COMPOSITE HIGH VOLTAGE INSULTATION MATERIALS AND METHODS FOR PREPARING THE SAME

1 . Anhydride-free curable epoxy resin composition for use as insulation, comprising

a bisphenol A based epoxy resin having an epoxy content ≧5.6 equ./kg,

at least one reactive diluent, and

at least one catalyst.

2 . Anhydride-free curable epoxy resin composition according to claim 1 , wherein the reactive diluent is selected from the group consisting of styrene, vinyl toluene, alpha-methyl styrene and methacrylate and combinations thereof.

3 . Anhydride-free curable epoxy resin composition according to claim 1 , wherein the catalyst is selected from the group consisting of metal acetylacetonate, phenolic compound and combinations thereof.

4 . Anhydride-free curable epoxy resin composition according to claim 1 , further comprising a second anhydride-free epoxy resin.

5 . Anhydride-free curable epoxy resin composition according to claim 1 , wherein the anhydride-free curable epoxy composition has a viscosity at 25° C. of <200 mPa.

6 . Anhydride-free curable epoxy resin composition according to claim 1 , wherein the anhydride-free curable epoxy composition is precipitation-free.

7 . Anhydride-free curable epoxy resin composition according to claim 1 , wherein the anhydride-free curable epoxy composition, after curing, exhibits a standard deviation of Tg of at most±5.0° C.

8 . Anhydride-free curable epoxy resin composite, comprising the anhydride-free curable epoxy resin composition according to claim 1 and further comprising a mica compound.

9 . Anhydride-free curable epoxy resin cellulose composite, comprising the anhydride-free curable epoxy resin composition according to claim 1 and further comprising a cellulose component.

10 . Insulating material comprising:

an anhydride-free curable epoxy resin composition including

a bisphenol A based epoxy resin having an epoxy content ≧5.6 equ./kg;

at least one reactive diluent:

at least one catalyst and

wherein the anhydride-free curable epoxy resin composition is cured.

11 . The insulating material according to claim 10 , wherein the insulating material comprises an HV insulation layer.

12 . The insulating material according to claim 10 , wherein the insulating material comprising an insulation layer of an Electrical machine coil.

13 . Process for producing an anhydride-free curable epoxy resin composition comprising mixing together a bisphenol A based epoxy resin having an epoxy content ≧5.6 equ./kg, at least one reactive diluent, at least one catalyst, and optionally a filler.

14 . Process for producing an anhydride-free curable epoxy resin composition comprising the steps of

a) providing masterbatch A comprising a first anhydride-free epoxy resin, wherein the first anhydride-free epoxy resin is a bisphenol A based epoxy resin having an epoxy content ≧5.6 equ./kg,

b) providing masterbatch B, comprising a second anhydride-free epoxy resin,

c) mixing masterbatch A with masterbatch B to obtain an anhydride-free curable epoxy resin composition.

15 . Process according to claim 14 ,

wherein step a comprises the steps of

providing a bisphenol A based epoxy resin having an epoxy content ≧5.6 equ./kg,

mixing the bisphenol A based epoxy resin with a catalyst to obtain a mixture A,

mixing a reactive diluent and optionally a filler with mixture A to obtain masterbatch A, and

wherein step b comprises the steps of

providing a second anhydride-free epoxy resin,

mixing the second anhydride-free epoxy resin with a catalyst to obtain a mixture B,

mixing a reactive diluent and optionally a filer with mixture B to obtain masterbatch B.

16 . Process according to claim 14 , wherein the second anhydride-free epoxy resin is a bisphenol A based epoxy resin having an epoxy content ≧5.8 equ./kg.

17 . Process according to claim 13 , further comprising at least one of steps d and e:

step d bringing the reactive anhydride-free epoxy resin composition in contact with a mica compound to obtain an anhydride-free curable epoxy resin mica composite;

step e curing the anhydride-free curable epoxy resin composition of iii) or the anhydride-free curable epoxy resin mica composite of iv) to obtain an insulating material.

18 . Process according to claim 14 ,

wherein at least one of step a or step b includes:

wherein step b comprises the steps of

providing a bisphenol A based epoxy resin having an epoxy content ≧5.6 equ./kg,

mixing the bisphenol A based epoxy resin with a catalyst to obtain a mixture A,

mixing a reactive diluent and optionally a filler with mixture A to obtain masterbatch A, and

wherein step b comprises the steps of

providing a second anhydride-free epoxy resin,

mixing the second anhydride-free epoxy resin with a catalyst to obtain a mixture B,

mixing a reactive diluent and optionally a filler with mixture B to obtain masterbatch B.

19 . Anhydride-free curable epoxy resin composition according to claim 1 , wherein the phenolic compound is selected from the group consisting of catechol, resorcinol, hydroquinone and pyrogallol and combinations thereof.

20 . Anhydride-free curable epoxy resin composition according to claim 1 , further comprising a bisphenol F based epoxy resin having an epoxy content ≧6.2 equ./kg.