Title:  Dentrifice comprising calcium carbonate granules

United States Patent:  6,808,700

Issued:  October 26, 2004

Inventors:  Kiji; Shinji (Tokyo, JP); Oshino; Kazushi (Tokyo, JP)

Assignee:  Kao Corporation (Tokyo, JP)

Appl. No.:  096660

Filed:  March 14, 2002

Abstract

A dentrifice comprising granules consisting essentially of calcium carbonate particles, the granules having an average size of 50 to 500 um and a crushing resistance of 1 to 20 g/granule, and the calcium carbonate particles having a primary particle size of 0.01 to 0.5 um.

Description of the Invention

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a calcium-carbonate-granule-containing dentifrice which permits tactile sensation of cleaning effects in the mouth, can be prepared at a low cost, is free from adsorption of a flavoring component and is excellent in the refreshed feeling after use.

2. Description of the Related Art

Various oral compositions blended with granules or granule-like materials have conventionally been known. For example, medicinal components such as medicaments and enzymes are incorporated in granules to exhibit their effects or to give an aesthetic appreciation to the products. Some granules are adjusted to have a size or strength perceivable in the mouth. Described specifically, granules are prepared so that they can be perceived immediately after toothbrushing is started but can no more be perceived along the toothbrushing process, whereby the cleaning degree of plaque can be found by the tactile sensation. Some granules are, on the other hand, prepared so that they cannot be perceived at all from the very beginning of the toothbrushing, but the cleaning effect can be confirmed only with the eyes.

As an oral composition containing granules, a granule-containing dentifrice available by binding the granules with an inorganic or organic binder is proposed (Japanese Patent Application Laid-Open No. 299211/1989, Japanese Patent Application Laid-Open No. Hei 243815/1992). In addition, an oral composition substantially free of an organic and/or inorganic binder and comprising an aggregate formed of at least two fine-grain materials different in particle size is proposed (Japanese Patent Application Laid-Open 506885/1998).

Also proposed is use of a special synthesizing method for preparing particles substantially free of a binder and having a specific particle size and shape (Japanese Patent Application Laid-Open No. 59716/1998).

The above-described compositions or process, however, is accompanied with such a problem as cumbersome preparation processor high production cost, because it needs addition of an organic or organic binder, aggregation or granulation of a mixture of at least two different materials, or a special synthesizing process. Moreover, a flavoring gent contained in a dentifrice is adsorbed to the granules owing to the organic or inorganic binder or the special shape of the granules formed as a result of the synthesis, which disturbs the dentifrice from exhibiting refreshed feeling. Furthermore, when granulation is conducted without using particles other than ordinarily-employed polishing particles having an average primary particle size of 1 to 20 .mu.m, it is difficult to control the particle size and crushing size.

An object of the present invention is therefore to provide a calcium-carbonate-granule-containing dentifrice which permits tactile sensation of cleaning effects in the mouth, can be prepared at a low cost, is free from al adsorption of a flavoring component and is excellent in the refreshed feeling after use.

Another object of the present invention is to provide a process for preparing the calcium carbonate granules and calcium carbonate granules prepared by the process.

SUMMARY OF THE INVENTION

Paying attention to the cohesive force of calcium carbonate particles having a markedly fine average primary particle size, the present inventors have found that incorporation of granules composed substantially singly of calcium carbonate in a dentifrice permits tactile sensation of the granules in the mouth and recognition of cleaning effects without giving almost no unpleasant feeling of foreign matters; enhances cleaning power without scratching tooth; and does not impair the refreshed feeling of the dentifrice.

In one aspect of the present invention, there is thus provided a dentifrice comprising granules which are composed substantially of calcium carbonates alone and which have an average granule size of 50 to 500 .mu.m and the crushing resistance of 1 to 20 g/granule, said granules being obtained by binding thereto calcium carbonate particles having an average primary particle size of 0.01 to 0.5 .mu.m.

In another aspect of the present invention, there is also provided a process for preparing calcium carbonate granules, which comprises granulating calcium carbonate particles of an average primary particle size of 0.01 to 0.5 .mu.m, which has been obtained by allowing a CO₂ gas to pass through a calcium hydroxide suspension using a medium selected from a group consisting of calcium carbonate, calcium hydroxide and water, and then drying the resulting granules in a CO₂ -containing gas.

In a further aspect of the present invention, there is also provided a process for preparing calcium carbonate particles, which comprises introducing, to a suspension containing 1 to 20 wt. % of calcium hydroxide, a CO₂ -containing gas until a carbonating ratio reaches at least 90% but less than 100%, granulating the resulting suspension and then converting the resulting granules to calcium carbonate ones in a CO₂ -containing gas.

In a still further aspect of the present invention, there is also provided the above-described process for preparing calcium carbonate granules, wherein the calcium carbonate granules thus obtained have an average granule size of 50 to 500 .mu.m and crushing resistance of 1 to 20 g/granules.

The dentifrice according to the present invention permits tactile sensation of the granules in the mouth and recognition of their effects but hardly gives an unpleasant feel of foreign matters; has enhanced cleaning power without scratching tooth; and is excellent in refreshed feeling.

A process for preparing calcium carbonate granules is reduced in a production cost owing to the simplification of preparation steps and the granules obtained by this process are excellent as calcium carbonate granules for dentifrice.

BEST MODE FOR CARRYING OUT THE INVENTION

Calcium carbonate granules to be used in the present invention are obtained by granulating calcium carbonate particles having an average primary particle size of 0.01 to 0.5 .mu.m, preferably 0.01 to 0.1 .mu.m in order to impart the granules with a predetermined strength, thereby making it possible to sense the granules in the mouth and recognize their effects while hardly giving an unpleasant feel of foreign matters, and to enhance their cleaning power without scratching tooth. The average particle size of the calcium carbonate particles of the present invention means a value measured by microscopy (that is, a method of taking a photograph of particles magnified 40000 times through an electron microscope and visually measuring the particle size). The calcium carbonate granules are prepared by binding calcium carbonate particles while making use of their adhesiveness upon precipitation in water. This makes it possible to incorporate the granules in a dentifrice without impairing refreshed feeling. Calcium carbonate granules have an average granule size of 50 to 500 .mu.m, preferably 75 to 250 .mu.m. Such an average granule size makes it possible to sense the granules in the mouth and recognize their effects while hardly giving an unpleasant feel of foreign matters, and to enhance their cleaning power without scratching tooth. The average granule size of the granules means a value measured by the sifting method (sonic sifter, "SW-20-AT", manufactured by Tsutsui Rikagaku Kikai Co., Ltd.). The crushing resistance of the calcium carbonate granules is 1 to 20 g/granule, preferably 5 to 15 g/granule. Such crushing resistance makes it possible to sense the granules in the mouth and recognize their effects while hardly giving an unpleasant feel of foreign matters, and to enhance their cleaning power without scratching tooth. With regards to crushing resistance, crushing resistance of each of 10 to 20 granules having a granule size close to an average one is measured using a micro compression testing machine ("MCTM-500", manufactured by SHIMADZU CORP) and then, a mean value is calculated. Crushing resistance is expressed as this mean value. The calcium carbonate granules are desired to have similar resistance when incorporated in a toothpaste (wet state). They are preferred to have wet crushing resistance of 1 to 20 g/granule, preferably 5 to 15 g/granule. Such wet crushing resistance makes it possible to sense the granules in the mouth and recognize their effects while giving almost no unpleasant feel of foreign matters, and to enhance their cleaning power without scratching tooth.

Calcium carbonate granules can be prepared by allowing a CO₂ gas to pass through an aqueous suspension of calcium hydroxide to prepare calcium carbonate particles, granulating the particles and then, drying and sifting the resulting granules.

The above-described process is more preferred when calcium carbonate granules are prepared by granulating calcium carbonate particles of an average primary particle size of 0.01 to 0.5 .mu.m, preferably 0.03 to 0.1 .mu.m, which have been prepared by allowing a CO₂ gas to pass through an aqueous suspension of calcium hydroxide, by using one or more than one media selected from the group consisting of calcium oxide, calcium hydroxide and water; and then drying the resulting granules in a CO₂ -containing gas. Drying in a high-temperature CO₂ -containing gas is more preferred for controlling crushing resistance.

For controlling crushing resistance, preferred is addition of calcium oxide or calcium hydroxide serving as a medium in an amount of 0.05 to 10 parts by weight, preferably 0.1 to 1.0 part by weight based on 100 parts by weight of calcium carbonate particles.

Calcium carbonate particles having an average primary particle size of 0.01 to 0.5 .mu.m can be prepared, for example, by reacting a calcium hydroxide suspension having a concentration of 1 to 20 wt. %, preferably 1 to 10 wt. %, at a reaction temperature of 5 to 35^oC., preferably 5 to 20^oC., a CO₂ concentration of 15 to 70 wt. %, preferably 30 to 50 wt. %, and a CO₂ gas flow rate of 500 to 1200 mL/min, preferably 500 to 1000 mL/min. The reaction time is 0.5 to 1.5 hours, preferably 0.5 to 1 hour.

The calcium carbonate granules to be used in the present invention can be prepared by granulating 100 parts by weight of the calcium carbonate particles prepared as described above while using 0 to 10 parts by weight of calcium oxide or calcium hydroxide and 10 to 70 parts by weight of water as media. For granulation, a suited method is selected as needed from roll granulation, extrusion granulation, compress granulation, agitating granulation, fluidized-bed granulation and spray drying granulation. The resulting granules thus formed are then dried for 1 to 5 hours in a gas stream containing 0 to 100 wt. % of a CO₂ gas, having a flow rate of 100 to 1000 mL/min and having a gas stream temperature of 80 to 200^oC.

Most preferred is a process for preparing calcium carbonate granules by introducing a CO₂ -containing gas into a suspension containing 1 to 20 wt. %, preferably 1 to 10 wt. % of calcium hydroxide until a carbonation ratio (a conversion ratio of calcium hydroxide in the suspension into calcium carbonate) reaches at least 90% but less than 100%; granulating the resulting suspension; and then converting the granules into calcium carbonate granules in a CO₂ -containing gas.

In the dentifrice of the present invention, the calcium carbonate granules are preferably incorporated in an amount of 1 to 30 wt. %, preferably 2 to 20 wt. %, because such an amount permits tactile sensation of the granules in the mouth and recognition of their effects while giving almost no unpleasant feeling of foreign matters.

The dentifrice is prepared in a manner known per se in the art. It may contain another component ordinarily employed for dentifrices. As a thickening binder, carboxymethylcellulose sodium, hydroxyethyl cellulose, thickening silica, poly (sodium acrylate), carrageenan, xanthan gum, sodium alginate and the like are usable. As a medicinal component, allantoin, tranexamic acid, Vitamin E, Vitamin C, sodium monofluorophosphate, glycyrrhetinic acid, benzethonium chloride, cetylpyridinium chloride and the like are usable. As a flavoring agent, menthol, peppermint, spearmint, anethole, carvone, menthone, tymol, limonene, cineol, eugenol, cinnamic aldehyde, methyl salicylate, ethyl butyrate and the like are usable. In addition, a humectant, abrasive, sweetening agent, antiseptic, surfactant and the like can be added.

The granules prepared in such a manner are incorporated in various dentifrices such as toothpaste or tooth powder, but toothpaste is particularly preferred for aesthetic appreciation of granules.

Claim 1 of 16 Claims

What is claimed is:

1. A dentifrice comprising:

a dentifrice vehicle; and

granules consisting essentially of calcium carbonate particles, having an average granule size of 50 to 500 .mu.m as measured by particle sifting, and a crushing resistance of 1 to 20 g/granule, wherein said calcium carbonate particles have an average primary particle size of 0.01 to 0.5 .mu.m as measured by microscopy.

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.