JPS6310087B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to spherical anhydrous dicalcium phosphate and a method for producing the same. For more details, the average roundness is 0.6 to 1.0, and the amount of liquid absorption is
0.4-0.6ml/g, angle of repose 15-50°, specific surface area 5
The present invention relates to a spherical anhydrous dicalcium phosphate having a particle size of ~60 m ² /g and an average particle size of 10 to 30 μ, and a method for producing the same. [Prior art and problems to be solved by the invention] Conventionally, anhydrous dicalcium phosphate has generally been prepared by combining phosphoric acid or a salt such as ammonium phosphate or sodium phosphate with calcium oxide, calcium hydroxide, calcium carbonate or calcium chloride. etc. 50
It is produced by reacting at ~100°C. Although calcium salts of phosphoric acid such as anhydrous dicalcium phosphate are compounds that can be produced at low cost, most of them are used only as abrasives for toothpaste, and there has been little development of applications for other fields. That is the reality. The present inventors believed that by adding special functions to calcium phosphate, they could not only improve products that currently use calcium phosphate as a raw material, but also be able to expand it to other uses. As a result of intensive research into the development of calcium phosphate having the following properties, we succeeded in developing spherical anhydrous dibasic calcium phosphate, resulting in the present invention. That is, the shape of anhydrous dicalcium phosphate obtained by the conventional method is plate-like, columnar and needle-like crystals, or a mixture thereof. However, the present inventors surprisingly discovered that by carrying out the reaction under special conditions as described below, it was possible to obtain a completely new, hitherto unknown spherical anhydrous dicalcium phosphate. It is something that [Means for solving the problems] That is, the present invention has an average roundness of 0.6 to 1.0, a liquid absorption amount of 0.4 to 0.6 ml/g, an angle of repose of 15 to 50°, and a specific surface area of 5 to 60 m ² /g. g, spherical anhydrous dicalcium phosphate having an average particle size of 10 to 30μ. The spherical anhydrous dicalcium phosphate of the present invention has an average roundness of 0.3 to 0.4, a liquid absorption amount of 0.2 to 0.4 ml/g, and an average angle of repose of 50 to 60° compared to conventional general anhydrous dicalcium phosphate. Compared to something,
They have completely different characteristics not only in shape but also in physical properties. The spherical anhydrous dicalcium phosphate of the present invention is produced by reacting a calcium compound such as calcium oxide with a phosphoric acid compound such as phosphoric acid at a temperature of 60°C or higher in the presence of a phosphoric acid condensate selected from pyrophosphoric acid and polyphosphoric acid. can get. [Function] Next, the method for producing spherical anhydrous dicalcium phosphate of the present invention will be explained in detail. Calcium compounds that can be used in the present invention include calcium oxide (including quicklime), calcium carbonate (including limestone), calcium hydroxide (including milk of lime), and calcium chloride, which are usually commercially available for industrial use or as reagents. It is a mixture. On the other hand, as the phosphoric acid compound, in addition to phosphoric acid, ammonium phosphate and alkali metal phosphate salts such as sodium phosphate and potassium phosphate can be used. However, both the calcium compound and the phosphoric acid compound must be used in a dispersed or dissolved state in water. Here, an example will be explained in which milk of lime obtained by digesting quicklime with water is used as the calcium compound, and an aqueous solution of phosphoric acid is used as the phosphoric acid compound. The concentration of lime milk to be used is not particularly limited, but it is 300 g/less or less in terms of CaO, preferably 200 g/
It is desirable that it is less than g/g/. If the amount exceeds 300 g, the milk of lime becomes viscous, making it difficult to feed with a pump, and at the same time, the dispersibility of the milk of lime particles in the reaction solution deteriorates, making it difficult to obtain the desired spherical anhydrous dicalcium phosphate. It can be difficult. The concentration of the phosphoric acid aqueous solution used is 80% by weight or less.
It is desirable to use it in a state where the concentration is preferably adjusted to 75% by weight or less. When a phosphoric acid aqueous solution with a concentration exceeding 80% by weight is used, calcium phosphates other than dibasic calcium phosphate, such as calcium phosphate salts with high solubility such as monobasic calcium phosphate, are generated, which often reduces the stability of dibasic calcium phosphate. . The phosphoric acid condensate used in the present invention is a compound commonly called strong phosphoric acid or superphosphoric acid and salts thereof, specifically pyrophosphoric acid,
Polyphosphoric acids such as tripolyphosphoric acid, tetrapolyphosphoric acid, hexapolyphosphoric acid, decapolyphosphoric acid, and mixtures thereof, or mixtures of the polyphosphoric acids and their salts with metals from the alkali group, alkaline earth group, or aluminum group can be used. . The amount of the phosphoric acid condensate added is determined by converting the raw material calcium compound into calcium oxide, that is, in terms of CaO.
It is necessary to use 10 parts by weight or more per 100 parts by weight. However, if a polyphosphate is used as the phosphoric acid condensate, the weight shall be converted to the corresponding polyphosphoric acid. If it is less than 10 parts by weight, the average roundness will be
It is not possible to obtain spherical anhydrous dicalcium phosphate with a diameter of 0.6 to 1.0. On the other hand, although there is no particular limitation on the upper limit, there is no significant effect even if it is added in excess of 100 parts by weight. Therefore, in practice, the amount may range from 10 parts by weight to 100 parts by weight, and within this range, the larger the amount added, the smoother the surface of the spherical bodies can be obtained. The reaction between milk of lime and phosphoric acid can be carried out by injecting milk of lime into an aqueous solution of phosphoric acid, or by injecting milk of lime and an aqueous solution of phosphoric acid into a reaction mother liquor at the same time. The purpose can be achieved no matter which method is used. Here, the former case will be explained as an example. In this method, a reaction tank is first filled with an appropriate amount of phosphoric acid aqueous solution, milk of lime is added thereto, and the mixture is reacted. However, in the case of the present invention, the reaction mother liquor is heated to 60°C or higher, preferably in the range of 70 to 100°C, before adding milk of lime.
It is also necessary to maintain the temperature of the reaction solution within this range during the reaction. When milk of lime and phosphoric acid are reacted at a temperature below 60°C, dicalcium phosphate dihydrate, which must be prevented from forming by-products, is produced alone or mixed with anhydrous dicalcium phosphate. Therefore, the object of the present invention cannot be achieved. Special Publication No. 39-3272 or Special Publication No. 39-3273
The publication describes a technique in which calcium hydroxide and phosphoric acid are reacted in the presence of pyrophosphate, etc., but since the reaction temperature at that point is below 50°C, dibasic calcium phosphate dihydrate is used. However, the spherical anhydrous dicalcium phosphate of the present invention was not obtained. The addition and presence of a phosphoric acid condensate in the reaction is one of the major features of the present invention, and even if the reaction between milk of lime and phosphoric acid is performed in the absence of a phosphoric acid condensate, the spherical anhydrous As mentioned above, dibasic calcium phosphate cannot be obtained, but when adding the phosphoric acid condensate, it is necessary to add it simultaneously with milk of lime. If the phosphoric acid condensate is mixed in milk of lime and/or an aqueous phosphoric acid solution in advance, the spherical anhydrous dicalcium phosphate of the present invention cannot be obtained. To add the phosphoric acid condensate, start adding the milk of lime to the phosphoric acid aqueous solution, and continue adding it until the anhydrous dicalcium phosphate starts to become turbid, that is, when the pH value of the reaction solution is 2.0 to 2.5. It is most effective to start the addition. Conversely, it is most preferable that the addition of the phosphoric acid condensate is discontinued at the same time as the supply of milk of lime is discontinued. For example, the above-mentioned Japanese Patent Publication No. 39-3272 and
In Publication No. 39-3273, as shown in the examples, the phosphoric acid condensate is mixed with milk of lime, calcium hydroxide, or phosphoric acid in advance, so even if the temperature is 50°C,
Even if they are reacted at the above reaction temperature, the spherical anhydrous dicalcium phosphate of the present invention cannot be obtained.
As described in the above publication, the present invention cannot be achieved even when milk of lime and phosphoric acid are reacted in the absence of a phosphoric acid condensate. Milk of lime and phosphoric acid may be mixed and reacted using a known general method, and there are no particular operating conditions that should be limited, but the reaction may be carried out at a pH of 7 or less, preferably 5 or less. desirable. When the reaction is carried out at a pH of 7 or higher, non-spherical calcium phosphate is often produced, and finely powdered anhydrous dicalcium phosphate tends to be produced more easily. However, after the reaction is completed, PH is adjusted as PH adjustment.
There is no problem in making it 7 or more. After the reaction is completed, the product is separated by conventional methods, washed with water,
dry. The spherical anhydrous dicalcium phosphate of the present invention obtained by the above method has an average roundness of 0.6 to 1.0, a liquid absorption of 0.4 to 0.6 ml/g, an angle of repose of 15 to 50°, and a specific surface area of 5 to 60 m ² /g. g, with an average particle size of 10 to 30μ. [Effects of the Invention] The spherical anhydrous dibasic calcium phosphate of the present invention has various characteristics not found in conventional anhydrous dicalcium phosphate, so by using this, it is possible to use conventional calcium phosphate as a raw material as described below. It is possible to significantly improve products that have been previously used. The main use of anhydrous dicalcium phosphate at present is as an abrasive for toothpaste. However, anhydrous dicalcium phosphate has the disadvantage that it has a higher hardness than the dentin on the surface of the tooth, and that it damages the dentin of the tooth because of the sharp edges of the plate-like, columnar, and needle-like crystals. On the other hand, dibasic calcium phosphate dihydrate is also used as an abrasive for tooth brushing, similar to anhydrous dicalcium phosphate, but dibasic calcium phosphate dihydrate has low hardness and has abrasive and cleaning power for teeth. Both are known to be weak. Although the spherical anhydrous dicalcium phosphate of the present invention has higher hardness than the dentin on the tooth surface, it does not have sharp edges, making it ideal for polishing and cleaning teeth without damaging the tooth surface. Can be used as an abrasive for toothpaste. On the other hand, anhydrous dicalcium phosphate is also used as a carrier for phosphors used in fluorescent lamps. Anhydrous dicalcium phosphate, which has been used as a carrier for fluorescent materials, is used as calcium halophosphate by spraying the raw material of the fluorescent material on its surface and then firing it. However, with the conventionally used anhydrous dicalcium phosphate in the form of plate-like crystals, the sharp corners of the plate-like crystals break during firing to form calcium halophosphate, making it difficult to collect and collecting the phosphor. The reality is that the ratio has worsened significantly. If spherical anhydrous dicalcium phosphate is used instead of plate crystals, it does not have sharp edges and is not powdered, thus improving the yield of the phosphor. In addition, dicalcium phosphate is currently used as an excipient for tablets, etc., but since most of it is dihydrate dihydrate, it lacks thermal stability and has low hardness as a tablet. have. On the other hand, anhydrous dicalcium phosphate has the drawback of polishing the punches of tablet manufacturing equipment, and is currently not widely used as an excipient. On the other hand, if the spherical anhydrous dibasic calcium phosphate of the present invention is used as an excipient, there is no need to polish the punch.
Furthermore, not only can tablets with good thermal stability be obtained, but also tablets with uniform weight can be produced due to the good fluidity due to the spherical shape.Furthermore, the tablets have excellent strength and have a very glossy surface. In good condition. Furthermore, spherical anhydrous dicalcium phosphate has extremely good fluidity due to its spherical shape, so it can be mixed with powders that have poor fluidity to improve their fluidity, and can be used as a so-called fluidity improver. Can be done. In particular, dicalcium phosphate is recognized as a food additive, and is also used in medicine as a calcium and phosphorus reinforcing agent, so it can be used as a fluidity improver for powdered foods such as wheat flour, raw materials for medicines, or their fluidity improvers. You can also. [Examples] The spherical anhydrous dicalcium phosphate of the present invention will be explained in detail below using Examples, but the present invention is not limited to these Examples. First, we will explain how to measure various physical property values. The roundness is determined by Wadell's formula (J.
Geol. 40 443-451, 1932). That is, roundness = R + r ₁ + r ₂ +... + r _o /RN In this formula, R is the radius of the maximum inscribed circle of the powder particle, r is the radius of curvature of the corner of the powder particle, and N is the number of measurements of r. , the rounder the powder particle shape, the more roundness value
It will be close to 1.0. To determine the amount of liquid absorbed, a certain amount of sample is weighed out onto a smooth glass plate, and glycerin (42.5%) is added dropwise. Stir well with a spatula so that the liquid is evenly mixed throughout, then drip the glycerin. Finally, use a spatula to collect the sample in the center of the glass plate and try to peel it off from the glass plate. The end point is when it comes off cleanly, and the amount of glycerin required per unit weight of the sample is defined as the amount of liquid absorbed. The angle of repose was measured by the injection method (edited by the Chemical Industry Association, Chemical Industry Handbook, p. 987 (1978); referenced by Maruzen Co., Ltd.). Specifically, a Konishi FK type angle of repose measuring instrument manufactured by Konishi Seisakusho was used. On the other hand, the specific surface area by the BET method was measured using a Cantersolve manufactured by Yuasa Battery. Furthermore, the average particle size was measured using a Microtrac particle size analyzer manufactured by Leed & Northrup. Example 1 (1) Preparation of milk of lime 380 g of quicklime was poured into the hot water of step 3 heated to 80° C. under stirring, and stirring was continued for 30 minutes to emulsify the quicklime and prepare milk of lime.
The milk of lime was sieved through a 100-mesh sieve to remove coarse particles, and the concentration of the milk of lime was 124 g/calcium oxide. (2) Production of spherical anhydrous dicalcium phosphate 50% phosphoric acid aqueous solution 1 was heated to 85°C, and the milk of lime prepared in (1) was added at a rate of 600 ml/hour while stirring. The reaction solution became milky when about 200 ml of milk of lime was added, so addition of pyrophosphoric acid at a rate of 0.3 g/min was started concurrently with the addition of milk of lime. When the pH of the reaction solution reached approximately 5, the addition of milk of lime and pyrophosphoric acid was stopped, and only stirring was continued for an additional 30 minutes to complete the reaction. The total amounts of milk of lime and pyrophosphoric acid added during this reaction were 3.1 and 86 g, respectively, so the amount of pyrophosphoric acid added to calcium oxide was equivalent to 23 parts by weight. Thereafter, the reaction solution was filtered, the filter cake was washed with water, and then dried at 60° C. for 24 hours to obtain spherical anhydrous dibasic calcium phosphate. The characteristic values of the obtained spherical anhydrous dicalcium phosphate are shown in Table 1. The shape of this spherical anhydrous dicalcium phosphate is shown in FIG. Examples 2 to 4 In Example 1, the amount of pyrophosphoric acid added was
Spherical anhydrous dicalcium phosphate was produced in exactly the same manner as in Example 1 except for the changes shown in the table. The characteristic values of the obtained spherical anhydrous dicalcium phosphate are shown in Table 1. Comparative Example 1 Anhydrous dicalcium phosphate was produced in exactly the same manner as in Example 1, except that pyrophosphoric acid was not added at all.
The obtained anhydrous dicalcium phosphate is not a spherical body, and the average roundness and liquid absorption amount are 0.33 and 0.36, respectively.
It was hot. Comparative Example 2 In Example 1, pyrophosphoric acid was not added at the same time as milk of lime, but all milk of lime was added, and after the reaction between milk of lime and phosphoric acid was completed, Anhydrous dibasic calcium phosphate was produced in exactly the same manner as in Example 1, except that pyrophosphoric acid was added and stirred. were 0.31 and 0.38, respectively. Examples 5 to 8 Spherical anhydrous dicalcium phosphate was produced in exactly the same manner as in Example 1, except that the phosphoric acid condensate shown in Table 1 was used instead of pyrophosphoric acid. The characteristic values of the obtained spherical anhydrous dicalcium phosphate are shown in Table 1. Comparative Example 3 Approximately 3 50% phosphoric acid aqueous solution was added to an internal volume of approximately 5
The phosphoric acid aqueous solution was heated to 80°C. Powdered calcium hydroxide containing about 0.04% free water and sifted through a 40-mesh sieve was continuously added to the phosphoric acid aqueous solution for about 4 hours until the pH of the reaction solution reached about 7.0, A neutralization reaction between phosphoric acid and calcium hydroxide was carried out. After the neutralization reaction was completed, while stirring the product, 0.8% by weight of sodium tripolyphosphate was added to the anhydrous dibasic calcium phosphate produced. In order to completely disperse the sodium tripolyphosphate into the reaction solution, stirring alone was continued for an additional 30 minutes, after which the product was filtered and dried. However, the obtained anhydrous dicalcium phosphate was a fine plate-like crystal with an average particle size of about 0.9 μm. Reference Example For comparison with the spherical anhydrous dibasic calcium phosphate of the present invention, the physical property values of a conventional anhydrous dibasic calcium phosphate (manufactured by Toyo Stouffer Chemical Co., Ltd.) are shown below.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a photograph substituted for a drawing showing the shape of the spherical anhydrous dicalcium phosphate obtained in Example 1 of the present invention, and is an electron micrograph at a magnification of 4000 times.

Claims (1)

[Claims] 1. Average roundness is 0.6 to 1.0, and liquid absorption is 0.4 to 0.6.
ml/g, angle of repose 15~50°, specific surface area 5~60
Spherical anhydrous dicalcium phosphate having a particle size of m ² /g and an average particle size of 10 to 30 μ. 2. When producing anhydrous dibasic calcium phosphate by reacting calcium oxide or calcium hydroxide with phosphoric acid at a temperature of 60°C or higher, the production is characterized in that it is produced in the presence of a phosphoric acid condensate selected from pyrophosphoric acid and polyphosphoric acid. The average roundness is 0.6~
1.0, liquid absorption amount 0.4-0.6ml/g, angle of repose 15-50°,
Specific surface area is 5-60m ² /g and average particle size is 10-30μ
A method for producing spherical anhydrous dicalcium phosphate. 3 Calcium oxide or calcium hydroxide CaO
3. The method for producing spherical anhydrous dicalcium phosphate according to claim 2, wherein the phosphoric acid condensate is present in an amount of 10 to 100 parts by weight per 100 parts by weight. 4. Addition of phosphoric acid condensate should be started from the time when the reaction solution becomes milky when mixing and neutralizing calcium oxide or calcium hydroxide with phosphoric acid, and until the end of the neutralization reaction or before that. The method for producing spherical anhydrous dicalcium phosphate according to claim 2 or 3, characterized in that the addition of the entire amount is completed. 5. The method for producing spherical anhydrous dicalcium phosphate according to any one of claims 2 to 4, wherein the reaction temperature is 70 to 100°C.