JPS5835934B2 - Dibasic calcium phosphate-calcium carbonate composite structure and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to, for example, stabilizers or nucleating agents or fillers for dentifrice base materials or abrasives, vinyl chloride resins and other synthetic resins, solid acid catalysts in chemical reactions, and absorbents for salt and other substances. It can be used as an alternative to dibasic calcium phosphate in a wide range of applications, such as anti-caking agents for foods or seasoning powders, excipients and other food additives for foods and luxury goods, and excipients or diluents for pharmaceuticals. The present invention relates to a dibasic calcium phosphate-calcium carbonate composite structure having a novel particle structure that can be used with t.

Dibasic calcium phosphate (CaHPO4・nH2O: n is usually O~2) is substantially water-insoluble and is used for various purposes, but in many cases, it is effectively used on its particle surface. The reality is that the interior, which accounts for most of the particles, is not used effectively.

On the other hand, as an industrial method for producing dibasic calcium phosphate, the reaction between slaked lime [Ca(OH)2] and ortho-IJ acid is most commonly adopted, but since ortho-IJ acid is used, which is expensive, As can be understood from the viewpoint of price and the above-mentioned actual situation, there are many restrictions on its use from the viewpoint of its effective utilization rate.

Therefore, it is desired to provide dibasic calcium phosphate that can be produced inexpensively and easily and that can overcome the above-mentioned limitations, and to develop a method for producing the same.

Calcium carbonate is coated with dibasic calcium phosphate only on the part of the particle surface that can be used effectively (Thus, in order to meet the above requirements, fine particles of calcium carbonate are submerged in water using the reaction between calcium carbonate and dilute phosphoric acid. A proposal was made (Japanese Patent Publication No. 42-844) to suspend the particles and add dilute phosphoric acid while stirring to form a film of dicalcium phosphate on the surface of the calcium carbonate particles.

The present inventors conducted a detailed study of the surface structure of the above-proposed product obtained by the direct reaction of calcium carbonate and dilute phosphoric acid in an aqueous medium using a selected area electron diffraction apparatus.

As a result, a stable coating layer in which dibasic calcium phosphate is chemically strongly bonded to the calcium carbonate base particles cannot be formed by the direct reaction between the calcium carbonate particles and dilute phosphoric acid, and fine particles of dibasic calcium phosphate cannot form a stable coating layer. It has been discovered that only a product can be formed in which the surface layer consists essentially of a mixture with the calcium carbonate particles consumed in the dibasic calcium phosphate forming reaction.

According to the research conducted by the present inventors, it is assumed that this is because once formed dicalcium phosphate is relatively easily dissolved in phosphoric acid in the reaction between calcium carbonate particles and dilute phosphoric acid, but the calcium carbonate particle surface leaches out, forms nuclei of dibasic calcium phosphate in the reaction aqueous medium, grows, becomes independent dibasic calcium phosphate particles, and forms a stable dibasic calcium phosphate coating layer chemically bonded to the calcium carbonate substrate particles. A weak physical adhesion coating that is difficult to form and, for example, when ultrasonic vibration is applied in a suspension state, substantially all of the secondary calcium phosphate particles that may remain attached easily separate from the calcium carbonate base particles. It was discovered that only

As a result of further research, for example, water-soluble secondary or tertiary phosphate salts such as alkali metal salts or ammonium salts of dibasic or tertiary phosphoric acid and calcium carbonate particles were combined in an alkaline solution in an aqueous medium. These water-soluble secondary or tertiary phosphates are chemically adsorbed on the surface of the calcium carbonate particles by contacting the calcium carbonate particles under conditions of about It has been discovered that by applying a pH adjusting treatment such as an addition treatment, it is possible to form a selective layer coating of dicalcium phosphate particles on the surface of calcium carbonate substrate particles.

Furthermore, this dicalcium phosphate layer forms a chemically strongly bonded structural complex, as shown by the fact that it does not detach from the calcium carbonate base particles even when subjected to ultrasonic vibration in a suspension state. , the product was discovered to have a novel particle structure.

Furthermore, according to the new reaction means, a structural composite in which the secondary calcium phosphate layer is bonded to calcium carbonate base particles (sometimes referred to as a secondary calcium phosphate-calcium carbonate composite structure or the structural composite of the present invention) is produced. ) were selectively formed, with virtually no independent dibasic calcium phosphate particles forming in the reaction aqueous medium.

Thus, according to the present invention, a novel product consisting of a dibasic calcium phosphate-calcium carbonate composite structure and having a significantly improved utilization rate and substantially free of independent dibasic calcium phosphate particles can be produced at low cost. Moreover, it was found that it can be provided by industrially easy means.

Accordingly, it is an object of the present invention to provide a novel dibasic calcium phosphate-calcium carbonate composite structure coated with a dibasic calcium phosphate layer chemically bonded to calcium carbonate substrate particles.

Another object of the present invention is to provide a method for manufacturing the structural composite of the present invention by industrially easy means and at low cost.

The above objects and many other objects and advantages of the present invention will become more apparent from the following description.

After the structural composite of the present invention has been subjected to ultrasonic treatment to remove physical deposits, the particle surface can be determined by observing an electron microscope image of the particle surface using a selected area electron diffraction device. The second chemically bonded to the calcium carbonate base particles
It is observed that it is coated with a layer of microcrystals of calcium phosphate.

Furthermore, when this surface layer was examined by selected area electron diffraction, the surface layer image showed the highest intensity of dibasic calcium phosphate, 7.
．． It shows the presence of a diffraction image of 57±0.15 people, and it is recognized that the surface layer observed by the electron microscope image is formed of dibasic calcium phosphate.

On the other hand, in the product obtained by the conventional proposal, when observing the same electron microscope image as above, it is found that the surface layer is composed of the consumed calcium carbonate particles and a large number of secondary particles. A product with a mixture of independent particles of calcium phosphate was observed, and the same electron diffraction pattern as described above does not substantially show the presence of the characteristic diffraction pattern of dibasic calcium phosphate.

An electron microscope showing an example of this situation! Photographs and their implied sketches are attached in Figures 1, i-A, 2 and 2-
Shown in Figure A.

Figure 1 is an electron micrograph (20,000x) showing an example of the novel structural composite of the present invention, and Figure 2 is a similar electron micrograph (20,000x) showing an example of a conventional product. FIG. i-A is a suggestive sketch diagram showing an example of the novel structural composite of the present invention, and FIG. 2-A is a similar diagram of a conventional product.

As is more clearly seen from the attached FIGS. 1 and 1-A, the structural composite of the present invention (here, a particle structure coated with a dibasic calcium phosphate layer chemically bonded to a kylcium carbonate substrate particle) In contrast, as is clearer from the attached Figures 2 and 2-A, in the conventional product, the particles with the calcium carbonate surface consumed in the reaction and the microcrystals of dibasic calcium phosphate are It can be seen that it has a mixed particle structure.

Furthermore, analysis of the particle surface layer image of the particle surface layer of the structural composite of the present invention by selected area electron diffraction revealed that the particles forming the surface layer were 757±0.15 people. However, in the conventional product, the diffraction image of 7.57±0.15A was not substantially observed on the surface of the calcium carbonate base particles, indicating that it was calcium carbonate. .03±0.05 people's diffraction image is strong, and the diffraction image of the microcrystals that exist independently in large numbers around it is the strongest diffraction image of dicalcium phosphate ff57.57±0.15 person's diffraction image is recognized.

The above-mentioned secondary calcium phosphate-calcium carbonate composite structure of the present invention is produced by, for example, calcium carbonate particles having a water-fermentable secondary or tertiary phosphate adsorbed under alkaline conditions in an aqueous medium at a pH of about By processing under conditions of 8 or less, the formation can be more easily and selectively performed.

Examples of the water-soluble secondary or tertiary phosphates include secondary or tertiary sodium phosphates, secondary or tertiary potassium phosphates, secondary or tertiary ammonium phosphates, etc. Preferred examples include water-soluble alkali metal salts and ammonium salts of tertiary phosphoric acid.

There are no particular restrictions on the particle size of the calcium carbonate particles, but from a practical standpoint, particle sizes of about 1 to about 20 microns are preferred.

The means for adsorbing water-soluble secondary or tertiary phosphate to calcium carbonate particles can be carried out in any desired manner. For example, water-soluble salts such as those exemplified above or their salts are added to a suspension of calcium carbonate in an aqueous medium. Adding an aqueous solution and maintaining it under stirring conditions until sufficient adsorption, or alternatively,
It is also possible to add calcium carbonate or a suspension thereof to an aqueous solution of these water-soluble salts and carry out a similar adsorption treatment, or to spray an aqueous solution of water-soluble salts or other means. Any means capable of chemically adsorbing calcium carbonate and water-soluble secondary or tertiary phosphates onto the calcium carbonate particles by contacting the salts under conditions can be employed.

Since the water-soluble secondary or tertiary phosphates are dissolved in water to form an aqueous medium system having a pH of about 10 to about 13, it is not necessary to add any alkaline substance to the system.

Under conditions where the system is neutral or acidic, the chemical adsorption described above is substantially 2
This will not occur.

This can be easily understood from what has already been said about Japanese Patent Publication No. 42-844.

The amount of these water-soluble salts to be used is preferably an amount sufficient to adsorb the salts on the entire surface of the calcium carbonate particles, and the larger the size of the calcium carbonate crystal particles, the smaller the amount required. Calcium is preferably used in an amount of about 0.05 times the mole or more per mole.

The salts are present in the aqueous medium in an amount that exceeds the amount that can be adsorbed so that the entire surface of the calcium carbonate particles is covered with a monomolecular layer of these salts.

Generally, the amount used is often about 0.05 to about 0.2 times the mole of calcium carbonate.

According to the method of the present invention, the calcium carbonate particles on which the water-soluble secondary or tertiary phosphate has been adsorbed as described above are acid-treated under conditions of −8 or less, preferably about 7 or less.

This acid treatment at a pH of about 8 or less can be carried out by bringing the adsorbed calcium carbonate particles into contact with an appropriate acid to form the p ridge.

There are no particular restrictions on the means of this treatment, but for example, a system of adsorbed calcium carbonate particles in an aqueous medium that has been adsorbed with water-soluble secondary or tertiary phosphates, or adsorption-treated calcium carbonate particles. Once separated from the system and then resuspended in an aqueous medium, an appropriate acid or its aqueous solution can be added, or the adsorption-treated calcium carbonate particles can be added to an appropriate acid aqueous solution. This can be carried out by suspending, dispersing, or applying an appropriate aqueous acid solution to the adsorption-treated calcium carbonate particles by means such as spraying or sprinkling.

Such acids may include orthophosphoric acid, phosphoric acid, other inorganic acids such as hydrochloric acid, nitric acid, carbonic acid, and, if desired, organic acids such as acetic acid, formic acid, citric acid, tartaric acid. can be used.

In addition, there are no particular restrictions on the amount of these acids used, but water-soluble secondary or tertiary phosphate used in the adsorption treatment 1
It is preferably used in an amount of about 3 times the mole or less.

It is more preferably about 2 times the mole or less, particularly preferably about 0.5 to about 1 time the mole.

In the above-described adsorption treatment and pH adjustment treatment, the treatment concentration of water-soluble secondary or tertiary phosphate and acid is preferably dilute, and in the case of acids, it is particularly preferable to employ dilute concentration conditions.

For example, it is preferable to use dilute concentration conditions such as 20 mmol/l of dibasic sodium phosphate and 10 mmol/l of orthophosphoric acid.

Further, all of these treatments can be performed at room temperature and do not particularly require cooling or heating, but such conditions may be used.

Generally, temperatures in the range of preferably from about 10°C to about 80°C, more preferably from about 0°C to about 60°C, are utilized.

These treatments are preferably carried out under stirring conditions (C), and it is particularly preferable to carry out the treatment with acids by gradually adding the acids under sufficient stirring conditions.

The structural complex of the present invention formed as described above is
It can be separated and collected by any solid-liquid separation means such as filtration or decanting, and if desired, washed with water and dried.

The thus obtained structural composite of dibasic calcium phosphate and calcium carbonate of the present invention can be distinguished from conventional products using a selected area electron diffraction apparatus, as described above. These methods will be described in more detail below.

(1) Identification by electron beam microscopic image A sample suspension of 50 to 100 μg of sample grains was made to appear in ethanol for 10 days, and then heated to 400K using an ultrasonic vibrator.
Ultrasonic vibration treatment at Hz for 5 minutes to remove physical deposits.

The sample particles in the treated sample suspension are observed as a 20.000x microscopic image using an electron microscope means of a selected area electron diffraction device.

This observation shows that the structural composites of the present invention do not contain substantial amounts of individual dibasic calcium phosphate particles (as shown by way of example in the accompanying drawings) and that the selected field of view described below Analysis of electron diffraction images shows that the highest intensity of dibasic calcium phosphate is 7.57±O, which is confirmed by the presence of 15 diffraction images.The particle surface layer coating of dibasic calcium phosphate covers substantially the entire surface of the particles. This is recognized and distinguishes it from conventional products.

(11) Identification by selected area electron diffraction image: A selected area electron diffraction image is taken using the surface layer of the same sample particle used to observe the above electron microscope image, and its analysis reveals that the second
The presence or absence of a diffraction image of a person with the highest intensity of calcium phosphate 7.57±0.15 is examined.

If the presence of the dibasic calcium phosphate surface layer is not clear by observation of the electron beam microscopic image, take the above diffraction image at four locations where two straight lines orthogonal through the center of the grain intersect with the grain surface layer, The presence or absence of the diffraction image of the above 7.57 and 0.15 people is confirmed, and if it is confirmed that the above diffraction image exists in at least two places, the particles that substantially (have) the coating layer of the dibasic calcium phosphate of the present invention It can be determined that

If at least three locations are diffraction images of 3.03 x 0.05, indicating calcium carbonate, it can be determined that the particle has no substantial G content in the dibasic calcium phosphate coating layer.

Next, some representative examples of the novel structural composite of the present invention and its manufacturing method will be illustrated by Examples.

Example 1 100L of calcium carbonate with an average particle size of about 2μ? into 1 ton of water (approximately 20°C) and stir thoroughly.

This suspension system was added with disodium phosphate (Na2HPO4.1
2H20) Hydroxic acid solution iz containing 36 r (approximately 0.1 mo
z) was gradually added under stirring conditions over about 10 minutes, and left to stand for an additional 10 minutes after mixing.

Subsequently, 0.1 mol/l orthophosphoric acid 800-
is gradually added over about 20 minutes under stirring conditions.

After finishing Ebetsu, it was filtered, washed with water, filtered, and dried at 80°C.

The electron microscope image of the obtained structural complex of the present invention is the first
As shown in the figure, it was confirmed that the surface of the calcium carbonate particles was coated with a second calcium phosphate layer that did not come off during the ultrasonic vibration treatment.

Further, the formation of independent dibasic calcium phosphate particles was substantially not observed.

Example 2 100v of calcium carbonate with an average particle size of about 5μ is 0.05
mol/l triammonium phosphate [(NH4)3PO
4.3H20] Add 1 t of water solution (approximately 30°C) and add approximately 1
Stir for 0 minutes.

To this suspension system, 0.1 mol/L of hydrochloric acid (1,000 ml) was slowly added under stirring conditions, and the mixture was fully heated in about 30 minutes.

Thereafter, it is filtered, washed with water, and dried at about 80°C.

The electron microscope image was similar to that shown in FIG. 1, and it was confirmed that the surface of the calcium carbonate particles was covered with a second calcium phosphate layer that was not detached by the ultrasonic vibration treatment.

Furthermore, no substantial formation of independent dibasic calcium phosphate particles was observed.

Example 3 100L of calcium carbonate with an average particle size of about 1μ? dipotassium phosphate (K2HP) equivalent to about 0.15 mol;
O4) into an aqueous solution containing 26f (add it and stir thoroughly.

After that, 0.1 mol/l of or-IJ acid 8
00ml was gradually added under stirring conditions, and the entire amount was added in about 10 minutes.

This is filtered, washed with water, and dried at 80°C.

The electron microscope image and the electron diffraction image show that the calcium carbonate particles are coated with a chemically bonded dibasic calcium phosphate layer, as in Example 1.2, and are separated from the independent dibasic calcium phosphate particles. The formation of was also virtually not observed.

[Brief explanation of the drawing]

Figure 1 is an electron micrograph (20,000x) showing an example of the novel structural composite of the present invention, and Figure 2 is a similar electron micrograph (20,000x) showing an example of a conventional product. FIG. i-A is a suggestive sketch diagram showing an example of the novel structural composite of the present invention, and FIG. 2-A is a similar diagram of a conventional product.

Claims (1)

[Claims] 1. A particle surface layer image obtained by selected area electron diffraction method shows the existence of a diffraction image with the highest intensity of dibasic calcium phosphate of 7.57±0.15, and the particle surface is formed on a calcium carbonate base particle. A dibasic calcium phosphate-calcium carbonate composite structure coated with a chemically bonded dibasic calcium phosphate layer. 2. A selected area electron diffraction method characterized in that calcium carbonate particles on which a water-soluble secondary or tertiary phosphate has been adsorbed under alkaline conditions in an aqueous medium are treated with an acid at a pH of about 8 or less. The particle surface layer image showed the presence of a diffraction image with the highest intensity of dibasic calcium phosphate of 7.57 ± 0.15, indicating that the particle surface was covered with a dibasic calcium phosphate layer chemically bonded to the calcium carbonate base particle. A method for producing a dibasic calcium phosphate-calcium carbonate composite structure. 3. Contacting calcium carbonate with a water-soluble secondary or tertiary phosphate in an aqueous medium, and adding an acid to the system to adjust the pH of the system to about 8 or less. The manufacturing method according to claim 2.