JP2000169121A - Amorphous calcium phosphate slurry and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide sufficient fluidity even at a high solid content concentration of, for example, 15% by weight or more, and have excellent dispersibility and storage stability. A novel amorphous calcium phosphate slurry capable of maintaining a uniform dispersion state without being separated over a period of time, and a method for producing the same. SOLUTION: An aqueous slurry of amorphous calcium phosphate containing a polycarboxylic acid having three or more carboxyl groups or a salt thereof is finely pulverized using a medium stirring mill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to biomaterials such as artificial bone materials and dental repair materials, pharmaceuticals such as calcium reinforcing agents and calcium-containing foods, foods, ion exchange materials, adsorbents, pigments, and the like. Cosmetics, dispersants for suspension polymerization,
The present invention relates to an amorphous calcium phosphate slurry having applicability in a wide range of fields, such as an anti-blocking agent, and a method for producing the same.

[0002]

2. Description of the Related Art Amorphous calcium phosphate is a substance which is widely distributed on the earth in the form of phosphate rock, bones and teeth of living organisms, and is industrially used as an aqueous solution containing a calcium component such as calcium hydroxide. An aqueous solution of a phosphorus component such as phosphoric acid is added to the suspension of
Is adjusted to 6 to 11, an aqueous slurry containing fine amorphous calcium phosphate fine particles having an average primary particle size of about 0.1 μm or less is synthesized.

[0003] The average particle diameter of the particles described in this specification is a value measured by a laser diffraction method. The above-mentioned amorphous calcium phosphate makes use of its biocompatibility with biomaterials such as artificial bone materials and tooth repair materials, pharmaceuticals such as calcium reinforcing agents and calcium-containing foods, and foods. Because of its high safety and high safety, it can be used for ion exchange materials, adsorbents such as filters, pigments, cosmetics, and even as a slurry, it can be used as a dispersant for suspension polymerization of synthetic resins and plastic films. It is expected to be used in various fields such as an anti-blocking agent during production.

However, the fine primary particles of amorphous calcium phosphate generated in the slurry during the above synthesis tend to agglomerate into large aggregates having an average particle size of about 1 to 100 μm. Since the aggregate has extremely low dispersibility in water, the storage stability of the slurry is poor, and water and precipitates (aggregates of amorphous calcium phosphate) are obtained in a short time.
There is a problem that they are separated.

In order to reduce the cost of storage and transportation of the slurry, it is desirable that the solid content be as high as possible. Generally, however, the higher the solid content, the higher the viscosity and the easier the handling becomes. In the case of a slurry of amorphous calcium phosphate, when the concentration of amorphous calcium phosphate as a solid content exceeds about 15% by weight, the fluidity of the slurry is remarkably reduced. It places a heavy burden, making it practically difficult to use, and an additional 20% by weight.
If it exceeds, there is also a problem that it becomes solid and cannot be put to practical use at all.

For this purpose, in particular, the dispersant for suspension polymerization,
An amorphous calcium phosphate, such as an anti-blocking agent, a pharmaceutical, a food, a cosmetic, a UV absorber, or a coating solution for a filter adsorbent, has an average particle size of about 1 dispersed particles.
At present, practical application in a field where it is desired to use an aqueous slurry having a size of not more than μm is not progressing as expected.

[0007]

In order to enhance the dispersibility and storage stability of the apatite-based aqueous slurry and to prevent separation in a short time, for example, Japanese Patent Application Laid-Open No. Hei 9-142817 discloses the use of the above slurry. It is possible to carry out a fine pulverization treatment using a bead mill, and Japanese Unexamined Patent Publication No. 9-301708 discloses a method in which an apatite previously synthesized and separated is re-dispersed in a water-soluble organic solvent, and a stirring mill is used. And grinding and dispersion treatment, respectively, and it is conceivable to divert these treatment methods to a slurry of amorphous calcium phosphate.

However, in the former method, the sedimentation half-life, which is an indicator of the dispersibility and storage stability of the slurry, that is, when the slurry is poured into a fixed-size tube such as a measuring cylinder and allowed to stand, The time required for the volume of the sediment that has settled to the bottom of the water to become half of the volume of the slurry immediately after the injection is extended by about 5 to 25 minutes slightly longer than before, to about 1 hour. The effect is insignificant.

In consideration of industrial use, the slurry is required to be stable for at least several days without causing separation or the like, and the above method is insufficient in its effect. In the latter method, once the step of separating apatite from the synthesized aqueous slurry and redispersing it in an organic solvent increases, not only does productivity lower, leading to cost increase, but also the organic solvent is reduced. The use of a large amount causes a problem in terms of safety, and there is a possibility that the use in medicines and foods is particularly restricted.

Japanese Patent Application Laid-Open No. 9-48672 discloses a method for improving the dispersibility and storage stability of an apatite-based aqueous slurry by adding a chelating agent such as citric acid or a salt thereof to the aqueous slurry. And Japanese Patent Application Laid-Open
Japanese Patent No. 289877 discloses a method in which apatite fine powder is treated with a solution containing citric acid or a salt thereof and then slurried to improve the dispersibility and storage stability.

However, according to studies by the present inventors, when these methods are applied to a slurry of amorphous calcium phosphate, particularly a high-concentration slurry having a solid content of 15% by weight or more, the fluidity at the beginning of production is improved. Although not only cannot prevent the separation of the slurry, but also the separated sediment presents a sludge-like state and cannot be re-dispersed even with stirring, so that the dispersibility and storage stability are not improved at all. Became clear.

It is an object of the present invention to provide sufficient fluidity even when the solid content is as high as 15% by weight or more, excellent dispersibility and storage stability, and a longer period of time after production than before. To provide a novel amorphous calcium phosphate slurry capable of maintaining a uniform dispersion state without being separated over a period of time, and a method for producing the same.

[0013]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors reexamined a method for improving the characteristics of a slurry which has been performed so far. As a result, as a dispersant, a nonionic or cationic dispersant has no effect at all, and an alkyl sulfate dispersant, which is the most common anionic type, or a monocarboxylic acid type (acetic acid, lactic acid or the like) Salts) and dispersants of dicarboxylic acid type (such as oxalic acid or a salt thereof) have no effect.
A carboxylic acid (polycarboxylic acid) or a salt thereof (hereinafter referred to as "polycarboxylic acids" when both are collectively referred to) has a remarkable effect as a dispersant, but is merely a polycarboxylic acid. Is merely added as a dispersant, the precipitate separated from the slurry as described above may exhibit a sludge state, and may not be able to be redispersed even with stirring. In contrast, the above polycarboxylic acids Aqueous slurry of amorphous calcium phosphate added as a dispersant,
When finely pulverized using a medium stirring mill, for example, so that the average particle size of the dispersed particles is 1 μm or less, even if the solid content is as high as 15% by weight or more, it has sufficient fluidity. The present inventors have found that a uniform dispersion state can be maintained without separation even after several days from the production, and the present invention has been completed.

Accordingly, the amorphous calcium phosphate slurry of the present invention is produced by pulverizing an aqueous slurry of amorphous calcium phosphate containing a polycarboxylic acid having three or more carboxyl groups using a medium stirring mill. It is characterized by the following. Further, the method for producing an amorphous calcium phosphate slurry of the present invention is characterized in that an aqueous slurry of amorphous calcium phosphate containing the above-mentioned polycarboxylic acids is finely pulverized using a medium stirring mill.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. The amorphous calcium phosphate slurry of the present invention is produced by pulverizing an aqueous slurry of amorphous calcium phosphate containing a polycarboxylic acid having three or more carboxyl groups as described above using a medium stirring mill. You.

Amorphous calcium phosphate is tricalcium phosphate containing water of crystallization as represented by the general formula: Ca ₃ (PO ₄ ) ₂ .nH ₂ O, and its crystal structure is particularly amorphous. Say quality. In addition, a part of the calcium of the amorphous calcium phosphate,
For example, elements such as barium, strontium, zinc, magnesium, sodium, potassium, iron, aluminum, and titanium may be in solid solution, or part of calcium may be ion-exchanged or replaced by the above elements. A part of PO ₄ is, for example, VO ₄ , Si
It may be substituted by one or more of atomic groups such as O ₄ and CO ₄ . Further, calcium phosphate may be combined with one or more metal oxides. As metal oxides,
For example, but not limited to, titanium oxide, zinc oxide,
Cerium oxide and the like can be mentioned.

The aqueous slurry containing the above-mentioned amorphous calcium phosphate is synthesized as follows. That is, while maintaining the liquid temperature at 50 ° C. or lower, a solution of the phosphorus component is added to the suspension containing the calcium component with stirring to finally adjust the pH of the liquid to 6 to 11, preferably 6 to 8. By adjusting, fine particles of amorphous calcium phosphate in an aqueous medium can be obtained.
An aqueous slurry in which the secondary particles are dispersed is synthesized.

At this time, maintaining the liquid temperature at 50 ° C. or lower is because if the temperature is exceeded, the crystallinity of calcium phosphate is increased and water of crystallization is dropped, so that the activity such as adsorption performance may be reduced. Because. In addition, the final pH of the solution is adjusted to 6 to 11 when the pH is lower than this range, that is, when the acidity is strong, the crystallinity of calcium phosphate also increases, and the water of crystallization drops, resulting in a decrease in activity. On the other hand, if the pH exceeds this range, that is, if the pH is strong, the synthesis reaction of calcium phosphate is insufficient, and a large amount of unreacted substances may remain in the slurry.

In order to adjust the pH to the above range, for example, an acid or an alkali may be added. Examples of the combination of the calcium component and the phosphorus component used in the above step include calcium hydroxide and phosphoric acid, calcium carbonate and sodium phosphate, and calcium hydrogen phosphate and sodium phosphate.

As the aqueous medium, besides water, a mixed solvent of water and a water-soluble organic solvent can be used. However, it is preferable to use water alone in consideration of safety and cost. As described above, the average particle size of the primary particles of the amorphous calcium phosphate contained in the aqueous slurry is about 0.1.
It is preferably 1 μm or less, particularly preferably about 0.01 to 0.06 μm.

In order to adjust the average particle size of the primary particles, for example, when the phosphorus component is added to the suspension containing the calcium component or after the addition in the above-mentioned aqueous slurry synthesis step, The stirring speed or the like may be adjusted. Although the solid content of the slurry is not particularly limited, according to the present invention, as described above, the slurry having a solid content of 15% by weight or more, which has been conventionally difficult to be practically used, has fluidity, Since the dispersibility and storage stability can be significantly improved, the solid content of the slurry can be set higher than before.

However, if the solid content exceeds 80% by weight, it is difficult to maintain the above-mentioned properties even if the constitution of the present invention is employed. It is preferred that In particular, in consideration of actual use, the solid content concentration of the slurry is more preferably about 50% by weight or less even within the above range.

However, it goes without saying that the structure of the present invention can be applied not only to the above-mentioned high-concentration slurry but also to a normal-concentration slurry having a solid concentration of about 14% by weight or less. In this case as well, there is an advantage that the dispersibility and storage stability are dramatically improved as compared with the related art. Examples of the polycarboxylic acids having three or more carboxyl groups, which are added as a dispersant to the slurry, include citric acid and salts thereof as described above, and have a molecular weight of several hundred or more, preferably several thousand to ten. About tens of thousands of high molecular weight polycarboxylates can also be used.

Among them, the salts of citric acid include, for example, alkali metal salts (sodium salt, potassium salt), alkaline earth metal salts (magnesium salt, calcium salt), ammonium salt and the like. These salts may be normal salts in which all three carboxylic acids in the citric acid molecule are converted to salts, or hydrogen salts in which one or two carboxylic acids are not salts but remain carboxylic acids.

Examples of the high molecular weight polycarboxylates include alkali metal salts, alkaline earth metal salts and ammonium salts of high molecular weight polycarboxylic acids such as polyacrylic acid. Specific examples of such high molecular weight polycarboxylates include, but are not limited to, Nopcosperse 44C (trade name) manufactured by San Nopco Co., Ltd.
(Sodium polyacrylate, molecular weight 12000, anion 40%), SN dispersant 5468 (ammonium polyacrylate, molecular weight 12000, anion 4
0%), SN Dispersant 5020 (ammonium polyacrylate, molecular weight 30,000, anion 40)
%), SN Dispersant 5044 (sodium polyacrylate, molecular weight: 12,000, anion: 40%) and the like, or Ceramo D- manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
134 (polyammonium acrylate, molecular weight 1000
0), trade name CELNA E-503 (polyammonium acrylate, molecular weight 10,000) manufactured by Chukyo Yushi Co., Ltd., and the like.

The amount of the polycarboxylic acid to be added depends on the amount of amorphous calcium phosphate 1 as a solid contained in the slurry.
It is specified in parts by weight relative to 00 parts by weight. The lower limit of the preferred range tends to increase according to the solid concentration of the amorphous calcium phosphate, specifically, as the solid concentration increases. This is because the viscosity of the slurry itself is sufficiently low in a system with a low solid content, so that the amount of the polycarboxylic acid added may be small.However, the viscosity of the slurry increases as the solid content increases, and it is practically used. This is because it is necessary to increase the amount of the polycarboxylic acid added to lower the range.

The specific correspondence between the solid content concentration (% by weight) of the amorphous calcium phosphate and the lower limit of the preferable range of the amount of the polycarboxylic acid added is not limited to this, but is not limited thereto. In terms of the addition amount (parts by weight) based on 100 parts by weight of the crystalline calcium phosphate, for example, the solid content concentration is 1
About 0.24 parts by weight for a 2% by weight system, about 0.4 parts by weight for a 14% by weight system, and about 0.5 parts by weight for a 19% by weight system.
It is about 0.68 parts by weight in a system of 5 parts by weight and 25% by weight. In other words, it is preferable that the range of the amount of the polycarboxylic acid added in the system having each solid content concentration is not less than the above lower limit value. If the amount of the polycarboxylic acid added in the system having each solid content is lower than the above lower limit, the fluidity of the slurry may be reduced.

The amount of the polycarboxylic acid to be added is preferably about 10 parts by weight or less, preferably 5 parts by weight or less with respect to 100 parts by weight of the amorphous calcium phosphate in the system having any solid content. Is more preferred.
This is because, even if a large amount of polycarboxylic acid is added beyond this range, no further addition effect can be obtained, and it is economically disadvantageous.

Incidentally, citric acid and many of its salts are supplied in the form of hydrates.
The amount of addition may be set so that the amount in terms of anhydride falls within the above preferred range. In addition, the above-mentioned commercially available high-molecular-weight polycarboxylates are often supplied in the form of a solution dissolved in water, ethanol, or the like in consideration of handling properties and the like. What is necessary is just to set the addition amount of a solution so that the quantity of a pure content (solid content) may be in the said preferable range.

The polycarboxylic acids may be added later to the aqueous slurry synthesized in the above-mentioned synthesis step, or may be added in advance to at least one of the calcium component and the phosphorus component before the synthesis. May be. In the latter case, the polycarboxylic acids not only do not inhibit the reaction of the two components, but also function to prevent the primary particles of amorphous calcium phosphate formed in the slurry from aggregating.

For this reason, especially in a high-concentration slurry having a solid content concentration of more than 20% by weight, a polycarboxylic acid is added to any of the components before the synthesis in advance, so that the non-synthesis can be performed simultaneously with the synthesis. Since it is possible to prevent the agglomeration of the crystalline calcium phosphate and the loss of fluidity, the above-mentioned high-concentration slurry, which had previously been solidified and was difficult to use as a slurry, was put to practical use at the industrial level. There is an advantage that it can be provided.

Next, in the present invention, the aqueous slurry to which the polycarboxylic acids are added as described above is used as a medium stirring mill as described above, and the average particle size of the dispersed particles is as follows:
Preferably, the fine pulverization treatment is performed until the thickness becomes 1 μm or less as described above. As the medium stirring mill, any conventionally known various types such as a screw type, a flow tube type (such as a disk type), a stirring tank type, and an annular type can be used.

Examples of the pulverizing medium used for finely pulverizing the aqueous slurry using the medium stirring mill include metals such as iron and stainless steel, glass, and the like.
Beads and balls made of ceramics such as alumina and zirconia and having a particle size of 5 mmφ or less, particularly 1 mmφ or less are preferable. When the particle size of the grinding medium exceeds 5 mmφ, the processing time required for sufficiently pulverizing the amorphous calcium phosphate in the slurry until the average particle size of the dispersed particles is within the above range is long. It is not preferable in terms of productivity.

The time of the fine pulverization treatment is about 10 to 240 minutes, especially 10 to 120 minutes in consideration of productivity.
Preferably, it is on the order of minutes. As described above, the amorphous calcium phosphate slurry thus produced has sufficient fluidity even at a high solid content of 15% by weight or more, and has excellent dispersibility and storage stability. Thereafter, a uniform dispersion state can be maintained without separation over a longer period than before.

Thus, according to the present invention, practical use in a field where it is desired to use amorphous calcium phosphate in the form of an aqueous slurry in which the average particle size of dispersed particles is about 1 μm or less is desired. It has an unprecedented unique function and effect. Incidentally, the amorphous calcium phosphate slurry of the present invention, regardless of the manufacturing method described above, amorphous calcium phosphate powder previously manufactured, polycarboxylic acids as a dispersant, and an aqueous medium, It can also be produced by subjecting a predetermined amount, a weighed amount, and a mixture, respectively, so as to fall within the ranges of the solid concentration and the addition amount to fine pulverization using a medium stirring mill as described above.

In addition, various design changes can be made without departing from the spirit of the present invention.

[0037]

The present invention will be described below with reference to examples and comparative examples. Example 1 1000 g of calcium hydroxide as a calcium component was added to 6 liters of ion-exchanged water, and stirred and mixed with a stirrer to form a suspension.

Next, while stirring this suspension and maintaining the liquid temperature at 50 ° C. or lower, 85%
Diluent 2 obtained by diluting a phosphoric acid aqueous solution with 3 times ion exchange water
760 g is gradually added dropwise over 2 hours.
By adjusting H to 6 to 11, an aqueous slurry of amorphous calcium phosphate was synthesized. The solid concentration of the obtained slurry was 14.1% by weight.

Next, the aqueous slurry was allowed to stand and separated, a part of the supernatant was removed to adjust the solid concentration to 18.9% by weight, and then trisodium citrate [Na ₃ C ₆ H
₅ O ₇ · 2H the ₂ O], in anhydrous [Na ₃ C ₆ H ₅ O _7] terms, added at a ratio of 2 parts by weight with respect to the amorphous calcium phosphate 100 parts by weight in the aqueous slurry, then the vertical An amorphous calcium phosphate slurry was produced by pulverizing under a condition described below using a medium (disk type) medium stirring mill [batch type desktop sand mill manufactured by Campe Hapio Co., Ltd.].

Pulverization processing conditions Bethel capacity: 2 liters Medium used: zirconia beads (particle diameter 0.5 mmφ) Medium weight: 1500 g Slurry weight: 700 g Stirring disk: 100 mm diameter x 4 Outer peripheral speed: 7.8 m / sec Processing time : 60 minutes Examples 2 to 7 An amorphous calcium phosphate slurry was produced in the same manner as in Example 1 except that the following dispersants were used instead of trisodium citrate.

Example 2: Citric acid [C ₆ H ₈ O ₇ .H ₂ O] Example 3: Triammonium citrate [(NH ₄ ) ₃ (C ₆
H ₅ O ₇ )] Example 4: High-molecular-weight sodium polyacrylate [supra, trade name SN Dispersant 5044 manufactured by San Nopco Co., Ltd.] Example 5: High-molecular-weight ammonium polyacrylate [supra. Example 6: High molecular weight ammonium polyacrylate [Ceramo D-13 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.]
4] Example 7: High molecular weight ammonium polyacrylate [Cerna E-503, trade name, manufactured by Chukyo Yushi Co., Ltd.] Citric acid used in Example 2 above is also an anhydride In terms of [C ₆ H ₈ O ₇ ], 2 parts by weight were added to 100 parts by weight of amorphous calcium phosphate in the aqueous slurry, and triammonium citrate (anhydride) used in Example 3 was As it was, it was added at a ratio of 2 parts by weight to 100 parts by weight of the amorphous calcium phosphate in the aqueous slurry.

The high-molecular-weight dispersants used in Examples 4 to 7 are supplied as solutions dissolved in water or ethanol, respectively. Amorphous calcium phosphate 100
The addition amount of the solution was set so as to be 2 parts by weight with respect to parts by weight. Example 8 In 2 liters of ion-exchanged water, a quencher having a ratio of 2 parts by weight in terms of anhydride [Na ₃ C ₆ H ₅ O ₇ ] based on 100 parts by weight of amorphous calcium phosphate in the aqueous slurry after synthesis. and trisodium _{[Na 3 C 6 H 5 O 7} · 2H 2 O ], plus the calcium hydroxide 1000g as calcium component, stirring at a stirrer, the suspension was prepared by mixing.

Next, while stirring the suspension and maintaining the liquid temperature at 50 ° C. or lower, 85%
Diluent 2 obtained by diluting a phosphoric acid aqueous solution with 3 times ion exchange water
760 g is gradually added dropwise over 2 hours.
By adjusting H to 6 to 11, an aqueous slurry of amorphous calcium phosphate was synthesized. The resulting slurry had a solids concentration of 24.8% by weight, and had sufficient fluidity despite such a high concentration.

Then, this aqueous slurry was finely pulverized using a medium stirring mill under the same conditions as in Example 1,
An amorphous calcium phosphate slurry was produced. Comparative Example 1 Amorphous calcium phosphate was prepared in the same manner as in Example 1 except that the aqueous slurry having a solid content of 18.9% by weight was finely pulverized using a medium stirring mill without adding trisodium citrate. A slurry was produced.

Comparative Example 2 Trisodium citrate was added to an aqueous slurry having a solid concentration of 18.9% by weight, and then stirred and mixed almost uniformly using a stirrer. An amorphous calcium phosphate slurry was produced in the same manner as in Example 1 except that the pulverization was not performed.

Comparative Examples 3 to 5 Amorphous calcium phosphate slurries were produced in the same manner as in Example 1 except that the following dispersants were used instead of trisodium citrate. Comparative Example 3: Sodium acetate [NaC ₂ H ₃ O ₂ ] Comparative Example 4: Sodium lactate [NaC ₃ H ₅ O ₃ ] Comparative Example 5: Sodium oxalate [Na ₂ C ₂ O ₄ ] In any case),
2 parts by weight were added to 100 parts by weight of amorphous calcium phosphate in the aqueous slurry.

The following tests were performed on the amorphous calcium phosphate slurries produced in the above Examples and Comparative Examples to evaluate the characteristics. Dispersion particle size measurement During the production of the amorphous calcium phosphate slurries of Examples and Comparative Examples, before and after pulverization using a medium stirring mill, the average particle size of each dispersion particle was measured by laser diffraction. It was measured by the method. That is, the slurry of each sample was stirred for 10 minutes using a stirrer and then diluted, and the average particle size of the dispersed particles was measured using a laser diffraction type particle size analyzer [both manufactured by Nippon Laser Co., Ltd.
Combination of ELOS-KF and wet dispersion unit SUCELL].

Storage Stability Test The amorphous calcium phosphate slurries of Examples and Comparative Examples were allowed to stand for one week immediately after production and then visually observed to evaluate the storage stability. Coatability test Among the slurries after the above-mentioned storage stability test, those that had fluidity, those that were not separated were left as they were, and those that were separated were re-stirred and dispersed, and then the spray gun was turned on. 1 g of solid content was cut on the surface of a B-flute-sized corrugated honeycomb (cell height: 2.8 mm) cut into a length of 100 mm x a width of 100 mm x a thickness of 10 mm.
And dried at 60 ° C. to produce a filter.

Then, the state from application to after drying was observed to evaluate its coatability. Table 1 shows the above results.

[0050]

[Table 1]

As can be seen from the table, the slurries of Comparative Example 1 in which no dispersant was added and Comparative Examples 3 to 5 in which a monocarboxylic acid-based dicarboxylic acid-based dispersant was used were finely milled using a medium stirring mill. On the contrary, the average particle size of the dispersed particles is increased and the storage stability is reduced by the pulverization treatment, and powder fall occurs from the coating film after coating and drying with the increase in the particle size of the dispersed particles. I understand.

The slurry of Comparative Example 2 to which sodium citrate, which is a polycarboxylic acid, was added as a dispersing agent but was not pulverized using a medium stirring mill was used.
It was found that the separated precipitate was sludge-like and could not be redispersed even with stirring, so that it could not be used for coating.
On the other hand, all of the slurries of the examples were finely pulverized using a medium stirring mill to reduce the average particle size of the dispersed particles to 1 μm or less. It was confirmed that the coating film had stability and could form a good coating film without powder dropping.

Examination of the amount of the dispersant added The solid content was synthesized in the same manner as in Example 1 above.
An aqueous slurry of 1% by weight was supplied to a spray dryer [L-8 manufactured by Okawara Kakoki Kikai Co., Ltd.] by means of a metering pump, and dried and granulated by a spray drying granulation method to obtain an amorphous having an average particle diameter of 10 μm. Calcium phosphate particles were produced.

On the other hand, an aqueous solution prepared by dissolving 1.68 g of sodium citrate as a dispersing agent in 50 ml of ion-exchanged water is divided into 10 units, each having a unit of 5 ml (the amount of sodium citrate in one unit is 0.168 g). ) To 0 units (no addition) to 10 units (total addition)
Until the amount added was changed by one unit at a time.
The above-mentioned amorphous calcium phosphate particles were added to each kind of ion-exchanged water such that the solid content concentration became 12% by weight, 14% by weight, 19% by weight and 25% by weight, respectively. 11 × 4 = 4 after pulverization
Four samples were made. The amount of the amorphous calcium phosphate particles used at each concentration was 70 g (solid content concentration 12% by weight), 84 g (14% by weight), and 122 g, respectively.
(19% by weight) and 172 g (25% by weight).

Then, the slurry of each sample was stirred,
Even though the viscosity was somewhat high, stirring was as easy as in Example 1. The addition amount of sodium citrate in the sample with the smallest number of addition units was determined by adjusting the amount of amorphous calcium phosphate (ACP) 100 in the slurry. When converted to parts by weight relative to parts by weight, the results in Table 2 below were obtained.

[0056]

[Table 2]

According to the above table, a suitable addition amount of sodium citrate as a dispersant is 10% of amorphous calcium phosphate.
In terms of parts by weight based on 0 parts by weight, 0.24 parts by weight or more for a system having a solid concentration of 12% by weight and 0.1% for a system having a solids concentration of 14% by weight.
4 parts by weight or more, 0.55 parts by weight or more in a system of 19 parts by weight,
And it was confirmed that it changed according to the solid content concentration of the slurry to 0.68 parts by weight or more in the system of 25% by weight.

[0058]

As described in detail above, according to the present invention, even if the concentration is high, it has sufficient fluidity, excellent dispersibility and storage stability, and can be produced for a longer period of time after production. It is possible to provide a novel amorphous calcium phosphate slurry capable of maintaining a uniform dispersion state without being separated over the whole, and a method for producing the same.

Therefore, according to the present invention, the amorphous calcium phosphate is dispersed with an average particle diameter of about 1 μm.
m, which is an unprecedented unique function and effect that it can be put to practical use in a field where it is desired to use it in the state of an aqueous slurry of not more than m.

Claims (6)

[Claims] 1. A non-aqueous slurry of amorphous calcium phosphate containing a polycarboxylic acid having three or more carboxyl groups or a salt thereof, which is produced by finely pulverizing the slurry using a medium stirring mill. A crystalline calcium phosphate slurry. 2. The aqueous slurry as a solid content,
The amorphous calcium phosphate slurry according to claim 1, wherein the concentration of the amorphous calcium phosphate is 15% by weight or more. 3. An amorphous calcium phosphate slurry comprising an aqueous calcium phosphate slurry containing a polycarboxylic acid having three or more carboxyl groups or a salt thereof, which is finely pulverized using a medium stirring mill. Manufacturing method. 4. An aqueous slurry is prepared by adding a solution of a phosphorus component to a suspension of a calcium component with stirring while maintaining the temperature of the solution at 50 ° C. or lower, and finally adjusting the pH of the solution to 6 to 11. The method for producing an amorphous calcium phosphate slurry according to claim 3, wherein the slurry is adjusted and synthesized. 5. The method for producing an amorphous calcium phosphate slurry according to claim 4, wherein a polycarboxylic acid having three or more carboxyl groups or a salt thereof is added to the synthesized aqueous slurry. 6. The method for producing an amorphous calcium phosphate slurry according to claim 4, wherein a polycarboxylic acid having three or more carboxyl groups or a salt thereof is added to at least one of the calcium component and the phosphorus component before synthesis.