COMPOSITIONS FOR AN INSULATION TAPE

Abstract

The invention generally relates to a composition that may be used for producing an insulation tape. In one embodiment, the composition being used to fix a non-conductive material to a reinforcing layer.

Claims

1. A composition comprising: a) a novolac produced by condensation of a substituted or unsubstituted phenol with an aldehyde, where the molar mass of the novolac is from 250 to 1000 g/mol; b) a catalyst selected from the group of the boron(II) halides and/or amine complexes thereof, imidazoles, acetylacetonates, tin(IV) chloride and/or tertiary amines and/or tetramethylguanidine, and combinations thereof; and c) optionally other additives.

2. The composition of claim 1, wherein the composition comprises from 50 to 90% by weight of novolac, from 1 to 30% by weight of catalyst and from 0 to 49% by weight of other additives based on the entirety of all of the components of the composition.

3. The composition of claim 1, wherein the composition comprises from 5 to 30% by weight of catalyst based on the weight of the novolac.

4. The composition of claim 1, wherein the novolac has been produced by condensation of phenol and/or cresol with formaldehyde.

5. The composition of claim 1, wherein the molar mass of the novolac is from 250 to 500 g/mol.

6. The composition of claim 1, wherein the catalyst comprises an imidazole.

7. The composition of claim 1, wherein the nonconductive material is mica.

8. The composition of claim 1, wherein the reinforcement layer is composed of a woven fabric, knitted fabric, nonwoven fabric or foil made of glass and/or rockwool and/or polyimide and/or polyester and combinations thereof.

9. The use of a composition of claim 1 for the production of mica tapes, the insulation of medium- and high-voltage devices, or both.

10. A process comprising: (I) providing an insulation tape comprising a nonconductive material and a reinforcement layer adhesive-bonded to one another by means of a composition, wherein the composition comprises: a) a novolac produced by condensation of a substituted or unsubstituted phenol with an aldehyde, where the molar mass of the novolac is from 250 to 1000 g/mol; b) a catalyst selected from the group of the boron(III) halides and/or amine complexes thereof, imidazoles, acetylacetonates, tin(IV) chloride and/or tertiary amines and/or tetramethylguanidine, and combinations thereof; and c) optionally other additives; (II) winding the insulation tape around an electrical conductor; and (III) impregnating the insulation tape wound around the conductor with a resin based on epoxy resin.

11. (canceled)

12. (canceled)

Description

[0029] Examples of resin components that can be used are inter alia the following: polyepoxides based on bisphenol A (e.g. Epikote 162 or 828) and/or bisphenol F (e.g. Epikote 158 or 862), and also mixtures thereof, and cycloaliphatic epoxy resins (e.g. Epikote 760 products obtainable from Hexion Inc.), and mixtures comprising reactive diluents (e.g. Heloxy Modifier AQ).

[0030] The impregnation resin can also optionally comprise other components, e.g. wetting agents, which serve to control surface tension. It would also be possible to add other constituents having curing action, but it is preferable here to avoid use of anhydrides in the impregnation resin.

[0031] The impregnation in step (III) particularly preferably takes place in vacuo (VPI process), thus ensuring that the impregnation resin achieves almost complete impregnation of the composite made of the conductor around which mica tape has been wound. The impregnation procedure is generally followed by hardening in a drying oven in the temperature range from 80 C. to 180 C., as required by the impregnation resin used.

[0032] The invention will be explained in more detail with reference to an embodiment: [0033] 1. Production of the mica tape [0034] The adhesive component for production of the mica tape is first formulated as follows: [0035] 1000 g of the novolac (Bakelite PH 8505) is heated to 60 C. and 150 g of 2-phenylimidazole are admixed therewith. [0036] The mixture is homogenized at 60 C. within a period of one hour. An 80% solution in methyl ethyl ketone is then produced at 60 C. and cooled to room temperature. The resultant adhesive is used to fix a layer of mica paper, thickness 100 m, on a nonwoven glass fabric with layer weight 23 g/m.sup.2. To this end, 20 g/m.sup.2 of the adhesive are sprayed onto the nonwoven glass fabric and bonded to the mica paper, and the composite is dried at 70 C. in vacuo (10 mbar). [0037] The resultant mica tape is cooled to room temperature. [0038] 2. Production of the impregnation system in the VPI process [0039] The mica tape produced as described above is cut to size to give sheets measuring 1010 cm. Ten layers of the mica tape are placed in layers on top of one another to give a total layer thickness of about 2 mm and, at 40 C. and 5 mbar in a metal mold with two open sides, impregnated with an impregnation resin consisting of 250 g of EPIKOTE Resin 162, 750 g of EPIKOTE Resin 158 and 150 g of Heloxy Modifier AQ within a period of 60 minutes. A gauge pressure of 6 bar is used for continued impregnation for a further 60 minutes. [0040] The excess impregnation resin is discharged, and the metal mold is transferred to a curing oven. Curing takes place in two stages, firstly 3 hours at 90 C. and then 15 hours at 140 C. [0041] 3. Insulation properties [0042] The composite made of impregnation resin and adhesive leads to the following temperature-dependent loss factors (tan(8)) after curing:

TABLE-US-00001 Temp. in C. tan() 25 0.005 50 0.00715 75 0.0104 100 0.017 120 0.0522 140 0.2425 180 1.206 [0043] These are at a level comparable with those comprising anhydride hardeners in the impregnation resin, and the impregnation system of the invention therefore also provides the desired insulation properties.