Compound applied to temperature controller and synthesis method thereof
N-(2-methyl-3-phthalimino)phenylhexahydrophthalimide was prepared by a two-step synthesis method, which solved the stability and cost of the compound in the thermostat, achieved high purity and melting range stability of the compound, and met the application requirements of the thermostat.
Patent Information
- Application Number
- CN202510653540.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-21
- Publication Date
- 2025-08-22
AI Technical Summary
The prior art lacks a reasonable price and stable performance compound to replace tri-disc ene for thermostats, and needs to meet the requirements of no active hydrogen, non-conductive, non-corrosive, non-toxic, non-radioactive, non-halogen and thio.
N-(2-methyl-3-phthalimino)phenylhexahydrophthalimide was prepared by a two-step synthesis method. By controlling the reaction conditions and purification steps, the high purity and melting range stability of the compound are ensured. The specific steps include dehydration and ring-closing reaction and purification treatment.
The high purity and melting range stability of the compound are achieved, and can replace tri-disc olefins for thermostats to meet the application needs of electronic components, and have a low cost.
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Abstract
Description
Technical Field
[0001] The invention relates to a compound applied to a temperature controller and a synthesis method thereof. Background Art
[0002] A thermostat is a series of automatic control components that physically deform within the switch in response to ambient temperature changes, causing it to open or close. They are also called temperature switches, temperature protectors, or temperature controllers. Their principle is to pack a compound into a sealed ceramic box connected to a live wire, a neutral wire, and a connecting rod. When the temperature of the wires reaches the melting point of the compound, it transforms from a solid into a liquid, expanding in volume. This pushes the connecting rod connected to the ceramic box, thereby opening the circuit. Once disconnected, the application temperature drops, causing the compound to transform from a liquid back into a solid, shrinking in volume, causing the connecting rod connected to the ceramic box to rebound, thus closing the circuit. Thermostats have a wide range of applications, and the compound they contain has specific melting range requirements depending on the application scenario and the specific appliance.
[0003] Based on the principles of thermostats, the compound must meet several requirements before it can be used in a thermostat. First, the compound must maintain stable physical and chemical properties, resist decomposition, and maintain a constant melting point during multiple melting, solidification, and remelting cycles. Second, the compound must be non-conductive, meaning it cannot contain active groups such as active hydrogen, and must not be a metal organic compound. Third, the compound must not be corrosive, toxic, or radioactive. Furthermore, as environmental standards for electrical appliances become increasingly stringent worldwide, domestic requirements for compounds used in electrical components require that they contain no halogens, sulfur, or phosphorus.
[0004] In recent years, both domestic and international markets have been using tristyrene for thermostats requiring a trip temperature of 252-255°C. While tristyrene meets all the aforementioned performance requirements, it costs over 6,000 yuan per kilogram. With no stable domestic manufacturer, it is a custom-made product with limited availability. Finding a compound with a melting range similar to tristyrene and meeting all the requirements for thermostats, and developing a synthesis method for it, holds significant economic and social significance for the domestic thermostat industry.
[0005] After a large number of synthesis screening tests, it was determined that the melting range of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide was 252-255°C. Summary of the Invention
[0006] The present invention aims to provide a compound for use in a thermostat and a method for synthesizing the same, namely, a method for synthesizing N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide. The chemical structure of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide is as follows:
[0007]
[0008] The N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide provided by the present invention has two five-membered imine rigid rings in its molecule and has the characteristics of stable physical and chemical properties. The N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide has no active groups and is non-conductive. The N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide is not a hazardous chemical with properties such as corrosiveness, toxicity, and radioactivity. The N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide does not contain halogen, sulfur, or phosphorus elements. The N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide with a liquid phase content of more than 99% has a stable melting range between 253 and 254°C.
[0009] Based on these properties, pure N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide was pressed into a thermostat and subjected to fatigue testing. After 1,000 cycles of disconnection, melting, and solidification, the thermostat continued to function normally. N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide can replace tris(e)ene in thermostats and other electronic components.
[0010] A compound used in thermostats and its synthesis method, namely, a method for synthesizing N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide, is achieved through the following technical scheme: 2,6-diaminotoluene, phthalic anhydride, and hexahydrophthalic anhydride are used as raw materials and subjected to dehydration and ring-closure reactions in a solvent to obtain the product. The chemical reaction formula is as follows:
[0011]
[0012] Theoretically, the molar ratio of 2,6-diaminotoluene to phthalic anhydride and hexahydrophthalic anhydride is 1:1:1. However, when the materials are added simultaneously in equal proportions, two phthalimide products and two hexahydrophthalimide products will react, resulting in two by-product impurities, with the following structures:
[0013]
[0014] It is difficult to remove both type A and type B impurities at the same time.
[0015] In order to control the single impurity of the final product and improve the purity of the final product, the present invention selects a two-step synthesis. The reaction formula is as follows:
[0016] first step:
[0017]
[0018] Step 2:
[0019]
[0020] First, an excess of 2,6-diaminotoluene and phthalic anhydride react in acetone to produce N-(2-methyl-3-amino)phenylphthalamic acid, product c, as shown in the first step of the reaction equation. N-(2-methyl-3-amino)phenylphthalamic acid has low solubility in acetone and can be obtained by filtration. The filter cake is then rinsed with fresh acetone or slurried to yield high-purity N-(2-methyl-3-amino)phenylphthalamic acid. This N-(2-methyl-3-amino)phenylphthalamic acid and hexahydrophthalic anhydride are then added to a solvent and reacted at a specific temperature for a period of time to yield the high-purity final product.
[0021] In the first step, an excess of 2,6-diaminotoluene is used. This results in an amide compound formed from a monoamino group and phthalic anhydride. The excess 2,6-diaminotoluene is removed with the acetone during filtration, yielding the highly purified intermediate N-(2-methyl-3-amino)phenylphthalamic acid. In practice, the molar ratio of 2,6-diaminotoluene to phthalic anhydride is (1-1.2):1, and the reaction temperature is kept below 15°C. Theoretically, an excess of 2,6-diaminotoluene and hexahydrophthalic anhydride can be used in acetone to generate N-(2-methyl-3-amino)phenylhexahydrophthalamic acid, which is then reacted with phthalic anhydride to yield the final product. However, experiments have shown that N-(2-methyl-3-amino)phenylhexahydrophthalamic acid has a high solubility in acetone, significantly reducing the yield.
[0022] In the second step, N-(2-methyl-3-amino)phenylphthalamic acid and hexahydrophthalic anhydride are mixed in a 1:1 molar ratio and dehydrated in toluene under reflux to yield a high-purity final product. Trace amounts of the intermediate structure C and the impurity structure D shown below can be removed by washing with dilute sodium carbonate.
[0023]
[0024] The experimental procedure of the present invention is as follows: ① Measured amounts of 2,6-diaminotoluene and acetone are placed in a reaction flask. Solid phthalic anhydride is added in batches at 10°C, maintaining the system temperature below 15°C throughout the process. After the phthalic anhydride is added, the reaction is incubated for a period of time before filtering. The filter cake is rinsed with fresh acetone and dried to obtain the intermediate. ② Measured amounts of the intermediate, hexahydrophthalic anhydride, and toluene are added to the reaction flask. The reaction is heated to reflux for separation of water. After the reaction is complete, the reaction is cooled to room temperature. Filtering is performed, and the filter cake is washed with fresh toluene, methanol, a 5% aqueous sodium carbonate solution, and water, respectively, before drying to obtain the final product.
[0025] The two-step reaction of the present invention has mild reaction conditions, simple operation, high reaction yield, and the total molar conversion rate of the two-step reaction can reach more than 83%. DETAILED DESCRIPTION
[0026] Example 1
[0027] To a 250ml four-necked flask equipped with a mechanical stirrer, electric heating mantle, spherical condenser, water trap, and thermometer, 14.8g of phthalic anhydride (0.1mol), 15.4g of hexahydrophthalic anhydride (0.1mol), 100ml of toluene, and 12.2g of 2,6-diaminotoluene (0.1mol) were added in sequence. The mixture was then heated to reflux. As the reaction proceeded, condensate from the condenser dripped into the water trap, with water droplets settling to the bottom. The reflux reaction was maintained for 24 hours. The mixture was cooled to room temperature and filtered. The filter cake was rinsed with 100ml of fresh toluene, 100ml of methanol, and 100ml of a 5% sodium carbonate solution, followed by 5000ml of deionized water. The mixture was then dried to yield 35g of a white crystalline powder.
[0028] The melting point was measured, with an initial melting point of 226°C and a final melting point of 243°C. The liquid content was 73.11%.
[0029] Example 2
[0030] Step 1: Synthesis of N-(2-methyl-3-amino)phenylphthalamide acid:
[0031] To a 250ml double-layer reaction flask equipped with a mechanical stirrer, a circulating refrigeration unit, and a thermometer, add 12.2g of 2,6-diaminotoluene (0.1mol) and 100ml of acetone. Stirring is initiated, and after dissolution, a refrigerant solution is introduced into the interlayer of the reaction flask. When the system temperature drops below 10°C, 14.8g of phthalic anhydride (0.1mol) is added in batches. As the phthalic anhydride is added, heat is released within the system, and the temperature rises. The addition rate of phthalic anhydride is controlled so that the system temperature does not exceed 15°C during the addition process. After the phthalic anhydride is added, stir at 10-15°C for 1 hour. Filter, rinse the filter cake with 300ml of fresh acetone, and dry to yield 22g of a white powder with a melting point of 189-193°C and a liquid content of 97.82%. The molar yield (calculated as phthalic anhydride) is 81.5%.
[0032] Step 2: Synthesis of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide:
[0033] In the 250ml four-necked flask that is equipped with mechanical stirrer, electric heating mantle, spherical condenser, water trap and thermometer, add above-mentioned 22g first step product N-(2-methyl-3-amino) phenylphthalamide acid (0.082mol), 100ml toluene and 12.6g hexahydrophthalic anhydride (0.082mol).Be heated to reflux immediately, along with the carrying out of reaction, when condensate drips into water trap in the condenser, water globule is had to sink to the bottom.Keep back flow reaction 21 hours, cool to room temperature.Filter, filter cake is 5% sodium carbonate aqueous solution drip washing with 100ml fresh toluene, 100ml methyl alcohol, 100ml massfraction respectively, uses 5000ml deionized water drip washing again, oven dry and obtain 30.6g white crystalline powder.
[0034] The melting point was measured to be 252.7-254.2°C, the liquid content was 98.91%, and the total molar yield of the two steps (calculated as phthalic anhydride) was 78.9%.
[0035] Example 3
[0036] Step 1: Synthesis of N-(2-methyl-3-amino)phenylphthalamide acid:
[0037] To a 5000ml double-layer reaction flask equipped with a mechanical stirrer, a circulating refrigeration unit, and a thermometer, add 500g of 2,6-diaminotoluene (4.09mol) and 1500ml of acetone. Stirring was initiated, and a refrigerant solution was introduced into the interlayer of the reaction flask. When the system temperature dropped below 10°C, 510g of phthalic anhydride (3.44mol) was added in batches. As the phthalic anhydride was added, heat was released within the system, and the temperature rose. The addition rate of phthalic anhydride was controlled so that the system temperature did not exceed 15°C during the addition process. After the phthalic anhydride was added, the mixture was stirred at 10-15°C for 1 hour. The mixture was then filtered, and the filter cake was transferred to a 5000ml flask. 1500ml of fresh acetone was added, and the mixture was stirred and beaten at room temperature for 30 minutes. The mixture was filtered and dried to yield 863g of a white powder with a melting point of 190.7-192.2°C and a liquid content of 99.13%. The molar yield (calculated as phthalic anhydride) was 93.02%.
[0038] Step 2: Synthesis of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide:
[0039] To a 5000ml four-necked flask equipped with a mechanical stirrer, electric heating mantle, spherical condenser, water trap, and thermometer, 863g of the first-step product, N-(2-methyl-3-amino)phenylphthalamic acid (3.2 mol), 2000ml of toluene, and 493g of hexahydrophthalic anhydride (3.2 mol) were added. The mixture was then heated to reflux. As the reaction proceeded, condensate from the condenser dripped into the water trap, with water droplets settling to the bottom. The reflux reaction was maintained for 24 hours, then cooled to room temperature and filtered.
[0040] The filter cake was transferred to a 5000ml flask, and 2000ml of methanol was added. The mixture was stirred and slurried at room temperature for 30 minutes. Filtered. The filter cake was then transferred to a 5000ml flask, and 2000ml of a 5% sodium carbonate aqueous solution was added. The mixture was stirred and slurried at room temperature for 30 minutes. Filtered. The filter cake was washed with deionized water until neutral and dried to obtain 1121g of white crystalline powder.
[0041] The melting point was measured to be 253.2-253.8°C, the liquid content was 99.10%, and the total molar yield of the two steps (calculated as phthalic anhydride) was 83.99%.
[0042] Example 4
[0043] Step 1: Synthesis of N-(2-methyl-3-amino)phenylhexahydrophthalamide acid:
[0044] To a 250ml double-layer reaction flask equipped with a mechanical stirrer, a circulating refrigeration unit, and a thermometer, add 13g of 2,6-diaminotoluene (0.11mol) and 100ml of acetone. Start stirring, and after the solution has dissolved, introduce a refrigerant solution into the interlayer of the reaction flask. When the system temperature drops below 10°C, add 15.4g of hexahydrophthalic anhydride (0.1mol) in batches. As the hexahydrophthalic anhydride is added, heat is released in the system and the temperature rises. Control the addition rate of the hexahydrophthalic anhydride so that the system temperature does not exceed 15°C during the addition process. After the hexahydrophthalic anhydride is added, stir at 10-15°C for 1 hour. Filter and dry the filter cake to obtain 5.5g of a white powder with a melting point of 161-163°C and a liquid content of 99.98%. The filtrate was placed in a refrigerator overnight to precipitate white crystals, which were filtered and dried to obtain 3 g of white needle-shaped crystals with a melting point of 162-163° C. and a liquid content of 99.52%.
[0045] The combined filter cakes from the two extractions totaled 8.5 g, with a molar yield (based on hexahydrophthalic anhydride) of 30.8%.
[0046] Step 2: Synthesis of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide:
[0047] In the 100ml four-necked flask equipped with mechanical stirrer, electric heating mantle, spherical condenser, water trap and thermometer, add above-mentioned 8.5g first step product N-(2-methyl-3-amino) phenyl hexahydrophthalamide acid (0.031mol), 50ml toluene and 4.6g phthalic anhydride (0.031mol). Be heated to reflux immediately, along with the carrying out of reaction, when condensate drips into water trap in the condenser, water globule is had to sink to the bottom. Keep back flow reaction 20 hours, cool to room temperature.Filter, filter cake oven dry, obtain 11g white crystalline powder.
[0048] The melting point was measured to be 253.5-253.9°C, the liquid content was 99.15%, and the total molar yield of the two steps (calculated as hexahydrophthalic anhydride) was 28%.
Claims
1. A compound used in a thermostat and a synthesis method thereof, characterized in that: This compound is N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide, and its molecular structure is: The synthesis method of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide comprises the following two-step reaction: In the first step, 2,6-diaminotoluene and phthalic anhydride are reacted in acetone to generate N-(2-methyl-3-amino)phenylphthalamic acid; In the second step, N-(2-methyl-3-amino)phenylphthalamic acid and hexahydrophthalic anhydride react to generate N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide; The chemical reaction formula of the two steps is as follows: first step: Step 2:
2. The synthetic method of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide according to claim 1, wherein In the first step reaction, the molar ratio of 2,6-diaminotoluene to phthalic anhydride is (1-1.2):1, and the reaction temperature is lower than 15°C.
3. The synthetic method of N-(2-methyl-3-phthalimido)phenylhexahydrophthalimide according to claim 1, characterized in that: In the second step reaction, toluene is used as solvent, and the molar ratio of N-(2-methyl-3-amino)phenylphthalamic acid to hexahydrophthalic anhydride is 1:1.