GB1587176A

GB1587176A - Abrasive compositions for incorporation in a toothpaste and methods for their production

Info

Publication number: GB1587176A
Application number: GB2648879A
Authority: GB
Original assignee: JM Huber Corp
Current assignee: JM Huber Corp
Priority date: 1976-09-15
Filing date: 1977-09-01
Publication date: 1981-04-01

Description

tz4) IMPROVEMENTS IN OR RELATING TO ABRASIVE COMPOSITIONS FOR INCORPORATION IN A TOOTHPASTE AND METHODS FOR THEIR PRODUCTION (71) We, J. M. HUBER CORPORATION, a Corporation of the State of New Jersey, United States of America, at Navesink & River Road, Locust, New Jersey, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to abrasive compositions for incorporation in a toothpaste which will prevent corrosion of an unlined aluminium tube, and to a method for the production of such abrasive compositions.

Broadly speaking, there are two types of modern day dentifrices on the market which may be described as opaque and clear-gel dentifrice compositions.

Each type of above mentioned dentifrice is marketed under two different versions: A. Cosmetic Type B. Therapeutic Type.

A cosmetic type toothpaste is one which contains no fluoride and is promoted for whitening and brightening of the teeth. A therapeutic toothpaste, however, contained fluoride as anticaries agent.

Therapeutic dentifrice compositions such as toothpastes normally contain a fluoride therapeutic agent such as stannous fluoride, monofluorophosphate, or derivatives thereof, as well as polishing agents, humectants, and other materials. These compositions are usually placed in aluminium or plastic tubes for sale on the commercial market. It is usually preferred to use aluminium tubes but it has been discovered that when such toothpaste compositions contain a therapeutic fluoride compound, a reaction with the interior of the unlined aluminium tube takes place so that staining and other corrosive action occurs apparently because of some reaction or incompatibility between the bare aluminium surface and one or more of the materials in the toothpaste. This incompatibility appears in the form of gas production, swelling of the tube, corrosion, and black stains on the inside surface of unlined aluminium container. Accordingly, the standard practice in the marketing of therapeutic toothpastes today has been to line the aluminium tube with a plastic, lacquer or other material, which therefore substantially adds to the cost of packaging and marketing the toothpaste.

Many prior art attempts have been made to solve this problem because unlined aluminium tubes are much more economical to use and are generally lighter in weight than the lined tubes. For example, U.S. Patents 3,662,060 and 3,624,199 disclose compositions which are said to overcome this problem. Further, U.S. Patent 3,678,155 discloses that monofluorophosphate ions prevent corrosion of unlacquered aluminium tubes when the toothpaste contains milled alpha-alumina trihydrates as an abrasive. Also U.S. Patent 3,864,471 discloses a dentifrice composition containing a monofluorophosphate and a polishing agent containing alkaline earth metal carbonate and insoluble alkali metal phosphate, alumina or mixture thereof, to minimize corrosion in unlined aluminium containers.

It is an object of this invention to provide a novel abrasive for use in toothpaste compositions which will not stain or otherwise corrode unlined tubes, and provide a method for the production of such abrasive compositions. A further object of the invention is to provide a therapeutic dentifrice composition containing an abrasive composition.

Other objects and advantages of the present invention will become apparent as the description thereof proceeds.

According to one aspect of the present invention an abrasive composition useful for incorporation into a therapeutic toothpaste composition and for preventing fluoride-caused corrosion and staining of an unlined aluminium tube containing said toothpaste composition consists essentially of a silica which has been treated with a water soluble salt, oxide or hydroxide of an alkaline earth metal so as to have present therein from 168-7000 ppm of the alkaline earth metal, said silica being suitable for use in a toothpaste composition having an RDA value of between 200 and 400 functioning as a carrier for the alkaline earth metal. Preferably, said silica is selected from amorphous precipitated silica, sodium aluminosilicates, silica xerogels and mixtures thereof; said abrasive composition being prepared, when amorphous precipitated silica is selected as the silica, by preparation of an amorphous silicon dioxide by precipitation through acidulation of an alkali metal silicate solution with a mineral acid in the presence of an alkali metal sulfate, isolating a wet cake of said precipitated product, and treating said wet cake with the salt of said alkaline earth metal.

According to a second aspect of the invention, a method for the production of an abrasive composition for incorporation in a toothpaste which will prevent corrosion of an unlined aluminium tube when an amorphous precipitated silica is selected as the silica comprises forming an aqueous solution of an alkali metal silicate having an SiO2 to X2O mole ratio of 2.0 to 2.7 and of an alkali metal sulfate at a reaction temperature in the range of 66 to 830C., wherein X represents the alkali metal; acidulating said aqueous solution with a mineral acid with continuous agitation until precipitation of silicon dioxide is substantially complete at a pH of 8.0 to 10.4; continuing the mineral acid addition until the pH is 6.0 or less; digesting at a temperature that is 10-300C. higher than the reaction temperature for a period of 10 to 30 minutes; filtering the resulting slurry and washing the solid product with fresh water; reslurrying the resulting wet cake in water, and under agitation conditions, adding thereto at ambient temperature a water soluble salt, oxide or hydroxide of an alkaline earth metal in an amount sufficient to add to said wet cake from 168-7000 ppm of the alkaline earth metal based on the dry recoverable product; agitating the resulting mixture to provide adherence of the effective level'of said metal on the surface of said silicon dioxide; and drying and recovering said abrasive composition.

It has been discovered that the problem of corrosion of unlined aluminium tubes when filled with a therapeutic dentifrice composition can be overcome by incorporation within the toothpaste composition of a controlled amount of an alkaline earth metal. The alkaline earth metal may be calcium, magnesium, strontium or mixtures thereof. Calcium is preferred because of its ready availability, inexpensiveness and ease of incorporation into the dentifrice. The metal may be incorporated into the dentifrice or toothpaste mixture in any substantially water soluble form such as the nitrate, oxide, hydroxide or choride. The most preferred materials for incorporation into the therapeutic dentifrice compositions of this invention include calcium nitrate, calcium oxide, calcium hydroxide, and calcium chloride. It should also be noted however, that organic salts such as calcium acetate, calcium formate may also be used. Corresponding strontium and magnesium salts may also be used. The only limitations to be placed on the alkaline earth metal salt, oxide or hydroxide are that it be substantially soluble, not cause any problems of safety in the compositions and remain available to combat corrosion.

There are of course dentifrice and other toothpaste compositions known in the art which contain calcium salts in substantial amounts, as taught for example in U.S. Patent 3,864,471 which contains 40-50% of calcium carbonate, and U.S. Patent 3,624,199 which contains 20-75% calcium carbonate. However, calcium carbonate is generally insoluble, and is not effective to inhibit corrosion of the tube. Therefore an important aspect of the present invention resides in the carefully controlled amount of water-soluble alkaline earth ion which is incorporated into the toothpaste composition. According to the present invention, the controlled amount of alkaline earth metal ion which is present must be sufficient to be effective and available to prevent corrosion but yet insufficient to stoichiometrically interfere with fluoride availability in the toothpaste. The specified amount of the alkaline earth metal 0.005 to 0.20 wt.% is considered essential to prevent corrosion and yet avoid interference with fluoride availability.

The precipitated silicon dioxides of the present invention are prepared by charging a 3-15 weight percent aqueous solution of alkali metal sulfate, preferably sodium sulfate, to a reactor and adding a solution of an alkali metal silicate solution, preferably a sodium silicate solution, to the reactor to achieve a pH of 8-10.4. This results in prepolymerization of the alkali metal silicate. The aqueous sodium silicate solution should have a silicate concentration range of 10-25 weight percent and more preferably 18to 22 weight percent, and a composition of Na2O 2.6 SiO, for best results. The aqueous solution is then raised to a temperature of 66" to 83"C (150 to 1800F) and with continuous agitation the solution is acidulated by the addition of an aqueous solution of a mineral acid having a concentration of 10-25 weight percent at a substantially constant pH in the range of 8.0 to 10.4. Preferably the mineral acid and alkali metal silicate are added simultaneously as described in my U.S. Patent No. 3,960,586. The mineral acid is preferably sulfuric acid as sulfuric acid provides best results but as known in the art as in my prior U.S. Patent 3,960,586, other acidulation agents such as nitric acid, phosphoric acid, hydrochloric acid, carbonic acid and the like may also be employed. The time period over which the alkali metal silicate and/or sulfuric acid are added to the reactor can be predetermined and is generally based on the volume of the reactor and the difficulties in control on the volume of the reactor and the difficulties in control of the temperature and agitation. After completion of the additions, the acidulation acid is continued to be added until the pH of the slurry falls below about 6.0 and preferably in the range of 4.8-5.0. The resulting slurry is the precipitated silicon dioxide contained in the reaction medium.

After the pH of below 6.0 is obtained, the slurry is then heated for a digestion period of 10 to 30 minutes at a temperature of 10 to 300C. above the reaction temperature and the reaction pH again adjusted as necessary. The resulting slurry is then filtered and washed with additional water to remove any reaction by-product such as sodium sulfate which may be contained in the silicon dioxide product.

In the process of the present invention, at the point of filtration and washing of the silicon dioxide wet cake, the material is then subjected to treatment with alkaline earth metal ions to produce the new abrasive products of the present invention. In accordance with the process of the present invention, the wet wash filter cake is then reslurried in its own water or with the addition of fresh water at ambient temperature with agitation'. While under agitation, this slurry is then treated with sufficient alkaline earth metal ions and preferably calcium ions, in the form of substantially soluble salt, oxide or hydroxide to provide sufficient alkaline earth metal ions corresponding to provide about 30 to 2000 parts per million, intimately associated with the silicon dioxide, this amount being based on 100 parts of dentifrice. The amount of alkaline earth metal ions added is based on the total weight of the dry product contained in the wet cake form, that is recoverable solid. Since the amount of abrasive may vary in dentifrice compositions, the amount of alkaline earth metal salt, oxide or hydroxide will also be varied.

The calcium ions may be incorporated into the silicon dioxide at this stage in any substantially water soluble form such as the nitrate, oxide, hydroxide, or chloride, but lime or calcium hydroxide is preferred. Food grade salts should be used. By soluble salt, oxide or hydroxide is meant that any reasonably soluble salt of calcium may be used since it is only necessary to provide extremely small amounts of the calcium ions to the mixture. Also, organic salts such as calcium acetate, or calcium formate, may also be used. The corresponding strontium and magnesium salts of the alkaline earth class may also be used.

The only limitations to be placed on the alkaline earth metal salt, oxide or hydroxide to be added are that it be sufficiently water soluble to provide the ions, not present any problems of safety in the resulting toothpaste compositions, and be effective to provide the necessary fluoride compatibility.

After treatment with the alkaline earth metal ion, the cake slurry is then agitated vigorously for 10-20 minutes, preferably 15 minutes, to provide the effective level of alkaline earth metal for treatment on the surface of the silicon dioxide abrasive. The resulting product is then filtered, spray dried, preferably at an inlet temperature of 483"C.

(900"F.) and outlet temperature of 122"C. (250"F.) as known in the art, and subsequently milled to the desired degree of fineness.

The precipitated amorphous silicas which are preferably used in this embodiment may be characterized by the following combinations of properties: Oil Absorption-Rub-Out Method (cc/100g) = 80-120 BET Surface Area (m2/g) = 75-325 MSA Average Aggregate Size (microns) = 1-10 Bulk Density (lbs./cu.ft.) = 10-30 As has been referred to above, the invention includes other types of silica polishing agents including Xerogels as described in U.S. Patent 3,538,230. Commercially available Xerogels such as Syloid 63 (Registered Trade Mark) manufactured by Davison Division of W. R. Grace & Co., can be utilised when incorporated with controlled amounts of calcium ion or alkaline earth metal ions or pretreated with calcium ion or alkaline earth metal ions, as described herein. It is also to be understood that sodium aluminosilicate polishing agents can be formulated in therapeutic compositions according to this invention when the sodium aluminosilicate materials are combined with the critical amounts of alkaline earth metal as described herein.

As known in the art, a dentifrice may contain; e.g., humectant materials and binders to give the dentifrice a smooth texture and good flowability. The specific formulations of toothpastes are well known in the art and are disclosed for example in U.S. Patents 2,994,642 and 2,538,230 and numerous publications. A further detailed disclosure of dentifrice formulations is given in U.S. Patent 3,726,961.

Most dental cream formulations use one of several conventional phosphate materials as the polishing agent. Examples of the phosphate polishing agents are dicalcium phosphate, anhydrous dicalcium phosphate, tricalcium phosphate, thermally converted dicalcium phosphate, and insoluble sodium metaphosphate. The amount of phosphate materials added to the dental formulations will range between 5 percent and 60 percent by weight.

The most widely used humectants in toothpaste are glycerine and sorbitol. Propylene glycol is also used in small amounts and to a very limited extent. The primary function of humectant as part of the liquid phase is to retain moisture which provides good texture and maintains an attractive glossy appearance when the paste is exposed to air.

A binder can be employed in the toothpaste composition to prevent separation of the liquid and solid phases. The most conventionally used binders are the seaweed colloids and synthetic derivatives of cellulose, specifically Carrageenan and sodium carboxymethyl cellulose. Others such as gums have been used. Combinations of these binders have also been employed.

Since the natural and synthetic water dispersions of organic binders are subjected to microbial or mold attack, a relatively small amount of preservatives is added to the paste.

Examples of preservatives used in the industry are the esters of parahydroxyl benzoates.

The function of the detergents within the dental formulation is to provide greater cleansing action due to the lowering of the surface tension and the sudsing action in the mouth. Among detergents used are sodium N-lauryl sarcosinate, sodium lauryl sulfate, sulfoculaurate, sodium alkyl sulfoacetate, and sodium dioctyl sulfosuccinate.

Since toothpaste flavouring probably represents the greatest single factor in consumer acceptance, great care has been employed in selecting balanced blends of different essential oils. These are rarely, if ever, used alone. Combinations of principal flavours are wintergreen, peppermint, and sassafras, and are used with secondary oils such as pimento, clove and anise.

Saccharin and sodium cyclamate are widely used to improve taste and enhance the flavour qualities of the toothpaste. The synthetic sweeteners may be used in combination to obtain optimum sweetness and absence of after-taste. Their desirable properties are obtained at very low concentrations and consequently they have negligible influence on the toothpaste consistency.

Since water is such a common element, it is important in obtaining stable toothpaste formulations to employ substantially pure water therein. It is common practice to demineralize the water that is employed.

The invention is operable with respect to any of the therapeutic agents now being used in therapeutic dentifrice compositions including the alkali metal fluorides such as sodium fluoride, sodum monofluorophosphate, or stannous fluoride, all of which are well known.

In general, such dentifrice compositions will normally contain 5-50 wt.% of polishing agent, up to 1 wt.e of fluoride-containing therapeutic agent, 30-40 wt. % deionized water, and the remainder being liquid phase carrier materials such as glycerine or sorbitol. As indicated above, according to the present invention, the composition will also contain 0.005 up to 0.20 parts of alkaline earth metal, preferably calcium ion, based on the toothpaste composition. It has been found that this amount of alkaline earth metal is sufficient to overcome problems with staining and corrosion of unlined aluminium tubes, but is insufficient to interfere with the fluoride availability in the paste and thus not interfere with the therapeutic action of the dentifrice composition.

With respect to incorporation of the controlled amount of alkaline earth metal in the compositions of the present invention, it is to be noted that in Degussa Technical Bulletin No. 9, there is a disclosure of an "Aerosil 200" (Registered Trade Mark) polishing agent for use in chalk toothpastes, and it is pointed out on page 8 of this Bulletin that in toothpastes containing the cheaper polishing agent, chalk, the use of "Aerosil 200" is worthwhile to the extent that the less expensive unlacquered aluminium tubes can be used since corrosion protection for unlacquered aluminium tubes is by formation of minute quantities of insoluble calcium silicate from this composition. A minimum of 1% of "Aerosil 200" is required. However at page 8 of the same Bulletin, it is stated that even with the use of "Aerosil", it is not possible to attain effective corrosion protection for nontreated aluminium tubes when the toothpaste compositions contain fluorine in the form of monofluorosodium phosphate. However, this reference does teach on page 8, that when 3-5 weight percent of Light Hydrated Alumina W-16 is incorporated into the fluoridecontaining toothpaste, corrosion protection can be obtained. Contrary to the teachings of this Technical Bulletin, it has been discovered according to the present invention that fluorine-containing toothpastes can be placed in unlined aluminium tubes if there is placed therein a controlled amount of alkaline earth metal ion.

Silica abrasives are preferably used at loadings of about 15-30 wt. % in the dentifrice.

They contain a minimum of 168 ppm calcium at 30 wt. % and 336 ppm at 15 wt. % to provide minimum amounts of calcium. However they can also contain up to 7000 ppm.

The following specific examples are further illustrative of the nature of the present invention, but it is to be understood that the invention is not limited thereto. The compositions are prepared in the conventional manner and all amounts of the various ingredients are by weight unless otherwise specified. In the following examples and throughout the specification parts are by weight unless otherwise indicated.

EXAMPLES In the following examples the toothpaste compositions were prepared and compared with commercial products or controls. In evaluating the toothpaste compositions, a chart was used to rate the interior tube wall to determine the presence or absence of staining and corrosion. As basis for the chart, each composition was prepared and then aged at 490C. for nine weeks. The percentage of soluble fluoride ion and tube compatibility data were determined periodically during the nine-week storage stability period. In this examination, each three weeks under the aging conditions (49"C.) corresponds to about one year aging at room temperature. During the studies, the unlined tubes containing the compositions were opened periodically and examined for any staining/corrosion on the tube interior wall. The following legend was used for rating the tube properties of the compositions: Rating Tube Interior Wall 10 No air on wall, no discoloration on wall 8-9 No air on wall, light gray stain on wall 6-7 Air on wall, light gray stain on wall 4-5 Air on wall, gray stain on wall 2-3 Air on wall, dark gray stain on wall 1 Air on wall, black stain with pitting of wall In all of the following examples, the alkaline earth metal was calcium and was added as soluble calcium nitrate to provide the amount of calcium indicated in each composition.

EXAMPLES 1-4 Dentifrice Compositions in which Calcium was added to the Toothpaste The following dentifrice compositions were prepared with a low structure silica polishing agent and a known level of calcium was added to the composition to provide tube compatibility properties.

Examples 1-4 Composition 1 2 3 4 Sodium monofluorophosphate 0.76 0.76 0.76 0.76 Low Structure silica 30.00* 29.970 29.941 29.587 Calcium as water soluble Ca(NO3)2 . 4H2O** 0.00 0.0295 0.059 0.413 Glycerine 23.00 23.00 23.00 23.00 Sodium carboxymethylcellulose 1.30 1.30 1.30 1.30 Hydrated alumina 1.00 1.00 1.00 1.00 Sodium lauryl sulfate 2.00 2.00 2.00 2.00 Sodium benzoate 0.50 0.50 0.50 0.50 Sodium Saccharin 0.20 0.20 0.20 0.20 Flavour 0.90 0.90 0.90 0.90 Water (deionized) Balance Balance Balance Balance Total 100.00 100.00 100.00 100.00 * low structure silica containing 5 ppm calcium **The conversion factor for calcium nitrate .4H2O to calcium is 5.9. 'The molecular weight of Ca (NO3)2 . 4H2O is 236. The Atomic weight of calcium is 40. Therefore 236 parts of calcium nitrate . 4H2O provide 40 parts of calcium ion, or 236/40 or 5.9 parts of calcium nitrate . 4H2O, which corresponds to one part of calcium.

In compositions 2, 3, and 4, calcium nitrate . 4H2O was added in the dentifrice composition which corresponds to calcium level of 0.0295/5.9 or 50 ppm (0.005%): 100 ppm (0.01%) and 700 ppm (0.07%), respectively. The tube compatibility data for these Examples are set forth in following Table 1.

TABLE 1 Rating of Tube Properties - 49"C Aging Study Weeks Composition 0 1 3 6 9 1 10 4 3 3 1 2 10 10 10 10 10 10 3 10 10 10 10 10 4 10 10 10 10 10 It is clear from above data that composition 1 was unacceptable in tube compatibility properties because it did not contain the minimum critical level of calcium in the therapeutic dentifrice composition.

EXAMPLES 5-8 The following dentifrice compositions were prepared wherein the content of sodium monofluorophosphate in each is equivalent to 0.1% of fluoride ion.

Composition Parts Sodium monofluorophosphate 0.76 0.76 0.76 0.76 Low Structure silica 30.00(A) 30.00(B) 30.00(c) 30.00(D) Glycerine 23.00 23.00 23.00 23.00 Sodium carboxymethylcellulose 1.30 1.30 1.30 1.30 Hydrated alumina 1.00 1.00 1.00 1.00 Sodium lauryl sulfate 2.00 2.00 2.00 2.00 Sodium benzoate 0.50 0.50 0.50 0.50 Sodium saccharin 0.20 0.20 0.20 0.20 Flavour 0.90 0.90 0.90 0.90 Water (deionized) 40.34 40.34 40.34 40.34 Total 100.00 100.00 100.00 100.00 (A) low structure silica of composition 5 contained 5 ppm calcium (B) low structure silica of composition 6 contained 168 ppm calcium (C) low structure silica of composition 7 contained 406 ppm calcium (D) low structure silica of composition 8 contained 688 ppm calcium The low structure silicas employed in Examples 5, 6, 7 and 8 were characterized by the following combination of properties: Oil Absorption - Rub-Out Method (cc/100 mg) = 80-120 BET Surface Area (m2/g) = 75-325 MSA Average Aggregate Size (microns) = 1-10 Bulk Density (pounds/cu.ft.) = 10-30 The calcium treated low structure silicas of compositions 5, 6, 7 and 8 were prepared by the following procedure Dry sodium sulfate was added to 10.0 gallons of water in a 200 gallon reactor so that 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. (150"F.). The sodium silicate solution had an SiO2. Na2O mole ratio of 2.5 and a concentration of 2.0 pounds per gallon. Sodium silicate was added to the reaction medium for 4 minutes. At this point the sodium silicate addition was stopped and sulfuric acid of 11.4% concentration was added to the reaction medium until the pH of 9.0 was reached. At this point the sodium silicate solution and the sulfuric acid solution was added simultaneously for a period of 35 minutes. At the end of the 35 minute period of silicate addition, the silicate was discontinued and the acid addition was continued until a slurry pH of 5.5 was obtained. The batch was digested at 77"C. (170"F) for 20 minutes and the resulting wet cake recovered and washed.

The wet cake was then divided into four separate portions and treated by the following procedure.

Each batch of wet wash filter cake was then reslurried without water addition at ambient temperature with agitation. While under agitation, the slurry was treated with sufficient Codex grade (U.S. purity food grade) hydrated lime (calcium hydroxide) to provide the amount of calcium ion treatment described in compositions 5, 6, 7 and 8. The amount of calcium hydroxide was based on the weight of dry recoverable solid product in the wet cake form. After treatment with the calcium ion, the cake slurry was agitated vigorously for 15 minutes to provide the effective level of calcium ion treatment on the surface of the silicon dioxide abrasive. Each resulting product is then spray dried at an inlet temperature of 483"C. and outlet temperature of 122"C. milled and characterized.

Compositions 5, 6, 7 and 8 were aged at 490C. for nine weeks and tube compatibility data were determined periodically during the nine-week storage stability period. The results for tube compatibility properties are listed below in Table 2.

TABLE 2 Rating of Tube Properties - 49"C Aging Study Weeks Composition 0 1 3 6 9 5 10 4 3 3 1 6 10 10 10 10 10 7 10 10 10 10 10 8 10 10 10 10 10 It will be noted from Table 2 that dentifrice composition 5 caused a severe degree of black stain and pitting on the tube wall after nine weeks of aging study. Compositions 6, 7 and 8 were stable and showed excellent tube compatibility properties. Thus, it is very clear that when a silica polishing agent contains a minimum critical level of calcium, it does not corrode the unlined aluminium tubes.

EXAMPLES 9-11 Stabilization of Xerogel Therapeutic Dentifrices with Calcium Therapeutic dentifrices were prepared with xerogel polishing agents. All compositions contained a known level of calcium ions (added as water soluble calcium nitrate) except composition 9. The compositions were prepared in the conventional manner and packaged in unlined aluminium tubes. All amounts of the various ingredients were by weight unless otherwise specified.

The following dentifrice compositions were prepared. The content of sodium monofluorophosphate in each was equivalent to 0.1% fluoride ion.

Composition Parts 9 10 11 Glycerine (99.5% solution) 22.00 22.00 22.00 Sodium benzoate 0.50 0.50 0.50 Sodium saccharin 0.20 0.20 0.20 CMC - 7 MF 1.00 1.00 1.00 Sodium monofluorophosphate 0.76 0.76 0.76 Water (deionized) 36.54 36.54 36.54 Xerogel (Syloid 63) 35.00 34.82 34.70 Hydrated alumina 1.00 1.00 1.00 TiO2 0.50 0.50 0.50 Sodium lauryl sulfate 1.50 1.50 1.50 Calcium nitrate . 4H2O* 0.00 0.18 0.30 Flavour 1.00 1.00 1.00 * 0.18% and 0.30% calcium nitrate . 4H20 in composition properties were then determined when the dentifrices were aged at 49"C for nine weeks and were rated at intervals of 1, 3, 6 and 9 weeks. The following Table 3 shows the degree of corrosion or staining of the unlined aluminium tubes.

TABLE 3 Tube Compatibility Properties - 49"C Aging Study Weeks Composition 0 1 3 6 9 9 10 > 7 6 6 5 10 10 10 10 10 10 11 10 10 10 10 10 From the data in Table 3 it is clear that the compositions of Examples 10 and 11 exhibit excellent tube compatibility properties. Note that rating of 10 means no discoloration of the unlined tube container. Since composition 9 did not contain the critical level of calcium, the tube compatibility properties were found to be unacceptable after nine weeks storage at 49 C.

According to the suppliers bulletin, the Xerogel, Syloid 63, has the following properties: Loss on ignition 6.5 5% slurry pH 4.1 % SiO2 ignited basis 99.5 Particle size, microns 9.0 Surface area, m2/g 625 Oil absorption, &num;/100 lb 60 Bulk density, pounds/cu. ft. 29 In addition to above properties, Syloid 63 has the following chemical composition (from supplier's bulletin) Chemical Analysis (dry basis) Aluminium as A1203 0.04 Titanium as TiO2 Calcium as CaO 0.01 Sodium as Na2O 0.02 Zirconium as ZrO2 0.01 Trace element (oxides) 0.02 EXAMPLE 12 Effect of Calcium on Commercial Toothpastes "Aim" (Registered Trade Mark) clear-gel therapeutic toothpaste is packaged in a lined container to prevent corrosion and staining of tube interior wall.

"Colgate Dental Cream" (Registered Trade Mark) (CDC) is also packaged in a lined container to avoid the corrosion and staining of the tube interior wall.

To check the effectiveness of calcium addition in solving the tube compatibility problem, both "Aim" and "CDC" were purchased from the supermarket and each paste was divided into three parts.

"Aim" toothpaste was divided in parts A, B, and C. Part A was packaged in an unlined aluminium tube without any addition of calcium to the toothpaste. Parts B and C were mixed with a known level of calcium and then packaged in unlined aluminium tubes.

"CDC" (Colgate Dental Cream) was also divided into three parts D, E, and F. Part D was packaged in an unlined aluminium tube without the addition of any calcium. To parts E and F, a known level of calcium was added. The data obtained with "Aim" and "CDC" compositions packaged in unlined containers are listed in Table 6 and the compositions for each are as follows EXAMPLE 12 Commercial Composition % Calcium (3) % Dentifrice A 0.00 100.00 (1) B 0.10 99.41 (1) C 0.16 99.16 (1) D 0.00 100.00 (2) E 0.10 99.41 (2) F 0.16 99.16 (2) Aim Aim toothpaste, purchased from supermarket 2) Colgate Dental Cream, purchased from supermarket 3 Added as Ca(NO3)2.4 H2O TABLE 4 Tube Compatibility Properties - 49"C Aging Study Weeks Composition 1 3 6 9 A 5 4 3 1 B 10 10 10 10 C 10 10 10 10 D 5 5 4 2 E 10 10 10 10 F 10 10 10 10 Compositions B, C, E and F have excellent tube compatibility properties when compared with compositions A and D. The addition of the calcium thus helped stabilize these therapeutic dentifrice compositions.

Examples 13-17 The following dentifrice compositions were prepared to illustrate the use of sodium aluminosilicates (SAS) as polishing agents. The composition of Example 13 was used as a control in which no calcium was added. Known amounts of calcium were added to the compositions of Examples 13, 15, 16 and 17. The compositions were as follows Parts Composition 13 14 15 16 17 Glycerine (99.5%) 22.00 22.00 26.00 25.00 30.00 Sodium benzoate 0.50 0.50 0.50 0.50 0.50 Sodium saccharin 0.20 0.20 0.20 0.20 0.20 CMC - 7 MF 1.00 1.00 1.00 1.00 1.00 Sodium monofluorophosphate 0.76 0.76 0.76 0.76 0.76 Calcium nitrate . 4H2O* 0.00 0.20 0.20 0.20 0.24 Deionized water 36.54 36.34 39.54 38.54 43.30 SAS Polishing agent 35.00(A) 35.00(A) 27.80(B) 29.80(C) 20.00(D) Hydrated alumina 1.00 1.00 1.00 1.00 1.00 TiO2 0.50 0.50 0.50 0.50 0.50 Sodium lauryl sulfate 1.50 1.50 1.50 1.50 1.50 Flavour 1.00 1.00 1.00 1.00 1.00 *Note that in compositions 14, 15 and 16, 0.2% Ca(NO3)2.

4H2O corresponds to 0.03% calcium ion and 0.24% Ca(NO3)2.

4H2O in composition 17 corresponds to 0.04% calcium ion.

(A) The SAS product used in compositions 13 and 14 has a SiO2/Al203 ratio of 11.0.

(B) The SAS product used in composition 15 has a SiO2/Al203 ratio of 2.5 (C) The SAS product used in composition 16 has a SiO2/Al203 ratio of 130 (D) The SAS product used in composition 17 has a SiO2/Al203 ratio of 400 The preferred sodium aluminosilicates (SAS) have the following molar chemical composition x Na2O . y Al2O3 . z SiO2 . w H20 wherein x denotes the moles of Na2O y denotes the moles of Al203 z denotes the moles of SiO2 w denotes the moles of water When y is fixed at 1, the value of z corresponds to the silica/alumina molar ratio of SAS.

The low structure SAS abrasives and polishing agents have a silica/alumino ratio or z values of 2.5 to 400.

The properties of SAS polishing agents are Oil Absorption, Rub-Out Method (cc/100g) = 75 - 125 BET Surface Area (m2/g) = 50 - 300 MSA Average Aggregate Size (microns) = 1 - 10 Bulk Density (pounds/cu.ft.) = 12 - 35 Compositions 13 through 17 were aged at 49"C for nine weeks and the tube compatibility properties were evaluated at intervals of 1, 3, 6 and 9 weeks and the results are shown in the following Table 5.

TABLE 5 Tube Compatibility Properties, 49"C.

Weeks Composition 1 3 6 9 13 1 1 1 1 14 10 10 10 10 15 10 10 10 10 16 10 10 10 10 17 10 10 10 10 Note that compositions 14 through 17 have excellent tube compatibility properties.

In co-pending Application number 36509/77 (Serial No. 1587175), there is described and claimed an article of manufacture comprising an unlined aluminium tube containing a toothpaste composition and to a method of preventing the corrosion and staining by toothpaste of an unlined aluminium tube, and no claim is made to such articles of manufacture and methods of preventing the corrosion and staining by toothpaste of an unlined aluminium tube herein.

WHAT WE CLAIM IS: 1. An abrasive composition useful for incorporation into a therapeutic toothpaste composition and for preventing fluoride-caused corrosion and staining of an unlined aluminium tube containing said toothpaste composition, said abrasive composition consisting essentially of a silica which has been treated with a water soluble salt, oxide or hydroxide of an alkaline earth metal so as to have present therein from 168-7000 ppm of the alkaline earth metal, said silica being suitable for use in a toothpaste composition having an RDA value of between 200 and 400 functioning as a carrier for the alkaline earth metal.

2. An abrasive composition as in claim 1, wherein said silica is selected from amorphous precipitated silica, sodium aluminosilicates, silica xerogels and mixtures thereof.

3. An abrasive composition as in claim 2, wherein said amorphous precipitated silica has the following properties: Oil Absorption-Rub-Out Method (cc/lOOg) = 80-120 BET Surface Area (m2/g) = 75-135 MSA Average Aggregate Size (microns) = 1-10 Bulk Density (lb./cu.ft.) = 10-30 4. An abrasive composition as in claim 2, wherein said sodium aluminosilicates have the following properties: Oil Absorption-Rub-Out Method (cc/100g) = 75-125 BET Surface Area (m2/g) = 50-300 MSA Average Aggregate Size (microns) = 1-10 Bulk Density (lb./cu.ft.) = 12-35 5. An abrasive composition as in claim 1, wherein said alkaline earth metal is selected from calcium, strontium and magnesium, and mixtures thereof.

6. An abrasive composition as in claim 1, wherein the amount of alkaline earth metal present ranges from 336-7000 ppm.

7. An abrasive composition as in claim 5, wherein the alkaline earth metal is calcium provided by a salt, oxide or hydroxide selected from calcium hydroxide, calcium oxide, calcium nitrate and calcium chloride.

8. A method for the production of the abrasive composition of claim 2, when an

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

TABLE 5 Tube Compatibility Properties, 49"C.

Weeks Composition 1 3 6 9

13 1 1 1 1

14 10 10 10 10

15 10 10 10 10

16 10 10 10 10

17 10 10 10 10 Note that compositions 14 through 17 have excellent tube compatibility properties.

In co-pending Application number 36509/77 (Serial No. 1587175), there is described and claimed an article of manufacture comprising an unlined aluminium tube containing a toothpaste composition and to a method of preventing the corrosion and staining by toothpaste of an unlined aluminium tube, and no claim is made to such articles of manufacture and methods of preventing the corrosion and staining by toothpaste of an unlined aluminium tube herein.

WHAT WE CLAIM IS: 1. An abrasive composition useful for incorporation into a therapeutic toothpaste composition and for preventing fluoride-caused corrosion and staining of an unlined aluminium tube containing said toothpaste composition, said abrasive composition consisting essentially of a silica which has been treated with a water soluble salt, oxide or hydroxide of an alkaline earth metal so as to have present therein from 168-7000 ppm of the alkaline earth metal, said silica being suitable for use in a toothpaste composition having an RDA value of between 200 and 400 functioning as a carrier for the alkaline earth metal.
2. An abrasive composition as in claim 1, wherein said silica is selected from amorphous precipitated silica, sodium aluminosilicates, silica xerogels and mixtures thereof.
3. An abrasive composition as in claim 2, wherein said amorphous precipitated silica has the following properties: Oil Absorption-Rub-Out Method (cc/lOOg) = 80-120 BET Surface Area (m2/g) = 75-135 MSA Average Aggregate Size (microns) = 1-10 Bulk Density (lb./cu.ft.) = 10-30
4. An abrasive composition as in claim 2, wherein said sodium aluminosilicates have the following properties: Oil Absorption-Rub-Out Method (cc/100g) = 75-125 BET Surface Area (m2/g) = 50-300 MSA Average Aggregate Size (microns) = 1-10 Bulk Density (lb./cu.ft.) = 12-35
5. An abrasive composition as in claim 1, wherein said alkaline earth metal is selected from calcium, strontium and magnesium, and mixtures thereof.
6. An abrasive composition as in claim 1, wherein the amount of alkaline earth metal present ranges from 336-7000 ppm.
7. An abrasive composition as in claim 5, wherein the alkaline earth metal is calcium provided by a salt, oxide or hydroxide selected from calcium hydroxide, calcium oxide, calcium nitrate and calcium chloride.
8. A method for the production of the abrasive composition of claim 2, when an

amorphous precipitated silica is selected as the silica, said method comprising forming an aqueous solution of an alkali metal silicate having an SiO2 to X2O mole ratio of 2.0 to 2.7 and of an alkali metal sulfate at a reaction temperature in the range of 66 to 830C., wherein X represents the alkali metal; acidulating said aqueous solution with a mineral acid with continuous agitation until precipitation of silicon dioxide is substantially complete at a pH of 8.0 to 10.4; continuing the mineral acid addition until the pH is 6.0 or less; digesting at a temperature that is 10-300C. higher than the reaction temperature for a period of 10 to 30 minutes; filtering the resulting slurry and washing the solid product with fresh water; reslurrying the resulting wet cake in water, and under agitation conditions, adding thereto at ambient temperature a water soluble salt, oxide or hydroxide of an alkaline earth metal in an amount sufficient to add to said wet cake from 168-7000 ppm of the alkaline earth metal based on the dry recoverable product; agitating the resulting mixture to provide adherence of the effective level of said metal on the surface of said silicon dioxide; and drying and recovering said abrasive composition.
9. A method as in claim 8, wherein the mineral acid is selected from sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid and carbonic acid.
10. A method as in claim 8 or claim 9, wherein the alkaline earth metal is selected from calcium, strontium and magnesium, and mixtures thereof.
11. A method as in claim 10, wherein the alkaline earth metal is calcium provided by a salt, oxide or hydroxide selected from calcium nitrate, calcium oxide, calcium hydroxide and calcium chloride.
12. A method as in claim 8, wherein the mineral acid addition is continued until the pH is 4.8 to 5.0.
13. A method as in claim 8, wherein said abrasive composition is dried by spray drying.
14. A method as in claim 8, wherein the alkali metal silicate is sodium silicate, the alkali metal sulfate is sodium sulfate, the acidulating acid is sulfuric acid, and the alkaline earth metal is added in the form of calcium nitrate to provide 168-7000 ppm of calcium in said abrasive composition.
15. A therapeutic dentifrice composition containing a fluoride therapeutic agent and, as the abrasive, the abrasive composition of claim 1; the silica of said abrasive composition being used in loadings of 15-30 wt.% in said therapeutic dentifrice composition, and said alkaline earth metal being present in an amount of 168 to 336 ppm.
16. A therapeutic dentifrice composition as in claim 15 which contains 20-50 wt.% of humectant, 0.5 to 2.5 wt.% of thickener, 1-2 wt.% of a detergent 0.1 to 0.2 wt.% of the fluoride therapeutic agent and water.
17. An abrasive composition as in claim 1, and substantially as hereinbefore described.
18. A method for the production of an abrasive composition as in claim 8, and substantially as hereinbefore described.
19. A therapeutic dentifrice composition as in claim 15, and substantially as hereinbefore described.