JP2533006B2 - Method for producing N-phosphonomethylglycine - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to N which is useful as a herbicide.
-A novel method for producing phosphonomethylglycine and its salts .

[0002]

BACKGROUND OF THE INVENTION N-phosphonomethylglycine and its salts effective as agricultural chemicals (sodium salt, ammoniu)
Salts, isopropylamine salts, dimethylamine salts, tris
Methylsulfonium salts and the like) are compounds that are biodegradable and are effective as herbicides even when used in a small amount, and are widely used (US Pat. No. 3,799,759, Yoroshi).
Patent Application Publication No. 369,076) . Although many methods for producing N-phosphonomethylglycine are known, several methods for producing N-phosphonomethylglycine using aminomethylphosphonic acid as a raw material are also known as techniques related to the present invention.

For example, a method in which aminomethylphosphonic acid is added to an aqueous glyoxal solution at 40 to 45 ° C. and then heated (Japanese Patent Laid-Open No. 62-61992), the same reaction is carried out using aminomethylphosphonic acid and glyoxal as raw materials in the presence of sulfur dioxide. Method (European Patent No. 81459 and US Patent No. 4369142), a method of reacting aminomethylphosphonic acid with glyoxylic acid and then reducing with hydrogen in the presence of a palladium catalyst (European Patent 186648), aminomethylphosphonic acid and chloro. A method of heating acetic acid to about 80 to 120 ° C. in the presence of an acid acceptor such as sodium hydroxide (Polish Patent 120759 and Spanish Patent 5
04479), a method in which aminomethylphosphonic acid and diethyl malonate bromide are reacted under alkaline conditions and then hydrolyzed under sulfuric acid acidity (Spanish Patent No. 545456) is known. It is not always satisfactory because a difficult gas is used, the reaction operation is complicated, or the reaction yield is not sufficient.

Further, US Pat. No. 4,221,583 discloses that aminomethylphosphonic acid is reacted with formaldehyde in the presence of an alkali necessary to form a monosalt of aminomethylphosphonic acid, and aminomethylphosphonic acid is converted into an N-methylol compound. , A method for producing N-phosphonomethylglycinonitrile or a monosalt thereof by reacting potassium cyanide between pH 7 and 10 is disclosed. Further, it is described in the patent that N-phosphonomethylglycine can be obtained by hydrolyzing N-phosphonomethylglycinonitrile synthesized by the method. However, according to the description of the examples of the patent, N-phosphonomethylglycinonitrile is as low as 66% even when the highest yield is obtained, and in order to increase the conversion rate of aminomethylphosphonic acid, For methylphosphonic acid,
A large excess of 2.4 times the molar amount of potassium cyanide is required. Further, the yield of hydrolysis of N-phosphonomethylglycinonitrile is 90% at the maximum according to the examples. Therefore, the yield of N-phosphonomethylglycine based on aminomethylphosphonic acid is 60%. It will be about.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing N-phosphonomethylglycine which uses aminomethyl sulfonic acid as a raw material and is easy to operate and excellent in yield. .

[0006]

Means for Solving the Problems The present inventors have conducted various studies on a method for producing N-phosphonomethylglycine using aminomethylphosphonic acid. As a result, aminomethylphosphonic acid and glycolonitrile were replaced with aminomethylphosphonic acid. When reacting by adding an amount of alkali metal hydroxide capable of converting the acid to a dialkali metal salt, and then performing hydrolysis, use an amount of alkali metal hydroxide sufficient to neutralize the carboxylic acid formed. It was found that N-phosphonomethylglycine can be obtained in an extremely high yield by the method and completed the present invention.

That is, according to the present invention, aminomethylphosphonic acid and glycolonitrile are reacted in the presence of an alkali metal hydroxide at a temperature of 60 ° C. or lower, and then a sufficient amount of carboxylic acid is neutralized. The present invention provides a method for producing N-phosphonomethylglycine, characterized by further adding an alkali metal hydroxide and performing hydrolysis.

The present invention will be described in more detail.
In the reaction of aminomethylphosphonic acid with glycolonitrile, alkali metal hydroxide is added because aminomethylphosphonic acid is an amphoteric compound having an amino group and a phosphono group in the same molecule, and aminomethylphosphonic acid and glycolonitrile. This is because it is necessary that the amino group of aminomethylphosphonic acid is not in the ionic form in order for nitrile to react. That is, when at least one of the two acidic hydroxyl groups of aminomethylphosphonic acid is not neutralized with an alkali metal hydroxide, a part of the amino group of aminomethylphosphonic acid or a general amphoteric compound is used. Almost all become so-called zwitterions in the form of ions and do not react with glycolonitrile. As can be seen from this, it is desirable that the alkali metal is added in an amount of twice or more moles of alkali metal hydroxide with respect to aminomethylphosphonic acid. The value of the molar ratio of alkali metal to aminomethylphosphonic acid is not so strict, but when alkali metal hydroxide is added in excess and a substantial amount of substantially free alkali metal hydroxide is present, glycolonitrile Decomposition causes a decrease in yield, and when the amount of alkali metal hydroxide is small, the reactivity of aminomethylphosphonic acid decreases due to the reason described above, which also causes a decrease in yield. Therefore, it is preferable to add the alkali metal hydroxide in the range of 1.5 to 2.5 times, more preferably 1.8 to 2.2 times the molar amount of the aminomethylphosphonic acid, which is increased or decreased by about 0.5 mol based on the 2-fold molar amount. The alkali metal hydroxide used here is preferably sodium hydroxide or potassium hydroxide.

Regarding the amount of glycolonitrile to be subjected to the reaction, if it is within the above-mentioned quantitative relationship between the alkali metal hydroxide and aminomethylphosphonic acid, the theoretical amount, that is, equivalent to aminomethylphosphonic acid, is obtained. Molar is preferred. This value is also not so strict, but when glycolonitrile is large relative to aminomethylphosphonic acid, an excess amount of glycolonitrile causes a side reaction, and when it is small, relatively expensive aminomethylphosphonic acid is generated. It is desirable to avoid both because they remain unreacted. For this reason, glycolonitrile is added in an amount of 0.5 to 1.5 times the molar amount of aminomethylphosphonic acid based on the equimolar amount, more preferably 0.8 to 1.5 times by mol.
It is preferred that the reaction is carried out in the range of about 1.2 times by mole.
Since the pH of the reaction solution varies depending on the charged concentration of the raw materials and the reaction temperature, it cannot be generally stated, but when the reaction is carried out under the above conditions, the pH of the reaction solution becomes 10.5 or more.

The reaction system is not particularly limited, but usually, an aqueous solution of glycolonitrile is added dropwise to a stirred mixed aqueous solution of aminomethylphosphanoic acid and an alkali metal hydroxide, and the reaction is continued by further stirring. To complete. The reaction temperature of aminomethylphosphonic acid and glycolonitrile is preferably 60 ° C. or lower. If the temperature is too high, side reactions occur and the yield decreases. On the other hand, if the temperature is too low, the reaction becomes slow, and therefore, the temperature is usually 0 to 60 ° C, preferably 10 to 40 ° C. Further, the time required for the reaction is about 30 minutes to 3 hours, although it depends on the temperature.

The amount of the alkali metal hydroxide added at the time of hydrolysis needs to be sufficient to neutralize the carboxylic acid produced by the hydrolysis. Hydrolysis does not proceed when the amount of alkali metal hydroxide is small, and when it is added in an excessive amount, the amount of salt produced increases during the isolation of the product N-phosphonomethylglycine by acid precipitation. Therefore it is desirable to avoid it. The temperature of this hydrolysis reaction is not particularly limited, but it is usually performed in the range of 60 ° C. to the boiling point of the reaction solution. The reaction time depends on the temperature, but is usually about 1 to 3 hours. When the reaction is carried out below the boiling point of the reaction solution, it is desirable to boil the reaction solution at least once before the completion of the reaction in order to remove ammonia generated by the hydrolysis reaction.

From the thus obtained reaction solution, N-phosphonomethylglycine can be easily isolated by acid precipitation after appropriately diluting or concentrating the reaction solution. Alternatively, other conventional means such as an ion exchange resin may be used alone or in combination for isolation and purification, or may be further purified by recrystallization. Further known methods such as sodium
Salt, ammonium salt, isopropylamine salt, dimethyl
Derives to salts such as amine salts and trimethylsulfonium salts
Can be

[0013]

According to the method of the present invention for reacting aminomethylphosphonic acid and glycolonitrile under the above-mentioned conditions,
N-phosphonomethylglycine or
Can obtain its salt . That is, the conversion rates of aminomethylphosphonic acid and glycolonitrile were both 95
%, And the selectivity for N-phosphonomethylglycine reaches 95% or more.

US Pat. No. 42215 described in the prior art section.
In the example of the specification of No. 83, aminomethylphosphonic acid and formaldehyde are added to 1.
After reacting in the presence of 3-fold molar sodium hydroxide to form the N-methylol form of aminomethylphosphonic acid, 1.1-fold molar potassium cyanide is added to aminomethylphosphonic acid while maintaining the pH at 8-9 with an aqueous hydrochloric acid solution. Although it is described that the conversion rate of aminomethylphosphonic acid is 80%, compared with this method, the advantage of the method of the present invention using glycolonitrile without passing through the N-methylol form of aminomethylphosphonic acid is advantageous. That is clear.
Further, a pH of 8 to as described in the above-mentioned U.S. Pat.
Under the reaction conditions of 9, even if glycolonitrile was produced from unreacted formaldehyde and sodium cyanide existing in the system, it was clear that the reaction with aminomethylphosphonic acid did not occur for the reason described above. Therefore, under the condition that the reaction of aminomethylphosphonic acid and glycolonitrile is sufficient, that is, 1.5 to 2.5 times mol of alkali metal hydroxide with respect to aminomethylphosphonic acid is added and pH is 10.5 or more. Below, the method of the present invention of reacting glycolonitrile with aminomethylphosphonic acid can be said to be a unique method which cannot be predicted from the description of said US patent.

[0015]

EXAMPLES Hereinafter, a representative example of the method for producing N-phosphonomethylglycine according to the present invention will be specifically described. However, these are examples for facilitating the understanding of the present invention, and it goes without saying that the present invention is not limited to this, and should not be construed as being limited thereto.

Example 1 A 200 ml four-necked flask was equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser. 50g water, 16.7g
48% aqueous sodium hydroxide solution (200 mmol), 11.1
A mixture of g of aminomethylphosphonic acid (100 mmol) was added and stirred. PH at this time (20 with a buffer of pH 7)
Measured with a calibrated pH meter at ° C. The same applies hereinafter) was 13.1. The reactor was cooled in ice water, and 14.3 g of a 40% glycolonitrile solution (100 mmol) was added dropwise over 30 minutes while keeping the reaction solution at 5 ° C or lower. After completion of the dropping, the mixture was stirred at 5 ° C or lower for 30 minutes, returned to room temperature and stirred for 1 hour.
The pH at this time was 11.0. Then 48% of 8.4 g
An aqueous solution of sodium hydroxide (100 mmol) was added, and the mixture was heated under reflux for 2 hours. When the liquid after completion of the reaction was analyzed by HPLC, it contained 94 mmol of N-phosphonomethylglycine. The reaction yield was 94% based on the starting material aminomethylphosphonic acid and glycolonitrile. The reaction solution was neutralized to pH 2 with concentrated hydrochloric acid and then left overnight to crystallize N-phosphonomethylglycine. The crystallized N-phosphonomethylglycine was filtered off. Weight after washing and drying is 13.4
and the purity determined by HPLC was 98%.
The yield from the starting materials aminomethylphosphonic acid and glycolonitrile was 78%.

Example 2 The procedure of Example 1 was repeated, except that the temperature of the reaction solution at the time of dropwise addition of glycolonitrile was maintained at about 20 ° C., and after the completion of dropping, the mixture was stirred at about 20 ° C. for 1 hour. The liquid after the reaction is
As a result, the reaction yield of N-phosphonomethylglycine was 95% based on the starting material aminomethylphosphonic acid and glycolonitrile.

Example 3 The procedure of Example 1 was repeated, except that the temperature of the reaction solution at the time of dropwise addition of glycolonitrile was maintained at about 60 ° C., and after the completion of dropping, the mixture was stirred at about 60 ° C. for 1 hour. When the liquid after completion of the reaction was analyzed by HPLC, the reaction yield of N-phosphonomethylglycine was 72% based on the starting material aminomethylphosphonic acid and glycolonitrile.

Example 4 In an apparatus similar to that of Example 1, 50 g of water, 8.4 g of 48%
A mixed solution of an aqueous sodium hydroxide solution (100 mmol) and 11.1 g of aminomethylphosphonic acid (100 mmol) was added and stirred. The pH at this time was 9.7. Cool the reaction solution in ice water and keep the reaction solution below 5 ° C.
A glycolonitrile aqueous solution (100 mmol) was added dropwise over 30 minutes. After completion of the dropping, the mixture was stirred at 5 ° C or lower for 30 minutes, returned to room temperature and stirred for 1 hour. The pH at this time was 9.5. HP
When analyzed by LC, the conversion rates of the raw material aminomethylphosphonic acid and glycolonitrile were 5% or less.

Next, while maintaining the reaction solution at 20 ° C., 8.4
A 48% aqueous sodium hydroxide solution (g) was added dropwise over 15 minutes. The pH after the dropping was 11.2. 20 as it is
Stirred at C for 1 hour. When this reaction solution was analyzed by HPLC, the conversion rates of the starting material aminomethylphosphonic acid and glycolonitrile were 95% or more. Then 8.4 g
48% aqueous sodium hydroxide solution (100 mmol) was added and the mixture was heated under reflux for 2 hours. When the liquid after the reaction was analyzed by HPLC, the reaction yield of N-phosphonomethylglycine was 91% based on the starting material aminomethylphosphonic acid and glycolonitrile.

Claims (4)

(57) [Claims] [Claim 1] After the aminomethylphosphonic acid and glycolonitrile was reaction in the presence of an alkali metal hydroxide,
N for a sufficient amount of alkali metal hydroxide to produce carboxylic acids to neutralize characterized by pressurized forte hydrolysis
-A method for producing phosphonomethylglycine or a salt thereof . 2. Aminomethylphosphonic acid and glycolonite
Ril in the presence of an alkali metal hydroxide at a temperature below 60 ° C
The N-phosphonomethylglycol according to claim 1, which is reacted with
A method for producing Shin or a salt thereof. 3. The method for producing N-phosphonomethylglycine or a salt thereof according to claim 1, wherein the reaction between aminomethylphosphonic acid and glycolonitrile is carried out at pH 10.5 or higher. 4. Aminomethylphosphonic acid and 0.5 to 1.5 times mol of glycolonitrile with respect to aminomethylphosphonic acid and 1.5 to 1.5 with respect to aminomethylphosphonic acid.
2.5 moles of claim 1 is reacted in the presence of an alkali metal hydroxide N--phosphonomethylglycine also
Is a method of producing the salt .