Method of producing high voltage electrical insulation

1. A method for producing electrical insulation for electrical coils, transformers, bushings, long-rods, composite and cap-type insulators, switches, sensors, converters, and cable end seals, the method comprising the steps of:

(i) providing an ultra-violet radiation as well as thermally curable composition, comprising at least one of each of (a) to (c):

(a) one UV-curable and heat-curable epoxy resin;

(b) one cationic photo-initiator;

(c) one cationic thermal-initiator;

(ii) applying ultra-violet radiation as well as heat to said curable composition in any desired sequence for a time long enough until complete curing of said curable composition is obtained as a cured composition; and

(iii) including the cured composition obtained in (ii) as a material in the production of electrical insulation systems for electrical coils, transformers, bushings, long-rods, composite and cap-type insulators, switches, sensors, converters, and cable end seals, wherein the cationic photo-initiator is a cationic photo-initiator compound which is composed of a sulphonium cation and/or iodonium cation combined with an anion selected from the group consisting of BF 4 − , PF 6 − , and AsF 6 − , and

wherein the cationic thermal-initiator comprises at least one of the following:

(1) a salt with an ytterbium cation, and

(2) a metal salt of triflic acid.

2. The method of claim 1 , wherein the UV-curable and heat-curable epoxy resin represents an aromatic and/or cycloaliphatic reactive glycidyl compound containing at least two 1,2-epoxy groups per molecule.

3. The method of claim 2 , wherein the UV-curable and heat-curable epoxy resin represents an aromatic and/or cycloaliphatic reactive glycidyl compound containing at least two 1,2-epoxy groups per molecule and having a molecular weight between 200 and 1200, and an epoxy value (equiv./100 g) of at least three.

4. The method of claim 3 , wherein the UV-curable and heat-curable epoxy resin is liquid at room temperature or when heated to a temperature of up to about 65° C.

5. The method of claim 2 , wherein the UV-curable and heat-curable epoxy resin represents an aromatic and/or cycloaliphatic reactive glycidyl compound containing at least two 1,2-epoxy groups per molecule and having a molecular weight between 200 and 1000, and having an epoxy value (equiv./100 g) of at least four.

6. The method of claim 2 , wherein the UV-curable and heat-curable epoxy resin represents an aromatic and/or cycloaliphatic reactive glycidyl compound containing at least two 1,2-epoxy groups per molecule and having a molecular weight between 200 and 1000, and having an epoxy value (equiv./100 g) of about 4.9 to 5.1.

7. The method of claim 1 , wherein the sulphonium cation is a triarylsulphonium cation, optionally substituted at one or more of the aryl substituents, and the iodonium cation is a diaryliodonium cation, optionally substituted at one or more of the aryl rings.

8. The method of claim 1 , wherein the cationic photo-initiator is present within the curable composition within the range of 0.2% by weight to 3.0% by weight calculated to the weight of the epoxy resin present.

9. The method of claim 1 , wherein the cationic thermal-initiator compound is present within the curable composition within the range of 0.05% by weight to 2.0% by weight calculated to the weight of the epoxy resin present.

10. The method of claim 1 , wherein

heat is applied to said curable composition at temperatures of about 80° C. to 130° C.

11. The method of claim 1 , wherein

first UV-irradiation is applied and subsequently the curable composition is heated to a temperature within the range of 80° C. to 120° C.

12. The method of claim 1 , wherein

the UV-irradiation is carried out with UVA and/or UVB-light and with irradiation energy of about 1200 mJ/cm 2 .

13. The method of claim 1 , further comprising incorporating into the curable composition a fiber reinforcing material.

14. The method of claim 13 , further comprising incorporating to the curable composition continuous mineral or organic fibers, as single fibers or in the form of filaments or woven filaments, or as chopped fibers or a combination thereof;

wherein the mineral fibers are selected from the group consisting of glass fibers, ceramic fibers, aluminum oxide fibers, basalt fibers, and glass fibers; and

the organic fibers are selected from aramid fibers and polyester fibers.

15. The method of claim 14 , wherein the method is carried out by using a wet filament winding process wherein the filaments are pre-impregnated with the ultra-violet radiation and thermally curable composition followed by winding the impregnated filaments on a mandrel.

16. The method of claim 1 , wherein the curable composition further contains optional additives selected from filler materials, wetting/dispersing agents, plasticizers, antioxidants, and light absorbers.

17. A method of producing electrical insulation for electrical coils, transformers, bushings, long-rods, composite and cap-type insulators, switches, sensors, converters, and cable end seals as a fiber-reinforced composite, the method comprising the steps of:

(i) providing an ultra-violet radiation and thermally curable composition, comprising at least one UV-curable and heat-curable epoxy resin, at least one cationic photo-initiator, at least one cationic thermal-initiator, and further a fiber reinforcing material; and

(ii) applying ultra-violet radiation as well as heat to said curable composition in a sequence and time to obtain complete curing of said curable composition,

wherein the cationic photo-initiator is a cationic photo-initiator compound which is composed of a sulphonium cation and/or iodonium cation combined with an anion selected from the group consisting of BF 4 − , PF 6 − , and AsF 6 − , and

wherein the cationic thermal-initiator comprises at least one of the following:

(1) a salt with an ytterbium cation, and

(2) a metal salt of triflic acid.