DE19531955A1 - Insulating tape useful for making insulating sleeve for electric wire - Google Patents

Abstract

Insulating tape, for making insulating sleeves for electric wires impregnated with a reactive resin compsn. based on epoxide and isocyanate by the VPI (vacuum conditioning and pressure impregnation) technique, contains dielectric inorganic material, a binder and an amine accelerator for curing the impregnating resin. The accelerator is a reaction prod. (I) of a mono-OH-functional tert. amine (II) and an aromatic polyisocyanate (III) and is free from OH and NCO gps..

Description

The invention relates to an insulating tape for producing a with an impregnating resin in the form of a reaction resin compound Epoxy / isocyanate base impregnated using the VPI technique Insulating sleeve for electrical conductors, the dielectric inorganic material, a binder and an amine Contains accelerators for the hardening of the impregnating resin.

Rotating electrical machines are used in space these days commonly manufactured for temperature class F, d. H. for ther mixed loads up to 155 ° C. Especially with rail engines due to its more compact design and higher performance Temperature class H (limit overtemperature from 180 K according to VDE 0535, part 1).

The windings of rotating electrical machines and Railway motors consist of individual winding elements that composed of several sub-conductors insulated from each other set, which are surrounded by a main insulation. The Main insulation is made up of several layers of insulating tape, generally a mica tape, built up by Ver stick mica on a flexible surface such as glass silk, is produced. For the production of an insulating sleeve for electrical conductors, for example for winding elements an electrical machine, the insulating tape is around the Winding elements wrapped. This "dry winding" will at elevated temperature (approx. 30 to 70 ° C) in a vacuum tioned and then impregnated with an impregnating resin under excess pressure decorated. The impregnation is preferably carried out after VPI technology, i. H. after the vacuum pressure impregnation process. For the production of class H winding insulation silicone resins and esterimide resins are used as insulation systems.  

To achieve the required mechanical properties, however, additional measures for reinforcement are required. As Impregnating resins have recently also been based on systems of epoxides and isocyanates and on the basis of iso cyanates and unsaturated compounds.

A reaction accelerator is included in the insulating tape causes that which penetrates into the tape during impregnation Impregnating resin at low temperatures (approx. 30 to 40 ° C) inside half of about 4 to 6 hours so that after removal the winding from the drinking bath and when heating up the Post-curing temperature does not remove the impregnating resin again Insulation runs out. Because of running out of potions Resin-poor insulation is particularly unsafe sufficient electrical properties.

Insulations for electrical, wound from mica tapes Head of high-voltage machines and rail motors for the Class H are used with reaction resin systems in the whole drinker impregnated technology. With epoxy / isocyanate impregnating resin systems (EP / IC resins) can, if necessary by adding olefinic unsaturated compounds (without active hydrogen), Insulating molded materials are produced that meet the requirements class H (see: DE-OS 23 08 802, DE-OS 24 32 952, DE-OS 24 44 458 and DE-OS 27 22 400). The Ver work of such EP / IC resins according to the VPI technology Extremely high demands especially on the reaction accelerator changes. To ensure short impregnation or gelling cycles and low drip loss after impregnation gear and to reduce energy consumption through moderate Impregnation temperatures become highly reactive Accelerator needed. Because the conditioning of the to be impregnated Parts carried out in a vacuum, the must Isolation tape contained a reaction accelerator from have sufficiently low vapor pressure. Low boiling be accelerator components can be used for conditioning  Degas from the insulating tape and in this way the Ferti negatively affect security and compliance endanger occupational hygiene requirements. Because highly reactive Be accelerators have a good ability to migrate and that half the required storage stability of the impregnating resin supply attempts can no longer be guaranteed with reaction accelerators undertaken in the isolation band can be installed. Through such built-in Be The impregnator's service life should accelerate let resin mixtures increase significantly.

As already mentioned, are used for the production of heat existing insulation systems of class H - in addition to esterimide and silicone resins - so-called EP / IC resins used (see also: DE-OS 36 44 382 and DE-OS 39 04 156). The from the sen EP / IC resins, the olefinically unsaturated compounds can contain, manufactured molded materials stand out due to high thermal resistance and good mechanical and dielectric properties, also at higher temperatures. These properties become the shape mainly due to the predominance of the network their isocyanurate structures. The network building The desired formation of isocyanurate rings is decided influenced by the accelerator used. Therefor usually tertiary amines and imidazoles are used, which are active even at moderate temperatures and which Initiate crosslinking of the resin system (see: EP-PS 0 130 454). Reaction accelerators are particularly suitable aliphatic and aromatic tertiary mono-, di- and triamines as well as substituted imidazoles and other N-substituted ones Heterocycles.

The hardening of EP / IC resins of the type mentioned will Temperatures in the range from room temperature to approx. 50 ° C carried out. The reasons for this are compliance with the MAK Limit values for the isocyanate component used or  olefinically unsaturated compound (production security), saving energy costs when using a large impregnating resin only be heated to a lower temperature must (approx. 40 ° C), and the increase in the required viscosity stability of the impregnating resin mixture.

Because the viscosity stability is one of the most important requirements representations of impregnation resin systems are constantly striving undertaken to improve them. For impregnation Reaction resins used, which have a latent reaction include accelerators (see: EP-PS 0 130 454) an excellent bearing without thermal stress bility. Around these reactive resins in the winding insulation to gel in a reasonable period of time, however, higher temperatures must be used. This can however, after a few soaks to a clear Chen increase viscosity, so that the manufacturing safe is no longer fully guaranteed.

For this reason, as already mentioned, the reaction accelerator no longer presented in the impregnation resin stock, son deposited in the place where the gelling process should preferably be initiated, namely in the insulating tape (See, for example: EP-OS 0 355 558). This can be due to done in different ways. Either the electrical tape with a solution containing the reaction accelerator acts (by brushing, spraying or dipping) or those prepared for the impregnation process with insulating tape machine parts are wound into an accelerator solution submerged. Then, in both cases, the solution medium removed again.

Have adsorptively bound accelerators in insulating tapes often the property during the impregnation process in the Soak resin to migrate, especially at higher temperatures. This gradual contamination of the resin supply is associated with  a steady increase in viscosity associated with very reactive accelerators is more pronounced. It exists hence, as already mentioned, interest in reaction accelerations like that can be chemically incorporated into the insulating tape adhesive and thereby guarantee the required manufacturing security most.

With the EP / IC insulation technology lies a less complex and thus an inexpensive alternative to esterimide and Silicone resins before that the level of properties of these resins partly surpasses. This technology is currently used Silicone-based insulating tape used with the EP / IC Impregnation resin are not fully compatible. Furthermore tre ten of the reactive accelerators used so far, which due to a low vapor pressure for processing appear suitable according to the VPI technique, after the gelling process significant drip losses, which the dielectri negative properties of the winding insulation rivers.

The object of the invention is an insulating tape of the beginning mentioned type, the one the hardening reaction of the EP / IC Contains impregnating accelerator, such from design that it is an insulation together with the impregnating resin system of temperature class H with good bond properties results. It is necessary that the ent in the insulating tape holding reaction accelerators sufficient reactivity has, so that, for example, after a gel time of 3 to 5 hours at approx. 30 to 40 ° C with the VPI method none Drip losses occur. Furthermore, the accelerator VPI be compatible to ensure manufacturing safety and he must not during the watering process migrate into the drinking resin supply so that the required visco stability of about six months (at room temperature) is guaranteed.  

This is achieved according to the invention in that the accelerator niger a reaction product free of OH and NCO groups a monohydroxy-functional tertiary amine and an aro is matical polyisocyanate.

The subject matter of the present invention is as follows significant. The previously used to accelerate the reaction Highly reactive amines generally assign one high vapor pressure and are therefore for the production of Insulating sleeves using VPI technology are not suitable. Both Accelerators according to the invention, the reaction products of are hydroxy-functional amines with polyisocyanates on the other hand, a decrease in the Vapor pressure causes. This is a processability the VPI technology guarantees.

The amine component of the reaction accelerator after the Erfin manure advantageously has the following structure:

with X = CH₂, O or NR³,
R¹, R² = C₁ to C₈ alkyl,

and R³, R⁴, R⁵ = C₁ to C₈ alkyl,
x = 2 to 5.

The amine is preferably an N-substituted 1-amino 2-hydroxypropane, especially bis- (N, N-dimethylaminopropyl) - 1-aminopropan-2-ol, i.e. H. a connection of the following structure:

The isocyanate component (polyisocyanate) in which the NCO Sitting on aromatic cores is advantageous Diisocyanate of the structure OCN-R⁶-NCO or a triisocyanate Structure CH₃-CH₂-C (R⁷-NCO) ₃, where the following applies:

with R⁸ = [(CH₂) _m -O] _n -,
m = 2 or 3 and n = 1 to 10;

The polyisocyanates are preferably urethane-modified Di- or triisocyanates, d. H. they have urethane groupings -NH-CO-O- on.

The reaction between the hydroxy functional amine and the Polyisocyanate, in which urethane groups are formed, runs for example according to the following reaction equation:

The reaction itself is dried in a low boiling solvents, such as dichloromethane. Here is generally a solution of the polyisocyanate under Stir added dropwise to a solution of the amine. Since the OH radio tional amines have a very high basicity is not Catalyst required. In addition, the implementation can Room temperature. But it is necessary that no unreacted OH or NCO radio in the end product functionalities remain, d. H. the implementation product should essentially free of hydroxyl groups (OH) and isocyanate groups pen (NCO).

The reaction products of the monohydroxy-functional tertiary Amines with the aromatic polyisocyanates are highly viscous brown liquids; they are characterized by good ver workability and good compatibility with EP / IC drinker resin out. Reaction products made of urethane-modified poly Surprisingly, isocyanates also have very good properties as mica tape adhesive. In this case, the reak quations chemically into the binder of the Insulated tape installed.

The reactivity of the VPI process in the insulating tape stocky impregnation resin depends among other things on the content of the Insulating tape on accelerating functions. The one Position of the set of accelerating functions is about the accelerator content and the molar ratio of  Amine and isocyanate component of the accelerator adjustable. Since an OH group with a NCO group is implemented (and no unconverted radio functionalities should remain), carry out implementations Polyisocyanates with a high NCO value for products with a high content of accelerating functions, d. H. ter tertiary N atoms.

The accelerator content of the insulating tape is before partly between 0.5 and 20 g / m², preferably between 1 and 10 g / m², each based on the insulating tape. General it is necessary that the insulation tape is sufficiently high Accelerator concentration is present in order to gel the the insulation penetrated impregnating resin it at low tem guarantee temperature within the desired period of time most.

The insulating tapes according to the invention with the special reak tion accelerators offer the further advantage that conventional tape adhesive, d. H. Binders that can be used for example silicone and urethane glue. With more suitable The reaction products can be selected as the isocyanate component even from hydroxy-functional amine and polyisocyanate themselves can be used as binders. The content of the iso lierband of binder is generally in general about between 5 and 20 g / m², based on the insulating tape.

Advantageous embodiments of the insulating tape according to the Invention are

• - That the inorganic material from mica flakes or Fine mica layers exist,
• - That the binder is a silicone or urethane adhesive and
• - That the impregnating resin is also an olefinically unsaturated Contains compound, especially styrene or vinyl toluene (Methyl styrene).

The insulating tapes are preferably used for the production of  Insulating sleeves for the winding bars or coils electrical Machinery.

Using the special reaction accelerator according to the Erfin drawing manufactured insulating materials based on EP / IC are characterized by very good composite properties, which above all on the high compatibility between the binder and the Impregnating resin can be attributed. It is only through this reak tion accelerator a processing of the EP / IC impregnating resin according to the VPI technology. Furthermore, the Soaking bath stability and the shelf life of the accelerator containing insulating tape improved.

The invention is intended to be based on exemplary embodiments are explained in more detail.

example 1 Manufacture of reaction accelerators

The monohydroxy radio is used to manufacture the accelerators tional tertiary amine bis- (N, N-dimethylaminopropyl) -1-amino propan-2-ol (OH value: 0.408 mol / 100 g), hereinafter briefly Called "amine". It becomes a solution of 0.2 mol of Amine in 50 ml of dried dichloromethane at room temperature slowly stirring a solution of 0.1 mol of a polyiso cyanates (see Table 1) in 15 ml of dried dichlor dripped methane. When the reaction is complete, the solvent removed in vacuo (to constant weight). The received Implementation products - medium to highly viscous, brownish ge colored liquids - are characterized in Table 1.  

Table 1

Example 2 Reactivity of EP / IC impregnating resin mixtures

To investigate the reactivity, the gel times of EP / IC impregnating resin mixtures, which are the reaction accelerators included according to Example 1, at different temperatures certainly. Mixtures of 100 parts by weight of diphenyl methane diisocyanate (NCO value: 0.793 mol / 100 g) and 3.2 mass bisphenol A diglycidyl ether (EP value: 0.57 mol / 100 g) Heated to 90 ° C for 6 h; after cooling to room temperature 30 parts by weight of styrene are mixed. The one received EP / IC impregnating resin mixtures each contain such an amount Reaction accelerators added that they are in the mixture  a proportion of the tertiary amine component of 1.33 mass divide or corresponds to 1.0 mass%. The addition of the accelerator nigers takes place at room temperature with stirring within 10 min or within one for complete dissolution required period.

To measure the gelation time, test tubes are used that have the accelerator-containing impregnating resin mixture are filled in on Thermostats set at 30 ° C, 50 ° C or 70 ° C are immersed. The gelation point is reached when the resin level at horizontal position of the test tube within 10 to 15 s is no longer mobile. An hour after gelling the 30 ° C samples are heated to a temperature of approx. Heated to 100 ° C. By inserting a spatula into the heated one Sample is then checked to see if there is any liquefaction of the gel th impregnation resin has occurred, d. H. whether that when gelling polymerization is reversible (presence of a B-Zu status). The test results are summarized in Table 2 summarized, whereby - for comparison - the amine is also listed.

Table 2

Example 3 Investigation of the gelling behavior with insulating tapes

In the same way as with technical impregnation processes insulating tapes containing accelerators are accelerated  Tanning-free impregnating resin dipped, at a defined temperature temperatures. For this purpose, mica tapes are used, each of which a layer of fine mica (basis weight: 140 g / cm²) and glass silk fabric (basis weight: 35 g / m²) are built up; in between there is a tape adhesive (content: 10 to 12 g / m²). The mica tapes are ver with the reaction accelerator see (proportion of tertiary amine component: approx. 1.0 g / m²) and on small steel cylinders wound up. These samples are 16 h conditioned at room temperature in a vacuum (<1 mbar) and then immersed in the soaking resin. At intervals of one Hour, one of the samples is genomized from the impregnating resin men, and then the force is determined that unrolls the Mica tape from the steel cylinder is required. Of time gelling point is reached at a soak time at which a rolling force of 2 to 3 N is required. Pulls here the resin namely thread, d. H. it will continue advanced gelling process indicated; the mica tape rolls are then dry inside. The determined rolling force is a indirect measure of the state of gelation and quality of the composite in the insulation. In Table 3 is the roll force given as a function of the gelling time, whereby - to Comparison - also the values for the amine are given.

Table 3

Example 4 Mold properties after thermal-oxidative aging

To investigate the mechanical and thermal properties of EP / IC insulating molding materials, an EP / IC impregnating resin mixture corresponding to Example 2 is used, which contains 1.04 parts by mass of reaction accelerator RB 1. This resin mixture is used to produce steel standard rods in multiple standard rod shapes (DIN 7708). These standard bars are hardened according to the following temperature program:
6 h at room temperature, 16 h at 60 ° C, 1 h at 80 ° C, 2 h at 100 ° C, 2 h at 120 ° C, 2 h at 140 ° C, 2 h at 160 ° C, 2 h at 180 ° C and 24 h at 200 ° C.

The bending strength, the impact, is then on the standard bars toughness (impact resistance) and heat resistance speed (temperature of the marten) and weight loss are determined, before and after thermal aging - each for 16 weeks - at 180, 200, 220 and 240 ° C. It appears, that the mechanical properties decrease with aging, while the dimensional stability remains unchanged. The Ge weight loss remains below 5% at 220 ° C for up to 16 weeks and, like the other results, points to the good one thermal resistance of the insulating material system. The The results of the measurements are summarized in Table 4, where first the initial values and then the values after 16 weeks of aging at different temperatures are specified.  

Table 4

Claims (10)

1. Insulating tape for the production of an insulating sleeve for electrical conductors impregnated with an impregnating resin in the form of an epoxy / isocyanate-based reactive resin compound according to the VPI technique, which contains dielectric-resistant inorganic material, a binder and an amine accelerator for the hardening of the impregnating resin, characterized in that that the accelerator is an OH- and NCO-group-free reaction product of a monohydroxy-functional tertiary amine and an aromatic polyisocyanate. 2. Insulating tape according to claim 1, characterized in that the tertiary amine has the following structure with X = CH₂, O or NR³,
R¹, R² = C₁ to C₈ alkyl, and R³, R⁴ ′ R⁵ = C₁ to C₈ alkyl,
x = 2 to 5. 3. Insulating tape according to claim 2, characterized ge indicates that the amine is an N-substituted 1-Amino-2-hydroxypropane, especially bis- (N-N-dimethyl aminopropyl) -1-aminopropan-2-ol.   4. Insulating tape according to one of claims 1 to 3, characterized in that the poly isocyanate is a diisocyanate of the structure OCN-R⁶-NCO or a triisocyanate of the structure CH₃-CH₂-C (R⁷-NCO) ₃, where the following applies: with R⁸ = - [(CH₂) _m -O] _n -,
m = 2 or 3 and n = 1 to 10; 5. Insulating tape according to claim 4, characterized ge indicates that the polyisocyanate is urethane-modified di- or triisocyanate. 6. Insulating tape according to one of claims 1 to 5, there characterized in that the content of Accelerator is between 0.5 and 20 g / m², preferably between 1 and 10 g / m². 7. Insulating tape according to one or more of claims 1 to 6, characterized in that the inorganic material from mica flakes or fine mica layers exist.   8. Insulating tape according to one or more of claims 1 to 7, characterized in that the binder is a silicone or urethane adhesive. 9. Insulating tape according to one or more of claims 1 to 8, characterized in that the impregnating resin additionally an olefinically unsaturated Ver contains bond, especially styrene or vinyl toluene. 10. Use of the insulating tape according to one or more of the Claims 1 to 9 for the production of insulating sleeves for the Winding bars or coils of electrical machines.