GB1586583A - Alkali metal aluminium phosphate - Google Patents

Description

(54) IMPROVED ALKALI METAL ALUMINIUM PHOSPHATE (71) We, STAUFFER CHEMICAL COMPANY, a corporation organised under the laws of the State of Delaware, United States of America, of Westport, Connecticut 06880, 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 an improved alkali metal aluminium phosphate; more particularly, the present invention relates to alkali metal aluminium phosphate granules having a calcium-rich layer thereon characterized by improved flow and dusting properties without a loss in leavening acid performance properties. The product may be used as a leavening acid in moist doughs and liquid batters, such as pancake batters and other pre-mixed liquid batters.

Crystalline sodium aluminium phosphate (or SALP) was first disclosed in U.S.

Patent No. 2,550,490 and an early baking powder composition incorporating SALP was disclosed in U.S. Patent No. 2,550,491. U.S. Patent No. 2,550,490 specifically discloses a SALP having a Na:Al:PO4 ratio of 1:3:8. Since that time, several modifications of sodium aluminium phosphate have been developed which give different reactivities and performance characteristics. These include a dehydrated SALP, U.S. Patent No. 2,957,750; a 3:3:8 SALP, U.S. Patent No. 3,223,479; a 3:2:8 SALP, U.S. Patent No. 3,501,314; a 2:3:6 SALP, U.S. Patent No. 3,574,536; an amorphous SALP, U.S. Patent No. 2,995,421; a 3:3:9 SALP, U.S. Patent No.

3,726,962; and the continuous crystallization of SALP, U.S. Patent No. 3,311,448.

Sodium aluminium phosphate is a well known leavening agent in the baking industry. It finds use in baking powders, self-rising mixes, pre-leavened pancake flours and mixes, prepared biscuit mixes and prepared cake mixes. (See U.S. Patent Nos; 2,550,491; 3,109,738; 3,041,177; and 3,096,178). It is also used as a meltcontrolling additive in cheese and as a meat binding agent.

It is taught in U.S. Patent No. 2,550,490 that the speed of the gas developing reaction of the sodium aluminium phosphate may be accelerated by the use of an accelerator, such as monocalcium phosphate. The monocalcium phosphate may be formed on the surface of the sodium aluminium phosphate crystals. This may be accomplished by preparing the SALP as usual, but omitting an alcohol wash to remove excess phosphoric acid. The excess phosphoric acid is then neutralized with hydrated lime. Specifically, the sodium aluminium phosphate was prepared by dissolving aluminium in phosphoric acid and adding sodium carbonate. After concentrating to a thick slurry, the slurry was added to a mixer containing hydrated lime. Vigorous agitation was continued until the mixture solidified into small granular lumps. After drying, the product was milled to provide a dry, nonhydroscopic powder having a neutralizing value of 100.4. It was tested in the baking of biscuits and found to have baking characteristics equal to that of standard commercial phosphate-alum baking powders. Results of baking at a neutralizing value of 90 showed the baked biscuits to have a specific volume of 2.6, a pH of 7.4 and a fine open grain structure.

These results required milling of the SALP to obtain particle sizes sufficiently small to be usable in baking.

Sodium aluminium phosphate is generally employed in baking applications in a finely divided state due to its substantial insolubility. Furthermore, if relatively large particles of sodium aluminium phosphate are used in bakery applications, they may impart an undesirable, gritty property. Sodium aluminium phosphate has several inherent deficiencies, the most serious of which is dusting and hygroscopicity. Sodium aluminium phosphate dust is very light and rapidly permeates the air in food processing plants, creating cleaning and sanitation problems and unsatisfactory working conditions for the employees. An additional problem - in handling sodium aluminium phosphate is that the finely divided particles do now flow easily.

Sodium aluminium phosphate is also an inherently hygroscopic material which will absorb a large quantity of atmospheric moisture, usually from 28 to 29%, by weight. Originally produced, SALP is a dry, white crystalline product. If permitted to stand exposed in a hot, humid atmosphere, it rapidly absorbs moisture, first forming water droplets or caking at the surface, then becoming what may be termed a viscous semi-fluid. Commercially, this phenomenon is minimized somewhat by the use of sealed, air-tight containers. Nevertheless, the precautions required are time consuming and expensive and, in practical applications, the problem remains a significant disadvantage.

Several proposals have been made in the past for improving the physical handling properties of sodium aluminium phosphate, particularly directed to improving flow characteristics and dust properties. These approaches have generally been directed to agglomerating or pelletizing the SALP as disclosed, for example, in U.S. Patent No. 3,620,972 which utilizes water as an agglomerating medium. Other methods have involved the employment of various binders, such as sugars and crystallizing syrups. Still other approaches utilize the addition of small amounts of colloidal SiO2 or tricalcium phosphate to the SALP as flow conditioners to improve physical handling properties.

In connection with SALP 3:2:8 disclosed in U.S. Patent No. 3,501,314, it is known to dry blend a flow conditioner with dry SALP crystals. The flow conditioner may be any alkali or alkaline earth metal phosphate, calcium hydroxide or aluminium oxide. It is taught that the dry flow conditioner particles are adhered to dry SALP particles as a dry coating. The flow conditioners are taught to increase flowability and reduce hygroscopicity. However, flow conditioners in general are known to only improve handling characteristics to a slight degree.

U.S. Patent 3,255,073 describes a potassium-modified sodium aluminium acid phosphate having decreased hygroscopicity. This result is accomplished by modifying the original sodium aluminium phosphate molecule with the introduction of potassium. The potassium is explained as replacing hydrogen atoms in the crystalline lattice of sodium aluminium phosphate. This improved potassiummodified sodium aluminium phosphate is described as having hygroscopic properties wherein it does not increase in weight by more than 20%, preferably not more than 10% of its original weight during continued exposure at 350C. and 75% relative humidity for 140 hours.

An improvement over U.S. Patent No. 3,205,073 is U.S. Patent No. 3,411,872 which attempts to improve the flow characteristics of the potassium-modified sodium aluminium phosphate by incorporating the potassium ions in a solvent suspension of an alkanol.

A further improvement over U.S. Patent No. 3,205,773 is disclosed in U.S.

Patent No. 4,054,678. In that specification, a specific ratio of sodium and potassium is used to prepare a potassium-modified SALP. The improved SALP product is characterized by increased density and reduced dusting properties. Among the advantages accrued thereby, are ease of packaging, use of smaller bags that pelletize more easily, decreased hygroscopicity and improved flow characteristics.

All of these properties enable better handling, in general, especially under conditions of high humidity.

In accordance with the present invention, it has been found that a calciumtreated aluminium phosphate having improved handling characteristics and useful as a leavening agent particularly in moist doughs and liquid batters may be prepared by contacting a slurry of a complex aluminium phosphate corresponding to the formula: MaAIbHC (PO4)d .H2Oe, wherein M represents a cation selected from sodium, potassium ammonium and, mixtures thereof; a, b, c and d each represent a number; e represents a number of from 0 to n; and n represents an integer; with a calium compound, followed by granulating the calcium-treated product while- drying under such conditions that a majority of the granulated particles are less than 840 micron (through 20 mesh) and at least 90% less than 2000 micron. There is provided granulated complex aluminium phosphate granules with at least a calcium-rich outer surface. The process according to the present invention may also be included as part of the processes for preparing SALP and potassium-modified SALP. This involves contacting an alkali metal aluminium phosphate with a calcium compound subsequent to the initial formation of alkali metal aluminium phosphate crystals and prior to completion of the drying of the slurry. The granulation while drying is then accomplished.

The products according to the present invention show improved handling characteristics and as leavening acids improved holding and storage characteristics in moist doughs and liquid batters. Improved hygroscopicity means improved storage stability of dry blends.

Accordingly, the present invention provides a phosphate corresponding to the following general formula: Ma Al b H (P04)d .(H2O)9 wherein M represents sodium and/or potassium and/or ammonium; a, b, c and d each represent a number; e represents a number of from 0 to n; and n represents an integer; which is in the form of particles, the outer surfaces of which having calcium uniformly dispersed and bound therein, more than 50% of the particles being less than 840 microns in diameter and at least 90% of the particles being less than 2000 microns in diameter.

The present invention also provides a process for the preparation of such a phosphate which comprises contacting a slurry of a phosphate corresponding to the above-defined general formula with a calcium compound and, while drying, granulating the product so as to obtain the desired particle size distribution.

The slurry is generally prepared by contacting a food grade phosphoric acid having a concentration of from 70 to 90 weight percent with sodium ions and/or potassium ions and/or ammonium ions and with aluminium ions.

The present invention further provides the use of such a phosphate as a leavening acid.

Referring to the accompanying drawings, Figure 1 is a representation of an electron probe analysis for calcium made on the cross-section of a particle according to the present invention magnified 1,000 times.

Figure 2 is a representation of an electron probe analysis for phosphorus on the same particle cross-section as in Figure 1.

Figure 3 is a representation of an electron probe analysis for aluminium on the same particle cross-section as in Figure 1.

Figure 4 is a representation of an electron probe analysis for calcium on the cross-section of a particle produced in accordance with U.S. Patent No. 2,550,490, magnified 462 times.

Figure 5 is a representation of an electron probe analysis for phosphorus on the same particle cross-section as in Figure 4.

Figure 6 is a representation of an electron probe analysis for aluminium on the same particle cross-section as in Figure 4.

The product according to the present invention is a calcium-treated alkali metal aluminium phosphate corresponding to the formula: Ma Alb Hc (PO4)d .(H2O)6 wherein M represents sodium, potassium, ammonium or a mixture thereof.

(Ammonium is generally included within the class of alkali metals because of its similar chemical properties). The letters a, b, c, and d are numbers representing the various numerical ratios possible in preparing alkali metal aluminium phosphates.

The letter e relates to the quantity of water of\hydration present which may range from 0 upward. Representative ratios are shown above. It is only intended to cover those ratios which will form an alkali metal aluminium phosphate. At present, two SALP's are commercially available as leavening acids, i.e. 1:3:8 and 3:2:8, and these are intended to be covered specifically. SALP compounds are traditionally prepared by mixing an alkali metal hydroxide or carbonate, such as sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, ammonium carbonate, ammonium hydroxide or mixtures thereof, with from 70 to 90% acid, preferably from 85 to 88% acid, more preferably about 86% acid, in an amount sufficient to provide the ratio of alkali metal to PO4 which is desired. The selection of these ratios may be easily ascertained by one skilled in the art. The temperature during this mixing period is generally maintained above 40"C. and below 100"C. This material is then treated with an aluminium compound, such as alumina trihydrate. The aluminium compound is generally added incrementally.

The temperature during aluminium addition may rise to about 140"C. and then drop to about ll00C.

At this point, the reaction product is usually cooled to from 60 to 750C. for from 15 to 30 minutes to form a slurry of crystalline alkali metal aluminium phosphate. The slurry is then directed to a "Kneadermaster" kneader conveyor blender where the product is dried and granulated simultaneously.

The "Kneadermaster" mixers or blenders comprise jacketed vessels having an operating pressure of from 80 to 120 psig of steam. Hot air at a temperature of about 300"C. is fed into the central portion of the vessel. The slurry of reaction product traverses the length of the "Kneadermaster" blender, moved along by rotating blades. A particular length of the "Kneadermaster" is designated as the "wet zone" and is indicative of the distance the slurry traverses in the "Kneadermaster" before becoming substantially particulate and dry in appearance. Some processes utilize a "short wet zone" or a "regular wet zone". In general, the length of the wet zone may be varied and is determined by the loss on ignition (LOI) of the final product. LOI is a measurement of the % weight loss of a 2 gram sample of the product when ignited in a muffle furnace at a temperature of from 750 to 8500C., preferably 800"C., for a period of about 10 minutes. Variation in LOI may vary the rate of gas release of the product in a leavening system. LOI's may be varied to provide different rates for different leavening acid systems.

The calcium-treated alkali metal aluminium phosphate according to the present invention may be prepared using any known acid-soluble alkali metal aluminium phosphate material, the preferred materials being 1:3:8 and 3:2:8 SALP, more preferably 1:3:8 SALP.

For ease, the remaining description will relate to SALP (sodium aluminium phosphate) 1:3:8, though it is to be understood that this description applies to all aluminium phosphates generically encompassed by the present invention, unless otherwise indicated.

After the initial formation of SALP crystals in a slurry and prior to drying in the reactor or by reslurrying-dried SALP crystals, the SALP slurry is added to or has added to it a calcium compound, such as calcium hydroxide. Any calcium compound may be used as long as it is reactable with the system and does not have an anion which -will interfere with the reaction. Illustrative of such calcium compounds are calcium oxide, calcium hydroxide, calcium carbonate and mixtures thereof. The preferred material is hydrated lime.

It is preferred to add the hydrated lime to the SALP slurry to prevent dusting losses. Addition is generally made incrementally with agitation at a temperature of from 80 to 1000C. The calcium compound may be added with equal effectiveness at any time after the initial formation of SALP crystals and before drying. It is preferred that the SALP slurry be cooled and that the slurry contain a high percentage crystals prior to calcium treatment. At least some free water or other solvent must be present for effective treatment.

It is critical that the calcium-treated SALP be granulated while drying the product under such conditions that a majority of the particles are less than 840 microns (20 mesh) and 90% are less than 2000 microns (10 mesh). By "majority" is meant at least 50%, preferably at least 60%. Less than 10% of the product as prepared is larger than 2000 microns. If proper granulation is not undertaken, large lumps are formed on drying (5000 micron and above) which must be milled in order to obtain a product having a working particle size distribution of less than 60 mesh. The milled product has a faster rate of gas release than SALP and acts like a blend of SALP and monocalcium phosphate. If, however, the product is granulated while drying so that a majority of the particles are less than 840 microns under such conditions that the large lumps are not allowed to form prior to complete drying, the product has the same rate of gas release as SALP in a doughnut dough rate of reaction test, but slower in a baking powder rate of reaction test (both tests being described below). any soft lumps formed during the drying procedure may be broken and remain in the granulator until the drying is complete. Any large lumps should not be allowed to completely dry.

In theory, a calcium layer has been formed on the SALP which is frangible if milled. By granulating the product while drying, the particles are sufficiently small that extensive milling is not required. Depending on the particle size range desired, a fraction, such as the on 60 mesh fraction, may be separated, milled and admixed with the remaining fraction, i.e. the through 60 mesh fraction, to obtain a product of commercially acceptable particle size. Since most of the particles as produced are small (less than 2000 microns) so that substantial milling is not required, there is generally obtained a granule which has at least a calcium-rich outer surface.

It has also been found that an improved potassium-modified alkali metal aluminium phosphate granule having a calcium-enriched outer surface may be prepared. This product is characterised by a considerable improvement in dust properties and flow characteristics over SALP alone or with a flow conditioning agent without loss of baking performance. The potassium-modified alkali metal phosphate is prepared by the controlled substitution of potassium ion for a portion of the sodium ion used in producing the sodium aluminium phosphate as is disclosed in U.S. Patent No. 4,054,678.

It appears that when controlled amounts of potassium ion are contacted with a mixture of sodium-treated food grade phosphoric acid which is subsequently reacted with alumina trihydrate, (Al203.3H2O), to produce sodium aluminium phosphate, changes in the crystal structure occur that appear to stabilize the crystal habit of the potassium-modified sodium aluminium phosphate. The potassiummodified SALP has better flow characteristics and less dust than the prior art SALP compositions, while maintaining reduced hygroscopic properties. This change in the crystal structure manifests itself in the form of a doublet pattern as shown by xray diffraction powder patterns. This doublet suggests that there may be direct substitution of potassium for some of the sodium within the alkali metal aluminium phosphate molecule.

In accordance with the present invention, the improved calcium-treated potassium-modified sodium aluminium phosphate is produced by contacting a food grade phosphoric acid with a sufficient amount of potassium hydroxide to provide an analysis of from 0.5 to 1.2, more preferably from 0.6 to 1.0, weight percent of potassium oxide (K2O) in the potassium-modified SALP. Other potassiumcontaining compounds may also be utilized, such as K2CO3, KHCO3 and K3PO4, with the proviso that the anion attached to the potassium not contaminate the reaction media or product.

It appears that the K2O analysis is a critical factor in helping to achieve change in crystal structure of the final product which contributes to good flow and dust properties of the product.

The potassium-treated phosphoric acid is then contacted with a sufficient amount of sodium carbonate (Na2CO3) to provide an analysis of from 2.4 to 3.2, preferably from 2.6 to 3, weight percent of sodium oxide (Na2O) in the potassiummodified SALP. The Na2CO3 is generally added in a dry or anhydrous state.

The temperature of the phosporic acid should generally be maintained above 40"C. and below 100"C. to prevent crystallization of sodium and/or potassium phosphate.

Other sodium-containing compounds may also be used, such as NaOH, NaHCO3 and Na3PO4, with the proviso that the anion attached to the sodium not contaminate the reaction media or product.

The order of addition of sodium and potassium compounds is not critical though it is preferred to add the potassium compound first.

The sodium/potassium-treated phosphoric acid then generally has its temperature adjusted to a temperature of from 40 to l000C., preferably about 80"C., and is contacted with a sufficient amount of an aluminium compound, such as alumina trihydrate, to provide a desired concentration of Al203 in the final product. The alumina trihydrate is generally contacted with the treated phosphoric acid under conditions of agitation so that it is uniformly distributed throughout the treated acid.

The addition of finely divided alumina trihydrate is generally accomplished incrementally generally over a period such that the extensive boiling does not occur, i.e. at a rate of from 1 to 3% a minute. The temperature initially rises tofrom 120 to 140"C. and then drops to about 110"C.

The reaction of the sodium/potassium-treated phosphoric acid with alumina trihydrate produces a slurry of potassium-modified sodium aluminium phosphate.

The reaction generally takes from 1 to 3 hours at about 1100C. to complete.

The reactor may then be cooled to from 60 to 750C. for from 15 to 30 minutes.

A calcium compound, such as hydrated lime, is then incrementally added with mixing to the slurry of the potassium-modified sodium aluminium phosphate. After thorough mixing, the reaction mass is held until the reaction subsides and then the reaction product is directed to a "Kneadermaster" blender or mixer, wherein the material is dried and granulated simultaneously.

The conditions of the "Kneadermaster" blender are maintained so that the dry calcium-treated potassium-modified SALP exiting the Kneadermaster preferably has a loss on ignition (LOI) of from 16 to 22 weight percent.

After exiting the "Kneadermaster", the calcium-treated SALP proceeds to a classification system wherein the product is classified by particle size in an air separator or other equivalent apparatus. Depending on the particle size desired, the larger size particles, such as on 60 mesh, may be separated, milled and reblended with the remaining material. The calcium-treated potassium-modified SALP product is then in a commercial form ready to be placed into large bins for packaging and shipping. The LOI of the finished calcium-treated potassium-modified SALP product is preferably from 16 to 22 weight percent.

It is desirable to control the amount of excess phosphoric acid present in the reaction mixture after formation of SALP crystals. Since the reaction never goes to completion and since it is known that some of the added alumina trihydrate does not react, an excess of phosphoric acid is generally present. A greater excess ol phosphoric acid is generally desired for the inclusion of larger amounts of calcium in the product. The acid may be used in an excess ranging from 0.1 to 65%. This amount may be achieved by the addition of excess acid at the start of the reaction or to the crystal slurry. Preferably, the excess acid is achieved by decreasing the amount of aluminium used in the reaction. The amount of aluminium may be decreased to 50%, preferably to 75%, more preferably to from 85% to 95%, of the amount required to form a desired SALP having a desired alkali metal:Al:PO4 ratio. If only the aluminium reactant is decreased, an excess of alkali metal ion is also present in the reaction mixture, as well as excess phosphate ion. Evidence has been uncovered which shows that the excess alkali metal ion is part of the surface of the calcium-treated SALP granule. It has also been noted that it appears that the alkali metal- and calcium-containing surface is less frangible than the surface containing less alkali metal. The latter may be achieved by using only an excess of phosphoric acid in the reaction mixture. It is, therefore, preferred to treat a system with calcium which has excess alkali metal compound, as well as phosphoric acid.

This may be effectively achieved by reducing the stoichiometric quantity of aluminium required in the reaction.

At least a portion of the excess acid is neutralized by the calcium compound.

The calcium compound may also be added in excess of the amount needed to neutralize the excess acid.

It is theorized that the calcium compound is neutralizing excess phosphoric acid present in the reaction mixture. There is analytical evidence which appears to indicate the presence of monocalcium phosphate on the particle.

Referring to the accompanying drawings, Figure 1 is a representation of an electron probe for calcium of a cross-section of a single particle of the product according to the present invention prepared in accordance with Example 3 below embedded in epoxy resin. As may be seen, calcium is abundant at the outer edge of the particle, but deficient in the central portions. Figure 2 shows the phosphorus content of the same particle in the same position as in Figure 1 which is fairly evenly distributed over the entire cross-section of the particle. Figure 3 shows the aluminium content of the same particle as Figure 1. It is noted that the aluminium is abundant in the centre of the particle where Figure 1 shows the particle to be calcium-deficient. The aluminium is deficient at the sides of the particle where the calcium is abundant. Since the particle is a cross-section, this evidence is interpreted'to show that the particle has a calcium-rich outer surface and a SALP inner core.

Figure 4 shows a representation of an electron probe for calcium of the crosssection of a particle prepared in accordance with U.S. Patent No. 2,550,490 as reported in Example 20 below. As may be seen, calcium is evenly distributed over the entire cross-section of the interior of the particle. Figure 5 shows that the phosphorus content of the same particle is evenly distributed over the entire crosssection of the particle. Figure 6 shows that the aluminium is likewise evenly distributed over the entire cross-section. This evidence appears to show that the material according to the present invention has a calcium-rich outer layer superimposed on a core of material which is not calcium-rich in contrast to that of the prior art.

The calcium-treated potassium-modified sodium aluminium phosphate is characterized by a more uniform consistency, is more easily handled and has a lower hygroscopicity than the potassium-modified SALP alone.

The calcium-treated potassium-modified SALP particles are harder than the potassium-free SALP particles. The particle hardness contributes to the improved handlability of the product.

In addition, the material dries quickly and granulates easily. Mill down times for cleaning have been decreased over the non-calcium-treated potassiummodified SALP due to improved milling properties. Increased density of the calcium-treated potassium-modified SALP improves packaging operations. Bags and drums are easily filled with sufficient space remaining to make quick and positive closures.

As noted above, good dust and flow characteristics of leavening acids, such as the calcium-treated SALP or potassium-modified SALP, are extremely important in plants which mix and package dry mixes for the preparation of, for example, baked products by using automatic feeders for metering the ingredients. The leavening acid is generally placed in storage bins having funnel-like openings at the bottom. Ideally, it is desired that the leavening acid be removable from the bins at a steady, controlled rate. However, it has been found during the course of removing the leavening acid from the storage bins, intermittent flow sometimes occurs and, on some occasions, flow will completely cease. This cessation of flow is called "bridging" and is caused by an open path extending from the bottom of the storage bin to the top of the leavening acid. The problems of bridging may sometimes be ameliorated by the addition of flow control agents, such as "Cab-O-Sil" (Registered Trade Mark), a form of SiO2 sold by Cabol Chemical Company, or tricalcium phosphate, to the leavening acid. The drawbacks of this approach, however, are these these flow agents are expensive, sometimes unpredictable in the effect they will have on flow characteristics and, unfortunately, may also create dust problems of their own.

The calcium-treated SALP A reaction slurry was prepared by treating 60% phosphoric acid with a sufficient amount of potassium hydroxide to provide an analysis of 0.8 + 0.2 weight percent potassium oxide (K2,O) in the final product. The potassium-treated phosphoric acid was then reacted with a sufficient amount of dry sodium carbonate (Na2CO3) to provide an analysis of 2.8 + 0.2 weight percent sodium oxide (Na2O) in the final product. These percentages were used unless otherwise indicated in Table I. The temperature was maintained above 40"C. to prevent sodium and/or potassium phosphate crystallization.

After adjusting the temperature of the mixture to above 800 C., alumina trihydrate was then admixed with the sodium/potassium-treated phosphoric acid in a quantity less than the amount needed to form a 1:3:8 sodium aluminium phosphate. The amount of alumina added is recorded in Table I. The addition of the alumina'trihydrate was accomplished incrementally with slow agitation to ensure uniform mixing of the alumina trihydrate in the acid. The mixture was then reacted for the time given in Table I at a temperature of about 110 C to form a reacted slurry.

A small quantity (See Table I) of the reacted slurry was placed in a tub shaped covered jacketed mixer having two contra-rotating mixing arms with downwardly dependent mixing blades. The cover was provided with an ingredient inlet and a steam outlet. After covering the tub, the hydrated lime was added at a controlled rate. Process variations are shown in Table I. After the lime had reacted, the product was dried while under conditions of sufficient mixing to granulate the product.

The dried product was finally milled in a Raymond Laboratory Hammer Mill fitted with a screen having 1/16 inch (1.59 mm) openings. The product had the elemental analysis and sieve analysis as shown in Table II.

TABLE I Example 1 2 3 4 5 6 7 8 9 10 11

Amount Alumina trihydrate % 90 46.6 68.2 68.2 68.2 89 89 50 50 100 100 Added to original slurry (100%) = 3379 lbs.) lbs 3033 1570 2300 2300 2300 3000 3000 1685 1685 3370 3370 Minutes in Reactor - 15 15 20 20 20 20 30 30 - K2O % - - - 0.67 0.67 0.71 0.71 0.78 0.78 reported if changed Na2O % - - - 2.90 2.90 2.68 2.68 2.75 2.75 Reactor Slurry lbs. 12 12 11 8.5 8.5/85@ 10.5 8.4/85 8.25 8.75/85 10.88 7.0 Calcium (Hydrated Lime) gms 146 1020 550 429 429 128 102 668 85 24.7 63.5 Amount Req. to Neutralize 194 1039 560 438 186 149 665 84 - Mixer Speed - High X X - - - - X X Mixer Speed - Low X X X X X X X X Order of addition A A A A B A A A A A A Time Ca(OH2) addition - 300 g. incre@ -2 - 1 min. 1 min. 6 min. - - ments 2-3 mins. min.

Mixing Time - Minutes 40 40 70 30 50 30 60 40 Temperature - Initial C. - 100 100 90 85 80 85 94 100 - After Ca(OH)2 C. - 115 110 106 108 94 98 118 121 85-90 100-120 Final (after C. 85 100 95 90-110 108-120 80-90 90-102 100-110 100-120 - granulation) A = Lime to slurry B = Slurry to Lime TABLE II Example 1 2 3 4 5 6 7 8 9 10 11

Neutralizing Value 98.2 86.4 86.6 90.8 91.8 97.4 97.0 87.2 80.4 97.2 93.8 (-60m) 88.0 Loss on Ignition (LOI) % - 17.76 18.83 18.95 19.2 21.6 20.9 18.01 15.8 21.3 21.2 Free Acid (Acetone Free) - 0.49 0.78 0.39 0.69 0.10 0.20 0.15 0.20 0.10 0.05 Acid) % CaO % 2.3 14.24 10.51 8.26 7.41 2.62 2.62 14.08 16.47 0.97 2.0 (-60m) (-60m) 2.05 P2O5 % - - - 57.7 - 58.0 - 57.2 - 58.9 Al2O3 % - 7.24 11.57 11.3 11.21 15.2 15.2 8.1 7.9 16.1 16.1 K2O % - 0.78 0.68 0.68 - 0.72 - 0.73 - 0.71 Na2O % - 2.70 2.55 2.55 - 2.60 - 2.60 - 2.70 Sieving Data Percent, by Weight on 60 12.2 18.8 29.3 19.1 22.9 29.5 14.2 27.5 32.3 33.7 30.0 through 60 on 100 19.2 21.5 23.8 19.2 19.1 21.0 22.4 18.5 19.6 19.5 20.5 through 100 on 140 15.6 14.0 11.8 14.6 10.0 11.3 14.5 12.2 11.5 10.1 10.9 through 140 - remainder 53.0 45.7 35.1 47.1 48 38.2 48.9 41.8 36.6 36.7 38.6 A standard method for evaluating baking performance of a leavening acid is the baking powder rate of reaction test (BPRR). In this test, a baking powder is formulated comprising a leavening acid, sodium bicarbonate, starch and water.

The purpose of the BPRR test is to observe and measure the rate of carbon dioxide discharge from the baking powder as a means of evaluating the suitability and quality of the leavening acid candidate as a baking acid.

Ideally, there should be a sufficient initial release of carbon dioxide in the baking mix to facilitate mixing and blending of the constituents. The mixture should also be capable of suppressing the release of carbon dioxide until such time as the-mix is placed in an oven and heated, whereupon more carbon dioxide is released during baking. The BPRR test is conducted at a temperature of 27"C. t 0.5"C. The leavening acid and sodium bicarbonate are used in proportions that are theoretically capable of liberating 200 cc of carbon dioxide. More details regarding reaction rate testing, as well as the apparatus required, may be found in Cereal Chemistry, Volume 8, pages 423--433 (1933). The baking powder rate of reaction tests for Examples I to 11 are given in Table III.

TABLE III Example 2 min. 4 min. 10 min.

48 61 85 2 66 77 92 3 50 64 84 4 63 79 103 5 58 72 94 6 45 61 85 7 46 59 85 8 63 73 96 9 44 56 75 10 40 57 85 11 31 45 67 -60m 38 51 75 -60m = through 60 mesh EXAMPLES 12 TO 15.

A slurry of potassium-modified sodium aluminium hydrated phosphate was prepared as in Example 1. After cooling to about 80 C, lime was then incrementally added to the reaction mass in the reactor and agitated for reaction periods of from 1. to 4 minutes between additions. The conditions of reaction are given in Table IV.

The slurry of calcium-treated potassium-modified sodium aluminium phosphate is directed to a "Kneadermaster" kneader-conveyor blender or mixer, wherein the material is dried and granulated. The conditions of the "Kneadermaster" blender are maintained so that the dry calcium-treated potassium-modified SALP exiting the "Kneadermaster" has a loss on ignition (LOI) of about 22 weight percent.

After exiting the "Kneadermaster", the calcium-treated potassium-modified SALP proceeds to a mill and air classification system wherein the product is milled and classified by particle size in an air separator. The sieving analysis is shown in Table V. The calcium-treated potassium-modified SALP product is then in a commercial form ready to be packaged and shipped. The LOI of the finished potassium-modified SALP product is from 19.5 to 20.5 weight percent.

The product was free flowing, non-dusting and did not blind the screens when milled. The analysis for the product is given in Table V.

TABLE IV Example 12 13 14 15

Percent Alumina Trihydrate % 89 89 96.4 91 Added to Slurry/lbs. 3000 1100+ 3250 3070 Lbs. 1900 Calcium (hydrated Lime)/lbs. 400 400 100 300 Amount Required to Neutralize/lbs. 526.5 526.5 171 427 How Added Dry Dry Slurry Slurry 70 gal.

37 gal. H2O 56 C. H2O, 55 C.

Order of Addition Al/Ca Al/Ca/Al - Time of Ca(OH)2 Addition 60 lbs/min. 50.lbs/min.

Add 2-6 min. Add 1-2 min. react 1-3 min. react 2-4 min.

Temperature During Lime Addition - - 125 C. 125 C.

TABLE V Examples 12 13 14 15

Neutralizing Value 98.6 101.2 100.0 101.0 Loss on Ignition (LOt) % 20.52 19.85 20.16 20.08 CaO % 2.34 1.82 0.50 1.40 P2O, % 58.35 60.00 59.60 60.20 Al203 % 15.21 14:84 16.24 15.15 K2O % 0.72. 0.75 0.76 0.78 Na2O % 2.75 2.80 2.80 2.85 Sieving Analysis Percent, by weight on 60 0,6 0.8 0.6 1.5 Through 60 on 100 3.4 5.7 8.6 6.8 Througll 100-on 14 4:0 10.4' 17.5 9.7 Through 140-Remainder 92 83.1 73.3 82 EXAMPLES 16 TO 19.

In a reactor fitted with a condenser, thermometer and mechanical stirrer was placed phosphoric acid in the amounts given in Table VI. The acid was heated to assist in dissolving the ingredients to be added (from 40 to 500 C.). Sodium carbonate and, in some instances, potassium hydroxide (in a 45% aqueous solution) were slowly added to the heated acid at such a rate that the reaction was allowed to subside. The amount added is given in Table VI. A clear solution was obtained. The temperature of this solution was adjusted to from 80 to 850C. Hydrated alumina (A12O3.3H2O) was slowly added to this solution at from 80 to 850C. over a 1 hour period. The amount of hydrated alumina added is given in Table VI. The temperature of the mixture increased to from 110 to 1200C. After all the hydrated alumina was added, the mixture was allowed to react from about + hour at from 110 to 1200C. A white viscous slurry was obtained.

The slurry was transferred to the mixer bowl of a kitchen-type mixer.

Hydrated lime in the amount given in Table VI was added to the slurry. The slurry was mixed at low speed scraping the walls of mixer bowl until the lime was well blended. A white and creamy material was obtained.

This material was transferred to a farinograph (a jacketed sigma-bladed blender) which was maintained at 980C. to granulate and dry the product. Time required to dry was from 30 to 454 minutes. On occasion soft lumps were formed when too much material was being dried. The soft lumps were broken up before the product had completely dried and drying was continued. A fine white powder was obtained.

TABLE VI EXAMPLES 16 17 18 19 Reactants H2PO4 646.7g/75% acid 600g/85% acid 623 g/85% acid 732 g/85% acid Na2CO3 24.1 g 28.94 g 32.94 g 42.06 g KOH. - 13.0g of 45% sol. 6.73 g of 45% sol. Al2O3#3H2O 106.47 g 106.6 g 110.7 g 130.0 g Ca(OH)2 65.05 g 65.05 g 67.50 - 79.3 g

Excess rioo Moles for 1:3:8 SALP n\o ov, TOTAL \do; i0CD .. 0 0 0oCD CD Excess ~ < woo 0 Molar Amounts 'Moles Moles for > 5.20 3.64' e 5.40 m 1.61 6.35 4:44 1.91 1:3:8 SALP ' ' 0.46 0.46 o TOTAL o 0 1.37 1.37 N 1.42 1.42 0 1.67 1.67 0 Moles Ca 0.88 0.88 0.91 1.07 Moles Ca/Moles 0.67 0.56 0.56 0.56 Excess acid ooo Moles for e > o &commat; 1:3:8SALP no ~ TOTAL onOm > m Excess ~ o o Moles for e > XN 1:3:8SALP o TOTAL o t X O o X 2 S X Z - U XS o O o o o s ~ o o ae 2 Z 2 2 X EXAMPLE 20.

Control: Preparation in accordance with U.S. Patent No. 2,550,490 In a reactor fitted with a condenser, thermometer and stirrer were placed 844 grams of 75% phosphoric acid. The acid was heated to 70 C. and 27 grams of sodium carbonate was slowly added. The mixture was allowed to react until a clear solution was obtained. The clear solution was heated to 90 C. and 114.5 grams of hydrated alumina was added at such a rate that the charge did not boil over (about 20 minutes). The condenser was removed and the charge was allowed to boil down until a white viscous slurry was obtained. Initial temperature was 135 C.

Evaporation temperature was generally from 115 to 120 C.

The slurry was transferred to the bowl of a home-type mixer containing 11.84 g of hydrated lime. The slurry and lime were mixed at low speed until well blended. A white, creamy material was obtained. This material was transferred to a Hobart (Registered Trade Mark) mixer and mixed until it solidified into large lumps; The product was oven dried at 980C. for four hours. The product was milled in Raymond Laboratory Hammer Mill, fitted with a screen. The elemental and sieving analyses are given in Table VII.

TABLE VII Moles Required TOTAL for 1:3:8 SALP Excess Moles P 6.46 3.92 2.54 Moles Na. 0.51 0.49 0.02 Moles Al 1.47 1.47 0 Moles Ca 1.60

Moles Ca/ l 0.63 Moles Excess P ) 0.02 Excess Na/Moles Sieving Analysis on 60 8% through 60 on 100 42% through 100 on 140 20% through 140 30% The compounds according to the present invention may be used effectively in preparing self-rising flour biscuits.

Self-rising flour (or SRF) is defined in the U.S. Federal Register of May 2, 1961, Title 21, Part 15, section 15.50(a), Definition and Standards of Identity, as follows: "Self-rising flour, self-rising white flour, self-rising wheat flour, is an intimate mixture of flour, sodium bicarbonate and one or more of the acid-reacting substances monocalcium phosphate, sodium acid pyrophosphate and sodium aluminium phosphate. It is seasoned with salt. Then it is tested by the method prescribed in paragraph (c) of this section not less than 0.5 percent of carbon dioxide is evolved. The acid-reacting substance is added in sufficient quantity to neutralize the sodium bicarbonate. The combined weight of such acid-reacting substance and sodium bicarbonate is not more than 4.5 parts to each 100 parts of flour used." The term "self-rising flour" as used herein is intended to describe. compositions within the above definition.

Baking response was determined by adding a specified portion of the product according to the present invention to a standard self-rising flour formulation comprising: Sodium Bicarbonate 3.3 gms Leavening Acid See Table VIII Self-rising Salt 5.4 gms Flour Mixture Flour 240 gms.

Shortening 32 gms Milk 165-170 cc.

The amount of leavening acid required may be determined by its neutralizing value. Its neutralizing value is a measurement of the parts, by weight, of sodium bicarbonate which will be neutralized by exactly 100 parts, by weight, of a given leavening acid. The amount of leavening acid required was obtained by multiplying the amount of sodium bicarbonate used (in this case 3.3 gms) by 100 and dividing the result by the neutralizing value of the leavening acid. This amount was added to the self-rising flour formulation. Biscuits were baked under controlled conditions as follows: (1) Heat electric oven to 340OF; (2) Weigh out self-rising flour, shortening and milk; (3) Cut shortening into self-rising flour in Hobart blender for lt minutes until mix is fine and crumbly; (4) Roll on cloth covered board with +" gauge rails using dusting- flour and cloth covered rolling pin; (5) Cut dough using 2 inch cutter and bake 18 minutes at 450OF.

Biscuit bake tests and evaluation of the results therefrom is explained in Cereal Laboratory Methods, 6th Ed., American Association of Cereal Chemists, 1957 pp. 46--48. The results of the biscuit bakes including the amount of leavening acid used are reported in Table VIII. The biscuit weight is the weight of 7 biscuits just after baking. The six most evenly sloped biscuits are then measured to provide biscuit height in inches. The volume is the number of cc's of rope seed displaced by six biscuits. The specific volume is obtained by dividing the volume by biscuit weight. Amount of acid used, dough weight and biscuit weight are in grams.

TABLE VIII Baking Results - Biscuits

Condition Amount of Neutralizing Acid Dough Biscuit Specific Product of Particles Value Used Weight Weight Height Volume Volume Comments pH Example 1 as is 98.2 3.35 235 210 9 550 2.62 a & d 7.79 Example 1 -60 m 98.2 3.35 232 204 9 530 2.60 a & d 7.54 Example 2 as is 86.2 3.85 235 210 9 1/4 540 2.54 a, d & b 7.81 Example 2 -60 m 86.2 3.85 230 200 9 520 2.60 a & d 7.72 Example 3 as is 86.6 3.80 232 206 9 1/4 550 2.67 a & c 7.84 Example 3 -60 m 86.6 3.80 230 201 9 540 2.69 a & d 7.70 Example 14 as is 100 3.3 230 203 9 1/4 560 2.76 d & g 7.70 Example 15 as is 101 3.3 235 207 9 575 2.78 e & b 7.42 a - yellowish crumb b - white crumb c - alkaline d - slightly alkaline e - normal f - black specks g - slightly yellowish crumb The products according to the present invention were tested in a doughnut dough reaction rate test. The doughnut dough reaction rate test is an analytical method used for reactivity studies of baking acids. The test procedure involves reacting the acid with sodium bicarbonate while the reactants are suspended in a moist doughnut dough at a temperature of 27 C. # 0.5 C. The proportions of acid and bicarbonate employed are those which are capable of theoretically liberating 200 cc. of CO2 gas as 0 C. The remainder of the ingredients are outlined in a paper on reaction rate testing which appeared in Cereal Chemistry, Vol. 8, American Association of Cereal Chemists, St. Paul, Minnesota, 1931, pp. 423-33. Both milled and unmilled samples were tested. The results are reported in Table IX below. All results are relative to the bicarbonate of soda blank or control.

TABLE IX Doughnut Dough Rate of Reaction Minutes Product of Example %CaO 2 15 % on 60 mesh 1 2.3 42 54 12 12.2 3 10.5 51 65 14 29.3 2 14.2 60 78 18 18.8 14 0.5 43 56 13 0.6 15 1.4 49 64 15 1.5 Product of U.S.

Patent No. 4,054,678 0 42 56 14 Bicarbonate of Soda Blank 0 31 35 4 Doughnut dough rate of reaction tests were conducted on a single sample milled and unmilled at the same particle size. The data as reported in the Table X below shows that milled samples of the same particle size generally have a faster rate of reaction than the unmilled.

Similar studies are also reported in Table X.

TABLE X DOUGHNUT DOUGH RATE OF REACTION TEST ON SIEVED FRACTIONS OF THE PRODUCT OF EXAMPLE 5 DOUGHNUT DOUGH RATE OF REACTION IN MINUTES Unmilled Milled Mesh 2 15 A 2 15 A 60-100 46 61 15 47 61 15 100-140 44 59 15 48 62 14 140200 49 66 17 55 76 21 200-400 48 66 18 52 72 20 SODA Blanks 29-32 32-36 34 Sieving, %, By Weight Unmilled Milled On 60 64.5 24.7 Through 60 On 100 13.8 23.2 Through 100 On 140 6.4 12.4 Through 140 On 200 6.4 15.8 Through 200 On 400 5.3 17.8 Through 400 3.6 6.1 TABLE X Cont'd Product of Example 5: 70% Alumina 91.8 Neutralizing Value K2O = 0.67% Na2O = 2.90% TABLE XI DOUGHNUT DOUGH RATE OF REACTION ON SIEVE FRACTIONS Doughnut Dough Rate of Reaction Minutes Product of Example Mesh Fraction Type 2 15 A 6 60-100 Unmilled 36 49 13 6 60-100 Milled 38 50 12 20 60-100 Milled 71 95 18 20 140-200 Milled 75 93 18 16 60-100 Unmilled 47 64 17 16 60-100 Milled 45 63 18 16 140-200 Unmilled 49 70 21 16 140-200 Milled 55 75 20 19 60-100 Unmilled 52 78 26 19 60-100 Milled 63 86 23 19 140-200 Unmilled 70 94 24 19 140-200 Milled 75 100 25 3 140-200 Milled 54 75 21 Blends of potassium-modified SALP and anhydrous monocalcium phosphate were prepared. An increased rate in the doughnut rate of reaction was obtained as is shown in Table XII which follows.

TABLE XII DOUGHNUT DOUGH RATE OF REACTION TESTS ON VARIOUS LEAVENING ACIDS Material Amount-Grams Doughnut Dough Rate of Reaction in Minutes 2 15 # Product of Example 3 0.87 48 61 13 Product of U.S. Patent No. 4,054,678 0.74 46 59 13 Anhydrons Monocalcium Phosphate 0.94 120 131 11 2/3 Product of U.S. Patent No. 4,054,678 0.49 44 54 10 1/3 Anhydrous Monocalcium Phosphate 0.31 61 69 8 Blend 0.49 & 0.31 69 84 15 Bicarbonate of Soda Blank - 37 42 5 Humidification tests were run on a number of samples to determine the amount of moisture pick-up over an extended period of time in order to obtain an indication of the hydroscopisity of the sample. The tests were run in accordance with the procedure outlined in U.S. Patent No. 3,205,073. The following data was obtained: TABLE XIII Percent Weight Gain from Original Sample Weight Product Product Product Total Time Product of Product of Product of Humidification of Example 1 of Example 2 of Example 3 Days Example 1 (-60 Mesh) Example 2 (-60 Mesh) Example 3 (-60 Mesh) 1 4.88 4.84 6.14 6.40 6.00 5.94 2 8.98 9.10 6.90 7.10 7.86 7.66 3 12.28 12.08 6.90 7.14 9.00 8.88 6 19.44 19.40 5.96 6.30 10.70 10.94 7 21.48 21.52 5.76 6.10 11.28 11.18 8 23.38 23.12 5.34 5.70 11.90 11.96 9 24.68 24.06 5.06 5.40 13.20 13.20 10 24.84 23.96 4.72 5.06 14.22 14.48 13 22.96 21.80 5.12 5.56 17.94 17.69 14 22.22 20.51 4.94 5.22 17.42 16.90 15 22.32 20.70 5.25 5.30 17.16 16.06 16 21.18 4.67 TABLE XIII (Continued) Percent Weight Gain from Original Sample Weight Total Time Product Product Product Product Product Product Humidification of of of of of of Days Example 4 Example 6 Example 8 Example 9 Example 10 Example 11 1 5.12 4.88 6.48 6.32 4.72 5.44 2 7.06 9.38 7.86 7.32 8.38 9.48 3 7.80 13.60 8.12 7.64 11.86 12.60 4 8.26 17.00 8.04 8.12 14.96 15.98 7 10.96 23.94 17.76 9.06 24.22 23.54 8 11.52 23.70 17.68 9.18 25.94 24.26 9 12.26 22.80 18.52 9.36 27.24 30.36 10 13.47 22.12 18.52 9.72 27.84 31.66 11 14.58 21.24 18.72 10.06 27.88 27.10 14 20.26 20.10 19.68 11.02 25.92 40.04 15 20.94 19.70 19.82 11.06 25.32 39.03 16 20.48 19.48 20.56 18.72 25.04 36.74 17 20.40 18.44 23.30 TABLE XIII (Continued) Percent Weight Gain from Original Sample Weight Product Product Total Time Product of Product of Humidification of Example 14 of Example 15 Product of Product of Days Example 14 (+TCP) Example 15 (+TCP) A B 1 7.94 7.66 7.16 5.72 8.62 3.76 2 13.46 11.16 10.96 9.88 13.46 7.74 3 16.34 15.54 14.52 13.40 16.80 11.00 4 20.24 18.88 17.50 16.60 20.96 14.64 7 26.80 25.62 23.92 22.26 30.01 24.10 8 27.14 26.60 25.00 23.74 31.74 26.00 9 26.80 26.96 25.62 24.98 33.20 27.06 10 26.24 26.60 26.10 26.02 34.04 27.46 11 25.40 25.72 26.18 26.44 33.40 26.72 14 24.38 24.34 26.44 26.67 31.48 24.80 15 24.14 24.06 25.96 26.00 30.50 24.12 16 24.52 24.46 25.70 25.72 29.60 23.50 17 23.58 23.46 Foot Note: A = Product prepared in accordance with U.S. Patent No. 4,054,678.

B = Same as A; the through 60 mesh fraction.

TCP = tricalcium phosphate.

TABLE XIV A sieving analysis of a 25 gram sample was run on the unmilled products of Example 5, 17 and 20 as follows (each number has a relative error of up to 5%): Particle Size Example 5 Example 17 Example 20

Duplicate Duplicate (Micron) grams % % grams % % grams % on 20 840 7.2 29.3 - 7.75 32.0 - 23.35 93.4 through 20 on 40 420 5.55 22.6 - 2.40 9.9 - 1.25 5.0 through 40 on 60 250 3.65 14.8 64.5 3.30 13.6 59.3 0.25 1.0 through 60 on 100 149 3.40 13.8 13.8 3.50 14.4 12.1 0.10 0.4 through 100 on 140 105 1.65 6.7 6.4 1.60 6.6 5.2 0.10 0.4 through 140 on 200 74 1.65 6.7 6.4 1.40 5.8 4.6 0.05 0.2 through 200 on 400 38 0.90 3.7 8.9 <SE EXAMPLE 21.

In order to test the holding qualities of the leavening acid according to the present invention in liquid batter, pancake batter was prepared and held for various periods of time. Pancakes were baked daily. Volume of gas and bubble formulation in the batter and pancakes were noted.

The pancakes were prepared from the following recipe: 3 cups sifted self-rising flour 4 tablespoons sugar 2 eggs, beaten 2+ cup milk 6 tablespoons oil The self-rising flour was prepared by blending together: 400 gms. flour 5.5 gms. sodium bicarbonate 9.0 gms. salt 3.76 gms. product of Example 3 After initial baking, ' cup milk was added to thin the batter slightly. The batter was refrigerated in a covered polypropylene bowl. Pancakes were baked using about 4 cup per pancake each day for seven days from the refrigerated batter. The pancakes were observed to have the same similar light texture. The pancakes were tender and pleasant tasting. No pressure build-up was observed in the bowl. The number of bubbles observed during baking appeared to be the same throughout the test period.

EXAMPLE 22.

Pancakes were also prepared according to Example 21 using 7.52 grams of the product of Example 3 in place of the 3.76 grams used in Example 21. The batter was prepared in the evening and refrigerated. Pancakes were baked the next day and the following days for a total of eight days.

These pancakes were compared with those made using a commercially available leavening acid prepared in accordance with the process of U.S. Patent No. 4,054,678.

The pancakes prepared using the leavening acid according to the present invention were noticeably lighter than those prepared using the commercial leavening system held for the same length of time. Pancakes made using the leavening acid according to the present invention had good texture, but those made using the commercial leavening acid were slightly tough and did not rise as much as based on visual observation.

(All mesh sizes herein refer to the U.S. Stand Sieve series).

Claims (31)

WHAT WE CLAIM IS:

1. A phosphate corresponding to the following formula: Ma Al b H (PO4)d .(H2O)e wherein M represents sodium and/or potassium and/or ammonium; a, b, c and d each represents a number; e represents a number of from 0 to n; and n represents an integer; which is in the form of particles, the outer surfaces of which having calcium uniformly dispersed and bound therein, more than 50% of the particles being less than 840 microns in diameter and at least 90% of the particles being less than 2000 microns in diameter.

2. A phosphate as claimed in Claim 1 wherein M represents sodium.

3. A phosphate as claimed in Claim I wherein M represents sodium and potassium.

4. A phosphate as claimed in Claim 3 wherein the ratio of na+K: Al: PO4 is about 1:3:8.

5. A phosphate as claimed in any of Claims I to 4 wherein the outer surface contains sodium.

6. A phosphate as claimed in Claim 1 substantially as herein described.

7. A phosphate as claimed in Claim I substantially as herein described with reference to the Examples and/or the accompanying drawings.

8. A process for the preparation of a phosphate as claimed in Claim I which comprises contacting a slurry of a phosphate corresponding to the general formula defined in Claim I with a calcium compound and, while drying, granulating the product so as to obtain the desired particle size distribution.

9. A process as claimed in Claim 8 in which the slurry has been prepared by contacting a food grade phosphoric acid having a concentration of from 70 to 90 weight percent with sodium ions and/or potassium ions and/or ammonium ions and the aluminium ions.

10. A process as claimed in claim 9 in which the phosphoric acid has a concentration of from 85 to 88 weight percent.

11. A process as claimed in claim 9 or claim 10 in which a temperature of about 400C is used.

12. A process as claimed in any of claims 8 to 11 in which the calcium compound is contacted with the cooled slurry.

13. A process as claimed in any of claims 8 to 12 in which the calcium compound is calcium oxide and/or calcium hydroxide and/or calcium carbonate.

14. A process as claimed in claim 13 in which the calcium compound is calcium hydroxide.

15. A process as claimed in any of claims 9 to 14 in which the acid is contacted with sodium ions.

16. A process as claimed in any of claims 9 to 14 in which the acid is contacted with potassium ions.

17. A process as claimed in any of claims 9 to 14 in which the acid is contacted with sodium ions and potassium ions.

18. A process as claimed in any of claims 9, 15 or 17 in which the sodium ions are provided by sodium carbonate and/or sodium hydroxide and/or sodium bicarbonate and/or sodium phosphate.

19. A process as claimed in claim 18 in which the sodium ions are provided by sodium carbonate.

20. A process as claimed in any of claims 9, 16 or 17 in which the potassium ions are provided by potassium hydroxide and/or potassium carbonate and/or potassium phosphate.

21. A process as claimed in claim 20 in which the potassium ions are provided by potassium hydroxide.

22. A process as claimed in any of claims 9 to 21 in which the aluminium ions are provided by alumina trihydrate.

23. A process as claimed in any of claims 9 to 22 in which an excess of phosphoric acid is used which is at least partially neutralized by the calcium compound.

24. A process as claimed in claim 23 in which at least 80% of the excess acid is neutralized.

25. A process as claimed in claim 23 or claim 24 in which the excess acid results from an adjustment in the ratio of phosphoric acid: sodium ions and/or potassium ions and/or ammonium ions: aluminium ions.

26. A process as claimed in claim 25 in which the excess acid results from a decrease in the ratio of aluminium ions: phosphoric acid.

27. A process as claimed in claim 26 in which the amount of aluminium ions is decreased to from 85 to 95% of the stoichiometric amount.

28. A process as claimed in claim 8 substantially as herein described.

29. A process as claimed in claim 8 substantially as herein described with reference to the Examples and/or the accompanying drawings.

30. A phosphate' as claimed in claim I when prepared by a process as claimed in any of claims 8 to 29.

31. The use of a phosphate as claimed in any of claims 1 to 7 or 30 as a leavening acid.