Capacitor oil having excellent properties in wide temperature range

Abstract

The present invention provides a capacitor oil that can maintain breakdown voltage at a high level in a wide temperature range of 50 C. to 30 C., extremely unlikely precipitates as crystals in particular at 50 C. and thus has excellent properties both at normal temperature and a lower temperature. The capacitor oil of the present invention comprises 1,1-diphenylethane and benzyltoluene, wherein the mass ratio of 1,1-diphenylethane to benzyltoluene is 0.8 to 2.0, the total amount of the ortho-isomer and para-isomer in the benzyltoluene is 90 percent by mass or less, and the composition has a 40 C. kinematic viscosity of 3.00 mm.sup.2/s or lower.

Claims

1. A capacitor oil comprising 1,1-diphenylethane and benzyltoluene, wherein the mass ratio of 1,1-diphenylethane to benzyltoluene is 0.8 to 2.0, the total amount of the ortho-isomer and para-isomer in the benzyltoluene is 90 percent by mass or less and more than 72 percent by mass, and the oil has a 40 C. kinematic viscosity of 3.00 mm.sup.2/s or lower.

2. The capacitor oil according to claim 1 further comprising an epoxy compound in an amount of 0.01 to 1.0 percent by mass.

3. The capacitor oil according to claim 1 wherein the chlorine content is 1 ppm by mass or less.

4. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 1 and at least partially composed of a polypropylene film.

5. The capacitor oil according to claim 2 wherein the chlorine content is 1 ppm by mass or less.

6. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 2 and at least partially composed of a polypropylene film.

7. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 3 and at least partially composed of a polypropylene film.

8. The capacitor oil according to claim 1 wherein the oil has breakdown voltages of 100V/m or higher at 50 C. and 140V/m or higher at 30 C.

9. The capacitor oil according to claim 2 wherein the oil has breakdown voltages of 100V/m or higher at 50 C. and 140V/m or higher at 30 C.

10. The capacitor oil according to claim 3 wherein the oil has breakdown voltages of 100V/m or higher at 50 C. and 140V/m or higher at 30 C.

11. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 8 and at least partially composed of a polypropylene film.

12. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 9 and at least partially composed of a polypropylene film.

13. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 10 and at least partially composed of a polypropylene film.

14. The capacitor oil according to claim 1 wherein the oil has a 40 C. kinematic viscosity of 2.66 mm.sup.2/s or higher.

15. The capacitor oil according to claim 1 wherein the oil has a crystal precipitation temperature of 50 C. or lower.

16. A capacitor oil comprising 1,1-diphenylethane and benzyltoluene, wherein the mass ratio of 1,1-diphenylethane to benzyltoluene is 0.8 to 2.0, the total amount of the ortho-isomer and para-isomer in the benzyltoluene is 90 percent by mass or less and the oil has a 40 C. kinematic viscosity of 2.66 to 3.00 mm.sup.2/s and a crystal precipitation temperature of 50 C. or lower.

17. The capacitor oil according to claim 16 further comprising an epoxy compound in an amount of 0.01 to 1.0 percent by mass.

18. The capacitor oil according to claim 16 wherein the chlorine content is 1 ppm by mass or less.

19. A capacitor comprising a dielectric impregnated with the capacitor oil according to claim 16 and at least partially composed of a polypropylene film.

Description

EXAMPLES

(1) The present invention will be described in more detail with the following examples but is not limited thereto.

Example 1

(2) A mixed oil was prepared to comprise 60 percent by mass of 1,1-diphenylethane and 40 percent by mass of benzyltoluene and subjected to the following crystallization experiment at 50 C. (Experimental Example A) and experiments for evaluating test oils with a model capacitor (Experimental Example B). In Experimental Example B, the above mixed oil is mixed with the epoxy compound described in Experimental Example B. The results are set forth in Table 1. The benzyltoluene used in this example was an isomer mixture of 3 percent by mass of ortho-isomer, 51 percent by mass of meso-isomer and 46 percent by mass of para-isomer, prepared by blending an isomer mixture (o-isomer 4 percent by mass, m-isomer 59 percent by mass, p-isomer 37 percent by mass) produced by following the procedures of Reference Production Example of Japanese Patent Publication No. 8-8008 and each isomer of the benzyltoluene produced by following the production of an electrically insulating oil described in Japanese Patent Application Laid-Open Publication No. 62-180907.

Example 2

(3) A mixed oil was prepared to comprise 50 percent by mass of 1,1-diphenylethane and 50 percent by mass of benzyltoluene and subjected to Experimental Examples A and B described below. The results are set forth in Table 1. The benzyltoluene used in this example was the same as that of Example 1.

Example 3

(4) A mixed oil was prepared to comprise 60 percent by mass of 1,1-diphenylethane and 40 percent by mass of benzyltoluene and subjected to Experimental Examples A and B described below. The results are set forth in Table 1. The benzyltoluene used in this example was an isomer mixture of 24 percent by mass of ortho-isomer, 28 percent by mass of meso-isomer and 48 percent by mass of para-isomer, prepared by blending an isomer mixture (o-isomer 4 percent by mass, m-isomer 59 percent by mass, p-isomer 37 percent by mass) produced by following the procedures of Reference Production Example of Japanese Patent Publication No. 8-8008 and each isomer of the benzyltoluene produced by following the production of an electrically insulating oil described in Japanese Patent Application Laid-Open Publication No. 62-180907.

Example 4

(5) The following Experimental Example A was carried out using the same mixed oil as that of Example 3 and the following Experimental Example B was also carried out with the same procedures except that the amount of the epoxy compound was changed to 0. 95 percent by mass.

Example 5

(6) The following Experimental Example A was carried out using the same mixed oil as that of Example 3 and the following Experimental Example B was also carried out with the same procedures except that the epoxy compound was not added.

Comparative Example 1

(7) A mixed oil was prepared to comprise 73 percent by mass of 1,1-diphenylethane and 27 percent by mass of benzyltoluene and subjected to Experimental Examples A and B described below. The results are set forth in Table 1. The benzyltoluene used in this example was the same as that of Example 1. The oil precipitated as crystals after 1030 hours in Experimental Example A, but in Experimental Example B the breakdown voltage could be measured because it took about 200 hours to complete the measurement.

Comparative Example 2

(8) A mixed oil was prepared to comprise 20 percent by mass of 1,1-diphenylethane and 80 percent by mass of benzyltoluene and subjected to Experimental Example A described below. The results are set forth in Table 1. The benzyltoluene used in this example was the same as that of Example 1. Experimental Example B was not carried out because the oil fully solidified before it passed 1030 hours.

Comparative Example 3

(9) A mixed oil was prepared to comprise 60 percent by mass of 1,1-diphenylethane and 40 percent by mass of benzyltoluene and subjected to Experimental Examples A and B described below. The results are set forth in Table 1. The benzyltoluene used in this example was an isomer mixture of 44 percent by mass of ortho-isomer, 6 percent by mass of meso-isomer and 50 percent by mass of para-isomer, prepared by blending an isomer mixture (o-isomer 4 percent by mass, m-isomer 59 percent by mass, p-isomer 37 percent by mass) produced by following the procedures of Reference Production Example of Japanese Patent Publication No. 8-8008 and each isomer of the benzyltoluene produced by following the production of an electrically insulating oil described in Japanese Patent Application Laid-Open Publication No. 62-180907.

Comparative Example 4

(10) A mixed oil was prepared to comprise 80 percent by mass of benzyltoluene and 20 percent by mass of dibenzyltoluene and subjected to Experimental Examples A and B described below. The results are set forth in Table 1. The benzyltoluene used in this example was the same as that of Comparative Example 3.

Comparative Example 5

(11) A mixed oil was prepared to comprise 66 percent by mass of 1,1-diphenylethane and 34 percent by mass of benzyltoluene and subjected to Experimental Examples A and B described below. The results are set forth in Table 1. The benzyltoluene used in this example was the same as that of Comparative Example 3.

Experimental Example A

Crystallization Experiment at 50 C.

(12) Concerning the relationship of temperature and crystallization, an capacitor oil does not desirously precipitate as crystals until the lowest acceptable temperature of 50 C. reached in order to maintain the properties of a capacitor. In order to confirm the crystal precipitation of the capacitor oils, the oils of Examples 1 to 5 and Comparative Examples 1 to 5 (hereinafter referred to as test oils) were each put into a 100 ml sample bottle, left in a low temperature thermostatic bath, the temperature of which was then kept for 1030 hours and thereafter whether crystals precipitated or not was visually observed. The results are set forth in Table 1. Good denotes a state where the oil exhibited transparency and no crystal precipitation was observed in the oil while Bad denotes a state where the oil exhibited no transparency and was fluidized although it partially precipitated as crystals or a state where the oil precipitated as crystals and solidified as the whole. The insulating oil compositions of the present invention did not solidify even at 50 C. or lower and thus can maintain the properties of a capacitor until the lowest acceptable temperature reaches.

Experimental Example B

Evaluation of Test Oils using a Model Capacitor

(13) The capacitor used in this experiment was as follows. The solid insulating material used herein was a simultaneously biaxially stretched polypropylene film of easy-impregnation type that was manufactured by Shin-Etsu Film Co., Ltd. through a tubular method.

(14) Two sheets of this polypropylene film of a 12.7 m thickness (weight method) were wound together with two sheets of aluminum foil electrode to produce a capacitor device of 0.2 to 0.3 F in electrostatic capacity, which was then put in an tin can. The can was made flexible so as to compensate sufficiently the shrinkage of an insulating oil at low temperatures. The end portions of the electrode was slit but was kept unfolded.

(15) A method for connecting between the electrode and the terminal is generally used, in which a ribbon-shaped lead foil is inserted into the device. However, if an oil precipitates as crystals, this method undergoes a loose connection between the lead foil and the electrode surface and as the result causes partial discharge from the electrode, possibly resulting in a failure to the measurement. Therefore, in the present experiment, similarly to a method used for a high frequency capacitor, the ends of the electrodes protruding beyond the respective edges of the polypropylene films were crimped and then one of the ends was spot-welded to lead wires.

(16) The can-type capacitor thus prepared was subjected to vacuum drying in a conventional manner, and under the same vacuum condition, it was impregnated with an insulating oil, followed by sealing. The capacitor was then subjected to heat treatment at a maximum temperature of 80 C. for two days and nights in order to maintain the impregnation uniformly and stably. After leaving it to stand at room temperature for 5 days or longer, the capacitor was applied with AC 1270 V (corresponding to 50 V/m) in a thermostatic bath kept at 30 C. for 16 hours and then was used for an experiment.

(17) Two sheets of polypropylene film of 12.7 m thick were laminated to be used as a dielectric material, and wound and laminated together with an electrode of aluminum foil in accordance with a conventional manner thereby producing a model capacitor for oil-impregnation.

(18) This capacitor was impregnated with each mixed oil under vacuum to produce an oil-impregnated capacitor with a capacitance of 0.26 F. Before impregnation, each of the electrical insulating oil compositions was pre-treated with an activated earth. That is, an activated earth galeonite #036, manufactured by MI ZUSAWA INDUSTRIAL CHEMICALS, LTD. was added in an amount of 10 percent by mass to each of the. electrical insulating oil compositions and stirred at a liquid temperature of 25 C. for 30 minutes and then filtered. After filtration, 0.65 percent by mass of a chlorine trapping agent that is an epoxy compound (alicyclic epoxide; product name: CELLOXIDE 2021P manufactured by Daicel Corporation) was added and used for impregnation.

(19) Thereafter, the oil-impregnated capacitors were applied with an alternating voltage at a predetermined temperature by a predetermined method to obtain the breakdown voltage from the voltage and time at which the capacitor had insulation breakdown in accordance with the following formula. The predetermined method for applying voltage is a method wherein an applied voltage is continuously raised from a potential gradient of 50 v/m at a rate of 10 v/m every 24 hours.

(20) Breakdown voltage (v/m)=V+S(T/1440)

(21) wherein V: applied voltage (v/m) at insulation breakdown

(22) S: raised voltage (v/m) every 24 hours

(23) T: time period till insulation breakdown occurs after raising applied voltage (minute)

(24) TABLE-US-00001 TABLE 1 Capacitor oil composition Isomer ratio in BT Ortho- Experiment Experiment B 40 C. isomer/ 1,1- A Breakdown kineMatic 1,1- Ortho- Metha- Para- Para- DPE/ Chlorine Epoxy Crystal voltage V/m viscosity DPE BT DBT isomer isomer isomer isomer BT content compound precipitation 50 C. 30 C. mm.sup.2/s Example 1 60 40 0 3 51 46 49 1.5 0.0 0.65 Good 101 148 2.61 Example 2 50 50 0 3 51 46 49 1.0 0.0 0.65 Good 100 148 2.53 Example 3 60 40 0 24 28 48 72 1.5 0.6 0.65 Good 101 143 2.66 Example 4 60 40 0 24 28 48 72 1.5 0.6 0.95 Good 103 147 2.66 Example 5 60 40 0 24 28 48 72 1.5 0:6 0.00 Good 100 141 2.66 Comparative 73 27 0 3 51 46 49 2.7 0.0 0.65 Bad 78 140 2.65 Example 1 Comparative 20 80 0 3 51 46 49 0.3 1.2 0.65 Bad 2.46 Example 2 Comparative 60 40 0 44 6 50 94 1.5 0.0 0.65 Good 102 138 2.70 Example 3 Comparative 0 80 20 44 6 50 94 0.0 3.0 0.65 Bad 91 148 3.55 Example 4 Comparative 66 34 0 44 6 50 94 1.9 0.0 0.65 Bad 100 135 2.73 Example 5

(25) In Table 1, 1,1-DPE denotes 1,1-diphenylethane, BT denotes benzyltoluene, and DBT denotes dibenzyltoluene.

(26) In Experiment B, the test oils of Examples 1 to 5 exhibited breakdown voltages of 100 V/m or higher at 50 C. and 140 V/m or higher at 30 C. and thus was confirmed that they exhibited sufficient electric insulation properties and thus can be deemed a capacitor oil exhibiting superior properties in a wide temperature range of 50 to 30 C.

INDUSTRIAL APPLICABILITY

(27) The capacitor oil of the present invention is excellent in properties in a wide temperature range of 50 C. to 30 C. Furthermore, since each component of the oil gives no adverse effect on living bodies, the oil of the present invention is extremely excellent for practical use as an electrical insulating oil composition.