DE2215206A1 - Wrapping tape for the insulation of electrical machines - Google Patents

Description

Swiss Isola Works, Breitenbach (Switzerland)

VJiekelband-for the insulation of electrical machines

In the case of electric motors and generators for medium and high voltage and power, the conductors are insulated with gliromer products. In the case of high-voltage windings, the. Conductor before installation in the grooves with a mica product according to the foil process or insulated by wrapping. In VJicklungen with operating voltages up to 6 kV and now also the so-called Ganztränkverfahren is used, that is, the GaN ze winding with porous Glimmerbänderη and isolated after insertion into the grooves is the final "winding

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impregnated with a solvent-free resin.

Whether in the production of the high tension cable, • ter, which are only inserted into the groove in the completely insulated state or, in the case of the complete impregnation process, with the Winding already in the groove, the mica insulation must be made with a solvent-free synthetic resin for both processes to be completely soaked "

Is the resin built up from isolated individual conductors only after the tape has been wound up and glued conductor bar brought into the winding by impregnation, so is a prerequisite for the success of the process that the mica insulation is completely in a vacuum printing process with the Harai is saturated. The wrapping tape used must therefore be porous so that it can absorb the resin, especially if it is a few millimeters thick acts.

The V'ickelbander look together a carrier material, for example a glass silk fabric of about 25 g / m 2 surface weight or a nonwoven made of glass or Synthetic fibers and a layer of mica.

The carrier material must give the composite • the necessary mechanical strength. However, so that the material can be handled at all, the carrier and mica must be combined with one another by means of a binding agent.

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to be connected. .. _τ

The following are essential to this "procedure Requirements placed on the source materials:

The wrapping tape must be mechanically resistant and withstand the stresses of machine wrapping be grown. On the other hand, it has to be practically binder-free be so that the winding of the resin completely can be penetrated »-

As you can see, both requirements contradict each other. A rocker belt is actually mechanical in and of itself the stronger, the more carrier and mica are bound by flexible binding agent. The binder prevents but the impregnation to be carried out later. Therefore, one strives for point-by-point gluing of carrier and mica on.

In the case of the wrapping tapes, which are made of mica paper because of the visually weak tensile strength of the Giimmerpaper and a tensile and heat-resistant fabric (glass fabric or synthetic fibers), the following conclusions are evidently made for the binding agent to deliver: .

1. With a minimal amount of binder, it should be as good as possible. Create a bond between the mica paper and the carrier, so that machine winding is guaranteed; . '■ ■ ■ ".. ■" - ■

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2. With the required good bonding, the binder should penetrate the mica paper as little as possible and mainly or only serve to bond mica paper and carrier (thus the subsequent Impregnation can take place unhindered);

3. The binder needs to be used with the one to be used later Soak resin tolerated.

With all the required dielectric properties, the impregnating resin must be so low-viscosity that it can be used in the porous insulation is able to penetrate and after curing it with the conductor bundle to form a compact, inclusion-free insulation glued.

There are also a number of requirements for the impregnating resin:

1. The impregnating resin should wet the mica insulation well;

2. Its viscosity should be low and at the impregnation temperature be below 3OO cP if possible;

3. In order to be able to be stored in a tank without any changes, its viscosity must remain constant over time, even if it is frequently heated ^{to 50 to 60 ° C. during operation;}

4 “When hardening, it should increase as quickly as possible the viscosity, so that little resin drips off and curing takes place quickly, which means that the oven is covered is of short duration;

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5. The resin should be so heat-resistant that the

Winding can be operated at the operating temperatures customary today (class F, 155 ⁰ C). At this temperature it must therefore not: - ■ ■ soften strongly; also, at this temperature, it does not have to suffer any or only a slight weight loss in continuous operation.

Low dielectric losses are required from high-voltage insulation, that is to _say . a small increase in tgi as a function of voltage and temperature. The insulation must not soften up to the peak temperatures during operation. These two requirements exclude resins mixed with large amounts of reactive thinner. Reactive thinners are monofunctional epoxy compounds of low viscosity which, because of their monofunctionality, act as chain stoppers and thus prevent the formation of long polymer chains. As a result, in the hardened state, the Martens point (according to DIN 53 462) or the dimensional stability (according to ISO R 75) are shifted to lower temperatures compared to the mixture containing no thinners Viscosities below 1000 cP at 20 ^° C. s

Since the resin in the winding at low vis-

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If the viscosity penetrates more easily, try the temperature to increase. As a result, the impregnating resin begins to react, which increases the viscosity; if now the throughput is not large ^ so that new resin is always added the mixture soon becomes unusable for its intended purpose. So you want a resin system, that reacts as little as possible at the impregnation temperature, e.g., an epoxy resin and a liquid anhydride. However, these systems have the disadvantage of dripping off for a long time, because they react slowly even at higher temperatures.

That is why the thought arose of adding an accelerator to the wrapping tape. Usual Types of accelerators for such systems include metal naphtenates and octoates, e.g. cobalt or zinc naphtenate or octoate, tertiary amines such as benzyldimethylamine, Dimethylaminomethyl phenol, 2,4,6-tri (diniethylaminoethyl) phenol or tri (methoxycarbonylethyl) amine, and Boron trifluoride-amine complexes, e.g. boron trifluoride-ethylamine, -Piperidine or -pyridine. For example, the German Auslegeschriften No. 1,162,898 and No. 1 219 55 ^ a method that pre-fabricates tape rolls to dip in a solution of an accelerator and dry it before wrapping. After the swaddling comes that Impregnating resin in the belt is in contact with the accelerator and the acceleration of the reaction should be practically local take place in the winding. Since it is low ■

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Molecular substances are involved, they are partially dissolved out by the impregnating resin and thus end up in the resin supply. This will make the accelerating effect also in-Tränkharzvorrat contends particularly because the resin in the impregnation 50 "" to 6o ⁰ C hot- is.

Surprisingly, a binder has now been found for gluing the mica paper to the carrier, which optimally meets the requirements placed on it and at the same time has a catalytic effect on the stable resin hardener systems mentioned. The new binder consists of a Oxyaminharz of formula I, which is prepared by having a melting point above 50 ⁰ C (ASTM E 28) and at least two oxirane groups per molecule with a secondary amine of the formula III is quantitatively an epoxy resin of the formula II implements:

CH - CH ₀ + HN _: - ± , -CH-CHo-N

² \ I ² \

₂ OH ^H 2

(H) (HD (!)

In the above formulas, R-, and

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one straight-chain alkyl group with up to 4 carbon atoms or together a lower alkylene group which can be interrupted by a hetero atom.

The reaction described leads to a new class of tertiary amines, namely oxyamine resins of partial formula I, which acts as a binder for the carrier and mica and at the same time as an accelerator the curing of the epoxy resin systems subsequently added for impregnation.

It is necessary that the implementation is quantitative, because if it were incomplete, the resulting ones would be tertiary amine groups initiate the reaction of the oxirane groups remaining in the molecule and that The binder would not be stable.

Of the epoxy resins, the novolak types and those based on bisphenol are particularly suitable or heterocycles; Cycloaliphatic resins, on the other hand, are less suitable.

"Epoxy novolaks have the following basic structure:

0-CH ₀ -CH-CH,

C. c

-CH,

0-CH ^ - CH- CiL

■ CH,

0-CH ₀ -CH-CH,

-v

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They are therefore chain-like phenol-formaldehyde novolaks, the phenolic hydroxyl groups being substituted by glycidyl groups.

Since the oxyarnines obtained usually have a lower melting point than the starting resins, the starting resins chosen will be those with a higher melting point.

Examples of suitable amines with straight-chain alkyl groups or of suitable cyclic groups Amines are dimethylamine, diethylamine, di ~ n-propylamine, Pyrrolidine, piperidine, morpholine, thiomorpholine, etc. In the case of branched chains, the accelerator effect does not appear, or only to a limited extent, because of steric effects Mass a. For practical reasons, the reaction with diethylamine is preferred.

The reaction with the amine is advantageously carried out in a solvent, the amine being used in an amount of 1 to 3 equivalents, based on the epoxy resin. So that the oxyamine formed can be freed from the excess of the amine and the solvent easily and without damage, ^{ketones boiling below 150 °} C., aromatic hydrocarbons or mixtures thereof are preferably used as the solvent. '

Ins-209843/0687 is a suitable porous carrier material

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in particular a glass silk fabric or a mushroom made of glass or synthetic fibers.

The following procedure, for example, can be used to produce the binder and accelerator will:

l) 260 g of an epoxy novolac resin having an epoxy equivalent of about 200 and a melting point of 80 ⁰ C are dissolved at 100 ° C in the same amount of toluene. After cooling to about 50 ⁰ C, 280 g of diethylamine are added under vigorous stirring. After 5 hours reaction at reflux at 60 to YO ⁰ C, the temperature was gradually raised and distilled the excess diethylamine and the toluene. A resin having a melting point of 75 ⁰ C. It is not necessary, an epoxy novolac resin

to use. One can just as easily from a bisphenol resin proceed as described below.

2) 175 g of an epoxy resin with bisphenol melting point v / ground at 80 ⁰ C in 120 g of toluene dissolved 80 ⁰ C and epoxide equivalent 555th After cooling to 50 ⁰ C 70 g of diethylamine are added and heated for 4 hours under reflux at 60 ⁰ C. The temperature is then slowly increased in order to distill the excess diethylamine and the toluene; the last remnants of it are removed at I50 ⁰ C under vacuum.

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A resin with a melting point of 78 ° C. is obtained with a no longer detectable epoxy equivalent and a hydroxyl number of 230,

The product obtained can be dissolved in acetone or, better, in methyl ethyl ketone, dissolves in xylene in the warm, but precipitates again in the cold. Alcohols and aqueous solvents do not dissolve it. 3) 56o g of epoxy resins from two existing (a bisphenol and a Novolaktypus) mixture having a melting point of ⁰ YO C and an epoxy equivalent of 58o are dissolved in 500 g of toluene at 100 ⁰ C. After cooling to 60 ⁰ C, 102 g of diethylamine are added and the solution for 3 hours under reflux without heating allowed to react. Subsequently, a distillation head is attached and slowly raised the temperature to I50 ⁰ C, excess Diäthylaiain and toluene distill off. The mixture is then kept under vacuum at the same temperature until the distillation ceases. No more epoxy groups can be detected in the product obtained; the melting point is 70 ' ⁰ C-. · 4) 575 g of an epoxy resin on bisphenol having an epoxy equivalent of 560 are dissolved in 500 g of toluene at 100 ⁰ C. After cooling to about 60 * C ⁰ 0 rerden 1.4 'g of dipropylamine was added and the

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Solution stirred for 3 hrs. At 6O ⁰ C. The temperature is then slowly raised to 150 ⁰ C and the Arninüberschuss and the toluene distilled off. The reaction mixture is kept under vacuum at the same temperature until the distillation stops. The product obtained softens at 70 ^° C. and is soluble in methyl ethyl ketone.

In the low-viscosity epoxy curing agent mixtures as they are used to impregnate the finished coils, the binder does not dissolve in the cold, but increasingly soluble at temperatures above ⁰ C βθ.

The binder produced in this way can now be used to bond mica paper and carrier will. For this purpose, the resin is in a suitable solvent, e.g. a ketone or an aromatic hydrocarbon or mixtures thereof, dissolved and applied to the carrier material, e.g. a thin glass fabric. One will choose the concentration of the solution depending on the chosen painting device so that about 2 to

20 g of resin can be applied per square meter. The glass fabric treated in this way is machine-sized with the mica paper glued. The material, which is rolled up in roll form, can be used on tape cutting machines the wrapping tapes are cut. The amount of resin should be kept to a minimum, which leads to a

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a firm connection of the two layers is just sufficient, so that the 'cutting of the tapes and their mechanical Wrapping is possible without difficulty. The smaller this amount, the easier it will be afterwards Impregnation of the finished winding »

Since the tape and the winding produced with it also contain the accelerator for the impregnating resin, can do this itself, without accelerator, in the impregnation tank being held; the impregnating resin will last much longer as a result. Nevertheless, the hardening proceeds the impregnated winding in the oven, quick as the Accelerator of the binder acted in the tape Since the accelerator is also resinous, it becomes during the impregnation, even at 50 to βθ%, not washed out, while e.g. metal salts get into the impregnating resin under these conditions and its durability .define "

The following figures are intended to illustrate these relationships:

A liquid epoxy resin with an epoxy equivalent of about 180 was mixed with an equivalent amount of hexahydrophthalic anhydride. The freshly prepared mixture has a viscosity of QOO to 1000 cps. at 20 ⁰ C.

The following tests were carried out with it: '

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a) The mixture was kept in a glass vessel at 50 ^° C. in the thermostat and samples were taken over the course of time and their viscosity at 20 ^° C. was determined.

b) The mixture was reacted with a band gernäss of the invention, in contact and left with it for 2 hours at 50 ⁰ C in contact. Thereupon, the tape was removed and the mixture stirred at 50 ⁰ C. The viscosity of the mixture was checked ^{at 20 ° C. again.}

c) The procedure was similar to that under b) with a tape which had previously been soaked with a 1J-strength cobalt naphthenate solution (accelerator). After removing the tape, the viscosity of the I-iischung at 20 ⁰ C determined.

Table I :: shows the results:

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- 15 Table I.

attempt

Viscosity of the mixture, Initial value

Viscosity, measured at ⁰ C '20

after 2 hours' at 50 ⁰ C

after 24 hrs. at 50 ⁰ C

after 3 days at 50 ^° C

Blind test (a)

Booking with tape according to invention (b)

Experiment with tape previously in cobalt naphthenate solution was dived (c)

930 cps

930 cps

1112 cps

1022 cps

1573 cps

1731 cps

2004 cps

1Q6O cps

930 cps

IO68 cps

1806 cps

cps

The following conclusions can be drawn from this: The band according to the invention influences the resin hardener system of the mixture used in the experiment not, i.e. the belt will not become an accelerator detached. In contrast, the strip pretreated with cobalt naphthenate becomes the low molecular weight strip Accelerator dissolved, which shows in the considerable increase in viscosity.

On the other hand, it can be demonstrated that the binder contained in the tape according to the invention

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the gel time of the same resin-hardener mixture, as used in the previous experiments, is greatly reduced at a higher temperature. The gel time at 130 ⁰ C and ΐβθ ⁰ C was determined in a thermostat.

The gel time is the time between the moment when the resin-hardener-accelerator mixture is brought to the reaction temperature in the thermostat until the moment when the mixture is no longer flows freely, but becomes a jelly. One can determine this with a fine glass rod that one every couple Seconds into the mixture and pulls out. As long as drops are forming, gelation has not occurred, Ultimately, with increasing viscosity, threads form which break off at the moment of gelation «

Table II

ro σ co co

Mix without
accelerator Mixture '+ 0.25 ^
Benzyldimethyl
amine Mixture + binder
Accelerator off
starting from diethylamine 0.5 % 18 min. Mixture + 'binder-
Accelerator off
starting from dipropylamine 0.5 % 1 / o I. Mixture + binder
Additive. Starting from
Diisobutylamine or lamin (
0.5 % for ver
same)
1 , -ο temperature 0.25 % 28 min. 5 min. 0 * 25 % .. ' 55 min. 28 min. Dibenzy
0.25 % ^ 3 hours >, 3 days not measurable 60 kin. 46 min. 9 min., 54 min. Ill min. 7i Kin. > 5 hours > 2 hours > 2 hours 15O ⁵⁰ C 4 to 5 hours 55 min. 16 min. 17i min. > 2 hours • Ο
'16'0 " ⁰ C
• i · AD
O

ο co

K)

Table II shows that the new binder is still significant in its accelerating effect has a stronger effect than an accelerator often recommended in practice for such resin hardener systems.

From both Tables I and II it is clear that the resins with tertiary amine groups, as they are called Binders of the tape according to the invention are used, on the one hand, not from the tape due to the solvent-free Impregnating resin are dissolved out, but on the other hand on the impregnating resin remaining in the winding at the Temperature at which windings are pressed in practice has a strong accelerating effect on hardening. A suitably structured binder and accelerator based on dialkylamines with branched ones In contrast, alkyl radicals have practically no accelerating effect.

The invention therefore becomes an essential one technical progress achieved:

1. With the new wrapping tape, the impregnation process can be carried out without additional treatment of the tape for application .an accelerator, since binder and accelerator are now one and the same.

2. The hardening of the solvent-free used for impregnation Resin is strongly accelerated by the binding agent of the tape.

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3. Because the binder of the tape is solvent-free Impregnation resin hardly soluble during the impregnation time slowly curing resin systems can be used as impregnating resins are used, which hardly change when stored in the cold and also at the impregnation temperature show only a slight increase in viscosity.

Claims (8)

Claims C 1. j Wrapping tape consisting of a porous carrier material, mica paper and a binding agent for the insulation of electrical machines according to the impregnation process, characterized in that an oxyamine resin of the formula: pU OTT previous year ( T \ yw-uiig-iM ^ i; OH ^R o in which PL and Rp each mean a straight-chain alkyl group with up to 4 carbon atoms or together a lower alkylene group, which can be interrupted by a hetero atom, is used, which is obtained by quantitative conversion of an epoxy resin with a melting point above 50 ^° C. (according to ASTM E 28) and at least two oxirane groups per molecule, and a secondary amine of the formula: / ^R i NH (III) in which R ₁ and R _{g have the} above meaning, is prepared. 2. Wrapping tape according to claim 1, characterized in that that the porous carrier material is a glass silk fabric or a felt made of glass or synthetic paint. 209843/0687 3. Wrapping tape according to claim 1 or 2, characterized in that the oxyamine resin used as a binder and accelerator comes from an epoxy resin of the novolak type or from one based on bisphenol or heterocycles. 4. Wrapping device according to one of claims 1, 2 and 3, characterized in that in the formula des Oxyamine resin R-. and R "each represent an ethyl group. 5. A method for producing a winding tape according to claim 1, characterized in that the porous carrier material and the mica paper by means of an oxyamine resin of the above formula I in straight Adequate amount is glued together and the material obtained is cut into ribbons. 6. The method according to claim 5, characterized in that that the oxyamine resin in an organic solvent such as a ketone or an aromatic hydrocarbon, in such concentration dissolves that when the solution is subsequently applied the carrier material about 2 to 20 g of oxyamine resin per m Surface to be applied. 7 «Means for carrying out the procedure according to claim 5 or 6, characterized in that it consists of an oxyamine resin of formula I above. 8. Use of the according to the procedure according to 0 38 43/0687 one of claims 1 to 6 produced wrapping tape for the insulation of electrical machines. 2 O 9 8 i 3 / O