FI58227B - LINDNINGSBAND FOER ISOLERINGEN I ELMASKINER - Google Patents

Description

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• (^) Paterit inoiJelat ^ ~ ^ (51) K ».ik? /Int.a.3 H 01 B 3 / 0ή> FINLAND —FIN LAND pi) l ^ ttll ^ mui-P« intiniei «l». 979/72 (22) HaV * ml «p * ivt - An * eknlnpd« f 07.0 ^ +. 72 (23) AlkupUv * —GUtlthetjdag 07.01 + .72 (41) Tullut JulklMk * l - Bllvlt offmtllg 09.10.72

Pttantti. J * National Board of Registration for NIHUvtaipto J. Kuutjullutau pvm. -

Patent- och reglsterstyrelsen AiwMun utiagd ech uti. $ Krnt * n public · ^ 29.08.80 (32) (33) (31) Requested «Tuoikuut — e ^ ird priority 08.0¾.71

Switzerland-Switzerland (CH) 5170/71 ^ (71) Schweizerische Isola-Werke, 1 + 226 Breitenbach, Switzerland-Switzerland (CH) (72) Hans Mosiman, Breitenbach, Peter Heim, Basel, Walter Lutz, Laufen, Switzerland-Switzerland (CH) (7¾) Oy Kolster Ab (5¾) Wrapping tape for insulation of electrical machines - Lindningsband för isoleringen i elmaskiner In electric motors and generators, cables for medium and high voltages and powers are insulated with mica products. In high-voltage windings, the wire is then insulated with a mica product according to the f © method or by wrapping it before placing it in the grooves. In windings with an operating voltage of up to about 6 kV, the so-called full impregnation method, i.e. the entire winding is insulated with porous mica strips and, after being placed in the grooves, the finished winding is impregnated with a solvent-free impregnating resin.

Whether it is the manufacture of high-voltage wires which are placed in a groove in a pre-insulated space or the full impregnation method with the winding already in the groove, in both methods the mica insulation must be completely impregnated with an insoluble synthetic resin.

If the resin is placed on the winding rod built and glued from the private conductors insulated only after the strip has been wrapped, it is a prerequisite for the success of the method that the mica insulation in the vacuum-pressure process is completely impregnated with the resin. The wrapping tape used must therefore be porous in order to be able to receive the resin, especially in the case of layer thicknesses of a few millimeters.

58227 Wrapping tapes consist of a carrier material, possibly of glass silk fabric 2 with a basis weight of about 25 g / m or of glass or man-made cardboard gauze and a layer of mica.

The carrier must provide the necessary mechanical strength to the combined material. However, in order for the substance to be treated at all, the carrier and the mica must be bound together by a binder.

Essential to this method are the following requirements for starting materials: The wrapping tape must be mechanically resistant and suitable for mechanical wrapping. On the other hand it will be practically binder-material, so that impregnation can fully penetrate through the wrapper.

As can be seen, these two requirements are in conflict. The wrapping tape is in itself mechanically stronger the more the carrier and the mica are connected to one another by a flexible binder. However, the binder prevents - subsequent impregnation. Therefore, the aim is to glue the carrier and the enamel as spot as possible.

Wrapping tapes, which, due to the low tensile strength of mica paper, consist of mica paper and a strong and heat-resistant fabric (glass cloth or synthetic fibers), obviously have the following requirements for the binder: 1. The minimum amount of binder must be the best possible gluing of the mica paper and carrier. 2. With the required good gluing, the binder should penetrate the mica paper as little as possible and generally only act as an adhesive between the mica paper and the carrier (so that subsequent impregnation can take place without hindrance); 3. The binder must be able to tolerate the impregnating resin to be used later.

The impregnating resin, with all the required dielectric properties, must be so low in viscosity that it can penetrate the porous insulation and, after curing, glue with this conductive to a compact, "hollow insulation".

A number of requirements must also be set for the impregnating resin: 1. The impregnating resin must be well moistened with mica insulation; 2. It shall have a low viscosity and, if possible, an impregnation temperature of less than 500 cP; 5. In order to keep it as constant as possible in the tank, its viscosity must remain constant over time, even when it is frequently heated to 50 to 60 ° C during use; 4. During curing, the viscosity must increase as quickly as possible so that a little resin drips and curing takes place quickly, which makes the oven life short-lived; 5 58227 5. The resin must be so heat-resistant that the winding can be used. o.

currently operating at normal operating temperatures (class F, 155 C). It must therefore not soften strongly at this temperature; nor must it lose any weight at all at this temperature or suffer only a slight loss of weight.

Low dielectric losses are required for a high voltage insulator, i. slight tanb rise as a function of voltage and temperature. The insulation must also not soften up to the maximum temperature during heating. Both of these requirements preclude resins with large amounts of reactive diluent. Reactive diluents are monofunctional, low viscosity epoxide compounds which, due to their monofunctionality, act as chain stoppers and thus prevent the formation of long polymer chains. As a result, in the hardened state, the Martenspiste (DIN 55 462) or _ shape resistance (ISO R 75) is shifted towards lower temperatures compared to a mixture without any thinner. If the already mentioned thinned resins are excluded, then little suitable impregnating resin systems with viscosities below 1000 cP at 20 ° C are found.

Since the resin with low viscosity more easily penetrates the winding (wrapper), an attempt is made to raise the temperature. In this case, the impregnating resin starts to react, as a result of which the viscosity increases; now that the permeation is not large, so that a new resin can always be included, the mixture soon becomes unusable for the intended purpose. Thus, there would be a need for a resin system that reacts as little as possible at the reflux temperature, for example, an epoxy resin and a liquid anhydride. However, these systems have the disadvantage of long dripping because they react slowly even at higher temperatures.

Therefore, the idea of adding an accelerator to the wrapping tape has arisen. Common types of accelerators for such systems include metal naphthenates and octoates, for example cobalt or zinc naphthenate or octoate, tertiary amines such as e.g. benzyldimethylamine, dimethylaminomethylphenol, 2,4,6-tri (dimethylamino) ethyl methoxycarbonylethyl) amine and boron trifluoride-amine complexes, e.g. boron trifluoride-ethylamine, piperidine or pyridine. Thus, for example, German Auslegeschrift Nos. 1 162 890 and No: 1 219 554 describe a method for dipping and drying belt rolls in an accelerator solution before wrapping. After wrapping, the impregnating resin in the strip comes into contact with the speed and the acceleration of the reaction should take place practically locally in the wrapping (winding). Since these are small molecules, they become partially detached from the impregnating resin and thus enter the resin storage. As a result, an accelerating effect also occurs in the resin stock, especially since the impregnation is at temperatures of 50 to 60 ° C.

We have now surprisingly found a binder for gluing mica paper to a support which best meets the requirements imposed on it and at the same time catalytically affects said stable resin hardener systems. The new binder consists of an oxamine resin of formula I prepared by quantitatively converting epoxy resin II, melting point above 50 ° C (ASTM E 28) and containing at least two oxirane groups in the molecule with a secondary amine of formula III: XRi Λ \ a 2 v I2 \ xr2 Oh r2 (II) (III) (I)

In the above formulas, R 1 and R 8 each represent a straight-chain alkyl group having up to 4 carbon atoms or together a low alkylene group which may be truncated by a heteroatom.

The described modification achieves a new class of tertiary amines, namely oxamine resins of formula I, which are well suited as binders for the carrier and the enamel and at the same time to accelerate the curing of the epoxy resin system subsequently added to the impregnation.

It is necessary for the change to occur quantitatively, because if it were incomplete, the resulting tertiary amine groups would initiate the reaction of the oxirane groups remaining in the molecule and the binder would not be stable.

Of the epoxy resins, novolak types and those based on bisphenol and heterocyclene are particularly suitable; cycloaliphatic resins, on the other hand, are less well suited.

Epoxide lacquers have the following basic structure:

A ~ A 1 A

O-CH2-CH-CH2 O-CH2-CH-CH2 O-CH2-CH-CH2

AA aSi AA

ϊ — c * 2 —rr j-ch2 —te J

AA AA

It is thus a question of chain-shaped phenol-formaldehyde novolaks in which the phenolic hydroxyl groups have been replaced by glycidyl groups.

Since the obtained oxamines most often have a lower melting point than the starting resins, those having a higher melting point are selected as the starting resins.

Examples of suitable amines having straight-chain alkyl groups or suitable cyclic amines are dimethylamine, diethylamine, di-n-propylamine, pyrrolidine, piperidine, morpholine, thiomorpholine, etc. Branched chains do not appear to be present. For practical reasons, the reaction with diethylamine is preferred.

The reaction with the amine is preferably carried out in a solvent, the amine being added in an amount of 1 to 3 equivalents based on the epoxy resin. In order to easily and harmlessly liberate the formed oxamine from the excess amine and solvent, the solvent preferably used is a ketone boiling below 150 ° C, an aromatic hydrocarbon or mixtures thereof.

Particularly suitable porous carriers are glass bulging fabric or felt made of glass or synthetic fibers.

For the preparation of a binder and an accelerator, for example, the procedure can be as follows: 1. 260 g of an epoxydovolac resin having an epoxide equivalent of about 200 and a melting point of 80 ° C are dissolved at 100 ° C in an equal amount of toluene. After cooling to about 50 [deg.] C., 280 g of diethyl are added with vigorous stirring. o amine. After 5 hours of reaction, returning to 60-70 ° C, the temperature is gradually raised and excess diethylamine and toluene are distilled off. A resin having a melting point of 75 ° C is obtained.

It is not necessary to use an epoxy novolac resin. It is equally possible to start from a bisphenol resin as described below: 2. 175 g of a bisphenol-based epoxy resin having a melting point of 80 ° C and an epoxide equivalent of 555 ° are dissolved at 80 ° C in 120 g of toluene. After cooling to 50 [deg.] C., 70 g of diethylamine are added and the mixture is heated at 60 [deg.] C. for 4 hours under reflux. The temperature is then slowly raised to distill excess diethylamine and toluene; their last residue is removed at 150 ° C in vacuo. A resin having a melting point of 78 ° C, no longer having a detectable epoxide equivalent and a hydroxide number of 230 is obtained.

The product obtained can be dissolved in acetone or better in methyl ethyl ketone, soluble in xylene on heat but falling off again in the cold. Alcohols and aqueous solvents do not dissolve it.

Dissolve a mixture of two epoxy resins (one of the hisphenol type and the other of the novolac type) with a melting point of 70 ° C and an epoxide equivalent of 580 in 500 g of toluene at 100 ° C. After cooling to 60 [deg.] C., 102 g of diethylamine are added and the solution is allowed to react for 3 hours under reflux without heating. A further distillation is then added and the temperature is slowly raised to 150 ° C, distilling off excess diethylamine and toluene. It is then kept at the same temperature under vacuum until distillation ceases. Epoxy groups can no longer be detected in the resulting product; melting point 70 ° C.

4. Dissolve 575 g of a mixture of epoxy resins based on bisphenol, epoxide equivalent 560, in 500 g of toluene at 100 ° C. After cooling to about 60 ° C, 140 g of dipropylamine are added and the solution is stirred for 3 hours at 60 ° C.

The mixture is then slowly raised to 150 ° C and the excess amine and toluene are distilled off. The reaction mixture is kept at the same temperature in vacuo until distillation ceases. The product obtained softens at 70 ° C and dissolves in methyl ethyl ketone.

In thin-flow epoxy-resin compositions used to impregnate finished windings, the binder does not dissolve in the cold, but increasingly dissolves at temperatures above 60 ° C.

The binder prepared in this way can now be used to glue the mica paper and the support to each other. For this purpose, the resin is dissolved in a suitable solvent, for example a ketone or an aromatic hydrocarbon or a mixture thereof, and placed on a support, e.g. a glass cloth. The concentration of the solution is selected according to the chosen varnishing device so that about 2-20 g of resin per surface m is applied to the surface 2. The glass fabric thus treated is glued together with mica paper the width of the machine. Wrapping strips can be cut from the material which is wound into a roll. The amount of resin must be kept to a minimum, which is just enough to firmly join both layers so that the strips can be cut and mechanically wrapped without difficulty. The smaller this amount, the easier it is to impregnate the later-wrapped (coil).

Since the tape and the wrapper thus prepared at the same time contain an accelerator for the impregnating resin, the latter without accelerator can be kept in the impregnating agent container; the impregnating resin thus becomes much longer durable. Nevertheless, the impregnated coil cures rapidly in the furnace because the binder accelerator acts on the strip. At the same time, since the accelerator is resinous, it does not rinse off during impregnation, even at temperatures of 50 to 60 ° C, whereas, for example, metal salts under these conditions enter the impregnating resin and impair its durability.

The following chapters illustrate these conditions:

A flowable epoxy resin having an epoxide equivalent of 180 was mixed with an equivalent amount of hexahydronaphthalic anhydride. The viscosity of the freshly prepared mixture is 900-1000 cP at 20 ° C.

The following experiments were performed: a) The mixture was kept in a glass vessel at 50 ° C in a thermostat and over time o samples were taken and their viscosity was determined at 20 ° C.

b) The mixture was brought into contact with the strip according to the invention and allowed to contact it for 2 hours at 50 ° C. The tape was then removed and the mixture was kept at 50 ° C. The viscosity of the mixture was again controlled at 20 ° C.

c) In the same way as in b) the procedure was followed with a strip previously impregnated with 1 11a cobalt naphthenate solution (accelerator).

7 58227

After removing the tape, the viscosity of the mixture at 20 ° C was determined.

The results are given in the following Table I:

Table I

Viscosity at 20 ° C

Experience the viscosity of the mixture - 2 pounds after. 24Qh disgusting. After 3 days

set an initial value of 50 ° C at 50 ° C at 50 ° C

Shock test (a) 930 cP 1112 cP 1573 cP 2004 cP

Test with the tape according to the invention (h) 930 cP 1022 cP 1731 cP I960 cP

Experiment with a strip first dipped in cobalt naphthenate

to account solution (c) 930 cP 1069 cP 1806 cP 4065 cP

The following conclusions can be drawn from the results:

The tape according to the invention does not affect the resin-hardener system of the mixture used in the experiment, i. no accelerator dissolves from the tape. In contrast, a low molecular weight accelerator dissolves from the cobalt naphthenate pretreated strip, which is reflected in a significant increase in viscosity.

On the other hand it can be shown that the binder contained in the invention according to the tape at higher temperatures strongly shorten used in the above experiments the resin-curing agent mixture clotting time. In this case, the coagulation time was determined in a thermostat at 130 ° C and 160 ° C.

By clotting time is meant the time interval from the moment when the resin-hardener-accelerator mixture in the thermostat is brought to the reaction temperature, until the moment when the mixture no longer flows freely but becomes a gel. This can be seen with a thin glass rod that is immersed in the mixture every second and lifted off. As long as droplets form, no clotting has occurred. Finally, as the viscosity increases, wires are formed which break at the time of coagulation.

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? 58227

It can be seen from Table II that the accelerating effect of the new binder is even stronger than the accelerator generally recommended for such resin-hardener systems in practice.

Tables I and II shows clearly that the resin having tertiary amine groups, such as the tape binder according to the invention, on the other side should not be dissolved away by the strip solvent-free impregnation resin, but the other side of strongly of accelerating affect the remaining winding impregnating resin curing temperature at which the windings normally pressed . On the other hand, the correspondingly formed binder and accelerator with branched alkyl residues on the dialkylamine base show practically no accelerating effect.

The invention therefore achieves a substantial technical advance: 1. With the new wrapping tape, the impregnation process can be carried out without further treatment of the tape to introduce an accelerator, since the binder and the accelerator are now the same.

2. The curing of the solvent-free resin used for impregnation is greatly accelerated by the tape binder.

5. Because the tape binder is almost insoluble in the solvent-free impregnating resin during impregnation, slow-curing resin systems can be used as impregnating resins, which hardly change during cold storage and also show only a slight increase in viscosity at impregnation temperature.

Claims (8)

1. Of a porous support material, mica paper and an epoxy resin and a secondary amine derived binder, which is at the same time the accelerator for the insulation impregnated resin impregnated resin wrap; of electrical machines according to the impregnation process, characterized in that as an adhesive and at the same time as an accelerator for curing the subsequently added impregnation resin, an oxyamine resin of formula: - CH - (I) OH B2 is used and each is a straight chain alkyl group having up to 1 carbon atoms or together, a lower alkylene group which may be interrupted by a heteroatom, which oxyamine resin is prepared by quantitative reaction of an epoxide resin having a melting point above 50 ° C (according to ASTM E 28) and at least two oxirane groups per molecule, and a secondary amine of formula: Wherein R 1 and R 2 are as defined above, so that the given oxyamine resin no longer has a single oxirane group. 2. Winding tape according to claim 1, characterized in that the porous support material is a glass-side fabric or a blanket of glass or artificial fibers. Winding strip according to claim 1 or 2, characterized in that the oxyamine resin used as a binder and accelerator is based on a novolac type epoxy resin or on a bisphenol or heterocycle base resin. k. Winding strip according to any of claims 1-3, characterized in that in the formula for the oxyamine resin, R 2 and R are each an ethyl group. Process for making a winding tape according to claim 1, characterized in that the porous support material and the mica paper are bonded with an oxyamine resin of formula I above, in exactly sufficient quantity and cut the obtained material into strips. Process according to claim 5, characterized in that the oxyamine resin is dissolved in an organic solvent, such as a ketone or a