Preparation method of bromotriazine

Abstract

The invention belongs to the technical field of flame retardants, and particularly relates to a preparation method of bromotriazine, which comprises the following steps: adding phenol and deionized water into a reaction container, dropwise adding hydrogen peroxide and liquid bromine into a reaction system in a staggered manner, and adding a catalyst; after the reaction is finished, separating the catalyst, firstly carrying out quenching treatment on the filtrate, then carrying out extraction treatment, and carrying out reduced pressure distillation on the extracted organic phase to obtain tribromophenol; dissolving the prepared tribromophenol in dichloromethane, adding triethylamine and tetrabutylammonium bromide, stirring to form a homogeneous system, adding cyanuric chloride into the homogeneous system, and regulating and controlling the pH in stages; concentrating the organic phase which is washed to be neutral, adding n-hexane to initiate primary nucleation, dropwise adding ethyl acetate to adjust the polarity of the solvent, and promoting crystal growth; and filtering and drying in vacuum to obtain the bromo-triazine. Through staged pH / temperature regulation and control, the composite catalyst system realizes efficient synthesis of bromotriazine.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardants, and particularly relates to a method for preparing bromotriazine. Background Art

[0002] Bromotriazine is a new type of bromine / nitrogen synergistic flame retardant, mainly used for flame retardant of polymer materials such as polystyrene, polyester, polyolefin (PP, PE). At the same time, due to its high initial decomposition temperature and good thermal stability, it is particularly suitable for flame retardant modification of plastic products processed at higher temperatures.

[0003] The existing preparation method is mainly based on the condensation reaction of tribromophenol and cyanuric chloride (such as the Chinese invention patents with publication numbers CN113214175A or CN114349716A), but the pH control is extensive. The existing technology adds a sufficient amount of strong alkali solution at one time, resulting in too high pH, ​​which easily causes hydrolysis of cyanuric chloride and leads to the generation of impurities (such as triazine ring opening products), affecting the purity, performance and application range of the product. Summary of the invention

[0004] In view of the problems of easy hydrolysis, high number of by-products and low product purity of cyanuric chloride in the prior art, the present invention proposes a method for preparing bromotriazine to achieve efficient synthesis through multi-dimensional technical optimization. Specifically, it is achieved through the following technical solutions: A method for preparing bromotriazine comprises the following steps: (1) Phenol and deionized water are added to a reaction vessel, and the mixture is continuously stirred. At low temperature, hydrogen peroxide is added dropwise to the reaction system. After 30 to 40 minutes, liquid bromine is added dropwise to the reaction system. The molar ratio of liquid bromine to hydrogen peroxide is controlled at (1 to 1.5):1, and the molar ratio of liquid bromine to phenol is controlled at (3 to 3.5):1. After the addition of liquid bromine is completed, 2 to 3 wt% of a catalyst is added based on the total mass of the reaction liquid, and the reaction is carried out for 2 to 3 hours. (2) After the reaction is completed, the catalyst is separated, the filtrate is first quenched and then extracted, and the organic phase after extraction is distilled under reduced pressure to obtain tribromophenol; (3) dissolving the prepared tribromophenol in dichloromethane, adding triethylamine and tetrabutylammonium bromide, wherein the molar ratio of triethylamine to tribromophenol is controlled within the range of (0.1-0.2):1, and the molar ratio of tetrabutylammonium bromide to tribromophenol is controlled within the range of (0.01-0.02):1, stirring to form a homogeneous system, adjusting the pH to 10.5 in stages, adding cyanuric chloride to the homogeneous system, wherein the molar ratio of cyanuric chloride to tribromophenol is controlled within the range of 1:(2.9-3.1), and after the reaction is completed, separating the liquids to remove the aqueous phase, and washing the organic phase to neutrality; (4) Concentrate the washed neutral organic phase to 1 / 3 of the original volume, add n-hexane to initiate primary nucleation, cool to 5°C at 1°C / min, and add ethyl acetate dropwise to adjust the solvent polarity and promote crystal growth; (5) Filter the resulting crystals, wash with cold n-hexane, and dry in vacuo at 60°C for 6 hours to obtain bromotriazine.

[0005] Preferably, the pH control step in stages comprises: (1) Add NaOH solution to the homogeneous system to adjust the pH to 8.0, add cyanuric chloride, control the temperature at 15°C, and react for 1 to 1.5 hours; (2) Raise the temperature to 35°C, add NaOH solution to adjust the pH to 9.0, and react for 1.5 to 2 hours; (3) NaOH solution was added to adjust the pH to 10.5, and 0.5-1 wt % zinc oxide nanoparticles were added based on the total mass of the reaction system, and the reaction was carried out for 1-1.5 h.

[0006] Preferably, the mass concentration of the NaOH solution is 20%.

[0007] Preferably, the quenching step comprises: (1) Slowly add 10% NaHSO3 solution to the filtrate until the yellow color of the filtrate fades; (2) Use starch-KI test paper to check whether there is residual Br2 in the filtrate. If the test paper turns blue, continue to add NaHSO3 solution.

[0008] Preferably, the extraction step comprises: (1) Add ethyl acetate to the quenched solution, mix evenly, let stand to separate the layers, separate the lower aqueous phase, extract with ethyl acetate twice, and combine the organic phases; (2) The organic phase after extraction is washed with saturated brine.

[0009] Preferably, the catalyst is a magnetic catalyst Fe3O4@SiO2.

[0010] Preferably, the mass concentration of the hydrogen peroxide is 30%.

[0011] After adopting the above technical solution, the beneficial effects of the present invention are: The staged pH control reduces the hydrolysis of cyanuric chloride. The efficient synthesis of bromotriazine is achieved through staged pH / temperature control and a composite catalyst system. Compared with traditional technologies, the purity of the product is significantly improved. DETAILED DESCRIPTION

[0012] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the following specific embodiments will further describe the present invention in detail. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention.

[0013] Example 1 The present invention provides a method for preparing bromotriazine, comprising the following steps: (1) In a 500 mL four-necked flask, 1 mol of phenol was dispersed in 200 mL of deionized water at 5 °C (ice-water bath) to form an emulsion.

[0014] Phenol is used as a reaction substrate to provide a benzene ring skeleton. Low temperature treatment is intended to reduce the spontaneous oxidation rate of phenol, reduce unnecessary side reactions, and ensure the high efficiency of the reaction and the purity of the product.

[0015] (2) Maintaining stirring, add 0.3 mol of 30% hydrogen peroxide to the emulsion at a rate of 1 mL / min. After 30 min, add 2 wt% of magnetic catalyst Fe3O4@SiO2 based on the total mass of the reaction liquid, and then add 3 mol of liquid bromine at a rate of 2 mL / min. The temperature is controlled at 10 °C in an ice-water bath and the reaction is carried out for 2.5 h.

[0016] The magnetic properties of Fe3O4@SiO2 facilitate rapid recovery through an external magnetic field after the reaction, reducing the impact of catalyst residues on the product. Hydrogen peroxide generates highly active hydroxyl radicals on the surface of Fe3O4@SiO2 through the Fenton reaction, which preferentially attacks the ortho / para hydrogen of phenol, enhancing its electrophilic substitution activity and forming highly active ortho / para phenoxyl radical intermediates. With the addition of liquid bromine, the SiO2 coating of Fe3O4@SiO2 restricts the free diffusion of bromine molecules through the steric hindrance effect, and at the same time, the surface silanol (Si-OH) adsorbs Br through hydrogen bonds. + , forming a local high concentration of bromide cations. This directional adsorption guides Br + It preferentially attacks the activated ortho / para positions of the benzene ring, inhibits the formation of meta-position by-products, and thus directs the generation of tribromophenol (2,4,6-tribromophenol).

[0017] (3) After the reaction is completed, the catalyst is separated by magnetic separation or filtration, the filtrate is first quenched and then extracted, and the organic phase after extraction is distilled under reduced pressure to obtain high-purity tribromophenol.

[0018] Quenching treatment: The purpose of quenching treatment is to remove unreacted liquid bromine through chemical reduction reaction. Transfer the filtrate to a beaker and slowly add a 10% NaHSO3 solution in an ice-water bath until the yellow color of the filtrate fades (indicating that Br2 is completely reduced). Use starch-KI test paper to check whether there is residual Br2 in the filtrate. If the test paper turns blue, continue to add NaHSO3 solution.

[0019] Extraction treatment: The quenched filtrate was transferred to a separatory funnel, 50 mL of ethyl acetate was added to dissolve tribromophenol, the mixture was shaken evenly, and the mixture was allowed to stand for stratification. The separated lower aqueous phase was extracted twice with 30 mL of ethyl acetate, and the organic phases were collected and combined. The extracted organic phase was washed twice with 20 mL of saturated brine to reduce the water content of the organic phase through the salting-out effect, which was beneficial for faster removal of the solvent during the subsequent vacuum distillation and improved the drying efficiency of the product.

[0020] Vacuum distillation: The extracted organic phase was transferred to a rotary evaporator, the system pressure was slowly reduced to 20 mmHg, the water bath temperature was set to 50°C, and distilled until about 20 mL of concentrate remained in the flask.

[0021] After stopping the distillation, immediately add 10 mL of n-hexane precooled to 5°C and stir to fully mix the n-hexane with the concentrate. Place the mixture in an ice-water bath (0°C) for 1 hour. After n-hexane (low polarity) and ethyl acetate (medium polarity) are mixed, the polarity and temperature of the system decrease, and the solubility of tribromophenol drops sharply, resulting in the precipitation of crystals.

[0022] The crystals collected by filtration were washed twice with 5 mL of n-hexane precooled to 5° C., and then dried under vacuum at 40° C. for 2 h to obtain high-purity tribromophenol.

[0023] (4) The prepared tribromophenol is subjected to a triazine ring condensation reaction, taking 1 mol of tribromophenol as an example.

[0024] Preparation of premix: In a 1500 mL beaker, tribromophenol was dispersed in 800 mL of dichloromethane, and 0.1 mol of triethylamine and 0.01 mol of tetrabutylammonium bromide were added, and stirred to form a homogeneous system.

[0025] Triethylamine, as an organic base, captures the HCl generated by the reaction, maintains the pH stability of the system, prevents the system from acidifying and causing the protonation of the phenol oxide anion, and maintains the nucleophilic activity. Tetrabutylammonium bromide, as a phase transfer catalyst, transfers the phenol oxide anion from the aqueous phase to the organic phase (dichloromethane) through the ion pair effect, significantly improving the reaction efficiency at the interface between the two phases and reducing the sensitivity of the interfacial reaction to pH.

[0026] The degree of deprotonation of phenolic hydroxyl groups is controlled in stages, and the chlorine atoms are replaced step by step through the synergistic effect of pH and temperature: In the first stage, a 20% NaOH solution was added dropwise to adjust the pH to 8.0, 1 mol of cyanuric chloride was added, the temperature was controlled at 15°C, and the reaction was carried out for 1 hour; In the second stage, the temperature was raised to 35°C, and NaOH solution was added to adjust the pH to 9.0 to promote the substitution of the remaining chlorine atoms, and the reaction lasted for 1.5 hours; In the third stage, the current temperature was maintained, NaOH solution was added to adjust the pH to 10.5, and 0.5 wt % zinc oxide nanoparticles were added based on the total reaction system mass, and the reaction was carried out for 1 hour.

[0027] Cyanuric chloride and tribromophenol are concentrated in the organic phase (dichloromethane), while OH in the aqueous phase of NaOH - Tetrabutylammonium bromide is selectively transferred to the organic phase to inhibit the hydrolysis side reaction of cyanuric chloride. - It preferentially participates in the deprotonation of the hydroxyl group of tribromophenol to generate phenol oxide anion. The nucleophilicity of phenol oxide anion is significantly stronger than that of OH - , preferentially attacking the chlorine atom of cyanuric chloride to complete the substitution reaction. - Transfer to the water phase interface and re-engage OH - transfer, forming a catalytic cycle.

[0028] In the first stage, under weak alkaline conditions of pH 8.0, the hydroxyl group of tribromophenol is partially deprotonated to generate phenoloxy anions, which have enhanced nucleophilicity and preferentially attack the most active chlorine atom (α-position chlorine) in cyanuric chloride, eventually forming a monochlorodiphenol triazine intermediate, which still retains two unsubstituted chlorine atoms. Low temperature can inhibit the spontaneous hydrolysis side reactions of cyanuric chloride (such as the formation of cyanuric acid), while limiting the simultaneous substitution of multiple chlorine atoms, ensuring high selectivity of single-substituted products.

[0029] In the second stage, the electronic effect of cyanuric chloride is changed due to the introduction of the first substituent, and the activity of β-position chlorine is reduced. However, efficient substitution can still be achieved through alkalinity enhancement and temperature compensation to generate a dichloromonophenol triazine intermediate with one unsubstituted chlorine atom remaining.

[0030] In the third stage, under strong alkaline conditions, the phenolic hydroxyl group is completely deprotonated to eliminate the effect of steric hindrance on the substitution of the third chlorine atom (γ-chlorine), and finally a trisubstituted product, namely bromotriazine, is generated. The hydroxyl groups on the surface of zinc oxide nanoparticles can act as Lewis acids to activate the chlorine atoms (γ-chlorine) of cyanuric chloride, reducing the activation energy of the substitution reaction. At the same time, under light conditions, the conduction band electrons and valence band holes of ZnO can produce active oxygen species (such as hydroxyl radicals), remove organic byproducts in the reaction system, and improve the purity of the product.

[0031] (5) After the reaction, the layers were separated and the aqueous phase was removed. The organic phase was washed twice with 200 mL of 5% NaHCO3 solution and then washed with deionized water until neutral.

[0032] (6) The washed neutral organic phase is transferred to a rotary evaporator, heated, and concentrated to 1 / 3 of the original volume to increase the supersaturation of the target product in the solution and provide a driving force for subsequent crystallization.

[0033] Add 200 mL of n-hexane to the concentrate, cool to 5°C at 1°C / min, slowly drop 100 mL of ethyl acetate to adjust the polarity of the solvent, promote orderly growth of crystals and inhibit impurity coprecipitation. Place in an ice-water bath and stand at 5°C for 1 hour to allow the crystals to fully grow and stabilize the crystal form.

[0034] (7) Filter the obtained crystals, wash them twice with 50 mL of n-hexane precooled to 5°C, transfer the crystals to a vacuum drying oven, and dry them in vacuum at 60°C for 6 hours to obtain bromotriazine.

[0035] Example 2 The present invention provides a method for preparing bromotriazine, comprising the following steps: (1) In a 500 mL four-necked flask, 1 mol of phenol was dispersed in 200 mL of deionized water at 5 °C (ice-water bath) to form an emulsion.

[0036] (2) Maintaining stirring, add 0.35 mol of 30% hydrogen peroxide to the emulsion at a rate of 1 mL / min. After 35 min, add 2.5 wt% of magnetic catalyst Fe3O4@SiO2 based on the total mass of the reaction liquid, and then add 3.3 mol of liquid bromine at a rate of 2 mL / min. The temperature is controlled at 15 °C in an ice-water bath and the reaction is carried out for 3 h.

[0037] (3) After the reaction is completed, the catalyst is separated by magnetic separation or filtration, the filtrate is first quenched and then extracted, and the organic phase after extraction is distilled under reduced pressure to obtain high-purity tribromophenol.

[0038] (4) Disperse 1 mol of tribromophenol in 800 mL of dichloromethane, add 0.15 mol of triethylamine and 0.015 mol of tetrabutylammonium bromide, and stir to form a homogeneous system. Control the degree of deprotonation of phenolic hydroxyl groups in stages, and achieve step-by-step substitution of chlorine atoms through the synergistic effect of pH and temperature: In the first stage, a 20% NaOH solution was added dropwise to adjust the pH to 8.0, 1.2 mol of cyanuric chloride was added, the temperature was controlled at 15°C, and the reaction was carried out for 1.2 hours; In the second stage, the temperature was raised to 35°C, and NaOH solution was added to adjust the pH to 9.0 to promote the substitution of the remaining chlorine atoms, and the reaction lasted for 1.8 hours; In the third stage, the current temperature was maintained, NaOH solution was added to adjust the pH to 10.5, and 0.8 wt % zinc oxide nanoparticles were added based on the total reaction system mass, and the reaction was continued for 1.2 h.

[0039] (5) After the reaction, the layers were separated and the aqueous phase was removed. The organic phase was washed twice with 200 mL of 5% NaHCO3 solution and then washed with deionized water until neutral.

[0040] (6) Transfer the neutral organic phase to a rotary evaporator, heat it up, and concentrate it to 1 / 3 of the original volume. Add 200 mL of n-hexane to the concentrate, cool it down to 5°C at 1°C / min, and slowly add 100 mL of ethyl acetate to adjust the polarity of the solvent. Place it in an ice-water bath and let it stand at 5°C for 1 hour to allow the crystals to grow fully and stabilize the crystal form.

[0041] (7) Filter the obtained crystals, wash them twice with 50 mL of n-hexane precooled to 5°C, transfer the crystals to a vacuum drying oven, and dry them in vacuum at 60°C for 6 hours to obtain bromotriazine.

[0042] Example 3 The present invention provides a method for preparing bromotriazine, comprising the following steps: (1) In a 500 mL four-necked flask, 1 mol of phenol was dispersed in 200 mL of deionized water at 5 °C (ice-water bath) to form an emulsion.

[0043] (2) Maintaining stirring, add 0.4 mol of 30% hydrogen peroxide to the emulsion at a rate of 1 mL / min. After 35 min, add 3 wt% of magnetic catalyst Fe3O4@SiO2 based on the total mass of the reaction liquid, and then add 3.5 mol of liquid bromine at a rate of 2 mL / min. Control the temperature at 15 °C in an ice-water bath and react for 2 h.

[0044] (3) After the reaction is completed, the catalyst is separated by magnetic separation or filtration, the filtrate is first quenched and then extracted, and the organic phase after extraction is distilled under reduced pressure to obtain high-purity tribromophenol.

[0045] (4) Disperse 1 mol of tribromophenol in 800 mL of dichloromethane, add 0.2 mol of triethylamine and 0.02 mol of tetrabutylammonium bromide, and stir to form a homogeneous system. Control the degree of deprotonation of phenolic hydroxyl groups in stages, and achieve step-by-step substitution of chlorine atoms through the synergistic effect of pH and temperature: In the first stage, a 20% NaOH solution was added to adjust the pH to 8.0, 1.5 mol of cyanuric chloride was added, the temperature was controlled at 15°C, and the reaction was carried out for 1.5 hours; In the second stage, the temperature was raised to 35°C, and NaOH solution was added to adjust the pH to 9.0 to promote the substitution of the remaining chlorine atoms, and the reaction lasted for 2 hours; In the third stage, the current temperature was maintained, NaOH solution was added to adjust the pH to 10.5, and 0.8 wt % zinc oxide nanoparticles were added based on the total reaction system mass, and the reaction was carried out for 1.5 h.

[0046] (5) After the reaction, the layers were separated and the aqueous phase was removed. The organic phase was washed twice with 200 mL of 5% NaHCO3 solution and then washed with deionized water until neutral.

[0047] (6) Transfer the neutral organic phase to a rotary evaporator, heat it up, and concentrate it to 1 / 3 of the original volume. Add 200 mL of n-hexane to the concentrate, cool it down to 5°C at 1°C / min, and slowly add 100 mL of ethyl acetate to adjust the polarity of the solvent. Place it in an ice-water bath and let it stand at 5°C for 1 hour to allow the crystals to grow fully and stabilize the crystal form.

[0048] (7) Filter the obtained crystals, wash them twice with 50 mL of n-hexane precooled to 5°C, transfer the crystals to a vacuum drying oven, and dry them in vacuum at 60°C for 6 hours to obtain bromotriazine.

[0049] The bromotriazine preparation methods of Examples 1-3 were used to prepare finished bromotriazine products, and the performance of the finished products was tested. The results are shown in Table 1.

[0050] Table 1 Bromotriazine performance test data table

[0051] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing bromotriazine, characterized in that: The steps include: (1) Phenol and deionized water are added to a reaction vessel, and the mixture is continuously stirred. Hydrogen peroxide is added dropwise to the reaction system. After 30 to 40 minutes, liquid bromine is added dropwise to the reaction system. The molar ratio of liquid bromine to hydrogen peroxide is controlled at (1 to 1.5):1, and the molar ratio of liquid bromine to phenol is controlled at (3 to 3.5):

1. After the addition of liquid bromine is completed, 2 to 3 wt% of a catalyst is added based on the total mass of the reaction liquid, and the reaction is carried out for 2 to 3 hours. (2) After the reaction is completed, the catalyst is separated, the filtrate is first quenched and then extracted, and the organic phase after extraction is distilled under reduced pressure to obtain tribromophenol; (3) dissolving the prepared tribromophenol in dichloromethane, adding triethylamine and tetrabutylammonium bromide, the molar ratio of triethylamine to tribromophenol is controlled within the range of (0.1-0.2):1, the molar ratio of tetrabutylammonium bromide to tribromophenol is controlled within the range of (0.01-0.02):1, stirring to form a homogeneous system, adjusting the pH to 10.5 in stages, adding cyanuric chloride in the pH adjustment stage, the molar ratio of cyanuric chloride to tribromophenol is controlled within the range of 1:(2.9-3.1), after the reaction is completed, separating and removing the aqueous phase, and washing the organic phase to neutrality; (4) Concentrate the washed neutral organic phase to 1 / 3 of the original volume, add n-hexane to initiate primary nucleation, cool to 5°C at 1°C / min, and add ethyl acetate dropwise to adjust the solvent polarity and promote crystal growth; (5) The obtained crystals are filtered, washed with n-hexane, and dried under vacuum at 60°C for 6 hours to obtain bromotriazine.

2. The method for preparing bromotriazine according to claim 1, characterized in that: The pH control steps are as follows: (1) Add NaOH solution to the homogeneous system to adjust the pH to 8.0, add cyanuric chloride, control the temperature at 15°C, and react for 1 to 1.5 hours; (2) Raise the temperature to 35°C, add NaOH solution to adjust the pH to 9.0, and react for 1.5 to 2 hours; (3) NaOH solution was added to adjust the pH to 10.5, and 0.5-1 wt % zinc oxide nanoparticles were added based on the total mass of the reaction system, and the reaction was carried out for 1-1.5 h.

3. The method for preparing bromotriazine according to claim 2, wherein: The mass concentration of the NaOH solution is 20%.

4. The method for preparing bromotriazine according to claim 1, characterized in that: The quenching step comprises: (1) Add 10% NaHSO3 solution to the filtrate until the yellow color of the filtrate fades; (2) Use starch-KI test paper to check whether there is residual Br2 in the filtrate. If the test paper turns blue, continue to add NaHSO3 solution.

5. The method for preparing bromotriazine according to claim 4, characterized in that: The steps of the extraction process include: (1) Add ethyl acetate to the quenched solution, mix evenly, let stand to separate the layers, separate the lower aqueous phase, extract with ethyl acetate twice, and combine the organic phases; (2) The organic phase after extraction is washed with saturated brine.

6. The method for preparing bromotriazine according to claim 1, characterized in that: The catalyst is a magnetic catalyst Fe3O4@SiO2.

7. The method for preparing bromotriazine according to claim 1, characterized in that: The mass concentration of the hydrogen peroxide is 30%.

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