CA1168857A - Corona-resistant resin compositions - Google Patents
Corona-resistant resin compositionsInfo
- Publication number
- CA1168857A CA1168857A CA000357082A CA357082A CA1168857A CA 1168857 A CA1168857 A CA 1168857A CA 000357082 A CA000357082 A CA 000357082A CA 357082 A CA357082 A CA 357082A CA 1168857 A CA1168857 A CA 1168857A
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- corona
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- micron
- alumina
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L101/00—Compositions of unspecified macromolecular compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
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- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Organic Insulating Materials (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A corona-resistant resin composition comprises an epoxy resin, ester imide, unsaturated polyester, other resin or a thermplastic film containing 5% to about 40%
by weight of a dissolved organosilicate or dissolved organoaluminate or dispersed silica or dispersed alumina particles of a finite size less than about 0.1 micron. A
method of providing corona-resistant insulation for an electrical conductor employs the above composition.
A corona-resistant resin composition comprises an epoxy resin, ester imide, unsaturated polyester, other resin or a thermplastic film containing 5% to about 40%
by weight of a dissolved organosilicate or dissolved organoaluminate or dispersed silica or dispersed alumina particles of a finite size less than about 0.1 micron. A
method of providing corona-resistant insulation for an electrical conductor employs the above composition.
Description
This invention relates to corona-resistant resins and films and to electrical insulation systems wherein such corona-resistant resins and films are used.
Resin compositions are generally understood to be relatively low molecular weight materials that, on heating or addition of hardener, are converted to high-molecular weight solids having useful properties.
These materials are known as thermosetting materials, Another general class of polymeric (that is, plastic) materials is understood to be thermoplastic. These thermoplastic materials are generally handled in their high-molecular weight state. Thermoplastic materials exhibit good solutility in solvents, while cured thermosetting resins are insoluble. Many thermoplastic materials also soften but do not flow when heated.
Both cured thermosetting resins and thermoplastic films are employed as dielectric materials, Accordingly, as used herein and in the appended claims the term polymeric material refers to both thermosetting resins and to thermoplastic films.
However, dielectric materials used as insulators for electrical conductors may fail as a result of corona occurring when the conductors and dielectrics are 3L 16~7 subjected to voltages above the corona starting voltage. This type of failure may occur for example in certain electric motor applications. Corona induced failure is particularly likely when the insulator material is a solid organic polymer. Improved dielectric materials having resistance to corona discharge~induced deteriora-tion would therefore be highly desirable. For some applications, mica-based insulation systems have been used as a solution to the problem, whereby corona resistance is offered by the mica. Because of the poor physical properties inherent in mica, however, this solution has been less than ideal.
Solid, corona-resistant dielectric materials are particularly needed for high-voltage apparatus having open spaces in which corona discharges can occur. This is especially true when the space is over approximately 1 mil in thickness and is located between the conductor and the dielectric, or when there is a void located in the dielectric material itself. The service life of the dielectric is much shorter when these gaps or spaces are present.
Resins containing a minor amount of organo-metallic compound of either silicon, germanium, tin, lead, phosphorus, arsenic, antimony, bismuth, iron, ruthenium or nickel are disclosed by McKeown (U. S. Patent 3,577,346) as having improved corona resistance. Corona lives of up to four hundred times that of polymers without the organometallic 885~
additive are disclosed. There is no mention, however, of the use of organosilicates or organoaluminates.
A composition having anti-corona properties is disclosed, by DiGiulio et al, in U. S. Patent 3,228,883, to consist of a mixture of ethylene-alpha-oleEin copolymer, a homo- or copolymer covulcanizable therewith and a non-hygroscopic mineral filler, such as zinc, iron, aluminum or silicon oxide. However, there is no appreciation whatsoever in this patent that the use of submicron-sized alumina or silica particles is necessary to achieve significant improvement in corona resistance. See tables below.
A molded epoxy resin composition which contains alumina and silica is disclosed by Linson, in U. S. Patent 3,645,899, as having good weathering and erosion resistance, but appears to have no particular resistance to corona breakdown.
Epoxy resins containing significant amounts of reactive organosiloxane derivatives are disclosed by Markovitz in U. S. Patents 3,496,139 and 3,519~670.
However, these materials are less than ideal since their high reactivity results in a diminished shelf-life, a characteristic often of considerable importance. Moreover, the amine silicones in the 3,496,139 patent are polysiloxanes which are made from difunctional and trifunctional silicones, that is, the silicon atoms have either two Si-O bonds and two Si-C bonds, or three Si-O bonds and a single Si-C bond.
This is in distinct contrast to the present invention which, as seen below, employs silicates and aluminates, both of which exhibit tetrafunctional bonding with oxygen atoms.
~ ~ 6 ~ 7 Epoxy resins containing metal acetylacetonates in amounts below 5% by weight are disclosed in U. S.
Patent 3,812,214, but these resins have no corona-resistant properties.
Polymeric resins containing silica and talc as fillers appear to be disclosed in U. S. Patent 3,7A2,084 issued June 26, 1973 to Olyphant et al. However, there is no appreciation that submicron particle sizes are critical for improved corona resistance when silica is employed.
Likewise, resins containing submicron silicon appear to be disclosed in U. S. Patent 4,102,851 issued July 25, 1978 to Luck et al. ~owever, silica is added only as a thixotropic agent and there is no appreciation or concern with corona-resistant properties.
Polyethylene resin with various fillers, including alumina and silica, appears to be disclosed in U. S. Patent
Resin compositions are generally understood to be relatively low molecular weight materials that, on heating or addition of hardener, are converted to high-molecular weight solids having useful properties.
These materials are known as thermosetting materials, Another general class of polymeric (that is, plastic) materials is understood to be thermoplastic. These thermoplastic materials are generally handled in their high-molecular weight state. Thermoplastic materials exhibit good solutility in solvents, while cured thermosetting resins are insoluble. Many thermoplastic materials also soften but do not flow when heated.
Both cured thermosetting resins and thermoplastic films are employed as dielectric materials, Accordingly, as used herein and in the appended claims the term polymeric material refers to both thermosetting resins and to thermoplastic films.
However, dielectric materials used as insulators for electrical conductors may fail as a result of corona occurring when the conductors and dielectrics are 3L 16~7 subjected to voltages above the corona starting voltage. This type of failure may occur for example in certain electric motor applications. Corona induced failure is particularly likely when the insulator material is a solid organic polymer. Improved dielectric materials having resistance to corona discharge~induced deteriora-tion would therefore be highly desirable. For some applications, mica-based insulation systems have been used as a solution to the problem, whereby corona resistance is offered by the mica. Because of the poor physical properties inherent in mica, however, this solution has been less than ideal.
Solid, corona-resistant dielectric materials are particularly needed for high-voltage apparatus having open spaces in which corona discharges can occur. This is especially true when the space is over approximately 1 mil in thickness and is located between the conductor and the dielectric, or when there is a void located in the dielectric material itself. The service life of the dielectric is much shorter when these gaps or spaces are present.
Resins containing a minor amount of organo-metallic compound of either silicon, germanium, tin, lead, phosphorus, arsenic, antimony, bismuth, iron, ruthenium or nickel are disclosed by McKeown (U. S. Patent 3,577,346) as having improved corona resistance. Corona lives of up to four hundred times that of polymers without the organometallic 885~
additive are disclosed. There is no mention, however, of the use of organosilicates or organoaluminates.
A composition having anti-corona properties is disclosed, by DiGiulio et al, in U. S. Patent 3,228,883, to consist of a mixture of ethylene-alpha-oleEin copolymer, a homo- or copolymer covulcanizable therewith and a non-hygroscopic mineral filler, such as zinc, iron, aluminum or silicon oxide. However, there is no appreciation whatsoever in this patent that the use of submicron-sized alumina or silica particles is necessary to achieve significant improvement in corona resistance. See tables below.
A molded epoxy resin composition which contains alumina and silica is disclosed by Linson, in U. S. Patent 3,645,899, as having good weathering and erosion resistance, but appears to have no particular resistance to corona breakdown.
Epoxy resins containing significant amounts of reactive organosiloxane derivatives are disclosed by Markovitz in U. S. Patents 3,496,139 and 3,519~670.
However, these materials are less than ideal since their high reactivity results in a diminished shelf-life, a characteristic often of considerable importance. Moreover, the amine silicones in the 3,496,139 patent are polysiloxanes which are made from difunctional and trifunctional silicones, that is, the silicon atoms have either two Si-O bonds and two Si-C bonds, or three Si-O bonds and a single Si-C bond.
This is in distinct contrast to the present invention which, as seen below, employs silicates and aluminates, both of which exhibit tetrafunctional bonding with oxygen atoms.
~ ~ 6 ~ 7 Epoxy resins containing metal acetylacetonates in amounts below 5% by weight are disclosed in U. S.
Patent 3,812,214, but these resins have no corona-resistant properties.
Polymeric resins containing silica and talc as fillers appear to be disclosed in U. S. Patent 3,7A2,084 issued June 26, 1973 to Olyphant et al. However, there is no appreciation that submicron particle sizes are critical for improved corona resistance when silica is employed.
Likewise, resins containing submicron silicon appear to be disclosed in U. S. Patent 4,102,851 issued July 25, 1978 to Luck et al. ~owever, silica is added only as a thixotropic agent and there is no appreciation or concern with corona-resistant properties.
Polyethylene resin with various fillers, including alumina and silica, appears to be disclosed in U. S. Patent
2,888,424 issued May 26, 1959 to Precopio et al. But again, there is no concern or appreciation of corona-resistant properties; the fillers, including such counterproductive materials for corona properties as carbon black, are added only to improve mechanical properties.
Resins containing submicron silica also appear to be disclosed in U. S. Patent 3r697,467 issued October 10, 1972 to Haughney. Like the patent to Luck et al., however, this patent discloses no appreciation or concern for corona-resistant properties.
Thus, there is a continuing need for corona-resistant materials which are easily fabricated for use as electrical insulation and a further need for additives which can convert dielectric materials susceptible to 1 16~
corona damage to corona-resistant materials. Accordingly, it is the principal object o~ the present invention to provide a corona-resistant resin, useful in various electrical insulation forms to satisfy these long-felt needs.
Summary of the Invention The present invention provides a corona-resistant resin composition containing a polymeric material and an additive thereto of approximately 5~ to approximately ~0%
by weight of either an organosilicate or organoaluminate compound, or submicron-sized particles of either alumina or silica. The additives are characterized by the common inclusion of either aluminum or silicon and, preferably, in that the aluminum and silicon are atomically bound only with oxygen. Either conventional or epoxy resins may be used in the invention, with, in the case of epoxy resins, the organo compounds serving also as reactive curing agents.
Likewise, the polymeric material also includes thermo-plastic film. Compositions containing the organoaluminate or organosilicate compounds are homogeneous, solution-type compositions whereas those containing silica or alumina particles are formed with the particles substantially uniformly disposed throughout the resin. The silica and alumina particles are preferably less than about 0.1 micron in size. Similarly, a method of providing corona-resistant insulation for an e-ectrical conductor employs the above-mentioned composition.
In accordance with this invention, the corona-resistant resin can be used to coat conductors or conductor wires or to impregnate laminated electrical insulating, thus 1 ~68~r~
providing superior electrical insulating systems.
Brief Description of the Drawing The drawing is a schematic representation of the needle point corona test apparatus used to evaluate resin compositions formulated according both to the presenk invention and to conventional resin compositions so that corona resistance can be assessed and compared.
Detailed Description of the Invention Resins useful for the practice of this invention include, for example, epoxy resins, polyester resins, and ester-imide resins. Epoxy resins formulated according to the invention require a curing agent as is the usual case with such resins. Useful thermoplastic films for the present invention include both polyamide films and polyimide films, such as Kapton(R). These films are used in their high-molecular weight state and do not require curing.
Typical of epoxy resins which can be used are resins based on bisphenol-A diglycidyl ether, epoxy novolac resins, cycloaliphatic epoxy resins, diglycidyl ester resins, glycidyl ethers of polyphenols and the like. These resins preferably have an epoxy equivalent weight of the order of 130-1500. Such resins are well known in the art and are described, for example, in many patents including 2,324,483;
2,444,333; 2,494,295; 2,500,600; and 2,511,913.
Catalytic hardeners, or curing agents, for the epoxy type resins, include aluminum acetylacetonate, aluminum di-sec-butoxide acetoacetic ester chelate or tetraoctylene glycol titanate in combination with phenolic accelerators, including resorcinol, catechol or hydroquinone and the corresponding dihydroxynaphthalene compounds. Compositions 1 ~6~85~
of this type have been described in 3,776,978 and 3,812,214.
In the present invention, the organoaluminate catalysts can also serve as the reactive organoaluminum compound, but they are used in much higher amounts khan heretofore disclosed in order to produce the corona-resistant product.
Also useful as curing agents for epoxy resins in the practice of this invention are polyester-polyacid resins, especially those with an acid number of 200-500. Those preferred have an acid number of 300-400.
Ester-imide resins useful in the practice of this invention include those used to coat magnet wire.
Examples of compositions which may be used are disclosed in U. S. Patents 3,426,098 and 3,697,471.
Organosilicate and organoaluminate compounds which can be used for the purposes of this invention include those compounds which are reactive toward epoxy groups of epoxy resins. The silicate and aluminate compounds are further characterized by containing only silicon-to-oxygen or aluminum-to-oxygen primary valence bonds. These compounds react to produce clear, hard resins containing Si-O or Al-O bonds throughout the body of the resin according to the structural formulas:
l 1 O-Si-O -O-Al-O-Typical of compounds which are useful for this purpose are the products of ethyl silicate (or any alkyl silicate) with ethanolamine or other alkanolamines, whereby an amino-functional organosilicate compound is produced. Organo-aluminate compounds which can be used are aluminum $ 7 acetylacetonate, aluminum di-sec-butoxide acetoacetic ester chelate, aluminum di-iso-propoxide acetoacetic ester chelate, aluminum iso-propoxide stearate acetoacetic ester chelate, aluminum tri-iso-propoxide or aluminum tri(sec-butoxide).
In the above-mentioned patent (3,496,139) issued to the present inventor, polysi:Loxanes are used in preparing the curing agents for the epoxy resins. However, in the present invention organosilicates are employed. Polysiloxanes are not organosilicates in which the silicon atoms exhibit only Si-O bonds. That ls to say, the organosilicates of the present invention are made from tetrafunctional silicones.
The epoxy resins cured by organosilicates are more strongly cross-linked than epoxy resins cured from polysiloxanes and therefore are better suited as corona-resistant compositions.
The organosilicate or organoaluminate can be used as the sole curing agent for the epoxy resin or can be used in combination with other known, typically used curing agents.
Eor example, the phenolic accelerators, such as catechol, are necessary to properly cure epoxy resins when aluminum acetylacetonate is employed as an additive/hardener.
Epoxy resins preferred in the present invention, include those cured by an organosilicate which is the reaction product of ethyl silicate and ethanolamine and those cured by an organoaluminate which is either aluminum acetylacetonate or aluminum di-sec-butoxide acetoacetic ester chelate and accelerated by a phenolic such as catechol.
Preferred polyester-imide resins include those modified by aluminum acetylacetonate.
In one embodiment of this invention, the 11688S ~ 17~.1Y 2870 corona-resistant composition comprises a conventional epoxy, or ester imide resin or other resin wherein there is dispersed alumina or silica particles of size less than about 0.1 micron. In this embodiment, the epoxy composition requires a curing agent specifically to set the resin. The curing system can be of any of the usual polyamines, polyacids, acid anhydrides, or catalytic curing agents commonly used to cure epoxy resins; or a phenolic such as resorcinol or catechol can be used as an accelerator with a catalytic hardener selected from reactive organoaluminum, organo-titanium, or organozirconium compound, of which tetraoctylene glycol titanate is typical as described in 3,776,978 and
Resins containing submicron silica also appear to be disclosed in U. S. Patent 3r697,467 issued October 10, 1972 to Haughney. Like the patent to Luck et al., however, this patent discloses no appreciation or concern for corona-resistant properties.
Thus, there is a continuing need for corona-resistant materials which are easily fabricated for use as electrical insulation and a further need for additives which can convert dielectric materials susceptible to 1 16~
corona damage to corona-resistant materials. Accordingly, it is the principal object o~ the present invention to provide a corona-resistant resin, useful in various electrical insulation forms to satisfy these long-felt needs.
Summary of the Invention The present invention provides a corona-resistant resin composition containing a polymeric material and an additive thereto of approximately 5~ to approximately ~0%
by weight of either an organosilicate or organoaluminate compound, or submicron-sized particles of either alumina or silica. The additives are characterized by the common inclusion of either aluminum or silicon and, preferably, in that the aluminum and silicon are atomically bound only with oxygen. Either conventional or epoxy resins may be used in the invention, with, in the case of epoxy resins, the organo compounds serving also as reactive curing agents.
Likewise, the polymeric material also includes thermo-plastic film. Compositions containing the organoaluminate or organosilicate compounds are homogeneous, solution-type compositions whereas those containing silica or alumina particles are formed with the particles substantially uniformly disposed throughout the resin. The silica and alumina particles are preferably less than about 0.1 micron in size. Similarly, a method of providing corona-resistant insulation for an e-ectrical conductor employs the above-mentioned composition.
In accordance with this invention, the corona-resistant resin can be used to coat conductors or conductor wires or to impregnate laminated electrical insulating, thus 1 ~68~r~
providing superior electrical insulating systems.
Brief Description of the Drawing The drawing is a schematic representation of the needle point corona test apparatus used to evaluate resin compositions formulated according both to the presenk invention and to conventional resin compositions so that corona resistance can be assessed and compared.
Detailed Description of the Invention Resins useful for the practice of this invention include, for example, epoxy resins, polyester resins, and ester-imide resins. Epoxy resins formulated according to the invention require a curing agent as is the usual case with such resins. Useful thermoplastic films for the present invention include both polyamide films and polyimide films, such as Kapton(R). These films are used in their high-molecular weight state and do not require curing.
Typical of epoxy resins which can be used are resins based on bisphenol-A diglycidyl ether, epoxy novolac resins, cycloaliphatic epoxy resins, diglycidyl ester resins, glycidyl ethers of polyphenols and the like. These resins preferably have an epoxy equivalent weight of the order of 130-1500. Such resins are well known in the art and are described, for example, in many patents including 2,324,483;
2,444,333; 2,494,295; 2,500,600; and 2,511,913.
Catalytic hardeners, or curing agents, for the epoxy type resins, include aluminum acetylacetonate, aluminum di-sec-butoxide acetoacetic ester chelate or tetraoctylene glycol titanate in combination with phenolic accelerators, including resorcinol, catechol or hydroquinone and the corresponding dihydroxynaphthalene compounds. Compositions 1 ~6~85~
of this type have been described in 3,776,978 and 3,812,214.
In the present invention, the organoaluminate catalysts can also serve as the reactive organoaluminum compound, but they are used in much higher amounts khan heretofore disclosed in order to produce the corona-resistant product.
Also useful as curing agents for epoxy resins in the practice of this invention are polyester-polyacid resins, especially those with an acid number of 200-500. Those preferred have an acid number of 300-400.
Ester-imide resins useful in the practice of this invention include those used to coat magnet wire.
Examples of compositions which may be used are disclosed in U. S. Patents 3,426,098 and 3,697,471.
Organosilicate and organoaluminate compounds which can be used for the purposes of this invention include those compounds which are reactive toward epoxy groups of epoxy resins. The silicate and aluminate compounds are further characterized by containing only silicon-to-oxygen or aluminum-to-oxygen primary valence bonds. These compounds react to produce clear, hard resins containing Si-O or Al-O bonds throughout the body of the resin according to the structural formulas:
l 1 O-Si-O -O-Al-O-Typical of compounds which are useful for this purpose are the products of ethyl silicate (or any alkyl silicate) with ethanolamine or other alkanolamines, whereby an amino-functional organosilicate compound is produced. Organo-aluminate compounds which can be used are aluminum $ 7 acetylacetonate, aluminum di-sec-butoxide acetoacetic ester chelate, aluminum di-iso-propoxide acetoacetic ester chelate, aluminum iso-propoxide stearate acetoacetic ester chelate, aluminum tri-iso-propoxide or aluminum tri(sec-butoxide).
In the above-mentioned patent (3,496,139) issued to the present inventor, polysi:Loxanes are used in preparing the curing agents for the epoxy resins. However, in the present invention organosilicates are employed. Polysiloxanes are not organosilicates in which the silicon atoms exhibit only Si-O bonds. That ls to say, the organosilicates of the present invention are made from tetrafunctional silicones.
The epoxy resins cured by organosilicates are more strongly cross-linked than epoxy resins cured from polysiloxanes and therefore are better suited as corona-resistant compositions.
The organosilicate or organoaluminate can be used as the sole curing agent for the epoxy resin or can be used in combination with other known, typically used curing agents.
Eor example, the phenolic accelerators, such as catechol, are necessary to properly cure epoxy resins when aluminum acetylacetonate is employed as an additive/hardener.
Epoxy resins preferred in the present invention, include those cured by an organosilicate which is the reaction product of ethyl silicate and ethanolamine and those cured by an organoaluminate which is either aluminum acetylacetonate or aluminum di-sec-butoxide acetoacetic ester chelate and accelerated by a phenolic such as catechol.
Preferred polyester-imide resins include those modified by aluminum acetylacetonate.
In one embodiment of this invention, the 11688S ~ 17~.1Y 2870 corona-resistant composition comprises a conventional epoxy, or ester imide resin or other resin wherein there is dispersed alumina or silica particles of size less than about 0.1 micron. In this embodiment, the epoxy composition requires a curing agent specifically to set the resin. The curing system can be of any of the usual polyamines, polyacids, acid anhydrides, or catalytic curing agents commonly used to cure epoxy resins; or a phenolic such as resorcinol or catechol can be used as an accelerator with a catalytic hardener selected from reactive organoaluminum, organo-titanium, or organozirconium compound, of which tetraoctylene glycol titanate is typical as described in 3,776,978 and
3,812,214.
Preferably, the alumina or silica has a particle size of from approximately 0.005 to approximately 0.05 micron, as may be obtained either by the gas phase hydrolysis of the corresponding chloride or other halide, or as may be obtained by precipitation. These oxides, when disposed within the polymer material, form chain-like particle networks. Those oxide particles useful in the present invention and formed from the gas phase are also known as fumed oxides. Typical of commerically available fumed oxides are those manufactured and sold by the Cabot Corporation under the trade marks Cabosil(R) (silica) or Alon(R) (alumina);
or those made and sold by Degussa, Inc., under the trade marks Aerosil(~) (silica) or Aluminum Oxide C(R) . Typical precipitated silicas which may be used include those manufactured and sold by the Philadelphia Quartz Co., under the trade mark Quso(R) or those of PPG Industries sold under the trade mark Lo-Vel(R) .
From approxlmately 5% to approximately 40~
by weight of organosilicate, organoaluminate, submicron silica or submicron alumina are used in the resin compositions of this invention, while loadings of 5% to approximately 30%
by weight are preferred.
Preferred compounds of the organoaluminate and organosilicates are those which are soluble and which contain only Si-O or Al-O primary valence bonds on the silicon or the aluminum as was mentioned ahove. The use of these compounds produces clear resins, in which organoaluminate or organosilicate compounds are dissolved, and thus homo-geneous with the resin.
As can be seen from the tables below the use of submicron particles is critical for the use of alumina and silica additives. Table I shows that polyimide films fail after an average of only 9 hours under the test conditions described herein and under the voltage stress shown. In stark contrast, the use of 20% dispersed alumina having an average particle size of approximately 0.020 microns produces average sample life in excess of 2776 hours. The use of 40% finely ground alumina having a particle size in excess of one micron produced better results than no additive but significantly worse results than the submicron sample.
TAsLE I
Stress Hours to Fail Aver-Sample Volts/Mil for Various Samples age Polyimide film 250 7, 8, 13 9 Polyimide film with 250 2187, 3071-~, 3071+ 2776 20% alumina of 0.020 micron size Polyimide film with 208 78, 130, 513, 310 258 40% alumina of greater than 1 micron size 8 ~ 7 The ~1+11 sign in the tables indicates that the sample had still not failed at the time the data was taken.
Similar results are obtained with the use of a polyamide film with submicron alumina. These are summariæed 5in Table II below:
TA~LE IX
Stress Hours to Fail Aver-Sample Volts/Mil for Various Samples age -Polyamide film 250 - 10 Polyamide film with 250 629+, 629-~, 629~ 629-~
20% alumina of 0.020 micron size 357 629+, 629+, 629+ 629+
The particles are disposed within the film material by con-ventional manufacturing methods prior to transformation to the high-molecular weight state.
Like results are obtained in the use of resins rather than the above-described films. These results are summarized in Tables III-A and III-B below. Except for the first entry illustrating epoxy resin "A" with no additives, Table III-A shows the corona test results when submicron alumina particles are used. In stark contrast Table III-B
shows the results when the additive comprises particles having a size greater than one micron.
1 :~6~85~
17M~-2870 TABLE III-A
Needle Point Corona Test, Sample Hours to Failure RangeAvera~e Epoxy resin "A", 18-32 25 no additives Epoxy resin "A" with 10% No failures3,900-~
fumed silica of 0.013 aftex 3,900 micron size hour '3 Epoxy resin "A" with 10% No failures precipitated silica of after 3,9003,900+
0.014 micron size hours Epoxy resin "A" with 10% No failures5,000+
furned alumina of 0.03 after 5,000 micron size hours TABLE III-B*
Needle Point Corona Test, Sample Hours to Failure RangeAverage Epoxy resin "Al' with 10~ 80-274 165 alumina (made from dehy-drating Al(OH)3 gel Epoxy resin "A" with 10~ 27-32 30 kaolin (A12O3 SiO2 2H2O) Epoxy resin with 25% alumina 48-66 59 Epoxy resin with 31.5~116-216 166 alumina Epoxy resin with 31.5%110-218 162 alumina (repeat of above experi-ment) Epoxy resin with 25% silica 29-39 34 *All additives shown in this ta~le have particle sizes greater than one micron.
Thus it is seen from the tables above that resins too require the use of submicron alumina and silica particles to exhibit ~ ~ 6 ~
17~Y-2~70 the wholly unexpected increases in corona-resistant properties shown.
In another aspect, this invention relates to laminated electrical components which contain an organo-S silicate or an organoaluminate as part of the binder composition. For convenience, the organosilicate or organoaluminate containing composition may be dissolved in a solvent, e.g., methylene chloride, benzene, or methyl ethyl ketone and used as an :impregnant for these laminate materials, e.g., polyester mats, ceramic paper, mica paper, glass web or the like.
In yet another aspect of the invention, a dispersion of the submicron silica or submicron alumina particles in resin is used to treat the laminate materials wherein the resin acts as a binder. The laminate may be prepared by coating a dispersion of the submicron silica or submicron alumina in resin or solvent between layers during the lay-up of the laminate. The laminates, after being subjected to heat and pressure under conventional conditions to cure the laminates, have greatly enhanced resistance to corona-induced deterioration and improved insulating properties.
In still another aspect, this invention relates to a conductor or conductor wire coated with a resin, i.e., epoxy, ester-imide resin, or other resin containing organoaluminate, organosilicate, submicron silica or submicron alumina part~icles, as described above. The coatings are applied in a conventional manner to give products exhibiting greatly enhanced resistance to corona-3a induced deterioration.
In using the resin compositions of this invention to provide insulated conductors resistant to corona-induced 8 8 ~ ~1 17MY~287Q
deterioration the conductor can be wrapped with an insulating paper, e.g., mica paper tape, impregnated with a resin composition of this invention.
The fo]lowing examples depict in more detail the preparation and use of representative compositions in accordance with the principles of this invention.
Standardized test conditions and apparatus, described as follows, were used in all of the examples hereinafter described.
The corona test apparatus, shown in Fig. 1, comprises a needle electrode, a plane electrode and a sample of dielectric material therebetween. The test consists of applying a potential of 2500 volts A.C.
between the needle electrode and the plane electrode at a frequency of 3000 ~ertz.
Dimensions of the samples used in the corona lifetime evaluations were standardized at 30 mils (7.6 x 10 2cm.) thickness. The distance between the point of the needle and the surface of the dielectric was 15 mils (3.8 x 10 2 cm.). Corona lifetimes wexe determined in atmospheres of air and/or hydrogen. Test results, where data averages and ranges are given, are based on four to six samples of a given composition.
(a) Test of conventional thermoplastic resin composition -- polyethylene terephthalate: Polyethylene terephthalate resin film was stacked to a thickness of 30 mils and tested in the needle point electrode corona test apparatus depicted in the Figure and described above.
1 ~L6~3~57 The samples failed in 17-26 hours, with an average of 21 hours to failure.
(b) Test of conventional resln composition --aromatic polyimide: Under the conditions described above, - 5 an aromatic polyimide film tRapton(R)) failed after an average of 41 hours.
(c) Test of conventional resin composition --cross-linked epoxy resin: Bisphenol-A diglycidyl ether epoxy resin with an epoxide equivalent of 875-1025 was cross-linked by a polyester-polyacid resin having an acid number of 340-360. A 30-mil film tested in accordance with the above, failed after 22 hours.
(a) Preparation of epoxy-reactive organo-silicate: Ethanolamine (732 grams) was added to 624 grams of ethyl silicate 40 (a polysilicate having an average of 5 silicon atoms per molecule). The mixture, which was originally incompatible, became a clear and homogeneous solution upon heating. At the end of four hours of heating at 65-185C, 471.2 grams of liquid, which was mostly ethanol, had distilled from the reaction mixture. The mixture was heated at 99-143C at a pressure of 2-3 millimeters of mercury for 65 minutes to remove unreacted ethanolamine (151 grams were collected). The residue, a liquid amino-functional silicate, was used as a hardener for epoxy resin compositions.
(b) Preparation and test of epoxy resin cured by epoxy-reactive silicate: A mixture was prepared from 80 parts by weight of epoxy resin CY 183, a cycloaliphatic ~ ~88$'`~
epoxy resin having an epoxide equivalen~ of 147-161, and 20 parts by weight of amino-functional silicate prepared in (a), above. The mixture was cured to a clear, yellow solid. A film of the solid 30 mils in thickness was tested in the needle point electrode test apparatus of Example l(a). The samples failed after 437-770 hours, with an average life to fail~lre oi 611 hours.
(c) Test of conventi~
cured with N-aminoethylpiperazine: The average time to failure of an epoxy resin cured with N-aminoe~hylpiperazine was 17 hours, with a range of 3-23 hours, EXAMP~E 3 (a) Test of conventional epoxide resin:
A resin was obtained from a mixture of bisphenol-A epoxy resin, resorcinol and tetraoctylene glycol titanate as described in U.S. Patent 3,776,978. This resin, at a thickness of 30 mils, failed after an average of 25 hours on the needle point electrode test; the range to failure was 18-32 hours.
(b) Preparation and test of epoxide resin and submicron silica filler: A composition was prepared from 90 parts by weight of resin prepared in (a),above, and lO.0 parts by weight of fumed silica (Cabosil(R) M 5, Cabot Corporation) having a particle size of about 0.013 micron. The resin cured without settling of the silica, that is, the cured resin had the submicron silica uniformly dispersed therethrough. Samples tested in the needle point electrode apparatus had not failed after more than 3900 hours.
1~
8 8 ~ ~
(c) Preparation and test of epoxide resin and submicron silica filler: A composition obtained from 90.0 parts by weight of resin obtained in (a), above, and 10.0 parts by weight of microfine precipitated silica (Quso(R)G32, Philadelphia Quartz Co.), having a particle size of 0.014 micron, cured to a product which contained finely dispersed silica through the body of the resin. This product had not failed after more than 3900 hours in the needle point corona testing apparatus.
_XAMPLE 4 (a) Test of conventional resin cured with organoaluminate: Epoxy resins containing metal acetyl-acetonates as epoxy resin catalytic hardeners with phenolic accelerators were disclosed in U. S. Patent 3,812,214.
The metal acetylacetonate was limited to a maximum of 5.0~ by weight of the epoxy resin. No disclosure of corona-resistance was made in the patent. Samples of this material failed within 40 hours in the needle point test due to the low metal acetylacetonate content.
(b) Preparation and test of epoxide resin containing organoaluminate: A clear homogeneous solution was prepared by dissolving aluminum acetylacetonate (25.0 parts by weight) and catechol (5.0 parts by weight) in 100.0 parts by weight of a liquid bisphenol-A epoxy resin having an epoxy equivalent weight of 180-188. The mixture was cured to a clear solid in which dissolved Al-O
compounds were dispersed homogeneously. The Al content was 1.60% by weight. Samples tested in air by the needle point corona test failed after an average of 930 hours, ~ ~68~
with a range of 542-1360 hours to failure. The average lifetime increased to 245~ hours when tested in an atmos-phere of hydrogen.
(c) Preparation and test of epox~v resin containing organoaluminate: A clear resin was prepared by curing a mixture of 100.0 parts by weight of a liquid bisphenol-A epoxy resin, 29.0 parts by weight of aluminum acetylacetonate and 5.0 parts by weight of catechol. The cured resin contained 1.80~ of aluminum dissolved in the resin in the form of Al-O compounds. The average time to failure in the needle point electrode corona test was 2072 hours, with a range of 1500-3015 hours.
(d) Preparation and test of epoxy resin containing organoaluminate: A clear resin solution was obtained by dissolving 25.0 grams of aluminum acetyl-acetonate and 5.0 grams of catechol in 75.0 grams of a liquid bisphenol-A diglycidyl ether resin of epoxide equivalent weight 180-188. The solution was cured to a clear resin containing 1.98% of Al in the form of dissolved Al-O compounds. None of the samples failed in the needle point corona test after more than 1850 hours.
(e) Preparation and test of epoxy resin containing organoaluminate: Catechol (0.5 part by weight) and 40.0 parts by weight of aluminum di-sec-butoxide acetoacetic ester chelate were dissolved in 99.5 parts by weight of epoxy resin ERL 4221, a 3,4-epoxycyclohexyl-methyl-3,4-epoxycyclohexane carboxylate epoxy resin with an epoxide equivalent weight of 131-143. The resin was cured to a clear solid containing 2.55% of Al in the form of dissolved Al-O compounds. The time to failure in the needle point electrode corona test was 1600 hours on the average, with a range of 1152-2045 hours.
(a) Test of convent _ nal epoxy resin: See Example 3(a) for preparation. The average time to failure was 25 hours, with a range of 18-32 hours.
(b) Preparation and test of epoxy resin containing submicron alumina: Epoxy resin obtained according to Example 3(a) (94.0 grams) was mixed with 6.0 grams of fumed alumina (Alon( ), Cabot Corporation), obtained by hydrolysis of aluminum chloride in a flame process and having a particle size of about 0.03 micron.
The mixture was cured without settling of the alumina particles. The average time to failure in the needle point electrode corona test was 275 hours, with a range of 169-423 hours.
(c) Preparation and test of epoxy resin containing fumed alumina: A sample was prepared from 90.0 parts by weight of the resin of Example 3(a) and 10.0 parts by weight of fumed alumina. The alumina particles did not settle during curing. Samples were removed from the needle point corona test apparatus after more than 5000 hours without failure.
(a) Preparation and test of laminate --epoxy-impregnated polyester: A laminate 30 mils in thick-ness made from 19 layers of polyester mat and the epoxy-polyester polyacid resin described in Example l(c) was 1 16~85~
17M~ 2870 subjected to the needle point electrode corona test.
The range of time to failure was 11-16 hours, with an average of 14 hours.
(b) Preparation and test of laminate - epoxy resin containing organoaluminate: The experiment of Example 6(a) was repeated using polyester mats treated first with a 20~ solution of aluminum acetylacetonate in benzene, dried~ and then treated with an epoxy-polyester polyacid resin as in (a). The samples failed after 154-~58 hours of testing, with an average of 278 hours to failure.
(c) Preparation and test of laminate - ePOxy_ impregnated ceramic paper- A laminate made by pressing and curing three pieces of ceramic paper (nominal thickness 15 mils) impregnated with epoxy resin described in U.S.
3,812,214, failed after 168 hours, on the average, in the corona test apparatus. This occurred althou~h the paper consisted mainly of alumina fibers.
(d) Preparation and test of laminate - ceramic paper impregnated with epoxy-organoaluminate modified resin:
A laminate 30 mils thick was made from 3 layers of ceramic paper impregnated with the epoxy-aluminum acetylacetonate resin of Example 4(d). None of the cured samples failed after more than 1700 hours testing.
(e) Pre aration and test of laminate - ceramic _P
paper impregnated with epoxy-fumed alumina composltion.
A laminate of ceramic paper impregnated with a mixture of 90.0 parts by weight of epoxy-resorcinol-tetraoctylene -~ ~8~
glycol titanate according to Example 3(a) and 10.0 parts by weight of fumed alumina did not fail after more than 3800 hours in the needle point electrode corona test.
EXAMPI.E 7 (a) Preparation test of conventional wire enamel: An ester-imide enamel, such as that described in U. S. Patents 3,426,098 and 3,697,~71, was cast to a thickness of 7 mils on a metal plate. A needle point electrode was placed above the sample with a gap of 15 mils between the needle and the surface of the enamel.
The sample was tested at a stress of 2400 volts, 3000 Hz and 105C. Failure occurred after an average of 13 hours.
(b) Preparation and test of organoaluminate-modified enamel: Ester-imide enamel modified by dis~
solution therein of 20% of aluminum acetylacetonate based on enamel solids (1.66% of Al based on dried solids) coated to a thickness of 7 mils on a metal plate failed after an average of 118 hours under the conditions described in (a), above.
(c) Preparation and test of submicron silica modified wire enamel: Ester imide resin modified witn sub-micron silica exhibits the same or greater improvement in corona resistance as in (b) above. Similar results are obtained when submicron alumina is added to the resin.
(a) Preparation and test of wrapped conductor --conventional resin: A conductor was insulated by wrapping a resin-rich mica paper tape (resin as in Example 3(a), above), to a total of 13 layers, around the conductor.
:1 16~8~7.
The insulation failed after 1870 hours of testing at 190 volts/mil~
(b) Preparation and test of wrapped conductor --fumed alumina applied between layers: A conductor, wrapped as in (a), above, except that a dispersion of 5.0~ by weight of fumed alumina in methylene chloride was brushed between the layers of tape, was tested at a stress of 199-200 volts/mil. None of the samples had failed after 5064 hours of testing.
(c) Preparation and test of wrapped conductor =-microfine silica applied between layers: A conductor, wrapped as in (a), above, except that a dispersion of 5.0~ by weight of microfine precipitated silica in methylene chloride was brushed between layers of tape, was tested in the needle point corona apparatus at 190-191 volts/mil.
None of the samples failed after 5064 hours of testing.
By these examples and results of testing as described herein, the advantages and improvements provided by the present invention are apparent. It will be appreciated that a new and improved corona-resistant insulating material has been disclosed, such material comprising a conventional or epoxy type resin composition formulated to include about 5% to about 40% of an organo-aluminate or organosilicate compound or, alternatively, to include about 5% to about 40% of microscopic particles of either alumina or silica to form a substantially uniform resinous dispersion.
8 8 5 ~
While the invention has been clescribed in detail herein in accord with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended by the appended claims to cover all such modifi-cations and changes which fall within the true spirit and scope of the invention.
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Preferably, the alumina or silica has a particle size of from approximately 0.005 to approximately 0.05 micron, as may be obtained either by the gas phase hydrolysis of the corresponding chloride or other halide, or as may be obtained by precipitation. These oxides, when disposed within the polymer material, form chain-like particle networks. Those oxide particles useful in the present invention and formed from the gas phase are also known as fumed oxides. Typical of commerically available fumed oxides are those manufactured and sold by the Cabot Corporation under the trade marks Cabosil(R) (silica) or Alon(R) (alumina);
or those made and sold by Degussa, Inc., under the trade marks Aerosil(~) (silica) or Aluminum Oxide C(R) . Typical precipitated silicas which may be used include those manufactured and sold by the Philadelphia Quartz Co., under the trade mark Quso(R) or those of PPG Industries sold under the trade mark Lo-Vel(R) .
From approxlmately 5% to approximately 40~
by weight of organosilicate, organoaluminate, submicron silica or submicron alumina are used in the resin compositions of this invention, while loadings of 5% to approximately 30%
by weight are preferred.
Preferred compounds of the organoaluminate and organosilicates are those which are soluble and which contain only Si-O or Al-O primary valence bonds on the silicon or the aluminum as was mentioned ahove. The use of these compounds produces clear resins, in which organoaluminate or organosilicate compounds are dissolved, and thus homo-geneous with the resin.
As can be seen from the tables below the use of submicron particles is critical for the use of alumina and silica additives. Table I shows that polyimide films fail after an average of only 9 hours under the test conditions described herein and under the voltage stress shown. In stark contrast, the use of 20% dispersed alumina having an average particle size of approximately 0.020 microns produces average sample life in excess of 2776 hours. The use of 40% finely ground alumina having a particle size in excess of one micron produced better results than no additive but significantly worse results than the submicron sample.
TAsLE I
Stress Hours to Fail Aver-Sample Volts/Mil for Various Samples age Polyimide film 250 7, 8, 13 9 Polyimide film with 250 2187, 3071-~, 3071+ 2776 20% alumina of 0.020 micron size Polyimide film with 208 78, 130, 513, 310 258 40% alumina of greater than 1 micron size 8 ~ 7 The ~1+11 sign in the tables indicates that the sample had still not failed at the time the data was taken.
Similar results are obtained with the use of a polyamide film with submicron alumina. These are summariæed 5in Table II below:
TA~LE IX
Stress Hours to Fail Aver-Sample Volts/Mil for Various Samples age -Polyamide film 250 - 10 Polyamide film with 250 629+, 629-~, 629~ 629-~
20% alumina of 0.020 micron size 357 629+, 629+, 629+ 629+
The particles are disposed within the film material by con-ventional manufacturing methods prior to transformation to the high-molecular weight state.
Like results are obtained in the use of resins rather than the above-described films. These results are summarized in Tables III-A and III-B below. Except for the first entry illustrating epoxy resin "A" with no additives, Table III-A shows the corona test results when submicron alumina particles are used. In stark contrast Table III-B
shows the results when the additive comprises particles having a size greater than one micron.
1 :~6~85~
17M~-2870 TABLE III-A
Needle Point Corona Test, Sample Hours to Failure RangeAvera~e Epoxy resin "A", 18-32 25 no additives Epoxy resin "A" with 10% No failures3,900-~
fumed silica of 0.013 aftex 3,900 micron size hour '3 Epoxy resin "A" with 10% No failures precipitated silica of after 3,9003,900+
0.014 micron size hours Epoxy resin "A" with 10% No failures5,000+
furned alumina of 0.03 after 5,000 micron size hours TABLE III-B*
Needle Point Corona Test, Sample Hours to Failure RangeAverage Epoxy resin "Al' with 10~ 80-274 165 alumina (made from dehy-drating Al(OH)3 gel Epoxy resin "A" with 10~ 27-32 30 kaolin (A12O3 SiO2 2H2O) Epoxy resin with 25% alumina 48-66 59 Epoxy resin with 31.5~116-216 166 alumina Epoxy resin with 31.5%110-218 162 alumina (repeat of above experi-ment) Epoxy resin with 25% silica 29-39 34 *All additives shown in this ta~le have particle sizes greater than one micron.
Thus it is seen from the tables above that resins too require the use of submicron alumina and silica particles to exhibit ~ ~ 6 ~
17~Y-2~70 the wholly unexpected increases in corona-resistant properties shown.
In another aspect, this invention relates to laminated electrical components which contain an organo-S silicate or an organoaluminate as part of the binder composition. For convenience, the organosilicate or organoaluminate containing composition may be dissolved in a solvent, e.g., methylene chloride, benzene, or methyl ethyl ketone and used as an :impregnant for these laminate materials, e.g., polyester mats, ceramic paper, mica paper, glass web or the like.
In yet another aspect of the invention, a dispersion of the submicron silica or submicron alumina particles in resin is used to treat the laminate materials wherein the resin acts as a binder. The laminate may be prepared by coating a dispersion of the submicron silica or submicron alumina in resin or solvent between layers during the lay-up of the laminate. The laminates, after being subjected to heat and pressure under conventional conditions to cure the laminates, have greatly enhanced resistance to corona-induced deterioration and improved insulating properties.
In still another aspect, this invention relates to a conductor or conductor wire coated with a resin, i.e., epoxy, ester-imide resin, or other resin containing organoaluminate, organosilicate, submicron silica or submicron alumina part~icles, as described above. The coatings are applied in a conventional manner to give products exhibiting greatly enhanced resistance to corona-3a induced deterioration.
In using the resin compositions of this invention to provide insulated conductors resistant to corona-induced 8 8 ~ ~1 17MY~287Q
deterioration the conductor can be wrapped with an insulating paper, e.g., mica paper tape, impregnated with a resin composition of this invention.
The fo]lowing examples depict in more detail the preparation and use of representative compositions in accordance with the principles of this invention.
Standardized test conditions and apparatus, described as follows, were used in all of the examples hereinafter described.
The corona test apparatus, shown in Fig. 1, comprises a needle electrode, a plane electrode and a sample of dielectric material therebetween. The test consists of applying a potential of 2500 volts A.C.
between the needle electrode and the plane electrode at a frequency of 3000 ~ertz.
Dimensions of the samples used in the corona lifetime evaluations were standardized at 30 mils (7.6 x 10 2cm.) thickness. The distance between the point of the needle and the surface of the dielectric was 15 mils (3.8 x 10 2 cm.). Corona lifetimes wexe determined in atmospheres of air and/or hydrogen. Test results, where data averages and ranges are given, are based on four to six samples of a given composition.
(a) Test of conventional thermoplastic resin composition -- polyethylene terephthalate: Polyethylene terephthalate resin film was stacked to a thickness of 30 mils and tested in the needle point electrode corona test apparatus depicted in the Figure and described above.
1 ~L6~3~57 The samples failed in 17-26 hours, with an average of 21 hours to failure.
(b) Test of conventional resln composition --aromatic polyimide: Under the conditions described above, - 5 an aromatic polyimide film tRapton(R)) failed after an average of 41 hours.
(c) Test of conventional resin composition --cross-linked epoxy resin: Bisphenol-A diglycidyl ether epoxy resin with an epoxide equivalent of 875-1025 was cross-linked by a polyester-polyacid resin having an acid number of 340-360. A 30-mil film tested in accordance with the above, failed after 22 hours.
(a) Preparation of epoxy-reactive organo-silicate: Ethanolamine (732 grams) was added to 624 grams of ethyl silicate 40 (a polysilicate having an average of 5 silicon atoms per molecule). The mixture, which was originally incompatible, became a clear and homogeneous solution upon heating. At the end of four hours of heating at 65-185C, 471.2 grams of liquid, which was mostly ethanol, had distilled from the reaction mixture. The mixture was heated at 99-143C at a pressure of 2-3 millimeters of mercury for 65 minutes to remove unreacted ethanolamine (151 grams were collected). The residue, a liquid amino-functional silicate, was used as a hardener for epoxy resin compositions.
(b) Preparation and test of epoxy resin cured by epoxy-reactive silicate: A mixture was prepared from 80 parts by weight of epoxy resin CY 183, a cycloaliphatic ~ ~88$'`~
epoxy resin having an epoxide equivalen~ of 147-161, and 20 parts by weight of amino-functional silicate prepared in (a), above. The mixture was cured to a clear, yellow solid. A film of the solid 30 mils in thickness was tested in the needle point electrode test apparatus of Example l(a). The samples failed after 437-770 hours, with an average life to fail~lre oi 611 hours.
(c) Test of conventi~
cured with N-aminoethylpiperazine: The average time to failure of an epoxy resin cured with N-aminoe~hylpiperazine was 17 hours, with a range of 3-23 hours, EXAMP~E 3 (a) Test of conventional epoxide resin:
A resin was obtained from a mixture of bisphenol-A epoxy resin, resorcinol and tetraoctylene glycol titanate as described in U.S. Patent 3,776,978. This resin, at a thickness of 30 mils, failed after an average of 25 hours on the needle point electrode test; the range to failure was 18-32 hours.
(b) Preparation and test of epoxide resin and submicron silica filler: A composition was prepared from 90 parts by weight of resin prepared in (a),above, and lO.0 parts by weight of fumed silica (Cabosil(R) M 5, Cabot Corporation) having a particle size of about 0.013 micron. The resin cured without settling of the silica, that is, the cured resin had the submicron silica uniformly dispersed therethrough. Samples tested in the needle point electrode apparatus had not failed after more than 3900 hours.
1~
8 8 ~ ~
(c) Preparation and test of epoxide resin and submicron silica filler: A composition obtained from 90.0 parts by weight of resin obtained in (a), above, and 10.0 parts by weight of microfine precipitated silica (Quso(R)G32, Philadelphia Quartz Co.), having a particle size of 0.014 micron, cured to a product which contained finely dispersed silica through the body of the resin. This product had not failed after more than 3900 hours in the needle point corona testing apparatus.
_XAMPLE 4 (a) Test of conventional resin cured with organoaluminate: Epoxy resins containing metal acetyl-acetonates as epoxy resin catalytic hardeners with phenolic accelerators were disclosed in U. S. Patent 3,812,214.
The metal acetylacetonate was limited to a maximum of 5.0~ by weight of the epoxy resin. No disclosure of corona-resistance was made in the patent. Samples of this material failed within 40 hours in the needle point test due to the low metal acetylacetonate content.
(b) Preparation and test of epoxide resin containing organoaluminate: A clear homogeneous solution was prepared by dissolving aluminum acetylacetonate (25.0 parts by weight) and catechol (5.0 parts by weight) in 100.0 parts by weight of a liquid bisphenol-A epoxy resin having an epoxy equivalent weight of 180-188. The mixture was cured to a clear solid in which dissolved Al-O
compounds were dispersed homogeneously. The Al content was 1.60% by weight. Samples tested in air by the needle point corona test failed after an average of 930 hours, ~ ~68~
with a range of 542-1360 hours to failure. The average lifetime increased to 245~ hours when tested in an atmos-phere of hydrogen.
(c) Preparation and test of epox~v resin containing organoaluminate: A clear resin was prepared by curing a mixture of 100.0 parts by weight of a liquid bisphenol-A epoxy resin, 29.0 parts by weight of aluminum acetylacetonate and 5.0 parts by weight of catechol. The cured resin contained 1.80~ of aluminum dissolved in the resin in the form of Al-O compounds. The average time to failure in the needle point electrode corona test was 2072 hours, with a range of 1500-3015 hours.
(d) Preparation and test of epoxy resin containing organoaluminate: A clear resin solution was obtained by dissolving 25.0 grams of aluminum acetyl-acetonate and 5.0 grams of catechol in 75.0 grams of a liquid bisphenol-A diglycidyl ether resin of epoxide equivalent weight 180-188. The solution was cured to a clear resin containing 1.98% of Al in the form of dissolved Al-O compounds. None of the samples failed in the needle point corona test after more than 1850 hours.
(e) Preparation and test of epoxy resin containing organoaluminate: Catechol (0.5 part by weight) and 40.0 parts by weight of aluminum di-sec-butoxide acetoacetic ester chelate were dissolved in 99.5 parts by weight of epoxy resin ERL 4221, a 3,4-epoxycyclohexyl-methyl-3,4-epoxycyclohexane carboxylate epoxy resin with an epoxide equivalent weight of 131-143. The resin was cured to a clear solid containing 2.55% of Al in the form of dissolved Al-O compounds. The time to failure in the needle point electrode corona test was 1600 hours on the average, with a range of 1152-2045 hours.
(a) Test of convent _ nal epoxy resin: See Example 3(a) for preparation. The average time to failure was 25 hours, with a range of 18-32 hours.
(b) Preparation and test of epoxy resin containing submicron alumina: Epoxy resin obtained according to Example 3(a) (94.0 grams) was mixed with 6.0 grams of fumed alumina (Alon( ), Cabot Corporation), obtained by hydrolysis of aluminum chloride in a flame process and having a particle size of about 0.03 micron.
The mixture was cured without settling of the alumina particles. The average time to failure in the needle point electrode corona test was 275 hours, with a range of 169-423 hours.
(c) Preparation and test of epoxy resin containing fumed alumina: A sample was prepared from 90.0 parts by weight of the resin of Example 3(a) and 10.0 parts by weight of fumed alumina. The alumina particles did not settle during curing. Samples were removed from the needle point corona test apparatus after more than 5000 hours without failure.
(a) Preparation and test of laminate --epoxy-impregnated polyester: A laminate 30 mils in thick-ness made from 19 layers of polyester mat and the epoxy-polyester polyacid resin described in Example l(c) was 1 16~85~
17M~ 2870 subjected to the needle point electrode corona test.
The range of time to failure was 11-16 hours, with an average of 14 hours.
(b) Preparation and test of laminate - epoxy resin containing organoaluminate: The experiment of Example 6(a) was repeated using polyester mats treated first with a 20~ solution of aluminum acetylacetonate in benzene, dried~ and then treated with an epoxy-polyester polyacid resin as in (a). The samples failed after 154-~58 hours of testing, with an average of 278 hours to failure.
(c) Preparation and test of laminate - ePOxy_ impregnated ceramic paper- A laminate made by pressing and curing three pieces of ceramic paper (nominal thickness 15 mils) impregnated with epoxy resin described in U.S.
3,812,214, failed after 168 hours, on the average, in the corona test apparatus. This occurred althou~h the paper consisted mainly of alumina fibers.
(d) Preparation and test of laminate - ceramic paper impregnated with epoxy-organoaluminate modified resin:
A laminate 30 mils thick was made from 3 layers of ceramic paper impregnated with the epoxy-aluminum acetylacetonate resin of Example 4(d). None of the cured samples failed after more than 1700 hours testing.
(e) Pre aration and test of laminate - ceramic _P
paper impregnated with epoxy-fumed alumina composltion.
A laminate of ceramic paper impregnated with a mixture of 90.0 parts by weight of epoxy-resorcinol-tetraoctylene -~ ~8~
glycol titanate according to Example 3(a) and 10.0 parts by weight of fumed alumina did not fail after more than 3800 hours in the needle point electrode corona test.
EXAMPI.E 7 (a) Preparation test of conventional wire enamel: An ester-imide enamel, such as that described in U. S. Patents 3,426,098 and 3,697,~71, was cast to a thickness of 7 mils on a metal plate. A needle point electrode was placed above the sample with a gap of 15 mils between the needle and the surface of the enamel.
The sample was tested at a stress of 2400 volts, 3000 Hz and 105C. Failure occurred after an average of 13 hours.
(b) Preparation and test of organoaluminate-modified enamel: Ester-imide enamel modified by dis~
solution therein of 20% of aluminum acetylacetonate based on enamel solids (1.66% of Al based on dried solids) coated to a thickness of 7 mils on a metal plate failed after an average of 118 hours under the conditions described in (a), above.
(c) Preparation and test of submicron silica modified wire enamel: Ester imide resin modified witn sub-micron silica exhibits the same or greater improvement in corona resistance as in (b) above. Similar results are obtained when submicron alumina is added to the resin.
(a) Preparation and test of wrapped conductor --conventional resin: A conductor was insulated by wrapping a resin-rich mica paper tape (resin as in Example 3(a), above), to a total of 13 layers, around the conductor.
:1 16~8~7.
The insulation failed after 1870 hours of testing at 190 volts/mil~
(b) Preparation and test of wrapped conductor --fumed alumina applied between layers: A conductor, wrapped as in (a), above, except that a dispersion of 5.0~ by weight of fumed alumina in methylene chloride was brushed between the layers of tape, was tested at a stress of 199-200 volts/mil. None of the samples had failed after 5064 hours of testing.
(c) Preparation and test of wrapped conductor =-microfine silica applied between layers: A conductor, wrapped as in (a), above, except that a dispersion of 5.0~ by weight of microfine precipitated silica in methylene chloride was brushed between layers of tape, was tested in the needle point corona apparatus at 190-191 volts/mil.
None of the samples failed after 5064 hours of testing.
By these examples and results of testing as described herein, the advantages and improvements provided by the present invention are apparent. It will be appreciated that a new and improved corona-resistant insulating material has been disclosed, such material comprising a conventional or epoxy type resin composition formulated to include about 5% to about 40% of an organo-aluminate or organosilicate compound or, alternatively, to include about 5% to about 40% of microscopic particles of either alumina or silica to form a substantially uniform resinous dispersion.
8 8 5 ~
While the invention has been clescribed in detail herein in accord with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended by the appended claims to cover all such modifi-cations and changes which fall within the true spirit and scope of the invention.
-23~
Claims (5)
1. A method for providing corona-resistant insulation for an electrical conductor having good high-temperature dimensional stability comprising covering at least a portion of said conductor with a polyester wire enamel substantially free from vinyl compound containing an amount of an additive effective to provide unique corona resistance selected from the group consisting of organo-aluminate compounds, organo-silicate compounds, silica of particle size from approximately 0.005 micron to approximately 0.05 micron and alumina of particle size from approximately 0.005 micron to approximately 0.05 micron.
2. The method of claim 1, wherein the additive is alumina particles which comprise fumed alumina of particle size from approximately 0.005 microns to approximately 0.050 microns and said alumina particles are substantially uniformly disposed through said polyester wire enamel.
3. The method of claim 1, wherein said polyester wire enamel is an ester-imide resin, said additive being an organo-aluminate, said organo-aluminate being aluminum acetylacetonate.
4. The method of claim 1, wherein said polyester wire enamel is an ester-imide resin, said additive being silica particles of size from approximately 0.005 microns to approximately 0.050 microns.
5. An electrically insulated structure comprising:
at least a portion of an electrically conductive member;
a covering disposed on said portion, said covering comprising a polyester wire enamel substantially free from vinyl compound containing an amount of an additive effective to
5. An electrically insulated structure comprising:
at least a portion of an electrically conductive member;
a covering disposed on said portion, said covering comprising a polyester wire enamel substantially free from vinyl compound containing an amount of an additive effective to
Claim 5 continued:
provide unique corona resistance selected from the group consisting of organo-silicate compounds, organo-aluminate compounds, silica of particle size from approximately 0.005 micron to approximately 0.05 micron and alumina of particle size from approximately 0.005 micron to approximately 0.05 micron.
provide unique corona resistance selected from the group consisting of organo-silicate compounds, organo-aluminate compounds, silica of particle size from approximately 0.005 micron to approximately 0.05 micron and alumina of particle size from approximately 0.005 micron to approximately 0.05 micron.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US6170079A | 1979-07-30 | 1979-07-30 | |
| US61,700 | 1979-07-30 | ||
| US14594780A | 1980-05-02 | 1980-05-02 | |
| US145,947 | 1980-05-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1168857A true CA1168857A (en) | 1984-06-12 |
Family
ID=26741386
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000357082A Expired CA1168857A (en) | 1979-07-30 | 1980-07-25 | Corona-resistant resin compositions |
Country Status (4)
| Country | Link |
|---|---|
| KR (1) | KR840001365B1 (en) |
| CA (1) | CA1168857A (en) |
| IT (1) | IT1149817B (en) |
| MX (1) | MX155403A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999008288A1 (en) | 1997-08-06 | 1999-02-18 | Schenectady International, Inc. | Coating which is resistant to partial discharges, for enamelled wire |
| US5989702A (en) * | 1994-08-15 | 1999-11-23 | General Electric Canada Inc. | Sandwich insulation for increased corona resistance |
| CN106750428A (en) * | 2016-11-30 | 2017-05-31 | 哈尔滨理工大学 | A kind of method that corona-resistant film high is prepared using chemical mixed nanometer technology |
| CN108976991A (en) * | 2018-07-10 | 2018-12-11 | 丹阳市沃德立电工材料有限公司 | A kind of high resistant anticorona varnish and preparation method thereof applied to HV Electric Machine Coil |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5521121B2 (en) | 2012-03-07 | 2014-06-11 | 古河電気工業株式会社 | Insulated wire, electrical equipment, and method of manufacturing insulated wire |
-
1980
- 1980-07-25 CA CA000357082A patent/CA1168857A/en not_active Expired
- 1980-07-30 KR KR1019800003041A patent/KR840001365B1/en active
- 1980-07-30 IT IT23793/80A patent/IT1149817B/en active
- 1980-07-30 MX MX183375A patent/MX155403A/en unknown
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5989702A (en) * | 1994-08-15 | 1999-11-23 | General Electric Canada Inc. | Sandwich insulation for increased corona resistance |
| WO1999008288A1 (en) | 1997-08-06 | 1999-02-18 | Schenectady International, Inc. | Coating which is resistant to partial discharges, for enamelled wire |
| US6337442B1 (en) | 1997-08-06 | 2002-01-08 | Schenectady International, Inc. | Coating which is resistant to partial discharges, for enamelled wire |
| CN106750428A (en) * | 2016-11-30 | 2017-05-31 | 哈尔滨理工大学 | A kind of method that corona-resistant film high is prepared using chemical mixed nanometer technology |
| CN108976991A (en) * | 2018-07-10 | 2018-12-11 | 丹阳市沃德立电工材料有限公司 | A kind of high resistant anticorona varnish and preparation method thereof applied to HV Electric Machine Coil |
| CN108976991B (en) * | 2018-07-10 | 2020-07-28 | 丹阳市沃德立电工材料有限公司 | High-resistance anti-corona paint applied to high-voltage motor coil and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| MX155403A (en) | 1988-02-29 |
| IT1149817B (en) | 1986-12-10 |
| KR840001365B1 (en) | 1984-09-20 |
| IT8023793A0 (en) | 1980-07-30 |
| KR830003535A (en) | 1983-06-21 |
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