Indian Patents. 207655:A METHOD OF PREPARING IMPREGNATED METALLIZED POLYMER FILM OF A WOUND COIL FOR A SELF-HEALING CAPACITOR AND AN IMPREGNATED WOUND COIL FOR A SELF-HEALING CAPACITOR

Title of Invention	A METHOD OF PREPARING IMPREGNATED METALLIZED POLYMER FILM OF A WOUND COIL FOR A SELF-HEALING CAPACITOR AND AN IMPREGNATED WOUND COIL FOR A SELF-HEALING CAPACITOR
Abstract	The present invention relates to the use of insulating fluids, selected from the group consisting of aliphatic esters, alkylbenzenes, crosslinkable compositions comprising at least one polydiene polyol, at least one polyisocyanate and at least one chemically inert liquid charge, for the impregnation of the wound coils of self-healing capacitors.

Full Text	The present invention relates to the field of electrical capacitors. More specifically, it relates to insulating fluids for use in impregnation of the wound coils of self-healing capacitors having metallized plates. By self-healing capacitor is meant in the present context capacitors which include at least one plate comprising a very thin layer of metal of a few hundred angstroms in thickness, the main property of which is that, when the capacitor breaks down, the said plate volatilizes at the point where the said breakdown occurs. This plate may either be a thin layer of metal, such as aluminum or zinc or an alloy of these two metals, deposited directly on a polymer film, such as polypropylene or polyester, which constitutes the solid dielectric, or may be deposited on both facns of a paper, this plate then being associated with one or more polymer tilmo which act as a dielectric. In the latter case, the doubly-metallized paper does not act a s a d i a J. e c t r i c . The wound coils of these capacitors are advantageously impregnated with an insulating fluid. Impregnation typically takes place after the solid materials nave been wound, by introducing, under reduced pressure, an insulating fluid which, at the time of impregnation, is in the form of a low-viscosity liquid. Once the impregnation has been completed, the capacitors may undergo a heat treatment. This is necessary when the insulating fluid consists of systems having 2 polycondensable and/or croBslinkable components which are to a greater or lesser extent charged with an inert liquid so as to minimize the shrinkage - The Applicant Company has observed that, when the impregnation of the metallized polymer films of the wound coils tor self-healing capacitors is carried out using certain aromatic liquids, such as mixtures of mono- and dibenzyltoluene, phenylxyly]ethanes, the said capacitors have a very short lifetime under voltage. It. has aow been discovered that it is possible to use, for the impregnation of the metallized polymer films of the wound coils for self-healing capacitors, at least one insulating fluid selected from the group consisting of aliphatic esters, alkylbenzenes, crosslinkable compositions comprising at least one polydiene pclyol, at least on Regarding the aliphatic esters, the compounds used in the present invention are preferably dioctyl sebacate, dioctyl adipate, dibutyl sebacate and diethyl succinate - Among these compounds, dibutyl sebacate is meet particularly prrsferrud. Regarding the crosslinkable composition* which can be used according to the present; invention. it is preferred to use those which comprise at least one polydiene polyol, at least one polyisocyanate having a functionality greater than 2 and a quantity of inert liquid charge at least equal to 80% by weight of the composition so as to maintain a viscosity of less than 100 mPas throughout the duration of the impregnation, The chemically inert liquid charge is an insulating liquid, which can completely dissolve the polydiene polyols and the polyisocyanates and may be selected from alkylbenzenes, such as decylbenzanes and dodecylbenzenes; dielectric esters which are, for example, products of the reaction of polyvalent alcohols, such as pentaerythritol, with monovalent carboxylic acids, such as n-heptanoic acid; aliphatic esters, such as dioctyl sebacateP dioctyl adipate and dibutyl sebacate; alkyl phthalates, such as dibutyl phthalate and dioctyl phthalate; alkylpolyaromati r. compounds, such as monoisopropylbiphenyl (MIPB); vegetable oils, such as colza oils, mai2e oils and soya oils, as well as the combination of at least, two of the ribovementioned insulating liquids. Preferably, aliphatic esters, such as dibutyl sebacate and dioctyl adipate, alkyl phthalates, such as dioctyl phthalate, or vegetable oils, such as colza oil, will be used as the chemically inert liquid charge. The polyisocyanate used to produce the usable crosslinkabie composition according to the present invention may be selected from aromatic, aliphatic and cycloaliphatic poiyisocyanates and those polyisocyanatea which contain in their molecule an ieocyanurate ring, having at least two isocyanate functional groups in their molecule, these being able to react with hydroxyl functional groups of a polyol in order to form a three-dimensional polyurethane network causing the composition to gel. By way of illustration of aromatic polyiso-cyanates, mention will be made of 4,4'-diphenylmethane diisocyanate (MDI), polymeric MDIs and triphenylmethane tviisocyanate. By way of illustration of an aliphatic polyisocyanate, mention may be made of the biuret of poiyisocyanates, mention may be made of isophorone diisocyanate (IPDI)/ cyclohexyl diisocyanate (CHDI) and 4,4' -dicyclohexyimethane diisocyanate. By way ofc illustration of poiyisocyanates which contain in their molecule the isocyanurafce ring, mention may be made of the trimers of hexamefchylene diisocyanate which are sold by Rhone-Pouleno under the name TOLONATE HDT and tri socyanatomethyl)-1,3,3 • trimethylcyclohexane] iaocyanurate sold by Huls under the name VESTANAT T 1890/100. The amount of polyisocyanate is suitably choaen in such a way that the NCO/OH molar ratio ie about 1 and ia preferably between 0.85 and 1.15. The poly-ileus polyol in suitably a hydroxytelechelic conjugated-diene oligomer which may be obtained by various processes, such as the radical polymerization of a conjugated diene having from 4 to 20 carbon atoms in the presence of a polymerization initiator, such a» hydrogen peroxide, or an azo compound, such as 2,2-azobis [2-methyl-N» (2-hydroxyet;hyl)propionamide] , or the anionic polymerization of a conjugated diene having from 4 to 2 0 carbon atoms in the presence of a catalyst, nuch as; dilithium naphthalene. According to the present invention, the conjugated diene of the polydiene polyol i« selected xroni the group comprising butadiene, inopreno, chioroprene, 1,3-pentadiene and cyclopentadiene. It is also possible to une hydroxytelechelic oligomers of conjugated dienes which are epoxidized along the chain, as well as hydroxytelechelic hydrogenated oligomers of conjugated dnenes. The polyaifane pulyols may have number-average molar masses at most equal to 7000 and preferably of between 1000 and 3000, They suitably have functionalities ranging from 1.8 to 3 and a dynamic viscosity measured at 30°C at least equal to 600 mPa,s. By way of illustration of polydiene polyols, mention may be made of the hydroxylated polybutadienes sold by Elf Atochem S.A. under the names PolyBd* 45 HT and PolyBd* 20 LM. The crosslinkable composition may comprise, in addition to the polydiene polyol, one or more polyols of low molarmaon. By polyols of low molar mass are meant polyols having molar masses ranging from 50 to 800, By way of illustration of such polyols, mention may be made of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polye therpolyols, 1,4-butanediol, 1,6-hexanediol, 2-ethyl-l,3-hexanediol, N,N-bis(2-hydroxypropyl)-aniline, 3-methyl-1,5-pentanediol, trimethylolpropane, pentaerythritol, propoxylated bisphenol A sold by Akzo under the name DIANOI. 320, and the mixtixre of at least two aforementioned polyols. In the case in which a polyol of low molar mass is used, the NCO/OH molar ratio will have to he calculated taking into account the hydroxylated functional groups provided by the said polyol of low molar maas• Although the use of a catalyst is not absolutely essential, it will be possible, in some Gases, if desired, to use a catalyst of the organometallic type, such as dibutyltin dilaurate (DBTL), dibutyltin acetate or organic derivatives of bismuth. The unable crowslinkable composition according to the present invention may bo produced by mixing, at room temperature (approximately 20°C), the various constituents using any means of stirring sufficient to ensure gcod dispersion of the constituents. The* crosslinfcable composition may also contain one or more additives, such as antioxidants, an epoxide or anthrraqinone. The inert charge may optionally undergo a dielectx-ie treatment on an adsorbent earth. The wound Ooils impregnated by mcann of the ixiaulating fluids according to the present invention have the advantage of withstanding high voltage gradients. In the rase of the crosslinkabi compostitions, compositions, the capacitors obtained furthermore have the advantage of no longer having free liquid capable of contaminating the environment should thr In addition, this absence of fre The examples which follow illustrate the invention. Metallized film sapacitors Data relating to the capacitors The wound coils are manufactured from a rough polypropylene film which ia vacuum-metallized using an aluminium/zinc alloy sold by Bollore under the name PP3M. The film has a thickness (by weight) of The round wound coils are sprayed with zinc using the Schoop process in order to allow them to be connected. The wound coiln are placed in crimped cylindrical cases. Preparation of the capacitors Before impregnation, the capacitors undergo treatment for 4 hours at 115°C followed, after returning to room temperature, by an electrical treatment in order to eliminate, from the wound coil m before impregnation, the main weak points in the metallized film. This treatment is carried out by rapidly discharging a 30 capacitor, charged beforehand at ISO V DC, into each wound coil Insulalay fluids used: - dibutyl sebacate (hereafter referred to as DBS) having a viscosity at 20°C equal to 3.9 mPa.s; - dioctyl sebacate (hereafter referred to a« DOS) having a viscosity at 2 0°C equal to 22.4 mPa.s; - dioctyl adipate (hereafter referred to as having a viscosity at 20°C equal to 14.1 mPa.s; - Jarylec C100 (hereafter referred to as JARYLEC) consisting of 75% by weight of benzyltoluenes and of 25% by weight of (benzyl)benzyltoluenes having a viscosity at 20tC of 6. Pa.s, * The croasl inkable compouitiona were prepared using the following constituents: - PolyBa* 45 HT (hereafter referred to as PolyBd), namely a hydroxylated polybutadiene of M„ equal to 2800 (determined by steric exclusion chromatography)/ having a hydroxyl number expressed in milliequivalents per gramme (meq/g) equal to 0.83, a viscosity equal to 5000 mPa.s at 30°C and a relative density equal to 0.90; - Tolonate HDT/LV (hereafter referred to as Tolonate), namely tris(6-iaocyanatohexyl) isocyanurate, having an NCO content equal to 23%, a functionality of approximately 3.4 and a viscosity at 25°C equal to 1200 (jr .3 00) mPa»s; - col2a oil of food-grade quality, having a viscosity at 200 equal to 69.5 mPa.s; - DBS; - JARYLEC. + Preparation of tho crosslinkable compositions: - Crosslinkable compositions comprising colza oil as the inert char ge The colza oil is treated beforehand with attapuigite. To do this, the colza oil plus 3% by weight oi attapuigite are mixed at 60°C for 4 hours/ filtered under reduced pressure and then deganned at 60ftC. TOLONATE is dissolved in the treated colza oil at 60CC, PolyBd and DBTL, as catalyst, are added and then the mixture ia degassed under reduced prensure at 60C. - Crosslinkable compositions comprising DBS as inert charge TOLONATE is dissolved at room temperature in DBS treated with attapuigite according to the protocol described above in the case of colza oil, the mixture is heated to 60yC, PolyBd and DBTL are added and the mixture degassed under reduced preaoure at 60°C. _: Croaalinkable compositions comprising JARYLEC as inert charge (not,in accordance .with.the ii'V_erition) Dissolved separately in J'arylen are, on the one hand, PolyBd (mixture A) and, on the other hand, Toionate (mixture B) . To each of the mixtures, A and B, are added 3 g of attapuigite per 100 g of mixture, the mixtures are stirred separately at room temperature for 3 hours and then the mixtures are filtered under reduced pressure♦ Next, mixture A and mixture R are-brought into contact with each other in a glass reactor provided with ntixrina. Impregnation of the capacitors If the insulating fluid is a crosslinkable composition, this composition is introduced into the capacitors under reduced pressure at 60 °C. Next, the capacitors are held at 6 0°C for 3 days and then heated to 90 °C and held at thi3 temperature for 9 days in order to gel. If the insulating fluid is DBS, DOS, DOA or JARYLEC, the said fluid is introduced into the capacitors under reduced pressure at room temperature, then the capacitors are heated to 60°C, which temperature is maintained for 3 days, and then the capacitors are heated to 906C, which temperature is maintained for one day. ► Ageing under increasing T)C volta.gon We carried out tests under voltage. For thene tests, the capacitors are subjected to DC voltages which increase in steps every 24 hours. The maintained at S0ftC throughout the duration of the test. (During the weekends, the voltage is brought back down to the level of the first step The lifetimes of the capacitors are evaluated in the form of curves of capacitance = f (voltage gradient)/ which are plotted in Figures 1 to 7. In these figures, we have shown as ordinates the change in capacitance C, expressed in , at 60 °C and as abscissae the voltage gradient, expressed in . In Table 1 below, we have indicated for each lest; - the nature of the insulating impregnation fluid; - liquid such as Jarylec, DBS, DOA and DOS •* Tests 1 to «, - Orosslinkable coropositions •* Teats 9 to 14, (the percentage or the constituents of the orosslinkable compositions are percentages by weight); - the number of the figure and the symbol used to represent the corresponding curve. In this table, NC means "not according to the invention"- The test is continued until the capacitor breaks down or is stopped when the drop in capacitance becomes too g- Crosslinkable compositions, comprising POP as the inert charge Dissolved separately in DOP are, on the one hand, PolyBd (mixture A) and, on the other hand, Tolonate (mixture B). 3% of attapulgite is added to each of the mixtures and these mixtures are stirred overnight at 60°C. Each mixture is then filtered and degassed. Next, the mixtures are brought into contact with each other in a stirred glass reactor. Crosslinkable compositions comprising a D9/D0? mixture as the inert charge A solution containing, by weight, 80% of D9 and 20% of DOP is prepared. Dissolved separately in this solution are. on the one hand, PolyBd (mixture A) and, on the other hand, Tolonate (mixture B). 3% of attapulgite is added to each of the mixtures and these mixtures are stirred overnight at 60°C. Each mixture 1B then filtered and degassed. Next, the mixtures ?ire brought into contact with each other in a stirred glass reactor. Crossiinkab 1 e compositions cpmpriping, a DQP/JARYLEC mixture as the inert charge A solution containing, by weight, 50% of DOP and 50% of JARYLEC is prepared. Dissolved separately in this solution are, on the one hand, PolyBd (mixture A) and, on the other hand, Tolonate (mixture B)* 3% of attapulgite is added to each of the mixtures and these mixtures are stirred overnight at 60 aC. Each mixture is then filtered and degassed. Next, the mixtures are brought into contact with each other in a stirred glass reactor. ► Capacitor impregnation conditions. If the insulating fluid is a crosslinkable composition, this composition ia introduced into the capacitors (dried beforehand at 100 °C under reduced pressure) at 60°C under reduced pressure. Next, the capacitors are heated to 90°C and are held at this temperature for J o days, If the insulating fluid is a liquid such as DOP, the said fluid is introduced into the capacitors (dried beforehand at 100°C under reduced pressure) at 60gC under reduced pressure and then the capacitors are heated to 90°C and held at this temperature for 6 days. ► Ageing te.tft under AC voltage. The capacitance of tha capacitors wan measured at 70°CThe capacitors were then subjected to an ageing test at 70°C under a voltage of 825 V* During this test, the capacitance and the losses of each element were regularly measured, After 1077 hours, the voltage was raised to 510 V, The test was stopped after 203 hours under this volragw. The results are plotted in Figure 8. In this figure, we have shown as ordinates the variation in the capacitance, 6C/C, in % and as abscissae the time in hours. In Table 2 below, we have indicated for each teat: - the nature of the insulating impregnation fluid; - POP Test 15 - Groselinkable compositions Testa 16 to 19 (the percentages of the constituents of the crosslinkabie compositions are percentages by weight); - the symbol used to represent the curve &C/C = t(time)/ corresponding to each test, plotted in Figure 8. In this table, NC means "not in accordance with the invention". The capacitors impregnated with a JARYLEC/DOP mixture - Test 19 - broke down 5 hours after applying a voltage of .910 v. No breakdown was observed in the case of the other capacitor?. I_I£ ^MM. talli z § d - filmic aj^ojLlprj? * Data relating to the capacitors The wound coils are manufactured using aluminium-metallized polypropylene film sold by Bollore under the name PP2. The "crenellated" metallisation of this film haa a surface resistance of 2 Q/Q, The film has a thickness,, by weight, of 7.4 /im * The flattened wound coils are sprayed with zinc using the Schoop process in order to allow them to be connected and are placed, in groups of twos, in parallel epipedctl OUOCF . * Insulating fluids unud: - Jarylec C100 (hereafter referred to as C100); - dibutyl sebacate (hereafter referred to as DBS) ; - dodecylbenzene (hereafter referred to aa D9); - dioctyl phthalate (hereafter referred to as DOP) ♦ These liquids were treated beforehand with 3% of activated attapulgite overnight, with stirring, at 20°C and then filtered and degassed under reduced pressure. ► Crossliukahle compositions They were obtained by adding PolyBd and Tolonate to the .innulating liquid. ^ Impregnation of the capacitors Before impregnation, the capacitors undergo a 46-hour treatment at 70°C, under reduced pressure/ and are then cooled down to room temperature (approximately 20°C). The impregnation is carried out under reduced pressure. After the impregnation has been completed, the capacitors are brought back to atmospheric pressure and left at room temperature for approximately one week. Next, they are subjected to a S0°C heat treatment for at least one wn^fc ► Ageing of the capacitors under DC voltage We carried out tests in which the capacitors are subjected to DC voltages increasing in step* every 24 hours (during the weekends, the voltage is brought back down, to the level of the first step) , The temperature is maintained at 55 °C throxighout the duration of the test. This is stopped when the drop in capacitance becomes too great. The capacitance of the wound coils is measured at the end of each step. The lifetimes of the capacitors are evaluated in the form of curves, of capacitance = f(voltage gradient), which are plotted in Figures 9 to 11 below- In these figures, we have shown as abscissae the voltage gradient. expressed in V//un, and as ordinates the variation in the capacitance, &C/C, expressed in %. In Table 3/ we have indicated for each beat: * the nature of the impregnating compound; ~ the number of the figure; - the ayjttbol vised to represent the correnponding curve, In this table, NC means "not in accordance with the invention". WE CLAIM! 1. A method of preparing impregnated metallized polymer film of a wound coil for a self-healing capacitor, which method comprises impregnating the wound coil with an insulating fluid selected from the group consisting of aliphatic esters, alkylbenzenes, and crosslinkable compositions comprising at least one diene polyol, at least one polyisocyanate and at least one chemically inert liquid charge. 2. A method according to Claim 1, in which the aliphatic eater is chosen from diootyl sebacate, dioctyl adipate and dibutyl aebacate. 3. A method according to Claim 1 or 2, in which the aliphatic ester is dibutyl nebacate 4. A method according to Claim in which the crosslinkable composition compriaen at least one polydiene polyol, at least one polyisocyanate having a functionality greater than 2 and an amount of inert liquid charge at least equal to 80% by weight of the composition, 5* A method according to Claim 4, in which the polydiene polyol is a hydroxytelechelic butadiene oligomer of number-average molar mass at most 7000, and having a functionality of 1.0 to 3- 6, A method according to Claim 5 in which the hydroxytelechelic butadiene oligomer is of number- average molar mass of between 1000 and 3000, 7. A method according to Claim 1 or 4r in which the inert liquid charge is selected from alkylbenzenes, aliphatic esters, alkyl phthalates and vegetable oils, 8. A method according to Claim 7, in which the alkylbenaiene i s dodecylbenzene. 9. A method according to Claim 7, in which the aliphatic ester is dibutyl sebacate. 10. A method according to Claim 7, in which the alkyl phthalate is dioctyl phthalate. 11- A method according to Claim 7, in which the vegetable oil is colaa oil. 12. A method according to any one of Claims 1 to 11, in which the polyisocyanate is selected from aromatic, aliphatic and cycloaliphatic polyisocyanates and those polyigocyanatea which contain in their molecule an ieocyanurate ring having at least two isocyanate tunc, t.i onal groups. 13, A method according to Claim 12, in which the polyisocyanate is tria (6-isocyanafcoh«?xyl) isocyanurate. 14, A method according to any one of Claims 1 and 4 to 13 in which the crosslinkable composition is heated to effect crosslinking after impregnation. 15. An impregnated wound coil for a self- healing capacitor prepared by the method claimed in any one of Claims 1 to 14 - 16. A gelt-healing capacitor comprining a wound coil as claimed in Claim 14. 17. Use of at least one insulating fluid for the impregnation of the metallized polymer film of the wound coil for a self-healing capacitor, in which the insulating fluid is selected from the group consisting of aliphatic esters, alkylbenzenes, and crosslinkablc compositions comprising at least one diene polyol, at least one polyisocyanate and at least one chemically inert liquid charge. 18. Use according to Claim 17, in which the insulating fluid is as defined in any one of Claims 2 to 13. 19. A method of preparina impregnated metallized polymer film of a wound coil for a self-healinq capacitor, substantially as hereinabove described and illustrated with reference to the

Full Text

The present invention relates to the field of electrical capacitors. More specifically, it relates to insulating fluids for use in impregnation of the wound coils of self-healing capacitors having metallized
plates.
By self-healing capacitor is meant in the present context capacitors which include at least one plate comprising a very thin layer of metal of a few hundred angstroms in thickness, the main property of which is that, when the capacitor breaks down, the said plate volatilizes at the point where the said breakdown occurs. This plate may either be a thin layer of metal, such as aluminum or zinc or an alloy of these two metals, deposited directly on a polymer film, such as polypropylene or polyester, which constitutes the solid dielectric, or may be deposited on both facns of a paper, this plate then being associated with one or more polymer tilmo which act as a dielectric. In the latter case, the doubly-metallized paper does not act a s a d i a J. e c t r i c .
The wound coils of these capacitors are advantageously impregnated with an insulating fluid. Impregnation typically takes place after the solid materials nave been wound, by introducing, under reduced pressure, an insulating fluid which, at the time of impregnation, is in the form of a low-viscosity liquid. Once the impregnation has been completed, the

capacitors may undergo a heat treatment. This is necessary when the insulating fluid consists of systems having 2 polycondensable and/or croBslinkable components which are to a greater or lesser extent charged with an inert liquid so as to minimize the shrinkage -
The Applicant Company has observed that, when the impregnation of the metallized polymer films of the wound coils tor self-healing capacitors is carried out using certain aromatic liquids, such as mixtures of mono- and dibenzyltoluene, phenylxyly]ethanes, the said capacitors have a very short lifetime under voltage.
It. has aow been discovered that it is possible to use, for the impregnation of the metallized polymer films of the wound coils for self-healing capacitors, at least one insulating fluid selected from the group consisting of aliphatic esters, alkylbenzenes, crosslinkable compositions comprising at least one polydiene pclyol, at least on Regarding the aliphatic esters, the compounds used in the present invention are preferably dioctyl sebacate, dioctyl adipate, dibutyl sebacate and diethyl succinate -
Among these compounds, dibutyl sebacate is meet particularly prrsferrud.
Regarding the crosslinkable composition* which can be used according to the present; invention.

it is preferred to use those which comprise at least one polydiene polyol, at least one polyisocyanate having a functionality greater than 2 and a quantity of inert liquid charge at least equal to 80% by weight of the composition so as to maintain a viscosity of less than 100 mPa*s throughout the duration of the impregnation,
The chemically inert liquid charge is an insulating liquid, which can completely dissolve the polydiene polyols and the polyisocyanates and may be selected from alkylbenzenes, such as decylbenzanes and dodecylbenzenes; dielectric esters which are, for example, products of the reaction of polyvalent alcohols, such as pentaerythritol, with monovalent carboxylic acids, such as n-heptanoic acid; aliphatic esters, such as dioctyl sebacateP dioctyl adipate and dibutyl sebacate; alkyl phthalates, such as dibutyl phthalate and dioctyl phthalate; alkylpolyaromati r. compounds, such as monoisopropylbiphenyl (MIPB); vegetable oils, such as colza oils, mai2e oils and soya oils, as well as the combination of at least, two of the ribovementioned insulating liquids.
Preferably, aliphatic esters, such as dibutyl sebacate and dioctyl adipate, alkyl phthalates, such as dioctyl phthalate, or vegetable oils, such as colza oil, will be used as the chemically inert liquid charge.
The polyisocyanate used to produce the usable

crosslinkabie composition according to the present invention may be selected from aromatic, aliphatic and cycloaliphatic poiyisocyanates and those polyisocyanatea which contain in their molecule an ieocyanurate ring, having at least two isocyanate functional groups in their molecule, these being able to react with hydroxyl functional groups of a polyol in order to form a three-dimensional polyurethane network causing the composition to gel.
By way of illustration of aromatic polyiso-cyanates, mention will be made of 4,4'-diphenylmethane diisocyanate (MDI), polymeric MDIs and triphenylmethane tviisocyanate.
By way of illustration of an aliphatic
polyisocyanate, mention may be made of the biuret of

poiyisocyanates, mention may be made of isophorone diisocyanate (IPDI)/ cyclohexyl diisocyanate (CHDI) and 4,4' -dicyclohexyimethane diisocyanate.
By way ofc illustration of poiyisocyanates which contain in their molecule the isocyanurafce ring, mention may be made of the trimers of hexamefchylene diisocyanate which are sold by Rhone-Pouleno under the

name TOLONATE HDT and tri socyanatomethyl)-1,3,3 • trimethylcyclohexane] iaocyanurate sold by Huls under the name VESTANAT T 1890/100.
The amount of polyisocyanate is suitably choaen in such a way that the NCO/OH molar ratio ie about 1 and ia preferably between 0.85 and 1.15.
The poly-ileus polyol in suitably a hydroxytelechelic conjugated-diene oligomer* which may be obtained by various processes, such as the radical polymerization of a conjugated diene having from 4 to 20 carbon atoms in the presence of a polymerization initiator, such a» hydrogen peroxide, or an azo compound, such as 2,2-azobis [2-methyl-N» (2-hydroxyet;hyl)propionamide] , or the anionic polymerization of a conjugated diene having from 4 to 2 0 carbon atoms in the presence of a catalyst, nuch as; dilithium naphthalene.
According to the present invention, the conjugated diene of the polydiene polyol i« selected xroni the group comprising butadiene, inopreno, chioroprene, 1,3-pentadiene and cyclopentadiene.
It is also possible to une hydroxytelechelic oligomers of conjugated dienes which are epoxidized along the chain, as well as hydroxytelechelic hydrogenated oligomers of conjugated dnenes.
The polyaifane pulyols may have number-average molar masses at most equal to 7000 and preferably of between 1000 and 3000, They suitably have

functionalities ranging from 1.8 to 3 and a dynamic viscosity measured at 30°C at least equal to 600 mPa,s.
By way of illustration of polydiene polyols, mention may be made of the hydroxylated polybutadienes sold by Elf Atochem S.A. under the names PolyBd* 45 HT and PolyBd* 20 LM.
The crosslinkable composition may comprise, in addition to the polydiene polyol, one or more polyols of low molarmaon.
By polyols of low molar mass are meant polyols having molar masses ranging from 50 to 800,
By way of illustration of such polyols, mention may be made of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polye therpolyols, 1,4-butanediol, 1,6-hexanediol, 2-ethyl-l,3-hexanediol, N,N-bis(2-hydroxypropyl)-aniline, 3-methyl-1,5-pentanediol, trimethylolpropane, pentaerythritol, propoxylated bisphenol A sold by Akzo under the name DIANOI. 320, and the mixtixre of at least two aforementioned polyols.
In the case in which a polyol of low molar mass is used, the NCO/OH molar ratio will have to he calculated taking into account the hydroxylated functional groups provided by the said polyol of low molar maas•
Although the use of a catalyst is not absolutely essential, it will be possible, in some Gases, if desired, to use a catalyst of the

organometallic type, such as dibutyltin dilaurate (DBTL), dibutyltin acetate or organic derivatives of bismuth.
The unable crowslinkable composition according to the present invention may bo produced by mixing, at room temperature (approximately 20°C), the various constituents using any means of stirring sufficient to ensure gcod dispersion of the constituents. The* crosslinfcable composition may also contain one or more additives, such as antioxidants, an epoxide or anthrraqinone.
The inert charge may optionally undergo a dielectx-ie treatment on an adsorbent earth.
The wound Ooils impregnated by mcann of the ixiaulating fluids according to the present invention have the advantage of withstanding high voltage gradients.
In the rase of the crosslinkabi compostitions, compositions, the capacitors obtained furthermore have the advantage of no longer having free liquid capable of contaminating the environment should th*r In addition, this absence of fre The examples which follow illustrate the invention.

Metallized film sapacitors
Data relating to the capacitors
The wound coils are manufactured from a rough polypropylene film which ia vacuum-metallized using an aluminium/zinc alloy sold by Bollore under the name
PP3M.
The film has a thickness (by weight) of
The round wound coils are sprayed with zinc using the Schoop process in order to allow them to be connected.
The wound coiln are placed in crimped cylindrical cases.
Preparation of the capacitors
Before impregnation, the capacitors undergo treatment for 4 hours at 115°C followed, after returning to room temperature, by an electrical treatment in order to eliminate, from the wound coil
m
before impregnation, the main weak points in the metallized film. This treatment is carried out by rapidly discharging a 30 capacitor, charged beforehand at ISO V DC, into each wound coil*
Insulalay fluids used:
- dibutyl sebacate (hereafter referred to as DBS) having a viscosity at 20°C equal to 3.9 mPa.s;
- dioctyl sebacate (hereafter referred to a« DOS) having a viscosity at 2 0°C equal to 22.4 mPa.s;
- dioctyl adipate (hereafter referred to as

having a viscosity at 20°C equal to 14.1 mPa.s;
- Jarylec C100 (hereafter referred to as
JARYLEC) consisting of 75% by weight of benzyltoluenes
and of 25% by weight of (benzyl)benzyltoluenes having a
viscosity at 20tC of 6. Pa.s,
* The croasl inkable compouitiona were prepared using the following constituents:
- PolyBa* 45 HT (hereafter referred to as PolyBd), namely a hydroxylated polybutadiene of M„ equal to 2800 (determined by steric exclusion chromatography)/ having a hydroxyl number expressed in milliequivalents per gramme (meq/g) equal to 0.83, a viscosity equal to 5000 mPa.s at 30°C and a relative density equal to 0.90;
- Tolonate HDT/LV (hereafter referred to as Tolonate), namely tris(6-iaocyanatohexyl) isocyanurate, having an NCO content equal to 23%, a functionality of approximately 3.4 and a viscosity at 25°C equal to 1200 (jr .3 00) mPa»s;
- col2a oil of food-grade quality, having a viscosity at 20*0 equal to 69.5 mPa.s;
- DBS;
- JARYLEC.
+ Preparation of tho crosslinkable compositions:
- Crosslinkable compositions comprising colza
oil as the inert char ge
The colza oil is treated beforehand with

attapuigite. To do this, the colza oil plus 3% by weight oi attapuigite are mixed at 60°C for 4 hours/ filtered under reduced pressure and then deganned at 60ftC.
TOLONATE is dissolved in the treated colza oil at 60CC, PolyBd and DBTL, as catalyst, are added and then the mixture ia degassed under reduced prensure
at 60*C.
- Crosslinkable compositions comprising DBS as inert charge
TOLONATE is dissolved at room temperature in DBS treated with attapuigite according to the protocol described above in the case of colza oil, the mixture is heated to 60yC, PolyBd and DBTL are added and the mixture degassed under reduced preaoure at 60°C.
_: Croaalinkable compositions comprising
JARYLEC as inert charge (not,in accordance .with.the ii'V_erition)
Dissolved separately in J'arylen are, on the one hand, PolyBd (mixture A) and, on the other hand, Toionate (mixture B) . To each of the mixtures, A and B, are added 3 g of attapuigite per 100 g of mixture, the mixtures are stirred separately at room temperature for 3 hours and then the mixtures are filtered under reduced pressure♦ Next, mixture A and mixture R are-brought into contact with each other in a glass reactor provided with ntixrina.

Impregnation of the capacitors
If the insulating fluid is a crosslinkable composition, this composition is introduced into the capacitors under reduced pressure at 60 °C. Next, the capacitors are held at 6 0°C for 3 days and then heated to 90 °C and held at thi3 temperature for 9 days in order to gel.
If the insulating fluid is DBS, DOS, DOA or JARYLEC, the said fluid is introduced into the capacitors under reduced pressure at room temperature, then the capacitors are heated to 60°C, which temperature is maintained for 3 days, and then the capacitors are heated to 906C, which temperature is maintained for one day.
► Ageing under increasing T)C volta.gon
We carried out tests under voltage. For thene tests, the capacitors are subjected to DC voltages which increase in steps every 24 hours.
The maintained at S0ftC throughout the duration of the test. (During the weekends, the voltage is brought back down to the level of the first step The lifetimes of the capacitors are evaluated in the form of curves of capacitance = f (voltage gradient)/ which are plotted in Figures 1 to 7. In these figures, we have shown as ordinates the change in capacitance C, expressed in , at 60 °C and as abscissae the voltage gradient, expressed in .

In Table 1 below, we have indicated for each lest;
- the nature of the insulating impregnation
fluid;
- liquid such as Jarylec, DBS, DOA and DOS •* Tests 1 to «,
- Orosslinkable coropositions •* Teats 9 to 14,
(the percentage or the constituents of the orosslinkable compositions are percentages by weight);
- the number of the figure and the symbol
used to represent the corresponding curve.
In this table, NC means "not according to the invention"-
The test is continued until the capacitor breaks down or is stopped when the drop in capacitance becomes too g-

Crosslinkable compositions, comprising POP as
the inert charge
Dissolved separately in DOP are, on the one hand, PolyBd (mixture A) and, on the other hand, Tolonate (mixture B). 3% of attapulgite is added to each of the mixtures and these mixtures are stirred overnight at 60°C. Each mixture is then filtered and degassed. Next, the mixtures are brought into contact with each other in a stirred glass reactor.
Crosslinkable compositions comprising a D9/D0? mixture as the inert charge
A solution containing, by weight, 80% of D9 and 20% of DOP is prepared. Dissolved separately in this solution are. on the one hand, PolyBd (mixture A) and, on the other hand, Tolonate (mixture B). 3% of attapulgite is added to each of the mixtures and these mixtures are stirred overnight at 60°C. Each mixture 1B then filtered and degassed. Next, the mixtures ?ire brought into contact with each other in a stirred glass reactor.
Crossiinkab 1 e compositions cpmpriping, a DQP/JARYLEC mixture as the inert charge
A solution containing, by weight, 50% of DOP and 50% of JARYLEC is prepared. Dissolved separately in this solution are, on the one hand, PolyBd (mixture A) and, on the other hand, Tolonate (mixture B)* 3% of attapulgite is added to each of the mixtures and these mixtures are stirred overnight at 60 aC. Each mixture is

then filtered and degassed. Next, the mixtures are brought into contact with each other in a stirred glass reactor.
► Capacitor impregnation conditions.
If the insulating fluid is a crosslinkable composition, this composition ia introduced into the capacitors (dried beforehand at 100 °C under reduced pressure) at 60°C under reduced pressure. Next, the capacitors are heated to 90°C and are held at this temperature for J o days,
If the insulating fluid is a liquid such as DOP, the said fluid is introduced into the capacitors (dried beforehand at 100°C under reduced pressure) at 60gC under reduced pressure and then the capacitors are heated to 90°C and held at this temperature for 6 days.
► Ageing te.tft under AC voltage.
The capacitance of tha capacitors wan measured at 70°CThe capacitors were then subjected to an ageing test at 70°C under a voltage of 825 V*
During this test, the capacitance and the losses of each element were regularly measured,
After 1077 hours, the voltage was raised to 510 V, The test was stopped after 203 hours under this
volragw.
The results are plotted in Figure 8.
In this figure, we have shown as ordinates the variation in the capacitance, 6C/C, in % and as

abscissae the time in hours.
In Table 2 below, we have indicated for each teat:
- the nature of the insulating impregnation
fluid;
- POP Test 15
- Groselinkable compositions Testa 16 to 19 (the percentages of the constituents of the crosslinkabie compositions are percentages by weight);
- the symbol used to represent the curve
&C/C = t(time)/ corresponding to each test, plotted in
Figure 8.
In this table, NC means "not in accordance
with the invention".

The capacitors impregnated with a JARYLEC/DOP mixture - Test 19 - broke down 5 hours after applying a voltage of .910 v.
No breakdown was observed in the case of the other capacitor*?.
I_I£ ^MM. talli z § d - filmic aj^ojLlprj?
** Data relating to the capacitors
The wound coils are manufactured using aluminium-metallized polypropylene film sold by Bollore under the name PP2. The "crenellated" metallisation of this film haa a surface resistance of 2 Q/Q,
The film has a thickness,, by weight, of 7.4 /im *
The flattened wound coils are sprayed with zinc using the Schoop process in order to allow them to be connected and are placed, in groups of twos, in parallel epipedctl OUOCF .
* Insulating fluids unud:
- Jarylec C100 (hereafter referred to as
C100);
- dibutyl sebacate (hereafter referred to as
DBS) ;
- dodecylbenzene (hereafter referred to aa
D9);
- dioctyl phthalate (hereafter referred to as
DOP) ♦
These liquids were treated beforehand with 3% of

activated attapulgite overnight, with stirring, at 20°C and then filtered and degassed under reduced pressure.
► Crossliukahle compositions
They were obtained by adding PolyBd and Tolonate to the .innulating liquid.
^ Impregnation of the capacitors Before impregnation, the capacitors undergo a 46-hour treatment at 70°C, under reduced pressure/ and are then cooled down to room temperature (approximately 20°C). The impregnation is carried out under reduced pressure. After the impregnation has been completed, the capacitors are brought back to atmospheric pressure and left at room temperature for approximately one week. Next, they are subjected to a S0°C heat treatment for at least one wn^fc
► Ageing of the capacitors under DC voltage
We carried out tests in which the capacitors
are subjected to DC voltages increasing in step* every 24 hours (during the weekends, the voltage is brought back down, to the level of the first step) , The temperature is maintained at 55 °C throxighout the duration of the test. This is stopped when the drop in capacitance becomes too great. The capacitance of the wound coils is measured at the end of each step. The lifetimes of the capacitors are evaluated in the form of curves, of capacitance = f(voltage gradient), which are plotted in Figures 9 to 11 below- In these figures, we have shown as abscissae the voltage gradient.

expressed in V//un, and as ordinates the variation in the capacitance, &C/C, expressed in %.
In Table 3/ we have indicated for each beat:
* the nature of the impregnating compound;
~ the number of the figure;
- the ayjttbol vised to represent the correnponding curve,
In this table, NC means "not in accordance with the invention".

WE CLAIM!
1. A method of preparing impregnated metallized polymer film of a wound coil for a self-healing capacitor, which method comprises impregnating the wound coil with an insulating fluid selected from the group consisting of aliphatic esters, alkylbenzenes, and crosslinkable compositions comprising at least one diene polyol, at least one polyisocyanate and at least one chemically inert liquid charge.
2. A method according to Claim 1, in which the aliphatic eater is chosen from diootyl sebacate, dioctyl adipate and dibutyl aebacate.
3. A method according to Claim 1 or 2, in which the aliphatic ester is dibutyl nebacate
4. A method according to Claim in which the crosslinkable composition compriaen at least one polydiene polyol, at least one polyisocyanate having a functionality greater than 2 and an amount of inert liquid charge at least equal to 80% by weight of the composition,
5* A method according to Claim 4, in which the polydiene polyol is a hydroxytelechelic butadiene oligomer of number-average molar mass at most 7000, and having a functionality of 1.0 to 3-
6, A method according to Claim 5 in which the hydroxytelechelic butadiene oligomer is of number-

average molar mass of between 1000 and 3000,
7. A method according to Claim 1 or 4r in which the inert liquid charge is selected from alkylbenzenes, aliphatic esters, alkyl phthalates and vegetable oils,
8. A method according to Claim 7, in which the alkylbenaiene i s dodecylbenzene.
9. A method according to Claim 7, in which the aliphatic ester is dibutyl sebacate.
10. A method according to Claim 7, in which the alkyl phthalate is dioctyl phthalate.
11- A method according to Claim 7, in which the vegetable oil is colaa oil.
12. A method according to any one of
Claims 1 to 11, in which the polyisocyanate is selected
from aromatic, aliphatic and cycloaliphatic
polyisocyanates and those polyigocyanatea which contain
in their molecule an ieocyanurate ring having at least
two isocyanate tunc, t.i onal groups.
13, A method according to Claim 12, in which the polyisocyanate is tria (6-isocyanafcoh«?xyl) isocyanurate.
14, A method according to any one of Claims 1 and 4 to 13 in which the crosslinkable composition is heated to effect crosslinking after impregnation.
15. An impregnated wound coil for a self-
healing capacitor prepared by the method claimed in any
one of Claims 1 to 14 -

16. A gelt-healing capacitor comprining a
wound coil as claimed in Claim 14.
17. Use of at least one insulating fluid for
the impregnation of the metallized polymer film of the
wound coil for a self-healing capacitor, in which the
insulating fluid is selected from the group consisting
of aliphatic esters, alkylbenzenes, and crosslinkablc
compositions comprising at least one diene polyol, at
least one polyisocyanate and at least one chemically
inert liquid charge.
18. Use according to Claim 17, in which the
insulating fluid is as defined in any one of Claims 2
to 13.
19. A method of preparina impregnated metallized polymer film of a wound coil for a self-healinq capacitor, substantially as hereinabove described and illustrated with reference to the

Documents:

1321-mas-1997- abstract.pdf

1321-mas-1997- claims duplicate.pdf

1321-mas-1997- claims original.pdf

1321-mas-1997- correspondence others.pdf

1321-mas-1997- correspondence po.pdf

1321-mas-1997- description complete duplicate.pdf

1321-mas-1997- description complete original.pdf

1321-mas-1997- drawings.pdf

1321-mas-1997- form 1.pdf

1321-mas-1997- form 26.pdf

1321-mas-1997- form 3.pdf

1321-mas-1997- form 4.pdf

« Previous Patent

Next Patent »

Patent Number

207655

Indian Patent Application Number

1321/MAS/1997

PG Journal Number

27/2007

Publication Date

06-Jul-2007

Grant Date

19-Jun-2007

Date of Filing

18-Jun-1997

Name of Patentee

ELF ATOCHEM S. A

Applicant Address

4 & 8 COURS MICHELET, 10 F-92800 PUTEAUX.

Inventors:

#	Inventor's Name	Inventor's Address
1	NCELLE BERGER	4,RESIDENCE DE CHARRIEE BLANCH 69130.

PCT International Classification Number

B32B027/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA