HK1132276B - Process for preparing triallyl isocyanurate (taic) - Google Patents

Description

Process for preparing triallyl isocyanurate (TAIC)

The present invention aims to provide Cu via triallyl cyanurate (TAC) at a temperature of at least 90 DEG C²⁺An improved and operationally reliable process for the preparation of triallyl isocyanurate (TAIC) by catalytic rearrangement.

Triallyl isocyanurate [ triallyl s-triazine-2, 4, 6(1H, 3H, 5H) -trione; TAIC is a trifunctional polymerizable monomer which is used as a crosslinking component for high-value thermoplastic materials and synthetic rubbers, and as a raw material for the preparation of flame retardants. Furthermore, TAIC is also used as a copolymerization component in the polymerization of ethylene, allyl and acrylic monomers.

TAIC can be prepared essentially by three methods:

in the process according to U.S. Pat. No. 3,322,761, Triallylisocyanurate (TAIC) is obtained by reacting cyanuric acid with allyl chloride and sodium hydroxide in the presence of copper chloride as catalyst. The disadvantages of this process are the very excessive amounts of allyl chloride (6mol/mol cyanuric acid), allyl alcohol and diallyl isocyanurate formed as hydrolysis products, and the complicated removal and purification of the resulting TAIC.

A more industrially useful route to TAIC is the in situ trimerization of allyl isocyanate. In this case, the alkali metal cyanate is reacted with allyl chloride in a dipolar aprotic solvent, preferably dimethylformamide, at a temperature of about 130 ℃ as described, for example, in JP 52-109627 or DE-A2839084. Despite the good yields of this process, the disadvantages are the formation of large amounts of organically contaminated sodium chloride, the use of toxic solvents and the rather costly purification steps required to provide TAIC quality which meets the market requirements.

A third method of preparation of TAIC is the Claisen rearrangement of Triallylcyanurate (TAC), which is itself obtained on an industrial scale by reacting cyanuric chloride with allyl alcohol in the presence of a catalyst (cat).

In the process according to EP 0078567 a1, the rearrangement from TAC to TAIC is carried out in the presence of a quaternary amine compound. The disadvantages of this process are the long reaction times and the risk of spontaneous polymerization of the entire mixture. When the inventors of the present application reproduced this process, polymerization at temperatures > 200 ℃ and intense smoking occurred after a few minutes.

Balitskaya et al, in Ukr.Khim.Zh.40(8), 881, (1974), describe the isomerization of cyanurate to isocyanurate in the presence of metallic copper. The rearrangement of TAC to TAIC at 70 ℃ in the presence of 20% copper is said to be complete within 5 hours. In contrast, the present application and the attempts of the inventors of EP 0078567 a1 did not achieve such results.

The soviet union patent 1121259 teaches a process for preparing TAIC by isomerizing TAC in toluene at a temperature of 95-130 ℃ in the presence of copper and a reducing agent selected from tin (II) chloride and iron (II) chloride. The molar ratio of the individual components here is: TAC (1); toluene (1.3-4.1); copper (0.39-0.8); reducing agent (0.0013-0.0026). The reaction time is 1-20h depending on the temperature and the catalyst concentration. The disadvantages are the very high catalyst quantities and the long reaction times.

Soviet Union patent 1121260 claims the isomerization of TAC to TAIC in toluene as solvent using Cu salts (such as CuCl)₂·2H₂O、CuAc₂·2H₂O、CuCl、CuSO₄·5H₂O、CuF₂·2H₂O、Cu(NO₃)₂·3H₂O and CuBr) as catalyst. The molar ratio of TAC, toluene and catalyst is 1 to (1.3-4) to (0.0015-0.0073). The processes of SU 1121259 and SU 1121260 were carried out batchwise, the catalyst being initially charged to a glass reactor and mixed with a portion of the toluene solution of TAC. After heating to about 100 ℃, adding the residual TAC/toluene mixture within 3h, and continuing to react for 2 h; thereafter, the reaction mixture was worked up by distillation.

In reproducing the process of SU 1121260, it was found that the process could not be used reliably and safely on an industrial scale for the preparation of triallyl isocyanurate. Although the SU document teaches the use of a minimum amount of toluene to prevent explosive processes, there are uncontrollable process states that remain in the reproduction of the process. The document does not give any information on how to operate the process continuously and without any safety risk on an industrial scale.

A further disadvantage of the process described in SU 1121260 is the formation of a polymeric product: since TAIC remains in the reactor for a long time, as found by the inventors of the present application, up to 20% by weight of oligomers may be formed, which cannot be detected in gas chromatography, but precipitate with methanol after the solvent is distilled off. It has also been found that the use of the hydrate-containing Cu salts taught in the SU literature results in unsatisfactory conversion or formation of by-products. Through applicants' experiments, it was found that water removes allyl alcohol from TAC under the catalytic action of copper salts, thereby forming diallyl isocyanurate as a by-product.

It is therefore an object of the present invention to provide an improved and operationally reliable process for the preparation of TAIC by Cu salt catalyzed rearrangement of TAC. The process should be simple to operate. In a further object, embodiments are also provided in which the amount of solvent used is minimized. In a further object, TAIC should be obtainable in high yield and purity. In a further object, the present process should substantially avoid the formation of oligomeric and polymeric by-products.

From the description, it is clear that the above objects and further objects are achieved by the process according to the invention according to the embodiments of the independent claims, in particular of the dependent claims. The process according to the invention is a continuous process which overcomes the problems in batch processes.

The present invention has found a process for the preparation of triallyl isocyanurate (TAIC), which comprises rearranging triallyl cyanurate (TAC) at a temperature of at least 90 ℃ in the presence of a Cu salt, characterized in that Cu is present in an amount of 0.01 to 1 wt. -%, based on the TAC²⁺Mixing TAC and Cu²⁺Salt is continuously introduced into a reaction mixture containing TAIC, the TAC and Cu²⁺The salts are introduced separately or in the form of a mixture comprising these components, the reaction mixture containing TAIC being passed through Cu at a temperature of at least 90 DEG²⁺TAC is rearranged in the presence of salts and thereafter not cooled below 90 ℃, the rearrangement being carried out under these conditions while maintaining the temperature in the range from 90 to 160 ℃ and the amount of reaction mixture corresponding to the amount added is continuously discharged and TAIC is isolated therefrom.

It has been found that the isomerization of TAC to TAIC under Cu salt catalysis is likely an autocatalytic process with an induction time (accumulation time) dependent on the type of catalyst used, the catalyst concentration, the temperature and the solvent used.

700kJ/kg TAC was released as the isomerization proceeded. Measurements in the Contraves calorimeter also showed that more than 90% of the total exotherm was released in about 5 minutes. This situation causes problems in the currently known methods. These problems are solved by the method according to the invention.

In the process according to the invention, the composition of the starting phase and thus of the starting mixture of the reaction is of great importance for the safety performance of the overall reaction. Cu from TAC to TAIC²⁺It is important that the starting mixture for the catalytic isomerization is not cooled below 90 c before use. Will contain TAIC and Cu²⁺Cooling the starting mixture to a value below 90 ℃ to deactivate the catalyst or catalyst composite; simple heating of the mixture does not enableReactivation thereof; instead, another induction time is required after addition of TAC. The use of the reaction mixture of the invention, in which TAC is introduced continuously, avoids spontaneous reactions which occur before the end of the induction time and which may not be controlled.

In a particular embodiment, the isomerization is carried out in the presence of a polymerization inhibitor; such as hydroquinone, hydroquinone monomethyl ether, tert-butyl phenol and alkyl phenols. Such inhibitors are often already present in TAC.

The relationship between the induction time and the concentration of the catalyst in toluene as a solvent is shown in Table 1.

Table 1: relationship between Induction time and catalyst concentration

Cu2+Concentration [% ]]	Induction time [ min ]]
		0.5	13-14
0.4	17
		0.3	20
0.2	28
		0.1	＞35

The measurements were carried out in a 100ml flask present in a silicone oil bath at 120. + -. 2 ℃. The onset of isomerization is marked by a sudden rise in temperature which causes vigorous boiling of the contents throughout the flask. Gas chromatography analysis consistently showed that little reaction had previously occurred. The volume ratio of TAC to toluene is 1: 2; the catalyst used is CuCl₂·2H₂O; the amounts therein are percentages based on TAC.

In addition to aromatic hydrocarbons, other solvents have been found in which isomerization can be carried out. Suitable solvents are, in addition to toluene, those relative to Cu²⁺And TAC such as aliphatic, cycloaliphatic or aromatic hydrocarbons, diesters of carbonic acid, esters and ethers of aromatic and aliphatic carboxylic acids. In a preferred embodiment, TAIC itself acts as a solvent and is used for evaporative cooling. Table 2 shows some of the solvents and induction times determined from them.

Table 2: isomerization in various solvents

TAC and solvent in the volume ratio of 1 to 2, and catalyst Cu²⁺Cu at a concentration of 0.4% or 0.25%²⁺

When the operation is not carried out under pressure, the choice of solvent is determined by the boiling temperature, preferably in the range of 110 ℃ to 160 ℃. A reaction temperature of 110 ℃ and 140 ℃ was found to be advantageous. Higher boiling solvents (such as TAIC) can be brought into this preferred working range by applying a vacuum. Alcohols, ketones, anhydrides and many dipolar aprotic solvents are less suitable or not at all suitable because they form by-products.

All problems affecting the isomerization of TAC are prevented by the continuous process according to the invention, since the operation here is carried out with a small operating volume and very short residence times. This minimizes the potential risk of spontaneous polymerization and prevents polymerization due to long-term thermal stress.

The basis of the process is the finding that once reacted in the presence of Cu²⁺Can be maintained by supplying TAC or a mixture of TAC and solvent, in which the catalyst can additionally be dissolved or finely dispersed, an amount corresponding to the amount supplied can be discharged from the reaction vessel simultaneously, in particular in the form of distilled-off TAIC or in the form of TAIC and Cu²⁺The catalyst is discharged in the form of a solution in a specific solvent.

Copper (II) chloride shows the surprising property of being readily soluble in a mixture of toluene and TAC, showing a blue colour, but being poorly soluble in the pure starting components. This system is therefore particularly preferred, also for the reason that CuCl₂Is easy to obtain. Slightly soluble Cu²⁺The catalysts can be used in the continuous process only if they are ground to fine particles by means of suitable dispersing devices before or during the reaction.

In a preferred embodiment, Cu is used²⁺The catalyst is an anhydrous salt, in particular selected from CuCl₂、CuBr₂、CuI₂、Cu(RCOO)₂(wherein R ═ alkyl or aryl) salts. Generally, the rearrangement is from 0.01 to 1% by weight of Cu, based on the TAIC present in the starting reaction mixture being converted (TAC is almost quantitatively converted within a few minutes after its addition)²⁺(particularly 0.02-0.2 wt.% Cu)²⁺) In the presence of oxygen. When the discharged amount of the catalyst-containing reaction mixture reaches the amount of TAC and solvent supplied, the catalyst concentration also needs to be maintained by supplying the catalyst.

In a preferred embodiment, the reaction is carried out in the absence of added solvent (i.e., TAIC is the reaction medium). In this case, TAC is introduced continuously into a TAIC-containing starting reaction mixture which is passed at least 90 ℃ over Cu²⁺Formed by rearrangement of TAC in the presence of a salt, and thereafter without cooling to below 90 ℃, said rearrangement being carried out at from 90 to 160 ℃ (in particular 110-The distillation rate of IC (g TAIC/min) was substantially equivalent. The advantages of this embodiment are no need for additional solvent, use of catalyst only once and simple clean up.

In a preferred embodiment, the process according to the invention can be carried out by the following process steps:

starting reaction: a mixture of TAC, solvent and catalyst is introduced into a reaction vessel. In order to reliably control the exotherm and start the reaction relatively quickly, TAC: solvent: cu²⁺Is selected to be about 250ml TAC per liter of solution: 750ml of solvent: 3g of CuCl₂. The reactor was heated to an internal temperature of 110-. After about 15-17 minutes, the rearrangement of TAIC begins, which is marked by a vigorous boiling of the contents of the reactor.

The continuous method comprises the following steps: once the reaction has begun, the mixture of TAC, solvent and catalyst is continuously pumped into the reactor, especially in an amount such that the average residence time of the TAC is not less than about 10 minutes and not more than 60 minutes. The amount of solvent in the supplied solution may vary within wide limits, but it is preferred to reduce the content of solvent in order to reduce the work of distillation.

It is also possible in principle to work without solvent; in this case, the TAIC formed serves as reaction medium and the heat of isomerization is removed here by evaporative cooling under reduced pressure. The ratio of reactants may vary from about 1: 4 to 1: 0 by volume of TAC to solvent. Once the reaction starts (initial reaction), the catalyst concentration can be greatly reduced. 0.15g Cu per liter of reactant solution²⁺The concentration of (c) is still effective.

Separation of TAIC: while the same amount of TAIC/solvent/catalyst as the added amount of reactants was pumped out of the reactor. When CuCl is used₂And toluene or diethyl carbonate, the incoming TAC solution has a blue color and the outgoing TAIC solution has a green color. The reaction was monitored by gas chromatography. Once the solvent is distilled off, the TAIC is purified by vacuum distillation. The bottom effluent contains Cu²⁺. In a particular embodiment of the process, Cu can be largely dispensed with²⁺The treatment of (1):in this case, the substrate of the vacuum distillation, whose proportion is set higher, is pumped directly to the reaction vessel while it is still hot, and here ensures maintenance of the catalyst concentration. However, activity is only maintained when the temperature of the substrate is maintained at least 90 ℃; after the substrate was cooled to room temperature and reheated, the reaction could no longer be maintained.

The process according to the invention can be carried out reliably and without the risk of spontaneous reactions. The fast reaction and continuous process largely avoids the formation of by-products and oligomers.

The following examples are intended to illustrate the process in detail:

example 1

25ml of TAC, 0.3g of CuCl₂The (anhydrous) solution in 75ml of toluene was introduced into a jacketed stirred vessel having a capacity of 500ml, which was heated by means of a thermostatted silicone oil bath set to 130 ℃. The temperature in the flask was adjusted to 113 ℃ and 115 ℃. After 16 minutes, vigorous reflux was started; the initial blue solution was converted to a dark olive green solution. After the reaction had slowed, 3000ml of TAC, 3.0g of CuCl were added by means of a metering pump₂And 3000ml of toluene were continuously pumped at 10 ml/min. At the same time, 10 ml/min of the reaction solution was discharged by the second metering pump. The reaction temperature rose to about 123-125 ℃.

When the system is operated with a higher TAC concentration (higher space-time yield), the reaction temperature is limited to a maximum of 140 ℃ by applying a suitable vacuum.

The conversion rate is more than 99.9 percent. The by-product formed from residual water in TAC and toluene is a small amount of diallyl isocyanurate. The process was operated without any problem during a period of 10 h.

Example 2

The process according to example 1 is followed with the difference that diethyl carbonate is used as solvent. Reaction mixture of the initial reactionBy mixing TAC and diethyl carbonate in a volume ratio of 1-3 per liter of reactant solution and adding 2.5g CuCl₂To be prepared and then ultra-finely ground in a wet mill. After starting the addition of 200ml of this solution, heating to 130 ℃ and waiting for the start of the reaction, a homogeneous dispersion of TAC and diethyl carbonate in a volume ratio of 1: 1 per liter of solution and 0.4g of CuCl were pumped in at 15 ml/min₂At the same time, the green TAIC solution was discharged at 15 ml/min. The conversion of TAC was > 99.8%. The process was maintained for 8h without any upset or reduction in yield and purity.

Example 3

The procedure is as in example 1, with the difference that after the start of the initial reaction 1000ml of TAC and 0.25g of anhydrous CuCl are metered in₂The homogeneous ultra-finely dispersed mixture of (a). The amount of the mixture is 10 ml/min; at the same time, 10 ml/min of the reaction solution was pumped out. As the toluene distills, the toluene content in the reactor vessel decreases over time and the operating temperature in the reactor increases. To prevent polymerization, a vacuum was applied at a temperature of 140 ℃ in the flask to maintain a constant operating temperature by evaporative cooling of the TAIC formed. The vacuum required for this purpose is 2.0-3.0 hPa. The process gave TAIC with a purity of 98.5%; the isomerization rate of TAIC is more than 99.8%.

Claims (12)

1. A process for preparing triallyl isocyanurate (TAIC), which comprises Cu at a temperature of at least 90 ℃²⁺Rearranging triallyl cyanurate (TAC) in the presence of a salt, characterized in that:

cu in an amount of 0.01-1 wt% based on TAC²⁺Mixing TAC and Cu²⁺Salt is continuously introduced into a reaction mixture containing TAIC, the TAC and Cu²⁺The salts are introduced separately or in the form of a mixture comprising these components, the reaction mixture containing TAIC being passed through Cu at 90-160 deg.C²⁺Formed by rearranging TAC in the presence of a salt, and thereafterNot cooled to 90 ℃ or below, said rearrangement being carried out under these conditions while maintaining the temperature in the range of 90-160 ℃ and the amount of reaction mixture corresponding to the amount added being continuously discharged and TAIC being isolated therefrom,

wherein said Cu²⁺The salt is selected from CuCl₂、CuBr₂、CuI₂、Cu(RCOO)₂Salt, Cu (RCOO)₂Wherein R is alkyl or aryl.

2. Process according to claim 1, characterized in that the rearrangement of TAC to TAIC is carried out in the presence of an aprotic solvent at 90-160 ℃ with respect to Cu²⁺And TAC are stable in combination.

3. A process according to claim 1 or 2, characterized in that TAC and, if desired, further Cu are added²⁺The salt is introduced into the reaction mixture in the form of an aprotic solvent at 90-160 ℃ with respect to Cu²⁺And TAC are stable in combination.

4. A process according to claim 1 or 2, characterized in that TAC and Cu are added²⁺The salts are introduced separately or in the form of a mixture into a reaction mixture containing TAIC, where the individual components or the mixture may additionally comprise an aprotic solvent, which is at the reaction temperature relative to Cu²⁺And TAC, the reaction mixture containing TAIC being at 90-160 deg.C in Cu²⁺Formed by rearrangement of TAC in the presence of a salt and an aprotic solvent, which is at the reaction temperature relative to Cu²⁺And TAC are stable in combination.

5. The process according to claim 2, characterized in that the aprotic solvent used is an aliphatic, cycloaliphatic or aromatic hydrocarbon, a diester of carbonic acid, an ester of an aliphatic or aromatic carboxylic acid, or an ether.

6. The process according to claim 1 or 2, characterized in that the rearrangement is carried out at a temperature in the range of 110-140 ℃.

7. Process according to claim 1 or 2, characterized in that the catalyst fed continuously to the reaction mixture is CuCl based on TAC₂，Cu²⁺The amount of (B) is 0.02-0.2 wt%.

8. Method according to claim 1 or 2, characterized in that the Cu is supplied continuously²⁺The salt is the bottom product obtained by distillation of TAIC from the continuously withdrawn reaction mixture, the temperature of which is not cooled to a temperature below 90 ℃ before reuse.

9. A method of making TAIC comprising Cu at a temperature of at least 90 ℃²⁺Rearranging triallyl cyanurate (TAC) in the presence of a salt, characterized in that:

TAC is continuously introduced into a TAIC-containing starting reaction mixture which is passed at 90-160 ℃ in Cu²⁺Formed by rearranging the TAC in the presence of the salt, and thereafter not cooling to below 90 ℃, under these conditions while maintaining the temperature in the range of 90-160 ℃, and continuously distilling the formed TAIC out of the reaction mixture under reduced pressure, the addition rate of the TAC being substantially equivalent to the distillation rate of the TAIC in g TAC/min and the distillation rate of the TAIC in g TAIC/min,

wherein said Cu²⁺The salt is selected from CuCl₂、CuBr₂、CuI₂、Cu(RCOO)₂Salt, Cu (RCOO)₂Wherein R is alkyl or aryl.

10. The process according to claim 9, characterized in that Cu is present in an amount of 0.01 to 1% by weight, based on the TAC used for the preparation of the starting reaction mixture²⁺In the presence ofAnd (4) rearranging.

11. The process according to claim 9 or 10, characterized in that the rearrangement is carried out at 110-140 ℃.

12. Process according to claim 9 or 10, characterized in that TAC is added at such a rate that the TAIC distilled off is virtually free of unconverted TAC.