DK158561B - Abrasives for use in dentifrices and methods of manufacture thereof - Google Patents

Description

"DK 158561 B

The present invention relates to improved dental services. More particularly, the invention relates to novel alkaline earth-precipitated precipitated silica abrasives suitable for use in therapeutic dentifrices 5 containing both soluble fluorides as agents for reducing the solubility of the enamel and soluble phosphates as denture penetrants. The invention further relates to processes for the preparation of these improved precipitated silicon dioxide abrasives.

10

The function of an abrasive in preparations intended for use in the oral cavity is to remove various deposits, including membrane films from the surface of the teeth. Mesh films are firmly adherent and often contain brown or yellow pigments and therefore give the teeth an unappealing appearance. An advantageous toothpaste abrasive should maximize film removal without causing too much grinding of the hard gum tissue. Dental scientists are constantly working to develop toothpaste abrasives that show a satisfactory degree of cleansing and which are not too abrasive and harmful to the oral tissue.

20

In addition to abrasives, therapeutic toothpastes typically contain sources of fluoride ion. The beneficial reduction in the incidence of dental caries by topical application to teeth enamel surfaces of solutions containing fluoride ions is well known. Especially at pH values of the solution between ca. 4 and 8, fluoride ions are assumed to react with the enamel and decrease the acid solubility of this enamel. Thus, enamel treated with fluoride is more resistant to caries formation. Therapeutic dentifrices, therefore, are formulated so as to provide available fluoride ion in toothbrushing solutions formed in the oral cavity during use.

It has been postulated that the efficacy of fluoride treatment to provide anticariogenic benefits and advantages with respect to the insolubility of the enamel depends on the amount of fluoride ion available to absorb the enamel being treated. Of course, it is therefore desirable to formulate toothpastes which provide maximum availability of fluoride ion in brush solutions formed therefrom. Efforts to utilize such ionic anticarogenic fluoride agents i

DK 158561 B

However, 2 toothpastes suitable for home use have been unable to provide the theoretical maximum soluble fluoride due to the tendency of ionic fluoride to be inactivated and thereby rendered inaccessible for uptake into the enamel. That is, the toothpaste at storage (at rates increasing with temperature) loses the ability to provide the theoretically maximum amount of soluble fluoride.

Sources of fluoride ion tend to react with toothpaste units and with such toothpaste components as abrasives, buffers and so on. This reaction reduces the ability of the fluoride source 10 to provide "soluble fluoride" upon use. The propensity of the toothpastes disclosed herein to maintain their level of soluble fluoride after storage is hereinafter expressed as "toothpaste fluoride compatibility". Thus, the toothpaste fluoride compatibility of a given toothpaste is the percentage of the theoretical maximum amount of fluoride source that is actually measured as soluble fluoride after storage for a specified time and at a specified temperature (eg, a week at 49 ° C). The propensity of such a dentifrice component, such as the abrasive, to react with the fluoride source to decrease the measured soluble fluoride level from the theoretically maximum amount of fluoride source (especially in the presence of membrane penetration agents described in detail below) is expressed. in a manner similar to "abrasive fluoride compatibility". The test methods used in the present specification to determine "toothpaste fluoride compatibility" and "abrasive fluoride compatibility" values are described in more detail below.

A toothpaste component that may cause particular difficulties in the composition of fluoride toothpaste is a precipitated silica as abrasive component. Precipitated silica abrasives are desirable for use in toothpastes because they have desirable low dentin abrasives. Certain known precipitated silica abrasives are generally compatible with soluble fluoride sources but have insufficiently high abrasiveness to provide effective cleaning. Certain other known precipitated silica abrasives provide acceptable cleaning, but have low abrasive fluoride compatibility as measured by the method described below. It is believed that no previously known precipitated silicon = dioxide abrasive provides both high "abrasive fluoride compatibility" and 3: 85 158561Β acceptable cleaning performance (as shown by standard radioactive dentin abrasive values). Thus, there is a clear need to assemble precipitated silica abrasives which exhibit high "abrasive fluoride compatibility" and acceptable cleaning performance. It is therefore an object of the invention to provide precipitated silica abrasives that exhibit high "abrasive fluoride compatibility" and acceptable cleaning performance.

Another dentifrice component which can be particularly damaging to the soluble fluoride content of certain dentifrice compositions is soluble phosphate. Soluble phosphates serve in toothpaste use to enhance the ability of fluoride ions to permeate the dental film. For this reason, soluble phosphates are conveniently included in fluoride dentifrices. However, especially in combination with silica tooth solvents, soluble phosphate as a membrane penetration agent tends to promote the loss of soluble fluoride in toothpastes containing these materials, and the toothpastes therefore exhibit low fluoride compatibility values.

Thus, there is a clear need to assemble precipitated silicon dioxide abrasives which provide high toothpaste fluoride compatibility when used in fluoride toothpastes containing soluble phosphates as film penetration agents.

Surprisingly, it has been found that the above object can be realized, the invention disclosing a novel precipitated silica dioxide abrasive that has been treated with an alkaline earth metal material, especially calcium. By using the present tooth abrasives, fluoride toothpastes containing soluble phosphates can be prepared which have high toothpaste 1 inoride compatibility and excellent cleaning performance.

30

Of course, it is well known that therapeutic dentifrices contain calcium phosphate materials as abrasives, but these calcium materials are present in large quantities as described above and illustrated e.g. in U.S. Patent Nos. 3,624,199 and 3,864,471. There are also known dentifrices containing small amounts of alkaline earth metal ions, such as calcium ions, and compositions of this type are illustrated by U.S. Patent No. 3,991,177. This patent discloses dental care.

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agents containing a stabilizer activator for a dextranase enzyme agent, wherein the stabilizer activator is a salt such as calcium chloride present in an amount of 0.001 to 0.3% by weight. This agent may also contain therapeutic fluoride and the abrasive is calcium carbonate.

Another prior art which describes dentifrices containing alkaline earth metal compounds or ions is US Patent No. 3,095. 356, 3,122,483, 3,669,221, 3,782,446, 3,842,168, and 3,689,537. However, none of these patents disclose therapeutic dentifrices which contain as abrasive a precipitated low-structure silica containing approx. 10 to 300 parts per million alkaline earth metal = ion as described below.

The present invention discloses a novel dentifrice abrasive comprising a precipitated amorphous silica which has been used to react with a salt or a compound of an alkaline earth metal, and is characterized in that the precipitated amorphous silica is prepared. of a freshwater alkali metal aliquot solution by acidification, which silica has been made to react intimately with the salt or compound of a metal alkali such that there are 10-300 parts per million alkaline earth metal ions exhibiting an amorphous silica exhibiting a radioactive dentin settling value of at least 40, a packed bulk weight of approx. 0.24 to 0.55 g / ml, an oil absorption of approx.

70-95 cm 3/100 g, a BET surface area of approx. 100-250 m2 / g and a percent loss on annealing of approx. 4-6%.

The invention further relates to a process for preparing the novel abrasives in which a) an aqueous solution of an alkali metal silicate having a molar ratio of SiO2: X20 of 2.0-2.7, where X represents an alkali metal, is prepared at a reaction temperature of 77-91 ° C, 35 b) the alkali metal silicate solution is acidified with a mineral acid until the precipitation of silica is substantially complete, after which the mineral acid addition is continued until a pH of 6.0 or less, c) matures at a temperature of 10-30 ° C higher than the reaction temperature for a period of 10 to 30 minutes, and 5

DK 158561B

d) filtering the resulting slurry and washing the solid product with fresh water, which is characterized in that e) the resulting wet cake is resuspended in water under stirring; f) a sufficient amount of alkaline earth metal ions is added in the form of a sufficiently soluble soil alkaline metal compound in sufficient quantity to add to the wet cake, alkaline earth metal ions in an amount of 10-300 ppm, calculated on dry extractable product in the slurry; g) the resulting mixture is stirred to create adherence to the effective amount of and (h) the solid abrasive is dried and recovered.

15

Fluoride-containing dentifrices comprising the amorphous precipitated silica dioxide abrasives of the invention, a source of fluoride ions, a binder, a moisture-binding agent and water, give a pH of 4.0 to 8.0 when slurried with water 20 in a weight ratio of 3: 1 between water and the agent.

The present abrasives are low structure silicon dioxide materials. They preferably contain 10 to 100 parts per minute. million of alkaline earth metal ions, preferably calcium ions, based on the amount of recoverable dry material. In addition, they preferably have an RDA value of 70 to 120.

The tooth sizing agents according to the invention are precipitated silicon dioxides which are prepared by the general methods described e.g. in U.S. Patent Nos. 3,893,840 and 3,988,162. Abrasives prepared by such processes are then treated with alkaline earth metal ions in the manner described herein. The process of preparing the silicon dioxides generally comprises acidifying an aqueous alkaline metal silicate solution with a mineral acid to effect the precipitation of silica. The acid addition is continued to an acidic pH and the resulting precipitated silica is then removed, e.g. by filtration and washed to remove any

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by-products such as alkali metal sulfate to form a wet cake. The resulting wet cake is then resuspended in its own water or with additional water and then treated with the required amount of alkaline earth metal ions in the form of a soluble salt to give the abrasive materials of the invention.

The abrasive of the invention differs from the precipitated silica materials which have been treated with 10 alkaline earth metal ions and which are described in Danish Patent Application No. 4103/77. The silicon dioxides treated with alkaline earth metals, as stated, are abrasives useful for incorporation in dentifrices to prevent corrosion of unpainted all-aluminum toothpastes. These anti-corrosion-prevented precipitated silicon dioxides, described in Application No. 4103/77, are silicon dioxides prepared by the so-called sulphate liquid method. In this method, an electrolyte such as alkali metal sulfate is mixed with alkali metal silicate liquid during acidification with mineral acid, described e.g.

No. 20 of U.S. Patent Nos. 3,960,586 and 3,928,541. The products of Application No. 4103/77 can be described as precipitated Si T in -cium dioxides, which thoroughly mix an amount of alkaline earth metal ions within the range of the present invention, but the abrasive products of the invention have other properties than the silicon dioxides obtained by the sulphate liquid method. The silica materials produced by the sulphate liquid method, when used in certain fluoride-containing dentifrices, do not provide the better fluoride compatibility obtained by the present invention. The 30 better values for fluoride compatibility of the tooth abrasives of the present invention are obtained only with silica produced by the so-called freshwater alkali metal silicate method described below.

35 7

DK 158561B

The silica abrasives of the present invention are treated with alkaline earth metal precipitated precipitated silica made from fresh water silicate solutions. Such a process does not use any electrolyte, such as sodium sulfate, to prepare the crude precipitated silica. In addition, in the products of the present invention, it has been found that the presence of alkaline earth metal ions intimately associated with the resulting silicon dioxide dioxide must be present within a particularly narrow range to provide the fluoride compatibility necessary for use in the invention. Thus, abrasive products of the present invention have fluoride compatibility values of at least 90S, whereas the abrasives described in Application No. 4103/77 generally provide compatibility values of 89% or less determined by the toothpaste fluoride compatibility test which is described in the present application.

It is believed that the improved fluoride compatibility of the present tooth abrasives is based on the manner in which the silanol groups therein are bonded to the surface of the silica product. Thus, in the silicon dioxide produced by the fresh water silicate method of the invention, the silanol groups on the surface of the material are assumed to be more accessible than on the silica obtained by the sulfate-liquid method as described in Application No. 4103/77. Furthermore, due to the silanol groups, the surface acidity of the fresh water silica is higher than the corresponding acidity of the silica obtained by the sulphate liquid method. Because the silanol groups are different in these two materials, the actual surface acidity does not react well to calcium treatment for fluoride compatibility in products prepared by the sulfate liquid method. The products of application No. 4103/77 also have higher abrasive values than the silicon dioxides of the present application. The present abrasives therefore differ from those with alkaline earth metal. treated Si = 35 lithium dioxides described in co-application No. 4103/77.

The present precipitated silicon dioxide abrasives are preferably prepared by filling an aqueous solution of an alkali metal silicate solution, preferably a sodium silicate solution in an acid reactor. The aqueous sodium silicic acid 8 DK 158561 B.

solution is a fresh water solution with a sodium sicat concentration in the range of about 10 to 17 wt.% And preferably 12.5 to 15.5 wt.% And a composition of sodium lactic acid of Na220.2.6 SiO2 to obtain the best results. The aqueous sodium sulfate solution is then raised to a temperature of ca. 50 to 95 ° C, and with still stirring, the solution is acidified by the addition of an aqueous solution of a mineral acid with a concentration of ca. 10 to 20% by weight to a substantially constant pH value in the range of approx. 8.5 to 10 10.5. The mineral acid is preferably sulfuric acid as sulfuric acid gives the best results, but as is known (see US Patent Nos. 3,988,162 and 3,893,840) other acidifying agents such as nitric acid, phosphoric acid, hydrochloric acid, carbonic acid and the like can also be used.

In the most preferred embodiment, only a portion of the alkali metal silicate solution is charged to the reactor, brought to the desired temperature 20 with stirring, and the sulfuric acid and the remainder of the alkali metal silicate solution are simultaneously added to the first added silicate solution at the reaction temperature. Preferably, approx. 8 to 12% by weight of the metal silicate from the beginning added to the reactor. The remaining part is then added together with the sulfuric acid. The period within which the alkali = 25 metal silicate and sulfuric acid are added to the alkali metal silicate in the reactor can be predetermined and is generally based on the volume of the reactor and the difficulties in controlling the temperature and stirring. After completion of the addition of the alkali metal silicate solution, the acidifying agent is added continuously until the pH of the reaction slurry drops below approx. 6.0 and preferably in the range of approx. 4.6 to 5.0. The resulting slurry is the precipitated silicon dioxide contained in the reaction medium.

After reaching the pH below 6, Q, the slurry is then heated for a ripening period to a temperature of 10 to 30 ° C above the reaction temperature and the pH of the reaction mixture is adjusted again if necessary. The resulting slurry is then filtered and washed with additional water to remove any reaction by-products, such as sodium sulfate, which may be contained in the silica product. The moisture content of the wet cake in the resulting filter cake is in the range of approx. 60 to 66% and the material is of low structure. The above reaction

DK 158561B

The reaction to this point is generally the same as described in U.S. Patents Nos. 3,893,840 and 3,988,162 to the production of silica of freshwater alkali metal silicate.

In the process of the present invention, after filtering and washing the wet cake of cilium dioxide, the material is then subjected to treatment with alkaline earth metal ions to prepare the novel abrasive product of the invention.

In the process of the invention, the wet washed filter cake is then resuspended in its own water or with the addition of fresh water at ambient temperature with stirring. While stirring, the slurry is then treated with sufficiently much alkaline earth metal ion, preferably calcium ions in the form of a salt which is sufficiently soluble to yield an amount of alkaline earth metal metal equivalent to about 10%. 10 to 300 parts per million or 0.001 to 0.03% by weight (based on the weight of the dry extractable silica = umdioxide) alkaline earth metal ions intimately linked to the silica.

The alkaline earth metal ion added at this point is preferably calcium ion because it is readily available, inexpensive and easy to incorporate into the silica. The calcium ions can be incorporated into the silica at this stage in any sufficiently water-soluble form (i.e., soluble in water to a minimum of 0.07 g / 100 cm 3 at 20 ° C), such as solutions of calcium nitrate, calcium oxide, calcium hydroxide. or calcium chloride. Lime or calcium hydroxide is preferred. Solutions of organic salts such as calcium acetate, calcium formate and the like may also be used. The corresponding strontium and magnesium salts of the class of alkaline earth metals can also be used. 30 food-grade salts should be used.

After treatment with the alkaline earth metal ion, the slurry of the cake is stirred vigorously for 10 to 20 minutes, preferably 15 minutes, to give the effective amount of alkaline earth metal for treatment on the surface of the silica abrasive. The resulting product is then dried. Preferably, the drying is carried out in a spray dryer having an inlet temperature of 483 ° C and an outlet temperature of 122 ° C, as is known in the art, and then ground to the desired degree of fineness.

DK 158561 B

The following examples are given to illustrate the invention.

In the examples, the parts are by weight, unless otherwise stated.

Example 1.

Into a 30,000 liter stainless steel reactor with steam heating jacket was placed 1794 liters of sodium silicate solution (3.78% Na 2 O, 9.53% SiC 2) having a density of 1.121 and containing 42 g Na2 <9 per liter. liter. The reaction medium was heated to 88 ° C with still stirring. At this time, 10% sulfuric acid solution (density 1.066) and sodium silicate solution were added simultaneously to the reaction medium at a rate of 151.4 l / min, acid and 351 l / min. sodium silicate while maintaining the reaction temperature at 88 ° C - 1 ° C. These two solutions were added to the reaction medium for a predetermined period. The silica-I5 addition was discontinued after 47 minutes, but the acid addition was continued until the pH of the slurry was between 4.8 and 5.0. The reaction slurry was boiled at 100 ° C for 20 minutes and the pH of the reaction mixture was adjusted again to between 4.8 and 5.0.

The resulting slurry of silica was filtered and washed to remove most of the reaction by-product (sodium sulfate) and the filter cake was dried and the dry product ground to the desired degree of fineness. The dry silica was subjected to various physicochemical tests, the analyzes of which are set forth below (see Table I). This example is the preparation of a control product to which no alkaline earth metal is added.

Example 2.

To a 30,000 liter stainless steel reactor with steam heating jacket 30 was added 1794 liters of sodium silicate solution (3.78% 2 O, 9.53% SiC 2) having a density of 1.112 and containing 42 g of Na 2 O per liter. liter. The reaction medium was heated to 88 ° C with still stirring. At this point, 10% sulfuric acid solution (density 1.066) and sodium silicate solution were added simultaneously to the reaction medium at a rate of 35 of 151.4 l / min, acid and 351 l / min of sodium silicate while maintaining the reaction temperature at 88 ° C. 1 ° C. These two solutions were added to the reaction medium for a predetermined period. The silicate addition was discontinued after 47 minutes, but the acid addition was continued until the pH of the slurry was between 4.8 and 5.0. Reaktionsopslæm-

11 DK 158561 B

the mixture was boiled at 100 ° C for 20 minutes and the pH of the reaction mixture was adjusted again to between 4.8 and 5.0. The resulting silica slurry was filtered and washed to remove most of the reaction by-product (sodium sulfate).

5

The washed filter cake was then resuspended without addition of water at ambient temperature with stirring. While stirring, the slurry was treated with 102 g of Codex grade (American Food Grade) hydrated lime (calcium hydroxide) to yield 25 ppm of calcium ion based on the total weight of dry recoverable solid product in the slurry form. After treatment with the calcium ion, the slurry of the cake was stirred vigorously for 15 minutes to give the effective amount of calcium ion on the surface of the silica abrasive. The resulting product is then spray dried at an inlet temperature of 483 ° C and an outlet temperature of 122 ° C, ground and characterized in terms of abrasive properties and physical properties in the same manner as the abrasive of Example 1.

Example 3.

The procedure in this example was the same as in Example 2 except that the rate of addition of sulfuric acid was 162.7 liters per liter. and the calcium addition was 204 g of calcium hydroxide, which gives 50 ppm of calcium ion. The product was then characterized.

Example 4

This example was the same as Example 2 except that the rate of addition of sulfuric acid was 166.5 liters per liter. and the calcium addition was 408 g of calcium hydroxide to form 100 ppm of calcium ion in the silica. The product was then characterized.

Example 5

In this example, a silica dentifrice abrasive was prepared by first adding 1420 liters of sodium silicate solution (4.09% Na 2 O, 10.31% SiO 2) having a density of 1.131 and containing 46.3 g Na 2 liter to the reactor as reaction medium.

The reactor was heated to 91 ° C with still stirring. On this

12 DK 158561 B

At that time, 12% sulfuric acid (density 1.08) and sodium silicate solution were added simultaneously to the reaction medium at a rate of 162.7 l / min, acid and 315 ^ 7 l / min, sodium silicate while maintaining the reaction temperature of 91-1 ° C. The silicate addition was discontinued after 5 47 minutes, but the acid addition was continued until the pH of the slurry was between 4.6 and 4.8. The reaction slurry was boiled at 100 ° C for 20 minutes and the pH of the reaction mixture was again adjusted to between 4.6 and 4.8. The resulting slurry of silica was filtered and washed to remove the by-product sodium sulph = 10 barrels.

The washed filter cake was then resuspended without addition of water at ambient temperature with stirring. While stirring, the slurry was treated with 510 g of Codex grade (American food grade) hydrated lime (calcium hydroxide) to give 125 ppm of calcium ion based on the total weight of the dry extractable silica present in the slurry form. After treatment with calcium ion, the slurry of the cake was stirred vigorously for 15 minutes to give the effective amount of 20 calcium ion on the surface of the silica abrasive. The resulting product was then spray dried at an inlet temperature of 483 ° C and an outlet temperature of 122 ° C, ground and then characterized.

Example 6

This example was the same as Example 5 except that 1608 liters of sodium silicate solution was initially added to the reactor as reaction medium and the rate of acid addition was increased to 170.3 liters / minute, but the rate of silicate addition was kept at 315.7 1 / min.

The washed filter cake was treated with 816 g of calcium hydroxide to form 200 ppm of calcium ion on the surface of the abrasive of silica = 35 cesium dioxide. The product was then characterized.

Example 7

This example was the same as Example 2 except that the 40 calcium ion addition was 2,040 g of calcium hydroxide to form

13 DK 15856 IB

of 500 ppm calcium ion. The product was then characterized.

After preparation of the products of Examples 1 to 7, they were characterized in terms of physical properties and the results 5 are given in the following Table I.

14 DK 158561 B

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DK 158561B

Several representative toothpastes according to the invention are mentioned in the following examples in which the precipitated silica abrasive abrasives are used herein.

Example 8 ♦

A toothpaste is formulated using the precipitated silica dioxide abrasive of Example 2 which has the following composition:

Component Amount (% by weight) Precipitated silica abrasive (Example 2) 16.0

Sodium Fluoride (NaF) 0.28 Sorbit Solution (70%) 32.0

Glycerin 13.0

Sodium carrageenin 0.75

Monosodium Orthophosphate Monohydrate (NaH 2 PO 4, H 2 O) 2.15

Disodium orthophosphate dihydrate (Na2HPO4.2H2O) 8.34

Sodium alkyl sulfate solution (28.8%) 6.0

Coconut monoglyceride sodium sulfonate 0.9

Aroma 1.22

Sodium Saccharin 0.3 Color (FD&G Blue # 1 Solution 1%) 0.35

Titanium dioxide (TiC> 2) 0.5

Trisodium citrate dihydrate 0.25 (C6H5Na307.2H2O)

Distilled water q.s.

Total 100.0

The above dentifrices are prepared by mixing the components in a normal manner for toothpaste manufacture. Preferably, the water component is first added to a suitable container, to which is then added, under moderate stirring, in order of the permeability agents, the flavor, the moisture binder and then the remaining components.

A 3: 1 slurry by weight of the above freshly prepared agent with water (3: 1 water / agent) gives a pH of approx. 7.1.

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DK 158561 B

This dentifrice provides beneficial fluoride treatment of toothed tissue which is brushed thereby, due to the high compatibility of toothpaste with fluoride. The toothpaste also provides good cleaning and an RDA of 100. When stored for a long time at 27 ° C, such a toothpaste exhibits minimal loss of soluble fluoride.

Toothpastes which provide substantially the same benefits in terms of fluoride treatment, compatibility between toothpaste and fluoride and purity can be realized when the sodium fluoride in the composition of Example 8 is replaced by an equivalent amount of stannofluoride, sodium = chlorofluoride, potassium fluoride, potassium fluoride, potassium fluoride, zinc fluoride or ammonium fluoride.

Toothpastes which give substantially the same benefits in terms of fluoride treatment and substantially the same purity are obtained when the mixture of phosphate in the composition of Example 8 is replaced by an equivalent amount of NaH2PO4, NaH2PO4, H2O, NaH2PO4.2H20,

Na2HPO4, Na2HPO4.2H2O, Na2HPC> 4.7H2O, Na3PC> 4.6H2O, Na3PO4.8H2O, KH2PO4, K2HPO4, K2HPO4.2H2O, K2HPO4.6H2O, K3PO4.3H2O, K3PO4.7H20, K3PO4.7H2O H2PO4, (NH4) 2HPC> 4, (NH4) 3PO4, other mixtures of

NaH 2 PO 4, H 2 O, and Na 2 1: 3 to 1: 5, mixtures of NaH2 PO4, H2O and K2HPO4.2H2O in weight ratios of sodium to potassium salt from about 1: 3 to 1: 5, t = tracalium pyrophosphate, tetrasodium pyrophosphate, disodium pyrophosphate = 25 phate, sodium tripolyphosphate, potassium tripolyphosphate, mono potassium meta phosphate, sodium trimetaphosphate, sodium hexametaphosphate, or sodium phosphate from 4.0 to 8.0.

Example 9.

A high abrasive toothpaste is formulated using the precipitated silica abrasive of Example 3, which toothpaste has the following composition:

17 DK 158561B

Component. Amount (% by weight) Precipitated silica abrasive (Example 3) 35.0

Sodium Fluoride (NaF) 0.22 Glycerin 5.0

Sorbit solution (70S) 20.0

Carboxymethyl cellulose (0.7 D.S.) 0.5

Magnesium Aluminum Silicate (Veegum Flakes) 0.3

Monosodium Orthophosphate Monohydrate (NaH 2 PO 4, H 2 O) 0.3

Disodium orthophosphate dihydrate (Na 2 HPO 4,2H 2 O) 0.3

Sodium alkyl sulfate solution (28.8%) 2.3

Coconut monoglyceride sodium sulphonate 0.7

Flavor 0.9 15

Sodium saccharin 0.2

Titanium Dioxide (TiO 2) 0.5

Spot staining material 0.5

Distilled water q.s.

Total 100.0.

20

Toothpastes which provide substantially similar benefits in terms of fluoride treatment, toothpaste and fluoride compatibility, and cleaning performance are obtained when the abrasive component of precipitated silica, prepared as in Example 3, is replaced by an equivalent amount of abrasives prepared in Examples 2. , 4, 5 and 6.

Toothpastes which give substantially the same benefits in terms of fluoride treatment and substantially similar purity are obtained when in the composition of Example 9 the phosphate mixture is replaced by an equivalent amount of NaH2 PO4, NaH2PO4, NaH2PO4, H2Q, NaH2PC> 4.2H20,

Na2HPO4, Na2HPO4.2H2O, Na2HPO4.7H2O, Na3PO4.6H2O, Na3PC> 4.8H2O, KH2PO4, k2hpo4, k2hpo4,2h2o, k2hpo4,6h2o, k3po4,3h2o, k3po4,7h2o, k3p4 , (NH4) 2HPO4, (NH4) 3PO4, other mixtures of NaH2PO4, H2O and Na2HPO4.2H2O in a weight ratio of monosodium and disodium salt 1: 3 to 1: 5, mixtures of NaH2 PO4, H2O and K2HPO4.2H2O in a weight ratio of sodium to potassium salt from ca. 1: 3 to 1: 5, tetra = potassium pyrophosphate, tetrasodium pyrophosphate, disodium pyrophosphate, sodium tripolyphosphate, potassium tripolyphosphate, monocal potassium metaphosphate, sodium trimetaphosphate, sodium hexametaphosphate, or sodium hepta = 1 solution provided that an 18

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pH from 4.0 to 8.0.

Example 10.

A clear toothpaste is prepared using the precipitated silica abrasive of Example 4, which toothpaste has the following composition:

Component Amount (% by weight) Precipitated silica abrasive (Example 4) 20.0

Sodium fluoride (NaF) 0.24

Sorbit solution (70%) 57.0

Glycerin 15.0 Sodium carrageenin 0.5

Phosphoric acid (85%) 0.10

Sodium alkyl sulfate solution (28.8%) 4.0

Aroma 1.0

Sodium saccharin 0.2 20 Color (FD&C Blue # 1 solution 1%) 0.05

Distilled water g, p.

Total 100.0

Example 11.

25

A mild abrasive toothpaste is formulated using the precipitated silica abrasive of Example 3, which toothpaste has the following composition: Component Amount (% by weight) Precipitated silica abrasive (Example 3) 6.0

Stannofluoride (SnF4) 0.40

Sorbit Solution (70%) 51.0 Glycerin 25.6

Sodium carboxymethyl cellulose (0.7 DS) 1.0

Sorbitan monoisostearate 2.00

Sodium alkyl sulfate solution (28.8%) 6.0

Flavor 1.20 40 Sodium saccharin 0.28

19 DK 158561 B

Color (FD&C Blue ft 1 solution 1%) 0.25

Pyrogenic Colloidal Silica (Aerosil 200V) 5.00

Distilled water e.g.

Total 100.0 5 x Negotiated by Degussa, Inc.

Toothpastes which provide substantially the same advantages with regard to fluoride treatment, the same compatibility between toothpaste and fluoride LO and the same purity are obtained when the precipitated silica abrasive in the composition of Example 10 is replaced by an equivalent amount of abrasives prepared in Examples 2, 3, 5 and 6th

A toothpaste that provides substantially the same benefits in terms of fluoride treatment and improved anti-tooth effect is obtained when the composition of Example 10 further contains approx. 1.0% by weight di = sodium ethane-1-hydroxy-1,1-diphosphonate.

The precipitated silica abrasives of the invention may be used to prepare particularly desirable therapeutic dentifrices containing soluble phosphate as membrane penetration agents.

These agents provide both high abrasive and fluoride compatibility and yet have good tooth cleansing performance. The following tests and assessments serve to show the excellent fluoride compatibility afforded by the precipitated silica tooth abrasives of the invention in the dentifrice of the invention. It is also shown below that the abrasives of the invention provide higher compatibility between abrasive and fluoride than abrasives prepared in a similar manner that have not been treated so as to contain the essential amounts of alkaline earth metal. The excellent cleaning performance of the dentifrices of the invention is also demonstrated. Finally, it is shown that abrasives made by a process of acidifying sulfate liquid, although containing an alkaline earth metal, cannot give the high fluoride compatibility values as the fresh water precipitated silica abrasives of the invention.

Compatibility between abrasive and fluoride.

Precipitated silica tooth abrasives can be sorted by their rela-> 1

2o DK 158561B

tive compatibility with fluoride materials by a 24 hour slurry test. Such a test can be used to obtain data that can predict the availability of soluble fluoride in certain types of fluoride toothpastes after storage for a period of approx. 4 weeks 5 at 27 ° C.

The 24-hour abrasive slurry sample is used to develop fluoride compatibility values defined as the percentage of theoretically maximum available fluoride that is actually measured after 24 hours as soluble fluoride by the following test method. By this method (Orion Specific Ion Electrode Method), a standard sodium fluoride stock solution containing 1624 ppm of fluoride is prepared by dissolving 2.80 g of sodium fluoride, 21.5 g of Na

83.4 g ^ 2 ^ 0 ^, 21 ^ 0 in 672.5 g of deionized distilled water and store it in a polyethylene bottle. Weigh 30 g of this solution then. 7 g of the silica abrasive being tested is then dispersed in the solution and contacted for 24 hours at a temperature of 37.8 ° C. After 24 hours, the mixture of precipitated silica abrasive and fluoride solution is centrifuged for 20 minutes at 15000 »0 rpm. minute, or until the overlying liquid is clear. Then pipette 10 ml of the overlying liquid into a plastic bottle. Then pipette 10 ml of EDTA / THAM solution into the plastic bottle. (EDTA / THAM solution is 0.2 molar with respect to EDTA (ethylenediaminetetraacetic acid, disodium salt) and 0.2 molar with respect to '5 THAM (2-amino-2-hydroxymethyl-1,2-propanediol) and adjusted to pH

8.0 with sodium hydroxide). A magnetic stir bar is added and gentle stirring is initiated. The fluoride ion concentration is determined by direct potentiometers with the Orion fluoride electrode (model 95-09). Emf is converted into parts per million (ppm) fluoride in the supernatant by a logarithmic equation. The fluoride compatibility value is then calculated by expressing the measured ppm of soluble fluoride as a percentage of the theoretically available soluble fluoride.

Using this method, the relative compatibility J5 values for abrasive and fluoride for the various abrasives prepared according to Examples 1 to 7. are determined. The results of these determinations are given in the following Table II.

21 DK 158561 B

label II

Compatibility of abrasive and fluoride

Ex. No. Calcium Treatment Abrasive Fluoride Compatibility 5 (PPm) __ 1 (Control) 0 76% 2 25 93% 3 50 94% 4 100 93% 10 5 125 91% 6 200 90% 7 500 88% 15 The data in Table II shows that the precipitated silica abrasives of the invention containing certain amounts of an alkaline earth metal give significantly better compatibility of abrasives and fluoride compared to that obtained with an alkaline earth metal-free abrasive material which is otherwise manufactured in the same way. Therefore, the precipitated silica = 20 dioxide abrasives prepared in Examples 2 to 6 would be suitable for preparing toothpastes containing fluoride and membrane penetration agents which exhibit high compatibility between abrasive and fluoride.

25 Compatibility of abrasive and fluoride in toothpastes.

Preferred toothpastes of the invention containing precipitated silica dioxide abrasives and membrane penetration agents are assessed for abrasive fluoride compatibility. The toothpastes prepared for evaluation have the same composition as the toothpaste of Example 8 and differ only in a variation in the abrasive component.

To determine fluoride compatibility values for the tested toothpastes, a method of determining soluble fluoride, similar to the method described above for determining abrasive and fluoride compatibility values, is used. In this method, the toothpastes are stored in a laminated tube for a given time. Then, 15.0 g of the agent is placed in a 100 ml beaker and then 45.0 g of distilled water is added. The mixture is then stirred to form one

22 DK 158561B

slurry in which the toothpaste is uniformly distributed. The slurry is then centrifuged for 20 minutes at 15000 rpm. minute, or until the overlying liquid is clear.

The supernatant liquid is then treated as by the method described above for determination of abrasive and fluoride compatibility. The concentration of soluble fluoride is similarly measured and similarly an abrasive and fluoride compatibility value is calculated for each toothpaste. The compatibility values for toothpaste and 10 fluoride for the respective toothpastes examined are shown in Table III. The abrasives tested are those prepared as described in Examples 1 to 7 and characterized in Table I.

Table III 15

Compatibility of toothpaste and fluoride.

Abrasive Calcium Treatment Toothpaste Fluoride Compatibility (Ex. No.) _ (ppm) _ (1 week 27 ° C) _ 20 1 (control) 0 76% 2 25 99% 3 50 98% 4 100 99% 5 125 97% 25 6 200 94 % 7 500 90%

The data in Table III shows that the preferred toothpastes of the invention using the present precipitated silica abrasives provide better values for abrasive and fluoride compatibility than a similar dentifrice containing the precipitated silicon dioxide abrasive prepared by the method of Example 1. , which is not treated with alkaline earth metal. The data in Table III further shows that the availability of the soluble fluoride from the source of fluoride ion is not appreciably diminished by storage when the silicon dioxide abrasives of the invention are used in the preferred toothpastes.

40 Of course, it must be recognized that the amount of soluble available

23 DK 158561 B

fluoride, even in the dentifrices of the invention, will decrease to some extent as a function of increasing time and temperature upon storage. Thus, the values for toothpaste compatibility and fluoride for toothpastes stored for longer periods or at more demanding temperatures are generally lower than those exemplified above.

Additional data on abrasive and fluoride compatibility for several toothpastes showing prolonged storage and at higher temperatures are shown in Table IV.

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24 DK 158561 B

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25

The data in Table IV shows that the preferred toothpastes of the invention retain their relatively high fluoride and abrasive compatibility, even under longer storage or under more demanding storage conditions.

5

Cleaning Ability.

The dental cleanliness of the silica abrasives of the invention can be assessed by the sample of radioactive dentin abrasive 10 (RDA). RDA values can be used to judge the relative purity of various abrasives for a given type of toothpaste abrasive. Thus, for precipitated silica abrasives, an RDA value (measured by the method described below) of at least 40, preferably between 70 and 120, is required to ensure that the abrasive has sufficient abrasion to be an effective toothpaste agent. Previously known precipitated silica abrasives which exhibit high fluoride and toothpaste compatibility are generally poor oral hygiene cleaners, as demonstrated by low RDA values. The abrasives treated with alkaline earth metal, on the other hand, provide both effective tooth cleaning and high fluoride compatibility.

Several commercially precipitated silica abrasives exhibiting relatively high compatibility of toothpaste and fluoride, as measured in the present application, are selected for rating 25 for RDA values. The test is carried out in a standard toothpaste matrix having the same composition as the toothpaste of Example 8 and differs only by variation in the abrasive component.

The procedure used to determine the RDA values for tooth paste listed in Table V is described below. This study method is described in detail in the Journal of Dental Research, July-August 1976 by Hefferren, pages 563-573. The individual steps for determining RDA values are as follows: 35 A. Selection and preparation of teeth.

Healthy, permanent teeth with a single root that are caries-free and vital at extraction are selected. The teeth are then scraped clean with a scalpel. The crown and root tip of each tooth are removed using a grinding wheel to make a dentine specimen 14 mm long

26 DK 158561B

and at least 2 mm wide at the narrow end. Cut pieces of root (dentin shavings) or, alternatively, an additional tooth are also prepared for later use to determine a corrosion factor for radiation self-absorption.

5 B. Radiation of Dentin.

The prepared roots and dentine chips described in step A, 12 2 are subjected to a neutron current of 2 x 10 neutrons per second. cm for 3 10 hours.

C. Mounting of roots.

After irradiation, the irradiated roots are embedded in a substrate of 15 curing dental methacrylate resin and mounted on a cross-brushing machine. Toothbrushes used throughout the sample are "Pepsodent" toothbrushes with 50 brush strokes, which are of medium size and flat.

20 D. Pre-treatment of the dentine surfaces.

Prior to the first experiment, the freshly mounted irradiated roots are brushed with a reference slurry (10 g of calcium pyrophosphate + 50 ml of a 0.5% CMC-10% glycerine solution) with 6,000 brush strokes. At the beginning of each subsequent day's trial, the roots are brushed with 1,000 strokes.

E. Proceedings of trials.

After pretreatment, the dentin samples are then conditioned with the reference slurry (the same slurry as in step D) with 1500 brush strokes at the beginning number during and at the end of each experiment. The course of the experiment consists of brushing dentine samples with 1500 brush strokes with a slurry of the test product (25 g of dentifrice 35 + 40 ml of deionized distilled water).

F. Preparation of correction factors.

The correction factors are prepared by dissolving the dentine shavings or alternatively an additional tooth from step B in 5 ml of concentrated

27 DK 158561 B

HCl filled with distilled water to a volume of 250 ml. One ml of this solution is added to the test pastes and reference slurries, prepared in a similar manner to those of Step E, and then neutralized with 0.1 N NaOH.

5 Radioactive trace count.

The radioactivity of the slurry samples (1.0 ml) is determined with an Interteknik SL-30 liquid scintillation counter. Alternative count-10 method: 3-ml portions of each slurry are transferred to small flat-bottomed stainless steel boxes of dimensions 2.5 cm x 0.8 cm and counted using the Nuclear Chicago Geiger Counting System.

Calculations.

15

The radioactive dentin wear value (RDA) for a given paste will be the ratio of the average corrected number of this paste to the average number of the reference multiplied by 100. The reference abrasive is given in an arbitrary dentine wear value of 100 units.

The results of these RDA valuations are listed in the following Table V.

Table V.

Radioactive dentin wear values

Toothpaste Fluoride Compounds-Abrasive_RDA_Length 1 Week (27 ° C) _ A. (Ex. No.) 1 Control 75-7 76% 2 80-21 99% 3 67-8 98% 4 80-1 99% 5 103-5 97% 6 1111½ 94% 35 + 7 56-4 90% B. Industrial precipitated silicon = dioxides 8 Sident 3 14 14 92% 40 9 Neosyl 25- 78% i

28 DK 158561B

Table V (continued)

Tandpastafluoridforene-

Abrasive_RDA_ Equality 1 Week (27 ° C) _ 10 QUSO G-30 3 '; 22-2 87% 5 11 Neosyl ET 4 * 26-4 84% 1. A precipitated silica marketed by Degussa, Incorporated (N.Y.C) 2. A precipitated silica marketed by Joseph Crosfield & Sons, Limited (London, England).

10 3. A precipitated silica sold by the Philadelphia Quartz Company (Valley Forge, Pennsylvania).

4. A precipitated silica marketed by Joseph Crosfield & Sons, Limited.

The data in Table V shows that the industrial precipitated silica = 15 abrasives may well exhibit high compatibility between abrasive and fluoride, but are not sufficiently abrasive to be useful as dental abrasives. Surprisingly, the present novel precipitated silica abrasives provide excellent abrasive-fluoride compatibility and at the same time excellent RDA abrasive values, which values can be used as an indicator of relative tooth cleaning performance.

"Fresh water" versus "sulfate liquid" abrasives.

25

As mentioned above, the abrasive products of the present invention are related to, but different from, the calcium-treated silicon dioxides of claim no. 826,901. In order to demonstrate such a difference, the following assessment is made to compare the fluoride compatibility of the products of application No. 826,901 with the fluoride compatibility of the abrasive products of the present invention. The tested "sulfate liquid" silica materials are prepared by the procedure described in Application No. 826,901 and U.S. Patent No. 3,960,586 as follows: 35 Dry sodium sulfate was added to 38 liters of water in a 760 liter reactor, thus the sodium sulfate concentration in the reaction medium was 10%. The pH of the reaction medium was then adjusted to 9.0 by the addition of sodium silicate. The reaction temperature was 65 ° C. The sodium sulfate solution had a molar ratio of SiO 2 / Na 2 O of 2.5 and a concentration of 0.24 kg / l. Sodium silicate was added to the reaction mixture.

29 DK 158561B

the medium for 4 minutes. At this point, the addition of sodium = silicate was stopped and sulfuric acid with a concentration of 11.4% was added to the reaction medium until a pH of 9.0 was reached.

At this point, the sodium silicate solution and the sulfuric acid solution were added simultaneously for a period of 35 minutes. After the 35 minute silica addition period, it was discontinued and the acid addition continued until a slurry having a pH of 5.5 was obtained. The portion was left to ripen at 77 ° C for 20 minutes and the resulting wet cake was recovered and washed.

10

The wet cake was then treated in the manner described in Example 2, divided into 6 portions, and treated with 50, 100, 200, 400 and 800 parts, respectively. million calcium from aqueous solutions of calcium hydroxide. Each wet cake was then dried and processed as described in Example 2 and characterized in the following Table VI, the first abrasive being a control in which no calcium was added. Table VI indicates the results of the assessment.

Table VI.

20

Ca addition Abrasive fluoride precursor "Sulfate liquid abrasive_ (ppm) compatibility x A A (control) 88 B 50 89 C 100 88 25 D 200 88 E 400 86 P 800 82

Determined by the test described in connection with Table II.

30

As will be seen from the data in Table VI, the calcium sulfate liquid abrasives of application No. 826,901 provide abrasive and fluoride compatibility values which are generally lower than those obtained with "fresh water" silica abrasives of the present invention. invention (see Table II). Furthermore, the addition of alkaline earth metal to abrasives produced by the "sulfate liquid" method does not result in a dramatic improvement in the compatibility of abrasive and fluoride. As will be seen in a comparison with Table II, the addition of equivalent amounts of alkaline earth metal to silica abrasives of the invention produced

Claims (16)

30 SDK 158561BW by the "fresh water" method, conversely in dramatic improvements in the compatibility of abrasive and fluoride. Patent claims. 5 ____________________ An abrasive for use in dentifrices, said abrasive comprising a precipitated amorphous silicon dioxide which has been reacted with a salt or a compound of an alkaline earth metal, characterized in that the precipitated amorphous silicon dioxide is made from a fresh water alkali. -silicate silicate solution by acidification, which silica has been made to react intimately with the salt or compound of an alkaline earth metal, so that therein there are 10-300 parts per million alkaline earth metal ions, which exhibit a radioactive dentin wear value of at least 40, an amorphous sieve of dioxide, a packed bulk weight of approx. 0.24 to 0.55 g / ml, an oil absorption of approx. 70-95 cm3 / 100 g, a BET surface area of approx. 100-250 m2 / g and a percent loss on annealing of approx. 213 4-6%. An agent according to claim 1, characterized in that the alkaline earth metal ions are of the group consisting of calcium, strontium and magnium. 25 An agent according to claim 1, characterized in that the concentration of the alkaline earth metal ion is from approx. 10 to 100 ppm. Agent according to claim 1, characterized in that the alkaline earth metal ion is calcium ion. 5. An agent according to claim 1, characterized in that the abrasive is prepared by preparing an amorphous silica by precipitation by acidifying a fresh-water alkali metal solution with a mineral acid, isolating a wet cake from the precipitated product and reacting the wet product. cake with a solution of a salt or a compound of the alkaline earth metal. 31 DK 158561 B Agent according to claim 5, characterized in that the mineral acid is selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid and carbonic acid. Agent according to claim 6, characterized in that only part of the alkali metal silicate is initially added to the reaction vessel, the remaining part of the alkali metal silicate solution being added simultaneously with the mineral acid and the addition of the silicate solution being stopped after a predetermined time, wherein the mineral acid is added to a pH of less than 6.0 and the wet cake is isolated by filtration and washing. An agent according to claim 7, characterized in that the alkaline earth metal ion is calcium and is added in the form of a solution of a salt of the group consisting of calcium hydroxide, calcium oxide, calcium nitrate and calcium chloride. A process for preparing an abrasive 20 according to claim 1, in which a) an aqueous solution of an alkali metal aliquot having a molar ratio SiO 2: X 2 O of 2.0-2.7, wherein X represents an alkali metal, is prepared at a reaction temperature of (B) the alkali metal silicate solution is acidified with a mineral acid until the precipitation of silica is substantially complete, after which the mineral acid addition is continued until a pH of 6.0 'or less, (c) matures at a temperature at 10-30 ° C higher than the reaction temperature for a period of 10 to 30 minutes, and d) the resulting slurry is filtered and the solid product washed with fresh water, characterized in that e) the resulting wet cake is resuspended in water with stirring f) a sufficient amount of alkaline earth metal ions is added in the form of a sufficiently soluble soil 1k1imetha compound in sufficient quantity to add the alkaline earth metal ions to the wet cake at a concentration of 10-300 ppm, calculated on dry recoverable product in the slurry; 32 DK 158561B the effective amount of the alkaline earth metal on the surface of the silica, and h) the solid abrasive is dried and recovered. Process according to claim 9, characterized in that the mineral acid is selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid and carbonic acid. Process according to claim 10, characterized in that only part of the alkali metal silicate is initially acidified with the mineral acid and the remaining part is added to the alkali metal silicate solution simultaneously with the mineral acid. Process according to claim 10, characterized in that the alkaline earth metal ion is of the group consisting of calcium, strontium and magnesium. Process according to claim 10, characterized in that the alkaline earth metal ion is calcium and is added as a salt 20 of the group consisting of calcium hydroxide, calcium oxide, calcium nitrate and calcium fluoride. Process according to claim 10, characterized in that the alkaline earth metal salt or compound is reacted with the slurry of the wet cake at ambient temperature. Process according to claim 14, characterized in that the silica treated with alkaline earth metal is dried 30 by spray drying. Process according to claim 10, characterized in that the alkali metal silicate is sodium silicate, the acidifying agent is sulfuric acid, the alkaline earth metal ion is added in the form of calcium hydroxide to form 10 to 100 parts per liter. million calcium O O ion, intimately reacted with the silica product.