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  Electrical insulating oil compositionUSPTO Application #: 20070208205Title: Electrical insulating oil composition Abstract: An electrical insulating oil having a flash point (PMCC) of 130° C. or more and a pour point of −40° C. or lower, comprising hydrorefined mineral oil and/or synthetic hydrocarbon oil and in the range of from 0.5 to 10 wt. % of bright stock oil, based on the total weight of the electrical insulating oil composition. (end of abstract)
Agent: Shell Oil Company - Houston, TX, US Inventors: Yoshiharu Baba, Hiroyuki Takahashi, Norimitsu Tanaka, Hideto Terai USPTO Applicaton #: 20070208205 - Class: 585006300 (USPTO) Related Patent Categories: Chemistry Of Hydrocarbon Compounds, Product Blend, E.g., Composition, Etc., Or Blending Process Per Se, Fluent Dielectric The Patent Description & Claims data below is from USPTO Patent Application 20070208205. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED CASES [0001] The present application claims priority from Japanese application 2006-039407, filed Feb. 16, 2006, which is incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to an electrical insulating oil composition. BACKGROUND OF THE INVENTION [0003] Transformers, high-pressure circuit breakers and other high-pressure electrical devices are filled with electrical insulating oil compositions before use. However, it must be possible for such electrical devices to be used maintenance-free for long periods after the start of operation. Similarly, such compositions are required to maintain stable physical properties and electrical properties over a long period. [0004] It is known that when electrical insulating oil compositions are used for a long period, they deteriorate, causing a decrease in anti-corrosion properties and a decrease in insulating properties due to an increase in the acid value of the electrical insulating oil compositions and the formation of sludge. Hence, with the trend towards higher pressure, larger size and longer service life for high pressure electrical devices, the stability of electrical insulating oil compositions used therein has become more important. [0005] The IEC (International Electrotechnical Commission) has specified the required performance for electrical insulating oil compositions used for filling transformers, high pressure circuit breakers and other electrical devices, and the performance required for mineral oil insulating oil compositions capable of withstanding long-term use as the standards IEC 296 and IEC 60296. Meanwhile, with the advances in mineral oil refining technology, the hydrorefining method has been widely adopted, making it possible to obtain oils from which polycyclic aromatics, unsaturated components, nitrogen content and sulphur content have been adequately removed. At first, it had been considered that it was better for electrical insulating oil composition to contain no nitrogen or sulphur content. [0006] Subsequently, however, Japanese Laid-Open Patent Application No. 2000-345177 A disclosed that with regard to oxidation stability and other aspects it was preferable for electrical insulating oil compositions to contain a certain amount of these components. Thus, it has been proposed in JP 2000-345177 A that by reducing the resin content in an electrical insulating oil composition to .ltoreq.100 ppm, and also incorporating minute amounts of sulphide-type sulphur content and total nitrogen content, the stability of the electrical insulating oil composition is increased, and increases in electric charge are inhibited. [0007] In fact, it is extremely difficult to refine a crude oil by petroleum refining processes to a state wherein the nitrogen content or sulphur content are such as to be suitable for use in an electrical insulating oil composition. Accordingly, at present, although there have been attempts to adjust the components therein by adding an appropriate combination of additives or the like having a nitrogen content or sulphur content to highly purified refined oils, there are restrictions as to the additives which can be used, depending on the electrical insulating oil specification, moreover, there are cost problems, and production management complications. [0008] It is therefore highly desirable to be able to obtain an electrical insulating oil composition having a balance of excellent electrical properties, low temperature performance, thermal oxidation stability and anti-corrosion properties by an economical and simple method. SUMMARY OF THE INVENTION [0009] In the present invention it has been surprisingly found that, through the addition of small quantities of bright stock oil to hydrorefined mineral oil and/or synthetic hydrocarbon oil, it is possible simply and economically to increase the thermal oxidation stability and obtain electrical insulating oil compositions which are capable of fulfilling the various types of performance required of electrical insulating oil compositions in the IEC Standard 296 and the IEC Standard 60296. [0010] Accordingly, the present invention provides an electrical insulting oil composition having a flash point (PMCC) of 130.degree. C. or more and a pour point of -40.degree. C. or lower, which composition comprises hydrorefined mineral oil and/or synthetic hydrocarbon oil and in the range of from 0.5 to 10 wt. % of bright stock oil, based on the total weight of the electrical insulating oil composition. [0011] In a preferred embodiment of the present invention, the electrical insulating oil composition has a pour point of -45.degree. C. or lower. [0012] In a preferred embodiment of the present invention, the electrical insulating oil composition has a flash point (PMCC) of 135.degree. C. or more. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0013] The hydrorefined mineral oil that may be present in the electrical insulating oil composition of the present invention may be refined by hydrogenating mineral oil. Examples of hydrorefined mineral oils that may be conveniently used include hydrorefined naphthenic mineral oil and hydrorefined paraffinic mineral oil. [0014] Through the hydrorefining of mineral oils, polycyclic aromatic substances, unsaturated components, sulphur compounds and nitrogen compounds are preferably removed. Compared to the hydrorefined paraffinic mineral oils, the hydrorefined naphthenic mineral oils may have better low temperature flow properties and lower oxidation stability, and, conversely, compared to the hydrorefined naphthenic mineral oils, the hydrorefined paraffinic mineral oils may have inferior low temperature flow properties, but better thermal oxidation stability. [0015] Examples of synthetic hydrocarbon oils that may be conveniently used in the electrical insulating oil composition of the present invention include polypropylene, polybutene, polypentene and other isoparaffinic synthetic hydrocarbon oils, poly-.alpha.-olefins (PAO) falling within Group IV in the API (American Petroleum Institute) base oil classification stated below in Table 1, and Gas to Liquid (GTL) synthetic oils. Synthetic hydrocarbon base oils sold by the Shell group under the trade designation "XHVI" may be conveniently used. [0016] Japanese Laid-Open Patent Application 52-072706 A and Japanese Laid-Open Patent Application 07-228876 describe methods of manufacturing synthetic hydrocarbon oils that may be conveniently used in the electrical insulating oil composition of the present invention. [0017] The afore-mentioned hydrorefined mineral oils and synthetic hydrocarbon oils may be used alone. However, the pour point, kinematic viscosity, thermal oxidation stability and the like of the electrical insulating oil composition of the present invention may be optimally adjusted by appropriate combination of several substances. [0018] The hydrorefined mineral oil and/or synthetic hydrocarbon oil used in the electrical insulating oil composition of the present invention each have a preferred kinematic viscosity at 40.degree. C. in the range of from 8.0 to 24 mm.sup.2/s. [0019] Preferred hydrorefined mineral oils may be selected from hydrorefined naphthenic mineral oils and/or API base oil classification Group II or Group III hydrorefined paraffinic mineral oils. Continue reading... Full patent description for Electrical insulating oil composition Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electrical insulating oil composition patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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