A method for synthesizing high-purity tri (epoxypropyl) isocyanurate

Abstract

This invention discloses a method for synthesizing high-purity tri(epoxypropyl)isocyanurate, comprising the following steps: (1) adding cyanuric acid, catalyst, and polar solvent to a reactor and mixing them evenly; (2) adding epichlorohydrin dropwise to react with cyanuric acid, and separating to obtain an intermediate; (3) reacting the intermediate and calcium oxide in an organic medium; (4) separating while hot, removing the solid, cooling the liquid to crystallize, and separating to obtain the product TGIC. This method effectively controls the hydrolysis side reactions of the product and intermediates, achieving a product yield of over 96% and a purity of 99%.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, and specifically to a method for synthesizing tris(epoxypropyl)isocyanurate. Background Technology

[0002] Tri(epoxypropyl) isocyanurate (TGIC) is mainly used as a curing agent for powder coatings of carboxyl-containing polyesters and carboxyl-containing acrylic resins. Due to its ability to impart good weather resistance, thermal stability, and mechanical properties to the products, it has a wide range of applications. High-purity TGIC also possesses excellent high-temperature electrical properties and can be used in the manufacture of electrical insulation materials, printed circuits, and as a stabilizer for laminates and plastics.

[0003] Currently, the main methods for synthesizing TGIC include the epoxidation of triallyl isocyanurate, the dichloropropanol method, and the two-step method using epichlorohydrin.

[0004] The triallyl isocyanurate epoxidation method uses triallyl isocyanurate and hydrogen peroxide as raw materials to epoxidize an olefin and obtain triglycidyl isocyanurate. However, the triallyl isocyanurate used in this method is expensive, resulting in high costs.

[0005] The dichloropropanol method, disclosed in patent CN 112321576 A, is a novel preparation method for TGIC. This method involves heating cyanuric acid with excess dichloropropanol in the presence of an alkaline environment and solvent to produce TGIC. However, the excess dichloropropanol used in this method has a high boiling point and is difficult to recover after the reaction, resulting in a large amount remaining in the product. This leads to low product quality and significantly limits its application.

[0006] The two-step method for epichlorohydrin synthesis is a widely used process. It involves reacting cyanuric acid with epichlorohydrin to obtain an intermediate, which is then cyclized with sodium hydroxide to yield TGIC. This method has several drawbacks: ① It requires depressurization and azeotropic distillation during the cyclization process to promptly remove water from the system and prevent side reactions. The feeding rate, dehydration rate, and reaction rate need to be highly matched, making the operation complex and challenging. ② In reality, relying solely on azeotropy, water cannot be removed from the system in a timely manner. Furthermore, the water absorption rate of desiccant such as molecular sieves and anhydrous sodium sulfate is relatively slow, making it difficult to completely avoid the formation of hydrolysis byproducts of TGIC, resulting in low product yield and poor quality. ③ Since the first step is a reversible reaction, the first step typically uses epichlorohydrin as a solvent (with a molar ratio of 8–18:1 to cyanuric acid), with a significant excess of epichlorohydrin to ensure complete reaction of the cyanuric acid.

[0007] Patent CN 101367796A discloses a method for producing triepoxypropyl isocyanurate, in which a small amount of water is added to epichlorohydrin to form a mixed solvent during the first step of synthesizing the intermediate. However, this method actually still uses epichlorohydrin as the solvent for the reaction. US Patent 3,547,918A has reported that excess epichlorohydrin continues to react with the intermediate generated in the first step, producing some epoxidized products and 1,3-dichloro-2-propanol byproducts. This consumes a large amount of epichlorohydrin, increasing costs. Furthermore, the 1,3-dichloro-2-propanol produced has a high boiling point and is easily retained in the product.

[0008] Therefore, developing a low-cost, high-yield, and high-quality TGIC synthesis process is an urgent need in the industry. To overcome the shortcomings of existing technologies, this invention provides an innovative technical solution. Summary of the Invention

[0009] A method for synthesizing high-purity tris(epoxypropyl)isocyanurate involves reacting cyanuric acid with epichlorohydrin to obtain an intermediate, followed by an epoxidation reaction with calcium oxide to yield TGIC. The specific reaction formula is as follows:

[0010]

[0011] Specifically, the following steps are included:

[0012] (1) Add cyanuric acid, catalyst, and polar solvent to the reactor and mix thoroughly;

[0013] (2) Add epichlorohydrin slowly at 75-90℃, and keep warm for 2-6 hours after the addition is complete;

[0014] (3) Cool down to below 40℃ and separate to obtain a white powder intermediate;

[0015] (4) Add the intermediate and calcium oxide to the organic medium, start stirring, and keep the reaction at 50-60°C for 4-6 hours.

[0016] (5) Separate while hot to remove solids, cool the liquid to crystallize, and separate to obtain the product TGIC.

[0017] The polar solvent used in this invention is water, methanol, ethanol, or a mixture thereof, preferably water, and is used in an amount of 4 to 7 times the weight of cyanuric acid. Since the first step reaction is reversible, the polar solvent does not dissolve the intermediate and replaces excess epichlorohydrin as a solvent, allowing the intermediate generated in the reaction to precipitate out of the medium in a timely manner. This ensures complete conversion of the raw material cyanuric acid while significantly reducing the amount of epichlorohydrin used.

[0018] This invention uses a polar solvent as the reaction medium and adopts the method of adding epichlorohydrin dropwise to carry out the reaction, so that epichlorohydrin can react with cyanuric acid in time and be consumed, thereby avoiding the large amount of extra consumption of epichlorohydrin and the generation of the byproduct 1,3-dichloro-2-propanol caused by the continued reaction of a large excess of epichlorohydrin with the intermediate.

[0019] The catalyst described in this invention is a quaternary ammonium salt phase transfer catalyst, such as hexadecyltrimethylammonium bromide, tetramethylammonium chloride, or triethylbenzylammonium chloride, preferably hexadecyltrimethylammonium bromide, and is used in an amount of 1% to 2.5% of the weight of cyanuric acid.

[0020] The organic medium described in this invention is methanol, ethanol, or a mixture thereof. Since commercially available solvents of this type contain water, it is not necessary to add additional water for activation in this invention. The amount of water used is 4 to 7 times the weight of cyanuric acid.

[0021] In this invention, the molar ratio of cyanuric acid, epichlorohydrin, and calcium oxide is 1:3.5 to 7:2.5 to 3.0.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) A solvent that does not dissolve intermediates is selected as the medium for the first step of the reaction, so that the intermediates generated by the reaction can be precipitated from the medium in time, thereby allowing the raw material cyanuric acid to be completely converted and greatly reducing the amount of epichlorohydrin used.

[0024] (2) Calcium oxide is used instead of alkali in the epoxidation reaction. Since calcium oxide reacts rapidly with water to produce calcium hydroxide, the calcium hydroxide undergoes dehydrochlorination with the intermediate to epoxidize and obtain the product. This method allows the water in the system and the generated water to be rapidly absorbed by calcium oxide, and the generated calcium hydroxide can continue to react with the intermediate to obtain the product. Since the alkali is provided by the calcium hydroxide produced from the reaction of calcium oxide and the generated water, the alkali in the system can be maintained at a low concentration, reducing the occurrence of side reactions.

[0025] (3) Since the generated calcium chloride also has a certain water absorption capacity, the present invention can contain two water-absorbing agents in the system, and the water removal capacity is much higher than that of the existing process. Therefore, the present invention can greatly avoid the occurrence of hydrolysis side reactions, thereby achieving a product yield of over 96% and a purity of over 99%, which can meet the high quality requirements of the electronics industry for TGIC and improve the added value of the product. Detailed Implementation

[0026] The following detailed description is based on specific embodiments of the present invention, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0027] Example 1

[0028] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 530 g of water were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 323.82 g of epichlorohydrin was added dropwise over approximately 0.5 h. The mixture was kept at this temperature for 6 h, then cooled to below 40 °C and filtered to obtain the intermediate.

[0029] The intermediate and 143.05 g of calcium oxide were added to 526.8 g of methanol, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. Crystallization was then performed, filtered again, and dried at 40 °C to obtain 293.11 g of TGIC. The yield was 98.61%, and the purity, as determined by HPLC, was 99.01%.

[0030] Example 2

[0031] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 530 g of water were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 323.82 g of epichlorohydrin was added dropwise over approximately 0.5 h. The mixture was kept at this temperature for 6 h, then cooled to below 40 °C and filtered to obtain the intermediate.

[0032] The intermediate and 143.05 g of calcium oxide were added to 526.8 g of methanol, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. Crystallization was then performed, filtered again, and dried at 40 °C to obtain 293.15 g of TGIC. The yield was 98.62%, and the purity was 99.24% as determined by HPLC.

[0033] Example 3

[0034] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 660 g of methanol were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 647.64 g of epichlorohydrin was added dropwise over approximately 0.5 h. After maintaining the temperature for 6 h, the temperature was lowered to 50–60 °C, and 143.05 g of calcium oxide was added. The mixture was stirred, and the temperature was raised to 50–60 °C. After reacting for 5 h, the mixture was filtered while hot. The filtrate was stirred and cooled to 0 °C for crystallization and filtration. The mother liquor was collected, and the solid was dried at 40 °C to obtain 286.32 g of TGIC. The yield was 96.32%, and the purity was 99.54% as determined by HPLC.

[0035] Example 4

[0036] 131.70 g of cyanuric acid (98% purity), 1.65 g of cetylammonium bromide, and the mother liquor collected in Example 3 were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 370 g of epichlorohydrin was added dropwise over approximately 0.5 h. After maintaining the temperature for 6 h, the temperature was lowered to 50–60 °C, and 143.05 g of calcium oxide was added. The mixture was stirred, and the temperature was raised to 50–60 °C. After reacting for 5 h, the mixture was filtered while hot. The filtrate was stirred and cooled to 0 °C for crystallization and filtration. The mother liquor was collected, and the solid was dried at 40 °C to obtain 290.02 g of TGIC. The yield was 97.57%, and the purity was 99.04% as determined by HPLC.

[0037] Example 5

[0038] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 920 g of ethanol were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 647.64 g of epichlorohydrin was added dropwise over approximately 0.5 h. After maintaining the temperature for 6 h, the temperature was lowered to 50–60 °C, and 143.05 g of calcium oxide was added. The mixture was stirred, and the temperature was raised to 50–60 °C. After reacting for 5 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. The filtrate was then crystallized, filtered, and dried at 40 °C to obtain 288.62 g of TGIC. The yield was 97.10%, and the purity was 99.42% as determined by HPLC.

[0039] Example 6

[0040] 131.70 g of cyanuric acid (98% purity), 1.32 g of tetramethylammonium chloride, and 530 g of water were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 323.82 g of epichlorohydrin was added dropwise over approximately 0.5 h. The mixture was kept at this temperature for 6 h, then cooled to below 40 °C. The mixture was filtered, and the mother liquor was collected to obtain the intermediate.

[0041] The intermediate and 143.05 g of calcium oxide were added to 526.8 g of methanol, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was stirred and cooled to 0 °C for crystallization and filtration. The mother liquor was collected, fixed, and dried at 40 °C to obtain 292.05 g of TGIC. The yield was 98.25%, and the purity was 99.13% as determined by HPLC.

[0042] Example 7

[0043] 131.70g of cyanuric acid (98% purity), 1.32g of tetramethylammonium chloride, and 530g of water were added to a 2L flask and stirred. The temperature was raised to 75-80℃, and 323.82g of epichlorohydrin was added dropwise over approximately 0.5 hours. The mixture was kept at this temperature for 6 hours, then cooled to below 40℃ and filtered to obtain the intermediate.

[0044] The intermediate and 143.05 g of calcium oxide were added to the mother liquor collected in the second step of Example 6, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. Crystallization was then performed, filtered again, and dried at 40 °C to obtain 294.05 g of TGIC. The yield was 98.92%, and the purity was 99.02% as determined by HPLC.

[0045] Example 8

[0046] 131.70 g of cyanuric acid (98% purity), 1.32 g of tetramethylammonium chloride, and the mother liquor from the first step of Example 6 were added to a 2 L flask and stirred. The temperature was raised to 75–80 °C, and 323.82 g of epichlorohydrin was added dropwise over approximately 0.5 h. After maintaining the temperature for 6 h, the temperature was lowered to below 40 °C, filtered, and the mother liquor was collected to obtain the intermediate.

[0047] The intermediate and 143.05 g of calcium oxide were added to 526.8 g of methanol, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. Crystallization and filtration were then performed. The mother liquor was collected, fixed, and dried at 40 °C to obtain 293.16 g of TGIC. The yield was 98.63%, and the purity was 99.10% as determined by HPLC.

[0048] Example 9

[0049] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 530 g of water were added to a 2 L flask and stirred. The mixture was heated to 90 °C, and 323.82 g of epichlorohydrin was added dropwise over approximately 0.5 h. The mixture was kept at 90 °C for 2 h, then cooled to below 40 °C and filtered to obtain the intermediate.

[0050] The intermediate and 143.05 g of calcium oxide were added to 526.8 g of methanol, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. Crystallization was then performed, filtered again, and dried at 40 °C to obtain 293.23 g of TGIC. The yield was 98.65%, and the purity, as determined by HPLC, was 99.11%.

[0051] Comparative Example 1

[0052] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 323.82 g of epichlorohydrin were added to a 500 mL flask and stirred. The mixture was heated to 75–80 °C and kept at this temperature for 6 hours. Unreacted cyanuric acid was removed by filtration to obtain the intermediate solution.

[0053] 143.05 g of calcium oxide was added to the intermediate solution, stirred, and heated to 50–60 °C. After reacting for 4 h, the solution was filtered while hot. 526.8 g of methanol was added to the filtrate, and the mixture was stirred, cooled to 0 °C to crystallize, filtered, and dried at 40 °C to obtain 118.92 g of TGIC. The yield was 40.00%, and the purity was 99.89% as determined by HPLC.

[0054] Comparative Example 2

[0055] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, and 1665 g of epichlorohydrin were added to a 2 L flask and stirred. The mixture was heated to 75–80 °C and kept at this temperature for 6 hours to obtain a clear intermediate solution.

[0056] 143.05 g of calcium oxide was added to the intermediate solution, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot. Epichlorohydrin was recovered from the filtrate under reduced pressure below 80 °C. 526.8 g of methanol was added to the remaining crude product, and the mixture was stirred, cooled to 0 °C to crystallize, filtered, and dried at 40 °C to obtain 284.76 g of TGIC. The yield was 95.80%, and the purity was 97.86% as determined by HPLC.

[0057] Comparative Example 3

[0058] 131.70 g of cyanuric acid (98% purity), 3.3 g of cetylammonium bromide, 323.82 g of epichlorohydrin, and 530 g of water were added to a 2 L flask and stirred. The mixture was heated to 75–80 °C and held at that temperature for 6 hours. Then, the temperature was lowered to below 40 °C, and the mixture was filtered to obtain the intermediate.

[0059] The intermediate and 143.05 g of calcium oxide were added to 526.8 g of methanol, stirred, and heated to 50–60 °C. After reacting for 4 h, the mixture was filtered while hot, and the filtrate was cooled to 0 °C with stirring. Crystallization was then performed, filtered again, and dried at 40 °C to obtain 282.12 g of TGIC. The yield was 94.91%, and the purity was 97.06% as determined by HPLC.

[0060] The following are the main testing methods and results for TGIC.

[0061] (1) Determination of epoxy value (0.97~1.06 is acceptable):

[0062] ① Take 2g (accurate to 0.1mg) of TGIC powder prepared in each of the above examples and comparative examples, add 20ml of hydrochloric acid-acetone solution (1ml of concentrated hydrochloric acid diluted with reagent acetone to 40ml, freshly prepared and used immediately), shake well to dissolve the TGIC powder, let stand in a cool place for 1h, and titrate with 0.1mol / L KOH-CH:OH standard solution until a pink color appears and does not fade within 10s. Repeat the above operation without adding TGIC particles to serve as a blank group.

[0063] ②Epoxy value (equivalent / 100g) = (V1-V2)×N / 10m.

[0064] Where V1 is the titration volume of the blank group, V2 is the titration volume of the experimental group and the control group respectively, N is the concentration of KOH-C2H5OH standard solution (0.1mol / L), and m is the weight of TGIC powder (2g).

[0065] (2) Comprehensive trait test

[0066] ① Particle size: Laser particle size analyzer ② Epichlorohydrin residue: Dispersion solid-phase extraction-gas chromatography

[0067] (3) The test results are shown in the table below.

[0068]

[0069]

Claims

1. A synthesis method of tris (epoxypropyl) isocyanurate, comprising the following steps: (1) adding cyanuric acid, a catalyst, and a polar solvent into a reactor and mixing uniformly; the polar solvent is water, and the amount of water is 4-7 times the weight of cyanuric acid; the catalyst is a quaternary ammonium salt phase transfer catalyst, and the amount of the catalyst is 1%-2.5% of the weight of cyanuric acid; (2) slowly adding epichlorohydrin at 75-90°C, and keeping for 2-6 hours after the addition is completed, the reaction is a reversible reaction, and the polar solvent does not dissolve the intermediate, so that the intermediate generated in the reaction is precipitated from the medium in time; the reaction is carried out by adding epichlorohydrin dropwise, so that epichlorohydrin is consumed in time, and the additional consumption of epichlorohydrin and the generation of a byproduct 1,3-dichloro-2-propanol are avoided; (3) cooling to below 40°C, and separating a white powder intermediate, and collecting the mother liquor of the first step reaction; (4) adding the intermediate and calcium oxide into an organic medium, starting stirring, and keeping for 4-6 hours at 50-60°C; the organic medium is methanol, ethanol, or a mixture thereof, and the amount of the organic medium is 4-7 times the weight of cyanuric acid; in the system, water and generated water are rapidly absorbed by calcium oxide, and the generated calcium hydroxide continues to react with the intermediate to obtain the product, the alkali in the reaction is provided by the calcium hydroxide generated by the reaction of calcium oxide and water, and the alkali in the system is continuously kept at a low concentration, so that the occurrence of side reactions is reduced; (5) separating while hot, removing the solid, cooling and crystallizing the liquid, and separating the product TGIC, and collecting the crystallization mother liquor; the molar ratio of cyanuric acid, epichlorohydrin, and calcium oxide is 1:3.5:2.5-3.0; the yield of the product TGIC is more than 96%, and the purity is more than 99%.

2. The process for synthesis of tri (epoxypropyl) isocyanurate as claimed in claim 1 wherein: the catalyst is cetyltrimethylammonium bromide, tetramethylammonium chloride, or triethylbenzylammonium chloride.

3. The process for synthesis of tri (epoxypropyl) isocyanurate as claimed in claim 2, wherein the process comprises the steps of: a) reacting the isocyanuric acid with the propylene oxide in the presence of the catalyst to obtain the tri (epoxypropyl) isocyanurate. the catalyst is cetyltrimethylammonium bromide.

4. The synthesis method of tris (epoxypropyl) isocyanurate according to any one of claims 1-3, further comprising a recycling step of the polar solvent and the organic solvent, specifically as follows: (1) adding cyanuric acid, a catalyst, and the mother liquor of the first step reaction into a reactor and mixing uniformly; (2) adding epichlorohydrin dropwise at 75-90°C, and keeping for 2-6 hours after the addition is completed; (3) cooling to below 40°C, and separating a white powder intermediate; (4) adding the intermediate and calcium oxide into the crystallization mother liquor, starting stirring, and keeping for 4-6 hours at 50-60°C; (5) separating while hot, removing the solid, cooling and crystallizing the liquid, and separating the product TGIC.

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