JPH11130703A - Purification of fluorine-based inactive liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorine-based inactive liquid generating hydrogen fluoride in an extremely small amount on the thermal employment of the fluorine-based inactive fluid. SOLUTION: This method for purifying a fluorine-based inactive fluid comprises bringing the fluorine-based inactive fluid into contact with an alkaline aqueous solution, such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution, containing an onium compound, e.g. a quaternary ammonium compound such as tetrabutyl ammonium bromide.

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 generates 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 heat conductivity, and are non-toxic. It is used for liquids, liquids for electronic components, liquids for reliability tests, liquids for vapor phase soldering, and the like. However, when a fluorine-based inert liquid is used in a heated state, there is a problem that hydrogen fluoride is generated. Hydrogen fluoride is highly corrosive and highly toxic, and poses problems in terms of corrosion of equipment materials, deterioration of electrical insulation, safety to human bodies, and the like.

For this reason, a method for purifying a fluorine-based inert liquid has been conventionally proposed. For example, a method of purification 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 an aqueous solution of a secondary amine such as diisobutylamine, and a fluorine-based inert liquid for a long period of time (particularly) 58-96061
JP-A-5-112496) and a method of contacting a specific fluorine-based inert liquid with activated carbon (Japanese Patent Laid-Open No. 5-112496). However, it is difficult to sufficiently reduce the generation of hydrogen fluoride by any of the above methods, 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
Intensive research has been continued with the aim of obtaining a fluorine-based inert liquid that generates little hydrogen fluoride during heating.

[0005]

As a result, it has been found that the above object can be achieved by bringing a fluorine-based inert liquid into contact with an aqueous alkali solution containing an onium compound, and the present invention has been completed.

That is, the present invention is a method for purifying a fluorine-based inert liquid, which comprises contacting a fluorine-based inert liquid with an alkaline aqueous solution containing an onium compound.

[0007] The fluorine-based inert liquid to be purified in the present invention is an inert liquid having a fluorine atom, as long as it has substantially no reactivity even when brought into contact with an alkali containing an onium compound. Known objects are subject without any limitation. In general, a compound in which all the hydrogen atoms of an organic compound having a carbon-hydrogen bond are substituted by fluorine atoms, or when an organic compound having a carbon-hydrogen bond contains an unsaturated bond, substitution of a hydrogen atom with a fluorine atom Compounds obtained by adding a fluorine atom to an unsaturated bond can be mentioned. Preferably, those which are liquid at normal temperature are preferable.

Specifically, compounds such as perfluoroalkanes, perfluoroethers, perfluorotertiary amines, perfluoroaminoethers and the like can be mentioned. These preferably have 5 to 20 carbon atoms. In particular, perfluorotertiary amines and perfluoroaminoethers are preferred because they have a large effect according to the present invention. Examples of the above substances include perfluoroalkanes such as perfluoropentane, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, perfluoromethylcyclohexane, and perfluorodecalin; and perfluoroethers such as perfluorodibutyl ether and perfluoro (2
-Butyltetrahydrofuran) and perfluoro (2-propyltetrahydropyran) such as perfluorotertiaryamines such as perfluorotrihexylamine, perfluorotripentylamine, perfluorotributylamine, perfluorotripropylamine, and perfluoro (N, N-dimethylhexyl) Amines), perfluoro (N, N-dimethylcyclohexylamine), perfluorotriethylamine, and the like, as perfluoroaminoethers, perfluoro-N-methylmorpholine, perfluoro-N-ethylmorpholine, perfluoro-N-propylmorpholine, perfluoro-N- Butylmorpholine and the like. These may be used alone or in combination of two or more. Also,
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 a fluorine-based inert liquid, a 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 method in which a monomer in which hydrogen atoms are substantially completely replaced by fluorine atoms is polymerized or copolymerized. A polymerization method, a method in which these are appropriately combined, and the like are suitably employed.

A feature of the present invention resides in that these fluorine-based inert liquids are brought into contact with an alkaline aqueous solution containing an onium compound.

As the onium compound used in the present invention, known compounds can be used without limitation. Specifically, a phosphonium compound (R ₄ PX) and an arsonium compound (R ₄ As)
X), stibonium compound (R ₄ SbX), oxonium compound (R ₃ OX), sulfonium compound (R ₃ S
X), selenonium compound (R ₃ SeX), stannonium compound (R ₃ SnX), iodonium compound (R ₂ I
X) and the like. In these onium compounds, R is not particularly limited, but may be a methyl group,
Preferably an alkyl group having 1 to 20 carbon atoms such as an ethyl group, a propyl group, a butyl group, a pentyl group, a dodecyl group, a hexadecyl group, a cyclopropyl group and a cyclohexyl group, an aryl group such as a phenyl group, a tolyl group and a naphthyl group And aralkyl groups such as benzyl group and the like and groups having a substituent are preferable, and they may be the same or different. X is, for example, a halide ion such as a fluoride ion, a chloride ion or a bromide ion, or an anion such as a hydroxide ion, a sulfate ion, a carbonate ion, a nitrate ion or a phosphate ion.

Among the above onium compounds, typical examples of the phosphonium compounds used are as follows: tetraphenylphosphonium chloride, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride, cyclopropyltriphenylphosphonium bromide, tetrabutylphosphonium bromide And quaternary phosphonium compounds such as tributylhexadecylphosphonium bromide, tetrabutylphosphonium hydroxide, tetrabutylphosphonium sulfate, and tetrabutylphosphonium carbonate. Among them, it is particularly preferable to use a quaternary phosphonium salt in which X is a halide ion. In particular, those having 10 to 30 carbon atoms, such as benzyltriphenylphosphonium chloride, tetrabutylphosphonium bromide and tributylhexadecylphosphonium bromide, are particularly advantageous in the present invention and are suitable. These onium compounds can be used in the form of a commercially available powder or solution.

The alkali is not particularly limited as long as it shows alkalinity in an aqueous solution.
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.

Since the amount of the onium compound, the contact temperature, the contact time, the amount of the alkaline aqueous solution, or the alkali concentration of the alkaline aqueous solution varies depending on the target fluorine-based inert liquid, it is necessary to conduct preliminary experiments in advance to determine the contact conditions. Is desirable. Generally, the amount of the onium compound is 0.00 0.00 parts by weight based on 100 parts by weight of the fluorine-based inert liquid.
It is preferably from 5 to 10 parts by weight, more preferably from 0.01 to 3 parts by weight.

It is preferable to select a high contact temperature in order to shorten the contact time. If a high temperature is selected, the onium compound may be consumed by decomposition. Therefore, the temperature may be selected in consideration of the contact time and the amount of the onium compound added. Usually, 10 to 100 ° C is preferable, and 30 to 90 ° C is more preferable. When the contact temperature exceeds the boiling point of the fluorine-based inert liquid, the contact may be performed under pressure.

The contact time is preferably as long as possible, but is usually preferably selected from the range of 1 minute to 50 hours, more preferably 0.5 to 24 hours.

The amount of the aqueous alkali solution is not particularly limited, but is usually 1 to 100 parts by weight of the fluorine-based inert liquid.
A range of 300 parts by weight, preferably 10 to 200 parts by weight, is suitable. The alkaline aqueous solution may be used repeatedly.

The alkali concentration of the aqueous alkali solution is usually preferably from 5 to 60% by weight, more preferably from 20 to 50% by weight, for good purification.

As a method for contacting the fluorine-based inert liquid with the onium compound and the aqueous alkali solution, a known method for efficiently bringing the three into contact can be used without any limitation. For example, a method of stirring in a stirring tank or the like, a method of dispersing droplets of a fluorine-based inert liquid in an alkaline aqueous solution in which an onium compound is dissolved or dispersed, circulating a mixture of an alkaline aqueous solution containing an onium compound, and For example, a method of introducing a fluorine-based inert liquid into the mixture and mixing them is preferably used. The contact may be performed batchwise or continuously.

After bringing the fluorinated inert liquid into contact with an aqueous alkali solution containing an onium compound, it is necessary to separate the fluorinated inert liquid from the aqueous alkaline solution. Since the fluorine-based inert liquid is insoluble in water and has a higher specific gravity than water, it can be easily separated by standing. The separated fluorine-based inert liquid may slightly dissolve or disperse the onium compound and the aqueous alkali solution.
A distillation operation or a dehydration operation using a dehydrating agent such as silica gel, alumina, zeolite, or silica-alumina gel may be performed.

[0021]

According to the present invention, by contacting a fluorine-based inert liquid with an alkaline aqueous solution containing an onium compound, a fluorine-based inert liquid which generates very little hydrogen fluoride when heated and used is used. An active liquid can be obtained. In addition, an effect that the electrical insulation of the fluorine-based inert liquid is unlikely to decrease over a long period of time is also recognized.

Although the reason is not clear, the present inventors presume as follows. That is, even after distillation or a known purification method, a very small amount of by-products is contained in the fluorine-based inert liquid, and these by-products are gradually decomposed and fluorinated. Although hydrogen is evolved, it is believed that by performing the process according to the invention most of the by-products are decomposed, thereby increasing the stability of the fluorinated inert liquid.

The fluorine-based inert liquid purified according to the present invention has inertness, stability and reliability as a liquid for electrical insulation, a liquid for electronic parts, a liquid for reliability test, a liquid for vapor phase soldering, and the like. Particularly, it can be suitably used for required applications.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Hereinafter, the fluorine-based inert liquid is abbreviated as IL.

Example 1 Using hydrofluoric anhydride and tributylamine as raw materials, the concentration of the latter was set to 10% by weight, and electrolytic fluorination was carried out using a nickel electrolytic tank (electrode area: 15 dm ² , current: 30 A, capacity: 6 L). went. While continuously supplying anhydrous hydrofluoric acid and tributylamine, the generated fluoride was intermittently extracted from the lower part of the electrolytic cell. The produced fluorinated product was brought into contact with a 5% by weight aqueous solution of sodium hydroxide at room temperature to neutralize hydrogen fluoride. Further, distillation under reduced pressure was performed to obtain perfluorotributylamine as IL.

Next, using a glass reactor having a reflux condenser and a stirrer, perfluorotributylamine, tetrabutylphosphonium bromide and a 50% by weight NaOH aqueous solution were stirred at a stirring speed of 600 rpm under the conditions shown in Table 1. Then, the perfluorotributylamine was brought into contact with the onium compound and the aqueous alkali solution. The mixture of perfluorotributylamine, onium compound and aqueous alkali solution was transferred to a separating funnel, and the lower layer of perfluorotributylamine was extracted. The obtained perfluorotributylamine was dried by silica-alumina gel to obtain a purified perfluorotributylamine. 100 g of the purified perfluorotributylamine was placed in a 200 ml eggplant type flask equipped with a reflux condenser at the top, and the solution was heated and boiled under atmospheric pressure for 5 days. Liquid temperature is 177
° C. During this time, nitrogen gas at a flow rate of 80 ml / min was blown into the liquid for 5 days, and the generated hydrogen fluoride was
It was absorbed in ml of 0.01 mol / l aqueous potassium hydroxide solution. The concentration of fluorine ions contained in this aqueous potassium hydroxide solution was measured using an ion chromatograph (Yokogawa Hokushin Electric,
The amount of hydrogen fluoride generated was determined by measuring with a model IC 100), and the amount of hydrogen fluoride generated per unit weight of IL was determined. The results are shown in Table 1. The amount of hydrogen fluoride generated during boiling for 5 days is referred to as the amount of HF generated.

Table 1 shows, as comparative examples, a case where only an onium compound was brought into contact with perfluorotributylamine (Comparative Example No. 1), a case where only an aqueous alkali solution was brought into contact (Comparative Example No. 2), and before purification. The results of measurement of the amount of HF generated in perfluorotributylamine (Comparative Example No. 3) are also shown.

[0029]

[Table 1]

Example 2 As IL, perfluorotripentylamine, perfluorotriethylamine, perfluoro-N-methylmorpholine, perfluoro-N-propylmorpholine, perfluorohexane, perfluorodecalin, perfluorodibutyl ether, perfluoro (2-butyltetrahydrofuran) Was. For each IL, IL100
0.2 parts by weight of tetrabutylphosphonium bromide and 50 parts by weight of an aqueous NaOH solution (concentration: 40% by weight) were brought into contact with each other at 50 ° C. for 8 hours while stirring at a stirring speed of 600 rpm. After the contact, the liquid was separated, and the amount of HF generated was determined. The results are shown in Table 2. Also,
Table 2 shows that H generated during boiling for 5 days using IL before contacting the above-mentioned onium compound with an aqueous alkali solution.
The result of the amount of F generated was also shown as the amount of HF generated before purification.

[0031]

[Table 2]

Example 3 As IL, perfluorotributylamine, onium compounds shown in Table 3 and various aqueous alkali solutions were used. Under conditions of a temperature of 50 ° C. and a contact time of 8 hours, IL10
0.2 parts by weight of the onium compound and 50 parts by weight
A part by weight of the alkaline aqueous solution was simultaneously brought into contact with the IL while stirring at a stirring speed of 600 rpm. After contact, liquid separation was performed to determine the amount of HF generated. The results are shown in Table 3.

[0033]

[Table 3]

Example 4 Using perfluorotributylamine as IL,
0.1 part by weight of tetrabutylphosphonium bromide and 50 parts by weight of NaOH aqueous solution (concentration: 50 parts by weight) per 100 parts by weight
(% By weight) and a contact time of 8 hours while stirring at a stirring speed of 600 rpm. After contact, liquid separation was performed to obtain purified perfluorotributylamine.

The purified perfluorotributylamine was placed in an eggplant-shaped flask having a reflux condenser at the top, and then placed in a flask.
The liquid was heated to 100 ° C. for days.

The volume resistivity and dielectric breakdown voltage of the purified perfluorotributylamine before and after heating for 10 days were measured in accordance with JIS except that the respective measurement temperatures were 25 ° C.
It was measured according to C2101. Before measurement, a dehydration operation using silica gel and a filtration operation using a 0.2 μm membrane filter were performed. The volume resistivity and the breakdown voltage before heating were 5.1 × 10 ¹⁵ Ωcm and 57 kV, respectively, and after heating at 100 ° C. for 10 days, the values were 4.8 and 4.8, respectively.
× 10 ¹⁵ Ωcm, 55 kV.

On the other hand, as a comparative example, perfluorotributylamine before purification was directly heated to 100 ° C. for 10 days in the same manner as above, and the volume resistivity and dielectric breakdown voltage of perfluorotributylamine before and after heating were measured in the same manner as above. It was measured. As a result, the volume resistivity and the breakdown voltage were 4.7 × 10 ¹⁵ Ω cm and 55 kV, respectively, before heating, and 2.3 × 10 ¹³ Ω cm after heating for 10 days, respectively.
The value was 35 kV.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07C 209/84 C07C 209/84 211/15 211/15 C07D 265/30 C07D 265/30 307/18 307/18

Claims (1)

[Claims] 1. A method for purifying a fluorine-based inert liquid, comprising contacting the fluorine-based inert liquid with an alkaline aqueous solution containing an onium compound.