JPH07267617A - Production of tetracalcium phosphate, tetracalcium phosphate obtained by the same method and composition for cement containing the same tetracalcium phosphate - Google Patents

Abstract

PURPOSE:To provide a method for producing tetracalcium phosphate by which the high-purity tetracalcium phosphate can simply be produced by using a well- known calcium raw material and a phosphoric acid raw material, obtain the tetracalcium phosphate prepared by this method and produce a composition for a cement consisting essentially of the tetracalcium phosphate. CONSTITUTION:This method for producing tetracalcium phosphate from calcium raw material powder and phosphoric acid raw material is to blend both the raw materials so as to provide 2 molar ratio of Ca/P, then add and mix a titanium compound in an amount of 0.1-10 pts.wt. based on 100 pts.wt. theoretically produced amount of the tetracalcium phosphate expressed in terms of TiO2 therewith, then, as necessary, press form the prepared mixture and bake the resultant mixture in an atmosphere at >=1350 deg.C for >=1hr. Thereby, the produced massive tetracalcium phosphate has 2.5-3.5g/cm<3> bulk density or tetracalcium phosphate powder has <=30mum grain diameter and 1.0-2.0g/cm<3> bulk density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing tetracalcium phosphate, tetracalcium phosphate obtained by this method, and a cement composition containing this tetracalcium phosphate.

[0002]

2. Description of the Related Art Tetracalcium phosphate (hereinafter, abbreviated as 4CP) is a calcium phosphate-based compound that is a main component of bones and teeth in our living body, but it has high chemical activity and various inorganic acids at room temperature. It is known that it easily reacts with an aqueous solution such as a homopolymer or copolymer of an unsaturated organic acid or a physiological saline solution and hardens, and is expected to be used in the fields of medicine and dentistry. There is.

For example, in the field of surgery and orthopedics, for medical use, it is considered to be used as a repairing material or a bone filling material generated in a bone defect or a void due to a traffic accident, excision of a bone tumor, etc. For inlays,
Adhesive used for adhesion of crowns, filler material of composite resin used for cavity repair, etc., lining and table covering used for pulp protection or role of dentin replacement layer, root used for root canal treatment Tube filling material, pit and fissure filling material used to prevent early caries in infants, temporary sealing material used as temporary filling material during treatment, periodontal pocket filling material used for periodontal disease treatment, marginal alveolar bone It has been considered to be used as a bone graft material for repairing defects of bone.

By the way, hitherto, hydroxyapatite (hereinafter referred to as HAP), tricalcium phosphate (hereinafter referred to as TCP) and the like have been used as bone filling materials in the medical field, however, HAP has biocompatibility. However, since it is a stable substance by itself, it does not react with an acid and therefore cannot be used in a self-curing cement composition. On the other hand, TCP has lower biocompatibility than HAP, but it is used as a composition for self-hardening cement by reacting with acid, but 4CP is said to be superior in terms of new bone formation ability.

In the field of dentistry, Zn has been conventionally used.
Restorative materials that combine O, SiO ₂ , phosphoric acid, and polyacrylic acid have been used, but hardened bodies made of these compositions are not biocompatible because they are different from tooth and bone components. There is a problem.

Therefore, in recent years, 4CP, which is said to have a biocompatibility equal to or higher than that of HAP or TCP and has a new bone formation ability superior to that of HAP or TCP, has been attracting attention. This 4CP is said to be a precursor of HAP, which is the main component of the bones and teeth that make up the human body, and is known to have the property of being gradually absorbed in the living body and being replaced with HAP.

In the production of 4CP, CaCO ₃ , CaO, Ca (OH) ₂ as a calcium raw material and P ₂ O ₅ , H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) as a phosphorus raw material. ₂ H
As a substance containing both PO ₄ , Ca and P sources, Ca
HPO ₄ .2H ₂ O, CaHPO ₄ , Ca ₂ P ₂ O _7, etc. are used. As a method of producing 4CP using these raw materials, for example, 1) CaHPO ₄ .2H ₂ O (hereinafter referred to as brushite) is heated at 500 ° C. for 2 hours to obtain γ-Ca ₂ P ₂ O ₇ ( Hereinafter, a method in which CaCO ₃ is mixed in an amount of 2 times the molar amount of calcium pyrophosphate) and calcined at 1680 ° C. for 1 hour (JP-A-61-2)
70249), 2) CaCO ₃ and CaHPO ₄ or CaHPO ₄ .2H ₂ O
Are mixed in an equimolar ratio and baked at 1500 ° C. or higher for 1 hour or longer (for example, JP-A-64-61408 and JP-A-1-96).
No. 006, etc.) are known. The former method is not efficient because it undergoes a two-step reaction of powdering calcium pyrophosphate obtained by once firing brushite at around 500 ° C. and further firing it with CaCO ₃ in a molar ratio. The latter method described above is for avoiding such a two-step reaction, but in this method, 4CP alone is not obtained unless it is rapidly cooled at a rate of 10 ° C / min or more up to 500 ° C after firing. Moreover, since it contains a large amount of HAP, there is a problem that high-purity 4CP cannot be stably obtained.

Recently, it has been found that a small amount of an aluminum compound is added during the production of 4CP to reduce the HAP content (Japanese Patent Laid-Open Nos. 2-18705 and 3-159946). The 4CP thus obtained also has the drawback of low crystallinity and poor storage stability. The 4CP produced in this manner is also not sufficient as a dental material in terms of low bulk density and compressive strength of the molded body, and the color of the fired body is pale for use as a dental material. It was a problem because it was different from the color tone of quality.

[0009]

The problem to be solved by the present invention is to provide a method for easily producing high-purity and high-hardness tetracalcium phosphate using known calcium raw materials and phosphorus raw materials, and It is intended to provide a composition for cement containing tetracalcium phosphate as a main component.

[0010]

Thus, according to the invention of "Claim 1" of the present application, "a calcium raw material powder and a method for producing tetracalcium phosphate from a phosphorus raw material powder are used. Incorporate so that P = 2 molar ratio, and theoretically produce tetracalcium phosphate 1
0.1 to 10 of titanium compound in terms of TiO ₂ with respect to 00 parts by weight
By adding and mixing parts by weight, and calcining this mixture in an atmosphere of 1350 ° C or higher for 1 hour or longer, a powdery tetracalcium phosphate having a particle size of 30 µm or less and a bulk density of 1.0 to 2.0 g / cm ³ is obtained. For producing tetracalcium phosphate characterized by
Will be provided.

The present invention also comprises a method for producing massive tetracalcium phosphate, that is, a "calcium raw material powder and a method for producing tetracalcium phosphate from phosphorus raw material powder, as shown in claim 2 of the present application, Both of these raw materials were blended so that the Ca / P = 2 molar ratio was obtained, and 0.1 to 10 parts by weight of a titanium compound in terms of TiO ₂ was added and mixed with respect to 100 parts by weight of the theoretical production amount of tetracalcium phosphate. After this mixture is press-molded, it is baked in an atmosphere of 1350 ° C. or higher for 1 hour or longer to obtain a bulk density of 2.5 to 3.5 g / cm ^3.
The method for producing tetracalcium phosphate, characterized in that the block-shaped tetracalcium phosphate is obtained.

In any of the above production methods of the present invention, examples of the calcium raw material powder and the phosphorus raw material powder include CaCO ₃ , CaO, Ca (OH) ₂ , P ₂ O ₅ , and H ₃ P.
O ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , CaHPO ₄ ·
2H ₂ O, CaHPO ₄ , Ca ₂ P ₂ O _{7 and the} like known in the art can be used as they are. Of these, CaH
A combination of PO ₄ .2H ₂ O and CaCO ₃ is preferable in terms of safety and raw material cost.

Regarding the particle diameters of the calcium raw material powder and the phosphorus raw material powder, as shown in claim 4 of the present application, the calcium raw material powder has an average particle diameter of 1 to 30 μm, and the phosphorus raw material powder mentioned above. Average particle size 1-40μ
The thing of m is preferable from the viewpoint of crystallinity, purity and hardness of the finally obtained tetracalcium phosphate (hereinafter, abbreviated as 4CP).

In the manufacturing method of the present invention, a titanium compound is added to the mixture of the calcium raw material powder and the phosphorus raw material powder. The addition of this titanium compound is one of the features of the present invention, and is a quenching operation that was conventionally required in the production of 4CP (that is, 10 ° C / ° C in the range up to 500 ° C after firing).
In addition to not requiring the operation of cooling at a speed of about a minute,
It is possible to produce 4CP at a relatively low temperature, suppress a large amount of HAP content, etc., and produce high-purity 4CP. Examples of the titanium compound used in the present invention include TiO ₂ , Mg ₂ TiO ₄ ,
PbTiO ₃ , CaTiO ₃ , FeTiO ₃ , TiN, TiC, Ti
B, TiB ₂ , TiSi and the like. These are used alone or in combination of two or more. Of the above titanium compounds, Ti
O ₂ meets Japanese Pharmacopoeia standards and obtains 4 CP
Is preferable from the viewpoint of safety when it is used as a so-called biomedical restorative material in the fields of medicine and dentistry. In the production method of the present invention, the titanium compound is preferably used in the form of powder having a particle size of 1 μm or less, and the average particle size is 0.2
It is preferably about μm. When the titanium compound is titanium oxide, as shown in the claim 4 of the present application, the particle size is 0.1
It is preferably about 1.0 μm. If it is smaller than 0.1 μm, it is not economical, and if it is 1.0 μm or more, a large amount must be used, which allows a large amount of impurities to be mixed in, which is not preferable in these respects.

In the production method of the present invention, the calcium raw material and the phosphorus raw material are blended so as to have a Ca / P = 2 molar ratio. When it is less than 2 mole ratio, HAP is produced, and when it is more than 2 mole ratio, CaO is produced, which are not preferable.

The above titanium compound is the theoretical production amount of 4CP.
It is used in a proportion of 0.1 to 10 parts by weight converted to TiO ₂ with respect to 100 parts by weight. When the addition amount of the titanium compound is less than the above 0.1 parts by weight, the fired body obtained by spontaneously cooling to room temperature in the furnace after firing does not become 4CP alone and contains a large amount of HAP. become. When the amount of the titanium compound added is more than 10 parts by weight, not only is the effect of the titanium compound in the obtained fired product increased and the biocompatibility is decreased, but the firing is too accelerated. There is also a possibility that melting will occur.

In the manufacturing method of the "claim 1" and "claim 2" of the present application, the calcium raw material, the phosphorus raw material and the titanium compound are uniformly mixed in, for example, a ball mill or the like and then subjected to a firing treatment. In the case of the manufacturing method according to the "claim 2" of the present application, the mixture is subjected to press molding before being subjected to the firing treatment. The pressure of this press molding is 10
~ 500 kgf / cm ² can be mentioned. The higher the pressing pressure is, the higher the density is. However, in view of the bulk density of the powder obtained by crushing the fired body after press molding, the pressure range normally used is sufficient. When performing the above press molding,
A small amount of purified water, a CMC solution, an MC solution, or other non-biologically harmful substance is generally used as a binder in the above mixture. In the manufacturing method of the present invention, the firing treatment has a temperature of 13
The treatment time is set to 1 hour or longer at 50 ° C or higher. Temperature is 1350
If the temperature is lower than 0 ° C. or the treatment time is shorter than 1 hour, unreacted portions may remain, which is not preferable.
Further, if it is 1600 ° C. or higher, it is not preferable because it melts. After the above-mentioned firing treatment, it is naturally cooled in the furnace to room temperature, but this cooling operation may be rapidly cooled at a rate of about 10 ° C / minute as in the conventional case.

4CP obtained as described above is HA
The P content is very low, the purity is high, the porosity is low, the crystallinity is excellent, and it may be in any form such as powder, granules, and lumps. Moreover, the bulk density (that is, the fired body) is 2.5 to 3.5 g / cm ³ , and the average particle size is 30.
In the case of powder of μm or less, the bulk density is 1.0 to 2.0 g / cm ^3, which is higher than that of 4CP obtained by the conventional production method, it is extremely hard and toughened, and it has excellent compressive strength. It is a highly yellowish yellow one.

The 4CP obtained by the above method can be provided as a raw material for a bio-restorative material used in the fields of medicine, dentistry and the like due to its purity, hardness and color tone. Therefore, according to the invention of "Claim 6" of the present application, the powder obtained by pulverizing 4CP obtained by the above method to have an average particle size of 30 µm or less, inorganic acid and carboxyl group Containing at least one organic acid, one or more acid components selected from the group consisting of homopolymers of polyacrylic acid and copolymers thereof, the main component being the acid component with respect to the tetracalcium phosphate powder. Provided is a composition for cement, which is used in a proportion of 20 to 40% by weight.

In the cement composition of the present invention, 4C
P is used as a powder having an average particle size of 30 μm or less. As the above-mentioned inorganic acid, those known in the art are used, and examples thereof include phosphoric acid and the like, but the inorganic acid is not limited thereto, and any one can be used as long as it is harmless to the living body. The above-mentioned phosphoric acid is preferable because it enhances the compressive strength. Examples of the organic acid containing two or more carboxyl groups include malic acid, citric acid, tartaric acid, malonic acid, itaconic acid, lactic acid, tannic acid and succinic acid, with malic acid and citric acid being preferred. The polyacrylic acid homopolymer or copolymer thereof preferably has an average molecular weight of 5,000 to 80,000, more preferably 10,000 to 50,000.

The above-mentioned acid component may be used as a solid as it is, or may be used as an aqueous solution known in the art. In any case, it is prepared so that the acid component (as solid) is 20 to 40% by weight based on the 4CP powder. The composition for cement of the present invention may be prepared as a powder or granule, or may be prepared as an aqueous composition or a paste composition.

When prepared into an aqueous composition, the 4C of the present invention
It is preferable that P is adjusted to a powder / liquid ratio of 1.0 to 2.0 (gram ratio). When preparing an aqueous composition,
The above-mentioned acid component may be used as an aqueous solution, and in this case, it is adjusted to a solution concentration known in the art. This concentration is, for example, 30 to 60% by weight. In this case, 60% by weight
If the content is more than 30% by weight, the curing time is shortened when the obtained cement composition is used as a dental cement, and if it is less than 30% by weight, the compressive strength of the cured product of the obtained cement composition decreases. However, the disintegration rate becomes high, which is not preferable. In the case of preparing the above-mentioned aqueous composition, when relatively mechanical strength is not required, the acid component may be used in a ratio sufficiently smaller than the above-mentioned mixing ratio. You may add and mix 0.8-1.0 weight% sodium chloride solution. Further, brushite or the like may be optionally added to the aqueous composition for the purpose of adjusting pH or adjusting the reaction rate.

When the composition for cement of the present invention is used as a paste-like composition, it is particularly preferably prepared as a one-component curable paste-like composition. In this case, as an example of blending, the above 4CP powder is 30 to 50% by weight, organic acid is 5 to 15% by weight, polyhydric alcohol is 25 to 35% by weight.
Etc.

The composition for cement of the present invention may contain Ba for the purpose of imparting X-ray contrast property and antibacterial property, if necessary.
SO ₄ , BaCO ₃ , (BiO) ₂ CO ₃ , CHI _{3 and the} like may be added. In addition, the composition for cement of the present invention may optionally contain a non-harmful component such as MgO, SiO ₂ , ZO ₂ and ZrO ₂ as a preparation agent.

[0025]

The present invention will be described in detail below with reference to the illustrated embodiments, but the present invention is not limited thereto. Example 1 A mixture of CaHPO ₄ .2H ₂ O and CaCO ₃ in a molar ratio of _{2 and} 1.5 parts by weight of TiO ₂ added to 100 parts by weight of theoretically produced tetracalcium phosphate was homogenized in a ball mill. After mixing, press mix (30-60
kgf / cm ² ) and then subjected to firing treatment at 1500 ° C. for 2 hours under atmospheric pressure in a firing furnace, and then naturally cooled to room temperature in the furnace. Table 1 shows the bulk density of the obtained fired molded body. next,
Grind the above-mentioned baked molded product in an automatic mortar for 7 hours, and
The powder was classified to 27 μm or less. Table 1 shows the bulk density of this classified powder. When this classified powder was subjected to X-ray diffraction, the X-ray diffraction chart shown in FIG. 1 was obtained. According to the chart, the highest first peak (A) among the 4CP peaks is obtained very sharply. From the above X-ray diffraction chart, the intensities of the first peak of 4CP and the peak (B) of HAP (hereinafter abbreviated as HAP) were obtained, and the relative ratio was calculated from these, and this was expressed as the ratio of 4CP generation. Shown in 1. The HAP peak (B) in the X-ray diffraction chart has the diffraction angles (2θ) of the fourth peak because the first, second, and third peaks overlap with the 4CP peak.
Was used to measure its strength. From the above production rate results, it can be seen that high-purity 4CP is produced by this production method.

Example 2 A fired molded body was obtained in the same manner as in Example 1 except that after firing, it was taken out of the furnace and rapidly cooled to room temperature at a rate of 10 ° C./min.
Table 1 shows the bulk density of this fired molded product. Further, this fired molded body was classified into particles having a particle size of 27 μm or less in the same manner as in Example 1 to obtain powder. The bulk density of this classified powder is also shown in Table 1. The classified powder was subjected to X-ray diffraction to obtain an X-ray diffraction chart shown in FIG. The production ratio of 4CP was determined from the chart in the same manner as in Example 1, and the results shown in Table 1 were obtained. From the result of the production ratio, it is found that high-purity 4CP is produced by this production method.

Example 3 The same process as in Example 1 was carried out except that the addition amount of TiO ₂ was 3.0 parts by weight to obtain a fired molded product and its classified powder. These bulk densities are shown in Table 1. The X-ray diffraction chart of this classified powder is shown in FIG. 3, and the production ratio of 4CP obtained therefrom is shown in Table 1. From this result, it is understood that high-purity 4CP is produced by this production method.

Comparative Example 1 A fired compact and its classified powder were obtained by the same procedure as in Example 1 except that the titanium compound (TiO ₂ ) was not added. These bulk densities are shown in Table 1. The X-ray diffraction chart of this classified powder is shown in FIG. 4, and it can be seen that the growth of the fourth peak of HAP is remarkable and that it is substantially a complex of HAP and 4CP. 4 obtained from this chart
Table 1 shows the production rate of CP.

Comparative Example 2 A fired molded product and its classified powder were obtained by the same process as in Example 1 except that TiO ₂ was changed to Al ₂ O ₃ . These bulk densities are shown in Table 1. Further, the X-ray diffraction chart of this classified powder is shown in FIG. 5, and it can be seen that the first peak (A) of 4CP is lower than that of the example and the crystallinity is poor. Further, although the fourth peak of HAP was suppressed to a relatively low level, its production was recognized, and the production rate of 4CP calculated from this chart is shown in Table 1.

Comparative Example 3 The same procedure as in Example 1 was carried out except that the amount of Al ₂ O ₃ added was 3.0 parts by weight to obtain a fired molded product and its classified powder. These bulk densities are shown in Table 1. Further, the X-ray diffraction chart of this classified powder is shown in FIG. 6, and it can be seen that the first peak (A) of 4CP is lower than that of the example and the crystallinity is poor. Further, although the main peak of HAP was suppressed to a relatively low level, its production was recognized, and the production rate of 4CP calculated from this chart is shown in Table 1.

[0031] From the above results, it can be seen that the fired molded product and classified powder obtained by the present invention have high bulk density, and thus have low porosity and high mechanical strength. In addition, conventional powders have high bulk and are difficult to mix with liquid agents, whereas when the classified powder of the present invention is kneaded with liquid agents, they are low in volume and easy to mix, and have excellent reproducibility of desired physical properties. I understand that. Further, according to the present invention, not only is the ratio of impurities (HAP) in the fired product lower than that of the fired product obtained by the conventional manufacturing method,
3 is compared with FIGS. 4 to 6, it can be seen that the fired molded body and classified powder obtained by the present invention have high peaks and excellent crystallinity.

Example 4 Each classified powder obtained in Examples 1 to 3 and Comparative Examples 1 to 3 and the following two aqueous solutions: a) 45 wt% malic acid aqueous solution b) 20 wt% malic acid + 20% by weight citric acid + 6% by weight polyacrylic acid copolymer (copolymerization ratio = acrylic acid 6: itaconic acid 4) aqueous solution was mixed at a [powder / liquid] ratio (gram ratio) shown in Table 2 below. In accordance with JIS T6602 Dental Zinc Phosphate Cement Standard Consistency Testing Method, the standard consistency is determined to prepare each cement composition, and these are cured to measure their curing time and compressive strength. The results shown in Table 2 below were obtained.

[0033]

From the results shown in Table 2, it is understood that the cement hardened products obtained in the examples of the present invention have excellent compressive strength. Therefore, it is understood that the composition for cement of the present invention exhibits sufficient mechanical strength even when used as a bio-restorative material represented by a dental material. Therefore, the cementitious composition of the present invention enables use of 4CP in the medical and dental fields where the application range has been limited due to insufficient mechanical strength. Moreover, the fact that the curing time is slightly longer than that of the conventional cement composition means that the operation time by the operator can be taken longer, and the kneaded product of the cement composition can be more effectively used. It is possible to accurately fill the filling target site.

Example 5 The classified powder obtained in Example 1 and the following aqueous solution were kneaded at a [powder / liquid] ratio (gram ratio) shown in Table 3 below to prepare a cement composition, The consistency was determined, this was cured and the curing time was measured, and the results shown in Table 3 below were obtained. Aqueous solution: 4% by weight citric acid + 2% by weight malic acid + 0.2% by weight phosphoric acid + 0.85% by weight sodium chloride As a result, in the case of a composition for cents which is applied to applications where relatively high mechanical strength is not required, 4CP of the present invention is used as described above, and the mixing ratio of the acid component to this 4CP is reduced, and the inorganic salt aqueous solution is used. It is possible to provide a cement composition which has a long curing time by being mixed with.

[0036]

According to the present invention, by adding the titanium compound, the firing temperature can be lowered and the firing time can be shortened, so that the production can be performed with low power consumption. It is no longer necessary to perform the quenching operation and dehumidifying / drying in the firing furnace that were conventionally performed during the production of 4CP. Therefore, it is possible to manufacture in a normal firing furnace without the need for a firing furnace with a special configuration, and in the firing furnace. Since it can be naturally cooled and taken out, it can be manufactured easily and safely.

Since the production method of the present invention hardly absorbs moisture in the atmosphere even if the cooling rate is slow, it is possible to suppress the production of HAP and produce 4CP of high purity and stable quality. Moreover, when titanium oxide is used as the titanium compound, 4CP having high crystallinity and excellent storage stability and high commercial value can be obtained. 4CP obtained by the production method of the present invention has a high bulk density and a high purity and is also pale yellow, and is suitably used not only as a dental material but also as a bioremediation material. When it is used as a dental material, it is possible to obtain a material that is close to the tooth structure and has high aesthetics.

Furthermore, 4 obtained by the production method of the present invention
The cement composition using CP, when kneaded with various liquid agents, has a slightly longer curing time and higher compressive strength of the cured product than conventional ones. From this point as well, it is a dental material. As a matter of course, it is possible to provide a material suitable as a general bioremediation material.

[Brief description of drawings]

1 is an X-ray diffraction chart of 4CP of the present invention manufactured in Example 1. FIG.

2 is an X-ray diffraction chart of 4CP of the present invention manufactured in Example 2. FIG.

FIG. 3 is an X-ray diffraction chart of 4CP of the present invention manufactured in Example 3.

4 is an X-ray diffraction chart of 4CP manufactured in Comparative Example 1. FIG.

5 is an X-ray diffraction chart of 4CP manufactured in Comparative Example 2. FIG.

6 is an X-ray diffraction chart of 4CP manufactured in Comparative Example 3. FIG.

Claims (6)

[Claims] 1. A method for producing tetracalcium phosphate from a calcium raw material powder and a phosphorus raw material powder,
Both of these raw materials were blended so that the Ca / P = 2 molar ratio was obtained, and 0.1 to 10 parts by weight of a titanium compound in terms of TiO ₂ was added and mixed with respect to 100 parts by weight of the theoretical production amount of tetracalcium phosphate. By firing this mixture in an atmosphere of 1350 ° C or higher for 1 hour or longer, a particle size of 30 μm or less and a bulk density of 1.0
A method for producing tetracalcium phosphate, which comprises obtaining powdery tetracalcium phosphate at about 2.0 g / cm ³ . 2. A method for producing tetracalcium phosphate from a calcium raw material powder and a phosphorus raw material powder,
Both of these raw materials were blended so that the Ca / P = 2 molar ratio was obtained, and 0.1 to 10 parts by weight of a titanium compound in terms of TiO ₂ was added and mixed with respect to 100 parts by weight of the theoretical production amount of tetracalcium phosphate. The bulk density can be obtained by press-molding this mixture and then firing it in an atmosphere of 1350 ° C or higher for 1 hour or longer.
A method for producing tetracalcium phosphate, which comprises obtaining a mass of tetracalcium phosphate of 2.5 to 3.5 g / cm ³ . 3. The method for producing tetracalcium phosphate according to claim 1, wherein the titanium compound is titanium oxide. 4. The calcium raw material powder has an average particle diameter of 1 to 30 μm, and the phosphorus raw material powder has an average particle diameter of 1 to 40 μm.
4. The method for producing tetracalcium phosphate according to claim 3, wherein the particle size of titanium oxide is 0.1 to 1.0 μm. 5. Tetracalcium phosphate obtained by the production method according to claim 1. 6. A powder obtained by pulverizing the tetracalcium phosphate according to claim 5 to have an average particle size of 30 μm or less, an inorganic acid, an organic acid containing two or more carboxyl groups, a homopolymer of polyacrylic acid, and For cement, which comprises, as a main component, at least one acid component selected from the group consisting of the copolymers, and the acid component is used in a ratio of 20 to 40% by weight based on the tetracalcium phosphate powder. Composition.