CH640841A5 - PROCEDURE FOR THE PRODUCTION OF CHLORINE-BIS (ALCHYLAMINE) -S-TRIAZINE. - Google Patents

Description

The present invention relates to the preparation of clo-15 ro-bis (alkylamino) -s-triazines by means of a process which allows to eliminate, or at least substantially reduce, the formation of tris (alkylamino) -s-triazines.

Chlor-bis (alkylamino) -s-triazines are compounds that can be defined by the general formula:

20

gl

(THE)

ff

IT

25

R

1s

mSR

IT

<3

E4

30 where R1; R2, Rj, R4 independently represent hydrogen, an alkyl radical containing from 1 to 5 carbon atoms, or particular groups of a nature other than alkyl.

Chloro-bis (alkylamino) -s-triazines constitute pre-35 herbicides and the best known compounds belonging to this group are: 2-chloro-4-ethylamino-6-isopropylamino-s-triazma (Atrazine), 2-chlorine -4,6-bis (ethylamino) -s-triazine (Simazine) and 2-chloro-4,6-bis {isopropylamino) -s-triazine (Propazine). The herbicidal characteristics of these compounds, as well as 40 of other similar ones, are described in US patent 2,891,855.

The chloro-bis (alkylamino) -s-triazines are generally prepared from cyanuryl chloride by subsequent replacement of two chlorine atoms, as for example reported by W. Pearlman and C.K. Banks in J. Am. Chem. Soc. 70, 45 3726 (1948).

In practice we operate according to the general scheme:

(II)

c (

/ M

et et

R.

TO

+ + Mo «->

R,

/

+ Mce + HO

^ \ / R1

° and ce

»~ Tr there

(III) À A + **

R ,. ] f

3> r8 + tfoH -> ü I + noe + h "o

„-Îr \ / R.,

Ct

IS.

1 \

y

N

R2

R /

3

where M represents an alkaline metal.

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640841

In particular, the preparation of Atrazine is generally carried out with discontinuous conduction, by making the cyanuryl chloride interact with isopropylamine in the presence of sodium hydroxide in the first stage of reaction to give 2,4-dichloro-6-isopropylamino-s-triazine. The latter is made to interact, in a second stage, with ethylamine and with a further quantity of sodium hydroxide with consequent formation of the desired product: 2-chloro-4-ethylamino-6 - isopropylamino-s-triazine.

The reactions described can be carried out in an aqueous medium or in an organic medium. Generally, it is preferred to resort to aqueous-organic media, in which the organic component is a solvent for cyanuryl chloride but is insoluble in water, or is partially or totally soluble therein. Thus two-phase or single-phase aqueous-organic systems are created.

Generally the above reaction (II) is carried out with the stoichiometric amount of the reactants to give 2,4-dichloro-6-alkylamino-s-triazine, while in the conduct of the reaction (III) one operates with a quantity of alkylamine and sodium hydroxide higher than that required for the production of chlorine-bis (alkylamino) -s-triazine. This way of proceeding is justified by the need to completely eliminate the 2,4-di-chloro-6-alkylamino-s-triazine from the medium in which it operates, and this in view of the undesired characteristics of this compound. In fact, for example, 2,4-dichloro-6-isopropylamino-s-triazine has skin irritating properties, so much so that it must not be present in the final product in quantities greater than about 0.5% by weight. On the other hand, the excess of alkylamine entails the drawbacks deriving from the formation of tris (alkylamines) -s-triazine, by reaction of the excess alkylamine with the chlorine-bis (alkali <amino) -s-triazine. For example, the reaction of ethylamine with 2-chloro-4-ethylamino-6-isopropiI-amino-s-triazine leads to the formation of 2,4-bis (ethylamino) -6-isopropylamino-s-triazma. The latter compound is undesirable as it makes it difficult to recover the Atrazine of the reaction products, hinders the grinding of the dried Atrazine and decreases the stability and fluidity of the liquid formulations containing this Atrazine. These side effects are likely to be caused at least in part by 2,4-bis (ethylamino) -6-isopropiIamino - s-triazine, which is a low-melting solid, waxy in appearance and with stickiness characteristics. This substance, more than during the reaction (III) reported above, is formed in the recovery phase of the products of the reaction itself, especially in the distillation phase of the organic solvent used in the reaction medium.

Various techniques have therefore been proposed in the art tending to separate or in any case inactivate the alkylamine which remained unchanged at the end of the reaction (III) and in particular to separate or deactivate the ethylamine in the case of the preparation of Atrazine. Thus, for example, according to U.S. Patent 3 681 335, upon completion of the chlorine-bis (alkyl-amino) -s-triazine formation reaction, an acid is added to the reaction medium to bring the pH from 11.5-12 to values of the order of 5-9 (better than the order of 6.5-7.5). In this way the alkylamine is deactivated and it is therefore possible to proceed with the distillation of the organic solvent without the danger of the formation of tris (alkylamino) -s-triazine. According to said US patent, the pH is brought back to values of the order of 11.5-12 in the residual suspension of the distillation containing chlorine-bis (alkylamino) -s-triazine before proceeding to the separation of the latter by filtration. In this way the filterability characteristics are improved.

According to U.S. Pat. No. 3 681 337, immediately after the end of the reaction (III) the quantity of cyanuryl chloride capable of blocking the free amine in the form of dichloro-alkylamino-s-tri-azine is fed to the reaction mixture, which it is then hydrolyzed together with the free cyanuryl chloride. Since the hydrolysis products are soluble in water, their removal is easy.

Finally, according to U.S. Pat. No. 3 705 156, formaldehyde is added to the products of reaction (III), so as to cause the formation of condensation products between formaldehyde and free alkylamine. Said condensation products are removed during distillation and subsequent filtration.

These known processes, while achieving the aim of avoiding, or at least reducing, the formation of tris (alkylamine-no) -s-triazine, essentially entail the drawbacks deriving from the addition of further substances to the reaction mixture with consequent formation of new species chemical. Such a way of operating can lead to problems relating to the purity of the desired final product. Furthermore, the procedures themselves are expensive for the number and type 1 of treatments required.

The object of the present invention is to avoid the drawbacks mentioned above.

The invention therefore provides a process for the preparation of chloro-bis (alkylamino) -s-triazines by substitution in stages of two atoms of the cyanuryl chloride with alkyl groups in an alkaline medium comprising water and a liquid organic compound which is solvent for the cyanuryl chloride forms a biphasic system with water, in which a molar excess of alkylamine is used in the second substitution stage and in which the said organic compound is removed by distillation from the reaction mixture obtained in the second substitution stage, characterized by the fact that, after the completion of the second stage, the said reaction mixture is deprived of its aqueous phase and the remaining suspension or solution of chlorine-bis (alkylthmmino) -s-triazine in said organic compound is mixed with water, before or during the distillation of the organic compound, added in an amount of 30-150% by volume with respect to the volume of the pre aqueous phase cedently eliminated.

At the end of the reaction (III) the chlorine-bis (alkylamino) -s-triazine can be dissolved in the liquid medium, or partially or totally suspended in the medium itself, and this according to the conditions in which said reaction (III) is carried out . In one case or another according to the present invention, the aqueous phase is first separated and then the organic residue is reintegrated with water before and / or during the distillation of the organic solvent.

In this way, after the distillation of the organic compound, an aqueous suspension of the chlorine-bis (alkylamino) -s-triazine remains as residue, from which the latter tris-free (alkylamino) -s-tri-azine free product can be separated or in any case with a content of this lower than 0.05% by weight.

The process of the present invention also has the advantage deriving from the fact that, together with the excess alkyl-amine, any substances deriving from the hydrolysis of the cyanuryl chloride, as well as the alkaline chloride formed during the reaction, are eliminated with the aqueous phase. . The aqueous suspension of the chlorine-bis (alkylamine-no) -s-triazine which is obtained after the distillation of the organic compound contains the polluting substances said only in traces and, depending on the desired final product, can be treated in one of the ways that they follow:

a) if you want to obtain chlorine-bis (alkylam-no) -s-triazine as a technical product, the suspension is sent

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640841

4

filtration, or centrifugation and this without those washes that would otherwise be required to eliminate alkaline chloride and water-soluble hydrolysis products, after which drying is carried out, which can be carried out with the spraying technique;

b) if chlorine-bis- (alkylamino) -s-triazine is to be obtained directly as a concentrated liquid suspension, the water added before or during the distillation of the organic solvent is regulated, so as to produce as a distillation residue a suspension having the desired concentration of solids, which can be used directly for the preparation of liquid formulations. In particular, the co-formulants can be added and the whole is sent to a mill for the treatment of wet grinding. In order to improve the flow characteristics, it is possible to resort to the addition of suitable dispersants, such as for example ligninsolphonates, said addition being able to be carried out before, during or after the distillation of the organic solvent;

c) if you want to obtain chlorine-bis- (alkylamino) -s-triazine directly in the form of wettable powder, simply add the necessary co-formulants to the aqueous suspension obtained after distillation of the organic compound and then proceed to wet grinding and drying, especially with the spray technique.

In any case, the formulations thus obtained are characterized by great ease of use and greater herbicidal efficacy. In particular, these formulations do not present any of the drawbacks deriving from the presence of tris (alkylamino) - s-triazines upon storage and use.

By the process of the present invention all the compounds definable by the general formula (I) can be prepared in which R1 R2, R3, R4 are as defined herein above.

Examples of alkyl radicals are: methyl, ethyl, isopro-pile, cyclopropyl, n-butyl and tert-butyl. In the more detailed description 15 that follows, specific reference will be made to the preparation of 2-choro-4-ethylamino-6-isopropiamine-no-s-triazine and this for the sake of simplicity, while it is understood that quite similar considerations apply to the others. chloro-bis (alkylamino) -s-triazines.

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2,4-dichloro-6-isopropylamino-s-triazine preparation (stage a)

In step a) cyanuryl chloride, isopropylamine and sodium hydroxide are reacted to produce 2,4-dichloro-25 -6-isopropylamino-s-triazine according to the reaction:

01

there is

(IV)

IT

there

IT

IT

IT

TT '

(CH ^ CHKTHg + ITaOH>

TO

01

there

IT

+ ITaCe + H20

ithch (ch ^) 9

35 The quantities of isopropylamine and sodium hydroxide are equivalent or approximately equivalent to those required for the formation of 2,4-dichloro-6-isopropylamino-s-triazine. Instead of sodium hydroxide, sodium carbonate, or hydroxide or carbonate of other alkaline metals such as lithium and potassium, can be used. The organic solvent used for cyanuryl chloride must be inert under the reaction conditions, immiscible or not very miscible with water and must have a good solvent power towards cyanuryl chloride. Suitable organic solvents for the purpose are: diethyl ether-45 co, benzene, toluene, xylene, chlorobenzene, methyl ethyl ketone, carbon tetrachloride, or any other solvent, having the above characteristics, known in the preparation technique of chlorine-bis (alkylamino) -s-triazine. Preferred aqueous-organic aqueous systems for the purposes of the present invention are water-toluene and water-chlorobenzene.

Conveniently the cyanuryl chloride is fed in the form of solution in the selected organic solvent, while the inorganic base and the alkylamine are fed in the form of an aqueous solution. In the selection of the solvent 55 it is also necessary to take into account the separability of the same by distillation from the finally produced chlorine-bis (alkylamino) -s-triazine.

The quantities of organic solvent and water fed into the medium in which it operates are not particularly critical; 60 it is however convenient to maintain weight ratios between the two constituents in the biphasic system from 3/1 to 3/2. Furthermore, good results are obtained by adjusting the feeds so that the concentration of 2,4-dichloro-6-isopro-pilamino-s-triazine at the end of stage a) is from 10 to 65 20% by weight with respect to the selected organic solvent . The temperature range in which it operates is generally included in a range of values from -5 to 60 ° C. Overpressure typically does not apply, or only applies

5

640841

the overpressure necessary to keep the medium in which it operates in liquid phase. At the end of step a) it is possible to separate the aqueous phase, but generally the reaction mixture is sent as it is in step b) that follows.

5

Preparation of 2-chloro-4-ethylamino-6-isopropylamino-s - triazine (stage b)

In step b) the mixture containing the 2,4-dicoro-6-isopropylamino-s-triazine coming from stage a), ethylamine and sodium hydroxide are reacted to produce 2-chloro-4-ethylamino-6-isopropylamino -s-triazine according to the reaction:

CZ CI

H IT

+ C2H5WH2 + ÎTaOïï> AM + NaCe + H20

NHCH (CH3) 2 C2E5ÎTIÎ N MHCH (CH3) 2

The quantities of ethylamine and sodium hydroxide are in excess of the stoichiometric value, conveniently of at least 1% to 6% and normally of the order of 3%, expressed in moles. Ethylamine and sodium hydroxide are conveniently fed in the form of an aqueous solution. The temperatures at which it operates are included in a range of values from -5 to 80 ° C and the time is that required to react all 2,4-dichloro-6-isopropylamino-s - triazine or at least to reduce the quantity of said compound at values lower than 0.5% by weight. The other modalities for stage b) are completely similar to those of stage a).

The above described with respect to steps a) and b) apply with particular convenience to the preparation of Atrazine with a semicontinuous process, by feeding the amine and sodium hydroxide to a reaction foot containing the cyanuryl chloride dissolved in the selected organic solvent. By this way of proceeding, at the end of step b) a suspension of Atrazine in the liquid medium is generally recovered and said suspension can be subjected to the treatments described above.

The obtaining of a reaction product in which Atrazine is completely dissolved in the liquid phase is possible by carrying out the reaction with short contact times and at relatively high temperatures. In particular, these conditions occur by operating continuously and in total times of less than about 10 minutes, at temperatures up to about 90 ° C in the first replacement and up to 100 ° C in the second replacement of the chlorine atoms of the cyanuryl chloride, maintaining the reaction mass under turbulent conditions within a tubular reactor and discharging a reaction product consisting of an aqueous phase and an organic phase which contains Atrazine in dissolved form. With this procedure, in the replacement of the second chlorine atom of the cyanuryl chloride it is possible to avoid the formation of the precipitate even in a range of temperatures lower than those corresponding to the solubility of the reaction product in the medium in which it is operated, and this above all thanks the short residence times required. Also in this case, a reaction product is obtained in which Atrazine is dissolved, albeit in conditions of over-saturation.

Elimination of excess ethylamine and separation of the reaction products (stage c)

The suspensions or solutions of Atrazine in the aqueous-organic biphasic medium, obtained from the preceding step b), are first deprived of the aqueous phase. This phase separation can be carried out at a temperature in the range from the ambient one (20 ° C) up to 25 100 ° C. Obviously it is convenient to operate at high temperatures in the case of Atrazine in solution and this in order to maintain this physical state. It has also been noted that the supersaturated solutions obtained by means of the rapid continuous process described in relation to step b), remain in this state for sufficiently long times to allow easy separation of the aqueous phase, provided that there is no substantial lowering in said separation of temperature with respect to that of the mixture leaving stage b). The separation of the aqueous phase can also be carried out continuously. To the remaining organic phase, thus obtained, water is added in a volumetric quantity from 30 to 150% with respect to the volume of the discharged aqueous phase and preferably equal to the volume of said aqueous phase. According to a preferred embodiment, the added water is gradually fed to the organic phase during the distillation of the organic solvent. The distillation can be carried out at a pressure equal to or lower than the atmospheric one and the residue of the distillation itself is in any case made up of an aqueous suspension of the Atra-45 zina. Said suspension can be filtered and dried, or sent directly to a spray dryer, or formulated directly as a concentrated liquid suspension, or as a wettable powder. In any case, the Atrazine thus obtained contains a quantity of tris (alkylamino) -s-triazine less than about 0.05% by weight.

Example 1

A 20 liter reactor is used, equipped with a stirrer, thermometer and separate openings for 55 feeding the reagents. The reactor is also equipped with cooling means. A solution of about 1,840 g (10 moles) of cyanuryl chloride is initially charged into the reactor in about 5,000 g of toluene (boiling point 110.6 ° C). As soon as the temperature of the solution stabilizes at around 5 ° C, 840 g of a 7% by weight aqueous solution of isopropylamine (10 moles) and 1,340 g of a 30% aqueous solution are added under strong stirring. weight of sodium hydrate (10 moles). The addition of the two solutions is carried out simultaneously through the two inlets with which the reactor is provided and their feed rate is regulated so that the addition of the isopropylamine solution ends after 25 minutes and that of the sodium hydroxide after 28 minutes. du-

640841

during the addition, the temperature rises from 5 ° C to 20-22 ° C, while the pH rises from an initial value of 2-3 to a maximum value of 9.5 and then drops to 6-7 ..

When the addition of the two solutions is complete, about 915 g of a 50% by weight aqueous solution of ethylamine (10, 15 moles) and about 1,353 g of a 30% by weight aqueous solution are added to the reaction mixture under strong stirring. sodium hydroxide (10, 15 moles). The methods of adding these solutions are the same as those described above. During this second addition the temperature rises from 25 ° to 50 ° C and the final pH is equal to 12.5.

A dense suspension is thus obtained, which is divided into two parts as quickly as possible. A part (A) is subjected to distillation to eliminate toluene in the form of azeotrope with water, operating at 85-100 ° C. 1,500 ml of water are added to the distillation residue and the suspension thus obtained is filtered at about 60 ° C. The solid residue is washed until the disappearance of sodium chloride. After drying for 10 hours in an oven at 100 ° C, 2-chIoro-4-ethylamino-6-isopropiIamino-s-triazine (sample A) is obtained with a yield of about 96% and a purity of about 98%.

The other part (B) of the suspension is deprived of its aqueous phase, which is replaced with the same volume of water. The mixture is then subjected to the distillation operations of toluene and recovery of Atrazine under the conditions already described for part (A), however omitting the washing step. The product thus obtained (sample B) consists of Atrazine, with a yield of about 96% and purity of about 98%.

From the two samples (A) and (B) suspensions are prepared at a concentration of 45% by weight by dispersion of the finely ground samples in a liquid medium formed by water, wetting, dispersing and suspending agents. The fluidity of these suspensions is determined immediately after preparation, and then after 3 to 6 months of storage in environmental conditions. The results are tabulated in Table I.

Examples 2 and 3

One works as in example 1 using 3% and 6% of excess in moles of ethylamine respectively with respect to the stoichiometric value. The results are reported in Table I. In all the samples (B) reported in Table the quantity of 2,4-bis (ethylamino) -6-isopropylamino-s-triazine is less than the analytically determinable quantity.

TABLE I

Example

Sample

% excess moles EtNHfe

Initial

Fluidity after 5 months after 6 months

1

TO

1.5

thick fluid

-

1

B

1.5

fluid fluid fluid

2

TO

3.0

thick fluid

-

2

B

3.0

fluid fluid fluid

3

TO

6.0

thick fluid

-

3

B

6.0

fluid fluid fluid

4

there

3.0

fluid fluid fluid

4

c2

3.0

thick fluid

-

Example 4

A reactor consisting of a stainless steel tube, 10 meters long, internal diameter 4 mm and external 6 mm is used. The tube is filled with sand grains having dimensions 1.2-1.8 mm, with pile density 1.48 g / cm3 and specific gravity 2.6 g / cm3.1 first 2.5 meters are used for the formation 2,4-dichloro-6-alkylamino-s-triazine (stage a) and the remaining part is destined for the production of 2-chloro-4-ethylamino-6-iso-propylamino-s-triazine (stage b). For this purpose, 43 ml / min of a toluene solution at 15% by weight of cyanuryl chloride and independently 13.8 ml / min of an aqueous solution at 12.77% by weight of isopropylamine and 8.85% by weight of sodium hydroxide. In this way the molar ratio between cyanuryl chloride, isopropylamine and sodium hydroxide at the entrance of stage a) is equal to 1: 1: 1. It is also operated adiabatically, with an inlet temperature at stage a) equal to 18 ° C and with a mixture temperature after 2.5 meters from the inlet equal to 55 ° C.

No heat exchange is carried out in the passage between the two reaction stages and at the beginning of stage b) 11.4 ml / min of a 12.15% aqueous solution by weight of ethylamine (equal to 3 % excess on the stoichiometric value) and 11.25% by weight of sodium hydroxide. Said solution is fed at a temperature of 18 ° C. Also in step b) one operates abiably and the temperature of the mixture discharged at the other end of the reactor is 70 ° C. On leaving the reactor, the reaction mixture is sent to a phase separator heated to 70 ° C, operating continuously, where the aqueous phase is separated from the toluene phase containing Atrazine.

Said toluene phase is gradually fed to a continuously operating distiller, to which water is also fed at a speed of 25 ml / min. An aqueous suspension of Atrazine is recovered from the distiller, to which the co-formulants are added and which is sent to the mill for wet grinding (sample Cj). For the purpose of comparison, a part of the reaction mixture discharged from the tubular reactor is sent directly to the distiller and the Atrazine is separated and separated as an aqueous suspension at the bottom of the distiller itself. Also in this case, the co-formulants are added and wet grinding (sample C2). The characteristics of fluidity over time are examined on the two samples and the result is shown in table I.

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Claims (10)

640841 1. Process for the preparation of chlorine-bis (alkyl-amino) -s-triazine by substitution in stages of two cyanuryl chloride atoms with alkyl groups in an alkaline medium comprising water and a liquid organic compound which is solvent for the chloride of cyanuryl and forms a biphasic system with water, in which in the second substitution stage a molar excess of alkylamine is used and in which the said organic compound is removed by destillation from the reaction mixture obtained in the second substitution stage, characterized in that , after the completion of the second stage, the said reaction mixture is deprived of its aqueous phase and the remaining suspension or solution of chlorine-bis (alkylamino) -s - triazine in said organic compound is mixed with water, before or during the distillation of the organic compound, added in an amount of 30-150% by volume with respect to the volume of the previously eliminated aqueous phase. 2. Process according to claim 1, characterized in that said organic compound is diethyl ether, benzene, toluene, xylene, chlorobenzene, methyl ethyl ketene or carbon tetrachloride. 2 3. Process according to claim 1 or 2, characterized in that the weight ratio between said organic compound and the water in the biphasic system is from 3: 1 to 3: 2. 4. Process according to claim 1, characterized in that the said molar excess of alkylamine is from 1 to 6 mol. %. 5. Process according to claim 1, characterized in that the aqueous phase is removed at: a temperature from 20 ° to 100 ° C. 6. Process according to claim 1, characterized in that the quantity by volume of the added water is substantially equal to that of the removed aqueous phase. 7. Process according to claim 1, characterized in that said water is gradually added to said suspension or solution during the distillation of the organic compound. 8. Process according to claim 1, characterized in that the quantity of water added is regulated so as to obtain, as a residue of the distillation of the organic compound, an aqueous suspension of chlorine-bis (alkylammmo) -s-triazine which can be used directly for the preparation of liquid formulations or in the form of wettable powders. Method according to one of claims 1 to 7, characterized in that the chloro-bis (alkylamino) -s-tri- s azine is separated from the suspension obtained as a residue of the distillation of said organic compound and is dried directly without any preliminary washing. 10. Process according to claim 9, characterized in that the chloro-bis (alkylamino) -s-triazine is the io 2-chloro-4-ethylamino-6-isopropylamino-s-triazine.