A process for the preparation of trihydroxyethyl isocyanurate

Abstract

The application discloses a preparation method of trihydroxyethyl isocyanurate and belongs to the technical field of organic compound synthesis. The preparation method comprises the following steps: S1, cyanuric acid, a catalyst and ethylene carbonate are added into a reaction kettle, vacuum is drawn after nitrogen is introduced, temperature is raised and stirring is started; S2, after the temperature of the reaction kettle is raised to 80-100 DEG C, ring-opening etherification reaction is carried out by introducing ethylene oxide; S3, after the ring-opening etherification reaction is completed, temperature is continuously raised, so that the unreacted phenolic hydroxyl groups in the cyanuric acid react with the ethylene carbonate, and carbon dioxide is discharged; S4, after the reaction is completed, a small amount of unreacted ethylene carbonate and the catalyst are removed, and the trihydroxyethyl isocyanurate product is obtained. The preparation method is simple, solvent recovery and crystallization process are not needed, the trihydroxyethyl isocyanurate product with no odor and high purity can be obtained, and the application range of the product is greatly widened.

Description

Technical Field

[0001] This invention relates to the field of organic compound synthesis technology, and specifically to a method for preparing trihydroxyethyl isocyanurate. Background Technology

[0002] Trihydroxyethyl isocyanurate (Syc) is an important trifunctional triazine monomer and fine organic chemical intermediate, which is widely used in the production of heat-resistant and solvent-resistant coatings, molding compounds, reinforced plastics, adhesives, flame retardants and other industries.

[0003] Currently, the main industrial method for preparing trihydroxyethyl isocyanurate is as follows: Cyanuric acid and the alkaline catalyst triethylamine are dispersed in an organic solvent, ethylene glycol monomethyl ether or methanol. Ethylene oxide is then introduced to initiate an addition reaction. After the reaction, some of the organic solvent is removed, and the mixture is decolorized with activated carbon, cooled, crystallized, and centrifuged to obtain the trihydroxyethyl isocyanurate product. The mother liquor is then distilled, the solvent is recovered and reused, and the crude liquid cyclade is obtained from the bottom of the still. Due to the high melting point (>360℃) and high polarity of cyanuric acid, the amount of organic solvent used in this process is more than twice that of the raw material cyanuric acid, resulting in a long process flow and high energy consumption. Furthermore, the crude liquid cyclade byproduct of this process is inexpensive, and its yield is only about 10-15% of the total trihydroxyethyl isocyanurate product.

[0004] To address the above issues, Chinese patent CN 113234033A discloses a method using DMF as the reaction solvent and a mixture of tetramethylammonium chloride and triethylamine as the catalyst to catalyze the ring-opening of cyanuric acid into ethylene oxide to prepare trihydroxyethyl isocyanurate, which can increase the overall yield of the product from the current 88% to 95%. However, the high boiling point of DMF results in a certain amount of DMF residue in the product, thus affecting its odor. US patent US 3313812 discloses a method that does not add solvent or catalyst during the reaction, dissolving cyanuric acid in at least 50% of the weight of trihydroxyethyl isocyanurate at 120-250°C, and then introducing at least three times the molar amount of ethylene oxide to obtain the trihydroxyethyl isocyanurate product. However, the product prepared by this process has low purity and requires a dissolution-recrystallization process to obtain a high-purity product. US Patent 6046326 discloses a process in which cyanuric acid and at least three molar amounts of ethylene carbonate react to produce a trihydroxyethyl isocyanurate polyol solution, which can be directly used as a crosslinking agent for polyesters. This process involves using a small amount of polyol as a solvent and a specific heterocyclic amine as a catalyst, under open conditions at 160-170°C, to produce a solution of cyanuric acid and ethylene carbonate. However, this process does not purify the product from the polyol, thus limiting its application range.

[0005] Therefore, there is an urgent need to develop a method for preparing odorless and high-purity trihydroxyethyl isocyanurate without the need for solvent recovery and crystallization processes. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing trihydroxyethyl isocyanurate. This method has a simple process, does not require solvent recovery or crystallization, and can obtain odorless and high-purity trihydroxyethyl isocyanurate products, which greatly expands the application range of the products.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0009] S1. Add cyanuric acid, catalyst and ethylene carbonate to the reactor, add nitrogen and then evacuate, heat and start stirring.

[0010] S2. After raising the temperature of the reactor to 80-100°C, ethylene oxide is introduced to carry out the ring-opening etherification reaction;

[0011] S3. After the ring-opening etherification reaction is completed, continue to raise the temperature so that the unreacted phenolic hydroxyl groups in cyanuric acid react with ethylene carbonate and release carbon dioxide.

[0012] S4. After the reaction is complete, a small amount of unreacted ethylene carbonate and catalyst are removed to obtain the trihydroxyethyl isocyanurate product.

[0013] In a preferred embodiment of the present invention, the catalyst in step S1 is dimethylacetamide. The purity of the dimethylacetamide is ≥99.9%.

[0014] More preferably, the amount of catalyst used in step S1 is 1 to 5‰ of the sum of the mass of cyanuric acid, ethylene carbonate, and ethylene oxide.

[0015] In a preferred embodiment of the present invention, the molar ratio of cyanuric acid to ethylene carbonate in step S1 is 1:0.5 to 1.0.

[0016] In a preferred embodiment of the present invention, the temperature is raised to 60-80°C before stirring is started in step S1.

[0017] In a preferred embodiment of the present invention, the reaction pressure of the ring-opening etherification reaction in step S2 is ≤0.4 MPa and the reaction time is 4 to 16 h.

[0018] In a preferred embodiment of the present invention, the molar ratio of cyanuric acid to ethylene oxide in step S2 is 1:2.05 to 2.55.

[0019] In a preferred embodiment of the present invention, the reaction temperature in step S3 is 140–170°C and the reaction time is 2–10 h.

[0020] As a preferred embodiment of the present invention, the conditions for removing a small amount of unreacted ethylene carbonate and catalyst in step S4 are: degassing pressure ≤100pa, degassing temperature 170℃, and degassing time 2h.

[0021] In a preferred embodiment of the present invention, the trihydroxyethyl isocyanurate obtained in step S4 has a purity of ≥98.5%.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The present invention uses ethylene carbonate to react with cyanuric acid. Ethyl carbonate is both the solvent in step S1 and the raw material in the ring-opening etherification reaction in step S2. Compared with the process of preparing trihydroxyethyl isocyanurate using the traditional solvent method, the present invention saves the solvent recovery and reuse step.

[0024] 2. This invention uses dimethylacetamide as a catalyst, which has a weaker odor compared to traditional processes that use aliphatic amines and aromatic amines and their salts as catalysts; combined with high vacuum and high temperature degassing processes, the final trihydroxyethyl isocyanurate product is essentially odorless.

[0025] 3. Compared with traditional preparation processes, the present invention can obtain high-purity (≥98.5%, LC) trihydroxyethyl isocyanurate products without crystallization process, and the process is simpler.

[0026] 4. Compared with processes that use only ethylene carbonate and cyanuric acid as reaction raw materials, the present invention achieves a higher yield (≥80%) and lower cost, making it suitable for large-scale industrial production. Attached Figure Description

[0027] Figure 1 This is a liquid chromatogram of the trihydroxyethyl isocyanurate product prepared in Example 4 of the present invention. Detailed Implementation

[0028] The preparation method of trihydroxyethyl isocyanurate provided by the present invention specifically includes the following steps:

[0029] S1. Add cyanuric acid, catalyst and ethylene carbonate to the pressure-resistant reactor, replace the air with nitrogen three times and then evacuate. Heat the pressure-resistant reactor to 60-80°C and start stirring.

[0030] S2. After raising the temperature of the pressure-resistant reactor to 80-100℃, ethylene oxide is introduced to carry out the ring-opening etherification reaction at a reaction pressure ≤0.4Mpa for 4-16 hours.

[0031] S3. After the ring-opening etherification reaction is completed, continue to raise the temperature to 140-170℃ and allow the unreacted phenolic hydroxyl groups in cyanuric acid to react with ethylene carbonate under normal pressure for 2-10 hours. The carbon dioxide produced by the reaction is discharged into the atmosphere through a pressure regulating valve.

[0032] S4. After the reaction is completed, a small amount of unreacted ethylene carbonate and catalyst are removed under the conditions of degassing pressure ≤100pa and degassing temperature 170℃. The degassing time is 2h, and a trihydroxyethyl isocyanurate product with a purity ≥98.5% (LC) is obtained.

[0033] In the above preparation method, in step S1, the molar ratio of cyanuric acid to ethylene carbonate is 1:0.5 to 1.0; the catalyst is dimethylacetamide, the purity of which is ≥99.9%, and the amount of catalyst used is 1 to 5‰ of the sum of the mass of cyanuric acid, ethylene carbonate, and ethylene oxide; in step S2, the molar ratio of cyanuric acid to ethylene oxide is 1:2.05 to 2.55.

[0034] In the above preparation method, this invention controls the reaction temperature of step S2 to 80–100°C, ensuring that the catalyst dimethylacetamide can only catalyze the ring-opening of ethylene oxide with cyanuric acid at this temperature, while cyanuric acid and ethylene carbonate do not react significantly. This is mainly because ethylene carbonate has a five-membered ring structure with relatively low ring strain energy, and therefore does not undergo ring-opening within this temperature range; while ethylene oxide has a three-membered ring structure with a much higher ring strain energy than the five-membered ring structure of ethylene carbonate. Therefore, within this temperature range, the catalyst dimethylacetamide can effectively catalyze the ring-opening of ethylene oxide with cyanuric acid. In other words, within this temperature range, the reaction rate constant of dimethylacetamide catalyzing the ring-opening of ethylene oxide with cyanuric acid is much greater than that catalyzing the ring-opening of ethylene carbonate with cyanuric acid (k1 >> k2).

[0035]

[0036] In the above formula, k1 represents the rate constant of the reaction of dimethylacetamide catalyzing the ring-opening of ethylene oxide with cyanuric acid; k2 represents the rate constant of the reaction of dimethylacetamide catalyzing the ring-opening of ethylene carbonate with cyanuric acid.

[0037] The product obtained by this invention has high purity and does not require crystallization. This is mainly because: ethylene carbonate has a five-membered ring structure, which is relatively stable; dihydroxyethyl isocyanurate also contains an active hydrogen structure (RNH), allowing dimethylacetamide to effectively catalyze its ring-opening ethylene carbonate production; while trihydroxyethyl isocyanurate only contains a relatively inert alcohol hydroxyl structure, and dimethylacetamide cannot effectively catalyze its ring-opening ethylene carbonate production. That is, in the reaction stage of step S2, the reaction rate constant of dimethylacetamide catalyzing the ring-opening ethylene carbonate production of dihydroxyethyl isocyanurate is much greater than that of trihydroxyethyl isocyanurate (k3 >> k).3' ).

[0038]

[0039] In the above formula, k3 represents the rate constant of the reaction of dihydroxyethyl isocyanurate ring-opening ethylene carbonate with dimethylacetamide as a catalyst; k 3' This represents the rate constant for the reaction of trihydroxyethyl isocyanurate ring-opening ethylene carbonate with dimethylacetamide as a catalyst.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0043] S1. Add 645g of cyanuric acid, 220g of ethylene carbonate, and 2.84g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 70°C before starting the stirrer.

[0044] S2. After stirring for 30 minutes, raise the temperature of the pressure vessel to 95°C and start introducing 555g of ethylene oxide. The introduction will be completed in about 4 hours. Continue the reaction for about 2 hours while keeping the pressure of the vessel constant.

[0045] S3. After the ring-opening etherification reaction is complete, continue heating the reactor to 160°C. As the reaction proceeds, the pressure in the reactor gradually increases. When the pressure in the pressure-resistant reactor is slightly higher than 1 atmosphere, connect the oil seal to the vent at the top of the reactor, and then slowly open the vent valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After 4 hours of reaction, when no more gas is released from the reactor, continue the reaction for another hour.

[0046] S4. After the reaction is complete, continue heating the reactor to 170°C and degas for 2 hours. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1303g of trihydroxyethyl isocyanurate.

[0047] Example 2

[0048] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0049] S1. Add 645g of cyanuric acid, 264g of ethylene carbonate, and 4.33g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 80°C before starting the stirrer.

[0050] S2. After stirring for 30 minutes, raise the temperature of the reactor to 85°C and start introducing 535g of ethylene oxide. The introduction will be completed in about 10 hours. Continue the reaction for about 2 hours while keeping the reactor pressure constant.

[0051] S3. After the ring-opening etherification reaction is complete, continue heating the reactor to 150°C. As the reaction proceeds, the reactor pressure gradually increases. When the pressure in the pressure-resistant reactor slightly exceeds one atmosphere, connect the oil seal to the vent at the top of the reactor, and then slowly open the vent valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After 7 hours of reaction, when no more gas is released from the reactor, continue the reaction for another hour.

[0052] S4. After the reaction is complete, continue heating the reactor to 170°C and degas for 2 hours. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1305g of trihydroxyethyl isocyanurate.

[0053] Example 3

[0054] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0055] S1. Add 645g of cyanuric acid, 308g of ethylene carbonate, and 1.47g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 75°C before starting the stirrer.

[0056] S2. After stirring for 30 minutes, raise the temperature of the reactor to 100°C and start introducing 515g of ethylene oxide. The introduction will be completed in about 2 hours. Continue the reaction for about 2 hours while keeping the reactor pressure constant.

[0057] S3. After the reaction is complete, continue heating the reactor to 170℃. As the reaction proceeds, the pressure in the reactor gradually increases. When the pressure in the reactor is slightly higher than 1 atmosphere, connect the oil seal to the exhaust port at the top of the reactor, and then slowly open the exhaust port valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After reacting for 2 hours, when the gas in the reactor stops escaping, continue reacting for another hour.

[0058] S4. After the reaction is complete, maintain the reactor temperature at 170℃ and degas for 2 hours. After degassing, cool the reactor to 140℃, discharge the product, and obtain approximately 1302g of trihydroxyethyl isocyanurate.

[0059] Example 4

[0060] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0061] S1. Add 645g of cyanuric acid, 352g of ethylene carbonate, and 5.95g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 70°C before starting the stirrer.

[0062] S2. After stirring for 30 minutes, raise the temperature of the reactor to 85°C and start introducing 489g of ethylene oxide. The introduction will be completed in about 10 hours. Continue the reaction for about 2 hours while keeping the reactor pressure constant.

[0063] S3. After the reaction is complete, continue heating the reactor to 145℃. As the reaction proceeds, the pressure in the reactor gradually increases. When the pressure in the pressure-resistant reactor is slightly higher than 1 atmosphere, connect the oil seal to the vent at the top of the reactor, and then slowly open the vent valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After 5 hours of reaction, when no more gas is released from the reactor, continue the reaction for another hour.

[0064] S4. After the reaction is complete, continue heating the reactor to 170°C and degas for 2 hours. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1302g of trihydroxyethyl isocyanurate.

[0065] Example 5

[0066] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0067] S1. Add 645g of cyanuric acid, 396g of ethylene carbonate, and 4.53g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 65°C before starting the stirrer.

[0068] S2. After stirring for 30 minutes, raise the temperature of the reactor to 90°C and start introducing 469g of ethylene oxide. The introduction will be completed in about 6 hours. Continue the reaction for about 2 hours while keeping the reactor pressure constant.

[0069] S3. After the reaction is complete, continue heating the reactor to 150℃. As the reaction proceeds, the pressure in the reactor gradually increases. When the pressure in the pressure-resistant reactor is slightly higher than 1 atmosphere, connect the oil seal to the exhaust port at the top of the reactor, and then slowly open the exhaust port valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After reacting for 1 hour, when no more gas is released from the reactor, continue reacting for another hour.

[0070] S4. After the reaction is complete, continue heating the reactor to 170°C and degas for 2 hours. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1305g of trihydroxyethyl isocyanurate.

[0071] Example 6

[0072] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0073] S1. Add 645g of cyanuric acid, 440g of ethylene carbonate, and 7.69g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 60°C before starting the stirrer.

[0074] S2. After stirring for 30 minutes, raise the temperature of the reactor to 80°C and start introducing 451g of ethylene oxide. The introduction will be completed in about 13 hours. Continue the reaction for about 3 hours while keeping the reactor pressure constant.

[0075] S3. After the reaction is complete, continue heating the reactor to 140℃. As the reaction proceeds, the pressure in the reactor gradually increases. When the pressure in the pressure-resistant reactor is slightly higher than 1 atmosphere, connect the oil seal to the vent at the top of the reactor, and then slowly open the vent valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After 5 hours of reaction, when the gas in the reactor stops escaping, continue the reaction for another hour.

[0076] S4. After the reaction is complete, continue heating the reactor to 170°C and degas for 2 hours. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1302g of trihydroxyethyl isocyanurate.

[0077] Comparative Example 1

[0078] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0079] S1. Add 645g of cyanuric acid, 264g of ethylene carbonate, and 4.33g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 80°C before starting the stirrer.

[0080] S2. After stirring for 30 minutes, raise the temperature of the reactor to 85°C and start introducing 535g of ethylene oxide. The introduction will be completed in about 10 hours. Continue the reaction for about 2 hours while keeping the reactor pressure constant.

[0081] S3. After the reaction is complete, continue to heat the reactor to 120°C. As the reaction proceeds, the pressure in the reactor will gradually increase. When the pressure in the pressure-resistant reactor is slightly higher than 1 atmosphere, connect the oil seal to the exhaust port at the top of the reactor, and then slowly open the exhaust port valve at the top of the reactor to allow the generated carbon dioxide to be discharged from the reaction system.

[0082] S4. After reacting for 8 hours, the reactor was heated to 170°C and degassed for 2 hours. After degassed, the reactor was cooled to 150°C and the product was discharged, yielding approximately 1233g of trihydroxyethyl isocyanurate.

[0083] Comparative Example 2

[0084] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0085] S1. Add 645g of cyanuric acid, 352g of ethylene carbonate, and 5.95g of triethylamine catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 70°C before starting the stirrer.

[0086] S2. After stirring for 30 minutes, raise the temperature of the reactor to 85°C and start introducing 489g of ethylene oxide. The introduction will be completed in about 10 hours. Continue the reaction for about 2 hours while keeping the reactor pressure constant.

[0087] S3. After the reaction is complete, continue heating the reactor to 145℃. As the reaction proceeds, the pressure in the reactor gradually increases. When the pressure in the pressure-resistant reactor is slightly higher than 1 atmosphere, connect the oil seal to the vent at the top of the reactor, and then slowly open the vent valve at the top of the reactor to allow the generated carbon dioxide to escape from the reaction system. After 5 hours of reaction, when no more gas is released from the reactor, continue the reaction for another hour.

[0088] S4. After the reaction is complete, continue heating the reactor to 170°C for degassing. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1304g of trihydroxyethyl isocyanurate.

[0089] Comparative Example 3:

[0090] A method for preparing trihydroxyethyl isocyanurate, comprising the following steps:

[0091] S1. Add 645g of cyanuric acid, 1338g of ethylene carbonate, and 2.84g of dimethylacetamide catalyst to a 2.5L pressure vessel. Connect the ethylene oxide metering vessel to the pressure vessel. Replace the air with nitrogen three times, evacuate the vessel, and heat the vessel to 70°C before starting the stirrer.

[0092] S2. After stirring for 30 minutes, raise the temperature of the pressure vessel to 160℃. As the reaction proceeds, the pressure in the vessel gradually increases. When the pressure in the pressure vessel is slightly higher than 1 atmosphere, connect the oil seal to the vent at the top of the vessel, and then slowly open the vent valve to allow the generated carbon dioxide to escape from the reaction system. After 9 hours of reaction, when no more gas is released from the vessel, continue the reaction for another hour.

[0093] S3. After the reaction is complete, continue heating the reactor to 170°C and degas for 2 hours. After degassing, cool the reactor to 140°C and discharge the product to obtain approximately 1305g of trihydroxyethyl isocyanurate.

[0094] The purity and acid value of the trihydroxyethyl isocyanurate products prepared in Examples 1-6 and Comparative Examples 1-2 were tested. The purity was determined by liquid chromatography (LC), and the results are shown in Table 1 and 2. Figure 1 .

[0095] Table 1. Detection data of trihydroxyethyl isocyanurate products prepared in Examples 1-6 and Comparative Examples 1-2.

[0096] Example 1 99.2 91.7 Tasteless Example 2 99.3 90.3 Tasteless Example 3 99.0 88.6 Tasteless Example 4 98.7 87.6 Tasteless Example 5 98.9 86.4 Tasteless Example 6 99.1 84.7 Tasteless Comparative Example 1 78.6 85.4 Tasteless Comparative Example 2 99.1 87.8 A distinct fishy smell Comparative Example 3 98.8 65.8 Tasteless

[0097] From Table 1 and Figure 1 It is evident that the trihydroxyethyl isocyanurate product prepared using the method of this invention has higher purity and a weaker odor. Compared to Example 2, Comparative Example 1 uses a lower reaction temperature (120°C) in step S3. At this temperature, the ring-opening rate of ethylene carbonate is slower and the reaction is incomplete, resulting in lower yield and product purity in Comparative Example 1. Compared to Example 4, Comparative Example 2 uses triethylamine as the catalyst. Triethylamine has a strong odor, and even a small amount of residue will leave a fishy smell in the material. Comparative Example 3 uses only cyanuric acid and ethylene carbonate as raw materials. Compared to the method using ethylene oxide, the scheme using cyanuric acid and ethylene carbonate as raw materials generates a large amount of carbon dioxide, resulting in a lower reaction yield.

[0098] In summary, the preparation method of the present invention uses ethylene carbonate and cyanuric acid to react under the catalysis of dimethylacetamide. It eliminates the need for solvent recovery and crystallization processes, and the process is simple. It can obtain odorless and high-purity trihydroxyethyl isocyanurate products, which greatly expands the application range of the products.

[0099] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing trihydroxyethyl isocyanurate, characterized in that: Includes the following steps: S1. Add cyanuric acid, catalyst, and ethylene carbonate to a reaction vessel, add nitrogen, then evacuate, heat, and start stirring; the catalyst is dimethylacetamide; the molar ratio of cyanuric acid to ethylene carbonate is 1:0.5~1.

0. S2. After raising the temperature of the reactor to 80~100℃, ethylene oxide is introduced to carry out a ring-opening etherification reaction; the molar ratio of cyanuric acid to ethylene oxide is 1:2.05~2.

5. S3. After the ring-opening etherification reaction is completed, continue to raise the temperature so that the unreacted phenolic hydroxyl groups in cyanuric acid react with ethylene carbonate and release carbon dioxide. S4. After the reaction is complete, a small amount of unreacted ethylene carbonate and catalyst are removed to obtain the trihydroxyethyl isocyanurate product.

2. The method for preparing trihydroxyethyl isocyanurate according to claim 1, characterized in that: The amount of catalyst used in step S1 is 1 to 5‰ of the sum of the mass of cyanuric acid, ethylene carbonate and ethylene oxide.

3. The method for preparing trihydroxyethyl isocyanurate according to claim 1, characterized in that: In step S1, the temperature is raised to 60~80℃ before stirring is started.

4. The method for preparing trihydroxyethyl isocyanurate according to claim 1, characterized in that: In step S2, the reaction pressure for the ring-opening etherification reaction is ≤0.4 MPa and the reaction time is 4~16 h.

5. The method for preparing trihydroxyethyl isocyanurate according to claim 1, characterized in that: The reaction temperature in step S3 is 140~170℃ and the reaction time is 2~10h.

6. The method for preparing trihydroxyethyl isocyanurate according to claim 1, characterized in that: The conditions for removing a small amount of unreacted ethylene carbonate and catalyst in step S4 are: degassing pressure ≤100pa, degassing temperature 170℃, and degassing time 2h.

7. The method for preparing trihydroxyethyl isocyanurate according to claim 1, characterized in that: The trihydroxyethyl isocyanurate obtained in step S4 has a purity of ≥98.5%.

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