JPS6310923B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dentifrice composition using as an abrasive a spherical calcite-type calcium carbonate obtained by heat-treating spherical vaterite-type calcium carbonate. Calcium carbonate includes calcite, which is a rhombohedral crystal as shown in Figure 1, rod-shaped aragonite as shown in Figure 2, and calcite, which is a rhombohedral crystal as shown in Figure 2.
Spherical vaterite (Vaterite) as shown in the figure,
There are three types of crystal polymorphs (1 to 3).
All figures are micrographs at 3000x magnification of calcium carbonate synthesized by double decomposition method), normal (room temperature,
At normal pressure), calcite is the stable phase. but,
Under conditions of room temperature and pressure, the free energy difference between these three polymorphs is small, and therefore, both in nature and when calcium carbonate is synthesized in the laboratory, vaterite and aragonite precipitate as metastable phases. It may exist. Conventionally, attempts have been made to spheroidize various powders because spheroidizing powders improves various powder properties such as filling properties, dispersibility, and abrasiveness, and imparts desirable characteristics. For this reason, spherical vaterite-type calcium carbonate has attracted attention, and the carbon dioxide gas blowing method (Special Publication No. 1973-
25148, Special Publication No. 48-35159), interfacial polymerization method [Nikka Shi, 5 , 732 (1976)], double decomposition method of salts (Japanese Patent Publication No. 55
-95617) have been proposed. Furthermore, as an example of application of spherical vaterite type calcium carbonate, it has been proposed to use it as an abrasive for tooth brushing (Japanese Patent Application Laid-open No. 32133/1983). However, this spherical vaterite-type calcium carbonate is unstable in water and will not change to calcite at room temperature and pressure if water is not present.
If even a small amount of water is present around the particles, the spherical morphology is easily damaged and the particles are transformed into rhombohedral calcite. Such transformation from the spherical vaterite type to the rhombohedral calcite type not only causes a loss of spherical properties, but also often impairs the quality stability of compositions containing it. The present inventors conducted intensive research on stable spherical calcium carbonate that can maintain its spherical shape even in water for a long period of time, and found that it has a vaterite-type structure that is unstable in water, cannot maintain its spherical shape, and undergoes crystal transition. By heat-treating spherical calcium carbonate at a temperature of 400 to 800°C for 0.5 to 24 hours, the spherical vaterite-type calcium carbonate transforms into calcium carbonate with a calcite structure, which is the most stable under normal conditions, and transforms into spherical calcite. We found that this spherical calcite-type calcium carbonate maintains its spherical shape stably for a long period of time even in the presence of water. Calcium carbonate is also used as a filler in rubber, plastic, etc., or as an abrasive for tooth brushing, as it is a cheap and easily available substance in Japan, where resources are scarce. The calcium carbonate used is called heavy calcium carbonate and light calcium carbonate as shown in Figures 4 and 5, respectively.
(Figures 4 and 5 are both magnified at 3000x), and both are powders with sharp corners (or tips), and this type of calcium carbonate is also used as an abrasive for toothpaste. Dibasic calcium phosphate・
Compared to dihydrates, insoluble sodium metaphosphate, calcium pyrophosphate, etc., they have problems such as being too abrasive to teeth and having a poor feel when used. However, when the spherical calcite type calcium carbonate is used as an abrasive for toothpaste,
It has less abrasiveness than conventional heavy or light calcium carbonate, has mild abrasiveness on teeth, and can polish the tooth surface well, improving the gloss of teeth. It improves the dispersibility of toothpaste in the mouth, giving it a more pleasant feeling of use, and as mentioned above, spherical calcite-type calcium carbonate is stable and maintains a stable spherical shape for a long period of time in toothpaste formulations containing water. It was discovered that the spherical calcite type calcium carbonate obtained under the above heat treatment conditions without impairing the quality stability of the product can be effectively used as an abrasive for toothpaste, and the present invention was made based on this finding. It is. The present invention will be explained in more detail below. The calcite-type calcium carbonate used in the present invention has a spherical shape as shown in Figs. , including those with a short axis/long axis ratio of 1/1 to 1/2), and have physical properties similar to those of normal rhombohedral calcite-type calcium carbonate.
In addition, this spherical calcite type calcium carbonate
The ray diffraction pattern is as shown in FIG. 6, and it has the same X-ray diffraction pattern as conventional rhombohedral calcite type calcium carbonate. The calcium carbonate having a spherical calcite structure is
Obtained by heat treating spherical vaterite type calcium carbonate. The heat treatment is preferably carried out at 1 to 10 atmospheres, in the atmosphere or in an inert gas atmosphere, and the treatment temperature is 400 to 800°C, and the treatment time is 0.5
~24 hours. In particular, from the point of converting spherical vaterite type calcium carbonate to spherical calcite type with almost 100% conversion rate, it is necessary to heat it at 400℃ for more than 2 hours and at 600℃.
It is preferable to set it as 0.5 hour or more, and 0.5 to 24 hours at 800 degreeC. The dentifrice composition of the present invention contains calcium carbonate having a spherical calcite structure obtained by the above heat treatment as an abrasive. In this case, the calcium carbonate having the spherical calcite structure is not only stable at room temperature and pressure, but also stable in water, and can maintain its spherical shape for a long period of time. Therefore,
It maintains its spherical properties not only in dry conditions but also in wet conditions, and for this reason, it can be effectively used as an abrasive for tooth brushing, with mild abrasiveness and excellent polishing properties, without damaging teeth. To give gloss and luster to teeth, improve the dispersibility of toothpaste in the mouth, and provide an excellent feeling of use. In addition, when manufacturing a toothpaste using spherical calcite type calcium carbonate as an abrasive, other ingredients that are usually used in the manufacture of toothpaste can be used, such as carboxymethyl cellulose, hydroxyethyl cellulose, carrageenan, xanthan gum, and guar gum. , binders such as locust bean gum, starch, and gum tragacanth, humectants such as glycerin, propylene glycol, and sorbitol, surfactants such as anionic active agents and nonionic active agents, sweeteners such as saccharin sodium, fragrances, Preservatives, fluorides and other active ingredients may be added. In addition, other abrasives such as dicalcium phosphate dihydrate and anhydride, aluminum hydroxide, silicon dioxide, calcium pyrophosphate, insoluble sodium metaphosphate, calcium sulfate dihydrate and anhydride, etc. may be used in combination. You can also do it. In this case, if these abrasives are used in an amount of 20% by weight or less based on the total amount of abrasives, the properties and effects of the spherical calcite type calcium carbonate will not be impaired. Next, the present invention will be explained in more detail by showing Examples and Comparative Examples. Examples and Comparative Examples Production of spherical calcite-type calcium carbonate Spheroidal vaterite-type calcium carbonate was used as a starting material, and after heat treatment at the treatment temperature and treatment time shown in Table 1 under normal pressure and atmosphere, X-ray diffraction analysis was performed. The rate of transition from spheroidal vaterite type calcium carbonate to spheroidal calcite type calcium carbonate was measured. The results are shown in Table 1. Note that the spherical vaterite-type calcium carbonate was synthesized by an equimolar aqueous solution reaction of calcium chloride and sodium carbonate. Moreover, the metastasis rate to calcite was calculated using the following formula. f= _(c) =I _104(c) /I _110(v) +I _112(v) +I _114(v) +I _104(
c) Calcite transition rate (%) = 100 × f _(c) For example, I _{104 (c)} is the X-ray peak intensity at the 104 plane of calcite, and I _{110 (v)} is the X-ray peak intensity at the 110 plane of vaterite. It is strength.

[Table] From the results in Table 1, it was found that spherical calcite-type calcium carbonate can be suitably obtained by heat-treating spherical vaterite-type calcium carbonate at 400-800°C for 0.5-24 hours. The X-ray diffraction pattern of the obtained spherical calcite-type calcium carbonate (sample No. 4) is shown in FIG. Measurement conditions Target: Cu-Kα Filter: Ni Voltage: 30KV Current: 16MA Scanning speed: 2゜2θ/min Angle range: 60-10゜ For comparison, the X-ray diffraction diagram of conventional spherical vaterite calcium carbonate is shown below. It is shown in Figure 7. In addition,
The peak appearing at 29-30° in FIG. 7 is a peak of calcite, indicating that a small amount of calcite crystals are mixed in the spherical vaterite-type calcium carbonate used for this X-ray diffraction. Next, add 400 g of spherical vaterite type calcium carbonate.
Spheroidal calcite-type calcium carbonate obtained by heat treatment at ℃ for 24 hours was poured into water at 80℃, samples were taken at predetermined time intervals, and changes in shape were observed using a scanning electron microscope. For comparison, a similar experiment was conducted using spherical vaterite-type calcium carbonate. 8 to 27 are micrographs showing the above experimental results. In addition, Table 2 shows the relationship between the types of calcium carbonate, the water injection time, and the photographic magnification with respect to FIGS. 8 to 27 (microscopic photographs).

【table】

[Table] As is clear from the micrograph results, spherical vaterite-type calcium carbonate loses its spherical shape and becomes rhombohedral crystals after about 3 hours in water at 80°C.
Calcite formation begins to become noticeable and becomes almost complete in 5 hours, whereas calcite type calcium carbonate obtained by heat treating spherical vaterite type calcium carbonate is placed in water at 80℃ for 7 hours. It is clear that the spherical shape does not change at all even if the spherical shape is maintained. Next, using a suspension of 10 g of powder and 30 g of water shown in Table 3, the polishing power and polishing power of each powder was examined by the following method. The results are shown in Table 3. Polishing power test Place each suspension in a polishing container and apply a load of 200
The polishability was evaluated by brushing the copper plate under the conditions of 20,000 strokes and measuring the change in weight of the copper plate. Polishing power test Bovine teeth cut into 5 x 5 mm were embedded in resin, and the enamel surface was smoothed with sandpaper to achieve a gloss level of approximately 80 on a gloss meter. Next, the above-mentioned suspension was poured into a polishing container in which the above-mentioned bovine teeth were set, and brushed under the conditions of a load of 800 g and 600 strokes, and an increase or decrease in gloss was measured using a gloss meter.

[Table] From the results in Table 3, spherical calcite-type calcium carbonate has mild abrasive power and can be polished smoothly without damaging the enamel surface, making it suitable as an abrasive for tooth brushing. was discovered. Next, an example of a toothpaste formulation of the present invention using spherical calcite type calcium carbonate as an abrasive will be shown.

【table】

【table】 [Brief explanation of the drawing]

Figure 1 is a micrograph showing conventional rhombohedral calcite-type calcium carbonate, Figure 2 is a micrograph of aragonite-type calcium carbonate, Figure 3 is a micrograph of vaterite-type calcium carbonate, and Figure 4 is a heavy one. A microscopic photograph of calcium carbonate, FIG. 5 is a microscopic photograph of light calcium carbonate, FIG. 6 is an X-ray diffraction diagram of the spherical calcite-type calcium carbonate of the present invention,
Figure 7 is an X-ray diffraction diagram of vaterite type calcium carbonate, Figures 8 and 9 are micrographs each showing an example of spherical calcite type calcium carbonate of the present invention, and Figures 10 to 17 are each of the present invention. Figures 18 and 19 are micrographs showing conventional spherical vaterite calcium carbonate, respectively, and Figures 20 to 27 are micrographs showing the state when spherical calcite-type calcium carbonate is placed in water for a predetermined period of time. are micrographs showing the morphological changes when spherical vaterite-type calcium carbonate is placed in water for a predetermined period of time.

Claims (1)

[Claims] 1. A toothpaste composition containing as an abrasive calcium carbonate having a spherical calcite structure obtained by heat treating calcium carbonate having a spherical vaterite structure at 400 to 800°C for 0.5 to 24 hours. thing.