Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Reexamination Certificate
1999-08-06
2001-06-26
Ford, John M. (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
C544S216000
Reexamination Certificate
active
06252073
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for producing alkali metal salts or alkaline earth metal salts of 2,4-dicloro-6-hydroxy-s-triazine, especially the sodium salt (DCHT-Na), by reacting cyanuric chloride with an alkali hydroxide or alkaline earth hydroxide. The method can be operated on an industrial scale.
BACKGROUND OF THE INVENTION
Alkali metal salts of 2,4-dichloro-6-hydroxy-s-triazine are used as raw material for reactive dyes, as cross-linking agents for photo gelatins and recently as formaldehyde-free cross-linking agents for producing wrinkle-proof and easy-care properties of fibrous materials containing cellulose—see EP-A 0,616,071. Due to the decomposable nature of the solid triazine derivative the latter is usually not isolated but rather processed further in an aqueous phase.
It is known that cyanuric chloride can be hydrolyzed with alkali hydroxides to 2,4-dichloro-6-hydroxy-s-triazine and 2-chloro-4,6-dihydroxy-s-triazine—see Smolin and Rappoport, The Chemistry of Heterocyclic Compounds, S-Triazines and Derivatives (1967), 53-54. According to this document the hydrolysis does not stop at the desired first stage but rather the second and third chlorine atom are hydrolyzed at least partially in some instances.
According to German Patent DD 115 121, the 2,4-dichloro-6-hydroxy-s-triazine-Na salt, abbreviated in the following as DCHT-Na, is produced by the addition of cyanuric chloride dissolved in benzene or chloroform to an aqueous solution of sodium carbonate or sodium bicarbonate at 15° C. The use of organic solvents and the development of C
0
2
from Na
2
CO
3
or NaHCO
3
are disadvantageous. In the method according to JP-A
59-106474, 2.0
to 2.6 mol NaHCO
3
are added in the hydrolysis per mole cyanuric chloride together with a buffer, e.g., a phosphate buffer.
If cyanuric chloride is to be converted into DCHT-Na by sodium hydroxide solution instead of by sodium bicarbonate, according to SU-A 1051082, a buffer is again used and the reaction carried out at pH 8.5 to 8.8. However, the buffer is frequently undesirable since the solution is processed further. In addition, there is the risk of the pH dropping to values below 7 in this method of operation on account of the limited buffer capacity and thus an increased formation of the di- and trihydroxytriazine derivatives.
K. Matsui and J. Sakomoto show in Yuki Gosei Kagaku 18 (1960), H.3, 175-183 (45-53) that for the production of 2,4-dichloro-6-hydroxy-s-triazine (DCHT-Na) sodium hydroxide solution should be added at 0 to 5° C. to a suspension of cyanuric chloride. On the other hand, for the production of 2-chloro-4,6-dihydroxytriazine-Na salt (CDHT-Na) a cyanuric chloride suspension is charged into a sodium hydroxide solution. It was found during the reworking of the method described in this document that DCHT-Na can be produced in this way on a laboratory scale, but that this method poses safety problems on an industrial scale. Reaction heat is released which is difficult to control or, alternatively, the reaction rate is too slow.
SUMMARY OF THE INVENTION
An object of the invention is to optimize the hydrolysis of cyanuric chloride to DCHT-Na using sodium hydroxide solution in such a manner that the reaction remains reliably controllable even on an industrial scale.
The problem is solved by a method of producing an alkali metal salt or an alkaline earth metal salt of 2,4-dicloro-6-hydroxy-s-triazine by hydrolyzing cyanuric chloride with aqueous alkali hydroxide or alkaline earth hydroxide at a temperature equal to or below 10° C. 1 to 2.5 Equivalents of alkali hydroxide or alkaline earth hydroxide per mole cyanuric chloride in the form of an aqueous solution or suspension are placed in a receiver and cyanuric chloride in powder form or in the form of an aqueous suspension is added thereto while maintaining the pH in the range of 9.5 to 14 and cooling. In the case of a less than stoichiometric amount of alkali hydroxide or alkaline earth hydroxide being used, the remaining amount, including an excess of up to 25%, is added during and/or after the addition of cyanuric chloride for the purpose of maintaining the pH. The reaction is terminated when the pH essentially no longer changes at the temperature selected.
It has surprisingly been found that, in the method of the invention, cyanuric chloride can be hydrolyzed with high selectivity to the corresponding DCHT salt in spite of an excess of alkali hydroxide or alkaline earth hydroxide in the receiver. Only a small quantity of the 2-chloro-4,6-dihydroxy-s-triazine salt is formed. The method can also be safely operated on an industrial scale because the heat of reaction can be reliably removed or controlled and the pH maintained preferably above 10. A batch operation in accordance with the invention can be carried out at least partially and can also be followed by a continuous method of operation: In this case a suspension of cyanuric chloride and an alkali lye or a suspension of alkaline earth hydroxide are added in an approximately stoichiometric ratio into the reaction mixture of the batch. At the same time, and under cooling and monitoring of the pH, an amount corresponding to the amount added is drawn off from the reactor, which is advantageously designed as a circulation reactor, and the latter amount maintained at reaction temperature in a reactor connected at the outlet side, e.g., a tubular reactor, until the end of the reaction.
The alkaline metal salts to be produced in accordance with the invention are in particular, the Li—, Na—or K— salts. The alkaline earth metal salts are, in particular, the Mg—, Ca— Sr— or Ba— salts. The Na salt is particularly preferred. The concentration of the alkali hydroxide solution or alkaline earth hydroxide solution is adjusted according to the final concentration of DCHT-Na that is desired. Cooling may take place by direct cooling with ice or by indirect cooling. For a more rapid reaction, a wetting agent can be added to the alkali lye or suspension of alkaline earth hydroxide or suspension of cyanuric chloride placed in the receiver. A more rapid addition of cyanuric chloride makes faster removal of heat necessary.
Even though the theoretical molar ratio of alkali hydroxide to cyanuric chloride is 2 to 1, it can be advantageous to add alkali hydroxide in an excess of up to 25%, preferably in an excess up to 10%, during the last phase of the reaction, that is, after the end of the addition of cyanuric chloride, in order to maintain the pH and stabilize the reaction mixture. According to a preferred embodiment, alkali hydroxide is placed in the receiver in an amount of 1.2 to 2.2 moles, preferably 1.5 to 2.0 moles, per mole cyanuric chloride. When alkaline earth hydroxides are used the previously cited molar ratio corresponds to the equivalent ratio.
It is important to maintain the pH at values above 9.5, preferably above 10, during the addition of cyanuric chloride and during the postreaction period. The final pH should preferably be in a range of 10 to 12. At a pH below 9.5 there is a danger that the pH will drop into the acidic range with a consequent increased formation of salts of dihydroxymonochlorotriazine (CDHT) and cyanuric acid. The reaction is usually carried out at a temperature in the range of −10° to +10° C., preferably −5° to +5° C., and more preferably at 0 to 3° C.
The method can be reliably managed and operated with a high space-time yield. The DCHT salt obtained contains only a very small amount of the undesirable byproduct CDHT salt.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
REFERENCES:
patent: 115 121 (1975-09-01), None
patent: 29 10 726 (1979-10-01), None
patent: 44 24 733 A1 (1995-01-01), None
patent: 0 597 312 A1 (1994-05-01), None
patent: 0 616 071 A1 (1994-09-01), None
patent: 59-106474 (1984-06-01), None
patent: 1 051 082 (1983-10-01), None
Smolin & Rapoport, Cyanuric Acid & Derivatives, Chp. 1 (1967), pp. 53-54.
Klatte Christoph
Krimmer Hans Peter
Kunz Kurt
Leutner Josef
Ohlemacher Jurgen
Balasubramanian Venkataraman
Degussa-Huls AG
Ford John M.
Pillsbury & Winthrop LLP
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