JPH0524819A - Production of zinc orthosilicate precursor and production of zinc orthosilicate - Google Patents

Abstract

PURPOSE:To produce a precursor capable of providing high-purity zinc orthosilicate by mixing a solution of sodium orthosilicate or sodium metasilicate with a solution of a zinc salt under conditions of a specific temperature for a specific time. CONSTITUTION:Sodium orthosilicate or sodium metasilicate or both are dissolved in a solvent such as water. On the other hand, a zinc salt such as zinc nitrate is dissolved in a solvent such as water. Both the resultant solutions are mixed at ambient temperature to 110 deg.C, preferably about 95-110 deg.C for about >=0.5hr, preferably 2-5hr. The above-mentioned method for mixing is preferably performed by dropping and mixing the solution of the zinc salt with the solution of the sodium silicate while heating and refluxing or the atomic ratio Zn/Na is preferably regulated to the stoichiometric ratio in mixing. The formed precipitates are then collected and dried to provide a precursor of zinc orthosilicate. The resultant precursor is subsequently burned at 850-1300 deg.C for >=0.5hr, preferably at about 900-1200 deg.C for about 1-10hr to afford the objective zinc orthosilicate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a precursor used for producing zinc orthosilicate and a method for producing zinc orthosilicate using the precursor.

[0002]

BACKGROUND OF THE INVENTION Zinc silicate is zinc silicate ore.
Naturally produced as ₂ SiO ₄ ). Zinc silicate is used as a coating material for improving the corrosion resistance of steel, as an additive to various ceramics, and as a luminous body of a cathode ray tube. Recently, many reports have been made on the use of steel as a protective agent, but few reports on a method for synthesizing zinc silicate.

JP-A-60-11219 and JP-A-60-11219
0-11220 discloses a method for producing zinc silicate. The zinc silicate obtained by the manufacturing method described in these publications is mainly used as an additive for a zinc oxide voltage linear resistor. Further, according to these publications, the obtained product has a Zn / Si ratio of about 1, and the X-ray pattern shows a single phase. Therefore, the obtained zinc silicate is zinc metasilicate ( ZnSiO ₃ ).

[0004]

OBJECT OF THE INVENTION It is an object of the present invention to provide a novel method for producing zinc orthosilicate. Another object of the present invention is to provide a method for producing a precursor used in such a novel method for producing zinc orthosilicate.

[0005]

SUMMARY OF THE INVENTION A method for producing a zinc orthosilicate precursor according to the present invention comprises a solution obtained by dissolving sodium orthosilicate and / or sodium metasilicate in a solvent and a solution obtained by dissolving a zinc salt in the solvent. It is characterized by mixing at room temperature to 110 ° C. for 0.5 hours or more.

In the method for producing zinc orthosilicate according to the present invention, the above precursor is added at 850 to 1300 ° C.
It is characterized by firing for 0.5 hours or more.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The method for producing a zinc orthosilicate precursor and the method for producing zinc orthosilicate according to the present invention will be specifically described below.

In the method for producing a zinc orthosilicate precursor according to the present invention, sodium orthosilicate or sodium metasilicate, or both of them and a zinc salt are used as starting materials.

Commercially available reagents can be used as sodium orthosilicate and sodium metasilicate without particular limitation. Among these sodium silicates, it is particularly preferable to use sodium metasilicate.

As the zinc salt, zinc chloride, zinc sulfate, zinc nitrate, zinc phosphate, organic zinc complex and the like are used, and these may be used alone or in combination of two or more. Among these zinc salts, it is particularly preferable to use nitrate.

In the present invention, a solution of sodium silicate dissolved in a solvent and a solution of the zinc salt dissolved in a solvent are mixed to produce a zinc orthosilicate precursor.

As the solvent in which the sodium silicate is dissolved, water, methanol, ethanol, propanol,
Isopropanol, n-hexane, acetone, tetrahydrofuran or the like is used, and preferably water is used.
The concentration of the sodium silicate solution is not particularly limited.

As the solvent in which the zinc salt is dissolved, water, methanol, ethanol, propanol, isopropanol, n-hexane, acetone, tetrahydrofuran or the like is used, and water is preferably used. The concentration of the zinc salt solution is not particularly limited.

In the present invention, the sodium silicate solution is mixed with the zinc salt solution. The mixing method may be any method. When mixing, Zn / Na
It is preferable to use the sodium silicate solution and the zinc salt solution in such a ratio that the (atomic ratio) becomes a stoichiometric ratio. The temperature at the time of mixing is room temperature to 110 ° C., particularly preferably 95 to 1
It is 10 ° C. The mixing time is 0.5 hours or more, particularly preferably 2 to 5 hours.

In the present invention, the sodium orthosilicate solution and the zinc salt solution are mixed as described above to produce a zinc orthosilicate precursor. Among the above-mentioned mixing methods, it is particularly preferable to add the zinc salt solution dropwise to the sodium silicate solution while heating and refluxing the sodium silicate solution (95 to 110 ° C.) and react for about 2 to 5 hours. .

A precipitate is formed by this mixing operation. Then, the precipitate is collected by means such as filtration, washed with distilled water or the like, and dried to obtain a zinc orthosilicate precursor.

The obtained zinc orthosilicate precursor is usually white in color, and its X-ray pattern shows a low crystalline or amorphous pattern. Further, from the composition analysis, the presence of Na was hardly recognized, and it was found that it had a composition of Zn ₂ SiO ₄ .

In the method for producing zinc orthosilicate according to the present invention, zinc orthosilicate is produced by heat-treating the zinc orthosilicate precursor obtained as described above.

The heat treatment temperature is 850 to 1300 ° C., preferably 900 to 1200 ° C., and particularly preferably 900 to 1000 ° C. Although the heat treatment time varies depending on the heat treatment temperature and cannot be said to be the same, it is generally 0.5 to 20 hours, preferably 1 to 10 hours. The heat treatment is performed in an atmosphere such as air, oxygen or vacuum, and preferably in an oxygen atmosphere or air.

Composition analysis revealed that the calcined product obtained by heat treating the zinc orthosilicate precursor as described above had a composition of Zn ₂ SiO ₄ . Silicon in zinc silicate was volatilized as SiF ₄ with HF-HNO ₃ mixed acid, and the remaining zinc was quantified by atomic absorption spectrometry. The volatilized silicon content was also quantified at the same time. Further, the existence of elements other than zinc, silicon and oxygen, for example, elements such as sodium, potassium and iron was scarcely recognized, and all were 1 ppm or less.

Further, the X-ray diffraction pattern of this fired product showed a pattern peculiar to zinc orthosilicate, and no impurity peak was observed. From the above results, it was found that the fired product obtained by heat-treating the precursor was high-purity zinc orthosilicate.

Observation of the obtained zinc orthosilicate by an electron microscope revealed that porous orthosilicate is usually produced, although it cannot be said that it varies depending on the preparation conditions of the precursor or the heat treatment conditions thereof. It was When the specific surface area of the product was measured by a light transmission method, it was 5600 to 6500 cm ² / g.

[0023]

According to the present invention, it is possible to provide a novel method for producing zinc orthosilicate. Further, according to the present invention, it is possible to provide a method for producing a precursor used in such a novel method for producing zinc orthosilicate.

[0024]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0025]

[Reagent] Sodium metasilicate (Na ₂ SiO ₃ .9H ₂ O) manufactured by Wako Pure Chemical Industries, Ltd. was used. For zinc chloride (ZnCl ₂ ), a special grade reagent manufactured by Kanto Kagaku was used.

[0026]

[Example 1]

[0027]

[Determination of sodium metasilicate / zinc chloride (charge ratio)]
21.32 g of sodium metasilicate (Na ₂ SiO ₃ .9H ₂ O)
(0.075 mol) was dissolved in 100 ml of water to prepare a sodium metasilicate solution. Zinc chloride (ZnCl ₂ ) was dissolved in water to prepare a zinc chloride aqueous solution having a concentration of 6 mol / liter. The sodium metasilicate solution was heated to reflux with stirring, and an aqueous solution of zinc chloride was added dropwise at a rate of 1 to 2 ml / min so that the molar ratio was as shown in Table 1. The dropping of a predetermined amount was completed, and stirring and heating under reflux were continued for 5 hours. After 5 hours, the mixture was allowed to cool to room temperature for about 1 hour, cooled and suction filtered to collect the precipitated product, which was washed with distilled water (300 ml) and vacuum dried at room temperature (about 30 ° C.). The product was assumed to be Zn ₂ SiO ₄ and the yield was calculated.

The results are shown in Table 1.

[0029]

[Table 1] From this result, it was found that zinc chloride / sodium metasilicate (molar ratio) of 2.0 to 3.0 showed a good yield. Thereafter, the experiment was advanced with zinc chloride / sodium metasilicate (molar ratio) set to 2.0.

[0030]

Example 2

[0031]

[Determination of concentration of zinc chloride solution] Sodium metasilicate (N
21.32 g (0.075 mol) of a ₂ SiO ₃ .9H ₂ O) was dissolved in 100 ml of water to prepare a sodium metasilicate solution. Concentration is 1.25 mol / l, 2.50 mol / l
Lithium, 3.75 mol / liter, 4.00 mol / liter, 5.00 mol / liter, and 6.00 mol / liter zinc chloride solutions were prepared. The zinc chloride solution was added dropwise to the sodium metasilicate solution under the same conditions as in Example 1 in such an amount that the zinc chloride / sodium metasilicate (molar ratio) was 2.0, and the product was obtained after filtration, washing and drying. It was The product was assumed to be Zn ₂ SiO ₄ and the yield was calculated.

The results are shown in Table 2.

[0033]

[Table 2] From this result, the concentration of zinc chloride solution was 2.50 mol /
It was found that the best yield was obtained at liters. After that, the experiment was advanced with the concentration of the zinc chloride solution being 2.50 mol / liter.

[0034]

Example 3

[0035]

[Determination of reaction time] Concentration of zinc chloride solution 2.50 mol /
Under the same conditions as in Example 1, the amount of zinc chloride / sodium metasilicate (molar ratio) was 2.0, the zinc chloride solution was added dropwise to the sodium metasilicate solution, the reaction time was changed, and the predetermined reaction was performed. After a lapse of time, a product was obtained after filtration, washing and drying. The product was assumed to be Zn ₂ SiO ₄ and the yield was calculated. Further, the same experiment was conducted with the reaction temperature set to room temperature.

The results are shown in Table 3.

[0037]

[Table 3] As shown in Table 3, under heating under reflux, there was no significant difference in yield, and the product was obtained. On the other hand, in the reaction at room temperature, the apparent yield was 100%, but fine crystals floating in the aqueous solution and fine powder which could not be confirmed as a by-product Zn (OH) ₂ but was considered to be silica were mixed. The product obtained was obtained.

From this result, the experiment was proceeded thereafter with a reaction time of 5 hours.

[0039]

Example 4

[0040]

[Determination of reaction temperature] Concentration of zinc chloride solution 2.50 mol /
Under the same conditions as in Example 1, the amount of zinc chloride / sodium metasilicate (molar ratio) was 2.0, the zinc chloride solution was added dropwise to the sodium metasilicate solution, and the reaction time was 5 hours. The reaction was carried out at a temperature of 23 ° C. and 60 ° C. under heating reflux, and after 5 hours, filtration, washing,
After drying, the product was obtained. The product was assumed to be Zn ₂ SiO ₄ and the yield was calculated.

The results are shown in Table 4.

[0042]

[Table 4] As shown in Table 4, in the reaction at 23 ° C., the apparent yield was 100%, but it could not be confirmed as fine crystals floating in the aqueous solution or Zn (OH) _{2 as a by-} product. A product was obtained in which fine powder, which seems to be silica, was mixed.

From these results, it was found that the reaction is preferably carried out at 60 ° C. or higher or under heating under reflux. Less than,
The product thus obtained is called a "precursor".

[0044]

Example 5

[0045]

Characterization of Precursor The sample obtained in Example 4 was subjected to X-ray diffraction analysis. Each of the samples showed a pattern of low crystallinity or non-crystallinity, but the profile was slightly different, which indicated that the samples had different crystal forms.

The results of thermal analysis of the sample obtained under the heating and refluxing conditions of Example 4 are shown in FIG. The thermal analysis was performed using an analyzer XD-610 manufactured by Shimadzu Corporation in the atmosphere at a temperature rising rate of 10 ° C / min. The endothermic curve around 1400 ° C. has a fluctuation in the TG curve, and the weight loss is not observed so much, which is considered to be the melting point of zinc silicate. On the other hand, the DTA exothermic peak near 810 ° C. is presumed to be associated with a change in crystal type because the TG curve has no change.

The results of infrared absorption analysis are shown in FIG.
As a result, an absorption band due to H ₂ O was observed near 3500 cm ⁻¹ , and an absorption band due to Si—O bond was observed near 1200 to 900 cm ⁻¹ .

The average particle size of this sample was 17 μm.
m, and its specific surface area was 1400 cm ² / g. The measurement was performed by the light transmission method.

[0049]

Example 6

[0050]

[Calcination of precursor] Precursor prepared under various conditions
Firing was performed in an air atmosphere at 00 ° C. The zinc content and sodium content of the obtained sample were measured by atomic absorption spectrometry.

The results are shown in Table 5.

[0052]

[Table 5] The X-ray diffraction pattern of the fired product showed that of zinc orthosilicate.

From the above results, it was confirmed that high-purity zinc orthosilicate was obtained. The electron micrograph of the obtained zinc orthosilicate revealed that the product was porous.

The average particle size and specific surface area of these products were measured by a light transmission method. The average particle size was 4 to 5 μm, and the specific surface area was 5600 to 6500 cm ² / g. The infrared absorption analysis result and the thermal analysis result of this product are shown in FIGS. 3 and 4.

[Brief description of drawings]

FIG. 1 shows the results of thermal analysis of a zinc orthosilicate precursor.

FIG. 2 shows an infrared absorption analysis result of a zinc orthosilicate precursor.

FIG. 3 shows an infrared absorption analysis result of zinc orthosilicate obtained by the present invention.

FIG. 4 shows the thermal analysis (DTA) results of zinc orthosilicate obtained according to the present invention.

Claims (2)

[Claims] 1. A solution in which sodium orthosilicate and / or sodium metasilicate is dissolved in a solvent and a solution in which a zinc salt is dissolved in a solvent are mixed at room temperature to 110 ° C. for 0.5 hour or more. A method for producing a zinc orthosilicate precursor, comprising: 2. A solution in which sodium orthosilicate and / or sodium metasilicate is dissolved in a solvent and a solution in which a zinc salt is dissolved in the solvent are mixed at room temperature to 110 ° C. for 0.5 hour or more. A method for producing zinc orthosilicate, which comprises firing the obtained zinc orthosilicate precursor at 850 to 1300 ° C. for 0.5 hour or more.