JP4834365B2 - Method for producing amorphous calcium phosphate-coated particles and the particles - Google Patents

Description

  The present invention relates to a method for producing particles containing amorphous calcium phosphate and the particles. More specifically, the present invention relates to an amorphous material useful as a compounding component for cosmetics, paints, inks, toners, greases, rubbers, plastics, ceramics and the like. The present invention relates to a method for producing particles containing fine calcium phosphate and the particles.

  Conventionally, natural or man-made clay minerals, such as talc, kaolin (white clay), bentonite, mica group minerals (sericite, muscovite, phlogopite, biotite), calcined kaolin, etc., having scale-like or plate-like particle shapes And processed products thereof, or surface treated products (hereinafter collectively referred to as “clay minerals”) are excellent in slipperiness to the skin due to their particle shape, so that powder white powder, solid white powder, foundation, etc. As a main ingredient of so-called powder base makeup cosmetics, in particular, extender pigments that diminish the color of color pigments, or adsorbents that adsorb sebum (oil) and sweat (moisture) that are secretions from the skin It has been widely used as a component having several functions.

  Of these, talc is transparent and has a characteristic that the touch when applied to the skin is particularly smooth and has excellent adhesion. Kaolin is inferior to talc in terms of smoothness, but it has a relatively large adsorption power for adsorbing secretions from the skin and a concealing power for concealing the foundation, and it exhibits weak acidity suitable for skin health. It has the characteristic.

  Therefore, until now, these two parties have often been used in combination as main ingredients of base makeup cosmetics. Recently, however, sericite, which is highly transparent even in the mica family, and titanium oxide-coated particles with a pearly luster (such as titanium mica) have also been used for base makeup cosmetics with a new cosmetic feel. Demand is expanding.

  Especially for sericite, it is popular among clay minerals, and domestic high-purity raw materials are scarce or expensive, and raw materials with low purity from overseas are imported, refined and used. This is the current situation. For this reason, sericite and other mica group minerals are usually distinguished by the names “sericite” and “mica”. Titanium oxide-coated particles such as titanium mica are processed products in which fine particles of titanium oxide with a high refractive index are coated on the surface of pulverized materials such as muscovite and phlogopite, sericite, talc, synthetic mica, etc. Depending on the thickness of the titanium layer, various interference colors are produced, which are preferred as pearl luster. Furthermore, in recent years, products that have been coated with iron oxide or chromium oxide instead of titanium oxide, titanium oxide that has been further coated with iron oxide or chromium oxide, or those that are combined with dyes or pigments have been developed. It is called pearl pigment or pearl luster pigment. This pearl pigment includes titanium mica, bengara-coated mica, bengara-coated titanium mica, black iron oxide-coated titanium mica, carmine-coated titanium mica, conjugate-coated titanium mica, carmine-conjoux-coated titanium mica, chromium oxide-coated titanium mica, bengara-black Iron oxide coated titanium mica, black iron oxide carmine coated titanium mica, black iron oxide conger coated titanium mica, titanium mica + yellow 4, titanium mica + red 202, titanium mica + blue 1, titanium mica + blue 1 + Yellow 4 and so on.

  In actual use, these clay minerals, that is, mineral particles having a scaly or plate-like particle shape, are appropriately blended according to the purpose, and a small amount of oily components, coloring pigments, and the like. A base makeup cosmetic is produced by mixing with the above ingredients.

By the way, conventionally, calcium phosphates such as hydroxyapatite and tricalcium phosphate are excellent in adsorption performance of organic substances such as oil, and thus are used in deodorants and cosmetics.
Patent Document 1 discloses an odorless cold perm solution containing an alkali agent mainly composed of hydroxyapatite. By using hydroxyapatite with a large specific surface area (100m ² / g or more), the odorless cold perm solution can remove the main thioglycolic acid odor and cysteine odor, shorten amino acid elution time by amino acid adsorption ability, and ion exchange It has effects such as elimination of harmful heavy metals from the human body via hair.

Such adsorption performance of calcium phosphate can be improved by increasing the specific surface area of the particles even if the blending amount of calcium phosphate is the same.
Therefore, calcium phosphate is blended to give adsorption performance to cosmetics, paints, inks, toners, greases, rubbers, plastics, ceramics, etc. in which mineral particles having scale-like or plate-like particle shapes as described above are used. In some cases, for example, it is possible to increase the specific surface area of calcium phosphate and to improve the adsorption performance by coating calcium phosphate on the above-described mineral particles, rather than simply adding granular calcium phosphate. be able to.
Further, in that case, the adsorption performance can be further improved by coating the surface of the mineral particles over a wide range with calcium phosphate to reduce the portion not covered with calcium phosphate. .

On the other hand, Patent Document 2 describes a method for producing amorphous calcium phosphate composite particles in which the surface of scaly or plate-like particles is coated with fine particles of amorphous calcium phosphate. Describes a method of depositing amorphous calcium phosphate on the surface of a pigment. Patent Document 3 also describes the use of sericite as a pigment.
However, in these patent documents, although it is described that mineral particles having a scaly or plate-like particle shape are coated with amorphous calcium phosphate, the mineral particles are not coated with amorphous calcium phosphate. No investigation has been made on suppressing the occurrence of the portion.
Therefore, conventionally, no consideration has been given to improving the adsorption performance by improving the coverage of the amorphous calcium phosphate-coated particles.
That is, the amorphous calcium phosphate is coated at a high coverage on the base material composed of at least one of scale-like or plate-like mineral particles, as in the case of these amorphous calcium phosphate-coated particles that have been required to improve the adsorption performance. The method for producing amorphous calcium phosphate-coated particles desired to be produced has a problem that it is difficult to produce amorphous calcium phosphate-coated particles having an improved coverage.

JP 58-83607 A JP 2000-169122 A Japanese Patent No. 2914460

  An object of the present invention is to provide a production method for producing amorphous calcium phosphate-coated particles having an improved coverage with amorphous calcium phosphate, and amorphous calcium phosphate-coated particles obtained by this production method.

As a result of intensive studies to improve the coverage of amorphous calcium phosphate-coated particles, the present inventor has found that a substrate material composed of at least one of scale-like or plate-like mineral particles is coated with amorphous calcium phosphate. When producing crystalline calcium phosphate-coated particles, iron, titanium, calcium, silicon, aluminum, potassium, magnesium, etc. are adhered to the surface of the base material, and the base materials are aggregated. Inhibits the surface of the individual substrate material particles from being coated with amorphous calcium phosphate. Furthermore, the substrate material is treated with acid, washed, mixed with calcium hydroxide, and suspended. It was found that by adding phosphoric acid to the suspension and improving the above-mentioned inhibition situation, the present invention was completed. A.
That is, the present invention is a method for producing amorphous calcium phosphate-coated particles in which a base material consisting of at least one of scale-like or plate-like mineral particles is coated with amorphous calcium phosphate in order to solve the above-described problem, (1) An acid treatment step in which the surface of the substrate material is washed with an acid having a pH of 1.5 or less by mixing the substrate material with an acid having a pH of 1.5 or less; A washing step of washing the substrate material treated in the acid treatment step with water so that the pH of the suspension dispersed in water at 1 to 50% by mass is 2.0 or more; (3) the washing An alkaline step of preparing an alkaline suspension in which the base material washed in the step and calcium hydroxide are mixed; and (4) adding phosphoric acid to the alkaline suspension prepared in the alkaline step. Calcium phosphate coating step of coating the surface of an amorphous calcium phosphate, which provides amorphous calcium phosphate-coated particles produced by the production method and the production method of the amorphous calcium phosphate-coated particles, characterized in that is carried out.

According to the present invention, since the acid treatment step of washing the surface of the amorphous calcium phosphate with an acid having a pH of 1.5 or less is performed, the surface of the base material composed of at least one of scale-like or plate-like mineral particles is applied. Adhering iron, titanium, calcium, silicon, aluminum, potassium, magnesium, and the like can be removed with an acid, and aggregation of the base material can be suppressed. Therefore, it is possible to improve the situation where the coating of the surface of the base material with amorphous calcium phosphate is hindered by these factors.
That is, the coverage of the amorphous calcium phosphate-coated particles can be improved as compared with the conventional one.

The preferred embodiments of the present invention will be described below.
In the method for producing amorphous calcium phosphate-coated particles in the present embodiment, a base material composed of at least one of scale-like or plate-like mineral particles is used.
Further, in the method for producing amorphous calcium phosphate-coated particles of the present embodiment, an acid treatment step of mixing the base material and an acid and washing the surface of the base material with an acid having a pH of 1.5 or lower, and a base material A washing step for washing the substrate material treated in the acid treatment step so that the pH of the suspension dispersed in water at a solid content concentration of 0.1 to 50% by mass is 2.0 or more, the washing step An alkaline step of preparing an alkaline suspension in which the base material washed with calcium hydroxide is mixed, and phosphoric acid is added to the alkaline suspension prepared in the alkaline step to form a surface of the base material. A coating step of coating with amorphous calcium phosphate is performed to coat the surface of the substrate material with amorphous calcium phosphate.

In the acid treatment step, an acid cleaning process is performed, and deposits such as iron, titanium, calcium, silicon, aluminum, potassium, and magnesium adhering to the surface of the base material are used as deposit ions from the surface of the base material. While removing, it suppresses aggregation of base material. As this acid treatment step, it is possible to employ a general granular material washing treatment method such as a method of showering an acidic liquid in a substrate material or a method of immersing and washing a substrate material in an acidic liquid. It is preferable to perform a method of immersing the base material in an acidic liquid from the viewpoint that the entire surface can be washed uniformly and sufficiently.
In this regard, the solid content concentration of the base material dispersed in the acid at the time of pickling is preferably 0.1 to 50% by mass, more preferably 1 to 50% by mass, More preferably, it is 5-30 mass%. The solid content concentration is preferably within such a range. When the solid content concentration exceeds 50% by mass, the effects such as the removal of the adhering ions and the suppression of the aggregation described above are uniformly and sufficiently applied to the entire substrate material. Even if the solid content concentration is less than 0.1% by mass, not only can the above-mentioned effects be expected to be more uniform and sufficient, but also the equipment to be used becomes large. This is because there is a possibility that productivity may be lowered, for example, the amount of the amorphous calcium phosphate-coated particles obtained with respect to the amount of acid used is reduced.
Moreover, in the point from which the same effect as the effect mentioned above is acquired, as the said pickling, a base material is 0.1 to 200 hours, Preferably, it is 1 to 72 hours, More preferably, it is 1 to 24 hours. It is preferable to immerse in an acid.

  The acid used in the method of immersing the base material in the acidic liquid is not particularly limited, but is usually a strong acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc. used for iron removal, citric acid, Weak acids such as malic acid, acetic acid and oxalic acid can be used alone or in combination. Further, these acids can be used in the same concentration or diluted. In addition, as such an acid, it can suppress that the calcium ion added by an alkaline process of a latter stage is consumed by anions other than a phosphate ion, and in the calcium-phosphate coating process, on the surface of a base material, It is preferable to use phosphoric acid in that amorphous calcium phosphate can be generated more efficiently.

  Examples of the substrate material include sericite, mica (muscovite, phlogopite, saucite, biotite, lithia mica, synthetic mica), talc, kaolin, vermiculite, smectite, titanium oxide-coated mica (titanium mica), and oxidation. Various scale-like or plate-like mineral particles such as pearl pigments such as titanium-coated sericite and titanium oxide-coated talc can be mentioned.

Of these, sericite, mica, and talc are preferable as the base material because amorphous calcium phosphate can be uniformly coated.
In addition, when using talc as this base material, it is preferable to implement the water kneading process of kneading with water 0.1 to 3 times the weight of the base material prior to the acid treatment process.
It is preferable to carry out such a water kneading step on a base material in which talc is used because talc is usually produced from ore by dry pulverization and is in a state of exhibiting water repellency. By carrying out such a water kneading step, the hydrophilicity of talc can be increased, the dispersibility in an acidic liquid in the acid treatment step can be enhanced, and the workability of the acid treatment step can be improved.
It is also possible to use talc produced by wet pulverization instead of performing the water kneading step on talc produced by such dry pulverization. Examples of talc produced by this wet pulverization include trade names such as Fit Powder FK-500S, FK-300S, FKG-30, CT-30, CT-35, AT-350EX manufactured by Yamaguchi Mica Industry Co., Ltd. Can be used commercially available.
Further, whether or not the dry pulverized talc subjected to this water kneading step or the talc produced by wet pulverization has hydrophilicity that exhibits the workability improvement effect of the acid treatment step, for example, at room temperature It can be determined by floating about 0.5 g of talc in a dry state on the surface of the ion-exchanged water that has been allowed to stand and checking whether 90% or more of the talc is submerged after 1 hour.

  Moreover, as such a base material, for example, scale-like or plate-like mineral particles having an average particle diameter of 1 to 300 μm can be used. In addition, the said average particle diameter in this specification means the value of 50 vol% of the curve which shows the cumulative particle size distribution calculated | required by the laser diffraction method, for example, the brand name of "Rodos" from Japan Laser Corporation. It can be measured by a commercially available laser diffraction type particle size distribution measuring device.

Normally, a commercially available product can be used as such for the base material, but classification may be performed if necessary. The amorphous calcium phosphate covering the surface of the base material is tricalcium phosphate containing water of crystallization as represented by the general formula: Ca ₃ (PO ₄ ) ₂ .nH ₂ O. The crystal structure is amorphous. In addition, since the crystal structure is amorphous, amorphous calcium phosphate has a large amount of water of crystallization, so that the pattern of the powder X-ray diffraction method is illustrated in FIG. 5 as compared to crystalline calcium phosphate. It can be confirmed from the broad.
As long as the effects of the present invention are not impaired, an element such as barium, strontium, zinc, magnesium, sodium, potassium, iron, aluminum, titanium, or the like is dissolved in a part of the calcium of the amorphous calcium phosphate. Alternatively, it may be ion-exchanged or substituted, and a part of PO ₄ may be substituted with one kind of atomic group such as VO ₄ , SiO ₄ , and CO ₄ .
Furthermore, calcium phosphate may be combined with one or more metal oxides. Although it does not specifically limit as a metal oxide, For example, a titanium oxide, a zinc oxide, a cerium oxide etc. are mention | raise | lifted.

In the cleaning step, the concentration of deposit ions removed from the surface of the substrate material during the acid treatment described above is reduced, and in the subsequent calcium phosphate coating step, the deposit ions are transferred to the surface of the substrate material by amorphous calcium phosphate. The inhibition of the coating is suppressed.
At this time, the substrate material after washing is washed so that the suspension in which water is dispersed in water at a solid concentration of 0.1 to 50% by mass, preferably 1 to 50% by mass, has a pH of 2.0 or more.
As a cleaning method in this cleaning process, the substrate material in the pickled state may be washed simply by adding water, and the substrate material in the pickled state may be washed with an acidic liquid by centrifugal dehydration or the like as described above. It is possible to use a method such as rinsing by adding water until the pH of the suspension in which the substrate material is dispersed after discharging the kimono ions out of the system and dehydrating is 2.0 or more. It is also possible to adopt a method of repeating the above.

In addition, when hydrochloric acid, nitric acid, sulfuric acid, or citric acid is used as the acid, it is possible to suppress consumption of calcium ions by anions other than phosphate ions such as chloride ions and sulfate ions. This washing step is preferably carried out until the suspension in which the substrate material is dispersed in water at a solid content concentration of 0.1 to 50% by mass, preferably 1 to 50% by mass, has a pH of 6.0 or higher.
In the alkaline process, an alkaline suspension is prepared by mixing the base material washed in the washing process and calcium hydroxide. Here, the base material and calcium hydroxide are mixed to make the suspension alkaline. When the subsequent calcium phosphate coating step is performed in an acidic state, the added phosphoric acid forms calcium hydrogen phosphate. This is because it becomes difficult to coat the surface of the base material with amorphous calcium phosphate.

  In the calcium phosphate coating step, amorphous calcium phosphate is adhered to the surface of the base material by adding phosphoric acid to the alkaline suspension prepared in the alkaline step. At this time, as described above, if the suspension is in an acidic state, in particular, a pH of less than 5.0, there is a possibility that calcium hydrogen phosphate may be formed. Therefore, phosphorous is added to the alkaline suspension in the calcium phosphate coating step. The addition of the acid is preferably performed in a state where the pH is maintained at 5.0 or higher. In addition, if necessary, the pH may be maintained at 5.0 or higher by alternately performing the alkali process and the calcium phosphate coating process to suppress the formation of calcium hydrogen phosphate. In addition, in the calcium phosphate coating step, the temperature of the suspension is increased by reaction heat by adding phosphoric acid, and therefore, for example, it is preferable that the suspension is cooled to a temperature of 50 ° C. or lower. . By performing this cooling, the step of adding phosphoric acid can be prevented from being performed in multiple steps, and the method for producing amorphous calcium phosphate-coated particles can be made more efficient.

  As described above, the produced amorphous calcium phosphate-coated particles can employ general drying means such as spray drying and cake drying, but do not require a step such as crushing, and are amorphous at the time of crushing. It is preferable to employ a drying means by spray drying from the viewpoint that the calcium phosphate-coated particles can be rubbed with each other and the amorphous calcium phosphate can be prevented from falling off from the surface of the amorphous calcium phosphate-coated particles.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
(Test example)
Mica manufactured by Yamaguchi Mica Industry Co., Ltd. (product name “Y-2400”), Sericite manufactured by Sanshin Mining Co., Ltd. (product name “FSE”), and Titanium Mica manufactured by Nippon Koken Kogyo Co., Ltd. (product name “PEARL-GLIZE”). MV-100R ") was analyzed using a fluorescent X-ray analyzer (" RIX-2100 "manufactured by Rigaku Corporation). The results are shown in Table 1. As can be seen from this table, impurities such as TiO ₂ and Fe ₂ O ₃ are contained as impurities in addition to K ₂ O, Al ₂ O ₃ and SiO ₂ which are the main components of sericite and mica.
Therefore, we prepared two sets of these mica, sericite, and titanium mica that weighed 0.5 g each and put them in separate Erlenmeyer flasks. In the first set, 15 g of ion-exchanged water was added, and the second set Was added with 7.5% by mass phosphoric acid (pH 0.5) and stirred with a stirrer for 1 hour. Then, each was set to No. The filtrate filtered using 1 filter paper was diluted 5-fold with ion-exchanged water, and elemental analysis was performed with ICP (“SPS-4000” manufactured by SII Nanotechnology Inc.).
For mica and sericite, elemental analysis was similarly performed using 2N hydrochloric acid, 1N nitric acid, 2N sulfuric acid, and 1 mol / L citric acid. The results are shown in Table 2.
It can be seen from this table that impurities such as TiO ₂ and Fe ₂ O ₃ can be removed from the surface of the scale-like or plate-like mineral particles by treating the scale-like or plate-like mineral particles with an acid having a pH of 1.5 or less. I understand.

Example 1
450 g of scaly mica (Yamaguchi Mika Kogyo Co., Ltd. “Y-2400”: average particle size of about 9.66 μm) as a base material was put in 1 liter of ion-exchanged water, and a 7.5 mass% phosphoric acid aqueous solution was stirred. After stirring for 10 minutes to make a suspension, the suspension was allowed to stand overnight to carry out an acid treatment step. The pH of the suspension at this time was measured with a pH meter and found to be 0.1.
Furthermore, the scaly mica was separated by suction filtration, and the washing step was performed by adding ion-exchanged water and creating a resuspension until the pH became 2.0 or more at a solid content concentration of 20%.
Next, using a homomixer, a calcium hydroxide suspension in which 37.3 g of calcium hydroxide is dispersed in 1 liter of ion-exchanged water is prepared, and the pH of the resuspension is compared to the resuspension. This calcium hydroxide suspension was added until 12.5 to carry out an alkaline step to prepare an alkaline suspension.
Furthermore, while maintaining the liquid temperature of this alkaline suspension at 50 ° C. or lower, a 7.5% by mass aqueous phosphoric acid solution was added until the final pH was 6.5 and stirred for 30 minutes, followed by a calcium phosphate coating step. Carried out.
Further, spray drying (Okawara Kako Machinery Co., Ltd. “L-8”) was used for spray drying to perform the above-mentioned alkali process and this calcium phosphate coating process alternately twice (total 3 times each). Granulation was performed to produce amorphous calcium phosphate coated particles.

(Example 2)
The washing with ion-exchanged water was carried out until a resuspension with a pH of 6.0 or higher was obtained in the washing step, except that the alkaline step and the calcium phosphate coating step were alternately carried out four times in total. In the same manner as in Example 1, amorphous calcium phosphate-coated particles were produced.

(Example 3)
As the base material, sericite (trade name “FSE”: average particle diameter of about 8.17 μm, flat plate major axis average value of about 8 μm, minor axis average value of about 5 μm, thickness average value of about 0.0. Amorphous calcium phosphate-coated particles were produced in the same manner as in Example 1 except that 1 μm) was used.

Example 4
Amorphous calcium phosphate coating as in Example 1 except that titanium mica (trade name “PEARL-GLAZE MV-100R”: average particle diameter of about 17.65 μm) manufactured by Nihon Koken Kogyo Co., Ltd. was used as the base material. Particles were produced.

(Example 5)
450 g of talc (“JA-46R” manufactured by Asada Flour Milling Co., Ltd .: average particle size of about 15.40 μm) produced by dry pulverization as a base material was placed in 0.9 liter of ion-exchanged water and kneaded for 10 minutes in a kneader. The water kneading process was carried out. After the water kneading step, 1 liter of ion-exchanged water was added to what was left overnight, and 1500 g of 7.5% by mass phosphoric acid aqueous solution was added with stirring and stirred for 10 minutes to obtain a suspension. The acid treatment step was carried out by allowing to stand overnight. The pH of the suspension at this time was measured with a pH meter and found to be 0.9.
Furthermore, talc was separated by suction filtration, and a washing step was performed by creating a resuspension by adding ion-exchanged water until the pH became 2.0 or more at a solid concentration of 20%.
Next, using a homomixer, a calcium hydroxide suspension in which 37.3 g of calcium hydroxide is dispersed in 1 liter of ion-exchanged water is prepared, and the pH of the resuspension is compared to the resuspension. This calcium hydroxide suspension was added until 12.5 to carry out an alkaline step to prepare an alkaline suspension.
Furthermore, while maintaining the liquid temperature of this alkaline suspension at 50 ° C. or lower, a 7.5% by mass aqueous phosphoric acid solution was added until the final pH was 6.5 and stirred for 30 minutes, followed by a calcium phosphate coating step. Carried out.
Further, spray drying (Okawara Kako Machinery Co., Ltd. “L-8”) was used for spray drying to perform the above-mentioned alkali process and this calcium phosphate coating process alternately twice (total 3 times each). Granulation was performed to produce amorphous calcium phosphate coated particles.

(Example 6)
Instead of talc produced by dry pulverization, wet pulverized talc (“Fit Powder FK-300S” manufactured by Yamaguchi Mica Industry Co., Ltd .: average particle size of about 15.40 μm) was used, and the water kneading step was not performed. Except that, amorphous calcium phosphate-coated particles were produced in the same manner as in Example 5.

(Comparative Example 1)
Example 3 is the same as Example 3 except that the acid treatment step was not carried out, and in the calcium phosphate coating step, an 8.5 mass% phosphoric acid aqueous solution was used and the final pH was 9.0 to 10.0. Similarly, amorphous calcium phosphate-coated particles were produced.

(Comparative Example 2)
Amorphous calcium phosphate-coated particles were produced in the same manner as in Example 1 except that the acid treatment step was performed at pH 2.0.

(Comparative Example 3)
Without carrying out the acid treatment step, the base material was dispersed in 3 liters of ion-exchanged water at 90 ° C., an alkaline suspension was prepared using an alkaline aqueous solution of 25 g / liter of calcium acetate in the alkaline step, and calcium phosphate coating In the same process as in Example 3, except that the alkaline suspension was added to a final pH of 7.0 using an aqueous sodium hydrogen phosphate solution while maintaining the liquid temperature at 90 ° C. Crystalline calcium phosphate coated particles were produced. In this comparative example, amorphous calcium phosphate-coated particles were produced according to the production method described in Patent Document 3.

(Comparative Example 4)
Example 6 is the same as Example 6 except that the acid treatment step was not carried out, and in the calcium phosphate coating step, an 8.5 mass% phosphoric acid aqueous solution was used and the final pH was 9.0 to 10.0. Similarly, amorphous calcium phosphate-coated particles were produced.

(Comparative Example 5)
Amorphous calcium phosphate-coated particles were produced in the same manner as in Example 6 except that the acid treatment step was performed at pH 2.0.

(Particle size change)
The average particle diameter of the amorphous calcium phosphate-coated particles produced in Examples 1 to 4 and Comparative Examples 1 to 3 was measured and compared with the average particle diameter of the base material. The results are shown in Table 3.

(Oil content adsorption)
First, a blank sample prepared by drying amorphous calcium phosphate-coated particles under conditions of 350 ° C. × 1 h was prepared. Next, 4.5 g of oleic acid was added to 0.5 g of this blank sample and allowed to stand at 37 ° C. for 24 hours to adsorb oleic acid. Further, the sample was washed three times with 15 ml of diethyl ether and air-dried to obtain an adsorption sample.
About 14 to 17 mg each of the blank sample and the adsorbed sample were collected, and the oil absorption amount was obtained by performing TG-DTA measurement at a heating rate of 20 ° C./min from 30 ° C. to 600 ° C. in a nitrogen gas stream. .
More specifically, the difference between the residual heating rate (%) at 30 to 600 ° C. and the residual heating rate (%) at 30 to 150 ° C. is obtained as a weight loss rate (%), and each of the blank sample and the adsorption sample is obtained. The difference in weight loss rate (%) was taken as the adsorption rate (%), and this adsorption rate (%) was multiplied by 10 to obtain the oil adsorption amount (mg / g).
Similarly, the amount of oil adsorbed was also determined for mica (“Y-2400”) alone. Table 4 shows the measurement results of the amorphous calcium phosphate-coated particles of Examples 1 and 3 to 6 and Comparative Examples 2 to 5 and the measurement result of the mica alone.

(Microscopic observation)
Scanning electron micrographs of Examples 1, 5, 6 and Comparative Examples 1 to 5 are shown in FIGS.
From this figure, in Example 1, the amorphous calcium phosphate-coated particles A are in the same disparity state as the substrate material state, and the fine spherical amorphous calcium phosphate B is uniform over the entire surface of the substrate material. It turns out that it adheres to. Further, the state in which the fine spherical amorphous calcium phosphate is uniformly attached to the entire surface of the base material is the same as in Examples 5 and 6. In addition, since the enlarged scanning electron micrograph of the amorphous calcium phosphate-coated particles of Example 5 is the same as that of Example 6, it is omitted here.
In Comparative Examples 1, 2, 4, and 5, the surface of the base material is roughly covered with a large rod-like amorphous calcium phosphate C, and a base exposed portion D where the base material is exposed is partially seen. . Furthermore, in Comparative Example 3, giant particles E having a diameter of nearly 100 μm, in which many base particles are aggregated, are formed. Furthermore, the surface of the giant particle E of Comparative Example 3 is also roughly covered with a large rod-like amorphous calcium phosphate C, and a substrate exposed portion D where the substrate material is exposed is partially seen.
Such differences in the coating state of amorphous calcium phosphate and the shape of the amorphous calcium phosphate-coated particles are also reflected in the average particle diameters and oil adsorption amounts shown in Tables 3 and 4.

  As described above, when producing amorphous calcium phosphate-coated particles in which a substrate material composed of at least one of scale-like or plate-like mineral particles is coated with amorphous calcium phosphate, the substrate material and an acid having a pH of 1.5 or less To mix the surface of the substrate material with an acid having a pH of 1.5 or less, wash the substrate material treated in the acid treatment step, and disperse the washed substrate material. A washing step for setting the pH of the suspended suspension to 2.0 or more, an alkali step for preparing an alkaline suspension in which the base material washed by the washing step and calcium hydroxide are mixed, created in the alkali step By carrying out a calcium phosphate coating step of adhering amorphous calcium phosphate to the surface of the substrate material by adding phosphoric acid to the prepared alkaline suspension The surface of the substrate material in the amorphous calcium phosphate, can be coated on the wider part, it can be seen that can improve the coverage of the amorphous calcium phosphate-coated particles.

1 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Example 1. FIG. An enlarged photograph of FIG. The enlarged photograph of FIG. 6 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Example 5. FIG. 4 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Example 6. FIG. The enlarged photograph of FIG. 2 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Comparative Example 1. FIG. 4 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Comparative Example 2. FIG. 4 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Comparative Example 3. The enlarged photograph of FIG. 4 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Comparative Example 4. FIG. 6 is a scanning electron micrograph of amorphous calcium phosphate-coated particles of Comparative Example 5. FIG. The powder X-ray-diffraction chart of an amorphous calcium phosphate and crystalline calcium phosphate.

Explanation of symbols

A Amorphous calcium phosphate coated particle B Spherical amorphous calcium phosphate C Rod-shaped amorphous calcium phosphate D Substrate exposed part E Giant particle

Claims (6)

A method for producing amorphous calcium phosphate-coated particles in which a base material composed of at least one of scale-like or plate-like mineral particles is coated with amorphous calcium phosphate,
(1) An acid treatment step of washing the surface of the base material with an acid having a pH of 1.5 or less by mixing the base material and an acid having a pH of 1.5 or less,
(2) The substrate material treated in the acid treatment step is treated with water so that the pH of the suspension in which the substrate material is dispersed in water at a solid content concentration of 0.1 to 50% by mass is 2.0 or more. in the washing step of washing,
(3) An alkaline process for preparing an alkaline suspension in which the base material washed by the washing process and calcium hydroxide are mixed;
(4) A calcium phosphate coating step of coating the surface of the base material with amorphous calcium phosphate by adding phosphoric acid to the alkaline suspension prepared in the alkaline step.
A method for producing amorphous calcium phosphate-coated particles, wherein   The method for producing amorphous calcium phosphate-coated particles according to claim 1, wherein phosphoric acid is used as an acid in the acid treatment step. Either hydrochloric acid, nitric acid, sulfuric acid or citric acid is used as the acid in the acid treatment step, and the substrate material is dispersed in water at a solid content concentration of 0.1 to 50% by weight as the washing in the washing step. The method for producing amorphous calcium phosphate-coated particles according to claim 1 , wherein the suspension is washed with water so that the pH of the suspension is 6.0 or more.   The method for producing amorphous calcium phosphate-coated particles according to any one of claims 1 to 3, wherein a base material using any one of mica, sericite, and talc is used.   5. The water kneading step of kneading the base material and water having a weight 0.1 to 3 times that of the base material using a base material made of talc is performed before the acid treatment step. A method for producing amorphous calcium phosphate-coated particles.   An amorphous calcium phosphate-coated particle produced by the method for producing an amorphous calcium phosphate-coated particle according to any one of claims 1 to 5.