Stannous pyrophosphate and its production method

Abstract

Dental health care compositions comprising tin pyrophosphate and methods for producing the same are provided. In an exemplary embodiment, the method for producing the tin pyrophosphate comprises combining tin tetrafluoroborate with a pyrophosphate salt composition to produce a precipitate, the precipitate comprising tin pyrophosphate and tetrafluoroborate. The tetrafluoroborate salt is then removed from the precipitate.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 638,5392, filed November 4, 2022, which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present disclosure relates generally to stannous pyrophosphate and methods for making same. More specifically, the present disclosure relates to producing stannous pyrophosphate by reacting stannous boron tetrafluoride with a pyrophosphate composition. [Background technology]

[0003] Stannous ion sources improve many oral care products, providing favorable clinical benefits such as reducing gingivitis and reducing tooth demineralization due to erosion. Stannous fluoride is a well-known example of such a stannous ion source and has been used for many years. However, stannous fluoride is somewhat unstable in aqueous solution, at least in part due to the reactivity of stannous ions. Stannous salts hydrolyze at pH values ​​above 4 and then precipitate from the solution. The precipitated stannous salts may have reduced therapeutic properties.

[0004] Soluble stannous ions can also undesirably react with certain rheology modifiers, such as some types of cellulose and gums. Such compounds can be considered incompatible soluble stannous ions, and these compounds are often used in dental health products.

[0005] Stannous pyrophosphate, known as a dentifrice abrasive, can overcome the above limitations. Stannous pyrophosphate, having the formula Sn2P2O7, contains a tetravalent pyrophosphate ion and a divalent stannous cation (i.e., Sn(II)). Stannous pyrophosphate is substantially insoluble in water, especially under acidic conditions. However, the use of stannous pyrophosphate has been limited by its high cost. Furthermore, for incorporating stannous pyrophosphate into dental health care products, a small particle size is desirable. Although several methods for producing stannous pyrophosphate have been reported, a method for producing high-purity stannous pyrophosphate with a small particle size remains desirable.

[0006] Therefore, it would be desirable to find new stannous pyrophosphate production techniques that produce a high purity product. Additionally, it would be desirable to find production techniques that produce stannous pyrophosphate with small particle sizes suitable for incorporation into dental health care products. Furthermore, other desirable features and characteristics of the present embodiments will become apparent from the following detailed description and the appended claims, taken in conjunction with this background. Summary of the Invention

[0007] Dental health care compositions comprising tin pyrophosphate and methods for producing the same are provided. In an exemplary embodiment, the method for producing the tin pyrophosphate comprises combining tin tetrafluoroborate with a pyrophosphate salt composition to produce a precipitate, the precipitate comprising tin pyrophosphate and tetrafluoroborate. The tetrafluoroborate salt is then removed from the precipitate.

[0008] In another embodiment, a dental health care composition is provided. The dental health care composition includes tin pyrophosphate at a concentration of about 96 to about 99.999 weight percent, based on the total weight of the dental health care composition. The dental health care composition also includes sodium tetrafluoroborate at a concentration of about 10 to about 1,000 ppm by weight, based on the total weight of the dental health care composition.

[0009] Another method for producing tin pyrophosphate is provided in yet another embodiment. A tin tetrafluoroborate solution is provided, comprising tin tetrafluoroborate and a tin tetrafluoroborate solvent, the tin tetrafluoroborate solvent comprising water. A pyrophosphate is provided, comprising a pyrophosphate solvent and tetrasodium pyrophosphate, the pyrophosphate solution comprising water. The pyrophosphate solution is adjusted to about 60 to about 85°C. The tin tetrafluoroborate solution and the pyrophosphate solution are combined to produce a precipitate comprising tin pyrophosphate and sodium tetrafluoroborate. The precipitate is rinsed with a rinse solution to reduce the sodium tetrafluoroborate concentration to a level such that the boron concentration is less than about 100 ppm by weight, based on the total weight of the precipitate. [Brief explanation of the drawings]

[0010] The present embodiments are described below in conjunction with the following drawings: [Figure 1] FIG. 1 illustrates a technique for forming a tin tetrafluoroborate solution. [Figure 2] FIG. 1 illustrates a technique for forming a pyrophosphate solution. [Figure 3] 1A-1D illustrate various embodiments of techniques for forming reaction products comprising tin pyrophosphate. [Figure 4] 1A-1D illustrate various embodiments of techniques for forming reaction products comprising tin pyrophosphate. [Figure 5] 1A-1D illustrate various embodiments of techniques for forming reaction products comprising tin pyrophosphate. [Figure 6] FIG. 1 illustrates an embodiment for washing sediment. [Figure 7] FIG. 1 illustrates an embodiment for drying the precipitate. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following Detailed Description is merely exemplary in nature and is not intended to limit the various embodiments described herein or the application and uses of the embodiments. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding Technical Field, Background, Summary, Brief Description of the Figures, or the following Detailed Description or drawings.

[0012] Stannous pyrophosphate is a relatively stable salt with very low solubility in water. Stannous pyrophosphate, sometimes called stannous pyrophosphate, has the chemical formula Sn2P2O7. The tin 2+ cation is preferred over the tin 4+ cation and is the most prevalent in the reactions described below. Generally, stannous tetrafluoroborate, having the chemical formula Sn(BF4)2, is combined with a pyrophosphate compound to produce stannous pyrophosphate and a tetrafluoroborate by-product, which has the chemical formula NaBF4 in embodiments where the pyrophosphate is sodium pyrophosphate. The reactants may be in solution when combined, in which case they are more soluble in polar solvents. The tin pyrophosphate forms as a precipitate when formed in solution, and the size of the precipitate particles can be controlled as described below.

[0013] See Figure 1. Tin 10 tetrafluoroborate is available as a raw material and can be purchased in sufficient quantities from various suppliers, often in a 50 / 50 weight percent aqueous solution based on the total weight of the aqueous solution. Tin 10 tetrafluoroborate is typically used as a plating and / or surface treatment agent. Tin 10 tetrafluoroborate is a solid material with a melting point above 130 degrees Celsius (°C), is miscible with water, and forms a colorless, stable aqueous solution.

[0014] Tin tetrafluoroborate solvent 12 can be combined with tin tetrafluoroborate 10 to form tin tetrafluoroborate solution 14. Tin tetrafluoroborate solvent 12 includes water and may include about 50 to about 100 weight percent water, based on the total weight of tin tetrafluoroborate solvent 12. In some embodiments, tin tetrafluoroborate solvent 12 is about 95 to about 100 weight percent water, although other components may be included in other embodiments. For example, alcohols or other polar compounds may be included in tin tetrafluoroborate solvent 12. Exemplary alcohols have 1 to 6 carbon atoms, although other alcohols or other types of solvents may also be used. Generally, tin tetrafluoroborate solvent 12 is capable of dissolving tin tetrafluoroborate 10. In some embodiments, tin tetrafluoroborate solution 14 is acidic and has a pH less than 7, so the tin tetrafluoroborate solvent may also have an acidic pH. In some embodiments, tin tetrafluoroborate is formed by adding a tin salt to an acid solution of tetrafluoroborate, and the tin tetrafluoroborate is isolated by electrolysis. However, in other embodiments, different production methods may be utilized.

[0015] Referring to FIG. 2 , pyrophosphate compound 16 is combined with pyrophosphate solvent 18 to form pyrophosphate solution 20. Pyrophosphate compound 16 may include tetrasodium pyrophosphate, which has a chemical formula of Na4P2O7, although sodium pyrophosphate compound 16 may also include disodium pyrophosphate, which has a chemical formula of Na2H2P2O7. In other embodiments, the pyrophosphate may include a metal other than sodium as the salt cation, or a metal in combination with sodium. By way of non-limiting example, the cation may include one or more of potassium, rubidium, calcium, magnesium, iron, or others. In an exemplary embodiment, pyrophosphate compound 16 includes tetrasodium pyrophosphate in an amount of about 50 to 100 weight percent, based on the total weight of pyrophosphate compound 16. Pyrophosphate compound 16 is readily commercially available in a variety of grades and purities.

[0016] Because pyrophosphate compound 16 is slightly soluble in water, pyrophosphate solvent 18 may contain water in an amount of about 50 to 100 weight percent, based on the total weight of pyrophosphate solvent 18. However, other solvents, such as alcohol or other solvents, may also be included in pyrophosphate solvent 18. Because the solubility of pyrophosphate compound 16 in pyrophosphate solvent 18 is limited, pyrophosphate solution 20 may be heated to facilitate dissolution. In an exemplary embodiment, pyrophosphate solution 20 is heated to a pyrophosphate solution temperature 22 of about 60 to about 85°C, although other temperature ranges are possible. Tetrasodium pyrophosphate has a solubility in water of 6.7 grams per milliliter (g / mL) at 25°C, which increases to 42.2 g / mL at 100°C. In exemplary embodiments, pyrophosphate compound 16 is present in pyrophosphate solution 20 in an amount of about 10 to about 500 grams per liter, or in an amount of about 100 to about 300 grams per liter.

[0017] With continued reference to FIGS. 1 and 2 , and with reference to FIG. 3 , tin tetrafluoroborate 10 is added to pyrophosphate compound 16 to produce tin pyrophosphate in reaction product 38. In the exemplary embodiment shown in FIG. 3 , tin tetrafluoroborate solution 14 is added to pyrophosphate solution 20, where the two compositions react to form tin pyrophosphate contained in precipitate 30. The reaction between tin tetrafluoroborate 10 and pyrophosphate compound 16 can be controlled at a reaction temperature 32 of about 50 to about 100° C., although other reaction temperature ranges are possible. For example, a reaction temperature range of about 50 to about 80° C. or about 60 to about 70° C. can also be utilized. Tin tetrafluoroborate 10 can be added to pyrophosphate solution 20 over an addition time of about 5 minutes to about 12 hours, although other addition times are possible. For example, the addition time can be about 20 minutes to about 2 hours, or in another embodiment, about 30 minutes to about 60 minutes. In the reaction of tin tetrafluoroborate 10 with pyrophosphate compound 16, a tetrafluoroborate salt, such as sodium tetrafluoroborate, is produced as a by-product when sodium pyrophosphate salt is present in pyrophosphate compound 16. Thus, tetrafluoroborate salts are present in reaction product 38.

[0018] Tin tetrafluoroborate 10 and pyrophosphate compound 16 react to produce tin pyrophosphate and tetrafluoroborate products. By examining the chemical formula, a chemist can determine the stoichiometric amounts of tin tetrafluoroborate 10 and pyrophosphate compound 16, where a stoichiometric amount is the theoretical amount in which all reactants (tin tetrafluoroborate 10 and pyrophosphate compound 16) will react to produce the product. In an exemplary embodiment, tin tetrafluoroborate 10 and pyrophosphate compound 16 are combined in about 100 percent stoichiometric amounts, where 100% of the stoichiometric amount is the stoichiometric amount. The term "about 100 percent stoichiometric amount" herein means within about 5% of the stoichiometric amount. In another embodiment, the tin tetrafluoroborate 10 may be added in greater than stoichiometric amounts, such that the tin tetrafluoroborate is added in an amount of about 100 to about 125% of the stoichiometric amount for reaction with the pyrophosphate composition 16. In yet another embodiment, the tin tetrafluoroborate is added in an amount of about 75 to about 100% of the stoichiometric amount. Other embodiments are possible.

[0019] Many different embodiments are possible for the combination of tin tetrafluoroborate 10 and pyrophosphate compound 16. For example, as shown in FIG. 4, tetrafluoroborate 10 may be added as a solid to pyrophosphate solution 20. In another embodiment, as shown in FIG. 5, tin tetrafluoroborate solution 14 and pyrophosphate solution 20 are simultaneously injected into a microjet reactor 34. In an exemplary embodiment, a reaction gas 36 is added along with the reactants, and a reaction product 38 is discharged, which in this case includes a precipitate 30 having tin pyrophosphate. Another alternative possibility includes the continuous simultaneous addition of tin tetrafluoroborate 10 and pyrophosphate compound 16 to a continuous reactor (not shown), in which case tin tetrafluoroborate 10 and / or pyrophosphate compound 16 may be added as a solid or as a solution. Other possible reaction mechanisms are also possible.

[0020] As shown in the exemplary embodiment of FIG. 6 with continued reference to FIGS. 1-5, the precipitate 30 can be removed from the reaction product 38 by filtration, sedimentation, centrifugation, or other separation techniques. The precipitate 30 may be washed to increase the purity of the tin pyrophosphate and reduce the concentration of tetrafluoroborate. In the exemplary embodiment, the precipitate 30 is washed by rinsing with a rinse solution 40, although other techniques for removing tetrafluoroborate are possible. For example, the precipitate 30 may be reslurried and refiltered, the tin pyrophosphate may be further purified by recrystallization, or other purification techniques may be used to remove the tetrafluoroborate. In the exemplary embodiment for rinsing the precipitate 30, the rinse solution 40 comprises water in an amount of about 50 to about 100 weight percent, based on the total weight of the rinse solution 40. Because tin pyrophosphate is much less soluble in water than the tetrafluoroborate by-product, the tetrafluoroborate preferentially dissolves and is washed away from the tin pyrophosphate in the precipitate 30 during rinsing or washing. Since tin pyrophosphate has a boron specification of 100 ppm in an exemplary embodiment, precipitate 30 may be washed until the tetrafluoroborate concentration is reduced to a point where the boron concentration is 100 ppm or less, based on the total weight of precipitate 30 after drying. Thus, precipitate 30 may be washed until the tetrafluoroborate concentration is about 10 to about 1,000 ppm, measured based on the total weight of precipitate 30 after drying. In an exemplary embodiment, the amount of rinse solution 40 used is about 500 grams of water per 100 grams of tin pyrophosphate in precipitate 30 to reduce the tetrafluoroborate to about 1,000 ppm or less, based on the total weight of tin pyrophosphate in precipitate 30. In another embodiment, about 300 grams or about 400 grams of water is used per 100 grams of tin pyrophosphate. Rinsing may be repeated until the impurities are reduced to a level sufficient for use in dental products. In an exemplary embodiment, rinsing may be repeated until the rinse liquid has a conductivity of about 500 microsiemens or less after passing through precipitate 30. In alternative embodiments, other techniques may be utilized to verify the desired purity.

[0021] As shown in FIG. 7 with continued reference to FIGS. 1-6, after the precipitate 30 is washed, it may be dried, such as in a spray dryer. The precipitate 30 may be slurried or otherwise fed into a spray dryer 50. A drying gas 52, such as hot air, is fed into the spray dryer 50 along with the precipitate 30, the drying gas 52 exiting the spray dryer 50 as exhaust gas 54, and tin pyrophosphate 56 exiting the spray dryer 50 as a solid product. The precipitate 30 may also be dried using many other techniques, such as fluidized bed, tray dryer, vacuum dryer, freeze dryer, etc. The type of dryer utilized may affect the particle size of the product, including tin pyrophosphate 56.

[0022] The tin-56 pyrophosphate in the product may be present in a concentration of about 96 to about 99.99 wt. % based on the total weight of the product, and the product may be a dental health care composition. The boron concentration may be about 0.1 to about 100 ppm by weight based on the weight of the product. Sodium tetrafluoroborate (or other tetrafluoroborate salts) may be present in the product in a concentration of about 10 to about 1,000 ppm by weight based on the total weight of the product, in which case the tetrafluoroborate salts typically remain in a minor amount. In exemplary embodiments, the presence of sodium tetrafluoroborate (or other tetrafluoroborate salts) in the product strongly indicates that the tin-56 pyrophosphate was produced using tin tetrafluoroborate and sodium pyrophosphate compound (or other pyrophosphate compound 16) as reactants. The tin-56 pyrophosphate product may contain a wide variety of other impurities in various embodiments, which may be derived from the raw materials used. Exemplary impurities that may be present include trace elements such as arsenic (As), cadmium (Cd), cobalt (Co), mercury (Hg), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V), chlorine (Cl), chromium (Cr), potassium (K), etc. Generally, these trace elements may optionally be present at concentrations ranging from 0 to about 500 ppm.

[0023] The resulting tin pyrophosphate 56 in the product desirably has a small average particle size to facilitate incorporation into oral hygiene products as a dental health care composition. Various techniques can be incorporated into the production process to reduce the average particle size in the product. For example, particle size reduction can be achieved by using a spray dryer 50. Adding an acid to the pyrophosphate solution 20 prior to the reaction can lower the pH, which slows the reaction and can help reduce the average particle size. An example of an acid that can be used is phosphoric acid, although other acids, such as hydrochloric acid, sulfuric acid, citric acid, and acetic acid, are also possible. In exemplary embodiments, the acid can be added to the pyrophosphate solution 20 in an amount of about 0.01 to about 1.0 weight percent, which can lower the pH of the pyrophosphate solution 20 to a range of about 10 to about 6, about 9.5 to about 7, or about 9.5 to about 9 in various embodiments. In other embodiments, a scale inhibitor 24 may optionally be added to pyrophosphate solution 20 in an amount of about 0.05 to about 0.5 weight percent or 0.1 to about 0.5 weight percent, based on the total weight of pyrophosphate solution 20. The scale inhibitor 24 may be selected from the group consisting of citric acid, nitrilotris(methylene)triphosphonic acid (NTMP), etidronic acid (also known as hydroxyethylidene(1,1-diphosphonic acid)) (HEDP), phosphonobutanetricarboxylic acid, ethylenediaminetetra(methylenephosphonic acid), hexamethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), and combinations thereof. Small particle sizes can also be produced by the use of a microjet reactor 34.

[0024] Testing has shown that the tin pyrophosphate 56 in the product can have an average particle size D95 of about 0.1 to about 100 microns, although larger particle sizes are possible depending on the materials and production process used. The D95 particle size means that 95% of the particles are below the specified particle size. In an exemplary embodiment, particle size is determined by laser diffraction through the suspension, although other techniques may be used in alternative embodiments. In an exemplary embodiment, the use of phosphoric acid and / or other scale inhibitors 24 can reduce the particle size D95 of the tin pyrophosphate 56 in the reaction product 38 to about 0.1 to about 100 microns. Ultrasonic application of ultrasonic waves to the slurried precipitate 30 also resulted in particle sizes D95 of about 0.1 to about 100 microns. Furthermore, addition times of about 5 to about 12 hours resulted in particle sizes D95 of about 0.1 to about 100 microns.

[0025] Other techniques can also be used to reduce the particle size of the reaction product 38. For example, the precipitate 30 can be slurried and subjected to ultrasonic procedures, high-speed mixing, homogenization, and / or other rapid agitation techniques. Additionally, the reaction product 38 can be milled, grinded, or otherwise processed to reduce particle size, or the product can be sieved to recover smaller particles. Longer addition times can also slow the reaction and thereby reduce particle size. Various approaches to particle size reduction have advantages and disadvantages that must be considered and balanced. For example, milling or grinding uses extra energy and can create dust problems. Increased dosing times slow the production process, which increases labor costs, depreciation costs, and other associated costs. The cost of the scale inhibitor 24 and the cost of maintaining additional product in the production process must also be considered.

[0026] Experimental data Several batches were made in the lab using the above technique, and the results are shown below. In Table 1, all charge amounts are in grams unless otherwise stated.

[0027] [Table 1] 1 Scale inhibitor weight in grams. 2 The dosing time is the time during which the tin tetrafluoroborate solution is added to the pyrophosphate solution. 3 The "end temperature" is the temperature at which the precipitate is filtered off. 4 All rinse steps used 70 milliliters of deionized water. 5 Particle size of dried precipitate. 6 The concentration of elemental boron in the dried precipitate is in ppm by weight based on the total weight of the dried precipitate.

[0028] [Table 2] 7 Scale inhibitor weight in grams. 8 The dosing time is the time during which the tin tetrafluoroborate solution is added to the pyrophosphate solution. 9 The "end temperature" is the temperature at which the precipitate is filtered off. 10 All rinse steps used 70 milliliters of deionized water. 11 Particle size of dried precipitate. 12 The concentration of elemental boron in the dried sediment is in ppm by weight based on the total weight of the dried sediment.

[0029] [Table 3] 13 DTPMP is diethylenetriaminepenta(methylenephosphonic acid), NTMP is nitrilotris(methylene)triphosphonic acid, and HEDP is etidronic acid. 14Antiscalant weight in grams 15 The dosing time is the time during which the tin tetrafluoroborate solution is added to the pyrophosphate solution. 16 The "end temperature" is the temperature at which the precipitate is filtered off. 17 All rinse steps used 70 milliliters of deionized water. 18 Particle size of dried precipitate. 19 The concentration of elemental boron in the dried precipitate is in ppm by weight based on the total weight of the dried precipitate.

[0030] As shown in the results presented above, higher yields are obtained by adding tin tetrafluoroborate 10 and pyrophosphate compound 16 in near stoichiometric amounts. The use of scale inhibitors 24 can reduce particle size, with some scale inhibitors 24 being more effective than others. Increasing the addition time (referred to as "dosing time" in Table 1) can reduce particle size, but the results are not significant until the addition time is extended to several hours.

[0031] While several embodiments have been presented in the foregoing detailed description, it should be understood that numerous variations exist. It should also be understood that the embodiment or embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description provides those skilled in the art with convenient guidance for implementing various embodiments of the asphalt composition, and it will be understood that various changes can be made in the function and arrangement of the elements described without departing from the scope set forth in the appended claims and their legal equivalents.

Claims

1. 1. A method for producing tin pyrophosphate, comprising: combining a stannous tetrafluoroborate and a pyrophosphate composition to form a precipitate comprising said stannous pyrophosphate and tetrafluoroborate; removing said tetrafluoroborate salt from said precipitate.

2. 10. The method of claim 1, further comprising providing a tin tetrafluoroborate solution comprising the tin tetrafluoroborate and a tin tetrafluoroborate solvent, wherein the tin tetrafluoroborate solvent comprises water, and wherein the tin tetrafluoroborate solution is generated prior to combining the tin tetrafluoroborate and the pyrophosphate composition.

3. 10. The method of claim 1, further comprising forming a pyrophosphate solution comprising the pyrophosphate composition and a pyrophosphate solvent, wherein the pyrophosphate solvent comprises water, and wherein combining the stannous tetrafluoroborate and the pyrophosphate composition comprises combining the pyrophosphate solution and the stannous tetrafluoroborate.

4. 4. The method of claim 3, further comprising bringing the pyrophosphate solution to a pyrophosphate solution temperature of about 60 to about 85 degrees Celsius (°C) before combining the stannous tetrafluoroborate and the pyrophosphate solution.

5. 4. The method of claim 3, wherein combining the stannous tetrafluoroborate and the pyrophosphate solution comprises adding the stannous tetrafluoroborate to the pyrophosphate solution.

6. 6. The method of claim 5, further comprising providing a tin tetrafluoroborate solution comprising the tin tetrafluoroborate and a tin tetrafluoroborate solvent, and wherein combining the tin tetrafluoroborate with the pyrophosphate solution comprises adding the tin tetrafluoroborate solution to the pyrophosphate solution over an addition time of from about 5 minutes to about 12 hours.

7. 4. The method of claim 3, wherein the pyrophosphate solution further comprises phosphoric acid to provide a pyrophosphate solution with a pH of about 9.5 to about 7.

8. 4. The method of claim 3, wherein the pyrophosphate solution further comprises phosphoric acid in an amount sufficient to produce the precipitate having an average particle size of from about 0.1 to about 100 microns.

9. 4. The method of claim 3, wherein the pyrophosphate solution further comprises a scale inhibitor in an amount of about 0.01 to about 1 weight percent based on the weight of the pyrophosphate solution, the scale inhibitor being selected from the group consisting of citric acid, nitrilotris(methylene)triphosphonic acid, etidronic acid, phosphonobutanetricarboxylic acid, ethylenediaminetetra(methylenephosphonic acid), hexamethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and combinations thereof.

10. 4. The method of claim 3, wherein the pyrophosphate solution further comprises a scale inhibitor in an amount sufficient to produce the precipitate having an average particle size of from about 0.1 to about 100 microns, the scale inhibitor being selected from the group consisting of citric acid, nitrilotris(methylene)triphosphonic acid, etidronic acid, phosphonobutanetricarboxylic acid, ethylenediaminetetra(methylenephosphonic acid), hexamethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and combinations thereof.

11. 10. The method of claim 1, wherein the pyrophosphate composition comprises tetrasodium pyrophosphate.

12. 10. The method of claim 1, wherein the stannous tetrafluoroborate is added in an amount of about 100 to about 125% of the stoichiometric amount for reaction with the pyrophosphate composition.

13. 10. The method of claim 1, wherein the stannous tetrafluoroborate and the pyrophosphate composition are combined in a microjet reactor.

14. The method of claim 1 further comprising spray drying the precipitate.

15. 10. The method of claim 1, wherein removing the tetrafluoroborate comprises rinsing the precipitate with a rinse solution, the rinse solution comprising from about 50 to about 100 weight percent water, based on the total weight of the rinse solution.

16. 10. The method of claim 1, wherein removing the tetrafluoroborate comprises washing the precipitate until the boron concentration in the precipitate is from about 0.1 to about 100 ppm by weight, based on the total weight of the precipitate.

17. The method of claim 1 further comprising drying the precipitate after removing the tetrafluoroborate salt.

18. 1. A dental health care composition comprising: stannous pyrophosphate in a concentration of about 96 to about 99.999 weight percent based on the total weight of the dental health care composition; sodium tetrafluoroborate at a concentration of about 10 to about 1,000 ppm by weight, based on the total weight of the dental health care composition; 1. A dental health care composition comprising:

19. 20. The dental health care composition of claim 18, wherein the stannous pyrophosphate has an average particle size of about 0.1 to about 100 microns.

20. 1. A method for producing tin pyrophosphate, comprising: providing a tin tetrafluoroborate solution comprising tin tetrafluoroborate and a tin tetrafluoroborate solvent, wherein the tin tetrafluoroborate solvent comprises water; providing a pyrophosphate solution comprising tetrasodium pyrophosphate and a pyrophosphate solvent, wherein the pyrophosphate solvent comprises water; adjusting the temperature of the pyrophosphate solution to about 60 to about 85 degrees Celsius (°C); combining the tin tetrafluoroborate solution and the pyrophosphate solution to form a precipitate comprising the tin pyrophosphate and sodium tetrafluoroborate; and rinsing the precipitate with a rinse solution to reduce the sodium tetrafluoroborate concentration to a level such that the boron concentration is less than about 100 ppm by weight based on the total weight of the precipitate.

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