JPH05973A - Method for purifying perfluorocarbon - Google Patents

Abstract

PURPOSE:To provide a method for purifying a perfluorocarbon in which uncondensable substances such as air dissolved in a liquid can highly be removed with a good efficiency according to simple operation. CONSTITUTION:The subject method is to purify a perfluorocarbon as follows. A liquid (5) of the perfluorocarbon is subjected to deaeration treatment and the aforementioned treated liquid is then vaporized in a state of <=10mmHg partial pressure of a gas of a different kind in the vapor phase part on the treated liquid at a temperature above ambient temperature. The initial distillate is subsequently removed. Thereby, the liquid of the perfluorocarbon at a high deaeration degree is efficiently and stably obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an efficient method for purifying perfluorocarbons.

[0002]

2. Description of the Related Art Perfluorocarbons are expected to be used as an alternative to CFCs, which have problems of environmental destruction. However, the amount of dissolved non-condensable gas such as air and carbon dioxide is particularly large, and even if decompression degassing is performed until the bubbles of non-condensable gas are not generated by the freezing method according to CFC, it can be applied to heat pipes. There was a problem that a highly degassed perfluorocarbon could not be obtained and could not be sufficiently purified by the conventional method.

[0003]

The object of the present invention is to develop a refining method capable of efficiently and highly degassing perfluorocarbon.

[0004]

According to the present invention, a perfluorocarbon liquid is degassed and then treated under the condition that the partial pressure of a different gas in the gas phase portion on the treatment liquid is 10 mmHg or less. The present invention provides a method for purifying perfluorocarbon, characterized in that the initial fraction is vaporized at a temperature of room temperature or higher.

[0005]

[Operation] By vaporizing the perfluorocarbon degassed liquid at room temperature or higher under the condition that the partial pressure of the different gases in the gas phase is 10 mmHg or lower, the non-condensable dissolved residual gas is drastically increased. It is released and transferred into the initial fraction of the perfluorocarbon degassate. Therefore, a highly degassed perfluorocarbon can be efficiently obtained by removing the initial fraction and utilizing the residual fraction.

[0006]

Examples of Components of the Invention In the present invention, various perfluorocarbon liquids are targeted for purification. Above all,
Average molecular weight represented by the chemical formula of C _n F _{2n + 2} is 100 to
000, or those having a boiling point of 30 to 300 ° C. are targeted. It may contain 1% by weight or less, especially 0.1% by weight or less, of different elements such as oxygen, nitrogen and hydrogen. Such perfluorocarbon is commercially available, for example, as Fluorinert (trade name, manufactured by 3M Co., Ltd.).

In the present invention, the perfluorocarbon liquid is first degassed. The degassing treatment may be performed by an appropriate method. Examples thereof include known methods such as a freezing method and an equilibrium vapor pressure method, as well as a stirring method or a vibration treatment method (Japanese Patent Application No. 2-193414) and a boiling method (Japanese Patent Application No. 2-193).
No. 415), a method of blowing an inert gas or hydrogen gas (Japanese Patent Application No. 2-193416). Above all, degassing treatment by the equilibrium vapor pressure method under reduced pressure is preferable.

The degree of degassing treatment is preferably as high as possible, but generally, the degree of degassing may be a normal degree in each degassing method. By the way, in the above equilibrium vapor pressure method, the partial pressure of the different gases is 10 to 1/10 ⁵ mmHg, preferably 1 in a state where the liquid of perfluorocarbon is cooled, for example, in a state of being cooled to 0 to −50 ° C. ~ 1/10 ³ mmHg
The degassing treatment may be performed by stirring for 1 to 30 minutes under reduced pressure.

The deaerated perfluorocarbon liquid in the present invention is then vaporized at a temperature of room temperature or higher under the condition that the partial pressure of the different gas in the vapor phase portion on the treated liquid is 10 mmHg or less, and Remove the initial fraction.

The above-mentioned different gas means a gas other than the vapor of perfluorocarbon to be treated. Further, the partial pressure of different gases means the sum of the partial pressures of the different gases. In the usual case, the different gas is air, and in that case, if the total of the partial pressures of the gases forming the air is 10 mmHg or less,
The treatment liquid may be vaporized without depressurizing the vapor phase portion. On the other hand, when the partial pressure of the foreign gas in the gas phase exceeds 10 mmHg, as in the case where the above degassing process is performed under atmospheric pressure, decompression operation is performed so that the partial pressure of the foreign gas is 10 mmHg or less. The processing solution is vaporized.

The vaporization of the treatment liquid of perfluorocarbon is
In the state where the partial pressure of different gases in the gas phase is as small as possible,
Especially, it is preferable to carry out under 5 mmHg or less, especially under 1 mmHg or less. The temperature of vaporization is room temperature (20 ° C)
Above temperature, especially above 30 ℃, especially boiling point (760
mmHg) or higher temperature is preferable. Note that vaporization treatment is generally performed at a temperature of 50 ° C. or higher higher than the boiling point from the viewpoint of pressure resistance of the container, but not limited to this.

The vaporization of the perfluorocarbon treatment liquid is
The treatment liquid may be gently vaporized without being boiled, or the treatment liquid may be vaporized while boiling by a method of quickly distilling the vaporized perfluorocarbon vapor out of the system. In the present invention, generally, the method of vaporizing the treatment liquid under boiling is preferable because the early release of the dissolved residual gas is effectively achieved, probably because of the stirring action by the boiling.

The refining method of the present invention will be described by taking as an example the case where the degassing treatment is carried out under reduced pressure by the equilibrium vapor pressure method, and then the treated liquid is vaporized under heating to remove the initial fraction. FIG. 1 illustrates a refining device used in that case. 1 is a trap, 2 is a cooler containing liquid nitrogen or the like, 3 is an exhaust pipe, 4 is a purification container, 5 is a perfluorocarbon to be purified, 6 is a stopper, 7 is a purification liquid take-out pipe, and 8 is an initial stage. The distillate is stored, and 9 is a take-out pipe.

In FIG. 1, the perfluorocarbon liquid 5 contained in the purification container 4 is first degassed under reduced pressure by the equilibrium vapor pressure method. The decompression in the purification container 4 is performed by a decompression pump or the like (not shown) via the trap 1 in which the exhaust pipe 3 communicates with the valve 71 and the valve 72 closed and the valve 31 opened. Therefore, the gas generated by the degassing process is exhausted to the outside of the system through the pressure reducing system while the valve 31 is open. The degassing conditions may be the same as above.

The deaerated perfluorocarbon liquid 5 (treatment liquid) is then vaporized under heating. In the vaporization process, it was confirmed that the partial pressure of the different gas in the gas phase portion in the purification container 4 was 10 mmHg or less (in many cases, it was almost equal to the pressure in the trap 1 (the vapor pressure of perfluorocarbon was substantially The pressure may be used for the judgment.) The valve 31 is closed, and the entire region within the dotted line including the purification container 4 and the like is maintained at a predetermined high temperature to heat the liquid 5. As a result, the pressure of the gas phase portion in the purification container 4 becomes a vapor pressure according to the heating temperature.

Then, the valve 71 is opened (the valve 72 is kept closed) to promote vaporization of the liquid 5, and the vaporized initial fraction is trapped in the initial fraction reservoir 8. At that time, the static vaporization state (transfer amount: small) or boiling state (transfer amount: large) of the liquid 5 is controlled by adjusting the transfer amount of the vaporized vapor from the purification container 4 to the initial fraction reservoir 8. can do.

In the apparatus shown in the figure, the initial fraction 51 is trapped in the initial fraction reservoir 8 through the exhaust pipe 7 by the cooling system using the cooler 21 containing liquid nitrogen or the like, and can be reused. The removal of the initial fraction is due to the large amount of the non-condensable dissolved gas, but the dissolved amount of the non-condensable gas in the liquid (treatment liquid) 5 gradually decreases as the vaporization process progresses.

Therefore, the amount of the initial fraction 51 to be removed is appropriately determined according to the degassing degree of perfluorocarbon required for the purpose of use such as a heat exchange medium in a heat pipe or insulating oil in a transformer or the like. It Generally, 5% by weight of perfluorocarbon subjected to vaporization treatment
Above all, about 10 to 50% by weight is removed. When the necessary initial fraction is removed, the desired high-purity perfluorocarbon is obtained.

In the illustrated apparatus, when the removal of the initial fraction is completed via the exhaust pipe 7, the valve 71 is closed and the valve 72 is opened (the valve 31 remains closed), and the outside air is taken out via the take-out pipe 9. While preventing contact with the obtained purified solution,
For example, it can be supplied to a heat pipe manufacturing process.

[0020]

According to the present invention, non-condensable substances such as air dissolved in the liquid of perfluorocarbon can be efficiently and highly removed by a simple operation, and the perfluorocarbon of high degassing degree can be obtained. The liquid can be efficiently and stably obtained.

[0021]

【Example】

Example 1 100 ml of tetradecafluorohexane (average molecular weight 340, boiling point 56 ° C.) was placed in a 500 ml container, and the inside of the container was in a depressurized state of 28 to 30 mmHg (vapor pressure of tetradecafluorohexane and heterogeneous gas mainly composed of air). Sum of partial pressure of
Degassing treatment (equilibrium vapor pressure method) at -20 ° C for about 5 minutes while maintaining at 20 ° C, and then maintaining the reduced pressure state (1/10 ² mmHg based on measurement in trap 1) of the entire container at 60 ° C. It was boiled by heating to about 5 ml and the initial fraction was removed. Then, the obtained purified liquid was vacuum-injected into a copper pipe having an outer diameter of 16 mm, an inner diameter of 14 mm and a length of 800 mm at a vacuum degree of 8/10 ³ Torr and sealed to obtain a heat pipe.

Example 2 A heat pipe was obtained in the same manner as in Example 1 except that about 10 ml was removed as an initial fraction.

Example 3 A heat pipe was obtained in the same manner as in Example 1 except that about 20 ml was removed as an initial fraction.

Example 4 A heat pipe was obtained in the same manner as in Example 1 except that about 50 ml was removed as an initial fraction.

Comparative Example According to Example 1, a heat pipe was obtained according to Example 1 by using only the degassing treatment by the equilibrium vapor pressure method.

Evaluation test Input of 60 W for the heat pipes obtained in Examples and Comparative Examples
I checked the heat resistance at. The results are shown in Table 1.

[Table 1]

[Brief description of drawings]

FIG. 1 is an explanatory view illustrating a refining device for carrying out the present invention.

[Explanation of Codes] 3, 7: Exhaust pipe 4: Purification container 5: Perfluorocarbon liquid

Claims (1)

Claims: 1. A perfluorocarbon liquid is degassed, and then the treatment liquid is kept at room temperature under the condition that the partial pressure of a different gas in the vapor phase portion of the treatment liquid is 10 mmHg or less. A method for purifying perfluorocarbon, which comprises vaporizing at the above temperature and removing the initial fraction.