JP5190729B2 - Method for producing high purity aluminum metaphosphate - Google Patents

Description

  The present invention relates to a method for producing a high-purity aluminum metaphosphate useful as a raw material for optical materials that does not require a pulverization step.

  Currently, phosphates are used for amplification fibers, optical lenses, and the like, and aluminum metaphosphate is most frequently used among phosphates, depending on the application. In general, high-purity raw materials are required for optical glass applications. Among them, transition metals such as iron, chromium, nickel, manganese, zinc, and copper cause glass coloring. Therefore, high purity is also required for aluminum metaphosphate for optical glass, and in particular, the impurity concentration of these metals is required to be reduced to 5 ppm or less. In order to prevent problems such as poor handling and fluctuations in the refractive index of the glass, the loss on ignition and free phosphoric acid are required to be 2% by weight or less.

In the present invention, what is represented by the formula Al (PO ₃ ) ₃ is generically referred to as aluminum metaphosphate, and includes A type having a cyclic structure and B, C, D, and E types having a chain structure.

Aluminum metaphosphate is produced by firing a phosphoric acid source and an aluminum compound, or an aluminum phosphate compound, but it is not easy to work because it is solidified, and further requires steps such as grinding. This is a cause of contamination.
Several methods for preventing this consolidation have been proposed. In Non-Patent Document 1, the reaction liquid of primary aluminum phosphate is heated at 700 to 750 ° C. using a spray dryer, but it is inevitable that impurities come from the spray nozzle. Patent Document 1 describes a method in which raw material powder is mixed with aluminum metaphosphate and fired. However, the added amount of aluminum metaphosphate to be mixed is 50 to 70% of the total amount of the material to be fired, and the amount of aluminum metaphosphate newly formed in one reaction is small and the reaction efficiency is low. Moreover, when producing the aluminum metaphosphate to be mixed, solidification is inevitably caused in the first time, and it is inevitable that impurities are caused due to the firing container or pulverization. As in Patent Document 1, as a method for preventing caking, Patent Document 2 discloses that a viscous liquid is obtained by reacting phosphoric acid with an aluminum compound, and aluminum metaphosphate powder is laid on a baking container. A method of baking by adding a liquid is described. The amount of aluminum metaphosphate to be spread is 40 to 60% of the entire material to be fired, and this method is also inefficient. Furthermore, as specified in the Examples, the resulting aluminum metaphosphate is in the form of a lump and is not a method of completely preventing consolidation, and the degree of consolidation increases as the scale increases. Therefore, in this method, pulverization is indispensable, and contamination of impurities due to the material of the pulverizer cannot be avoided.
Non-Patent Document 2 shows that when aluminum metaphosphate is ground, the dissolution rate increases rapidly with the grinding time. As described above, the pulverization is a process in which impurities are mixed and free phosphoric acid is increased. Therefore, the pulverization step is a step that should be avoided as much as possible as a method of producing aluminum metaphosphate for optical glass, and when pulverization is performed, it is preferable that the product has a shape that is easy to pulverize so that it is not burdened as much as possible.
Japanese Patent No. 3865604 Japanese Patent No. 3802916 Kuz'menkov, MI and three others, “Manufacture of aluminum metaphosphate”, 1982, Khimicheskaya Promyshlennost, 10, p.595-597 Toshiaki Nishinomiya, “Mechanochemistry of Aluminum Metaphosphate”, 1975, Tokyo Institute of Technology Research Report, 7 p.79-84

  An object of the present invention is to provide a production method in which aluminum metaphosphate is obtained in high purity without being consolidated.

  As a result of diligent research in view of the above-mentioned problems of the prior art, the inventors of the present invention have made it possible to produce aluminum metaphosphate by calcining at about 210 to 370 ° C., then absorbing moisture or water, and then calcining at 400 ° C. or higher. The present invention has been completed by discovering that it can be prevented.

That is, the present invention
A first step of reacting or mixing a phosphoric acid source and an aluminum compound;
A second step of firing the product obtained in the first step at 210-370 ° C.,
A third step of absorbing or absorbing the product obtained in the second step;
The product obtained in the third step alone, or further mixed with the product obtained in the first step, and composed of a fourth step of baking at 400 ° C. or higher,
A method for producing high-purity aluminum metaphosphate that does not require a pulverization step (claim 1),
The P / Al molar ratio of the phosphoric acid source and the aluminum compound in the first step is 2.9 to 3.1 (Claim 2).
The firing temperature in the second step is 275 to 350 ° C. (Claim 3);
The phosphoric acid source in the first step is phosphoric acid, and the reaction is stopped at 120 to 130 ° C. until foaming starts and stopped in a viscous liquid state (Claim 4),
Moisture absorption or water absorption in the third step is performed under pressurized steam (Claim 5),
Moisture absorption or water absorption in the third step is performed by water immersion (Claim 6).
The firing temperature in the fourth step is 500 to 800 ° C. (Claim 7);
The firing container used in the second step and the fourth step is made of metal aluminum or alumina (claim 8),
The product of the fourth step is washed with water and dried to remove free phosphoric acid (claim 9);
Is a method for producing high-purity aluminum metaphosphate with added features such as,
Each colored metal element of the impurity is at least one of iron, chromium, nickel, manganese, zinc, or copper (Claim 11) and 5 ppm or less (Claim 10).
The free phosphoric acid content is 2% by weight or less (claim 12).
The ignition loss is 2% by weight or less (claim 13).
Is a method for producing high-purity aluminum metaphosphate that does not require a pulverization step.

  In the present invention, the fact that the aluminum metaphosphate produced by firing is not consolidated or can be easily loosened and obtained in a state of 100 μm or less is expressed as “no pulverization step is required”.

  According to the present invention, there is provided a production method in which high-purity aluminum metaphosphate is not consolidated. In addition, this eliminates the pulverization step, prevents impurities from being mixed by pulverization, and provides high-purity aluminum metaphosphate.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. Unless otherwise specified in the following description, “%” and “ppm” are based on weight.

  As the phosphoric acid source used in the first step, phosphoric acid, phosphoric anhydride, polyphosphoric acid, ammonium dihydrogen phosphate and the like are used. In particular, phosphoric acid is commercially available as a high-purity product for electronic materials, and when producing high-purity aluminum metaphosphate, it is preferable in terms of workability, availability, and purity. As the aluminum compound, for example, aluminum hydroxide, α-alumina, β-alumina, γ-alumina and the like are used. In particular, aluminum hydroxide is preferable because a high-purity product can be easily obtained.

When phosphoric acid is used as the phosphoric acid source, it can be reacted with an aluminum compound at room temperature or under heating. The reaction temperature is 150 ° C. or less, preferably 100 to 130 ° C., and may be solidified, but is particularly preferably 120 to 130 ° C. from the viewpoint of mixing impurities from the reaction vessel, handling properties, and reactivity in the subsequent steps. When foaming starts, it is preferable to stop heating and take out in a viscous liquid state.
When phosphoric anhydride or polyphosphoric acid is used as the phosphoric acid source, they may be simply mixed, but may be mixed with water as appropriate so that the uniformity of the composition and operability are improved.
When using phosphate powder such as aluminum dihydrogen phosphate, aluminum orthophosphate, aluminum pyrophosphate, aluminum tripolyphosphate as the phosphoric acid source, the phosphate and the aluminum compound may be simply mixed.

When phosphoric acid and aluminum hydroxide are used as raw materials, the outline of the formation reaction of aluminum metaphosphate is expressed by the following formula, and the P / Al molar ratio of aluminum metaphosphate is 3 stoichiometrically.
Al (OH) ₃ + 3H ₃ PO ₄ → Al (H ₂ PO ₄ ) ₃ + 3H ₂ O (Formula 1)
Al (H ₂ PO ₄ ) ₃ → Al (PO ₃ ) ₃ + 3H ₂ O (Formula 2)
In the present invention, the P / Al molar ratio of the entire raw material is preferably 2.7 to 3.3, more preferably 2.9 to 3.1. If the molar ratio is within this range, products other than unreacted materials and aluminum metaphosphate can be reduced.

  The firing temperature in the second step is 210 to 370 ° C, more preferably 275 to 350 ° C. Since the properties of the product in the second step vary depending on the P / Al molar ratio of the raw material and the moisture content of the material to be fired, the firing temperature can be adjusted appropriately within this range. The firing time in the second step varies depending on the amount of the material to be fired, the firing temperature, the amount of water in the material to be fired, etc., but usually requires 1 hour or longer.

As a method of absorbing moisture or absorbing water in the third step, there are a method of absorbing moisture in the air by leaving it at room temperature, a method of spraying water vapor, a method of treating under high temperature humidification, a method of immersing in water, etc. There is no limitation. It is preferable to carry out under pressurized steam from the viewpoint of maintaining the P / Al molar ratio and moisture absorption efficiency. Moreover, it is preferable to carry out by water immersion at the point which reduces free phosphoric acid. In the case of immersion in water, subsequent filtration will remove the soluble components and destroy the P / Al ratio of the final product. Adjust the firing temperature and firing time so that soluble ortho salts and unreacted products do not remain. It is preferable to perform the second step.
In the fourth step, “the product obtained in the third step alone” or “the mixture of the product obtained in the first step and the product obtained in the third step” is calcined at 400 ° C. or higher. Either one can be selected. When the product to be fired in the fourth step is “the product obtained in the third step alone”, it can be regarded as a two-step firing method including the first step to the fourth step. In addition, as an example in which the product to be fired in the fourth step is “a mixture of the product obtained in the first step and the product obtained in the third step”, the product of the first step is used as a main raw material, The product of the third step prepared in advance is mixed to prevent caking.

  The firing temperature in the fourth step is 400 ° C. or higher, preferably 500 to 800 ° C., more preferably 550 to 700 ° C. The optimum firing temperature is determined by the amount, composition, moisture content, etc. of the object to be fired. The optimum firing time varies depending on the amount, composition, moisture content, etc. of the material to be fired, but is preferably 2 hours or longer. If the calcination temperature is too low or the amount of the object to be baked is too large, free phosphoric acid tends to increase because dehydration is not completed. Moreover, there is no restriction | limiting in particular in the upper limit of baking temperature, It depends on melting | fusing point etc. of a baking container. When the firing container is made of metallic aluminum, the upper limit of the firing temperature is about 650 ° C.

The firing container used in the second step and the fourth step is not particularly limited, but a container made of metallic aluminum or alumina is preferable in order to achieve high purity and particularly not mix colored metal.
The product of the fourth step may be further washed with water and dried to remove free phosphoric acid. As a result, excess phosphoric acid content is removed to increase the purity, and surface moisture absorption and lumps due to residual phosphoric acid can be prevented.

By appropriately selecting raw materials, equipment materials, and conditions for each step, for example, the concentration of each colored metal element such as iron, chromium, nickel, manganese, zinc, or copper is 5 ppm or less, and the free phosphoric acid content is 2 A high-purity aluminum metaphosphate having a weight percent or less and a loss on ignition of 2 weight percent or less can be produced.
According to the method of the present invention described above, the aluminum metaphosphate is not consolidated, or can be easily loosened, and can be produced with high purity without requiring a pulverization step.
In the production of other metal salts of metaphosphoric acid, it is easy to consolidate in the conventional method, but if the method of the present invention is applied instead of the desired metal compound, the other metal salt of metaphosphoric acid, It can be produced with high purity without requiring a pulverization step.

Next, examples of the present invention will be specifically described in comparison with comparative examples, but the present invention is not limited to these examples.
<Example 1>
31.2 g of high purity aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., product name CHP-340S) and 138.4 g of high purity phosphoric acid (manufactured by Rin Chemical Industry Co., Ltd., product name 85% phosphoric acid EL grade) in a beaker Mixed. The P / Al molar ratio of the raw material was 3.0. When the beaker was placed on a hot plate at about 150 ° C. and heated at 120-130 ° C. until foaming, a viscous liquid was obtained (first step). This viscous liquid was put into an alumina crucible and baked at 300 ° C. for 2 hours using an electric furnace (second step). A white expanded hard lump was formed, which was placed in a pressure device set at 105 ° C. and humidity 100% and left for 20 minutes (third step). The product was broken into pieces and peeled from the crucible. The product was again placed in an alumina crucible and baked at 550 ° C. for 4 hours (fourth step). When the obtained product was subjected to X-ray diffraction, it was found that the A-type aluminum metaphosphate was 100%.

<Example 2>
The viscous liquid prepared in the same manner as in the first step of Example 1 was poured into an alumina crucible and baked at 300 ° C. for 3 hours using an electric furnace. After calcination, when immersed in a beaker containing 400 ml of pure water with a crucible, a product of fine particles having an average particle diameter of 4.8 μm was obtained. After being well dispersed in water, it was suction filtered using a filter paper (5C), placed in a dryer at 45 ° C., and dried for 3 hours with occasional loosening with a plastic spoon. The dried product was again put in an alumina crucible and baked at 500 ° C. for 4 hours. Although aggregates were mixed, they collapsed when touched by hand to obtain aluminum metaphosphate having a fine particle size. The average particle size was 5.1 μm.

<Example 3>
7.8 g of high-purity aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., product name CHP-340S) and 34.6 g of phosphoric acid (manufactured by Phosphorus Chemical Industry Co., Ltd., product name: 85% phosphoric acid for food use) were mixed in a beaker. did. The P / Al molar ratio of the raw material was 3.0. The beaker was heated and dried on a hot plate to obtain 37.0 g of a solid (first step). Half of this was placed in an alumina crucible and baked at 240 ° C. for 2 hours using an electric furnace (second step). The product of the second step was allowed to stand in air at room temperature for 2 days (third step). The same amount of the product from the first step and the product from the third step were mixed, placed in an alumina crucible, and baked at 450 ° C. for 2 hours using an electric furnace. Almost no particle adhesion or adhesion to the container was observed in the product, and it was confirmed by X-ray diffraction that it was aluminum metaphosphate.

<Example 4>
High purity aluminum hydroxide (product name: CHP-340S, manufactured by Sumitomo Chemical Co., Ltd.) 140.4g and high purity phosphoric acid (product name: 85% phosphoric acid EL grade, manufactured by Phosphor Chemical Industry Co., Ltd.) in a 2 liter beaker And mixed. The P / Al molar ratio of the raw material was 3.0. When the beaker was placed on a hot plate at about 150 ° C. and heated at 120-130 ° C. until foaming, a viscous liquid was obtained. This viscous liquid was put into an alumina crucible and baked at 350 ° C. for 2 hours using an electric furnace. This was placed in a pressure device set at 105 ° C. and humidity 100% and left for 20 minutes. When the product was touched with a plastic spoon, it collapsed easily and could be removed from the crucible. The product was again put in an alumina crucible, fired at 550 ° C. for 4 hours, allowed to cool, washed with water and dried to obtain aluminum metaphosphate. When X-ray diffraction was performed, the proportion of A-type aluminum metaphosphate was 70%, and the remainder was aluminum metaphosphate having different types.

<Example 5>
34.5 g of ammonium dihydrogen phosphate (manufactured by Junsei Chemical Co., Ltd., special grade) and 7.8 g of high purity aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., product name CHP-340S) were sufficiently mixed in a menor mortar. The P / Al molar ratio of the raw material was 3.0. This mixture was placed in an alumina crucible and baked at 300 ° C. for 2 hours using an electric furnace. This was placed in a pressure device set at 105 ° C. and humidity 100% and left for 10 minutes. When the product was touched with a plastic spoon, it collapsed easily and could be removed from the crucible. Thereafter, it was calcined at 600 ° C. for 3 hours, allowed to cool, then washed with water and dried to obtain aluminum metaphosphate.

<Comparative Example 1>
15.6g of high purity aluminum hydroxide (product name CHP-340S, manufactured by Sumitomo Chemical Co., Ltd.) and 69.2g of high purity phosphoric acid (product name: 85% phosphoric acid EL grade, manufactured by Phosphorous Chemical Industry Co., Ltd.) in a beaker Mixed. The P / Al molar ratio of the raw material was 3.0. The beaker was heated and dried on a hot plate to obtain 73.6 g of a solid. This solid was put in an alumina crucible and fired at 550 ° C. for 4 hours using an electric furnace. The product was a hard mass fixed to the crucible and scraped with a stainless spoon, but not all could be removed. This was pulverized with an agate mortar to obtain aluminum metaphosphate.

<Comparative example 2>
A viscous liquid was prepared in the same manner as in the first step of Example 1. The viscous liquid was put into an alumina crucible in which aluminum metaphosphate of a reagent (manufactured by Aldrich Chemical Company) was spread on the bottom and the wall surface, and was baked at 550 ° C. for 4 hours using an electric furnace and allowed to cool. The produced aluminum metaphosphate was not fixed to the crucible, but the central part became a hard lump, and was pulverized in an alumina mortar.

<Comparative Example 3>
7.8 g of high-purity aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., product name CHP-340S) and 34.6 g of phosphoric acid (manufactured by Phosphorus Chemical Industry Co., Ltd., product name: 85% phosphoric acid for food use) were mixed in a beaker. did. The P / Al molar ratio of the raw material was 3.0. The beaker was heated and dried on a hot plate to obtain 37.0 g of a solid (first step). This solid was put into an alumina crucible and baked at 500 ° C. for 2 hours using an electric furnace. The product was a lump fixed to the crucible and scraped with a stainless spoon, but not all could be removed. This was pulverized with an agate mortar to obtain aluminum metaphosphate. Similarly, the first step was performed, and the product and the pulverized aluminum metaphosphate prepared earlier were mixed in the same amount, placed in an alumina crucible, and baked at 500 ° C. for 2 hours using an electric furnace. The product showed sticking to the crucible and could not completely prevent caking.
About the aluminum metaphosphate obtained by the Example and the comparative example, it measured with the following method.
[Purity measurement]
(1) P ₂ O ₅ content (1) Accurately weigh 1 g of sample into a quartz flask.
(2) Add 30 ml of sodium hydroxide solution (20 wt / vol%).
(3) Dissolve by heating on a sand bath.
(4) After cooling to room temperature, 18 ml of hydrochloric acid was added and heated. Hydrochloric acid is added, and a small amount of pure water is added when crystals are precipitated.
(5) After cooling to room temperature, transfer to a 250 ml volumetric flask, add water to the marked line, shake well, and use this as the test solution.
(6) Dispense 25 ml into a 250 ml volumetric flask, add water up to the marked line and shake well.
(7) 20 ml of the solution prepared in (6) was dispensed into a 100 ml volumetric flask, and at the same time, 10 ml of diphosphorus pentoxide standard solution (1 ml = 0.58 mg P ₂ O ₅ ), diphosphorus pentoxide standard solution (1 ml = 0) .66 mg P ₂ O ₅ ) is dispensed into two 100 ml volumetric flasks, and pure water is added to each sample to make about 30 ml.
(8) Add 4 ml of nitric acid (1 + 1) and heat on a hot plate (about 170 ° C.) for 15 minutes.
(9) Add water to make the liquid volume about 70 ml, and cool in a water bath for about 20 minutes.
(10) Add 20 ml of ammonium vanadomolybdate coloring reagent, add water up to the marked line, shake well, and let stand for 30 minutes to make the sample solution, standard first solution and standard second solution, respectively.
(11) Using a spectrophotometer (420 nm, cell 20 mm), using the standard first solution as a control solution and performing cell correction, read the transmittance of the sample solution and the standard second solution to one decimal place. The absorbance is obtained from the transmittance, and the absorbance of the sample solution is A, and the absorbance of the standard second solution is B.
(12) Obtain the P ₂ O ₅ content (wt%) from the following formula to one decimal place.

(2) Al ₂ O ₃ content (1) Use a co-test solution decomposed and prepared at the time of measuring P ₂ O ₅ content.
(2) Dispense 15 ml of the co-test solution into three 200 ml beakers.
(3) Using a pH meter, add 5% ammonium acetate solution to adjust the pH to 3-4.
(4) Add 0.5 ml of Cu-PAN indicator, and add 0.01 mol / l EDTA solution (1 ml = 0.27 mg Al) from reddish purple to yellow.
(5) When the yellow color changes to reddish purple again when heated, the end point is the point where EDTA is continuously added dropwise and does not change even if heated to boiling for 1 minute.
(6) Obtain the Al ₂ O ₃ content (wt%) from the following formula to one decimal place.

(3) Purity
Calculate the sum of the P ₂ O ₅ content and the Al ₂ O ₃ content.
(4) P ₂ O ₅ / Al ₂ O ₃ molar ratio Calculated from the following formula.

(5) Free phosphoric acid content (1) Accurately weigh 2 g of sample into a 250 ml volumetric flask and add about 150 ml of water.
(2) Heat the volumetric flask on the hot plate for about 5 minutes. After cooling, add water up to the marked line in the volumetric flask and shake well.
(3) Filter the liquid in the volumetric flask using dry filter paper (No. 5C).
(4) Dispense 100 ml of the filtrate into a 300 ml beaker using a whole pipette.
(5) Add 2 to 3 drops of methyl orange / indigo carmine mixed indicator to the above beaker and titrate with 0.1 mol / l sodium hydroxide solution. The end point is the point where the color of the liquid has changed from purple to lead gray.
(6) Obtain the content (wt%) of free phosphoric acid from the following formula to one digit after the decimal point in terms of P ₂ O ₅ .

(6) Loss on ignition (1) Put 5 g of sample in a magnetic crucible of known weight and measure accurately to 0.1 mg.
(2) Place the crucible in an electric furnace maintained at 500 ° C. and ignite for 1 hour.
(3) Remove the crucible from the electric furnace, let it cool in a desiccator, and accurately weigh the sample to 0.1 mg.
(4) Using the measured value, calculate the ignition loss (wt%) from the following formula to one decimal place.

(7) Colored element content (1) Put 0.3 g of sample and (1 + 2) 10 ml of sulfuric acid into a Teflon container.
(2) Place the Teflon container in a SUS pressure container and heat at 230 ° C. for 16 hours.
(3) After cooling, place in a 100 ml volumetric flask and dilute.
(4) Perform analysis by flameless atomic absorption.

  Table 1 shows an outline of conditions and performance evaluation results of the examples and comparative examples.

As described above in detail, in the method for producing aminium metaphosphate of the present invention, the produced aluminum metaphosphate is easily powdered to the extent that it is loosened, and the product is easy to handle. Further, by selecting a material and a device material and using this method, a high-purity product required as a raw material for the optical material can be efficiently produced at low cost.

Claims (13)

A first step of reacting or mixing a phosphoric acid source and an aluminum compound;
A second step of firing the product obtained in the first step at 210-370 ° C.,
A third step of absorbing or absorbing the product obtained in the second step;
The product obtained in the third step alone, or further mixed with the product obtained in the first step, and composed of a fourth step of baking at 400 ° C. or higher,
A method for producing high-purity aluminum metaphosphate that does not require a pulverization step. 2. The production method according to claim 1, wherein the P / Al molar ratio of the phosphoric acid source and the aluminum compound in the first step is 2.9 to 3.1. The manufacturing method according to claim 1 or 2, wherein the firing temperature in the second step is 275 to 350 ° C. The phosphoric acid source of the first step is phosphoric acid, and the reaction is stopped at 120 to 130 ° C. until foaming starts and stopped in a viscous liquid state. Production method. The manufacturing method according to any one of claims 1 to 4, wherein moisture absorption or water absorption in the third step is performed under pressurized steam. The manufacturing method according to claim 1, wherein moisture absorption or water absorption in the third step is performed by water immersion. The manufacturing method according to any one of claims 1 to 6, wherein the firing temperature in the fourth step is 500 to 800 ° C. The manufacturing method according to any one of claims 1 to 7, wherein the firing container used in the second step and the fourth step is made of metal aluminum or alumina. The product according to any one of claims 1 to 8, wherein the product of the fourth step is washed with water and then dried to remove free phosphoric acid. The manufacturing method in any one of Claims 1-9 whose each colored metal element density | concentration of the impurity of high purity aluminum metaphosphate is 5 ppm or less. The manufacturing method of Claim 10 whose each colored metal element of the impurity of high purity aluminum metaphosphate is at least 1 sort (s) of iron, chromium, nickel, manganese, zinc, or copper. The manufacturing method in any one of Claims 1-11 whose free phosphoric acid content of high purity aluminum metaphosphate is 2 weight% or less. The manufacturing method in any one of Claims 1-12 whose ignition loss of high purity aluminum metaphosphate is 2 weight% or less.