Document 0gwZjzbVKM1DqX26gGVwNmJyb

I----------------------------------- \ Monsanto fROM (NAME * LOCATION! H. S. Bergen - B2SL DATE January 20, 1975 SUBJECT REFERENCE. REQUEST FOR RELEASE OF PUBLICATION "NEW CAPACITOR FLUIDS" __________ TO R. H. Munch - TIB T a JtiJ CC: T. L. Gossage W. R. Richard - T3A W,, W. Withers - B2SA You have my approval to publish said paper with the changes I have indicated on the attached copy. Summarizing these changes, they relate to the following factors: 1. We should strongly indicate that the new fluids are recently introduced and more commercial life experience is needed. 3. I have commented somewhat on the commercial and availability aspects. 1}. I have taken out some repetition and redundancy. In overall summary, I feel the paper is timely, informative and needed. It's presented in a straightforward, excellent manner. HSB/tl Attachment 00419^0 EX P-3114 Page 1 of 22 PCB-ARCH0748129 MONSANTO INDUSTRIAL CHEMICALS CO. REQUEST FOR RELEASE OF PUBLICATION (To be Accompanied by Manuscript) DATE: January 17, 1975 TITLE OF ARTICLE: AUTHORS: New Capacitor Fluids R. H. Munch AUTHOR HANDLING CORRESPONDENCE: R. H. Munch, TIB MEETING AT WHICH PAPER WILL BE PRESENTED: or JOURNAL SUBMITTED TO: Institute of Electrical and Electronic Engineers Meeting January 27-30, 1975 ' New York, New York APPROVALS: (Attach manuscripts to approval form and send to each individual whose approval is required. Allow three weeks for responses.) . Approval Required Approved Date 1. Research Group Leader Yes 2. Director/Manager, R&D Yes 3. Patent Department (2 copies) Yes 4. Director, Technology Planning and Evaluation Yes 5. Other: , a. J)ipectorV_u8'ihess Group b. PTant Manager c. Director/Manager, Manufacturing d. Medical e. Law f. Marketing g. Commercial Development h. Other 6. Public Relations (2 copies) Yes When approved, author should send copies to: . . . - Technical Reports Library 4 copies Director/Manager, R&D EX P-3114 * Pa98 PCB-ARCH0748130 NEW CAPACITOR IMPREGNANTS R. H. Munch* ABSTRACT Three major classes of fluids useful as capacitor dielectric impregnants are discussed. These include chlorinated di phenyl fluids, esters ana ester base and hydrocarbon base fluids with additive to give dielectric constant equal to trichlorodiphenyl. Some of the relative ad vantages and disadvantages of these classes of fluids are discussed, 'Tn-rve cAjA1 ' \ * Monsanto Industrial Chemicals Co. 800 North Lindebergh St. Louis, Mo. 63166 QQ^qlZ EX P-3114 Page 3 of 22 PCB-ARCH0748131 NEW CAPACITOR IMPREGNANTS BACKGROUND Capacitors are indispensable in present day distribution and use of electrical energy. Their applications range from large banks of power factor correction capacitors through motor start-run capacitors and capacitors for fluorescent lamp ballasts to the many types used in electronic devices. Many types of construction are required depending on the size and use for which they are intended. This paper is concerned with those constructed of a sheet dielectric, either paper or film or a - combination of these, using either foil electrodes or electrodes formed by evaporating a metallic film onto the surface of the dielectric. A number of advantages can be achieved by impregnating capacitors of the types described above with a suitably chosen liquid. These are: 1) The dielectric strength of a liquid is greater than a gas permitting higher voltage rating for a given interelectrode spacing. 2) Corona discharge inception and extinction voltages for liquid impregnated systems are much higher than for unimpregnated ones. 3) The capacitance for a given electrode area and spacing can be greatly increased because liquids have much higher dielectric constants than gases. 4) Better distribution of electrical stress within the composite dielectric system can be achieved EX *-3114 Page 4 of 22 PCB-ARCH0748132 -2- by proper choice of dielectric constant of the liquid. 5) Heat transfer through the capacitor roll is im proved. 6) As a result of the preceding factors, capacitors which give better performance at lower cost can be produced. They use less material, occupy less space, weigh less, and last longer. In summary, impregnation is essential for the production of capacitors with working voltages required in a wide variety of present day power transmission and use technology. The first impregnants used were hydrocarbon oils, natural esters, such as castor oil and waxes. All of these had relatively low dielectric constants. They were displaced to a large extent by penta chloro biphenyl type material such as Aroclor* 1254 which had a higher dielectric constant, was more stable, easily purified, fire resistant and low in cost. Later trichloro biphenyl fluids such as Aroclor 1242 were substituted to obtain the advantage of still higher dielectric constant in making still better capacitors at a still lower cost. * Monsanto Trade Name EX P-3114 Page 5 of 22 PCB-ARCH0748133 -3- The properties of the trichloro biphenyl type fluids were ideal with one major exception. Jensen (1) in 1966 discovered that chlorinated biphenyls could be detected in natural waters and in fish and marine birds. Because of the similarity in chemical nature and properties of these materials to the insecticide DDT, they were assumed to be equally hazardous in the environment. In this country Monsanto stopped sale of polychlorinated biphenyls (PCB's) for all purposes except for use in capacitors and trans formers where the use was considered to be non dissipative and essential to the electrical industry. The U.S. Government Inter departmental Task Force on PCB's carried out a broad investiga tion of the problem (2) and stated that ''Their continued use for transformers and capacitors in the near future is considered necessary because of the significantly increased risk of fire and explosion and the disruption of electrical service which would result from a ban on PCB use". At this point it should be stated that the chlorinated biphenyl type fluids are mixtures of individual chlorinated biphenyls which vary in the number of chlorine atoms contained and in the way that the chlorine atoms are positioned on the molecule. A typical chlorinated biphenyl fluid such as Aroclor 1242 contains about 70 components. Its average chlorine content is that of trichloro biphenyl but it contains components with fewer as well as more chlorines per molecule. EX P-3114 Page 6 of 22 PCB-ARCH0748134 -4In a further effort to minimize any possible harmful effects in the environment, Monsanto produced a new trichlorobiphenyl fluid, Aroclor 1016, made to decrease the concentration of more highly chlorinated materials (5 or more chlorine atoms per molecule of chlorinated biphenyl) by a factor of eight. The rational for this is that the more highly chlorinated material biodegrades at a lower rate than material containing less chlorine. Another fluid, MCS' 1043, essentially a dichlorobiphenyl, was also developed as a possible substitute for Aroclor 1016 should government regula tions require it but this was never offered commercially because * of its lower fire resistance^ * Measures to insure that remaining users understood the need to cut discharge of PCB products into the aquatic environment were also taken by ANSI Committee C 107. EX P-3114 Page 7 of 22 PCB-ARCH0748135 4a It is interesting to note that the various measures taken by industry have resulted in a forty-fold decrease in the concentration of PCB type products found in North Atlantic Ocean survace waters since 1972 (3). In spite of the efforts by industry to minimize environmental contamination by PCB's and the Government Task Force statement that their continued use should be permitted, there was a need for non-PCB fluids to fill the export market to Japan where their use was banned. There was also need to have non-PCB fluids to insure the continued ability to produce efficient low-cost capaci tors without PCB should other facts come to light which would^*t^-2-<r erc-e Ar Government to change its attitude and ban PCB use. For these reasons, many organizations, Monsanto among them, under took programs to develop non-PCB capacitor impregnants. To aid such development, we must understand the requirements. Properties important to the satisfactory use of a fluid as a capacitor im- pregnant are listed in Table I. * OO^l9*7 EX P-3114 Page 8 of 22 PCB-ARCH0748136 TABLE I IMPORTANT PROPERTIES OF CAPACITOR IMPREGNATION FLUIDS 1. Dielectric Constant - 6 or above at 25C 2. Low Dissipation Factor < 0.05 @ 100C 60 Hz 3. High Resistivity > 500 x 109 O cm @ 100C 4. High Dielectric Strengh ^ 40 KV per ASTM D877 5. High Crona Inceptionand Extinction Voltage 6. Ease of Purification 7. East of Impregnation 8. Compatibility with paper, film,elastomers, etc. 9. No Acid Gas Formed on Arcing 10. Wide Liquid Range 11. Fire Resistance 12. Stability in Use and Storage 13. Biodegradability, 14. Low Toxicity 15. Low Absorption by Organisms 16. Commercially Available or Readily Synthesized This list could easily be expanded by subdividing individual items With this many constraints on the choice of fluid, it is obvious that the probability of finding promising candidates is not high. Q{Ki9*!8 EX P-3114 Page 9 of 22 PCB-ARCH0748137 -6- The basic molecular structure requirements to produce a material of the desired electrical properties are: 1) The chemical bonds involved in its structure must have a minimum of ionic character so that the material can have low power factor and high resistivity; 2) To achieve high dielectric constant there must be a highly unsymetrical distribution of charge within the molecule; 3) The bonds involved must be highly stable but not so stable that the product will not biodegrade; 4) The molecular weight and functional groups present must be such as to give the desired liquid range with minimum toxicity. Using these concepts and the list of detailed requirements in Table I as guides, representatives of each of the likely classes of compounds were chosen and evaluated. The result was a decision not to try to combine all the desired properties in one molecule but to choose a high dielectric constant component which could be added to lower dielectric constant materials to give whatever dielectric constant was required. Diaryl sulfones emerged as a tantalizing class of materials. They possess high dielectric constants and can be readily synthesized from available industrial raw materials. Unfortunately, many of them are high melting solids with very low solubility in suitable base fluids. Worse still, they imparted unacceptably high conduc tivity to fluids. Their use had been suggested long ago (4) but had never been practiced, probably because of this problem, which seemed to be inherent. 0041929 EX P-3114 Page 10 of 22 PCB-ARCH0748138 1 -7- To determine i the conductivity was inherent to sulfones, a sample of diphenyl sulfone was exhaustively purified by crystallization from solvent and by zone refining. This experiment proved that sufficiently purified sulfones were satisfactory high delectric constant components for capacitor impregnating fluids. This fact made possible design of a series of capacitor impregnation fluids which satisfy the criteria for capacitor impregnants per haps better than any others with the exception that only those made with polychlorinated biphenyl as the base fluid are as fire re sistant as the Aroclor fluids. NEW' FLUIDS Table II gives data on chlorinated biphenyl type fluids. The'top portion of Table II gives the pertinent properties of three chlorinated diphenyl base fluids; the bottom portion gives data on standard 2 pF ballast type capacitors impregnated with these fluids. Data on Aroclor 1016 are given for comparison because it is the most widely used capacitor impregnant. Figure 1 shows the capaci tance and dissipation factor of an Aroclor 1016 capacitor as a function of temperature. With the exception of possible objections on environmental grounds it is a nearly ideal impregnant. MCS 1043 was mentioned earlier in this paper as a dichlorobiphenyl type fluid which could be substituted for trichlorobiphenyl type P-3114 Page 11 of 22 PCB-ARCH0748139 -8- fluids such as Aroclor 1016 if environmental concern should dictate that Aroclor 1016 could not be uv--sei d but a lower chlorinated material would be acceptable. It gives equally good performance in capacitors as Aroclor 1016 with one exception. It is not as fire resistant. It would also be sp^^hftt more expensive to produce. At present it is not commercially available, although it could be produced on short hotice if necessary. . A MCS 1489 is designed as a higher dielectric constant fluid to per mit savings in the amounts of paper and foil required to build a capacitor and thus lower the cost of manufacture. As can be seen from the lower part of Table II, it gives about 121 greater capaci tance for the same area and thickness of dielectric as Aroclor 1016 gives. Figure 2 gives the capacitance and dissipation factor data for a capacitor impregnated with MCS 1489. It has been extensively tested in our laboratories and by industrial users. Capacitors made using it are currently being field tested. A second class of fluids of some interest are esters and ester base sulfone blends. Table III gives the properties of three ester type fluids and capacitors made from them. Two of these dioctyl phthalate (DOP) and di iso nonyl phthalate (DINP) are commercial plasticizers which have recently been used to some ex tent by the capacitor industry (5). The third MCS 1475 is a patented(6) Monsanto ester base fluid designed to have the same dielectric constant as Aroclor 1016. Figure 3 shows capacitance 00'IEX3P-3114 Page 12 of 22 PCB-ARCH0748140 and dissipation factor of an MCS 1475 impregnated capacitor as a function of temperature. Performance of these three fluids as capacitor impregnants is equivalent with the exception that the higher dielectric constant of MCS 1475 requires a smaller area/ thickness ratio and permits manufacture of capacitors of the same capacitance in the same size cans as would be used with Aroclor 1016. Capacitors made with all three of these fluids have been sold by various capacitor manufacturers. . A third class of fluids are hydrocarbon base sulfone blends. These too are covered by a Monsanto patent (?). Data for three such fluids are given in Table IV. Capacitance and dissipation factor data as a function of temperature are given in Figure 4 for MCS 1588 which is typical of the group. Again these fluids have been designed to have the same dielectric constant as Aroclor 1016. Capacitors made from them give excellent results in accelerated life tests. Of the three, only MCS 1588 is offered for sale at present. MC&\1238 or MCS 1633 might/'oJ'fer advantages under-different con ditions afect\ng ^rice^and ava^rlrabili^y^^The^bj.s'estock^x. DISCUSSION Many factors affect the performance of a capacitor impregnant. In all cases, they must be properly purified. This is usually done by treatment with adsorbents such as fuller's earth, various grades EX *#114 Page 13 of 22 PCB-ARCH0748141 -10- of alumina, silica gel or molecular sieves. It is essential that the capacitor roll be thoroughly dried -- particularly if ester base fluids which are subject to hydrolosis are to be used. Use of proper stabilizers is necessary too. All of the fluids described above should be used \tfith a suitable epoxide type stabilizer for A.C. capacitors. Capacitors for D.C. use require stabilizers such as anthraquinone. Quality of the solid dielectric is all important. Film or paper may have soluble, ionizable impurities which dissolve in the fluid and increase dissipation factor. Or, there may be mechanical imperfections. Uniform fabrication of test capacitors is also essential to avoid mechanical defects. The degree of electrical and thermal stress which the design and use conditions impose are also critical. The suitability of a fluid as a capacitor impregnant must be judged on the basis of performance in capacitors. Accelerated life tests and field performance data may indicate that a fluid which might not have been thought suitable on the basis of measurements on the fluid itself gives satisfactory performance, or vice versa. We therefore evaluate fluids by impregnating, under carefully controlled conditions, commercial 2 yF capacitors bought in large quantities. These are life tested under conditions specified by E.I.A. and under even more rigorous conditions to assess fluid performance on a comparative basis. EX P-3114 Page 14 of 22 PCB-ARCH0748142 This type of testing plus field results reported to us indicate that any of these fluids can be used to produce acceptable commercial capacitors. However, it is important to recognize that there are significant differences among them which a capacitor maker must evaluate for himself in the light of his production methods and facilities, the design he proposes to use, the use for which the Capacitor is intended and his desire for ultimate performance. He must also evaluate the relative importance of environmental factors and fire resistance. Last but not least he .must examine the economics of the complete operation It is probably safe to say that trichlorobiphenyl fluids give the ultimate in performance in a broad range of impregnated capacitor types with exceptions which represent only a very small part of t field. Ho-wersTT~W^ioTed--ahev-e--they_.hajye been acGused--of--bein environmental pollutants e\will txfell what /their real U /jUl/ , If / effect has been and what Treasures/already taker/by industry and. contemplated by.gove ent wiTxsa-hctidjr their continuedvu.se The fire resistance of the trichlorobiphenyl fluids is an advantage which should not be given up without considering whether advantages to be gained are worth the loss. Fires from capacitors are so rare that we have come to discount the possibility. This is be cause of the fact that gases expelled by a failed trichlorobiphenyl capacitor are not ignited even by a spark such as is used to ignite an oil furnace burner. Those from capacitors impregnated with 0041934 EX P-3114 Page 15 of 22 PCB-ARCH0748143 -12- the other types of fluids discussed above ignite and burn like a gas flame. Esters are widely available low price materials. Against the low price per unit volume the manufacturer must weigh the fact that they require special purification. Because of their susceptibility to hydrolosis, excess recycled material from capacitor production may be especially difficult to upgrade for reuse. Special care is required during the impregnation operation in order to produce capacitors with good service reliability (5a). The hydrocarbon base fluids described above are preferred by some manufacturers because they are more easily treated, the recovered material is more easily up-graded for reuse and because they seem to have greater ultimate performance in A.C. capacitors than the ester fluids. This difference was demonstrated in a test under rather greater stresses than normal , but very long term tests at lower stresses show the same trend in less dramatic fashion. TABLE V A.C. TEST DATA ' Impregnant Percent Failed Unit Hours Aroclor 1016 MCS 1475 MCS 1588 25% 100 25 7844 988 7936 Test conditions: 8 capacitors per set, paper dielectric, 1000 volts A.C./mil, 90C, Total Possible unit hours/set 10,208 hrs. PCB-ARCH0748144 MCS 1475 and MCS 1588 also seem to have promise in D.C. capacitors. Data in support of this are shown in Table VI. TABLE VI D.C. TEST DATA Impregnar.t % Failed Unit Hours Aroclor 1016 + 0.3% Unox 4221 Aroclor 1016 + 0.5% anthraquinone MCS 1489 + 0.5% anthraquinone MCS 1475 + 0.5% anthraquinone MCS 1588 + 0.5% anthraquinone 87.5% 25 25 12.5 0.0 2,498 hrs. 3,497 3,857 3,933 4,416 Test conditions: 8 capacitors per set, paper dielectric, 1000 volts D.C./mil, 85C, Total possible unit hours/set 4,416 hrs. It is well known that chlorinated biphenyl fluids must have an additive to make them useful in D.C. capacitors. As can be seen from the data in Table VI, Aroclor 1016 plus epoxide, a good A.C. stabilizer, gives relatively poor D.C. performance. With anthra quinone, the results are much better. MCS 1489 with the same stabilizer gives slightly better performance. MCS 1475 with the same stabilizer still better results and MCS 1588 shows no fail ures to date. As can be seen by comparison of data in Figures 1, 2, 3 and 4, both esters and hydrocarbon base fluids can be used to much lower 0041936 EX P-3114 Page 17 of 22 PCB-ARCH0748145 -14temperatures than trichlorobiphenyl. However, suitable trichlorobiphenyl-trichlorobenzene mixtures can also be used at very low temperatures. Another important difference among these types of fluid is that trichlorobiphenyl is not ideal for use in metallized paper or film capacitors which are expected to "self heal". This is because the chlorinated compounds generate hydrogen chloride which may lead to permanent breakdown even when a very minor discharge takes place. MCS 1475 is reported to show good performance in metallized paper capacitors. MCS 1588 would probably be even better. This \ . may seem surprising in view of their sulfur content which many would expect would lead to the formation of sulfuric acid under arcing conditions within a capacitor. In fact, however, the conditions during arcing are highly reducing so that the sulfone decomposition products are polysulfones and hydrogen sulfide, neither of which cause permanent failure. . In summary, it can be said that the capacitor maker now has a number of possible alternate fluid impregnants to choose among. He must evaluate these carefully and make his choice giving suitable weight to the importance of each of the factors involved. 0041937 EX P-3114 Page 18 of 22 PCB-ARCH0748146 REFERENCES 1. Jensen, Soren, Report of a New Chemical Hazard, New Scientist 32: 612. 2. Interdepartmental Task Force on PCB's COM-72-10419, 20 Mar. 1972. 3. Decline of PCB Concentrations in North Atlantc Surface Water, G. R. Harvey, W. G. Steinhaver and H. P. Miklas, Nature 252 387 (1974). 4. a. U.S. Pat. 2,211,019, Electrical Condenser, W. Lommel and R. Englehardt. b. U.S. Pat. 2,410,714, Dielectric and Insulating Composition, F. M. Clark. c. U.S. Pat. 2,434,540, Capacitor and Dielectric Therefor, L. V. Berberich. 5. a. A New Liquid Dielectric for Capacitors, B. H. Goldy and W. 0. Solberg, Insulation/Circuits, January 1975, p. 39. ' b. U.S. Pat. 3,754,173, Stabilized Ester Impregnated Capacitor, J. W. Eustance. 6. Development of a New Electrical Fluid, A. J. Rulkowski and E. 0. Forester (Presented before IEEE 1974). 6. U.S. Pat. 3,811,077, Liquid Impregnated Capacitor, R. H. Munch. 7. U.S. Pat. 3,796,934, Capacitor with Non Halogenated Impregnant, R. H. Munch. OQ'tl**38 EX P-3114 Page 19 of 22 PCB-ARCH0748147 TABLE II . * PROPERTIES OF AROCLOR TYPE DIELECTRIC FLUIDS - Properties Sp. G. 25/25C DK 25C 100C Tan 6 60 Hz 100C R$ 100C x 1C9 ft cm Viscosity, cs. 0 100F. . 0 210F Flash Point F. Fire Point F AIT F. . Hydrolysis ** Aroclor 1016 MCS 1043 . Data on Fluids MCS 1489 1.368 5.9 4.85 . 0.0025 . 150,000 1.246 6.0 5.0 0.0006 ` 10,000 1.348 8.1 6.5 0.05 2,000 14.3 2.12 358 None to BP (620) 1185 0.00 5.6 . 1.47 318 None to BP (515) 1155 0.00 21.5 2.54 358 610 1125 0.00 Capacitance 0 25C. Dissipation Factor 0 25C. Capacitance @ 90C. . Dissipation Factor 0 90C. Terminal to Case Resist. Data on 2 yF Capacitors* Imprean-ited with Above Fluids 1.95 1.99 . 2.20 0.0034 1.83 0.0032 240 x 109 0.0037. 1.89 0.0037 0.0040 2.07 0.0033 89 x 109 . * 0041939 1 * Standard 2 yF, 585 VAC Capacitors, 2 layers 0.00066, 0.90 density paper, 0.3% Unox added. ** Neutralization number of sample with 0.5% water added heated for 168 hrs. at EX pT3dd4>on. Page 20 of 22 PCB-ARCH0748148 TABLE III PROPERTIES OF ESTER TYPE DIELECTRIC FLUIDS Properties Sp. G. 25/25C DK 25C 100C Tan 6 60 Hz 100C R$ 100C x 109 ft cm Viscosity, cs. 0 100F. G> 210F Flash Point F. Fire Point F * AIT F. Hydrolysis** . OO CO r*v OO *=r *3* DOP 0.983 5.3 4.3 0.075 211 29.0 4.3 - - 0.11 DINP Data on Fluids MCS 1475 4.6 3.9 0.01 1900 0.988 6.2 5.0 0.022 500 430 495 26.4 4.33 432 495 - 0.15 0.17 Capacitance 0 25C. Dissipation Factor 0 25C. ' Capacitance 0 90C. Dissipation Factor 0 90C. Terminal to Case Resist. Data on 2 yF Capacitors* Impregnated with Above Fluids 1.85 1.95 0.0033 - 0.0034 1.84 1 x 109 0.0032 2.6 x 109 * Standard 2 yF, 585 VAC Capacitors, 2 layers 0.00066, 0.90 density paper, 0.3% Unox added. . Pagee2i of2$ou- PCB-ARCH0748149 Properties Sp. G. 25/25C DK 25C 100C Tan 6 60 Hz 100C R$ 100C x 109 a cm Viscosity, cs. 0 100F. & 210F Flash Point F. Fire Point F AIT F. Hydrolysis ** Data on Fluids 1.018 6.0 5.1 . 0.046 1,000 1.030 6.1 5.1 o.i 620 9.1 1.98 303 328 7.14 . 1.96 325 350 1.0507 6.2 5.1 f 0.1 1,500 9.68 2.08 275 285 OO 835 0.00 870 0.00 0.00 Capacitance 0 25C. Dissipation Factor 0 25C. , Capacitance @ 90C. . Dissipation Factor 0 90C. Terminal to Case Resist. Data on 2 pF Capacitors* Impregnated with Above Fluids 1.97 1.98 ; 1.97 0.0037 1.87 0.0036T 1.87 0.0038 1.87 0.0039 0.0035 51 x 109 0.0034 00^l9^i * Standard 2 pF, 585 VAC Capacitors, 2 layers 0.00066, 0.90 density paper, 0.3% Unox added. ** EX ^P-3if4 Page^ o?c22on- + s a PCB-ARCH0748150