DE2215206C2 - - Google Patents

Description

R ₁

-CH-CH ₂ -N (I)

I \

OH R ₂

in which R, and R ₂ each represent 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 reaction of an epoxy resin with a melting point above 5 ° C (according to ASTM E 28) and at least two oxirane groups per molecule, and a secondary amine of the formula

Ri

NH m

R ₂

in which R ₁ and R _{2 have the} above meaning, so that no more oxirane groups are present in the oxyamine resin obtained, has been produced

2. Wrapping tape according to claim 1, characterized in that the porous carrier material is a glass silk fabric or a felt made of glass or synthetic fibers.

jr. 3. Wrapping tape according to claim 1 or 2, characterized in that the oxyamine resin used as a binder and accelerator consists of an epoxy resin of the novolak type or of such on the Base derived from bisphenol or heterocycles.

4. Wrapping tape according to one of claims 1, 2 and 3, characterized in that in the formula of the oxyamine resin R _x and R ₂ 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 gliinmer paper by means of an oxyamine resin of the above formula! glued together in just enough quantities and cut the material obtained into ribbons

6. The method according to claim 5, characterized in that the oxyamine resin in an organic Solvent, such as a ketone or an aromatic hydrocarbon, dissolves in such concentration that when the solution is subsequently applied to the carrier material, about 2 to 20 g of oxyamine resin per nr Surface to be applied.

7. Means for performing the method according to claim S or 6, characterized in that it consists of an oxyamine resin of the above formula I consists.

In electric motors and generators for medium and high voltage and power, the conductors are insulated with mica products. In the case of high-voltage windings, the conductor is in front of dey. Installation in the Grooves with a mica product after the molding process or isolated by treatment. For windings with operating voltages of up to about 6 kV, the so-called full impregnation process is also used today, d. that is, the whole effect is isolated with porous mica tapes, and after being inserted into the grooves, becomes the finished winding is impregnated with a solvent-free impregnating resin.

Whether in the production of the high-voltage conductors, which are only inserted into the groove in the fully insulated state, or in the complete impregnation process with the winding already in the groove, the mica must be used for both processes insulation must be completely impregnated with a solvent-free synthetic resin.

If the resin is only built up after the tape has been wound onto a single conductor made of insulated conductors

glued conductor bar brought into the winding by impregnation, so is a prerequisite for success the method that the mica insulation is completely impregnated with the resin in a vacuum pressure process will. The wrapping tape used must therefore be porous so that it can take up the resin, especially if the layers are a few millimeters thick.

The wrapping tapes are composed of a carrier material, for example a glass silk fabric with a ^{weight per unit area of about g / m 2} or a fleece made of glass or synthetic fibers, as well as a layer of mica.

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

The following requirements placed on the raw materials are essential to this process: The winding tape must be mechanically resistant and the stresses of machine winding

be grown. On the other hand, it must be practically binder-free so that the impregnation resin is completely removed from the winding can be penetrated.

As you can see, both requirements contradict each other. A wrapping tape is actually mechanical in and of itself the stronger, the more carrier and mica are bound by flexible binding agent. The binder but prevents 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 weak tensile strength of the mica paper and a tensile and heat-resistant fabric (glass fabric or synthetic fibers), the following requirements must obviously be made of the binding agent:

1. With a minimal amount of binder, the best possible gluing of mica paper and Generate carrier so that machine winding is guaranteed;

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 must be compatible with the impregnating resin to be used later.

With all the required dielectric properties, the impregnating resin must be so low-viscosity that it can be absorbed into the porous insulation is able to penetrate and after curing it with the conductor bundle to form a compact, including 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, should be below 300 cP if possible;

3. In order to be able to store it in a tank without any changes, its viscosity must remain constant over time, even if it is frequently heated to 50 to 60% l during operation;

4. During curing, the viscosity should increase as quickly as possible so that little resin drips off and the curing takes place rapidly, as a result of which the furnace occupancy is of short duration;

5. The resin should be so heat-resistant that the winding at the operating temperatures customary today can be operated (class F, 155 ° C). It must therefore not soften much at this temperature; also at this temperature there is no or only a slight weight loss in continuous operation suffer.

High-voltage insulation is required to have low dielectric losses, ie a slight increase in tg <5 as a function of voltage and temperature. The insulation must not soften up to the peak temperatures during operation. These two requirements exclude resins to which large amounts of reactive thinner have been added. Reactive thinners are monofunctional, deeply viscous epoxy compounds which, due to their monofunctionality, act as chain stoppers and thus prevent the formation of long polymers. As a result, in the hardened state, the Martens point (according to DIN 53 462) or the dimensional stability (according to ISO R 75) is shifted towards lower temperatures compared to the mixture containing no thinners. If the dilute resins already discussed are excluded, there are few suitable impregnating resin systems with viscosities below 1000 cP at 20 ^° C.

Since the resin penetrates the winding more easily at low viscosity, one tries to increase the temperature. As a result, the resin begins to react, which increases the viscosity; if now the throughput is not large so that new resin can always be added, the mixture will be used for its intended purpose soon unusable. So you want a resin system that reacts as little as possible at the impregnation temperature, z. B. 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. Common types of accelerators for such systems include so

Metal naphtenates and octoates, e.g. B. cobalt or zinc naphtenate or octoate,
tertiary amines, such as. B. Benzyldimethylamine, dimethylaminomethyl-phenol,
2,4,6-tri (dimeth.vlaminoäthyl) phenol or tri (methoxycarbonylethyl) amine, and
Boron trifluoride amine complexes, e.g. B. boron trifluoride ethylamine, piperidine or pyridine.

To describe z. B. the German Auslegeschriften No. 1162 898 and No. 1219 554 a method to swap the tape rolls before winding them in a solution of an accelerator and to dry them. After winding, the impregnating resin in the tape comes into contact with the accelerator and the acceleration of the reaction should take place practically locally in the winding. If these are low molecular weight substances, they are partially dissolved out by the impregnating resin and thus end up in the resin supply. As a result, the accelerating effect is also felt in the impregnating resin supply, especially because the resin is 50 to 60 ^° C. during the impregnation.

The invention is based on a winding tape according to the preamble of claim 1. It is the Task of specifying a binding agent for gluing the mica paper to the carrier, which is attached to it The requirements formulated above are met in the best possible way and at the same time catalytically responsive to the aforementioned stable resin hardener systems.

This object is achieved according to the invention by what is stated in the characterizing part of claim 1

Features solved.

Thus, the new binder consists of a Oxyaminharz the Formei I, which has been prepared by reacting an epoxy resin of formula II with a melting point above 50 ⁰ C (ASTM E 28) and at least two Oxirangmppen per molecule with a secondary amine of the formula III implements quantitatively:

-CH- \

-CH ₂ + HN

R ¹ /

R.

(Π)

-CH-CH ₂ -N OH

In the above formulas, R ₁ and R 2 each denote 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.

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 be quantitative, because if it were incomplete, the resulting ones would be tertiary amine groups solder the reaction of the remaining oxirane groups in the molecule and the binding agent! 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:

/
O-CH ₂ -CH

CH ₂

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

Since the oxy amines obtained usually have a lower melting point than the starting resins the starting resins are those with a higher melting point.

Examples of suitable amines with straight-chain alkyl groups or of suitable cyclic amines are dimethylamine, diethylamine, di-n-propylamine, pyrrolidine, piperidine, morpholine, thiomorpholine, etc. At Because of steric effects, the acceleration effect does not occur or only occurs in branched chains to a limited extent. 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, the solvents used are preferably ^{ketones boiling below 150 °} C., aromatic hydrocarbons or mixtures thereof.

A glass silk fabric or a felt made of glass or synthetic fibers is particularly suitable as the porous carrier material.

To produce the binder and accelerator, the following procedure can be used, for example:

1) 260 g of an epoxy novolac resin having an epoxy equivalent of about 200 and a melting point of 8O ⁰ C are dissolved at 100 ⁰ C in the same amount of toluene. After feeling to approximately 50 ⁰ C will g with vigorous stirring 280 diethylamine added. " After 5 hours of reaction under reflux at 60 to 70 ⁰ C, the temperature was gradually raised and distilled the excess diethylamine and the toluene. A resin with a melting point of 75 ° C. is obtained.

It is not necessary to use an epoxy novolak resin. One can just as well assume a bisphenol resin, as described below.

2) 175 g of an epoxy resin with bisphenol melting point 8O ⁰ C and epoxide equivalent 555 were dissolved at 80 ⁰ C in 120 g of toluene. After cooling to 50 ⁰ C 70 g of diethylamine are added and heated to reflux for 4 hours at 60 ⁰ C. The temperature is then slowly increased in order to distill off the excess diethylamine and the toluene; the last remnants of it are ^{removed at 150 °} C. under vacuum.

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

The product obtained can be dissolved in acetone or, better still, in methyl ethyl ketone, and dissolves in xylene in the Warmth on, but fails again in the cold. Alcohols and aqueous solvents do not dissolve it.

3) 560 g of an epoxy resins of two existing (a bisphenol and a Novolaktypus) mixture having a melting point of 70 ⁰ C and an epoxy equivalent of 580 are dissolved in 500 g of toluene at 100 ° C. After cooling to 6O ⁰ C, 102 g of diethylamine are added and the solution for 3 hours under reflux without heating allowed to react. A distillation attachment is then connected and the temperature is slowly ^{increased to 150 °} C., excess diethylamine and toluene distilling off. It 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 ^° C.

4) 575 g of an epoxy resin mixture based on bisphenol with an epoxy equivalent of 560 are dissolved in 500 g of toluene at ICO ⁰ C. After cooling to about 60 ⁰ C 140 g Diproylamin are added and the solution was stirred for 3 hrs. At 6O ⁰ C. Subsequently, the temperature is slowly increased to 150 ⁰ C and the excess of amine 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 over 60 ⁰ C.

The binding tape produced in this way can now be used to glue mica paper and carrier. To do this, the resin is dissolved in a suitable solvent, e.g. B. a ketone or an aromatic hydrocarbon mixture of these, dissolved and applied to the carrier material, ζ. Β. a thin glass fabric applied. The concentration of the solution will be chosen, depending on the lacquering device chosen, so that about 2 to 20 g of resin are ^{applied per m 2 of} area. The glass fabric treated in this way is glued to the mica paper in the width of the machine. The wrapping tapes can be cut on tape cutting machines from the material that is wound up in roll form. The amount of resin should be limited to a minimum, which is just sufficient for a firm connection of the two layers, so that the cutting of the strips and their machine winding is possible without difficulty. The smaller this amount, the easier it is to impregnate the finished winding afterwards.

Since the tape and the winding produced with it also contain the accelerator for the impregnating resin, the resin itself can be kept in the impregnation tank without an accelerator; the impregnating resin will last much longer as a result. In spite of this, the impregnated winding cures quickly in the oven, since the accelerator of the binding agent acts in the tape. Since the accelerator is also resin-like, it is ^{not washed out during the impregnation, even at 50 to 60 0} C, while z. B. metal salts get into the impregnating resin under these conditions and affect its durability.

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 900 to 1000 cps at 20 ° C.

The following tests were carried out with it:

a) The mixture was kept in a glass jar at 50 ⁰ C in the thermostat and samples taken over time and determines the viscosity at 20 ⁰ C.

b) The mixture was brought into contact with a tape according to the invention and left in contact with it at 50 ^° C. for 2 hours. 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 that had previously been impregnated with a 1% cobalt naphthenate solution (accelerator). After the tape had been removed, the viscosity of the mixture at 20 ^° C. was determined

Table I shows the results: Table I.

55

attempt

Viscosity of the

Mixture,

Initial value Viscosity, measured at 20 ^° C

after 2 hr. at 50 ⁰ C

after 24 hrs. at 50 ⁰ C

after 3 days at 50 ° C

60

Blind test (a)

Test with tape according to the invention (b) Test with tape that was previously immersed in cobalt naphthenate solution (c)

930 cps 930 cps 930 cps

1112 cps 1022 cps 1068 cps

1573 cps 1731 cps 1806 cps

2004 cps 1960 cps 4065 cps

65

The following conclusions can be drawn from this:

The tape according to the invention affects the resin-hardener system of the mixture used in the experiment not D. That is, no accelerator is released from the belt. In contrast, the low molecular weight accelerator is released from the strip pretreated with cobalt naphthenate, which is reflected 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 greatly shortens the gelation time of the same resin-hardener mixture as was used in the previous experiments at a higher temperature. The gelling time at 13O ⁰ C and 16O 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 does not flows more freely, but becomes a jelly. One can determine this with a fine glass rod, which one all dips into the mixture for a few seconds and pulls it out. As long as drops form, gelation has not occurred. Finally, with increasing viscosity, threads form which break at the moment of gelation.

Table II Temperature mix without mix mix + binder accelerator Accelerator + · 0.25% benzyl- based on diethylamine

dimethylamine never «nc» /. do

130 ° C not measurable 60 min. 46 min. 28 min. 18 min.

160 ⁰ C 4 to 5 hours 35 min. 16 min. 9 min. 5 min.

Table II (continued)

Temperature mixture + binder accelerator based on mixture + binder additive Dipropylamine from diisobutylamine or dibenzylamine

(for comparison)

0.25% 0.5% 1% 0.25% 0.5% 1%

130 ⁰ C 54 min. 35 min. 28 min.> 3 hours> 3 hours> 3 hours

16O ⁰ C 17 ¹ A min. 11'Λ min. 7V2 min.> 2h > 2h > 2h

Table II shows that the accelerating effect of the new binder is even more pronounced than that of an accelerator often recommended in practice for such resin-hardening systems.

From the two tables i and Π it becomes clear that the resins with tertiary amine groups, as used as binders of the tape according to the invention, are not dissolved out of the tape by the solvent-free impregnating resin, on the one hand, but on the other hand on the impregnating resin remaining in the winding the The temperature at which windings are pressed in practice has a strong accelerating effect on the hardening process. A correspondingly structured binder based on dialkylamines with branched alkyl radicals is shown however, practically no accelerating effect.

The invention therefore achieves a significant technical advance: 45

1. With the new wrapping tape, the impregnation process can be used without additional treatment of the tape Applying an accelerator can be carried out because binders and accelerators are now one and the other are the same.

2. The hardening of the solvent-free resin used for impregnation is caused by the binding agent of the belt is greatly accelerated.

3. Since the binding agent of the tape is hardly soluble in the solvent-free impregnating resin during the impregnation time is, slow-hardening resin systems can be used as impregnation resins, which are in the Hardly change the cold and show only a slight increase in viscosity even at the impregnation temperature.

Claims (1)

Patent claims: 1. From a porous carrier medium, mica paper and a binder derived from an epoxy resin and a secondary amine, which at the same time accelerates the curing of the subsequent S is added impregnation resin, existing winding tape for the insulation of electrical machines the impregnation process, characterized in that an oxyamine resin of the formula is used as the binder and at the same time as the hardening accelerator of the subsequently added impregnation resin