JP2889019B2 - Production method of polyfluorobiphenyl - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate material for highly functional materials having excellent heat resistance, weather resistance, various stability, water repellency, etc., for example, an intermediate material for engineering plastics such as polyimide resin, and an epoxy resin. The present invention relates to a method for producing polyfluorobiphenyl, which is expected as an intermediate material for a crosslinking agent such as a fluorine-based rubber.

[0002]

2. Description of the Related Art Several methods are known for producing polyfluorobiphenyl, for example, "Chem. Ber.", Vol. 100, Nos. 3016-30.
On page 23, a synthesis method is described by reacting sodium acetate of pentafluorobenzoic acid with copper acetate or silver nitrate.

In this method, first, copper acetate or silver nitrate is reacted with a sodium salt of pentafluorobenzoic acid in an aqueous solvent according to the following reaction formula (3) or (5) to form a corresponding pentafluorobenzoate. Then, these salts are reacted at a high temperature without solvent to synthesize the target decafluorobiphenyl as shown in the following formula (4) or (6).

[0004]

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(Where Ac represents an acetyl group)

[0006]

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[0007]

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[0008]

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However, in the synthesis method using sodium pentafluorobenzoate and copper acetate, the reaction rate of the above formula (3) is 54% based on the sodium benzoate, and the reaction rate of the following formula (4) Is 8.2% in crude yield based on the double salt of benzoic acid, and thus the total crude yield of decafluorobiphenyl is only 4.3% based on sodium pentafluorobenzoate as a starting material. .

In the synthesis method using pentafluorobenzoic acid sodium salt and silver nitrate, the reaction rate of the above formula (5) is 84.7% in crude yield relative to the sodium benzoate salt, The conversion of (6) was 56% based on the silver salt of benzoic acid, and the total crude yield of decafluorobiphenyl was 47.4% based on sodium pentafluorobenzoate as a starting material. Is not good.

Furthermore, since the reaction of the reaction formula (5) is a solventless reaction accompanied by extremely large heat generation, it is difficult to control the reaction and there is a high risk of runaway of the reaction. Due to the high cost, it is inevitable that the cost will increase. Thus, the synthesis method described in the above-mentioned literature is
It is practically difficult to adopt it as an industrial production method.

[0012]

In recent years, engineering plastics such as polyimide resins and aramid resins have been attracting attention in the field of plastics, and these materials have even better heat resistance, weather resistance and various stability. There is a strong need for the development of excellent high-functional materials.

The present inventors have conducted intensive studies to obtain the above-mentioned compound which is extremely promising as an intermediate material for such a high-functional material. As a result, pentafluorobenzoic acid was converted into an alkaline solvent such as sodium hydroxide in an aqueous solvent. Neutralized with an alkali metal compound of the formula to form an alkali metal salt of benzoic acid, and then reacted with a water-soluble strong acid cupric salt such as cupric chloride to form a cupric benzoic acid salt;

Next, the cupric salt is heated at, for example, 220 to 230 ° C.
It was found that the desired product, decafluorobiphenyl, was distilled off at a considerably higher yield than the above-mentioned conventional method, and further research was carried out to complete the present invention.

[0015]

According to the present invention, there is provided a compound represented by the following general formula:
Reacting at least one alkali metal salt of polyfluorobenzoic acid selected from the polyfluorobenzoic acids represented by (1) with a water-soluble cupric acid salt in an aqueous solvent to obtain polyfluorobenzoic acid It is an object of the present invention to provide a method for producing polyfluorobiphenyl of the following general formula (2), which comprises producing a cupric salt of the following, and then heating the cupric salt of the polyfluorobenzoic acid.

[0016]

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[0017]

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(Where n and n ′ are 5 ≧ n ≧ n ′
Is an integer that satisfies ≧ 1)

Hereinafter, the present invention will be described in detail.

Examples of the polyfluorobenzoic acid of the general formula (1) (hereinafter sometimes abbreviated as FnBA) used in the present invention include, for example, pentafluorobenzoic acid, 2,3,4,5-tetrafluorobenzoic acid Examples thereof include benzoic acid, 2,3,5,6-tetrafluorobenzoic acid, 2,4,5-trifluorobenzoic acid, 2,6-difluorobenzoic acid, and 2-fluorobenzoic acid.

In the present invention, one or more FnBAs selected from these FnBAs are used.

In the reaction of the present invention, for example, when sodium hydroxide is used as an alkaline alkali metal compound and cupric chloride is used as a water-soluble cupric acid strong acid salt, the following formula (7)
It is thought that it will proceed according to (9).

[0023]

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[0024]

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[0025]

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(Where n and n ′ are integers satisfying 5 ≧ n ≧ n ′ ≧ 1)

Since the reaction of the above formula (7) (hereinafter sometimes referred to as neutralization reaction) and the reaction of (8) (hereinafter sometimes referred to as salt exchange reaction) proceed sequentially, the reaction is carried out in an aqueous solvent. First, an alkaline alkali metal compound such as sodium hydroxide is added to the starting material FnBA to solubilize it, and then a water-soluble cupric acid salt such as cupric chloride is added and reacted to form a cupric salt of FnBA. Crystals can be produced.

The obtained crystals of the cupric salt of FnBA are separated and dried by means such as filtration, and then, for example, at 200 to 330 ° C.
By heating to a certain degree, a target product polyfluorobiphenyl (hereinafter sometimes abbreviated as FxBP) can be synthesized (hereinafter sometimes referred to as a coupling reaction).

[Neutralization Reaction Step] This reaction step is a step of adding an alkaline alkali metal compound to the starting material FnBA in an aqueous solvent to form an alkali metal salt of FnBA. FnBA is a compound having relatively low solubility in water, but becomes water-soluble when neutralized by the alkali metal compound.

Examples of the alkali metal compound include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide;
Alkali metal carbonates such as sodium carbonate and potassium carbonate; for example, lithium hydrogen carbonate, sodium hydrogen carbonate,
Alkali metal bicarbonates such as potassium bicarbonate; and the like.

Of these, use of sodium hydroxide or potassium hydroxide is most preferable from the viewpoints of easy availability, good reaction operability, good reactivity, and the like.

The amount of the alkali metal compound to be used per 1 mol of the starting material FnBA is stoichiometrically 1 mol, preferably 0.8 to 2 mol, particularly preferably 0.9 mol, as apparent from the above formula (7). It is preferably 1.5 mol.

The “aqueous solvent” used in this step is
Water or a mixed solvent of water and a water-soluble organic solvent.

The above-mentioned water-soluble organic solvent dissolves in an amount of 50 parts by weight or more with respect to 100 parts by weight of water, and does not cause a harmful side reaction in the neutralization reaction in this step or the salt exchange reaction described later. Anything can be used without any restrictions,

For example, C 1 -C 1 such as methyl alcohol, ethyl alcohol, n- or i-propyl alcohol, etc.
3 aliphatic monohydric alcohols; for example, other monohydric alcohols such as allyl alcohol and furfuryl alcohol;

For example, aliphatic polyhydric alcohols having 2 to 3 carbon atoms such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerin; polyethylene glycol which is liquid at room temperature;

For example, ethylene glycol such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether and the like having 1 carbon atom
Mono- or dietherified compounds with aliphatic monohydric alcohols of 4 to 4;

For example, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,
Diethylene glycol such as diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and C1-C1
A mono- or di-etherified compound with an aliphatic monohydric alcohol of 4;

For example, a monoetherified product of glycerin such as 1-glycerin monomethyl ether and an aliphatic monohydric alcohol having 1 to 3 carbon atoms;
Cyclic ethers such as 1,3-dioxane and 1,4-dioxane;
And the like.

When these organic solvents are used, these organic solvents can be used alone or in combination of two or more. Among these organic solvents, aliphatic monohydric alcohols can be particularly preferably used from the viewpoints of availability and economics.

Of the above-mentioned aqueous solvents, use of water is particularly preferred from the viewpoint of cost reduction.

The reaction temperature is generally 0-100 ° C., preferably 10-50 ° C., and the reaction time is generally about 1-60 minutes, preferably about 3-30 minutes.

Subsequently, a salt exchange reaction is performed using the obtained aqueous solvent solution containing the alkali metal salt of FnBA.

[Salt exchange reaction step] In this reaction step, a water-soluble cupric acid strong acid salt is added to an aqueous solvent solution containing an alkali metal salt of FnBA obtained in the neutralization reaction step to effect salt exchange.
This is a step of precipitating a second copper salt crystal of FnBA.

"Water-soluble" in the above-mentioned "water-soluble cupric acid cupric salt" means that the solubility in water (the number of grams of the compound dissolved in 100 g of water) is 5 or more.
The term "strong acid" refers to an inorganic or organic acid having a pH of 0.1N aqueous solution in the range of 1-2.

Examples of such a strong acid cupric salt include cupric chloride, cupric bromide, cupric fluoride, and cupric chloride.
Cupric halides such as cupric potassium, cupric lithium chloride, cupric cesium chloride and the like; for example, cupric sulfate, cupric potassium sulfate, cupric sodium sulfate, cupric rubidium sulfate, sulfated copper Cupric sulfate such as copper cesium; cupric nitrate; cupric chlorate; cupric perchlorate; and hydrated crystals of these salts.

Of these, cupric chloride, cupric sulfate, cupric nitrate, or hydrated crystals thereof are preferably used from the viewpoint of availability. Further, since the obtained cupric copper salt of FnBA has some water solubility as described later, in order to suppress a decrease in the yield of the cupric salt due to dissolution,
It is preferable to minimize the amount of water in the reaction system in this step. From this viewpoint, it is particularly preferable to use cupric chloride or a water-containing crystal thereof having particularly high water solubility.

The amount of the water-soluble cupric acid salt used is determined by the formula
(8) As is clear, the starting material FnBA (two or more kinds of FnBA
In the case where is used, its total) is generally 1 mole,
It is 0.5 mol or more, preferably 0.5 to 1 mol, particularly preferably 0.5 to 0.8 mol.

The reaction temperature is generally from 0 to 200 ° C., preferably from 10 to 50 ° C., and the reaction time is generally from 5 to 180 minutes, preferably from about 5 to 120 minutes.

The precipitated FnBA cupric salt crystals are filtered off,
After washing with water and drying, the next coupling reaction can be performed.

Since the cupric copper salt of FnBA is slightly soluble in water, a mixed solution of the filtrate after washing the crystals of the cupric copper salt and the washing liquid is used to improve the yield of the method of the present invention. It is good to reuse as a solvent in the exchange reaction step.

The neutralization reaction step and the present salt exchange reaction step are preferably carried out sequentially as described above. However, an alkali metal salt of FnBA prepared in advance as a starting material is used.
A method of adding a water-soluble strong acid cupric salt to the aqueous solution, conversely, a method of adding an alkali metal salt of FnBA to an aqueous solution of a water-soluble strong acid cupric salt, ,
A method of adding an alkali metal salt of FnBA and a water-soluble cupric acid strong acid salt can also be employed.

The obtained cupric salt of FnBA can be filtered, washed with water and dried, and then subjected to the next coupling reaction.

[Coupling Reaction Step] The cupric salt of FnBA obtained in the salt exchange reaction step can be subjected to a coupling reaction by heating preferably in a substantially solvent-free state.

The term "substantially solvent-free" used herein means that a solvent is not used except for the moisture and impurities inevitably contained in the cupric salt of FnBA. In this case, the amount of the solvent in the reaction system is, for example,
An example is about 10% by weight or less, preferably about 5% by weight or less.

In such a substantially solvent-free state, the target compound FxBP produced is distilled off as the reaction proceeds. For this reason, the distilling route is preferably kept at a temperature equal to or higher than the melting point of FxBP in order to prevent clogging due to precipitation of the FxBP crystals.

The reaction temperature is generally from 200 to 330 ° C., preferably from 220 to 300 ° C. When the reaction temperature is higher than the lower limit temperature, the coupling reaction proceeds at a sufficient reaction rate, and the generated target compound FxBP is preferably smoothly distilled off. This is preferable because control can be easily performed.

The reaction time is generally about 0.5 to 10 hours, preferably about 1 to 5 hours.

The obtained crude crystals of FxBP have a high purity of usually 95% by weight or more, but if necessary, for example, a mixed solvent of water / methanol [water / methanol = 1/8 (weight ratio) etc.] It can be recrystallized using an appropriate solvent to obtain higher purity.

[0060]

The present invention will be described in more detail with reference to the following examples.

Example 1 (Neutralization reaction and salt exchange reaction) In a 3000 ml glass separable flask equipped with a stirrer and a dropping funnel, 1540 g (about 2.31 mol) of a 6% by weight aqueous sodium hydroxide solution and pentafluorobenzoate were added. 500 g of acid (purity: about 98% by weight: about 2.31 mol) was charged and dissolved by stirring at room temperature.

Then, 411 g of a 40% by weight aqueous cupric chloride solution
(About 1.22 mol) was dropped from the dropping funnel. Along with this dropping, a formed cupric salt of pentafluorobenzoic acid was precipitated. After completion of the dropwise addition, the precipitated crystals were filtered by a conventional method and dried.

The amount of crystals of the cupric salt of pentafluorobenzoic acid obtained was 534 g (about 1.1 mol), and the yield based on the charged pentafluorobenzoic acid was about 95%.

(Coupling reaction) In a 2000 ml glass separable flask equipped with a stirrer and a Liebig condenser, 534 g (about 1.1 mol) of crystals of the cupric salt of pentafluorobenzoic acid obtained in the above reaction were obtained. , 220 ~ 240 ℃
For 3 hours. Decafluorobiphenyl produced as the reaction progressed was distilled off. During this time, the cooling tube was kept at 70 ° C. or higher to prevent clogging of the distilled decafluorobiphenyl with crude crystals.

The amount of the obtained crude crystals was 318 g (purity: about 99.4% by weight; about 0.95 mol), the crude yield with respect to the cupric salt of pentafluorobenzoic acid was about 86%, The crude yield based on benzoic acid was about 82%.

Then, the crude crystals were treated with water / methanol [water /
Methanol = 1/8 (weight ratio)]
The mixture was filtered while hot at ℃ and cooled to 20 ℃ to recrystallize, and the crystals were separated by filtration and dried. The obtained purified decafluorobiphenyl crystal (purity 99.8% by weight) was 297 g (about 0.89 mol), and the yield based on the cupric salt of pentafluorobenzoic acid was about 81%.
And the yield based on the starting material pentafluorobenzoic acid was about 77%.

The physical properties of the obtained decafluorobiphenyl are as shown in Table 1 below.

[0068]

[Table 1]

Example 2 (Neutralization reaction and salt exchange reaction) Instead of using 410 g (about 1.22 mol) of a 40% by weight aqueous cupric chloride solution in Example 1, 973 g of a 20% by weight aqueous cupric sulfate solution was used. (About 1.22 mol)
The reaction was carried out in the same manner except that was used. The amount of the obtained crystals of the cupric salt of pentafluorobenzoic acid was 448 g (approximately
0.92 mol), and the yield based on the charged pentafluorobenzoic acid was about 80%.

Using the above crystals of the cupric salt of pentafluorobenzoic acid, crude crystals of decafluorobiphenyl were obtained in the same manner as in Example 1.

Examples 3 to 6 FxBP was synthesized in the same manner as in Example 1, except that various FnBAs were used instead of pentafluorobenzoic acid. Table 2 shows the type and amount of FnBA used as a raw material, the yield of copper salt of FnBA, and the yield, yield, and melting point of the obtained FxBP.

[0072]

[Table 2]

[0073]

According to the method of the present invention, for example, polyfluorobiphenyl such as decafluorobiphenyl, which is extremely promising as an intermediate material for high-performance materials, can be prepared by a relatively safe and relatively simple operation. Can also be produced industrially in fairly high yields.

Continuation of the front page (72) Inventor Hiroshi Shibuchi 3-24-26 Yokodai, Isogo-ku, Yokohama-shi, Kanagawa Japan Nippon Carbide Industry Co., Ltd. Yokohama Dormitory Examiner Osamu Sato (56) References JP-A-3-284639 (JP, A JP-A-64-25737 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 25/18 C07C 17/26

Claims (1)

(57) [Claims] 1. An aqueous solution of at least one alkali metal salt of a polyfluorobenzoic acid selected from polyfluorobenzoic acids represented by the following general formula (1) in a water-based solvent: To react with the second of polyfluorobenzoic acid
A method for producing polyfluorobiphenyl of the following general formula (2), characterized by forming a copper salt and then heating the cupric salt of polyfluorobenzoic acid. Embedded image Embedded image (Where n and n ′ are integers satisfying 5 ≧ n ≧ n ′ ≧ 1)