Title of Invention	IMPROVED PROCESS FOR PREPARING N-PHOSPHONO-METHYL IMINO DIACETIC ACID
Abstract	[00039] The present invention discloses a process to prepare PMIDA using Mono chloro Acetic Acid (MCA) as the raw material. The process of the present invention comprises the key steps of getting imino diacetic acid calcium salt from the starting materials, MCA, hydrated lime and aqueous ammonia. The calcium salt of imino diacetic acid is heated with HC1 to get Imino diacetic acid hydrogen chloride (IDA-HC1). IDA-HC1 thus obtained is filtered and after removal of mechanical impurities charged into a glass reactor fitted with a D/S system. Phosphorous Acid and HC1 are added to the reaction mixture comprising IDA-HC1. Excess of water is removed through azeotropic distillation implemented through the D/S system. Formaldehyde is finally added to the reaction mixture to obtain the desired product, PMIDA. Unreacted formaldehyde is removed using vacuum. Glyphosate prepared using PMIDA of the present invention are clear in appearance with no haziness.

Title of Invention

IMPROVED PROCESS FOR PREPARING N-PHOSPHONO-METHYL IMINO DIACETIC ACID

Abstract

[00039] The present invention discloses a process to prepare PMIDA using Mono chloro Acetic Acid (MCA) as the raw material. The process of the present invention comprises the key steps of getting imino diacetic acid calcium salt from the starting materials, MCA, hydrated lime and aqueous ammonia. The calcium salt of imino diacetic acid is heated with HC1 to get Imino diacetic acid hydrogen chloride (IDA-HC1). IDA-HC1 thus obtained is filtered and after removal of mechanical impurities charged into a glass reactor fitted with a D/S system. Phosphorous Acid and HC1 are added to the reaction mixture comprising IDA-HC1. Excess of water is removed through azeotropic distillation implemented through the D/S system. Formaldehyde is finally added to the reaction mixture to obtain the desired product, PMIDA. Unreacted formaldehyde is removed using vacuum. Glyphosate prepared using PMIDA of the present invention are clear in appearance with no haziness.

Full Text	IMPROVED PROCESS FOR PREPARING N-PHOSPHONO-METHYL IMINO DIACETIC ACID FIELD OF INVENTION [0001] The present invention relates to an improved process for preparing N-phosphono-methyl imino diacetic acid (PMIDA). More specifically, the invention relates to a process that reduces the time cycle to prepare PMIDA from its starting materials. The PMIDA prepared in accordance to the present invention can be used to make N-phosphonomethylglycine (glyphosate) of superior quality. BACKGROUND OF THE INVENTION [0002] N-phosphono-methyl imino diacetic acid (PMIDA) is a commercially well known intermediate used in the synthesis of Glyphosate - a broad spectrum herbicide. PMIDA is structurally represented as Fig 1. (Figure Removed) [0003] PMIDA has been conventionally prepared using various approaches, starting with different starting materials. One of the earliest developed methods of synthesizing PMIDA uses diethanol amine as raw material. Herein, diethanol amine is reacted with caustic solution under a pressure of 0.9-1.05 Mpa and neutralized with HC1 to make imino diacetic acid. The imino diacetic acid thus formed is further reacted with 37% formaldehyde and ortho-phosphorus acid resulting in a condensation reaction. Alkali is used to neutralize the mixture. PMIDA, thus formed, is centrifuged and dried. [0004] Another commonly followed approach uses imino diacetonitrile (IDAN) as raw material. In such a method, iminodiacetonitrile is reacted with 22% caustic solution. The reaction proceeds with evolution of ammonia gas. The reaction mixture is decolorized by active carbon and acidified by trickling hydrochloric acid to bring the pH in the range of 6-7. After completion of the reaction, the material is filtered through micro porous filter to get a light yellow transparent solution of iminodiacetic acid mono sodium. To the iminodiacetic acid mono sodium solution thus formed, phosphorus acid is added. Next, hydrochloric acid is added and the reaction mixture is stirred at temperature controlled below 80°C. The temperature is then raised to 115°C to do an azeotropic distillation to remove water. At this stage, formaldehyde solution is trickled in for 6-7 hours at a temperature of 110°-112°C and the temperature is maintained for 2 hours. The reaction mixture is then diluted with water at a temperature of 40°C followed by neutralization with alkaline solution till pH is 0.8-1.0. The temperature is brought down to 20°C and maintained as such for 2 hours. The solid of PMIDA is centrifuged out and washed with water. The PMIDA is subsequently dried and is ready to be used as PMIDA cake. [0005] More recently, PMIDA is being prepared from Mono chloro acetic acid (MCA). First described in US 4931585, this process comprises formation of Imino-diacetic acid calcium salt by reacting MCA, ammonia and calcium hydroxide. The un-reacted ammonia is taken away by vacuum. Imino-diacetic acid calcium salt thus obtained is heated with concentrated hydrochloric acid in a molar ratio 2-3:1 at temperature 50-100°C to get imino-diacetic acid hydrogen chloride (IDA-HC1). IDA-HC1 is separated, dissolved in water and reacted with phosphorus acid (in a molar ratio 1.0-1.2:7) and with the aqueous solution of formaldehyde (in a molar ratio of 1.0-1.4:1) under stirring and the product is isolated. [0006] Such existing methods for preparing PMIDA have their own drawbacks. Existing methods, for instance, involve discharge of harmful pollutants in the environment including ammonia which is highly undesirable. Moreover, the existing methods are time consuming and take around 40 hours to complete for a single cycle. This not only adds to the cost to the manufacturer but also makes the entire process lesser efficient. Use of pressure conditions in such methods is another disadvantage as it makes the entire process prone to multiple hazards. A further common drawback in almost all the existing methods is the haziness that appears in the final product - glyphosate - prepared using the PMIDA from the existing methods. Haziness in glyphosate is undesirable and hence even though the existing methods to prepare PMIDA give purity of around 96%, such methods suffer from an inherent disadvantage of rendering the final product poorer in quality. [0007] There is, therefore, a need in the art to devise a process to prepare PMIDA that does not involve formation of side products which are potential pollution hazards. Moreover, such process must also be time efficient, taking lesser time to complete one full cycle than the existing methods. It would also be desirable that such process involves no high pressure conditions. Lastly, a process of such nature must also fulfill the long standing need in the art to prepare PMIDA that forms a glyphosate with minimal haziness thus imparting a superior quality. OBJECTS OF THE INVENTION [0008] It is an object of the invention to provide an improved process to prepare N-phosphono-methyl imino diacetic acid (PMIDA). [0009] It is an object of the invention to provide an improved process to prepare PMIDA which does not involve formation of pollution causing side products. [00010] It is an object of the invention to provide an improved process to prepare PMIDA which does not result in any evolution of ammonia. [00011] It is an object of the invention to provide an improved process to prepare PMIDA which has a lesser time cycle than the existing processes. [00012] It is an object of the invention to provide a process to prepare PMIDA which does not involve any high pressure conditions. [00013] It is an object of the invention to provide a process to prepare PMIDA which result in forming glyphosate that is not hazy in appearance. [00014] It is an object of the invention to provide a process to prepare PMIDA which does not compromise on the yield and purity of the PMIDA obtained. [00015] It is an object of the invention to provide a process to prepare PMIDA which ensures completion of reaction at each step. BRIEF DESCRIPTION OF THE DIAGRAMS [00016] Figure 1 is a representation of a reactor fitted with a D/S system as used in accordance to an embodiment of the present invention. [00017] Figure 2 is a comparative snapshot of the Glyphosate appearance, prepared using PMIDA in accordance to an embodiment of the present invention (Figure 2a) and using PMIDA from existing methods (Figure 2b). SUMMARY OF THE INVENTION [00018] The present invention discloses a process to prepare PMIDA using Mono chloro Acetic Acid (MCA) as the raw material. Process of the present invention comprises the key steps of getting imino diacetic acid calcium salt from the starting materials, MCA, hydrated lime and aqueous ammonia. Calcium salt of imino diacetic acid is heated with HC1 to get Imino diacetic acid hydrogen chloride (IDA-HCl). IDA-HCl thus obtained is filtered and after removal of mechanical impurities charged into a glass reactor fitted with a D/S system. Phosphorous Acid and HC1 are added to the reaction mixture comprising IDA-HCl. Excess of water is removed through azeotropic distillation implemented through the D/S system. Formaldehyde is finally added to the reaction mixture to obtain the desired product, PMIDA. Unreacted formaldehyde is removed using vacuum. Glyphosate prepared using PMIDA of the present invention are clear in appearance with no haziness. DETAILED DESCRIPTION OF THE INVENTION [00019] In an embodiment of the present invention, PMIDA is prepared using Mono Chloro Acetic Acid (MCA), aqueous ammonia and hydrated lime as the starting material. In a first step, hydrated lime is reacted with aqueous ammonia. MCA solution is added slowly to get imino diacetic acid calcium salt. The Imino diacetic acid calcium salt thus obtained is heated with 37% HC1 to get Imino diacetic acid hydrogen chloride (IDA-HCl). In an embodiment of the present invention, the IDA-HCl is recovered by filtration. In another embodiment, aqueous solution of the recovered IDA-HCl is then prepared and filtered to remove the mechanical impurities. The resultant solution is then transferred to a glass reactor and treated with phosphorus acid in the ratio 1.0-1.2:1 followed by an addition of hydrochloric acid in the reaction mix. Excess of water is removed by azeotropic distillation using the D/S system till the temperature rises to 115°C which ensures the formation of phosphorus trichloride. [00020] Figure 1 depicts an embodiment of the present invention with a D/S system fitted into the glass reactor and the reaction being carried out with removal of excess water through azeotropic distillation. In an embodiment of the present invention, an aqueous solution of formaldehyde in a molar ratio of 1.0-1.4:1 can be added at a temperature of about 112-115°C under constant stirring with the temperature being maintained at 112°C for an hour. Vacuum can then be used to remove the formaldehyde. After completion of the reaction, the product obtained (PMIDA) can be isolated. [00021] In a specific embodiment, to prepare PMIDA using the method of the present invention, 60% slurry of hydrated lime is made in a glass reactor. 25% ammonia solution is added to it at temperature 35 ± 5°C for 1-2 hours with agitation. 70% solution of MCA is added slowly under temperature 50 ± 5°C. The temperature is maintained for 3 hours at 50-55°C. This step is in sharp contrast to the existing methods; particularly the one followed in US 4931585 where 7 hours maintenance is needed. Next, 37% HC1 is trickled in for 1 hour at 60-80°C. The temperature is maintained at 80-85°C for 1 hour. The reaction mixture obtained is cooled to 10-20°C. It is then crystallized for 2-3 hours and filtered. The product thus obtained is Imino diacetic acid hydrogen chloride (IDA-HCl). Compared to the 20 hours time that is taken to prepare IDA-HCl using existing process, particularly the one described in US 4931585, the process of the present invention takes only 14.5 hours, thus considerably reducing the time period to reach to get IDA-HCl. [00022] An aqueous solution of IDA-HC1 is prepared and filtered to remove mechanical impurities to obtain 80% yield of the theoretical amount is obtained. [00023] Next, the aqueous solution of IDA-HC1 is taken in a glass reactor fitted with a Dean-Stark (D/S) System. To the glass reactor, 37% HCl is added. This mixture is then heated with phosphorus acid in a molar ratio of 1.0-1.2:1 with azeotropic distillation and stirred at boiling point to remove water until the temperature reaches 112-115°C. Then aqueous solution of formaldehyde in the molar ratio of 1.0-1.4:1 is added at temperature 110-115°C for 4 hours and this temperature is maintained for 1-2 hours. The temperature is then brought down to 80°C followed by addition of water. At this temperature, un-reacted formaldehyde is removed under vacuum. The temperature is then brought down to 40°C and the reaction mixture is diluted with water and cooled at 8-10°C. The reaction mixture is crystallized for 2-3 hours and is filtered. [00024] The filtered material is given two rounds of washing with water at 45°C. The material is dried upto 100°C in fluid bed drier. The dried material is PMIDA and the purity obtained is 96-98% with 82% yield calculated on IDA-HC1 basis. Yield calculated to MCA basis is 65-68%. The total process time starting from IDA-HC1 to PMIDA is about 14 hours, which is again lesser than the 16.5 hours that is taken using the process described in US 4931585. Thus, in totality, the time cycle to prepare PMIDA from the process of present invention is 28.5 hours, whereas the same using existing methods, and particularly the one described in US 4931585 is 36 hours. A net saving of 7.5 hours per cycle of PMIDA synthesis is a marked difference and of immense industrial application. [00025] In an embodiment of the present invention, to the aqueous IDA-HC1 solution, phosphorus acid is added and then D/S method is applied to remove the water azeotropically to bring the temperature to 115-116°C. Then, formaldehyde solution is added to the reaction mixture. Due to the D/S method, excess water comes out which helps in crystallizing the final product and thus the crystallization time is substantially reduced. This is a significant advantage over the existing art which depends on evaporation and hence the time cycle is substantially increased. [00026] The present invention uses vacuum to remove the unreacted formaldehyde which is in contrast to no such use in any of the existing methods. Timely removal of the un-reacted formaldehyde gives the process of the present invention its most crucial advantage. In the synthesis of PMIDA according to the process disclosed in US 4931585, 2.5% formaldehyde remains unreacted in the PMIDA. When Glyphosate is prepared from this PMIDA and further formulated into 41% SL, the SL is not transparent and is hazy in appearance. In contrast, by virtue of the vacuum assisted removal of un-reacted formaldehyde in the process of present invention, the Glyphosate prepared from PMIDA obtained from the present invention, when formulated in 41% SL, is clear & transparent with no haziness. Figure 2 depicts a comparative snapshot of Glyphosate obtained after preparing it from PMIDA obtained using the process of the present invention (Fig 2a) vis-a-vis the existing method, particularly the method described in US 4931585 (Fig 2b). It is very evident that Glyphosate prepared from PMIDA obtained from the process of the present invention is clear, transparent and free of any haziness in appearance. [00027] Conventionally, preparation of PMIDA from IDA-HC1 involves using an autoclave and carrying out high pressure reactions that involve both time and risks associated with conducting high pressure reactions. The present invention does away with the use of autoclave. Instead, it uses a glass reactor fitted with a D/S system that not only saves time but also bypasses the use of a high pressure reaction condition. EXAMPLES EXAMPLE 1 [00028] 156 gm of hydrated lime was loaded in a 1000 ml reactor with agitation. 100 gm of water was added and agitated to make homogenous slurry. The temperature was brought to 30°C. 90 gm of 25% ammonia solution was added slowly at 30-35°C in 1-1/2 hour. This temperature was maintained for 1 hour. 70% solution of MCA was prepared by taking 190 gm MCA in 80 gm of water. MCA solution was charged in additional funnel and added slowly in 3 hours controlling the temperature at 50-52°C. The temperature was maintained at 54-55°C for 3 hours with continued agitation. 400 ml of 37% HC1 is trickled in 1 hour at temperature 55-75°C. The temperature was maintained at 75-80°C for 1 hour. The reaction mixture was then cooled to 10°C and after stirring for 3 hours iminodiacetic acid hydrogen chloride (IDA-HCl) was filtered out. 200 gm of moist IDA-HCl was obtained having 30% moisture. [00029] Thereafter, the IDA-HCl so obtained was dissolved in 200 ml of water to make an aqueous solution and filtered to remove the mechanical impurities. 2.7 gm of mechanical impurities was removed. The aqueous solution contained 138 gm of IDA-HCl which was 81.6% yield of theoretical amount. [00030] The aqueous solution of IDA-HCl was taken in coolable and heatable 1 litre reactor equipped with a stirrer, thermometer and D/S system. 95 gm of phosphorus acid was added, 70 gm of 37% HC1 was then added by measuring flask to control temperature below 80°C. Temperature was increased to remove water through azeotropic distillation. At temperature 115°C, 120 gm of 37% formaldehyde solution was trickled in for 6 hours at 110-112°C. The temperature was maintained at 110-112°C for 2 hours. [00031] The reaction mixture was then cooled to 40°C and unloaded in neutralizing kettle having 100 ml water. The temperature was further cooled to 8°C and maintained for 2 hours for crystallization. The material was filtered. Precipitated crystals of PMIDA was given two washing with water and dried. 158 gm of PMIDA was obtained with purity of 96.5%. Yield of the PMIDA was 85% and yield calculated to MCA is 69%. ADVANTAGES OF THE INVENTION [00032] The present invention provides a process to prepare PMIDA in a significantly reduced time cycle. [00033] The present invention provides a process to prepare PMIDA wherein no pollution causing side products are released. [00034] The present invention provides a process to prepare PMIDA wherein the haziness in the Glyphosate prepared from the PMIDA of the present invention is substantially reduced. [00035] The present invention provides a process to prepare PMIDA wherein there is no evolution of ammonia. [00036] The present invention provides a process to prepare PMIDA wherein no high pressure reaction condition is used. [00037] The present invention provides a process to prepare PMIDA wherein each step of the process undergoes completion of reaction. [00038] The present invention provides a process to prepare PMIDA wherein the yield and purity of the PMIDA is not compromised. We claim, 1. A process to prepare N-phosphono-methyl amino diacetic acid, comprising the steps of, (a) reacting hydrated lime with aqueous ammonia and mono chloro acetic acid solution to obtain imino diacetic acid calcium salt; (b) heating said imino diacetic acid calcium salt with hydrochloric acid to get imino diacetic acid hydrogen chloride; (c) reacting said imino diacetic acid hydrogen chloride with phosphorus acid and formaldehyde; and (d) obtaining N-phosphono-methyl amino diacetic acid by cooling and crystallizing reaction mixture obtained in step (c); wherein, step (c) further comprises azeotropic distillation to remove water. 2. The process as claimed in claim 1, wherein step (a) comprises first reacting said hydrated lime with said aqueous ammonia and subsequently adding said mono chloro acetic acid solution to reaction mix. 3. The process as claimed in claim 1, wherein unreacted formaldehyde from step (c) is removed under vacuum. 4. The process as claimed in claim 1, wherein said azeotropic distillation is carried out after reacting said imino diacetic acid hydrogen chloride with said phosphorus acid and before reacting with said formaldehyde. 5. The process as claimed in claim 1, wherein said azeotropic distillation is carried out in a glass reactor fitted with a Dean-Stark (D/S) System. 6. The process as claimed in claim 1, wherein said N-phosphono-methyl amino diacetic acid is further used to prepare N-phosphonomethylglycine. 7. The process as claimed in claim 6, wherein said N-phosphonomethylglycine is substantially free of haziness in appearance. 8. The process as claimed in claim 1, wherein total time cycle for said process is not more than 30 hours. 9. The process as claimed in claim 1, wherein said process is substantially free of any high pressure employing step. 10. The process as claimed in claim 1, wherein said imino diacetic acid hydrogen chloride obtained in step (b) is filtered to remove mechanical impurities.

Full Text

IMPROVED PROCESS FOR PREPARING N-PHOSPHONO-METHYL IMINO
DIACETIC ACID FIELD OF INVENTION
[0001] The present invention relates to an improved process for preparing N-phosphono-methyl imino diacetic acid (PMIDA). More specifically, the invention relates to a process that reduces the time cycle to prepare PMIDA from its starting materials. The PMIDA prepared in accordance to the present invention can be used to make N-phosphonomethylglycine (glyphosate) of superior quality.
BACKGROUND OF THE INVENTION
[0002] N-phosphono-methyl imino diacetic acid (PMIDA) is a commercially well known intermediate used in the synthesis of Glyphosate - a broad spectrum herbicide. PMIDA is structurally represented as Fig 1.
(Figure Removed)

[0003] PMIDA has been conventionally prepared using various approaches, starting with different starting materials. One of the earliest developed methods of synthesizing PMIDA uses diethanol amine as raw material. Herein, diethanol amine is reacted with caustic solution under a pressure of 0.9-1.05 Mpa and neutralized with HC1 to make imino diacetic acid. The imino diacetic acid thus formed is further reacted with 37% formaldehyde and ortho-phosphorus acid resulting in a condensation reaction. Alkali is used to neutralize the mixture. PMIDA, thus formed, is centrifuged and dried.
[0004] Another commonly followed approach uses imino diacetonitrile (IDAN) as raw material. In such a method, iminodiacetonitrile is reacted with 22% caustic solution. The reaction proceeds with evolution of ammonia gas. The reaction mixture is decolorized by active carbon and acidified by trickling hydrochloric acid to bring the pH in the range of 6-7. After completion of the
reaction, the material is filtered through micro porous filter to get a light yellow transparent solution of iminodiacetic acid mono sodium. To the iminodiacetic acid mono sodium solution thus formed, phosphorus acid is added. Next, hydrochloric acid is added and the reaction mixture is stirred at temperature controlled below 80°C. The temperature is then raised to 115°C to do an azeotropic distillation to remove water. At this stage, formaldehyde solution is trickled in for 6-7 hours at a temperature of 110°-112°C and the temperature is maintained for 2 hours. The reaction mixture is then diluted with water at a temperature of 40°C followed by neutralization with alkaline solution till pH is 0.8-1.0. The temperature is brought down to 20°C and maintained as such for 2 hours. The solid of PMIDA is centrifuged out and washed with water. The PMIDA is subsequently dried and is ready to be used as PMIDA cake. [0005] More recently, PMIDA is being prepared from Mono chloro acetic acid (MCA). First described in US 4931585, this process comprises formation of Imino-diacetic acid calcium salt by reacting MCA, ammonia and calcium hydroxide. The un-reacted ammonia is taken away by vacuum. Imino-diacetic acid calcium salt thus obtained is heated with concentrated hydrochloric acid in a molar ratio 2-3:1 at temperature 50-100°C to get imino-diacetic acid hydrogen chloride (IDA-HC1). IDA-HC1 is separated, dissolved in water and reacted with phosphorus acid (in a molar ratio 1.0-1.2:7) and with the aqueous solution of formaldehyde (in a molar ratio of 1.0-1.4:1) under stirring and the product is isolated.
[0006] Such existing methods for preparing PMIDA have their own drawbacks. Existing methods, for instance, involve discharge of harmful pollutants in the environment including ammonia which is highly undesirable. Moreover, the existing methods are time consuming and take around 40 hours to complete for a single cycle. This not only adds to the cost to the manufacturer but also makes the entire process lesser efficient. Use of pressure conditions in such methods is another disadvantage as it makes the entire process prone to multiple hazards. A further common drawback in almost all the existing methods is the haziness that appears in the final product -
glyphosate - prepared using the PMIDA from the existing methods. Haziness in glyphosate is undesirable and hence even though the existing methods to prepare PMIDA give purity of around 96%, such methods suffer from an inherent disadvantage of rendering the final product poorer in quality. [0007] There is, therefore, a need in the art to devise a process to prepare PMIDA that does not involve formation of side products which are potential pollution hazards. Moreover, such process must also be time efficient, taking lesser time to complete one full cycle than the existing methods. It would also be desirable that such process involves no high pressure conditions. Lastly, a process of such nature must also fulfill the long standing need in the art to prepare PMIDA that forms a glyphosate with minimal haziness thus imparting a superior quality.
OBJECTS OF THE INVENTION
[0008] It is an object of the invention to provide an improved process to
prepare N-phosphono-methyl imino diacetic acid (PMIDA).
[0009] It is an object of the invention to provide an improved process to
prepare PMIDA which does not involve formation of pollution causing side
products.
[00010] It is an object of the invention to provide an improved process to
prepare PMIDA which does not result in any evolution of ammonia.
[00011] It is an object of the invention to provide an improved process to
prepare PMIDA which has a lesser time cycle than the existing processes.
[00012] It is an object of the invention to provide a process to prepare
PMIDA which does not involve any high pressure conditions.
[00013] It is an object of the invention to provide a process to prepare
PMIDA which result in forming glyphosate that is not hazy in appearance.
[00014] It is an object of the invention to provide a process to prepare
PMIDA which does not compromise on the yield and purity of the PMIDA
obtained.
[00015] It is an object of the invention to provide a process to prepare PMIDA which ensures completion of reaction at each step.
BRIEF DESCRIPTION OF THE DIAGRAMS
[00016] Figure 1 is a representation of a reactor fitted with a D/S system as
used in accordance to an embodiment of the present invention.
[00017] Figure 2 is a comparative snapshot of the Glyphosate appearance,
prepared using PMIDA in accordance to an embodiment of the present
invention (Figure 2a) and using PMIDA from existing methods (Figure 2b).
SUMMARY OF THE INVENTION
[00018] The present invention discloses a process to prepare PMIDA using Mono chloro Acetic Acid (MCA) as the raw material. Process of the present invention comprises the key steps of getting imino diacetic acid calcium salt from the starting materials, MCA, hydrated lime and aqueous ammonia. Calcium salt of imino diacetic acid is heated with HC1 to get Imino diacetic acid hydrogen chloride (IDA-HCl). IDA-HCl thus obtained is filtered and after removal of mechanical impurities charged into a glass reactor fitted with a D/S system. Phosphorous Acid and HC1 are added to the reaction mixture comprising IDA-HCl. Excess of water is removed through azeotropic distillation implemented through the D/S system. Formaldehyde is finally added to the reaction mixture to obtain the desired product, PMIDA. Unreacted formaldehyde is removed using vacuum. Glyphosate prepared using PMIDA of the present invention are clear in appearance with no haziness.
DETAILED DESCRIPTION OF THE INVENTION
[00019] In an embodiment of the present invention, PMIDA is prepared using Mono Chloro Acetic Acid (MCA), aqueous ammonia and hydrated lime as the starting material. In a first step, hydrated lime is reacted with aqueous ammonia. MCA solution is added slowly to get imino diacetic acid calcium salt. The Imino diacetic acid calcium salt thus obtained is heated with 37% HC1
to get Imino diacetic acid hydrogen chloride (IDA-HCl). In an embodiment of the present invention, the IDA-HCl is recovered by filtration. In another embodiment, aqueous solution of the recovered IDA-HCl is then prepared and filtered to remove the mechanical impurities. The resultant solution is then transferred to a glass reactor and treated with phosphorus acid in the ratio 1.0-1.2:1 followed by an addition of hydrochloric acid in the reaction mix. Excess of water is removed by azeotropic distillation using the D/S system till the temperature rises to 115°C which ensures the formation of phosphorus trichloride.
[00020] Figure 1 depicts an embodiment of the present invention with a D/S system fitted into the glass reactor and the reaction being carried out with removal of excess water through azeotropic distillation. In an embodiment of the present invention, an aqueous solution of formaldehyde in a molar ratio of 1.0-1.4:1 can be added at a temperature of about 112-115°C under constant stirring with the temperature being maintained at 112°C for an hour. Vacuum can then be used to remove the formaldehyde. After completion of the reaction, the product obtained (PMIDA) can be isolated. [00021] In a specific embodiment, to prepare PMIDA using the method of the present invention, 60% slurry of hydrated lime is made in a glass reactor. 25% ammonia solution is added to it at temperature 35 ± 5°C for 1-2 hours with agitation. 70% solution of MCA is added slowly under temperature 50 ± 5°C. The temperature is maintained for 3 hours at 50-55°C. This step is in sharp contrast to the existing methods; particularly the one followed in US 4931585 where 7 hours maintenance is needed. Next, 37% HC1 is trickled in for 1 hour at 60-80°C. The temperature is maintained at 80-85°C for 1 hour. The reaction mixture obtained is cooled to 10-20°C. It is then crystallized for 2-3 hours and filtered. The product thus obtained is Imino diacetic acid hydrogen chloride (IDA-HCl). Compared to the 20 hours time that is taken to prepare IDA-HCl using existing process, particularly the one described in US 4931585, the process of the present invention takes only 14.5 hours, thus considerably reducing the time period to reach to get IDA-HCl.
[00022] An aqueous solution of IDA-HC1 is prepared and filtered to remove mechanical impurities to obtain 80% yield of the theoretical amount is obtained.
[00023] Next, the aqueous solution of IDA-HC1 is taken in a glass reactor fitted with a Dean-Stark (D/S) System. To the glass reactor, 37% HCl is added. This mixture is then heated with phosphorus acid in a molar ratio of 1.0-1.2:1 with azeotropic distillation and stirred at boiling point to remove water until the temperature reaches 112-115°C. Then aqueous solution of formaldehyde in the molar ratio of 1.0-1.4:1 is added at temperature 110-115°C for 4 hours and this temperature is maintained for 1-2 hours. The temperature is then brought down to 80°C followed by addition of water. At this temperature, un-reacted formaldehyde is removed under vacuum. The temperature is then brought down to 40°C and the reaction mixture is diluted with water and cooled at 8-10°C. The reaction mixture is crystallized for 2-3 hours and is filtered. [00024] The filtered material is given two rounds of washing with water at 45°C. The material is dried upto 100°C in fluid bed drier. The dried material is PMIDA and the purity obtained is 96-98% with 82% yield calculated on IDA-HC1 basis. Yield calculated to MCA basis is 65-68%. The total process time starting from IDA-HC1 to PMIDA is about 14 hours, which is again lesser than the 16.5 hours that is taken using the process described in US 4931585. Thus, in totality, the time cycle to prepare PMIDA from the process of present invention is 28.5 hours, whereas the same using existing methods, and particularly the one described in US 4931585 is 36 hours. A net saving of 7.5 hours per cycle of PMIDA synthesis is a marked difference and of immense industrial application.
[00025] In an embodiment of the present invention, to the aqueous IDA-HC1 solution, phosphorus acid is added and then D/S method is applied to remove the water azeotropically to bring the temperature to 115-116°C. Then, formaldehyde solution is added to the reaction mixture. Due to the D/S method, excess water comes out which helps in crystallizing the final product and thus the crystallization time is substantially reduced. This is a significant advantage
over the existing art which depends on evaporation and hence the time cycle is substantially increased.
[00026] The present invention uses vacuum to remove the unreacted formaldehyde which is in contrast to no such use in any of the existing methods. Timely removal of the un-reacted formaldehyde gives the process of the present invention its most crucial advantage. In the synthesis of PMIDA according to the process disclosed in US 4931585, 2.5% formaldehyde remains unreacted in the PMIDA. When Glyphosate is prepared from this PMIDA and further formulated into 41% SL, the SL is not transparent and is hazy in appearance. In contrast, by virtue of the vacuum assisted removal of un-reacted formaldehyde in the process of present invention, the Glyphosate prepared from PMIDA obtained from the present invention, when formulated in 41% SL, is clear & transparent with no haziness. Figure 2 depicts a comparative snapshot of Glyphosate obtained after preparing it from PMIDA obtained using the process of the present invention (Fig 2a) vis-a-vis the existing method, particularly the method described in US 4931585 (Fig 2b). It is very evident that Glyphosate prepared from PMIDA obtained from the process of the present invention is clear, transparent and free of any haziness in appearance. [00027] Conventionally, preparation of PMIDA from IDA-HC1 involves using an autoclave and carrying out high pressure reactions that involve both time and risks associated with conducting high pressure reactions. The present invention does away with the use of autoclave. Instead, it uses a glass reactor fitted with a D/S system that not only saves time but also bypasses the use of a high pressure reaction condition.
EXAMPLES
EXAMPLE 1
[00028] 156 gm of hydrated lime was loaded in a 1000 ml reactor with agitation. 100 gm of water was added and agitated to make homogenous slurry. The temperature was brought to 30°C. 90 gm of 25% ammonia solution was
added slowly at 30-35°C in 1-1/2 hour. This temperature was maintained for 1 hour. 70% solution of MCA was prepared by taking 190 gm MCA in 80 gm of water. MCA solution was charged in additional funnel and added slowly in 3 hours controlling the temperature at 50-52°C. The temperature was maintained at 54-55°C for 3 hours with continued agitation. 400 ml of 37% HC1 is trickled in 1 hour at temperature 55-75°C. The temperature was maintained at 75-80°C for 1 hour. The reaction mixture was then cooled to 10°C and after stirring for 3 hours iminodiacetic acid hydrogen chloride (IDA-HCl) was filtered out. 200 gm of moist IDA-HCl was obtained having 30% moisture. [00029] Thereafter, the IDA-HCl so obtained was dissolved in 200 ml of water to make an aqueous solution and filtered to remove the mechanical impurities. 2.7 gm of mechanical impurities was removed. The aqueous solution contained 138 gm of IDA-HCl which was 81.6% yield of theoretical amount.
[00030] The aqueous solution of IDA-HCl was taken in coolable and heatable 1 litre reactor equipped with a stirrer, thermometer and D/S system. 95 gm of phosphorus acid was added, 70 gm of 37% HC1 was then added by measuring flask to control temperature below 80°C. Temperature was increased to remove water through azeotropic distillation. At temperature 115°C, 120 gm of 37% formaldehyde solution was trickled in for 6 hours at 110-112°C. The temperature was maintained at 110-112°C for 2 hours. [00031] The reaction mixture was then cooled to 40°C and unloaded in neutralizing kettle having 100 ml water. The temperature was further cooled to 8°C and maintained for 2 hours for crystallization. The material was filtered. Precipitated crystals of PMIDA was given two washing with water and dried. 158 gm of PMIDA was obtained with purity of 96.5%. Yield of the PMIDA was 85% and yield calculated to MCA is 69%.
ADVANTAGES OF THE INVENTION
[00032] The present invention provides a process to prepare PMIDA in a
significantly reduced time cycle.
[00033] The present invention provides a process to prepare PMIDA
wherein no pollution causing side products are released.
[00034] The present invention provides a process to prepare PMIDA
wherein the haziness in the Glyphosate prepared from the PMIDA of the
present invention is substantially reduced.
[00035] The present invention provides a process to prepare PMIDA
wherein there is no evolution of ammonia.
[00036] The present invention provides a process to prepare PMIDA
wherein no high pressure reaction condition is used.
[00037] The present invention provides a process to prepare PMIDA
wherein each step of the process undergoes completion of reaction.
[00038] The present invention provides a process to prepare PMIDA
wherein the yield and purity of the PMIDA is not compromised.

We claim,
1. A process to prepare N-phosphono-methyl amino diacetic acid,
comprising the steps of,
(a) reacting hydrated lime with aqueous ammonia and mono
chloro acetic acid solution to obtain imino diacetic acid calcium salt;
(b) heating said imino diacetic acid calcium salt with
hydrochloric acid to get imino diacetic acid hydrogen chloride;
(c) reacting said imino diacetic acid hydrogen chloride with
phosphorus acid and formaldehyde; and
(d) obtaining N-phosphono-methyl amino diacetic acid by
cooling and crystallizing reaction mixture obtained in step (c); wherein,
step (c) further comprises azeotropic distillation to remove water.
2. The process as claimed in claim 1, wherein step (a) comprises first reacting said hydrated lime with said aqueous ammonia and subsequently adding said mono chloro acetic acid solution to reaction mix.
3. The process as claimed in claim 1, wherein unreacted formaldehyde from step (c) is removed under vacuum.
4. The process as claimed in claim 1, wherein said azeotropic distillation is carried out after reacting said imino diacetic acid hydrogen chloride with said phosphorus acid and before reacting with said formaldehyde.
5. The process as claimed in claim 1, wherein said azeotropic distillation is carried out in a glass reactor fitted with a Dean-Stark (D/S) System.
6. The process as claimed in claim 1, wherein said N-phosphono-methyl amino diacetic acid is further used to prepare N-phosphonomethylglycine.
7. The process as claimed in claim 6, wherein said N-phosphonomethylglycine is substantially free of haziness in appearance.
8. The process as claimed in claim 1, wherein total time cycle for said process is not more than 30 hours.
9. The process as claimed in claim 1, wherein said process is substantially free of any high pressure employing step.
10. The process as claimed in claim 1, wherein said imino diacetic acid hydrogen chloride obtained in step (b) is filtered to remove mechanical impurities.

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Patent Number

279045

Indian Patent Application Number

2093/DEL/2010

PG Journal Number

02/2017

Publication Date

13-Jan-2017

Grant Date

09-Jan-2017

Date of Filing

03-Sep-2010

Name of Patentee

INSECTICIDES INDIA LIMITED

Applicant Address

401-402, LUSA TOWER, AZADPUR COMMERCIAL COMPLEX, DELHI-110033

Inventors:

#	Inventor's Name	Inventor's Address
1	KUMAR, MUKESH	401-402, LUSA TOWER, AZADPUR COMMERCIAL COMPLEX, DELHI-110033
2	SINGHAL, BHIM SINGH	401-402, LUSA TOWER, AZADPUR COMMERCIAL COMPLEX, DELHI-110033

PCT International Classification Number

C07C 1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA