Toothpaste

The following Examples are given to illustrate this invention further. In this application all proportions are by weight unless otherwise indicated.

A toothpaste is prepared by forming a gel by mixing a gelling agent, in this case sodium carboxymethyl cellulose ("CMC") with glycerol and water (in the presence of a sweetener, sodium saccharin, a flavor and a preservative, sodium benzoate), then adding to the gel, sodium bicarbonate (baking soda) chalk, and titanium dioxide powder and thereafter degassing the mixture under vacuum. The proportions used are: baking soda, 10%; chalk, 35%; titanium dioxide, 0.4 %; deionized water, 16.1%; glycerol, 34.0%; CMC, 1.2%, solution of 35% sodium N-lauroyl sarcosinate in a mixture of 35% water and 30% glycerol, 2%; sodium lauryl sulfate, 0.98; sodium benzoate, 0.5%; sodium saccharin, 0.2%; flavor, 0.9%.

The baking soda powder is U.S.P. grade having the following particle size distribution in which percentages represent the cumulative per cent retained on the named sieve, and sieve sizes are U.S. Standard: No. 45 sieve, trace; No. 70 sieve (sieve opening 210 microns), 27%; No. 80 sieve (sieve opening 177 microns) 66.5%; No. 100 sieve (sieve opening 149 microns), 92.5%; No. 170 sieve (sieve opening 88 microns), 99%.

The chalk is U.S.P. precipitated calcium carbonate containing at least 98% CaCO.sub.3 with no more than 0.2% insoluble in dilute HCl. Its particle size is such that over 99% passes through a U.S. Standard No. 325 mesh sieve, the particles being principally in the 1 to 10 micron size, the average particle size being about 3 microns. A grit free U.S.P. non Fer Al Chalk of similar properties may also be employed with accompanying adjustment of gelling agent and viscosity.

The titanium dioxide used is a grit-free anatase powder at least 99.0% of which passes through a No. 325 U.S. Standard sieve and whose mean particle diameter (as measured on a Kahn sedimentation balance) is below 1 micron. Microscopic measurements indicate its averge particle diameter is 0.3 micron.

The toothpaste has good cleaning power and whiteness and ages well in tests at 8.degree.F, 40.degree.F, 110.degree.F, 120.degree.F. The toothpaste has a pleasant smell during brushing; while the large particles of baking soda are moderately palpable they break down to smaller particles easily under the pressure of the toothbrush and under the action of the saliva.

Example 1 is repeated except that the level of chalk is reduced to 25% and the level of sodium bicarbonate increased to 20%.

Example 1 is repeated except that 5% hydrated alumina is substituted for 5% of the chalk, the proportion of baking soda remains the same, the flavor used is a mixture of essential oils, largely peppermint.

The hydrated alumina has the following particle size distribution, and is alpha alumina trihydrate:

28-40% finer than 5 microns

56-67% finer than 10 microns

85-93% finer than 20 microns

94-99% finer than 30 microns

Example 3 is repeated except that instead of the 5% of hydrated alumina there is employed 5% zirconium silicate powder of the following particle size distribution:

80% finer than 1.25 microns

90% finer than 1.77 microns

95% finer than 2.15 microns

99% finer than 2.50 microns

Example 3 is repeated except that instead of the 5% of hydrated alumina there is used 5% of micronized silica, and half the baking soda is replaced by a more finely divided baking soda having the following particle size distribution (in which percentages represent the cumulative per cent retained on the named sieve, and sieve sizes are U.S. Standard): No. 45 sieve (sieve opening 350 microns), trace; No. 100 sieve (sieve opening 149 microns), 0.5%; No. 170 sieve (sieve opening 88 microns), 20%; No. 200 sieve (sieve opening 74 microns), 35%; No. 325 sieve (sieve opening 44 microns), 70%; No. 400 sieve, 80%.

It is also within the broader scope of the invention to use calcium pyrophosphate (e.g. the B or .gamma. form of calcium pyrophosphate, or mixtures of those forms in various proportions such as in about 1:1 ratio, e.g. 53% B, 47% .gamma.), having an average particle size below about 20 microns, e.g. about 1 or 2 to 10 microns, for part of the water-insoluble abrasive in the toothpaste.

Another aspect of this invention relates to the degassing of toothpastes containing the sodium bicarbonate particles. It is found that when such toothpastes are subjected to high vacuum, e.g. above 26 inches of mercury, the paste bubbles and expands but, unlike conventional toothpastes, it does not contract to substantially its original volume on continuted vacuum treatment, but instead continues to expand. It has now been found that an excellent deaerated product, having good stability and desirable rheological chracteristics can be produced by subjecting the toothpaste containing sodium bicarbonate to a vacuum of at least 26 inches of mercury so that it expands to a volume which is at least 150% (e.g. about 200%) of its volume at atmospheric pressure and then discontinuing the treatment at high vacuum when the expanded mixture begins to contract but while its volume is still at least 150% of its volume at atmospheric pressure.

This Example illustrates the degassing treatment of this invention. 18.3 parts of glycerol; 1.1 part of sodium carboxymethyl cellulose; 0.5 part of sodium benzoate; 0.2 part of sodium saccharin and 15.4 parts of water are mixed at 110.degree.-115.degree.F. for 20 minutes and placed in a vertical cylindrical container equipped with a stirrer, specifically a Dopp mixer which has a series of intermeshing counter-rotating radially disposed mixing rods located all along its height. Then 25 parts of calcium carbonate (chalk), 20 parts of sodium bicarbonate, 0.4 part of titanium doxide are added and mixed slowly while a vacuum of 27 1/2 inches of mercury is applied; the speed of mixing is then increased; during this vacuum treatment, which lasts about 5 minutes, the batch rises to a volume about 2/3 greater than its volume before vacuum is applied and then decreases somewhat. The mixture is then vented to the atmosphere and 0.975 parts of sodium lauryl sulfate and 2 parts of a solution of 35% sodium lauroyl sarcosinate in a water-glycerol (35%-30%) mixture are then added, a vacuum 28.2 inches of mercury is applied and the mixture is kept under the vacuum for about 5 minutes while stirring; during this time, the volume of the batch increases and decreases somewhat, the volumes being little greater than observed during the preceding vacuum treatment. The mixture is then vented to the atmosphere. 15.1 parts of glycerol are added and the mixture is then stirred under a vacuum of 28 inches of mercury for about 5 minutes during which treatment its volume increases by more than 100% (i.e. to a volume which is more than 200% of the original volume) and then begins to decrease somewhat. At the conclusion of this 5 minutes period, the vessel is vented to the atmosphere while the volume of the mixture is still about 75-100% greater than its volume just prior to this vacuum treatment. One part of essential oil flavor is then added, stirring is resumed while a vacuum of 28 1/2 inches is applied; stirring under this vacuum is continued for about 12 minutes, after which the vessel is vented to the atmosphere; during this 12 minute period, the expansion of the mixture is similar to that observed during the immediately preceding vacuum treatment. Just before the mixture is vented to the atmosphere, the expansion of the mixture is still evident.

It is preferable to discontinue the vacuum treatment, even though expansion may continue before the change in pH (i.e. the pH of the vacuum treated mixture minus the pH of the mixture without vacuum treatment) reaches one pH unit and preferably less, e.g. 1/2 unit; this avoids decomposition of sodium bicarbonate and production of sodium carbonate during degassing.

In accordance with a further embodiment of the invention, the toothpaste may be prepared and degassed as follows:

The gel mix is prepared by adding the formula amount of glycerine, then adding CMC to vortex of mixing liquid and without heat, mixing for 2 minutes, then adding saccharin and sodium benzoate and further mixing for one minute. Thereafter there is added the formula amount of water, sodium lauryl sulfate and flavor. Mixing is then continued for 15 minutes. Mixing is continued until ready to drop the batch. The cover of the Dopp crutcher is then closed and there is applied 28 inches vacuum and then the vacuum valve is closed. Half the gel mix is then drawn in. The mixer is then turned off, the vacuum released and there is added formula amounts of: Titanium dioxide, Sodium N-lauroyl sarcosinate, after which there is applied vacuum to 28inch, while maintaining vacuum until the level of the cream drops. There is then drawn in the other half of gel mix and it is dearated for 5 minutes at 28 inches vacuum. Mixer is turned off, vacuum released and calcium carbonate and sodium bicarbonate added; apply vacuum with mixing. Continue mixing for 15 minutes under full vacuum. With mixer at lower speed, release vacuum and discharge cream.

This Example illustrates the use of alpha alumina flakes in the baking soda toothpaste.

The toothpaste is made up (using, for instance, the method of Example 1) of 10% of the baking soda powder of Example 1, 30% chalk, 5% of alpha-alumina flakes, 0.4% titanium dioxide of Example 1, 33.4% glycerol, 15.4% deionized water, 1.1% CMC (Hercules 7MF), 2% of a solution of 35% sodium N-lauroyl sarcosinate in a mixture of 35% water and 30% glycerol, 1% sodium lauryl sulfate, 1% flavor (water-insoluble essential oil flavoring agent; e.g., essential oil mixture rich in peppermint oil), 0.5% sodium benzoate and 0.2% sodium saccharin.

The alpha alumina flakes have a mean (by weight) particle diameter of about 4 microns, all the particles thereof have diameters less than 10.1 microns, about 85-95% (by weight) have diameters less than 6.0 microns and about 30-35% have particle diameters less than 3.5 microns.

The characteristics of the toothpaste of this Example are like those given in Example 1 above. It has very good resistance to flavor separation.

Example 7 is repeated except that the toothpaste contains 0.22% sodium fluoride (the glycerine content being correspondingly decreased by 0.22%. The toothpaste shows excellent aging characteristics including very good resistance to flavor separation on aging and very good retention of fluoride content. Like the toothpaste of Example 8, it has a high polishing effect on enamel; its percent repolish is 64%.

The percent repolish is determined by a test in which sections of human dental enamel, upon which have been ground flat areas, are first polished, then dulled with chalk, and then brushed with a slurry of a dentifrice for 5000 reciprocal strokes. A "Monsanto Tooth Reflectance Instrument" is employed to measure the specular reflectance of the surface after each step described above. The dulled surface is adjusted so that it is approximately 150 units (Monsanto Instrument) lower then the polished surface. The polishing ability of the dentifrice is expressed by the following equation: ##EQU2## where SR.sub.polished, SR.sub.dulled and SR.sub.5000 strokes are respectively specular reflectance values of the enamel surface after the initial polishing, after dulling with chalk, and after brushing with a dentifrice slurry.

Example 7 is repeated except that the toothpaste contains 0.76% sodium monofluorophosphate (the glycerine content being correspondingly decreased by 0.76%).

Examples 7, 8 and 9 are repeated except that the alphaalumina flakes have a mean particle diameter of 5 microns, substantially all being less than about 12 microns in diameter.

This Example illustrates the use of unlined aluminum toothpaste tubes with certain baking soda toothpastes.

a. A toothpaste is made up (using, for instance, the method of Example 1) of 20% of the baking soda powder (of Example 1) 25% of calcium carbonate, (of Example 1), 0.4% titanium dioxide of Example 1, 34.02% glycerol, 16.1 deionized water, 1.2% CMC (Hercules 7MF), 2% of a solution of 35% sodium N-lauroyl sarcosinate in a mixture of 35% water and 30% glycerol, about 0.9 flavor (water-insoluble essential oil flavoring agent; e.g., essential oil mixture rich in peppermint oil), 0.5% sodium benzoate, and 0.2% sodium saccharin.

b. Example 11a is repeated except that 0.5% of fumed silica (Cab-O-Sil) is included, the amount of calcium carbonate is raised to 35%, the amount of baking soda is decreased to 10%.

c. Example 11b is repeated except that the amount of sodium bicarbonate is decreased to 5% with accompanying changes in other ingredients.

d. Example 11 is repeated four times, with additional inclusion of various proportions of non-acidic dicalcium phosphate dihydrate in the formulation, i.e., in amounts of 0.04%, 0.2%, and 0.8% (based on the weight of the formulation without said phosphate); the first case 0.04%) the titanium dioxide is omitted. The dicalcium phosphate dihydrate is of dentifrice grade and has an average particle diameter of about 4 microns and its pH (measured in 20% slurry thereof in water is in the range of 9.3 to 9.9; it yields phosphate ions on contact with water.

e. Example 11a is repeated with the additional inclusion of insoluble sodium metaphosphate in the formulation in the amount of 0.8% (based on the weight of the formulation without said phosphate). The insoluble sodium metaphosphate is of dentrifrice grade having an average particle size of about 5 microns; its pH (measured in 20% slurry thereof in water) is in the range of 5.3 to 6.3; it yields phosphate ions on contact with water.

f. Example 11a is repeated except that 5% micronized silica is substituted for 5% of the calcium carbonate, a different essential oil flavor is used, the amount of flavor is 0.9% and the amount of glycerol is 33.5%.

g. Example 11a is repeated except that 3% micronized silica is substituted for 3% of the calcium carbonate, and the toothpaste contains 0.9% of an essential oil flavor.

h. Example 11a is repeated except that 5% precipitated silica is substituted for 5 % of the calcium carbonate:

i. Example 11a is repeated except that 5% anhydrous dicalcium phosphate is substituted for 5% of the calcium carbonate; the toothpaste contains 0.9% of an essential oil flavor. The anhydrous dicalcium phosphate is a fine non-acidic powder of dentifrice grade. Its pH (as measured on a 20% slurry thereof water) is 7.6-7.8; it yields phosphate ions, in low concentration, on contact with water.

j. Example 11a is repeated except that 5% zirconium silicate of Example 3 is substituted for 5% of the calcium carbonate (with minor change in proportion and type of flavor).

k. Example 11a is repeated except that 5% beta phase calcium pyrophosphate is substituted for 5% of the calcium carbonate. The calcium pyrophosphate is a fine powder of dentifrice grade. Its pH (as measured on a 20% slurry thereof in water) is 5.2-5.3.

Each of the foregoing toothpastes is placed in an individual toothpaste tube of unlined aluminum of high purity(99.7% A1 or purer) and aged. On aging at 120.degree.F. the tube filled with the 11a toothpaste tends to swell or is found to have a foamy product film in contact with the inner aluminum walls of the tube, tubes filled with the 11b, c, d, f, g, h, i, j and k toothpastes do not show such effects. The 11 preceeding toothpastes show substantially less tendency to react with the walls of the tube than the 11a toothpaste.

The fumed silica (as in Example 11b) is described in Eneyclopedia of Chemical Technology Kirk-Othmer 2nd Edition, Vol. 18 at pages 62 and 67, for instance. It is within the broader scope of the invention to use the fumed silica in baking soda toothpaste from which the compatible water-insoluble abrasive (such as calcium carbonate) has been omitted, in unlined aluminum tubes. It is also within the broader scope of the invention to employ, in place of the fumed silica, very finely dispersed or dissolved silica in other forms such as alkali metal silica such as sodium silicate, e.g. hydrated sodium silicate supplied in flake form containing Na.sub.2 O . SiO.sub.2.H.sub.2 O in a ratio of about 1:2-3.2:5, or sodium silicate solutions (water glass) such as those in which the Na.sub.2 O:SiO.sub.2 ratio is at least about 1:2, or sodium silicate formed in situ in the dental cream, or colloidal silica or precipitated silica (see Encyclopedia of Chemical Technology Kirk-Othmer, 2nd edition Vol. 18, pages 63 and 66-67, for instance) or other silicate.

The dicalcium phosphate dihydrate of Example 11d is a commercial stabilized dentifrice grade of this material. A description of the method of preparation of dicalcium phosphate dihydrate and of its stabilization is found in U.S. Pat. of Schlaeger et al No. 3,169,096 Feb. 9, 1965, whose disclosure is incorporated herein by reference. See also "Cosmetic Science" Vol. 1 pub. 1972 (Wiley Interscience) edited by Balsam and Sagarin pages 477-479. One typical analysis of dicalcium phosphate dihydrate indicates that its content of water-soluble material is 0.18% (and its percent water-solubles expressed as P.sub.2 O.sub.5 is 0.11%). A typical stabilizer content is a mixture of about 1-2% of sodium calcium pyrophosphate and a smaller amount, e.g. about 0.4%, of pyrosphosphoric acid.

The insoluble sodium metaphosphate of Example 11c is a commercial dentifrice grade of this material. Its method of preparation and properties are described in the previously cited "Cosmetic Science" at pages 480-481 and "Phosphorus and Its Compounds" by Van Wazer Vol. 2 pub. 1961 (Interscience) pages 1652-1653.

The anhydrous dicalcium phosphate of Example 11i and the calcium pyrophosphate of Example 11k are commercial dentifrice grades of these materials. See the previously cited "Phosphorus and Its Compounds" page 1651 and "Cosmetic Science" pages 479-480.

Example 11a is repeated except that the toothpaste contains added anhydrous disodium phosphate (incorporated as a water-soluble powder) in amount of (a) 0.05% and (b) 0.01%, the amount of water in the toothpaste being adjusted accordingly to total 100%. In each case, on aging in unlined aluminum tubes (as in Example 11) the filled tubes do not swell or gas and (after 9 weeks aging at 120.degree.F.) the inner walls of the tubes are found to be gold-colored, the wall color in the tube containing the 12b toothpaste being very light. On inspection of the inner walls of the unlined aluminum tubes containing the 10d toothpastes (again after 9 weeks at 120.degree.F.) they are found to be dark (when the pastes contain 0.8% or 0.4% of the dicalcium phosphate dihydrate) or golden (when the tubes contain 0.04% and 0.2% of the dicalcium phosphate dihydrate); on inspection of the inner walls of the unlined aluminum tubes containing the 11k toothpaste they are found to be golden after 3 and 6 weeks aging at 120.degree.F. and dark after 9 weeks of such aging. It is believed that the toothpastes containing the dicalcium phosphate dihydrate contain (or form, on aging) small amounts of dissolved phosphate ions (e.g. orthophosphate and/or pyrophosphate) which may act on the aluminum walls, or on the aluminum oxide layer on said walls, to form a protective layer thereon. The amount of dissolved phosphate ion present in the preferred composition is sufficient to inhibit the gas-forming reaction between the alkaline toothpaste composition and the aluminum walls of the tube but the amount of the phosphate or acidic ingredient therein is insufficient to cause a gas-forming reaction (e.g. resulting in swelling or bursting of the tube) between the ingredients of the toothpaste; the tendency for the latter reaction can, of course, be tested by placing the composition in a suitably lined aluminum tube (whose walls are thus substantially inert to the composition) and aging for several weeks (e.g. 9 weeks) at an elevated temperature (e.g. 120.degree.F.)

Storage of the toothpastes of other types in unlined aluminum tubes is discussed in such patents as U.S. Pat. Nos. 3,662,066 and 3,678,155 and Austrian Pat. No. 267,070. As is well known to consumers of toothpastes, aluminum toothpaste tubes are squeezed and deformable to express the toothpaste from the nozzle of the tube and the main body of the tube is of relatively thin, ductile, aluminum.

This Example illustrates the use of olefin sulfonate surfactant in a baking soda toothpaste; these olefin surfactants are found to produce very good foaming during tooth brushing despite the fact that the medium (saliva and baking soda toothpaste) has a relatively high concentration of dissolved electrolyte.

a. The toothpaste formulation is the same as that of Example 10 except that in place of the solution of the sarcosinate there is included about 0.7% of a sodium olefin sulfonate detergent and the amount of water is increased to about 16.6%.

b. The toothpaste formulation is the same as in Example 10 except that in place of the sodium lauryl sulfate and the solution of the sarcosinate there is included about 1.7% of a sodium olefin sulfonate detergent and the amount of water is increased to about 16.5%.

The olefin sulfonate detergent used in Example 13 is a reaction product of SO.sub.3 and an olefin mixture (such as may be obtained by cracking paraffin wax) containing approximately equal amounts of 15, 16, 17 and 18 carbon atom olefins and having an average chain length of about 16 1/2 carbon atoms. Other olefin sulfonate surfactants may be employed in the baking soda dentifrice. The olefin sulfonate surfactants are well known in the detergent art. Generally they contain long chain alkenyl sulfonates or long chain hydroxyalkane sulfonates (with the OH being on a carbon atom which is not directly attached to the carbon atom bearing the --SO.sub.3 --group). More usually, the olefin sulfonate detergent comprises a mixture of these two types of compounds in varying amounts, often together with long chain disulfonates or sulfate-sulfonates. Such olefin sulfonates are described in many patents, such as U.S. Pat. Nos. 2,061,618; 3,409,637; 3,332,880; 3,420,875; 3,428,654; 3,506,580, and British Pat. No. 1.139,158, and in the article by Baumann et al in Fette-Seifen-Anstrichmittel 72 no. 4 p. 247-253 (1970). All the above-mentioned disclosures are incorporated herein by reference. As indicated in these patents and published literature, the olefin sulfonates may be made from straight chain .alpha.-olefins, internal olefins, olefins in which the unsaturation in a vinylidene side chain (e.g. dimers of alpha olefins), etc. or, more usually, mixtures of such compounds, with the .alpha.-olefin usually being the major constituent. The sulfonation is usually carried out with sulfur trioxide under low, partial pressure, e.g. SO.sub.3 highly diluted with inert gas such as air or nitrogen or SO.sub.3 under vacuum. This reaction generally yields an alkenyl sulfonic acid, often together with a sultone; the resulting acidic material is generally then made alkaline and treated to open the sultone ring to form hydroxyalkane sulfonate and alkenyl sulfonate. The number of carbon atoms in the olefin is usually within the range of 10 to 25, more commonly 12 to 20, e.g. a mixture of principally C 12, C14 and C16 having an average of about 14 carbon atoms or a mixture of principally C14, C16 and C18 having an average of about 16 carbon atoms. The preferred olefin sulfonates are sodium salts but it is within the broader scope of the invention to use other water-soluble salts such as ammonium or potassium salts.

The baking soda used in the Examples is a product made by precipitation from solution (as by treating a sodium carbonate solution with carbon dioxide to precipitate the bicarbonate) followed by drying, curing with carbon dioxide gas and screening to the desired particle size (generally without substantial crushing or pulverizing).

These particles are generally monoclinic crystals or tablets or conglomerated thereof (e.g. twinned crystals) some having projecting spike-like portions of generally rhombohedral shape with many reentraut angles.

The toothpastes of the foregoing Examples are noneffervescent. Thus when diluted with water they do not actively evolve bubbles of carbon dioxide.

The toothpastes of this invention have an alkaline pH, generally in the range of about 8.5 to 10.0, usually about 9.3 to 9.9.

The dentin abrasion of the toothpastes may be determined by the procedure based on a radioactive technique described by Grabenstetter et al in the "Journal of Dental Research", Volume 37, P. 1060 (1958) as modified by the description by Stookey et al. in the "Journal of Dental Research", Volume 47, page 524 (July-August 1968).

It is understood that the foregoing detailed description is given merely by way of illustration and that variations may be made therein without departing from the spirit of the invention. The "Abstract" given above is merely for the convenience of technical searchers and is not to be given any weight with respect to the scope of the invention.