JP2001163618A - Production process of high purity zinc borofluoride hexahydrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide production process for a high purity zinc borofluoride hexahydrate by which a crystalline product of high purity zinc borofluoride hexahydrate can simply be produced at a low cost without requiring such operation as evaporation or concentration and also without using any expensive solvent such as alcohol, with only a stoichiometric means. SOLUTION: This production process comprises a step reacting zinc or a zinc compound with a borofluoride compound, wherein: the total amount of water participating to the reaction is equal to or slightly smaller than the amount of water required to form zinc borofluoride hexahydrate by hydrating zinc borofluoride; and as the above zinc compound, zinc fluoride tetrahydrate and/or anhydrous zinc fluoride can preferably be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-purity zinc borofluoride hexahydrate, and more particularly to, for example, epoxy resin curing when coating an inner surface of a metal can with an epoxy resin. The present invention relates to a method for producing high-purity zinc borofluoride hexahydrate used as an agent.

[0002]

2. Description of the Related Art Zinc borofluoride hexahydrate has a 1809 Ga
Numerous studies have been made since it was invented by y-Lussac et al. The production method is mainly a method of reacting a zinc compound with borofluoric acid.

A method using boron trifluoride is known as Me.
studied by Yerhofer and described in Brit. Pat
ent 226, 491 (Dec, 20, 1923).

[0004] Zinc borofluoride is used for zinc plating and Wa.
It is used as a curing agent for epoxy resins for sh and wear processing.

[0005] For these applications, zinc borofluoride hexahydrate is used as an aqueous solution. Therefore, instead of a crystalline product, an aqueous solution containing, for example, 40 to 50% of zinc borofluoride was preferred.

In recent years, zinc borofluoride hexahydrate has been used as a curing agent for an epoxy resin when coating the inside of a can with an epoxy resin. For such applications, a crystalline product of zinc borofluoride hexahydrate having a low water content is frequently used.

[0007] This crystalline product is very difficult to obtain from aqueous solutions by conventional manufacturing methods. When the aqueous solution is concentrated, it eventually becomes a syrup and does not readily crystallize. Even if the concentrated solution is cooled to obtain crystals, the yield is extremely low and uneconomical. If there is excess water in the reaction system, there is a problem that the product is dissolved in the water and crystals do not precipitate, or even if it precipitates, it is difficult to dry.

For this reason, means for dehydrating and drying with alcohol which is more easily evaporated is used. In this case, alcohol must be used as a solvent, and operations such as dehydration and drying are troublesome. Therefore, this method increases the cost. Furthermore, this method results in a high cost since the final yield is at most 70-75%.
In addition, unless the solvent alcohol is collected and reused, it causes environmental pollution.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for producing a crystalline product of zinc borofluoride hexahydrate without resorting to operations such as evaporation and concentration, and without using expensive solvents such as alcohol. An object of the present invention is to provide a method for producing high-purity zinc borofluoride hexahydrate that can be produced simply and inexpensively simply by using stoichiometric means.

[0010]

An object of the present invention is to provide a method for producing zinc borofluoride hexahydrate by reacting zinc or a zinc compound with a borofluoride compound to produce zinc borofluoride hexahydrate. A method for producing high purity zinc borofluoride hexahydrate, characterized in that the reaction is carried out so that the total amount of water to be formed is equal to or slightly less than the amount of hydrated zinc borofluoride to hexahydrate. Is done.

Further, the zinc compound is preferably zinc fluoride tetrahydrate and / or anhydrous zinc fluoride.

[0012]

The present inventor has carefully observed and studied the physical properties of zinc borofluoride hexahydrate when crystallizing it, and as a result, it was needless to say that the balance of the quantities of zinc, boron, fluorine, etc. was tightly adjusted. It was found that the presence of the water involved had a significant effect. The reaction is performed such that the total amount of water involved in the reaction is equal to or slightly less than the amount of zinc borofluoride hydrated to hexahydrate. The point of this production method is to grasp the total amount of water derived from the raw materials and the water generated by the reaction and to cause the reaction.

The total amount of water present in the reaction system is limited to 6 mol or slightly less than 6 mol per mol of zinc borofluoride.

The raw materials are combined so that the sum of the water contained in the raw materials and the reaction water is 5.5 to 6 mol, and the shortage may be compensated by adding water.

Materials satisfying this condition may be selected from the following group and combined. Zn raw material: zinc not, zinc oxide, zinc fluoride tetrahydrate, anhydrous zinc fluoride borofluoride raw material: BF ₃ (gas), BF ₃ .H ₂ O, 2
_{BF 3 · 3H 2 O, BF} 3 · 2H 2 O, CH 3 OH · BF 3,
C ₂ H ₅ OH.BF ₃ , (CH ₃ ) ₂ O.BF ₃ , (C ₂ H ₅ )
₂ O ・ BF ₃

Several examples of these combinations are illustrated by chemical formulas. _{Zn + 2HF + 2BF 3 · 3H} 2 O + 3H 2 O → Zn (B
_{F 4) 2 · 6H 2 O} + H 2 ZnO + 2HF + 2 (BF 3 · 2H 2 O) + H 2 O → Zn
(BF ₄ ) ₂ .6H ₂ O ZnF ₂ .4H ₂ O + 2 (BF ₃ .H ₂ O) → Zn (B
_{F 4) 2 · 6H 2 O} ZnF 2 + 2BF 3 · 3H 2 O + 3H 2 O → Zn (BF 4) 2
6H ₂ O ZnF ₂ .4H ₂ O + 2 (CH ₃ OH.BF ₃ ) + 2H ₂ O
→ Zn (BF ₄ ) ₂ .6H ₂ O + 2CH ₃ OH ZnF ₂ +2 ｛(C ₂ H ₅ ) ₂ O.BF ₃ ｝ + 6H ₂ O → Zn
(BF ₄ ) · 6H ₂ O + 2 (C ₂ H ₅ ) ₂ O

As a raw material of Zn, zinc fluoride tetrahydrate or anhydrous zinc fluoride obtained by heating and dehydrating this compound at 110 ° C. is suitable for obtaining a product of high purity.

In the method of synthesizing zinc fluoride with zinc powder or zinc oxide and hydrofluoric acid and adding boron trifluoride to this to obtain zinc borofluoride, the reaction is slow and compared with the above method. And high purity products are difficult to obtain.

Borofluoride raw materials include BF ₃ .H ₂ O, 2BF ₃ .3H ₂ O, and BF ₃ in addition to boron trifluoride gas.
Water complex salts such as ₃ · 2H ₂ O are preferred.

A boron trifluoride complex salt such as alcohol or ether reacts well with zinc fluoride, but after releasing BF ₃ , alcohol or ether is liberated. Since a large amount of zinc borofluoride dissolves in the by-produced alcohol or ether, it is necessary to crystallize by heating, evaporating, concentrating and cooling the alcohol or ether to obtain crystalline zinc borofluoride hexahydrate. Is not preferred.

The present inventors have studied in detail the effect of water when preparing zinc borofluoride hexahydrate.

The anhydrous zinc fluoride obtained by dehydrating the zinc fluoride tetrahydrate is reacted with a boron trifluoride water complex having a composition of 2BF ₃ .3H ₂ O to form 1 mol of zinc borofluoride hexahydrate. As a result of examining the effect by changing the amount of water in the range of 5 mol to 6.25 mol by 0.25 mol at the time of adjustment,
As shown in Table 1.

The formation reaction of zinc borofluoride hexahydrate largely depends on the excess or deficiency of water. If water is insufficient, the reaction does not proceed completely, and gas is generated from the product. The lower the water, the greater the degree.

[0024]

Table 1 Influence of excess or deficiency of water when preparing zinc borofluoride hexahydrate

When this product is supplemented with a shortage of water, it reacts immediately and becomes a normal powdery product. At this time, heat is generated, but this heat is presumed to be heat of hydration. Incompletely hydrated products are considered to be unstable and prone to gasification.

On the other hand, if there is excess water, the crystals dissolve in the water and become partially syrup-like and become wet, making it difficult to obtain a powdery product even when dried.

As described above, the key point for obtaining high-purity zinc borofluoride hexahydrate is water management. The total amount of water present in the reaction system, such as water contained in the raw materials and reaction product water, is preferably 5.5 to 6.25 mol, more preferably 5.75 to 6 mol, per mol of zinc borofluoride. Control.

The production method of the present invention provides a method for obtaining a high-purity product in one step by eliminating troublesome operations such as dissolution / filtration / purification and recrystallization, but it is carried out under strict conditions. However, the product contains ethyl alcohol-insoluble components at about 1.5% at most. As a result of X-ray diffraction analysis, this insoluble matter was confirmed to be zinc fluoride.

It has been found that the insoluble content of ethyl alcohol is gradually reduced by curing the product after storage. The condition of storage curing can be accelerated in a shorter time if the condition is kept at a temperature of about 60 ° C., but the cost is high, so that the condition at room temperature is sufficient. FIG. 1 shows an example of the results of a test for reducing ethyl alcohol insolubles conducted at room temperature. The storage curing is preferably performed with the product placed in a bottle or the like and covered. Zinc borofluoride hexahydrate has a high affinity for water and has high hygroscopicity, so that it is stored and cured in a container such as a bottle in order to shield it from an atmosphere containing moisture.

According to the results, the ethyl alcohol insoluble content, which was about 1% on the day of preparation, decreased rapidly after one day due to curing and aging, and further decreased after three days.
Then it gradually decreases. About three days is enough even at room temperature to achieve a high purity of 99.5% or more of zinc borofluoride dissolved in ethyl alcohol.

[0031]

The following examples are provided to further illustrate the method of the present invention.

(Example 1) 12.5 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate was added in a volume of 1 L (liter).
And 13.0 g of pure water was added to the PFA bottle to form a suspension.

When 16.5 g of boron trifluoride gas was added, a vigorous exothermic reaction occurred, and the temperature rose to 112 ° C. Since a small amount of boron trifluoride gas remained, the gas was purged through nitrogen gas. The product was powdery crystals with a yield of 41.8 g, equivalent to theory.

The product was analyzed and found to have an ethanol-insoluble content of 0.62% and a content (from Zn) of 99.8%.

(Example 2) 131.6 zinc fluoride tetrahydrate
g and 25.9 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate are placed in a 1 L PFA bottle, and 2BF ₃
· 3H boron trifluoride water complexes 191 having the composition ₂ O.
When 5 g was added, the mixture violently reacted and generated heat, and the temperature was raised to 80 ° C. The mixture was further shaken to further promote the reaction, and after 1 hour, 348.3 g of a solid powdery product was obtained (yield: 99.9%).
8%). Content (from Zn) 100.2%.

After aging at room temperature for 7 days, the same analysis was carried out to find that the content insoluble in ethanol was 0.20% and the content (from Zn)
It was 100.6%.

Example 3 103.8 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate was placed in a 1 L PFA bottle, and boron trifluoride water having a composition of BF ₃ .H ₂ O was used. When 171 g of a complex salt was gradually added, a little
Temperature. When 72 g of pure water was added little by little to the mixture and mixed and reacted, the mixture vigorously reacted and generated heat.
The temperature was raised to 7 ° C. Analysis was conducted 8 hours after the reaction, whereupon ethanol insoluble content was 1.35%, content (from Zn) 10
1.8%.

After storage and curing at room temperature for 7 days and analysis in the same manner, 0.16% of an ethanol-insoluble content and a content (Z
(from n) 101.3%.

Example 4 830.4 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate was put into a 5 L PFA bottle, and boron trifluoride having a composition of 2BF ₃ .3H ₂ O was used. When 1532 g of a water complex salt was added, a slurry having a temperature of 60 ° C. was obtained. When 418 g of pure water was gradually added to this mixture and mixed and stirred, the mixture vigorously reacted and the temperature was raised to 125 ° C. 2773 g (yield 99.8%) of the product was obtained. When analyzed after 8 hours, ethanol insoluble content 1.16%,
Content (from Zn) 101.1%. After storage and aging at room temperature for 7 days, the same analysis revealed that the ethanol-insoluble content was 0.1% and the content (from Zn) was 100.0%.

Example 5 209.5 g of an aqueous complex of boron trifluoride having a composition of BF ₃ .H ₂ O was mixed with 103.8 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate. did. Upon mixing, the temperature slightly increased to 65 ° C.

When 36 g of water was added to the mixture and mixed well, the mixture vigorously reacted and generated heat, and the temperature was raised to 112 ° C.

When analyzed after 8 hours, the ethanol-insoluble content was 1.45% and the content (from Zn) was 100.6%.

After storage and aging at room temperature for 7 days, the same analysis revealed that the content of ethanol-insoluble matter was 0.32% (from Zn) 100.9%.

Comparative Example 1 Zinc Fluoride Tetrahydrate 175.4
g was placed in a 1 L PFA bottle, and 191.5 g of a boron trifluoride water complex salt having a composition of 2BF ₃ .3H ₂ O was added. The reaction was syrupy.

After treating with a nitrogen gas in an 80 ° C. water bath for 5 hours, a dry solid product was not obtained.

Comparative Example 2 Zinc Fluoride Tetrahydrate 175.4
g was placed in a 1 L PFA bottle, and 191 g of a boron trifluoride water complex salt having a composition of 2BF ₃ .3H ₂ O was added and reacted. When the reaction occurred, a heat was generated and the temperature was raised to 84 ° C.

This was added with 200 ml of ethanol and filtered.

The unreacted zinc fluoride solid was filtered off to obtain a clear filtrate.

The filtrate was concentrated for 8 hours in a 100 ° C. water bath while passing nitrogen through.

After cooling, the crystallized crystals were filtered off to obtain wet crystals containing ethyl alcohol.

This was dried on a 100 ° C. water bath while passing nitrogen gas to obtain 211 g of zinc borofluoride hexahydrate. Yield 60.8% The product was analyzed and found to be ethanol-insoluble 0.22%, content (from Zn) 100.0%
%Met.

In this method, filtration, concentration and drying are troublesome, expensive alcohol is used as a solvent, and the yield is low.

(Comparative Example 3) An alcohol complex salt of boron trifluoride is reacted with anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate to obtain zinc borofluoride hexahydrate. The reaction is performed according to the following reaction formula.

ZnF ₂ + 2CH ₃ OH.BF ₃ + 6H ₂ O →
Zn (BF ₄ ) ₂ .6H ₂ O + 2CH ₃ OH ZnF ₂ + 2C ₂ H ₅ OH.BF ₃ + 6H ₂ O → Zn (B
_{F 4) 2 · 6H 2 O} + 2C 2 H 5 OH

51.8 g of anhydrous zinc fluoride and 130.4 g of a boron trifluoride methanol complex salt having a BF ₃ content of 52% were mixed.

When 54.0 g of pure water was added to this mixture and mixed and stirred, the mixture violently reacted to generate heat, and the temperature was raised to 95 ° C.

The reaction product obtained is a transparent liquid,
All the generated zinc borofluoride is dissolved in the by-produced methanol, and it is necessary to further evaporate and concentrate methanol and ethanol to obtain crystals.

(Comparative Example 4) An ether complex salt of boron trifluoride and anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate are reacted to obtain zinc borofluoride hexahydrate. The reaction is performed according to the following reaction formula.

ZnF ₂ +2 (CH ₃ ) ₂ O.BF ₃ + 6H ₂
O → Zn (BF ₄ ) ₂ .6H ₂ O + 2 (CH ₃ ) ₂ O ZnF ₂ +2 (C ₂ H 5) ₂ O.BF ₃ + 6H ₂ O → Zn
_{(BF 4) 2 · 6H 2} O + 2 (C 2 H 5) 2 O

22.0 g of anhydrous zinc fluoride was mixed with a boron trifluoride ethyl ether complex salt having a BF ₃ content of 48.3%.
5 g was added and mixed.

When 22.9 g of pure water was added to this mixture and mixed and stirred, about half of the by-product ethyl ether was volatilized by the reaction heat generated by the vigorous reaction, but the remaining half remained in the reaction system. The resulting zinc borofluoride was dissolved to obtain a liquid product. To obtain crystals, the remaining ether must be evaporated to dryness.

Comparative Example 5 32.7 g of zinc-free, 40 g of 50% hydrofluoric acid and 7 g of pure water were mixed. The reaction proceeded only slowly, and the reaction was carried out on a hot water bath for 2 hours, but unreacted zinc remained. 2BF ₃
95.8 g of boron trifluoride water complex salt having a composition of 3H ₂ O
Was added. This reaction has the relationship shown in the following equation. _{Zn + 2HF + 3H 2 O +} 2BF 3 · 3H 2 O → Zn (B
_{F 4) 2 · 6H 2 O} + H 2

After standing for 24 hours, analysis was carried out to find 3.8% ethanol-insoluble content and 86.1% content (from Zn).
Therefore, a very practical product could not be obtained.

(Comparative Example 6) 20.35 g of zinc oxide and 50
% Hydrofluoric acid and 2BF ₃
· Boron trifluoride water complex having a composition of 3H ₂ O 47.4
g was reacted.

This reaction has the relationship shown in the following equation. _{ZnO + 2HF + 2BF 3 · 3H} 2 O + 2H 2 O → Zn
_{(BF 4) 2 · 6H 2} O

This reaction is less likely to proceed than expected,
After reacting in a hot water bath for 10 hours, analysis showed that the ethanol-insoluble content was 3.23% and the content (from Zn) was 81.degree.
5% was obtained. The purity was so low that it could not be put to practical use.

[0067]

According to the present invention, for example, a solid product of zinc borofluoride hexahydrate, which is frequently used as an epoxy resin hardener for coating a resin on the inner surface of a can, can be easily and inexpensively prepared and supplied by stoichiometric means.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between curing time and ethyl alcohol insoluble matter.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroshi Yazaki 1-41 Rinkai-cho, Izumiotsu-shi, Osaka

Claims (9)

[Claims] 1. A method for producing zinc borofluoride hexahydrate by reacting zinc or a zinc compound with a borofluoride, wherein the total amount of water involved in the reaction is such that zinc borofluoride is produced. A method for producing high-purity zinc borofluoride hexahydrate, wherein the reaction is carried out so as to be equal to or slightly less than the amount of hydrated hexahydrate. 2. The method for producing high-purity zinc borofluoride hexahydrate according to claim 1, wherein the zinc compound is zinc fluoride tetrahydrate and / or anhydrous zinc fluoride. 3. The high-purity zinc borofluoride hexahydrate according to claim 1, wherein the anhydrous zinc fluoride is anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate. Production method. 4. The high-purity zinc borofluoride hexahydrate according to claim 1, wherein the borofluoride compound is boron trifluoride and / or a boron trifluoride complex salt. Manufacturing method. 5. The boron trifluoride water complex salt is BF ₃ .H _{2
O, 2BF 3 · 3H 2 O} , the method of producing a high-purity zinc borofluoride hexahydrate according to claim 4, wherein it is a BF ₃ · 2H ₂ O. 6. The method according to claim 1, wherein the total amount of water present in the reaction system is at least 5.5 mol and less than 6.25 mol per 1 mol of zinc borofluoride. A method for producing high-purity zinc borofluoride hexahydrate according to claim 1. 7. The high-purity zinc borofluoride 6 water according to claim 6, wherein the total amount of water present in the reaction system is 5.75 mol or more and 6 mol or less per 1 mol of zinc borofluoride. Method for producing salt. 8. The zinc borofluoride hexahydrate obtained by the method according to any one of claims 1 to 7, which is further stored and aged at 60 ° C. or lower for 3 days or more to obtain an ethyl alcohol insoluble content of 0.5%.
% Or less of high purity zinc borofluoride hexahydrate. 9. The method for producing high-purity zinc borofluoride hexahydrate according to claim 8, wherein the storage aging is performed at room temperature.