JP7383446B2 - Manufacturing method of vanadium compound - Google Patents

Description

The present invention relates to a method for producing a vanadium compound.

Many materials increase in length and volume due to thermal expansion when the temperature rises. On the other hand, there are also known materials that exhibit negative thermal expansion (hereinafter sometimes referred to as "negative thermal expansion materials") whose length and volume decrease as the temperature rises. It is known that by using a material exhibiting negative thermal expansion together with other materials, it is possible to suppress the thermal expansion of the material due to temperature changes.

Examples of materials exhibiting negative thermal expansion include β-eucryptite, zirconium tungstate (ZrW ₂ O ₈ ), zirconium phosphotungstate (Zr ₂ WO ₄ (PO ₄ ) ₂ ), and Zn _x Cd _{1- x} (CN) ₂ , manganese nitride, bismuth nickel iron oxide, etc. are known.

The coefficient of linear expansion of zirconium tungstate phosphate is -3.4 to -3.0 ppm/°C in the temperature range of 0 to 400°C, and it is known that it has a large negative thermal expansion property. By using this zirconium tungstate phosphate in combination with a material exhibiting positive thermal expansion (hereinafter sometimes referred to as a "positive thermal expansion material"), a material with low thermal expansion can be manufactured (Patent Document 1). ~2nd place). It has also been proposed to use a polymer compound such as a resin as a positive thermal expansion material in combination with a negative thermal expansion material (see Patent Document 3, etc.).

Furthermore, Non-Patent Document 1 discloses that Cu _1.8 Zn _0.2 V ₂ O ₇ has a large linear expansion coefficient of -14.4 ppm/K in the temperature range of 200 to 700 K, As a method for producing this Cu _1.8 Zn _0.2 V ₂ O ₇ , a method is described in which a mixture is obtained using CuO, ZnO and V ₂ O ₅ as raw materials, and then the mixture is fired.

However, in the method of Non-Patent Document 1, the vanadium compound after firing is obtained as a sintered body and adhered to the reaction vessel, so it is difficult to recover the target product, and it is difficult to powder it industrially. Another problem was that it was difficult to manufacture the body.

Japanese Patent Application Publication No. 2005-35840 JP 2015-10006 Publication JP 2018-2577 Publication

Appl. Phys. Lett. 113 (2018) 181902

Therefore, an object of the present invention is to provide a vanadium compound useful as a negative thermal expansion material, which can suppress adhesion of vanadium components to a reaction vessel such as a crucible during firing, and easily recover the vanadium compound from the reaction vessel after firing. The purpose is to provide a manufacturing method.

In view of the above circumstances, the present inventors have conducted extensive research, and as a result, the present inventors have discovered a paste-like reaction precursor of the vanadium compound obtained by removing the solvent from a raw material mixture solution in which a Cu source, a Zn source, and a V source are dissolved. The present inventors have discovered that by firing the reaction precursor using a method, a fired product of a vanadium compound that can be easily taken out from a crucible or the like can be obtained, and the present invention has been completed.

That is, the present invention is a method for producing a vanadium compound represented by the following general formula (1), which includes the following first to third steps.
(Cu _2-x Zn _x )V ₂ O ₇ (1)
(In the formula, x is 0<x<2.)
First step: A step of preparing a raw material mixture solution in which a Cu source, a Zn source, and a V source are dissolved in a water solvent.
Second step: a step of removing the water solvent from the raw material mixture to prepare a reaction precursor of the vanadium compound represented by the general formula (1).
Third step: a step of firing the reaction precursor.

According to the production method of the present invention, adhesion of the vanadium component to a reaction vessel such as a crucible during firing is suppressed, and the vanadium compound can be easily recovered from the reaction vessel after firing, so it is possible to use negative heat in an industrially advantageous manner. Vanadium compounds useful as intumescent materials can be produced as powders.

2 is an X-ray diffraction diagram of fired product 1 obtained in Example 1. FIG. 1 is a SEM photograph of vanadium compound 1 obtained in Example 1. 3 is an X-ray diffraction diagram of a sintered body obtained in Comparative Example 1. FIG.

The present invention will be described below based on preferred embodiments.
The vanadium compound obtained by this production method is represented by the following general formula (1).
(Cu _2-x Zn _x )V ₂ O ₇ (1)
(In the formula, x is 0<x<2.)

In general formula (1), x satisfies 0<x<2, and from the viewpoint of particularly excellent negative thermal expansion characteristics, x in the formula preferably satisfies 0.05≦x≦1.5.

The method for producing the vanadium compound of the present invention is characterized by including the following first to third steps.
First step: A step of preparing a raw material mixture solution in which a Cu source, a Zn source, and a V source are dissolved in a water solvent.
Second step: a step of removing the water solvent from the raw material mixture to prepare a reaction precursor of the vanadium compound represented by the general formula (1).
Third step: a step of firing the reaction precursor.

The first step is a step of preparing a raw material mixture solution in which a Cu source, a Zn source, and a V source are dissolved in a water solvent.
The aqueous solvent refers to a solvent containing more than 50% by mass of water, and may be composed only of water, or may be a mixed solvent of water and a hydrophilic organic solvent. A hydrophilic organic solvent is an organic solvent that dissolves in water in any proportion.

The Cu source for the first step is not particularly limited as long as it can be dissolved in an aqueous solvent, but examples include organic carbon atoms such as copper gluconate, copper citrate, copper sulfate, copper acetate, and copper lactate. Examples include copper salts of acids and mineral acids.

The Zn source is not particularly limited as long as it can be dissolved in an aqueous solvent, but examples include zinc salts and halides of organic carboxylic acids such as zinc gluconate, zinc citrate, zinc chloride, and zinc lactate. Can be mentioned.

The V source is not particularly limited as long as it can be dissolved in an aqueous solvent, and examples thereof include vanadic acid, their sodium salts, potassium salts, ammonium salts, vanadium salts of carboxylic acids, and the like.
Vanadium salts of carboxylic acids include monocarboxylic acids such as formic acid, acetic acid, glycolic acid, lactic acid, and gluconic acid; dicarboxylic acids such as oxalic acid, maleic acid, malonic acid, malic acid, tartaric acid, and succinic acid; Examples include carboxylic acids such as citric acid where is 3.
Among these, ammonium vanadate and vanadium gluconate are preferred from the viewpoint of obtaining the target product with few impurities.

In addition, when using a vanadium salt of carboxylic acid as a V source, vanadium pentoxide, a reducing agent, and a carboxylic acid are added to an aqueous solvent, heat-treated at 60 to 100°C to generate a vanadium salt of carboxylic acid, and the reaction is performed. The liquid may be used as it is for preparing a raw material mixture.
As the reducing agent, reducing sugars are preferable, and examples of the reducing sugars include glucose, fructose, lactose, maltose, sucrose, etc. Among these, lactose and sucrose are particularly preferable from the viewpoint of having excellent reactivity. .
The amount of reducing sugar added is preferably 0.7 to 3.0, and preferably 0.8 to 2.0 in molar ratio (C/V) of C in reducing sugar to V in vanadium pentoxide. This is more preferable from the viewpoint of efficiently performing the reduction reaction.
The amount of carboxylic acid added is preferably 0.1 to 4.0 in molar ratio to vanadium pentoxide, and 0.2 to 3.0 is said to efficiently obtain a transparent vanadium solution. From this point of view, it is more preferable.

In the preparation of the raw material mixture according to the first step, the amounts of the Cu source, Zn source, and V source added to the water solvent are such that the Cu source, Zn source, and V source in the raw material mixture are expressed by the general formula (1) above. It is preferable to prepare it appropriately according to the composition of the vanadium compound represented.
The concentration of the V source in the raw material mixture is preferably 1 to 40% by mass, and more preferably 2 to 30% by mass from the viewpoint of producing a homogeneous solution and the efficiency of water evaporation in the next step.

The order in which the Cu source, Zn source, and V source are added to the water solvent is not particularly limited; It is preferable to prepare a dissolved (liquid B) and mix these liquids A and B to obtain a raw material mixture liquid. Although the method of mixing liquid A and liquid B is not particularly limited, it is preferable to add liquid B to liquid A from the viewpoint of obtaining a homogeneous solution.

The concentration of the V source in liquid A is preferably 1 to 40% by mass, and more preferably 2 to 30% by mass from the viewpoint of producing a homogeneous solution and the efficiency of water evaporation in the next step.
Note that in order to increase the solubility of the V source in the A solution, an alkali may be added, the temperature may be increased, or both may be treated.

The total concentration of Cu source and Zn source in liquid B is preferably 1 to 40% by mass, and 2 to 30% by mass from the viewpoint of producing a homogeneous solution and increasing the efficiency of water evaporation in the next step. , more preferred.

The second step is a step of preparing a reaction precursor by heating the raw material mixture prepared in the first step while stirring to remove the water solvent until it becomes paste-like or solid.
In this step, it is not necessary to remove all the water solvent to obtain the mixture in solid form, and the mixture may be in the form of a paste containing a small amount of water solvent. Note that paste-like refers to a state with considerable viscosity.

The heating temperature in the second step is not particularly limited as long as the water solvent can be removed, but it is preferably a temperature that can maintain a boiling state, usually 90 to 120°C, more preferably 100 to 120°C.
In this way, a reaction precursor of the vanadium compound represented by the general formula (1) can be obtained.

The third step is a step of baking the reaction precursor prepared in the second step to produce the vanadium compound targeted by the present invention.

The firing temperature in this step is preferably 580 to 700°C, more preferably 600 to 680°C. The reason for this is that when the firing temperature is lower than 580°C, the production of the vanadium compound represented by the general formula (1) tends to be insufficient, and when the firing temperature is higher than 700°C, the composition changes due to volatilization of the vanadium oxide component. This is because it tends to fluctuate.

The firing time in this step is not particularly limited, and the reaction is carried out for a sufficient time until the vanadium compound represented by the general formula (1) is produced. The production of the vanadium compound can be confirmed, for example, by X-ray diffraction analysis. In many cases, when the firing time is 1 hour or more, preferably 2 to 20 hours, almost all of the reaction precursor of the vanadium compound becomes the vanadium compound. Furthermore, the firing atmosphere is not particularly limited, and may be any of an inert gas atmosphere, a vacuum atmosphere, an oxidizing gas atmosphere, and the air.

In this step, firing may be performed once or multiple times as desired. For example, in order to make the powder properties uniform, the fired product may be ground, and the ground material may be further fired.

After firing, it is appropriately cooled, and if necessary, pulverization, crushing, classification, etc. are performed to obtain the desired vanadium compound.

In the present invention, in order to obtain a vanadium compound that does not substantially contain coarse particles having a particle size exceeding 20 μm, it is preferable to provide a pulverization step after the third step.

The pulverization treatment may be a dry pulverization treatment or a wet pulverization treatment. Examples of the wet grinding device include a ball mill, a bead mill, and the like. Examples of the dry pulverizer include known pulverizers such as jet mills, pin mills, roll mills, ball mills, and bead mills.

The average particle diameter of the vanadium compound obtained by the method for producing a vanadium compound of the present invention is preferably 0.05 to 5 μm, particularly preferably 0.05 to 3 μm, and the BET specific surface area of the vanadium compound is 0.05 to 5 μm, particularly preferably 0.05 to 3 μm. 1 to 50 m ² /g, particularly preferably 0.1 to 20 m ² /g. It is preferable that the average particle diameter and BET specific surface area of the vanadium compound are within the above ranges, since the vanadium compound can be easily handled when used as a filler for resins, glasses, etc.
Note that the average particle diameter is the average value of 50 or more particles arbitrarily extracted through scanning electron microscopy (SEM), and when the particle shape is not spherical, the particle diameter is determined by the maximum transverse length of each particle. This is the diameter.

The vanadium compound obtained by this production method is particularly useful as a negative thermal expansion material exhibiting negative thermal expansion, and has a linear expansion coefficient of -15×10 ^-6 /K to -1× in the temperature range of 25 to 300°C. It is preferably 10 ⁻⁶ , more preferably −15×10 ⁻⁶ /K to −3×10 ⁻⁶ /K.

The vanadium compound obtained by this production method is used as a powder or paste. When the obtained vanadium compound is used as a paste, it can be used in a paste state with a liquid resin having low viscosity. Alternatively, the obtained vanadium compound may be dispersed in a liquid resin with low viscosity, and if necessary, a binder, a flux material, a dispersant, etc. may be added thereto, and used in the form of a paste.

The vanadium compound obtained by this production method can be used in combination with various organic compounds or inorganic compounds as a composite material. Examples of organic compounds include, but are not limited to, rubber, polyolefin, polycycloolefin, polystyrene, ABS, polyacrylate, polyphenylene sulfide, phenol resin, polyamide resin, polyimide resin, epoxy resin, silicone resin, polycarbonate resin, polyethylene resin, Examples include polypropylene resin, polyethylene terephthalate resin (PET resin), and polyvinyl chloride resin. Examples of inorganic compounds include silicon dioxide, graphite, sapphire, various glass materials, concrete materials, and various ceramic materials.

Since the above composite material contains a vanadium compound that becomes the negative thermal expansion material according to the present invention, it is possible to achieve a negative thermal expansion coefficient, zero thermal expansion coefficient, or low thermal expansion coefficient depending on the blending ratio with other compounds. It is possible.

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

{Example 1}
(1st step)
5 g of ammonium vanadate (NH ₄ VO ₃ ), 10 ml of aqueous ammonia, and 50 ml of pure water were placed in a beaker and heated to 60° C. while stirring to obtain a solution A. Next, add 17.5 g of copper gluconate (manufactured by Fuso Chemical Industry Co., Ltd.) and 2.2 g of zinc gluconate (manufactured by Fuso Chemical Industry Co., Ltd.) to 50 ml of pure water and stir. Add solution B to solution A and make a homogeneous solution. A certain raw material mixture was obtained.
(Second process)
The raw material mixture was stirred and heated to a temperature that maintained a boiling state to remove water, thereby obtaining a paste-like reaction precursor of a vanadium compound.
(3rd step)
The paste-like reaction precursor of the vanadium compound was fired in a crucible in the atmosphere at 650° C. for 4 hours to obtain a fired product. Note that after firing, the target product could be easily recovered by inverting the crucible.
When the obtained fired product was subjected to X-ray diffraction analysis, a diffraction peak of Cu _1.8 Zn _0.2 V ₂ O ₇ was detected. The X-ray diffraction diagram of the fired product is shown in FIG.
Next, the fired product was pulverized using an AO jet mill (manufactured by Seishin Enterprises) to obtain vanadium compound 1. A SEM photograph of vanadium compound 1 is shown in FIG.

{Example 2}
(1st step)
4 g of vanadium pentoxide (V ₂ O ₅ ), 2 g of lactose, 40 g of 50% gluconic acid solution, and 60 ml of pure water were placed in a beaker and heated at 80° C. for 3 hours with stirring to obtain Solution A. Next, add 17.5 g of copper gluconate (manufactured by Fuso Chemical Industry Co., Ltd.) and 2.2 g of zinc gluconate (manufactured by Fuso Chemical Industry Co., Ltd.) to 50 ml of pure water and stir. Add solution B to solution A and make a homogeneous solution. A certain raw material mixture was obtained.
(Second process)
The raw material mixture was stirred and heated to a temperature that maintained a boiling state to remove water, thereby obtaining a paste-like reaction precursor of a vanadium compound.
(Third step)
The paste-like reaction precursor of the vanadium compound was fired in a crucible in the atmosphere at 650° C. for 4 hours to obtain a fired product. Note that after firing, the target product could be easily recovered by inverting the crucible.
When the obtained fired product was subjected to X-ray diffraction analysis, a diffraction peak of Cu _1.8 Zn _0.2 V ₂ O ₇ similar to that in Example 1 was detected.
Next, the fired product was pulverized using an AO jet mill (manufactured by Seishin Enterprises) to obtain vanadium compound 2.

{Comparative example 1}
10 g of vanadium pentoxide (V ₂ O ₅ ) and 30 g of oxalic acid dihydrate were placed in a beaker, and 200 ml of pure water was added and stirred to obtain a solution 1. To solution 1, add solution 2 obtained by adding 5.6 g of zinc gluconate to 100 ml of pure water and stirring, and further add 9.7 g of copper hydroxide and 0.1 g of polycarboxylic acid ammonium salt as a dispersant. A raw material mixture was prepared. Next, using a ball mill using zirconia balls with a diameter of 5 mm as a medium, pulverization and mixing were performed for 12 hours to obtain a raw material mixed slurry. _D50 of the solid content in the raw material mixed slurry determined by laser diffraction/scattering method was 1 μm or less.
The entire amount of the obtained raw material mixed slurry was dried in the atmosphere at 200° C. for 24 hours to obtain a reaction precursor of a vanadium compound (Cu _1.8 Zn _0.2 V ₂ O ₇ ).
Next, the reaction precursor was fired in a crucible in the atmosphere at 650°C for 4 hours, resulting in a sintered body that firmly adhered to the crucible, and even when the crucible was turned over, the target object remained firmly attached and was easily removed. could not be recovered.
When the sintered body was peeled off with a spatula and analyzed by X-ray diffraction, it was found to be single-phase Cu _1.8 Zn _0.2 V ₂ O ₇ (see FIG. 3).

<Physical property evaluation>
The average particle diameter, BET specific surface area, and thermal expansion coefficient of the vanadium compounds obtained in Examples were measured. Further, the thermal expansion coefficient of the sintered body (Cu _1.8 Zn _0.2 V ₂ O ₇ ) obtained in the comparative example was measured. The results are shown in Table 1.
The measurement method is as follows.

[Average particle diameter]
It was determined as the average value of 50 or more particles arbitrarily extracted by scanning electron microscopy (SEM). In addition, when the particle shape was not spherical, the particle diameter was defined as the maximum transverse length of each particle.
[BET specific surface area]
The BET specific surface area was measured using a specific surface area measuring device Macsorb manufactured by Mountech.

[Measurement of thermal expansion coefficient]
(Preparation of molded body)
0.15 g of the sample was ground in a mortar for 3 minutes, and the entire amount was filled into a φ6 mm mold. Next, a powder molded body was produced by molding using a hand press at a pressure of 1 ton. The obtained powder molded body was fired in an electric furnace at 600° C. for 2 hours to produce a ceramic molded body.
(Measurement of thermal expansion coefficient)
The thermal expansion coefficient of the produced ceramic molded body was measured using a thermomechanical measuring device (TMA4000SE manufactured by NETZSCH JAPAN). The measurement conditions were a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 250°C.

As shown in the examples, according to the production method of the present invention, it is possible to suppress adhesion of vanadium components to a reaction vessel such as a crucible during firing, and it is possible to easily recover the vanadium compound from the reaction vessel after firing. Therefore, it was confirmed that it is easy to obtain a vanadium compound as a powder.

Claims (8)

A method for producing a vanadium compound represented by the following general formula (1), including the following first to third steps.
(Cu _2-x Zn _x )V ₂ O ₇ (1)
(In the formula, x is 0<x<2.)
First step: Cu source selected from organic carboxylic acids and copper salts of mineral acids , Zn source selected from zinc salts of organic carboxylic acids and zinc halides , vanadic acid, sodium salt of vanadic acid, potassium salt of vanadic acid. , a step of preparing a raw material mixture solution in which a V source selected from ammonium salts of vanadate and vanadium salts of carboxylic acids is dissolved in a water solvent.
Second step: a step of removing the water solvent from the raw material mixture to prepare a reaction precursor of the vanadium compound represented by the general formula (1).
Third step: a step of firing the reaction precursor. The first step is to prepare a solution (solution A) in which a V source is dissolved in an aqueous solvent and a solution (solution B) in which a Cu source and a Zn source are dissolved, and to mix solutions A and B to prepare a raw material mixture solution. The method for producing a vanadium compound according to claim 1, wherein the vanadium compound is obtained. The method for producing a vanadium compound according to claim 1 or 2, wherein the V source is ammonium vanadate. The method for producing a vanadium compound according to claim 1 or 2, wherein the V source is a vanadium salt of a carboxylic acid. 3. The method for producing a vanadium compound according to claim 2, wherein liquid A is a solution in which a vanadium salt of carboxylic acid is dissolved in an aqueous solvent. 3. The method for producing a vanadium compound according to claim 2, wherein the liquid A contains a vanadium salt of a carboxylic acid obtained by mixing vanadium pentoxide, a reducing agent, and a carboxylic acid and heat-treating the mixture. 7. The method for producing a vanadium compound according to claim 6, wherein the reducing agent is a reducing sugar. The method for producing a vanadium compound according to claim 1, wherein a pulverization step is provided after the third step.