CA1128284A - Production of sodium polyphosphate - Google Patents
Production of sodium polyphosphateInfo
- Publication number
- CA1128284A CA1128284A CA357,635A CA357635A CA1128284A CA 1128284 A CA1128284 A CA 1128284A CA 357635 A CA357635 A CA 357635A CA 1128284 A CA1128284 A CA 1128284A
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- sodium carbonate
- reaction
- solution
- sodium
- mole ratio
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Abstract
ABSTRACT OF THE DISCLOSURE
Stable aqueous solutions of sodium polyphosphate useful in granulating dry solid cleaning composition components are formed by direct reaction of polyphosphoric acid with sodium carbonate generally at a temperature of about 50°C. The reactants are used in an Na:P ratio of 1.2:1 to 1.5:1, and the product solution contains about 32 to about 37% w/w P2O5 of which a high proportion is present as polyphosphate and has a pH of about 5 to about 6.5.
Stable aqueous solutions of sodium polyphosphate useful in granulating dry solid cleaning composition components are formed by direct reaction of polyphosphoric acid with sodium carbonate generally at a temperature of about 50°C. The reactants are used in an Na:P ratio of 1.2:1 to 1.5:1, and the product solution contains about 32 to about 37% w/w P2O5 of which a high proportion is present as polyphosphate and has a pH of about 5 to about 6.5.
Description
?~.~4 TITLE OF INVENTION
PRODUCTION OF SODIU~5 POLYPHOSPHATES
FIELD OF INVENTION
The present in~ention relates to the produckion o~
5 sodium polyphosphates.
BACKGROUND TO THE INVENTION
Sodium polyphosphates are widely used as a seques-tering agent in various cleaning compositions. Solid sodium polyphosphate is conventionally produced by reacting ortho-10 phosphoric acid with sodium carbonate~ drying the sodiumorthophosphate so formed, and calcining the dried product to form the sodium polyphosphate. The calcining step which is used in this procedure requires considerable energy to effect~
SUMMARY OF INVENTION
The present invention is concerned with a procedure which enables the pLoduction of a relatively stable solution of sodium polyphosphates highly concentrated with respect to P205 content to be obtained, which is suitable for granulation of ` other cleaning composition components or which may be dried ! 20 to form a solid sodium polyphosphate, without the necessity to utilize a calcining step and the energy involved therein.
In accordance with the present inven~ion, sodium ¦ carbonate is reacted with polyphosphoric acid at a mole ratio of Na:P of about 1.2:1 to about 1.5:1 and at a pH of 1 25 about 5 to about 6.5 to result in a sodium polyphosphate ! solution containing about 32 to about 37~ w/w of P2050 The water present with the reactants, namely, the sodium carbonate and the polyphosphoric acid, is controlled so as to provide the required pH value and to result in the 30 required P205 concentration in the product.
GENERAL DESCRIPTION OF INVENTION
The final P205 content of the product, ranging from 32 to 37% w/w, is critical in that if the P205 content is below the lower limit, solids precipitate from the `35 product solution while i the P205 content is above the upper ,. .~ ; ~
limit, the viscosity of the solution ~ises rapidly leading to lack of pumpability and inhibition of disengagement o carbon dioxide bubbles. A viscosity of solution in the range of about 50 to about 200 cps usually is acceptable.
It is preferred to provide the P2O5 content of the product solution as high as possible while preserving pump-ability. The P2O5 content is preerably about 35 to abou~
37% w/w.
It is preferred to utilize as reactants polyphos-phorie acid containing about 80 to about 85% by weight P2O5, since polyphosphoric acids of this concentration are commer-cially available and a slurry of sodium carbonate containing about 50 to about 55% Na2CO3, since such slurries are nor-mally used in industrial operations involving sodium carbonate.
Other concentrations, however, may be used consis-tent with the requirement for a P2O5 range in the product of about 30 to about 37~ w/w.
The reaction is effected with quantities of reactant corresponding to a ratio of Na:P of about 1.2:1 to about 1.5:1 r preferably about 1.4:1. The pH of the reaction medium,and hence of the product, is another important parameter and must be controlled in the range of about 5 to about 6.5. If the pH value is above about 6.5, solidification of the solution occurs, while if the - pH value is below about 5, the rate of hydrolysis of the ~olyphosphates increases unacceptably. The highest pH
compatible with liquid stability is preferred, i.e~, about 6.4 to 6.5.
The temperature at which the reaction of the polyphosphoric acid and the sodium carbonate occurs is not critical but preferably is about 45 to about 50C. to minimize h~drolysis of the polyphosphates. Higher temperatures accelerate hydrolysis of the polyphosphates while lower temperatures result in viscosity values which render the polyphosphate solution difficult to pump.
A temperature in the range of about 36 to about 45C. for the sodium carbonate slurry prior to reaction, is : ~ , :
,-. ~ :
3preferred, since solid sodium carbonate is in the monohydrate form and is at or near its maximum solubility in this range.
The sodium polyphosphate solutions which result from this process preferably are characterized by at least about 75%, o~ten over about ~0~ of ~he P205 being present ~g polyphosphates of various chain lengths, depending on the strength o~ the initial acid. Lesser polyphosphate P2O5 values may be present but are less pre~erred, in view of the decreased sequestering properties of such products. The sodium polyphosphate solutions also have extended useful shelf-lives of at least several weeks.
The present invention, therefore, includes a novel sodium polyphosphate composition consisting of an aqueous solution of sodium polyphosphates characterized by:
(a~ a P205 content of about 32 to about 37% w/w, (b) a mole ratio of Na:P of about 1.2:1 to about 1.5:1, and (c) a pH of about 5 to about 6.5 The solutions may be used as a source of high P205-content liquid polyphosphates for a variety of purposes.
For example, the solutions may be used as granulating liquids to make a variety of solid polyphosphate-containing cleaning compositions from solid building chemicals capab~e of hydra-ting and absorbing waterl such as, sodium tripolyphosphate, trisodium phosphate, sodium carbonate, sodiùm sulphate, zeo-lites and nitrilotriacetic acid. If desired, a solid sodium polyphosphate may be recovered from the solution by spray drying.
The process of the invention, therefore, utilizes the direct reaction of sodium carbonate and polyphosphoric acidto form a sodium polyphosphate. The calcining step of the prior art and the energy requirements thereof are avoided. The sodium polyphosphate produced by this invention is in a unique stable liquid form, useful for granulation.
BRIEF DESCRIPTION OF DRAMING
The accompanying drawing is a schematic flow sheet o~ one embodiment of the process of the invention.
DESCRIPTION OF PREFERRED E~ODIMENT
Re~erring to the drawing, a slurry of sodium carbonate in line 10 and polyphosph~r~ic acid in line 12 are separately fed into a recycle stream in line 14, which passes the reactants to a mixin~ tank 15 and then feeds the mixture to a reactor and carbon dioxide disengaging vessel 16, wherein the polyphosphoric acid and the sodium carbona~e reactants react to form an aqueous solution o sodium poly-phosphate and carhon dioxide produced in the reackion is disengaged from the li~uid phase.
! The liquid sodium polyphosphate product is removed by line 18. Recycle material is removed from the ! j reactor tank 16 by line 20 and pumped by pump 22 through '¦ a heat exchanger 24 to remove excess heat of reaction and to recycle the same to the reactor tank 16 by line 14.
Il Carbon dioxide gas disengaged from the liquid phase is vented i 15 from the vessel 16 by line 260 EXAMZLES
Example 1 Polyphosphoric acid containing 83.4% P2O5 was slowly added with stirring to a slurry of sodium carbonate in water containing 54.3% total Na2CO3. After reaction ceased, there was obtained a clear viscous solution which exhibited no tendency to crystallize after 10 days standing at ambient temperature ~20 to 25C).
The solution was analyzed and the results of the analysis are as summarized in the following Table I:
TABLE I
Total P2O5 36.0% w/w 1 P2O5 percent as ortho 10.0% w/w ! Viscosity at 40C 200 cps at 23C 1060 cps Density 1.7 g/cc pH 5.8 Na:P mole ratio 1.34 Sequestering value 9.7g P2o5/g Ca A sample of the solution was p~ adjusted by the addition of solid Na2CO3 to a pH of 7Ø Crystallization of solid phase sodium polyphosphate occurred rapidly.
,~ .
- : .
',:, Example 2 t An apparatus for the continucus production of produc*
was set up utilizing the elements illustrated in the drawing. A series of four runs was carried out in the apparatus to produce product conkaining increasing proportions of P2O5. During the runs, ~he reaction temperature was controlled to about 45C and ~he pH was controlled in the range of 6 to 6.5.
The products obtained from the four runs were analyzed and the results of the analyses are summarized in the following Table II:
TABLE II
Run No. 1 2 3 4 Total P2O5 21.2 27.8 32.0 34.0 %P2O5 as 10.0 5.0 9.0 9.0 Na:P mole ratio 1.406 1.385 pH 6.5 6.5 6.2 Specific gravity 1.346 1.490 1.615 1.636 Viscosity-cps 25~C 250 370 45C sa 87.5 - The samples from the first tws runs crystallized and hence viscosity determinations were not possible. The samples from the latter two runs exhibited stability against crystallization and were found to be useful in granulation of solid cleaning composition components.
SUMMARY OF DISCLOSURE
In summary of the disclosure of this application, the present invention provides novel sodium polyphosphate compositions which are produced by a novel procedure in-volving direct reaction between sodium carbonate and poly-phosphoric acid. Modifications are possible within the scope of this invention.
:: ,
PRODUCTION OF SODIU~5 POLYPHOSPHATES
FIELD OF INVENTION
The present in~ention relates to the produckion o~
5 sodium polyphosphates.
BACKGROUND TO THE INVENTION
Sodium polyphosphates are widely used as a seques-tering agent in various cleaning compositions. Solid sodium polyphosphate is conventionally produced by reacting ortho-10 phosphoric acid with sodium carbonate~ drying the sodiumorthophosphate so formed, and calcining the dried product to form the sodium polyphosphate. The calcining step which is used in this procedure requires considerable energy to effect~
SUMMARY OF INVENTION
The present invention is concerned with a procedure which enables the pLoduction of a relatively stable solution of sodium polyphosphates highly concentrated with respect to P205 content to be obtained, which is suitable for granulation of ` other cleaning composition components or which may be dried ! 20 to form a solid sodium polyphosphate, without the necessity to utilize a calcining step and the energy involved therein.
In accordance with the present inven~ion, sodium ¦ carbonate is reacted with polyphosphoric acid at a mole ratio of Na:P of about 1.2:1 to about 1.5:1 and at a pH of 1 25 about 5 to about 6.5 to result in a sodium polyphosphate ! solution containing about 32 to about 37~ w/w of P2050 The water present with the reactants, namely, the sodium carbonate and the polyphosphoric acid, is controlled so as to provide the required pH value and to result in the 30 required P205 concentration in the product.
GENERAL DESCRIPTION OF INVENTION
The final P205 content of the product, ranging from 32 to 37% w/w, is critical in that if the P205 content is below the lower limit, solids precipitate from the `35 product solution while i the P205 content is above the upper ,. .~ ; ~
limit, the viscosity of the solution ~ises rapidly leading to lack of pumpability and inhibition of disengagement o carbon dioxide bubbles. A viscosity of solution in the range of about 50 to about 200 cps usually is acceptable.
It is preferred to provide the P2O5 content of the product solution as high as possible while preserving pump-ability. The P2O5 content is preerably about 35 to abou~
37% w/w.
It is preferred to utilize as reactants polyphos-phorie acid containing about 80 to about 85% by weight P2O5, since polyphosphoric acids of this concentration are commer-cially available and a slurry of sodium carbonate containing about 50 to about 55% Na2CO3, since such slurries are nor-mally used in industrial operations involving sodium carbonate.
Other concentrations, however, may be used consis-tent with the requirement for a P2O5 range in the product of about 30 to about 37~ w/w.
The reaction is effected with quantities of reactant corresponding to a ratio of Na:P of about 1.2:1 to about 1.5:1 r preferably about 1.4:1. The pH of the reaction medium,and hence of the product, is another important parameter and must be controlled in the range of about 5 to about 6.5. If the pH value is above about 6.5, solidification of the solution occurs, while if the - pH value is below about 5, the rate of hydrolysis of the ~olyphosphates increases unacceptably. The highest pH
compatible with liquid stability is preferred, i.e~, about 6.4 to 6.5.
The temperature at which the reaction of the polyphosphoric acid and the sodium carbonate occurs is not critical but preferably is about 45 to about 50C. to minimize h~drolysis of the polyphosphates. Higher temperatures accelerate hydrolysis of the polyphosphates while lower temperatures result in viscosity values which render the polyphosphate solution difficult to pump.
A temperature in the range of about 36 to about 45C. for the sodium carbonate slurry prior to reaction, is : ~ , :
,-. ~ :
3preferred, since solid sodium carbonate is in the monohydrate form and is at or near its maximum solubility in this range.
The sodium polyphosphate solutions which result from this process preferably are characterized by at least about 75%, o~ten over about ~0~ of ~he P205 being present ~g polyphosphates of various chain lengths, depending on the strength o~ the initial acid. Lesser polyphosphate P2O5 values may be present but are less pre~erred, in view of the decreased sequestering properties of such products. The sodium polyphosphate solutions also have extended useful shelf-lives of at least several weeks.
The present invention, therefore, includes a novel sodium polyphosphate composition consisting of an aqueous solution of sodium polyphosphates characterized by:
(a~ a P205 content of about 32 to about 37% w/w, (b) a mole ratio of Na:P of about 1.2:1 to about 1.5:1, and (c) a pH of about 5 to about 6.5 The solutions may be used as a source of high P205-content liquid polyphosphates for a variety of purposes.
For example, the solutions may be used as granulating liquids to make a variety of solid polyphosphate-containing cleaning compositions from solid building chemicals capab~e of hydra-ting and absorbing waterl such as, sodium tripolyphosphate, trisodium phosphate, sodium carbonate, sodiùm sulphate, zeo-lites and nitrilotriacetic acid. If desired, a solid sodium polyphosphate may be recovered from the solution by spray drying.
The process of the invention, therefore, utilizes the direct reaction of sodium carbonate and polyphosphoric acidto form a sodium polyphosphate. The calcining step of the prior art and the energy requirements thereof are avoided. The sodium polyphosphate produced by this invention is in a unique stable liquid form, useful for granulation.
BRIEF DESCRIPTION OF DRAMING
The accompanying drawing is a schematic flow sheet o~ one embodiment of the process of the invention.
DESCRIPTION OF PREFERRED E~ODIMENT
Re~erring to the drawing, a slurry of sodium carbonate in line 10 and polyphosph~r~ic acid in line 12 are separately fed into a recycle stream in line 14, which passes the reactants to a mixin~ tank 15 and then feeds the mixture to a reactor and carbon dioxide disengaging vessel 16, wherein the polyphosphoric acid and the sodium carbona~e reactants react to form an aqueous solution o sodium poly-phosphate and carhon dioxide produced in the reackion is disengaged from the li~uid phase.
! The liquid sodium polyphosphate product is removed by line 18. Recycle material is removed from the ! j reactor tank 16 by line 20 and pumped by pump 22 through '¦ a heat exchanger 24 to remove excess heat of reaction and to recycle the same to the reactor tank 16 by line 14.
Il Carbon dioxide gas disengaged from the liquid phase is vented i 15 from the vessel 16 by line 260 EXAMZLES
Example 1 Polyphosphoric acid containing 83.4% P2O5 was slowly added with stirring to a slurry of sodium carbonate in water containing 54.3% total Na2CO3. After reaction ceased, there was obtained a clear viscous solution which exhibited no tendency to crystallize after 10 days standing at ambient temperature ~20 to 25C).
The solution was analyzed and the results of the analysis are as summarized in the following Table I:
TABLE I
Total P2O5 36.0% w/w 1 P2O5 percent as ortho 10.0% w/w ! Viscosity at 40C 200 cps at 23C 1060 cps Density 1.7 g/cc pH 5.8 Na:P mole ratio 1.34 Sequestering value 9.7g P2o5/g Ca A sample of the solution was p~ adjusted by the addition of solid Na2CO3 to a pH of 7Ø Crystallization of solid phase sodium polyphosphate occurred rapidly.
,~ .
- : .
',:, Example 2 t An apparatus for the continucus production of produc*
was set up utilizing the elements illustrated in the drawing. A series of four runs was carried out in the apparatus to produce product conkaining increasing proportions of P2O5. During the runs, ~he reaction temperature was controlled to about 45C and ~he pH was controlled in the range of 6 to 6.5.
The products obtained from the four runs were analyzed and the results of the analyses are summarized in the following Table II:
TABLE II
Run No. 1 2 3 4 Total P2O5 21.2 27.8 32.0 34.0 %P2O5 as 10.0 5.0 9.0 9.0 Na:P mole ratio 1.406 1.385 pH 6.5 6.5 6.2 Specific gravity 1.346 1.490 1.615 1.636 Viscosity-cps 25~C 250 370 45C sa 87.5 - The samples from the first tws runs crystallized and hence viscosity determinations were not possible. The samples from the latter two runs exhibited stability against crystallization and were found to be useful in granulation of solid cleaning composition components.
SUMMARY OF DISCLOSURE
In summary of the disclosure of this application, the present invention provides novel sodium polyphosphate compositions which are produced by a novel procedure in-volving direct reaction between sodium carbonate and poly-phosphoric acid. Modifications are possible within the scope of this invention.
:: ,
Claims (16)
1. An aqueous solution of sodium polyphosphates which is stable to separation of a solid phase sodium polyphosphate and characterized by:
(a) a P2O5 content of about 32 to about 37% w/w, (b) a mole ratio of Na:P of about 1.2:1 to about 1.5:1, and (c) a pH of about 5 to about 6.5.
(a) a P2O5 content of about 32 to about 37% w/w, (b) a mole ratio of Na:P of about 1.2:1 to about 1.5:1, and (c) a pH of about 5 to about 6.5.
2. The solution of claim 1 wherein at least about 75 w/w of the P2O5 is present as polyphosphates of varying chain lengths.
3. The solution of claim 1 wherein at least about 90%
w/w of the P2O5 is present as polyphosphates of varying chain lengths.
w/w of the P2O5 is present as polyphosphates of varying chain lengths.
4. The solution of claim 1 wherein said mole ratio is about 1.4:1.
5. The solution of claim 1, 2 or 4 wherein said pH
is about 6.4 to 6.5.
is about 6.4 to 6.5.
6. The solution of claim 1 wherein at least about 90% w/w of the P2O5 is present as polyphosphates of varying chain lengths, said mole ratio is about 1.4:1 and said pH
is about 6.4 to 6.5
is about 6.4 to 6.5
7. A process for the production of an aqueous solu-tion of a sodium polyphosphate, which comprises reacting polyphosphoric acid and sodium carbonate in such proportions as to provide an Na:P ratio in the range of about 1.2:1 to about 1.5:1, such reaction being effected at a pH of about 5 to about 6.5 in the presence of water in quantities such as to provide a product solution containing about 32 to about 37% w/w of P2O5.
8. The process of claim 7 wherein said water is introduced only with the reactants which are utilized in the form of polyphosphoric containing about 80 to 85%
w/w P2O5 and a slurry of sodium carbonate containing about 50 to about 55% w/w Na2CO3.
w/w P2O5 and a slurry of sodium carbonate containing about 50 to about 55% w/w Na2CO3.
9. The process of claim 7 wherein said proportion of reactants are such as to provide an Na:P of about 1.4:1.
10. The process of claim 7, 8 or 9 effected at a temperature of about 45° to about 50°C.
11. The process of claim 7, 8 or 9 effected at a tem-perature of about 45° to about 50°C and wherein said slurry of sodium carbonate has a temperature of about 36° to about 45°C.
12. A continuous process for the production of an aqueous solution of sodium polyphosphate, which comprises:
continuously feeding a slurry of sodium carbonate of concentration about 50 to about 55% w/w Na2CO3 into a recycle stream at a temperature of about 36° to about 45°C, continuously feeding polyphosphoric acid having a P2O5 content of about 80 to 85% into said recycle stream following said sodium carbonate slurry feed thereto, mixing said sodium carbonate slurry and said polyphosphoric acid to form a reaction mixture, continuously forwarding said reaction mixture to a reaction zone to permit reaction of said polyphosphoric acid with said sodium carbonate to occur, continuously controlling the relative proportions of polyphosphoric acid and sodium carbonate fed to said recycle stream to provide a mole ratio of Na:P of about 1.2 to about 1.5:1 and a pH of about 5 to about 6.5 in said reaction mixture, continuously venting carbon dioxide formed in said reaction from said reaction zone, continuously withdrawing a portion of the reacted reaction mixture from said reaction zone as a product stream of aqueous solution of sodium polyphosphate containing about 32 to about 37% w/w of P2O5, continuously removing the remainder of said reacted reaction mixture from said reaction zone as said recycle stream, and subjecting said recycle stream to heat exchange to maintain said reaction temperature prior to said addition of sodium carbonate slurry thereto.
continuously feeding a slurry of sodium carbonate of concentration about 50 to about 55% w/w Na2CO3 into a recycle stream at a temperature of about 36° to about 45°C, continuously feeding polyphosphoric acid having a P2O5 content of about 80 to 85% into said recycle stream following said sodium carbonate slurry feed thereto, mixing said sodium carbonate slurry and said polyphosphoric acid to form a reaction mixture, continuously forwarding said reaction mixture to a reaction zone to permit reaction of said polyphosphoric acid with said sodium carbonate to occur, continuously controlling the relative proportions of polyphosphoric acid and sodium carbonate fed to said recycle stream to provide a mole ratio of Na:P of about 1.2 to about 1.5:1 and a pH of about 5 to about 6.5 in said reaction mixture, continuously venting carbon dioxide formed in said reaction from said reaction zone, continuously withdrawing a portion of the reacted reaction mixture from said reaction zone as a product stream of aqueous solution of sodium polyphosphate containing about 32 to about 37% w/w of P2O5, continuously removing the remainder of said reacted reaction mixture from said reaction zone as said recycle stream, and subjecting said recycle stream to heat exchange to maintain said reaction temperature prior to said addition of sodium carbonate slurry thereto.
13. The process of claim 12 wherein said reaction temperature is about 45° to about 50°C.
14. The process of claim 12 wherein said Na:P mole ratio is about 1.4:1.
15. The process of claim 12 wherein said pH is about 6.4 to 6.5.
16. The process of claim 12 wherein said reaction temperature is about 45° to about 50°C, said Na:P mole ratio is about 1.4:1 and said pH is about 6.4 to 6.5.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7928330 | 1979-08-14 | ||
| GB7928330 | 1979-08-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1128284A true CA1128284A (en) | 1982-07-27 |
Family
ID=10507196
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA357,635A Expired CA1128284A (en) | 1979-08-14 | 1980-08-05 | Production of sodium polyphosphate |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1128284A (en) |
-
1980
- 1980-08-05 CA CA357,635A patent/CA1128284A/en not_active Expired
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| MKEX | Expiry |