US3018165A

US3018165A - Phosphorus-nitrogen compounds

Info

Publication number: US3018165A
Application number: US856655A
Authority: US
Inventors: Morris L Nielsen
Original assignee: MOUSANTO CHEMICAL Co
Current assignee: MOUSANTO CHEMICAL Co
Priority date: 1959-12-02
Filing date: 1959-12-02
Publication date: 1962-01-23
Anticipated expiration: 1979-01-23

Description

atent 3,0i8,l65 Patented Jan. 23, 1.962

of imidodiphosphoric acid such as tetrasodium imidodi- The production of the other alkali salts such as lithium, rubidium and cesium is also a part of this invention.

Tetrasodium imidodiphosphate has been made by older methods, but these processes have been characterized by the production of a very impure product, and also a very low yield. It has now been found that the production of these very useful salts as well as other alkali salts of imidodiphosphoric acid may be improved by conducting the reaction in the presence of a flux comprising a molten salt. The reactant which is employed as the raw material in this process is a dialkali phosphoramidate such as the sodium or potassium phosphoramidate. The disodium phosphoramidate has the formula It has been found that when this compound is heated to a temperature in the range of from 200 C. to 250 C., a preferred temperature range being from 215 C. to 230 C. in the presence of a molten salt as a medium or flux, the production of the desired salt of imidodiphosphoric acid, such as tetrasodium imidodiphosphate is greatly improved. The proportion of the flux is not critical, and it has been found that wide variations such as all proportions above 10% by weight of flux relative to the weight of disodium phosphoramidate may be used. A preferred range is 10 to 1,000% by weight. The prior art methods of producing this salt without the aid of a flux required a reaction in the solid state which results only in a very slow reaction between particles of the solid material. It has now been found that the use of a flux makes it possible for the reaction to be more readily conducted and with a greatly superior reaction rate. In carrying out the prior art method, it was found that 24 hours reaction time gave a 6% yield of product accompanied by seven times its weight of impurities. In comparison, the present process in the same period gave a 35% yield of product accompanied by one fourth its weight of impurities.

The molten medium or flux which is employed in the present process is composed of the salts which are liquid in the range of from 150 C. to 300 C. A preferred flux for this purpose is potassium formate, while other desirable fluxes are sodium phenoxide, potassium phenoxide, and mixtures thereof in all proportions. An example of another organic salt which is of utility in this relationship is cesium formate.

The following examples illustrate spechic embodiments of the present invention:

EXAMPLE 1 This example shows the preparation of tetrasodium imidodiphosphate from disodium phosphoramidate with potassium formate as the flux. One hundred grams of disodium phosphoramidate hexahydrate was dehydrated under vacuum, raising the temperature to 90 C. over a six hour period, held at 110 C. for 24 hours and finally at 125 C. for 2 hours. The dry solids were ground in a dry-box and mixed with twice as much powdered potassium formate. (This had been prepared by heating commercial potassium formate to 220 C. and adding about one gram potassium hydroxide for every 500 grams potassium formate so that a 2% solution in water would indicate a pH of 11.3 with a pH meter; on cooling the cake was crushed to a powder.) The mixture was heated in a glass vessel under vacuum as follows: one hour at 160 C., three hours at 200 C., and twenty four hours at 230 C. It was cooled and dissolved in 250 ml. water. On chilling the solution to 5 C. and adding an equal volume of denatured ethanol, the product precipitated as needles, and was filtered oif from the major proportion of the impurities which remained in solution. The crystals were Washed and dried. The yield was 40 grams of purity of the decahydrate.

In order to obtain the anhydrous salt, the decahydrate was dried under 3 mm. pressure at 50-60" C. The identity of the product was determined by nuclear magnetic resonance measurements.

EXAMPLE 2 This experiment shows a condensation with potassium phenoxide present. Forty grams of disodium phosphoramidate hexahydrate, Na PO NH -6H O, was dehydrated under oil pump vacuum (1 mm), with P 0 in a side-bulb, by the following schedule: 65, 4 hrs.; 2 hrs; 16 hrs; 2 hrs. The product was cooled, crushed to a fine powder in a dry-box, and mixed intimately with 50 g. finely crushed potassium phenoxide. The solids were heated under oil pump vacuum, with KOH in a side-bulb, by the following schedule: 1 hr.; 200, 3 hrs; 230, 24 hrs. On cooling, the solids, which had sintered together, were broken up and dissolved in 250 ml. water and precipitated with ethanol. On reprecipitating from water, with 4 g. NaOH present, by slowly adding excess ethanol, needles were obtained. Yield, 32 g. (89%). Purity, by NMR, was about 95%, with small amounts of phosphoramidate, orthophosphate and pyrophosphate present.

It has been found that detergent formulations of unusual efiiciency, particularly liquid detergent concentrates may be formulated with the alkali imidodiphosphates and in particular the potassium imidodiphosphate as an essential constituent. Both wet and dry detergent compositions may be formulated with the alkali imidodiphosphate. The said alkali imidodiphosphates may be present accordingly as dry salts in conventional dry detergent formulations and also in high concentration liquid detergent concentrates. It has been found that development of automatic detergent apparatus such as dishwashing machines, clothes washing machines, etc. requires the use of a very high concentration of the active components when such liquid concentrates are to be fed by automatic proportioning machines into the washing apparatus. It is therefore a particular advantage of the present alkali imidodiphosphates that they are characterized by unusually high solubility in Water so that they may be present as components of the active solutions in high concentration.

The alkali imidodiphosphates have been found to act as sequestrants and also as alkaline builders in the detergent formulation. The said alkali imidodiphosphates have been found therefore to suppress the precipitation of calcium soaps, i.e., the formation of soap scum and also to provide a buffered or controlled proportion of alkali which enables the conventional active organic components such as sodium dodecyl benzene sulfonate to operate at maximum efiiciency.

EXAMPLE 3 A representative detergent formulation based upon the use of tetrasodium imidodiphosphate was prepared with the following components:

Percent Sodium salt of dodecyl benzene sulfonic acid 35 Sodium carbonate Sodium sulfate 13.5 Tetrasodium imidodiphosphate 40 Sodium metasilicate 5 Carboxyrnethylcellulose 1.5

The above formulation was tested as a detergent composition and found to be effective in removing various types of soil.

EXAMPLE 4 Certain of the compositions of the present invention were also tested for calcium sequestration properties.

The procedure is based on the fact that the oxalate ion will not precipitate calcium from the calcium-sequestrant complex in alkaline solution (over pH The sequestering agent is titrated with a standard calcium solution in the presence of oxalate indicator. When the sequestering agent is completely complexed, a slight excess of calcium will precipitate as calcium oxalate indicating that the end point has been reached. If the sequestering solution is too dilute, the end point is delayed.

Determination of sequestering efiectiveness (1) A sample (5-20 grams) of the sequestering agent is weighed accurately to 0.01 g. and made up to 500 ml. with distilled water in a volumetric flask.

(2) Pipette 3100 ml. aliquots of this solution into 3 250 ml. beakers.

(3) Pipette 10 ml. of 5.0% ammonium oxalate indicator into each aliquot.

(4) The pH value of the aliquot is determined with the Beckman pH meter. The pH value is adjusted to exactly 11.0 with dilute sodium hydroxide. All aliquots must be adjusted to the same pH value.

(5) Fill a 10 ml. burette with the standard 0.50 M calcium chloride solution. Titrate the aliquots with calcium chloride solution until a faint permanent turbidity is observed, which is the end point. The end point can be more easily detected if the beaker is placed on a black background. Record mls. of standard calcium chloride used to the nearest 0.01 ml. It is suggested that the first aliquot be titrated to give the approximate end point, and then the other 2 aliquots titrated carefully to give the exact end point.

(6) A blank is run using distilled Water and the indicator. The blank is subtracted from the sample titrations.

The sequestering action of tetrasodium imidodiphosphate is shown by the following data, determined by the above procedure:

Comparison of solubility and calcium sequestration It is seen from the above data that per g. saturated solution in water at 25 0, sodium imidodiphosphate will sequester 2.5 times as much calcium as sodium pyrophosphate.

EXAMPLE 5 The above detergent formulation was also prepared with tetrapotassium imidodiphosphate; similar tests were also made to determine the solubility and calcium sequestration ability which again proved to be superior to conventional pyrophosphate.

What is claimed is:

1. Process for the preparation of tetrasodium imidodiphosphate which comprises heating disodiurn phosphoramidate in the presence of a molten salt selected from the group consisting of potassium formate, cesium formate, sodium phenoxide, potassium phenoxide, and mixtures thereof at a temperature in the range of from 200 C. to 250 C. the said salt being present in the proportion of at least 10% by weight relative to the weight of the said disodium phosphoramidate, and thereafter recovering the tetrasodium imidodiphosphate from the reaction mixture.

2. Process for the preparation of tetrasodium imidodiphosphate which comprises heating disodium phosphorarnidate in the presence of a molten salt selected from the group consisting of potassium formate, cesium formate, sodium phenoxide, potassium phenoxide, and mixtures thereof at a temperature in the range of from 200 C. to 250 C., the said salt being present in the proportion of from 10% to 1,000% by weight relative to the Weight of the said disodium phosphoramidate, and thereafter recovering the tetrasodium imidodiphosphate from the reaction mixture.

3. Process for the preparation of tetrasodium imidodiphosphate which comprises heating disodium phosphoramidate in the presence of potassium phenoxide as a fiux at a temperature in the range of from 200 C. to 250 C. the said flux being present in the proportion of at least 10% by weight relative to the weight of the said disodium phosphoramidate, and thereafter recovering the tetrasodium imidodiphosphate from the reaction mixture.

4. Process for the preparation of tetrasodium imidodiphosphate which comprises heating disodium phosphoramidate in the presence of potassium formate as a flux at a temperature in the range of from 200 C. to 250 C. the said flux being present in the proportion of at least 10% by Weight relative to the weight of the said disodium phosphoramidate, and thereafter recovering the tetrasodium imidodiphosphate from the reaction mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,503,381 Eichwald Apr. 11, 1950 2,897,052 Teuber July 28, 1959 2,906,601 Koster et al Sept. 29, 1959 2,932,616 Blake Apr. 12, 1960

Claims

1. PROCESS FOR THE PREPARATION OF TETRASODIUM IMIDODIPHOSPHATE WHICH COMPRISES HEATING DISODIUM PHOSPHORAMIDATE IN THE PRESENCE OF A MOLTEN SALT SELECTED FROM THE GROUP CONSISTING OF POTASSIUM FORMATE, CESIUM FORMATE, SODIUM PHENOXIDE, POTASSIUM PHENOXIDE, AND MIXTURES THEREOF AT A TEMPERATURE IN THE RANGE OF FROM 200* C. TO 250* C. THE SAID SALT BEING PRESENT IN THE PROPORTION OF AT LEAST 10% BY WEIGHT RELATIVE TO THE WEIGHT OF THE SAID DISODIUM PHOSPHORAMIDATE, AND THEREAFTER RECOVERING A TETRASODIUM IMIDODIPHOSPHATE FROM THE REACTION MIXTURE.