BRPI0714504A2 - process for the preparation of triallyl cyanurate - Google Patents

Abstract

PROCESS FOR PREPARING TRIALILLA CYANURATE. The present invention relates to an improved process of preparing trialyl cyanurate (TAC) by reacting cyanuric chloride with allyl alcohol in the presence of an alkaline acid metal and in the absence of an organic solvent other than allyl alcohol. According to the present invention, TAC is obtained with a purity of more than 99% with an APHA color number below 10 with a yield of more than 90% when from 3.9 moles to 6.0 moles of allyl alcohol and 3.0 equivalents to 3.2 equivalents of the acid receptor are used per moi of the cyanuric chloride, the cyanuric chloride and acid receptor are added simultaneously or successively with respect to anhydrous or aqueous allyl alcohol with at least 50% by weight and The reaction is carried out in one or more stages at a temperature in the range of -5 <198> C to 50 <198> C.

Description

Descriptive Report of the Invention Patent for "TRIALYL CYANURATE PREPARATION PROCESS".

description

The present invention relates to a process for the preparation of triallyl (2,4,6-tris (allyloxy) -s-triazine) cyanurate, hereinafter referred to as the high yield and high purity TAC1, including a number APHA less than or equal to 10.

Trialyl cyanurate (TAC) is a trifunctional monomer that is especially versatile in polymer chemistry and has three reactive allyl double bonds - see Kirk-Othmer, volume 2, p. 123 to 127. The uses of TAC include it as a crosslinking component in the preparation of alkyd resins, polyurethanes, polyesters and as a comonomer in vulcanization processes and also as an adhesion promoter in rubber latex blends for tires. In addition, TAC serves as a curing medium for a wide variety of different polymers; for example, methacrylate TAC copolymers give rise to glasslike substances with excellent optical and mechanical properties, such as those required for the production of high quality optical glasses.

For many of the possible uses mentioned, a very pure TAC is required, which also exhibits characteristics of a very low degree of discoloration, expressed as the APHA color number, which should not exceed 10 as much as possible.

TAC is known to be obtained by reacting cyanuric chloride with allyl alcohol in the presence of an acid receptor, preferably an alkali metal hydroxide. The reaction may be performed in the presence or absence of an organic solvent. Known processes so far suffer from various shortcomings, for example, too low yield, inadequate purity or excessively complicated process technology for the preparation and isolation of the TAC. U.S. Patent No. 2,510,564 describes a

process for obtaining TAC by adding cyanuric chloride to a suspension of sodium carbonate in 90% allyl alcohol (molar fraction 1: 3.0: 13.51 at temperatures up to 40 ° C, with further heating up to 80 ° C) . In a modification of this method, sodium hydroxide powder is used as the acid receptor and the reaction is performed at room temperature. In both cases, it is necessary to filter from the formed sodium chloride. Opalescent to haze reaction products are obtained whose purity, below 90%, leaves a large part yet to be desired. The yields given in the examples (85% and 76%) are equally unsatisfactory.

In US Pat. Nos. 2,631,148 and US 3,644,410, the reaction is carried out in the presence of toluene below 10 ° C and 50 to 80 ° C, respectively. Even with both processes providing acceptable results in product yield and purity, the process implementation is complicated. The use of an organic solvent is quite problematic and makes the process more expensive due to the necessary equipment and power supply for the complete extraction of the aqueous phase solvent containing the TAC.

U.S. Patent No. 3,635,969 teaches a process whereby the reaction of cyanuric chloride with the sodium hydroxide and allyl alcohol solution is carried out in the absence of another organic solvent separate from the allyl alcohol reagent. The molar fraction used from cyanuric chloride to allyl alcohol to sodium hydroxide is 1: 4.5: 3.3; the sodium hydroxide concentration is 40 ± 0,5% by weight. The reagents are added to the 70% aqueous allyl alcohol maintaining a reaction temperature of 15 ± 3 ° C and a weakly alkaline pH. The disadvantages of this process, which allows the preparation of the TAC with an approximately 10 APHA number with approximately 90% yield, are:

- long addition and post-reaction times, for example around about a total of 10 hours, leading to low spatiotemporal yields;

- phase separation takes time and the conformation of

formed emulsions entail additional technical measures, for example those of coalescing bodies; - Following alcohol extraction by distillation of the TAC-containing aqueous phase, a purification / filtration step, if appropriate using activated carbon, is required for flocculation removal.

In reworking U.S. Patent No. 3,635,969, the applicant of the present Application has also found that, in the development of the aqueous phase of the reaction and the washing phases to recover excess allyl alcohol, contamination of allyl alcohol with ammonia. The reuse of such an allylic alcohol thus contaminated in the preparation of the TAC results in the conformation of triazine compounds that cannot be washed away, thereby leading to an increase in the APHA color number and a corresponding reduction in TAC quality.

It is an object according to the present invention to improve the known process of U.S. Patent No. 3,635,969, so as to at least partially remedy the indicated disadvantages. The process should also allow the TAC to be prepared on an industrial scale with a yield of over 90% based on cyanuric chloride and an APHA color number below 10 so that it is possible to allow recovered allyl alcohol to be reused without reducing the TAC quality. A process has been found to prepare trialyl cyanurate

(TAC) having an APHA number of less than or equal to 10 by reacting cyanuric chloride with allyl alcohol in the presence of an alkali metal acid receptor and in the absence of an organic solvent other than allyl alcohol, removing the salt formed by the addition of water and further phase separation by extracting the organic phase by washing with water and distilling off water and allyl alcohol from the organic phase containing TAC, which is characterized by the fact that 3.9 mois to 6.0 mois allyl alcohol and 3.0 equivalents to 3.2 equivalents of the acid receptor are used per mol of cyanuric chloride, the cyanuric chloride and the acid receptor being added simultaneously or successively to the anhydrous allylic alcohol or with at least 50% by weight water and the reaction being performed in one or more steps at a temperature in the range of -5 ° C to 50 ° C. Surprisingly, it has been found that a reduction in the amount of acid receptor in the molar fraction of reagent use compared to known processes thus far allows the reaction to be performed in a shorter time and without the extremely limited temperature control required so far and additionally allows the TAC to be obtained with a relatively low APHA color number, i.e. below 10. This has allowed the increase in the timeline yield to be increased and the TAC to be obtained at a purity greater than 99% with yields greater than 90%. Surprisingly, the TAC-containing organic phase and the aqueous phase can be further separated from each other quickly and without any problem after the reaction and washing and recovered allyl alcohol can be reused without reducing the quality of the TAC.

The process according to the present invention is technically simple to perform requiring a lower level of technical complexity compared to the process known hitherto, since the phase separation problems and the filtration step do not occur.

In the process according to the present invention, alkali metal compounds which are suitable as acid receptors may be used. Essentially, they can be alkali metal oxides and hydroxides. Sodium hydroxide is especially preferred as an acid receptor. In principle, the acid receptor may be introduced into the reaction mixture as a powder or as an aqueous solution or a suspension.

The acid receptor is preferably used as an aqueous solution, especially sodium hydroxide solution. Although the concentration of the sodium hydroxide solution used in the process known so far has to be extremely restricted, the concentration in the process according to the present invention is less critical; typically, the concentration will be between 30 wt% and 50 wt% NaOH, with preference being given to a maximum concentration, i.e., especially approximately 50 wt%, as thus the amount of the aqueous phase in the reaction mixture may be be kept low. In accordance with the present invention, from 3.9 mo to 6.0 mo of allyl alcohol and 3.0 equivalents to 3.2 equivalents of the acid receptor are used per mole of cyanuric chloride. However, preferably from 4.9 equivalents to 5.2 equivalents and especially from 3.05 equivalents to 3.10 equivalents of the acid receptor are used per mol of cyanuric chloride. If sodium hydroxide solution is used as the acid receptor, the specified numerical values are directly equivalent to the molar fraction of the reagents.

The temperature range selected for the reaction is between -5 ° C and + 50 ° C, preferably between 0 ° C and 40 ° C; In a single stage version, a temperature range of + 5 ° C to + 30 ° C is preferred. The reaction may be carried out isothermally at low temperature or semi-diabatically at a single stage or by raising the temperature at various stages. Preference is given to a two-step process: in this process, the reaction in the first stage is carried out to a conversion of 65% to 80% at low temperature, for example from 0 ° C to + 15 ° C and preferably +5 ° C. ° C to + 10 ° C; In the second step, the reaction is continued until essentially 100% conversion at elevated temperature, preferably from + 30 ° C to + 40 ° C. Cyanuric chloride and acid receptor reagents, especially

sodium hydroxide solution, are introduced by any method into the initially charged excess allyl alcohol which may contain up to 59% by weight of water. Preference is given to the use of aqueous allyl alcohol having an allyl alcohol content of 75 wt% to 90 wt%. The acid receptor, which is preferably used as an aqueous solution, may be added to a mixture of allyl alcohol or aqueous allyl alcohol with the total amount of cyanuric chloride. Alternatively, it is also possible to introduce cyanuric chloride and the acid receptor simultaneously or with a certain initial feed of the cyanuric chloride into the initially charged anhydrous or aqueous allyl alcohol or a mixture comprising allyl alcohol and at least some of the cyanuric chloride. In a further but less preferred alternative, cyanuric chloride is introduced into a mixture of allyl alcohol and the aqueous acid receptor solution. In an especially preferred embodiment of the process, the sodium hydroxide solution, with and without the simultaneous addition of cyanuric chloride, is introduced into a mixture of cyanuric chloride and allyl alcohol with optionally some water.

To suppress secondary hydrolytic reactions which thus reduce yield, the reagents are sufficiently and rapidly combined so that the addition time, which is most of the total reaction time, is kept to a minimum. The total reaction time, that is, that required for the combination of reagents including the post reaction, is preferably no longer than 3 hours, and preferably less than 2 hours, especially from 1 to 1.5 hours.

In view of the high enthalpy of the reaction, in order to achieve the short reaction times, intensive cooling is required, for example cooling using brine. On an industrial scale, heat is removed particularly efficiently through an external cooling circuit with a suitable heat exchanger along with a circulation pump.

As already detailed, the excess acid receptor is restricted to minimum values in the process according to the present invention. In principle, the excess can be reduced to zero, but a minimal excess is useful in relation to minimizing post-reaction time. Only a very small excess of the acid receptor is considered to be advantageous in two ways in the process according to the present invention: firstly, decomposition of hydrolysis-sensitive TAC is suppressed so that only negligible yield losses occur if there are any; Secondly, due to the low alkalinity of the aqueous phase of the reaction and the washing solutions in the distillation recovery of the excess allyl alcohol used, there is no contamination of it with the ammonia resulting from the hydrolytic cleavage of the triazine compounds present in the aqueous phases. .

After completion of the reaction, water is added to the reaction mixture only sufficiently for the precipitated chloride to return to solution. After the stirrer has been turned off, two phases form within a very short time: an upper organic phase comprising substantially all of the TAC and a lower inorganic phase comprising salt. Typically, the phases are separated almost instantaneously or within a few minutes and give rise to an accurate line of separation without the formation of a residue layer. After removal of the aqueous phase, the organic phase is washed at least once, preferably two to three times with water, to deplete the allyl alcohol content and wash away the salt residues. Wash extraction is preferably performed at temperatures around 30 ° C, which can be easily adjusted under process conditions. If appropriate, preheated water may also find use for maintaining the wash temperature of approximately 30 ° C. Washing of the organic phase may be carried out in batch or continuously in a standard extraction apparatus. After washing, the organic phase generally still contains approximately 2% to 7% allyl alcohol and 1% to 3% water. The volatile constituents mentioned are, upon addition of a suitable polymerization inhibitor, typically a hydroquinone derivative, distilled off gently at elevated temperature and under reduced pressure. The TAC obtained as the background product in yields significantly above 90% is a clear aqueous liquid having a purity of at least 99.5%, an APHA number from 0 to 10, preferably from 0 to 5 and a solidification point. equal to or greater than 27 ° C. The allyl alcohol present in the combined aqueous reaction and washing phases is preferably recovered from them as a 60% to 73% azeotrope with water, supplemented with the 100% allyl alcohol and fed to a subsequent batch.

The following examples illustrate the process according to the present invention without restricting it. In a series of comparative experiments, the influence of excess sodium hydroxide amount, reaction temperature, post-reaction time on cleavage caused by hydrolysis, and the associated decomposition of the TAC formed was examined: hence in the case of the present invention, with a very small acid receptor excess, the degradation rate of the TAC is significantly lower than when using the mentioned acid receptor excess (sodium hydroxide solution) in the known process up to now. In view of this finding, it is surprising that the significance of a very low acid receptor excess has not been recognized before. The APHA number has been measured according to EN ISO 6271-1: 2004 (D). Example 1

A cool reaction vessel was initially charged with 354 g (5.0 mo) of 82 wt% allyl alcohol and cooled to 10 ° C. Thereafter, 184.5 g (1 mol) of the cyanuric chloride was added and 3.09 mo of the 50 wt% sodium hydroxide solution was added dropwise with intense stirring and cooling for 60 minutes, during which time the mixture was added. The temperature was maintained at 9 ° C to 10 ° C until 75% of the sodium hydroxide solution had been consumed. After that, the cooling medium was removed and the remaining alkaline material was added quickly so that the temperature increased to 40 ° C. The mixture was stirred at 40 ° C for another 15 minutes during which time complete conversion was achieved according to analytical monitoring. Subsequently, 335 ml of water was added and the precipitated sodium chloride was put into solution by the addition of water. After agitation was turned off, two phases, with a well-defined separation line, were formed immediately. The upper organic phase was washed twice each time with 200 ml of water, which reversed the phases and the phase containing the TAC was removed as the lower phase. The phase containing the TAC was stabilized with 100 ppm of monomethyl hydroquinone ether and then transferred to a rotary evaporator, de-alcoholized at 90 ° C under water jet vacuum. This yielded 231.7 g of triallyl cyanurate melting at 27 ° C, corresponding to a yield of 93.0%. The APHA number was determined to be 5, the purity being 99.9%. Example 2

The procedure was the same as in Example 1, except that the proportion of the sodium hydroxide solution measured at 10 ° C was increased to 80 L and the corresponding measurement time was 65 minutes. The remaining alkaline material was added rapidly and without cooling, during which time the temperature increased to 30 ° C. After 15 minutes post-reaction time and the development specified in Example 1, 235.5 g of triallyl cyanurate (= 94.5% yield) with a purity above 99.9% and a number APHA color equal to zero. 164.0 g of 70% allyl alcohol containing less than 50 ppm ammonia was distilled from the combined aqueous phases under virtually azeotropic conditions and reused (see Example 3). Examples 3 to 6

Example 2 was repeated except that from 60 wt.% To 70 wt.% Of aqueous allyl alcohol which had been recovered essentially as an azeotrope of the preceding example in each case was supplemented to 5.0 mol with allyl alcohol 100. % by weight and initially loaded. The yield, purity and APHA number were almost identical in examples 3 to 6 and essentially equivalent to the values of example 2; the APHA number was always significantly below 10. Example 7

A brine-cooled reaction vessel was initially

charged with 290.4 g of pure allylic alcohol which was cooled to -5 ° C. Thereafter, 184.5 g of cyanuric chloride was added with stirring and the addition of 50% sodium hydroxide solution was started. Within 60 minutes, a total of 248.1 g (3.10 mo) of sodium hydroxide solution was measured such that the temperature did not rise above 0 ° C. Thereafter, the mixture was allowed to continue reacting without cooling for approximately another 30 minutes until complete conversion was achieved. Thereafter, the mixture was heated to 30 ° C; To dissolve the precipitated sodium chloride, 409 ml of preheated water at 30 ° C were added and, after the stirrer was turned off, the phases that formed were separated within a few minutes. The organic phase was removed, washed twice each time with 200 ml of water and, after stabilization with 100 ppm of monomethyl hydroquinone ether, was released from the volatile constituents on a rotary evaporator under reduced pressure. This provided 240.5 g (corresponding to 96.5% yield) of pure trially cyanurate with an APHA number of 0. Example 8

A jacketed agitation reactor with an external heat exchange circuit composed of chiller and circulation pump was initially loaded with 119.0 kg (2049 mo) of allyl alcohol and 26.5 kg of water; 75.0 kg of cyanuric chloride was then added with stirring. After that, the brine-loaded cooling circuit was put into operation and the circulating mixture was cooled to 8 ° C. Addition of a total of 101.0 kg = 66.2 L (1262 mo) of the 50 wt% NaOH solution was then initiated, during which the reaction temperature was maintained from 9 ° C to 14 ° C to 54 ° C. L had been consumed. Subsequently, the cooling circuit was closed and allowed

the remaining sodium hydroxide solution would flow in as soon as possible. During flow, the reactor internal temperature increased to 35 ° C. The total introduction time was approximately 70 minutes. To complete the conversion, stirring was continued for another 20 minutes; 140 L of water was then added to the precipitated sodium chloride solution. After the stirrer was turned off, two clear phases were formed within a few minutes, and were separated by means of a separating vessel. The organic phase was recycled into the reactor and washed twice each time with 80 liters of water. After the second extraction, the washed TAC still contained 2.1% water and 6.5% allyl alcohol. To remove volatile fractions, the product, after stabilization with 100 ppm of monomethyl hydroquinone ether, was fed into a pendant film evaporator which distilled the low boiling products at 5 KPa (50 mbar) and 100 ° C. . This yielded 95.1 kg of triallyl cyanurate, corresponding to a 93.9% yield; 99.9% TAC purity, an APHA number from 0 to 5. Example 9

The reaction apparatus described in the previous example, which had been additionally equipped with a unit of measurement suitable for the volume of powdered material, was initially loaded with 145.5 kg of 81.8 wt% allyl alcohol (2049 mo) together with 15 kg (81.3 mo) of cyanuric chloride and the mixture was cooled to 8 ° C. The cyanuric chloride and sodium hydroxide solution present in a small excess (50 wt.% Concentration) were then simultaneously introduced continuously under quantitative control through the external heat exchanger circuit with intensive stirring and cooling, over which time. reaction temperature was maintained from 9 ° C to 10 ° C. Once a new addition of 60.0 kg (325.5 mo) of cyanuric chloride and 56 L (85.4 kg; 1061.7 mo) of the 50 wt% sodium hydroxide solution was completed, cooling was completed. turned off and the remaining 10.2 L (15.6 kg; 194.5 mo) alkaline material was allowed to flow in as fast as possible. After that, the temperature increased to 30 ° C. The mixture was stirred at this temperature for an additional 15 minutes; further development was carried out as described in example 8. This yielded 95.8 kg of pure triallyl cyanurate, corresponding to a yield of 94.6%. Product had an APHA number below 10. Example 10

The procedure was performed as in example 9, except that only 10% of the 75.0 kg of cyanuric chloride used was initially loaded with allyl alcohol. After cooling to 8 ° C, simultaneous addition of cyanuric chloride and a 50% by weight sodium hydroxide solution was initiated at a molar ratio of 1: 3.10, during which time the internal temperature of the tank was maintained at 9 ° C. ° C to 10 ° C. Moments before the end of the measured parallel addition, the reaction temperature was allowed to rise from 15 ° C to 17 ° C by proper cooling regulation. Once all of the cyanuric chloride had been added, cooling was removed and the remaining sodium hydroxide solution allowed to flow rapidly while the temperature increased further from 30 ° C to 32 ° C. The total reaction time to final temperature was approximately 80 minutes. After an additional 15 minutes post-reaction time, development was performed as described above. Product yield and quality are no different from the previous example. Example 11

The procedure was performed as in example 9, except that 50% of the cyanuric chloride was initially loaded with 81.8% by weight of 8 ° C allyl alcohol. After the end of the parallel addition, the reaction temperature was initially also kept at 10 ° C; Only after the addition of approximately 80 L of the total amount of sodium hydroxide solution has the cooling been closed. The total reaction time until the final temperature of 30 ° C to 35 ° C was reached was 75 minutes. The triallyl cyanurate yield was 94.1%, purity 99.9% and APHA color number 0 to 5. Example 12

The procedure was performed according to example 9 except that for this purpose allyl alcohol recovered as a 60% solution of this example was reused and supplemented with a total amount of 5.0 mmol / mole of cyanuric chloride with alcohol. Fresh allylic. This lowered the concentration of allyl alcohol used to 78.9%. 95.0 kg were obtained, corresponding to a yield of 93.8% triallyl cyanurate. The content was 99.7%; the APHA number was measured at 10. Example 13

To illustrate the improvement of the process according to the present invention over prior art process, it was determined in a series of comparative experiments the influence of excess sodium hydroxide, post-reaction temperature and post-reaction time on cleavage caused by hydrolysis, the TAC formed and its degradation rate as a function of the parameters mentioned herein.

In each case, a model mixture of TAC, allyl alcohol, water and NaCI prepared according to example 2 is used, provided that the reaction is carried out without excess sodium hydroxide (3.0 mo 50% NaOH by weight per mol of cyanuric chloride) and that, after the reaction was completed, no dilution water was added. The TAC content in the mixture was in each case from 64.0% to 64.2%. After the desired post-reaction temperature had been established, these model mixtures were mixed with a certain amount (corresponding to the desired excess) of the 50% by weight sodium hydroxide solution and stirred at constant temperature for several hours. Samples were taken at certain time intervals and their TAC content was compared to the TAC content of the initial sample (null sample) of the model mixture. Post-reaction temperature, excess NaOH added (mol per mol of cyanuric chloride) and TAC degradation rate (%) after 30, 60, 120 and 180 minutes of experiment are shown in the table below. The results demonstrate the detrimental influence of relatively high excesses of NaOH on the decomposition of the formed TAC. ω

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Claims (10)

1. A process for preparing trialyl cyanurate (TAC) having an APHA number of less than or equal to 10 by reacting cyanuric chloride with allyl alcohol in the presence of an acid receptor alkali metal and in the absence of an organic solvent other than alcohol the salt formed by the addition of water and subsequent phase separation, extraction by washing the organic phase with water and distilling off the water and allyl alcohol from the organic phase containing the TAC, characterized by the fact that 3.9 to 5.0 grams of allyl alcohol and 3.0 equivalents to 3.2 equivalents of the acid receptor are used per mol of cyanuric chloride, the cyanuric chloride and acid receptor are added simultaneously or successively to anhydrous or aqueous allylic alcohol of at least 50 % by weight and the reaction is carried out in one or more stages at a temperature in the range of -5 ° C to + 50 ° C. Process according to Claim 1, characterized in that the acid receptor used is an alkali metal hydroxide, preferably sodium hydroxide and is preferably used as a concentrated aqueous solution. Process according to claim 1 or 2, characterized in that from 4.9 mois to 5.2 mois allyl alcohol and 3.0 equivalents to 3.15 equivalents, preferably from 3.05 equivalents to 3 .10 acid receptor equivalents are used by cyanuric chloride moieties. Process according to any one of Claims 1 to 3, characterized in that the reaction is carried out at 0 ° C to 40 ° C. Process according to any one of Claims 1 to 4, characterized in that the reaction is carried out in two stages, a temperature of 0 ° C to + 15 ° C, preferably from 5 ° C to 10 ° C, with kept in the first stage until a conversion of 65% to 90% and a temperature of 30 ° C to 40 ° C being maintained in the second stage until a conversion of essentially 100%. Process according to any one of claims 1 to 5, characterized in that an aqueous allyl alcohol having an allyl alcohol content of 75 wt.% To 90 wt.% Is used. Process according to any one of claims 1 to 6, characterized in that the total reaction time, that is, time for the addition of reagents to the formation of allyl alcohol and the continuation of the reaction, is limited to no. more than 3 hours, preferably less than 2 hours. Process according to any one of Claims 1 to 7, characterized in that, in order to remove the salt and deplete excess allyl alcohol, the organic phase is washed at least once, preferably two to three times. , with water at temperatures around 30 ° C. Process according to any one of Claims 1 to 8, characterized in that the allyl alcohol present in the combined aqueous phases is distilled therefrom, preferably as an azeotrope with water and sent to a subsequent batch. Process according to any one of claims 1 to 9, characterized in that the cyanuric chloride is added in the initial feed with respect to the acid receptor, the initially charged anhydrous or aqueous allyl alcohol, or a mixture of allyl alcohol and at least some cyanuric chloride.