JPH01164712A - Surface-modified calcium hydrogenphosphate and surface coating method - Google Patents

Abstract

PURPOSE:To obtain surface-modified calcium hydrogenphosphate having characteristics as an abrasive for dentifrice such as good flavor and crispness and also having improved stability to fluorine by coating the surface of calcium hydrogenphosphate with hydroxyapatite. CONSTITUTION:Calcium hydrogenphosphate is brought into contact with an alkali metal or alkaline earth metal hydroxide or NH3 in an aq. suspension to coat the surface of the calcium hydrogenphosphate with 1-90wt.% hydroxyapatite. The concn. of the calcium hydrogenphosphate in the aq. suspension is <=80wt.%, preferably 50wt.%. The alkali is used as 2-8wt.% soln. in case of NaOH or KOH or as 10-30wt.% soln. in case of NH3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides calcium phosphate hydroxyapatite (
The present invention relates to calcium hydrogen phosphate whose surface is coated with lucium apatite (hereinafter abbreviated as lucium apatite) and a method for producing the same.

[Conventional technology]

Calcium hydrogen phosphate has been used as a main abrasive in toothpaste compositions such as toothpaste and toothpaste for a long time because of its good flavor and crispness when used as a toothpaste abrasive.

Calcium hydrogen phosphate has dihydrate salt and anhydrous salt.
Since anhydrous salt alone is highly abrasive to teeth, it has also been used as a toothpaste abrasive in combination with dihydrate salt.

However, in recent years, toothpastes with functionalities such as prevention of dental caries, alveolar pyorrhea, and prevention of plaque adhesion have been sought. In particular, the development of toothpaste to prevent cavities has made remarkable progress in other countries, and fluoride has been added as a medicinal ingredient to toothpaste compositions for the purpose of strengthening tooth structure and suppressing the occurrence of caries. It is also well known that it is usually added. The mineral that constitutes the main part of tooth porosity is expressed as hydroxyapatite (hydrophosphorus lime), which has low solubility due to interaction with fluoride in acidic media. It is thought that the solubility of tooth porosity is reduced by producing lime (calcium).

However, when fluoride is added to toothpastes based on calcium hydrogen phosphate and calcium carbonate,
It had the disadvantage of producing insoluble calcium fluoride and losing its medicinal efficacy.

Therefore, it has been desired to improve calcium hydrogen phosphate salts that have good compatibility with fluorides.

[Problem that the invention seeks to solve]

As a conventional technique for improving the compatibility with fluoride based on calcium hydrogen phosphate, the following methods have been proposed. (1) JP-A-57-209812, JP-A-5
In No. 9-121106 and Japanese Patent Publication No. 41-5090, primary calcium phosphate is first produced by a reaction between milk of lime and phosphoric acid, and at that point, a magnesium salt such as magnesium oxide is added, or after adding pyrophosphoric acid, How to neutralize.

(2) JP-A-58-120508 discloses a method of producing calcium hydrogen phosphate at low l)H. (3) Japanese Patent Publication No. 40-14318 discloses a method of producing calcium hydrogen phosphate in the presence of a magnesium salt. (4) Special Public Service 1977
-14319, 0.1 to 0.2 fluoride
How to add %. (5) Japanese Patent Publication No. 51-77596, 5
1-77597M, 51-77598, etc.,
Methods of adding aminophosphonic acid and azacycloalkanephosphonic acid have been proposed, but both methods only slightly improve fluorine stability compared to conventional calcium hydrogen phosphate, and do not show any substantial improvement. This has not yet been achieved.

[Means for solving problems]

In view of the above circumstances, the present inventors have conducted extensive research and have discovered a surprising surface modification that can improve fluorine stability, although it lacks the characteristics of a toothpaste abrasive such as flavor and sharpness. We have discovered pure calcium hydrogen phosphate and a method for modifying it.

That is, the gist of the present invention resides in a surface-modified calcium hydrogen phosphate whose surface is coated with calcium phosphate hydroxyapatite.

The calcium hydrogen phosphate is brought into contact with an alkali metal or alkaline earth hydroxide, or ammonia (hereinafter abbreviated as alkali) in a dispersion, and calcium apatite is deposited on the surface of the calcium hydrogen phosphate in an amount of 1 to 90%. It is produced by coating with a weight percent coating, and has significantly improved compatibility with fluoride.

[For production]

The calcium hydrogen phosphate raw material used in the present invention may be any calcium hydrogen phosphate, including direct method such as boat fishing,
Alternatively, calcium hydrogen phosphate produced by double decomposition method etc. can be used.

A calcium apatite coating can be applied to the surface of the calcium hydrogen phosphate using various alkalis. The alkali used includes calcium hydroxide, magnesium hydroxide, ammonia, sodium hydroxide, potassium hydroxide and the like, with ammonia being preferred. The coating on the surface of calcium hydrogen phosphate is carried out in the presence of an alkali at a reaction temperature of 1.
) H, -6= for controlling the amount of alkali added, calcium hydrogen phosphate optionally coated with calcium apatite can be obtained.

In the coating method according to the present invention, first, calcium hydrogen phosphate is placed in water! l! make it muddy At this time, it is desirable that the slurry concentration in the suspension water be 80% by weight or less, preferably 50% by weight or less. If the slurry concentration is too high, phosphates produced as a by-product during surface treatment will increase the viscosity of the slurry, making stirring difficult, making it difficult to achieve uniform surface treatment. Next, this suspended water is heated to a temperature of 1
00°C or less, preferably 90°C or less.

When the temperature exceeds 100°C, especially in the case of calcium hydrogen phosphate dihydrate, it undergoes crystal transformation to calcium hydrogen phosphate anhydrous salt, and loses its original characteristics as calcium hydrogen phosphate dihydrate. become. Therefore, in order to completely maintain the crystal shape, it is necessary to carry out the process at 90°C or lower. Furthermore, if the temperature is too low, the reaction to form calcium apatite will be slow, and if the temperature is below 30°C, the reaction will take a long time. After maintaining the temperature at the specified temperature, alkali is added dropwise. The alkali concentration is determined by the type of alkali. Typical examples include 2-8 wt.% solutions for sodium hydroxide and potassium hydroxide, or 10-30 wt.% solutions in the shell for ammonia, etc., depending on the reaction pH.
Use a concentration that is easy to control for one reaction.

Further, the amount of alkali added is 20% by weight or less, preferably 1 to 10% by weight, based on calcium hydrogen phosphate. The amount of alkali added is correlated with the thickness of the calcium apatite formed on the surface. Next, the pH of the reaction solution is maintained constant using the alkali. pH
The higher the value, the faster the production rate of calcium phosphate, but it becomes difficult to control the amount of calcium apatite produced, so it is desirable that the pH is <14. Especially 7<I
) H<11 is preferred.

The reaction to calcium apatization progresses through a reaction induction period. The reaction is complete when the pH of the reaction suspension is accompanied by a rapid drop.

The reaction end point for coating calcium apatite is higher than about 7.0, regardless of whether or not alkali is continuously added;
It is carried out at a pH below about 8.5.

The state of coating of calcium apatite upon addition of alkali to calcium hydrogen phosphate slurry is determined by the amount of alkali and the pH value maintained. As mentioned above,
Once a suitable calcium apatite-coated calcium hydrogen phosphate slurry has been produced, the reaction temperature is rapidly lowered to below 35°C.

Due to this reaction temperature reduction, the accelerated reaction to form amorphous calcium apatite is stopped while maintaining equilibrium at the current value of pI-(.Then, the product is separated into solid and liquid from the slurry. Separation of the product from the slurry can be accomplished by any conventional method.

These methods include, but are not limited to, decantation, centrifugation, filtration, and similar methods. - Wash the product once separated from the slurry with water. The washing water is used in an amount of 1 to 20 times the volume of the product. This washing step means the removal of by-products during the reaction, but it is also possible to omit the washing. Next, this product is dried to obtain a product in which the surface of calcium hydrogen phosphate of the present invention is coated with calcium apatite. This product is not compatible with reaction with appropriate fluorides. Suitable fluorine compounds can be any of the compounds described below that are used in some cases to provide available fluorine ions into cavities. That is, sodium monofluorophosphate, sodium fluoride, tin fluoride, titanium fluoride, and the like have been used in toothpastes and have shown good results in promoting dental hygiene. While brushing your teeth (100-5000 pl)
Good results can be achieved using an amount of fluorinated compound that provides available fluoride ions in the range m, preferably from 1000 to 2000 ppm.

〔Example〕

In order to further elaborate the invention, the following examples are included. However, this does not limit the scope of the invention.

In addition, soluble fluorine was measured by the method described below.

Soluble fluorine simple test method sample preparation Weigh out 8.57'J of calcium hydrogen phosphate sample into a 100d beaker, add sodium monofluorophosphate (M
60m of 100ppm solution as fluorine ion of FP)
1 and stir and mix using a magnetic stirrer for 10 minutes. Thereafter, it is left to stand for 2 to 5 days in a 50° C. constant temperature bath. It is taken out from the thermostatic chamber, cooled, stirred for 10 minutes, and then separated into solid and liquid using a centrifuge. 1 d of the supernatant liquid phase was taken into a 100 d volumetric flask, pure water was added to it, the dilution was diluted to the marked line, and the dissolved fluoride was removed using ion chromatography HLC.
-601 (manufactured by Tosoh) column IC-anion-PW
Measure with.

Example 1 Calcium hydrogen phosphate dihydrate, 30 to 9, was made into a 20% slurry by weight and heated to 50°C. To this, gradually add 'j to 4.84 of 26% ammonia solution to make pl-110. Then the ammonia solution is subsequently added while maintaining the l)H. After the addition, the pH changes after a reaction induction period.
A sharp decline is seen. When this pH decrease reaches 8, the reaction temperature is lowered to 35° C. or less by external cooling. The mixture is aged at this temperature for 1 hour, and then solid-liquid separation is performed using a centrifuge. Next, it was washed twice with 150 L of water and dried in a constant temperature bath at 40°C to obtain a product. A portion of this product was sampled and measured using a simple method for measuring soluble fluoride, and the results are shown in Table 1.

Examples 2 to 6 The reaction temperature, reaction 1) H, and ammonia amount were produced in exactly the same manner as in Example 1, except that the conditions were as shown in Table 1.

Comparative Example 1 Example 1 except that no ammonia was added
The operations after solid-liquid separation were performed in exactly the same manner as above.

Example 7 Calcium hydrogen phosphate anhydrous salt, 30! 50% by weight of j
Make a slurry and bring to 25°C. Gradually add 3.00 kg of 26% ammonia solution to this to make 1) H9. Then, while retaining the I)H, an ammonia solution is subsequently added. After the addition is complete, a rapid drop in pH is observed after a reaction induction period. When this decreasing pH reaches 8, the reaction temperature is lowered to below 35°C by external cooling. The mixture is aged at this temperature for 1 hour, and then solid-liquid separation is performed using a centrifuge. Next, it was washed twice with 1501 water and dried in a constant temperature bath at 40°C to obtain a product. The results of a simple measurement of soluble fluoride for this product are shown in Table 1.

Examples 8 to 10 Products were produced in exactly the same manner as in Example 7, except that the reaction temperature, reaction II, and amount of ammonia were as shown in Table 1.

Comparative Example 2 The same operation as in Comparative Example 1 was performed except that calcium hydrogen phosphate anhydrous salt was used.

13 Example 11 25% by weight of 'j in calcium hydrogen phosphate dihydrate, 30
Make a slurry and bring it to 50°C. To this, 20% by weight of sodium hydroxide (12 ml) was gradually added to adjust the pH to 10. Then the sodium hydroxide solution is subsequently added while maintaining the l)H. After the addition, after a reaction induction period, I
A rapid decrease in I is seen. When this pH decrease reaches 8, the reaction temperature is lowered to 35° C. or less by external cooling. The mixture is aged at this temperature for 1 hour, and then solid-liquid separation is performed using a centrifuge. Then washed twice with 150 L of water and heated to 40°C.
The product was obtained by drying in a constant temperature bath. The result of a simple measurement of soluble fluorine in this product was 820 ppm.

Example 12 Calcium hydrogen phosphate dihydrate, 15 Kg at 20% by weight
Make a slurry and bring to 50°C. 3 Kg of 20% by weight potassium hydroxide is gradually added to this to bring the pH to 9. Then, while maintaining the zero day, potassium hydroxide solution is subsequently added. After the addition, after a reaction induction period, I)
-1 sharp drop can be seen. This decrease l) H is 8
At that point, the reaction temperature was reduced to 35°C by external cooling.
Do the following.

The mixture is aged at this temperature for 1 hour, and then solid-liquid separation is performed using a centrifuge. Next, it was washed twice with 150 L of water and dried in a constant temperature bath at 40°C to obtain a product. The result of a simple measurement of soluble fluorine in this product was 870 ppm.

Example 13 Calcium hydrogen phosphate dihydrate, 20Ky, is made into a 20% by weight slurry and heated to 50'C. 6 kg of 20% by weight magnesium hydroxide is gradually added to this to bring the pH to 10. Magnesium hydroxide solution is then subsequently added while maintaining the pH. After addition-16=, a rapid decrease in II is observed after a reaction induction period. When this decreasing l)H value reaches 8, the reaction temperature is brought down to below 35°C by external cooling. At this temperature 1
After aging for a while, solid-liquid separation is performed using a centrifuge. then 1
The product was washed twice with 50 L of water and dried in a constant temperature bath at 40°C. The result of a simple measurement of soluble fluorine in this product was 910 ppm.

[Brief explanation of the drawing]

FIG. 1 shows an X-ray diffraction analysis of the surface treatment state of calcium hydrogen phosphate dihydrate used in the present invention to form calcium apatite. FIG. 2 is a similar X-ray diffraction pattern of the anhydrous calcium hydrogen phosphate used in the present invention. Third
The figure shows the surface treatment state of calcium hydrogen phosphate coated with calcium apatite according to the present invention, observed with an electron microscope at a magnification of 3,000 times. FIG. 4 is a chart showing the correlation between the amount of ammonia added, which is typical as an alkali in the present invention, and the loss on ignition of surface-modified calcium hydrogen phosphate. = 18- No. 3 CA Second A acid 7JIL nwa tε Burning quasimonia t (43%) Procedural amendment 1, Indication of case 1988 Patent application No. 322772 2, Name of invention Surface modified phosphoric acid Calcium hydrogen and its surface coating method 3
, Relationship with the case of the person making the amendment Patent applicant address: 8-11-37-4 Akasaka, Minato-ku, Tokyo Address of agent: 16-10 Kanda-kita Jorimono-cho, Chiyoda-ku, Tokyo
1. 3rd floor, Ei Building 5゜Detailed description of the invention in the specification subject to amendment Contents of amendment The following sections of the specification will be amended. Note 1: On page 3, line 16 of the specification box, the words "hydracid phosphoric lime" have been corrected to "hydracid apatite." 2. On the 19th line of the same page, the text "fluorinated phosphorous lime" has been corrected to "fluorinated apatite". 3. On page 7, line 9 of the specification, the phrase "because it will be difficult" has been corrected to "because it will be difficult." April 7, 1985 Commissioner of the Japan Patent Office / JX Month I Subeo 1, Indication of the case 1988 Patent Application No. 322772 Title Toyo Straf Co., Ltd. 7-Chemical Amendment Contents 1. Correct the brief description column of the drawing as follows. Figure 1 shows the surface treatment state of calcium hydrogen phosphate dihydrate used in the present invention to form calcium apatite.
Linear diffraction is shown. FIG. 2 is a similar X-ray diffraction pattern of the anhydrous calcium hydrogen phosphate used in the present invention. FIG. 3 is a chart showing the correlation between the amount of ammonia added, which is typical as an alkali in the present invention, and the loss on ignition of surface-modified calcium hydrogen phosphate. ”2, Attached drawing box 3
The figure has been corrected to a reference figure as shown in the attachment, and Figure 4 has been corrected to Figure 3.

Claims (6)

[Claims] (1) A surface-modified calcium hydrogen phosphate whose surface is coated with calcium phosphate hydroxyapatite. (2) Surface modification according to claim 1, wherein the calcium phosphate hydroxyapatite coating the surface is 1 to 900 parts by weight per 100 parts by weight of calcium hydrogen phosphate. Calcium hydrogen phosphate. (3) In suspension water of calcium hydrogen phosphate, pH is adjusted to 7 to 7 in the presence of 1 to 20 parts by weight of alkali metal or alkaline earth hydroxide or ammonia to 100 parts by weight of calcium hydrogen phosphate. 14. A surface coating method for converting the surface of calcium hydrogen phosphate into calcium phosphate hydroxyapatite by treating at a temperature of 0 to 100°C. (4) The amount of alkali added is 100% calcium hydrogen phosphate
The surface coating method according to claim 3, wherein the surface treatment can be performed in an amount of 1 to 20 parts by weight. (5) Calcium hydrogen phosphate is suspended in water at pH 7-1.
1. The surface coating method according to claim 3, wherein the surface coating method is controlled to be 1. (6) The surface coating method according to claim 3, wherein the temperature during the surface treatment reaction is in the range of 30 to 90°C.