the components polyester polyols and blocked isocyanate crosslinkers. The solids content is about 25 wt. %.

EXAMPLE 2

Preparation of ZrO2 Microparticle Sol from Undoped ZrO2 Particles

(2) Undoped ZrO.sub.2 particles were prepared via a controlled growing process at high pressure and high temperatures (hydrothermal process). To this end, 3,200 g of Zr-n-propylate was precipitated in controlled manner with appropriate additives and was treated in an autoclave at T=270 C. and 80 bar for 5 h. The powder cake made in this way was subsequently freeze-dried. The powder was then surface-modified in ethanol with trioxadecanoic acid. Approximately 1 kg of undoped ZrO.sub.2 was dispersed into this mixture. The whole suspension was subsequently homogenized for about 5 h under continuous grinding with ZrO.sub.2 grinding balls. Surface-modified, undoped ZrO.sub.2 microparticles are obtained.

EXAMPLE 3

Preparation of ZrO2 Microparticle Sol from Doped ZrO2 Microparticles

(3) Doped ZrO.sub.2 microparticles were made via a hydrothermal process in a manner analogous to that of Example 2. To this end, 230 g of yttrium nitrate (Y-nitrate) were dispersed as doping agent in 3,200 g of Zr-n-propylate. This was precipitated in controlled manner with appropriate additives and was subsequently treated in an autoclave at T=270 C. and 80 bar for 5 h. The powder cake made in this way was subsequently freeze-dried.

(4) The powder obtained was surface-modified in ethanol with trioxadecanoic acid. This was effected by adding 125 g of trioxadecanoic acid to 1,375 g of ethanol. Approximately 1 kg of doped ZrO.sub.2 particles was dispersed therein. The whole suspension was subsequently homogenized for about 5 h under continuous grinding with ZrO.sub.2 grinding balls. Surface-modified, doped ZrO.sub.2 microparticles are obtained.

EXAMPLE 4

Preparation of PU-ZrO2 Composite Sol with Undoped ZrO2 Microparticles

(5) To prepare PU-ZrO.sub.2 composite sol with undoped ZrO.sub.2 as insulation enamel, 300 g of undoped ZrO.sub.2 sol from Example 2 were dispersed with stirring in approximately 1.7 kg of PU matrix enamel from Example 1. This sol was exposed to the influence of ultrasound to obtain better dispersal. The entire PU composite sol was homogenized further for 12 hours with stirring. In this way, a homogeneous PU composite sol containing homogeneously dispersed, undoped ZrO.sub.2 was obtained, which was suitable for coating purposes.

EXAMPLE 5

Preparation of PU-ZrO2 Composite Sol with Doped ZrO2 Microparticles

(6) To prepare PU-ZrO.sub.2 composite sol with doped ZrO.sub.2 as insulation enamel, a similar procedure was used as in Example 4: 300 g of doped ZrO.sub.2 sol from Example 3 were dispersed in approximately 1.7 kg of PU matrix enamel from Example 1. This sol was exposed to the influence of ultrasound to obtain better dispersal. The entire PU composite sol was homogenized further for 12 hours with stirring. A homogeneous PU composite sol with homogeneously dispersed, doped ZrO.sub.2 microparticles was obtained, which was suitable for coating purposes.