WO2010012051A2 - Process of production of dielectric fluid obtained from vegetable oils and formulation of dielectric fluid using vegetable oils - Google Patents

Abstract

Patent of invention of a process for the production of a dielectric fluid, as well as its formulation, obtained from a mixture of vegetable oils of the triglyceride type, where the main component is a basic product obtained from a derivative of castor oil (Ricinus cummunis L), resulting in a renewable, biodegradable and ecologically correct product, applicable in equipment for electric distribution and transmission, such, as transformers, capacitors or cables for electric transmission lines; this product is different due to the fact that it uses a derivative of castor oil that has a mixture of connected acids which, when mixed with other saturated vegetable oils, considerably alters the formulation of dielectric, which is the main object of this invention, as the mixture has a particular chemical composition, composed of oleic fatty acids, connected fatty acids, besides other saturated ones.

Description

PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING

VEGETABLE OILS

This invention refers to the PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, thus originated from a renewable source, with biodegradable characteristics and consequently ecologically correct; these factors result in a product that can be applied to equipment of distribution and transmission of electric power such as, transformers, capacitors or transmission line cables. SUMMARY OF INVENTION

Vegetable oils are an Important class of agribusiness products and their importance is recognized in many countries, especially in countries like Brazil, Africa, China and India that employ thousands of people in their rural areas. Among the various vegetable oils produced in these countries, castor oil (Ricinus communis L) has a peculiar chemical composition as regards its high content of ricinoleic acid, a fact that has not yet been taken into consideration in previous patents related to dielectric properties, thus making a remarkable contribution to the qualities of dielectric, which is the object of this invention. The average composition by percentage of castor oil used in all the experiments that are related on this patent request is as follows: Ricinoleic acid

89,5%; Dihydroxystearic acid 0,7%; Palmitic acid 1 ,0%; Stearic acid 1,0%; Oleic acid 3,0%; Linoleic acid 4,2%; Linolenic acid 0,3%; and Eicosanoic acid 0,3%.

These figures were obtained based upon analysis originated from a Shimadzu chromatograph connected to a CG/MS, model QP 5050, mass spectrophotometer and are In accordance with the figures indicated in scientific and technological literature on the composition of this oil. The process referred to herein uses as its main raw material a derivative of clarified and filtered castor oil with a general type ϊ formulae, as shown in Figure 1, where Ri, R₂ e R3 are groups of saturated, unsaturated, unusual fatty acids or their mixture. The number of carbon atoms in these fatty acids is variable and it may be within a range of 12 to 22. Other oils can be used to complement the final formulation, in order to give exceptional properties to the use of electric transformers. This invention is based on studies of molecular modeling, which was performed with the purpose of evaluating the relationship between structure and property of the dielectric fluid mentioned herein, In order to do this, a DELL workstation, "Dimension" 4700 / Pentium IV was used to study the dielectric properties. Depending on the chemical composition and the number of carbon atoms of Ri, R2, R₃ groups existing in the molecules of fatty acids like triglycerides with a general type I formula (Figure 1), as weft as on the nature of the chemical transformations performed in this structure, important properties for the dielectric fluid may be obtained, making it an ideal insulating oil with remarkable properties such as: a high flashpoint to allow low volatility; a good viscosity range to allow fluidity; a high amount of specific heat to allow an efficient exchange of heat between the transformer nucleus and the external environment; a low fluidity point to allow the outflow of fluid at low temperatures; besides good breakdown voltage and a power factor comparable to the best insulating oils available on the market. The presence of an amount of oleic acid of 64% in the composition of the dielectric, based on triglyceride type oils, has been indicated in previous patents as a fundamental parameter to obtain a product with good dielectric properties. This invention is different from previous patents as it uses a derivative of castor oil which has a mixture of connected acids that when mixed with other saturated vegetable oils, considerably differentiates the formulation of the dielectric, which is the main object of this patent. TECHNICAL BACKGROUND The state of art related to the application of dielectric fluids in electric power equipment, such as transformers, capacitors and transmission cables, requires the establishing of the properties mentioned herein for dielectric fluid within very narrow ranges. This fact is directly related to the chemical changes performed in the molecule indicated in the general type I formulae (Figure 1 ), among which are especially a high content of connected fatty acids and a low amount of iinoleic acid. Certainly a recovery of these properties after being used in recovery processes of these fluids is afso required, aiming at, after use, the elimination of undesirable components that supply color, dispersion current and rupture of electric tension (loads) at low levels of the power applied; in other words, loss of electric stability.

Conventionally, petroleum derivatives, paraffinics or naphthenics have been used to meet the above mentioned requirements. In particular, hydro carbons with a high molecular weight (HMWH) have also been used in situations where high voltages are applied to transformers, as well as in cases where high operating temperatures are required and also where the need for maintenance becomes difficult. Synthetic fluids have also been used as dielectric fluids. These are designed to balance dielectric and environmental properties, besides low flammability. The basic problem of these fluids Is that as they are partially biodegradable they cause serious environmental problems to superficial water bodies and even to the ground and underground, due to typical spills or leakages, a fact that limits the applicability of these oils due to the environmental rules anά legislation in force.

Although vegetable oils, especially glycerol esters, were the first kind of vegetable oils used as dielectric oils in transformers in the United States of America, around 1885, the oils derived from petroleum, either paraffinic, naphthenic or their mixture, have been preferably used as dielectric oils in power transformers, capacitors or transmission cables, due to their good dielectric properties and the facility of industrial production, which allow their low cost. Nevertheless, they are considered undesirable nowadays from the environmental point of view, due to their low biodegradability; a predominant factor where spills and/or leakages occur in electrical equipment.

Historically, literature points out that the first patent related to the use of vegetable oils as a cooling dielectric fluid was due to Elihu Thomson, in 1882, and that ten years later, in 1892, Genera! Electric used mineral oils as a dielectric fluid in transformers. (McShane, Patric C; Vegetable-Oil-based Dielectric Coolants; IEE Industry Applications Magazine; May/June 2002). Following, the British patent GB 143,193 (Dr. Meilach Melamid, February 03, 1921), registered the use of strong oxidizing agents, such as permanganate, chromate, dichromate or chromic acid, for the treatment of fractions of oil of the anthracite type without phenol for the production of oil to be used in transformers. Then, American patent US 1,425,645; (Cyrus Howard Hapgood, August 15 1922) was trie first patent that proposed the use of basket-type centrifuges to dehydrate mineral oils in a continuous way, completely separating water from heavy oil and providing improved dielectric properties to this mineral oil. American patent US 3,000,807 (Esso Research and Engineering Company, September 19, 1961) refers to the invention related to the use of a mixture of two kinds of mineral oils as an insulating dielectric fluid, composed of a distilled solution treated with acid and a hydro-refined distϋfed solution. This kind of mixture provides better oxidation tests than each of its components separately. American patent US 3,095,366 (The Standard Oil Company, Cleveland, Ohio, June 25, 1963) describes the discovery of a dielectric oil which is a mixture of a substantial amount of decanted oil and of naphihenic lubricant oil, which gives it high electric stability, without the need of using additives to inhibit oxidation or a lower fluidity point. American patent US 3,406,111 (Sun Oil Company, Philadelphia, Pa., October 15, 1968) refers to a naphthenic oil distilled from petroleum at a distillation temperature between 238⁰C - 413⁰C, viscosity in the range of 50-65 cSt, at a temperature of 38⁰C, specific density between 0,84 and 0,92, and a nitrogen content of less than 4ppm, when submitted to the test of double oxidation in the absence of inhibiting additives and showing a neutralization index lower than 0,25mg KOH/g and the absence of formation of residues during an oxidation test that lasted 96 hours, it should be pointed out that the value of the power factor must be consistently lower than 2% during the whole oxidation test. American patent US 3,753,188 (Hitachi, Ltd.; Korea Industry Co.; Japan, August 14, 1973) deals with the invention related to the use of mixtures of oils of the poiycyclic hydrocarbon type, such as dielectric oils with a flashpoint higher than 15O⁰C, which have poiycyclic naphthenic hydro carbons containing from two to five rings and polycych^'c aromatic hydrocarbons that have from two to four rings, besides the fact that they must contain on each side of the respective rings of the alky! group, with a maximum of four carbon atoms. American patent US 4,082,866 (RTE Corporation, Waukesha, Wisconsin, April 04, 1978) refers to the use of hydrocarbons as a dielectric fluid, relatively non-flammable and environmentally safe, with between 500 and 700 units of molecular weight (HMWH) and an ignition temperature above 200⁰C.

The literature mentions that it was proposed to use a mixture of biphenyl oxide with carbon tetrachloride as dielectric fluid to replace mineral oils. This work originated the use of halogen compounds as dielectric fluid, described in the British patent GB 370,020 (Campbell Roger et al.; & Co., March 24, 1932). In the sequence of the development of these products, halogen derivatives were industrially used for a long time as they had better dielectric properties than the corresponding hydrocarbons and were not flammable. Normally, chlorine or fluorine is used as typical halogens. The registry of British patent GB 805,772 (General Electric Cc₁ October 12, 1955) covered the rights of this company upon this class of dielectric fluids, besides listing some dielectric properties of these products. The following halogen compounds (SF₆, C₃Fs e C4F10) are shown as reference products, in accordance with the structures with type Il general formulae, as shown in Figures 2A, 2B and 2C. An important group of halogen dielectric oils is the Askarel, a mixture of polychlorinated biphenyljcs compounds (PCB^'s) with trichlorobenzene, typically containing from 40 to 50% of trichlorobenzene. The PCB's type compounds have a type III general formulae, as shown in Figure 3, where the number of chlorine atoms varies from one to ten units per molecufe. At that time, these dielectric oils were used as insulating oils for high power transformers due to their high dielectric constants. Furthermore, PCB's have a power loss at low temperatures. Nevertheless, they were forbidden as dielectric fluids due to their high toxicity which was considered harmful to the environment. Synthetic dielectric oils are another large class of fluids used in electrical equipment of power distribution and transmission that were developed within the context of less flammable oils. Thus, American patent US 5,017,733 (Nippon Petrochemicals Company, of May 21, 1991) proposes the use of synthetic bicyclic aromatic hydrocarbons (HAB) with a type IV general formulae as shown in Figure 4A to replace the PCB's, where the R group of this formula may show six different groups of compounds, as follows: methyl, di-methyt, ethyl, tsopropyf, ter-butyl and ter- amyl. As a typical example of these synthetic products the following compounds can be mentioned: 1-phenyl-1-xylyl-ethane (PXE; Figure 4B) and mono- isopropyl-biphenyl (MIPB; Figure 4C), besides the mixture of mono-benzyl- toluene (MBT; Figure 4D) and di-benzyi-toluene (DBT; Figure 4E)₁ preferably used in capacitors. In its turn, American patent US 3,696,137 (General Electric Co., of October 03, 1972) refers to the use of blocks of copolymers with segments of polyphenilene oxides and segments of poly-di-methylsiloxane, which are used as superficial tension reducers of dielectric fluids, especially of the "Askarel" type fluids, as indicated in the type V general formulae shown in Figure 5. This property allows the dielectric fluid to penetrate the interstices of the equipment, expelling gas bubbles and efficiently wetting the internal surface of the device. The dielectric fluids based on synthetic esters have good insulating properties and are significantly more biodegradable than mineral oils with a high molecular weight (HMWH). This kind of dielectric fluid has a particularly excellent thermal stability and good dielectric properties at low temperatures. Its high cost as compared to that of other less flammable dielectric fluid limits its use in mobile transformers and other kinds of specific applications. The literature refers to seven different kinds of synthetic esters: di- esters, phthalates, tri-mellitates, pyromeiitates, dimeric acid esters, polyols and polyolates. An example of polyesters as commercial dielectric fluids is one made of branched monoacids with an amount of carbon atoms between five and eight (Cs - Ce), and pentaerytrito! alcohol. American patent US 6,444,626 (Hatco Corporation, of September 03, 2002) refers to synthetic ester compounds based on mixtures of poly-(neopentylpolyol) esters and polyol esters with at least two hydroxyl groups. This combination of fluids is adequate for use as a lubricant for rotating cooling compressors. American patent US 5,658,864 (Ethyl Corporation of August 19, 1997) refers to the use of poly- olefins, biodegradable compounds, such as Industrial fluids for use as lubricants, hydraulic fluids, fuel oils and other similar uses to reduce the fluidity point and improve stability to oxidation. American patent US 5,949,017 (ABB Power T & D Company inc., of September 7, 1999) refers to a vegetable oil of the triglyceride type, rich in oleic add, whose composition of fatty acids has at least 75% of oleic acid, less than 10% of di-unsaturated fatty acids, less than 3% of tri-unsaturated fatty acids and less than 8% of saturated fatty acids, with the following properties: minimum breakdown voltage of 35 KV / 100.mil with 2,50mm spacing between plates, power factor less than 0,05% at 25⁰C, acidity less than 0,03mg KOH/g, electric conductivity less than 1 pS/m at 25⁰C, flashpoint of at least 25O⁰C, and fluidity point of at least -15⁰C. Compounds of triglyceride oils referring to various dielectric fluids are shown, as well as the electric equipment and the process to prepare oils rich in oleic acids, the content of additives, between 0,2 and 2,0%, preferably from 0,5 to 1 ,0%. The additives used were from CIBA/GEIGY, of the IRGANOX, IRGAMET family, besides poly-methacrylate as an additive to tower the fluidity point. American patent US 6,037,537 (Cooper Industries, Inc. Houston, Texas, of March 14m 2000) refers to a new kind of transformer, whose tank contains; the nucleus, coiling, a dielectric fluid and &n antioxidant dissolved in this fluid, besides an additive to reduce to fluidity point, in such an amount that there is head space where a box with oxygen absorbing material is located, within polymeric material that seals the material, which may be eventually supplied again. The dielectric fluid is a mixture of vegetable oil esters, whose components contain saturated and unsaturated fatty acids with 14 to 22 carbon atoms, preferably soy, canoia and sunflower oil, separately or mixed with other oils. As regards oxygen absorbing material, American patent US 2,825,651 (Carnation Company, Los Angeles/USA of March 04, 1958) demonstrates that several kinds of metallic sulfites are oxidized to sulfates in the presence of oxygen. American patent US 5,958,851 of September 28, 1999 and the following American patent US 6,159,913; (Waverly Light and Power, Iowa/USA of December 12, 2000) refer to a dielectric fluid that is a mixture of vegetable oils containing soy oil as the basic oil. This mixture is characterized by the addition of other partially hydrogenated vegetable oils in order to obtain dielectric fluids with a high content of oleic acid. Sunflower oil is mostly recommended to be hydrogenated, forming a thin ester with a high content of oleic acid. The process of winterization can also be used to remove saturated components, improving even more the characteristics of the mixture as a dielectric fluid, as well as adding additives, antioxidants, improving point of fluidity and flashpoint. Furthermore, Cargill Incorporated of Minneapolis registered in the American patent system the document US 6,583,303 B1 in June 2003, related to the production of a triglyceride vegetable oil that contains more than 86% of oleic fatty acid and less than 2,5% of finoieic acid. The relevant property of this oil is a high oxidative stability, which certainly enables its use as a transformer fluid. A publication by the Electrical Engineering Department of the University of Moratuwa, together with Lanka Transformer Ltd, Angulana Station Road, refers to the use of whitened, refined and deodorized coconut oil (vacuum at 200⁰C) as a dielectric fluid. Unlike triglyceride vegetable oils with a high content of oleic acid, mixed with soy, which have more than 60% unsaturated compounds, coconut oil are characterized by the fact that it only has 9%. Oils with a high content of non-saturation usually are fluid at low temperatures, which is not true in the case of coconut oil as it solidifies at around 2O⁰C. On the other hand, the higher non-saturation level causes chemical instability due to the possibility of oxidation and consequently the formation of undesirable polar products, as they provide current escape. Coconut oil, however, is more stable and thus much better than sunflower oil in this respect. The use of additives to lower fluidity point was not effective for this purpose. Coconut oil when solidified kept its non- reduced breakdown voltage, which proves the potential of its use as a dielectric fluid under the conditions which exist In that country (Sri Lanka). DESCRIPTION OF FIGURES

For better understanding, the description of the invention is associated with illustrations. Figure 1 show the type i general formulae of a derivative of castor oil, where R₁, R₂ and R₃ are groups of saturated, unsaturated, unusual fatty acids or their mixtures.

Figures 2A, 2B and 2C, show the type !3 general formulae of halogen compounds SF₆, C3F8 e C4F10. Figure 3 shows the type III general formulae of PCB's type compounds.

Figure 4A shows the type IV general formulae of synthetic bicyclic aromatic hydrocarbons (HAB). Figures 4B, 4C₁ 4D and 4E, respectively show 1- phenil-1-xylyl-ethane (PXE), mono-isopropyl-biphenyl (MlPB), besides the mixture of mono-ben∑yl-toluene (MBT) and di-benzyl-toluene (DBT), which are preferentially used in capacitors.

Figure 5 shows the type V genera! formula of blocks of copolymers with segments of polyphenilene oxides and segments of poly-dimethylsiloxane, which are used as reducers of the superficial tension of dielectric fluids, especially of "Askarel"type fluids.

Figure 6 demonstrates the flowchart with all the stages of the productive process of the derivative of castor oil and the formulation of dielectric oil. Figures 7 and 8 are graphic representations of the results of breakdown voltage versus the number of switching.

Illustration 9 shows the results of the dielectricity tests. FUNDAMENTALS OF [NVENTlGN

In order to better understand this invention, the following is a detailed description of the productive process of the derivative of castor oil, the basic product for the formulation of this patent and of the technical specifications of the formulated product, object of this invention. All stages related to the production of the basic derivative and its formula is referred to in Illustration 6. Example 1: Sufficient type 1 industrial castor oil acquired from a commercial company accredited for this kind of supply was put inside a storage tank (1) to allow continuous operation of the pilot plant for about 10 hours. Previously, duplicate analyses of samples of this oil were performed and the same average amounts for their physico-chemical properties were observed as those supplied by the manufacturer, as follows: index of iodine = 85 (AOCS, Cd1-25); index of max. hydroxyl = 159 mg KOH/g (AOCS₁ Cd 13 - 60); max. humidity = 0.3%; max. content of free fatty acids = 1.0 (AOCS, Ca 5 a - 40); index of saponification = 185 mg KOH/g (AOCS , Cd 3 - 25). The temperature of the oil stored in the vase (1) was always around 3O⁰C during the whole operation of production of the derivative of castor oil, which began with the feeding of this oil into the heat exchanger (2), which provided preheating of oil to a temperature of approximately 25O⁰C by means of heat exchange with a Dowtherm fluid heated in the boiler (3). This oil then fed the pilot reactor (4) of the perfect mixture type (CSTR), which operates at a temperature of 300⁰C and is coupled to a condenser (5) for the collection of water generated during this reaction process. Commercial concentrated sulfuric acid originated from the container (6) was used as a catalyst at a ratio of 1-5% in weight related to the material in the reactor, in order to adjust its iodine index to a range of 100-110 (Wij^'s). This condition is considered essential to allow fluidity at a low temperature, around (- 2O⁰C). The mixture of the catalyst with the castor oil is carried out before the oil introduction into the reactor (4). The average flow of reacted material at the exit of this reactor was continuously evaluated and an approximate amount of 5,1L/hour was obtained. The derivative of castor oil obtained in this run was immediately cooled by means of the heat exchanger (7) to the environment temperature, 3O⁰C, with the aid of a coofing unit (8), which always operated with water at 5°C. This product was forwarded to the container (9) where it was stored. Samples of this basic oil were analyzed in duplicate, observing the following average amounts for their properties: index of iodine = 135 (AOCS, Cd1-25); max. index of hydroxyl = 20mg KOH/g (AOCS, Cd 13 - 60); max. humidity = 0.3%; max content of free fatty adds = 3.0 % (AOCS, Cd 3 a - 63); index of saponification = 182rng KOH/g (AOCS Tl 1 a - 64), viscosity = 90 cP at 40⁰C. Then this product was sent to special purification equipment that uses a membrane (10) to reduce the index of acidity to amounts lower than 0.03. The product thus obtained was sent to stock (11) for later formulation. The derivative of castor oil thus produced showed the following values for its properties as indicated in Table 1 , column referring to the experiment 1. Example 2:

In a second experimental run, once again a sufficient quantity of type 1 industrial castor oi! as in the previous example was put into the storage tank (1) to allow the continuous operation of the pilot plant for about 15 hours. Duplicate analyses of a sample of this oil showed average amounts for their physico- chemical properties as follows: index of iodine = 85 (AOCS, Cd1-25); index of max. hydroxyl = 159 mg KOH/g (AOCS, Cd 13 - 60); max. humidity = 0.3%; max. content of free fatty acids = 1.0 (AOCS₁ Ca 5 a - 40); index of saponification = 182 mg KOH/g (AOCS , Cd 3 - 25). The temperature of the oil stored in the vase (1 ) was always around 32⁰C during the whole operation of production of the basic derivative of castor oil, which began with the feeding of this oil into the heat exchanger (2), which provided preheating of the castor oil to a temperature of approximately 250⁰C by means of a Dowtherm oil heated in the boiler (3). This oil then fed the piSot reactor (4) of the perfect mixture type (CSTR), which operated at a temperature of 300⁰C and was coupled to a condenser (5) for the collection of water generated during the process of production of the derivative of castor oil. Commercial concentrated sulfuric acid originated from the container (6) was used as a catalyst at a ratio of 1 ,5% in weight related to the material in the reactor, in order to adjust its iodine index to a range of 100-110, an amount considered adequate to allow fluidity in the transformer at a low temperature (-2O⁰C). In this experiment, the average flow of reacted material at the exit of the reactor was continuously evaluated and an approximate amount of 5,3L/hour was obtained. The derivative of castor oil obtained was immediately cooled by means of the heat exchanger (7) to the environment temperature, 3O⁰C₁ with the aid of a cooling unit (8), which operated with water at 5⁰C. This product was forwarded to the container (9) where it was stored. Samples of this basic oil were analyzed in duplicate, observing the following average amounts for their properties: index of iodine = 133 (AOCS, Cd1-25); max, index of hydroxy! = 18mg KOH/g (AOCS, Cd 13 - 60); max. humidity = 0.25%; max content of free fatty acids = 3.0 % (AOCS, Cd 3 a - 63); index of saponification = 180mg KOH/g (AOCS Tl 1 a - 64), viscosity = 190 cP at 27.5⁰C. Then this product was sent to special purification equipment (10) that uses a membrane to reduce the index of acidity to amounts lower than 0,03 and was sent to the container (11) for storage. For its final formulation, the derivative of castor oil was then sent to the mixing tank (12) for final formulation. In this experiment 2, this product had the addition of BHT originated from the container (13), resulting in a dielectric fluid as indicated in Table 1 , column referring to the second experiment. Analysis of these amounts indicates an excellent result when compared to the amounts of the electric properties with those specified by international standards. Example 3:

Sufficient type 1 industrial castor oil acquired from a second accredited commercial company for this kind of supply was put into the storage tank (1) to allow the continuous operation of the pilot plant for about 30 hours. Previously, duplicate analysis of a sample of this oil were performed and showed the same average amounts for their physico-chemical properties as those supplied by the manufacturer, as follows: index of iodine = 85 (AOCS, Cd1-25); index of max. hydroxyl = 159 mg KOH/g (AOCS, Cd 13 - 60); max. humidity = 0.3%; max. content of free fatty acids = 1.0 (AOCS, Ca 5 a - 40); index of saponification = 182 mg KOH/g (AOCS , Cd 3 - 25). The temperature of the oil stored in the vase (1) was always around 3O⁰C during the whole operation of production of the derivative of castor oil, which began with the feeding of this oil into the heat exchanger (2), which provided preheating of the oil to a temperature of approximately 25O⁰C by means of a Dowtherm oil heated in the boiler (3). This oil then fed the pilot reactor (4) of the perfect mixture type (CSTR), which operated at a temperature of 300⁰C and was coupled to a condenser (5) for the collection of water generated during the reaction process. Commercial concentrated sulfuric acid originated from the container (6) was used as a catalyst at a ratio of 1,6% in weight related to the material in the reactor, in order to adjust the iodine Index to a range of 100-110, an amount considered adequate to allow fluidity at a low temperature (-2O⁰C)- The mixing of the catalyst with the castor oil was done before introducing the oil into the reactor (4). The average flow of reacted material at the exit of the reactor was continuously evaluated and an approximate amount of 4,1L/hour was obtained. The derivative of castor oil obtained in this run was immediately cooled by means of the heat exchanger (7) to the environment temperature (30⁰C), with the aid of a cooling unit (8), which operated with water at 5⁰C. This product was forwarded to the container (9) where it was stored. Samples of this oil were analyzed in duplicate, observing the following average amounts for their properties: index of iodine = 138 (AOCS, Cd1-25); max. index of hydroxyl = 21 mg KOH/g (AOCS, Cd 13 - 60); max. humidity = 0.3%; max content of free fatty acids = 3.0 % (AOCS, Cd 3 a - 63); index of saponification = 180mg KOH/g (AOCS Tl 1 a - 64), viscosity = 167 cP at 25⁰C. Then this product was sent to special purification equipment (10) that uses a membrane to reduce the index of acidity to amounts lower than 0,03. The product thus obtained was stored in the container (11), which feeds the mixing container (12). After the preparation of the basic derivative of castor oil, this product was formulated with 4,0% refined and deodorized soy oil coming from the recipient (14) with the purpose of reducing production costs. The final product was stored in recipient (15) and the results are indicated in Table 1 , column referring to the experiment 3. Example 4: In this experiment the oleic fraction of palm oil was analyzed according to

Table 1, column referring to the experiment 4. This fraction is obtained from palm oil by means of crystallization of the saturated fraction, thus remaining in unsaturated fraction that shows an index of iodine of 62 (Wifs method). The dielectricity tests performed with this fraction indicates its excellent dielectric properties after 50 switching test, as shown in Figure 8. Based upon this result, different samples of this fraction were prepared with 20%, 30% and 40% of the derivative of castor oil, thus producing stable mixtures with excellent dielectric capacities. Example 5: Experiments were performed with mixtures of castor oil and a derivative of Cashew Nut Shell Liqutd-CNSL (methyf ether from hydrogenated cardanol). It was observed that the use of this derivative avoids the use of additives, especially antioxidants. It was also noted that this product has excellent dielectric properties, which gives the mixture an exceptional dielectric character. The samples of the various derivative of castor oil after their purification as well as the product formulated with mixtures were submitted to continuous tests of switching (breakdown voltage) \n order to evaluate the stability of these products as regards this property. Illustrations 7 and 8 prove the excellent stabilities of the breakdown voltage of the derivative of castor oil and of the oleic fraction of palm oil after fifty consecutive switching tests.

In addition to the workbench tests, the dielectric fluids originated from this patent request; a derivative of castor oil, the oleic fraction of palm oil, or their mixtures, tests were also performed with these products in transformers installed in the distribution grid of Companhia Energetica do Ceara - COELCE₁ Fortaleza, Ceara, in the industrial district of Fortaleza.

Claims

1. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, characterized by the fact of using a derivative of castor oil mixed with other kinds of vegetable oHs, resulting in a product applicable to equipment of distribution and transmission of electric power, both for domestic and industrial use, and which has a high content of connected fatty acids, more than 80%, and also has a minimum breakdown voltage of 35 KV/ lOOmil, with spacing between plates of 2,54mm, low power factor, less than 0,5% at 25⁰C, acidity less than 0,03mg KOH/g, electric conductivity less than 1 pS/m at 25⁰C, flashpoint of at feast 250⁰C and fluidity point within the range of - 2O⁰C, also showing a high reaction yield of 90%.

2. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, in accordance with claim 1 , characterized by the fact that the type 1 commercial castor oil is stored in a tank made of carbon steel (1) from where it is pumped to a heat exchanger (2) where it is preheated to a temperature of approximately 25O⁰C before being admitted into a continuous reactor of the perfect mixture type (4), or a group of this kind of reactors, operating in cascade, where the preheating of the castor oil and the heating of the reactor are performed by means of the exchange of heat of these materials with a fluid of the Dowtherm type, originated from a boiler (3), which may receive heat from an electric resistance or from the burning of any kind of fuel; the oil referred to herein is appropriate for the exchange of heat at this temperature range without evaporation losses and where the temperature of the reactor (4) must be between 275°C and 35O⁰C, in order to produce a derivative of castor oil with a high degree of connected non-saturation; the yield of this reaction is about 80% when a feeding rate of approximately 1,0 l/min is used in pilot reactor with a capacity of 5,0 liters and a catalyst concentration of around 1 ,0% and where the reactor (4) operates coupled to the condenser (5), with the purpose of removing the water produced during the reaction; the reaction that takes place inside the reactor (4) may be catalyzed with concentrated sulfuric acid, phosphoric acid, phosphorous acid, or even acid resins originated from the vase (6) and preferably acid resin, as the product of the reaction is continuously cooled by means of a heat exchanger (7) until it reaches the environment temperature, approximately 3O⁰C, so that no polymerization may occur; this is done with the aid of a cooling fluid originated from the cooling unit (8); the product of the reaction is sent to the intermediate product tank (9) and then sent to special purification equipment that uses a membrane (10) to reduce the index of acidity to amounts lower than 0,03; then the product of the reaction is sent to a container (11) for storage and for its final formulation the basic derivative is sent to the mixture tank (12) where it receives additives from the container (13) and other vegetable oils previously selected from the tank (14), in specific proportions, in order to provide adequate dielectric and physico-chemical properties to the final product; then the formulated product is stored in the tank (15), after examining a!! its properties, in accordance with international standards.

3. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS_f in accordance with claims 1 and 2, characterized by the fact that reactor (4) can operate in batches; in a continuous or semi- continuous way, as the perfect mixture type or fixed tray, which must operate at a temperature range preferably between 2QO⁰C and 225⁰C, in order to produce a derivative of castor oil with a high degree of connected non-saturation with the yield of this reaction of about 90% when a continuous reactor of the perfect mixture type with a capacity of 5,0 liters is used, which operates with an output of approximately 5,0 l/min and a catalyst concentration of around 1 ,0%.

4. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, in accordance with claims 1, 2 and 3, characterized by the fact that in the mixture of connected fatty acids derived from castor oil other vegetable oils are added at the rate of up to 5% and where this mixture shows an iodine index of approximately 100 to 110 units when measured with the Wϊjs method; soy, maize, sunflower or even Jatropha oil are preferably used.

5. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, in accordance with claims 1, 2, 3 and 4, characterized by the fact that the basic derivative of castor oil avoids the use of additives to lower the fluidity point of the dielectric fluid to temperatures of less than -20⁰C.

6. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID

USING VEGETABLE OILS, ϊn accordance with claims 1,2 3, 4 and 5, characterized by the fact of using a mixture of other vegetable oils, especially hydrogenated cardanol, obtained from the cashew nut shell liquid - CNSL, which grants exceptional antioxidant properties to the dielectric fluid.

7. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED

FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, in accordance with claims 1 , 2, 3, 4, 5 and 6, characterized by the fact that other vegetable oils can be used in the mixture with the derivate of the castor oil, especially a methyl ether derived from hydrogenated cardanol obtained from the cashew nut shell liquid -CNSL

8. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, in accordance with claims 1, 2, 3, 4, 5, 6 and 7, characterized by the fact of using an oleic fraction of palm oil with the derivative of castor oil, purified in a mixture at rates of 20%_r 30% and 40%.

9. PROCESS OF PRODUCTION OF DIELECTRIC FLUID OBTAINED FROM VEGETABLE OILS AND FORMULATION OF DIELECTRIC FLUID USING VEGETABLE OILS, in accordance with claims 1, 2, 3, 4, 5, 6, 7 and 8, characterized by the fact of using the derivative of castor oil and/ or the oleic fraction of palm oil.