FI68922B - INSULATION FOR HOUSE- OIL MEDELSPAENNINGSLINDNINGAR OCH FOERFARANDE FOER FRAMSTAELLNING AV ISOLERINGEN - Google Patents

Abstract

1. An insulator for high and medium voltage windings, particularly for electrical machines, comprising a tape based on mica or mica paper which is glued on a textile or felt support made of glass or synthetic fibers, by means of an adhesive comprising the condensation product of a polyamine having the general formula H2 N-(CH2 )n -[NH-(CH2 )p ]q -NH2 with an epoxide resin, wherein n and p are integers from 1 to 5 and q is an integer from 0 to 5, said tape being impregnated after being wound on a conductor by an impregnation resin comprising an epoxide resin which is mixed with an equivalent quantity of liquid acid anhydride, and the tape and the adhesive containing a hardening accelerator of the impregnation resin, characterized in that the epoxide resin which is to condense with the polyamine is a solid epoxide resin of bisphenol A having two terminal oxyrane groups and an epoxide equivalent included between 400 and 1500, or a novolak epoxide resin having an epoxide equivalent included between 150 and 300 or a mixture of these latter products, and that the respective quantities of polyamine and of epoxide resin for condensation are chosen in such a way that an excess of amine functions subsist in the condensation product.

Description

* 1 68922

The present invention relates to an insulator for high and medium voltage windings, in particular for electrical machines, the insulator comprises a wedge-shaped glued to a support of a fabric or felt made of glass or synthetic resin-10 fibers by means of an adhesive which is a condensation product of polyamine and epoxy resin, said tape being impregnated with epoxy resin and an adhesive tape containing empregno after wrapping on a wire. accelerator. The invention further relates to a method for producing this insulator.

To wrap high voltage machines, the final insulation of the conductors is performed before being placed in the cavities. The resin is subjected under a vacuum-pressure method to an insulating wall 20 obtained by coating the conductor with a tape material, and the resin is polymerized with each conductor before winding the machine.

Medium voltage machines (1-6 kV) and some high voltage machines are wound, if their dimensions allow, by means of conductors coated with insulation on which the mica has been applied dry. The completely wound machine is then impregnated throughout with resin without the use of a solvent by a method called the "body impregnation" method, which comprises immersing the device in a resin without solvent and treating it with a vacuum pressure method suitable for the machine and the resin used for impregnation. .

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In order to function, a fiberglass carrier of fabric or felt or a carrier of synthetic resin must be such that the mica-based tape can withstand the tensile forces exerted on it by manual or machine winding. It ensures the mechanical reinforcement of the insulation as well as the best penetration of the resin to be absorbed, which is especially important in the production of very thick insulation.

German patent application 16 13 273 describes adhesives 10 consisting of condensation products of polyamines and epoxy resins. The number of oxirane groups of the latter compounds is greater than the number of amine groups, so that the condensation products are oxirane-terminated and their amine groups are secondary or tertiary. It is therefore suitable to use epoxy resins having a relatively low molecular weight (and according to the epoxide equivalent) in order to avoid reaction media having too high a viscosity when preparing condensation products. However, this often results in poorly condensed products, which can also be either tough or liquid at ambient room temperature and readily soluble.

These condensation products are placed on the insulating tape in dissolved form. Either they are able to prevent any changes in the curing of the binder 25 in the absorption shoulder vessel or there is a risk that they will gel. It is quite important to provide products that are highly condensed, solid, highly reactive, and do not have the risk of diffusing in the absorbent resin at temperatures below -30 on the gelation temperature.

The stoichiometric amount used in the preparation of the amine epoxide resin condensates according to German patent 16 13 273 results in products having an oxirane end group. These end groups have no catalytic effect on the curing reaction of the epoxide-anhydride of the impregnating resin. The course of this reaction is also not affected by intermediates other than certain secondary or tertiary amine groups which are located in the polycondensate chain but which are less sensitive and reactive.

It is an object of the present invention to obviate such disadvantages. The resulting condensation product is very solid at room temperature and can be placed on a solid insulating tape, while being rapidly soluble in the impregnating epoxy resin from a temperature of 80 ° C, which is generally a suitable gelling temperature for this resin. The resulting condensation product has end groups for primary amines and may contain groups of secondary and tertiary amines in its chain, making it quite reactive with the oxirane group of the impregnating resin, and causing it to accelerate the epoxide-acid anhydride of the impregnating resin. Therefore, it is possible to achieve rapid gelation of the impregnating resin and also to limit the resin losses during the maturation of the impregnated materials. It is a further object of the present invention to ensure that the tape adheres to the carrier mica using only a very small amount of adhesive without solvent, providing good adhesion to the mica tape thus prepared. Finally, its purpose is to perform the gluing in such a way that the glue does not form a continuous film, which would impair the porosity of the mica tape.

The insulator according to the invention is characterized in that the polyamine condensed with the epoxy resin to produce a condensation product has the general formula H2N - (CH2) - fNH - (CH2) 7 - NH2

Π tr H

68922 4 wherein n and p are integers from 1 to 5, and q is an integer from 0 to 5, that the epoxy resin condensable with the polyamine is a solid epoxy dihydro of bisphenol A having two oxirane groups at the chain end and 5 the epoxide equivalent is between 400-1500, or an epoxide novolak resin having an epoxide equivalent of between 150 and 300, or a mixture of the latter, and that the corresponding amounts of polyamine and condensable epoxy resin are sufficient to maintain an excess of amine groups in the condensate product.

The invention preferably achieves at least one of the following features: The melting point of the condensation product of the polyamine and the epoxy resin is between about 75 and 160 ° C.

15 - Polyamine is diethylenetriamine or tetraethylene pentamine.

- The epoxy resin to be condensed with polyamine is a solid epoxy resin of bisphenol A with an epoxide equivalent between 400 and 1000.

20 - Absorption epoxy resin is a cycloaliphatic epoxide resin mixed with an equivalent amount of liquid acid anhydride.

- The absorption epoxy resin is an epoxy resin of bisphenol A mixed with an equivalent amount of liquid acid anhydride.

- The liquid acid anhydride is selected from the group consisting of methyltetrahydrophthalic acid, methyl-hexahydrophthalic acid, methyldinamic acid, methylhiminic anhydrides.

The method of manufacturing an insulator according to the invention is characterized in that an adhesive comprising a condensation product obtained from a polyamine of the general formula H2N - (CH2) n - / NH - (CH2) p2q-NH2 is applied to the strip in powder form, in which n and p is an integer from 1 to 5, and q is from 0 to 5, and from a solid epoxide resin of bisphenol A having two oxirane groups at the chain end and an epoxide equivalent of between 400 and 1500, or from a novolak epoxy resin having 5 epoxide equivalents. is between 150 and 300, or a mixture of the latter two, the amounts of amine groups in the polyamine and the corresponding amounts of oxirane groups in the epoxy resin being such as to maintain an excess of amine groups in the condensation product, the amount of adhesive being between 2 and 20 g / m the purpose of the adhesive is, after heating, to cause the mica-based tape to adhere to the glass fiber or synthetic resin nonwoven fabric or felt; to the carrier, 15 and that the conductors to be insulated are coated with the obtained tape material, and the insulating tape is impregnated in hot with absorbent epoxy resins, and allowed to cool.

The following illustrates, by way of example and with reference to the drawings, the preparation of various condensation products which form the adhesives used in the manufacture of the insulators of the invention, as well as the properties of the impregnating resin when tested with such condensation products.

Example 1 100 parts by weight of an aromatic solvent (toluene) are added to 100 parts by weight of an epoxide resin of bisphenol A having an epoxide equivalent of about 500 and 20 parts by weight of diethylenetriamine. The mixture is heated under reflux at 60 ° to 70 ° C for 4-5 hours, after which the temperature is raised until the solvent and excess amine have distilled off. The remaining product is poured hot, cooled and ground. Its melting point is about 80 ° C.

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Example 2

The same procedures as in Example 1 are carried out using 100 parts by weight of solvent, 100 parts by weight of bisphenol A epoxy resin having an epoxide equivalent of about 900 and 12 parts by weight of diethylenetriamine.

The resulting adduct has a melting point of about 120 ° C.

Example 3

The same procedures as in Example 1 are performed using 100 parts by weight of a solvent, 100 parts by weight of a bisphenol 10 A epoxy resin having an epoxide equivalent of n.

500, and 32 parts by weight of tetraethylenepentamine. The product obtained has a melting point of about 85 ° C.

The powder pulps adhesives having a grain size of 100 to 400 microns prepared in the above examples are used for gluing mica paper or mica crystals 2 to a support 2-20 g / m by means of a known device specifically intended for applying powdery substances. The carrier and the mica paper or mica crystals are glued together warmly. The amount of adhesive used should be at least such as to ensure good adhesion between the enamel and the carrier.

Thus, the polymerization accelerator formed by the amine groups of the condensation product is attached to the insulator * strip and does not change in the resin-25 bath used for impregnation, even at temperatures around 60 ° C.

Example 4

A cycloaliphatic epoxy resin having an epoxide equivalent of about 160 and mixed with an equivalent amount of methyl hexahydrophthalic anhydride is applied to the tape material containing the adhesive of Example 1.

Figure 1 of the drawings shows the variations in resin bath viscosity and times T (in hours) at 80 ° C.

7 68922 millipascaleina / sec. (which is evidence of the reactivity of the resin).

Dashed line curve 1 shows the variations in viscosity of the new resin.

5 The solid line curve 2 shows the variations in the viscosity of the resin which has been previously contacted with the tape material by the vacuum-pressure method with the adhesive according to Example 1 over a period of 6 times for 4 hours at 40 ° C. The presence of resin reactivity 10 in the storage vessel was not observed, nor was any change in the adhesive in the resin during impregnation.

Monitoring the viscosity values of the resin of this example measured at 20 ° C before and after impregnation of the rods prepared using the adhesive tape of Example 1 (over a period of six to four hours at 40 ° C) shows that that the viscosity values do not change (290 mPas initial value, 290 mPas after 24 hours, 330 mPas after 100 hours, 480 mPas after 500 hours).

Figure 2 shows the percentage variation of the insoluble fraction of the same resin at 80 ° C as a function of T (hours), measured by extraction with a mixture of isopropanol (50% by volume) and toluene, this resin having been in contact with a porous strip with adhesive. a substance having no catalytic effect (curve 1 in broken lines), on the other hand, with a strip containing the adhesive according to Example 1 (curve 2 in solid lines). An accelerating effect of the adhesive on the resin is observed, which causes it to gel. 1

Example 5

The tape material containing the adhesive of Example 2 is contacted with an apoxy dihydric resin of bisphenol A having an epoxide equivalent of about 180 and mixed with an equivalent amount of methyl hexahydrophthalic anhydride.

Figure 3 shows the variations of the function of time T (hours) relative to the viscosity n at 80 ° C (millipascal / sec) in a resin bath. Curve 1 with dashed lines shows the viscosity variations in the new resin. Continuous curve 2 shows the variations in viscosity of a resin previously contacted under vacuum pressure with the tape material and the adhesive of Example 2 over a period of six 4 hours at 40 ° C. No change in the reactivity of the resin in the storage vessel and no change in the adhesive in the resin during absorption is observed.

Figure 4 shows the change in the percentage of insoluble matter in the same resin at 80 ° C as a function of T (hours) as determined by extraction with a mixture of isopropanol (50% v / v) and toluene after contact of this resin with a porous strip on the other hand. with a catalytically ineffective adhesive (dashed curve 1) and, on the other hand, with a strip having the adhesive of Example 2 (solid line curve 2).

Although the adhesive and its method of preparation, shown by way of example, appear to be preferred embodiments of the invention, polyamines other than diethylenetriamine and tetraethylenepentamine may be used, namely e.g. triethylenetetramine.

Claims (8)

1. Insulation for high and medium voltage windings, especially for electrical machines, which insulation comprises a mica-based strip or glitter paper, adhesive on a carrier consisting of fabric or felt made of glass or synthetic resin fibers, by means of an adhesive which is a condensation product of a polyamide and an epoxide resin, wherein said band, after winding around a conduit, is impregnated with an epoxy resin, and the adhesive band contains an impregnating resin curing accelerating agent, characterized in that the polyamide has the - (CH2) n- JHH - (CH2) p ^ 7 q - HN2 in which n and p are integers between 1 and 5 and q is an integer between 0 and 5, and that the epoxide resin condensing with the polyamine is a solid bisphenol A chain epoxide resin having two oxirane groups at the chain end and an epoxy equivalent of 400-1500, or an epoxide novolac resin having an epoxide equivalent of 150-2000, or a mixture of the latter two, and The effective amounts of polyamine and with this condensing epoxide resin are sufficient to maintain an excess of amine groups in the condensation product. 2. An insulation according to claim 1, characterized in that the condensation product of polyamine and epoxide resin has a melting point between about 75-160 ° C. Insulation according to claims 1 or 2, characterized in that the polyamine is diethylenetriamine or tetraethylenepentamine. 4. Insulation according to claims 1-3, characterized in that the epoxy resin condensing with the polyamine resides with a solid bisphenol A epoxy resin. an epoxide equivalent between 400-1000.