JPH083075A - Method for purifying fluorine-based inert liquid - Google Patents

Abstract

PURPOSE:To carry out purification and produce a liquid capable of being heated with scarcely generating HF, excellent in stability, safety, etc., and useful as, e.g. a liquid for electronic components by bringing a fluorine-based inactive liquid into contact with water or an aqueous alkali solution in the presence of silica, alumina or a silicate at a specified temperature. CONSTITUTION:This purification is carried out by bringing (A) a fluorine-based inactive liquid such as a perfluoro-tert-amine into contact with (C) water or an aqueous alkali solution in the presence of (B) silica such as diatomaceous earth, alumina or a silicate such as allophane at 0 to 100 deg.C to obtain the objective liquid. In addition, the component (B) is used preferably in an amount of 0.1 to 30 pts.wt., especially l to 20 pts.wt. based on 100 pts.wt. (A). The component (C) has 0.1 to 50wt.%, especially 2 to 20wt.% alkali concentration and the amount of used component (C) is 0.1 to 10 time the weight of the component (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining a fluorine-based inert liquid which produces less hydrogen fluoride when heated and used.

[0002]

2. Description of the Related Art Fluorine-based inert liquids are chemically and thermally stable, have good electrical insulation and thermal conductivity, and are nontoxic, so they are used for electrical insulation of transformers and the like. Used for liquids, liquids for electronic parts, liquids for reliability tests, liquids for vapor phase soldering, etc. However, there is a problem that hydrogen fluoride is generated when the fluorine-based inert liquid is used in a heated state. Hydrogen fluoride is highly corrosive and highly toxic, and causes problems in terms of corrosion of equipment materials, deterioration of electrical insulation, and safety for the human body.

Therefore, conventionally, a method for purifying a fluorine-based inert liquid has been proposed. For example, a method of purifying by distillation or gas chromatography, a method of refluxing an aqueous solution of an alkali metal hydroxide such as an aqueous solution of sodium hydroxide and a secondary amine such as diisobutylamine, and a fluorine-based inert liquid for a long time (special characteristics Kaisho 58-9606
1), a method of adsorbing a specific fluorine-based inert liquid with an adsorbent containing silica and / or alumina as a main component (JP-A-5-79669) and the like have been adopted. However, in any of the above methods, it is difficult to sufficiently reduce the generation of hydrogen fluoride, and there has been a demand for a method of obtaining a fluorine-based inert liquid having excellent stability.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present inventors
We have continued our research for the purpose of obtaining a fluorine-based inert liquid that produces less hydrogen fluoride when heated.

[0005]

As a result, the above object is achieved by contacting a fluorine-based inert liquid with water or an aqueous alkaline solution in the presence of silica, alumina or silicate at a temperature of 0 ° C to 100 ° C. As a result, they have completed the present invention.

That is, the present invention is characterized in that a fluorine-based inert liquid is contacted with water or an aqueous alkali solution at a temperature of 0 ° C. to 100 ° C. in the presence of silica, alumina or silicate. Is a purification method.

As the fluorine-based inert liquid to be purified in the present invention, known ones can be used without any limitation. Those that are liquid at room temperature are preferable. Specifically, compounds such as perfluoroalkanes, perfluoroethers, and perfluorotertiary amines are used. Particularly, perfluoro tertiary amines are preferable because they have a large effect according to the present invention. Examples of such compounds include perfluoroalkanes such as perfluoropentane, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluoromethylcyclohexane, and perfluoroethers such as:
Examples of perfluoro tertiary amines such as perfluorodibutyl ether, perfluoro (2-butyltetrahydrofuran), and perfluoro (2-propyltetrahydropyran) include perfluorotrihexylamine, perfluorotripentylamine, perfluorotributylamine, perfluorotripropylamine, perfluoro. Examples thereof include triethylamine, perfluoro (N, N-dimethylhexylamine), perfluoro (N, N-dimethylcyclohexylamine), perfluoromethylmorpholine and perfluoroethylmorpholine. These may be used alone or as a mixture of two or more kinds. Alternatively, a fluorine-based inert liquid that has been previously neutralized, washed with water, distilled, or purified by a known method may be used.

As a method for producing the fluorine-based inert liquid, any conventionally known method can be used without any limitation. For example, an electrolytic fluorination method, a direct fluorination method using fluorine gas, a fluorination method using a high-valent metal fluoride such as cobalt trifluoride, or a polymerization or co-polymerization of a monomer in which hydrogen atoms are substantially entirely replaced with fluorine atoms. A method of polymerizing, a method of appropriately combining these, or the like is suitably adopted.

The feature of the present invention resides in that these fluorine-based inert liquids are brought into contact with water or an aqueous alkali solution in the presence of silica, alumina or silicate.

The type of silica is not particularly limited, and amorphous silica, crystalline silica, silica hydrate and the like, specifically silica gel, diatomaceous earth and the like can be used.
The type of alumina is not particularly limited, and amorphous alumina, crystalline alumina, alumina hydrate and the like can be used. The silicate can be used without any limitation as long as it is a salt of silicon dioxide and a metal oxide. Specific examples include alkali silicates such as sodium silicate; alkaline earth metal silicates such as calcium silicate and magnesium silicate; and aluminum silicates such as silica alumina gel. As such a mineral containing silicate, zeolite, synthetic zeolite, kaolinite, activated clay, halloysite, montmorillonite, allophane, bentonite and the like can be used. Of these, allophane is preferably used because it can further enhance the effects of the present invention. Allophane is a naturally occurring hydrous silicate of aluminum (nSiO ₂ Al ₂ O ₃ mH ₂
O) is an amorphous clay mineral. The silica, alumina, or silicate may be used alone or as a mixture of two or more kinds.

The silica, alumina or silicate may be in the form of powder, granules or particles without particular limitation. From the viewpoint of contact efficiency with the fluorine-based inert liquid, the particle size is preferably small, and the average particle size is preferably smaller than 9 mm. Practically 0.3-5
mm is suitable.

The water used in the present invention may be industrial water, sea water or the like, but it is preferable to use clean water such as ion-exchanged water, distilled water or tap water. Alternatively, steam generated by a normal boiler may be used.

In the present invention, it is essential to use water in the presence of silica, alumina or silicate, but the effect of the present invention can be further enhanced by adding an alkali.

The alkali is not particularly limited as long as it shows alkalinity in an aqueous solution, and sodium hydroxide,
Examples thereof include alkali metal hydroxides such as potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, carbonates such as sodium carbonate and potassium carbonate, and ammonia. Practically, sodium hydroxide and potassium hydroxide are suitable.

The amount of silica, alumina or silicate, the contact temperature, the contact time, the amount of water or alkaline aqueous solution, or the alkaline concentration of the alkaline aqueous solution varies depending on the target fluorine-based inert liquid. It is desirable to go and find contact conditions. Generally, the amount of silica, alumina or silicate is preferably 0.1 to 30 parts by weight, and more preferably 1 to 20 parts by weight, based on 100 parts by weight of the fluorine-based inert liquid.

The contact temperature may be 0 to 100 ° C., but if a higher temperature is selected, the required amount of silica, alumina or silicate can be reduced, so that it is 40 to 10 ° C.
0 degreeC is preferable and 70-100 degreeC is especially preferable. In consideration of practicality, it is preferable that the contact temperature is selected as high as possible up to the boiling point of the fluorine-based inert liquid or the boiling point of water or the aqueous alkali solution, whichever is lower, and carried out under normal pressure. Of course, the contact may be carried out under pressure.

The contact time is preferably as long as possible, but usually 1 to 50 hours, more preferably 5 to 50 hours.
It is preferable to select from the range of 35 hours.

The amount of water or alkaline aqueous solution is not particularly limited, but it is usually in the range of 0.1 to 10 times the weight of the fluorine-based inert liquid. Further, water or an aqueous alkaline solution may be repeatedly used.

The alkaline concentration of the aqueous alkaline solution is preferably 0.1 to 50% by weight, and more preferably 5 to 20% by weight, for good purification. In order to use iron or stainless steel as the container material by contacting the fluorine-based inert liquid with the alkaline aqueous solution, the alkali concentration is preferably 5 to 20% by weight.

The material of the refining device is not particularly limited, but specifically, glass, metal, resin, etc. can be used, and iron, stainless steel, fluororesin, polypropylene, etc. are particularly preferable. is there.

As a method of contacting the fluorine-based inert liquid with silica, alumina or silicate and water or an aqueous alkali solution, known methods for efficiently contacting the three can be used without any limitation. Since silica, alumina or silicate, or water or an aqueous alkali solution is hardly dissolved in the fluorine-based inert liquid, a contact method capable of sufficiently mixing is particularly preferable. For example, a method of stirring in a stirring tank or the like, a method of continuously passing a fluorine-based inert liquid and water or an alkaline aqueous solution through a column filled with silica, alumina or silicate, or dispersing silica, alumina or silicate A method of dispersing droplets of a fluorine-based inert liquid in water or an alkaline aqueous solution, a method of dispersing droplets of water or an alkaline aqueous solution in a fluorine-based inert liquid in which silica, alumina, or a silicate is dispersed. It is preferably used.

After silica, alumina or silicate and water or alkaline aqueous solution are brought into contact with the fluorine-based inert liquid, silica, alumina or silicate is separated by a known filtration operation or the like. Since the fluorine-based inert liquid is adsorbed on the separated silica, alumina, or silicate, recover the fluorine-based inert liquid by heating, depressurizing, blowing nitrogen gas, etc. Is preferred.

After the silica, alumina or silicate is separated by filtration, the fluorine-based inert liquid is separated from water or an aqueous alkali solution. Since the fluorine-based inert liquid is insoluble in water and has a larger specific gravity than water, it can be easily separated by allowing it to stand. Since water or an alkaline aqueous solution is slightly dissolved in the separated fluorine-based inert liquid, a washing operation by washing with water, a distillation operation, and a dehydration operation using a dehydrating agent may be performed.

[0024]

According to the present invention, by bringing a fluorine-based inert liquid into contact with water or an aqueous alkaline solution in the presence of silica, alumina or silicate, fluorine which produces very little hydrogen fluoride during heating is used. A system inert liquid can be obtained.

Although the reason for this is not clear, the present inventors presume as follows. That is, the fluorine-based inert liquid contains an extremely small amount of by-products even after performing distillation or a known purification method, and these by-products are gradually decomposed to cause fluorination. Although hydrogen is generated, it is considered that most of the by-products are decomposed by carrying out the method of the present invention, which increases the stability of the fluorine-based inert liquid.

The fluorine-based inert liquid purified according to the present invention is inert, stable and reliable as an electric insulating liquid, an electronic component liquid, a reliability test liquid, a vapor phase soldering liquid, etc. It can be suitably used for a particularly required application.

[0027]

EXAMPLES The following examples are given to describe the present invention more specifically, but the present invention is not limited to these examples.

The fluorine-based inert liquid is abbreviated as IL hereinafter.

Example 1 Using hydrofluoric acid anhydride and tributylamine as raw materials, the concentration of the latter was adjusted to 10% by weight, and electrolytic fluorination was performed using a nickel electrolytic cell (electrode area 15 dm ² , current 30 A, capacity 6 L). went. While continuously supplying anhydrous hydrofluoric acid and tributylamine, the produced fluorinated product was intermittently withdrawn from the lower part of the electrolytic cell. This was contacted with 50% fluorine gas at 130 ° C., and then contacted with a 5 wt% sodium hydroxide aqueous solution at room temperature to neutralize hydrogen fluoride and fluorine gas. Further, vacuum distillation was performed to obtain perfluorotributylamine as IL.

Next, using a stainless steel reactor having a reflux condenser and a stirrer, perfluorotributylamine and S were added.
The molar ratio of iO ₂ / Al ₂ O ₃ is 1.97 and the average particle size is 2 m.
m of allophane (trade name "SECARD KW", manufactured by Shinagawa White Brick) and a 10 wt% NaOH aqueous solution are allowed to come into contact with allophane and the alkaline aqueous solution while stirring at a stirring speed of 300 rpm under the conditions shown in Table 1. It was

After contacting perfluorotributylamine with allophane and an aqueous alkaline solution, allophane was separated by filtration. Further, liquid separation was performed using a separating funnel to obtain purified perfluorobutylamine.

Purified perfluorotributylamine 1
00 g was put in a 200 ml eggplant-shaped flask with a reflux condenser placed above to heat the liquid, and boiled under atmospheric pressure for 48 hours. The liquid temperature was 177 ° C. During this time, 80 ml / min
A flow rate of nitrogen gas was blown into the liquid for 48 hours, and the generated hydrogen fluoride was absorbed in 100 ml of a 0.01 mol / l potassium hydroxide aqueous solution. The concentration of fluorine ions contained in this potassium hydroxide aqueous solution is measured with an ion chromatograph analyzer (Model IC100, manufactured by Yokogawa-Hokushin Electric Co., Ltd.) to determine the amount of hydrogen fluoride generated, and the amount of hydrogen fluoride generated per unit weight of IL. It was The results are also shown in Table 1. The amount of hydrogen fluoride generated during boiling for 48 hours is called the amount of HF generated.

In Table 1, as comparative examples, when allophane alone is contacted with perfluorotributylamine (Comparative Example 1), only alkaline aqueous solution is contacted (Comparative Example 2), and allophane and water-free alkaline solids are included. The results of measurement of the amount of HF generated in the case of contacting with (Comparative Example 3) and in perfluorotributylamine before purification (Comparative Example 4) are also shown.

[0034]

[Table 1]

Example 2 As IL, perfluorotripentylamine, perfluorotriethylamine, perfluorohexane, perfluorodecalin, perfluorodibutyl ether, and perfluoro (2-butyltetrahydrofuran) were used. For each IL, 5 parts by weight of allophane (trade name "Secard KW", made by Shinagawa White Brick, average particle diameter 2 mm) and 50 parts by weight of NaOH aqueous solution (concentration 10% by weight) were added to 100 parts by weight of IL. Using the same apparatus as in Example 1, the materials were contacted for 17 hours while stirring at a stirring speed of 300 rpm. The contact temperature with NaOH aqueous solution was 65 ° C for perfluorotriethylamine (bp.70 ° C) and 50 ° C for perfluorohexane (bp.57 ° C).
L was 90 ° C. After being brought into contact with each other, they were filtered and separated to determine the amount of HF generated. The results are shown in Table 2. Further, in Table 2, the results of determining the hydrogen fluoride generation amount generated during boiling for 48 hours using IL before contacting with the above-mentioned allophane and the alkaline aqueous solution are also shown as the HF generation amount before purification.

[0036]

[Table 2]

Example 3 Perfluorotributylamine, allophane (trade name "SECARD KW", manufactured by Shinagawa Shira brick, average particle size 2 mm) and water shown in Table 3 or various alkaline aqueous solutions were used. Using the same apparatus as in Example 1, under conditions of a temperature of 90 ° C. and a contact time of 17 hours, 5 parts by weight of allophane and 50 parts by weight of water or an alkaline aqueous solution were stirred at a stirring speed of 300 rpm with respect to 100 parts by weight of IL. While simultaneously contacting the IL. After the contact, they were filtered and separated to determine the amount of HF generated. The results are shown in Table 3.

[0038]

[Table 3]

Example 4 Perfluorotributylamine and silica, alumina, silicate, and water or an aqueous solution of NaOH (concentration 10% by weight) shown in Table 4 were used. Using the same apparatus as in Example 1, under the conditions of a temperature of 90 ° C. and a contact time of 30 hours, IL1
3 parts by weight of silica, alumina, silicate and 50 parts by weight of water or alkaline aqueous solution with respect to 00 parts by weight were simultaneously contacted with IL while stirring at a stirring speed of 300 rpm. After the contact, they were filtered and separated to determine the amount of HF generated. The results are shown in Table 4.

Further, as a comparative example, water or NaOH
Without using an aqueous solution, 3 parts by weight of silica, alumina, 100 parts by weight of perfluorotributylamine,
The temperature of the silicate is 90 ° C, the contact time is 30 hours, and the stirring speed is 3
After contacting under the condition of 00 rpm, filtration, separation, H
The results of obtaining the amount of F generated are also shown in Table 4.

[0041]

[Table 4]

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Claims (1)

[Claims] 1. A method for purifying a fluorine-based inert liquid, which comprises contacting the fluorine-based inert liquid with water or an aqueous alkali solution in the presence of silica, alumina or a silicate at a temperature of 0 ° C. to 100 ° C.