US3634234A

US3634234A - Stabilized ammonium phosphate solutions comprising a galactomannan gum and a metal salt

Info

Publication number: US3634234A
Application number: US885354A
Authority: US
Inventors: William W Morgenthaler
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1969-12-15
Filing date: 1969-12-15
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11

Abstract

AMMONIUM PHOSPHATE SOLUTIONS THICKENED WITH GALACTO MANNAN GUM ARE STABILIZED WITH REPECT TO VISOSITY BY THE ADDITION OF A MONOR AMOUNT OF A HAVEAY METAL ION SUCH AS CO++, CU++, OR MN++.

Description

3,634,234 STABILIZED AMMONIUM PHOSPHATE SOLU- TIONS COMPRISING A GALACTOMANNAN GUM AND A METAL SALT William W. Morgenthaler, Maryland Heights. Mo., assignor to Monsanto Company, t. Louis, M0. N Drawing. Filed Dec. 15, 1969, Ser. No. 885,354 Int. Cl. A62d 1/00 U.S. Cl. 2527 4 Claims ABSTRACT OF THE DISCLOSURE Ammonium phosphate solutions thickened with galactomannan gum are stabilized with respect to viscosity by the addition of a minor amount of a heavy metal ion such as Co++, Cu, or Mn++.

BACKGROUND OF THE INVENTION This invention relates to viscosity stabilized ammonium phosphate solutions which are used extensively in the field of fighting fires, particularly forest fires.

It is well known to thicken ammonium phosphate solutions with small amounts of galactomannan gum to improve its air drop patterns and its ability to stick to surfaces, e.g., trees and bushes with which they come into contact. See. for instance, US. Pat. 3,223,649 granted Dec. 14, 1965. So as to be ready at a moments notice, these thickened ammonium phosphate solutions are made up in advance. However, these solutions on prolonged standing often show a serious loss in viscosity. Various stabilizers have been proposed, =e.g., sodium sulfite, zinc sulfite, sodium thiosulfate, see US. Pat. 3,146,200, but the amount required is impractical.

Therefore it is an object of this invention to provide ammonium phosphate solutions having improved viscosity stability upon prolonged standing.

It is a further object to provide improved viscosity solutions with minimal amounts of stabilizers.

Other similar objects of the invention will become apparent to those skilled in the art as the invention is further described below.

SUMMARY OF THE INVENTION The viscosity stability of an ammonium phosphate solution thickened with a galactomannan material is improved by the addition of a minor, but stabilizing, amount of a transition, i.e., heavy, metal ion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ammonium phosphate solutions in which these transition metal ions perform particularly effectively are those that contain at least about 0.5 weight percent, and up to the level at about which the solutions are saturated therewith, of dissolved ammonium phosphate salts, including monoammonium orthophosphate and/or diammonium orthophosphate salts, and also including the diammonium and monoammonium mixed orthophosphate salts that also contain an alkali metal cation, such as monoammonium disodium orthophosphate, monoammonium dipotassium orthophosphate and the like, no matter from what source these materials were derived, or in what form the materials are initially introduced into the aqueous compositions. Generally, it is preferred that the inhibited aqueous phosphate solutions of this invention have a pH between about 3 and about 9. When monoammonium orthophosphate is the only ammonium phosphate salt present in the inhibited fire-control compositions of this invention, the preferred pH of these compositions is generally from about 3 to about 5. Similarly, when diammonium orthophosphate is the only ammonium phosphate 3,634,234 Patented Jan. 11, 1972 ice salt contained therein, the preferred pH is from about 7 to 9. When mixtures of monoammonium orthophosphate and diammonium orthophosphate are utilized, pHs between these preferred ranges are generally more desirable. However, compositions having pHs somewhat higher or lower than these preferred ranges can also be utilized to advantage in the practice of the present invention.

The galactomannan materials to which this invention relates are polysaccharides, generally termed hemicelluloses, and are long chain polymers of galactose and mannose units. While their exact composition is not known, they have been found to yield these two sugars on hydrolysis. They are gum-like materials, generally found in plant seeds. Examples of the galactomannans are guar gum, obtained from Cyamopsis tetragonolobus (a legume); locust bean gum, obtained from Ceratonia siliqua; and tara gum, obtained from Cesalpinia spinosa. These materials typically comprise about 5 to 15% by dry weight of the ammonium phosphate composition.

The viscosity stabilized ammonium phosphate solutions of the present invention can also contain other materials (compounds) without detracting substantially from the benefits that can be obtained by practicing this invention, for example, the solutions can contain minor amounts of surfactants; inorganic and organic complexing agents such as the alkali metal tripolyphosphates, pyrophosphates and trimetaphosphates, as well as the higher polyphosphates such as the hexametaphosphates and also can contain ethylenediamine tetraacetic acid and various alkali metal and ammonium salts thereof and the alkali metal and ammonium nitrilotriacetates; corrosion-inhibiting ingredients; and organic and inorganic pigments and dyes; as well as many other materials.

The viscosity stabilizers of this invention are the transition or heavy metal ions of the fourth and fifth order of the Periodic Table such as various zinc, copper, nickel, cobalt, manganese, chromium and cadmium ions. More preferred are the metal ions from the fourth order especially those having an atomic number below 30 and particularly preferred are the ions of metals having odd atomic numbers from 25 to 29 inclusively. These ions are added to the ammonium phosphate solution in an amount from about 10 to 70 parts per million (p.p.m.) and preferably from about 15 to p.p.m. (This phenomenon is somewhat surprising since these ions in the foregoing amounts are known to have the reverse effect in other thickeners such as ca'rboxymethylcellulose which has also been employed as a thickener for ammonium phosphate solutions.) The metal ions are conveniently added to the ammonium phosphate composition as a water soluble compound having an anion compatible with the composition, e.g., a chloride or sulfate.

The inhibited phosphate compositions of this invention can be manufactured via any of a number of manipulative methods, without any noticeably detrimental effects upon the ultimate performance of the compositions. For example, the sulfate compound can simply be dissolved by intermixing it into or with the otherwise completely formulated aqueous compositions, or at any other stage during the preparation of the fire-control composition. Via another method, the sulfate compound can first be dissolved in water and the resulting solution then intermixed subsequently with the ammonium phosphate materials.

Still another process for manufacturing the aqueous stabilized phosphate compositions described heretofore involves one of the preferred embodiments of the present invention. This preferred embodiment comprises a concentrate mixture of one or more of the ammonium phosphate salts described heretofore with one or more of the stabilizer compounds, generally in a particulated,

:olid form. Preferably the compound (s) and ammonium ihosphate salt(s) will be present in this concentrate com- :osition or mixture in amounts proportionate to those 'ound in the fire-control compositions described hereto- 'ore, so that the final fire-control composition can be nanufactured by simply dissolving the concentrate in a ufiicient amount of water. In other words, generally the referred concentrate compositions of this invention will :ontain at least one of the above-described ammonium )hosphate salts, a galactomannan gum and at least one )f the stabilizer compounds in a weight range, respecively, of from about 50.0 to 93.0 percent by weight, 5.0 o 15.0% and 0.05 to 1.50% with the balance being opional materials listed below. It is still further preferred hat these particulated, solid concentrate compositions :ontain a total of at least about 50 weight percent of me or more of the above-described ammonium phosihate salts. These preferred concentrate compositions can llSO contain effective amounts of practically any other ous air-drops of fire-control compositions, very little weighing and handling equipment is available that is capable of manufacturing the fire-control compositions from the individual components.

The following examples are included to illustrate the present invention but are not to be considered as limiting. Unless otherwise specified all parts are by weight.

EXAMPLE 1 TABLE I.VISCOSITY OF AMMONIUM PHOSPHATE SOLUTIONS CONTAINING COPPER (II) AS A FUNCTION OF STORAGE TIME Storage time in Weeks 1 Copper cone. on a total solution basis.

2 Percent retained= ngredients desired in the final fire-control compositions, .g., dyes, pigments, water-softening agents and the like, .11 of which should preferably be present in the concenrate compositions in minor amounts, as compared to the vmmonium phosphate salt(s) contained therein. Some of he advantages of these preferred concentrate composiions can readily be appreciated when it is realized that at most points from which aircraft are loaded for their vari- Current viscosity (cps) Initial viscosity (cps) EXAMPLE 2 An ammonium phosphate fire-control formulation containing a guar gum type thickener (0.9)% was dissolved in water containing varying amounts of copper, zinc or cadmium as the viscosity stabilizer. The metal ion was added as the chloride salt. Test conditions of Example 1 were used. The results are tabulated in Table II and Table III below.

TABLE II.VISCOSITY OF AMMONIUM PHOSPHATE SOLUTIONS CONTAINING COPPER (II), ZINC (II) AND CADMIUM (II) AS A FUNCTION OF STORAGE TIME Storage time in weeks Metal and Initial Percent Percent Percent Percent conc. viscosity Ops. ret. Cps. ret Cps. ret. Cps. r

Copper:

1 Metal ion concentration on a total solution basis ppm. 2 Last 2 columns 6 and 13 weeks storage.

TABLE IIL-VISCOSITY OF AMMONIUM PHOSPHATE SOLUTIONS CON- TAINING VARIOUS TRANSITION METALS AS A FUNCTION OF TIME Storage time in weeks Additive Initial Percent Percent Metal additive (ppm) 1 t'cps.) Ops. ret. Ops. ret

ontrol 1,730 1, 570 91.0 1, 340 77. 5 Chromium (III) 25 1, 720 1, 560 90. 7 1, 380 80. 3 50 1, 800 1, 600 89. 0 1, 440 80. 0 Manganese (II) 25 l, 850 1, 800 97.3 1, 470 81. 7 50 1, 790 1, 790 100. 0 1, 660 92. 8 Cobalt (II) 1, 760 l, 780 101. 2 1, 650 93. 8 5O ,1, 720 1, 720 100. 0 1, 600 93. 0 Z1110 (II) l, 720 1, 630 94. 8 1, 370 79. 6 50 l, 810 1, 690 93. 4 1, 360 75. 2 Nickel (II) 25 1, 740 1, 690 97. 2 1, 450 83. 4 50 1, 790 1, 690 94. 5 1, 430 80. 0 Copper (II) 25 1, 740 1, 710 98. 3 1, 620 93. 2 50 l, 870 1, 870 103. 3 1, 860 102. 8

1 Metal ion concentration on a total solution basis.

From the foregoing it will be seen that the degree of viscosity stabilization can be tailored to fit the particular requirement by choice of metal ion with due allowance for the nature of the galactomannan gum.

The foregoing examples have been described for the purpose of illustration and not limitation. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art based on this disclosure. These are intended to be comprehended as within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An ammonium phosphate solution containing (1) at least 0.5 weight percent of ammonium phosphate, (2) as a thickening agent a galactomannan gum in an amount of from about 5 to 15 weight percent, based on the dry weight of said ammonium phosphate and (3) as a viscosity stabilizer a transition metal salt selected from the group consisting of cobalt chloride, cobalt sulfate, copper chloride, copper sulfate, manganese chloride, manganese sulfate, chromium sulfate, chromium chloride, nickel chloride, nickel sulfate, cadmium chloride and cadmium sulfate, said salt being present in an amount to provide from about 10 to about 70 ppm. of metal ions.

2. The composition of claim 1 wherein the transition metal salt is cuprous chloride, cuprous sulfate, manganous sulfate, manganous chloride, cobaltus chloride or cobaltus sulfate.

3. A concentrated ammonium phosphate composition useful when diluted and dissolved in Water, said composition comprising at least one ammonium orthophosphate salt, a galactomannan gum and a transition metal salt selected from the group consisting of copper chloride, copper sulfate, manganese chloride, manganese sulfate, cobalt chloride, cobalt sulfate, chromium sulfate, chromium chloride, nickel sulfate, nickel chloride, cadmium chloride and cadmium sulfate, said respective weight percents being from about 50.0 to about 93.0; about 5 to about 15 and about 0.05 to about 1.5.

4. The composition of claim 3 wherein the transition metal salt is cuprous chloride, cuprous sulfate, cobaltus chloride, cobaltus sulfate, manganous sulfate or manganous chloride.

References Cited UNITED STATES PATENTS 3,084,057 4/1963 Jordan 106-208 3,146,200 8/ 1964 Goldstein 2528.5-5 3,223,649 12/1965 Langguth 2522 3,309,324 3/1967 Langguth et al. 2522 3,364,149 1/1968 Morgenthaler 2522 3,383,307 5/1968 Goetz 2522 JOHN T. GOOLKASIAN, Primary Examiner D. J. FRITSCH, Assistant Examiner U.S. Cl. X.R.