JPS6237005B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dicalcium phosphate dihydrate (molecular formula: CaHPO ₄ .2H ₂ O) composition suitable for tooth brushing, and a method for producing the same. Conventionally, dicalcium phosphate dihydrate has been produced by two methods: a direct method in which a phosphoric acid solution and a calcium salt are reacted, and a double decomposition method in which an alkali metal phosphate and a calcium salt are reacted in an aqueous solution. As a method for producing dicalcium phosphate using the latter double decomposition method, for example, the crystals of dicalcium phosphate dihydrate produced by the method disclosed in Japanese Patent Publication No. 45-8643 are oblate crystals with a thickness of 1 to 2 μm. When crushed and used as a toothpaste base, the bulk specific gravity is as small as 0.6 g/cc or less, so it exhibits dilatant properties and has the disadvantage of poor abrasiveness. On the other hand, if the bulk specific gravity is too high, the kneaded product will not stain the skin, so it is generally said that the preferred bulk specific gravity of dicalcium phosphate dihydrate for toothpaste is in the range of 0.7 to 1.0 g/cc. is adjusted by the size of the raw material calcium phosphate, grinding method, classification, etc. As a result of repeated research on dicalcium phosphate dihydrate, which has physical properties suitable as a toothpaste base material, the present inventors found that dicalcium phosphate dihydrate obtained by the reaction of an alkali metal phosphate and a calcium salt. It was discovered that the bulk specific gravity and abrasiveness of dicalcium phosphate were largely influenced by the shape of the dicalcium phosphate dihydrate particles, and that the above-mentioned alkali metal phosphate and calcium salt were reacted at a reaction temperature of 40°C or less. dicalcium phosphate 2
When producing water salt, the shape of dicalcium phosphate dihydrate is columnar to plate crystal at pH 2.5 to 3.5, and
It was found that flat crystals can be obtained in the range of 3.5 to 5.0. The present inventors have recently discovered that this columnar crystal ~
It was discovered that a mixture of plate crystals and flat crystals is excellent for toothpaste, and the present invention was developed based on this discovery. That is, the present invention relates to a dicalcium phosphate dihydrate composition for toothpaste containing a mixture of columnar to plate-like dicalcium phosphate dihydrate and flat crystal dicalcium phosphate dihydrate. . The thickness of the above columnar crystals to plate crystals is 10~
15 μm, flat crystals are 1 to 2 μm thick,
As mentioned above, in the reaction of alkali metal phosphate and calcium salt at below 40℃,
Obtained by adjusting the pH to 2.5 to 3.5 and 3.5 to 5.0. The mixing ratio of columnar to plate crystals and flat crystals is 5:5
The range is preferably 9:1, more preferably 6:1.
The ratio is 4 to 8:2. The present inventors have also discovered that a mixture of columnar to plate-like crystals and flat crystals of dicalcium phosphate dihydrate can be obtained by separately producing crystals of each shape as described above and mixing them. It has been found that it can be suitably produced from a phosphate and a calcium salt by a series of methods. That is, an alkali metal phosphate and a calcium salt are reacted at a reaction temperature of 40° C. or less at a pH of 2.5 to 3.5 in the first stage, and an alkali substance is added in the second stage to adjust the pH to 3.5 to 5.0. It is something. By adjusting the pH of the first and second stages of the reaction, the mixing ratio of columnar to plate crystals and flat crystals can be adjusted as appropriate.
Can be adjusted. To explain the reaction of the present invention more specifically, in the solution reaction between an alkali metal phosphate and a calcium salt, in the first step, an acid such as a mineral acid is added to adjust the pH.
Adjust the temperature to 2.5 to 3.5 and allow the reaction to proceed while stirring with a stirrer. The reaction temperature at this time is preferably kept at 40°C or lower. When the metathesis reaction progresses and dicalcium phosphate dihydrate crystals are formed and the reaction is completed, an alkaline substance is added in the second step to make the slurry.
The pH is raised to 3.5 to 5.0, the solubility of dicalcium phosphate dihydrate is decreased, and crystals of dicalcium phosphate dihydrate are precipitated. Thereafter, the dicalcium phosphate dihydrate crystals precipitated in the first and second stages are separated using a conventional separation means, such as a filter, and then dried. Dicalcium phosphate 2 obtained in this way
Water salt has columnar to plate-like crystals precipitated in the first stage,
It is a mixture of flat crystals precipitated in the second stage, with an average thickness of 5 to 10 μm and a bulk specific gravity of 0.85.
g/cc, and has extremely excellent polishing power and kneading properties. An important factor in the reaction conditions in the method of the present invention is the reaction pH.
and temperature. Regarding the pH in the solution reaction between alkali metal phosphate and calcium salt, a range of 2.5 to 3.5 is appropriate for the first reaction tank; if the pH is lower than this, the dicalcium phosphate dihydrate produced in the first reaction tank is The solubility of the tooth powder increases, and when the pH is set to 3.5 to 5.0 in the second reaction tank, more flat crystals crystallize, resulting in poor tooth brushing properties. On the other hand, if the reaction pH is 3.5 or higher, the crystals become mostly oblate crystals, and the dentifrice properties deteriorate as described above. Follow. The pH range of the first reaction tank is preferably 2.5 to 3.5.
It is 2.7-3.2. Next, the PH range in the second reaction tank is
It is 3.5 to 5.0, and if it is over 5.0, some calcium apatite will be generated, resulting in very poor tooth brushing properties. In addition, even if the reaction pH is within the range of 4.5 to 5.0, some calcium apatite will be produced if an alkaline substance is added locally, but if the addition of this alkaline substance is sprayed over the entire reaction tank, calcium apatite will be formed. can be prevented. Therefore, the pH range of the second reaction tank is 3.5 to 5.0, preferably 4.0 to 4.5. Regarding the reaction temperature, when it exceeds 40°C, anhydrous salt of dicalcium phosphate is produced. In particular, when performing the reaction at a pH of 3.0 or less in the first reaction tank, the temperature should be 35℃.
The following must be done. On the other hand, the reaction PH
If it is 3.0 or higher, it should be done at 40℃ or below. In the method of the present invention, the reaction is carried out at a pH of 2.5 to 3.5 to crystallize columnar to plate-shaped crystals, and then the slurry is dissolved in the slurry by raising the slurry pH to 3.5 to 5.0 using an alkaline substance. Crystallizes oblate crystals of dihydrate dicalcium phosphate. In this way, dicalcium phosphate dihydrate containing flat crystals mainly consisting of plate-shaped to columnar crystals is obtained. Depending on the pH of the first and second stages, a mixture ratio of columnar to plate crystals: flat crystals ≒ 5:5 to 9:1 can be obtained. When the pH is adjusted to 4.2 in the step, the ratio of columnar to plate crystals: flat crystals is about 8:2. When the dicalcium phosphate dihydrate composition of the present invention containing columnar to plate-like crystals and flat crystals is used as a toothpaste as a raw material, unlike dicalcium phosphate dihydrate, which has only flat crystals, it has good kneading properties. The polishing properties were good, and the polishability was also very excellent. In addition, in the case of only dicalcium phosphate dihydrate in columnar to plate-like crystals crystallized at pH 2.5 to 3.5, the polishing properties are excellent, but the kneading properties are poor.
When kneaded with glycerin etc., the texture was rough and the initial mixability was poor. As described above, in the present invention, by mixing and blending dicalcium phosphate dihydrate having different crystal shapes, a product suitable for tooth brushing and having good polishing properties and kneading properties can be obtained. In addition, when attempting to continuously obtain the dicalcium phosphate dihydrate composition by the two-step pH adjustment of the present invention, the pH is adjusted in the first and second reaction tanks, respectively, but of course, batch operation is not required. It can also be applied. By adjusting the pH in two stages as described above,
A dicalcium phosphate dihydrate composition containing a mixture of columnar crystals to plate crystals and flat crystals can be suitably obtained, but
As mentioned above, of course, it is also possible to carry out the reaction separately at each pH to obtain each crystal shape, and then mix them at an appropriate mixing ratio to make a toothpaste base material. The physical properties of the mixture are comparable to those obtained by the series of two-step reactions described above, but the method of individually producing and mixing them has the disadvantage that the process is complicated and uneconomical. Alkali metal phosphates used in the present invention include sodium phosphate, potassium phosphate, sodium ammonium phosphate, potassium ammonium phosphate, lithium phosphate, etc., and calcium salts include calcium chloride, calcium nitrate, slaked lime,
Calcium carbonate etc. are used. Example 1 Sodium ammonium hydrogen phosphate (hereinafter referred to as phosphorus salt) produced from wet phosphoric acid was added to 7% P ₂ O ₅
Phosphate salt solution diluted with warm water to give 20%
A CaCl ₂ solution was continuously added to the first reaction tank at a Ca/P molar ratio of 1.10 and a reaction temperature of 30°C, and at the same time, a 35% HCl solution was added while adjusting the reaction pH to 2.7.
Furthermore, in the second reaction tank, 20% Ca(OH) ₂ slurry was added.
Adjust the pH to 4.3 and continuously obtain a slurry of dicalcium phosphate dihydrate. Then, it is separated from the mother liquor, washed,
It was dehydrated and dried at 50°C. This one has an average thickness
Most of the crystals were columnar to plate-like crystals with a thickness of about 10 to 15 μm, and some flat crystals with a thickness of about 1 to 2 μm were present. The ratio of columnar to plate-like crystals to flat crystals is about 8:2. This micrograph is the first
As shown in the figure. Example 2 14% P ₂ O ₅ phosphorus salt solution and 14% CaCl ₂ solution were mixed with Ca/P
Continuously added to the first reaction tank at a molar ratio of 1.10 and a reaction temperature of 30°C, simultaneously added 35% HCl solution to make the reaction pH 2.7, and further added 20% NaOH to the second reaction tank.
A slurry of dicalcium phosphate dihydrate is continuously obtained while adjusting the pH to 4.5 with a solution. Hereinafter, the same operations as in Example 1 were performed. The mixing ratio of this is 8:2
It was moderately hot. Example 3 14% P ₂ O ₅ phosphorus salt solution and 14% CaCl ₂ solution were mixed with Ca/P
It was added continuously to the first reaction tank at a molar ratio of 1.00 and a reaction temperature of 35°C, and at the same time, 35% HCl solution was added so that the reaction pH was 3.3, and in the second reaction tank, 20% Ca was added.
(OH) ₂ is added to the slurry so that the pH becomes 4.3 to continuously obtain dicalcium phosphate dihydrate slurry. Hereinafter, the same operations as in Example 1 were performed. The mixing ratio of this product was about 6:4. Example 4 25% phosphoric acid-ammonium hydrogen solution and 10%
A CaCl ₂ solution was continuously added to the first reaction tank at a Ca/P molar ratio of 1.0 and a reaction temperature of 35°C, and at the same time, a 35% HCl solution was added so that the reaction pH was 3.0. % NaOH solution to continuously obtain a slurry of dicalcium phosphate dihydrate while adjusting the pH to 4.0.
Hereinafter, the same operations as in Example 1 were performed. The mixing ratio of this was 7:3. Example 5 10% disodium hydrogen phosphate solution and 10% calcium carbonate slurry at Ca/P molar ratio 1.2 and reaction temperature
Continuously added to the first reaction tank at 32℃, simultaneously 35%
A slurry of dicalcium phosphate dihydrate is continuously obtained by adding HCl solution so that the reaction pH becomes 2.6, and further adjusting the pH to 4.3 with 30% NaOH solution in the second reaction tank. Hereinafter, the same operations as in Example 1 were performed.
The mixing ratio of this was 8:2. Example 6 A 20% disodium hydrogen phosphate solution and a 10% calcium nitrate solution were mixed at a Ca/P molar ratio of 1.1 and a reaction temperature of 35
℃ continuously added to the first reaction tank and simultaneously 35%
A HCl solution is added to adjust the reaction pH to 3.0, and in the second reaction tank, a 10% Ca(OH) ₂ slurry is added to adjust the pH to 4.5 to continuously obtain a slurry of dicalcium phosphate dihydrate. Hereinafter, the same operations as in Example 1 were performed. The mixing ratio of this was 7:3. Example 7 A phosphorus salt solution prepared by diluting phosphorus salt with warm water to give a concentration of 7% P ₂ O ₅ and a 20% CaCl solution were mixed at a Ca/P molar ratio.
1.10, continuously added to the reaction tank at a reaction temperature of 30℃. At the same time, 35% HCl solution is added while adjusting the reaction pH to 2.7 to continuously obtain a slurry of dicalcium phosphate dihydrate. and separated from the mother liquor,
It was washed, dehydrated, and dried at 50°C. Further, a mother liquor from which dicalcium phosphate dihydrate was separated and a 20% Ca(OH) ₂ slurry are continuously added to the reaction tank. 20% at this time
Ca(OH) ₂ was added to adjust the pH to 4.3 to continuously obtain a slurry of dicalcium phosphate dihydrate. Then, dicalcium phosphate dihydrate was separated, washed, dehydrated, and dried at 50°C. The former and the latter dicalcium phosphate dihydrate at a ratio of 7:3
They were mixed well using a V-type mixer. Comparative example 1 14% P ₂ O ₅ phosphorus salt solution and 14% CaCl ₂ solution were mixed with Ca/P
Add it to the reaction tank at a molar ratio of 1.10 and a reaction temperature of 30℃, and at the same time add 35% HCl solution so that the reaction pH becomes 2.7.
Continuously obtain dicalcium phosphate dihydrate slurry. The mother liquor was then separated, washed, dehydrated and dried at 50°C.
This material consisted of only columnar to plate crystals having an average thickness of about 10 to 15 μm. This micrograph is shown in FIG. 2. Comparative Example 2 The reaction pH was set to 4.5 using the same procedure as in Comparative Example 1.
The obtained crystals were only flat crystals with an average thickness of about 1 to 2 μm. A micrograph of this is shown in FIG. 3. Comparative Example 3 25% phosphoric acid-ammonium hydrogen solution and 10%
Add CaCl ₂ solution to the reaction tank at a Ca/P molar ratio of 1.0 and a reaction temperature of 35℃, and at the same time adjust the reaction pH with 35% HCl solution.
3.0 to obtain a continuous slurry of dicalcium phosphate dihydrate. The mother liquor was then separated, washed, dehydrated and dried at 50°C. Comparative Example 4 The reaction pH was set to 4.0 using the same procedure as in Comparative Example 3. Comparative Example 5 10% disodium hydrogen phosphate solution and 10% calcium carbonate slurry at Ca/P molar ratio 1.2 and reaction temperature
Continuously add it to the reaction tank at 32°C, and at the same time add 35% HCl solution so that the reaction pH becomes 2.6 to continuously obtain dicalcium phosphate dihydrate slurry. The mother liquor was then separated, washed, dehydrated and dried at 50°C. Comparative Example 6 The reaction pH was set to 4.3 using the same procedure as in Comparative Example 5. Comparative Example 7 A phosphorus salt solution prepared by diluting phosphorus salt with warm water to give a concentration of 7% P ₂ O ₅ and a 20% CaCl ₂ solution were mixed at different Ca/P molar ratios.
1.10, continuously added to the first reaction tank at a reaction temperature of 30℃, and simultaneously added 35% HCl solution while adjusting the reaction pH to 2.0, and further added 20% to the second reaction tank.
Adjust the pH to 4.5 with Ca(OH) ₂ slurry to obtain a slurry of dicalcium phosphate dihydrate continuously. A vacuum filtration machine was used to separate the mother liquor, but it took an extremely long time because the crystals were very fine. The crystals were dehydrated at 50°C. As a result of analysis, 35% of anhydrous dicalcium phosphate was produced. The dicalcium phosphate dihydrate produced in the above Examples and Comparative Examples was crushed in a crusher and passed 350 # as a sample, and the following physical property tests were conducted. (a) Average particle size...by air permeation method. (b) Bulk specific gravity: Measured value after 50 tappings using a powder tester manufactured by Hosokawa Iron Works. (c) Dispersibility...Made a base of the sample and 80% glycerin and measured using a JISK-5101 grind meter. (d) Condition of kneading... Condition when squeezing the sample and 80% glycerin. (e) Oil absorption amount...Amount of glycerin when 30g of sample is kneaded with 80% glycerin to reach a constant viscosity. (f) Polishing power...The sample was suspended in a 30% glycerin solution, and a toothbrush of constant hardness was used to polish the Al
Weight loss when a piece is polished for a certain period of time. The results are shown in Table 1. Further, micrographs of the products of Example 1 and Comparative Examples 1 and 2, which were crushed using a crusher and passed through a 350# crusher, are shown in Figures 4, 5, and 6, respectively.

【table】

【table】 [Brief explanation of the drawing]

Figures 1 to 3 are microscopic photographs of dicalcium phosphate dihydrate of the present invention and comparative examples, and Figures 4 to 6 are photographs of the materials in Figures 1 to 3 after pulverization, respectively.

Claims (1)

[Scope of Claims] 1. The ratio of plate-like to columnar crystal dicalcium phosphate dihydrate to flat crystal dicalcium phosphate dihydrate is 5:5 to 9:
A dentifrice dicalcium phosphate dihydrate composition comprising a mixture of 1. 2. React the alkali metal phosphate and calcium salt at a reaction temperature of 40°C or less at a pH of 2.5 to 3.5 in the first stage, and raise the pH in the second stage from the first stage.
Phosphoric acid for toothpaste consisting of a mixture of dicalcium phosphate dihydrate in plate-like to columnar crystals and dicalcium phosphate dihydrate in flat crystals, characterized in that it separates from the crystals obtained as 3.5 to 5.0. A method for producing a dicalcium dihydrate composition.