JPS5822102B2 - Purification method for dinitroanilines - Google Patents

Abstract

Hydrochloric acid in either 20-38% concentration or gaseous form is effective is removing nitrosamines from a number of dinitroaniline herbicides.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying dinitroanilines, and more specifically, a novel purification method for dinitroanilines for removing nitrosamines contained as impurities in dinitroaniline derivatives useful as agricultural chemicals, especially herbicides. Regarding the law.

The method of the present invention aims to purify dinitroanilines by removing nitrosamines from dinitroanilines using hydrochloric acid or hydrogen chloride gas.

Compounds belonging to the dinitroanilines class include many commercially available herbicides.

Recently, a thermal energy analyzer (Thermal ener
A new analytical instrument known as a chromatography analyzer (TEA) was developed (Journal of Chromatography).
tography) Volume 107, page 351 (1975) and its cited references; and N-Nitroso Compounders in the Environment ((N-Nitr
oso Compounds in the Envi
roment): IARC Scientific Publications (Lyon, Int.
ernational Ag-ency for R
Published by e5earch on Cancer
t-1fic Publication) #9
(] 974), p. 40).

TEA is particularly used for the analysis of nitroso (-No) groups,
Much lower concentrations (i.e. 0.02
It is possible to detect nitroso groups (ppm concentration).

By analyzing various dinitroanilines with TEA, it has been revealed that some dinitroanilines contain trace amounts of nitrosamines.

Since certain nitrosamines have been shown to be carcinogenic to animals, the presence of nitrosamines, even in trace amounts, is considered undesirable.

The present invention is intended to remove nitrosamines from dinitroanilines.

The chemistry of aliphatic N-nitrone amines can be found in Ru5sian Chemical Reviews.
40 (1) pp. 34-50 1971
It was reviewed in 2010 (in English).

This document describes the reaction between nitrosamines and inorganic acids (see pages 41 et seq.).

The reaction itself between hydrochloric acid and hydrogen chloride gas and nitrosamines is also described.

The kinetics and mechanism of the conversion of nitrosamines to the corresponding simple amines by strong mineral acids have been reported (
Chem 1cke Listy
51, pp. 937-945 (1957)).

A method for producing di-n-propylamine by treating nitrosodi-n-propylamine with hydrogen chloride gas is known (Annaren der Hemi Nistos-Liebitsch).
Lieb, Ann, ) Vol. 345, pp. 277-288 (1
906)).

However, none of the above documents describes the use of hydrogen chloride (gas or acid) to remove nitrosamines from the specific dinitroanilines used in the present invention.

Furthermore, it was unexpected that hydrogen chloride (gas or acid) could be used to remove ditron amine impurities in dinitroanilines so effectively.

By the method of the present invention, the amount of nitrosamines present in dinitroaniline can be significantly reduced.

The present invention provides (1) general formula (■) containing nitrone amine impurities: [wherein R1 is H, C, ~C5 alkyl, monohalogen (C, ~C5) alkyl, R2 is C1~ C5 alkyl, monohalogen (C1-C6) alkyl, 01-
C5 alkenyl or C3-C5 cycloalkyl (C1
~C3) Alkyl; R3 is R1 no Roken, 01~C3
Alkyl or amino; R4 is C1-C5 alkyl, trifluoromethyl, sulfonamide or.

represents methylsulfonyl], (a) in the liquid phase, (b) after contacting with 20-38 dihydrochloric acid or hydrogen chloride gas reagent until the concentration of the nitrosamine impurity is reduced, (2) A method for purifying dinitroanilines is provided which comprises recovering dinitroaniline.

The present invention provides for contacting nitrosamine-containing dinitroanilines with a reagent selected from the group consisting of hydrochloric acid and hydrogen chloride gas until the nitrosamine concentration is reduced in the liquid phase, and then
The present invention is directed to a method for purifying dinitroanilines comprising recovering dinitroaniline.

The chemical names of typical dinitroanilines that can be purified by the purification method of the present invention are shown below (along with the general groups used).

(1) 4-) IJ fluoromethyl-2,6-sinitro N,N-di-n-propylaniline (tri-fluralin): (2) 4-
Improvir-2,6-sinitro Ns N-synfuroviraniline (inproparin (1sopropal)
in ) ) : (3) 4-trifluoromethyl-2
,6-sinitroN-n-7"f-N-ethylaniline (benef-in): (4) 4-trifluoromethyl-2,6-dinitro-N-ethyl-N
- methallylaniline (ethalfluralin)
(5) 4-tert-
Butyl-2,6-sinitro N-5ec-butralaniline (butralin): (6
)3.4-dimethyl-2,6-sinitro N-(1-ethylpropyl)aniline (tendimethalin
(7) 4-trifluoromethyl-2,6-dinitro-N-propyl-N-(2
-J'loloethyl)aniline (flufloralin (flu
chloralin) ): (8) 4-trif/lz
Oromethyl-2,6-sinitro N-propyl-N-(
cyclopropylmethyl)aniline (profluralin (p
rofluralin)): (9) 4-)lifluoromethyl-2,6-sinitro-3-amino-N,
N-diethylaniline (dinitramine)
(10) 4-)Lifluoromethyl-2,6-sinitro-3-chloro-N,N-diethylaniline (citramine)
) production intermediate); (11) 4-methyl-2,6
-Sinitro N, N-bis(2-chloroether)aniline; (12) 4-sulfamoyl-2,6-sinitro N, N-di-n-propylaniline (Oryzalin (
σμalin)L(13) 4-(methylsulfonyl)
-2,6-dinitroNp Nln 7'ropylaniline to tralin (ni tral in) L The dinitroanilines preferably purified in the present invention are trifluralin, inproparin, benefine and etalfluralin.

Generally, dinitroanilines, such as trifluralin, are produced by the following reaction route.

Small amounts of nitrogen oxides remaining as by-products of the nitration reaction may react with some of the amines in the amination reaction to form small amounts of nitrosamine impurities, which may appear in the final dinitroaniline product. It is believed that there is.

For this reason, it is assumed that the nitrosamine impurities that may appear in the product are nitroso derivatives of the alkylamines used in the amination.

However, it is assumed that trace amounts of other nitrone amines may also be produced.

It is desirable to remove nitrosamines regardless of the cause or type of by-product, and the method of the present invention satisfies this objective.

Although the reaction mechanism in the purification method of the present invention has not been definitively elucidated, it is thought that hydrogen chloride denitrifies the nitrosamine and converts it to other species, perhaps the hydrochloride of the corresponding amine. .

Additionally, although not yet proven, it is believed that the formation of nitrosyl chloride is possible as part of the denitrosation.

In any case, the real objective is to convert the undesired nitrosamines into water-soluble substances that can be easily removed from the dinitroanilines.

The purification process of the present invention substantially reduces the nitrosamine concentration regardless of its initial amount.

The method of the present invention can treat dinitroanilines containing nitrosamines at concentrations from about 10 ppm to several thousand ppm, and the nitrosamine concentration is generally reduced to about one-tenth or less of the initial amount.

In many cases, the nitrosamine concentration will be about 1 ppm or less.

Purification according to the invention is carried out in liquid phase.

In many cases of dinitroanilines, purification can be accomplished by heating the nitrosamine-containing dinitroaniline to or above its melting point and reacting it neat.

Further, the nitrosamine-containing dinitroanilines can be dissolved in a solvent to form a liquid phase.

Suitable solvents include alcohols such as ethanol, ketones such as acetone, and aliphatic and aromatic hydrocarbons.

Solvents with groups that react with hydrogen chloride must not be used.

For example, secondary and tertiary alcohols should not be used as they react with hydrogen chloride.

The reagent used for purification is either hydrochloric acid or hydrogen chloride gas.

If hydrochloric acid is used, it must contain at least 20% hydrogen chloride by weight.

Better results are obtained with more concentrated hydrochloric acid, for example containing 33-38% by weight.

Hydrogen chloride gas can also be used and is preferred in the present invention.

In the case of etalfluralin, hydrogen chloride gas is preferred over hydrochloric acid to avoid addition to the methallyl double bond.

The amount of hydrochloric acid or hydrogen chloride gas used is not critical, as long as it reduces the initial amount of nitrosamine.

The amount of hydrochloric acid is 0.04g per 100g of dinitroaniline.
was found to be sufficient.

Similarly, the amount of hydrogen chloride gas is 100g of dinitroaniline.
It has been found that 250 m1 is sufficient for this purpose.

Even larger quantities (3 times) are sufficient to purify, but this does not result in any particular benefit.

On a laboratory scale, it is sufficient to add hydrogen chloride gas per 100 g of dinitroaniline at a rate of 5 to 90 ml/min.

Preferably, hydrogen chloride gas is added at a rate of 8 to 121 rL/min per 7100 g of dinitroanili.

The reaction can be carried out over a wide temperature range.

Since there is a high risk of side reactions occurring at high temperatures, the temperature should be set at 140℃.
The temperature is preferably 100°C or lower.

When carrying out the reaction in a solvent, the satisfactory temperature range varies widely for the same solvent, but is generally carried out between room temperature and 100°C.

Net purification is carried out at a temperature above the melting point of the particular dinitroaniline.

When purifying trifluralin (melting point 54-55 °C), isoproparin (melting point 30 °C), benefin (melting point 65-66 °C) and etalfluralin (melting point 57-59 °C), the processing temperature is 70-90 °C. Good results are obtained.

The reaction can be carried out at normal pressure or higher pressure.

Using hydrogen chloride gas at 70-90℃, gas pressure of 1-1
It is advantageous to carry out the reaction at 0 p81g, preferably from 3 to 5 psig.

The presence of water in the nitrosamine-containing dinitroaniline in the purification process of the invention has a detrimental effect.

Particularly when hydrogen chloride gas is used, hydrogen chloride on the plate is required for denitrosation.

Therefore, when using hydrogen chloride gas, the nitrosamine-containing dinitroaniline should be kept relatively dry, e.g.
．． It is preferable to keep it at 2% or less.

The rate of purification according to the present invention varies depending on the nitrone amine concentration, temperature, hydrogen chloride reagent form and addition rate, and other conditions.

The progress of nitrosamine removal can be followed by gas chromography or fflEA analysis.

Denitrosation is generally complete within one hour.

When the reaction is examined over time, an initial decrease in the amount of nitrosamines is observed, and thereafter, if the reaction time is increased, the amount of nitrosamines may increase slightly in some cases.

This is believed to be due to the fact that (1) dinitroaniline and (2) the putative alkylamine denitrosation product may be left in the reaction state for longer periods of time to form additional nitrone amines.

Therefore, it is desirable to shorten the reaction time.

The reaction mixture is worked up in the usual manner.

Preferably, the water wash is followed by a weak basic wash to ensure that traces of hydrogen chloride are removed.

A reservoir must also be provided to remove gases produced by the denitrosation reaction.

Next, the purification method of the present invention will be explained in more detail with reference to Examples.

In the examples, nitrosamine concentrations are determined by gas chromatography with a sensitivity to about 0.5 unless otherwise specified.

Undetectable (hereinafter referred to as N, D) indicates that the nitrosamine content is about 0-5 ppm or less.

Hewlett-Pac
A model 5711A gas chromatograph was used, but any gas chromatograph apparatus equipped with a flame ionization detector can be used.

The column is a 4-foot x 1/8 inch (inner diameter) glass coil, and the packing material is 100/120 mesh AW.
-DMC8・Chromosorb
) Three-acting carbow wax with G as a carrier
ax) 20 M is used.

The operation is carried out at 100°C.

After eluting the nitrosamine peak, the column was
Heat to 0'C and hold at that temperature for about 15 minutes.

The helium flow rate is 60 ml/min.

The standard sample used has approximately the same concentration as the expected nitrosamine concentration in the sample.

Standard samples and measurement samples are prepared in methylene chloride.

In Examples in which TEA analysis was performed, that fact is stated.

Analysis using this method is basically described in the Journal of Chromatography (Journal of Chromatography).
109, p. 271 (197
It was carried out in the same manner as described in 2005).

As is clear from the gist of the present invention, the above analysis method is considered to detect nitrosamine concentrations up to 0.05 ppm.

If no nitrosamines are detected in the TEA analysis of the samples described below, they are marked as N or D.

In Example 2, analysis by gas chromatography/mass spectrometry was performed.

In this method, the sample is dissolved in benzene and purified by chromatography on an alumina column using benzene as eluent.

The nitrosamine content in the sample was determined by the 5-factor carbo wax (C
arbowax) LKB-9 with 20 M column
Measured using a 000 gas chromatograph/mass spectrometer.

Adjust the column temperature to 130°C and hold this temperature for 2 minutes for the nitrosodi-n-propylamine.

Magnetic force is applied to molecular ions (m/e2 130), and the resulting ion flow is recorded and detected on recording paper.

Example 1 Removal of nitrone amine from trifluralin (using 20% hydrochloric acid, solvent ethanol): 30 g of trifluralin containing 256 ppm of nitrone amine was mixed with 20 ml of 20% hydrochloric acid and 5 ml of ethanol.
Mix with.

Heat the mixture to 90°C and stir at 90°C for 3 hours.

Separate the layers and wash the organic layer with 10% sodium hydrocarbon.

The purified product was analyzed and no nitrosamines were detected.

Example 2 Removal of nitrosamines from trifluralin (hydrogen chloride gas, using benzene as solvent) 10 g of trifluralin containing 480 ppm of nitrosamines are dissolved in 200 ml of benzene and the solution is stirred and heated to reflux temperature (80° C.).

Hydrogen chloride gas is passed continuously through the solution for 1 hour under reflux.

The reaction mixture is cooled slightly and washed twice with the same volume of water.

Separate the benzene layer, dry with anhydrous magnesium sulfate,
After passing through the ocean, benzene is distilled off using a rotary evaporator.

The nitrosamine content of the treated trifluralin was analyzed by gas chromatography/mass spectrometry.

Nitrosamines were shown to be below lppm.

Example 3 Removal of nitrone amines from trifluralin (using hydrogen chloride gas) 50 g of neat trifluralin is heated to 70°C.

Hydrogen chloride gas is bubbled through at a rate of 3-12 m/min and samples are taken at 0, 30 and 60 minutes.

After each sample is washed with a 10% sodium carbonate solution and dried, it is analyzed for nitrosamine content.

Results (Nitrosamine concentration at sample collection time (minutes)
ppm) as shown below for 20 minutes - 32.6 ppm: 3
0 minutes - 2,9 ppm: 60 minutes - N, D,.

Example 4 Removal of Nitrosamines from Benefin (using 38% Hydrochloric Acid) Benefin 1 containing 130 ppm Ninitrosamine
Heat 5I to 70°C.

1.5 g of concentrated (38%) hydrochloric acid are added and the reaction mixture is stirred for 15 minutes.

Separate the organic layer and wash with IJ solution.

The nitrosamine content in the treated product was 17 ppm.

Example 5 Nitrosamine removal from Benefin (using hydrogen chloride gas) Benefin 2 containing 130 ppm of Ninitrosamine
Heat 5g to 70°C.

Hydrogen chloride gas is bubbled through at a rate of 8-12 ml/min.

Samples are taken after 10, 20 and 30 minutes.

After washing each sample with a 10% sodium carbonate solution, the nitrone amine content is analyzed.

Results (Nitrone amine concentration at sample collection time (minutes)
ppm) as follows = 10 minutes - 65 ppm: 20 minutes - 3
8 pprr &) Example 6 Removal of nitrosamines from etalfluralin (using hydrogen chloride gas): 100 g of monoethalfluralin is heated to 70°C.

Hydrogen chloride gas is bubbled through at a rate of 90 ml and 11 minutes.

Samples are taken periodically and each sample is washed with 2 ml of 10% sodium carbonate solution and, after drying, analyzed for nitrosamine content.

Results (Nitrosamine concentration at sample collection time (minutes)
ppm) as shown below for 10 minutes - 10,2; 15 minutes - N, D
,;99m 30 minutes-N,D, ;60 minutes-N,D,.

Example 7 Nitrosamine Removal from Trifluralin (Rapid Addition of Hydrogen Chloride Gas) Neat trifluralin 51 is washed with water for 30 minutes and then air dried for 30 minutes.

Next, hydrogen chloride gas was bubbled through at 70° C. at a rate of 35 ml/min.

Samples are taken at 0, 15, 30 and 60 minutes.

After washing each sample with 10% IJum, analyze for nitrosamine content.

Results (Nitrosamine concentration at sample collection time (minutes)
ppm)) for the following 20 minutes - 9.3ppm: 15
min-1 ppm or less; 30 min-1 ppm or less; 60 min-1
Less than ppm.

Example 8 Removal of nitrosamines from trifluralin (using hydrogen chloride gas, influence of water addition) 100 g of neat trifluralin was heated to 70°C, and water 0, 5
Add ml.

Hydrogen chloride gas is then bubbled through at a rate of 8 ml/min.

Samples are taken periodically and each sample is washed with a 10% sodium carbonate solution and, after drying, analyzed for nitrosamine content.

Results (Nitrosamine concentration at sample collection time (minutes)
ppm) is shown below.

0 min-27ppm; 10 min-14ppm: 20 min-6,
8 ppm; 30 minutes - 3,2 ppm: 45 minutes - N, D.

Example 9 Removal of nitrosamines from trifluralin (prolonged use of hydrogen chloride gas) 100 g of neat trifluralin is heated to 70°C.

Hydrogen chloride gas is bubbled through at a rate of 8 to 12 d/min.

Samples are taken every 2 hours. After each sample is washed with 10% sodium carbonate and dried, it is analyzed for nitrosamine content.

The results (nitrosamine 78 degrees (ppm) at the time of sample collection (hour)) are shown below: 20 hours - 48 ppm: 2 hours - N, D,; 4 hours - N, D,; 6 hours - N, D,; 8
Time - 1,3 ppmO Example 10 Nitrosamine removal from etalfluralin (using 38% hydrochloric acid) 85 g of etalfluralin containing 9 ppm of nitrosamines by knee TEA analysis are heated to 70°C.

15 g of concentrated (38%) hydrochloric acid are added and the mixture is stirred for 30 minutes.

Separate the layers and wash the organic layer with 15 mL of water.

Separate the layers again and wash the organic layer with 15 ml of water.

Dry the organic layer at 120°C for 15 minutes.

When the sample was analyzed with TEA, no nitrone amines were detected.

Example 11 Removal of Nitrosamines from Trifluralin (Rapid Addition of Hydrogen Chloride) Trifluralin 51 containing 18 ppm Ninitrosamines is heated to 70°C.

Bubble hydrogen chloride gas at a rate of 90ml/Z for 5 minutes.

Next, wash with 5 ml of 10% sodium carbonate and dry.

As a result of analysis, no nitrosamines were detected.

Example 12 Removal of nitrosamines from trifluralin (long-term reaction with 38% hydrochloric acid) 60 g of neat trifluralin is heated to 70°C.

Add 6 g of concentrated (38%) hydrochloric acid and stir the mixture.

Samples are taken periodically and analyzed for nitrosamine content.

The results (nitrosamine concentration (ppm) at the time of sample collection (time)) are shown below: 0 hours - 10 ppm: 0.5
Time - 1,4ppm: 1 hour - 1,5ppm: 2 hours -
1 ppm or less; 3.5 hours-1,4 ppm: 4 hours-1
・4ppm.

Example 13 Removal of nitrosamines from trifluralin (addition of hydrogen chloride gas at high temperature) Air was added to the surface of 100 g of neat trifluralin at 120°C for 3 hours.
Blow dry for 0 minutes.

Hydrogen chloride gas is passed at a rate of 12'I'ILlZ at 85°C.

After 20, 40, 60 and 90 minutes, sample 10.
Collect 9.

Each sample is washed with 5 TLl of 5% sodium carbonate solution and dried in a rotary evaporator at 90° C. for 15 minutes.

Results (Nitrone amine concentration at sample collection time (minutes)
ppm)) for the following 20 minutes - 11,1 ppm:
20 minutes - N, D, : 40 minutes - N, D,; 60 minutes - N, D
,;90 minutes-N,D,.

Example 14 Removal of nitrosamines from isoproparine (addition of hydrogen chloride gas under pressure) Hydrogen chloride gas was added to a xylene 10,100O solution of about 701 ni. Add.

Samples are taken periodically and each sample is washed with 5 parts of the sample volume of 5 part sodium carbonate solution.

Separate the layers and dry the organic layer at 60° C. for 10 minutes using a rotary evaporator.

The results of TEA analysis (nitrone amine concentration (ppm) at the time of sample collection (time)) are shown below for 10 hours-2
2ppm: 0.5 hours - 0.22ppm: 1 hour - 〇,
19ppm; 1.5 hours-0, 4ppm: 2 hours-0,
52ppm: 2.5 hours-0,40ppm; 3 hours-0
, 28 ppm; 3.5 hours - 0.24 ppm.

Example 15 Removal of nitrosamines from etalfluralin (using hydrogen chloride gas) 100 g of etalfluralin containing a total of 10.5 ppm of nitrosamine was heated to 70°C, and hydrogen chloride gas was removed by 8
Whip at a speed of 11 minutes.

Samples are taken periodically and analyzed for nitrosamine content by TEA.

Results (Nitrosamine concentration at sample collection time (minutes)
ppm)) as follows for 110 minutes - 10,9pprn:2
0 min-6,6ppm: 30 min-N, D; 40 min-N,
D.

Example 16 Removal of nitrosamines from trifluralin (using recycled 38% hydrochloric acid) 100 g of trifluralin containing 18 ppm of nitrosamines is heated to 70°C and 21 parts of 38% hydrochloric acid is added.

The mixture is stirred at 70°C for 30 minutes.

Next, each layer is separated, the organic layer is washed with 107 rLl of a 10% sodium carbonate solution, and then the nitrone amine concentration is analyzed.

The acid layer is saturated with hydrogen chloride gas, added to another 100 g of trifluralin, and used for reaction with nitrosamine.

The reaction conditions are the same as above (first recirculation).

The hydrochloric acid is recycled two more times.

The results (nitrone amine content of the samples) are shown below: Control sample (trifluralin starting material) - 18 ppm; first acid treatment - N, D,; first recycle - N, D,; second recycle - N, D, ; 3rd recirculation - N, D,.

Example 17 Removal of nitrosamines from trifluralin (using pressurized hydrogen chloride gas in a pilot plant): 210.0 kg of trifluralin was melted at 70° C. overnight (approximately 20 hours),
Pour into a still equipped with a 75-gallon glass tube.

This trifluralin is heated to 90° C. and hydrogen chloride gas is passed under pressure.

The reaction conditions are as follows.

Time Temperature HCl pressure Sample Nitrosamine□
No. Concentration (min) (psig) -□0 90
0 1 22ppm891 2
．． 5 2 37/16 90
2.5 3 N, D.

22 89 2.5 4 N,D.

39 90 2.5 5 N,D.

65 90 2.5 6 N, D
.

71 9.0 2.5 7 N,
D.

The reaction mixture was then neutralized with sodium carbonate and further samples were taken.

No nitrosamines were detected (total hydrogen chloride usage was 0.38 kg).

) Example 18 Removal of nitrosamines from trifluralin (using hydrogen chloride gas and solvent ethanol) Neat trifluralin 50m
Hydrogen chloride gas was bubbled through a mixture of 1 and 25 ml of ethanol at 70° C. at a rate of 12 ml/min.

Samples are taken after 30 minutes and 1 hour.

Each sample was evaporated for 15 minutes at 30°C using a rotary evaporator.
Next, wash and treat with 5 ml of IJum (5q/) carbonic acid.

Separate each layer and use a rotary evaporator to cool the organic layer at 90°C.
Evaporate for 5 minutes.

Results (Nitrosamine concentration at sample collection time (minutes)
ppm)) as follows: 0 min-44 ppm: 30 min-2
0 ppm: 60 minutes - 14 ppm 0 Example 1.9 Removal of nitrone amine from trifluralin (treated twice with 38% hydrochloric acid) 20 g of trifluralin containing 68 ppm of nitrone amine and 5 TL of 38% hydrochloric acid were mixed and treated at 70°C for 2 hours.
Stir for 0 minutes.

Separate each layer and add an additional 5 ml of 38% hydrochloric acid to the organic layer.

The reaction mixture is again stirred at 70° C. for 20 minutes.

Separate each layer and add the organic layer to 10ml of 10% sodium carbonate.
Wash with

The product is analyzed for nitrosamine content.

No nitrosamines were detected by gas chromatography or TEA.

Example 20 Removal of nitrosamine from dinitramine (using hydrogen chloride gas) 10 g of dinitramine containing 138 ppm of dinitrosamine was heated to about 110°C, and 35 m of hydrogen chloride gas was heated to about 110°C.
Add over 45 minutes at a rate of 1/min.

Collect 2g of sample (sample 1) and dilute the remaining hot liquid with 60ml of methylene chloride! Add gradually.

Add 15 ml of 10% sodium carbonate solution.

The organic layer was separated and the solvent was distilled off using a rotary evaporator at 45° C. for 15 minutes to obtain 8 g of a yellow solid (Sample 2).

Each sample is analyzed for nitrosamine content with TEA.

The results show the nitrosamine concentrations (ppm) as follows: Sample 1 - 0.2 ppm or less; Sample 2 - 0.2 ppm or less.

Claims (1)

[Scope of Claims] 1 General formula (■) containing nitrosamines as impurities [wherein R1 is H, C1-C5 alkyl or monohalogen (C, -C,)alkyl: R2UC0-C5 alkyl, Monohalogen (01-C5) alkyl Madadah C1-
C5) alkenyl: R3 represents H1 halogen, C0-C3 alkyl or amino: R4 represents C1-C5 alkyl or trifluoromethyl] A method for removing nitrosamines from dinitroanilines represented by in the liquid phase,
A method comprising recovering dinitroanilines after contacting them with a reagent selected from the group consisting of hydrochloric acid and hydrogen chloride gas to reduce the concentration of nitrosamines. 2. The method of claim 1, wherein the treatment temperature is between room temperature and 140°C. 3. The method according to claim 1, wherein the treatment temperature is between 70°C and 90°C. 4. The method according to any one of claims 1 to 3, wherein the molten dinitroanilines form a liquid phase. 5. The method according to any one of claims 1 to 3, wherein the treatment is carried out using a primary alcohol, a ketone, or an aliphatic or aromatic solvent. 6 Claim 1 in which the reagent is hydrochloric acid in units 33-38
5. The method according to any one of items 5 to 5. Claims 1 to 4, wherein the γ reagent is hydrogen chloride gas.
The method described in any of the paragraphs. 8. The method of claim 7, wherein the hydrogen chloride gas has a pressure of 1 to 10 psig. 9. The method of claim 8, wherein the hydrogen chloride gas has a pressure of 3 to 5 psig. 10 (1) Melted trifluralin and hydrogen chloride gas were heated at 70 to 90°C until the concentration of nitrosamines decreased.
, 2 to 5 psig, and then (2) recovering trifluralin. 11. Any one of claims 1 to 4, wherein (1) molten trifluralin and 38-group hydrochloric acid are brought into contact at 70 to 90°C until the concentration of nitrosamines is reduced, and then (2) trifluralin is recovered. The method described in.