KR100673874B1 - The method of preparing high purity ZnBF42 6H2O - Google Patents

Abstract

The present invention provides a high purity zinc fluoride 6 product easily and inexpensively by using a stoichiometric means for a product of the zinc borohydride hexahydrate crystalline state without the use of an evaporative concentration operation or an expensive solvent such as alcohol. The above object is the manufacturing method of the zinc borohydride hexahydrate which reacts zinc or a zinc compound with a borofluoride compound, and produces zinc borohydride, The total amount of water which participates in reaction. The zinc borohydride is hydrated and characterized in that it is equal to or less than the amount of hexahydrate to react. Moreover, it is preferable that the said zinc compound is characterized by being zinc fluoride tetrahydrate and or anhydrous zinc fluoride.

Description

The method of preparing high purity Zn (BF4) 2 6H2O}

1

It is a graph showing the relationship between curing time and ethyl alcohol insoluble fraction.

The present invention relates to a method for producing a high purity zinc borohydride hexahydrate, and more particularly, to a high purity zinc borohydride hexahydrate which is used as an epoxy resin hardener when coating an epoxy resin on the inner surface of a metal can, for example. It relates to a manufacturing method of.

Since the zinc fluoride hexahydrate was invented by Gay-Lussac et al. In 1809, a number of studies have been conducted. The manufacturing method is mainly a method of reacting a zinc compound with boric acid.

In addition, a method using boron trifluoride has been studied by Meyerhofer, Brit. Patent 226,491 (Dec, 20, 1923).

Zinc boride fluoride is used as a curing agent for zinc plating and wash and wear epoxy resins.

In such a use, zinc borohydride hexahydrate is used as the aqueous solution. Therefore, it is suitable if it is not a product of a crystalline state, but the aqueous solution which contains 40-50% of zinc borofluoride, for example.

In recent years, zinc borohydride hexahydrate is used as a curing agent for epoxy resins when coating epoxy resins on the inner surface of cans. For this application, a product in the form of a crystal of zinc borohydride hexahydrate having low moisture is used.

Products in this crystalline state are very difficult to obtain in aqueous solution through conventional manufacturing methods. Concentration of the aqueous solution soon leads to a syrup state, which rarely crystallizes. Cooling the concentrate to obtain crystals is very unlikely and economical. If there is residual moisture in the reaction system, there is a problem that the product is dissolved in the moisture and crystals do not precipitate or do not dry well even when precipitated.

Therefore, a means for dehydration and drying with alcohol which is more easily evaporated is used. In this case, alcohol cannot be used as a solvent, and operations such as dehydration and drying are separately required. Thus, this method raises the cost. In addition, the cost increases because the final yield is only 70-75%. Alcohol, which is a solvent, is a cause of environmental pollution unless it is recovered and recycled.

The present invention can be produced easily and inexpensively by using only stoichiometric means, without the use of expensive solvents such as alcohol or by operation such as evaporation, concentration or the like in the crystal state of zinc borohydride hexahydrate. An object of the present invention is to provide a method for producing a high purity zinc borohydride hexahydrate.

In the above problem, in the method for producing zinc borohydride in which zinc or zinc compound is reacted with a boron fluoride compound to produce zinc borohydride, zinc borohydride hydrates the total amount of water involved in the reaction. It is solved by a method for producing a high purity zinc borohydride hexahydrate, characterized in that the reaction is carried out in the same or less amount.

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

  When the zinc borohydride hexahydrate is crystallized, the inventors have carefully observed and examined the physical properties thereof. As a result, it is natural that the balance of water, such as zinc, boron, and fluorine, should be exactly matched. I found it crazy. The total amount of water involved in the reaction is made to be equal to or less than the amount of zinc borohydride to form hexahydrate and allowed to react. The point of this manufacturing method is to grasp the total amount of water generated by the reaction with the water derived from the raw material and to react it.

As for the total amount of water which exists in a reaction system, about 1 mol of zinc borofluoride is a little less than 6 mol or 6 mol.

The raw materials may be mixed so that the sum of the water and the reaction product water contained in the raw materials is 5.5 to 6 mol, and the insufficient amount may be supplemented with water.

What is necessary is just to mix the raw material which satisfy | fills this condition from the next group.

Zn raw materials: zinc powder, zinc oxide, zinc fluoride tetrahydrate, anhydrous zinc fluoride                     

Boron fluoride raw materials: BF ₃ (gas), BF ₃ H ₂ O, ₂ BF _{3 3} H ₂ O,

BF ₃ 2H ₂ O, CH ₃ OH BF ₃ , C ₂ H ₅ OH BF ₃

(CH ₃ ) ₂ OBF ₃ , (C ₂ H ₅ ) ₂ OBF ₃

Some examples of these mixtures are shown by the formula.

Zn + 2HF + 2BF ₃ 3H ₂ O + 3H ₂ O → Zn (BF 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 (BF 4) 2 · 6H 2 O

_{ZnF 2 + 2HF 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 OBF 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 and the anhydrous zinc fluoride obtained by heating and dehydrating this compound at 110 degreeC are the most suitable when obtaining a high purity product.

The method of obtaining zinc fluoride by synthesizing zinc fluoride from zinc powder or zinc oxide and hydrofluoric acid and adding boron trifluoride to it is slow in reaction and difficult to obtain a high purity product in comparison with the above method.

As the boron fluoride raw material, sorbent salts such as BF ₃ · H ₂ O, 2BF ₃ · 3H ₂ O, and BF ₃ · 2H ₂ O are most suitable besides boron trifluoride gas.

Boron trifluoride complex salts such as alcohols and ethers react well with zinc fluoride, but alcohol and ether are freed after BF ₃ has fallen. Since zinc borofluoride is dissolved in a large amount in by-produced alcohols and ethers, in order to obtain crystalline zinc borohydride hexahydrate, alcohols and ethers must be evaporated and concentrated cooled by heating to crystallize, which is undesirable.

The present inventors examined in detail the effect of water on the preparation of zinc borohydride hexahydrate.

To adjust 1 mole of zinc borohydride hexahydrate by reacting anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate with a boron trifluoride sorbate having a composition of 2BF ₃ · 3H ₂ O, the amount of water present is 5 mol to 6.25 mol As a result of examining the influence by changing it by 0.25 mol in the range of, it is as showing in Table 1.

The production reaction of zinc borohydride hexahydrate is highly dependent on the lack of water. If water is insufficient, the reaction does not proceed completely, and a large amount of gas is generated in the product. The less water, the greater the amount.

Effects of Water Excess on Adjusting Zinc Borosilicate Hexate Moles of added water Status of reaction product State after calibration 5  After 3 days, a lot of gas is somewhat damp.   When 1 mole of water is added, it generates heat and reacts to form a powder product. 5.25  After 3 days, the gas is somewhat damp.  When 0.75 mol of water is added, it exothermicly reacts to form a powder product. 5.5  After 3 days, a little gas is generated and a little damp.  When 0.5 mole of water is added, it reacts with exotherm, resulting in a powder product. 5.75  Powder products  Unnecessary 6  Powder products  Unnecessary 6.25  Wet state  It does not dry well with excess moisture.

When this product is replenished with insufficient water, it reacts immediately to give a normal powdered product. At this time, it is accompanied by heat generation and this heat is assumed to be a heat of hydration. Incomplete products of hydration are considered to be prone to gasification in an unstable state.

On the other hand, if there is excess water, crystals are dissolved in the water, and some of the water is in a syrupy state, and it becomes difficult to obtain a powdery product even when dried.

As mentioned above, the key point of obtaining high purity zinc borohydride hexahydrate is water management. The total amount of water present in the reaction system, such as water and the reaction product, contained in the raw material is preferably controlled to 5.5 to 6.25 mol, more preferably 5.75 to 6 mol relative to 1 mol of zinc borofluoride.

The manufacturing method of the present invention is to provide a method of obtaining a high-purity product in one step by eliminating the operation of dissolution, filter agent, recrystallization, etc., even if performed under strict conditions, ethyl alcohol is insoluble in the product although it is about 1.5%. Contains sea cucumbers. X-ray diffraction analysis confirmed that this insoluble fraction was zinc fluoride.

This ethyl alcohol insoluble content was found to gradually decrease through storage and curing of the product. If the storage curing is carried out under a temperature of about 60 degrees, it is accelerated in a shorter time, but it is enough to carry out at room temperature because of the cost. 1 shows an example of ethyl alcohol insoluble fraction reduction test conducted at room temperature. It is preferable to carry out storage curing in the state which put a product in a bottle etc. and closed the cover. Since zinc borohydride hexahydrate has high affinity with water and high hygroscopicity, it is put in a container such as a bottle to cure the air containing moisture and stored in a closed state.

According to this result, the ethyl alcohol insoluble fraction, which was around 1% on the day of preparation, rapidly decreases after 1 day due to curing maturity, further decreases on the third day, and then gradually decreases. In order for the zinc fluoride powder dissolved in ethyl alcohol to be finished with high purity of 99.5% or more, about 3 days at room temperature is sufficient.

EXAMPLE

An example is given below and the method of this invention is disclosed concretely.

Example 1

12.5 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate was placed in a volume of 1 L (liter) PFA bottle, and 13.0 g of pure water was added to make a suspended phase.

When 16.5 g of boron trifluoride gas was added, the exothermic reaction was severe and the temperature rose to 112 ° C. Boron trifluoride gas remained slightly and was removed using nitrogen gas. The product was a powdery crystal, the yield was 41.8g, which is the same as the theoretical value.

When the product was analyzed, the ethanol insoluble content was 0.62% and the content (at Zn) was 99.8%.

Example 2

131.6 g of zinc fluoride tetrahydrate and 25.9 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate are contained in a volume of 1 L PFA bottle, and a boron trifluoride sorbent having a composition of 2BF ₃ · 3H ₂ O.

When 191.5 g was added, it reacted violently and exothermed and it rose to 80 degreeC. When the mixture was shaken well and the reaction proceeded again, 348.3 g of a solid powder product was obtained after 1 hour (yield 99.8%). Content (at Zn) was 100.2%.

After aging for 7 days at room temperature, ethanol insoluble content 0.20%, content (Zn 100.6%.

Example 3

103.8 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate was added to a volume of 1 L PFA bottle, and when 171 g of boron trifluoride sorbate having a composition of BF ₃ · H ₂ O was gradually added, the reaction was slightly increased to 70 ° C. It was. When 72 g of pure water was added and mixed and reacted little by little to this mixture, it reacted violently, and exothermicly heated up to 117 degreeC. Analysis after 8 hours of reaction was 1.35% ethanol insoluble content and 101.8% content (at Zn).

After culturing for 7 days at room temperature, the same analysis yielded 0.16% ethanol insoluble content and 101.3% content (at Zn).

Example 4

830.4 g of anhydrous zinc fluoride obtained by dehydrating the zinc fluoride tetrahydrate was added to a volume 5 L PFA bottle, and 1532 g of boron trifluoride sorbate having a composition of 2BF ₃ · 3H ₂ O was added to give a suspension at a temperature of 60 ° C. When 418g of pure water was added little by little to this mixture, and it stirred and mixed, it reacted badly and it rose to 125 degreeC. 2773 g (product yield: 99.8%) of product was obtained. Analysis after 8 hours showed 1.16% ethanol insoluble content and 101.8% content (at Zn). After aging for 7 days at room temperature, the same analysis showed that 0.1% ethanol insoluble content and 100.0% content (at Zn).

Example 5

To 103.8 g of anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrachloride, 209.5 g of boron trifluoride sorbate having a composition of BF ₃ · H ₂ O was mixed. When mixed, it reacted a little and the temperature became 65 degreeC.

When 36 g of water was added to this mixture and mixed well, it reacted badly and exothermed, and it rose to 112 degreeC.

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

After aging for 7 days at room temperature, the ethanol insoluble content was 0.32% and the content (at Zn) was 100.9%.

Comparative Example 1

175.4 g of zinc fluoride tetrahydrate was placed in a volume 1 L PEA bottle, and when 191.5 g of boron trifluoride sorbate having a composition of 2BF ₃ .3H ₂ O was mixed, it reacted and exothermed and rose to 85 ° C. The reaction showed syrup state.

After 5 hours of treatment with nitrogen gas in a hot bath at 80 ° C., a dry solid product was not obtained.

Comparative Example 2

175.4 g of zinc fluoride tetrahydrate was placed in a volume 1 L PEA bottle, and when reacted with 191 g of boron trifluoride sorbate having a composition of 2BF ₃ · 3H ₂ O, the reaction was exothermic and rose to 84 ° C.

200 ml of ethanol was added thereto and filtered.

The unreacted zinc fluoride solid was filtered to give a very clear filtrate.

The filtrate was concentrated for 8 hours while passing nitrogen in 100 baths.

When the crystals formed after cooling were filtered, wet crystals containing ethyl alcohol were obtained.

When it was dried while passing nitrogen gas in a hot water bath at 100 ° C, 211 g of

Zinc borohydride hexahydrate was obtained. When the product having a yield of 60.8% was analyzed, the ethanol insoluble content was 0.22% and the content (at Zn) was 100.0%.

This manufacturing method is troublesome in filtration, concentration and drying, uses expensive alcohol as a solvent, and has a low yield.

Comparative Example 3

Zinc borohydride hexahydrate is obtained by reacting boron trifluoride alcohol complex salt with anhydrous zinc fluoride obtained by dehydrating zinc fluoride tetrahydrate. The reaction is carried out according to the following scheme.

_{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 (BF 4) 2 · 6H 2 O + 2C 2 H 5 OH

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

When pure water 54.0 was added and stirred for mixing the mixture, it reacted violently, exothermicly, and rose to 95 ° C.

The obtained reaction product was a transparent liquid, and all the produced zinc borofluoride was dissolved in by-product methanol, and it was necessary to evaporate and concentrate methanol and ethanol in order to obtain crystals.

Comparative Example 4

Zinc fluoride hexahydrate is obtained by reacting anhydrous zinc fluoride obtained by dehydrating an ether complex salt of boron trifluoride and a zinc fluoride tetrahydrate. The reaction is carried out 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 ) O ・ BF ₃ + 6H ₂ O → Zn (BF ₄ ) ₂ · 6H ₂ O + 2 (C ₂ H ₅ ) ₂ O

To 22.0 g of anhydrous zinc fluoride, 59.5 g of boron trifluoride ethyl ether complex salt having a BF ₃ content of 48.3% was added and mixed.

When 22.9 g of pure water was added to the mixture and mixed and stirred, about half of the amount of by-produced ethyl ether was evaporated by the reaction heat which was severely reacted and exothermic, and the remaining half remained in the reaction system, resulting in zinc borosilicate. Was dissolved to obtain a liquid product.

Comparative Example 5

32.7 g of zinc powder, 40 g of 50% hydrofluoric acid, and 7 g of pure water were mixed. The reaction proceeded slowly and was reacted for 2 hours in a bath, but unreacted zinc powder remained. To this mixture, 95.8 g of boron trifluoride sorbate having a composition of 2BF ₃ · 3H ₂ O was added. The reaction is as follows.

Zn + 2HF + 3H ₂ O + 2BF ₃ 3H ₂ O → Zn (BF ₄ ) ₂ 6H ₂ O + H ₂

Analysis after 24 hours of ethanol insoluble content, content (Zn) of 86.1%, a very practical product was not obtained.

Comparative Example 6

After mixing 20.35 g of zinc oxide and 20.0 g of 50% hydrofluoric acid, 47.4 g of boron trifluoride sorbate having a composition of 2BF ₃ · 3H ₂ O was reacted.

This reaction has the following relationship.

ZnO + 2HF + 2BF ₃ 3H ₂ O + 2H ₂ O → Zn (BF ₄ ) ₂ 6H ₂ O

This reaction did not proceed as well as expected, and after analysis for 10 hours in a 60 ° C. hot water bath, an ethanol-insoluble content of 3.23% and a content (at Zn) of 81.5% were obtained. Purity was low and could not be provided for practical use.

For example, it is possible to easily and inexpensively manufacture and supply a solid product of zinc borohydride hexahydrate used as an epoxy resin hardener for resin coating on the inner surface of a can by stoichiometric means.

Claims (9)

In the method for producing zinc borohydride, in which a zinc fluoride hexahydrate is prepared by reacting zinc or a zinc compound with a boride, the total amount of water involved in the reaction is equal to the amount of zinc borohydride hydrated to form a hexahydrate. A method for producing a high purity zinc borohydride hexahydrate, characterized in that the reaction is carried out by a little or less. The method for producing a high purity zinc borohydride hexahydrate according to claim 1, wherein the zinc compound is zinc fluoride tetrahydrate and / or anhydrous zinc fluoride. The method for producing a high purity zinc borohydride hexahydrate according to claim 1 or 2, wherein the anhydrous zinc fluoride is anhydrous zinc fluoride obtained by dehydrating a zinc fluoride tetrahydrate. 3. The method of claim 1 or 2, wherein the boron fluoride compound is boron trifluoride or boron trifluoride complex salt. 5. The method of claim 4, wherein the boron trifluoride sorbate is BF ₃ · H ₂ O, 2BF ₃ · 3H ₂ O, BF ₃ · 2H ₂ O. 6. The method for producing a high purity zinc borohydride hexahydrate according to claim 1 or 2, wherein the total amount of water present in the reaction system is 5.5 mol or more and less than 6.25 mol with respect to 1 mol of zinc borofluoride. The method for producing a high purity zinc borohydride hexahydrate 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 with respect to 1 mol of zinc borofluoride. The zinc borosilicate hexahydrate obtained by the method according to claim 1 or 2 is stored at 60 ° C. or lower for at least 3 days to obtain a high purity zinc borohydride salt having 0.5% or less ethyl alcohol insoluble content. Process for preparing zinc fluoride hexahydrate. The method for producing high purity zinc borohydride hexahydrate according to claim 8, which is stored at room temperature.

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