CA2237765A1 - Process for impregnating electrically conducting substrates - Google Patents
Process for impregnating electrically conducting substrates Download PDFInfo
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- CA2237765A1 CA2237765A1 CA 2237765 CA2237765A CA2237765A1 CA 2237765 A1 CA2237765 A1 CA 2237765A1 CA 2237765 CA2237765 CA 2237765 CA 2237765 A CA2237765 A CA 2237765A CA 2237765 A1 CA2237765 A1 CA 2237765A1
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- impregnation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/303—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups H01B3/38 or H01B3/302
- H01B3/306—Polyimides or polyesterimides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
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- Spectroscopy & Molecular Physics (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Macromonomer-Based Addition Polymer (AREA)
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- Chemically Coating (AREA)
- Electrodes Of Semiconductors (AREA)
Abstract
The process for impregnating substrates, in particular windings in electrical machines, with radical-hardened resin systems A) has the following features: the resin system A) is made up of A1) a resin which can be radical-hardened to form duroplasts, A2) at least one suitable hardening agent and optionally an accelerator, A3) optionally other comonomers and/or polymers with ethylenically unsaturated radical-polymerisable double bonds, the vapour pressure of A3) being low at the impregnation and hardening temperature, and A4) optionally other standard additives; the resin system A) is highly viscous, plastic and partially crystalline or crystalline at room temperature; and the resin system A) has low viscosity at impregnation temperature.
Description
- - CA 0223776~ 1998-0~-14 PAT 95 595 November 7, 1995 - Dr. Beck & Co. AG, Hamburg Process for impregnating electrically conductive substrate~
FILE,PH~ THIS~.~.d,~'lD~
TE~TRANSLA~N
Field of the invention The process according to the invention for impregnating substrates, in particular windings of electrical machines, comprises impregnating the substrate with a resin system A) which is highly viscous, plastic, semicrystalline or crystalline at room temperature and which has a low viscosity and [sic] is liquid at the application temperature and can be cured by a free radical method to give thermosetting plastics.
Prior art In the processes known from the prior art, the windings of electrical machines are usually impregnated by steeping. The object of this impregnation is to impart mechanical strength to the winding so that the winding can withstand mechanical and electromechanical forces and the winding is therefore protected from external harm~ul effects, such as, for example, the deposition of dust particles, collector abrasion, moisture, salts CA 0223776~ 1998-0~-14 and solvents, so that mechanical damage by particles, for example those sucked in by the fan, is prevented and so that the heat generated during operation of the electrical machines as a result of ohmic and dielectric losses can be transferred from the winding to the surrounding cooling means, helping to increase the service life of the electrical apparatus.
This impregnation is usually carried out by means of lacquers or resins which cure to give thermosetting plastics. Since, on the one hand, the requirements for the long-term thermal stability of these thermosetting plastics are very high and, on the other hand, the abovementioned properties, in particular the electrical insulation capacity, must also be present, there are a number of lacquers and resins which are tailored to the specific fields of use.
In the case of the solvent-containing lacquers whose solvent content must be removed before the curing process, thorough impregnation of the electrical windings in a single applic~ ion is as a rule poor.
Consequently, the transfer o~ dissipated ohmic and dielectric heat from the interior of the windings, which has already been discussed, is hindered.
Moreover, the removal of the solvent often requires long preheating times and complicated temperature programs during the curing of the lacquer. Furthermore, the solvent-containing lacquers require expensive plants for waste air purification, since otherwise solvent vapors produce considerable environmental pollution.
Apart from special cases, the lacquers in the electrical industry have therefore been replaced by solvent-free resins. Here, particularly the unsaturated polyester resins have become widespread since they have considerable advantages over other thermosetting resin systems. Thus, it is possible to ~ul~ill the recluired properties to a large extent by molecular tailoring of the unsaturated polyester resins, such as, ~or example, the selection o~ specific monomer building blocks or the establishment o~ specific molecular weights.
Furthermore, the reactivity of the unsaturated polyester resins can be influenced in such a way that short and hence economical production proc-sses ~or windings of electrical machines become possible.
CA 0223776~ 1998-0~-14 Particularly with regard to the requirement for long-term thermal stability, the unsaturated polyester resins, in particular the unsaturated polyesterimide resins, have outstanding properties.
In general, the unsaturated polyester resins are composed, on the one hand, of base resins, consisting, for example, o~ alpha,beta-unsaturated dicarboxylic acids, further modifying mono-, di- and/or polycarboxylic acids, di- and/or polyols and, in the case of the polyesterimides, of building blocks containing imido groups, hydroxyl groups and carboxyl groups, and, on the other hand, of comonomers which react with the alpha,beta-unsaturated dicarboxylic acid units o~ the base resin and can lead to thermosetting plastics. A preferred comonomer is styrene, which, owing to its good dissolution properties, is also used for establishing the processing viscosity. Stated comonomers are completely copolymerized during curing under suitable conditions. Such a solvent-free system is re~erred to as an impregnating resin. As in the case of the impregnating lacquers too, the vapor pressures of the comonomers at application temperature result in evaporation losses, which, however, are generally less than in the case of solvent-containing systems (50~, based on the amount of solvent used, evaporation loss -in the case of solvent-containing impregnating lacquers, from 10 to 30~ evaporation loss in the case of impregnating resins). Nevertheless, expensive purification of the waste air is required even with the use of impregnating resins based on unsaturated polyesters, but such waste air plants can be designed to have lower purification capacities than when impregnating lacquers are used, since the monomer losses can be reduced by suitable resin formulations and process adaptations.
The use of other resin systems, such as, for example, epoxy resins, have the disadvantage that long curing times are required, that the possibilities for adapting the processing properties to the production processes without suffering serious deterioration in the dielectric properties are low, and that some resin components, such as, for example, the highly heat-stable cycloaliphatic types in the case of the epoxy resins or the amines in the case of the curing agents, may have high toxicity.
- Sulmnar~y of the invention The prior art discussed so far gives rise to the object of developing a steeping and impregnation process which combines the known advantages of impregnation with resin systems which can be cured by a free radical method with a low-emission impregnation and curing technology. ~or this purpose, it is necessary to use resins which either require no comonomers for curing or contain comonomers which have very low vapor pressures at the processing and curing temperature. Such comonomers must also still have sufficiently high reactivity in order to cure in times which are sufficiently short to be economically acceptable.
Moreover, neither the resins nor the comonomers may release significant amounts of cleavage products at the processing and curing temperatures. The comonomers usually used are not suitable for achieving these objects since, for reasons relating to the processibility of the resins, the comonomers must be in the liquid state. As liquids at room temperature and in particular at the processing and curing temperature, such comonomers, such as, for example, vinyl or allyl compounds, have considerable vapor pressures which lead CA 0223776~ 1998-0~-14 to substantial evaporation losses in the case of the comonomers.
Thus, suitable comonomers are solid or highly viscous at room temperature, as are the resins themselves, which are present at room temperature in a highly viscous, plastic, semicrystalline or crystalline state.
In this case, impregnation of the objects must be carried out at temperatures at which the resins or the mixtures of resins and comonomers are present in a low-viscosity and/or in a molten state.
The use of molten resin systems in electrical insulation technology is prior art. Such molten resin systems are used as solvent-free wire enamels, extrudable cable sheathing compounds, self-bonding enamels or coating materials. The use of systems which cure by a free radical method is the exception since, in the case of such highly reactive systems, the processibility is very limited owing to the unacceptably short pot life (time for which the resin is present in the processibl. state). A further object of the present invention was thus to achieve stabilization of the resin systems used at elevated CA 0223776~ 1998-0~-14 application temperatures without causing excessively long curing times and excessively high curing temperatures at which decomposition phenomena in the resins and damage to the materials to be impregnated may occur.
JP-A-53 05 97 91 describes polyesterimide resins having at least tribasic carboxylic acids and polyesterpolyols as monomer building blocks, which are prepared using amines and further amounts of at least tribasic carboxylic acids. Such polyesterimide resins are used in molten form as insulation coating materials for electrically conductive substrates. The coatings have good electrical and mechanical properties. No toxic vapors are released during the coating process.
DE-A-26 48 3S1 and DE-A-26 48 352 relate to injection moldable resin compositions which consist of from 10 to 50~ by weight of unsaturated polyester resin, and from 0.2 to 2~ by weight of organic peroxide and of inert filler. The unsaturated polyesters are composed of the building blocks polyols, ethylenically unsaturated dicarboxylic acid and saturated dicarboxylic acid. SUch resin compositions are used for electrical or CA 0223776~ 1998-0~-14 g electronic components, such as, for example, _ insulators, housings for low-voltage and medium-voltage switches, cable insulations and plugs.
DE-A-16 40 428 describes the use of annular elements of unsaturated polyester resins, which are coated with waxes for improving the blocking resistance. These annular elements are used for impregnating windings by a procedure in which they are placed on a winding head of the winding. On heating, the unsaturated polyester resin melts, penetrates into the winding and is cured there.
Common to the prior art processes is that they generally achieve only some of the abovementioned objects set for impregnating resins.
Surprisingly, a process for impregnating windings of electrical machines has been found, in which the impregnating resin used is a resin system A) cont~;n;ng A1) a resin which can be cured by a free radical method to give thermosetting plastics, CA 0223776~ 1998-0~-14 A2) at least one su1table curing agent and, if required, accelerator, A3) if required, ~urther comonomers and/or further polymers having ethylenically unsaturated groups capable of free radical polymerization, the vapor pressure of A3) at the impregnating and curing temperature being low, and A4) if required, further conventional additives, the resin system A) being highly viscous, plastic, semicrystalline or crystalline at room temperature and the resin system A) being converted in the impregnation process, by increasing the temperature to the impregnating temperature, into the low-viscosity liquid state, so that impregnation can be carried out by the known processes of immersion impregnation, flooding, immersed rotation, dripping or casting, if necessary supporting the impregnation by employing reduced pressure.
Preferably, the resin component A1) is selected from the group consisting of unsaturated polyesters, unsaturated polyesterimides, bismaleimides, oligomeric diallyl phthalates, comonomer-rree vinyl es~ers, comonomer-free vinyl ethers, comonomer-free vinylurethanes and/or polybutadiene resins, alone or in combinations with one another.
The resin component A1) selected from the group consisting of unsaturated polyesters, unsaturated polyesterimides and bismaleimides in combination with the resin component A3~ selected from the group consisting of oligomeric diallyl phthalates, divinylethyleneurea, divinylpropyleneurea, N-vinyl-carbazole, N-vinylpyrrolidone, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes, polyesters containing vinyl and/or allyl groups, or mixtures thereof, is particularly preferred.
Preferably used curing agents A2) are peroxides which form ~ree radicals, in particular organic peroxides, and/or compounds which form free radicals as a result o~ cleavage of a carbon-carbon bond. The resin systems A) are pa ticularly preferably delivered in the activated state as single-component resins; in special cases, activation may also be ef~ected immediately CA 0223776~ l998-0~-l4 before impregnation using s~i~able mixingjmetering means.
The substrates to be impregnated are preferably preheated before the impregnation to a temperature which is equal to or greater than the impregnating temperature. Preheating of the substrates to be impregnated is carried out, for example, by Joule heat, induction heating, microwave radiation or infrared radiation. Moreover, it is possible for the winding to be impregnated to be further heated by current but also in the state immersed in the resin, and this heating may serve to compensate the heat losses due to thermal conduction or to increase the w;n~;ng temperature further in order to cause gelling of the resin which is penetrated into the winding, prior to removal from the resin. This process is particularly suitable because the resin materials used are low-emission products and therefore have a very low vapor pressure and hence a 20 high flashpoint at the processing temperature, so that special explosion-proofing measures are not required.
The resin reaches the hig~ temperatures only in the winding and in the immediate environment of the winding.
CA 0223776~ 1998-0~-14 ~ The impregnation of the substrates is pre~erab;y carried out by immersion, flooding, immersed rotation, dripping or casting, impregnation being carried out at a reduced pressure at which the components A1) to A4) used still have a negligibly low vapor pressure. In the case of impregnation by immersion or flooding, the substrate may remain immersed until gelling of the resin system A) in the substrate has occurred.
After the impregnation with the resin systems, curing of the resin systems is carried out at a temperature which is above the temperature of the resin melt and which is generated, for example, by Joule heat, induction heating, microwave radiation, infrared radiation or passage through a conventional heating oven, if necessary the surface drying being supported by the action of high-energy radiation, such as, for example, W or electron radiation.
Detailed description The components of resin system A) CA 0223776~ l998-0~-l4 Preferably used as component A1) ar~: unsaturated polyester resins which may have building blocks containing imido groups, bismaleimide resins, oligomeric diallyl phthalates, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and/or polybutadiene resins. Unsaturated polyester resins are known. Unsaturated polyester resins containing imido groups are described, for example, in DE-A-15 70 273, DE-A-17 20 323 and DE-A-24 60 768.
Examples of building blocks of the unsaturated polyester resins in addition to the conventional polyester buildings blocks are: polyols cont~in;ng polymerizable double bonds, such as glycerol monoallyl ether, trimethylpropane monoallyl ether and pentaerythrityl mono- and diallyl ether, and polycarboxylic acids cont~;n;ng polymerizable double bonds, or anhydrides thereof, such as fumaric acid, tetrahydrophthalic acid or tetrahydrophthalic anhydride and preferably maleic acid or maleic anhydride, and monocarboxylic acids cont~;n;ng polymerizable double bonds, such as, for example, acrylic and/or methacrylic acid. As described, for example, in DE-A-24 60 768, for CA 0223776~ 1998-0~-14 modification of the properties of unsaturated polyes~er resins some of the unsaturated dicarboxylic acid may be replaced by saturated dicarboxylic acids, such as, for example, adipic acid, perhydrogenated isophthalic acid, phthalic acid, phthalic anhydride and/or dimerized fatty acids. Examples of suitable components A3) copolymerizable with the unsaturated polyesters or polyesters A1) cont~;n;ng imido groups are: diallyl phthalate prepolymers, divinylethyleneurea, divinyl-propyleneurea, N-vinylcarbazole, N-vinylpyrrolidone, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and polyesters which contain vinyl or allyl groups and which differ ~rom A1), such as, for example, polyesters composed of saturated and/or unsaturated polycarboxylic acids with pentaerythrityl mono-, di- and/or triallyl ether and optionally modi~ying glycols as monomer building blocks. At the impregnating and curing temperatures, the copolymerizable components A3) have vapor pressures which are 80 low that no signi~icant immissions can occur.
CA 0223776~ 1998-0~-14 Any desired low molecular weight bismaleimide may be used as bismaleimide component Al). Bismaleimides of the formula I
C) ~ O O
where Rl is an aliphatic, cycloaliphatic, araliphatic or aromatic radical and the stated radicals may have further functional groups, such as ether, ester, amido, carbamate, keto, sulfonyl or hydroxyl groups, are advantageously used. R1 is preferably a straight-chain alkylene radical having 2 to 20, in particular 2 to 10, carbon atoms or a 4,4'-diphenylmethane, 2,4-toluylene or 1,3- or 1,4-phenylene radical. Suitable bismaleimides are, for example, ethylenebismaleimide, butylenebismaleimide, hexamethylenebismaleimide, 4,4'-diphenylmethanebismaleimide, 2,4,-toluylenebismaleimide 20 [6iC] and 1,3-phenylenebismaleimide or mixtures thereof. Examples of suitable components A3) which are copolymeriza le with the bismaleimides Al) are:
oligomeric diallyl phthalates, divinylethyleneurea, divinylpropyleneurea, N-vinylcarbazole, comonomer-free CA 0223776~ 1998-0~-14 vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and polyesters which contain vinyl or allyl groups and which differ from Al), such as, for example, those composed of saturated and/or unsaturated polycarboxylic acids with pentaerythrityl mono-, di-and/or triallyl ether and optionally modifying glycols as monomer building blocks. At the impregnating and curing temperatures, the copolymerizable components A3) have vapor pressures which are so low that no significant immissions can occur.
Furthermore, the following may be used as component Al), alone or as a mixture with other components mentioned under Al): oligomeric diallyl phthalates, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and/or polybutadiene resins.
Depending on resin system A), known peroxides having suitable decomposition temperatures or compounds which undergo thermal decomposition with formation of hydrocarbon radicals may be used as curing agent A2).
I~ necessary, compounds which accelerate the decomposition of the free radical initiators are CA 0223776~ l998-OS-l4 additionally present. It is essential to the inventionthat a significant free radical stream which effects curing of the resin system A) is produced by the curing agent A2) only at above the impregnating temperatures.
Examples of peroxides A2) which undergo significant decomposition into free radicals only at above the impregnating temperature are commercial organic peroxides, such as tert-butyl perbenzoate, tert-butyl perisononanoate or tert-butyl peroctoate, or peroxides in combination with accelerators, such as benzoyl peroxides in combination with tertiary amines or peresters with cobalt salts of organic acids.
Benzopinacol, substituted succinic acid derivatives and, preferably, silyl ethers of substituted ethylene glycols, as described, ~or example, in DE-A-26 32 294, may be mentioned as examples o~ curing agents A2) which undergo decomposition with formation of hydrocarbon radicals. Such silyl ethers according to DE-A-26 32 294 undergo partial decomposition into free radicals only at relatively high temperatures and, under certain circumstances, are very substantially stable even at temperatures above 80 degrees C in the res.~ system A) to be polymerized.
CA 0223776~ 1998-0~-14 For stabilization against premature curing, the resin systems A) may contain, as a constituent of component A4), stabilizers known per se for compounds capable of free radical polymerization, such as, for example, quinones, hydroquinones, sterically hindered phenols and/or sterically hindered amines and nitro compounds.
The conventional processing assistants for coating resins, such as, for example, surface-active or interface-active substances for improvin~ the leveling and the penetrating power, viscosity-influencing additives, such as pyrogenic silica or bentonites, and mineral or organic fillers, may be present as further constituents of component A4), which may or may not be present.
Impregnation and curing The impregnation of the substrates, for example the windings of electrical machines, is carried out using the resin systems A) according to the invention, consisting of the components A1), A2) and, if required, A3) and A4), in the melt of A) at temperatures which are below the curing temperature.
CA 0223776~ 1998-0~-14 The processing times of the resin systems A) are such that impregnation by the prior art processes are [sic]
possible. Examples of such impregnation processes are:
5 - impregnation of the substrate to be impregnated, which is optionally preheated, by immersion in the melt of the resin system A), retention of the substrate to be impregnated in the melt, until the resin melt has reached all parts to be impregnated, if necessary until gelling of the resin which has penetrated into the substrate, removal and shaking the drips off the impregnated substrate and subsequent curing of the absorbed resin system A), where heating of the object by means of Joule heat in the immersed state need not be interrupted, so that heat losses in the winding which occur as a result of thermal conduction can be compensated or the residence time until possible gelling under resin can be reduced by increasing the winding te,.,perature during immersion, - dripping o~ the melt of the resin system A) onto the substrate to be impregnated, the melt of the _ CA 0223776~ l998-0~-l4 resin sys~em A) ~eing dripped by means of suitable pumps onto the optionally preheated substrate, the curing agent A2), if required, being metered in by suitable mixing/metering apparatuses before the melt comprising A1 and, if required A3 and A4 is dripped on, or the resin system A) already being activated beforehand by addition of the curing agent A2, 10 - flooding with the melt of the resin system A), the optionally preheated substrate being flooded by a rising bath of activated melt of the resin system A) in such a way that sufficient impregnation of the substrate takes place, subsequently blowing off the melt of the resin system A), if required until gelling of the resin which has penetrated into the substrate, allowing the substrate to drip off and then curing the melt of the resin system A) absorbed by the substrate, where heating of the object by means of Joule heat in the immersed state need not be interrupted, so that heat losses in th winding which occur as a result of thermal conduction can be compensated or the residence time until possible gelling under resin can be CA 02237765 1998-0~-14 reduced by increasing the winding temperature during immersion, - immersed rotation with the melt of the resin system A), the optionally preheated substrate being rotated through the activated melt of the resin system A) in such a way that, in the case of windings of electrical machines as the substrate, only the winding or that part of the substrate carrying the winding is covered by the melt of the resin system A), until sufficient impregnation of the winding has occurred, and subsequent curing of the melt absorbed by the substrate (by the winding), preferably with rotation, where heating of the object by means of Joule heat during rotation need not be interrupted, 80 that heat losses in the winding which occur as a result of thermal conduction can be compensated or the residence time until possible gelling under resin can be reduced by increasing the winding temperature during rotation, and - casting of the substrates in reusable or captive form with a preactivated resin system A) or, with CA 0223776~ 1998-0~-14 the use of a suitable mixing/metering system, by m; ~; ng the curing agent A2) with the resin components Al and, if required, A3) and A4) immediately before casting.
The abovementioned impregnation processes can be carried out for improving the impregnation quality, preferably under reduced pressure or with alternating reduced pressure and superatmospheric pressure. The object can be preheated here too, heating of the winding by means of Joule heat during casting leading to a further reduction of viscosity, with the result that penetration into the winding is facilitated.
Gelling of the resin which has penetrated into the winding by increasing the temperature has the advantage that the volu~e shrinkage due to curing is compensated by further flow of the liquid resin from regions outside the w; n~; ng region.
The preheating of the substrates can be carried out, for example, by Joule heat (heating by electrical resistance), induction heating, microwav heating or infrared heating and by passage through a conventional heating oven.
CA 0223776~ l998-0~-l4 The curing of the resin system A) adhering to the substrate after the impregnation can be carried out, for example as in the case of the preheating of the substrates by Joule heat, induction heating, microwave heating or infrared heating and by passage through a conventional heating oven; and the curing at the substrate surface can optionally be supported by additional irradiation, for example by means of IR, W
or electron radiation.
The immissions occurring during curing are assessed as follows:
amounts as equal as possible of activated resin system 15 A) are introduced into a sample tray o~ a TGA
(Thermo~ravimetric Analysis) apparatus, and a constant air stream is passed over. Heating is then effected to the required curing temperature at a predetermined heating rate, and this temperature is then kept constant ~or the time required for curing. During this time, the loss of mass of the resin system A) was determined. In the case of conventional systems, containing unsaturated polyester resins and low molecular weight comonomers, the loss of mass during a CA 0223776~ l998-0~-l4 ~ heating time of 10 mlnu es to the curing temperature of 140 degrees C and a curing time of 1 hour at 140 degrees C is about 30~ by weight.
The Examples which follow are intended to illustrate the invention further. All stated percentages are by weight, unless stated otherwise.
Example~
Example 1:
An unsaturated polyesterimide A1) according to Example 2 of DE-C-24 60 768, composed of maleic anhydride, 15 neopentylglycol, trishydroxyisocyanurate and the reaction product of tetrahydrophthalic anhydride and monoethanolamine is mixed with lO~ by weight, based on the resin system A), of diallyl phthalate oligomer A3) (type Ftalidap 27, manufacturer Alusuisse) in the melt.
2~ by weight, based on the resin system A), o~
benzopinacol silyl ether (type Initiator BK, manufacturer Bayer AG) were admixed as curing agent A2). The resin system A) has an almost solid consistency at room temperature and a viscosity o~
1300 mPa.s at 80 degrees C. Ihe pot life Gf the resin system A) is 210 minutes at 80 degrees C, and the gelling time is 27 minutes at 140 degrees C. The stator of an electric motor, which was preheated to 120 degrees C in the heating oven, is slowly immersed in the molten resin system A) heated to 80 degrees C.
The stator re~; n~ in the molten resin system A) until no further bubbles rise. The stator is then slowly withdrawn and is allowed to drip off for about 2 minutes, and the resin system A) is then cured by heating in an oven at 160 degrees C for 30 minutes.
A~ter curing, the winding of the stator is suf~iciently stable. After the winding is sawn open, the stator shows adequately thorough impregnation. The thermogravimetrically determined loss of mass during heating in the TGA apparatus to 160 degrees C in 10 minutes and maintaining the temperature at 160 degrees C ~or 30 minutes is 3.4~ by weight, based on the resin system A).
Ex~ple 2:
CA 0223776~ l998-0~-l4 The unsaturated polyesterimide A1) according to Example 1 is mixed in a ratio of 2:1 with a polyester A3) which was prepared from 2 mol of pentaerythrityl triallyl ether, 4 mol of adipic acid and 3 mol of pentaerythrityl diallyl ether by condensation in the melt, and the resulting mixture is mixed with 2~ by weight, based on the resin system A), according to Example 1 tsic]. The mixture has a plastic consistency at room temperature and a viscosity of 570 mPa.s at 100 degrees C. The pot life of the resin system A) with 1~ by weight, based on the resin system A), of tert-butyl perbenzoate as an additional curing component A2), is 210 minutes at 100 degrees C, and the gelling time is 10 minutes at 160 degrees C. The stator of an electric motor, which was preheated to 120 degrees C in a heating oven, is slowly immersed in the molten resin system A) heated to 100 degrees C. The stator remains in the molten resin system A) until no further bubbles rise. The stator is then slowly withdrawn and is allowed to drip off for about 2 minutes, and the resin system A) is then cured by heating in an oven at 160 degrees C for 30 minut 3. After curing, the winding of the stator is sufficiently stable. A~ter the winding is sawn open, the stator shows su~ficiently thorough CA 0223776~ 1998-0~-14 impregnation. The thermogravimetrically determined loss of mass during heating in the TGA apparatus to 160 degrees C in 10 minutes and maint~;ning of the temperature at 160 degrees C for 30 minutes is 2.3~ by weight, based on the resin system A).
Example 3:
A monomer-free vinyl ester A1) (type Palatal A430-01, monomer-free, manufacturer BASF AG), which is solid at room temperature and has a viscosity of 500 mPa.s at 100 degrees C, is melted in the storage container of a conventional dripping apparatus. After ~m; ~; ng 1~ by weight, based on the total resin system A), of tert-butyl perbenzoate as curing agent A2) by means of aconventional mixing/metering head, the resin system A) prepared in this manner is dripped onto an armature whose winding had been heated to 140 degrees C by Joule heat. The resin system A) is cured at 140 degrees C in 20 the course of 15 minutes. After curing, the winding is sufficiently stable. After the winding is sawn open, it shows sufficiently thorough impreg ~tion. The thermogravimetrically determined loss of mass during heating in the TGA apparatus at 140 degrees C in 10 minutes and maintaining of the temper~ture at 140 degrees C for 15 minutes is 1.4~ by weight, based on the resin system A).
FILE,PH~ THIS~.~.d,~'lD~
TE~TRANSLA~N
Field of the invention The process according to the invention for impregnating substrates, in particular windings of electrical machines, comprises impregnating the substrate with a resin system A) which is highly viscous, plastic, semicrystalline or crystalline at room temperature and which has a low viscosity and [sic] is liquid at the application temperature and can be cured by a free radical method to give thermosetting plastics.
Prior art In the processes known from the prior art, the windings of electrical machines are usually impregnated by steeping. The object of this impregnation is to impart mechanical strength to the winding so that the winding can withstand mechanical and electromechanical forces and the winding is therefore protected from external harm~ul effects, such as, for example, the deposition of dust particles, collector abrasion, moisture, salts CA 0223776~ 1998-0~-14 and solvents, so that mechanical damage by particles, for example those sucked in by the fan, is prevented and so that the heat generated during operation of the electrical machines as a result of ohmic and dielectric losses can be transferred from the winding to the surrounding cooling means, helping to increase the service life of the electrical apparatus.
This impregnation is usually carried out by means of lacquers or resins which cure to give thermosetting plastics. Since, on the one hand, the requirements for the long-term thermal stability of these thermosetting plastics are very high and, on the other hand, the abovementioned properties, in particular the electrical insulation capacity, must also be present, there are a number of lacquers and resins which are tailored to the specific fields of use.
In the case of the solvent-containing lacquers whose solvent content must be removed before the curing process, thorough impregnation of the electrical windings in a single applic~ ion is as a rule poor.
Consequently, the transfer o~ dissipated ohmic and dielectric heat from the interior of the windings, which has already been discussed, is hindered.
Moreover, the removal of the solvent often requires long preheating times and complicated temperature programs during the curing of the lacquer. Furthermore, the solvent-containing lacquers require expensive plants for waste air purification, since otherwise solvent vapors produce considerable environmental pollution.
Apart from special cases, the lacquers in the electrical industry have therefore been replaced by solvent-free resins. Here, particularly the unsaturated polyester resins have become widespread since they have considerable advantages over other thermosetting resin systems. Thus, it is possible to ~ul~ill the recluired properties to a large extent by molecular tailoring of the unsaturated polyester resins, such as, ~or example, the selection o~ specific monomer building blocks or the establishment o~ specific molecular weights.
Furthermore, the reactivity of the unsaturated polyester resins can be influenced in such a way that short and hence economical production proc-sses ~or windings of electrical machines become possible.
CA 0223776~ 1998-0~-14 Particularly with regard to the requirement for long-term thermal stability, the unsaturated polyester resins, in particular the unsaturated polyesterimide resins, have outstanding properties.
In general, the unsaturated polyester resins are composed, on the one hand, of base resins, consisting, for example, o~ alpha,beta-unsaturated dicarboxylic acids, further modifying mono-, di- and/or polycarboxylic acids, di- and/or polyols and, in the case of the polyesterimides, of building blocks containing imido groups, hydroxyl groups and carboxyl groups, and, on the other hand, of comonomers which react with the alpha,beta-unsaturated dicarboxylic acid units o~ the base resin and can lead to thermosetting plastics. A preferred comonomer is styrene, which, owing to its good dissolution properties, is also used for establishing the processing viscosity. Stated comonomers are completely copolymerized during curing under suitable conditions. Such a solvent-free system is re~erred to as an impregnating resin. As in the case of the impregnating lacquers too, the vapor pressures of the comonomers at application temperature result in evaporation losses, which, however, are generally less than in the case of solvent-containing systems (50~, based on the amount of solvent used, evaporation loss -in the case of solvent-containing impregnating lacquers, from 10 to 30~ evaporation loss in the case of impregnating resins). Nevertheless, expensive purification of the waste air is required even with the use of impregnating resins based on unsaturated polyesters, but such waste air plants can be designed to have lower purification capacities than when impregnating lacquers are used, since the monomer losses can be reduced by suitable resin formulations and process adaptations.
The use of other resin systems, such as, for example, epoxy resins, have the disadvantage that long curing times are required, that the possibilities for adapting the processing properties to the production processes without suffering serious deterioration in the dielectric properties are low, and that some resin components, such as, for example, the highly heat-stable cycloaliphatic types in the case of the epoxy resins or the amines in the case of the curing agents, may have high toxicity.
- Sulmnar~y of the invention The prior art discussed so far gives rise to the object of developing a steeping and impregnation process which combines the known advantages of impregnation with resin systems which can be cured by a free radical method with a low-emission impregnation and curing technology. ~or this purpose, it is necessary to use resins which either require no comonomers for curing or contain comonomers which have very low vapor pressures at the processing and curing temperature. Such comonomers must also still have sufficiently high reactivity in order to cure in times which are sufficiently short to be economically acceptable.
Moreover, neither the resins nor the comonomers may release significant amounts of cleavage products at the processing and curing temperatures. The comonomers usually used are not suitable for achieving these objects since, for reasons relating to the processibility of the resins, the comonomers must be in the liquid state. As liquids at room temperature and in particular at the processing and curing temperature, such comonomers, such as, for example, vinyl or allyl compounds, have considerable vapor pressures which lead CA 0223776~ 1998-0~-14 to substantial evaporation losses in the case of the comonomers.
Thus, suitable comonomers are solid or highly viscous at room temperature, as are the resins themselves, which are present at room temperature in a highly viscous, plastic, semicrystalline or crystalline state.
In this case, impregnation of the objects must be carried out at temperatures at which the resins or the mixtures of resins and comonomers are present in a low-viscosity and/or in a molten state.
The use of molten resin systems in electrical insulation technology is prior art. Such molten resin systems are used as solvent-free wire enamels, extrudable cable sheathing compounds, self-bonding enamels or coating materials. The use of systems which cure by a free radical method is the exception since, in the case of such highly reactive systems, the processibility is very limited owing to the unacceptably short pot life (time for which the resin is present in the processibl. state). A further object of the present invention was thus to achieve stabilization of the resin systems used at elevated CA 0223776~ 1998-0~-14 application temperatures without causing excessively long curing times and excessively high curing temperatures at which decomposition phenomena in the resins and damage to the materials to be impregnated may occur.
JP-A-53 05 97 91 describes polyesterimide resins having at least tribasic carboxylic acids and polyesterpolyols as monomer building blocks, which are prepared using amines and further amounts of at least tribasic carboxylic acids. Such polyesterimide resins are used in molten form as insulation coating materials for electrically conductive substrates. The coatings have good electrical and mechanical properties. No toxic vapors are released during the coating process.
DE-A-26 48 3S1 and DE-A-26 48 352 relate to injection moldable resin compositions which consist of from 10 to 50~ by weight of unsaturated polyester resin, and from 0.2 to 2~ by weight of organic peroxide and of inert filler. The unsaturated polyesters are composed of the building blocks polyols, ethylenically unsaturated dicarboxylic acid and saturated dicarboxylic acid. SUch resin compositions are used for electrical or CA 0223776~ 1998-0~-14 g electronic components, such as, for example, _ insulators, housings for low-voltage and medium-voltage switches, cable insulations and plugs.
DE-A-16 40 428 describes the use of annular elements of unsaturated polyester resins, which are coated with waxes for improving the blocking resistance. These annular elements are used for impregnating windings by a procedure in which they are placed on a winding head of the winding. On heating, the unsaturated polyester resin melts, penetrates into the winding and is cured there.
Common to the prior art processes is that they generally achieve only some of the abovementioned objects set for impregnating resins.
Surprisingly, a process for impregnating windings of electrical machines has been found, in which the impregnating resin used is a resin system A) cont~;n;ng A1) a resin which can be cured by a free radical method to give thermosetting plastics, CA 0223776~ 1998-0~-14 A2) at least one su1table curing agent and, if required, accelerator, A3) if required, ~urther comonomers and/or further polymers having ethylenically unsaturated groups capable of free radical polymerization, the vapor pressure of A3) at the impregnating and curing temperature being low, and A4) if required, further conventional additives, the resin system A) being highly viscous, plastic, semicrystalline or crystalline at room temperature and the resin system A) being converted in the impregnation process, by increasing the temperature to the impregnating temperature, into the low-viscosity liquid state, so that impregnation can be carried out by the known processes of immersion impregnation, flooding, immersed rotation, dripping or casting, if necessary supporting the impregnation by employing reduced pressure.
Preferably, the resin component A1) is selected from the group consisting of unsaturated polyesters, unsaturated polyesterimides, bismaleimides, oligomeric diallyl phthalates, comonomer-rree vinyl es~ers, comonomer-free vinyl ethers, comonomer-free vinylurethanes and/or polybutadiene resins, alone or in combinations with one another.
The resin component A1) selected from the group consisting of unsaturated polyesters, unsaturated polyesterimides and bismaleimides in combination with the resin component A3~ selected from the group consisting of oligomeric diallyl phthalates, divinylethyleneurea, divinylpropyleneurea, N-vinyl-carbazole, N-vinylpyrrolidone, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes, polyesters containing vinyl and/or allyl groups, or mixtures thereof, is particularly preferred.
Preferably used curing agents A2) are peroxides which form ~ree radicals, in particular organic peroxides, and/or compounds which form free radicals as a result o~ cleavage of a carbon-carbon bond. The resin systems A) are pa ticularly preferably delivered in the activated state as single-component resins; in special cases, activation may also be ef~ected immediately CA 0223776~ l998-0~-l4 before impregnation using s~i~able mixingjmetering means.
The substrates to be impregnated are preferably preheated before the impregnation to a temperature which is equal to or greater than the impregnating temperature. Preheating of the substrates to be impregnated is carried out, for example, by Joule heat, induction heating, microwave radiation or infrared radiation. Moreover, it is possible for the winding to be impregnated to be further heated by current but also in the state immersed in the resin, and this heating may serve to compensate the heat losses due to thermal conduction or to increase the w;n~;ng temperature further in order to cause gelling of the resin which is penetrated into the winding, prior to removal from the resin. This process is particularly suitable because the resin materials used are low-emission products and therefore have a very low vapor pressure and hence a 20 high flashpoint at the processing temperature, so that special explosion-proofing measures are not required.
The resin reaches the hig~ temperatures only in the winding and in the immediate environment of the winding.
CA 0223776~ 1998-0~-14 ~ The impregnation of the substrates is pre~erab;y carried out by immersion, flooding, immersed rotation, dripping or casting, impregnation being carried out at a reduced pressure at which the components A1) to A4) used still have a negligibly low vapor pressure. In the case of impregnation by immersion or flooding, the substrate may remain immersed until gelling of the resin system A) in the substrate has occurred.
After the impregnation with the resin systems, curing of the resin systems is carried out at a temperature which is above the temperature of the resin melt and which is generated, for example, by Joule heat, induction heating, microwave radiation, infrared radiation or passage through a conventional heating oven, if necessary the surface drying being supported by the action of high-energy radiation, such as, for example, W or electron radiation.
Detailed description The components of resin system A) CA 0223776~ l998-0~-l4 Preferably used as component A1) ar~: unsaturated polyester resins which may have building blocks containing imido groups, bismaleimide resins, oligomeric diallyl phthalates, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and/or polybutadiene resins. Unsaturated polyester resins are known. Unsaturated polyester resins containing imido groups are described, for example, in DE-A-15 70 273, DE-A-17 20 323 and DE-A-24 60 768.
Examples of building blocks of the unsaturated polyester resins in addition to the conventional polyester buildings blocks are: polyols cont~in;ng polymerizable double bonds, such as glycerol monoallyl ether, trimethylpropane monoallyl ether and pentaerythrityl mono- and diallyl ether, and polycarboxylic acids cont~;n;ng polymerizable double bonds, or anhydrides thereof, such as fumaric acid, tetrahydrophthalic acid or tetrahydrophthalic anhydride and preferably maleic acid or maleic anhydride, and monocarboxylic acids cont~;n;ng polymerizable double bonds, such as, for example, acrylic and/or methacrylic acid. As described, for example, in DE-A-24 60 768, for CA 0223776~ 1998-0~-14 modification of the properties of unsaturated polyes~er resins some of the unsaturated dicarboxylic acid may be replaced by saturated dicarboxylic acids, such as, for example, adipic acid, perhydrogenated isophthalic acid, phthalic acid, phthalic anhydride and/or dimerized fatty acids. Examples of suitable components A3) copolymerizable with the unsaturated polyesters or polyesters A1) cont~;n;ng imido groups are: diallyl phthalate prepolymers, divinylethyleneurea, divinyl-propyleneurea, N-vinylcarbazole, N-vinylpyrrolidone, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and polyesters which contain vinyl or allyl groups and which differ ~rom A1), such as, for example, polyesters composed of saturated and/or unsaturated polycarboxylic acids with pentaerythrityl mono-, di- and/or triallyl ether and optionally modi~ying glycols as monomer building blocks. At the impregnating and curing temperatures, the copolymerizable components A3) have vapor pressures which are 80 low that no signi~icant immissions can occur.
CA 0223776~ 1998-0~-14 Any desired low molecular weight bismaleimide may be used as bismaleimide component Al). Bismaleimides of the formula I
C) ~ O O
where Rl is an aliphatic, cycloaliphatic, araliphatic or aromatic radical and the stated radicals may have further functional groups, such as ether, ester, amido, carbamate, keto, sulfonyl or hydroxyl groups, are advantageously used. R1 is preferably a straight-chain alkylene radical having 2 to 20, in particular 2 to 10, carbon atoms or a 4,4'-diphenylmethane, 2,4-toluylene or 1,3- or 1,4-phenylene radical. Suitable bismaleimides are, for example, ethylenebismaleimide, butylenebismaleimide, hexamethylenebismaleimide, 4,4'-diphenylmethanebismaleimide, 2,4,-toluylenebismaleimide 20 [6iC] and 1,3-phenylenebismaleimide or mixtures thereof. Examples of suitable components A3) which are copolymeriza le with the bismaleimides Al) are:
oligomeric diallyl phthalates, divinylethyleneurea, divinylpropyleneurea, N-vinylcarbazole, comonomer-free CA 0223776~ 1998-0~-14 vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and polyesters which contain vinyl or allyl groups and which differ from Al), such as, for example, those composed of saturated and/or unsaturated polycarboxylic acids with pentaerythrityl mono-, di-and/or triallyl ether and optionally modifying glycols as monomer building blocks. At the impregnating and curing temperatures, the copolymerizable components A3) have vapor pressures which are so low that no significant immissions can occur.
Furthermore, the following may be used as component Al), alone or as a mixture with other components mentioned under Al): oligomeric diallyl phthalates, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes and/or polybutadiene resins.
Depending on resin system A), known peroxides having suitable decomposition temperatures or compounds which undergo thermal decomposition with formation of hydrocarbon radicals may be used as curing agent A2).
I~ necessary, compounds which accelerate the decomposition of the free radical initiators are CA 0223776~ l998-OS-l4 additionally present. It is essential to the inventionthat a significant free radical stream which effects curing of the resin system A) is produced by the curing agent A2) only at above the impregnating temperatures.
Examples of peroxides A2) which undergo significant decomposition into free radicals only at above the impregnating temperature are commercial organic peroxides, such as tert-butyl perbenzoate, tert-butyl perisononanoate or tert-butyl peroctoate, or peroxides in combination with accelerators, such as benzoyl peroxides in combination with tertiary amines or peresters with cobalt salts of organic acids.
Benzopinacol, substituted succinic acid derivatives and, preferably, silyl ethers of substituted ethylene glycols, as described, ~or example, in DE-A-26 32 294, may be mentioned as examples o~ curing agents A2) which undergo decomposition with formation of hydrocarbon radicals. Such silyl ethers according to DE-A-26 32 294 undergo partial decomposition into free radicals only at relatively high temperatures and, under certain circumstances, are very substantially stable even at temperatures above 80 degrees C in the res.~ system A) to be polymerized.
CA 0223776~ 1998-0~-14 For stabilization against premature curing, the resin systems A) may contain, as a constituent of component A4), stabilizers known per se for compounds capable of free radical polymerization, such as, for example, quinones, hydroquinones, sterically hindered phenols and/or sterically hindered amines and nitro compounds.
The conventional processing assistants for coating resins, such as, for example, surface-active or interface-active substances for improvin~ the leveling and the penetrating power, viscosity-influencing additives, such as pyrogenic silica or bentonites, and mineral or organic fillers, may be present as further constituents of component A4), which may or may not be present.
Impregnation and curing The impregnation of the substrates, for example the windings of electrical machines, is carried out using the resin systems A) according to the invention, consisting of the components A1), A2) and, if required, A3) and A4), in the melt of A) at temperatures which are below the curing temperature.
CA 0223776~ 1998-0~-14 The processing times of the resin systems A) are such that impregnation by the prior art processes are [sic]
possible. Examples of such impregnation processes are:
5 - impregnation of the substrate to be impregnated, which is optionally preheated, by immersion in the melt of the resin system A), retention of the substrate to be impregnated in the melt, until the resin melt has reached all parts to be impregnated, if necessary until gelling of the resin which has penetrated into the substrate, removal and shaking the drips off the impregnated substrate and subsequent curing of the absorbed resin system A), where heating of the object by means of Joule heat in the immersed state need not be interrupted, so that heat losses in the winding which occur as a result of thermal conduction can be compensated or the residence time until possible gelling under resin can be reduced by increasing the winding te,.,perature during immersion, - dripping o~ the melt of the resin system A) onto the substrate to be impregnated, the melt of the _ CA 0223776~ l998-0~-l4 resin sys~em A) ~eing dripped by means of suitable pumps onto the optionally preheated substrate, the curing agent A2), if required, being metered in by suitable mixing/metering apparatuses before the melt comprising A1 and, if required A3 and A4 is dripped on, or the resin system A) already being activated beforehand by addition of the curing agent A2, 10 - flooding with the melt of the resin system A), the optionally preheated substrate being flooded by a rising bath of activated melt of the resin system A) in such a way that sufficient impregnation of the substrate takes place, subsequently blowing off the melt of the resin system A), if required until gelling of the resin which has penetrated into the substrate, allowing the substrate to drip off and then curing the melt of the resin system A) absorbed by the substrate, where heating of the object by means of Joule heat in the immersed state need not be interrupted, so that heat losses in th winding which occur as a result of thermal conduction can be compensated or the residence time until possible gelling under resin can be CA 02237765 1998-0~-14 reduced by increasing the winding temperature during immersion, - immersed rotation with the melt of the resin system A), the optionally preheated substrate being rotated through the activated melt of the resin system A) in such a way that, in the case of windings of electrical machines as the substrate, only the winding or that part of the substrate carrying the winding is covered by the melt of the resin system A), until sufficient impregnation of the winding has occurred, and subsequent curing of the melt absorbed by the substrate (by the winding), preferably with rotation, where heating of the object by means of Joule heat during rotation need not be interrupted, 80 that heat losses in the winding which occur as a result of thermal conduction can be compensated or the residence time until possible gelling under resin can be reduced by increasing the winding temperature during rotation, and - casting of the substrates in reusable or captive form with a preactivated resin system A) or, with CA 0223776~ 1998-0~-14 the use of a suitable mixing/metering system, by m; ~; ng the curing agent A2) with the resin components Al and, if required, A3) and A4) immediately before casting.
The abovementioned impregnation processes can be carried out for improving the impregnation quality, preferably under reduced pressure or with alternating reduced pressure and superatmospheric pressure. The object can be preheated here too, heating of the winding by means of Joule heat during casting leading to a further reduction of viscosity, with the result that penetration into the winding is facilitated.
Gelling of the resin which has penetrated into the winding by increasing the temperature has the advantage that the volu~e shrinkage due to curing is compensated by further flow of the liquid resin from regions outside the w; n~; ng region.
The preheating of the substrates can be carried out, for example, by Joule heat (heating by electrical resistance), induction heating, microwav heating or infrared heating and by passage through a conventional heating oven.
CA 0223776~ l998-0~-l4 The curing of the resin system A) adhering to the substrate after the impregnation can be carried out, for example as in the case of the preheating of the substrates by Joule heat, induction heating, microwave heating or infrared heating and by passage through a conventional heating oven; and the curing at the substrate surface can optionally be supported by additional irradiation, for example by means of IR, W
or electron radiation.
The immissions occurring during curing are assessed as follows:
amounts as equal as possible of activated resin system 15 A) are introduced into a sample tray o~ a TGA
(Thermo~ravimetric Analysis) apparatus, and a constant air stream is passed over. Heating is then effected to the required curing temperature at a predetermined heating rate, and this temperature is then kept constant ~or the time required for curing. During this time, the loss of mass of the resin system A) was determined. In the case of conventional systems, containing unsaturated polyester resins and low molecular weight comonomers, the loss of mass during a CA 0223776~ l998-0~-l4 ~ heating time of 10 mlnu es to the curing temperature of 140 degrees C and a curing time of 1 hour at 140 degrees C is about 30~ by weight.
The Examples which follow are intended to illustrate the invention further. All stated percentages are by weight, unless stated otherwise.
Example~
Example 1:
An unsaturated polyesterimide A1) according to Example 2 of DE-C-24 60 768, composed of maleic anhydride, 15 neopentylglycol, trishydroxyisocyanurate and the reaction product of tetrahydrophthalic anhydride and monoethanolamine is mixed with lO~ by weight, based on the resin system A), of diallyl phthalate oligomer A3) (type Ftalidap 27, manufacturer Alusuisse) in the melt.
2~ by weight, based on the resin system A), o~
benzopinacol silyl ether (type Initiator BK, manufacturer Bayer AG) were admixed as curing agent A2). The resin system A) has an almost solid consistency at room temperature and a viscosity o~
1300 mPa.s at 80 degrees C. Ihe pot life Gf the resin system A) is 210 minutes at 80 degrees C, and the gelling time is 27 minutes at 140 degrees C. The stator of an electric motor, which was preheated to 120 degrees C in the heating oven, is slowly immersed in the molten resin system A) heated to 80 degrees C.
The stator re~; n~ in the molten resin system A) until no further bubbles rise. The stator is then slowly withdrawn and is allowed to drip off for about 2 minutes, and the resin system A) is then cured by heating in an oven at 160 degrees C for 30 minutes.
A~ter curing, the winding of the stator is suf~iciently stable. After the winding is sawn open, the stator shows adequately thorough impregnation. The thermogravimetrically determined loss of mass during heating in the TGA apparatus to 160 degrees C in 10 minutes and maintaining the temperature at 160 degrees C ~or 30 minutes is 3.4~ by weight, based on the resin system A).
Ex~ple 2:
CA 0223776~ l998-0~-l4 The unsaturated polyesterimide A1) according to Example 1 is mixed in a ratio of 2:1 with a polyester A3) which was prepared from 2 mol of pentaerythrityl triallyl ether, 4 mol of adipic acid and 3 mol of pentaerythrityl diallyl ether by condensation in the melt, and the resulting mixture is mixed with 2~ by weight, based on the resin system A), according to Example 1 tsic]. The mixture has a plastic consistency at room temperature and a viscosity of 570 mPa.s at 100 degrees C. The pot life of the resin system A) with 1~ by weight, based on the resin system A), of tert-butyl perbenzoate as an additional curing component A2), is 210 minutes at 100 degrees C, and the gelling time is 10 minutes at 160 degrees C. The stator of an electric motor, which was preheated to 120 degrees C in a heating oven, is slowly immersed in the molten resin system A) heated to 100 degrees C. The stator remains in the molten resin system A) until no further bubbles rise. The stator is then slowly withdrawn and is allowed to drip off for about 2 minutes, and the resin system A) is then cured by heating in an oven at 160 degrees C for 30 minut 3. After curing, the winding of the stator is sufficiently stable. A~ter the winding is sawn open, the stator shows su~ficiently thorough CA 0223776~ 1998-0~-14 impregnation. The thermogravimetrically determined loss of mass during heating in the TGA apparatus to 160 degrees C in 10 minutes and maint~;ning of the temperature at 160 degrees C for 30 minutes is 2.3~ by weight, based on the resin system A).
Example 3:
A monomer-free vinyl ester A1) (type Palatal A430-01, monomer-free, manufacturer BASF AG), which is solid at room temperature and has a viscosity of 500 mPa.s at 100 degrees C, is melted in the storage container of a conventional dripping apparatus. After ~m; ~; ng 1~ by weight, based on the total resin system A), of tert-butyl perbenzoate as curing agent A2) by means of aconventional mixing/metering head, the resin system A) prepared in this manner is dripped onto an armature whose winding had been heated to 140 degrees C by Joule heat. The resin system A) is cured at 140 degrees C in 20 the course of 15 minutes. After curing, the winding is sufficiently stable. After the winding is sawn open, it shows sufficiently thorough impreg ~tion. The thermogravimetrically determined loss of mass during heating in the TGA apparatus at 140 degrees C in 10 minutes and maintaining of the temper~ture at 140 degrees C for 15 minutes is 1.4~ by weight, based on the resin system A).
Claims (13)
1. Process for impregnating substrates, in particular windings of electrical machines, with resin systems A) which can be cured by a free radical method, characterized in that the resin system A) is composed of:
A1) a resin which can be cured by a free radical method to give thermosetting plastics, A2) at least one suitable curing agent and, if required, accelerator, A3) if required, further comonomers and/or polymers having ethylenically unsaturated double bonds capable of free radical polymerization, the vapor pressure of A3) at the impregnating and curing temperature being low, and A4) if required, further conventional additives, that the resin system A) is highly viscous, plastic, semicrystalline or crystalline at room temperature and that the resin system A) has a low viscosity at the impregnating temperature.
A1) a resin which can be cured by a free radical method to give thermosetting plastics, A2) at least one suitable curing agent and, if required, accelerator, A3) if required, further comonomers and/or polymers having ethylenically unsaturated double bonds capable of free radical polymerization, the vapor pressure of A3) at the impregnating and curing temperature being low, and A4) if required, further conventional additives, that the resin system A) is highly viscous, plastic, semicrystalline or crystalline at room temperature and that the resin system A) has a low viscosity at the impregnating temperature.
2. Process for impregnation according to Claim 1, characterized in that the resin component A1) is selected from the group consisting of unsaturated polyesters, unsaturated polyesterimides, bismaleimides, oligomeric diallyl phthalates, comonomer-free vinyl ethers, comonomer-free vinyl esters, comonomer-free vinylurethanes, polybutadiene resins and/or mixtures thereof, and the unsaturated polyesters and unsaturated polyesterimides may contain copolymerizable vinyl and/or allyl groups.
3. Process for impregnation according to Claim 2, characterized in that the resin component A1) is selected from the group consisting of unsaturated polyesters, unsaturated polyesterimides and bismaleimides and that the resin component A3) is selected from the group consisting of oligomeric diallyl phthalates, divinylethyleneurea, divinylpropyleneurea, N-vinylcarbazole, N-vinyl-pyrrolidone, comonomer-free vinyl esters, comonomer-free vinyl ethers, comonomer-free vinylurethanes, polyesters containing vinyl and/or allyl groups, or mixtures thereof.
4. Process for impregnation according to any of Claims 1 to 3, characterized in that the curing component A2) is an organic peroxide and/or a compound which gives free radicals as a result of cleavage of one or more carbon-carbon bonds.
5. Process for impregnation according to any of Claims 1 to 4, characterized in that the resin systems A) are either delivered in the activated state or activated immediately before the impregnation step by addition of the curing component A2).
6. Process for impregnation according to any of Claims 1 to 5, characterized in that, before the impregnation, the substrates to be impregnated are preheated to a temperature which is equal to or greater than the temperature of the melt of the resin system.
7. Process for impregnation according to Claim 6, characterized in that the preheating of the substrates is carried out by Joule heat, induction heating, microwave radiation, infrared radiation or by passage through a conventional heating oven.
8. Process for impregnation according to any of Claims 1 to 7, characterized in that the impregnation of the substrates is carried out by simple immersion, by flooding, by immersed rotation, by dripping or by casting in or with the melt of the resin system A), where heating of the substrate during the impregnation process need not be interrupted
9. Process for impregnation according to any of Claims 1 to 8, characterized in that, in the case of impregnation by immersion or flooding, possibly with heating during the impregnation process, the substrate remains in the resin system A) until the resin contained in the substrate has gelled.
10. Process for impregnation according to any of Claims 1 to 9, characterized in that, after the impregnation step, curing of the melt of the resin system A) present in the substrate is carried out by Joule heat, induction heating, microwave radiation, infrared radiation, by passage through a conventional heating oven, at a temperature which is higher than the temperature of the melt of the resin system A).
11. Process for impregnation according to Claim 10, characterized in that the curing of the melt of the resin system A) present in the substrate is additionally supported by the action of high-energy radiation for surface drying.
12. Use of the process for impregnating substrates according to any of Claims 1 to 11 for electrically conductive substrates.
13. Use of the process according to Claim 12 for windings of electrical machines.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19542564.2 | 1995-11-15 | ||
| DE1995142564 DE19542564A1 (en) | 1995-11-15 | 1995-11-15 | Process for the impregnation of electrically conductive substrates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2237765A1 true CA2237765A1 (en) | 1997-05-22 |
Family
ID=7777522
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2237765 Abandoned CA2237765A1 (en) | 1995-11-15 | 1996-10-19 | Process for impregnating electrically conducting substrates |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0880785A1 (en) |
| JP (1) | JP2000500289A (en) |
| BR (1) | BR9611459A (en) |
| CA (1) | CA2237765A1 (en) |
| DE (1) | DE19542564A1 (en) |
| HR (1) | HRP960540A2 (en) |
| PL (1) | PL326654A1 (en) |
| TW (1) | TW319719B (en) |
| WO (1) | WO1997018567A1 (en) |
| YU (1) | YU60196A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10501656B2 (en) | 2011-08-09 | 2019-12-10 | Elantas Gmbh | Solvent-free wire enamel composition |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19648134A1 (en) * | 1996-11-21 | 1998-05-28 | Beck & Co Ag Dr | Process for impregnating components |
| DE19648133A1 (en) * | 1996-11-21 | 1998-05-28 | Beck & Co Ag Dr | Process for impregnating components |
| DE19711410A1 (en) | 1997-03-19 | 1998-09-24 | Beck & Co Ag Dr | Impregnating, casting and coating compounds for electrotechnical and / or electronic components and for carrier materials for flat insulating materials |
| US7096566B2 (en) | 2001-01-09 | 2006-08-29 | Black & Decker Inc. | Method for making an encapsulated coil structure |
| US7814641B2 (en) | 2001-01-09 | 2010-10-19 | Black & Decker Inc. | Method of forming a power tool |
| FR2910012B1 (en) * | 2006-12-15 | 2009-03-06 | Cray Valley S A Sa | UNSATURATED POLYESTERS RESINS FUNCTIONALIZED BY UNSATURATED CYCLOALIPHATIC IMIDES, FOR COATINGS AND MOLDING COMPOSITIONS |
| DE102009045200B4 (en) * | 2009-09-30 | 2021-02-11 | Inter-Consult Gmbh | Method and device for processing components of electrical machines |
| JP5500358B2 (en) * | 2010-04-22 | 2014-05-21 | 日立化成株式会社 | Resin composition for electrical insulation and electrical equipment using the composition |
| DE102010060515B4 (en) * | 2010-11-12 | 2016-01-21 | Gottlob Thumm Maschinenbau Gmbh | Impregnating plant with a cleaning device |
| DE202010017440U1 (en) * | 2010-11-12 | 2011-11-10 | Gottlob Thumm Maschinenbau Gmbh | Impregnating plant with a cleaning device |
| DE102011078592B4 (en) * | 2011-07-04 | 2013-07-25 | Siemens Aktiengesellschaft | Superconducting coil assembly and method for its production |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59221360A (en) * | 1983-05-31 | 1984-12-12 | Mitsubishi Electric Corp | Unsaturated polyester varnish composition |
| US4554470A (en) * | 1984-06-08 | 1985-11-19 | Westinghouse Electric Corp. | Polybutadiene VPI resin |
| JPH03105902A (en) * | 1989-09-20 | 1991-05-02 | Hitachi Ltd | Superconducting coil |
| JP2964530B2 (en) * | 1990-03-20 | 1999-10-18 | 日本曹達株式会社 | Curable resin composition |
| DE4140738A1 (en) * | 1991-12-11 | 1993-06-17 | Herberts Gmbh | CURABLE DIMENSIONS, METHOD FOR THE PRODUCTION THEREOF AND THE USE THEREOF FOR FIXING DEVELOPED GOODS |
| DE4331086A1 (en) * | 1993-09-11 | 1995-03-16 | Herberts Gmbh | Process for the fixation of wound goods with radically polymerizable masses |
-
1995
- 1995-11-15 DE DE1995142564 patent/DE19542564A1/en not_active Withdrawn
-
1996
- 1996-10-19 EP EP96934760A patent/EP0880785A1/en not_active Withdrawn
- 1996-10-19 CA CA 2237765 patent/CA2237765A1/en not_active Abandoned
- 1996-10-19 PL PL32665496A patent/PL326654A1/en unknown
- 1996-10-19 BR BR9611459A patent/BR9611459A/en not_active Application Discontinuation
- 1996-10-19 JP JP9518528A patent/JP2000500289A/en active Pending
- 1996-10-19 WO PCT/EP1996/004552 patent/WO1997018567A1/en not_active Application Discontinuation
- 1996-10-23 TW TW85113011A patent/TW319719B/zh active
- 1996-11-13 YU YU60196A patent/YU60196A/en unknown
- 1996-11-14 HR HRP960540 patent/HRP960540A2/en not_active Application Discontinuation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10501656B2 (en) | 2011-08-09 | 2019-12-10 | Elantas Gmbh | Solvent-free wire enamel composition |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0880785A1 (en) | 1998-12-02 |
| JP2000500289A (en) | 2000-01-11 |
| HRP960540A2 (en) | 1997-12-31 |
| BR9611459A (en) | 1999-02-17 |
| WO1997018567A1 (en) | 1997-05-22 |
| DE19542564A1 (en) | 1997-05-22 |
| PL326654A1 (en) | 1998-10-12 |
| YU60196A (en) | 1998-08-14 |
| TW319719B (en) | 1997-11-11 |
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