Phosphorus (P) is one of the major elements required by all living species to grow and develop. When the element phosphorus is oxidized to the fullest extent possible, its acid is termed phosphoric acid, [H3PO4 or PO(OH)3], and the salts of phosphoric acid are termed phosphates, e.g. K2HPO4. With phosphorus in a slightly less oxidized form, the phosphorus in the acid form is termed phosphorous acid, [H3PO3, or HPO(OH)2], and the salts of phosphorous acid are termed phosphites, e.g. K2HPO3. Phosphites are marketed either as an agricultural fungicide, bactericide or without research data as a superior source of plant phosphorus (P) nutrition.
Current commercial methods for making salt compositions from phosphoric acid and phosphorous acid (Phosphorus (P) acids), for foliar application to plants, are carried out by a batch process by separately manufacturing each potassium phosphorus salt. This is accomplished by reacting each P acid with an aqueous base metal hydroxide solution, e.g., potassium hydroxide, sodium hydroxide, ammonium hydroxide, or various combinations thereof, potassium carbonate, or other base metal solutions, into a mixing tank equipped with an agitator and a means of cooling.
As a first step or stage and by an individual process for each P acid, a base potassium solution may be combined with a mineral P acid. As an example a significant quantity of water is added to a typical 1,000 gallon open batch tank. Then 50 pound bags of dry mono potassium phosphate (MKP), which is not completely soluble, are slowly and partially dissolved by continuous agitation and kept agitated while dry bagged potassium hydroxide (KOH) is added. This is a slow, labor intensive, and not a very productive process which only generates a reaction temperature under about 40° C., and is actually only a blend process because MKP is already mostly reacted to a near neutral pH and not very much KOH needs to be added in order to achieve a balanced analysis and pH.
Then as a second step or stage, by an individual process, a base potassium solution may be combined, also separately, with a second P mineral acid. As an example water is added to a typical 1,000 gallon agitated batch tank and then alternately 50 pound bags of phosphorous acid and KOH are combined slowly in order to keep the reaction temperature as low as possible in order to prevent a “run away” reaction and the generation of phosphine gas. The process is very labor intensive, slow and unproductive and is capable of low analysis only.
Thirdly, an additional required step remains wherein these two individually produced potassium salts of each phosphoric and phosphorous acid must be pumped into an agitated batch tank and cold blended to produce a final useful, mixed solution. This is a complicated labor intensive, time consuming, inefficient process which requires additional equipment and storage tanks, and offers more opportunities for error in producing the final product.
In other processes, involving the use of phosphoric acid or by dissolving or wetting of potassium phosphates, such as mono or di-potassium phosphates are subject to a number of problems. The reason that the use of such mono and di-phosphates is desirable in these time proven processes is that most of the exothermic reaction has been completed, thus lending these processes to a safer and simpler but more costly process.
Less common and more dangerous is separately reacting by batch process, phosphoric acid and phosphorous acid with potassium hydroxide or carbonate directly in order to by a third step produce the desired blend mixtures of phosphates and phosphites.
The reactions can be violent and, on a large scale, even with good agitation and cooling, the reaction can “runaway” and has even resulted in fatalities and injuries. During the early stages of this process with either Phosphoric or phosphorous acid, even if the reaction does not “runaway”, localized excessive heat release occurs, at under 200° F. (94° C.), and in the case of the phosphorous acid, it is well known in the art that hazardous, toxic phosphine (hydrogen phosphide) gases physically characterized by garlic like malodorous fumes which have decomposed, from the reaction, and are emitted from the batch type reactor which can create a hazard if not properly absorbed and disposed of. In addition, oxygen can very readily be absorbed into phosphorous acid, with the counterproductive decomposition as a result of the oxidation of the phosphorous acid and resultant formation of orthophosphoric acid.
In addition to being more labor intensive, other problems incur in these batch processes due to the necessarily slow addition of materials, in order to prevent “runaway” reactions and the decomposition of phosphorous acid. More problematic is that there is insufficient heat generated with either acid, in the initial part of the reaction with the metal hydroxide solution, thus, preventing the formation of the polymers of phosphorous acid, or of phosphoric acid by heat of reaction. As a consequence, previous processes provide no polymeric conversion of orthophosphorous acid to polyphosphite, or orthophosphoric acid to polyphosphate, because of the imbalance of reactants and/or the insufficient temperature required for the conversion.
Another potential problem which occurs in a batch process is satisfactorily achieving the final pH because extreme caution must be observed in the final stages of the reaction because of the real potential of overshooting the final pH by over addition of either the acid or the base. Precautions must be taken in measuring the ingredients precisely. Careful monitoring is time consuming and lack of attention could lead to an explosion due to a “runaway” chemical reaction. Further, the batch process is known to be more labor intensive and with higher production costs.
U.S. Pat. Nos. 5,736,164; 5,800,837; 5,997,910; 5,925,383; 6,338,860 and 6,509,041 in general describe the blending of individually prepared solutions of potassium orthophosphate and potassium orthophosphite, utilizing only mostly reacted MKP and KOH, by a “batch” process as described above. The processes disclosed are generally labor intensive because dry bagged reactants are carefully, individually added to the batch processes where it is important to keep any heat of reaction as low as possible; because, as in the case of blending phosphorous acid with a base reactant, extreme caution must be exercised in order to prevent “runaway” reactions and to keep the temperature low enough so that poisonous phosphine gasses are not emitted. In any case, phosphate or phosphite polymers are not formed because the high temperatures necessary to produce polymeric compounds are not achieved in a batch process.
These patents describe formulating a potassium phosphate solution separately according to the methods herein described, a mono potassium phosphate is dissolved by the addition of water and further neutralized to desired levels generally with potassium hydroxide.
Both the potassium phosphate and phosphite solutions herein described have long been recognized by the Association of American Plant Food Control Officials (AAPFCO) as fertilizer ingredients, being useful for agriculture and their subsequent use in combined fertilizer mixtures. These patents do not disclose bactericidal attributes.
Then finally, the two individually prepared solutions are “cold blended” combining the two solutions in a third step.
Further, each of the processes disclosed by these patents has one or more of the above problems and disadvantages.
Commercial processes are shown for the preparation of ammonium polyphosphate in Hignett et al. U.S. Pat. No. 3,171,733 and Ries U.S. Pat. No. 3,950,495. Hicks et al. U.S. Pat. No. 3,985,538 shows the use of a pipe reactor to prepare ammonium polyphosphate. These processes result in the conversion of some of the normal orthophosphates to polyphosphates. Processes for improving yields are shown in Sansing et al. U.S. Pat. No. 4,637,921, McGill et al. U.S. Pat. No. 4,601,891, Kearns U.S. Pat. No. 3,464,808 and Ries U.S. Pat. No. 3,950,495. Fabry U.S. Pat. No. 4,724,132 shows a continuous process for the manufacture of a metal salt solution useful for fertilization.
There is a need for a novel process, as provided by this invention that does not rely on the use of MKP in order to form compositions that provide useful agricultural products that not only provide potassium orthophosphates and potassium orthophosphites in a single solution but also in a novel way, compositions that also include potassium polyphosphates and potassium polyphosphites, in a more efficient, safer and more cost effective way, in order to provide a single combination product that is both a superior, more effective fungicide and a safe and effective fertilizer, useful for agriculture.