Electrical Insulation System Based on Epoxy Resins for Generators and Motors

Abstract

Disclosed is an anhydride-free insulation system for current-carrying construction parts of an electric engine which comprises: (A) a mica paper or mica tape for wrapping parts of said electric engine that are potentially current-carrying during operation of the engine, which mica paper or mica tape is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises a complex of boron trihalogenide with an amine of the formula

BX.sub.3.Math.NR.sup.1R.sup.2R.sup.3 or R.sup.1R.sup.2NANR.sup.1R.sup.2, wherein X denotes halogen, R.sup.1, R.sup.2 and R.sup.3 are each independently of the others hydrogen, C.sub.1-C.sub.12alkyl, C.sub.5-C.sub.30aryl, C.sub.6-C.sub.36aralkyl or C.sub.6-C.sub.14cycloalkyl, which can be unsubstituted or substituted by one or more C.sub.1-C.sub.12alkyl groups, A is a bivalent aliphatic aromatic or cycloaliphatic radical; (B) a thermally curable bath formulation for the vacuum pressure impregnation comprising bisphenol A diglycidyl ether and optionally bisphenol F diglycidyl ether, which formulation is substantially or, preferably, entirely free of thermally activatable curing initiators for the epoxy resin formulation.

Claims

1. An anhydride-free insulation system for current-carrying construction parts of an electric engine which comprises: (A) a mica paper or mica tape for wrapping parts of said electric engine that are potentially current-carrying during operation of the engine, which mica paper or mica tape is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises a complex of boron trihalogenide with an amine of the formula
BX.sub.3.Math.NR.sup.1R.sup.2R.sup.3 or R.sup.1R.sup.2NANR.sup.1R.sup.2, wherein X denotes halogen, R.sup.1, R.sup.2 and R.sup.3 are each independently of the others hydrogen, C.sub.1-C.sub.12alkyl, C.sub.5-C.sub.30aryl, C.sub.6-C.sub.36aralkyl or C.sub.6-C.sub.14cycloalkyl, which can be unsubstituted or substituted by one or more C.sub.1-C.sub.12alkyl groups, A is a bivalent aliphatic aromatic or cycloaliphatic radical; (B) a thermally curable bath formulation for the vacuum pressure impregnation comprising bisphenol A diglycidyl ether and optionally bisphenol F diglycidyl ether, which formulation is substantially or, preferably, entirely free of thermally activatable curing initiators for the epoxy resin formulation.

2. The insulation system according to claim 1, wherein the mica paper or mica tape comprises the complex of BCl.sub.3 with a tertiary amine in an amount sufficient to cure the epoxy resin formulation taken up by the mica paper or mica tape and the construction part of the engine during the vacuum pressure impregnation step.

3. The insulation system according to claim 1 or 2, wherein the mica paper or mica tape (A) comprises the complex of BX.sub.3 with a tertiary amine in an amount of about 0.01 to about 100 g/m.sup.2 of the mica paper or mica tape, preferably about 2.0 to about 50 g/m.sup.2, more preferably about 2.0 to about 20 g/m.sup.2.

4. The insulation system according to any one of claims 1 to 3, wherein the complex of BX.sub.3 with a tertiary amine is BCl.sub.3.Math.N(CH.sub.3).sub.3 (boron trichloride-trimethyl amine complex) or BCl.sub.3.Math.N(CH.sub.3).sub.2C.sub.8H.sub.17 (boron trichloride-dimethyl n-octyl amine complex).

5. The insulation system according to any one of claims 1 to 4, wherein the thermally curable bath formulation for the vacuum pressure impregnation (B) comprises, or consists essentially of, diglycidylethers of bisphenol A having the formula: ##STR00003## wherein n is a number equal or greater than zero, in particular 0 to 0.3, and represents an average over all molecules of the applied resin, and 0 to 20 wt % of bisphenol F diglycidyl ether, based on the weight of the bath formulation for the vacuum pressure impregnation (B).

6. The insulation system according to any one of claims 1 to 5, wherein the thermally curable bath formulation furthermore comprises one or more reactive diluents selected from the group consisting of a) polyglycidyl ethers derived from epichlorohydrin and phenolic compounds other than bisphenol A and bisphenol F, b) diglycidylethers derived from epichlorohydrin and acyclic alcohols and c) cycloaliphatic epoxy resins comprising at least two oxirane rings fused to a cycloaliphatic ring.

7. The insulation system according to claim 6, wherein the thermally curable bath formulation (B) comprises, or consists essentially of, diglycidylethers of bisphenol A, 0 to 30 wt % of diglycidylethers of bisphenol F and 2 to 10 wt % of the reactive diluents.

8. The insulation system according to any one claims 1 to 7, wherein the epoxy resin bath formulation has a viscosity of not more than about 75 mPa.s at 60 C., more preferably of not more than about 50 mPa.s at 60 C.

9. The insulation system according to any one of claims 1 to 8, wherein the thermally curable epoxy bath formulation (B) further comprises micro particles, nano particles or a mixture thereof, preferably nano particles, which particles are selected from metal or semi-metal oxides, carbides or nitrides, in particular from metal or semi-metal carbides or nitrides and, optionally, a wetting agent.

10. A mica tape which is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation, comprising a complex of BX.sub.3 with a tertiary amine as defined in claim 1.

11. The mica tape according to claim 10, comprising the complex of BX.sub.3 with a tertiary amine in an amount of about 0.01 to about 100 g/m.sup.2 of the mica tape, preferably about 2.0 to about 50 g/m.sup.2, more preferably about 2.0 to about 20 g/m.sup.2.

12. The mica tape according to claim 10 or 11, comprising as the complex of BX.sub.3 with a tertiary amine either BCl.sub.3 N(CH.sub.3).sub.3 (boron trichloride-trimethyl amine complex) or BCl.sub.3 N(CH.sub.3).sub.2C.sub.8H.sub.17 (boron trichloride-dimethyl octyl amine complex).

13. An use of an anhydride-free insulation system for current-carrying construction parts of an electric engine in form of a kit of parts as claimed in any one of claims 1 to 9 in the manufacture of rotors or stators of electrical generators or motors.

14. A process for using an anhydride-free insulation system for current-carrying construction parts of an electric engine as claimed in any one of claims 1 to 9 or a mica tape according to any one of claims 10 to 12 in the manufacture of rotors or stators of electrical generators or motors, wherein (a) the potentially current-carrying parts of the rotor or stator or the construction part thereof are wrapped with a/the mica paper or mica tape which is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises a complex of BX.sub.3 with a tertiary amine as defined in claim 1, which is contained by said mica tape in an amount sufficient to cure the epoxy resin taken up by the mica tape and the construction part of the engine during a vacuum pressure impregnation step, (b) the rotor or stator or the construction part thereof is inserted into a container, (c) the container is evacuated, (d) a thermally curable bath formulation for the vacuum pressure impregnation as defined in claim 1, is fed into the evacuated container followed by a period of applying an overpressure e.g. of dry air or nitrogen to the container containing the rotor or stator or the construction part thereof, optionally under cautious heating in order to reduce the viscosity of the thermally curable bath formulation in the container sufficiently to allow that said formulation penetrates said mica tape and the gaps and voids existing in the structure of the rotor or stator or the construction part thereof within a desired time period forced by the pressure difference between the vacuum and the high pressure applied to the components, (e) the residual thermally curable bath formulation is removed from the container, and (f) the rotor or stator or the construction part thereof, impregnated with the thermally curable bath formulation, is removed from the container and heated after removal from the container in order to cure the thermally curable bath formulation comprised by said rotor or stator or the construction part thereof.

15. The process according to claim 14, wherein the thermally curable bath formulation (B) is fed into the evacuated container in step (d) from a storage tank and is returned to said to a storage tank again after removal from the container in step (e) and stored in the storage tank, optionally under cooling, for further use.

Description

EXAMPLES

[0084] The following Examples serve to illustrate the invention. Unless otherwise indicated, the temperatures are given in degrees Celsius, parts are parts by weight and percentages relate to percent by weight (weight percent). Parts by weight relate to parts by volume in a ratio of kilograms to litres.

[0085] (A) Description of ingredients used in the Examples:

TABLE-US-00001 MY 790-1 CH: distilled bisphenol A diglycidyl ether (BADGE), epoxy eq.: 5.7-5.9 eq./kg, supplier: Huntsman, Switzerland; PY 306 bisphenol F diglycidyl ether (BFDGE), epoxy eq.: 6.0-6.4 eq./kg, supplier: Huntsman, Switzerland; GY 250 undistilled BADGE, epoxy eq.: 5.3-5.45 eq/kg, supplier: Huntsman, Switzerland; DY 023 2,3-Epoxypropyl o-tolylether, reactive diluent, supplier: Huntsman, Switzerland HY 1102: methylhexahydrophthalic acid anydride (MHHPA), supplier: Huntsman, Switzerland; XD 4410: one-component epoxy-based VPI-resin based on BADGE, BFDGE and 2,3-epoxypropyl-o-tolylether, contains highly latent accelerator, supplier Huntsman, Switzerland; DY 9577: Neat borontrichloride-dimethyloctylamine complex (1:1), supplier: Huntsman, Switzerland; EP 455 Neat borontrichloride-trimethylamine complex (1:1), supplier: Syntor, UK PC: Propylene-carbonate: supplier: Huntsman

[0086] Mica tapes are composed of mica paper, optionally containing one or more additives or resins for consolidation of the mica paper, and a light-weight glass fabric made from E-glass or a polymer film that is adhered to the mica paper with a non-reactive or reactive adhesive for mechanical support. Following reference mica tapes were used in the Examples: Poroband ME 4020: mica tape containing zinc naphthenate, supplier: Isovolta, Austria; Poroband 0410: mica tape without accelerator, supplier: Isovolta, Austria.

[0087] Preparation of Mica Paper and Mica Tapes According to the Invention and Application Tests Thereof:

[0088] (C1) Mica tape with boron trichloride-dimethyl octyl amine complex as the BX.sub.3-amine complex

[0089] A mica paper sheet based on uncalcined mica flakes with an areal weight of 160 g/m.sup.2 was cut in a rectangular shape of the size 200100 mm. For mica paper impregnation a solution of DY 9577) in methyl ethyl ketone (MEK) was prepared which contained 3 wt % of DY 9577. The mica sheets were impregnated with 2.0 g of the solution and the solvent was removed in an oven at 120 C. for 3 min. The mica paper thus prepared contained 3 g/m.sup.2 boron trichloride-dimethyl octyl amine complex. Additionally, the mica sheets were impregnated either in the same step or in a second step with a consolidation resin. For the consolidation resin a 5% solution of polyol, polyester or modified polyester and/or polyol was prepared in MEK. The mica sheets were impregnated with 1.6 g of this solution. The solvent was removed in an oven at 120 C. for 3 min resulting in 4 g/m.sup.2 consolidation resin (polyol, polyester or a modified polyester and/or polyol).

[0090] The treated mica paper was used in combination with a glass fabric style 792 (23 g/m.sup.2, 2615, 5.5 tex/5.5 tex).

[0091] In one alternative the glass fabric was previously coated with 6 to 8 g/m.sup.2 of a polyester, polyol or polyester/polyol resin mixture. The coated glass was laid on top of the treated mica paper and laminated in a moulding device at 130 C. for 30 s. A mica tape was obtained which is designated in the following as (C1-1).

[0092] In another alternative the glass fabric, was previously coated with 3 g/m.sup.2 of an epoxy/acrylic resin mixture. The coated glass fabric was adhered to the mica tape using a solid epoxy resin having a melting point around 100 C. For this purpose the solid epoxy resin was evenly dispersed on the treated mica paper. Then the glass fabric was laid on top. The specimen was put into a heated press to melt the epoxy resin (130 C. for 30 s). A mica tape was obtained which is designated in the following as (C1-2).

[0093] In either of the two alternatives of mica tape the glass fabric and the mica paper stuck firmly together.

[0094] (C2) Mica tape with boron trichloride-trimethyl amine complex as the BX.sub.3-amine complex

[0095] A mica paper sheet based on uncalcined mica flakes with an area weight of 160 g/m.sup.2 was cut in a rectangular shape of the size 200100 mm. For mica paper impregnation a solution of EP 455 in MEK was prepared which contained 1.5% of EP 455. The mica sheets were impregnated with 2.66 g of the solution. The solvent was removed in an oven at 110 C. for 1 min resulting in 2 g/m.sup.2 EP 455. Additional, the mica sheets were impregnated either in the same step or in a second step with a consolidation resin. For the consolidation resin a 5% solution of polyol, polyester or modified polyester and/or polyol was prepared in MEK. The mica sheets were impregnated with 1.6 g of this solution. The solvent was removed in an oven at 120 C. for 3 min resulting in 4 g/m.sup.2 consolidation resin (polyol, polyester or a modified polyester and/or polyol).

[0096] The treated mica paper was used in combination with the same glass fabric and in either of the two coating and adhering alternatives as described for (C1). Mica tapes were obtained which are designated in the following as (C2-1), with mica paper and glass fabric being polyester/polyol resin adhered, and (C2-2), with mica paper and glass fabric being solid epoxy resin adhered.

[0097] Again, in either of the two alternatives (C2-1) and (C2-2) the glass fabric and the mica paper stuck firmly together.

[0098] The above obtained mica tape specimens (C1-1), (C1-2), (C2-1) and (C2-2) were each cut in half to give two equal 100100 mm sized samples.

[0099] Preparation of 4-Layered Composites with Inventive Mica Tapes and with Reference Mica Tapes and with Impregnation Resins, and Tests Thereof

[0100] Two 100100 mm samples from (C1-1) and two 100100 mm samples from (C1-2) were piled atop of each other with alternatingly 1.625 g evenly distributed impregnation resin after each mica tape layer, giving 4-layered mica tape composites with in each case having total resin weight of 6.5 g.

[0101] Analogously, four 100100 mm samples of either a Zn naphthenate-containing mica tape (Poroband ME 4020) or of an accelerator-free mica tape (Poroband 0410) were piled atop of each other with alternatingly 1.625 g evenly distributed impregnation resin after each mica tape layer, giving two further 4-layered mica tape reference composites with in each case having total resin weight of 6.5 g.

[0102] The impregnation resins used and the designations of the resulting 4-layered composites, as used in the following tests, are indicated in Table 1.

TABLE-US-00002 TABLE 1 Impregnation resin (wt % based on total resin) 3% DY 023 5% GY 250; 8% DY 023 20% PY 306; 3% GY 250; balance MY balance MY 20% PY MY 790- 790-1 CH; 790-1 CH; 306; 100% 1CH/HY (crystallisation- (crystallisation- balance MY 1102/DY free when free when MY 790- 790-1 9577/DY XD molten) molten) 1 CH CH 073 4410 Types (C1-1) (Inv I-1) (Inv H-1) (Inv G- (Inv F- of and [Inv bath I, DY [Inv bath H, 1) 1) mica (C1-2) 9577] DY 9577] [Inv bath [Inv tape G, DY bath F, 9577] DY 9577] (C2-1) (Inv I-2) (Inv H-2) (Inv G- (Inv F- and [Inv bath I, [Inv bath H, EP 2) 2) (C2-2) EP 455] 455] [Inv bath [Inv G, EP bath F, 455] EP 455] Poroband (Ref-1) ME 4020 Poroband (Ref- 0410 2)

[0103] For further comparison purposes the impregnation resins used in above inventive impregnated 4-layered mica tape composites (Inv I-1) to (Inv F-2) were each also homogeneously mixed in the absence of mica tape with small amounts of either DY 9577 or EP 455 and cured in the absence of any mica tapes. The compositions of these further, mica-tape free reference formulations and their designations, as used in the following tests, are indicated in Table 2:

TABLE-US-00003 TABLE 2 Impregnation resin (wt % based on total resin) 3% DY 023 5% GY 250; 8% DY 023 20% PY 306; 3% GY 250; 20% balance MY balance MY PY 790-1 CH; 790-1 CH; 306; (crystal- (crystallisa- balance balance lisation- tion-free MY MY free when when 790-1 790-1 molten) molten) CH CH Homo- 1.6% (I-2) (H-2) (F-2) geneously EP 455; [Inv I] [Inv H] [Inv F] added 2.0% (G-2) acceler- EP 455; [Inv G] ator 2.9% (G-1) (F-1) DY 9577 [Inv B] [Inv A] 3% (I-1) (H-1) DY 9577 [Inv E] [Inv D]

[0104] The curing conditions for all samples were as follows: [0105] Composites (Inv I-1), (Inv H-1), (Inv G-1) and (Inv F-1) with DY 9577: heating press; 100 C. at 20 bar for 4 h and then increasing the temperature to 170 C. at 20 bar for 10 h. [0106] Composites (Inv 1-2), (Inv H-2), (Inv G-2), (Inv F-2) with EP 455: heating press; 125 C. at 20 bar for 4 h and then increasing the temperature to 170 C. at 20 bar for 12 h. [0107] Reference composite (Ref-1): heating press; 160 C. at 20 bar for 12 h. [0108] Reference composite (Ref-2): heating press; 125 C. at 20 bar for 4 h and then increasing the temperature to 170 C. at 20 bar for 12 h; [0109] Reference formulation (H-2) with EP 455 and (H-1), (I-1) with DY 9577: heatable mould; 100 C. for 4 h and then increasing the temperature to 170 C. for 10 h; [0110] Reference formulations (F-1), (G-1) with DY 9577: heatable mould; 100 C. for 4 h and then increasing the temperature to 170 C. for 12 h;

[0111] Reference formulations (I-2), (G-2), (F-2) with EP 455: heatable mould; 125 C. for 4 h and then increasing the temperature to 170 C. for 12 h.

[0112] All cured 4-layered composites and cured reference formulations were subject to the following tests: [0113] 1) Tan measurement according to IEC 60250 at 155 C. in Tettex instrument using a guard ring electrode at 400V/50Hz; [0114] 2) Glass transition temperature Tg. For the 4-layered composites according to IEC 61006 via DMA at 5/min rate, using the temperature at which the maximal tan is observed as Tg; on 50 mm10 mm specimens of the composites. For the reference formulations directly via DSC.

[0115] The cured 4-layered composites were furthermore analysed for the mass ratio of accelerator to cured organic content, by ashing at 700 C./15 min and comparing sample weight before and after ashing; on 50 mm50 mm specimens of the composites. This ratio is R=m.sub.acc/m.sub.bath described in the general description.

[0116] The results of the above tests are summarised in below Table 3 (for the 4-layered inventive and reference composites) and in below Table 4 (for the corresponding reference formulations).

TABLE-US-00004 TABLE 3 4-layered composite (Inv I-1) (Ref-1) (Ref-2) [Inv bath (Inv I-2) (Inv H-1) (Inv H-2) (Inv G-1) (Inv G-2) (Inv F-1) (Inv F-2) [Comp [Comp I, DY [Inv bath [Inv bath H, [Inv bath H, [Inv bath G, [Inv bath G, [Inv bath F, [Inv bath A] B] 9577] I, EP 455] DY 9577] EP 455] DY 9577] EP 455] DY 9577] F, EP 455] Test tan 4.40% 22.80% 7.00% 5.50% 10.90% 6.00% 5.90% 5.70% 4.90% 4.60% Tg ( C.) 151.4 121.8 138.4 155.4 132.5 145.5 148.2 146.7 156.3 148.3 ratio R 5.38:94.62 5.08:94.92 8.00:92.00 5.35:94.65 6.50:93.50 4.64:95.36 5.08:94.92 5.66:94.34

TABLE-US-00005 TABLE 4 reference formulation (I-1) (H-1) (G-1) (F-1) (I-2) (H-2) (G-2) (F-2) [Inv E] [Inv D] [Inv B] [Inv A] [Inv I] [Inv H] [Inv G] [Inv F] Test tan 4.7% 5.9% 4.8% 7.4% 2.7% 2.6% 7.6% 5.7% Tg ( C.) 153/154 149/149 159/162 165/167 144/145 135/137 170/173 155.4

[0117] Conclusions based on the comparisons of inventive impregnated mica tapes with reference mica tapes and reference formulations

[0118] Firstly, all inventive 4-layered composites cured equally well as the corresponding impregnation baths with homogeneously admixed corresponding BCl.sub.3 amine complex. This can be derived from the observed Tg values, which all are above about 130 C. They cure comparably well as the reference 4-layered composite (Ref-1) containing a Zn-naphtenate mica tape and furthermore homogeneously admixed BCl.sub.3 amine complex. They cure better than the reference 4-layered composite (Ref-2) containing the standard one-component impregnation bath which contains a homogeneously dispersed highly latent curing accelerator.

[0119] Employing an impregnating resin bath consisting of essentially pure BADGE (distilled, n=0 to 0.3 in the formula of the general description) provides after curing the best tan values with either DY 9577 or EP 455 containing inventive mica tapes (see (Inv F-1) and (Inv F-2)), comparable to the reference 4-layered composite (Ref-1) containing Zn-naphthenate as accelerator.

[0120] Employing an impregnating resin bath consisting of essentially pure BADGE (distilled, n=0 to 0.3 in the formula of the general description) and 0 to about 20% by weight, based on the impregnating bath, of standard (unpurified) BFDGE, in combination with an inventive mica tape appears to give after curing in many cases better tan values than the same impregnation resin bath with the corresponding, but homogeneously admixed BCl.sub.3 amine complex: See (Inv F-1) vs. (F-1), (Inv F-2) vs. (F-2), (Inv G-2) vs. (G-2).

[0121] The inventive systems match the requirements with the crystallizing resins with both accelerators DY 9577 and EP 455. Further the inventive impregnation systems and mica tapes with both accelerators match the requirements regarding tan and Tg values. The accelerators used according to the invention have a similar consolidating effect on the mica paper, as is known from the prior art accelerator zinc naphthenate, so that the need of further consolidating additives is not necessary.

[0122] The bath formulations for the vacuum pressure impregnation used in the inventive system can contain further epoxy resins besides BADGE to tune the tan and Tg values.

[0123] Any of the bath formulations for the vacuum pressure impregnation used in the inventive system can be stored at elevated temperature, such as 70 C., to avoid crystallisation even if the bath formulations for the vacuum pressure impregnation in question should have a tendency to crystallise when stored at room temperature.

[0124] The inventive mica tapes can tolerate in the BCl.sub.3-amine complex contained therein variations in the chain length of R.sup.1 contained therein: DY 9577 has chain length 8 and EP 455 has chain length 1. They can also tolerate variations of the content of BCl.sub.3-amine complex (in g/m.sup.2) quite well with only minor effects on tan or Tg values. The tan and T.sub.g values can however be controlled by appropriately choosing curing temperature and time.